Color-tunable fluorescent silica-based hybrid film of stacked structure based on a single amphiphilic AIEgen

The large-area and color-tunable fluorescent (FL) films have great potential applications in light-emitting devices and color displays. Yet, the challenge of realizing truly color-tunable emissions using a single fluorophore remains. Herein, we present a large-area, transparent and ultra-stable free-standing FL silica-based film (FSFSF) with color-tunable emissions prepared by using an amphiphilic aggregation-induced emission (AIE) luminogen (AIEgen) as both a structure-directing agent and a light-emitting source. The color-tunable FSFSFs have been facilely prepared at the gas–liquid (GL-FSFSF) and solid–liquid interfaces (SL-FSFSF) by simply stacking the AIEgen/SiO2 composite layers with different self-assembled structures using an approach combining self-assembly with sol-gel process. These films exhibited variable excitation-dependent emission colors, emitting bright blue and green fluorescences as well as dark red fluorescence from one single visual field under excitation with UV, blue, and green lights, respectively. The research found that the resulting GL-FSFSF had a sandwich-like structure with an alternate arrangement of cylindrical and spherical AIEgen micelles in the silica matrix, and exhibited unusual excitation-dependent multi-wavelength and morphology-dependent dual-center emission characteristics. It has been reported that the luminescence of many AIE compounds is morphology-dependent. Therefore, we speculate that the two emission centers of the film are related to the two self-assembled morphologies of amphiphilic AIEgen. Its bright blue and green fluorescence is attributed to the same emission intensity of the two luminescent centers. This study has demonstrated that morphology- and excitation-dependent color-tunable emissions based on one AIE fluorophore can be achieved by incorporating AIEgen aggregates with different self-assembled morphologies in the matrix. Such a simple strategy can be extended to construct other multicolor-tunable FL hybrid materials.