Influence of Group Modification at the Edges of Carbon Quantum Dots on Fluorescent Emission

• Main Authors: Ju Tang, Jin Zhang, Yunfei Zhang, Yiming Xiao, Yanli Shi, Yunhua Chen, Lan Ding, Wen Xu
• Format: Article
• Language: English
• Published: SpringerOpen 2019-09-01
• Series: Nanoscale Research Letters
• Subjects: Carbon quantum dot; Functional group modulation; Fluorescent emission
• Online Access: http://link.springer.com/article/10.1186/s11671-019-3079-7

Abstract We present a detailed investigation on the effect of functional group modulation at the edges of carbon quantum dots (CQDs) on the fluorescence from the CQDs. The CQDs attached by N, S, and P elements are synthesized via pyrolysis of a mixture of citric acid and NH3H2O, H2SO4, and H3PO4, respectively. Thus, part of –COOH at the edges of CQDs can be converted into –C=O and functional groups such as –NH2, –SO2, –HSO3, and –H2PO4 can connect to the carbon bonds. We find that the formation of the N/S/P-CQDs can reduce the amount of –COOH that attaches to the edges of sp2-conjugated π-domains located at centers of these CQDs. This effect can result in the reduction of the non-radiative recombination for electronic transition in these CQDs. As a result, the quantum yield (QY) for fluorescence from the CQDs can be efficiently enhanced. We demonstrate experimentally that the QYs for N/S/P-CQDs can reach up to 18.7%, 29.7%, and 10.3%, respectively, in comparison to 9% for these without functional group modulation. This work can provide a practical experimental approach in improving the optical properties of fluorescent CQDs.