Aggregation-induced emission of azobenzene towards a sensitive indication on the self-assembly of a cellulose material†

Azobenzene is one of the most commonly used photochromic molecules, but is rarely used as a fluorescence probe in materials chemistry, due to its efficient photoisomerization providing competition for consumption of light energy. In this study, an azobenzene-containing ammonium surfactant was designed for fabricating an ionic cellulose material through an electrostatic complexation with carboxymethyl cellulose. Based on the AIE effect of the azobenzene motif, the cellulose material exhibited fluorescence. Furthermore, in aqueous conditions, the self-assembly of this cellulose material could be well regulated by effecting azobenzene isomerization under UV/Vis irradiation, which resulted in a remarkable change in the fluorescence intensity. As compared to the commonly used UV-Vis absorption, the fluorescence change of azobenzene was found to provide a more sensitive indication for tracking the dissolution and precipitation of the ionic cellulose-surfactant assemblies in aqueous conditions. This work has provided a useful strategy for fabricating photoresponsive fluorescent biomaterials based on azobenzene, opening a new opportunity for detecting drug-loading materials.