Cu-curcumin nanozyme for detection of Cr(vi) through an off–on strategy based on peroxidase mimicking activity

system color. After optimization of the experimental parameters, a novel colorimetric sensor for Cr(VI) assay has been successfully developed with a low limit of detection (LOD) of 31.5 nM, affirming its potential for accurate Cr(VI) quantification in environmental specimens. In addition, paper strips integrated with a smartphone platform enhance the versatility and portability of the Cr(VI) assay, achieving an LOD of 0.1 μM.