Cellulose nanofibril based graft conjugated polymer films act as a chemosensor for nitroaromatic

•Cellulose nanofibril based graft conjugated polymer film was prepared.•The modified CNF film is used as a fluorescent sensor for nitroaromatics.•Numerous cavities/pathways created would benefit the rapid diffusion of analytes.•The fluorescent sensor exhibits rapid response toward nitroaromatic vapors.

A cellulose nanofibril film is modified by chemical assembly of boronate-terminated conjugated polymer chains at its specific sites, C-6 carboxyl groups. The modified cellulose nanofibril film is used as a fluorescent sensor for nitroaromatic vapor. Thanks to the specific reactive sites, numerous loose cavities or pathways located in the film sensor's out-layer have been formed, and the fraction of easily accessible cavities of the novel fluorescent film sensor is up to 0.97, which could benefit the penetration and diffusion of analyte vapor. Therefore, the novel fluorescent film sensor exhibits high sensitivity toward nitroaromatic vapor with a fast response. The fluorescence quenching efficiency of the chemical-assembly film sensor is about 3 times larger than that of the spin-cast film sensor using the same conjugated polymer for 600 s exposure to DNT vapor. In addition, the novel fluorescent film sensor shows good reversibility.