An interface-assembled turn-on fluorescent nanofilm for highly selective detection of trifluoroacetic acid vapour via protonation-modulated ICT

Turn-on fluorescent nanofilms are attractive for gas sensing but rare, because protonation of donor-π-acceptor systems usually promotes charge separation and quenches emission. Here a gas-liquid interface-assembled DTH-DFP nanofilm shows protonation-induced blue-shifted turn-on fluorescence to trifluoroacetic acid (TFA) vapour, offering a transparent, fast, and sensitive platform (LOD 1.48 ppm).