Symposium EE15 : Materials for Sustainable Development---Integrated Approaches

Much Materials research today has, as its primary or one of its secondary aims, to contribute to the technologies that are more “sustainable” than those we now use. The immediate perception this creates is one of resource-efficiency: technology that is less energy intensive, less water intensive and less material intensive than at present. But if the claim of a sustainable development is to be justified, there are further considerations. Globally, the annual resource-consumption in question (energy, water, materials) are not measured in joules, ccs or grams but in petajoules, cubic kilometers, billions of tonnes. If the research material is to be “disruptive”, making a significant contribution to a more sustainable way of life, will have to be produced on a scale, and in a time-frame, that have a measureable effect on this consumption. If on this scale there are other consequences: markets are disturbed, people are affected – there are social and economic dimensions, when adverse short-term impacts may have to be justified by long-term gains. It is not the job of materials researchers to solve these problems but to be aware and if they are to make claims that their research has “sustainability” as a tag line, it would be responsible to survey how it might map-out on the larger scale.

The paper will focus on a methodology for thinking about this, starting from the proposed “sustainable development”, exploring the context: the nature of the innovation and the stakeholders that it involves
1. the material demands and the ability of the global supply chain to meet them;
2. the risks associated with a given material choice and ways of mitigating the risk by substitution;
3. the ultimate impact of the innovation on natural, manufactured, human and social capital.

Reversing combustion and recycling carbon dioxide and water back to liquid hydrocarbons is an attractive option for storing solar energy and mitigating the growth of atmospheric CO₂ concentrations. For any such process, high solar-to-fuel efficiency, appropriate materials thermodynamics, kinetics and availability is critical for large scale viability and favorable economics. Redox active mixed perovskite metal oxide-based thermochemical approaches for solar-to-fuel have the potential to be highly efficient as they have a tunable parameter space, avoid inherent limitations of photosynthesis (biofuels), and sidestep the solar-to-electric conversion necessary for electrolytic reactions. This presentation highlights progress from multidisciplinary and international efforts that has been progressing down a technical path for systems, novel reactors, and materials design and discovery for making liquid hydrocarbon fuels from concentrated sunlight, waste carbon dioxide, and brackish water based on a two-step metal oxide redox cycle motivated to address the dual challenges posed by the strategic and economic importance of petroleum and the increasing concentration of atmospheric carbon dioxide. One take-away message will be that given high enough efficiency (> 10% on a lifecycle basis – sunlight to fuel) energy conversion routes, supplanting a large fraction of global petroleum-derived liquid fuels with synthetic solar-fuels, are challenging but nonetheless possible; indeed they are quite plausible with affordable economics.

Renewable energy sources are unlikely to completely displace traditional thermal energy generating methods in the foreseeable future. Furthermore, renewables such as solar and wind power require traditional backup systems for windless and/or cloudy days. Consequently, finding routes to increase efficiency of traditional power generating approaches should be considered an integral part of sustainable development. This is not a simple task, since thermal power plants that operate on a steam cycle have been around and continually improved for over a hundred years. Finding routes to passively enhance steam condensation rate, which governs the back-pressure for the steam turbines, is one of the remaining materials-development opportunities in this area. Steam condensers are fundamental components of about 85% of electricity generation plants and 50% of desalination plants installed globally.¹ Consequently finding routes to even moderately improve efficiency of the condensation process could have substantial impact on sustainable development.
In this talk we will provide a brief overview of steam condensation fundamentals and how novel materials can be used to enhance efficiency of this phase change process. Since the 1930s, hydrophobization of metal surfaces has been known to increase heat transfer during water condensation by up to an order of magnitude,² whereby this surface modification switches the condensation mode from filmwise (FWC) to dropwise (DWC). However, use of hydrophobic coatings required to promote DWC introduces an additional resistance to heat flow. Thus, in simplified terms, to increase the total heat transfer rate, thermal resistance introduced by the hydrophobic coating must be significantly smaller than that posed by the water film during FWC. Unfortunately, most hydrophobic coatings suffer from longevity issues. We will review recent material developments in this area (rare earth oxides, grafted polymers, grapheme, and lubricant impregnated surfaces etc.) and durability challenges stemming from thin film nature of these hydrophobic coatings. We will also discuss our recent alternative to these thin film modifiers: metal matrix hydrophobic nanoparticle composites.³ We have recently demonstrated that with properly sized and distributed nanoparticles, such materials can sustainably promote DWC. Furthermore, due to the high thermal conductivity of the matrix, the composites have a potential to be used in bulk-like manner. This could dramatically enhance their longevity as compared to thin film hydrophobic promoters and thus provide a viable route of sustainably enhancing condenser, and with that power plant, efficiency.

1. Paxson et al. Adv. Mater., 2014.
2. Schmidt et al. Tech. Mech. Thermodyn., 1930.
3. Damle et al., Adv. Mater. Inter., 2015.

Significant efforts have been made to advance technologies that provide a reduction in the energy demands of consumers. For instance, bulbs made with light emitting diodes (LEDs) have been demonstrated to last longer and save substantial energy when compare to conventional incandescent lighting. Thin film solar cells provide improved efficiencies over conventional silicon based technologies, both of which offer energy from renewable sources rather than from fossil fuels. In the consumer electronics arena, recycling at end-of-life has become essential to recover valuable materials and ensure proper disposal of toxic substances. Yet all of these technologies, thought to be advancing the state of the art in sustainable design require the utilization of resources (materials and energy) and create potential environmental impacts (both human and ecological), as do all product fabrication processes. This paper will review a series of case studies on these technologies highlighting the various types of impacts associated with them, in an effort to guide future development of sustainable technologies such that they require less resource input, generate less environmental impact and/or use fewer toxic substances.

Sustainable development in material sciences includes societal aspects that encompass chemistry, physical sciences, toxicology, medicine, etc., in both academia and the industrial world. Nanomaterials and associated technologies are making their forays into many areas such as energy, transportation, communication, health (drug delivery, imaging and regenerative medicine), environment, and so on. All these applications should be developed keeping their life cycle in mind from production to recycling. A general panel discussion was organized by the French government and scientific institutions on nanotechnologies between 2009 and 2010 (National Commission Public Debate). Even if the idea of having exchanges between academics, politicians, experts and the general population was interesting, it was harder to execute. This is why certain studies in the field of Social Sciences and Humanities (SSH) have helped to understand which factors are involved in communication and how mental representations are built into these kinds of panel discussions with a large spectral band of communicants [1-2]. The dialogue among these disparate elements proved that a lot of headway needs to be made in this area. In that context, these representations depend not only on objective knowledge, but also on subjective perceptions of the benefits/risks ratio relating to the use of nanomaterials and nanotechnologies.
To this end, a specific project based on an interdisciplinary approach was developed in the Lorraine Region including researchers in SSH (psychology, history, and philosophy), materials, chemistry, physics, biology and medicine. Started in 2013, this exploratory project was called PERSONA (PERception of SOcial risks and NAnotechnology).
We will present herein how nanotechnologies, as a still young field, can evoke different perceptions and levels of acceptance. So far our research has been limited to specific school populations (high school and university) with the immediate aim of developing the survey protocol. Naturally, this is the first step to a much broader study to be carried out in conjunction with academic, and industrial players. We will also discuss the risks, threats, levels of acceptance, trustworthiness, perceived benefits, and understanding, all which are influenced by psychological, sociological and cultural factors. The classic risk/benefit model is not sufficient enough to understand and explain the complexity and uncertainty of the impact that nanomaterials have on health, the environment, etc. A new concept of assessing risks (objective as well as perceived), and safety, taking into account the entire life-cycle of nanomaterials. This study aims to contribute towards a more sustainable development and research methods concerning nanomaterials and nanotechnology.

[1] G.Gardner, G. Jones, A. Taylor, J. Forrester, L.Robertson Int. J. Sci. Educ. 32(14), 1951-1969 (2010).
[2] N. Gupta, A. Fischer, J. Frewer NanoEthics, 9(2), 93-108 (2015).

The disposal of materials at the end of their lifecycle, especially for complex manufactured products, presents challenges for protecting the environment and human health. In particular, used automobiles are disposed of by removal of various component parts, followed by shredding, which may emit particles into the atmosphere that may be subsequently deposited onto soil or into water. Further, worldwide automobile production is increasing (68 million cars in 2014 versus 41 million in 2010). In this study, air particulates were collected over several days by DRUM Impactor downwind of an automobile shredding operation located near the ocean, size separated, and analyzed by SEM and TEM, and EDXS, in order to determine their particle size distribution and corresponding chemical composition. Results for larger particles (2.5 to 10.0 μm aerodynamic particle size fraction) showed mainly diatoms and salts, consistent with the location of the plant near the ocean, and aluminosilicates, consistent with dust particles from geological sources. Sulfur, attributed to shipping traffic, was also detected. As aerodynamic particle size decreased from 10 μm to 0.09 μm, particle loading decreased and composition shifted to mainly carbon, oxygen, aluminum, and sulfur. Iron was also found and primarily present in the form of spherical particles that were ~ 1 μm in diameter, as determined by SEM, indicating they originated from a combustion process. Implications of these results for the environment, particularly soil and water deposition, and for human health, as a result of inhalation, are discussed.

Quantum dots are crystalline semiconductor nanoparticles with unique optical properties due to quantum confinement effects. They have some advantages over organic fluorescent dyes, such as high fluorescent brightness, photostability, and tunable emission wavelength, that is dependent upon particle size. Their unique optical properties have led to their increased application in a variety of devices, including diode lasers and television displays, and in biomedical research.
The most commonly used quantum dots are cadmium selenide (CdSe) quantum dots, which contain inherently toxic cadmium. Taking its ecotoxicological effects into consideration, a large focus has been dedicated to the design and synthesis of more benign quantum dots that achieve comparable luminescence properties. From this perspective, silicon quantum dots provide a good alternative to the CdSe quantum dots.
The enormous growth in the use of nanotechnology-based products, including semiconductor quantum dots, in the last ten years, means that there is an increased risk of environmental exposure to nanomaterials. Thus, it is imperative to investigate the fate and behavior of engineered nanomaterials in the environment, as well as their toxicity towards living organisms.
In this work, the focus is on the comparison of toxic effects of conventional CdSe quantum dots and the emerging silicon quantum dots, using bacteria as model organism. The bacteria models used are Shewanella oneidensis, which is a Gram-negative bacterium, and Bacillus subtilis, which is a Gram-positive bacterium. They are both ecologically beneficial bacteria, and have potential in environmental remediation. The motivation of this study is to assess the viability of the bacteria in the presence of the quantum dots, as well as to determine the mechanism of association and toxicity. This research assesses cell viability, via growth curve monitoring of bacteria by assessing the optical density and colony counting studies. Respirometry is done to evaluate any change in respiration pattern of the bacteria over an extended period of time. A live-dead fluorometric assay is done to assess any bacterial membrane damage induced by the presented nanoparticles. In addition, reactive oxygen species generation is monitored to achieve some mechanistic insight into the toxicity. This work is part of the University of Minnesota MRSEC grant. From the studies that I have carried out, it is evident that the silicon quantum dots present significantly low toxicity towards bacteria. These results are crucial, as they can guide the development of sustainable nanomaterials with minimal ecotoxicological effects.

