Symposium NM05—Functional Nanoparticle Materials—Synthesis, Property and Applications

This work is a continuation of a growing interest and effort to incorporate into nanocomposites functionalities beyond load-bearing. We report on the concepts and findings of engineering nanocomposites to acquire surface self-disinfection, self-enhanced cell adhesion and growth, on top of internal self-transport of nutrient and growth factors, self-healing and self-lubrication.

Biocomposites have been engineered to repair or replace human mechanics, damaged due to age or injury or deceases, and are of increasing clinical importance. In particular, many surgical procedures require implanting bone-like biomaterials to perform necessary operations. Oftentimes these operations lead to dangerous surgical site infections, as foreign surfaces are an attractive site for bacterial adherence, thus, biocompatibility studies on implantable device require a series of in-depth experiments analyzing both in vitro and in vivo applications.¹ Bone implant biomaterials are generally made of calcium phosphate ceramics, of which hydroxyapatite (HAp) and Whitlockite (WH) have shown notable biocompatibility and bioactivity. Previous research on HAp and WH biomaterials, has created novel advancements seen in dental work, bone implants, and biocoatings.

In an effort to advance such composites beyond the load-bearing function, we have succeeded in engineering a 3D network of nanochannels inside the composite that enables nutrient absorption and transport along with growth factors and enabled self-sustained bone cell growth for selfhealing² . With such a built-in network and its Laplace (capillary) force within, lubricants and coolants could also be delivered to the interface of a joint^{3 , 4} . We show a further advance of this effort – surface engineering to enable on-command self-infection and enhanced celladhesion/growth, via incorporation of TaN and/or TiO2 nanocomposites and photocatalytic and heterointerface field-induce reactions as representative approaches.

We plan to leverage the visible-light photocatalytic activity and electrical conductivity of copper oxide nanoparticles (CUO NPs) to further contribute to self-disinfection, self-enhanced cell adherence and growth material. Likely because of the electrical conductivity, CuO-Hap nanobiocomposites present high cell viability⁵, thus, we expect this to further the functionality of the TIO2-Hap composite, creating a strong application for the future of biocomposites. We hope by the end of this process we will have pioneered a technique that will help minimize the invasive and inflammatory effects of implant debris and microphage reactivity, setting a new ground for the future and reduction of osteogenesis infections.

Referneces:
1. Biocompatibility. (n.d.). Retrieved February 02, 2021, from https://www.sciencedirect.com/topics/materials-science/biocompatibility

2. Jang, H. L., Lee, K., Kang, C. S., Lee, H. K., Ahn, H.-Y., Jeong, H.-Y., Park, S., Kim, S. C., Jin, K., Park, J., Yang, T.-Y., Kim, J. H., Shin, S. A., Han, H. N., Oh, K. H., Lee, H.-Y., Lim, J., Hong, K. S., Snead, M. L., … Nam, K. T. (2015). Biofunctionalized Ceramic with Self-Assembled Networks of Nanochannels. ACS Nano, 9(4), 4447–4457

3. C. Wu, J-H Kim, Jimmy Xu System and methods for nanostructure protected delivery of treatment agent and selective release thereof, US Patent 14600188

4. J-H Kim, K-T Nam, Jimmy Xu, “Bioceramics with Self-Powered Fluidic Delivery and Lubircation”, 15th Conference and Exhibition of the European Ceramic Society, (ECerS 2017), Budapest, Hungary, July 9-13, 2017

5. Sahmani, S., Shahali, M., Ghadiri Nejad, M. et al. Effect of copper oxide nanoparticles on electrical conductivity and cell viability of calcium phosphate scaffolds with improved mechanical strength for bone tissue engineering. Eur. Phys. J. Plus 134, 7 (2019). https://doi.org/10.1140/epjp/i2019-12375-x

Intelligent nanoscale tuning of chirality in liquid crystal media holds great potential for deciphering the level of homochirality and origin of chirality in the living systems. Notably, we have reported some of the highest ever-reported value of the helical twisting power in achiral N-LCs for chiral ligand-coated GNRs [1-2]. Moreover, we demonstrate how the amplification of chirality facilitated by GNRs decorated with chiral molecules can be used to clearly distinguish the chiral induction strength of a homologous series of binaphthyl derivatives, differing only in the length of a non-tethered aliphatic chain, in the induced chiral N*-LC phase [3-4]. Recent further research shows that we are now able to accurately control the helical pitch and the helical twisting power values in N-LC/nanoparticle composites. These composites include mixtures of N-LCs with diverse chiral ligand-coated nano shapes (spherical, rod, prism, disk, and star) and varying aspect ratios (2-10) of gold nano shapes. Finally, we additionally support our experimentally derived arguments of a more comprehensive understanding of the chirality transfer’s dependency on shape by calculations of a suitable pseudoscalar chirality indicator [5].

References:
[1] Nemati, A., Shadpour, S., Querciagrossa, L., Mori, T., Gao, M., Zannoni, C., Hegmann, T., Nature Communication, 9, 1, 1-13 (2018).
[2] Sharma, A., Mori, T., Lee, HC., Worden, M., Bidwell, E., Hegmann, T., ACS Nano, 8, 12, 11966-11976 (2014).
[3] Nemati, A., Shadpour, S., Querciagrossa, L., Mori, T., Zannoni, C., Hegmann, T., ACS Nano, 13, 9, 10312-10326 (2019)
[4] Mori, T., Sharma, A., Hegmann, T., ACS Nano, 10, 1, 1552-1564 (2016).
[5] Nemati, A., Shadpour, S., Querciagrossa, L., Zannoni, C., Hegmann, T., Gonçalves, D., Cui, X., Ai, R., Wang, J., tbs.

The thermodynamics of solid-solution interfaces is one of the most basic topics of interest in colloid science. The work of interface formation, called in varying contexts the surface or interfacial energy or tension, is the thermodynamic parameter that dictates the stability and evolution of suspensions, gels, emulsions, and many other systems. From the perspective of the synthetic chemistry of solid nanoparticles, the interfacial energy usually is taken to be responsible for a serious obstacle in the preparation and use of these highly dispersed materials: where the free energy of interfaces is positive, systems will inevitably coarsen to minimize this quantity. Establishing a system in which interfaces are actually stable, by the controlled reduction of the interfacial energy, offers a framework for preparing stable, reproducible, and controllable nanoparticle dispersions for both fundamental and engineering applications. Such dispersions of solids, in analogy to the much better-characterized case of microemulsions, have been prepared but not yet systematized. From the statistical thermodynamics of nanoparticle dispersions and using the tools of classical nucleation theory and liquid mixtures, we provide a simple analytical expression giving a one-to-one correspondence between the measurable size distribution of a colloidal suspension at equilibrium and the size-dependent interfacial free energy. The size distribution can be given only in terms of parameters that are relatively easy to control, estimate, or measure, such as the molecular solubility, densities, and cohesive energies. Consideration of older experimental data, in light of this framework, allows us in principle to characterize different modes through which different colloidal solutions are stabilized in equilibrium, such as through preferred curvature or electrostatic charging. Finally, we indicate the parameters that must be optimized in order to solve the problem of preparing monodisperse nanoparticles and discuss whether previous syntheses may have reached the narrowest achievable size distribution allowed at equilibrium.

The trace analysis of xenon is an indicator of nuclear activity and as such the collection of Xe isotopes from the environment is of great importance for environmental monitoring and treaty verification. Silver clusters have been shown to selectively sorb Xe better from the environment when integrated into an aluminosilicate zeolite framework system vs. other systems such as MOFs. Despite the large amount of research on these Ag-zeolites, resolving the role of silver (Ag) in the sorption mechanism remains a complex issue with several contradictory reports in the literature. Prior to the design of novel sorption materials, research must first address the fundamental questions of why Ag-zeolites outperform other porous adsorbents with respect to Xe uptake. To better understand the role of silver ion cluster formation in the sorption of Xe, this talk will focus on using density functional theory (DFT) methods to identify specific structure-property relationships in Ag-exchanged chabazites which contribute to increased sorption uptake. The results show that small, highly charged clusters form high-index facets within the large cavities of the zeolite, which could allow for rapid sorption of Xe onto their surface. Optimization of these features must be considered when designing high-performance, low-cost adsorbents for noble gases. Ultimately, these results will be used to develop strategies for exploring Xe sorption uptake using a machine learning sorption model amenable to straightforward validation by first-principles simulation and experimental data.

In the past decade, nanoscale metals have found use in reactive metal inks due to its ability to fuse at lower temperatures and create electrically conductive traces. [1] This study examines a new class of nanoscale metals and their morphology evolution during sintering. Specifically, interdiffusion of atoms in nanostructured metals is investigated during low temperature (e.g. 44% of Tm of AuCu eutectic point) sintering of nanoporous Au thin films and Cu powders. Both powders and thin-films are synthesized by chemical dealloying yielding ligaments that are 46 and 64 nm, respectively, and the former is dispersed over the latter as an initial condition for sintering. Samples are transferred into the tube furnace while wet in dehydrated alcohol to prevent oxide formation [2] and are sintered in a reducing atmosphere (H₂/Ar mixture, 5% of H₂) at 400 °C. After sintering, cross-sections through the neck zone between powders and thin-film are obtained via focused ion beam milling and the concentration profiles across the welded interface are measured via energy dispersive X-ray spectroscopy with large diffusion penetration depths (0.8 μm) across the interface being detected. Before and after sintering SEM images not only show thermal coarsening of the ligaments in both materials, but also evidence of neck formation between ligaments bridged across their original interface. Our results will be presented in the context of existing literature for neck formation and welding between bulk and nanoscale metals. This study might shed a light on the interdiffusion of porous metals during low temperature sintering.

References:
[1] Lu, Y., Huang, J., Wang, C. et al. Cold welding of ultrathin gold nanowires. Nature Nanotech 5, 218–224 (2010). https://doi.org/10.1038/nnano.2010.4
[2] S. Brett Walker and Jennifer A. Lewis. Reactive Silver Inks for Patterning High-Conductivity Features at Mild Temperatures. Journal of the American Chemical Society 2012 134 (3), 1419-1421. DOI: 10.1021/ja209267c

The key to future fluorescence sensing lies in the use of new methods for fluorescence modulation, beyond what is currently available. DNA-templated silver nanoclusters (DNA/AgNCs; for instance, Ag₈, Ag₁₀ and Ag₁₆) offer such an opportunity as their fluorescence emission color can be tuned by their DNA hosts or activated by nearby DNA strands termed the activators. The resulting complexes, called NanoCluster Beacons (NCB), have found applications in sensing nucleic acids, proteins, small molecules, enzyme activities and cancer cells. Whereas new applications of this unique molecular probe are emerging across a broad range of disciplines, it is unclear what sequence features of the activators ultimately control the fluorescence activation color and brightness of NCB. Further diversification and optimization of NCB will require a large ligand composition space (of the activator) to be scanned, beyond what robotic plates or test tube method can provide.

Here we introduce a high-throughput approach to study the fluorescence activation behavior of silver nanoclusters. By using a next-generation sequencing (NGS) chip (Illumina MiSeq), more than 10⁴ activators can be screened in a single experiment, which is nearly 100-fold higher than the throughput of current robotic plate method. The activation results reveal that the middle six nucleobases (of the 18nt-long activator) are the most critical in determining the activation intensity of silver nanoclusters, as randomizing these nucleotides leads to many dark NCBs. Interestingly, position 4-6 of the activator are found particularly important in stabilizing yellow NCB, while position 2-4 are hotspots for creating red NCB.

Taking advantage of our high-throughput chip screening platform, we have identified many pairs of NCB which only differ by a single nucleotide in their activator sequences but give drastically distinct activation outcomes (either by color difference or intensity difference). These extreme pairs are termed the polar opposite twins (POT). We have identified red and yellow POTs with intensity difference as high as 8-fold (T to C at position 4) and 29-fold (C to G at position 5), respectively. Moreover, based on the NGS selection results, a workflow to generate new activator designs using random sampling and support vector machine is established. We successfully obtained a new red-emissive NCB having intensity difference as high as 2.9-fold compared to selected red NCB standard.

Advancing colloid science & engineering requires a detailed understanding of building blocks, their spatial arrangement and interaction with chemical and biological targets. In my group, we have developed a number of novel analytical approaches. I will introduce the measure of information entropy as a powerful statistical method to evaluate the dispersity of colloidal populations and optimise synthetic parameters [1]. We have recently established an alternative route to evaluate 2D colloidal ordering based on the so-called spatial distribution function [2]. In comparison to conventional approaches, such as the radial distribution function or the 2D fast Fourier transform, this method is particular powerful for assemblies displaying limited order. I will further elaborate on how a simple protocol, based on quartz crystal microbalance with dissipation monitoring (QCM-d), for the stepwise in situ quantification of AuNPs immobilisation and subsequent uptake and release of chemical and biological binding partners [3]. Crucially, the frequency shift patterns offered by QCM-d enabled us to model the binding kinetics and calculate binding parameters, such as the association and dissociation rate constants (k_on and k_off) and apparent binding constant K_a. In combination with a recently developed synthetic protocol for decoupled control of size and surface composition [4], this analytical toolbox provides a powerful platform for systematic studies on colloidal behaviour, ligand-shell mediated nanoparticle-stimuli interactions and rational optimisation of material design for environmental and biomedical applications.

References:
[1] Information entropy as a reliable measure of nanoparticle dispersity - N. MacFhionnlaoich, S. Guldin, Chemistry of Materials, vol. 32, pp. 3701 – 3706, 2020.
[2] Application of the Spatial Distribution Function to colloidal ordering - N. MacFhionnlaoich, R. Qi, S. Guldin, Langmuir, vol. 35, pp. 16605 – 16611, 2019.
[3] Probing nanoparticle-analyte interaction in real time via quartz crystal microbalance with dissipation monitoring - Y. Yang, G. Poss, N. Nianias, Y. Weng, R. Qi, H. Zheng, E. Kay, S. Guldin, Nanoscale, vol. 11, pp. 11107 – 11113, 2019.
[4] A versatile AuNP synthetic platform for decoupled control of size and surface composition - Y. Yang, L.A. Serrano, S. Guldin, Langmuir, vol. 24, pp. 6820 – 6826, 2018.

This talk will provide an overview of our work in the design of functionalised polymer and inorganic nanoparticles for applications in ultrasensitive biosensing [1]. We engineer simple conceptually novel approaches to detect disease biomarkers, such as abnormally regulated enzymes, to extend the detection window for early disease diagnostics. We aim to design biosensing strategies that are simple, cost-effective and easy deploy to the point-of-care to democratise access to advanced diagnostic technology. We will discuss impactful sensing applications for infectious and non-communicable diseases for example innovative smartphone enabled tests for epidemic surveillance in the field [2] and injectable nanoparticle-based sensing probes for in vivo detection of cancer that produce a colorimetric response in urine in under 1 hour [3]. This talk will also provide an overview of our recent advances in Raman spectroscopy characterisation techniques for high-throughput tracking of surface functionalisation in single nanoparticles [4].
[1] A. Creamer, C. S. Wood, P. D. Howes, A. Casey, S. Cong, A. V. Marsh, R. Godin, J. Panidi, C. H. Burgess, T. Wu, Z. Fei, I. Hamilton, M. A. McLachlan, M. M. Stevens, M. Heeney. “Quantitative post-polymerisation functionalisation of conjugated polymer backbones and its application in multi-functionalised semiconducting polymer nanoparticles.” Nature Communications. 2018. 9: 3237.
[2] C. S. Wood, M. R. Thomas, J. Budd, T. P. Mashamba-Thompson, K. Herbst, D. Pillay, R. W. Peeling, A. M. Johnson, R. A. McKendry, M. M. Stevens. “Taking connected mobile-health diagnostics of infectious diseases to the field.” Nature. 2019. 566: 467-474.
[3] C. N. Loynachan, A. P. Soleimany, J. S. Dudani, Y. Lin, A. Najer, A. Bekdemir, Q. Chen, S. N. Bhatia, M. M. Stevens. “Renal clearable catalytic gold nanoclusters for in vivo disease monitoring.” Nature Nanotechnology. 2019. 14: 883–890.
[4] J. Penders, I. J. Pence, C. Horgan, M. Bergholt, C. Wood, A. Najer, U. Kauscher, A. Nagelkerke, M. M. Stevens. “Single particle automated Raman trapping analysis.” Nature Communications. 2018, 9: 4256.

Phenomenon of Coulomb blockade (CB) due to single electron (local) charging in nanogranular metallic system has long been a scientific curiosity due to their exotic electronic properties. The attraction is an insulator-to-metal transition observed at cryogenic temperatures where the electron transport is affected by local charging of the nano-grains by just a single electron. We have observed functionally similar behavior in large nanoparticle array of a quasi-one dimensional (1D) nanoparticle necklace network (N³) of 10 nm Au particles from 4 K to room temperature (RT). Here, we demonstrate a new class of field effect transistor (FET) operating at RT where the conductance of N³ devices is modulated over two orders of magnitude by a gate electrode. The demonstrated gain is ~500x higher, sensing area is ~150x larger, and the current is 10⁴x higher than previously published close-packed nanoparticle array FET’s. Remarkably, the N³ FET I-V behavior exhibits universality, where the conduction gap is invariant and the I-V behavior can be superimposed in a master curve at different gate voltages. To understand universality of I-V behavior the network topology is quantitatively mapped by leveraging the local-1D structure of N³. Simulations using topological maps indicate that conduction pathways morph with “fractal-like” growth of conducting channels as charging barriers are systematically overcome by gate bias. Due to self-similar conduction path morphing, we conclude that at RT electron transport in these disordered systems is primarily driven by critical phenomenon, akin to second order phase transformations. The high gain, large sensing area, and flexibility for functionalization of Au can allow N³ devices to serve as a platform for a new class of high sensitivity sensors.

