Humidity- and Temperature-Tunable Multicolor Luminescence of Cucurbit[8]uril-Based Supramolecular Assembly

Fabrication of tunable luminescent materials by a single luminophore is a challenge owning to the limit of emissive properties of monofluorophores. Herein, a type of temperature and humidity dual-responsive luminescent material based on host-guest supramolecular self-assembly was developed. Included into the cavity of cucurbit[8]uril (CB[8]) to form a 1:2 host-guest binding motif, the highly blue-emissive thiazolothiazole methyl-viologen (TMV) molecules were promoted to stack closely with a sharp luminescence decrease at 460 nm and rise of the dimer emission at 535 nm, especially at high concentrations in aqueous solution, which was demonstrated by fluorescence spectra, UV-vis absorbance spectra, NMR, and ITC data. Accordingly, when printed on paper, the 1/2 CB[8]/TMV complex presented a reversibly humidity-dependent emissive behavior with luminescent color changing from greenish-yellow in wet to blue upon evaporation. Besides, the  sensitivity of the host-guest interaction endowed the CB[8]/TMV complexes with temperature-tunable emission which showed a considerably enhanced blue luminescence at higher temperature. Subsequently, a ratiometric temperature-responsive emitter which luminesced reversibly from pink to white and then to blue light at temperature ranging from 0 to 70 °C was fabricated by mixing the CB[8]/TMV complex with thermal-sensitized emitting GSH-Au nanoclusters. These fine-tuning abilities make the CB[8]/TMV supramolecular complex applicable in visual luminescent devices such as anti-counterfeiting labels and fluorescent thermometers.