Symposium S.NM01 : Nanodiamonds—Synthesis, Properties and Applications

Diamond particles hosting negatively charged nitrogen vacancy (NV-) centers have recently emerged as an intriguing platform to dynamically polarize nuclear spins both inside and outside the crystal lattice. This presentation surveys some recent work on the topic by our groups including the development and implementation of spin polarization methods insensitive to the orientation of the diamond particles, as well as proof-of-principle applications such as dual fluorescence and magnetic resonance imaging of diamond particles arrays. Further, we introduce recent observations using particles of varying dimensions down to nm sizes, and show that diamond annealing at elevated temperatures has important effects on the hyperpolarization levels, enhancing them by above an order of magnitude over materials annealed through conventional means. Electron and nuclear spin resonance measurements show this response correlates with NV- and 13C relaxation and coherence times, which points to improved recovery of the diamond lattice from radiation damage.

Detonation nanodiamonds (DNDs) attract much attentions due to the exceptional colloidal properties in aqueous media. In particular, the elementary particles of detonation nanodiamonds (EPDNDs), whose size is within a lower single-digit nanometer, should be a promising component in various fields that include nanoscale medicine. Whereas the characterization of EPDNDs is progressing rapidly^1,2, one of the remaining subjects is the fabrications of organized films of EPDNDs to confirm the agglutination mechanism as predicted based on the interfacial Coulombic interactions³ and to obtain clues to identify the surface structure. Furthermore, it is also beneficial if we can make heterojunctions between organized two-dimensional assemblies of EPDNDs and those of other chemical species.

We have already reported that nanosheets of DNDs are formed at the air/water interface by injecting a well-dispersed solution of DNDs (NanoAmando^®) below a Langmuir monolayer of arachidic acid (CH₃(CH₂)₁₈COOH, C₂₀) at the interface. We have also reported that the floating nanosheets can be transferred onto solid substrates, such as glass, quartz or Si wafers by the modified horizontal lifting method, during which the substrate is lifted up below the nanosheets keeping the substrate surface horizontally to the air/water interface. Since each nanosheet is strip-like or rectangular in shape and is birefringent, we postulate that they are of colloidal crystals of EPDNDs.

By our fabrication technique reported so far, however, we were not be able to fabricate continuous films based on EPDNDs (each nanosheet is isolated on the substrate surface). Therefore, it was practically impossible to perform layer-by-layer depositions to make multi-layered structures. Here we report a successful layer-by-layer depositions of the hybrid EPDND-C₂₀ films onto solid substrates by the Langmuir-Schaefer method, where the substrate is lowered toward the floating film keeping the substrate surface horizontally to the air/water interface and after the substrate touches the film surface, the substrate is lifted up. We would like to discuss the structure and properties of the hybrid EPDND-C₂₀ film based on FT-IR and Raman spectra together with morphological characterizations by atomic force microscopy and optical microscopy.

1) E. Osawa, in S. Soumiya (Eds), Handbook of Advanced Ceramics: Materials, Applications,
Processing and Properties, 2nd Ed., Chap. 2.3, p. 89-102 (Academic Press, Amsterdam, 2013).
2) T. Petit et al., J. Phys. Chem. Lett., 6, 2909 (2015).
3) A. S. Barnard, J. Mater. Chem., 18, 4038 (2008).

Diamond nanoparticles have a diverse array of applications from single photon sources and biomarkers to the seeds for diamond growth. Although there are a wide range of commercial suppliers, the purity of diamond nanoparticles is insufficient for some specific applications such as optical levitation and Coherent Anti-Stokes Raman Spectroscopy (CARS). There is also no commercial supplier for nanodiamonds containing the silicon vacancy centre or newer single photon sources.
In this work the production and purification of novel diamond nanoparticles containing custom colour centres will be detailed. First a diamond film containing NV/SiV centres was grown onto a substrate. Colour centre incorporation was confirmed by Photoluminescence and Hanbury Brown and Twiss measurements. The resulting diamond film was removed from the substrate and milled using a planetary mill based on either steel or SiN. The milled material was purified by acid reflux. To measure particle sizes, different slurries containing the diamond nanoparticles obtained were prepared and characterized by using Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA). XPS was also used to qualify the milling process contamination.
The control of surface sp² and zeta potential will also be demonstrated. Positive zeta potentials in hydrogenated nano- structured carbons could be explained due to the presence of basal planes of graphite which can become protonated. At the same time, sp² carbon creation on diamond nanoparticles surface eases low temperature (500°C) diamond nanoparticles hydrogenation and amination, previously demonstrated for detonation diamond (5nm). Applications of the positive zeta potential in nanodiamond will be proposed.

Applications of optically active point defects, or color centers, in nanodiamond encompass a wide range of disciplines including biofluorescent imaging of cellular components, quantum information data storage, and temperature, pressure, and magnetic sensing. Among the >100 different color centers in nanodiamond, the negatively charged silicon divacancy (SiV^-) is a remarkable single photon emitter whose advantageous optoelectronic properties are utilized in all these applications. Current technologies employ a top down approach of chemical vapor deposition grown (CVD) diamond in combination with ion irradiation and implantation to form the desired color center. CVD grown diamond is very pure, but because of the high energies of the implantation technique, the diamond crystal lattice becomes damaged which requires post processing techniques to correct. Doping diamond at high temperatures and pressures is also difficult due to diamond’s compact atomic lattice and low atomic diffusivities. In this work, we demonstrate a versatile, bottom-up approach to SiV^- fabrication based on molecular doping of amorphous carbonaceous precursors which are converted to diamond at high-pressure, high-temperature (HPHT) conditions (>15 GPa, >1800K) within a laser-heated diamond anvil cell. A molecular dopant, tetraethyl orthosilicate (TEOS), incorporates silicon heteroatoms into the HPHT grown nanodiamond compared to non-doped samples fabricated under similar conditions. Pressure dependent photoluminescence confirms not only the formation of SiV^- (λ ~ 738 nm), it also provides experimental juxtaposition for ab initio quantum cluster calculations modeling the pressure dependence of the center’s zero phonon line (~0.9 meV/GPa). Aberration corrected scanning transmission electron microscopy provides images of the silicon heteroatoms on the surface and the interior of converted diamond material. Scanning transmission x-ray absorption microscopy (STXM) measurements, along with electron energy loss spectroscopy (EELS), suggest limited graphitic surface reconstruction of the diamond nanocrystals, as compared to other nanodiamond synthetic avenues. Ab initio quantum cluster calculations also support the possibility of a graphitic reconstruction of the diamond nanocrystal’s surface along with significant distortions of the cubic diamond crystal lattice adjacent to the reconstruction. These results demonstrate the versatility of this approach to doping diamond and that it can be extended to the formation of more complex color centers in diamond.

Nanodiamond powders produced by detonation synthesis offer a great potential in many applications¹, including novel nanocomposites² and biomedical applications³. In the area of nanocomposites, much of work has been focused on polymer matrix composites, while significantly less has been done with other matrices, such as ceramics and metals⁴. At the same time, nanodiamonds have great potential in reinforcing as well as improving optical properties and wear behavior of metal- and ceramic-matrix composites.
We will review our progress in developing well dispersed nanodiamonds⁵ for composite applications with emphasis on novel and less studied nanodiamond-ceramic and nanodiamond-metal composites. Manufacturing and processing techniques, as well as properties of the composites will be discussed.
Another hot area of applications for nanodiamond is biomedical imaging and drug delivery. We will discuss our recent progress in drug delivery with nanodiamonds, emphasizing the effects of nanodiamond surface chemistry, and present novel processing techniques to produce luminescent nanodiamond particles from HPHT luminescent diamond for bioimaging, labeling, and other applications.

