N‐Alkyl Extension in Ionic Molecular Rotors: Facile Tuning of Sensing Modes for Albumin‐Based Host‐Guest Fluorescent Sensors

Establishing a strategy for fine‐tuning of fluorescent sensing modes (e.g., off ↔ on, ratiometric, fluorocolorimetric) in human serum albumin (HSA)‐dye involved supramolecular systems that can tackle the bottleneck for the development of functional fluorescent sensors and sensor arrays in specific practical applications. Here, we propose a simple strategy by extending the N‐alkyl on the pyridinium of triphenylamine diarylethene (TPA‐Ps), a classic ionic molecular rotor skeleton for protein binding and fluorescent sensing, to fulfill the modulation of sensing modes of TPA‐P@HSA. The structural effects on two factors corresponding to sensing modes, the initial fluorescence (TPA‐Ps dispersions) and the final fluorescence (TPA‐P@HSA), have been comprehensively investigated. The utility of the strategy was examined in the applications of fluorescent analysis of urinary albumin, construction of dye@HSA indicator‐displacement assays for the third analytes, fluorescent imaging, and building sensor arrays for classification. Finally, we demonstrated that this strategy can be generalized to other TPA‐P skeleton‐based dyes, resulting in substantially tunable sensing modes in response to HSA.