Dual-mode immunoassay for diethylstilbestrol based on peroxidase activity and photothermal effect of black phosphorus-gold nanoparticle nanohybrids

Nanozyme-mediated 3,3',5,5'-tetramethylbenzidine (TMB) - H2O2 systems have spawned the establishment of multiple colorimetric sensing platforms that are effective but sometimes subject to low sensitivity. Taking temperature as the output signal, photothermal effects lead to new strategies for sensitive detection. In this paper, a colorimetric and photothermal dual-mode immunoassay for diethylstilbestrol (DES) was constructed. It is based on the oxidation reaction of TMB catalyzed by black phosphorus-gold nanoparticle (BP/Au) nanohybrids, and the kinetics as well as catalytic mechanism of the nanohybrids were investigated in detail for the first time. Herein, the nanohybrids playcatalytic and photothermal dual roles. Moreover, the one-electron oxidation product of TMB (oxidized TMB) not only acts as chromogenic agent but also an excellent NIR laser-driven photothermal agent. The temperature (ΔT/°C) was gauged by a portable digital thermometer. Through an indirect competition strategy, a simple, sensitive, and economic immunosensor was proposed. Higher DES content in the sample correlated with less BP/Au nanohybrids conjugated to the surface of ELISA microplate, a weaker color change, and a lower temperature variation when exposed to laser irradiation. This method was applied for DES determination in real samples with gratifying recovery rates, showing great promise in food safety inspection applications.