Silica nanoparticles are known as versatile inorganic materials that provide an efficient platform to interact with biological molecules. These interactions are believed to have occurred on prebiotic Earth at the origin of life. Experimentally, the interaction between silica and biomolecules is granted feasible due to the ease of synthesis and the ease of their surface modification. Having rich surface chemistry due to the presence of silanol groups extending out of their surface and available for bonding, these nanoparticles can be conjugated with fluorescent dyes which can further be functionalized to be conjugated with biological and/or organic counterparts leading to a variety of colorful and interesting applications. In the present study, we have synthesized fluorescent silica nanoparticles by the reverse microemulsion method and using three different fluorescent dyes, fluorescein isothiocyanate (FITC), Rhodamine-B, and Tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (commonly known as Rubpy). In the synthesis, the microemulsion is prepared by mixing cyclohexane, n-hexanol, and Triton X-100 (or dioctyl sulfosuccinate sodium salt). To this microemulsion, the fluorescent dye which is conjugated with the linker, 3-aminopropyltriethoxysilane (APTES) is added followed by the silica precursor, tetraethylorthosilicate (TEOS). Hydrolysis and condensation are then initiated by adding ammonia. After stirring for 24 hours, the microemulsion is broken with acetone and the nanoparticles are recovered after centrifugation and washing. Scanning electron microscopy images showed spherical shaped particles with an average diameter of around 150 nm. These fluorescent silica nanoparticles showed excellent photostability and minimal dye leakage over a period of one hour which is a reasonably long duration for the proposed bioconjugation experiments. To facilitate the bioconjugation process, these dye-doped nanoparticles were functionalized, first with amine groups using APTES and then with carboxyl groups using succinic anhydride. Fourier Transform Infrared (FTIR) spectra confirmed the surface functionalization. These fluorescent silica nanoparticles were used to detect latent fingerprints on the surfaces of aluminum foil, stainless steel, glass, plastic, and wood using the powder dusting method and the suspension method. Powder dusting on aluminum foil produced the best results after exposing the surfaces to the nanoparticles for 30 minutes after the fingerprint was placed on the surface. On top of this, the most interesting application of these fluorescent silica nanoparticles was their use in the detection of Escherichia coli, which is considered the best biological indicator for coliform contamination in food and water. The anti-E. coli antibody was immobilized on the fluorescent nanoparticle surface by reacting the carboxyl functionalized nanoparticles with the protein at room temperature. Then the E. coli culture was mixed with the antibody-conjugated nanoparticles in phosphate-buffered saline (PBS). After incubation, a smear was made on a microscopic slide and observed under the fluorescence microscope. For the nanoparticles doped with all three dyes, FITC, Rhodamine-B, and Rubpy, fluorescence microscopic images were obtained with the resolution of observing up to a single bacterial cell. Staining of the moving live cells was also observed. These interesting results demonstrate the effectiveness of the fluorescent silica nanoparticles in the use of chemical and biological sensors. Their excellent photostability and the ability to retain the dye for longer periods in the nanoparticle matrix compared to the free dye in solution are added advantages when these sensors are developed.

Currently, a strong interest has been focused on the employment of nanoparticles as promising tools in biomedical research, diagnostics and therapy. In this frame, Nanodiamonds (NDs) earned a solid reputation due to their interesting features, such as inertness, fluorescence, biocompatibility and the possibility of modifying their surface termination [1]. Aim of this work is the realization of diamond-based drug delivery systems which are optically trackable during in-vitro experiments, by exploiting the fluorescence properties deriving from the Nitrogen–Vacancy (NV) lattice defects [2], consisting in a substitutional nitrogen atom nearby to a vacancy defect. This system is optically active, with a wide excitation spectrum around 500 – 600 nm and emission at 600 – 800 nm, and provides a photostable label suitable for different types of bio–imaging and bio–sensing applications. By mean of ion–beam induced damaging, more defects can be introduced in the crystal lattice, thus creating new NV centers and enhancing the fluorescence of NDs [3]. To this scope, in the first part of the work the NDs were irradiated with a 2 MeV proton beam, exploring a wide range of fluences (between 10¹⁴ – 10¹⁷ protons cm^–2). Raman and Photoluminescence (PL) spectroscopy were employed as elective investigation techniques to quantify the ion–implanted NDs fluorescence. As a result, PL spectra showed that the creation of new NV centers by proton–irradiation led up to two orders of magnitude increase in fluorescence with respect to the unirradiated samples.
In the second part of the work, the NDs surface was chemically modified to allow a proper covalent–linking functionalization with cetuximab (NDs–Ctx), a monoclonal antibody specific for EGFRs, which are receptors typically overexpressed on colon–rectal cancer cells membrane. The successful surface grafting procedure was verified by means of Thermogravimetric Analysis. NDs–Ctx were then administrated to cultured DiFi rectal carcinoma cells and their internalization degree (compared to a control sample of unmodified NDs) was evaluated by confocal microscopy. From the analysis of the acquired images, a high uptake level was observed in the platelets of NDs–Ctx treated DiFi cells, while weak or no NDs fluorescence signal was assessable inside the cells in the case of unirradiated NDs administration.
In conclusion, post–synthesis treatments and proton–beam irradiation of NDs were effective in strongly enhancing their fluorescence yield. Moreover, cetuximab was successfully conjugated on NDs surface and the targeting and uptake–inducing properties of the system were observed on DiFi cell line. These results reinforce the suitability of NDs as promising nano–tools for both biolabeling and drug delivery applications, worthy of further investigations to combine these two potentials.

[1] Mochalin, V. N., Shenderova, O., Ho, D., Gogotsi, Y. (2012) The properties and applications of nanodiamonds. Nat. Nanotechnol., 7:11–23
[2] Van der Laan, K., Hasani, M., Zheng, T., Schirhagl, R. (2018) Nanodiamonds for in vivo applications. Small, 14:1703838 (2018)
[3] Waldermann, F.C. et al. (2007) Creating diamond color centers for quantum optical applications. Dia. Relat.Mat., 16:1887–1895

Nanotechnology is providing new tools for cell imaging and diagnosis through the synthesis and tuning of nanophosphors with special physicochemical properties. Yttrium oxide (Y2O3) host has gained broad research interest due to its excellent chemical stability, good thermal stability and low cost; this host can be used to synthesized luminescence upconversion nanoparticles (UCNPs) and downconversion nanoparticles (DCNPs) that can be used as biolabels for fluorescence imaging. The UCNPs absorb near infrared photons to upconvert them to emit in the visible spectra; also, the DCNPs absorb UV photons and emit in the visible spectra. In this study we analyzed biocompatible UCNPs and DCNPs co-doped with rare earth ions, they were functionalized with amino groups and folic acid ligands (FA) that bind to folate receptors (FR) overexpressed on certain types of cancer cells, the functionalized nanoparticles (FA-NPs) were internalized into the cancer cells studied via endocytosis by the conjugation FA-FR. We present a nanotoxicological study that includes cytotoxicity, genotoxicity, hemocompatibility and in vitro inflammatory studies. The study demonstrated that bare and functionalized NPs are no cytotoxic and no genotoxic at the tested concentrations (0.01 to 20 mg/ml) in three cell lines (breast, skin cancer and osteoblasts). Also they are hemocompatible and do not exert nitric oxide production in vitro by macrophages. The FA-NPs were clearly localized into the cell cytoplasm with bright red luminescence. We can conclude that these nanoparticles are biocompatible and can be further used for cancer cells bioimaging.

Since 2019, institutions and governments around the world have faced the challenge of containing the progress of the COVID-19 pandemic caused by the Sars-CoV-2 coronavirus. According to the WHO, one of the main transmission routes for COVID-19 is contact with contaminated surfaces. For this reason, a thorough disinfection is essential to prevent contagion. In this sense, nanotechnology has attracted significant attention due to its cross-cutting properties in different disciplines. Silver nanoparticles (AgNPs) have been one of the most investigated nanomaterials and recently applied by various industries. In this work, the synergistic effect of the in vitro antimicrobial activity of hydrogen peroxide with biosynthesized AgNPs from a geranium plant extract was evaluated. AgNPs were characterized by HRTEM, UV-Vis spectroscopy as well as ICP-MS for their analytical determination where an average particle diameter less than 50 nm was obtained with a spherical morphology and a concentration of 1,474.6 mg / L. The air disinfection method (ADM) was used for the evaluation of the antimicrobial effect in vitro against Escherichia coli ATCC 25922. This test showed a 99.99% of bacterial growth reduction with a dose of 76.6 mg / L of AgNPs and 0.55% hydrogen peroxide, after eight minutes of nebulized exposure of the solution. These results provide valuable information on the way to explore new bionanotechnological antimicrobial agents to promote the safety, innocuousness and hygiene of products, spaces and surfaces.

Recently, antibacterial solutions have been investigated in the medical area, since the excessive use of antibiotics has caused microorganisms to express greater resistance to this type of antibiotics. In this research work, the effect of Ag nanoparticles on Pseudomonas aeruginosa bacteria (ATCC27853) was verified as a function of time. Different concentrations of colloidal solution were prepared and exposed during the incubation time in order to identify the minimum inhibitory concentration (1:2, 1:4, 1:8 and 1:16). Nanoparticles synthesized by the green route were used using Pelargonium spp extract as a reducing agent. Average diameters of nanoparticles <50 nm was obtained, which were characterized with a JEOL JEM1010 transmission electron microscope. The inhibitory effect of nanoparticles in Pseudomonas aeruginosa was verified by counting colony forming units (CFU) for 0, 2 and 4 hours of bacterial incubation. The tests showed that the 1: 2 concentration ratios exhibited a 100% inhibition since the initial interaction of the colloidal solution with the growing bacteria and during the four hours of monitoring. While in the 1: 4 ratio, 100% inhibition was observed up to 2 hours after the initial time of the nanoparticles-bacteria interaction. For the rest of the dilutions, there were gradual inhibitions as a function of time, however, they were not 100%. Finally, we conclude that the use of nanomaterials generated by green routes are an alternative for their application in biological systems that are currently a health problem in living beings. As a perspective of this work we suggest to perform cytoxicity tests in cellular biological systems for biomedical applications.

— Hydrogels are a macromolecular network of hydrophilic copolymers with physical or chemical cross-linking structure with significant water uptake capabilities. They are a promising substrate for Surface-enhanced Raman Spectroscopy (SERS) as they are both flexible and biocompatible materials. Conventional SERS-active substrates suffer from limitations such as instability and inflexibility which restricts their use in broader applications. Gelatin based hydrogels have been synthesised in a facile and relatively quick method without the use of any toxic cross-linking agents. Composite gel material was formed by combining the gelatin with simple polymers to enhance the functional properties of the gel. Gold nanoparticles, prepared by a reproducible seed-mediated growth method, was combined into the bulk material during gel synthesis. After gel formation, the gel was submerged in the analyte solution overnight. SERS spectra was then collected from the gel using a standard Raman spectrometer. A wide range of analytes were successfully detected on these hydrogels showing potential for further optimization and use as SERS substrates for biomedical applications.

Water purification by the removal of heavy metals is one of the most challenging fields of scientific research. In natural waters, heavy metals are generally present in trace amounts but most of them have a wide range of hazardous and detrimental effects to the human body even at very low concentrations. Heavy metals especially lead, and cadmium can cause severe health effects including cancer, nervous system damage, organ damage, and in extreme cases, death. Thus, it is very important to extract heavy metal from industrial wastewater along with drinking water. In this research, we used the Iron-Tannic Acid complex for the filtration of water and could successfully extract Pb²⁺, Cd^2+, and Ag⁺ cations from different water samples containing those heavy metal. The amount of heavy metal in the water was detected by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). The presence of large numbers of carboxylic acid groups in the Iron-Tannic Acid complex is therefore responsible for the strong binding of the heavy metal cations. Among all of the heavy metal filtration materials, the Iron-Tannic Acid complex has the greatest potential in heavy-metal extraction processes for future applications.
Keywords: Heavy metal extraction, Metal-organic complex, water purification

In the current study, the antibacterial activity and ecotoxicity of positively and negatively charged hematite (α-Fe₂O₃) nanoparticles were studied. α-Fe₂O₃ nanoparticles were obtained by simple green hydrothermal synthesis, while surface charge was controlled by a surface functionalization with citrate coating. The antibacterial activity was evaluated to Gram-negative bacterium Escherichia coli and Gram-positive bacterium Staphylococcus aureus. Microbes were exposed to different concentrations of α-Fe₂O₃ nanoparticles in deionized water for 30 minutes and 24 h at room temperature and evaluated for the post-exposure colony forming ability. The positively charged α-Fe₂O₃ showed E. coli bactericidal activity already after 30 minutes. Extending the exposure to 24 h increased the antibacterial effect with minimal bactericidal concentration values between 100-1000 mg/L. Bactericidal activity against S. aureus was not observed. Negatively charged α-Fe₂O₃ did not exhibit any activity against both tested bacteria. Our results confirmed that deionized water could be a model medium for the antibacterial testing. Additionally, ecotoxicity studies with Vibrio fischeri showed no ecotoxicity of α-Fe₂O₃ - EC₅₀ > 1000 mg/L. No reactive oxygen species production in abiotic or biotic conditions in the dark was observed. Confocal laser microscopy images analysis by MicrobeJ confirmed that more positively charged nanoparticles were associated with generally negatively charged bacterial cells than negatively charged nanoparticles and this effect was larger for E. coli which is also in concordance with positive charged α-Fe₂O₃ nanoparticles being more toxic to E. coli than S. aureus.

Acknowledgments: This work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure” of the Operational Programme “Growth and Employment” (No. 1.1.1.2/VIAA/2/18/331).

In-situ exsolution of reducible transition metals from geo-inspired perovskite precursors allows for the synthesis of strongly-adhered nanoparticles that are thermally-stable and homogeneous in size and shape. The perovskite oxides are materials that can reversibly exsolve transition-metal cations as nanoparticles under fluctuating reducing and oxidizing reaction conditions. The exsolution process occurs when the cation dopant diffuses from the bulk of the perovskite and form nanoparticles on the surface under reducing conditions. Earlier work on perovskite oxide precursors has determined that bulk defects can modulate the ionic diffusion of dopant metal monomers. This presentation extends the notion of exploring the rich defect chemistry of geo-inspired perovskite oxides to control the formation and growth of regenerable Ni-Fe nanoparticles from Ni-doped LaFeO₃ perovskite oxide precursors [1]. The Ni-doped lanthanum ferrite perovskite precursors were prepared with varying ratios of the La and Fe in the parent perovskite of either 0.9:1, 1:0.9, and 1:1. The exsolved Ni-Fe nanoparticles exhibited notable ranges in composition, size, and dispersion. The systems were characterized using High-angle annular dark-field imaging scanning transmission electron microcopy (HAADF – STEM), X-ray diffraction(XRD) and in situ X-ray Absorption Spectroscopy (XAS). This presentation will discuss recent work to address the existing materials chemistry challenges for Ni-based bimetallic nanoparticles' controlled formation.

1. S. Shah, S. Sayono, J. Ynzunza, R. Pan, M. Xu, X. Pan, K.L. Gilliard-Abdulaziz, The effects of stoichiometry on the properties of exsolved Ni-Fe alloy nanoparticles for dry methane reforming, AIChE J. In press (2020). https://doi.org/https://doi.org/10.1002/aic.17078.

Excitonic PbS nanoparticles have shown excellent photosensitivity in the IR region, but limited device efficiencies because short diffusion lengths restrict film thicknesses to less than the absorption length. They also have slow radiative recombination rates, which limit the performance of light-emitting diodes. To address these limitations, we work to couple PbS excitons with plasmons on the nanoscale in order to increase the radiative rates and absorption cross sections. For the plasmonic component, we use the doped plasmonic semiconductor, Cu_2-xS, which has a tunable plasmon resonance that can be designed to overlap with the excitonic absorption of PbS in the short-wave infrared regime.
We demonstrate a synthetic method to add a thin PbS shell layer, with a controlled thickness, to Cu_2-xS cores using Pb oleate and bis(trimethylsilyl)sulfide as the Pb and S precursors. Energy-dispersive X-ray maps and high angle annular dark field images collected with scanning transmission electron microscopy confirm the Cu_2-xS/PbS core/shell architecture. Absorbance spectroscopy shows a blueshift in the plasmon resonance of the Cu_2-xS/PbS core/shell nanoparticles relative to the parent Cu_2-xS nanoparticles. Using X-ray diffraction, we show that this blueshift is due to the oxidation of the Cu_2-xS cores (an increase in x) upon PbS shell deposition. The shell thickness is controlled by tuning the amount of Pb and S precursors. Transmission electron microscopy indicates progressive growth in the core/shell nanoparticle diameter with increasing Pb:Cu ratios and a monodisperse distribution of nanoparticles.
While no photoluminescence is observed from the PbS shell, these core/shell nanocrystals are highly promising for studying exciton-plasmon coupling in binary superlattices with PbS nanocrystals for three reasons: 1) the Pb shell increases the Cu_2-xS core solubility, aiding in assembly, 2) the PbS shell blueshifts and enhances the plasmon resonance of the Cu_2-xS core such that it overlaps better with the PbS exciton energy range, and 3) the PbS shell hinders the Cu_2-xS cores from chemically quenching the photoluminescence of neighboring PbS nanocrystals in solution. The ability to hinder quenching is dependent on the PbS shell thickness in the Cu_2-xS/PbS core/shell nanoparticles, with the thicker PbS shells better preserving the excitonic PbS photoluminescence. Thus, the Cu_2-xS/PbS core/shell nanoparticles provide an opportunity to controllably investigate plasmon-exciton coupling in a variety of binary superlattice symmetries and stoichiometries.

Pt-Ni nanoparticles were vastly explored because of the synthetic tunability and the high electrochemical performance toward oxygen reduction reaction (ORR), the application and high-efficiency catalytic activity are commonly confined for acidic medium due to the Pt corrosion in alkaline medium. The alternative Ni-rich nanoparticles investigated as oxygen evolution reaction (OER) catalyst have shown insufficient efficiency in the acidic medium because of the known transition metal leaching process. The novelty in our work is the ability to produce an active bifunctional catalyst that accomplishes both ORR and OER in alkaline medium. Our advance was accomplished by a comprehensive investigation of the synthesis parameters and by a rational material design.
The ultralow-platinum Pt@Ni@Pt core-bishell nanorods achieve an unprecedented (for a Pt-based catalyst) overpotential of 0.29 V at 10 mA cm^-2 and current density of 162 mA µg^-1_Pt at 1.6 V (vs. RHE) for the OER, while still maintaining a very decent value of 0.32 A mg^-1_Pt at 0.85 V for the ORR. These values outperform the standard Pt catalyst for the ORR and the Ni catalyst for the OER, using less than 1%wt. Pt. This work advances the field of ultra-low platinum content, which in our point of view will be one of the critical issues that will allow the green energy technology to be implemented.
Also, this research revealed a unique methodology that allows morphology and size tunability of Pt@Ni core-shell nanoparticles. The kinetic control of the core and the shell was achieved by combining two commonly used solvents as reducing agents while keeping the (111) plane electrochemically active. We highlight that the understanding of the relationships between the composition of a material and its structure and properties is a fundamental objective and a key challenge in nanoscience research.

Aluminum nanoparticles (ANPs) have been considered attractive additives for solid-fuel rockets due to a high energy density with an increased burning rate. Unfortunately, the use of the ANPs is limited by the following reasons: ANPs can be readily sintered and oxidized, prior to the combustion process, degrading the combustion performance. In order to resolve these problems, a surface coating of the ANPs by hydrocarbons has been proposed. while previous studies reported that the hydrocarbon coating is essential for the ANPs to be used combustible materials, atomic-scale understanding of thermal behaviors of the hydrocarbon-coated ANPs has yet to be achieved. Here we perform reactive molecular dynamics (RMD) simulations to investigate effects of hydrocarbon coating on the combustion performance of the ANPs. Our RMD simulations reveal detailed reaction steps for the sintering process of the bare/hydrocarbon coated ANPs. As such, our RMD simulations provides a valuable input for experimental synthesis of functional metal nanoparticle materials for energy conversion applications.