1. Mochalin, V. N.; Shenderova, O.; Ho, D.; Gogotsi, Y., The properties and applications of nanodiamonds. Nature Nanotechnology 2012, 7 (1), 11-23.
2. Mochalin, V. N.; Gogotsi, Y., Nanodiamond–polymer composites. Diam. Relat. Mat. 2015, 58, 161-171.
3. Turcheniuk, K.; Vadym, N. M., Biomedical applications of nanodiamond (Review). Nanotechnology 2017, 28 (25), 252001.
4. Turcheniuk, K.; Mochalin, V. N., Adsorption behavior and reduction of copper (II) acetate on the surface of detonation nanodiamond with well defined surface chemistry. Carbon 2016, 109, 98-105.
5. Turcheniuk, K.; Trecazzi, C.; Deeleepojananan, C.; Mochalin, V. N., Salt-Assisted Ultrasonic Deaggregation of Nanodiamond. ACS Applied Materials & Interfaces 2016, 8 (38), 25461-25468.

The nanodiamond-water interface plays a central role in nanodiamond reactivity in aqueous environment, which is relevant for nanomedicine, photocatalysis or environmental applications. Especially, the generation of solvated electrons can trigger N₂ or CO₂ reduction in aqueous environment, and probably strongly depend on the nanodiamond-water interface.
In this presentation, our latest results related to different spectroscopic approaches to probe the nanodiamond-water interface will be shown. In particular, the different surface reactivity with water related to hydrogen-termination will be compared to oxidized nanodiamond surfaces.
First, the vibrational and electronic structures of water molecules around nanodiamonds were probed by Fourier Transform Infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) directly in aqueous environment.¹ X-ray Photoelectron Spectroscopy (XPS) was also applied under near ambient pressure conditions (few mbar of water) to probe changes of the surface chemistry of nanostructured diamond upon exposure to water.
Finally, transient absorption spectroscopy (TAS) was applied to nanodiamond dispersions. The evolution of the visible light absorption spectra over time with a sub-picosecond time resolution was monitored after excitation of electrons into the diamond valence band using a UV laser pulse. This enables the observation of the emission of solvated electrons from nanodiamonds in water. The effect of surface chemistry on the electron emission will also be discussed.

This work has received funding from the European Union’s Horizon 2020 Program under Grant Agreement number 665085 (DIACAT).

1. Petit, T. et al. Unusual Water Hydrogen Bond Network around Hydrogenated Nanodiamonds. J. Phys. Chem. C 121, 5185−5194 (2017).

Color centers in solids are the fundamental building blocks of various applications ranging from lasers to light emitting diodes and sensors, as well as the foundation of advanced quantum information and communication technologies. Their photoluminescence properties are usually studied under Stokes excitation, in which the emitted photons are at a lower energy than the excitation ones.
We explore the opposite Anti-Stokes process, where excitation is performed with lower energy photons. The process is sufficiently efficient to excite even a single quantum system—the germanium-vacancy center in diamond.
As a proof of concept, we propose using Anti-Stokes excitation of diamond color centers for nanoscale thermometry. We leverage the temperature-dependent, phonon-assisted mechanism to realize an all-optical nanoscale thermometry scheme that outperforms any homologous optical method employed to date. We discuss other potential applications and show that our results frame a promising approach for exploring fundamental light-matter interactions in isolated quantum systems.

Free radicals, by definition containing unpaired electrons, constitute one of the major sources of magnetic signal in live cells. While these molecules are usually considered to be deleterious and are associated with ageing and pathological conditions, certain types of free radicals, such as nitric oxide (NO), perform important signaling functions in live systems. One of the major challenges in understanding the role of free radicals in health and disease is their high reactivity, which makes it hard to detect these molecules with desired spatial and temporal resolution. Moreover, the majority of methods of free radical detection rely on the reaction between the radical and the probe, thus interfering with the natural effects of the radicals [1]. Nitrogen vacancy (NV) centers of nanodiamonds allow for direct optical quantum-based sensing of the magnetic signal coming from the radicals.
We apply nanodiamond magnetometry for intracellular sensing of free radical production. As FNDs possess excellent biocompatibility and can be internalized by live cells [2], they can be used for in situ detection of radicals (nanoMRI on subcellular level). As a proof-of-concept model, we used J774 murine macrophages, which produce large amounts of free radicals as part of the normal immune response. One of these radical species is NO, which is generated by a specific enzyme, inducible nitric oxide synthase (iNOS). iNOS activity can be inhibited, resulting in lower levels of NO present in the cell.
We have for the first time recorded T1 relaxation curves from FNDs internalized by live macrophages. During the T1 acquisition, the cells were exposed to the iNOS inhibitor, L-NAME. We thenassessed the dynamic changes of T1 relaxation of the NV centers, for the first time observing the lengthening of T1 constant of FNDs internalized by the cells, as the NO production in the system was abolished. The changes in intracellular NO levels were confirmed with the conventional fluorescent assay (DAF-2 DA) by the means of microplate reader and confocal microscopy.
Our study shows the potential of nanodiamond-based nanoMRI for the direct optical monitoring of free radical production on a single-cell level with nanoscale sensitivity and a resolution in the second range.

References:
[1] Acc Chem Res. 2019 Jul 16; 52(7): 1739–1749. DOI: 10.1021/acs.accounts.9b00102
[2] Sensors (Basel). 2018 Feb; 18(2): 355. DOI: 10.3390/s18020355

Nanodiamond is a biocompatible nanomaterial which can accommodate various photoluminescent crystal defects. Nitrogen-vacancy (NV) centers show particularly high photostability and unique electronic sensitivity to magnetic and electric fields. Their spin properties can be read by optical means, which enables construction of various probes based on quantum mechanical interactions. For application in biological environment, a proper interface of the particles is required. Two conceptually different design of nanodiamond surface design will be discussed [1-3]. These includes polymer and biomimetic lipid terminations enabling further modification by chemically reactive groups. Selectivity of cell surface receptors targeting will be discussed.
Furthermore, specific and efficient regulation of the family of extracellular signaling molecules known as fibroblast growth factors (FGFs) using positively charged detonation nanodiamonds without any synthetically installed (bio)organic interface will be presented [4]. The FGF-based regulation of cell signalling using nanodiamonds can be performed in full sera. This nanotherapeutic approach can be potentially applied to mitigation of pathological FGF signaling and neutralization of disease-related activities of FGFs.

References
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A nanocarbon film consisting of nanocrystallites with mixed sp² and sp³ bonds formed by unbalanced magnetron sputtering was studied with respect to the changes in characteristics caused by surface oxygen concentration. Electrochemical pretreatment (ECP) was conducted to change the surface oxygen concentration of the nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of surface roughness (R_a) at the angstrom level after ECP, owing to stable structure containing 40 % of sp³ bonds. Electrode characteristics including potential window, and electrochemical properties for some redox species such as Ru(NH₃)₆^3+/2+, Fe(CN)₆^3-/4- and some biomolecules were investigated. The anodic potential limit became wider and ΔE_p of Fe(CN)₆^3-/4- became smaller at the treated nanocarbon film electrode than that of the electrode before the treatment. Based on these results, we realized to measure uridylic acid (UMP) and inosine triphosphate (ITP) with high oxidation potential by direct oxidation, which was difficult to measure at as-deposited nanocarbon film electrode.

