Volatile acid responsiveness of chiral nematic luminescent cellulose nanocrystal/9,10-Bis((Z)-2-phenyl-2-(pyridin-2-yl)vinyl)anthracene composite films

With the fast development of industrialization, various noxious gases released into the atmosphere have brought serious hazard to the natural environment and human health. In this work, chiral photonic composite films were manufactured by the coassembly of cellulose nanocrystals (CNCs) and an anthracene-centered luminophore (9,10-bis((Z)-2-phenyl-2-(pyridin-2-yl)vinyl)anthracene, BPP2VA) in an environmentally friendly way. The obtained hybrid films combining both photonic and fluorescence properties display unique responsiveness to various volatile acid vapors such as HCl, TFA, and HNO₃. Upon exposure to the HCl vapor in a wide range of concentrations (1 to 10³ ppm), the composite films exhibited high sensitivity in that the initial change of fluorescence intensity emerged in less than 5 s. Obvious fluorescence quenching and red shift of the emission peak (∼30 nm) were observed, and acid protonation may be the principal reason for these changes of fluorescence behaviors. Meanwhile, structural color variation also occurred due to the steric space effects, and the colorimetric naked-eye sensing rendered the detected result more accurate. Remarkably, the composite films can be reused in that the fluorescence properties such as fluorescence intensity and emission peak position could be recovered by the treatment with triethylamine. Accordingly, CNC-BPP2VA composite films provide a simple but effective platform to develop a user-friendly and economical sensor for the rapid detection of volatile acid vapors.