Selective and ultrafast sensing of 2,4,6-trinitrophenol-A nitro-explosive and mutagenic pollutant-In aqueous media by highly stable and recyclable metal-organic probes: Design principles and mechanistic studies

This work was aimed at explaining the design principles and an in-depth mechanistic study for the ultrafast detection of trace amount of highly explosive 2,4,6-trinitrophenol (TNP) in aqueous medium by eight Zn(II) and Cd(II) metal-organic probes that were strategically functionalized with pi-electron rich moieties and polar hydroxyl groups. All of these probes showed turn-off response towards TNP with LODs ranging from 0.24 to 1.35 ppm. These efficiently detected TNP in presence of other interfering nitroaromatics as confirmed with the help of competitive tests. Their recyclable nature and ultrafast response time made them suitable for use in such applications. With the help of PXRD and FTIR spectroscopy, any scope of structural degeneration was investigated after soaking them in TNP for three days. The nature of quenching (static or dynamic) involved for the interaction of TNP with the probes was determined by the time-correlated single photon counting (TCSPC) analysis where the average lifetime was considered with respect to the concentration change of TNP. A detailed mechanistic study of the quenching process was carried out by the DFT calculations and spectral overlap observation. On the basis of photoinduced electron transfer (PET) as the main reason behind quenching of the probes by TNP, possible sites and mode of interactions between the electron-rich probes and the electron-deficient analyte were also identified.