Advancements of CQDs in nano-medical applications: Achievements, challenges, and future outlook

In the quantum world, things really do behave differently. Once the particles achieve the properties of tiny-scale materials, they can be fine-tuned to optimize for a wide range of biomedical applications. In this regard, carbon quantum dots (CQDs) owe intrinsic fluorescence property, low toxicity, and desired environmental friendliness advantages of several synthetic routes. Recently, the functionalization and surface properties of CQDs sized up to 10 nm have been improved and tuned, which has gained attention for bio-imaging applications. When the material is minimized to such nanoscale dimensions, its quantum confinement helps the excitation-dependent photoluminescence properties be governed by size rather than electron count. Thus, in this paper, we will track the progress of CQDs with advanced physicochemical properties and their wide applications in cancer theranostic nanomedicine, cancer therapy, bio-imaging, drug delivery systems, antimicrobial activity, and present the various challenges and perspectives in their future promising fields.