Silver metal nano-matrixes as high efficiency and versatile catalytic reactors for environmental remediation

Nano-porous metallic matrixes (NMMs) offer superior surface to volume ratios as well as enhanced optical, photonic, and electronic properties to bulk metallic materials. Such behaviours are correlated to the nano-scale inter-grain metal domains that favour the presence of electronic vacancies. In this work, continuous 3D NMMs were synthesized for the first time through a simple diffusion-reduction process whereby the aerogel matrix was functionalized with (3-Mercaptopropyl)trimethoxysilane. The surface energy of the silica monolith templates was tuned to improve the homogeneity of the reduction process while thiol functionalization facilitated the formation of a high density of seeding points for metal ions to reduce. The diameter of NMMs was between 2 and 1000 nm, corresponding to a silver loading between 1.23 and 41.16 at.%. A rates of catalytic degradation kinetics of these NMMS which is three orders of magnitude higher than those of the non-functionalized silver-silica structures. Furthermore, the enhancement in mechanical stability at nanoscale which was evaluated by Atomic Force Microscopy force measurements, electronic density and chemical inertness was assessed and critically correlated to their catalytic potential. This strategy opens up new avenues for design of complex architectures of either single or multi-metal alloy NMMs with enhanced surface properties for various applications

Assessing the temporal stability of surface functional groups introduced by plasma treatments on the outer shells of carbon nanotubes

Plasma treatments are emerging as superior efficiency treatment for high surface to volume ratio materials to tune functional group densities and alter crystallinity due to their ability to interact with matter at the nanoscale. The purpose of this study is to assess for the first time the long term stability of surface functional groups introduced across the surface of carbon nanotube materials for a series of oxidative, reductive and neutral plasma treatment conditions. Both plasma duration dose matrix based exposures and time decay experiments, whereby the surface energy of the materials was evaluated periodically over a one-month period, were carried out. Although only few morphological changes across the graphitic planes of the carbon nanotubes were found under the uniform plasma treatment conditions, the time dependence of pertinent work functions, supported by Raman analysis, suggested that the density of polar groups decreased non-linearly over time prior to reaching saturation from 7 days post treatment. This work provides critical considerations on the understanding of the stability of functional groups introduced across high specific surface area nano-materials used for the design of nano-composites, adsorptive or separation systems, or sensing materials and where interfacial interactions are key to the final materials performance

Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption

Fresh water is one of the most precious resources for our society. As a cause of oxygen depletion, organic pollutants released into water streams from industrial discharges, fertilizers, pesticides, detergents or consumed medicines can raise toxicological concerns due to their long-range transportability, bio-accumulation and degradation into carcinogenic compounds. The Stockholm Convention has named 21 persistent organic pollutants (POP) so far. As opposed to other separation techniques, adsorption, typically performed with activated carbons, offers opportunities to combine low operation costs with high performance as well as fast kinetics of capture if custom-designed with the right choice of adsorbent structure and surface chemistry. Nanofibers possess a higher surface to volume ratio compared to commercial macro-adsorbents, and a higher stability in water than other adsorptive nanostructures, such as loose nanoparticles. This paper highlights the potential of nanofibers in organic pollutant adsorption and thus provides an up-to-date overview of their employment for the treatment of wastewater contaminated by disinfectants and pesticides, which is benchmarked with other reported adsorptive structures. The discussion further investigates the impact of adsorbent pore geometry and surface chemistry on the resulting adsorption performance against specific organic molecules. Finally, insight into the physicochemical properties required for an adsorbent against a targeted pollutant is provided

Catalytic electrospun nano-composite membranes for virus capture and remediation

International audienceViruses spread in the environment through solution and as aerosols, generating great risks of infection for exposed populations. Virus versatile chemistries and behaviours thus require remediation solutions encompassing both nanoscale controlled surface topography and chemical functionalities. Here, nano-composite electrospun nanofiber membranes were electrospun from tetraethoxysilane and ammonium tetrathiomolybdate mixed blended with poly(acrylonitrile) to produce defect-free and highly interconnected porous structure. The capture efficiency of the nano-composite electrospun based membranes for the Semliki Forest virus in solution was found to be largely related to the tuned fiber surface morphology and roughness as well as to the surface energy of the materials. The mechanically flexible and robust composite microfiltration membranes, with pore size distributions in the range of 0.8 to 3.1 mu m and specific surface areas on the order of 45.6 m(2)/g, exhibited virus removal efficiencies in single pass up to 98.9% and yet very high water permeation up to 26,000 L.m(-2).h(-1).bar(-1). The hybrid membranes also yielded excellent photocatalytic performance thus allowing for continuous flow operation as continuous membrane reactors. These ultra-thin membranes, facile to mass-produce, offer opportunities to provide cost-effective water remediation strategies for low-energy requirement separation systems for the simultaneous capture and degradation of pathogens, and to self-cleaning material

Amorphous Alumina Thin Films Deposited on Carbon Microfibers As Interface Layer for Thermal Oxidation Barriers

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Inorganic Nanoparticles/Metal Organic Framework Hybrid Membrane Reactors for Efficient Photocatalytic Conversion of CO₂

Photocatalytic conversion of carbon dioxide (CO₂) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO₂ adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photogenerated electrons to CO₂ molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining the high CO₂ adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons. Herein, controlled encapsulation of TiO₂ and Cu–TiO₂ nanoparticles within zeolitic imidazolate framework (ZIF-8) membranes was successfully accomplished, using rapid thermal deposition (RTD), and their photocatalytic efficiency toward CO₂ conversion was investigated under UV irradiation. Methanol and carbon monoxide (CO) were found to be the only products of the CO₂ reduction, with yields strongly dependent upon the content and composition of the dopant semiconductor particles. CuTiO₂ nanoparticle doped membranes exhibited the best photocatalytic performance, with 7 μg of the semiconductor nanoparticle enhancing CO yield of the pristine ZIF-8 membrane by 233%, and methanol yield by 70%. This work opens new routes for the fabrication of hybrid membranes containing inorganic nanoparticles and MOFs, with potential application not only in catalysis but also in electrochemical, separation, and sensing applications