Structural and Optical Properties of Ag-Decorated ZnO Nanoparticles Synthesised via Hydrothermal Method for Optoelectronic Devices

Zinc oxide (ZnO) nanoparticles have attracted considerable attention due to their wide bandgap and excellent physicochemical properties, making them promising materials for optoelectronic and photocatalytic applications. However, intrinsic defects such as zinc and oxygen vacancies introduce mid-gap trap states that promote charge carrier recombination, thereby limiting their performance. In this study, ZnO nanoparticles were synthesised via a hydrothermal method and subsequently modified with silver (Ag) nanoparticles through chemical reduction of AgNO₃ to enhance light absorption and reduce recombination losses. Structural characterisation using X-ray diffraction (XRD) confirmed the formation of a hexagonal wurtzite ZnO structure with distinct diffraction peaks. Additional diffraction peaks corresponding to metallic Ag indicate successful incorporation of Ag nanoparticles. Optical properties investigated using UV–visible spectroscopy revealed a characteristic absorption band of wurtzite ZnO. Pure ZnO exhibited an absorption peak at 263 nm, while Ag-modified samples showed red-shifted absorption peaks at 264, 270, and 286 nm for increasing Ag concentrations. The enhanced absorption intensity in both UV and visible regions suggests improved light-harvesting capability due to the surface plasmon resonance effect of Ag nanoparticles. Bandgap energies estimated from Tauc plots indicate a reduction in bandgap upon Ag modification, attributed to the introduction of intermediate energy states and plasmonic interactions. The improved optical absorption and bandgap tuning demonstrate that Agmodified ZnO nanocomposites are promising candidates for enhanced optoelectronic device applications.