Fabrication of dual-functional heterostructured p-CuO/n-ZnS nanocomposite for enhanced visible-light active photocatalytic response and fluorometric sensor for selective sensing of thiol-containing amino acids

Abstract

In this study, CuO, ZnS, and p-CuO/n-ZnS heterojunction composites were synthesized using a simple co-precipitation method for investigating their photocatalytic properties for dye degradation and fluorescence sensing of thiol-containing amino acids at room temperature. The synthesized CuO, ZnS, and p-CuO/n-ZnS heterostructures were analyzed using UV–vis, PL, XRD, and TEM. The results showed that the heterostructure exhibited enhanced absorption in the visible light range, and synthesized materials have spherical shape with an average particle size is 12 ± 5 nm. The photocatalytic activities of CuO, ZnS, and p-CuO/n-ZnS heterostructures were evaluated by the degradation of various dyes such as MB, MO, and MR under visible light irradiation. The p-CuO/n-ZnS heterostructure showed the best photocatalytic efficiency, with degradation rates of 98.3%, 94.2%, and 92.8% for MB, MO, and MR dyes, respectively, compared to CuO NPs (72.5%, 75.8%, and 73.5%) and ZnS NPs (76.2%, 79.1%, and 78.3%) within a 35 min of reaction. The enhanced photocatalytic efficiency of the p-CuO/n-ZnS heterostructure was attributed to its high charge separation efficiency, which remained stable for up to five cycles without any significant loss of activity. Furthermore, the p-CuO/n-ZnS heterostructure was used as a fluorescent sensor for detecting thiol-containing amino acids such as cysteine (Cys) and methionine (Met). The results showed that the heterostructure had good sensing performance for Cys and Met within the range of 1–100 μM, with a detection limit of 2.52 μM (Cys) and 5.14 μM (Met) based on the linear calibration range. Moreover, p-CuO/n-ZnS composite was used to detect Met in human serum and urine samples.