Synthesis and Applications of Red-Emissive Carbon Dots

Carbon dots (CDs), a new class of fluorescent carbon nanoparticles (less than 10 nm in size), have been widely applied in various fields, including sensors, bioimaging, catalysis, light-emitting devices (LEDs), and photoelectronic devices, owing to their unique properties such as low toxicity, bio-compatibility, high photostability, easy surface modification, and up-conversion fluorescence, over the past decades. Recently, multiple-color-emissive CDs, especially red-emissive CDs (RCDs), have drawn much attention owing to their unique advantages, like the ability to penetrate the animal bodies without the disturbance of strong tissue autofluorescence, multiple-color fluorescence displaying or sensing, and the capacity to be one essential component to obtain white LED (WLED). In this review, we focused on the progress of recently-emerging RCDs in the past five years, including their synthetic methods (hydrothermal, solvothermal, reflux condensation and microwave techniques), influencing factors (precursors, solvents, elements doping, surface chemistry) and various applications (bioimaging, sensor, photocatalysis and WLEDs), with a perspective on the future advancements.