In recent years, tremendous efforts have been devoted to explore various types of nano-agents with high near-infrared (NIR) absorbance for photothermal cancer treatment.Although many inorganic photothermal agents,such as various gold nanostructures and carbon nanomaterials, have already shown high efficacies for photothermal treatment of cancers in pre-clinical animal experiments, those inorganic nanomaterials are usually non-biodegradable and would retain in the body for long periods of time, preventing their further application in clinical cancer treatment due to the potential long-term toxicity concern.