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

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