Twisted-intramolecular-charge-transfer based fluorogenic nano-probes for ultrafast cyanide sensing in water and micellar medium

Twisted benzimidazoquinazoline based fluorogenic probes (Benz-d-CF₃ and Benz-m-CF₃) with varying pi-acidic terminal substituents showed TICT (twisted intramolecular charge transfer) behaviour. They formed self-assembled nano-aggregates in an aqueous CTAB medium, and only Benz-d-CF₃ displayed a selective fluorescence turn-on response toward CN⁻ in a 100% aqueous medium. However, the sensitivity and selectivity of fluorescence sensing towards CN⁻ enhanced exponentially in aqueous medium in the presence of CTAB. Probe Benz-d-CF₃ had a detection limit as low as 496.5 nM and a high-speed fluorescence response time, which promises its practical application for detecting CN⁻ in drinking water. The assistance of micelle systems facilitates a very fast, sensitive and selective detection of CN⁻ in water. The sensitivity as well as selectivity of the probes towards CN⁻ can just be fine-tuned by varying their terminal substituents.