Non-colorimetric sensing with 3,3′,5,5′-tetramethylbenzidine

3,3 ',5,5 '-Tetramethylbenzidine (TMB) is by far the most well-known colorimetric substrate in various colorimetric assays, including ELISA and typical H2O2/reactive oxygen species oxidation-involved colorimetric detections. For such a substrate, besides the well-known colorimetric applications, the intriguing spectroscopic and electrochemical properties are also recognized, such as fluorescence, photothermal and photoacoustic responses, surface-enhanced Raman scattering (SERS), and electrochemical property. The explorations of these properties greatly expanded the sensing toolbox and fruited the applications of TMB in chemo-/bio-sensing. Therefore, in this review, we provide a summary on the TMB-based non-colorimetric sensing applications, with a particular focus on the spectroscopic and electrochemical characteristics and their corresponding principles for sensor designs. Additionally, the typical sensors were summarized and their performances were also compared. Finally, the advantages, challenges, and future perspectives for TMB-based non-colorimetric sensing applications are also presented. Considering the importance of TMB in analytical chemistry, the non-colorimetric sensing applications would be an important supplement to the well-known colorimetric assays, and may also be a good example in how to better exploring the already existed and newly developed molecules.