Enhanced fluorescence detection of metal ions using light-harvesting mesoporous organosilica

Enhanced fluorescence detection of metal ions was realized in a system consisting of a fluorescent 2,2'-bipyridine (BPy) receptor and light-harvesting periodic mesoporous organosilica (PMO). The fluorescent BPy receptor with two silyl groups was synthesized and covalently attached to the pore walls of biphenyl (Bp)-bridged PMO powder. The fluorescence intensity from the BPy receptor was significantly enhanced by the light-harvesting property of Bp-PMO, that is, the energy funneling into the BPy receptor from a large number of Bp groups in the PMO framework which absorbed UV light effectively. The enhanced emission of the BPy receptor was quenched upon the addition of a low concentration of Cu(2+) (0.15-1.2×10(-6)  M), resulting in the sensitive detection of Cu(2+). Upon titration of Zn(2+) (0.3-6.0×10(-6)  M), the fluorescence excitation spectrum was systematically changed with an isosbestic point at 375 nm through 1:1 complexation of BPy and Zn(2+) similar to that observed in BPy-based solutions, indicating almost complete preservation of the binding property of the BPy receptor despite covalent fixing on the solid surface. These results demonstrate that light-harvesting PMOs have great potential as supporting materials for enhanced fluorescence chemosensors.