Composition and concentration-dependent photoluminescence of nitrogen-doped carbon dots

• DOI: 10.1016/j.apt.2022.103560
• Publication Date: 2022-04-18T10:06:17Z
• Authors: Mostafa Esmaeili; Zhiqing Wu; Dechao Chen; Amandeep Singh; Prashant Sonar; David Thiel; Qin Li
• Keywords: Chemical engineering; Photoluminescent nanoparticles; Materials engineering; Carbon dots; Nitrogen doping; 02 engineering and technology; 0210 nano-technology; 530; Hall effect measurement; Photoluminescence mechanism; 620

Photoluminescent carbon dots have received significant research interest in recent years owing to their extraordinary optical properties, biocompatibility, and versatile functionalities. Nitrogen-doping is a widely used strategy for enhancing the photo-electronic functionalities of carbon dots. However, there is a lack of systematic study on the composition and concentration-dependency emission behaviour of N-doped carbon dots in the literature. In this study, multicolour carbon dots (CDs) having different degree of nitrogen doping were synthesized by varying the molar ratio of citric acid to urea in the precursor via hydrothermal treatment. The effects of nitrogen doping on chemical, optical, and electronic properties of CDs were characterized using various techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR); fluorescence and absorption spectroscopy; fluorescence lifetime and Hall effect measurements. Three main emissive centres were recognized in concentration-dependent fluorescence study of N-CDs which can be ascribed to molecular type of fluorescence, core emission, and mid-gap nitrogen states on the edge/surface of CDs. A plausible mechanism in relation to the obtained results is proposed. This work provides insights on the opto-electro-tunability of CDs via N-doping.