During the last decade, the PV scientific community has been continuously trying to find new materials suitable for PV applications, in view of the many advantages OPV devices offer over their inorganic counterparts. Low-band-gap polymers (L-B-G) are very good candidates due to their capability of absorbing light above 600nm.
L-B-G-based OSCs have already reached significant PCEs and the current stage of research faces now other challenges in order to get to a “marketable” product: combining adequate lifetime with materials impacting as least as possible on man and environment.
A 8.7% PCE was reported for an inverted OSC based on PTB7:PCBM blended in o-xylene (XY) [1]. Since the solvent choice influences the OPV efficiency by determining PAL morphology and charge carrier mobility,it is reasonable to imagine that it may also induce solvent-specific degradation patterns [2].
We performed an extensive study to test solvent-related degradation effects on inverted PTB7:PCBM based OSCs, blended in Chlorobenzene (CB) and XY. Experiments were realized on PTB7:PCBM layer and PV device under shelf-life, 1sun and concentrated light.
The shelf-life experiment showed that the biggest loss was due to the FF. Optical and morphological investigations of the layer let us hypothesize a solvent-driven PAL vertical stratification, affecting donor and acceptor degradation evolution.
After 5-h light soaking under real sun,XY-cells suffered from a stronger sensitivity to UV-vis radiation,as pointed out by the Jsc drop. This was connected to the specific solvent’s stability towards UV light.In CB-cells,a deeper Voc drop had to do with a stronger PTB7 degradation. Absorption spectra of degraded films confirmed a stratification-dependent degradation over time.
Under concentrated sunlight, Jsc proved to be the mostly affected parameter with a stronger decrease for XY-cells, probably enhanced by some Ag-triggered solvent photo-catalysis,as well as by some residual XY in the OSC bulk.
Therefore,we suggest that optimized annealing can mitigate drawbacks induced by solvent traces in the bulk. Also, reliable encapsulation+UV filtering is mandatory for introducing PTB7:PCBM cells in commerce. Likewise, the PAL network immobilization via addition of crosslinkable materials [3] becomes crucial to develop durable cells for practical applications. Finally, exploring alternative electrodes could contribute to preserve the materials properties intact over time.

1. Susanna, G., et al., 8.7% Power conversion efficiency polymer solar cell realized with non-chlorinated solvents. Solar Energy Materials and Solar Cells, 2015. 134: p. 194-198.
2. Takayuki, K., et al., Effect of the solvent used to prepare the photoactive layer on the performance of inverted bulk heterojunction polymer solar cells. Japanese Journal of Applied Physics, 2014. 53(2S): p. 02BE06.
3. Rumer, J.W. and I. McCulloch, Organic photovoltaics: Crosslinking for optimal morphology and stability. Materials Today.

The polymer based energy harvesters are making more scientific ground than ones based on any other materials due to its flexibility, compatibility, light weight, durability and low cost. These devices promises to be the next generation of alternate energy sources, suitable for portable and low energy based devices. However, the longevity of electronic devices is getting shorter and their disposal poses serious ecological threats. In addition, biocompatibility is still a factor that is not properly addressed in polymer based devices, used in portable and bio-functional electronics. The solution could be found in DNA-mediated Poly(vinylidene fluoride) (PVDF) based hybrid-energy harvester, capable of operating as a solar cell and mechanical energy harvester. It is well known that PVDF films show piezoelectric properties when the electroactive phases (β- and γ- phases) are induced. However, to induce these phases, the films have to subject to high electric field and stretched which compromises the output of the mechanical energy harvester. Alternatively, we have been able to induce the β-phase in PVDF film by the introduction of DNA, which does not require any electrical poling or stretching. The device is capable of harvesting piezoelectric potential up to 20 V by the application of mechanical stress (~63 Pa) with high efficiency (~2.7%).¹ We have been able to charge various capacitors with this device and light up several (~55) blue LEDs. There have been reports of organic solar cells fabricated with DNA with high efficiencies.² This is attributed by the fact that DNA based solar cells can show large band gaps and high dielectric constant playing an important role in enhancing light capture. In this work, we have fabricated hybrid DNA-mediated device that can harvest both solar energy and mechanical vibration simultaneously. As such, by coupling flexible solar cells with flexible piezoelectric film, the device could be useful as an all-weather energy generator. The DNA-based thin film device not only shows ability to be mould into any shape suitable in any portable electronic devices, but is fully biocompatible and biodegradable. The device would be ideal for biomedical implants and sensors which can operate without storage.

Acknowledgment:
This work was financially supported by a grant from the Science and Engineering Research Board (SERB/1759/2014− 15), Government of India.
References
A.Tamang, S.K.Ghosh, S.Garain, M.M.Alam, J.Haeberle, K.Henkel, D.Schmeisser, D.Mandal. ACS Applied Materials & Interfaces 2015, 7, 16143−16147.
K.W.Lee, K.M.Kim, J.Lee, R.Amin, B.Kim, S.K.Park, S.K.Lee, S.H.Park, H.J.Kim. Nanotechnology 2011, 22, 375202.

Widely distributed water kinetic energy is an abundant source for large-scale applications. The energy provided by water is much less dependent on seasonality, daylight, weather, and/or temperature. Triboelectric nanogenerators (TENGs) have been recognized as one of the most promising approaches for harvesting wave energy, because they exhibit the desirable characteristics of simple structure, low cost, light weight, high efficiency and high power density, as well as the prospect of broad applications. However, a TENG with an open structure cannot work under harsh conditions in the presence of water, which significantly increases the structural design difficulty of TENG for efficient energy harvesting.
This work demonstrates a rolling-structured, freestanding triboelectric-layer-based nanogenerator (RF-TENG) for harvesting energy from low-frequency wave movements. A TENG was initially fabricated by using a rolling Nylon ball to contact with a Kapton film in an enclosed spherical shell. Relying on the surface contact electrification effect between conventional polymers, this RF-TENG is extremely lightweight, low cost, and capable of floating on the surface for wave energy harvesting. The freestanding design has a relatively linear charge transfer curve that assures good charge transfer efficiency, even under low amplitude vibration. In addition, the rolling design greatly reduces the energy loss through friction and improves energy conversion efficiency. Finally, this rolling design exhibits low natural frequency that can effectively achieve resonance with ocean waves. With these three advantages, the innovative design of a free-rolling ball surrounded by two arc electrodes is particularly suitable for energy harvesting under irregular wave oscillations.
To obtain the optimum performance, we propose both material and structural optimization to this design. We compared the Nylon/Kapton device and PTFE/Al device and found that the Nylon/Kapton device’s performance is much superior the latter one. In the structural design part, the ratio of the outer sphere diameter and inner ball diameter is the most important design consideration. From FEM simulation results and experiment demonstration, an optimized ratio was found to reach the highest performance. Besides, electrode structure optimization is also performed to better harvest ocean waves with random directions. With the optimization technique provided, a spherical TENG of 6 cm in diameter actuated by water waves can provide a peak current of 1 μA over a wide load range from a short-circuit condition to 10 GΩ, with an instantaneous output power of up to 10 mW. The performance of this TENG unit enables the direct driving of 70+ LEDs and commercial thermometers in a duty cycle of 26.5% with EDLCs, shows significant potential applications in environmental monitoring, hydrological research and other fields. [1]
Ref:
1. X. Wang, S. Niu, Z. L. Wang etc, Adv. Energy Mater. 2015, DOI: 10.1002/aenm.201501467

Several grand challenges in energy storage and conversion involve the discovery functional materials which many agree will be multi-element solid solution of metal oxides. Here, we present a concept of compositional controlled synthesis of mixed metal oxide particles using simple precursors with rapid reaction time scales. The conventional wet chemical methods for synthesis of multi-metal oxide often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control. The concept is demonstrated with binary, ternary and quaternary metal oxide with control over entire composition range using metal precursor solutions. For the ternary system, the results show the selective formation of metastable spinel solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMn_zFe_2-zO₄ (0 ≤ z ≤ 1), exhibits considerable electrocatalytic activity towards oxygen evolution reaction (OER), achieving an overpotential of 0.39V at a benchmarking current density of 10 mAcm^-2 for low manganese content at z = 0.2. Other examples include five element based pyrochlore deployed as a catalyst in diesel reforming reaction. Current efforts include the development of a tool for rapid, high throughput synthesis and combinatorial screening of oxide materials for a variety of applications.

Traditional photocatalysts in the form of nanometric powders typically exhibit high photocatalytic activity. However, these photocatalysts cannot be efficiently recycled, resulting in secondary contamination that limits their large-scale application. Immobilization has been a good option for the final application of various catalysts, and the thin film strategy is one of the best alternatives for application of semiconductor oxide to heterogeneous photocatalysis due to their relatively easy preparation.¹ However, there is a significant difference between the final catalytic properties of these films compared to the freestanding powders, which should be minimized by adjusting the processing variables to ensure better performance.² Therefore, this work describes the preparation of ZnO thin films using the polymeric precursor method, and the influence of two important film preparation parameters (i.e., thickness and calcination temperature) was investigated to achieve effective photocatalytic activity. The ZnO thin films were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance UV–vis spectroscopy, and atomic force microscopy. The results indicated that the average particle size increased from 14 to 45 nm as the calcination temperature increased from 400 to 600 °C, which is most likely due to the particles coalescing by induced rotation or abnormal growth. The number of deposited layers was a key parameter for the thickness of the films, which ranged from 150 to 220 nm. Thicker films obtained at lower calcination temperature exhibited better photoactivity for RhB photodegradation under UV irradiation which is primarily due to the higher amount of material deposited and the exposed high-energy facets of the ZnO thin films. In addition, the prepared films possess stable photocatalytic properties even after four successive re-uses in this model reaction. Therefore, these results demonstrate the possibility of achieving the optimum level of catalytic performance that is required in large-scale processes once the photoactivity of thin films can be significantly improved by adjusting their simple preparation parameters.

