Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

Novel red‐emissive carbon‐dots (C‐dots) with broad absorption in the region from 400 to 750 nm are prepared from polythiophene phenylpropionic acid. Upon near infrared laser irradiation, the red‐emissive C‐dots show strong photoacoustic response and high photothermal conversion efficiency (η ≈ 38.5%). These unique properties enable the C‐dots to act as multifunctional fluorescent, photoacoustic, and thermal theranostics for simultaneous diagnosis and therapy of cancer.

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