Enhanced antibacterial potential of silver-doped zinc oxide/ silver heterostructures

Doping and heterojunction are crucial techniques used to improve the ZnO antimicrobial activity. In this study, silver was incorporated into the ZnO lattice as a dopant using a simple sol-gel followed by a combustion approach. Besides, an intent contact was also formed between silver and ZnO crystals above the solubility level of silver. The doping and heterojunction have been successfully confirmed from the low-angle XRD pattern peak shift and occurrence of independent additional silver peaks, respectively. The HRTEM image d-spacing analysis results of 0.26 and 0.23 nm were also approved for the formation of independent ZnO and Ag crystals, respectively. Thus, Ag-doped ZnO/Ag heterostructure (SDSH) was successfully synthesized. The average crystallite size (XRD) of the SDSH is about 18 nm, and the particle size (TEM) ranges from 20 to 50 nm. Besides, the pure composition and good silver dopant distribution on the surface of ZnO were confirmed from the EDS elemental mapping analysis. The optical property improvement and presence of charge transfer were confirmed from the UV-vis DRS and PL spectrophotometer analysis results. The indirect bandgap values were found to be 3.09 and 2.82 eV for ZnO NPs and SDSH, respectively. The PL spectrum intensity of SDSH is much lower compared to the ZnO NPs, confirming the presence of electron-hole recombination hindrance. The SDSH also showed much better antibacterial potential compared to single ZnO NPs. The major antibacterial deactivation mechanism of SDSH is proposed to be due to the release of silver and zinc ions during NPs and bacterial cell interaction.