Eco-friendly synthesis of red-emissive carbon dots for visual alcohol detection and light-emitting diodes

Red-emissive carbon dots (R-CDs) is highly desired in developing full-color solid-state lighting and display applications based on CDs. Developing simple and eco-friendly methods to produce R-CDs is extremely desirable. In this work, two types of R-CDs were obtained via simple and eco-friendly grinding-heating or solvothermal methods using fresh spinach leaves as the carbon source, respectively. The obtained R-CDs naturally possess surface functional groups. These R-CDs were effectively used as sensitive probes for detecting alcohol (including alcohol gas and liquor detection) due to the synergistic effect of the nitrogen-containing surface groups on the RCDs and the oxhydryl groups in the alcohol solution. Finally, red electroluminescence was achieved by mixing the R-CDs with polyvinyl pyrrolidone as the phosphor layer on a blue light-emitting diode (LED) chip. This work paves the way for the further development of R-CDs in fluorescence probes and full-color LED applications.