To study the properties of diamond at the initial stages of boron doping, we conducted XPS, EPR, ¹¹B and ¹³C NMR study of a lightly boron-doped high pressure – high temperature (HPHT) microdiamond with 0.27% of boron. The total content of localized paramagnetic defects is 24 ppm, among them 12 ppm are due to substitutional nitrogen defects (P1). The P1 content is found to be much smaller than that usually observed in conventional HPHT diamonds. ¹¹B NMR shows two components assigned to boron atoms substituting carbon and those located within the conducting regions, respectively. The latter component demonstrates exceptionally short spin-lattice relaxation time (T₁ = 2.4 ms) characteristic of conductive compounds. Increase in the boron concentration would increase the number and size of the conductive clusters and would finally lead to connectivity between them. This will result in conductivity and superconductivity in the heavily B-doped regime.


A. M. Panich, A. M. Shames, S. D. Goren, N. Froumin, O. Shenderova, Materials Research Express 6 (2019) 075612.

The use of fluorescence microscopy to study fate and transport of nanoparticles in the environment can be limited by the presence of background signals such as autofluorescence and scattered light. Fluorescent diamond nanoparticles offer a solution to these limitations through the unique spin-related luminescence properties of nitrogen vacancy (NV) centers in diamond nanoparticles (NVND). NV centers have spin properties which affect their fluorescence, and which can be altered using applied magnetic or radio-frequency fields. I will present recent studies using magnetic fields to modulate the fluorescence of NVND for background-subtracted imaging of nanoparticles ingested by a model organism, C. elegans. By using small magnetic fields from an inexpensive electromagnet, the fluorescence of 40 nm NVND can be modulated by 10% in a widefield imaging configuration. We use differential imaging of magnet-induced changes in NVND fluorescence intensity to image and to isolate the emission arising from nanodiamond within the gut of C. elegans. This method represents a promising approach to probing the uptake of nanoparticles by organisms and to assessing the environmental fate and transport of nanoparticles in the environment.

Nanodiamonds (ND) have emerged since about a decade ago as a key platform for many developments in nanoscience and nanotechnology due to their outstanding mechanical performance, biocompatibility and unique properties. The NDs bearing biologically active fragments or immobilized on biomolecules are remarkably suitable for biomedical application [1]. Recently, NDs were reported to affect endothelial permeability to deliver anticancer drugs [2, 3].
The main strategy to manage acute poisoning with organophosphorus agents include, either for pre-treatment or for ex-post therapy, administration of oxime AChE reactivator, along with atropine and anticonvulsant drug. The reactivators based on mono- or bis-pyridinium scaffold are not able to diffuse readily into the central nervous system to restore activity of inhibited AcChE. A challenging issue is to design a scaffold providing as high antidotal efficiency towards inhibited AcChE as quaternary oximes along with their ability to come across the blood-brain barrier (BBB).
The NDs with a surface modified with the pyridinium oxime moieties have been synthesized. Using carboxylated NDs (ND-COOH) as starting material, there was elaborated method of attaching 4-oximino pyridinium (4-PAM) fragment via variable linkers. The amino-PEG3-amine linker has been selected for studying counterion effect on the modified ND properties. Using 3-chloropropionyl chloride instead of 2-bromoethyl bromide sufficiently increases yield and purity of the final material. The FTIR, elemental analysis, and solid state NMR (¹³C MAS and ¹³C CP-MAS) confirm the structure of the substituents and conversion of ND-COOH.
Following our green chemistry approach applied recently for the synthesis of inherently biodegradable ionic liquid-derived oxime surfactants [4] and antidotes [5], the closed bottle test was adapted to estimate biodegradability of the organic material covalently attached to of the nanoparticle and therefore evaluate potential impact of the transformation products on the environment.
The MDCK assay, an example of the tight junction cell line modelling BBB, has been selected to evaluate the ability of oxime-modified NDs to diffuse from the donor compartment through the MDCK cell membrane into the acceptor compartment. An separate experiment included noncovalent loading of the quaternary oximes on the ND-COOH. Concentrations of HI-6 or 2-PAM in acceptor wells (when the cell monolayer was exposed to NDs) were not elevated in comparison to untreated cell monolayers showing that noncovalent binding is not effective enough to come across the cellular barrier, compared to covalently bound oxime-functionalized NDs.
The AcChE reactivation have been performed against three toxic OP: banned insecticide paraoxon and two CWA – sarin (GD) and VX. Our study demonstrates that, as compared to obidoxime, 800 μg/ml of Ox-ND (bromide salt) demonstrate 25-30% of its activity (taken as 0.1 mM aq. solution). For GD and paraoxon, the reactivation with 800 μg/ml is similar to that in the presence of 400 μg/ml; for VX, obidoxime reveals 3 times higher percentage of reactivation. Switching to chloride remarkably elevates the antidotal potency.
The molecular docking was applied to estimate optimal distance between the oxime moieties attached to the ND and spacer properties (length, hydrophobicity, rigidity) to get the active cite of human AcChE and act as the antidote.
References:
[1] K. Turcheniuk, V. N. Mochalin Nanotechnology, 2017, 28, 27.
[2] M. I. Setyawati, V. N. Mochalin, and D. T. Leong. ACS Nano, 2016, 10, 1170.
[3] H. Li, D. Zeng, Z. Wang, L. Fang, F. Li, Z. Wang. Nanomedicine 2018, 13, 981
[4] Y. Karpichev et al, Journal of Molecular Liquids, submitted
[5] Y. Karpichev, I. Kapitanov, N. Gathergood, O. Soukup, V. Hepnarova, D. Jun, K. Kuca, Military Medical Science Letters, 2018, 87.

Over the past two decades, solid-state defects have emerged as one of the leading systems for a wide variety of quantum technologies. Solid-state hosts such as diamond are well studied, and a wide spectrum of fluorescing crystal defects have been identified and characterized. Nanodiamonds enable efficient control and readout of color centers within. Furthermore, nanodiamonds offer surface functionalization, nanometer-scale spatial positioning, and the compatibility with optical levitation. The fabrication of non-aggregated and uniformly-sized nanodiamonds with systematic integration of single quantum emitters has so far been lacking. Here, we present a top-down fabrication method to produce ~30 nm uniformly-sized single-crystal nanodiamonds by block copolymer self-assembled nanomask patterning together with directional and isotropic reactive ion etching. We show detected emission from bright single nitrogen vacancy centers hosted in the fabricated nanodiamonds. The lithographically precise patterning of large areas of diamond by self-assembled masks and their release into uniformly sized nanodiamonds open up new possibilities for quantum information processing and sensing. (Scientific Reports 9, 6914 (2019))

Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704.