S.H. and R.E. acknowledge the new tenure-track faculty start-up fund from School of Natural Science, Mathematics and Engineering at California State University, Bakersfield (CSUB).


References

[1] Yetter, R. A.; Risha, G. A.; Son, S. F. Metal Particle Combustion and Nanotechnology. Proc. Combust. Inst. 2009, 32, 1819−1838
[2] Park, K.; Rai, A.; Zachariah, M. Characterizing the Coating and Size-Resolved Oxidative Stability of Carbon-Coated Aluminum Nanoparticles by Single-Particle Mass-Spectrometry. J. Nanopart. Res. 2006, 8, 455−464.
[3] Guo, L.; Song, W.; Hu, M.; Xie, C.; Chen, X. Preparation and Reactivity of Aluminum Nanopowders Coated by Hydroxyl-Termi- nated Polybutadiene (Htpb). Appl. Surf. Sci. 2008, 254, 2413−2417.
[4] Senftle, T. P.; Hong, S.; Islam, M. M.; Kylasa, S. B.; Zheng, Y.; Shin, Y. K.; Junkermeier, C.; Engel-Herbert, R.; Janik, M. J.; Aktulga, H. M. The ReaxFF Reactive Force-Field: Development, Applications and Future Directions. npj Comput. Mater. 2016, 2, 15011.

Nanotechnology has studied applications in biomedical areas, for which several nanomaterials have been synthesized that present limitations such as toxicity and instability in organisms, so green methodologies have been developed that help reduce this problem. In this work we report the green synthesis of AuNPs using as a reducing agent lemon extract (Citrus limon), and the multiwave ultrasonic technique as an excitation element. As the precursor reagent, trihydrated chlorouric acid (HAuCl4.3H2O, Sigma Aldrich SKU 520918) was used, and as a reducing agent the lemon juice extract. The reaction was carried out in an ultrasonic bath at a frequency of 40kHz, at 55 ° C for one hour (Branson 2800 series). The final solution obtained showed a purple coloration, and was characterized by UV-VIS spectrophotometry and transmission electron microscopy (JEOL JEM 1010). Peak absorbance peak at 530 nm was observed and particle diameters between 12 and 16 nm were obtained. The reported results could be of interest to carry out fusion of nanometric inorganic materials by the ultrasonic technique, and by controlling the temperature and frequency, metal structures with different morphology and properties could be generated.

Porous Ni has many potential applications, such as energy storage, fuel cells, and catalysis, which account for its rapid rise in publication frequency in recent years. Nanoporous Ni is less commonly reported, but it is expected to have enhanced properties due its higher surface area. Dealloying is the most developed method for creating nanoporous metals, with Ni precursors including Ni-Mn, Ni-Mn-Cu, or the classic Ni-Al alloys, first developed and patented by Murray Raney in 1927, and therefore referred to as “Raney” nickel. The general strategy of dealloying is well-developed and provides a valuable method for achieving nanoscale porosity. The commonality among dealloying methods is the preferential removal of a sacrificial phase. That phase must be carefully removed in its entirety, as any residue will alter the final properties. Here we present the removal of a second phase to create nanoscale porosity in a scheme broadly similar to dealloying; however, the sacrificial phase is an oxide, not another metal. This oxide reduction provides a single-metal strategy for nanoporosity (e.g., Ni+NiO), thereby eliminating any source of metallic contamination. Furthermore, the opportunity exists to intentionally alloy with greater accuracy by alloying before or during oxide reduction. For example, Ni and Cu can be alloyed during milling in metallic phase or, as a simple extension, CuO would be added with NiO so that the desired metallic composition is obtained after reduction. Any number of permutations to this approach can be employed for completely unique control of the final structure and composition. This technique is remarkably simple and scalable. The precursors are created through standard powder metal processes (milling, compaction, etc.), and the required temperatures are quite modest. Additionally, this provides an environmentally friendly alternative to chemical etching by acids, which are commonly employed in dealloying. The processing, properties, and applications will be reviewed.

As a reaction generally used in industrial processes, the catalytic hydrogenation of organic compounds containing carbonyl groups using nanomaterials is extensively studied. Herein, we describe the preparation of an unusual nanomaterial, ruthenium nano-anadem decorated zirconium phosphate nanoplatelets, which can be used to realize the selective hydrogenation reaction of ketone. We choose acetophenone (AP) for main study as it is the simplest ketone and can lead to important hydrogenation products, such as ethylcyclohexane (EC) for bio-oils and 1-cyclohexylethanol (CE) for many polymers production and biofuel purpose.
α-zirconium phosphate (α-ZrP) serving as a solid support has been widely studied. We obtained α-ZrP nanoplatelets with high yield and good quality by using a modified refluxing method. Through an ion-exchange and reduction reaction pathway, Ru nanoparticles can be loaded on ZrP nanoplatelets to yield Ru-ZrP nano-anadem structures. The obtained Ru-ZrP composites with different loading amount were characterized via powder X-ray diffraction (PXRD), nitrogen adsorption and de-adsorption, transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and X-ray photoelectron Spectroscopy (XPS). We also explained the detailed growth mechanism. The successful synthesis of Ru-ZrP nanoplatelets were also supported by its excellent catalytic performance in the hydrogenation reaction of acetophenone. To obtain an optimized reaction condition, many factors such as reaction time, reaction temperature and pressure of hydrogen gas were investigated. Conversion and yield were determined by gas chromatography mass spectrometry (GCMS). Conversion rates of AP could be achieved 100% at room temperature. The resulting products include at least 93% yield rate of CE and EC as the rest. The stability and possible mechanism for Ru-ZrP catalyzed AP were discussed. It shows very good stability after 5 runs of recycle. The kinetics of this reaction were discussed as well as some rare intermediates in details. The results suggest that there is a great potential for this novel Ru-ZrP nanostructures in catalytic applications.

I will discuss my group’s two recent progresses on constructing a library of hybrid patchy nanoparticles. Synthetically, we applied the concept of “island formation” established for planar substrates, where ligands cluster as they adsorb, to preparing gold nanoparticles of diverse shapes with precisely sized polymer patches. These polymer patches adapt their configuration in response to external stimulus and modulate the self-assembly behaviors of the nanoparticles. Meanwhile, we applied machine learning based data-mining method to relate synthesis conditions with the patterns of the patchy nanoparticles, to allow for predictive synthesis and design. Such fundamental understanding of the synthesis, interaction and assembly of patchy nanoparticles can bear relevance to their increasing ramifications in addressing staggering national needs in environment, energy, and health.

We demonstrate a technique to quickly build and spatially map the frequency response of optoelectronic devices. The transfer function of a linear system is the Fourier transform of its impulse response. Such an impulse response is obtained from transient photocurrent measurements of devices such as photodetectors and solar cells. We introduce and apply Fourier Transform Impedance Spectroscopy (FTIS) to a PbS colloidal quantum dot (QD)/SiC heterojunction photodiode and validate the results using intensity-modulated photocurrent spectroscopy. Cutoff frequencies in the devices were as high as ~10kHz, showing their utility in advanced thin film and flexible electronics. The practical frequencies for FTIS lie in the mHz-kHz range, ideal for composite materials such as QD films that are dominated by interfacial trap states. These can lead to characteristic lengths for charge collection ~20-500 μm dominated by transmission line effects, rather than intrinsic diffusion and drift length scales, enabling extraction of interfacial capacitances and series/parallel resistances.

Rational synthesis of size- and composition-selected clusters with predetermined properties for applications in catalysis, energy conversion and storage, and chemical separations will be facilitated by a mechanistic understanding of cluster nucleation, growth, and etching in solution. We have characterized the formation of triphenylphosphine (PPh₃) ligated gold clusters in the Au_1-22 size range using online reaction monitoring combined with high-mass-resolution electrospray ionization mass spectrometry. To improve the sensitivity and mass resolution of larger clusters for unambiguous identification, we increased the number of scan averages and reduced the width of mass collection windows, thereby mitigating mass and abundance bias resulting from small gold-ligand species present in high abundance. We have identified new clusters including Au₅(PPh₃)₅⁺, Au₁₂(PPh₃)₉HCl²⁺, Au₁₅(PPh₃)₉Cl²⁺, Au₁₆(PPh₃)₁₀Cl₂²⁺, Au₁₇(PPh₃)₁₁³⁺, Au₁₈(PPh₃)₁₀²⁺, Au₁₉(PPh₃)₁₀Cl²⁺, Au₂₀(PPh₃)₁₂H₃³⁺, Au₂₁(PPh₃)₁₀Cl²⁺, and Au₂₂(PPh₃)₁₀Cl₂²⁺, indicating that a full range of clusters between Au_1–22 is present in solution. We present evidence that the Au_12–14 size range is a transition point in cluster nucleation where smaller clusters exhibit a one-to-one gold-to-ligand ratio while larger clusters feature additional gold atoms without an equal number of accompanying ligands. Our results show that differently functionalized phosphines may be used to direct the size and abundance of gold clusters in solution. While for PPh₃-ligated clusters the most abundant species are Au_6–9, for methyldiphenylphosphine (PPh₂Me) and dimethylphenylphosphine (PPhMe₂)-ligated clusters the most abundant species are Au_10–11 and Au_12–14, respectively. We also present evidence that small hydrogen-containing intermediates (Au₂(PPh₃)₂H⁺ and Au₄(PPh₃)₄H⁺) are responsible for the growth of larger clusters. Degradation of these intermediates and growth of larger clusters are shown to be dependent on irradiation of the solution with light. Together, our findings advance the mechanistic understanding of the size-selective synthesis of clusters in the subnanometer size regime where “each atom counts” toward tuning the properties of clusters for eventual applications.

Alternating current (AC) electric fields can be used for the reconfigurable, directed self-assembly of particles as a result of forces such as dielectrophoresis. Electrodes patterned via photolithography and 3D microprinting create a gradient in the AC electric field to control particle assemblies. Since these systems are spatially controllable and reconfigurable, they are of interest for realizing tunable metamaterials and optical responses. Here we focus on assemblies with topographical electrodes and particles with materials properties for desired interactions with electromagnetic radiation. Current work is focused on single and multicomponent assemblies with particles of varying composition (e.g. SiO2, TiO2, PMMA). Because of their different properties, each of the particle types has distinct assembly structures and orientations that can be obtained based on the electric field conditions. The various assembly structures can then have their own distinct interactions with light based on the particles present and their orientation.

Magnetic Tunnel Junction (MTJ)-based Molecular Spintronic Devices (MTJMSDs) can lead to new forms of metamaterials and devices for the futuristic computers. MTJMSD is produced by chemically bonding a paramagnetic molecule between two ferromagnetic layers of a MTJ. Variation in coupling strength and nature of molecule -FM layer can produce an unprecedented testbed to observe novel phenomenon. Fundamental understanding of MTJ-based devices and their characteristics needs investigation of various factors such as molecular coupling strength and nature with the two FM electrodes. It is extremely challenging to study the impact of wide range of molecule-FM coupling strengths on MTJMSD via experiments. This paper focuses on Monte Carlo Simulations (MCS) to investigate the impact of molecular coupling with two FM electrodes. We utilized continuous MCS process and Metropolis algorithm¹ to study molecular coupling effect. Our model is a cross junction form MTJMSD where molecules are placed between two elongated FM electrodes representing FM-molecule-FM configuration. In this paper we focused on Heisenberg type exchange coupling. We studied various permutations when molecule formed ferromagnetic or antiferromagnetic coupling with the two FM electrodes. The MTJMSD device used in this study was defined with H×W×L (=11×50×50) dimension where H is the height, W is the width and L is the length of device. Molecular plane is along the H side of the device structure and located between equal number of atomic FM layers (5×5). We changed the Heisenberg exchange coupling strengths and nature between the paramagnetic molecule and left FM electrode (JmL) and right FM electrode (JmR). To achieve the equilibrium energy state, we conducted 200 million iterations and studied the spatial and temporal evolution of the FM electrodes and MTJMSD as a function of JmL and JmR. The magnitude and nature of JmL and JmR affected the MTJMSD’s magnetization, heat capacity, and magnetic susceptibility. For positive JmL and JmR the MTJMSD attained the highest magnetization due to the molecule induced parallel configurations of the two FM electrodes. However, when JmL and JmR were opposite in nature, molecule induced antiparallel magnetizations on the two FM electrodes. With opposite JmL and JmR MTJMSD magnetic moment settled closed to zero. Our MCS study also showed that molecular coupling effect spreads over a long range with respect to the molecular junction sites. According to our MCS results, molecular coupling impacted the whole junction when the critical magnitude of JmL and JmR was ~20% of the Curie temperature of two FM electrodes. These MCS studies also explain the experimentally observed strong molecule induced exchange coupling. Our group observed long range effect of antiferromagnetic coupling between the FM electrodes of an MTJ via organometallic molecular clusters (OMCs) ^1-3. Studying the effect of different thermal energies on MTJMSD’s magnetization properties is the next milestone of this ongoing project and will be studied in parallel to experimental works.

This work is supported by National Science Foundation-CREST Award (Contract # HRD- 1914751), Department of Energy/ National Nuclear Security Agency (DE-FOA-0003945).

References:
1. P. Tyagi, C. Baker and C. D'Angelo, Nanotechnology 26, 305602 (2015).
2. P. Tyagi and E. Friebe, J. Mag. Mag. Mat. 453, 186-192 (2018).
3. P. Tyagi and C. Riso, Organic Electronics 75, 105421 (2019).

Motivated by the idea that 1D nanomaterials can be used as templates for polymer chain alignment and orientation, carbon nanotubes (CNTs), a typical 1D nanomaterial, have been widely used as nano-fillers for reinforcing the polymer matrix in order to improve mechanical/structural properties of composite materials. Dispersing CNTs in the polymeric matrix remains a major challenge to address in order to increase the efficiency of enhancement. Experimental work of our lab has shown that the use of a non-solvent induced phase separation process can lead to regions of complete CNT-polyacrylonitrile (PAN) interaction within the matrix. To systematically explore the mechanism behind this phenomenon, full atomistic simulation is used to study the energy profile within the CNT/PAN/DMF system. To connect the simulation with the experimental work, a coarse-grained model using dissipative particle dynamic (DPD) method has been built to scale-up the simulated system. In this study, small angle X-ray scattering and thermal gravimetric analysis (TGA) techniques are employed as a tool to validate the interaction parameter setting of our DPD model. This parameter will provide important information/feedback needed to estimate a ‘chi’ parameter for PAN-CNT interaction. More broadly this coarse-graining approach can also be applied to other 1D-polymer systems to determine whether selective interaction is possible.

Titanium dioxide (TiO₂) has been extensively studied for water splitting,¹ dye-sensitized solar cells,² and photocatalysis³ due to its chemical stability and efficient photon-electron transfer. However, the wide bandgap (3.0-3.2 eV) and rapid recombination rate limit its utilization of visible solar radiation when used as a photocatalyst. Nitrogen doping has proven to be an effective way to alter the band structure and extend the photoactive region to visible light.⁴ Despite these advantages, a single-step synthesis route with wide tunability of nitrogen doping is still desirable.
Here, we demonstrate the synthesis of nitrogen-doped titanium dioxide nanoparticles with enhanced visible light absorption and photocatalytic activity via a one-step nonthermal plasma route. We investigated the plasma power influence on the particle growth and nitrogen incorporation under various reactor geometries, which allows for tuning of the substitutional and interstitial nitrogen doping level, bandgap and thus light absorption behaviors. By adjusting the locations of the electrode and the oxygen injection into the plasma, the particles transitioned from entirely interstitial nitrogen-doped to substitutional nitrogen-doped. The reactor design also allowed for phase tuning from amorphous, to crystalline anatase, rutile, and mixed anatase/rutile.
Photocatalytic performances of the as-synthesized nanoparticles were evaluated through the degradation efficiency of organic dyes methyl orange (MO) and methylene blue (MB) under natural sunlight irradiation. The low concentration of TiO₂ required in this work for degradation of both MO and MB dyes without external facilitation of metal ion doping or hydrogen peroxide addition indicates that the nitrogen-doped TiO₂ nanoparticles are efficient visible-light photocatalyst.
This work expands the scope of nonthermal plasmas for functional oxide nanocrystal fabrication, demonstrating its versatility in tuning material composition and structure. The discussion on the relationship between plasma conditions and nanoparticle properties provides fundamental insights into engineering nanoparticle growth and functionalization.
This work was supported by the National Science Foundation under MRSEC grants DMR-1420013 and DMR-201140.
References:
[1] Tang, J.; Durrant, J. R.; Klug, D. R. Mechanism of Photocatalytic Water Splitting in TiO₂. Reaction of Water with Photoholes, Importance of Charge Carrier Dynamics, and Evidence for Four-Hole Chemistry. J. Am. Chem. Soc. 2008, 130 (42), 13885–13891.
[2] Hwang, Y.-K.; Park, S. S.; Lim, J.-H.; Won, Y. S.; Huh, S. Preparation of Anatase/Rutile Mixed-Phase Titania Nanoparticles for Dye-Sensitized Solar Cells. J. Nanosci. Nanotechnol. 2013, 13 (3), 2255–2261.
[3] Shah, M. W.; Zhu, Y.; Fan, X.; Zhao, J.; Li, Y. Facile Synthesis of Defective TiO_2−x Nanocrystals with High Surface Area and Tailoring Bandgap for Visible-Light Photocatalysis. Sci. Rep. 2015, 5, 15804.
[4] Cong, Y.; Zhang, J.; Chen, F.; Anpo, M. Synthesis and Characterization of Nitrogen-Doped TiO₂ Nanophotocatalyst with High Visible Light Activity. J. Phys. Chem. C 2007, 111 (19), 6976–6982.

Radiative cooling is a passive cooling technology that acts by reflecting sunlight and emitting radiation in the sky window. Although highly desirable, full daytime sub-ambient radiative cooling in commercial-like single-layer particle-matrix paints has not been achieved. Here, we demonstrate full daytime sub-ambient radiative cooling in CaCO₃-acrylic paint by using large band gap CaCO₃ fillers, a high particle concentration of 60%, and a broad size distribution. Our paint shows a high solar reflectance of 95.5% and a high normal emissivity of 0.94 in the sky window. Field tests show cooling power exceeding 37 W/m² and a surface temperature of >1.7°C below ambient at noon. A figure of merit RC is proposed to compare the cooling performance independent of weather conditions. The standard RC of our paint is 0.49, among the best radiative cooling performances, while offering the benefits of convenient paint form, low cost, and compatibility with commercial paint fabrication processes.