Acknowledgments
The authors are grateful to the CNPq (Under grants n° 300247/2013-3), FAPESP (Under grants n° 13/13888-0), CAPES and FINEP for financial support. We are also grateful to LIEC/UFSCar Brazil for providing DRS spectroscopy facilities.

References
¹Li, S. et al. Sci. Rep. 2014, 4, 3978/1-8.
²Nawi, M.A.; Zain, S. Md. Appl. Surf. Sci. 2012, 258, 6148-6157.

Semiconductors that can be activated by visible radiation have generated much scientific interest, because their can be activated by sunlight to applications in photocatalytic process.^1,2 Bismuth vanadate (BiVO₄) is a n-type semiconductor that presents remarkable properties, such as, band gap value of 2.4 eV and high chemical stability.^3,4 Therefore, the aim of this study was to develop a new method to obtain monoclinic BiVO₄ at a low temperature, and to evaluate the photocatalytic performance of this semiconductor under visible-light on oxidation of methylene blue (MB) and rhodamine B (RhB) dyes. The effect of the hydrothermal treatment (HT) on the structural, electronic, and morphologic properties of the BiVO₄ was described. Further, detailed photodegradation mechanism to MB oxidation was also proposed. The as-synthesized BiVO₄ materials were characterized by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and scanning electron microscopy. The hydrothermal treatment above 80 °C was required to obtain pure monoclinic BiVO₄ phase by releasing V⁵⁺ ions from vanadium peroxo complexes. With the increase in hydrothermal reaction temperature, the particle size decreased. All BiVO₄ samples presented large size and shape distribution and band gap of approximately 2.40 eV. The as-prepared BiVO₄ catalysts showed high photoactivity for decomposition of model pollutants, methylene blue and rhodamine B dyes, under exposure to visible-light. The photodegradation mechanism was evaluated by adding scavengers, DMSO and KBrO₃, which were used to probe ^●OH radical and conduction band (CB) electrons, respectively. It was observed that photodegradation of MB and RhB dyes is caused by the action of ^●OH radicals, and that BiVO₄ CB electrons do not have reduction potential sufficiently high to reduce dissolved oxygen to O₂^-●. It was proven that the indirect mechanism, i.e. ^●OH radical formation, plays the major role on the BiVO₄-assisted photodegradation process.

Acknowledgments:
The authors thank FAPESP (Under grant n° 13/13888-0), CNPq (Under grant n° 300247/2013-3), and FINEP for the financial support. The authors are also grateful Msc. Pablo Lemos and LIEC/UFSCar Brazil for help with DRS UV-visible facilities.

References:
1 - A. Kubacka, M. Fernández-García and G. Colón, Chem. Rev., 2012, 112, 1555–1614.
2 - C. Chen, W. Ma and J. Zhao, Chem. Soc. Rev., 2010, 39, 4206.
3 - Y. Park, K. J. McDonald and K.-S. Choi, Chem. Soc. Rev., 2013, 42, 2321–37.
4 - O. F. Lopes, K. T. G. Carvalho, G. K. Macedo, V. R. de Mendonça, W. Avansi and C. Ribeiro, New J. Chem., 2015, 39, 6231–6237.

The development of functional porous adsorbents is vitally important for drug separation, environmental protection and gas capture. Ionic liquids (ILs) with unique characteristics such as ultralow vapor pressure and designable structure play a fascinating role with exceptional separation efficiency in separation science. However, their application is restricted by their high viscosity, easy loss, inevitable toxicity and difficult recovery, thus there is an urgent need to immobilize ILs onto a suitable solid support. Exhilaratingly, mesoporous poly(ionic liquid)s (MPILs) meet the demand exactly and have been a subject of increasing research interest, due to combination of unique physicochemical properties of ILs and common features of polymeric architecture. In this talk, we will report our recent work on the preparation of mesoporous poly(ionic liquid)s. A class of novel anion-functionalized MPILs incorporating anionic surfactant carboxylate ILs has been obtained via facile copolymerization of ILs and crosslinker divinylbenzene under solvothermal conditions. Microphase separation takes place accompanied by crosslinking in the process with solvents acting as a pore template. Systematic investigations were carried out on solvent selection, crosslinker content, reaction temperature and time, and initiator dosage to optimize synthetic conditions. The prepared anion-functionalized MPILs possessed adequate IL content, disordered mesopores with relatively narrow distribution, and exhibited an apparent foam structure with morphology of sponge-like aggregation. Typically, as-synthesized polymers with IL content of 1.0 mmol/g showed the S_BET and V_total values of 352 m²/g and 0.53 cm³/g, respectively. Besides, the anion-functionalized MPILs demonstrated extraordinary adsorption capacity (197 mg/g for tocopherols) and excellent selectivity to the separation of bioactive homologues, which is an important process for the production of high-purity drug molecules but is very challenging because of their high structural similarity. The superior performance of anion-functionalized MPILs compared to common porous adsorbents is predominantly derived from distinct hydrogen-bonding interaction between tethered ILs and targeted solutes. Moreover, the MPILs were also utilized as powerful gas adsorbents, and show excellent CO₂ uptake (21.35 mg/g) and good selectivity to N₂ (15.05) at ambient conditions. In conclusion, rich porosity and unique molecular recognition ability of anion-functionalized MPILs make them be competent candidates for advanced separation.
Acknowledgements
The research was supported by the National Natural Science Foundation of China (21222601, 21476192, and 21436010), the Zhejiang Provincial Natural Science Foundation of China (LR13B060001), and the Fundamental Research Funds for the Central Universities (2014XZZX003-17).

The heterostructures development has been widely used to applications in photocatalysis heterogeneous such as, organic pollutant degradation, water-splitting and photosynthesis artificial.¹ A special feature of a suitable heterostructure is the possibility of increase the lifetimes of photogenerated electron–hole pairs by suppressing recombination.² In this sense, the system tailored between the BiVO₄ and Bi₂O₂CO₃ showed promising electronic properties to form the type II heterostructure (p-n junction) and additionally this heterostructure can be activated by visible-light.³ However, the production of such heterostructures by one-step methods has as the main the drawbacks the difficulty of controlling the simultaneous crystallization process of two different components.² Thus, the use of one preformed particle to build up heterostructures is of interest, because the morphology and interfaces creation is easily controlled. In this work, we study the formation of heterojunctions by the growth of BiVO₄ on the Bi₂O₂CO₃ self-sacrificial surface by hydrothermal treatment of Bi₂O₂CO₃ preformed with a vanadium precursor (V) driven by solubility difference. The as-synthesized Bi₂O₂CO₃/BiVO₄ heterostrucutures were characterized by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, thermogravimetric analysis, photoluminescence spectroscopy and scanning electron microscopy. The photocatalytic performance of samples was probed by methylene blue dye degradation under visible and UV irradiation. The amount of heterojunctions formed between the Bi₂O₂CO₃ and BiVO₄ was tuned by V precursor concentration. The Bi₂O₂CO₃/BiVO₄ heterostructures exhibited morphological characteristics relating to both phases in the same region, indicating the formation of interfaces between phases. Was observed that the formation of Bi₂O₂CO₃/BiVO₄ heterostructure caused a thermal stability of more than 100 °C for Bi₂O₂CO₃ demonstrating that there was a strong interaction between the phases on heterojunctions. The synthesis method was efficient on obtaining heterostructured semiconductors (Bi₂O₂CO₃/BiVO₄) enhancing their photocatalytic performance when compared to isolated phases under UV and visible irradiation. The photoluminescence results showed that the photoactivity enhancement occurs by increasing spatial separation of photogenerated electron/hole pair due to the formation of type II heterostructure.
Acknowledgements
The authors thank FAPESP (Under grant n° 13/13888-0), CNPq, CAPES and FINEP for the financial support.
References
1 J. Tian, Z. Zhao, A. Kumar, R. I. Boughton and H. Liu, Chem. Soc. Rev., 2014, 43, 6920–6937.
2 V. R. de Mendonça, C. J. Dalmaschio, E. R. Leite, M. Niederberger and C. Ribeiro, J. Mater. Chem. A, 2015, 3, 2216–2225.
3 Y. Park, K. J. McDonald and K.-S. Choi, Chem. Soc. Rev., 2013, 42, 2321–37.

Photocatalytic degradation of organic pollutants over semiconductor surfaces, particularly oxide semiconductors, are being explored to clean atmospheric air and water bodies by using solar energy. TiO₂ has received much attention in the past due to the biological and chemical inertness, strong oxidizing power, biocompatibility, non-toxicity, and long-term stability against photo and chemical corrosion. A strong limitation of this material is its wide band gap (~3.2 eV), which enable it to absorb only ultravioletpart of the spectrum, i.e. merely 3–5% of available solar energy due to which this material cannot support high throughput reactions with solar energy. Recently low dimension structure which supports easy manipulation of material properties are considered strong contenders of solar energy aided photoactivity and therefore being explored to address these issues. We are reporting, here, the results of our studied on bismuth oxychloride.
Wet chemistry offer a synthesis route which promise quality material in large quantities. We have synthesized bismuth oxychloride (BiOCl)from bismuth nitrate (Bi(NO₃)₃.5H₂O) and potassium chloride (KCl ) using five different solvent compositions under three different pH conditions. Synthesized material is characterized XRD, HRSEM, FTIR and UV-Vis spectroscopy. Photoactivity of this material was studied by degradation of methylene blue in aqueous solution under normal sunlight and UV light. Present studies have shown that BiOCl synthesized under particular conditions exhibits excellent bulk photoactivity under normal sunlight exposure with band energy absorption edge extends in the visible up to 550nm. This value differs from the standard reported value which falls in deep UV region corresponding to energy bandgap of ~ 3.5 eV. We have studied absorption properties of the synthesized material to establish relationship with the synthesis conditions. Cyclic voltameteric studies are being carried out to estimate the shift in energy bands and bandgap value. These results are awaited soon. We are exploring the mechanism of degradation of organic molecules by our material using energy from the sun and intend to present these results in spring meeting of MRS.

