Photoluminescence properties of l-cysteine-derived carbon dots prepared in non-aqueous and aqueous solvents
Photoluminescence properties of l-cysteine-derived carbon dots prepared in non-aqueous and aqueous solvents
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DOI：
10.1016/j.jlumin.2020.117260
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发表时间：
2020-08
影响因子：
3.6
通讯作者：
Taishu Yoshinaga;Moeka Akiu;Yoshiki Iso;T. Isobe
中科院分区：
文献类型：
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作者：
Taishu Yoshinaga;Moeka Akiu;Yoshiki Iso;T. Isobe
以L-半胱氨酸等氨基酸为原料，通过NH2和COOH基团之间的分子间脱水反应，然后碳化，可以制备荧光碳点(CDS)。这种脱水反应在水介质中可能会受到阻碍，因为氨基酸分子被水包围，所以我们使用了非水反应介质来促进脱水反应。在本研究中，L-半胱氨酸在高沸点258C的非水溶剂二苯醚中于230℃加热30min，得到了CdS-Na。为了进行比较，我们还在相同的温度和时间条件下，利用高压灭菌器和微波加热系统，以半胱氨酸为原料，在水中进行了水热合成CDS-A。水分散体系的最大光致发光强度是水分散体系的1.5倍。CdS-NA的绝对荧光量子产率(QY)为4.2%，是Cds-A的1.4倍，为3.0%。元素组成、颗粒性质和化学键状态的表征证实，非水溶剂不仅通过脱水反应促进了Cd的形成，而且还通过硫醇的氧化形成了磺酸基团。颗粒的快速长大和附加官能团的形成可能有助于提高CDS-NA的荧光强度和绝对PLQY。通过对非水溶剂中合成条件的优化，使硫化镉钠的绝对PLQY从4.2%提高到10.2%。
Fluorescent carbon dots (CDs) can be produced from amino acids such asl-cysteine by an intermolecular dehydration reaction between NH2and COOH groups, followed by carbonization. This dehydration reaction may be hindered in aqueous media because the amino acid molecules are surrounded by water; therefore, we used a non-aqueous reaction media to facilitate the dehydration reaction. In the present study,l-cysteine was heated at 230 °C for 30 min in a non-aqueous solvent, diphenyl ether, which has a high boiling point of 258 °C, to yield CDs-NA. For comparison, we also hydrothermally prepared CDs-A froml-cysteine dissolved in water, with the use of an autoclave and microwave heating system under the same temperature and time conditions. The maximum photoluminescence (PL) intensity of the water dispersion of CDs-NA was 1.5 times as high as that of the CDs-A. The absolute PL quantum yield (QY) of CDs-NA was 4.2%, which was 1.4 times as high as that of CDs-A, 3.0%. Characterization of the elemental compositions, particulate properties, and chemical bonding states confirmed that the non-aqueous solvent not only facilitated CD formation via the dehydration reaction but also contributed to the formation of sulfonic acid groups by oxidation of thiol groups. The rapid particle growth and formation of the additional functional groups might contribute to the increased PL intensity and absolute PLQY of CDs-NA. Through the optimization of the synthesis conditions in a non-aqueous solvent, the absolute PLQY of CDs-NA was increased from 4.2% to 10.2%.