Carbon dots (CDs) are a rapidly progressing class of nanomaterial which show promise towards applications in solar energy conversion due to their low toxicity, favorable electrochemical properties, and tunability. In recent years there have been a number of reported CD syntheses, both top-down and bottom-up methods, producing a diverse range of CDs with intrinsic properties dependent on the starting materials and utilized dopants. This work presents a citrate buffer-facilitated synthesis of nitrogen-doped carbon dots (NCD) and explores the impact of urea concentration on observed electrochemical and optical properties. Optical absorbance and quantum yield of NCDs were found to increase with the dopant concentrations present in the hydrothermal reaction mixture. Electrochemical analysis demonstrates that increased nitrogen content results in the shifting of carbon dot oxidation potentials without the need of post-synthesis surface modifications. Over the range of molar ratios of dopant-to-citrate tested, the oxidation potentials of NCDs shifted up to 150 mV towards more negative potentials. X-ray photoelectron spectroscopy confirms the addition of pyrrolic and pyridinic nitrogen at different levels in different batches of NCDs, which are likely the source of the observed changes.

中文翻译：

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水热合成氮掺杂碳点的光学和电化学调谐

碳点 (CDs) 是一类快速发展的纳米材料，由于其低毒性、良好的电化学性能和可调谐性，在太阳能转换中的应用前景广阔。近年来，已经报道了许多 CD 合成方法，包括自上而下和自下而上的方法，产生各种具有取决于起始材料和使用的掺杂剂的固有特性的 CD。这项工作提出了一种柠檬酸盐缓冲液促进氮掺杂碳点 (NCD) 的合成，并探讨了尿素浓度对观察到的电化学和光学性质的影响。发现 NCD 的光吸收和量子产率随着水热反应混合物中存在的掺杂剂浓度而增加。电化学分析表明，增加的氮含量会导致碳点氧化电位的变化，而不需要合成后的表面修饰。在测试的掺杂剂与柠檬酸盐的摩尔比范围内，NCD 的氧化电位向更负的电位移动高达 150 mV。X 射线光电子能谱证实在不同批次的非传染性疾病中添加了不同水平的吡咯和吡啶氮，这可能是观察到的变化的来源。