Rational Design of Nanoparticles with Efficient Lanthanide Luminescence Sensitized by Iridium(III) Complex for Time‐Gated Luminescence Bioimaging

A nanoprobe with highly efficient lanthanide luminescence sensitized by transition metal complex has been developed for luminescence imaging in living cells. In this work, Ir(III) complex as the sensitizer and Eu(III) complex as the energy acceptor have been chosen. Both the sensitizer and the energy acceptor have been embedded into the silica nanoparticles through covalent attachment. By optimizing the ligand structures and triplet energy levels of Ir(III) complex, efficient energy transfer from Ir(III) moiety to Eu(III) complex occurred in nanoparticles, which leads to the stable and intense red emission from Eu(III) complex in aqueous solution under the visible excitation of up to 488 nm. This nanoprobe exhibits multiple advantages, including long excitation wavelength, high quantum efficiency, long emission lifetime, narrow emission bands, high photostability, excellent water dispersibility, and good biocompatibility, all of which are very beneficial for applications in bioimaging. The successful application of nanoprobe in bioimaging with visible excitation has been demonstrated. Thus, the design strategy will be a versatile and convenient way to realize excellent lanthanide(III) complex‐based bioprobes for practical biomedical applications.