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.