Ratiometric fluorescent sensing of copper ion based on chromaticity change strategy.

Copper ions play a significant role in human bodies, as they are beneficial for many metabolism processes, but excessive Cu may cause various symptoms. Therefore, the development of strategies capable of both sensitive detection and visualization of Cu is greatly important for human health. In this work, a novel ratiometric fluorescence sensor for rapid and visual detection of Cu was designed based on green emission carbon dots (CDs) and red emission CdTe/CdS quantum dots (QDs). We have calculated the chromaticity coordinates of individual CDs and CdTe/CdS QDs, and the chromaticity coordinate of their mixture would change along the line between the two points of CDs and CdTe/CdS QDs in the chromaticity coordinate system. The red fluorescence of QDs can be influenced by Cu, and the fluorescence color of CDs-QDs changes from yellow to green as the chromaticity coordinates change with the addition of Cu. This traffic-light-type color change was more sensitive to the naked eye compared to conventional single emission-based sensors. This paper not only realized ratiometric fluorescence and visual detection of Cu through a convenient method but also provided a promising strategy of designing an assay kit for trace Cu. Graphical abstract Ratiometric fluorescent sensing of copper ion based on chromaticity change strategy.