Hetero-metal encapsulation induced ratiometric recognition of fluoride

Emissive lanthanide ions are considered as luminescent species or optical probes for the analytes in ambient conditions or even cellular environment. But a variety of factors determine the stability of photo-luminescent signals due to the excitation sources, statistical errors or the selection of solvents. In this way, ratiometric assays effectively circumvent such problem and lead to more sensitive and reliable results. Herein, an organic-inorganic hybrid material has been developed with the europium complex as the core and the terbium species can be attached onto the surface of silica host. As for the evaluation of the internal structure, the terbium complex has been integrated into the hybrid network via weak forces and its sensitizing moiety will be easily attacked by Lewis acid-base interactions. In a different manner, the europium complex has been shielded from perturbation due to the protection of the outside silica shells. Such sharp difference in response to fluoride induces drastic signal changes and the conversion of binding process between fluoride and molecular receptors (boronic group) into readable optical outputs has afforded the lower detection limit for F^- as 0.17 μM. In addition, the intracellular uptake and distribution of the hybrid material have been explored.