Observation of excellent photocatalytic and antibacterial activity of Ag doped ZnO nanoparticles

Abstract

Nanotechnology is the platform with the greatest promise for scientific advancements. One of the advancement is improvement in photocatalytic and antibacterial performance. This work was undertaken to synthesize un-doped and silver (Ag) doped zinc oxide (ZnO) nanoparticles (NPs) using an inexpensive wet chemical method and to investigate the structural and optical properties, photocatalytic and antibacterial activity. The structural analysis from X-ray diffraction (XRD) pattern of un-doped and Ag-doped ZnO NPs displayed hexagonal wurtzite crystal structure and shifting in the peak position confirms the incorporation of Ag in ZnO lattice. Morphological study done by scanning electron microscope reveals spherical shaped NPs and an increase in grain size with Ag doping, the HRTEM images showed the nanocrystalline nature of particle. The Raman spectra showed variation in vibrational characteristics of the nanoparticles with Ag doping. The functional groups were analyzed using Fourier transform-infrared spectroscopy (FTIR). The optical properties were investigated by UV-visible and photoluminescence (PL) spectroscopic techniques. The Ag-doped ZnO NPs have a notably lower band gap than that of un-doped ZnO NPs, i.e. from 3.04 eV to 2.81 eV as studied by UV-visible spectra. The PL study showed decrease in intensity at near band edge emission with increase in Ag doping concentration indicating reduction in the free charge carrier recombination. These variations in the properties play major role in the enhancement of photocatalytic and antibacterial activity with increase in Ag doping concentration as compared to un-doped zinc oxide nanoparticles. The photo degradation efficiency of 99.12 ± 1% against Methylene Blue dye was achieved in the shortest period of 45 minutes ever reported when irradiated under the solar light and efficiency of 97.33 ± 1% was achieved in 15 min under Xenon Short Arc lamp. The antibacterial study was conducted using the Agar well diffusion method where the diameter of the zone of inhibition (ZOI) was increased from 14 mm to 20 mm and 13 mm to 18 mm against the bacteria Escherchia coli and Bacillus subtilis respectively, rendering this material suitable for photocatalytic degradation and antibacterial applications.