Leyi Lü, Dingfang Hu, Zhouyu Chen, Jiancheng Zhou, Ruijuan Wen, Ling-Ya Peng*, Rongrong Huang*, Xiaogang Liu, Yu Fang*. Adv. Optical Mater. 2026, DOI: https://doi.org/10.1002/adom.71909

The development of fluorescent sensors capable of simultaneous ultrafast response and high reversibility poses a significant challenge, as these two-performance metrics are typically constrained by a trade-off. Here, we present a conformational locking strategy with built-in recognition, realized through a tetracoordinate boron-bridged fluorophore (Py-BF₂). In this design, the B←N Lewis pair rigidifies the molecular framework while extending π-conjugation, yielding an electronic structure that promotes a pronounced intramolecular charge transfer (ICT) state with a substantially enlarged Stokes shift relative to the unlocked analogue. This integrated architecture not only enhances fluorescence efficiency but also exploits the ICT state for sensitive SO₂ detection.

The resulting film-based sensor achieves a response time of under 2 seconds, a detection limit of 1 ppm, and remarkable cycling stability exceeding 100 cycles without performance degradation, effectively overcoming the conventional speed-reversibility trade-off. Practical applicability is validated through rapid screening of SO₂ residues in grapes and raisins, with results corroborated against the Chinese national standard method (GB 5009.34–2022) and enabling compliance determinations within minutes. This work establishes a generalizable design paradigm that unifies signal transduction and analyte recognition within a single molecular scaffold for reversible gas sensing applications.

First Author: Lyu Leyi, master’s student, Shaanxi Normal University

Correspondence Authors: Dr. Peng Lingya, Shaanxi Normal University; Dr. Huang Rongrong, Nanyang Technological University; Prof. Fang Yu, Shaanxi Normal University

Full Text Link: https://doi.org/10.1002/adom.71909