A simple "turn-on" fluorescence sensor for salicylaldehyde skeleton based on switch of PET-AIE effect

The selective detection of salicylaldehyde skeleton is of great significance in phytochemistry and biological research but rarely reported. In this research, a simple and highly selective "turn-on" fluorescence sensor (CDB-Am) for salicylaldehyde skeleton was developed based on switch of photoinduced electron transfer (PET) and aggregation-induced emission (AIE). CDB-Am bearing amino-cyanodistyrene structure responded to salicylaldehyde in the range of 3.1 to 40 μM with a detection limit of 0.94 μM. The sensing process of formation of Schiff-base adduct CDB-SA was confirmed by ¹H NMR, MS, and FT-IR spectra, revealing that a recovered AIE property accounted for the turn-on fluorescence response of CDB-Am and the intramolecular hydrogen bonding played a crucial role in the disruption of PET process. This sensing ability was successfully applied for both fluorescence qualitative test of salicylaldehyde skeleton on TLC analysis and quantitative detection of salicylaldehyde skeleton with good accuracy in the root bark of Periploca sepium, suggesting the extensive applications in phytochemistry and traditional Chinese herbal medicine. Furthermore, CDB-Am exhibited the first excellent fluorescence imaging ability in detecting salicylaldehyde skeleton in a living system. This work supplied a new strategy of preparing a novel "turn-on" fluorescence probe for detecting salicylaldehyde skeleton in complex environments and living bodies.