Semiconductor nanocrystals (NCs) continue to garner interest for their unique optoelectronic properties that are controllable through size, shape, and composition. CuInSe₂ NCs have been hailed as a less-toxic alternative to Cd and Pb based materials and exhibit bandgaps similar to Si making them ideal for photovoltaic application. Synthesis of these materials has allowed them to be prepared using a variety of ligands. Broadly it is well known that ligands play a key role in stabilitizing these colloids and passivating surfaces, but they can also be crucial to intraband and interband relaxation as well as electronic and thermal conductivity. Very little research has focused on the effects of ligands on photophysics in CuInSe₂. Here we demonstrate through a variety of optical techniques the strong impact that ligands have on carrier dynamics in CuInSe₂ NCs.

The performance of short-wave infrared (SWIR) photodetectors based on colloidal lead sulfide (PbS) depends critically on advances in passivation strategies to address the more complex surface structure of large-diameter particles. Nanocrystals prepared using PbCl₂ precursors result in formation of a thin PbCl_x shell, providing improved air stability and photoluminescence quantum yields compared to those derived from other lead sources. We directly compare the performance of SWIR photodiodes fabricated with PbS/PbCl_x (core/shell) nanocrystals versus their PbS-only (core) counterparts. Despite their inherently similar bulk properties, the core/shell-based devices exhibit greater external quantum efficiencies and reduced dark current densities, while the core-based devices suffer from shunting and inefficient charge extraction. To elucidate the implications of the shell chemistry on device performance, we evaluate the thickness-dependent energy level offsets and interfacial chemistry of the nanocrystal films with the zinc oxide electron-transport layer. Our results suggest the disparate device performance between the two synthetic routes is associated with unfavorable interface dipole formation and a high prevalence of surface defect states in the core-only system, due to incomplete removal of the native organic ligands using conventional thin-film halide exchange. The PbCl_x shell offers a promising route to passivate the additional surface facets of large nanocrystals, that previously established ligand treatments fail to adequately to address.

Printed electronics is a promising low-cost and high-throughput technology for electronic device fabrication. Printed electronics can create flexible electronics on flexible, large-area, thin, and lightweight substrates such as plastic or paper. Wearable electronics, flexible displays, and sensor tags are promising applications of flexible-printed electronics. Conductive, dielectric, and semiconductor patterns can be printed by adding different nanoparticles to a solvent with specific agents to improve printability and prevent particle agglomeration. Printed materials require drying to evaporate the solvent and solidify the material. Electrical conductivity is one of the most important properties of printed metal nanoparticle conductors. Conductivity should be the same irrespective of pattern design: size, location, or density of adjacent patterns. However, we demonstrate here that inconsistencies in the drying process for printed patterns with close proximity cause resistivity variations. We studied these resistivity variations experimentally in arrays of printed square electrodes. Silver nanoparticle ink is used to inkjet print 9, 25, and 49 square shape electrodes in 3x3, 5x5, and 7x7 arrays to study the resistivity variation between squares at different positions in the array. Electrical resistivity measurement shows higher resistivity for printed squares at the center of each array, while printed squares at the corners exhibit lower resistivity after drying on a hot plate. This variation depends not only on the location of each electrode in an array but also on the number of electrodes. This means, for the same drying temperature and duration, the array with a larger number of electrodes shows higher resistivity variation due to the higher evaporation rate of the corner electrodes than the center. As an example, the resistivity variation for 3x3 and 7x7 arrays is 40% and 69%, respectively. Compared to a single isolated electrode, the resistivity at the center of a 7x7 array is 81.7% higher. We studied this phenomenon also for printed squares with three times larger area (9 mm²), and the results show the same trend but with an overall larger resistivity. Different types of patterns, such as lines and square spirals, show the same trend when features are printed in close proximity, which is inevitable for a spiral. After drying, nanoparticles are sintered in a second post-treatment process to improve the electrical conductivity of the printed metal nanoparticle film. In the sintering process, metal nanoparticles melt and merge to form larger grains with fewer grain boundaries, so the modified morphology of the printed structure can improve the electrical conductivity. Conventionally, sintering is performed at an elevated temperature. Here, we find that sintering on a hotplate at 120 °C results in a reduction in the resistivity variation between different electrodes in a 7x7 array to 9.6%. Compared with conventional thermal sintering, intense pulsed light (IPL) sintering is preferable for high-throughput manufacturing. IPL, as a fast sintering method, applies short, high-intensity light pulses from a Xenon lamp to the printed patterns to improve their electrical conductivity while the substrate temperature stays low. Using IPL can also reduce the resistivity variations of the printed square patterns in an array. There are three parameters for controlling the total energy from the light pulses in IPL. Optimization is necessary to find an optimum number of pulses, on-time, and voltage to achieve the highest electrical conductivity of printed silver nanoparticle ink as well as the lowest resistivity variation. With optimum IPL parameters, the resistivity variation changed to 20% and 22% for 3x3 and 7x7 arrays, respectively. This understanding of printed metal conductor post-processing is important for circuit designers who need to consider resistivity variations and proximity effects in complex circuit patterns.

Oxygen vacancy defects in silicon dioxide substrates act as defect-mediated nucleating sites for metal nano-particles. Site-specific nucleation of metal catalyst particle and the subsequent growth of nanostructures could thus be accomplished by modulating the number density of these oxygen vacancies on specific substrate sites. This study demonstrates surface passivation dictated site-selective growth of vertically aligned multiwall carbon nanotubes (MW-CNTs), on a SiO₂/ Si patterned substrate. Contrasting choice of growth site of MWCNTs is observed for substrates pre-treated in a reducing atmosphere versus that pre-treated in a mildly oxidizing atmosphere. The different substrate pre-treatments alter the number density of oxygen vacancies on the SiO₂ and Si terraces of the substrate which in turn alters the preferred nucleation site for the metal catalyst particle, resulting in the observed switching of site-selectivity. Scanning electron microscopy of the as-synthesized CNT architectures revealed a high degree of site-selectivity in the growth pattern. Hermans orientation factor revealed a reasonably high degree of alignment of the MWCNTs for both the growth patterns. Transmission electron microscopy and Raman spectroscopy have been employed to study the structure and quality of the synthesized tubes and the catalyst particles. Auger electron spectroscopy was used to study the chemical state of the substrate surfaces and the nucleated catalyst particles. The results demonstrate the significance of surface defects in the nucleation and the subsequent growth of nanostructure.

The architectural diversity realized by plasmonic nanostructures is in large part due to seed-mediated colloidal growth modes that are seeded, not only by single-crystal seeds, but by seeds with a well-defined internal defect structure. Multi-twinned seeds have, for example, been used to generate colloids with icosahedral and decahedral structures while seeds with planar defects realize nanoplate geometries. Recently, we demonstrated a nanofabrication route that synergistically combines nanoimprint lithography, directed assembly, and liquid-phase epitaxy to obtain periodic arrays of complex noble metal nanostructures over a square centimeter area. This benchtop process leverages a synthetic strategy in which seed-mediated liquid-phase growth modes are carried out on substrate-immobilized seeds. While the strategy has led to the generation of substrate-based structures with considerable architectural diversity, it is fundamentally limited by the inability to fabricate seeds with the same internal defect structure as those routinely used in colloidal chemistry. Here, we demonstrate a large-area processing route for generating substrate-based Au seeds lined with stacking faults and use them to synthesize arrays of epitaxially aligned Au nanoplates using a plasmon-mediated growth mode. The work advances the possibility of bringing an exciting nanoplate chemistry to the substrate surface and, in doing so, provides the building blocks needed to enable on-chip plasmonic devices.

Nowadays, fabrication of biosensors for cancer detection, monitoring of angiogenesis or cancer metastasis and cancer imaging holds vast potential. We herein proposed a biosensor based on clustering of matrix metallopeptidase (MMP)-responsive gold nanoparticles (AuNP) and quantum dots (QD) by azide-alkyne copper-free click reaction. Briefly, AuNP were surface-decorated with two types of poly(ethylene glycol) (PEG); 1) short chain of azide-terminated PEG, 2) long chain composed of double PEG chains with a connecting peptide (MMP CP) vulnerable for MMP digestion. We precisely controlled the immobilized PEG ratios so that the azide moieties can be exposed only when MMP externally digests the long chain of PEG. De-shielded AuNPs will be subsequently clicked to alkyne-functionalized QD. Due to the high concentration of MMP at tumor site, the fluorescence resonance energy transfer (FRET) between QD and AuNP during clusters formation is speculated that can be used for tumor sensing. To characterize the surface decoration of AuNP, UV-Vis spectrum and Raman spectroscopy of decorated AuNP were analyzed. A red shift in UV-Vis spectrum according to the size change of AuNP during decoration and 2 distinct peaks for PEG in Raman spectrum were clearly observed confirmed the successful decoration of carboxylate-PEG and mPEG-MMP CP on AuNP surface. The size changes of decorated AuNP was further confirmed by DLS and TEM, where a huge increase in hydrodynamic diameter of the AuNP was confirmed in the order of AuNP (~40nm), AuNP/PEG (~60nm) and AuNP/PEG/MMP CP (~90nm). In consistence with the DLS results, shell thickness of AuNP obtained by analyzing TEM images showed the same trend according to stepwise decoration of AuNP. Moreover, when AuNP/PEG-azide was labeled with alkyne fluorescence dye, a significant increase of the fluorescence intensity was recorded by spectrofluorophotometer and IVIS in comparison to AuNP-dye suspension confirmed the click-functionality of AuNP/PEG-azide. Thus, AuNP/PEG-azide was speculated that can be used for click reaction toward alkyne-QD. The enzyme responsive clustering process was investigated by incubating with different concentration of MMP-2. There was a dramatic increase of AuNP diameter up to about 400nm and the FRET efficiency also increased up to ~58% after 2h of incubation confirmed the cluster formation of AuNP and QD. This results suggesting that AuNP and QD can be employed for tumor sensing due to the elevated MMP-2 concentration at tumor site. To stimulate in vivo clustering behaviors, AuNP and QD were incubated with the supernatants of cell cultured medium. The diameter of the clusters and FRET efficiency also increase after 2h of incubation. Furthermore, we monitored the fluorescence intensities of QD by IVIS when co-injected with AuNP to tumor bearing mice. Consequently, after 6h post injection, the fluorescence intensity of QD was clearly reduced confirmed the feasibility of our platform for real-time imaging and tumor sensor in vivo.

The use of metal nanoparticles (NPs) for printed conductive patterns are gaining a lot of attention because of the low cost and shorter manufacturing time in the fabrication of flexible electronic devices. Flexible electronics include organic thin film transistor (OTFT), organic light-emitting diode (OLED), sensors, and wearable devices. Metallic NP inks mainly comprised of metal NPs such as gold (Au), silver (Ag), and copper (Cu) are commonly used for printing of conductive patterns on flexible substrates. After printing of NP inks, sintering process is required to achieve high conductance of the patterns. Metallic NP inks also contain the organic capping molecules and additives which are barrier to high conductance. Through sintering process, these organic compounds should be removed. Ag NPs are the most widely used in many applications due to their high electrical conductivity and chemical stability. In this study, the effect of sintering atmosphere on the conductivity of printed patterns is investigated. Sintering atmosphere is chosen among air, nitrogen (N₂), and N₂-bubbled through formic acid. The sintering temperature is maintained below 200^oC to avoid the deformation and degradation of flexible substrate. The formic acid atmosphere shows a better removal of the organic compounds than air or N₂. At the beginning of thermal sintering, the organic capping molecules surrounding the NPs decompose and necking between the adjoining NPs occurs, followed by grain growth and densification. The electrical conductivity of Ag film is dependent on sintering conditions. It is observed that the resistances of Ag films decrease as the sintering temperatures increase when sintering atmosphere is chosen between air and N₂. Ag films sintered under N₂-bubbled through formic acid shows low resistances below 0.14 Ω even at temperatures below 100^oC. In comparison, the resistances of Ag films sintered under air or N₂ drastically decreases from 1.59-2.57 and 0.20-0.22 Ω when the sintering temperatures increase from 80 to 140^oC. The microstructure and chemical composition of the printed conductive patterns under different sintering conditions such as temperature, time, and type of atmospheres are analyzed. The grain growth, pore distribution, and level of organic residues determine the conductivity of the printed patterns. Formic acid vapors play an important role in decomposition of organic molecules, neck formation of NPs, and densification of the film, compared to the patterns sintered under air or N₂. The average hardness and elastic modulus of the films sintered under formic acid vapors and N₂ are higher than that sintered under air at sintering temperature of 140^oC.

SERS has received increased attention in recent years focusing toward biological and medical applications due to its great sensitivity as well as molecular specificity. In the context of biological samples there are generally two methodologies for SERS based applications: label free detection and the use of SERS tags. Necessity of tagging can make the process slower and limits the use for real life. Label-free detection offers the advantage that it reports direct spectroscopic evidence associated with the target molecule rather than the label. Reproducible, highly monodisperse gold nanoparticles (Au NPs) were synthesised using a relatively facile seed mediated growth method. Different capping agents (TRIS, citrate and CTAB) were used during synthesis and characterization was performed. They were then mixed with different analyte solutions before drop-casting onto a glass slide prior to Raman measurements to see which NPs displayed the highest SERS activity as well as their stability. A host of different analytes were tested, both non-biomolecules and biomolecules which were all successfully detected using this method at concentrations as low as 10^-3M with salicylic acid reaching a detection limit in the nanomolar range. SERS was also performed on samples with a mixture of analytes present whereby peaks from both target molecules were distinctly observed. This is a rapid and effective way of testing samples and offers potential applications in the biomedical field as a tool for diagnostic and treatment purposes.

Modification of physical and chemical phenomena is observed in vicinity of metamaterials may involve different mechanisms specific for nanostructured and plasmonic media. In order to better understand the factors responsible for modification of electrochemical reactions in plasmonic environment, we employ the cyclic voltammetry method and investigate how the vicinity to nanostructured metallic surfaces affects the electron-transfer process and charge transport kinetics. In addition, we explore effects of laser light illumination and discuss the results taking into account photoinduced electric potentials and plasmon-related heating.

Development of inexpensive energy storage devices is crucial due to the ever increasing demand for sustainable energy. The material used as the electrode material in energy storage devices is one of the most important factors affecting the device’s performance, price and sustainability. Asphaltene, as a high carbon content by-product of the oil sands industry, can be used as the base material for the electrodes in electrochemical double layer supercapacitors (EDLC), pseudocapacitors and the air electrode in Zn-air batteries (ZAB). Asphaltene is the most polar fraction and heaviest part of oil sands bitumen. Approximately 20 wt% of bitumen produced from the oil sands consists of asphaltene.
Carbon fibers (CF) derived from asphaltene were chemically activated to prepare activated carbon fibers (ACF). ACF were used to prepare stable and high performance flexible EDLC and pseudocapacitor electrodes as well as air electrodes for ZAB.
ACF used as the active electrode material in EDLC showed a specific surface area (SSA) as high as 2290 m² g^-1 and total porosity of 1.27 cm³ g^-1 that included 0.88 cm³ g^-1 of micropores (pore width < 2 nm) and 0.29 cm³ g^-1 of mesopores (2 nm < pore width < 50 nm). The maximum specific capacitance (C_s) reached was 311 F g^-1 at a specific current (I_s) of 0.04 A g^-1 that dropped to 248 F g^-1 at 1 A g^-1 (in 6 M KOH); capacitance retention was 91% after 10,000 cycles. This material was later used in an EDLC device with an ionic liquid electrolyte (EMIMBF₄, 1-ethyl-3-methylimidazolium tetrafluoroborate); specific energy (E_s) and power (P_s) values of 35.7 Wh kg^-1 at a P_s of 525.4 W kg^-1, respectively, were achieved. These were comparable to energy and power values delivered by some batteries. ¹
Because of the high performance and high conductivity of ACF used in the EDLC devices, this material was chosen to be used in ACF/MnO₂ composite electrodes to aid the pseudocapacitive performance of MnO₂. Birnessite-type MnO₂ (δ-MnO₂) was prepared through a hydrothermal process; its microstructure was subsequently thermally modified to reduce its crystallinity by introducing defects. These defects acted as active sites to enhance electrolyte ion adsorption/desorption, which can increase C_s, E_s and P_s. The maximum C_s reached by the composite electrode was 395 F g^-1 at a specific current of 0.04 A g^-1, with 282 F g^-1 at 1 A g^-1. Capacitance retention was 74% after 5,000 cycles. The maximum P_s in 6 M KOH for the composite electrode was 2.57 kW kg^-1 at E_s of 6 Wh kg^-1.
Asphaltene based carbon fibers were chosen to prepare homemade gas diffusion layers (GDL) for use in air electrodes in ZAB. Air electrodes were prepared with CF carbonized at three different temperatures, i.e., 500 ^oC, 800 ^oC and 1500 ^oC. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity of the electrodes, as well as commercially purchased electrodes, were tested in 1 M KOH. All homemade electrodes showed much better OER activity than the purchased ones. ORR activity was similar for both commercial electrodes and homemade electrodes prepared with CF at 1500 ^oC (CF-1500). CF-1500 will be tested in full ZAB cells to determine their performance and cycling behavior and compared with purchased electrodes. Finally, electrodes, prepared with CF-1500 and electrocatalysts consisting of Mn-mixed metal oxides, will be tested in ZAB half cells and full cells.

Plasmonic resonances in metal nanostructures have enabled the creation of a new class of chemical sensors, photocatalysts, and therapeutics. In particular, coupling plasmonic metals to other functional nanostructures provides an effective way to generate multi-functional materials, tailored to respond to controlled light inputs in specific ways. Remarkably, these advances have occurred despite a lack of understanding of how energy transfer occurs between metallic domains and the geometric and dielectric effects on the plasmonic properties in hetero-nanostructures. Here, we present a nanoparticle library approach designed to explore the plasmonic modes of metal nanojunctions with various geometries, metal types, and composition ratios. Polymer nanoreactors generated by scanning probe lithography were used to prepare location-encoded particle libraries on electron-transparent substrates where the individual nanoparticles have precisely defined size and composition. Single-particle level far-field light scattering and near-field energy-loss maps were sequentially collected from the same nanojunctions, allowing for mode identification of the entire plasmonic spectrum and correlation between the near-and-far-field properties of the system. Notably, a dipole injection from a plasmonically active metal to a lossy metal is revealed in the nanojunctions, suggesting that field enhancement on the surface of the lossy metal is responsible for photocatalytic “energy transfer” in reactions on the lossy metal. We report on a new group of hetero-nanoprisms containing both active and lossy metals in a planar configuration. The unique plasmonic mode distribution uncovered by our methods yields a design paradigm for creating the next generation of low-cost (due to elemental composition), multi-functional nanomaterials.

Polymer-inorganic nanocomposites based on polymer-grafted nanocrystals (PGNCs) are enabling technologically relevant applications owing to their unique physical and chemical properties. While diverse PGNC superstructures have been realized through evaporation-driven self-assembly, this approach presents multifaceted challenges in understanding and ultimately controlling the assembly kinetics and superstructure selection. In this presentation, I will first discuss our work on the rapid assembly of multicomponent superstructures from a homogeneous disordered PGNC mixture. We find that controlling the nature of assembly environment allows for exquisite control of the rate and extent of PGNC assembly. Characterization of kinetically arrested intermediates reveals a multistep crystallization pathway defying classical nucleation theory. Next, I will discuss examples on polymer-grafted anisotropic nanocrystals. It is found that the interplay between nanocrystal shape and interaction softness give rise to tunable assembly phase behavior.

