Colorimetric/spectral dual-mode analysis of sensitive fluorescent probe based on 2,3,3-trimethyl-3H-benzo[e]indole detection of acid pH.

Herein, a high-performance fluorescence probe, namely H4, based on intramolecular charge transfer (ICT) mechanism was developed. H4 could serve as fluorescent probe for detection acidic pH change in environment with outstanding sensitivity, short response time (<10 s), low hemolysis effect (<0.3%) and excellent photostability (>120 min). H4 exhibits a good linear relationship (R = 0.9901, Y = 22.0409X-58.3397) characteristics in range of pH 2.2-7.4 with pK 4.3. In addition, the probe can be also made as fluorescent test sheets and further used as a portable sensor to enhance the screening speed to achieve detection of H in real-time. Further, H4 determined H in real food samples (milk, shrimps, and scallops) has excellent recoveries (98-105%), which making it of great potential use in food freshness evaluation. Initially, its favorable behavior for detecting H change is successfully illustrated in living onion tissues and zebrafish, which allows qualitative visualization of acid pH changes in in biological systems.