Carbon dots (C dots) with biocompatibility, brightness, stability against photoirradiation and salt, and ease in preparation have become important materials for sensing and imaging. They can be prepared from natural materials and small organic molecules through hydrothermal, microwave-assistant, and electrochemical methods, with advantages of simplicity and low cost. To enhance the quantum yields of C dots in the red and near-infrared regions, doping of C dots with heteroatoms such as nitrogen and sulfur has been suggested. C dots both with and without being functionalized recognition elements...
