In the last couple of decades gold nanoparticles (GNPs), are used in a variety of applications, viz. photonics, therapeutics, diagnostics, and catalysis. Reduction of toxic 4-Nitrophenol (4-NP) into non-toxic 4-Aminophenol (4-AP) has become a research hotspot in recent years, and GNPs have been explored in catalyzing this reduction process. To study the effect of the capping agent and the shape of the GNPs on catalytic efficiency, here we have used gold nanoparticles-amphiphilic block copolymers conjugates. Stimuli-responsive polymers induce stability and recyclability to the GNPs. The high dispersion of the coated polymers in the reaction medium allows the reactant molecules to access the active site of the noble metal nanoparticle easily. In this work, we have designed and synthesized poly(N-isopropyl acrylamide)-<i>b</i>-(styrene-<i>r</i>-vinyl pyridine) of three different hydrophilic (NIPA) chain length and same styrene to vinyl pyridine ratio via reversible addition-fragmentation chain transfer (RAFT) polymerization to stabilize the GNPs which have different lower critical solution temperature (LCST). To get the information about the change in catalytic efficiency due to change in the gold nanoparticle shape, we have also synthesized polymer-stabilized gold nanorod and compared the efficiency with the nanoparticle. The temperature-dependent catalytic efficiency of the polymer-coated GNPs towards 4-NP reduction was also studied. The catalytic efficiency of gold nanoparticles was found to be influenced by changing the temperature below and above LCST, length of the hydrophilic chain of the coated polymer as well as the shape of the gold nanoparticles which was attributed to the altered accessibility of the reactants to the catalyst surface. There was nearly no loss of catalytic activity on recycling the polymer-coated GNPs confirms the stability of the polymer coating on GNPs. Hence, these new catalysts could be potentially useful in industrial applications.

Thermo-responsive block copolymers in stabilizing and controlling catalytic efficiency of gold nanoparticles

2019 Spring National Meeting

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