Fluorescence Sensing Properties of a Bibranched Cyanostilbene Derivative Containing -NH₂ for Trace Water and Picric Acid Determination

In order to design organic small molecule fluorescent materials with multiple sensing, a bibranched -NH₂ modified cyanostilbene derivative (AM) was synthesized. It exhibits solvent and aggregation-induced emission effects, with a solid-state quantum yield of 28%, which is seven times higher than that in THF. The synthesized sample AM demonstrated high sensitivity to trace water via a fluorescence “turn-off” response, achieving a low detection limit of 0.41 µM in THF and 0.80 µM in EtOH. AM also exhibits a “turn-off” response to picric acid, attributed to the photo-induced electron transfer effect it induces. The recognition of picric acid by AM demonstrates specificity and resistance to interference from nitro explosives, with a detection limit of 300 ppb and a linear relationship (R² = 0.9981) at the range of 0–4 equivalents AM. Such acid recognition can facilitate the design of qualitative test papers and safety inks. Additionally, AM can function as a temperature sensor with a linear relationship (R² = 0.9976) within the temperature range of 25–110 °C. Leveraging these unique characteristics, a series of methods were proposed for the direct quantitative determination of trace water in nonaqueous solvents, picric acid, and temperature.