Construction of AuNPs/Cu,I-CD-based colorimetric sensor: Catalytic oxidation of TBHQ and the catalytic inhibition of HCHO

Various research groups have been paying huge attention to tune the metal states in metal-carbon hybrid materials. Herein, a mixed-valence copper-iodine co-doped carbon dots (Cu,I-CDs, Cu²⁺/Cu⁺/Cu⁰) were prepared through a one-step hydrothermal method, which displayed an intrinsic reduction performance under given conditions. Moreover, AuNPs/Cu,I-CDs composite was fabricated using Cu,I-CDs as reductant and stabilizer. Among them, the AuNPs/Cu,I-CDs composite exhibited the highest oxidase- and peroxidase-like activities, which was used for the colorimetric detection of tert-butyl hydroquinone (TBHQ), with the detection limits of 23.45 μg/kg. Interestingly, the catalytic oxidation of TBHQ to oxidized TBHQ (TQ) could be inhibited by formaldehyde (HCHO). Therefore, a colorimetric sensor for HCHO was developed with the detection limit 0.335 mg/L. The catalytic mechanism for TBHQ was investigated by employing scavengers of different reactive species, indicating the significant roles of •O₂^- in the catalytic process. Therefore, it is believed that the as-prepared AuNPs/Cu,I-CDs nanozyme has promising potential applications in the fields of biomedicine and food safety.