Shinde Abhijeet, Huang Dali, Saldivar Mariela, Xu Hongfei, Zeng Minxiang, Okeibunor Ugochukwu, Wang Ling, Mejia Carlos, Tin Padetha, George Sasha, Zhang Lecheng, Cheng Zhengdong
Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77843 , United States.
Department of Materials Science and Engineering , Texas A&M University , College Station , Texas 77843 , United States.
ACS Nano. 2019 Nov 26;13(11):12461-12469. doi: 10.1021/acsnano.9b01573. Epub 2019 Oct 23.
Controlling colloidal self-assemblies using external forces is essential to develop modern electro-optical and biomedical devices. Importantly, shape anisotropic colloids can provide optical properties such as birefringence. Here we demonstrate that external temperature gradients can be effective in controlling nematic liquid crystalline (LC) order in suspensions of plate-like colloids also known as nanoplates. Nanoplates, in an isotropic suspension, wherein their orientations are random, could be effectively moved using a temperature gradient environment causing a phase transition to LC nematic phase. Such controllably formed nematic phase featured large nematic monodomains and enabled topologically more stable structures that were evident from the absence of hedgehog-type defects which are typically found in nematics formed spontaneously nucleation and growth mechanism in a sufficiently high concentration suspension of nanoplates. Due to their high surface area-to-volume ratio and excellent thermophoretic properties, nanoplates can prove to be ideal candidates for transport of biomolecules through temperature varying environments.
利用外力控制胶体自组装对于开发现代电光和生物医学设备至关重要。重要的是，形状各向异性的胶体可以提供诸如双折射等光学特性。在这里，我们证明了外部温度梯度可以有效地控制板状胶体（也称为纳米板）悬浮液中的向列型液晶（LC）有序性。在各向同性悬浮液中，纳米板的取向是随机的，利用温度梯度环境可有效地移动纳米板，使其发生相变进入LC向列相。这种可控形成的向列相具有大的向列单畴，并能形成拓扑结构更稳定的结构，这从没有刺猬型缺陷可以明显看出，而刺猬型缺陷通常出现在通过自发成核和生长机制在足够高浓度的纳米板悬浮液中形成的向列相中。由于其高的表面积与体积比和优异的热泳性质，纳米板可被证明是在温度变化环境中运输生物分子的理想候选者。