Diamond magnetometry has led to impressive results in physics. The technique provides magnetic resonance signals with nanoscale resolution. It is so sensitive that even the faint signal of single electrons can be detected. Here we have first applied the technique to measure free radical generation in cells. These radicals play a critical in the natural metabolism of cells. Examples of processes relying on radicals include, signalling, immune responses or cell death or ageing. However, they are also involved in numerous processes which indicate disease. Diseases where radicals play a key role includes cancer, cardiovascular diseases, bacterial or viral infection or arthritis. Despite their relevance and prevalence, we know very little about free radical generation. The reason is that they are small, short lived and reactive and thus difficult to measure for the state of the art.
For diamond magnetometry they are well visible due to their free electron spin. With this new technology we are able to detect stimulation and inhibition of radical production with subcellular resolution. On top of that we can differentiate different knock out cells (where certain metabolic processes have been turned off) as well as different production in mitochondria compared to the cytosol. The signals we receive are in principle equivalent to conventional MRI signals. However, the resolution and sensitivity are significantly improved

The extraordinary stability of the C-F bond imparts many commercially useful properties to poly- and per-fluoroalkyl substances (PFASs). Among the properties imparted by the stability of the C-F bond is a high resistance to degradation via traditional oxidative/reductive processes. As a consequence PFAS is a persistent contaminant upon environmental exposure; especially in water. In this work, we examine the impact of nanodiamond photochemistry on the degradation of one of the more resilient in the class of PFASs, perfluorooctane sulfonate (PFOS). Using nanosecond transient absorption we find that hydrated electrons result by photodetachment from hydrogen-terminated (negative electron affinity) detonation nanodiamond (HDND) suspensions in water upon sub-bandgap (266nm) irradiation. Hydrated electron photogeneration from oxygen-terminated (positive electron affinity) detonation nanodiamond (ODND), on the other hand, is not observed. The transient absorption data suggest the presence of an interaction between PFOS and HDND and, more so, an interaction between PFOS and the hydrated electrons. Finally, we show that prolonged sub-bandgap (254nm) irradiation of aqueous HDND in the presence of PFOS leads to full decomposition of PFOS by reductive fragmentation, consistent with hydrated electron reductive chemistry.

The biological impact of nanoparticles is largely controlled by the properties of their surfaces. However, on times scales relevant to most biological studies most nanoparticles undergo chemical changes, including oxidation and loss of surface functional groups. Nanodiamond is a nearly ideal system for investigation of nano-bio interactions because diamond can be functionalized with a wide range of organic moleucles via "all-carbon" scaffolding with unprecedented chemical stability, and because defects such as Nv centers in nanodiamond provide a way to detect nanodiamond via optical methods. In this talk I will present recent results investigating how the chemical structure of surface ligands affects the interaction of nanodiamond with cells and model membranes, and recent efforts using magnetically modulated Nv imaging to selectively identify nanoparticles within complex matrices. Together, the ability to functionalize nanodiamond and observe it with high selectivity and high sensitivity provides a nearly idea system for understanding nano-bio interactions in environmental systems.

In biological fluids, proteins are adsorbed onto the surface of nanoparticles (NPs) to form a coating known as protein corona. Most of the corona proteins act as opsonin which activates the macrophage from immune system to uptake NPs, leading to the rapid removal of NPs. This restricts the development of nanomedicine. Although conjugation with linear polyethylene glycol (PEG) is the standard approach to reduce protein attachment and to avoid non-specific uptake, it cannot fully prevent the opsonization. On the other hand, we have demonstrated polyglycerol (PG) as a promising alternative to PEG, because PG enhanced the aqueous dispersibility and gave stealth effect to NPs [1]. In order to understand the role of PG, we compare protein affinity and macrophage uptake of PG and PEG grafted nanodiamond (ND-PG and ND-PEG, respectively) with different polymer content in this paper. Protein analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that PG was much more resistant than PEG to adsorption of the opsonin proteins such as IgG and complement protein. In particular, there was almost no protein on the PG layer with high content. In addition, almost no ND-PG was observed in the TEM images of U937 macrophage, while there was ND-PEG in the macrophage. This indicates that PG has much better stealth effect than PEG [2]. Finally, the stealth effect was confirmed in vivo by preferential tumor accumulation of the ND-PG functionalized with near infrared fluorescence dye (Cy7) [3].

References: [1] L. Zhao, N. Komatsu, et al., Angew. Chem. Int. Ed. 2011; Adv. Funct. Mater., 2014; Biomater., 2014. [2] Y. Zou, N. Komatsu, et al., submitted. [3] F. Yoshino, Y. Zou, N. Komatsu, et al., Small, in press.

Fluorescent nanodiamonds (FNDs) have a great promise as robust and biocompatible fluorescent probes. Their most distinct property is the optically detected magnetic resonance of nitrogen vacancy color centers, which enables nanoscale sensing of surrounding physical properties, such as magnetic field, electric field and temperature.
I will talk about our recent activity to build up such microscope-based thermometry for biological applications. Temperature is a fundamental physical parameter of any biological activity, and in most cases, current biology assumes that temperature is uniform over the living space (including organisms themselves). However recent studies have revealed that sub-cellular temperature information is crucial to understand various biological events, such as embryogenesis, physiological thermogenesis, and thermotaxis. The FND quantum thermometry may tackle these biological issues.
I first present our effort to understand the basic spin properties of FND sensors when they are surface treated [1] or placed in various pH and ionic-strength solutions to quantify the sensor stability [2]. Second, we present a bio-dedicated ODMR measurement system to perform quantum thermometry assay for number of biological specimens [3]. Third, with these development, we demonstrate real-time subcellular quantum thermometry of live worms of C. elegans [4].

[1] Tsukahara, Fujiwara et al., ACS Appl. Nano Mater. 2, 3701 (2019).
[2] Fujiwara et al., RSC Adv. 9, 12606 (2019).
[3] Yukawa, Fujiwara et al., submitted.
[4] Fujiwara et al., submitted.

Because of unique sensitivity to lattice, Bragg coherent x-ray diffractive imaging (BCDI) is a powerful characterization tool to image three-dimensional map of strain and defect distribution inside nano-scaled materials with non-destructive measurements [1]. In-situ and operando imaging became a major driver for BCDI to address scientific questions on metal, metal oxide, and mineral in recent years.
In this talk, I will introduce basic concept and current state-of-art of BCDI and recent experimental results on in-situ and operando BCDI. High temperature BCDI reveals unique lattice distortion in ZSM-5 zeolites [2], annealing effect on gold grains on gold thin films [3] and relaxation of strain inside quantum materials such as nanodiamonds and silicon carbides [4, 5]. In addition, some estimates of BCDI in the future will be discussed

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Polyester is used as a matrix material in fiber-reinforced composites that have a wide range of applications, which include naval vessels, storage tanks, and pipelines. Improving the strength of polyester is highly desirable in these applications. Detonation nanodiamond is a promising filler material for polymer reinforcement because of its superior mechanical properties, small size, and chemical stability. Here we show that incorporating low concentrations (0.1 wt%) of commercially-available detonation nanodiamonds (3-10 nm in diameter) into isophthalic polyester results in significant enhancements in the strength of the polymer. A facile method of fabricating nanodiamond-polyester composites will be discussed. The method does not require additional nanodiamond purification steps or surface modification strategies to enhance the bonding of nanodiamond to polyester. Results from the uniaxial tensile testing of nanodiamond-polyester composites will be presented, and scanning electron microscopy images of specimen fracture surfaces will be shown. The results reveal the mechanical properties, dispersion, and possible strengthening mechanisms of nanodiamond-polyester composites.

