Green synthesis of silver doped nano metal oxides of zinc & copper for antibacterial properties, adsorption, catalytic hydrogenation & photodegradation of aromatics

Abstract

Silver doped copper and zinc nano metal oxides were synthesized in the presence of Sida rhombifolia leaf extract by self propagating sol-gel autocombustion process. X-ray diffraction studies indicated the formation of wurtzite hexagonal phase for ZnO, monoclinic for CuO and FCC structure for silver nanocomposites. The surface morphology of nanoparticles were studied using FESEM. FTIR studies confirmed the presence of silver & M–O bonds. UV–vis DRS studies revealed that silver doping reduced the band-gap energy which overcomes fast recombination rate of electron-hole pairs of the nanoparticles. TGA studies indicated enhanced thermal stability of doped nanocomposites. Hydrogenation of 4-nitrophenol to 4-aminophenol with NaBH4 showed that Ag/ZnO & Ag/CuO exhibited greater photoreduction capacity than undoped ZnO & CuO. ZnO, Ag/ZnO, CuO & Ag/CuO nanocomposites have antagonistic effect on the growth of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeroginosa, Streptococcus mutans and Staphylococcus aureus with greater inhibition zones. Ag/CuO NPs exhibited the highest sensitivity against various bacterial strains with MIC below 1 mg. Ag/CuO nanorods showed excellent adsorption properties with high removal capacity of MG of about 90%. Kinetic, thermodynamic and equilibrium studies on adsorption of MG onto Ag/CuO nanorods was carried out. The photocatalytic activity of ZnO and Ag/ZnO nanocomposites was investigated by studying the degradation of methylene blue & malachite green under UV irradiation. Ag/ZnO exhibited better photodegradation efficiency of MG & MB and follows pseudo first order kinetic model. Thus the simple, low-cost and eco-friendly herbal synthesis of oxides of silver doped zinc & copper provides nanocomposites with multifunctional applications.