A General Method to Develop Highly Environmentally Sensitive Fluorescent Probes and AIEgens

Abstract

Environmentally sensitive fluorescent probes (including AIEgens) play pivotal roles in numerous biological studies. Many of these functional materials are developed based on the twisted intramolecular charge transfer (TICT) mechanism. However, the TICT tendency of dialkylated amino groups in biocompatible main-stream fluorophores (i.e., coumarins and rhodamines) is weak, limiting their sensitivities. Herein, by replacing dialkylated amino donors with an N-methylpyrrole group to enhance TICT, a simple and general method to engineer highly environmentally sensitive fluorescent probes is reported. This method yields a platter of colorful fluorescent probes that demonstrates outstanding polarity and viscosity sensitivity with large turn-on ratios (up to 191 times for polarity and 14 times for viscosity), as well as distinct aggregation-induced emission (AIE) characteristics. The utilities of these probes in both wash-free bioimaging and protein detections are also successfully demonstrated. It is expected that this molecular design strategy will inspire the creation of many environmentally sensitive probes.

A dual-targeting fluorescent probe for simultaneous and discriminative visualization of lipid droplets and endoplasmic reticulum

“…1C); such a good relationship indicated that LDER has a twisted ICT (TICT) character. 33–35 The fluorescence intensity of LDER with dielectric constant ( ε ) of various media was also correlated, as shown in Fig. 1D.…”

Organic Near‐Infrared Luminescent Materials Based on Excited State Intramolecular Proton Transfer Process†

“…Environmentally sensitive fluorescent probes are a class of specially designed probes with high resolution, high visibility, and excellent specificity. [ 93 ] Its fluorescence properties are affected by local environmental changes (such as acidity, alkalinity, viscosity, polarity), [ 94 ] and it plays a vital role in biological research.…”

A General Twisted Intramolecular Charge Transfer Triggering Strategy by Protonation for Zero-Background Fluorescent Turn-On Sensing

“…17−19 Generally, the realization of the fluorescence turn-on mode requires the prequenching of the fluorophore before the occurrence of the specific recognition reaction between the probe and the analyte. 20 Therefore, significant efforts have been devoted to the molecular design strategies for precisely modulating the quantum yields to form the dark state of the fluorescent probe, 21 such as photoinduced electron transfer (PET), 22 fluorescence resonance energy transfer (FRET), 23 the internal filtering effect (IFE), 24 and twisted intramolecular charge transfer (TICT). 25−27 Among these methods, only TICT involves the internal rotational motion of a specific group that is driven by the change in the electron density distributions and often results in a decrease in the molecular energy accompanied by decoupling of the π-systems and nearly complete electron transfer between the two parts connecting the rotational bond.…”