SILAR-Synthesized CuO, ZnO and ZnO/CuO Thin Films: Structural, Optical and Photocatalytic Properties for Methylene Blue Degradation

Abstract

Thin films of ZnO, CuO, and ZnO/CuO heterostructures were successfully synthesized by the Successive Ionic Layer Adsorption and Reaction (SILAR) method using 50 deposition cycles. We systematically investigated the structural, morphological, and optical properties of the resulting films to establish their relationship with photocatalytic performance. X-ray diffraction (XRD) analysis confirmed the crystalline nature of the ZnO and CuO films and the coexistence of their characteristic phases in the ZnO/CuO heterostructure, indicating the successful formation of the composite system. Scanning electron microscopy (SEM) revealed continuous and relatively homogeneous surfaces with well-distributed grains, demonstrating good film quality. UV–Vis spectroscopy showed that ZnO predominantly absorbs in the ultraviolet region, whereas CuO exhibits an extended absorption response in the visible region. The ZnO/CuO heterostructure displayed broader optical absorption, suggesting improved utilization of the incident light and favorable characteristics for photocatalytic applications. The photocatalytic activity of the films was evaluated using a 3 ppm methylene blue (MB) aqueous solution as a model pollutant under light irradiation. Among the investigated samples, the ZnO/CuO heterostructure exhibited the highest photocatalytic efficiency, outperforming the individual ZnO and CuO films. This enhanced performance is attributed to the ZnO/CuO interface, which promotes interfacial charge transfer, improves electron–hole separation, and suppresses charge-carrier recombination. These results show that SILAR is a simple, versatile approach for fabricating ZnO/CuO heterostructured thin films with promising potential for photocatalytic water treatment and environmental remediation.

Keywords: SILAR; Thin films; photocatalysis