a School of Science, Jinling Institute of Technology, Nanjing 211168, Jiangsu,

China

b Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices，Huizhou University, Huizhou 516001, Guangdong, China

ZnO-TiO2 core-shell nanocomposites were fabricated via laser ablation in liquid (LAL), followed by post-annealing at various temperatures. The influence of annealing temperature on the structural and optical properties, as well as the photocatalytic activity of the resulting nanocomposites, was systematically investigated using X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) for powders, and ultraviolet-visible absorption spectroscopy for dye aqueous solutions. The morphology and elemental composition were analyzed by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). XRD and TEM analyses confirmed that the composites possessed excellent crystallinity and a well-defined core-shell structure, with ZnO as the central core and ultrasmall TiO2 nanoparticles constituting the shell layer.

Optical measurements showed pronounced ultraviolet absorption, with minimal variation in the optical band gap (3.30-3.32 eV) regardless of annealing temperature. The photocatalytic activity, assessed by Rhodamine B (RhB) dye degradation under ultraviolet (UV) irradiation, was significantly influenced by the annealing process, with samples annealed at 400 ℃ achieving the highest degradation efficiency of 73.3%. These findings demonstrate that careful control of post-annealing conditions can optimize the photocatalytic performance of ZnO-TiO2 core-shell nanocomposites, underlining their potential in UV-driven environmental remediation applications.