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Adv Mater. 2018 Apr;30(16):e1706261. doi: 10.1002/adma.201706261. Epub 2018 Mar 7.

Fabrication of a Stable New Polymorph Gold Nanowire with Sixfold Rotational Symmetry.

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Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, 16419, Republic of Korea.
Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon, 16678, Republic of Korea.
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.


Gold is known as the most noblest metal with only face-centered cubic (fcc) structure in ambient conditions. Here, stable hexagonal non-close-packed (ncp) gold nanowires (NWs), having a diameter of about 50 nm and aspect ratios of well over 400, are reported. Au NWs are grown in the confined system of nanotubular TiO2 arrays via photoelectrochemical reduction of HAuCl4 precursors. Some of the resulting Au NWs are proved to have sixfold rotational symmetry, observed by transmission electron microscopy tilting experiments. This new polymorph is identified as a hexagonal ncp-structure with lattice parameters of a = 2.884 Å and c = 7.150 Å, showing quite a large interplanar spacing (c/a ≈ 2.48). That is, Au atoms are close-packed along the ab plane, but each plane is not closely stacked along the c axis like in graphite. The structure is usually expected to be unstable, but the present ncp-2H gold is stable under ambient conditions and intense electron beam irradiation, and shows thermal stability up to 400 °C. Moreover, the resulting physical properties as a result of the corresponding change in electronic structures are investigated by comparing the optical properties of fcc and ncp-2H Au NWs.


ncp-2H Au; photoelectrochemical reduction; polymorphs; titanium dioxide nanotubes; transmission electron microscopy


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