The emergence of order from disorder has fascinated, puzzled, and inspired generations of scientists. Colloidal assembly of nanoscale objects is of particular interest as a wide range of hierarchical structures can be obtained simply by changing the size, shape, and surface chemistry of the nanomaterials. Over the past decade, advances in colloidal nanocrystal (NC) synthesis have provided access to a library of well-defined nanoscale building blocks. The organization of isotropic NCs, i.e. uniformly functionalized nanoscale spheres or pseudo-spheres, has been extensively studied and design rules have been empirically set or theoretically explained. In contrast, very few design rules exist for anisotropic NCs, such as asymmetrically functionalized spheres, rods, plates, and polyhedral NCs, and the rules that do exist are often challenged by unusual cases. Therefore, our current understanding of the self-organization process of anisotropic NCs has yet to achieve the leap from “discovery by chance” to “synthesis by design”. In this presentation, we present synthetic methodologies towards the assembly of designer 2D and 3D NC superlattices using DNA-functionalized polyhedral NCs and a series of geometry-inspited strategies.

For 2D structures, we have developed a shallow template-assisted DNA-mediated assembly strategy to precisely arrange colloidal NCs onto surfaces with single-particle orientational control across millimeter areas. In addition to our precise control over the in-plane arrangement, the oligonucleotide bonds between the NCs and substrate can be reversibly expanded and contracted, enabling post-synthetic tunability. As an example, we have synthesized a tunable NC-based metasurface that rapidly responds to changing solution polarity and, therefore, is promising for the fabrication of reconfigurable 2D optical devices. To achieve 3D structures, we have developed a series of PEG-DNA ligands that enabled the assembly of polyhedral NCs into ordered and dense-packed superlattices, which is challenging due to the rigiditiy of pure DNA. Taking advantage of the highly customizable nature of oligonucleotides and geometry inspired designs, polyhedral NCs of different sizes and shapes were densely assembled/co-assembled. This resulted in the introduction of eleven new structures to the DNA-engineered colloidal crystal family, including the first colloidal quasicrystal engineered with DNA. Moreover, we have shown the ability to inversely design and experimentally produce ordered superlattices based on polyhedral complementarity. Importantly, these colloidal organization platforms may enable systematic exploration of structure-functional relationships, as well as on-demand design and fabrication of highly ordered nanoscale architectures which will be of interest to the metamaterial communities.

Semiconductor quantum dots (QDs) are prime candidates as harvesters of light and donors of excited charge carriers for solar energy conversion. The unique properties of QDs can be exploited to generate desirable energetic offsets to promote interfacial charge transfer between QDs. Our group’s recent efforts have established the validity of utilizing carbodiimide-mediated coupling chemistry to selectively tether two QDs through the formation of an amide bond between the terminal functional groups of capping ligands [1]. We previously reported on excited-state hole transfer in colloidal CdS/CdSe QD heterostructures, which exhibit quasi-type-I interfacial energetic offsets [1]. Type-I energetics rely on the excitation of one QD component, which results in unidirectional charge transfer and hindered charge separation.
This presentation reports on our efforts to improve and expand upon our previous work in two ways. First, we synthesized and characterized covalently tethered colloidal CdSe/CdTe QD heterostructures via formation of amide bonds. These heterostructures exhibit type-II energetics that promote interfacial charge separation, irrespective of which constituent QD is initially excited, and afford enhanced control over the thermodynamic driving forces for charge transfer. Within these heterostructures, photogenerated electrons are transferred from CdTe to CdSe, and photogenerated holes are transferred from CdSe to CdTe, on timescales of 10^-8 s. Second, we prepared ternary CdSe/CdTe heterostructures by immobilizing a covalently-linked bilayer of these QDs on a metal oxide substrate. When compared to colloidal heterostructures, thin films consisting of QDs adsorbed to a metal oxide substrate introduce the possibility of an additional stepwise excited-state charge transfer process. We hypothesized that a stepwise process such as this should facilitate extended spatial separation of charge carriers and longer charge-separated state lifetimes, such that energy is harvested more efficiently and desirable processes can more effectively compete with recombination. Dynamic quenching of emission was observed in heterostructure-modified thin films, consistent with excited-state charge transfer. Rate constants for photoinduced electron and hole transfer between QDs are on the order of 10⁸ s^-1 and 10⁷ s^-1_, respectively.
The bidirectional interfacial charge transfer within these type-II QD heterostructures, both in dispersion and within films, further reveals the potential of this system for use in light harvesting and solar energy conversion. This presentation will highlight these recent results as well as our ongoing time-resolved spectroscopic characterization of photoinduced charge transfer in CdSe/CdTe QD heterostructures.

[1] Sellers, D. G.; Button, A. A.; Nasca, J. N.; Wolfe, G. E.; Chauhan, S.; Watson, D. F., Excited-State Charge Transfer within Covalently Linked Quantum Dot Heterostructures. The Journal of Physical Chemistry C 2015, 119 (49), 27737-27748.

Hydrogen production using abundant solar energy and semiconductor photocatalysts holds significant potential as a clean and sustainable energy system. Macroscopically sized aerogel monoliths synthesized from preformed anatase nanoparticles are promising three-dimensional photocatalysts due to their immense surface area, high porosity, translucency, and the nanoscale characteristics of the semiconducting crystalline building blocks. Recent studies showed that such titania aerogels decorated with metals are effective for gas-phase photocatalytic CO₂ reduction and H₂ production [1, 2]. However, TiO₂ nanoparticle-based aerogels remain limited to UV-driven photocatalysis due to the intrinsic wide bandgap (3.2 eV). To increase conversion efficiency from solar energy to H₂ production, visible-light sensitization is necessary. Here, we present a facile method for the doping of the aerogel monoliths postsynthetically to make them visible-light active for H₂ production. A CVD gas-phase reaction and plasma utilization at low temperature provided efficient nitrogen incorporation into preformed TiO₂ aerogels without affecting their initial properties. The nitridation improves the optical absorption and charge separation efficiency through an appropriate balance between doping amount and coexistent defects. In comparison to the non-doped sample, the nitrogen-doped aerogels show a significant enhancement in visible-light-driven photocatalytic H₂ production (3.1 mmol h^-1 g^-1) with excellent stability over 5 days. Our approach of gas-phase nitridation of preformed aerogel monoliths offers a powerful tool to improve their properties as visible-light active photocatalysts.

[1] F. Rechberger, et. al., Mater. Horiz. 4, 1115 (2017)
[2] A. L. Luna, et. al., Appl. Catal. B. 267, 118660 (2020)

Block copolymers (BCPs) provides a platform to sequester nanoparticles in a specific polymeric domain of a BCP system and fabricate aligned nanostructures that can be of significant importance in design of electrostatic capacitors. To aid in the dispersion of nanoparticles in the BCP system, polymer grafted nanoparticles were synthesized using grafting to and grafting from methods. Here, we report the influence of loading of polymer grafted nanoparticles (homopolymer and BCP grafted) on the dispersion and assembly of nanoparticles within cylinder forming BCP (c-BCP) of PS-b-PMMA films under static and sharp dynamic thermal gradient soft shear. The application of static thermal field via oven annealing on BCP-g-NP filled as-cast c-BCP films induced a morphology transition from poorly ordered cylinders to mixed morphology, while under dynamic thermal field via cold-zone annealing with soft-shear (CZA-SS), a morphology transition from poorly ordered cylinders to long range ordered parallel morphology was observed. However, at high nanoparticle loading (~10%), there is frustration in the unidirectional alignment of the BCP matrix due to aggregation of functionalized nanoparticles. These findings will be compared and contrasted with homopolymer grafted nanoparticles loaded BCP to establish the significance of graft ligand chemistry in entropic contribution to the frustration in the unidirectional alignment of BCP matrix.
This work is supported by NSF DMR1901127.

Colloidal crystal engineering with nucleic acid-modified nanoparticles is a powerful way for preparing 3D superlattices, which may be useful in many areas, including catalysis, sensing, and photonics. To date, the building blocks studied have been primarily based upon metals, metal oxides, chalcogenide semiconductors, and proteins. Here, we show that metal–organic framework nanoparticles (MOF NPs) densely functionalized with oligonucleotides can be programmed to crystallize into a diverse set of superlattices with well-defined crystal symmetries and compositions. Electron microscopy and small-angle X-ray scattering characterization confirm the formation of single-component MOF superlattices, binary MOF–Au single crystals, and two-dimensional MOF nanorod assemblies. Importantly, DNA-modified porphyrinic MOF nanorods (PCN-222) were assembled into 2D superlattices and found to be catalytically active for the photooxidation of 2-chloroethyl ethyl sulfide (CEES, a chemical warfare simulant of mustard gas). Taken together, these new materials and methods provide access to colloidal crystals that incorporate particles with the well-established designer properties of MOFs and, therefore, increase the scope of possibilities for colloidal crystal engineering with DNA.

The ability of thermoelectric (TE) materials to convert waste heat, produced from fossil fuels, into electricity is an interesting approach to harvest thermal energy. Till now, inorganic TE materials are best known for their high ZT values but they suffer from high toxicity, high cost, and hideous processing. On the other hand, the low TE efficiency of organic materials is lagging behind their inorganic counterparts. Therefore, we propose a hybrid material as an alternative to obtain a high dimensionless figure of merit.

We utilize the hybrid organic-inorganic approach by taking advantage of the low thermal conductivity of organic polymers, and large Seebeck coefficient of inorganic materials, which is essential for obtaining an improved TE efficiency. Nevertheless, accomplishing a high electrical conductivity whilst keeping a low thermal conductivity is difficult; and optimization of both parameters is of utmost importance.

To surmount the aforementioned difficulties, we propose a p-type hybrid composite made of an organic polymer poly (3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) filled with inorganic graphene oxide-titanium dioxide (GO-TiO₂), as a cost-effective and scalable outcome for future TE applications. A facile two steps synthesis route has been opted to synthesize GO-TiO₂@PEDOT: PSS hybrid nanocomposite. The oxo (C=O) and hydroxyl groups (-O-H) of GO have been firstly attached to TiO₂ nanoparticles and then used as a template for the oxidative polymerization of EDOT.

As-synthesized hybrid nanocomposites were analyzed by XRD, SEM, FTIR, UV-Vis spectroscopy, and TG-DSC. The thermal conductivity of the materials was done by the photothermal radiometry (PTR) technique and obtained results were in good agreement with the theoretical predictions proposed in Nan's model. Seebeck coefficient measurements were done by a home-made setup based on two probe method.

The influence of filler on the thermoelectric properties of PEDOT: PSS has been studied. It was observed that the thermal conductivity of PEDOT: PSS has been decreased by half; whereas, the Seebeck coefficient was increased by 2.5 times with the addition of 5wt% GO-TiO₂ into the PEDOT: PSS polymer matrix. The obtained hybrid material can be utilized in various applications such as power generation, cooling, and refrigeration, printing applications, etc. up to 300°C as suggested by the thermogravimetric analysis results.

PbSe nanorods have been considered as one of the most promising nanoparticles for solar energy field owing to their high multiple exciton generation yield. As a design rule in solar cell applications, strongly coupled nanoparticles with low exciton binding energy are necessary. In this respect, successful integration of nanorods into solar cells, where an efficient exciton dissociation is demanded, requires fundamental understanding of nanorod ligand interactions. This study discloses the effect of ligand type on the nanorod ordering and on the photovoltaic performance. We found that the ligands which are flexible and have free rotation about the axis of the ligand molecules lead to ordered nanorods whereas completely disordered nanorods are obtained when rigid ligand molecules with torsional degrees of freedom are used for the ligand exchange process. We utilized high-resolution transmission electron microscopy imaging technique to study the effect of ligand structure on nanorod ordering. Steady state photoluminescence measurements were performed to investigate the effect of degree of order on the photo-physical properties. Finally, photovoltaic characteristics of the solar cells based on different ligands were investigated.

Scalable graphene synthesis and facile large-area membrane fabrication are imperative to advancenanoporous atomically thin membranes (NATMs) for molecular separations. Although chemical vapordeposition (CVD) allows for roll-to-roll high-quality monolayer graphene synthesis, facile transfer withatomically clean interfaces to porous supports for large-area NATM fabrication remains extremely challenging.Sacrificial polymer scaffolds commonly used for graphene transfer typically leave polymer residues detrimentalto membrane performance and transfers without polymer scaffolds suffer from low yield resulting in high non-selective leakage through NATMs. Here, we systematically study the factors influencing graphene NATMfabrication and report on a novel roll-to-roll manufacturing compatible isopropanol-assisted hot lamination (IHL)process that enables scalable, facile and clean transfer of CVD graphene on to polycarbonate track etched(PCTE) supports with coverage ≥99.2%, without compromising support integrity/porosity. We demonstrate fullyfunctional centimeter-scale graphene NATMs that show ~2-3 orders of magnitude higher permeance andbetter selectivity than commercially available state-of-the-art polymeric dialysis membranes, specifically in the0-1000 Da range. Our work highlights a scalable approach to fabricate graphene NATMs for practicalapplications and is fully compatible with roll-to-roll manufacturing processes.

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Metal chalcogenide semiconducting nanoparticles (NPs) possess appealing optoelectronic properties that render a wide range of applications, including photovoltaics, photodetectors, and light-emitting diodes (LEDs). Yet, the instability of this class of low-bandgap NPs in ambient conditions remains a key challenge for their practical use. Herein, we demonstrate an unconventional strategy by employing star-like diblock copolymers as nanoreactors to in-situ craft monodisperse metal chalcogenide (e.g., PbSe) NPs with precisely tailorable size, surface chemistry, near-IR optical properties, and significantly improved stabilities in air. The surface of PbSe NPs is intimately and permanently ligated with polymer hairs (i.e., the outer blocks of star-like block copolymers), imparting the protection of PbSe NPs against oxidation and preventing them from aggregation. Intriguingly, alternating the composition and chain lengths of the outer blocks affords a remarkable control over the enhancement of stability of PbSe NPs in ambient conditions.

Semiconductor quantum dots like zinc sulfide have interesting potential applications, consequent to their size-dependent optical properties. These nanostructures can be used on agriculture, environmental chemistry, and fluorescence microscopy, among others. The great rise in nanotechnology has sparked interest in the scientific community in nanomaterials for the use of photodegradation in aquatic bodies. Quantum Dots (QDs) like ZnS nanoparticles (NPs) can absorb electromagnetic radiation and generate photo-excited nanostructures which would be generating reactive oxygen species directly in aqueous phase. The presence of ROS in aquatic environments can be used to destroy organic contaminants by photocatalysis processes. Previous studies had evidenced that the presence of impurities (i.e. copper) into the crystalline structures of QDs can enhance their optical properties and consequently their catalytic capacity. Because of this, the present investigation was focused on generating water-stable ZnS nanoparticles with catalytic properties. This work had three objectives: 1) synthesis of pure and doped ZnS nanoparticles following a reflux method; 2) characterize nanostructures; and 3) study the photocatalytic properties of these nanostructures. A redshift was observed in the photoluminescence peak of pure ZnS nanoparticles when they were doped with heavy metals. Pure ZnS NPs and Cu-doped ZnS NPs evidenced luminescent peaks at 446 nm and, 541 nm, respectively. Nanoparticles (pure and doped) evidenced sizes less than 5 nm and morphologies mainly spherical. Photodegradation studies were evaluated in presence of organic dyes like methylene blue and different concentrations of pure and doped quantum dots (250 and 500 ppm). The destruction of organic dyes in the presence of photo-excited ZnS nanoparticles is envisioned as a fast and clean technology.

Colloidal quantum dot (CQD) materials have many optoelectronic applications such as in photodetection, light emitting diodes and solar energy harvesting. However, CQD devices are limited in their efficiency in comparison to bulk semiconductor materials, particularly in the field of PbS CQD solar cells. We have identified the hole transport layer (HTL) as a critical component limiting the performance of these devices. Here, we introduce a new method of sulfur infusion via electron beam evaporation to the current ethanedithiol-passivated PbS CQD-based HTL (PbS-EDT), used in the highest-performing PbS CQD solar cell architectures, to increase the carrier mobilities and doping densities.

We used 1D optoelectronic simulations to identify specific factors associated with the HTL that limit the performance of PbS CQD solar cells, including low electron mobility, low doping density, and non-optimal energy band levels. Because the function of the HTL is to block electrons and transport holes, the discovery of low electron mobility in the HTL as a limiting factor in solar cell efficiency was an unexpected result. We hypothesized that this could indicate that significant photogeneration occurs in the HTL and that low electron mobility in this layer is therefore limiting the ability to extract those photogenerated charges. To further test this hypothesis, we increased the thickness of the PbS-PbX₂ (X = Br, I) CQD absorbing layer in simulations and found that there was a point at which an increase in electron mobility in the HTL no longer impacted the performance of the solar cell. This, along with optical simulations of the electric field distribution in the layered solar cell structure, confirmed our hypothesis.

Based on the results of the simulations, we aimed to develop a new HTL with high electron mobility and doping density. We performed stoichiometric control of the HTL by introduction of elemental sulfur to increase carrier mobilities and doping densities, testing effective sulfur thicknesses of 1-15 Å. To characterize our new HTL, we obtain doping densities using capacitance–voltage (Cap-V) measurements, carrier mobilities using space-charge-limited current (SCLC) measurements, and performed current density–voltage (J-V) measurements under simulated solar illumination to measure solar cell device performance parameters. We verified that our new HTL materials had increases in both doping density and electron mobility of an order of magnitude compared to the standard HTL materials, while the hole mobility remained relatively unchanged. We were also able to achieve a clear improvement in device performance of 1% absolute power conversion efficiency (PCE). The primary effects of our sulfur infusion method were an increase in electron mobility through reduction of the surface trap state density and an increase in p-type doping density by shifting the film stoichiometry. The improvement in these two properties correlated with an increase in the solar cell PCE through increases in the short circuit current and fill factor, as expected.

We demonstrated new HTL materials for CQD solar cells based on sulfur infusion of PbS-EDT CQDs that enable high electron mobility and doping density. Our new HTL increased device performance, from a maximum of 9.3% to 10.4% PCE. Elemental sulfur infusion is a facile and effective method to boost performance in PbS CQD solar cells and could provide a means for improved efficiencies in other PbS CQD-based optoelectronics.

