Direction-specific van der Waals attraction between rutile TiO2 nanocrystals
Direction-specific van der Waals attraction between rutile TiO2 nanocrystals
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DOI：
10.1126/science.aah6902
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发表时间：
2017-04
期刊：
影响因子：
56.9
通讯作者：
Xin Zhang;Yang He;M. Sushko;Jia Liu;L. Luo;J. D. De Yoreo;S. Mao;Chongmin Wang;K. Rosso
中科院分区：
文献类型：
--
作者：
Xin Zhang;Yang He;M. Sushko;Jia Liu;L. Luo;J. D. De Yoreo;S. Mao;Chongmin Wang;K. Rosso
当力取决于方向时 在定向附着中，小核或晶体会聚集在一起形成较大的晶体，但前提是互补的面彼此接近。这是否意味着两个纳米晶体之间的力存在方向依赖性？张等人。报告了一种测量金红石 TiO2 纳米晶体之间范德华吸引力的精密方法。他们利用环境透射电子显微镜对接触点进行了原位成像，从而可以准确测量颗粒间的距离。这阐明了纳米晶体的取向、表面水合和相互作用之间的关系。结果表明，有足够的力在晶体之间产生扭矩，以确保互补的相互作用。科学，本期第 14 页。 434 特定方向的范德华相互作用通过介入的溶剂水贡献附近纳米粒子之间的扭矩。相互晶格取向决定了晶体颗粒之间力的类型和大小。当晶格极化率是各向异性时，范德华色散吸引力原则上可以促成这种方向依赖性。我们报告了金红石纳米晶体之间这种吸引力的测量，作为它们相互取向和表面水合程度的函数。在数十纳米的分离处，吸引力很弱，并且不依赖于方位角排列或表面水合。在大约一层水化层的分离处，吸引力强烈依赖于方位角排列，并且随着中间水密度的增加而系统地降低。测量到的力与利夫希茨理论的预测非常吻合，并表明色散力可以在溶液中相互作用的颗粒之间以及材料中的颗粒之间产生扭矩。
When forces depend on orientation In oriented attachment, small nuclei or crystals come together to make a larger crystal, but only when complementary facets approach each other. Does this mean that there is an orientational dependence of the force between two nanocrystals? Zhang et al. report a delicate method to measure the van der Waals attraction between rutile TiO2 nanocrystals. They imaged the contact point in situ with environmental transmission electron microscopy, which allowed the interparticle distances to be measured accurately. This elucidated the relationship between the nanocrystals' orientations, surface hydrations, and interactions. The results suggest that there is enough force to generate a torque between the crystals to ensure a complementary interaction. Science, this issue p. 434 Direction-specific van der Waals interactions contribute torque between nearby nanoparticles across intervening solvent water. Mutual lattice orientations dictate the types and magnitudes of forces between crystalline particles. When lattice polarizability is anisotropic, the van der Waals dispersion attraction can, in principle, contribute to this direction dependence. We report measurement of this attraction between rutile nanocrystals, as a function of their mutual orientation and surface hydration extent. At tens of nanometers of separation, the attraction is weak and shows no dependence on azimuthal alignment or surface hydration. At separations of approximately one hydration layer, the attraction is strongly dependent on azimuthal alignment and systematically decreases as intervening water density increases. Measured forces closely agree with predictions from Lifshitz theory and show that dispersion forces can generate a torque between particles interacting in solution and between grains in materials.