Study of the effect of nitric acid on the structure and optical properties of alkali lignin-based carbon dots
Carbon Capture Science & Technology(2024)
摘要
Hydrothermal reactions can convert lignin into carbon dots, and the process often uses acids as additives, but the mechanism of action is not clear. In this study, lignin-based carbon dots were successfully prepared by HNO3-assisted one-pot hydrothermal method. The mechanism of the influence of the acidic environment on the structure and optical properties of lignin-based carbon dots was also investigated by changing the addition amount of HNO3. It was found that the particle size distribution of carbon dots collected was 1-5 nm, and they could emit bright blue fluorescence under violet light irradiation with the highest fluorescence quantum yield of 10.17%. HNO3 acts on the branched chains and ether bonds of alkali lignin, prompting the depolymerization of lignin and re-cross-linking and condensation to form lignin-based carbon dots. With the increase of HNO3 addition, the carbon core of lignin-based carbon dots gradually transformed from amorphous structure to complete graphene-like structure, and the emission wavelength of lignin-based carbon dots shifted from 517 nm to 499 nm, and the fluorescence quantum yield was increased from 2.61% to 10.17% by the effect of integrated N doping, which is of great significance for the analysis of the conformational relationship of lignin-based carbon dots, and for the guidance of the high-efficiency synthesis of lignin-based carbon dots.
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关键词
Alkali lignin,hydrothermal reaction,carbon dots,nitric acid,growth mechanism
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