Atomically dispersed Fe–Zn dual-site nanozymes with synergistic catalytic effects for the simultaneous detection of Cr(VI) and 8-hydroxyquinoline

Single-atom catalysts with atomically dispersed sites have been widely used as nanozymes for colorimetric sensing because their tunable M–Nx active centers are similar to those of natural enzymes. However, their low metal atom loading leads to insufficient catalytic activity and affects the sensitivity of colorimetric sensing, which limits their further applications. Herein, multi-walled carbon nanotubes (MWCNs) are selected as carriers to reduce the aggregation of ZIF-8 and improve the electron transfer efficiency of nanomaterials. Meanwhile, MWCN/FeZn-NC single-atom nanozymes with excellent peroxidase-like activity were prepared by pyrolysis on ZIF-8 doped with a second metal Fe. Based on the excellent peroxidase activity of MWCN/FeZn-NCs, a dual-functional colorimetric sensing platform for Cr(VI) and 8-hydroxyquinoline was established. The detection limits of the dual-function platform are 40 nM for Cr(VI) and 55 nM for 8-hydroxyquinoline. This work provides a highly sensitive and selective strategy for the detection of Cr(VI) and 8-hydroxyquinoline in hair care products, which has great application prospects in the field of pollutant detection and control.