Triphenyl benzene-bridged fluorescent silsesquioxane: shape-controlled hybrid silicas by hydrolytic conditions

A new silsesquioxane molecule was synthesized, in which triphenyl benzene was connected with three Si(OC2H5)3 groups using three urea groups as the bridge. The molecule could self-assemble through the intermolecular H-bonding among urea groups and pi-pi interaction of triphenyl benzene core in the solution and it could also be transferred into hybrid silicas by hydrolysis. When the non-preorganized silsesquioxane was hydrolyzed, isolated spherical hybrid silica was gained. However, when the silsesquioxane was preorganized before the hydrolyzation uniform interconnected spherical hybrid silica and intertwined nanofibrous one could be generated under acidic and basic conditions, respectively. The photoluminescence (PL) spectra of the obtained hybrid silicas showed that they still kept the emission properties of their precursor silsesquioxane, and the shift of the emission bands was due to the pi-pi interaction of triphenyl benzene in the course of polycondensation.