Detonation of TNT/RDX in oxygen-deficient conditions produces nanodiamonds terminated by various oxygen containing surface functional groups, which enable single digit state dispersion in aqueous media via deaggregation methods such as zirconia micro bead milling. We quantitatively investigated ozone oxidized DNDs by acid-base back potentiometric titration and XPS, revealing a large amount of oxygen containing surface groups in comparison to air oxidized DNDs. The most prominent feature of the ozone oxidized DNDs is its high tolerance to re-aggregation during horn sonication process, allowing longer sonication times to produce smaller particles (down to a single digit DND dispersion) without any milling media. Additionally, the deaggregated DNDs were investigated by UV-Raman and FTIR, suggesting that a large number of oxygen-containing surface groups (mainly anhydrides) produced by ozonation were further hydrolyzed to COOH during horn sonication. We will introduce the sonication-assisted hydrolysis of ozone oxidized DND as potentially a commercially viable technique to obtain single-digit COOH-terminated DND colloids due to a better control, milder conditions, and a lower burn-off of the smallest DND particles as compared to air oxidation.

The NV-center in nanodiamonds has been applied as a sensor for different applications. They are ideal for this application due to their sensitivity, low cytotoxicity and ability to work at room temperature. However, a limitation of using nanodiamonds to measure a change in the environment, is that one has to use the same nanodiamond. This is due to large variations between nanodiamonds. This study aims to address the differences between nanodiamonds and to develop a method which allows us to understand what contributes to the variation between T1 relaxation times of nanodiamonds. We aim to do this by controlling the size and surface chemistry of the nanodiamonds.
Previous studies in our group have shown that there is large size variation between nanodiamonds. We assume that the size of the diamonds does not only affect the brightness of the fluorescence, but also the T1 relaxation time of the diamonds. The NV-centers in smaller diamonds are in general closer to the surface than in larger diamonds. Therefore, the NV-centers in smaller diamonds are more sensitive to magnetic noise around the diamond compared to larger diamonds. Hence, larger diamonds have a longer T1 relaxation time compared to smaller diamonds.
Magnetic noise closest to the NV-center is noise that originates on the surface. We assume that by controlling the surface chemistry of the nanodiamonds, we can study the effects of the surface chemistry on the NV-centers. We assume that, the T1 relaxation time will vary depending on the properties of chemical compounds on the surface of the nanodiamonds. We assume that the T1 will become longer or shorter depending on the magnetic properties of the chemicals bound to the surface of the nanodiamond.
The T1 relaxtion times are measured on dry nanodiamonds. The procedure is to initialize the system by shining a green laser (532nm) onto the nanodiamonds. Afterwards the laser is turned off which allows the system to relax. This sequence is repeated for varying time of the laser being turned off. During this time the red photoluminescence of the nanodiamonds is recorded. The whole procedure is repeated approximately 10000 times to obtain sufficient statistics. To obtain the T1-value, the initial part of each pulse is integrated to obtain a T1-curve which is then fitted by the bi-exponential model.
To account for size, the nanodiamonds are centrifuged to select the average size of the diamonds in the suspension. Afterwards the T1 of the nanodiamonds is measured. The surface chemistry is controlled by applying plasma treatment to the diamonds. The diamonds are treated with different types of plasma (O2, H2, N2 and NH3) for 2, 5 and 10 minutes. Similarly as for size separation, the T1 relaxation times for different plasma treated nanodiamonds have been measured. The T1 curves were recorded for 9 nanodiamonds before plasma treatment and 8 diamonds after 5 minute plasma treatment with NH3. The plasma treated nanodiamonds showed a lower fluorescence than the pre-treatment nanodiamonds. The average T1 value of the bare nanodiamonds is 601(±170) μs and for NH3 treated nanodiamonds is 306(±66) μs.
The observed T1 relaxation times pre- and post-treatment show a clear difference between the T1 relaxation times. However, the proportional error for the plasma treated nanodiamonds only reduces by 6% (28% pre-treatment and 22% post-treatment). This shows that the plasma treatment with NH3 decreases the T1 relaxation time, but does not account for the variation between the nanodiamonds. This experiment was preliminary, therefore we did not account for the size variation between the nanodiamonds yet.

I will describe new quantum-assisted modalities to deliver enormous signal enhancements in conventional MRI and NMR mediated by quantum defects in nanodiamond powder. This relies on the use of Nitrogen-Vacancy (NV) center spins within the diamond particles that can be optically polarized at room temperature with modest laser powers. This polarization can be transferred to nuclei surrounding the NV spins to hyperpolarize them to levels far above Boltzmann levels, manifesting in a highly enhanced NMR signature. Nanodiamonds are particularly suited for this task, given their large surface areas, and the ability to arrange for close physical contact between the polarized NVs and analyte molecules of interest.

I will discuss our experimental effort in this direction, particularly focusing on the ability for ¹³C hyperpolarized nanodiamonds to serve as dual-mode (optical and MRI) imaging agents, and as transduced and deployable magnetometers.

The anisotropy of the precipitates from nanodiamond (ND) solutions suggests the existence of elementary diamond nanoparticles (EDIANs). The rectangular shapes of whiskers [1], nanocrystals[2], sheets[3], or nanosheets[4-6] should be formed from the particles being similar both in shape and size. We believe that there is a peculiar kind of similarity in the colloidal particles consisting the precipitates and that hydrated colloidal crystals are formed from them. We demonstrate herein two kinds of the rectangular precipitates, the whiskers and the nanosheets both of which were prepared from the solutions of NanoAmando® (Nano Carbon Research Institute Ltd.).
The former was prepared at the three-phase contact between air, an ND solution, and glass on the sidewall of its tubes[4]. The whiskers have the fine geometry of rectangular shapes as well as uniaxial uniform optical anisotropy. A laser microscopy image exhibited the surprisingly fine shape and crossed nicol polarized microscopic observations with a Berek compensator demonstrate the uniaxial birefringence of Δn=0.0016. The curvature of the sidewall is needed to show the birefringence and recent procedures furthermore provided a small ring (φ~7 mm) of a curved whisker on the wall. Although the ring was brittle, it was slightly elastic, being able to deform a little without breaking.
The nanosheets were crystallized from a diluted ND solution to the adsorbed ND particles on a Langmuir monolayer of arachidic acid (C₁₉H₃₉COOH). After opening the trough of the monolayer, we found innumerable ultra thin rectangular sheets on the water surface [4-6]. We postulate that the monolayer induces the crystallization under the PTFE bars of a Langmuir trough and that the precipitates of ultrathin rectangular nanosheets (~26 nm thick) are squeezed out from the undersurface of the bars to the water surface. Raman spectra showed that the nanosheets contain a negligible amount of the acid and such a process should result in the low content of it.
We think that the quality of NanoAmando® contributes to the self-assembly; recent small diameter values (2.6 nm) from dynamic light scattering (DLS) measurenents also suggest its appreciable content of EDIANs, considering that Raileigh scattering should force us to overestimate the diameters. We will discuss the origin of the self-assembly with respect to the colloidal nature of the multi-polar ND polyhedrons predicted by DFT calculations [7].

[1] E. Osawa; Diamond & Related Materials. 16, 2018(2007).
[2] M. L. Terranova, et.al., Crystal Growth & Design, , 9, 1245(2009).
[3] T. Petit,et.al.; Nanoscale, 5(19), 8958(2013).
[4] T.Tanaka, et al, Abstract of the 54th FNTG Symposium, 28(2018).
[5] T.Tanaka, et al, Abstract of the 53th FNTG Symposium, 67(2018).
[6] T.Tanaka, Y.F. Miura, T. Aoyama, K. Miyamoto, Y. Akagi, M. Uchiyama, E. Osawa, submitted for publication.
[7] A. S. Barnard, E. Osawa; Nanoscale 6, 1188 (2014).
Corresponding Author:Toshihiko Tanaka, Tanaka/Tel: +81-246-46-0810/E-mail: 3116566701@jcom.home.ne.jp

Fluorescent nanodiamonds (FNDs) are diamond nanoparticles containing color centers that emit visible light at room temperature. Among the color centers in FNDs, the negatively charged nitrogen-vacancy centers (NV^-) have drawn the most attention due to its excellent optical properties and great prospect in sensing and biomedical diagnostic applications. Thus, it is of great significance to further expand the potential of the NV^- centers in FNDs by understanding the effect of various factors including the NV distribution, particle morphology and surface properties of the particles.

