Full-spectrum luminescence of nitrogen-sulfur co-doped carbon dots and their applications in LED lighting and organelle-lysosome labeling

Heteroatom doping can achieve specific regulation of carbon dots by changing their nanostructure, electronic structure and band gap. Here, we synthesized nitrogen-sulfur co-doped carbon dots (N, S-CDs) with full-spectrum fluorescence emission capability. Through comprehensive structural analysis using XPS, FTIR, and other characterization techniques, it was revealed that most of the nitrogen atoms were integrated into the carbon core of the N, S-CDs. Meanwhile, sulfur atoms were identified on the surface of the N, S-CDs, incorporated as functional groups. This unique structural configuration provides a foundation for understanding the solvent effect on N, SCDs. Specifically, as the polarity of the solvent increases, the fluorescence emission of the N, S-CDs experiences a red-shift. The varying hydrogen donor abilities of different solvents contribute to changes in fluorescence emission. Notably, N, S-CDs exhibit near-infrared fluorescence emission when dissolved in acetic acid solvent. Under the synergistic effect of solvent polarity and hydrogen bonding, the fluorescence emission of N, S-CDs achieves full-spectrum luminescence, spanning from blue light to near-infrared. It is particularly interesting to observe that when N, S-CDs are dispersed in polyvinyl alcohol (PVA) films by dissolving them in three different solvents, the red, green, and yellow light emission can be achieved. When coated onto Light Emitting Diode (LED) lamp beads, these films exhibit versatile light emission properties. This provides inspiration for the development and preparation of LED fluorescent materials. Meanwhile, thanks to the excellent luminescent properties of N, S-CDs in water, they can be used for targeted localization of lysosomes in biological cells.