a 元素有机化学国家重点实验室, 南开大学化学学院, 天津 300071;
b 天津化学化工协同创新中心, 天津 300072
Construction and luminescent behavior of supramolecular hydrogel with white-light emission
Zhan Yia, Chen Yongb, Li Jingjinga, Liang Lua, Liu Yua,b
a State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China;
b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300072, P. R. China
Color-tunable luminescent supramolecular hydrogel with white-light emission is widely applied in the fields of light-emitting materials and fluorescence sensors due to their good physicochemical and biochemical properties. Using β-cyclodextrin, a class of cyclic oligosaccharide with seven D-glucose units linked by α-1,4-glucose bonds, and laponite as staring materials, we herein developed a photo-luminescent supramolecular hydrogel from laponite and pseudorotaxane that was constructed by the threading of ethylenediamine-modified β-cyclodextrins onto the poly (propyleneglycol) bis(2-amionopropylether) (PPG-NH2) chain. The supramolecular hydrogel properties thus obtained were characterized by rheological experiments, zeta potential measurements and scanning electron microscopy (SEM). The results showed that the supramolecular hydrogel possessed satisfactory mechanical properties, negative charges and porous three-dimensional structure. Then, thioflavin T (ThT) and 4-(4-dimethylaminostyryl)-1-methylpyridinium (DASPI), two typical distorted intramolecular charge transfer (TICT) molecules with dramatically increased fluorescence when the molecules are in confined region, were selected as model substrates. Generally, ThT and DASPI had almost no fluorescent emission at an excitation wavelength of 412 nm. By comparing the normalized fluorescence emission spectrum of ThT and the UV-visible absorption spectrum of DASPI, we found that the UV-Vis absorption band of DASPI showed a good overlap with the fluorescence emission band of ThT. Therefore, the fluorescence resonance energy transfer (FRET) process would occur between ThT and DASPI in the laponite/pseudorotaxane supermolecular hydrogel phase, where ThT acted as an energy donor and DASPI acted as an energy receptor. Then the fluorescence behavior of ThT/DASPI pairs in the supramolecular hydrogel phase was investigated. The results showed, after two TICT dyes, ThT and DASPI, were introduced in the hydrogel, the efficient FRET between ThT and DASPI led to the different emission colors including white light through adjusting the ratios of dyes. The convenient preparation and tunable luminescent behaviors of this supramolecular hydrogel will open a new practical path for water-based functional soft materials.