Photochemical Green Synthesis of Calcium-Alginate-Stabilized Ag and Au Nanoparticles and Their Catalytic Application to 4-Nitrophenol Reduction

Citation: Sandip Saha, Anjali Pal, Subrata Kundu, Soumen Basu, Tarasankar Pal (2009/11/6) Photochemical Green Synthesis of Calcium-Alginate-Stabilized Ag and Au Nanoparticles and Their Catalytic Application to 4-Nitrophenol Reduction. American Chemical Society (RSS)
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Summary

The aim of the reasearch was to synthesis Ag and AU nanocomposite materials using a greener approach, and to explore its possibilty as an eco-friendly heterogeneous catalyst for the conversion of 4-Nitrophenol to 4-aminophenol using NaBH4 as reducing agent. Metal nanopraticles are synthesised on hydrosol of sodium alganite hich provides a template for synthesis and is known as a stablizer. Alganite also has mild reducing ability and biocompatiblity. The resultant magnetically recoverable Au and nanocatalyst exhibited excellent Catalytic activity to the reduction of 4-nitrophenol (4-NP) with sodium borohydride. The reduction follows zero-order kinetics with respect to 4-nitrophenolate ion concentration with both Ag/CA and Au/CA as catalyst. The rate constant obtained from the slope of the kinetic curves has been related to catalyst dose, keeping other parameters such as initial 4-NP concentration and borohydride concentration the same. It was observed that with the increased amount of catalyst the rate constant increases in both cases and had a linear relationship. This is obvious because an increase of dose means an increase of surface area. The effectiveness of the as-prepared solid-phase alginate-stabilized Ag and Au as catalyst for 4-NP reduction to 4-AP by excess borohydride has been evaluated. The reaction was much faster in the case of Ag/CA compared to that of Au/CA. The reason behind this may be that Ag is a better catalyst or it may be due to the difference in surface coverage. In both cases, the reaction was very efficient and followed zero-order kinetics well. The catalyst efficiency was determined on the basis of TOF and recyclability. The new as-prepared biopolymer-based Ag and Au catalysts are stable, efficient, eco-friendly, easy to prepare, and recyclable and thus have potential for industrial applications.