Fluorescent Phenanthro-Imidazole-Based Chemosensors for the Detection of Primary and Nitro-aromatic Explosives
摘要
The sensitive and selective detection of nitroaromatic compounds remains a significant area of research due to environmental concerns and security risks. Herein, we report a series of novel phenanthro-imidazole-based fluorescent chemosensors (6a-h) capable of dual detection of lead azide (LA) and nitroaromatic compounds. The developed chemosensors exhibit strong fluorescence quenching in the presence of quencher molecules (TNP, PNT, LA), making them highly sensitive detection tools. All the synthesized compounds were characterized meticulously via various spectroscopic and spectrometric techniques. Fluorescence-sensing studies of these compounds were performed using a spectrofluorometer, which revealed strong interactions with the analytes. Time-correlated single photon counting (TCSPC) measurements confirm that the quenching mechanism is dynamic. Additionally, the electron-donating nature of the developed chemosensors was evaluated via density functional theory (DFT) calculations. Among the tested sensors, compounds 6a, 6d, and 6f showed excellent sensitivity towards TNP, PNT, and LA, with compound 6a displaying the lowest limit of detection (LOD) of 60.69 μM for TNP sensing. Moreover, among the tested analytes, TNP and LA displayed the highest quenching efficiencies with a Stern–Volmer constant in 104 M−1 range with linear ranges 10.87–106.34 µM, 6.53–64.75 µM, and 10.87–85.49 µM, respectively. However, PNT showed comparatively weaker quenching, highlighting the selectivity and forensic significance of the developed chemosensors. The chemosensors exhibited a rapid response, reaching a stable fluorescence signal within 20 s upon addition of the quencher. Furthermore, for rapid and portable detection, we developed fluorescent paper strips coated with compounds 6a, 6d, and 6f, which allow rapid visual detection of TNP and LA with a visual detection limit of 4.36 nM. Notably, the fluorescent test strips of compound 6a exhibited prominent visual detection of TNP and LA in both tap and industrial water samples, with high sensitivity and minimal interference from common environmental contaminants. Due to their high sensitivity, selectivity, portability, and visible fluorescence response under ambient conditions, the developed chemosensors exhibit strong potential for on-site detection of forensic analytes, such as TNP, PNT, and LA.