Nanostructured CuO, ZnO, and ZnO/CuO thin films synthesized by SILAR method and their enhanced photocatalytic activity for methylene blue degradation

Thin films of ZnO, CuO, and ZnO/CuO heterostructures were synthesized using the SILAR (Successive Ionic Layer Adsorption and Reaction) method with 50 deposition cycles, ensuring controlled thickness and uniform growth. The structural, morphological, and optical properties of the thin films were systematically characterized. X-ray diffraction (XRD) analysis confirmed the crystalline nature and phase purity of ZnO and CuO, as well as the successful formation of the heterostructure. Scanning electron microscopy (SEM) revealed uniform surface morphology with well-distributed grains, indicating good film quality. UV–Vis spectroscopy showed that ZnO films mainly absorb in the ultraviolet region, while CuO extends absorption into the visible region. The ZnO/CuO heterostructure exhibited improved optical absorption over a broader spectral range, thereby enhancing its photocatalytic potential. The photocatalytic performance of the films was evaluated through the degradation of methylene blue under UV–Vis light irradiation (λ = 310 nm). A 5 ppm methylene blue solution was used as a model pollutant. The results showed that the ZnO/CuO heterostructure film exhibited 17% methylene blue degradation compared to the individual ZnO (12%) and CuO (15%) films. This improvement is attributed to enhanced charge separation and reduced electron–hole recombination at the ZnO-CuO interface. Overall, this study highlights the potential of SILAR-fabricated ZnO/CuO thin films as efficient photocatalysts for environmental remediation applications.