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

Abstract

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 × 10⁶ and 2.73 × 10⁴ 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 °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.