Electrospun Fibers for Colorimetric Detection of Volatile Organic Compounds via Polyfluorene–Quinoxaline Copolymer Photoproperties Change

We report a volatile organic compound (VOC) sensing platform based on electrospun nanofibers of a single-component PFO–quinoxaline donor–acceptor copolymer, in which donor and acceptor units are covalently integrated within one conjugated chain. Unlike multicomponent systems governed by intermolecular geometry, this design enables VOC-responsive modulation of intrinsically defined excited-state energy flow and charge-transfer photophysics. By tuning the PFO/QX composition, the copolymer showed systematic changes in emission color and lifetime, reflecting composition-dependent donor-to-acceptor interactions. When processed into nanoporous electrospun nanofibers, these chain-level photophysical responses became strongly amplified by enhanced analyte accessibility and nonequilibrium chain packing. In particular, the 95:5 composition exhibited distinct blue-to-green emission changes, red-shifted photoluminescence, and shortened fluorescence lifetimes upon exposure to chloroform and tetrahydrofuran vapors, whereas spin-coated films showed only minor responses. These results show that VOCs can directly perturb the photophysical balance within a molecularly integrated donor–acceptor copolymer and demonstrate a simple strategy for visually readable optical gas sensing based on single-chain electronic structure and nanofiber morphology.