Iida Ryo, Mitomo Hideyuki, Niikura Kenichi, Matsuo Yasutaka, Ijiro Kuniharu
Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Research Institute for Electronic Science, Hokkaido University, Sapporo, 001-0021, Japan.
Small. 2018 Apr;14(14):e1704230. doi: 10.1002/smll.201704230. Epub 2018 Feb 19.
Gold nanorods (GNRs) coated with a single kind of ligand show thermoreponsive two-step assembly to provide a hierarchical structure. The GNRs (33 nm in length × 14 nm in diameter) coated with a hexa(ethylene glycol) (HEG) derivative form side-by-side assemblies at 30 °C (T ) as a steady state through dehydration. By further heating to over 40 °C (T ), larger assemblies, which are composed of the side-by-side assembled units, are formed as hierarchical structures. The dehydration temperature of the HEG derivative varies depending on the free volume of the HEG unit, which corresponds to the curvature of the GNRs. Upon heating, dehydration first occurs from the ligands on the side portions with a lower curvature, and then from the ligands on the edge portions with a higher curvature. The different sized GNRs (33 × 8 and 54 × 15 nm) also show two-step assembly. Both the T and T are dependent on the diameter of the GNRs, but independent of their length. This result supports that the dehydration is dependent on the free volume, which corresponds to the curvature. Anisotropic assembly focusing on differences in curvature provides new guidelines for the fabrication of hierarchical structures.
涂覆有单一类型配体的金纳米棒（GNRs）呈现热响应性两步组装以提供分级结构。涂覆有六乙二醇（HEG）衍生物的GNRs（长度为33nm×直径为14nm）在30°C（T₁）时通过脱水形成并排组装体作为稳态。通过进一步加热至40°C以上（T₂），由并排组装单元组成的更大组装体形成为分级结构。HEG衍生物的脱水温度根据HEG单元的自由体积而变化，这与GNRs的曲率相对应。加热时，脱水首先从曲率较低的侧面部分的配体发生，然后从曲率较高的边缘部分的配体发生。不同尺寸的GNRs（33×8和54×15nm）也显示出两步组装。T₁和T₂都取决于GNRs的直径，但与它们的长度无关。该结果支持脱水取决于自由体积，这与曲率相对应。关注曲率差异的各向异性组装为分级结构的制造提供了新的指导方针。