Recently, it has been reported that the brightness of the FND particles can be increased by etching the particles with molten salt (KNO₃). The increase of the brightness was attributed to the roundness and smoothness of the FND surface, as well as the removal of non-sp³ species after the surface treatment. In order to understand how the surface treatment impacts the surface structure and particle morphology, high-resolution transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were employed to reveal the detailed surface atomic and electronic structures.

We have previously demonstrated that it is possible to measure the electronic transitions of the NV center in nanodiamond using high-energy resolution EELS in a scanning transmission electron microscope (STEM). Using a crushed type 1a natural diamond with a nominal size of 70 nm, we detected signals at the ~1.3 and 2.16 eV assigned to [NVN]^- and [NV]⁰. The high spatial resolution afforded by this STEM also allows us to observe the atomic structure of the particles.

Here, we compare the different surface processing methods for FND (irradiation, acid treatment, molten salt treatment), and correlate the photoluminescence (PL) mapping with the transmission electron microscope (TEM) mapping of the same area. In addition, high-energy resolution EELS in a STEM at low voltage (30-60 kV) was used to measure the surface state of the FND particles, in combination with the high-resolution TEM images on the same particles.

Our initial finding from the PL and TEM mappings suggests that most of the molten salt (KNO₃) treated FND particles are photoluminescent, and the PL intensity has a correlation with particle size: the bigger the particle the higher PL intensity. High-resolution imaging shows that the molten salt (KNO₃) treated FND particles tend to have less rough surfaces, with fewer sharp-angle edges and less surface unevenness. The particle morphology population displays more round and polygonal shaped particles compared to the non-molten salt treated particles. However, we found a thin layer (1-2 nm) of amorphous carbon and graphite layers present on the particle surfaces. The EELS mapping also confirms this finding.

This paper focuses on describing a synergistic combination of ultrananocrystalline diamond (UNCD) coating on chemical mechanical nanostructured metallic dental implants to optimize the biocompatibility by a synergistic integration of both processes to optimize the performance of the particular implant.

UNCD films, with grain size in the range of 3-5 nm, exhibit excellent biocompatibility in addition to a unique set of complementary properties including much smoother surface as compared to microcrystalline and nanocrystalline diamond (NCD) (10-100 nm grain size), a superior conformal growth on 3-D structures such as the dental implants and protection of the coated metal-based implants from the chemical attack by oral fluids, enabling enhanced hermeticity [1]. Chemical mechanical nano-structuring (CMNS) is a new complementary technique that can be synergistically utilized to induce nano-scale smoothness or nano/micro-scale roughness on the bioimplant surfaces [2]. Furthermore, implementation of the CMNS process on titanium bio-implants helps cleaning the implant surface from potentially contaminated surface layers by removing a nano-scale top layer, limits any further contamination by creating a non-porous and continuous protective oxide film to minimize the risk of infection and prevent corrosion.

It is demonstrated by surface characterization through SEM imaging and Raman analyses that the CMNS process can be effectively implemented before the UNCD coating to modify surface roughness. Electrochemical evaluations in the simulated body fluid were also performed to demonstrate corrosion resistance improvements in addition to enhanced biocompatibility by adjustable surface nano-structuring, depending on the cell attachment requirements on the various parts of the dental implants.

O. Auciello, P. Gurman, M. B. Guglielmotti, D.G. Olmedo, A. Berra, M. J. Saravia, “Biocompatible Ultra-nanocrystalline Diamond Coatings for Implantable Medical Devices”, MRS Bulletin, 39, 621 (2014).
Z. Ozdemir, A. Ozdemir, G.B. Basim, “Biomedical Applications of Chemical Mechanical Polishing”, Materials Science and Engineering - Part C., 68 (1), P 383-396 (2016).

Due to the high refractive index and unique optical and mechanical properties of diamond, the nanodiamond (ND) glass composites are of great interest for advanced photonic devices and other applications [1]. However, it is difficult to employ conventional processing techniques to achieve good dispersion of NDs in glass. This is because most of these techniques start from solid powder precursors that may result in serious ND aggregation, leading to degradation of the properties of the composites.
In this presentation, an alternative fabrication method for ND-silica glass composites via sol-gel chemistry will be discussed. Optical and mechanical properties of the resulting ND-silica glass composites at various ND contents will be presented. Single digit (~4-10 nm) ND colloidal solutions in water were prepared by salt assisted ultrasonic deaggregation (SAUD) technique [2]. These colloidal solutions were then used to produce excellent dispersions of ND in ND-silica aerogels that were subsequently sintered into glass at 1100 °C. This proposed method for the integration of ND into silica glass has great potential for fabrication of ND-silica glass composites and could be extended to other nanoparticles and materials produced via sol gel chemistry. The improvements in mechanical properties, optical transmittance in ultraviolet (UV) and visible regions of the spectrum, as well as the refractive index of the ND-silica glass composites at various ND contents will be further discussed.









[1] V. N. Mochalin, O. Shenderova, D. Ho, and Y. Gogotsi, “The properties and applications of nanodiamonds,” Nat. Nanotechnol., vol. 7, no. 1, pp. 11–23, 2012.
[2] K. Turcheniuk, C. Trecazzi, C. Deeleepojananan, and V. N. Mochalin, “Salt-Assisted Ultrasonic Deaggregation of Nanodiamond,” ACS Appl. Mater. Interfaces, vol. 8, no. 38, pp. 25461–25468, 2016.

Thrombosis is the leading cause of morbidity and mortality in the United States. However, there is still a low understanding of its triggers, progression, and response to anticoagulant therapy. Fluorescence microscopy provides targeted, multi-color contrast, which has advanced the study of thrombus formation. However, photodegradation of fluorophores limits the application in processes that occur over longer periods of time (e.g. clot progression and/or dissolution). Fluorescent nanodiamond (FND) is a fluorophore which utilizes the intrinsic fluorescence of color centers located within and protected by the diamond crystalline lattice. Recent developments in diamond processing have allowed for the controlled production of nanodiamond emitting in multiple colors. In this work, FND is used to visualize clots and their degradation, and this imaging capability is compared to commonly used organic fluorophores. The use of FND for thrombus imaging paves the way for longitudinal studies to investigate biomarker expression in acute thrombosis, with the hope to ultimately improve clinical outcomes. These results represent the initial translation of FND research to clinical applications.

Detonation nanodiamonds (DND) are diamond nanoparticles synthesized through detonation process with sizes ranging 3-5nm. It's small size, non-toxic and biocompatibility has drawn huge interests, particularly in the biomedical field. In order to capitalize the large total surface areas afforded by the small particle size, dispersing DND have been one of the endeavor for the better utilizing DND for its applications. The consensus of DND dispersion has been that detonation nanodiamond is mono-dispersed single digit nanoparticles in water, largely based on the dynamic light scattering (DLS) measurements.

