LAUSR

Film-based fluorescence sensing is recognized as one of the most optimizing techniques for trace analysis of chemicals in the air after the invention of ion mobility spectrometry. The performance of the technique is highly dependent on the design of the film. This paper reports a new fluorescent film which shows unprecedented and discriminative sensing performance to the presence of phenol, o-cresol, m-cresol and p-cresol in the air with an ultralow detection limit less than 1 ppt, 1 ppt, 10 ppt and 1 ppt, respectively. The film was designed via combination of the advantages of aggregation-induced emission (AIE) and those of intra-molecular charge transfer (ICT), where the former provides the opportunity to avoid the widely encountered aggregation-caused quenching (ACQ) effect and the latter allows sensitive sensing of the microenvironment change of the film. The most challenge behind the design is to find a fluorophore possessing both AIE and ICT effects. Fortunately, a newly synthesized bi-phenyl derivative of o-carborane capped with azetidine moiety (BZPCarb) shows the properties as expected. Importantly, the fluorophore is photochemically stable, a pre-requirement for multiple uses of film device. In addition, the non-planar structure of the fluorophore is also favorable for film sensing as it could form porous films owing to screening of dense stacking of the molecules. It is the merits that make BZPCarb-based film show outstanding sensing and discriminative performances. Based on the fluorophore and the design, a conceptual high-performance fluorescent vapor sensor for phenolic compounds was developed.