For several decades additives have been incorporated into polymeric systems to improve desirable properties, and eliminate undesirable properties. When added to a polyethylene film, the additives migrate to the films' surface and their concentration decreases; over time the additive’s effect desists.
To solve this problem, efficient methods for extended performance are being sought.
Extended additives’ performance is necessary to avoid frequent substitution of polyethylene films for different applications (e.g. greenhouses plastic coverings); as a result, reducing plastic waste and contributing to environmental sustainability.
Over the course of our work, a new method of additives’ controlled migration has been developed, by grafting the additive molecules to nano-particles via a radical reaction. The particles were used as physical migration retarders. Nano-particles were chosen due to their small size, which does not scatter light significantly. It was thus possible to make composites that retain their optical clarity. Furthermore, the small size of the particles leads to a large interfacial area for grafting.

Engine aftertreatment components, such as the diesel particulate filter or oxidation catalyst, undergo aging such as increased filter pressure drop and reduction in catalytic activity due to several reasons including the accumulation of lubricant additive-derived ash which can be both mechanically and chemically bound to the catalyst surface. At the nanometer and micron scales, particle-particle and particle-surface adhesion forces result in ash accumulation on component surfaces which significantly reduce the service life of expensive engine aftertreatment components. Adhesion forces between lubricant-derived ash particles and a diesel particulate filter surface have been quantified in this study by way of Atomic Force Microscopy. The influences of ash chemistry and morphology and relative humidity on adhesion have also been investigated. The measured pairwise (ash-ash, ash-catalyst surface, ash-soot) adhesion forces investigated in this study have been found to be stratified and help to explain the physical mechanisms of ash agglomeration/accumulation within engine aftertreatment components which lead to reduced aftertreatment component functionality.

Recycling technology of scrapped superalloy are developping rapidly in recent years. To alleviate the negative influence of revert superalloy on mechanical properties and upgrade the quality of the melt and casting, remelting is a effective process. In the present work, the K418 alloys with various recycled proportion 0%, 10%, 30%, 50%, 100% were remelted by cold crucible induction furnace and cast into rods for compression test. Compressive mechanical properties tests were carried out in Gleeble 3500 Thermal-Mechanical Simulator. Each sample was heated to 850 centigrade and held for 60 seconds in the atmosphere of argon, when deformation reached 20% with rate 10-3/s, the sample was quenched into water. The microstructure were observed by an MeF3 optical microscopy and a Quanta FEG 450 scanning electron microscopy. Chemical compositions of micro-regions were analyzed by accessory energy disperse X-ray spectroscopy. Effects of cold crucible remelting on mechanical properties and segregation of various revert proportion K418 superalloy were studied. The results indicate that the mechanical properties tend to be uniform after remelting than before. Cold crucible remelting improve the even distribution of elements in grains and interdendritic area, which modify the average second dendrite arm spacing and distributed pattern of precipitated phases. Homogenization of composition is a key factor for mechanical properties stabilization. Present researches imply that electromagnetic cold crucible remelting may alleviate the negative influence on the addition of recycled scraps effectively.

A spectrally selective material have the ability to transmit the visible light of the solar spectrum and block the near infrared (near-IR) portion. This would present certainly an advantage from an energy efficiency perspective in now a days high-rise buildings. The solar spectral irradiation consist of 43% of visible radiation which is in the form of light and 46% near-IR which that translates into heat energy. In hot climate areas of the world, a major source of energy consumption is cooling systems, it amounts to around 40% of the total consumption. With the extensive use of glass facades buildings in modern day construction, this issue requires even further attention. As such the use of spectrally selective coated glass could help alleviate this challenge.
To compare different glass coating behavior in terms of visible light penetration and IR blocking, a selectivity parameter is commonly used within the glass construction industry, it is the ratio of visible transmittance and solar transmittance. The amount of solar radiation transmittance is calculated by taking into account AM1.5 spectral irradiance and the photooptic efficiency of the human eye. The maximum theoretical value of selectivity is found to be 2.07.
In this work, we have designed and fabricated a single layer tungsten oxide on glass as the spectrally selective material. It is found that the selectivity is 1.29 that is considerably high for a single layer of material. The selectivity is being further optimized with the analysis of various process parameters such as the deposition rate/duration, the growth temperature and the post-growth heat treatment. We study the effect of the free carriers’ concentration on the overall IR absorption within the tungsten oxide layer. Our first optical data allowed to estimate the bandgap to be of indirect nature and equal to 2.9 eV. The nanocrystallinity of the layer has been assessed using AFM and SEM techniques. To further assess the suitability of this layer coating for energy efficiency buildings we will simulate the energy savings for a typical glass building using the coated glass as a facade.
Hence we propose here a single layer of metal oxide thin film, easy to fabricate on a large scale, and using a less expensive material as opposed to multilayers coatings requiring noble metal layers and hence adding to the complexity of the process and the overall cost.

Vanadium dioxide (VO₂) is a well-known thermochromic material which can undergo a reversible metal-semiconductor transition between an infrared-transparent state and an infrared-reflective state at a critical temperature of 68 °C while maintaining visible transmittance. Thin films of VO₂ on transparent substrates can be used to keep the balance between solar energy gain and heat loss dynamically and are therefore of interest for maintaining indoor temperature at a comfortable level regardless of outdoor temperature. Such coatings onto glass or polymers are one of the most favorite candidates for smart glazing in energy efficient buildings.
The difficulties of VO₂ synthesis are associated with the co-existence of diverse oxide forms and various polymorphs. Therefore it is often a challenge to obtain pure phase of VO₂, which occurs only in a very narrow range of oxygen partial pressure. However, in the present work, a thermodynamic analysis, based on minimization of Gibb’s free energy, documented that a chemical reaction between V and SO₂ would lead to VO₂ within a wide window of process parameters. This prediction was verified by experiments: Metallic vanadium deposits in gaseous SO₂ can yield excellent thermochromic films without the stringent process control that frequently is an obstacle for making VO₂ by oxidation in O₂. Our new technique therefore offers some distinct advantages with regard to practical manufacturing of VO₂-based thin films or particle composites.

Significant research has been carried out since the seventies of the last century on the physical and mechanical properties of NOCMAT as engineering materials at macro, meso, micro and nano levels. A functionally graded distribution of fibers in bamboo has been identified. Gradations were observed in longitudinal and radial directions. Bamboo in its natural habitat acts as a cantilever beam with a fixed support in the soil and is subjected to its own weight and wind load. Therefore, it has a naturally optimized structure to resist bending moments. The strengths are highest along the outside and lowest in the inside surfaces. In general, the strengths are also highest in those sections closer to the ground. Further studies of the fracture and toughening mechanisms in bamboo structures were carried out which will be presented in this Symposium. An advanced research on Non-Conventional Materials and Technologies (NOCMAT) has shown that it is now possible to produce high performance Fibre Reinforced Composites (FRC) and bamboo composites meeting any engineering demand. Therefore the challenge of the 21st century is to meet the need for cost-effective, durable and eco-friendly construction materials which will meet the global needs of infrastructure regeneration and rehabilitation which alone can enhance the quality of life for all the peoples of the world and in special in developing countries where these materials exist in abundance. In this presentation it is shown that a judicious combination of pozzolanic/cementitious materials, chemical admixtures fibres and bamboo can produce a wide range of FRC that are durable, strong and stiff, highly crack resistant, very ductile and capable of absorbing large amounts of energy. Such materials will find extensive applications in engineering. In particular, the development of durable natural fibre cement composites and bamboo poses a gigantic challenge to science and skills of engineering, a challenge which, if successful, can create the most exciting, eco-friendly construction material backed by an endless supply of renewable natural resources in our world.

A great challenge to overcome is the replacement of traditional petroleum-based plastics with polymers derived from sustainable, alternative resources. Though there are many facets to the design of truly sustainable materials, including the raw material source, energy demands of processing, and fate of the material post-consumer use, utilization of a more eco-friendly raw material source is an important first step. Ultimately, the full life cycle of the materials must be evaluated, including end-of-life options such as recycling, composting, and disposal in landfills. Of particular interest is the design of structured polymers from sustainable, plant-derived sources with well-defined molecular characteristics and competitive properties to conventional, petroleum-derived materials.

Vegetable oils are an attractive source for polymers, due to their low cost, abundance, annual renewability, and ease of functionalization. Long-chain polyacrylates derived from vegetable oil-based fatty acids were investigated as components of thermoplastic elastomers, polymers which behave as an elastomer at room temperature yet are processable at elevated temperatures. The thermal and mechanical behavior of the polymers was readily tuned through variation of the alkyl side-chain length of the polyacrylate. Surprisingly, the alkyl side-chain length did not impact the thermodynamic interactions between the components of the thermoplastic elastomers. This provides a route to manipulating the physical properties of the polymers through variation of the side-chain length without impacting the phase behavior and morphology. The development of structure-property relationships in these polymers will enable the widespread implementation of fatty-acid derived materials.

Recycled asphalt concrete is an inevitable step in sustainable road transportation. However the amount of recycling allowed in the various layers of the road are limited by national standards. Such standards require that the materials containing recycled elements need to fulfil requirements of all virgin materials. However this does not always take into account the weakness of recycled aspha< specifically cold temperature behavior as well as raveling. Using a multi scale approach, this paper will demonstrate that pavements containing high amounts of recycled asphalt can result in chemical, mechanical and rheological properties that are equal to materials made of all virgin elements. Important parameters such as water sensitivity, fatigue behavior, permanent deformation, and cold temperature behavior are among the characteristics that are investigated. Of particular importance is the blending of the old materials with the new ones. Environmental scanning electron microscopy has shown that the blending is non uniform. Regions have been identified where the materials were well blended whereas in other regions formation of micro-cracks could be established.

