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Risk Reduction via Greener Synthesis of Noble Metal Nanostructures and Nanocomposites (Presentation)
Citation:
VARMA, R. S. Risk Reduction via Greener Synthesis of Noble Metal Nanostructures and Nanocomposites (Presentation). Presented at NATO Advanced Research Workshop , Faro, PORTUGAL, April 27 - 30, 2008.
Impact/Purpose:
To inform the public.
Description:
A brief account of greener production of nanoparticles which reduces or eliminates the use and generation of hazardous substances is presented. The utility of vitamins B1 and B2, which can function both as reducing and capping agents, provides an extremely simple, one-pot, greener method to synthesize bulk quantities of nanospheres, nanorods, nanowires, and nanoballs of aligned nanobelts and nanoplates of the metals in water without the need for large amounts of insoluble templates. A bulk and shape-controlled synthesis of noble nanostructures with various shapes such as prisms, cubes, and hexagons occurs via microwave (MW)-assisted spontaneous reduction of noble metal salts using an aqueous solution of a-D-glucose, sucrose, and maltose or alternatively in poly (ethylene glycol). The noble nanocrystals undergo catalytic oxidation with monomers such as pyrrole to generate noble nanocomposites which have potential functions in catalysis, biosensors, energy storage systems, and nanodevices. Wet synthesis of Ag cables wrapped with polypoyrrole has been demonstrated at room temperature without using any surfactant/capping agent and/or template. A general MW method has also been developed that accomplishes cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic systems such as Pt, Cu, and In; bimetallic systems, namely Pt-In, Ag-Pt, Pt-Fe, Cu-Pd, Pt-Pd and Pd-Fe; and single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT), and Buckminsterfullerene (C-60) in various shape forms such as spheres, dendrites, and cubes. The strategy is now extended to the formation of biodegradable carboxymethyl cellulose (CMC) composite films with noble nanometals that may find potential biological applications; such noble metal decoration and alignment of carbon nanotubes in carboxymethyl cellulose is also possible using this MW approach. Clean synthesis of core (Fe, Cu)-shell (Au, Pt, Pd and Ag) nanocrystals have been achieved using aqueous vitamin C. A newer form of carbon-doped porous titania that can be useful for visible-light induced photodegradation of pollutants has also been prepared using a benign natural polymer, dextrose (10). This general and eco-friendly protocol utilizes dextrose to create a spongy porous structure and can be extended to other transition metal oxides such as ZrO2, Al2O3, and SiO2.