Chemical Reactions in Thermal Carbonization Processing of Citric Acid-Urea Mixtures
Chemical Reactions in Thermal Carbonization Processing of Citric Acid-Urea Mixtures
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DOI：
10.21127/yaoyigc20210011
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Weixiong Liang;Ping Wang;Liju Yang;Christopher M. Overton;B. Hewitt;Ya‐Ping Sun
中科院分区：
文献类型：
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作者：
Weixiong Liang;Ping Wang;Liju Yang;Christopher M. Overton;B. Hewitt;Ya‐Ping Sun
碳量子点是小的碳纳米颗粒，其表面主要被有机物质钝化。对于这种简单且定义明确的纳米级结构，经典且最可靠的合成是使用预先存在的小碳纳米颗粒与有机分子进行表面化学官能化。然而，文献中更流行的合成方法是有机前体的“一锅法”碳化，其在适当的加工条件下原则上可以在所得的点状实体中产生局部结构，其可以与碳量子点中的结构构型相当，尽管碳化也可以容易地产生交联到样品结构中的有色有机材料。一个极端的例子是热处理特定的有机前体混合物，仅包括柠檬酸与甲酰胺或尿素，以产生红色/近红外吸收和发射特征的样品，这促使了“红色/近红外碳量子点”的权利要求。实际上，这些光谱特征与纳米级碳无关，更不用说碳量子点了，而是简单地与特定前体混合物在用于碳化的热加工条件下的化学反应中产生的分子染料/发色团相关。在这项工作中，负责分子染料/发色团的分离和鉴定。结果进一步证明了红/近红外吸收和发射特性与碳量子点无关的结论。
Carbon dots are small carbon nanoparticles with effective surface passivation by mostly organic species. For such a simple and well-defined nanoscale structure, the classical and most reliable synthesis is the use of pre-existing small carbon nanoparticles for surface chemical functionalization with organic molecules. However, a more popular synthetic approach in the literature has been the “one-pot” carbonization of organic precursors, which with appropriate processing conditions could in principle create local structures in the resulting dot-like entities that may be comparable to the structural configuration in carbon dots, though the carbonization can also easily produce colored organic materials crosslinked into the sample structures. An extreme example was the thermal processing of the specific organic precursor mixtures including only citric acid with formamide or urea to yield samples of red/near-IR absorption and emission features, which prompted the claims of “red/near-IR carbon dots”. In reality, these spectral features have nothing to do with nanoscale carbon, let alone carbon dots, but simply associated with molecular dyes/chromophores produced in chemical reactions of the specific precursor mixtures under the thermal processing conditions intended for carbonization. In this work, the isolation and identification of the responsible molecular dyes/chromophores were pursued. The results present further evidence for the conclusion that the red/near-IR absorption and emission features have nothing to do with carbon dots.