Unraveling the Sensing Mechanism of Probe <scp>BTFMB</scp> for <scp>H₂O₂</scp> Detection: A Theoretical Study

ABSTRACT The level of hydrogen peroxide (H 2 O 2 ) in the human body is significantly associated with various pathological and physiological states, making it crucial to investigate its fluorescence sensing mechanism for synthesizing effective fluorescent probes. Herein, we used density functional theory and time‐dependent density functional theory to investigate the fluorescence sensing mechanism of probe BTMFB for H 2 O 2 detection. The theoretical results show that the fluorescence quenching mechanism of BTMFB is due to a non‐radiative decay pathway dominated by the dark n π* state. Subsequently, BTMFB reacts with H 2 O 2 to form BTMB‐OH, resulting in the turn‐on fluorescence observed. The calculated potential energy curves indicate that BTFM‐OH would undergo the ESIPT process under photoexcitation. The turn‐on fluorescence is attributed to a local excitation mode for the bright ππ* state of the BTFM‐OH‐Keto. The reason for the high selectivity and rapid response speed of BTMFB for the detection of H 2 O 2 is also explained by the calculated binding energy and reaction barrier, respectively.