Synthesis of multiple-color emitting carbon dots by co-doping of sulfur and nitrogen

Herein, multiple color (blue, green and red) emissive carbon dots (CDs) were synthesized from the main pre-cursor via different protocols, with emission wavelengths of 439 nm, 528 nm and 623 nm, respectively, realizing the synthesis of fluorescent CDs spanning the fluorescence emission from short to long wavelengths. Their relative PLQYs reach up to 28.9%, 31.4% and 12.3%, respectively, exceeding the PLQYs of many similar CDs. The green CDs (G-CDs) and red CDs (R-CDs) show optimal photoluminescence performance in acetone (Me2CO); while the B-CDs have a pH-dependent response in the pH 2 to 12 range. All the three CDs have excellent pho-tostability and salt resistance. Finally, serving as fluorescent anti-counterfeiting ink was taken as an example to briefly introduce the application of multi-color CDs. This work provides a new strategy to develop low-cost multiple color phosphors for display device, biological imaging, analysis and detection and other fields.