Synthesis and Fluorescence Mechanism of Nitrogen-Doped Carbon Dots Utilizing Biopolymer and Urea

Fluorescent carbon dots are nontoxic nanoparticles composed of carbon, exhibiting advantageous properties for applications in bioimaging and functional materials. We present a methodology for synthesizing fluorescent nitrogen-doped carbon dots (N-CDs) using starch, a biopolymer, and urea as the sour...

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Bibliographic Details
Main Authors: Hikaru Yorozuya, Noor E Ashrafi, Kazuya Sato, Ahatashamul Islam, Rikuto Fukae, Yusuke Tagashira, Toshifumi Iimori
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Molecules
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Online Access:https://www.mdpi.com/1420-3049/30/9/2068
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Summary:Fluorescent carbon dots are nontoxic nanoparticles composed of carbon, exhibiting advantageous properties for applications in bioimaging and functional materials. We present a methodology for synthesizing fluorescent nitrogen-doped carbon dots (N-CDs) using starch, a biopolymer, and urea as the sources of nitrogen, via the microwave-assisted hydrothermal method. Furthermore, the dependence of the fluorescence spectra and fluorescence quantum yield of N-CDs on the initial concentration of urea in the reactant solution was examined, thereby providing a comprehensive understanding of the influence of nitrogen doping on the CDs. The fluorescence of N-CDs was tunable by varying the excitation wavelength. Stronger fluorescence intensity was observed for a moist phosphate salt/N-CD composite, in contrast to the weaker fluorescence exhibited by a dried one. Fluorescence lifetime measurements revealed that the change in fluorescence intensity can be attributed to the suppression of the non-radiative deactivation process. This observation highlights the critical importance of the interaction between water molecules and surface functional groups in controlling the photophysics of the excited state of N-CDs.
ISSN:1420-3049