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

Abstract

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 pH 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.