ZnO@ZnS core–shell nanocomposites enable ultra-enhanced ultraviolet exciton luminescence in ZnO

Abstract

ZnO materials play a crucial role in optoelectronic devices, such as ultraviolet (UV) photodetectors and radiation detectors, owing to their strong UV exciton emission. In this work, ZnO nanoparticles with high crystallinity were synthesized via a hydrothermal method, followed by surface sulfuration to form a dense ZnS shell, resulting in ZnO@ZnS core–shell nanocomposites with enhanced UV exciton emission. The mechanism underlying the ZnS shell-induced enhancement was systematically investigated. Although surface sulfuration increased the specific surface area, the ZnO@ZnS core–shell nanocomposites retained the original morphology of ZnO. With an increasing sulfuration degree, the UV exciton emission intensity of ZnO@ZnS gradually increased, reaching optimal performance at a thioacetamide/ZnO molar ratio of 4:10, where the emission intensity was enhanced by nearly an order of magnitude. This significant improvement is attributed to the ZnS shell acting as an “inert” passivation layer, which effectively suppresses surface defect states while providing a confined pathway for charge carrier transport, thereby reducing scattering and improving light absorption efficiency. Notably, the introduction of the ZnS shell does not prolong the photoluminescence decay time; instead, ZnO@ZnS exhibits a fast decay time of 0.65 ns, indicating efficient suppression of nonradiative recombination pathways. These findings provide an effective strategy for enhancing UV exciton emission in ZnO and highlight the potential of ZnO@ZnS nanocomposites for advanced optoelectronic applications.