Thermally stiffening polymer nanocomposites were synthesized by chemically grafting or physically adsorbing a high-glass-transition-temperature polymer onto a nanofiller and then embedding this into a polymer matrix that has a glass transition temperature that is less than that of the grafted/adsorbed polymer. In the current study, we investigate the effect of extrusion at three different shear rates on the structure and properties of two different thermally stiffening polymer nanocomposites: poly(bisphenol A carbonate), PC or poly(2–vinyl pyridine), P2VP-adsorbed silica nanofillers embedded in a poly(ethylene oxide), PEO, matrix. Results were compared to bare silica containing PEO nanocomposites and neat PEO. Results indicate that extrusion at 80 °C led to some degree of agglomeration of the silica nanofillers and formation of structures at different length scales as characterized by small engle X-ray scattering (SAXS). Crystallinity of PEO was found to decrease upon extrusion in all nanocomposite samples but those PC and P2VP-adsorbed systems had higher crystallinity compared to bare-silica containing nanocomposites, and the crystallinity of P2VP-adsorbed system was the highest among all nanocomposite samples. This was attributed to the formation of nanofiller agglomerates and to the greater isolation of the matrix PEO chains from the silica nanoparticles due to the presence of adsorbed polymer layer; which were also supported with attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) results. Viscoelastic properties of the PC-adsorbed systems were found to recover their pre-extruded properties whereas all other nanocomposites showed large degree of decreases in their viscoelastic responses upon extrusion.

Aluminum is the third-most abundant element in Earth's crust. As a result, aluminum hydroxide polymorphs, such as gibbsite, bayerite and nordstrandite are abundant minerals in soils and dominate aluminum ores. Because of their various properties such phases have been deployed widely as adsorbents, fire retardants, coatings, catalysts, and luminescence powders, as well as comprising important precursors to various alumina products. Understanding the crystallization pathways of the aluminum hydroxide polymorphs is thus important to geochemistry, environmental science, energy storage, catalysis, biomedicine, industrial processing, and even nuclear waste treatment. Here we use in situ magic angle spinning nuclear magnetic resonance (MAS-NMR), scanning electron microscopy (SEM), scanning/transmission electron microscopy (S/TEM), atomic force microscopy (AFM), small angle X-ray scattering (SAXS), X-ray absorption spectroscopy (XAS), electrospray ionization (ESI)-mass spectrometry, high resolution powder X-ray diffraction (XRD), and X-ray pair distribution function (PDF) techniques to probe the nucleation and crystal growth mechanisms of various aluminum hydroxide nanoparticles in details. By focusing on understanding the role of aluminum coordination change dynamics from tetrahedral in solution to octahedral in solids and vice versa, and by quantifying intermediate polyoxoaluminate cluster formation, some unifying principles governing these transformations emerge. Furthermore, various advanced techniques reveal the transformation and aggregation of aluminum-oxo clusters during the hydrothermal process, which indicate cluster assembly pathways to aluminum hydroxide nanoparticle nucleation and crystal growth. These findings are important for developing new methods to morphology and size-controlled synthesis of aluminum hydroxide nanoparticles, and may aid in the design of chemical processes for managing the aluminum inventory in nuclear waste.

A facile, rapid, and scable manufacturing method for nano-assembly of palladium nanoparticles (PdNPs) and graphene is desired for broad applications in energy storage and harvesting, sensing and detection, and catalysis. However, existing approaches to obtain the organic-inorganic hybrid nanostructuress involve multi-step processes for synthesis of constituent elements. Graphene nanomaterials are synthesized by chemical vapor deposition and reduction of graphene oxides and metal nanoparticles are combined by electrodeposition, solution-based chemical processing, and thermal annealing. Laser-based method recently demonstrated rapid, cost-effective production of 3D porous graphene called laser-induced graphene (LIG) by pulsed laser irradiation of various polymers as a carbon/graphene precursor such as polyimide, and the laser method and LIG showed a promise to facile, scalable, rapid manufacturing of nanostructured graphene and functional devices for broad applications including sensing and detection, energy storage and harversting and nanocatalysts. However, the laser photothermal generation of inorganic-organic nanostructured composite materials has not been explored. Here, we present a one-step, rapid, scalable laser photothermal nano-assembly method to synchronously generate Pd NPs and porous graphene by using polymer films that contains Pd and carbon precursors. We use the polymers of intrinsic microporosity (PIM-1) as a graphene precursor, which has high solubility in volatile solvent and miscibility with inorganic materials. The outstanding compatibility with inorganic materials and solubility in volatile organic solvents of PIM-1 allow for homogeneous films without phase separation, and formation of the films only by removing volatile solvents at ambient condition. A pulsed CO₂ laser irradiation on the homogeneous films of PIM-1 and Pd-ligands induces localized graphitization (carbon atoms in the polymer chains become sp² hybridized) yielding nano- to microscopic 3D porous graphene while the organic functional groups of Pd-ligands are vaporized and Pd atoms nucleate and crystallize in nanoparticles. Thus, our laser-induced photothermal local heating yields synchronous nano-assembly of highly dense and monodispersed PdNPs in porous nanostructured graphene. Based on low energy requirements of PdNPs to form palladium hydrides (PdHx) and exceptional electrical properties of the porous graphene including high conductivity and electron mobility we used the laser nanomanufactured hybrid nanostructures for highly sensitivity hydrogen gas sensing with the limit of detection down to 1 ppm. We also demonstrated fast and reversible hydrogen gas detection in the range of 1-50 ppm H₂, which is attributed to chemical reversibility of the hybrid nanostructues. We showed mechanically flexible, wearable H₂ sensor with outstanding mechanical flexiblity and reliability of the hybrid nanostructues under cyclic bending strain of 0.22% as well as cyclic twisting angles of ±90° up to 10,000 cycles. Furthermore based on our hybrid nanostructures we developed a wireless H₂ gas sensor platform enabling monitoring with a smartphone. Our approach combining the laser photothermal method and the versatile polymer of the PIM-1 has potential to manufacture hybrid nanostructred materials of various metal nanoparticles and porous graphene for broad fields in energy storage and harvesting, sensing and detection, and catalysis as well as diverse applications including electrochemical sensors, gas storage systems, and supercapacitors.

Photocatalytic hydrogen production is one of the most important techniques, which have to be part of a sustainable energy system to ensure the survival of our polluted planet. The search for the most efficient photocatalyst for this technique includes not only finding the right material, but as importantly, finding the right structure. We suggest 3D, translucent, nanoparticle-based aerogel monoliths as promising candidates for the photocatalytic hydrogen production in the gas phase. To achieve the best photocatalytic performance, the right fit between the geometries of especially 3D photocatalysts and reactors measuring their performance is crucial. Here, we report how we take control of the geometry of the photocatalyst by introducing 3D printed polymeric scaffolds into the aerogels. Thanks to these scaffolds, we can investigate the gas flow through the aerogel, the UV light penetration into the aerogel and the optimal fit with our custom-made continuous gas flow reactor to maximize the hydrogen production rate. We manage to raise the hydrogen production rate from originally 433 µmol g^-1 h^-1 by a factor of almost 4 to 1578 µmol g^-1 h^-1 just by modifying the geometry of the aerogels. Additionally, the rigid scaffolds enhance the mechanical stability of the fragile aerogels, increasing the fabrication yield and, therefore, saving material, money and time. With the possibility to engineer these 3D printed polymeric scaffolds, we can match the geometry of any 3D, template-free, self-supporting photocatalyst to the geometry of reactors built for any photocatalytic gas phase reaction and maximize the photocatalytic performance.

Printable dielectrics are important materials for flexible and inkjet-structured electronics. Many of them are composites with a polymer and a nanoparticle component. Non-conductive nanoparticles, for example oxides with high dielectric constant, form dielectric composites that can be described by effective-medium theory and often contain a large volume fraction of particles [1]. Conductive metal nanoparticles at low concentrations form dielectric polymer composites with properties that are usually discussed using percolation theory [2]. The volume fraction of the metal has to be kept low in order to avoid short circuits.
Here, we present a dielectric material with a microstructure and properties that range in between the two cases introduced above. We electrically insulate conductive gold nanoparticles with a covalently bound polystyrene shell. These hybrid core-shell nanoparticles are then dispersed and deposited in thin dielectric films. The distribution of the gold in the polystyrene matrix is controlled by the structure of the covalently bound polymer shell and its interactions. We tune the amount of the organic phase in the final dielectric layer by different conditions during ligand exchange, which leads to different polymer ligand densities on the gold core.
We will discuss the dielectric constants and the microstructure of dielectric layers prepared from ink of core-shell hybrid nanoparticles with 5 nm diameter gold cores and thiol-terminated polystyrene shells (PS) of different molecular weights (M_n=5000 Da or M_n=11000 Da) with different densities. Thermal Gravimetric Analysis (TGA) data of the dry films indicated gold volume content between 4.9 vol% and 21.1 vol% depending on the polymer shell density. Small-Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) revealed different microstructures of the dielectric films that ranged from crystalline bcc packings to fully disordered, but homogeneous packing as visible in TEM. Impedance measurements in the frequency range from 100 Hz up to 1 MHz indicated a dielectric constant of 3.5 for the highest grafting density of polystyrene at a dielectric loss of below 2% at 1 kHz, while the lowest grafting density of polystyrene led to a dielectric constant of up to 40 with a dielectric loss of below 5% at 1 kHz.
We believe that the covalent attachment of polymer ligands to metal cores is a promising approach to “molecular hybrid” films that can be deposited by wet processing without agglomeration. Our approach solves the problems of particle agglomeration in earlier nanocomposites of metal nanoparticles in polymers at high particle loading [3,4]. The strong attachment of the insulating polymer ligands prevents dielectric failure that otherwise besets nanocomposites at increased metal contents.

References:
[1] Dang, Zhi-Min; Yuan, Jin-Kai; Zha, Jun-Wei; Zhou, Tao; Li, Sheng-Tao; Hu, Guo-Hua (2012): Fundamentals, processes and applications of high-permittivity polymer–matrix composites. In Progress in Materials Science 57 (4), pp. 660–723. DOI: 10.1016/j.pmatsci.2011.08.001.
[2] Nan, C.-W.; Shen, Y.; Ma, Jing (2010): Physical Properties of Composites Near Percolation. In Annu. Rev. Mater. Res. 40 (1), pp. 131–151. DOI: 10.1146/annurev-matsci-070909-104529.
[3] Toor, Anju; So, Hongyun; Pisano, Albert P. (2017): Dielectric properties of ligand-modified gold nanoparticle/SU-8 photopolymer based nanocomposites. In Applied Surface Science 414, pp. 373–379. DOI: 10.1016/j.apsusc.2017.04.096.
[4] Toor, Anju; So, Hongyun; Pisano, Albert P. (2017): Improved Dielectric Properties of Polyvinylidene Fluoride Nanocomposite Embedded with Poly(vinylpyrrolidone)-Coated Gold Nanoparticles. In ACS applied materials & interfaces 9 (7), pp. 6369–6375. DOI: 10.1021/acsami.6b13900.

Chemiresistive gas sensors based on sol-gel synthesised colloidal materials with controlled size, shape and composition have demonstrated notable sensing properties [1]. In our earlier work we showed that ordered assemblies of ZnO nanorods produced in solution via wet chemical synthesis lead to formation of network like structures on electrodes, with sensing capabilities at room temperature [2]. Current passing through such a network between one electrode to another, is modulated based on the surface chemistry taking place between surrounding environment and material deposited [2].
In this work, we extend our previous work to assembly of CuO bundles forming a network between gold electrodes. Copper oxide (CuO) is a well-known p-type material used for variety of applications including chemiresistive gas sensors. CuO is known to have excellent optical and chemical properties which can be tuned for variety of applications. For example, Hou et al. have studied study the effect of morphology and surface structure of CuO nanostructures on the CO sensing properties [1]. In addition to this, CuO nanostructures have been found to be sensitive to a variety of reducing and oxidising gasses [2, 3, 4]. In this work, synthesis and characterisation of CuO bundles network is presented, followed by sensing response towards oxygen. The properties are tuned by annealing of the network, which acts on the junctions between the bundles. Moreover, we investigate the optical properties of such an assembly of structures to improve its electrical characteristics and enhance its gas sensing response using light activation.
[1] Hou, L., Zhang, C., Li, L., Du, C., Li, X., Kang, X. F., & Chen, W. (2018). CO gas sensors based on p-type CuO nanotubes and CuO nanocubes: Morphology and surface structure effects on the sensing performance. Talanta, 188, 41-49.
[2] Caicedo, N., Leturcq, R., Raskin, J. P., Flandre, D., & Lenoble, D. (2019). Detection mechanism in highly sensitive ZnO nanowires network gas sensors. Sensors and Actuators B: Chemical, 297, 126602.
[3] Hoa, N. D., Van Quy, N., Jung, H., Kim, D., Kim, H., & Hong, S. K. (2010). Synthesis of porous CuO nanowires and its application to hydrogen detection. Sensors and Actuators B: Chemical, 146(1), 266-272.
[4] Wang, C., Fu, X. Q., Xue, X. Y., Wang, Y. G., & Wang, T. H. (2007). Surface accumulation conduction controlled sensing characteristic of p-type CuO nanorods induced by oxygen adsorption. Nanotechnology, 18(14), 145506.

Sequential infiltration synthesis (SIS) is a route to the precision deposition of inorganic solids in analogy to atomic layer deposition (ALD), but occurs within (vs upon) a soft material template. We reveal a possible pathway for the sequential infiltration synthesis of InO_xH_y clusters in a PMMA host matrix and the inorganic films (after annealing) composed of sub-6 nm In₂O₃ nanocrystals. Interestingly, small InO_xH_y clusters with only 1 to 3 In atoms were found to form after a single SIS cycle. These small InO_xH_y clusters serve as sites for reaction in subsequent cycles and/or subsequent condensation with other small nuclei that first proceeds linearly and, later, more three-dimensionally. Although the structures of as-grown InO_xH_y clusters lack long-range crystallographic order, they exhibit local coordination environments similar to cubic In₂O₃ and In(OH)₃. Crystallization of the InO_xH_y clusters is easily achieved by annealing the hybrid InO_xH_y/PMMA thin films in air, which leads to the formation of denser, but still microporous, In₂O₃ thin films. The size and subtleties of the In₂O₃ structure depend on the number of SIS cycle used to deposit the inorganic phase before annealing. Lattice expansion, longer In-O bond lengths, and larger atomic displacement were observed in samples with greater SIS cycles. These methods and findings may provide fundamental insights into other SIS processes as well as map a route to the precision synthesis of discrete-atom-number clusters.

Metal oxide nanoparticles are attractive materials for many applications but have recently become an essential part of dye-sensitized solar cells and highly efficient catalysis materials. The material's efficiency depends on size, shape, and surface chemistry, which critically determine their properties and interaction.
Raman spectroscopy is a powerful method to investigate nanoparticles' vibrational properties, as the Raman band's peak and width are very sensitive to the local structure. Besides, phonons' behavior at the nanoparticles boundary strongly depends on the particle size and is a critical factor in creating a highly efficient material. It was shown that the Raman peak of TiO₂ at 142.9 cm^-1 shifted to a high-frequency region with a decrease in the nanoparticles' size. However, Raman spectroscopy of nanopowders of WO₃ and Y₂O₃ were not investigated yet. Nanopowders of TiO₂, WO₃, and Y₂O₃ with the mean size ranged from 5 to 40 nm were investigated by Raman spectroscopy in the broad spectral range. The phonon confinement model was applied to calculate the Raman spectra of these materials. The correlation length of the phonons calculated from the spectra of nanoparticles shows a significant difference between large (> 40 nm) and small (<10 nm) nanoparticles. Grain size can be extracted from the Raman spectra of nanomaterials by applying a model of confined phonons. Results showed a good correlation between grain sizes obtained from Raman spectra and XRD. Raman spectra are more sensitive to nanoparticles' structural motive compared to XRD. The Raman spectra may be different even if X-ray diffraction shows that the particle size is the same. It reflects the differences in the surface structure of nanoparticles.

Direct white light emission (WLE) from single-component emitters, free from rare-earth and toxic metals have been strongly required in industry, but it is still a grand challenge. Recently, fluorescent carbon dots (CDs) has emerged as a new class of metal-free luminescent materials that are composed mainly of C, O, H. Their fluorescence properties are tuned by the doping centre and surface functional groups leading to multiple emission in the entire visible spectra. The systematic investigation of the N-doping centres and surface functional groups has provided a vital understanding of the emission property. For example, the optimized synthetic strategy enabled us to dope graphitic N centres and lead to the broadband WLE extended in the entire visible spectra (400 to 750 nm). The decrease or increase of the graphitic N centres into the CDs led to the green and orange emission, respectively. Because the graphitic N creates mid-gap states within the HOMO−LUMO gap of the pristine CDs, as a result, the light absorption is red-shifted which gives rise to the low energy fluorescence in the visible spectrum. These as synthesized CDs show direct and ideal WLE both in solution and in solid forms with CIE value of (0.33, 0.34) and high colour rendering index (CRI 92). These CDs can form transparent and efficient WLE film with long term stability, when they are mixed in the polymer matrix and excited via UV light. This study provides an important guiding principle for CDs syntheses for realizing spectrally tuned emission and direct WLE.

Even though various porous adsorbents have been examined as NH₃ capture applications, these materials generally displayed insufficient NH₃ uptake, low affinity at the ppm level, and poor chemical stability against humid NH₃. Herein, we report the NH₃ capture properties of iso-reticular series metal-organic frameworks M₂(dobpdc) (M= Mg, Mn, Co, Ni, and Zn) that contain open metal sites. Among the series, the Mg analogue recorded highest ammonia uptake, outperforming any other existing benchmark materials with 23.9 mmol g^-1 at 1 bar and 8.25 mmol g^-1 at 570 ppm in ambient temperature. From the NH₃-temperature programmed desorption curves we could compare the strength of the interaction between NH₃ and Lewis acidic open metal sites and activation energy of desorption of NH₃, which was further supported with van der Waals-corrected density functional theory calculations. The structural stability of Mg₂(dobpdc) upon exposure to wet NH₃ was superior to that of the other M₂(dobpdc) and the frameworks tested, displaying intact structural integrity over 3 days. The NH₃ breakthrough experiments in humid conditions revealed that Mg₂(dobpdc) could selectively capture NH₃ in wet conditions without structural degradation or capacity loss for multiple cycles. The NH₃ adsorption mechanism of Mg₂(dobpdc) in dry and wet conditions was elucidated with in-situ FT-IR spectroscopy, showing that ammonium ion was accompanied in wet condition. To summarize, these results demonstrated that Mg₂(dobpdc) is a recyclable compound that selectively capture NH₃ with significant NH₃ affinity and capacity. We envision that Mg₂(dobpdc) is promising candidate for real-word NH₃-capture applications.

