Carbon Dots: A Small Conundrum

Carbon dots (CDs) with varying chemical structures have been successfully prepared through optimization of synthesis, doping/surface modification, and purification conditions. CD physicochemical properties (e.g., dispersibility, photoluminescence, and biocompatibility) have been rationally tuned to improve performance in several applications, including light-emitting diodes, bioimaging, and tumor therapy. CDs have been employed in emerging applications, including antibacterial agents, self-healing materials, and mass spectrometry. Several structure–property relationships have been uncovered, deepening the current understanding of CDs. Carbon dots (CDs) are an emerging subset of nanomaterials, defined by characteristic sizes of <10 nm. CDs possess a carbon core that is functionalized by various groups at the surface. These materials exhibit a wide range of physiochemical properties (e.g., photo-induced electron transfer and photoluminescence) making them an ideal platform for several important environmental, biological, and energy-related applications. However, elucidating the molecular origin and key factors controlling their varied physiochemical properties remains an outstanding challenge. Some properties (e.g., toxicity) are dictated primarily by the CD core, while other properties (e.g., dispersibility) are derived primarily from surface functional groups. This mini-review highlights the recent advances in CDs, with particular attention given to controllable syntheses method, bulk- versus surface-derived physiochemical properties, and key structure–property relationships. Carbon dots (CDs) are an emerging subset of nanomaterials, defined by characteristic sizes of <10 nm. CDs possess a carbon core that is functionalized by various groups at the surface. These materials exhibit a wide range of physiochemical properties (e.g., photo-induced electron transfer and photoluminescence) making them an ideal platform for several important environmental, biological, and energy-related applications. However, elucidating the molecular origin and key factors controlling their varied physiochemical properties remains an outstanding challenge. Some properties (e.g., toxicity) are dictated primarily by the CD core, while other properties (e.g., dispersibility) are derived primarily from surface functional groups. This mini-review highlights the recent advances in CDs, with particular attention given to controllable syntheses method, bulk- versus surface-derived physiochemical properties, and key structure–property relationships.