Synthesis of high quantum yield orange carbon dots as multifunctional fluorescence probe in VB12 detection and bio-imaging

Unique orange-emissive carbon dots (O-CDs) are synthesised via a solvothermal method by safranin T and 2,2’-dithiodibenzoic acid in ethanol. O-CDs show a maximum emission peak at 595 nm and a quantum yield of 81.63% when dissolved in dichloromethane. O-CDs are able to be fabricated into fluorescent hydrogels, powders and films exhibiting excellent fluorescence performance. The linear relationship is observed in the concentration range of 0-200 µM with R 2 of 0.9973, and the limit of detection is 0.19 µM. Meanwhile, this method is effectively utilized to analyze real food samples, such as egg yolk and milk, with recoveries ranging from 99.21% to 101.8%. Sensing mechanism is found to be the inner filter effect and dynamic quenching. Furthermore, O-CDs exhibit low toxicity and nice biocompatibility, facilitating the applications in bioimaging of B16F10-2 cells as well as zebrafish, and enabling VB12 detection in live cells. Therefore, the novel O-CDs developed present broad application prospects including food safety, biosensing, bioimaging and fluorescent films. Graphical