▎ 摘　　要

Design of functional nanomaterials as peroxidase mimics has attracted great attention due to promising applications in numerous fields, including biosensing, cancer diagnostics, immunoassays, environmental remediation, etc. Herein, we report a facile synthesis method for the decoration of semiconducting CuS nanoparticles on functionalized reduced graphene oxide composite (CuS-frGO). The CuS-frGO exhibits excellent peroxidase mimetic activity as well as photocatalytic properties. Indeed, the CuS-frGO catalyzes the decomposition of H2O2 to center dot OH radicals in the presence of Cr(VI) in acidic condition. The produced center dot OH radicals react with terephthalic acid, which acts as center dot OH scavenger, resulting in the formation of 2-hydroxyterephthalic acid exhibiting a fluorescence emission band at 425 nm. Based on this mechanism, CuS-frGO is utilized as a peroxidase mimic for the sensing of an inorganic pollutant, Cr(VI) ions, in aqueous medium. The proposed simple fluorescence technique with high selectivity and sensitivity is successfully utilized to detect Cr(VI) at a concentration of 26.60 nM within a linear range of 0-200 nM at pH 4. The synthesized material also displays efficient photocatalytic properties and achieved 99% photoreduction efficacy for Cr(VI) ions within 25 min under natural sunlight irradiation.