Effects of elemental doping, acid treatment, and passivation on the fluorescence intensity and emission behavior of yellow fluorescence carbon dots

• Published in: Optical materials 2022-06, Vol.128, p.112471, Article 112471
• Main Authors: Liang, Shaofeng, Wang, Muqun, Gao, Wei, Zhao, Xia
• Format: Article
• Language: English
• Subjects: Carbon dots; Fluorescence mechanism; Optical behavior; Quantum yield
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2022.112471

Hydrothermal methods are commonly used to synthesize carbon dots (CDs), but the synthesized CDs have the disadvantage of low quantum yields. In this paper, we used acid treatment, elemental doping, and passivation to treat the CDs, which could increase the quantum yield from 36% to 42%, 61% and 68%, respectively, and the doping and passivation treatments resulted in red-shifted and blue-shifted emission behavior of the CDs. The optical properties, morphology and chemical structure of CDs are analyzed to investigate the reasons for the quantum yield increase and the mechanism of excitation dependent emission (EDE) and excitation independent emission (EIE). The increase of quantum yield is mainly due to the increase of pyridine N content. The different optical behaviors depend mainly on the surface states of CDs. C–OH and C–O–C can create new energy levels leading to the appearance of EDE properties. C=O is an electron-absorbing group that weakens the conjugation effect leading to blue shift. •Alteration of the fluorescence emission behavior of carbon dots by element doping, acid treatment and passivation.•The quantum yield from the original 36% can be increased to 42%, 61%, and 68% after three treatments, respectively.•The fluorescence properties of carbon dots synthesized by hydrothermal method are mainly affected by the nitrogen-oxygen chemical bonds on the surface.