1D MnO2 nanowires as active oxidase mimics in fabrication of colorimetric/photothermal dual-mode detection system for cysteine in soy sauce

Dual-mode detection can effectively avoid external disturbances and lead to more accurate and reliable results in complex environment. Herein, a colorimetric/photothermal dual-mode sensing platform was reported for cysteine (Cys) detection in soy sauce. 1D MnO₂ nanowires (MnO₂ NWs) was used as active oxidase mimics to trigger 3,3′,5,5′-tetramethyl-benzidine (TMB) oxidation, with the generation of oxidized TMB (oxTMB). Due to the absorption in UV–vis region and the excellent photothermal effect (PE), oxTMB gives rise to colorimetric and photothermal signals at the same time. In presence of Cys, the oxidase mimetic activity of MnO₂ NWs was suppressed, followed by the faded color and decreased heat conversion. Therefore, a colorimetric/photothermal dual-mode detection for Cys was proposed, which shows high performance, with a low limit of detection of 0.05 and 0.09 μM, respectively. Moreover, it shows excellent feasibility and reliability for Cys detection in soy sauce.