A novel turn-off fluorescent probe based on TICT for the detection of NO2 and nitramines with high sensitivity and selectivity

Two new fluorescent probes based on a coumarin core have been developed for the detection of nitramines (RDX and HMX) via responding to their photo-degradated nitrogen dioxide (NO 2 ). Although both probes contain the same fluorophore and recognition site, they display different fluorescent responses to NO 2 and nitramines. 8- O xime-7-dimethylamino-coumarin (8-ODC) emits traditional turn-on fluorescence toward NO 2 , which is based on the C N isomerization. In contrast, 3- O xime-7-dimethylamino-coumarin (3-ODC) exhibits a unique turn-off response with strong fluorescence quenching (about 98%) as a result of a twisted intramolecular charge transfer mechanism (TICT). In addition, 3-ODC offers a highly selective and sensitive determination of nitramines via detecting NO 2 in solution. The limit of detection of 3-ODC for NO 2 , HMX and RDX was 90 ppb, 60   nM and 90   nM, respectively. Notably, main interferents such as TNT, PETN, NO, NO 2 + and H 2 O 2 showed no obvious interference to the detection of NO 2 and nitramines. Therefore, a novel fluorescent probe (3-ODC) based on the TICT mechanism was firstly developed to detect NO 2 and nitramines by fluorescence quenching with high selectivity and sensitivity.