Polymer microgel-based gold nanocomposites for reductive degradation of azo dyes

Stimuli responsive polymer microgels have gained attention due to their envisioned applications. The aim of this study is to organize Au-based poly(N-isopropylmethacrylamide-co-acrylamide) [Au-p-(NIPMAM-co-AAm)] microgels and to analyse their degradation potential. Microgels were analyzed via UV-Visible (ultraviolet-visible) spectroscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. Reductive degradation of Congo red (CR) was done to evaluate the catalytic activity of Au-based p-(NIPMAM-co-AAm) microgels that converts CR into less toxic products, that is, sodium 4-amino-1-naphthalene sulfate and biphenyl. Kinetic study of reaction reveals first order reaction and by altering the concentration of Congo red (CR) dye from 0.02 to 0.095 mM, the change in apparent rate constant (kapp) was noted from 0.0027 to 0.1235 min-1. Whereas the change in value of rate constant (kapp) was observed from 0.0716 to 0.2931 min-1 as catalytic dose was changed from 0.06 to 0.1 mL (60-100 mu L) at certain temperature. Reduction efficiency of recycled Au-based p-(NIPMAM-co-AAm) was also deliberated and not any remarkable reduction was observed in the percentage catalytic efficiency of nanocomposite until four cycles.