Catalysts provide enormous potential in enabling sustainable fabrication processes. This is recognized by programs such as the US Green Chemistry program which includes catalyst incorporation in over half of its 12 program goals. More directly, electrocatalytic processes such as carbon dioxide reduction or glycerol oxidation have the potential to directly reduce unwanted byproducts of energy production and generate low-carbon fuels or desired chemicals in the process. Before these electrocatalysts can be implemented, electrolysis cells must exhibit high faradaic efficiency and energetic efficiency at reasonable current densities. Despite the importance of both electrocatalyst composition and structure to catalyst performance, few studies to date have focused on the effects of electrode structure on performance. Even fewer studies have focused on the synergy between composition and structure on electrode performance [1]. To this end, biotemplating provides unique control in materials synthesis enabling control over nanoscale structural features as well as material composition. The M13 bacteriophage (M13) in particular, has been utilized as a material template for the synthesis of 3D networks as well as specific compositions of metal oxide nanowires [2,3].
This study demonstrates the ability of the M13 phage to serve as a synthetic functional handle to simultaneously tune several variables affecting the selectivity and activity of an electrocatalyst; these variables include surface area, composition, and porosity. Specifically, the M13 mediated fabrication process results in metallized nanofoams. The process has demonstrated synthetic control over the strut thickness from 50-200nm as well as control over the nanofoam porosity. With respect to composition, separate nanofoams of copper, cobalt, and nickel have been successfully fabricated. Each of these materials have been further modified to produce alloys and/or composites on a continuum of ratios of the former listed transition metals and one or more of the following materials: Copper, Nickel, Gold, and Zinc Oxide. Through a secondary biotemplating process of fabricated nanofoams, the surface area as well as surface morphology can be further controlled and altered. Electrocatalytic processes currently being explored with this catalytic system include electro-oxidation of glycerol as well as electro-reduction of carbon dioxide.
[1] Ma, Sichao, and Paul JA Kenis. "Electrochemical conversion of CO 2 to useful chemicals: current status, remaining challenges, and future opportunities."Current Opinion in Chemical Engineering 2.2 (2013): 191-199.
[2] Chen, Po-Yen, et al. "Versatile three-dimensional virus-based template for dye-sensitized solar cells with improved electron transport and light harvesting."ACS nano 7.8 (2013): 6563-6574.
[3] Oh, Dahyun, et al. "M13 Virus-Directed Synthesis of Nanostructured Metal Oxides for Lithium–Oxygen Batteries." Nano letters 14.8 (2014): 4837-4845.

The National Science Foundation created an umbrella program in 2010 entitled, Science, Engineering and Education for Sustainability (SEES) that encouraged cross-disciplinary cooperation to address the complex systems-level problems related to sustainable development. The Division of Materials Research (DMR) actively participated in two programs under the SEES umbrella: Sustainable Energy Pathways (SEP) and Sustainable Chemistry, Materials and Engineering (SusChEM). This presentation will showcase some of the funded projects and highlight outcomes, especially those related to new research partnerships developed for working towards the sustainable development of materials. New opportunities at NSF including a new initiative started in FY15, Innovations at the Nexus of Food, Energy, and Water (INFEWS) will also be discussed.

United Nations countries have signed a new sustainable development plan, the Agenda 2030 (http://www.un.org/sustainabledevelopment/), introducing seventeen goals to end poverty and protect the planet. Each goal has specific targets to be achieved over the next fifteen years. Many of these goals are related to materials research. For example, sustainable energy for all, which is central to nearly every major challenge of the world, sustainable industrial development as a primary source of income generation and building sustainable cities. Materials for a sustainable development require science-based technological and social innovation, characteristics of a knowledge society. Clearly this Agenda needs the work of researchers and productive investments, supported by the involvement of society as a whole through science communication activities.
Besides this international commitment, the Mexican National Development Plan 2012-2018 establishes that science and technology and innovation should be pillars of a sustainable economical and social progress. We will present here some of the programs on scientific research, innovation and science communication, that the National Council of Science and Technology (CONACyT) is fostering in order to fulfill its mission towards sustainability, in particular related to materials and energy. We will address activities that will contribute to the Agenda 2030.

This paper examines the key features characterizing the industrial innovation process and outlines the differences between industrial and academic approaches to innovation. Using examples from the author’s own research background, the paper explains mechanisms leading to breakthrough invention and focuses on the roles of intuition, imagination and serendipity. The development of a new product is a highly complex process which starts with an idea and undergoes many loops of modifications, improvements, optimization and scaling-up before it gets to manufacturing. All of these stages often require different types of expertise and variety of people. This means that the success of the entire innovation process largely depends on the effectiveness of interactions between people of various scientific backgrounds. Therefore skills such as persuasive communication and negotiation, understanding value chain and cost calculations as well as understanding how to effectively work and create in the complex multidisciplinary team environment become critically important tools for engineers. Unfortunately, while excelling in technical knowledge, today’s science and engineering graduates are often lacking these “other skills” so necessary for successful industrial carrier.
The author presents the argument that while most progressive companies and leading universities are trying to close this educational gap, a broader community commitment is required. Academia is in the best position to address this gap because the individual building blocks already exist in most universities. However a coordinated, collaborative effort between industry and academia is needed to develop an effective curriculum designed specifically for graduating science and engineering students.

Sustainability has become mainstream in both management practice and management research. Firms incorporate sustainability strategies into their core mission. University administrators promote sustainability as central to their curricula. Scholars pursue sustainability as a bona fide field of research inquiry. Given this level of attention and action, the world should be on the road to a sustainable future. But it is not. Environmental and social problems continue to get worse. This paper presents a model for understanding the progression of punctuated social change within the market that has taken us to the present reality, moving through three waves from 1970 to the present. We then present an assessment of where we may be going in the fourth wave, a punctuated shift that is predicated on the notion that we are now living in the Anthropocene, a new geologic epoch in which human activities have a significant impact on the Earth’s ecosystems. We present six elements of change within management systems that are reflected in the Anthropocene: systems thinking, which leads to new forms of: partnerships, materials use and supply chains, domains of corporate activity, organizations, and the economic models and metrics that are used to measure them.

Today, more than ever, consumers are considering sustainability in their purchasing decisions. Worldwide more than 460 ecolabels are used to identify the sustainable attributes of products within markets. The White House has issued Executive Orders requiring federal agencies to ensure that sustainability is included to federal purchasing criteria. Nearly every state has established procurement procedures that consider sustainability as a purchasing condition. Within this setting, businesses have significant incentives to reexamine their existing production processes and materials use, and incorporate sustainability principles into their business routines. However, in spite of the emerging institutional arrangements, most products are still produced unsustainably. This presentation offers a framework for understanding why, and elaborates on the sorts of change needed to encourage firms to produce more sustainable products and for consumers to purchase them. It emphasizes the opportunity created for materials scientists to innovate as firm/consumer incentives and demands align, and how material scientists can stay ahead of market trends, thus encouraging technology adoption and relevance.

Alkali-activated binders are a class of environmentally friendly materials with comparable mechanical and durability performance to that of conventional ordinary portland cement (OPC)-based binders. They are generally synthesized by activating waste/by-product materials such as fly ash using alkaline agents. While much is known about the chemical and physical properties of these materials, emphasis has not yet been provided as to the fundamental microstructural characterization of these systems that enables relevant engineering property predictions. This study reports a comprehensive experimental investigation of a fly ash-based geopolymer to culminate in reliable micromechanics-based prediction of macroscale mechanical properties.Microstructural and micromechanical investigation using: (i) synchrotron x-ray tomography (XRT) to determine the volume fraction and tortuosity of pores that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) scanning electron microscopy (SEM) combined with multi-label thresholding to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution, is reported. The micromechanical numerical model involves generation of 3D virtual microstructure based on microstructural features obtained from 3D high resolution synchrotron XRT images. After generation of the microstructure, the representative volume element (RVE) is meshed and periodic boundary conditions are implemented on the RVE as nodal displacement constraints. A homogenization module is developed to obtain effective volume-averaged RVE stress/strains or effective homogenized Young’s modulus of the material. The effective property predictions match those from experiments and are better than predictions from analytical homogenization models or simple volume fraction-based methods. The approach has also been implemented for a variety of random heterogeneous composites used as binder systems in infrastructure. The combination of experimental and numerical approach helps design sustainable infrastructural binders of the future.

Freely deformable characteristic of diverse inorganic semiconductor based electronics is required for wearable devices and miniaturized portable electronics. Traditionally most of the inorganic devices are fabricated on the rigid substrates restricting the flexibility and stretchability. Transfer printing process with optimized sacrificial layer is widely used to overcome this limitation. By etching the sacrificial layer, fabricated devices are separated from rigid substrates and transferred to target substrates easily. With transfer printing process, devices can be fabricated on the flexible and stretchable substrates without any constraints. But most of the optimized sacrificial layers use toxic etchants to selectively etch the sacrificial layer. Even with encapsulation of devices, there is a possibility that toxic etchant penetrate into devices through the encapsulation layer and induce the serious damage directly to the devices. In this report, we develop water-soluble sacrificial layer with germanium dioxides (GeO₂). Germanium dioxide sacrificial layer is easily fabricated by deposition with e-beam evaporator and thermal oxidation with furnace. Moreover, the water has no harmful influences to most of the inorganic devices. According to rapid development of IT, it is expected that diverse versions of flexible and stretchable electronics will post steep growth. Water soluble sacrificial layer for transfer printing of inorganic semiconductor based electronics leads to get over the conventional obstacles of fabrication processes of wearable devices.

Single-walled carbon nanotubes (SWCNTs) are being strongly considered as high-end nanocarbon due to their superior intrinsic properties and bulk applications in the area of energy storage and electronic devices. How to produce SWCNTs in a sustainable way is the first step to guarantee the availability of bulk samples. In this work, raw SWCNTs with a purity of about 5 % were synthesized by chemical vapor deposition (CVD) on Fe/MgO catalysts in a fluidized-bed reactor at a scale of about 1.0 kg h^-1. High-purity SWCNTs were obtained through facile acid treatment. The as-obtained Mg²⁺/Fe³⁺ mother liquor was used as a resource for Fe/MgO catalyst regeneration. An EDTA-2Na/Na₂CO₃-assistant one-step precipitation method was proposed to recover most of magnesium as basic magnesium carbonates without carrying impurities of iron. The Fe/MgO catalysts were then regenerated from these basic magnesium carbonates through metal loading and calcination. High-quality SWCNTs with a yield of 5.9 % were achieved based on these regenerated Fe/MgO catalysts, and a specific surface area larger than 1000 m² g^-1 was achieved. This work developed an effective process for recycling and regeneration of Fe/MgO catalysts, achieving the goal of circular utilization of magnesium resources.

Modern construction industry requires new technologies to comply with increasingly stricter environmental regulations. For instance, the cutback of cement demand in concrete fabrication lowers carbon dioxide emissions caused by its production. One solution is cement replacement by other materials with smaller carbon footprints and equivalent cementitious properties, such as fly ash (FA). This industrial waste material in contact with water turns into a cement-like paste. Alas, due to a slower reaction, at early age FA decreases the rate of development of properties in concrete. Such strength development with FA replacement at early age motivated the present research by incorporating a mineral additive to counteract the said strength loss. Nanostructured silica (nS) was used to that purpose. The study of concretes containing Portland cement (PC), nS, and FA, can be complex and time-demanding. Consequently, based on a statistical design of experiment for mixtures an optimized model was developed. This generated a controlled experimental design centered on the compressive strength as response variable, the levels of PC, FA and nS, as independent factors, and keeping the water-to-binder ratio constant. Five combinations of cement mixture components were obtained for this design. Compressive, flexural and tensile strength results were measured at 7, 28 and 90 days of curing. Density, absorption and permeability test were completed in order to better characterize the material and identify properties which can eventually have an effect on concrete durability and other mechanical properties.

