Transparent and visible-light harvesting acridone-bridged mesostructured organosilica film

Transparent and visible light-harvesting acridone-bridged periodic mesoporous organosilica (PMO) films were prepared by acidic sol-gel polycondensation of non-methylated and N-methylated acridone-bridged bis-triethoxysilane precursors in the presence of a template surfactant via evaporation-induced self-assembly (EISA). A muddy film containing small aggregates was obtained from the non-methylated precursor. The aggregate was formed by strong intermolecular hydrogen bonds between N-H and C=O of the acridone groups during EISA. However, a transparent PMO film was successfully formed from the N-methylated precursor. Capping of the amine group hindered the intermolecular hydrogen bonds and effectively suppressed aggregate formation. The obtained acridone-bridged PMO film showed a visible light absorption band with an edge at 430 nm and fluorescence emission centered at 500 nm. Furthermore, doping of a fluorescent dye into the mesochannels of the acridone-PMO promoted efficient energy funneling from the framework acridone groups into the dye, resulting in a strong fluorescence emission centered at 600 nm from the dye.