Simultaneous catalytic reduction of nitroarenes using silver nanoparticles fabricated in poly(N-isopropylacrylamide-acrylic acid-acrylamide) microgels

Abstract

Monodisperse multi-responsive poly(N-isopropylacrylamide-acrylic acid-acrylamide) [P(NIPAM-AAc-AAm)] polymer microgels were synthesized by precipitation polymerization in aqueous medium. Silver nanoparticles were fabricated inside the microgels by in situ reduction method. Poly(N-isopropylacrylamide-acrylic acid-acrylamide) [P(NIPAM-AAc-AAm)] microgels and Ag-poly(N-isopropylacrylamide-acrylic acid-acrylamide) [Ag-P(NIPAM-AAc-AAm)] hybrid microgels were characterized by Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy (UV–vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hybrid microgels were found to be temperature and pH sensitive in aqueous medium. They have long term stability under various conditions of pH of the medium. The hybrid microgels were used as catalysts for simultaneous reduction of various nitro compounds in aqueous medium. Nitroarenes like o-nitroaniline (o-NA), p-nitroaniline (p-NA), p-nitrophenol (p-NP) and nitrobenzene (NB) were individually and simultaneously reduced to corresponding aminoaromatic compounds by sodium borohydride in the presence of Ag-poly(N-isopropylacrylamide-acrylic acid-acrylamide) hybrid microgels catalyst. Catalytic activity of the hybrid microgels for individual and simultaneous reduction of nitroarenes was compared with each other. The retardation in catalytic reduction of each nitroarene in the presence of other nitroarenes was explained on the basis of simultaneous adsorption. Various factors affecting the catalytic reduction of p-nitroaniline (p-NA) like catalyst dose and pH of the medium were also investigated. Rate of reduction of p-nitroaniline was found to be increased with increase of catalyst dose and pH of the medium.