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 Cu2+ (0.15–1.2×10−6 M), resulting in the sensitive detection of Cu2+. Upon titration of Zn2+ (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 Zn2+ 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. Fluorescence chemosensors: Periodic mesoporous organosilica with a fluorescent 2,2′‐bipyridine receptor attached in the mesochannels showed enhanced fluorescence quenching or band shift upon the addition of a low concentration of metal ions (Cu2+, Zn2+, etc.) because of the unique light‐harvesting property of the mesoporous organosilica (see figure).