Thermal conductivity and surface resistance of epoxy matrix filled composites with dendritic Cu fillers with different surface treatments have been investigated. Thermal conductivity of the composites was measured by a guarded heat flow meter method. Thermal conductivity increased when the Cu fillers were treated by HNO₃ and 3-aminopropyltrimethoxysilane (APTMS). A parallel study on the effect of incorporation of PMMA bead in epoxy matrix was also carried out. PMMA beads led a good contact between Cu fillers and improved the thermal conductivity of the composites for all filler concentrations. The incorporation of 12.5 % of PMMA beads into epoxy matrix at Cu filler content of 50 wt% resulted in 0.65 W/mK of thermal conductivity, which is 45% increase compared to the epoxy matrix composites without PMMA beads. This study provides a simple and economical way to produce the thermally conductive polymer composites.

The dye-sensitized solar cell (DSC) and quantum-dot sensitized solar cell (QDSC) have attracted considerable attentions as next-generation solar cells. One of the issues with DSCs and QDSCs is the need to improve the transferring of electrons into the redox system and activating electrolyte reduction at the counter electrode (CE). Platinum (Pt) is traditionally the most popular material for the CE of DSCs and numerous substitutes such as graphene-based nanohybrids have been developed to replace or reduce the use of expensive Pt. Graphene-metal nanohybrids have been mostly synthesized through either chemical methods or physical methods. However, extreme conditions such as high temperature, low pressure, liquid environment, and chemical toxicity become drawbacks for the application of graphene-metal nanohybrids to large scale productions. Recently, we developed a new process of efficiently synthesizing supported Pt-NPs using dry plasma reduction (DPR) at near room temperature under atmospheric pressure. Herein, we demonstrate the DPR to synthesize various metal (or metal alloy) NPs on carbon-based materials under atmospheric pressure without using any toxic chemicals at near room temperature.

Gel polymer electrolytes (GPEs), consisting of polymer matrix, organic solvents and salts, are often the appealing choice as they combine high ionic conductivity, low cost, improved safety, and ease of fabrication into desired shape and size. Nevertheless, it should be pointed out that even with immense efforts directing towards GPEs, the conductivity of GPEs is still limited due to the organic solvents evaporation in GPEs reduces the volume of electrolyte; thus causes a decrease of the contact area between the electrolyte and electrode that lowers the conductivity.

Therefore, cross-linked GPEs need to be developed for alleviating the organic solvent evaporation. This idea may arise from the assumption that cross-linking structure, to a large extent, prevents the polymer flow, which then improves the organic solvent housing in cross-linked GPEs while maintains high ionic conductivity. In current work, the cross-linked poly(methyl methacrylate) (PMMA) is synthesized to form the matrix featuring side functional group –COOCH₃, which enables methyl methacrylate (MMA) structural units to trap and efficiently store organic liquids. Additionally, oxygen atoms in the polar function groups from the side chains of cross-linked PMMA will attract and provide accommodation sites for cations to transfer. When solvent evaporation occurs, the chains must move over each other with the polymer flow; however, since the short side chains formed in cross-linked GPEs, these fluid movements will be prevented. Consequently, the cross-linked GPEs are able to efficiently reduce solvent evaporation. The morphologies are obtained by scanning electron microscopy, and Gamry instruments are performed for electrochemical characterization.

Our results demonstrate that the cross-linked PMMA GPE possesses the high ionic conductivity 5.08 ×10^-3 S cm^-1 with 25 wt.% NaPF₆ additive. It also exhibits good safety and electrochemical stability as seeing the fact of wide chemical window (-3 V to 3 V) and only 5 % ionic conductivity loss after 30 days. Sodium ion transference number ranges from 0.829 to 0.938 that apparently suggest that GPEs are high ionic conductive electrolytes. This achievement confirmed that the main goal of the present research has built up a cross-linked PMMA based GPE with high ionic conductivity along good stability through overcoming the organic solvent evaporation.

Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil–water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil–water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO₂ nanoparticles (SiO₂ NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80°C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil–water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification.

Recent industrial activities has led to elevated concentrations of a wide range of heavy metals in groundwater and wastewater. Heavy metal ions such as Chromium (Cr (VI)) are highly toxic. Various methods have been attempted to remove Cr (VI) ions in water including adsorption/filtration, chemical precipitation, electrodeposition and etc., but more economic and effective Cr (VI) remediation in ground and waste water is still under investigation. Zero Valent Iron nanoparticles (ZVINPs) possess large capacity for remediating Cr (VI) in water owing to their large surface area, high reactivity, non-toxicity, and ease of production. However, ZVINPs alone are limited by their instability, aggregation and difficult separation from the treated solution. In this study, ZVINPs were synthesized and immobilized on electrospun carbon nanofibers (ECNFs) surface. The novel ZVINPs based nanomaterial, i.e. electrospun carbon nanofibers with surface attached ZVI nanoparticles (ZVINPs@ECNFs), has been evaluated for Cr (VI) ions removal from a series of samples with Cr (VI) concentration in the range of 10 ppm to 70 ppm, at varying pH and ZVI loading. ZVINPs@ECNFs outperformed ZVINPs in reducing Cr (VI). ZVINPs@ECNFs with 0.04 g ZVINPs loading could remove 100% Cr(VI) ions from 50 ppm Cr(VI) solutions at pH = 4. It is envisioned that ZVINPs@ECNFs is going to serve as a novel ZVINPs based nanomaterial for efficient heavy metal remediation in groundwater as well as waste water treatment.

The chromium (Cr(VI)) is present in industrial effluents coming from manufacturing processes, electroplating industry, metal finishing, pigments, wood protection, brass, electronic equipment, catalysis and leather tanning [1]. In contrast, Cr(III) is relatively nontoxic and readily precipitates as Cr(OH)₃ or as the solid solution Fe_xCr_1-x(OH)₃ under alkaline or even slightly acidic conditions. Consequently, the reduction of Cr(VI) to Cr(III) has become a key procedure for treating Cr(VI)-containing wastewater [2]. Thus the photoreduction of Cr(VI) ions in aqueous suspensions of semiconductors has received increasing attention due the simple operation, low cost, high efficiency, reusability, direct use of natural solar energy, clean and safe, and no use and no release of other unwanted chemicals [3]. However, further studies are needed of catalysts for these reactions for that might make them viable and energetically favorable, for example, activating these reactions by means of solar radiation. Among the materials of interest, the heteroestruturados have been investigated as an interesting option for photoactivated reactions, due to the increase in its photocatalytic efficiency. In this context, the objective of this study was to evaluate the properties and the photocatalytic activity of heterostructures of Nb₂O₅/CuO synthesized by hydrothermal method. The physical and chemical properties of the heterostructures were characterized by high transmission electron microscopy (HRTEM), X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DRS), and nitrogen physical adsorption (BET method). The photocatalytic activity was evaluated using the photoreduction Cr(VI) in aqueous solution under ultraviolet and visible irradiation. The Nb₂O₅/CuO heterostructure have been successfully synthesized by a facile hydrothermal method. The XRD of samples shows that all the diffraction peaks could be indexed to orthorhombic phase Nb₂O₅. However the sample with 10 wt% CuO on Nb₂O₅ heterostructure shows diffraction peaks related to monoclinic CuO phase and the orthorhombic Nb₂O₅ phase. The optimal mole ratio 10% of CuO on Nb₂O₅ displayed the highest photocatalytic performance than pure CuO and Nb₂O₅ for the Cr(VI) photoreduction under visible light irradiation, which is about 4.3 times higher than that of the pure Nb₂O₅ within 210 min. Such improvement is attributed to the heterostructure between CuO and Nb₂O₅, which enhanced absorbance in the visible light region, the facilitated charge transfer and the suppressed recombination of electron/hole pairs.

Work supported by EMBRAPA, Fapesp (2014/09014-7), CNPq and CAPES.

[1] Blowes D. Science, 295, 2024-2025(2002).
[2] Liu Y.-g. et al. Chem. Eng. J., 226, 131-138 (2013).
[3] Yang, Q.-L. Et al. Desalination, 266, 149-153 (2011).

Nano zinc oxide (ZnO) and Calcium doped zinc oxide (CZO) nanopowders were synthesized by sol–gel method from pyrogallol and formaldehyde (PF) mixtures in water using picric acid as catalyst. Calcium doped zinc oxide (CZO) were prepared at different Ca concentrations from 1 wt% to 5 wt%. The obtained nanopowders were characterized by transmission electron microscopy, X-ray diffraction and nitrogen porosimetry. The objective of this work is to find a new and highly efficient nanomaterial for the adsorption of heavy metals from waste water. For this reason, the nanopowders were used to uptake heavy metals from aqueous solution. The obtained results show that the incorporation of Ca in nanoparticles zinc oxide (ZnO) increases the capacity adsorption of nanopowders. In this work we studied also the equilibrium isotherms, adsorption reaction kinetic and mechanisms as well as, effect of initial concentration, pH values and temperature on the removal of heavy metal ions from aqueous solution by CZO.

The heterogeneous photocatalysis of organic contaminants in aqueous suspensions of semiconductors has received increasing attention due to the simple operation, low cost, high efficiency, reusability, direct use of natural solar energy, clean and safe.¹ Nevertheless, most of the widely used photocatalysts have two main limitations in practical applications: (i) the low solar energy conversion efficiency due to their wide band gap and (ii) the high recombination rate of photoinduced electron-hole pairs.² However, heterostructures formation between different semiconductors has attracted attention due to the great potential to provide a technically and financially viable alternative to improve the photocatalytic performance. Graphitic carbon nitride (g-C₃N₄) is gaining much attention in photocatalysis due to its semiconducting properties, which allow its activation by visible light. This material is of particular interest because of the increasing use of solar energy in many applications, but previous studies have confirmed that g-C₃N₄ is more useful when associated with another semiconductor in a heterostructured scheme. Among various materials with high potential to be designed as heterostructures with g-C₃N₄, Nb₂O₅ arises as an interesting material due to its electronic properties. Thus, this work describes the photocatalytic activity of a new series of g-C₃N₄/Nb₂O₅ heterostructures synthesized at different weight ratios by a combination of thermal oxidation and hydrothermal treatment. All of materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, and nitrogen physisorption. The heterostructures were assembled as Nb₂O₅ nanoparticles uniformly decorating the g-C₃N₄ surface. The heterostructured g-C₃N₄/Nb₂O₅ catalysts exhibited superior photocatalytic performance on the degradation of methylene blue and rhodamine B dyes under visible and ultraviolet irradiation than the pure semiconductors. The enhanced photoactivity was explained by the increase in the lifetime of the charge carries due to the formation of heterojunction between Nb₂O₅ and g-C₃N₄. The Nb₂O₅ phase preserved its high dye adsorption capacity after formation of heterostructures with g-C₃N₄ which may have contributed for the improved specific activity of the photocatalysts. A mechanistic investigation on the photocatalytic process was conducted by using different reactive species scavengers. The superoxide radical was found to be the main active specie for dye photodegradation activated by visible radiation.

