Synthesis and Characterization of pH-Responsive Organic-Inorganic Hybrid Material with Excellent Catalytic Activity

Poly(N-isopropylmethacrylamide-co-methacrylic acid) [p(NipAam-Mac)] microgels were synthesized and used as microreactors to fabricate silver nanoparticles. Pure and hybrid microgels were characterized using Ultraviolet-Visible (UV/Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). Catalytic activity of hybrid microgels and mechanism of catalysis by this system was explored using different reaction conditions. At the same temperature, apparent rate constant (k (app) ) was found to be varied from 0.0414 to 0.7852 min(-1) by increasing the concentration of NaBH4 from 2.49 to 22.41 mM at constant concentration of substrate and catalyst. However upon extra increase in concentration of NaBH4 from 22.41 to 37.35 mM reduced the value of k (app) to 0.2178 min(-1). Likewise, the value of k (app) was found to be increased from 0.1242 to 0.5495 min(-1) with increasing the concentration of 4-nitrophenol [Para-nitrophenol (p-Np)] from 0.063 to 0.079 mM keeping other parameters constant. Further increase in concentration of p-Np caused decline in the value of k (app) . Kinetic data reveals that catalytic reduction of p-Np obeys Langmuir-Hinshelwood mechanism and p-Np is converted to p-Ap on the surface of the silver nanoparticles passing through various reaction intermediates.