Two‐Step Assembly of Thermoresponsive Gold Nanorods Coated with a Single Kind of Ligand |
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Authors: | Ryo Iida Hideyuki Mitomo Kenichi Niikura Yasutaka Matsuo Kuniharu Ijiro |
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Affiliation: | 1. Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Japan;2. Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan;3. Global Station for Soft Matter, Global Institution for Collaborative Research and Education (GI‐CoRE), Hokkaido University, Sapporo, Japan;4. Department of Innovative Systems Engineering, and, Graduate School of Environmental Symbiotic System Major, Nippon Institute of Technology, Miyashiro, Saitama, Japan |
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Abstract: | 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 (TA1) as a steady state through dehydration. By further heating to over 40 °C (TA2), 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 TA1 and TA2 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. |
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Keywords: | curvature‐dependent dehydration gold nanorods hierarchical structure thermoresponsivity two‐step self‐assembly |
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