Multi-shell fullerenes, known as carbon nano-onions (CNOs) discovered by Ugarte in 1992, are structured by concentric shells of carbon atoms. Different methods for their synthesis have been developed and their properties have been widely studied. The chemical functionalization of CNOs has been investigated and several synthetic pathways were found to be applicable for the introduction of a variety of functional groups. CNOs exhibit poor solubility in both aqueous and organic solvents due to aggregation. This is promoted by strong intermolecular interactions such as van-der-Waals forces. To overcome this tendency to aggregate, functionalization of the surface of the carbon materials is the method of choice. The purpose of this project is to make the oxidized CNOs bear a relative centrifugal force at different time durations. Analyzing between two functionalizing methods, furnace and via synthesis. How well the material disperses, provides a fundamental concept for the synthesis efficiency. According to preliminary results, there is a tendency on which the concentrated CNOs (obtained via synthesis) difference in weight gets narrow, as duration of the centrifugal force increases. Because of their structure, high conductivities, and dispersion properties, CNOs acquired by synthesis are often used as conductive additives in electrochemical energy storage devices, such as battery and supercapacitor electrodes, where an increase in the rate performance (power) of the device is necessary. Chemically modified CNOs were probed in different fields of application and have revealed to be a promising nanomaterial that attracts a growing interest among researchers and opens new avenues for investigation. CNOs can be implemented as a catalytic support. In addition, this material can be used as a metal-free catalyst that can increase its catalytic performance by doping with polymers providing nitrogen or phosphorus atoms to the surface. Both methods start using nano-diamonds; a carbon nanomaterial of strong structure which undergo a temperature of approximately 1650°C inside a furnace to obtain the CNOs structure. The CNOs oxidized through synthesis requires a constant temperature and stirring to attain oxygen based functional groups. The preliminary elemental detection of oxygen atoms was gathered by Energy-Dispersive Spectroscopy. To detect states in the CNO’s molecular system, Raman Spectroscopy was utilized to confirm the carbon structure of CNOs by the identification of the peaks D and G characteristic of this carbon material. An in-depth characterization analysis was done using X-Ray Diffraction, providing detailed information about chemical composition, and crystalline structure. The morphology and microstructure of CNOs were studied using a Transmission Electron Microscope and Scanning Electron Microscopy.

Elemental carbon has important structural diversity, ranging from nanotubes through graphite to diamond. Previous studies of micron-size core\rim carbon spheres extracted from primitive meteorites; whose isotopic signatures indicate an origin in red-giant star nucleosynthesis [ApJLett 578 L152 (2002), Elements 10 441 (2014)], suggest they formed around such stars via the solidification of condensed carbon-vapor droplets, followed by gas-to-solid carbon coating to form the graphite rims. Similar core\rim particles result from the slow cooling of carbon vapor in the lab [Hundley LPSC 2018 HAL-02238804]. Although experimental indications from particle slicing suggest that this core material may not have special strength, it’s properties as a diffusion barrier may be quite interesting if one can synthesize material with graphene sheets as large (e.g. 600 atoms or 4 nm widths) and abundant (e.g. 6x1019/cc) as we find in the presolar cores [M&M 26 2838 (2020)]. Although we’ve not yet done any percolation theory modeling, the small size of pores in a single graphene sheet [Nature 579 229 (2020)] suggest that this material may be able to stop diffusion of even small atoms like helium over astrophysical (not just geologic) time scales. Before working on oven design, we first want to model nucleation and growth as a function of time at temperature to see what laboratory conditions are likely to be required. This is also relevant, of course, for astrophysicists in understanding conditions of carbon condensation around the types of stars that created the carbon atoms of which we are made [COSPAR 2021]. Our preliminary results suggest that the presolar cores solidified over longer times (say tens of seconds) at lower temperatures (say 2400K) compared to the laboratory cores (say tenths of seconds) at higher temperatures (say 3050K). The analytical models so far follow the “few parameter” approach of Turnbull and Fischer [JChemPhys 17 71 (1949)] for reaction (not diffusion) limited nucleation & growth. Using this model, with preliminary energy values extracted from atomistic data and/or experimental constraints in the lab-grown case, we generated an analytical growth model to compare with pre-solar and lab-grown data, which gave us the above-quoted preliminary numbers. We looked at our “liquid model” systems for set temperature molecular dynamics anneals at experimentally-estimated densities of 1.8 g/cc. Our system had a 42-atom graphene sheet with the rest of the liquid atoms randomly placed with a nearest neighbor > 1.9 Å. Looking at 2D growth, we see when at temperatures ranging from 1700 – 4200 K the growth rate increases as temperatures increase. Future work to refine these models will hopefully generate better-constrained energy values from our atomistic simulations, to use with such analytical models. Along with this, downward temperature ramps will be examined instead of fixed temperature anneals as rates of cooling are likely the key parameter in both laboratory and astrophysical settings. We will also be looking at models for supercooling thresholds with containerless liquid metals –[Nucleation in Condensed Matter (2010)] and the uses of dynamical atomistic models of both nucleation and growth [JPetrology 54 913 (2013), Handbook of Continuous Crystallization (2020)].

Development of human-interactive display enabling the simultaneous sensing, visualisation, and memorisation of a magnetic field remains a challenge. Here we report a skin-patchable magneto-interactive electroluminescent display, which is capable of sensing, visualising, and storing magnetic field information, thereby enabling 3D motion tracking. An alternating current (AC) EL display is developed with a magnetoactive conductive fluid of multi-walled carbon nanotubes (MWNTs), decorated with superparamagnetic iron oxide (Fe3O4) nanoparticles, in n-hexadecane on which an AC-field responsive emissive layer is placed with two parallel electrodes. By constructing mechanically flexible arrays of magneto-interactive displays, a spin-patchable and pixelated platform is realised. The magnetic field varying along the z-axis enables the 3D motion tracking (monitoring and memorisation) on 2D pixelated display. This 3D motion tracking display is successfully used as a non-destructive surgery-path guiding, wherein a pathway for a surgical robotic arm with a magnetic probe is visualised and recorded on a display patched on the abdominal skin of a rat, thereby helping the robotic arm to find an optimal pathway.

Radiative cooling allows for effective dissipation of heat into deep space, making it an environmentally clean as well as passive cooling technology. It has been shown to be effective at reducing energy consumption from the cooling requirements of many widespread systems including commercial and residential buildings and outdoor electronic equipment. The development of versatile and cost-effective materials with good radiative cooling performance is critical to furthering the range of applications of this technology as well as improving the potential for the technology within existing applications. The BaSO₄ nanoparticle-embedded coatings we have developed have consistently shown strong radiative cooling performance with a solar reflectance of greater than 95% and an emissivity of greater than 0.90 in the "sky window", which is the region of the atmosphere that is transparent (corresponding to 8-13 μm wavelengths). These performance parameters demonstrate these coatings to be a potentially promising material to continue to study for radiative cooling applications. Specifically, it is also highly desirable to reduce the coating thickness and preserve the high performance. Doing so promotes cost-effectiveness and maintains energy savings that the material can provide. The work presented demonstrates a thin and cost effective dual-layer BaSO₄-paper structure with a high radiative cooling performance. We have coated BaSO₄-nanoparticle–embedded layers with varying thickness on transparency films or commercial cotton-based paper, which allowed us to form a series of dual-layer thin films. Their spectral and total optical reflectance, transmittance and absorptance (or emissivity) are characterized across the ultraviolet, visible, near-infrared and mid-infrared wavelength range. The results allow for the decoupling of the effects of the developed BaSO₄ nanoparticle-embedded coatings from the effects of moderately-to-highly reflective substrates they may be applied over, demonstrating the effectiveness of the coatings themselves for radiative cooling applications versus other surfaces that appear visually similar. Furthermore, the transparency film substrates alone show high emissivity in the sky window but low reflectance in the solar spectrum, while the inexpensive and widely-available commercial cotton-based paper shows high emissivity in the sky window and moderately high reflectance in the solar spectrum. We have been able to demonstrate that by coating the paper with just a thin layer of our BaSO₄-based nanocomposites, we can significantly increase its radiative cooling performance to be comparable with other state-of-the-art approaches. This is demonstrative that the developed BaSO₄ nanoparticle-paper dual-layer film could be a cost effective and high performance radiative cooling material at small thicknesses.

A key step to assure the practical application of Li-air batteries involves replacing O₂ with air due to their expected high practical specific energy densities from 1000 to 2000 Wh kg^-1 which could even match with 1700 Wh kg^-1 of the gasoline energy system. The Lithium-air batteries involve the oxygen reduction reaction (ORR) during the discharge and the oxygen evolution reaction (OER) in the charging process thus structured ORR/OER electrocatalyst greatly governs the performance of the battery. The promising 2D materials like MXene gained much attention over recent years due to the displayed properties of both ceramics and metals, such as high electrical and thermal conductivity, certain softness, unusual damage tolerance, as well as excellent oxidation resistance, and withstand the volumetric expansion during lithiation. In order to maximize the benefits of MXene, the utilization of 3D MXene could further provide a larger surface area with high exposed specific active sites, high robustness, and 3D conductive network. In this study, we accessed the promise of incorporating the active and stable oxygen vacancies in Brown TiO₂ into the novel 3D network of MXene which is believed to accelerate the Li₂O₂ formation and decomposition by lowering the reaction energy barrier of the reversibly decomposing discharge products. Coupled electrochemical and spectroscopic analyses in the present study disclose the systematic discharge formation and decomposition through the controlled tailoring of active vacancy sites as well as manipulating the morphology of novel 3D MXene network.

Heterojunction design is an effective strategy for seperation of photogenerated charges and reduce recombination in a semiconductor. In the nanostructured form, such heterojunctions have the added advantage of higher specific surface area that serves as efficient catalyst , chemical sensors etc. CuO and Cu₂O , both p type materials with the band gap values of 1.6 and 2.1 eV respectively, form type II heterostructure , wherein electrons and holes are favorably seperated and migrate in opposite directions. The heterojunctions between these materials have been studied in planer or thin film configuration. Here we present fabrication of Cu₂O nanowire- CuO nanoflake heterojunctions fabricated by a combination of electrochemical anodization followed by hydrothermal porcessing techniques. The Cu₂O nanowires formed by electrochemical anodization of Copper foil are treated in hydrothermal conditions at 150 ^oC to grow CuO nanoflakes in a perpendicular direction on the nanowire surface. Such nanoscale 3D morphologies result in a photocurrent an order of magnitide higher than bare Cu₂O nanowires. The heterojunction system is characterised by x-ray diffraction, scanning and transmission electron microscope, optical absorption spectrocopy and photoelectrochemical impedance spectroscopy. Our investigations indicate that, in addtion to solar energy harvesting, the Cu₂O-CuO nanostructured heterojunctions can also be potentially effective in rechargable batteries and supercapacitpr applications.

Magnetic nanoparticles can exhibit a property known as superparamagnetism where they have extremely high susceptibility and a complete absence of magnetic hysteresis. This would represent an ideal inductor or transformer material if it could be maintained in a bulk material. To do this, magnetic nanoparticles must be densely packed without touching, as contact would lead to the formation of ferromagnetic domains and loss of superparamagnetism. The formation of bulk superparamagnetic materials can be discussed in terms of two fundamental steps. The first is the large-scale synthesis of precisely size controlled magnetic nanoparticles, and the second is the densification of these particles into a highly magnetic material. The properties of magnetic nanoparticles vary dramatically with size, with an abrupt transition from superaparmagnetic to ferromagnetic behavior. The highest magnetic susceptibility, however, is typically found just before this transition to ferromagnetism. Therefore, careful control of particle size and reproducibly of particle size are critical for real world application. The chose approach here is high temperature decomposition reactions with precise control over reaction kinetics. The second required step is densification while maintaining a critical separation. As particles move closer together, they undergo an abrupt transition where they begin forming multi-particle ferromagnetic domains. An ideal nanocomposite would be close to this critical distance to maximize magnetic particle loading without showing deleterious interparticle magnetic interactions. Careful control of the particles’ surface chemistry and appropriate chemical crosslinking can generate strong nanocomposites with excellent magnetic properties that extend to the MHz frequency regime with low losses and little to no decrease in susceptibility. We have designed and synthesized a number of these composites and are currently investigating their application in high frequency switching circuits for power electronics. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

The structural, magnetic and microwave characteristics of Sr_0.5Ba_0.5Sm_0.02Fe_11.98O₄ (SrBaSmFe) and x(Ni_0.8Zn_0.2Fe₂O₄) (NiZnFe) 1:x (0.0 ≤ x ≤ 3.0) hard/soft ferrites nanocomposites (NCs) are presented in this study. SrBaSmFe/x(NiZnFe) hard/soft ferrite NCs were synthesized applying one-pot citrate combustion approach. The structural analyses of all NCs were performed via XRD, SEM, TEM and HR-TEM. Room temperature (RT) 300 K and 10 K magnetization curves were investigated by VSM measurements. Both RT and 10 K magnetization and coercivity data have maximum values for SrBaSmFe/1.0(NiZnFe) NCs (i.e. x = 1.0) and continuously reduce with the increasing weight fraction of NiZnFe soft ferrite. Some magnetic hysteresis loops are seen with a kink shape. Magnetic analyses revealed the ongoing hard ferrimagnetic nature of NCs at both temperatures. Squareness ratios (SQRs) were specified to be inferior to the theoretical limit value of 0.50, assigning the multi-magnetic domain nature for NCs. The plots of switching field distribution (SDF) showed the presence of two distinct peaks. This means that the exchange coupling was not accomplished in these NCs by one-pot approach. Frequency dependence of microwave characteristics were discussed utilizing co-axial method in frequency range 0.7-18 GHz. Non-linear dependences of the main microwave properties with varying composition rate might originate from the soft magnetic phase influence. Behavior of the microwave properties are correlated well with the composite theory.

The COVID-19 pandemic highlighted the necessity to develop rapid in situ viral detection techniques to isolate infection breakouts. Current biochemical detection techniques, such as polymerase chain reaction (PCR), remain inadequate for initial response due to the delay associated with sequencing the viral genome and reagent development. Alternatively, physical properties of the virus such as mass and size can be quickly profiled and utilized for rapid detection using mass spectrometry (MS). The recent developments in Nanoelectromechanical Systems (NEMS) have made it possible to measure the mass of single particulates with high accuracy; however, significant challenges still exist in adapting NEMS-MS for real-life samples. Sample delivery to the sensing element generally requires the use of delicate vacuum systems and the sensing element suffers from low capture efficiency due to its miniscule size. Here, we develop a NEMS-MS device with an integrated polymeric electrostatic lens to enhance the capture efficiency by several orders-of-magnitude compared to the state-of-the-art, while allowing for operation under atmospheric conditions. After benchmarking and validating device performance with polystyrene and gold nanoparticles, we successfully detected the mass of single inactivated SARS-CoV-2 virions from cell lysates with minimum sample preparation. The results establish NEMS technology as an effective approach for the label-free detection of nanoparticles and emerging viruses.

Nowadays, separation of chemical elements is an important stake for applications as broad as ore mining, metal recycling or pharmaceutical industry. Although liquid-liquid extraction represents the most applied method at industrial scale, it involves many economic and environmental constraints related to the use of large quantities of solvents. There is therefore a growing interest for alternatives as solid-liquid separation and flotation processes, which however, would require re-designing the actual industrial installations. These alternatives present moreover limited performances, in terms of extraction and selectivity capacities. This project proposes to evaluate a new approach by replacing the organic phases of liquid-liquid extraction processes, with a porous liquid. The Oak Ridge Corporation proposed in 2014 [1], a new class of porous liquid, based on hollow silica nanospheres (HS) obtained by a surfactant templated silica sol gel. To form the “liquid material”, the HS are grafted with an organosilane and a PEG. This ionic bond between the functions gives the interesting property to render the HS liquid and to provide solid empty cavities in a liquid state, without any solvent. In this work, we evaluate the application of such liquid empty cavities to extract metals from an aqueous phase. This extraction approach would be at the exact junction between the conventional liquid-liquid and solid-liquid extraction processes, taking the advantages of the two processes.
To form the porous liquid, HS were prepared thanks to the self-assembly of a surfactant in presence of oil and silica precursors. After the synthesis, the surfactant is removed by calcination and monodisperse HS are made. Various synthesis parameters were investigated to control and understand the morphology of the HS. Indeed, the size of the core, the shape and the homogeneity of the particles could be changed and controlled.
TEM micrograph and SAXS data showed that we obtain highly monodisperse HS with a core radius of 6nm and silica shell of 7nm.
The HS are further grafted with an organosilane and a PEG interacting thanks to an ionic bond. This ionic corona has the property to turn the solid nanospheres into a liquid material.
For extraction application, it appears essential to characterize in details the structure and the permeability of these HS, not only to metallic species but in the first place, to aqueous solutions and gaz.
In order to optimize the synthesis route for enhanced permeability, adsorption of argon and nitrogen were carried out with the solid and the liquid to highlight the accessibility to gas of the porosity throughout all the steps of grafting. Gaz sorption reveals that the porosity is becoming less accessible after the grafting step, which means when the solid becomes liquid. This first result showed that the synthesis procedure has to be optimized to limit this loss of opened porosity (which may be due to a closure of the microporous network present in the silica shell of the HS).
An adsorption study was also conducted with liquid solutions by matching the contrast of various solvent and silica by SAXS and SANS to rely the permeability and the pores structure. The SANS signal of the non-grafted HS was completely extinguished with a H₂O/D₂O ratio matching the scattering length density of nanosphere’s silica. It allowed us understanding the permeability of reference HS to solvent, specifically if and how the grafting influences the solvent permeability.
Finally, some preliminary extraction tests performed on the solid non-grafted HS, showed that significant amounts of metallic cations can be extracted.
This study confirm that all the synthesis process has to be optimized and understood to maintain the extraction efficiency of the material when it is in the liquid state.
References
[1] J. Zhang, “Porous liquids: a promising class of media for gas separation” in Angew. Chem., 127, pp 946-950 (2015).

Recently there has been a renewed interest in exploring novel materials with a large magnetocaloric effect (MCE), due to the fact that solid magnetic refrigeration potentially could replace gas refrigerants. The ferromagnetic perovskite manganites have drawn attention due to its outstanding physical properties as this system displays a rich phase diagram in the magnetotransport, structural properties, and magnetocaloric. The typical way to enhance the MCE is to introduce an insulating phase to the grain boundaries and at the surfaces of manganites as a second phase. Therefore, the composite of the high resistive second phase compound and manganite could be an effective route to improve the MCE properties. In this view, the study is being conducted to understand the impact of the second phase (SrFe₁₂O₁₉) on the magnetization and magnetocaloric effect of the La_0.7Sr_0.3MnO₃ manganites. With the possibility of the exchange interaction between soft LaSrMnO₃ and hard-SrFe₁₂O₁₉, a modulation in MCE in the composite is expected.
One-pot auto-combustion technique followed by calcination at 1100 C was used to prepare magnetically hard-soft xSrFe₁₂O₁₉-x (100-x) wt % La_0.7Sr_0.3MnO₃ (x=0, 10, 20, 30, 40, 100) nanocomposites using nitrite salts. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structural properties of the samples. The XRD plots showed no trace of secondary phases in the composite. The hexagonal structure (spacegroup-P63) of SrFe₁₂O₁₉, as well as the perovskite cubic structure (spacegroup-Pm-3m) of La_0.7Sr_0.3MnO₃, were confirmed. Furthermore, magnetic and magnetocaloric properties were studied using SQUID analysis. An exchange coupling behavior was obtained between the soft LaSrMnO₃ and the hard SrFe₁₂O₁₉ phase. Magnetic isotherms are being collected using PPMS to study the magnetocaloric effect in the as-synthesized composites.