Acknowledgments
The authors are grateful to the CNPq (Grants n° 300247/2013-3), FAPESP (Grants n° 13/13888-0 and 14/09014-7), CAPES and FINEP for financial support.

References
¹Spasiano, D. et al. Appl. Catal., B 2015, 170-171, 90-123.
²Mills, A. et al. J. Photochem. Photobiol., A. 2015, 310, 66-105.

Applications of the nanotechnology-based methods for removal of oil in petroleum spills and its separation from water are presented. Oil spills during petroleum extraction and processing are frequently unavoidable and could lead to events of distinct scale, from small contaminations of ground and sea water to huge disasters. In addition to classic methods of oil removal, the “nano”-techniques have been developed, which use nano zero-valent iron (nZVI), expanded carbon nanotubes, sponges, aerogels and magnetic nanocomposites, metal and non-metal nanostructurized oxides, nitrides, salts, and zeolites. Some of these nanomaterials can be prepared by “greener” methods at lower costs and without damage for the environment. Main attention is paid to simplicity, costs and commercial availability of applied nanomaterials and their precursors, as well as to the efficiency of their applications for oil remediation. Special attention is paid to the use of ultrasound for expansion of CNTs volume in certain conditions and further capture of crude oil from its mixtures with water.

We introduce to self-powered water purification system that can be activated by itself as simple composite with PVDF-TrFE, as well as the photocatalysis of TiO₂-P25, even other substance activated by applied external energy. We have made PVDF-TrFE composites mixed TiO₂-P25 as catalyst materials and confirmed that the composite is able to fabricated free style which we want using properties as polymer. Consequently, the photocatalysis of TiO₂-P25 were activated by the piezoelectric potential without light irradiation. The piezoelectric potential induced catalytic self-power system showed the decomposition of the Rhodamine B fully in 6 hours in our experiment. Furthermore, the catalytic efficiency was higher than photo-catalytic one using UV-light (365nm) at the same conditions. In other words, we demonstrated the piezoelectric potential induced catalytic self-power system to decompose of organic contaminant in water using PVDF-TrFE composites for alternative green energy source to activate catalyst.

In order to achieve optimal desalination during capacitive deionization (CDI), CDI electrodes should possess high electrical conductivity, large surface area, good wettability to water, narrow pore size distribution and efficient pathways for ion and electron transportation. In this work, we fabricate a novel CDI electrode based on a three-dimensional graphene architecture by constructing interconnected graphene sheets with in-plane nanopores (NP-3DG). As compared to 3DG, NP-3DG features a larger specific surface area of 445 m2 g−1 and therefore the higher specific capacitance. The ultrahigh electrosorptive capacity of NP-3DG predicted from Langmuir isotherm is 17.1 mg g−1. This can be attributed to the interconnected macropores within the graphene networks and nanopores on graphene sheets. Both of macropores and nanopores are favorable for enhancing CDI peroformance by buffering ions to reduce the diffusion distances from the external electrolyte to the interior surfaces and enlarging the surface area.

Recent theoretical^1-2 and experimental studies³ report ultrahigh water permeability and salt rejection in nanoporous single-layer graphene. However, creating and controlling the size of nanometer-size pores in single-layer graphene pose significant challenges to application of these membranes for water desalination. Graphyne and hydrogenated-graphyne have tremendous potential as ultra-permeable membranes for desalination and wastewater reclamation due to its chemical and mechanical stability, flexibility, regular pore-distribution and atomic thickness. Using ReaxFF molecular dynamics simulations, we report the desalination performance of graphyne-2,3,4 and hydrogenated graphyne-2,3,4 membranes under realistic reverse-osmosis pressures (< 100 bar) as a function of its pore size, chemical functionalization and applied pressure. We find that adequately sized pores are essential to allow water passage while blocking ions and an increase in water flux with pore-size comes at the expense of reduced salt rejection performance. Hydrogenated graphyne-3 membranes have the best salt rejection performance while allowing water fluxes of ~100 *10⁶ g m^-2 s^-1 at 40 ^°C which is 2 orders of magnitude larger than the flux reported in recent experimental studies³ on nanoporous single-layer graphene. Hydrogenated graphyne-4 membranes selectively block positively charged ions (Na⁺, K⁺) while allowing negatively charged ions (Cl^-) to pass through. Membrane-functionalization can thus be a pragmatic approach to synthesize semipermeable membranes that separate differently charged ions in solution with possible applications in electrochemical cells. In summary, our simulations indicate that graphyne and hydrogenated-graphyne membranes have tremendous potential as water desalination and semipermeable membranes with water permeability that is orders of magnitude higher than nanoporous graphene and conventional reverse osmosis membranes.

(1). Cohen-Tanugi, D.; Grossman, J. C., Water Desalination across Nanoporous Graphene. Nano Lett. 2012, 12, 3602-3608.
(2). Cohen-Tanugi, D.; Grossman, J. C., Water permeability of nanoporous graphene at realistic pressures for reverse osmosis desalination. J. Chem. Phys. 2014, 141, 074704.
(3). Surwade, S. P.; Smirnov, S. N.; Vlassiouk, I. V.; Unocic, R. R.; Veith, G. M.; Dai, S.; Mahurin, S. M., Water desalination using nanoporous single-layer graphene. Nat. Nanotechnol. 2015, 10, 459-464.

Poly (amido amine) {PAMAM} dendrimers are nano-sized macromolecules, growing from a core amine unit through symmetric branching of amido-amine units.¹ These macromolecules have wide applications in many fields such as medicinal chemistry, sustainable chemistry, catalysis, drug-delivery, and host-guest chemistry.² Recent studies report the preparation of PAMAM based materials where the dendritic structures have been attached to ceramics, TiO₂, or silica surface.³ Here, we describe the preparation and properties of a novel PAMAM based magnetic gel and membrane . PAMAM based self-assembled structure was synthesized by attaching peripherally modified 4^th generation PAMAM (PAMAM-3-acryloyloxypropyl trimethoxysilane) in to Fe₂O₃ magnetic nanoparticles. These modified nanoparticles were characterized by SEM, TEM, FT-IR, DSC and TGA. The well characterized magnetic nanoparticles have been utilized to generate membrane in presence poly (ethylene glycol) and aerogel in presence of formaldehyde. All these materials are characterized by IR, SEM ,TEM, PXD and SQUID. The membrane has been used for desalination purposes, where the saline water (2 g/L NaCl) was allowed to pass through the membrane and the salt content was reduced by 92% in a single cycle.
References
1. Bosman, A.W.; Janssen, H. M.; Meijer, E. W. Chem. Rev. 1999, 99, 1665.
2. (a) Breinbauer, R.; Jacobson, E. N. Angew. Chem. Int. Ed. 2000, 39, 2498. (b) Liu, M.; Frechet, J. M. J. Pharma. Sci. Technol. Today. 1999, 2, 393. (c) Yang, K.; Weng, L.; Cheng. Y.; Zhang, H.; Zhang, J.; Wu, Q.; Xu, T. J. Phys. Chem. B. 2011, 10, 2185.
3. (a) Micheal, A.; Dimitris, T. Journal Of Hazardous Materials. 2009, 170, 35. (b) Chih-Chien, C.; Norio, U.; Toyoko, I. Chem. Mater. 2008, 20, 2669. (c) Micheal, A.; Dimitris, T.; Constantinos, M. P. Chem. Mater. 2003, 15, 2844.

We have recently demonstrated a revolutionary membrane design based on hierarchical assembly of fibrous materials with different fiber diameters (nm to μm). This design has led to breakthrough filtration performance from microfiltration to reverse osmosis, i.e., high flux, low energy and small system footprint. The key components of this technology are electrospun nanofibers (dia. ~100 nm) and carboxylate cellulose nanofibrils (dia. ~5 nm) extracted from biomass using a combined TEMPO-oxidation/defibrillation method. These nanofibers have large surface-to-volume ratio and high capacity for surface modification/charge, making them ideal materials for fabrication of highly permeable separation media, e.g., microfiltration filter that can simultaneously remove bacteria, viruses and toxic metal ions at gravity pressure. We further discovered that a simple two-chemical process can produce carboxylate nanocelluloses of different dimensions fusing biomass from different source. This ‘green’ method can bypass both electrospinning and conventional nanocellulose fabrication steps (extraction/pretreatment, bleaching and TEMPO oxidation) and generate inexpensive new nanostructured materials for water purification in a very sustainable manner.

Frequently occurring water pollution from oil and chemical spills/leaks as a result of accidents or natural disasters have resulted in a shortage of fresh water in many regions of the world. Water contaminants such as oil, organic solvents, and heavy metal ions can severely harm people and other living plants and animals. Thus, there is a growing demand for innovative absorptive materials possessing a high absorption capacity, high selectivity, and high efficiency. Here we demonstrate such a material that is produced via an environmentally friendly freeze-drying process; i.e., a cross-linked polyvinyl alcohol (PVA)–cellulose nanofibril (CNF) hybrid organic aerogel.The PVA/CNF hybrid organic aerogels have very low densities (<15 kg m^-3) and very high porosities (>98%).They were rendered both superhydrophobic and superoleophilic after being treated with methyltrichlorosilane via a simple thermal chemical vapor deposition process. Successful silanization on the surface of the porous aerogels was confirmed by various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), Fourier transform infrared spectroscopy (FTIR), and contact angle measurements. The silane-treated, cross-linked PVA/CNF aerogels not only exhibited excellent absorption performance for various types of oil (e.g., crude oil) and organic solvents (with a typical weight gain ranging from 44 to 96 times their own dry weight), but also showed remarkable scavenging capabilities for several types of heavy metal ions tested (e.g., Pb²⁺, Hg²⁺, etc.), making them a versatile absorbent for various potential applications. Furthermore, these PVA/CNF aerogle demonstrated excellent elastic and mechanical durability after silane-treatment as evidenced by cyclic compression tests. Thus, PVA/CNF aerogels made of renewable/sustainable materials through a simple and green process may offer many promising applications including water purification to clean up oil/chemical spills/leaks and heavy metal contamination, thereby protecting our environment and all living species.