We have recently shown that DND dispersion in water, without any surface modification, exhibit striking lacey network, formed dynamically by self-assembled chain-like superstructure. This discovery was carried out by a combination of DLS, small-angle x-ray scattering (SAXS) as well as cryo-TEM imaging. Our analysis shows that the superstructure morphology has strong size and particle shape dependence.

To further understand the three dimensional distribution of the lacey network, electron tomography was conducted on the plunge-freezing samples of DND dispersion. Using a cryo-TEM (Krios) equipped with a single-electron-detection camera, a series of 65 images with specimen tilts ranging from -65°to +65° was acquired, with a dose rate of 3 e^-/pixel/sec to avoid melting of the vitreous ice. Our initial result suggests that there is a preferential orientation of the chain-superstructure. We speculate that the reason behind the oriented chains is the screening effect from the interactions between water molecules surrounding the nanodiamond chains.

Bulk and nanoscale diamond host the nitrogen vacancy center, a unique atomic defect, a photostable emitter that has been used for magnetometry, electrometry and quantum computation. Wet chemical modification of 25-50 nm diamond surfaces, the typical host for nitrogen vacancy centers, is challenging and carboxylate moieties are the common target of nucleophiles for chemical protocols. Here we produce a carbocation-rich diamond surface by converting high-pressure high-temperature nanoscale diamond with tertiary-alcohols to highly reactive alkyl-bromides. The chemical reactivity of the brominated surface allows for carbon-nitrogen bond formation at room temperature without catalysts using low-cost amine precursors. We report that alkyl-bromine moieties are highly labile on diamond, prone to hydrolysis and intracrystallite Williamson ether-type reactions occur. Additionally, in contrast to traditional organic chemistry reactivity, alkyl-bromides on nanoscale diamond are more reactive than acyl-bromides and an explanation is given. The chemical lability of the alkyl-bromide surface leads to efficient amination with NH₃-THF at 298 K and weak conversion rates with condensed NH₃ at 195K. Other amine precursors were also probed to guage a range of nucleophilicities. Overlapping surface sensitive spectroscopies confirm our chemical assignments. Peptide bond formation with FND-NH₂ and folic acid was demonstrated using sulfo-NHS/EDC coupling reagents and reveals that chemical reactivity is maintained. Our work demonstrates that a robust pathway now exists to transform a chemically inert diamond surface into a highly reactive surface at room temperature and broadens the pathways of carbon-heteroatom covalent bond formation.

The mechanical energy dissipation between two sliding objects at macroscopic level leads to friction and wear and is explained by Amonton’s law where friction is directly proportional to the load applied but independent of the contact area. However, at nanoscale, contact area becomes dominant factor in controlling friction due to the nanoscale interactions at single asperity level and therefore interpretation of friction at nanoscale and macroscale has always been somewhat ambiguous due to the missing mesoscopic link that bridges nanoscale phenomenon with that of macroscopic world. Our research at CNM has always been focused on understanding atomic scale origin of the friction and how that can be linked to the macroscopic world. Our recent work utilizing combination of 2D materials and nanodiamond as a nanoscale lubricant have broken that barrier between nanoscale and macroscale world demonstrating near zero friction (superlubricity) at engineering scale for the first time [1-2]. We have further shown that it is possible to control friction at macroscale by manipulating nanoscale interactions at the tribological interface involving combination of various 2D materials and nanoparticles that generates superlubric tribolayer within the wear track resulting in near zero friction and negligible wear [3-4]. With the help of newly installed multifunctional tribometer at CNM in the superlubriicty lab, we systematically study evolution of tribochemical changes in the wear track using integrated Raman spectroscopy and 3D confocal microscopy and wear debris using HRTEM and EELS techniques. Combining that with the molecular dynamic simulation we elucidate the mechanism of friction and show possible pathways to manipulate friction at nanoscale that can directly influence friction at macroscale. The implications of this discovery are profound and already demonstrating its potential for some commercial applications that we are exploring with the industry. I’ll also discuss some new results on achieving superlubrcity in rolling/sliding contacts [5] that will have great potential in bearings industry.
References:
Berman and Sumant et al., Science, 348, 6239, 1118 (2015)
Berman and Sumant et al., ACS Nano, 12, 3, 2122 (2018)
Berman and Sumant et al., Nature Communications, 9, 1164 (2018)
Berman and Sumant et al., Advanced Materials Interfaces, 1901416 (2019)
Mutyala and Sumant et al., Applied Physics Letters, 115(10), 103103, (2019)

Nitrogen vacancy center (NVC) nanodiamonds (NDs) are useful for applications in biolabeling and biosensing due to their electron spin properties, biocompatibility and photostability. However, NVC imaging requires high photon fluxes (1 mW/um²), increasing autofluorescence from cells and tissues and reducing signal-to-noise ratios. Generating gold-diamond nanoarchitectures in a hexagonal packing geometry can lead to a 200X fold increase in fluorescence based on finite-dimension time-domain (FDTD) simulations. For maximum fluorescence enhancement these simulations also require a dielectric (SiO₂) to separate the diamond-gold assembly. Here, we satisfy these conditions using a core-shell diamond-SiO₂ nanoparticle using self assembly to generate a gold-nanodiamond heterostructures that is driven by gold-thiolate bond formation. Here we use 65nm gold nanoparticles to plasmonically enhance the far field emission of NV centers. Au NPs were synthesized via a seeded growth mechanism to yield 60-80nm citrate capped AuNPs. 15nm SiO₂ shells were synthesized on nanodiamond cores with sulfyl-hydryl and stabilizing moieties to provide a chemically inert dielectric platform. Both AuNPs and SiO₂ coated nanodiamonds were imaged via scanning electron microscopy (SEM) and probed in-situ via Dynamic Light Scattering (DLS). Self-assembly was found to be driven by entropic forces and the ratio of gold-chelating ligands to stabilizing moieties is discussed. These fundamental findings are a key metric in designing, preparing and deploying nanoscale NV diamond under low-light conditions.

We will report on a breakthrough method of production of multicolor diamond particulates using a rapid thermal annealing (RTA) approach with precise temperature and time control, enabling annealing of diamond particulates up to 2100 °C without extensive graphitization. The RTA method generates conditions which allow formation of one-, two- and three-atom nitrogen complexes with vacancies in electron irradiated type Ib synthetic diamond, providing vibrant luminescence in the red, green and blue spectral ranges, correspondingly. We will demonstrate opportunities for particulate diamond in a plethora of fluorescence imaging applications in biological and industrial fields based on controlled and highly reproducible formation of specific color centers previously not possible in type Ib synthetic diamond particles in micron- and nanometer size ranges.

Diamond nanoparticles have a diverse array of applications from single photon sources and biomarkers to the seeds for diamond growth. Although there are a wide range of commercial suppliers, the purity of diamond nanoparticles is insufficient for some specific applications such as optical levitation and Coherent Anti-Stokes Raman Spectroscopy (CARS). There is also no commercial supplier for nanodiamonds containing the silicon vacancy centre or newer single photon sources.
In this work the production and purification of novel diamond nanoparticles containing custom colour centres will be detailed. First a diamond film containing NV/SiV centres was grown onto a substrate. Colour centre incorporation was confirmed by Photoluminescence and Hanbury Brown and Twiss measurements. The resulting diamond film was removed from the substrate and milled using a planetary mill based on either steel or SiN. The milled material was purified by acid reflux. To measure particle sizes, different slurries containing the diamond nanoparticles obtained were prepared and characterized by using Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA). XPS was also used to qualify the milling process contamination.
The control of surface sp² and zeta potential will also be demonstrated. Positive zeta potentials in hydrogenated nano- structured carbons could be explained due to the presence of basal planes of graphite which can become protonated. At the same time, sp² carbon creation on diamond nanoparticles surface eases low temperature (500°C) diamond nanoparticles hydrogenation and amination, previously demonstrated for detonation diamond (5nm). Applications of the positive zeta potential in nanodiamond will be proposed.

