Phosphorescent Carbon Dots for Highly Efficient Oxygen Photosensitization and as Photo-oxidative Nanozymes.

Materials for photosensitized oxygen activation are extremely important for a suite of photodynamic applications in biomedical, analytical, and energy sectors. Carbon-based photosensitizers are attractive for their low cost and high stability, but most of them such as fullerene and graphene quantum dots suffer from low efficiency, and the rational design of carbon-based photosensitizers remains a challenge. Given the similar chemical origin of phosphorescence and photosensitization, we herein synthesized a series of nitrogen-doped carbon dots (C-dots) and confirmed that their photo-oxidation activity correlated with their phosphorescence quantum yields, providing a direction for the rational designing of such materials. Compared to other carbon nanomaterials and molecular photosensitizers, these C-dots have the highest activity, and they can finish oxidation reactions in a few seconds. The excellent photosensitized oxygen activation makes these water-soluble C-dots a promising oxidase-mimicking nanozyme for photodynamic antimicrobial chemotherapy and other applications.