Seawater desalination is the primary source of drinking water for many countries. Reverse osmoses (RO) has been demonstrated as the most energy efficient and feasible desalination technology. However, the main limitations of SWRO are the membrane fouling associated with particulate matter/colloids, organic/inorganic compounds, and biological growth. Advanced membranes are required to enable ultrafast permeance while maintaining good mechanical properties are very important to advance the water purification and desalination technologies. Two-dimensional Ti₃C₂T_x (MXene) has been recently explored as novel water desalination/purification membranes. MXenes are a new family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides that can challenge graphene and other well-studied 2D materials due to a unique combination of properties and a large diversity of compositions. In this work, we investigated the antibacterial properties of the colloidal solutions of two-dimensional (2D) single- and few- layer Ti₃C₂T_x MXene and micrometer-thick membranes coated on commercial polyvinylidene fluoride (PVDF) support. The anti-bacterial properties of Ti₃C₂T_x were tested against Escherichia coli (E. coli) and Bacillus Subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Compared with graphene oxide (GO), which has a similar 2D structure and has been widely reported as an antibacterial agent, Ti₃C₂T_x shows a much higher antibacterial efficiency toward both Gram-negative bacteria E. coli and Gram-positive bacteria B. subtilis. A significant decrease in bacterial cell viability was observed within 4 h of exposure both by colony-forming unit (CFU) and regrowth curve coupled with scanning electron microscopy (SEM) analysis. SEM and TEM studies reviled obvious physical damage to the cellular membrane induced by direct contact with MXene nanosheets. MXene membranes are expected to be resistant to bio-fouling and offer bactericidal properties. On the basis of these results, we introduce MXenes as a new family of 2D antimicrobial nanomaterials.

Reverse osmosis (RO) membrane technologies have played a pivotal role for a sustainable water supply, since they provide water of high quality from seawater and brackish water at low cost due to remarkable membrane performance and process improvements. However, still more performance enhancement is required to achieve lower energy consumption and higher quality of water. For a stable plant operation, chemical cleanings are needed to prevent fouling, which is a deterioration of membrane performance caused by foulants such as chemical substances and bioorganisms, especially for waste water reclamation. The membrane with both low-fouling property and chemical resistance achieves low-cost and reliable water treatment process because of less chemical cleanings and long term use. Thus, chemical tolerance and low-fouling tendency of the membranes are also important issues for creation of innovative RO membranes.
Composite polyamide membranes are widely used as high performance RO membranes. Cross-linked aromatic polyamide functional layer, which is formed on supporting membrane, affords separation properties. The polyamide functional layer has hierarchical structures, primary (molecular) to higher-order structures (molecular assembly, pores and surface structures). Detailed analysis and design of these hierarchical structures are important to the development of RO membranes with excellent performance and durability.
The functional layer has sub-μm-size protuberance structures and sub-nm-size pores. Morphological analysis by TEM gave us a precise cross-sectional image of RO membrane surface, and it enabled a quantification of surface morphology. We controlled the surface area, thickness, and uniformity of protuberance structures through the use of the analyses. The size distribution, volume, and the number of the fine pores were also measured in details. Moreover, chemical properties of membrane surface, which relates to solute rejection rate and fouling tendency, were also analyzed. Based on these results, we reached the new molecular design to achieve stable, uniform structures, which accounts for high solute rejection rate and chemical durability.
Through detailed analyses and precise control of primary and higher-order structures of polyamide, RO membranes with remarkable high water permeability, solute rejection rate, chemical tolerance, and low-fouling property were successfully developed. The developed RO membranes also make a great contribution to reduction of CO₂ emission. Life cycle assessment (LCA) is a useful tool to evaluate the environmental impacts of products to our society at all stages of its life cycle including the production of material, construction of plant, manufacture, and waste disposal. A comparison of the principal desalination technologies: thermal method and RO method was assessed by applying LCA. RO method with the developed membrane shows excellent low CO₂ emission less than a sixth of the emission in thermal method.

Water scarcity is a crippling issue of global proportions and based on a recent water development report from the United Nations, this problem will only worsen in the next 15 years or so. Among current technologies employed to combat the water crisis, desalination has emerged as a key strategy to solve worldwide water shortage. Commercial desalination technologies include reverse osmosis (RO) and thermal processes. However these processes consume large amounts of energy and have high maintenance costs. On the contrary, capacitive deionization (CDI) is membrane free and operates at low voltages which make it a promising low cost water desalination technique.
The concept of CDI follows the working principle of an electrical double-layer capacitor (EDLC). When an external voltage is applied, salt ions are electro-adsorbed on the electrical double-layer formed between the solution and the porous electrode interface. Once these pores are saturated with salt ions, a reverse voltage or a short circuit is applied to regenerate the electrodes. Therefore, the CDI performance depends strongly on physical properties and internal structure of the electrode materials. In principle, electrode materials for CDI should have high electrical conductivity, large surface areas, good wettability to water and a narrow pore size distribution.
Generally, carbon materials with high electrical conductivity and tunable structural properties have been considered as promising electrode materials for CDI. The list of carbon materials reported in literature include graphene, carbon nanotube, activated carbon, carbon aerogel and their composites. Among these materials, porous carbons with advantages of low-cost, high chemical stability, large surface area and good electrical conductivity make them ideal candidates for CDI application. Metal-organic frameworks (MOFs), constructed by metal (clusters) and carboxylate or/and N-involved ligand with huge diversity, intuitively should be a class of ideal precursors. The well-organized framework can be converted to carbon with uniform heteroatom decoration, and the long-range ordering and high porosity of MOFs can be partially preserved to afford high surface area of resultant porous carbons via facile pyrolysis.
In this work, we proposed a novel CDI electrode based on MOF-derived porous carbons. Fe-MOFs with different morphologies were prepared as templates, and systematic studies on the thermal decomposition process of these Fe-MOFs and the effect of template morphology on the products were carried out in detail. The as-prepared MOF-derived porous carbon exhibits a significantly high specific surface area of 579 m² g⁻¹, as well as a favorable pore size distribution of approximately a few nanometers. As expected, an ultrahigh electrosorptive capacity of 18 mg g⁻¹ was achieved in 500 mg l^-1 NaCl solutions, which is among the best performance of previously reported carbon electrodes for CDI.

Recently, separation of oil from oily wastewater has caught much attention due to the increased oil pollution caused by our daily life, industrial wastes, and offshore oil spills. However, conventional techniques still suffer from low efficiency, high cost, and second contamination to date. Diatom, a silica-based phytoplankton, is abundant in aqueous environment, and it produces almost 25% of the oxygen we breathe. With its water-absorbing and porous nature, diatom becomes a potential candidate for oil/water separation. In this study, we utilized diatomaceous earth as raw material to fabricate a hierarchically porous plate via the freeze-casting technique. After purification, the nanostructure of diatom could be well-preserved, and aligned hierarchical micro-sized channels and nano-sized pores were successfully synthesized through the optimized cooling rate and water content. The hierarchically porous plate displays both superhydrophilicity and underwater superoleophobicity evaluated by various oils, such as gasoline, soybean oil, hexane, and n-hexadecane. Additionally, our work demonstrates superior oil/water separation efficiency, high water permeation rate, and large intrusion pressure. Moreover, the as-synthesized plate shows low adhesion of oil underwater that the oil can be washed away easily by water flushing, and maintained good durability even after several separation cycles. Finally, the plate exhibits excellent environmental stability under a series of harsh environments, including strong acid, brine, and hot water. To recapitulate, we synthesize a cost-effective, eco-friendly, feasible, and robust diatom-based porous plate by freeze casting method which shows superior oil/water separation performance, reliability and stability. With these advantages, it has potential to be further applied in the separation of large amount of oily waste water and is suitable for long-term usage.

The increasing scarcity of clean water sources is making water treatment more and more important for our current societies. Treatment of organic pollutants by photocatalytic oxidation offers a viable option to remove the contaminants even at low concentrations. Photocaltalytic oxidation processes use a semiconductor material. When light shines on it, it creates a potential difference that is able to produce OH radicals to decompose harmful organic materials dissolved in water. The most widely used semiconductor in the field is TiO₂, which has a very high bandgap (3.3 eV). That is why, in most cases, UV light is used to excite the charge carriers in the semiconductor, increasing the amount of energy input needed in the system. Instead, we propose a BiVO₄ photoanode as a viable alternative. BiVO₄ is an earth-abundant material, currently used as yellow paint, with a bandgap of 2.5 eV. Its lower bandgap allows to efficiently use visible light instead of UV light for the photocatalytic oxidation process, reducing the energy input needed in the system and making this material very attractive for water treatment.
To better asses the advantages of this photoanode, we compare the properties of BiVO₄ with those of the commonly used TiO₂ under solar illumination. BiVO₄ films of different thicknesses and doping profiles have been tested. There are also two configurations used regarding the TiO₂, one deposited in a Ti flat plate and the other one deposited in a Ti mesh to increase the surface area. The material properties, optical characteristics and electrical performance have been characterized by XRD, AFM, IPCE, UV-Vis absorption measurements, EIS and cyclic voltammetry measurements. Finally, phenol degradation performance has been measured for all the TiO₂ and BiVO₄ samples. Different applied voltages were tested for degradation, being 1V the optimum both for BiVO₄ and TiO₂. The best performance for phenol degradation was found to be an undoped BiVO₄ film of 300 nm, reeducing the phenol concentration to 30.0% of the initial concentration in 4 hours. In contrast, the best results for the TiO₂ were obtained when deposited in a Ti plate, with 56.1% of the initial phenol concentration still remaining in the solution after 4 hours of degradation. This is assumed to be mainly due to the enhanced light absorption of BiVO₄, especially at higher wavelengths. In addition, the fact that a gradient tungsten doping of the BiVO₄ did not improve the performance suggest that this photoanode is not limited by charge carrier separation.
In conclusion, it was found that phenol can be effectively removed from water via photocatalytic oxidation using a BiVO₄ photoanode and solar light. This is a great advance in the field of water treatment, since it provides an effective, non-energy intensive way to remove organic contaminants from drinking water.