High-purity C₃N quantum dots for enhancing fluorescence detection of metal ions

A new type of two-dimensional layered material, namely C₃N, has been fabricated by polymerization and recommended to have great potential in various applications such as the development of electronic devices or photo-detectors, due to its enhanced conductivity, electronegativity, and unique optical properties. Actually, most of the present research on C₃N is limited in the scope of theoretical calculation, while experimental research is blocked by inefficient synthesis with low purity and homogeneity. Here, we report an optimized efficient synthesis method of high-purity C₃N QDs in aqueous solution by polymerization of DAP with combined centrifugation and filtration of products, with the synthesis yield up to 33.1 ± 3.1%. Subsequently, the C₃N QDs have been used as novel metal ion probes exhibiting a sensitive fluorescent response to various metal ions including monovalent alkaline metals (Li⁺, Na⁺, and K⁺), divalent alkaline-earth metals (Mg²⁺, Ca²⁺, and Sr²⁺), and multivalent transition metals (Cu²⁺, Co²⁺, Ni²⁺, and Au³⁺, Fe³⁺, Cr³⁺) due to the high electronegativity of the C₃N surface. Particularly, the fluorescent quenching response of Al³⁺, Ga³⁺, In³⁺, and Sc³⁺ ions is significantly different from the fluorescent enhanced response of most other carbon-based QDs, which is promising for enriching the detection methods of these metal ions and beneficial to improve the accuracy of ion recognition.