Carbon dots (CDs) have a wide range of applications in chemical, physical and biomedical research fields. We are particularly interested in the use of CDs as fluorescence nanomaterials for targeted tumor cell imaging. One of the important aspects of success is to enhance the fluorescence quantum yields (QY) of CDs as well as increase their targetability to tumor cells. However, most of the reported CDs are limited by relative low QY. In the current study, for the first time, one-step synthesis of highly luminescent CDs by using folic acid (FA) as single precursor was obtained in natural water through hydrothermal method. The as-prepared CDs exhibited QY as high as 94.5% in water, which is even higher than most of organic fluorescent dyes. The obtained CDs showed excellent photoluminescent activity, high photostability and favorable biocompatibility. The FA residuals in CDs led to extraordinary targetability to cancer cells and promoted folate receptor-mediated cellular uptake successfully, which holds a great potential in biological and bioimaging studies.

As novel fluorescent nanomaterials, carbon dots (CDs) exhibit excellent photostability, good biocompatibility, and high quantum yield (QY). Their superior properties make them promising candidates for biomedical assays and therapy. Among them, the red‐emission (>600 nm) CDs have attracted increasing attention in the past years due to their little damage to the biological matrix, deep tissue penetration, and minimum autofluorescence background of biosamples. This Review, summarizes the recent progress of far‐red to near‐infrared (NIR) CDs from the preparation and their biological applications. The challenges in designing far‐red and NIR CDs and their further applications in biomedical fields are also discussed.

No abstract