Optimization of silver ion concentration into the lattice of zinc oxide nanoparticles synthesized via a hydrothermal approach

Abstract

The exceptional properties of Ag-doped ZnO nanoparticles (NPs) make them highly promising for applications in environmental remediation and optoelectronics. However, the limited tunability of ZnO’s bandgap and its suboptimal performance in doping applications necessitates material modifications. In this study, a hydrothermal method was used to synthesize ZnO and Ag-doped ZnO (NPs). The study optimized the silver molar concentration to between 0.01 to 0.03 mol and characterized the nanoparticles for their optical, structural, and surface micrograph using different characterization techniques. As the wavelength increases from 300 to 1100 nm, nanoparticles show a decrease in absorbance. In both spectral regions, ZnO doped with 0.1 mol of Ag exhibited the highest absorbance, while ZnO doped with 0.2 mol of Ag showed the lowest absorbance. The energy bandgap of ZnO was measured at 2.19 eV, which deviates from the theoretical bandgap of ZnO at 3.3 eV. Introducing silver into the ZnO leads to changes in the band structure because of the creation of additional energy levels while the introduction of silver doping into ZnO lattice leads to a decrease in the bandgap energy to 1.50, 1.39, and 1.29 eV. These enabled electron transitions at lower energy levels because of the formation of defect states or interaction with ZnO. The XRD patterns of zinc oxide and Agdoped ZnO NPs reflect their hexagonal structure. The material showed a diffraction peak at (101) when measured at a 2θ angle of 44.863o. The hexagonal phase displayed distinct diffraction peaks at specific 2θ angles. Within the FTIR spectrum, Zn-O stretching vibrations are typically shown by distinct absorption bands, usually ranging from 400 to 750 cm-1. Introducing silver doping results in the emergence of new vibrational modes and a shift in existing peaks which indicate changes in the local environment around the ZnO lattice. These findings demonstrate that silver doping significantly enhances the optical and structural properties of ZnO an indication of its suitability for applications in advanced technologies requiring tunable bandgap and improved performance.