As one of the most promising nanomaterials for biomedical applications, carbon dots (CDs) hold great potential in the field of bioimaging, biosensing and biotherapy due to their low cytotoxicity, high water solubility, favorable biocompatibility, good photostability, tunable fluorescence emission and excitation. In this review, we will provide an update on the latest research of CDs on the synthetic routes, chemical modifications, optical properties and biomedical applications. We will mainly discuss their applications in bioimaging of normal and cancer stem cells and tumour cells, two-photon fluorescence imaging, in vivo imaging, biosensing, and cancer therapy including photothermal therapy, photodynamic therapy and chemotherapy. At the end, current challenges and future perspectives of CDs in biomedical applications will also be discussed. We hope that this review will provide valuable insights to inspire new discoveries on CDs and draw a roadmap towards a broader range of biomedical applications.

Flexible functional devices based on two dimensional (2D) materials are extremely suitable for malleable, portable and sustainable applications, such as health monitoring, electronic skin and optoelectronics. In this work, we developed a flexible photodetector based on a p-CuO/n-MoS₂ heterojunction with an enhancement in photocurrent and detection sensitivity. Because of the non-centrosymmetric structure in monolayer MoS₂, the piezo-potential induced by applied strain adjusts the band structure at the heterojunction interface and broadens the depletion region based on the piezo-phototronic effect. The border depletion can be discreetly used to improve the photo-generated carrier separation and transport to enhance photoresponse performance. When illuminated by a 532 nm laser, the photocurrent of the heterojunction can be enhanced 27 times under a tensile strain of 0.65% compared to strain free conditions and the detection sensitivity can reach up to 3.27 × 10⁸ Jones. As a result, our research provides a new strategy for novel design and performance optimization of 2D material heterostructures in the application of optoelectronics.