Nanozyme colorimetric sensor array-based Au as an electron bank facilitated surface charge redistribution of CeO2 for on-site detection and discrimination of sulfur-containing metal salts

Developing a highly efficient array-based sensing platform for sulfur-containing metal salt (SCM) analysis is imperious due to its potential to harm the environment and human health. Herein, we fabricated a ternary channel colorimetric sensor array technique to monitor multiple SCMs simultaneously, depending on the Au nanoparticle-loaded CeO₂ nanobelt (Au/CeO₂) heterostructure with excellent peroxidase-like (POD-like) activity. The results of XPS and DFT calculations revealed that Au NPs as an electron bank can promote the charge redistribution on the surface of CeO₂. This process increases the ratio of Ce³⁺/Ce⁴⁺, facilitates the release of OH* and the desorption of H₂O, and significantly enhances the POD-like activity. Subsequently, colorimetry- and sensor array-based Au/CeO₂ was developed, in integrating diverse degrees of TMB oxidation, owing to their various catalysis behaviors, leading to distinct patterns as "fingerprints" for different SCMs. The gained distinct patterns were recognized and processed via principal component analysis (PCA), enabling specific and sensitive identification and discrimination of different concentrations of SCMs with a detection limit of 5 μM. To advance the field determination of various SCM concentrations, we creatively constructed a portable smartphone device-based autonomous sensing platform with a linear range of 5-110 μM, which further indicates the potential utility of colorimetric sensor arrays. This work opens new avenues for efficient on-site SCM detection and discrimination by enhancing the POD-like activity of CeO₂ through surface electron redistribution.