Chemical sensors based on nano-sized lanthanide-grafted periodic mesoporous organosilica hybrid materials

In this work we introduce the use of nano-sized (50-70 nm) lanthanide-grafted periodic mesoporous organosilicas for both metal ion sensing and solvent sensing. For this study a PMO constructed from the N,N-bis(trimethoxysilylpropyl)-2,6-pyridine dicarboxamide linker and tetraethyl orthosilicate (at a 5 : 95 ratio) was employed. This material was grafted with Eu3+, Tb3+ or a mixture of Eu3+-Tb3+ chloride salts to obtain strongly emitting nano-sized luminescence materials. To further enhance the luminescence properties of the materials two different co-ligands were used - 1,10-phenanthroline (phen) and 5,5 '-dimethyl-2,2 '-dipyridyl (bpy). The luminescence properties of the developed series of hybrid materials were studied in detail in the solid-state and after dispersing in water. The materials were investigated for their use as ion sensors, with the Eu3+ and Tb3+ phen and bpy co-grafted materials showing selective turn on fluorescence for Pb2+ and Cr3+ ions (at a 10 ppm concentration of the ions). The Eu3+-Tb3+ co-grafted materials showed solvatochromism and could be used as a solvent sensor to distinguish between protic and aprotic solvents.