High-purity C 3 N quantum dots for enhancing fluorescence detection of metal ions.

A new type of two-dimensional layered material, namely C 3 N, 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 C 3 N 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 C 3 N 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 C 3 N 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 (Mg 2+ , Ca 2+ , and Sr 2+ ), and multivalent transition metals (Cu 2+ , Co 2+ , Ni 2+ , and Au 3+ , Fe 3+ , Cr 3+ ) due to the high electronegativity of the C 3 N surface. Particularly, the fluorescent quenching response of Al 3+ , Ga 3+ , In 3+ , and Sc 3+ 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.