Fundamental Study of Electrospun Pyrene–Polyethersulfone Nanofibers Using Mixed Solvents for Sensitive and Selective Explosives Detection in Aqueous Solution

Fluorescent pyrene–polyethersulfone (Py–PES) nanofibers were prepared through electrospinning technique using mixed solvents. The effects of mixed solvent ratio and polymer/fluorophore concentrations on electrospun nanofiber’s morphology and its sensing performance were systematically investigated and optimized. The Py–PES nanofibers prepared under optimized conditions were further applied for highly sensitive detection of explosives, such as picric acid (PA), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) in aqueous phase with limits of detection (S/N = 3) of 23, 160, 400, and 980 nM, respectively. The Stern–Volmer (S–V) plot for Py excimer fluorescence quenching by PA shows two linear regions at low (0–1 μM) and high concentration range (>1 μM) with a quenching constant of 1.263 × 10⁶ M–¹ and 5.08 × 10⁴ M–¹, respectively. On the contrary, S–V plots for Py excimer fluorescence quenching by TNT, DNT, and RDX display an overall linearity in the entire tested concentration range. The fluorescence quenching by PA can be attributed to the fact that both photoinduced electron transfer and energy transfer are involved in the quenching process. In addition, pyrene monomer fluorescence is also quenched and exhibits different trends for different explosives. Fluorescence lifetime studies have revealed a dominant static quenching mechanism of the current fluorescent sensors for explosives in aqueous solution. Selectivity study demonstrates that common interferents have an insignificant effect on the emission intensity of the fluorescent nanofibers in aqueous phase, while reusability study indicates that the fluorescent nanofibers can be regenerated. Spiked real river water sample was also tested, and negligible matrix effect on explosives detection was observed. This research provides new insights into the development of fluorescent explosive sensor with high performance.