Plurality of Luminophores of Super-Bright Carbon Dots Synthesized from Citric Acid and Ethylenediamine

Hydrothermal treatment of a mixture of citric acid (CA) and ethylenediamine (EDA) is known for production of carbon dots (CDs) with intense photoluminescence (PL) in the blue region with a quantum yield up to ∼95%. However, the specific result of the synthesis depends significantly on treatment’s parameters. In this manuscript, by studying CDs synthesized from an EDA : CA mixture of 1 : 1 at temperatures of 80, 140, or 200°C for 0.5–6 h, it was found that, in addition to the main PL peak with a maximum in the region of λ_ex/λ_em 350/440 nm/nm, 6 different peaks with lower PL intensity are observed at different stages of the synthesis, corresponding to different luminophores. The parameters and conditions of formation of these luminophores were studied, the quantum yields of their luminescence obtained.