Bent-core liquid crystal (LC) decorated gold nanoclusters: synthesis, self-assembly, and effects in mixtures with bent-core LC hosts
作者:Vanessa M. Marx、Hidy Girgis、Paul A. Heiney、Torsten Hegmann
DOI:10.1039/b802554a
日期:——
We present the first synthesis of a series of thiol-, thioacetate-, and xanthate-terminated bent-core derivatives, as well as the preparation of gold nanoclusters using the thiol-terminated bent-core compounds. The mesomorphic properties of the bent-core compounds have been investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and electro-optic tests. From this series, the mono-xanthate derivatives form rectangular or hexagonal columnar phases, and the mono-thiol derivative with shorter alkyl chains forms a metastable, likely smectic, phase. All other bent-core compounds and intermediates exclusively form disordered or multi-layer lamellar crystalline solid modifications. High-resolution transmission electron microscopy (HR-TEM) images of the bent-core functionalized gold nanoclusters prepared from the thiol-terminated derivatives, taken after slow evaporation of the solvent, provide evidence for the formation of self-assembled nanocluster arrays. Upon dispersion of these gold nanoclusters in two structurally related bent-core LC hosts (one forming a SmCPA, and the second with a terminal double bond displaying a Colr phase), a shift in the surface plasmon resonance was observed indicating a LC host-dependent aggregation of the nanoparticles. Finally, we report initial results on the effects of different concentrations of these nanoclusters on the thermal properties as well as the applied voltage/current response of the parent SmCPA host.
我们首次合成了一系列硫醇、硫代乙酸酯和黄原酸酯封端的弯核衍生物,并利用硫醇封端的弯核化合物制备了金纳米团簇。研究人员通过偏光光学显微镜(POM)、差示扫描量热仪(DSC)、小角 X 射线散射(SAXS)和电光测试研究了这些弯曲核化合物的介形态特性。在这一系列化合物中,单黄原酸酯衍生物形成了矩形或六角形柱状相,而烷基链较短的单硫醇衍生物则形成了一种易变相,很有可能是冶炼相。所有其他弯曲核化合物和中间体只能形成无序或多层片状结晶固体改性物。由硫醇端衍生物制备的弯曲核功能化金纳米簇在缓慢蒸发溶剂后拍摄的高分辨率透射电子显微镜(HR-TEM)图像证明了自组装纳米簇阵列的形成。将这些金纳米团簇分散在两种结构相关的弯曲核低聚物宿主(一种形成 SmCPA,另一种带有末端双键,显示 Colr 相)中时,观察到表面等离子体共振发生了变化,这表明纳米粒子的聚集取决于低聚物宿主。最后,我们报告了不同浓度的这些纳米团簇对热特性以及母体 SmCPA 宿主的外加电压/电流响应的影响的初步结果。