High dual-state blue emission of a functionalized pyrazoline derivative for picric acid detection

Developing dual-state fluorescence materials with high emission efficiency both in solution and solid states is still a challenge. Herein, a functionalized pyrazoline derivative (NF) was designed and synthesized. NF exhibited high blue emission efficiency in both THF solution and solid states with the absolute fluorescence quantum yields of 58% and 43%, respectively. The mechanism of this unique fluorescence behavior was systematically studied with the help of single-crystal structure analysis. The results showed that a close-knit molecular structure existed due to intramolecular C-H center dot center dot center dot pi interactions, which can impair the intramolecular rotation to accelerate the radiative transition in the mono-molecule state (in dilute solution). Moreover, the steric hindrance and intermolecular hydrogen-bond interactions of the substituent groups can restrict the close packing and prompt the formation of J-aggregates in the aggregation state, which resulted in high emission performance in the solid state. Meanwhile, the dual-state blue emission property of NF was utilized for the picric acid (PA) detection in the solution state and on a test paper by the synergistic effects of photo-induced electron transfer (PET) and Forster resonance energy transfer (FRET) processes. The limit of detection as low as 6.80 x 10(-7) M achieved in the THF-H2O mixture. This work provided a new scope for the design of high dual-state blue emission materials.

Automated summary

This study developed a dual-state blue emission material with high emission efficiency in both solution and solid states, successfully synthesizing and investigating its fluorescence behavior mechanism. The material can be utilized for picric acid detection in solution and exhibits high emission performance in the solid state.