A novel reversible fluorescent probe for the highly sensitive detection of nitro and peroxide organic explosives using electrospun BaWO4 nanofibers

Fabrication of highly stable, reversible, and efficient portable sensors for the detection of explosives for safety and security is challenging due to the robustness of the currently available detection tools, limiting their mass deployment to the explosion prone areas. This paper reports a new direction towards the sensing of nitro- and peroxide-based explosives using highly stable rare-earth-doped BaWO4 nanofibers with remarkable sensitivity and reversibility. BaWO4 nanofibers doped with Tb3+ and Eu3+ ions are fabricated through a sol-gel electrospinning process, and their emission characteristics and application as a fluorescent probe for the sensing of 2-nitrotoluene and H2O2, explosive taggants representing a broad class of explosives, are studied in detail. Scheelite structured BaWO4 nanofibers exhibit excellent luminescence characteristics, and the rare-earth ion doping in the polycrystalline BaWO4 nanofibers is tailored to achieve blue, green, red, and white light emissions. These nanofibers are extremely sensitive to 2-nitrotoluene and H2O2 with rapid response time, and sensitivity is observed within the range of 1-400 ppb and 1-10 ppm, towards 2-nitrotoluene and H2O2, respectively. The fluorescence quenching of BaWO4 nanofibers in the presence of 2-nitrotoluene and H2O2 is exponential with the quenching constants up to 1.73 x 10(6) and 2.73 x 10(4) L mol(-1), respectively, which are significantly higher than those of most of the fluorescent probes based on metal-organic frameworks and conjugated organic materials. After exposing to 2-nitrotoluene, the luminescence of the nanofibers is retained completely upon heating at 120 degrees C for 10 min and the sensory response is retained as fresh nanofibers, and currently available fluorescent explosive sensors could not achieve such a recovery. The high sensitivity and selectivity of scalable rare-earth-doped BaWO4 nanofibers provide a new platform for the simultaneous detection of two classes of explosives.