Color centers in solids are the fundamental building blocks of various applications ranging from lasers to light emitting diodes and sensors, as well as the foundation of advanced quantum information and communication technologies. Their photoluminescence properties are usually studied under Stokes excitation, in which the emitted photons are at a lower energy than the excitation ones.
We explore the opposite Anti-Stokes process, where excitation is performed with lower energy photons. The process is sufficiently efficient to excite even a single quantum system—the germanium-vacancy center in diamond.
As a proof of concept, we propose using Anti-Stokes excitation of diamond color centers for nanoscale thermometry. We leverage the temperature-dependent, phonon-assisted mechanism to realize an all-optical nanoscale thermometry scheme that outperforms any homologous optical method employed to date. We discuss other potential applications and show that our results frame a promising approach for exploring fundamental light-matter interactions in isolated quantum systems.

Nanodiamond is a biocompatible nanomaterial which can accommodate various photoluminescent crystal defects. Nitrogen-vacancy (NV) centers show particularly high photostability and unique electronic sensitivity to magnetic and electric fields. Their spin properties can be read by optical means, which enables construction of various probes based on quantum mechanical interactions. For application in biological environment, a proper interface of the particles is required. Two conceptually different design of nanodiamond surface design will be discussed [1-3]. These includes polymer and biomimetic lipid terminations enabling further modification by chemically reactive groups. Selectivity of cell surface receptors targeting will be discussed.
Furthermore, specific and efficient regulation of the family of extracellular signaling molecules known as fibroblast growth factors (FGFs) using positively charged detonation nanodiamonds without any synthetically installed (bio)organic interface will be presented [4]. The FGF-based regulation of cell signalling using nanodiamonds can be performed in full sera. This nanotherapeutic approach can be potentially applied to mitigation of pathological FGF signaling and neutralization of disease-related activities of FGFs.

References
1. Raabova H., Chvatil D., Cigler P., Nanoscale 11, 18537 (2019).
2. Neburkova J., Sedlak F., Zackova Suchanova J., Kostka L., Sacha P., Subr V., Etrych T., Simon P., Barinkova J., Krystufek R., Spanielova H., Forstova J., Konvalinka J., Cigler P., Mol. Pharmaceutics 15(8), 2932 (2018).
3. J. Vavra, I. Rehor, T. Rendler, M. Jani, J. Bednar, M. M. Baksh, A. Zappe, J. Wrachtrup, and P. Cigler, Adv. Funct. Mater. 28, 1803406 (2018).
4. L. Balek, M. Buchtova, M. Kunova Bosakova, M. Varecha, S. Foldynova-Trantirkova, I. Gudernova, I. Vesela, J. Havlik, J. Neburkova, S. Turner, M. A. Krzyscik, M. Zakrzewska, L. Klimaschewski, P. Claus, L. Trantirek, P. Cigler, P. Krejci, Biomaterials 176, 106 (2018).

The nanodiamond-water interface plays a central role in nanodiamond reactivity in aqueous environment, which is relevant for nanomedicine, photocatalysis or environmental applications. Especially, the generation of solvated electrons can trigger N₂ or CO₂ reduction in aqueous environment, and probably strongly depend on the nanodiamond-water interface.
In this presentation, our latest results related to different spectroscopic approaches to probe the nanodiamond-water interface will be shown. In particular, the different surface reactivity with water related to hydrogen-termination will be compared to oxidized nanodiamond surfaces.
First, the vibrational and electronic structures of water molecules around nanodiamonds were probed by Fourier Transform Infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) directly in aqueous environment.¹ X-ray Photoelectron Spectroscopy (XPS) was also applied under near ambient pressure conditions (few mbar of water) to probe changes of the surface chemistry of nanostructured diamond upon exposure to water.
Finally, transient absorption spectroscopy (TAS) was applied to nanodiamond dispersions. The evolution of the visible light absorption spectra over time with a sub-picosecond time resolution was monitored after excitation of electrons into the diamond valence band using a UV laser pulse. This enables the observation of the emission of solvated electrons from nanodiamonds in water. The effect of surface chemistry on the electron emission will also be discussed.

This work has received funding from the European Union’s Horizon 2020 Program under Grant Agreement number 665085 (DIACAT).

1. Petit, T. et al. Unusual Water Hydrogen Bond Network around Hydrogenated Nanodiamonds. J. Phys. Chem. C 121, 5185−5194 (2017).

We will report on a breakthrough method of production of multicolor diamond particulates using a rapid thermal annealing (RTA) approach with precise temperature and time control, enabling annealing of diamond particulates up to 2100 °C without extensive graphitization. The RTA method generates conditions which allow formation of one-, two- and three-atom nitrogen complexes with vacancies in electron irradiated type Ib synthetic diamond, providing vibrant luminescence in the red, green and blue spectral ranges, correspondingly. We will demonstrate opportunities for particulate diamond in a plethora of fluorescence imaging applications in biological and industrial fields based on controlled and highly reproducible formation of specific color centers previously not possible in type Ib synthetic diamond particles in micron- and nanometer size ranges.

Nanodiamond powders produced by detonation synthesis offer a great potential in many applications¹, including novel nanocomposites² and biomedical applications³. In the area of nanocomposites, much of work has been focused on polymer matrix composites, while significantly less has been done with other matrices, such as ceramics and metals⁴. At the same time, nanodiamonds have great potential in reinforcing as well as improving optical properties and wear behavior of metal- and ceramic-matrix composites.
We will review our progress in developing well dispersed nanodiamonds⁵ for composite applications with emphasis on novel and less studied nanodiamond-ceramic and nanodiamond-metal composites. Manufacturing and processing techniques, as well as properties of the composites will be discussed.
Another hot area of applications for nanodiamond is biomedical imaging and drug delivery. We will discuss our recent progress in drug delivery with nanodiamonds, emphasizing the effects of nanodiamond surface chemistry, and present novel processing techniques to produce luminescent nanodiamond particles from HPHT luminescent diamond for bioimaging, labeling, and other applications.

1. Mochalin, V. N.; Shenderova, O.; Ho, D.; Gogotsi, Y., The properties and applications of nanodiamonds. Nature Nanotechnology 2012, 7 (1), 11-23.
2. Mochalin, V. N.; Gogotsi, Y., Nanodiamond–polymer composites. Diam. Relat. Mat. 2015, 58, 161-171.
3. Turcheniuk, K.; Vadym, N. M., Biomedical applications of nanodiamond (Review). Nanotechnology 2017, 28 (25), 252001.
4. Turcheniuk, K.; Mochalin, V. N., Adsorption behavior and reduction of copper (II) acetate on the surface of detonation nanodiamond with well defined surface chemistry. Carbon 2016, 109, 98-105.
5. Turcheniuk, K.; Trecazzi, C.; Deeleepojananan, C.; Mochalin, V. N., Salt-Assisted Ultrasonic Deaggregation of Nanodiamond. ACS Applied Materials & Interfaces 2016, 8 (38), 25461-25468.