Waste toner-derived carbon dots for bioimaging and photodynamic therapy

Printer toner, which accounts for a large fraction of electrical and electronic wastes, poses serious environmental and health risks but cannot be efficiently recycled because of its high chemical durability and complexity. Specifically, only 20-30% of waste toner is recycled, while much of the remainder ends up in landfills and thus contributes to air/soil pollution and respiratory disease development. Herein, we report the one-pot hydro-thermal processing of waste toner into well-dispersed and uniform-sized carbon dots featuring abundant surface defects (e.g., radicals and dangling bonds), strongly interacting with UV (200-400 nm) light, and exhibiting intense photoluminescence in both UV (300 nm) and visible (400-500 nm) ranges. In particular, ethanolamine is used to chemically disintegrate the carbon black cores of toner particles into nanoparticles and simultaneously passivate the nanoparticle surface. According to the results of time-correlated single photon counting spectros-copy measurements, UV-and visible-region photoluminescence originates from amorphous carbon structures in the core and oxygen/nitrogen-containing functional groups on the surface, respectively. Finally, in view of their excellent visible-region optical properties and the ability to generate reactive oxygen species under laser irra-diation, the waste toner-derived carbon dots are demonstrated to be promising agents for bioimaging and photodynamic therapy, respectively.