Stimuli responsive microgel containing silver nanoparticles with tunable optical and catalytic properties

In this work, poly (vinylcaprolactam-co-itaconic acid) microgel was prepared by free radical polymerization. Silver nanoparticles were prepared in synthesized microgel networks by in situ reduction of Ag+ ions, loaded in microgel from aqueous solution of AgNO3. The prepared microgel was characterized by Fourier transformation infra-red spectroscopy, UV-Visible spectroscopy, fluorescence spectroscopy, X-ray diffraction, laser light scattering, thermal gravimetric analysis, differential scanning calorimetry and transmission electron microscopy. Swelling behavior of microgel was studied as a function of temperature and pH. The microgel was found to be in swollen state at low temperature and basic medium while in collapsed state at high temperature and acidic medium. A slight decrease in swelling capacity of microgel was observed after the fabrication of silver nanoparticles. A decrease in the emission intensity and a red shift in surface plasmon resonance wavelength of silver nanoparticles was observed with pI I induced swelling of microgel. Catalytic activity of the composite microgel was studied by using them as catalyst for the reduction of 4-nitrophenol, methyl orange and methylene blue. Effects of temperature and catalyst dose were also investigated. The reduction rates of 4-NP, MB and MO were found to be 0.859, 0.0528 and 0.167 min(-1), respectively. The change in catalytic performance and shift in absorption maxima and emission intensity of composite microgel as a function of temperature and pH reveals that this system has potential to be used as tunable catalyst and optical sensor.