Figure 2.

(a) General approaches for the synthesis of C-dots. In a top-down approach, C-dots are synthesized by transforming bulk carbon material into ultra-small powders via oxidation, laser ablation, ultrasounds, or electrochemical methods. In a bottom-up approach, C-dots are synthesized via physical or chemical treatments of molecular precursors that may get ionized, dissociated, evaporated, or sublimated and then condense/react to form C-dots, or via hydrothermal, sonochemical, pyrolitic treatments. (b) Reactions schemes for covalent strategies to C-dots functionalization: amide coupling (1,2), esterification (3), sulfonamide formation (4); tosylate-leaving group in nucleophilic substitution (5), sylilation (6).