Monte Carlo simulations were performed to study the effect of magnetic molecule induced exchange coupling on the magnetic properties of the magnetic tunnel junction based molecular spintronics devices (MTJMSD). We considered all the possible permutations and combinations and nature of interactions between a paramagnetic molecule and the two ferromagnetic (FM) electrodes of an MTJMSD to understand the experimental results. Experimentally observed molecule induced strong antiferromagnetic coupling was only possible when a molecule, with a net spin state, established ferromagnetic coupling with one FM electrode and antiferromagnetic coupling with the other FM electrode. Our MC simulations effectively explain the origin of the experimental data obtained from SQUID magnetometer, ferromagnetic resonance, and MFM studies on MTJMSD. The experimentally estimated molecular coupling strength was in agreement with our results of MC simulations. Increasing MTJMSD size was found to weaken the molecular coupling effect. However, it is quite possible that we underestimated the impact of molecular coupling on the MTJMSD size. In this study, we mainly focused on the Heisenberg type magnetic interaction among nearest neighbors. In reality, molecules are expected to have other modes of couplings such as biquadratic coupling, dipolar coupling, and most importantly paramagnetic molecules are also capable of invoking spin fluctuation assisted coupling between two FM electrodes

Covalently bonded Paramagnetic molecular bridges between two ferromagnets (FM) electrodes of a magnetic tunnel junction (MTJ) may enable highly efficient spin transport properties for futuristic computers. The MTJ based molecular spintronics device (MTJMSD) approach can solve the decades' long problems of fabricating robust and mass-producible molecular spintronics device[1]. MTJMSD provides opportunities to connect FM electrodes of a vast range of anisotropy properties to a variety of molecules of length scale. Our prior studies showed that the paramagnetic molecules can produce strong antiferromagnetic coupling with FM electrodes when the molecule establishes a ferromagnetic coupling with one FM electrode and antiferromagnetic coupling with another FM electrode of an MTJ[2]. The device properties of MTJMSD depends upon various factors such as the anisotropy of the FM electrodes, thermal energy (kT), ferromagnet-molecular coupling strengths, spin states of molecules, etc. In this paper, we report a theoretical Monte Carlo Simulation (MCS) study to explain the impact of anisotropy on the MTJMSD equilibrium properties and related experimental observations[3]. Our MCS also studied the impact of thermal energy (kT). The MTJMSD used in this study was represented by an 11x 50 x 50 Ising model, with 11 being the thickness of the MTJMSD and 5x10x50 being the size of each electrode. We ran Markov process for 200 to 500 Million iterations to reach the equilibrium state and record MTJMSD properties such as magnetization of each electrode and complete device. We also studied the energy variation of the MTJMSD system with time as a function of FM electrode anisotropy. We found that increasing anisotropy strength starts exhibiting diverse domain structures within an FM electrode. Increasing anisotropy was found to create stripe-shaped domains with opposite spins. These phases are impacting the overall magnetic properties of the FM electrode where anisotropy was varied. At kT = 0.1 we observed that for the high anisotropy magnitude the magnetic moment of the FM electrode settled close to zero. Our MCS study agreed with the experimentally observed stiped domain on MTJMSD and Magnetic force microscopy data[4]. MCS study showed that the anisotropy was the most influential parameter in defining the properties of MTJMSD. The effect of anisotropy enabled MTJMSDs to compete with the increasing thermal energy. High anisotropy enabled MTJMSD to conserve a high magnetization state close to Curie temperature. Anisotropy factor was instrumental even when all the coupling effects get nullified due to thermal energy induced disorders in the MTJMSD. These MCS studies are expected to inform the designing of the MTJMSD for the logic and memory operation.

This research is supported by National Science Foundation-CREST Award (Contract # HRD- 1914751), Department of Energy/ National Nuclear Security Agency (DE-FOA-0003945).


[1] P. Tyagi, Multilayer edge molecular electronics devices: a review, Journal of Materials Chemistry 21(13) (2011) 4733-4742.
[2] P. Tyagi, C. Baker, C. D’Angelo, Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device, Nanotechnology 26(30) (2015) 305602.
[3] M. Newman, G. Barkema, Monte carlo methods in statistical physics chapter 1-4, Oxford University Press: New York, USA1999.
[4] P. Tyagi, C. Riso, Magnetic force microscopy revealing long range molecule impact on magnetic tunnel junction based molecular spintronics devices, Organic Electronics 75 (2019) 105421.

Colloidal magnetic nanoparticles (MNPs) of metal oxides are becoming increasingly important for applications such as biomedical imaging, sensing, drug delivery, and hyperthermia. These exploit the very soft magnetism found in nanoscale ferrimagnets, often ferrites, which yield a strong collective response to applied alternating (AC) magnetic fields while simultaneously remaining dispersed in media. Their synthesis relies on reproducible, scalable, colloidal solution chemistry routes. Further, the size, shape, structure, and composition are tunable, which serve as levers to design and manipulate the magnetic behavior of these functional nanoparticle materials.

Remote 3D magnetic thermometry is an emerging application of MNPs. The technique employs colloidal nanoparticles to measure and image temperature remotely with high spatial resolution throughout a three-dimensional volume. This metrology is based on the temperature-dependent nature of the particles’ magnetization, their dispersibility throughout a liquid or solid of interest, and the ability of applied AC magnetic fields to penetrate through many materials. Although progress has been made in the development of magnetic nanothermometry, commercially available MNPs often lack several properties necessary for widespread application, including particle-to-particle consistency, thermosensitivity response, and a non-exothermic response to applied AC magnetic fields.

Here, we report colloidal MNPs specifically designed for remote 3D thermometry. A series of shape- and size-controlled colloidal MNPs based on ferrites were synthesized via the thermal decomposition of organometallic precursors. Further, we exploited compositional doping of transition metal elements and exchange coupling between core-shell magnetic heterostructures as means of generating improved temperature-dependent magnetization (200-400 K at <0.001 T applied AC field) from designed spin interaction within the nanoparticles. Extensive structural characterization was performed to better understand the underlying factors influencing the magnetic response. Results collected from X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution electron microscopies, including spatially resolved electron energy loss and energy-dispersive X-ray spectroscopies, revealed correlations between the nanoscale atomic structure of these particles with their magnetic performance. Finally, we used a home-built AC magnetic particle spectrometer to determine the magnetization-dependence of these nanothermometers as a function of temperature, frequency, and field amplitude. These studies allow us to interrogate the fundamental response dynamics of dispersed and deposited magnetic nanoparticles under AC driving fields. Collectively, we show that carefully designed complex metal oxide MNPs display tunable thermosensitivity and AC field signal response, which represents a potential pathway to the implementation of a practical 3D thermal imaging platform based on magnetometry.

Molecules are highly tunable nanostructures because synthetic chemistry can customize their optical, electrical, and magnetic properties. Thus, molecules used as active device elements open a new pathway towards the miniaturization of advanced logic and memory devices, as well as a new class of metamaterials altogether [1]. The anticipation is that molecular electronic devices will function at significantly low power and reach the ultimate device size limits [2]. Prior research [3] shows that when molecules are bridged between two ferromagnetic electrodes they can serve as novel molecular spintronics-based magnetoresistance devices. Moreover, when the molecule itself possesses a net magnetic spin and interacts with the electrodes' spin state, more dramatic results are observed. With the magnetic tunnel junction based molecular spintronics device (MTJMSD) we observed paramagnetic molecules produced strong exchange coupling between ferromagnetic electrodes. MTJMSD is fabricated by chemically bonding the molecular channels to the ferromagnetic electrodes of a prefabricated magnetic tunnel junction [4]. We observed that molecule impact was dependent on the type of MTJMSD’s ferromagnetic electrodes [5]. However, it is challenging to experimentally study the effect of a wide range of ferromagnetic electrodes on MTJMSD properties. This paper discusses our Monte Carlo simulation study focusing on understanding the effect of ferromagnetic electrodes on magnetic and physical properties of MTJMSD. This paper utilized the 3D Ising model to realistically simulate the experimentally studied MTJMSD design. We varied the Heisenberg exchange coupling parameter for the MTJMSD’s two ferromagnetic electrodes. This variation simulated the ferromagnetic electrodes with low to high Curie temperature. We recorded the evolution of MTJMSD magnetization with time and observed the impact of ferromagnet type on the nature of evolution of equilibrium state. We varied thermal energy to understand the role of ferromagnetic electrode type on MTJMSD. We also studied the effect of molecular coupling strength in conjunction with the ferromagnetic electrode’s Heisenberg exchange coupling. We have recorded spatial distribution of the magnetic moment of the ferromagnetic electrodes to elucidate the impact range of molecules as a function of ferromagnetic electrode type.

This work is supported by National Science Foundation-CREST Award (Contract # HRD- 1914751), Department of Energy/ National Nuclear Security Agency (DE-FOA-0003945).

References
1. Bogani, L. and W. Wernsdorfer, Molecular spintronics using single-molecule magnets. Nature Materials, 2008. 7(3): p. 179-186.
2. Tyagi, P., C. Riso, and E. Friebe, Magnetic Tunnel Junction Based Molecular Spintronics Devices Exhibiting Current Suppression At Room Temperature. Organic Electronics, 2019. 64: p. 188-194.
3. Rocha, A.R., et al., Towards molecular spintronics. Nature Materials, 2005. 4(4): p. 335-339.
4. Tyagi, P., Multilayer edge molecular electronics devices: a review. Journal of Materials Chemistry, 2011. 21(13): p. 4733-4742.
5. Tyagi, P., C. Baker, and C. D’Angelo, Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device. Nanotechnology, 2015. 26(30): p. 305602.

Multicomponent and high entropy alloys (HEAs) are a novel class of metallic material systems in the field of materials science and engineering. Such alloys are comprised multiple principal elements with various multicomponent compositions. HEAs are typically formed at elevated temperatures and require high-energy systems to promote high entropy of mixing and ensure equimolar concentration and distribution. However, our study investigated the idea of distributing metal ions inside a hydrogel nanofiber (NF) at ambient temperatures, with random probability and high entropy via absorption and strong interactions in the NF. The subsequent reduction of the metal ions and the formation of nanoparticles (NPs) in the NF will be influenced by this distribution, leading to the potential for kinetic control of HEA NPs. In this study, we have produced the quinary CoCrFeMnNi nanoalloy particles in stable flexible electrospun hydrogel fibers composed of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). The metal ions were loaded into the NFs by immersion into a solution mix containing the required metal salts, followed by chemical reduction to form the metal NPs. The composition of the metal in the alloy could be tuned by varying the metal salt ratio. The proposed method resulted in random capturing by the carboxyl groups of PAA where the metal ions were kinetically trapped and in minimizing the coalescence of the reduced metals. The hydrogel fiber matrix also allowed for aqueous absorption and provided a viscous environment to promote particle formation in the small diameter range. The fabrication process is beneficial in terms of controllability, simplicity and versatility. The HEA NP loaded fiber composite was characterized for alloy morphology and distribution, electronic states and overall composition. The structural and functional capabilities of the multicomponent nanoalloys create high-performance materials applicable in the aerospace, catalysis and energy industries. Catalysis is one field of interest to incorporate multicomponent nanoalloy composite because the various constituting metals enable an enhanced and more selective catalytic property when compared to monometallic NPs.

Fog formation is often unforeseen and rather hard to predict due to the thermodynamics and kinetics of fog formation overland type and surrounding air conditions Reduced visibility is one of the substantial causes of vehicular crashes. Despite having multiple meteorological equipment types for measuring and studying fog characteristics, many are suitable only for marine environments and ports. The current state-of-the-art real-time scattering of the light-based roadside fog detection system is riddled with false-negative and false-positive identifications. Considering this situation, we report a novel Upconverting nanoparticles (UCNPs) cameras-based fog sensor concept that is easy and cost-effective for roadside deployment. For the upconverting application, we have fabricated NaYF₄ (Yb, Er) nanoparticles using a facile hydrothermal based route. It has a primarily β- NaYF₄ (hexagonal) phase with an average particle size of around 15 nm and 5 nm and fluorescence spectroscopy showing multiple emission in blue-green-red spectrum with an excitation from NIR light (980 nm).
To eliminate false negatives/positives results, our sensor methodology utilizes two fog detection methods. First, based on Koschmieder’s law, it involves estimating visibility conditions and scattering light due to fog, and the second one based on contrast change of an engineered object in the field of view of a traffic camera. NIR light within a black background with UCNPs (in front of the camera utilized in a thin film outside of the front of the camera lens) acts as both a scattering source and an object for contrast measurement. UCNPs also take care of the automatic NIR light filters, common in roadside cameras during daytime use. We have observed fog detection at levels 1-6 (Thick fog to light haze) of the International visibility code at both day and nighttime conditions using the synergic complementary scattering-contrast measurement approach.

Metal-organic frameworks (MOFs) is a new type of adsorbents for removing CO₂. In particular, M₂(dobpdc) shows high performance in CO₂ capture. Shaping of M₂(dobpdc) is important for practical applications. Here, we present a scalable synthesis method for Mg₂(dobpdc) MOF and its shaped beads, which are obtained by using a spray dry method after mixing Mg₂(dobpdc) powders with alumina sol. The synthesized Mg₂(dobpdc)/Al beads have micron-sized diameters. In addition, N-ethylethylenediamine (een) functionalization and coating with long alkyl chain silanes results in een-MOF/Al-Si, which shows high CO₂ uptake and hydrophobicity. The een-MOF/Al-Si microbeads maintain their crystallinity and enhanced CO₂ uptake upon exposure to humid conditions for three days at a high temperature. More details can be found on the poster.

Flexible wearable sensor are widely reported as emerging tools for target diagnosis and healthcare management, mainly for detect biomarkers in various body fluids.[1] Place the sensing element on the skin and engineering a detector that can sense glucose without piercing the skin in real time. The rational design of sensing element is the key for the sensing performance of wearable electrochemical sensors.[2] Carbon materials (graphene, carbon nanotubes, carbon nanofibers, etc.), macromolecule polymers, metallic materials, and biological enzyme-based materials are used as highly efficient functional materials for biosensor with high sensitivity and low detection limit, but poor stability, inferior electrical conductivity, limited flexibility still hinder their practical application. [3-5]
Metal–organic frameworks (MOFs) have attracted considerable attention because their uniform-structured cavities and open channels pave the way for entering and escaping molecules. In particular, MOFs and transition metal-MOFs have been used as various sensors, such as gas sensors, DNA sensors, and glucose sensors.[6] In recent years, Co and Fe are an interesting transition metal that has catalytic activity for glucose oxidation due to the excellent catalytic performance and electronic properties.[7,8] Herein, we describe the development of cobalt-foil MOF nanowire array on ultrathin copper foam (Co-Fe MOF/CF) via hydrothermal method possesses high catalytic activity towards glucose electro-oxidation. Benefits from synergies between bimetals, this electrode shows a short response time of less than 3 s, a wide linear range of 0.04–7 mM, a low detection limit of 0.1 μM (S/N = 3), and a higher sensitivity of 4424.9 μA mM^–1 cm^–2, as well as satisfactory reproducibility,stability and selectivity. In general, our work provided an effective and stable flexible biosensor for the detection of small biological molecules which overcomes the disadvantages of traditional enzyme-based materials. This non-invasive electrochemical biosensor is expected to have considerable applications in personal health monitoring applications,sport and military applications.

References:
[1] Anneng Y., Feng Y. Flexible electrochemical biosensors for health monitoring. ACS Appl. Electron. Mater., (2020) DOI:10.1021/acsaelm.0c00534.
[2] Huanfen Y. et al. A contact lens with embedded sensor for monitoring tear glucose level. Biosens. Bioelectron., 26, (2011) 3290–3296 .
[3] Songyue L. et al. A flexible and highly sensitive nonenzymatic glucose sensor based on DVDlaser scribed graphene substrate. Biosens. Bioelectron., 110, (2018) 89–96 .
[4] Su-Kyoung K. et al. Hyaluronate−Gold Nanoparticle/Glucose Oxidase Complex for Highly Sensitive Wireless Noninvasive Glucose Sensors. ACS Appl. Mater. Interfaces, 11, (2019) 37347−37356 .
[5] Yagmur K. et al. Highly sensitive glucose sensor based on monodisperse palladium nickel/activated carbon nanocomposites. Anal. Chim. Acta., (2018) 1010, 37−43.
[6] Furukawa H., et al. The Chemistry and Applications of Metal-Organic Frameworks. Science, 341, (2013) 1230444.
[7] Yan W., et al. Preparation and characterization of reduced graphene oxide/Fe₃O₄ nanocomposite by a facile in-situ deposition method for glucose biosensor applications. Mater. Res. Bull., 101, (2018) 340–346.
[8] Pengcheng Q., et al. A hierarchical cobalt/carbon nanotube hybrid nanocomplex-based ratiometric fluorescent nanosensor for ultrasensitive detection of hydrogen peroxide and glucose in human serum. Anal. Bioanal. Chem., 411, (2019) 1517–1524.

With the development of soft electronics, an ionic electroactive polymer (i-EAP) actuator has dominated research in various fields because, they provide a lot of advantages such as lightweight, flexibility, simple process, and low operating power. However, many i-EAP studies have demonstrated some drawbacks including low blocking force, displacement and so on, in the utilization of various applications. In order to apply these i-EAP actuators to various fields, it is important to provide the optimum characteristics of the i-EAP actuator suitable for the target application. Among the various applications, for soft haptic feedback, it is required to achieve high blocking force as well as wide bandwidth. Thus, in order to enhance the blocking force of the i-EAP actuator, highly-performance actuators take advantage of inorganic materials having a high mechanical modulus. Although the inorganic material embedded EAP actuator possesses high blocking force, it’s application in soft haptic feedback is questionable due to the narrow bandwidth.
In this work, we described an ionic polymer-metal composite based mechanotransducer (IPMCM), with high blocking force and wide bandwidth consisting of ionic conducting polymer electrodes and a IPMCM material. The composite material based on hydrogen bond increases the actuation performance of blocking force and wide bandwidth through the high modulus of inorganic materials. Also, our actuator could control an interface between ionic polymer and electrodes using conducting polymer (PEDOT:PSS) with ionic liquids and DMSO as additives. As a result, the developed IPMCM with ionic conducting polymer was operated with a wide bandwidth of up to 100 Hz as well as a high blocking force of 1.0 mN. In addition, our ionic polymer-metal composite exhibited the different ion transport mechanism containing inorganic particles with similar activation energy of ionic polymers. We believe that our proposed actuator can serve as an ideal guide to human-machine soft haptic interface.