Research progress in preparation and application of high-color-purity fluorescent carbon dots

Narrow-band, high-color-purity luminescent materials are widely used in the fields of ultra-high-definition display and lighting, super-resolution imaging and sensing, bio-imaging and anti-counterfeiting. However, the high-color-purity fluorescent materials mainly used are Ⅱ-Ⅳ semiconductor quantum dots, halide perovskite nanocrystals and so on, which generally contains highly toxic transition metal ions such as Cd and Pb. Moreover, these materials often show low environmental stability. In contrast, carbon dots have many advantages including no heavy metal ions, high photo/chemical stability, low toxicity and wide source of raw materials. Therefore, developing fluorescent carbon dots with high-color-purity has important theoretical and practical significance. Here, the research progress of the synthesis and application of high-color-purity carbon dots was reviewed; the effects of precursor, synthetic methods and some factors on the position and the full width at half maximum of the carbon dots and the application in the field of LED, sensing and imaging were discussed. Additionally, the opportunities and challenges of high-color-purity carbon dots in large-scale synthesis, optical properties including the tune of PL position, the enhancement of the fluorescent quantum yield and color purity, understanding their photoluminescence mechanism as well as developing new applications were proposed.