Inhibition to dual enzyme-like activities of Ag/CeO2 nanozymes for the detection of thiourea

Although thiourea and its derivatives are applied in medical, food, and chemical industries, sensitive thiourea detection remains a challenging and noticeable topic. Surface-enhanced Raman spectroscopy assay based on an enzyme-inhibition strategy is promising for the detection of thiourea residues. Therefore, in this study, Ag/CeO2 nanomaterials with dual enzyme-Like Activities were synthesized to detection thiourea. We discovered that the Ag/CeO2 nanozymes demonstrated strong peroxidase-like activity and oxidase-like activity, moreover they can accelerate and catalyze 3,3′,5,5′-tetramethylbenzidine enzymatic reaction, with significantly increasing the Raman signal. Instead, once thiourea was introduced into Ag/CeO2 nanozymes, due to the influence of thiourea molecules occupation and nanozymes aggregation, the peroxidase-like activity and oxidase-like activity of Ag/CeO2 decreased sharply, and the colorless substrate 3,3′,5,5′-tetramethylbenzidine would not undergo color changes. Based on this observation, a Raman method for detecting thiourea using oxidized 3,3′,5,5′-tetramethylbenzidine as a probe molecule was developed. The Raman intensity showed a good linearity for the concentration of thiourea in the range of 10−11 M−10−1 M with a correlation coefficient of R2 = 0.9881, and the limit of detection is 2.4 × 10−13 M. Therefore, the proposed Raman mode sensors exhibited excellent selectivity and anti-interference ability which offers a new avenue for exploiting environmental monitoring.