SILVER NANOPARTICLES ENDOWED CORE/SHELL COMPOSITE MICRO PARTICLES FOR CATALYTIC DEGRADATION OF TOXIC CONGO RED

Abstract

Core shell microgels consist of polystyrene (pST) core and single layered poly(N-isopropyl methacrylamide (pNM) shell were prepared by seed mediated precipitation polymerization method. Single layered shell was endowed with Ag NPs by in-situ chemical reduction method using Ag NO3 salt as silver ions precursor. Core shell micro and composite micro particles were characterized by different techniques such as Uv-visible, FTIR spectroscopy, TEM, DLS and TGA. TEM analysis showed that core shell micro particles were spherical in shape. DLS analysis showed the particle size, size distribution and pH sensitivity. Catalytic activity of Ag-pST-pNM core shell composite micro particles was investigated by reducing the Congo red as benchmark reaction and reduction reactions were monitored on Uv visible spectrophotometer. It was observed that restriction of Ag NPs in single layered shell around the pST core facilitated the diffusion of reactants by reducing the mass diffusion barrier and enhanced the rate of reduction reaction. Due to single layered thickness of shell our reported catalyst showed high activity as compared to previously reported core shell and homogeneous hybrid microgels. Solid pST core induced the easy removability of catalysts from reaction mixture by mild centrifugation. Polymerized pNM monomer in shell of core shell microgels shifted the volume phase transition of particles to high temperature (44°C) and make possible of their use at high temperature as compared to already reported poly(Nisopropylacrylamide) based core shell microgels which show volume phase transition temperature around 32°C. Catalytic reduction of Congo red was also performed under different reaction conditions such as NaBH4, Congo red and catalyst to optimize the value of kapp. Reduction reactions followed the Langmuir Hinshelwood mechanism.