Cu-curcumin nanozyme for detection of Cr(Ⅵ) through off-on strategy of peroxidase mimicking activity

Abstract

Hexavalent chromium ions (Cr(VI)) possesse inherent poisonous and propensity for bioaccumulation in the natural setting. Herein, Cu-curcumin nanozyme was synthesized via the one-pot solvothermal method. Due to the high peroxidase-like activity of Cu-curcumin nanozyme, a novel and economical colorimetric platform has been developed to Cr(VI) assay. In the presence of hydrogen peroxide (H2O2), Cu-curcumin nanozyme could catalyze the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into the blue product oxTMB. 8-Hydroxyquinoline (8-HQ) could inhibit the catalysis of Cu-curcumin/TMB/H2O2 system, causing the blue color to fade. With the addition of Cr(VI), the peroxidase-like activity of Cu-curcumin nanozyme is lighted up significantly, leading to the restoration of the Cu-curcumin/TMB/H2O2 system 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 smartphone platform enhances the versatility and portability of Cr(VI) assay, achieving the LOD of 0.1 μM.