Rapid detection of hexavalent chromium using CuO/CN/LDH as an oxidase mimetic and the construction of a paper-based device

Abstract In this study, a ternary structure (CuO/CN/LDH) composed of LDH-anchored g-C 3 N 4 nanosheets loaded with CuO nanoparticles was successfully constructed via hydrothermal and co-precipitation methods, and a colorimetric sensing platform for Cr(VI) detection was proposed. The engineered nanomaterial demonstrates significantly enhanced oxidase-mimetic activity in the presence of Cr(VI), enabling rapid catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with distinct chromogenic response. Mechanistic investigations reveal that Cr(VI) facilitates the conversion of dissolved oxygen into superoxide anions via redox cycling, thereby accelerating TMB oxidation. The sensor exhibits exceptional analytical performance with high accuracy (recovery rates of 97.3-103.8%) and sensitivity (detection limit of 25 nM) in aqueous sample analysis. Notably, an innovative paper-based analytical device was developed in conjunction with smartphone-assisted colorimetric analysis, achieving on-site visual quantification of Cr(VI) within 15 min. This integrated system provides a field-deployable solution for environmental monitoring, combining operational simplicity with reliable detection capabilities. The proposed methodology advances current sensing technologies by merging nanomaterial engineering with portable detection platforms, demonstrating significant potential for heavy metal surveillance in water quality management. Based on this, this study also constructed a paper-based colorimetric detection sensor.