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

Abstract

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 (NO2). Although both probes contain the same fluorophore and recognition site, they display different fluorescent responses to NO2 and nitramines. 8-Oxime-7-dimethylamino-coumarin (8-ODC) emits traditional turn-on fluorescence toward NO2, which is based on the CN isomerization. In contrast, 3-Oxime-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 NO2 in solution. The limit of detection of 3-ODC for NO2, HMX and RDX was 90 ppb, 60nM and 90nM, respectively. Notably, main interferents such as TNT, PETN, NO, NO2+ and H2O2 showed no obvious interference to the detection of NO2 and nitramines. Therefore, a novel fluorescent probe (3-ODC) based on the TICT mechanism was firstly developed to detect NO2 and nitramines by fluorescence quenching with high selectivity and sensitivity.