A highly sensitive fluorescent nanofiber sensor functionalized with small organic molecules for specific analyte detection†

The rapid, sensitive, and efficient detection of nitroaromatic explosives is crucial for human health and public safety, particularly in detecting trace explosive vapors. In this study, a donor–acceptor (D–A) type fluorescent probe, 6-(6-(9H-carbazol-9-yl)pyridin-3-yl)-2-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione (PPBD), was synthesized by coupling carbazole and 1,8-naphthalimide via the Suzuki reaction. The probe exhibits characteristic intramolecular charge transfer (ICT) emission, which makes it highly efficient for detecting nitroaromatic explosives such as pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), 2-nitro-m-xylene cyclotetramethylene tetranitramine (HMX), and cyclotrimethylene trinitramine (RDX). Additionally, an electrospun fiber film of PPBD/PEO was fabricated, demonstrating high sensitivity in sensing nitroaromatic vapors via fluorescence testing. The quenching efficiencies for HMX, TNT, RDX, PETN, and 2-nitro-m-xylene are 92%, 89%, 76%, 64%, and 40%, respectively, with the highest selectivity for HMX vapor. This enhanced selectivity is attributed to the increased contact area between nanofibers and analytes in the film, facilitating effective fluorescence quenching. Proton transfer from analytes to PPBD blocks ICT emission, leading to the quenching of fluorescence.