Two-Photon Excited Near-Infrared Phosphorescence Based on Secondary Supramolecular Confinement

Organic phosphorescence materials have received wide attention in bioimaging for bio-low toxicity and large Stokes. Herein, a design strategy to achieve near-infrared (NIR) excitation and emission of organic room-temperature phosphorescence through two-stage confinement supramolecular assembly is presented. Via supramolecular macrocyclic confinement, the host-guest complexes exhibit phosphorescence with two-photon absorption (excitation wavelength up to 890 nm) and NIR emission (emission wavelength up to 800 nm) in aqueous solution, and further nano-confinement assembly significantly strengthens phosphorescence. Moreover, the nano-assemblies possess color-tunable luminescence spanning from the visible to NIR regions under different excitation wavelengths. Intriguingly, the prepared water-soluble assemblies maintain two-photon absorption and multicolor luminescence in cells or vivo.