Modifying Thermal Transport in Colloidal Nanocrystal Solids with Surface Chemistry
Modifying Thermal Transport in Colloidal Nanocrystal Solids with Surface Chemistry
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DOI：
10.1021/acsnano.5b05085
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发表时间：
2015-12-01
期刊：
影响因子：
17.1
通讯作者：
Wang, Robert Y.
中科院分区：
文献类型：
--
作者：
Liu, Minglu;Ma, Yuanyu;Wang, Robert Y.
系统地研究了表面化学对胶体纳米晶(NC)固体中热输运的影响。以PbS NCS为模型体系，我们改变了配体结合基团(硫醇、胺和原子卤化物)、配体长度(乙二硫醇、丁二硫醇、己二硫醇和辛二硫醇)和NC直径(3.3-8.2 nm)。我们的实验揭示了几个发现：(I)配体的选择可以改变NC固体的热导率，最高可达2.5倍。(Ii)配体与NC核的结合强度不会显著影响导热系数。(3)减小配体长度可以减小颗粒间距，从而增加导热系数。(4)增大纳米管直径可提高导热系数。(V)表面化学的影响可以超过NC直径的影响，并且随着NC直径的减小而变得更加明显。结合这些趋势，我们证明了纳米固体的导热系数可以变化4倍，范围类似于0.1-0.4W/m-K。我们用有效的介质近似模型来补充这些发现，并确定配体基质中的热传输是热传输的速率限制器。通过将这些模拟结果与我们的实验观察相结合，我们得出结论，未来提高NC固体导热系数的努力应该集中在相邻NC之间的配体界面上。
We present a systematic study on the effect of surface chemistry on thermal transport in colloidal nanocrystal (NC) solids. Using PbS NCs as a model system, we vary ligand binding group (thiol, amine, and atomic halides), ligand length (ethanedithiol, butanedithiol, hexanedithiol, and octanedithiol), and NC diameter (3.3-8.2 nm). Our experiments reveal several findings: (i) The ligand choice can vary the NC solid thermal conductivity by up to a factor of 2.5. (ii) The ligand binding strength to the NC core does not significantly impact thermal conductivity. (iii) Reducing the ligand length can decrease the interparticle distance, which increases thermal conductivity. (iv) Increasing the NC diameter increases thermal conductivity. (v) The effect of surface chemistry can exceed the effect of NC diameter and becomes more pronounced as NC diameter decreases. By combining these trends, we demonstrate that the thermal conductivity of NC solids can be varied by an overall factor of 4, from similar to 0.1-0.4 W/m-K. We complement these findings with effective medium approximation modeling and identify thermal transport in the ligand matrix as the rate-limiter for thermal transport. By combining these modeling results with our experimental observations, we conclude that future efforts to increase thermal conductivity in NC solids should focus on the ligand ligand interface between neighboring NCs.