Influence of ligand and impurities on optical properties of carbon dots: Narrow linewidth and controllable UV-Vis spectrum

Highlights: • Optical properties of CDs have been investigated with hydroxyl groups. • FWHM are influenced by the position of hydroxyl groups. • The number of hydroxyl groups has little influence on the width of FWHM. • Larger ligand would make the wavelength shift red and make FWHM broaden. • Sulfur impurities would make the wavelength shift to red larger. Optical properties of carbon molecules have been investigated with DFT. First, the results show that the wavelength of UV-Vis spectrum can be controlled by the number and the position of hydroxyl groups, while FWHM are only influenced by the position of hydroxyl groups. Second, study of molecules with different ligands (–Br, –OH, –COOH, –NH₂) have confirmed that larger ligands would make the peaks wavelength of UV-Vis spectrum shift to red and make FWHM broaden. Finally, the doping of sulfur impurity would make the peaks wavelength of UV-Vis spectrum shift to longer wavelength than those doped with boron and nitrogen impurities.