Colorimetric and photothermal dual-mode immunosensor based on Ti 3 C 2 T x /AuNPs nanocomposite with enhanced peroxidase-like activity for ultrasensitive detection of zearalenone in cereals.

A novel peroxidase-like nanozyme has been constructed by decorating two-dimensional Ti 3 C 2 T x nanosheets (Ti 3 C 2 T x NSs) with gold nanoparticles (AuNPs) to develop a colorimetric and photothermal dual-mode immunosensor. The Ti 3 C 2 T x /AuNPs nanocomposite-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB)-H 2 O 2 reaction system produces the one-electron oxidation product of TMB (oxTMB), which exhibits color change and strong near-infrared (NIR) laser-driven photothermal effect at 808 nm laser irradiation. Given these characteristics, the developed immunosensor achieves ultrasensitive dual-mode detection of zearalenone (ZEN) by measuring colorimetric and photothermal signals with a microplate reader and a portable infrared thermometer, respectively. Under optimal working conditions, the limit of detection (LOD) of ZEN is 0.15 pg mL -1 for the colorimetric mode and 0.48 pg mL -1 for the photothermal mode. In the analysis of actual contaminated cereals samples, the test result of this method was consistent with that of UPLC-MS/MS. The proposed colorimetric and photothermal dual-mode immunosensor offers a new strategy for the low-cost detection of hazardous substances. The application of a widely used household infrared thermometer makes the signal readout more convenient, which provides great prospects in food safety and environment inspection applications.