Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots.
Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots.
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高发光N掺杂石墨烯量子点的形成机理及优化
DOI：
10.1038/srep05294
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发表时间：
2014-06-18
影响因子：
4.6
通讯作者：
Sun Z
中科院分区：
文献类型：
--
作者：
Qu D;Zheng M;Zhang L;Zhao H;Xie Z;Jing X;Haddad RE;Fan H;Sun Z
光致发光石墨烯量子点（GQD）由于其独特的化学、电子和光学性质而受到极大的关注。本文采用水热法合成了一系列的GQD，以研究N掺杂GQD的形成过程和光学性质。以柠檬酸（CA）为碳前驱体，在碱性条件下自组装成片状结构，通过分子间脱水反应形成无氮GQD石墨骨架。使用一系列含N碱如尿素制备N掺杂的GQD。详细的结构和性能研究表明，N掺杂的GQDs的可调谐光发射的形成机制。水热条件促进了-NH 2和-COOH之间的酰胺的形成，在反应中存在胺。相邻的酰胺和COOH基团之间的分子内脱水导致在石墨烯框架中形成吡咯N。此外，在水热条件下，吡咯N转化为石墨N。N掺杂使量子点的光致发光量子产率（QY）有了很大的提高。通过优化反应条件，以CA为碳源，乙二胺为氮源，得到了最高的荧光量子产率（94%）。所得到的N掺杂GQD表现出激发无关的蓝光发射与单指数寿命衰减。
Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH2and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay.
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