Tunable Nano-Supramolecules\nBased on Cucurbiturils\nfor Near-Infrared Phosphorescence Imaging

Nano-supramolecules based on artificial macrocycles can\nnot only\nregulate assembly morphology but also boost phosphorescence resonance\nenergy transfer (PRET). Herein, a water-soluble phosphorescence supramolecule\nwas constructed from the hyaluronic acid-modified bromophenylpyridinium\n(HAPY), cucurbit[<i>n</i>]uril (CB[<i>n</i>], <i>n</i> = 7/8), and energy acceptor phenyl-bridged phenothiazine\nderivatives, displaying efficient PRET and achieving near-infrared\n(NIR) phosphorescence by macrocyclic CB[<i>n</i>] and the\nassembly confinements. As compared with weak phosphorescent nanofibers\nof HAPY/CB[7], the spherical nanoparticles of HAPY/CB[8] not only\ngave strong green phosphorescence with extended lifetime to 1.27 ms\nbut also could act as the energy donor and confine cationic phenothiazine\nin the secondary assemblies, leading to highly efficient PRET efficiency\n(87.27%) from the phosphors to triplet acceptors, realizing phosphorescence\nemission at 750 nm and an ultralarge Stokes shift of 440 nm. Ultimately,\nthe nanoassembly achieved by the multiscale confinements boosting\nPRET was successfully applied in targeted cancer cell imaging, providing\nnew insight for fabricating NIR phosphorescence materials.