Hydrophilic Ultralong Organic Nanophosphors.

Ultralong organic phosphorescence (UOP), enabling of persistent luminescence after removal of external excitation light, shows great promise in biological applications such as bioimaging in virtue of antibackground fluorescence interference. Despite of good biocompatibility and outstanding phosphorescent properties, most current organic phosphors are hydrophobic with poor water solubility in the form of bulk crystal with large size, limiting their potential in the biological field. Here, a facile and versatile approach is provided to obtain nanoscale hydrophilic phosphorescent phosphors (HPPs) by physically loading ultralong organic phosphors into hollow mesoporous silica nanoparticles. The as-prepared HPPs can be well suspended in aqueous solution and effectively internalized by HeLa cells with very low cytotoxicity. Such HPPs are successfully applied for afterglow bioimaging in living nude mice with a very high signal-to-noise ratio up to 31. The current study not only provides a universal strategy to realize UOP in aqueous media but also demonstrates their great potential for biomedical purposes as an advanced imaging indicator with long-lived emission lifetime.