Helical Gold Nanotube Synthesized at 150 K

Abstract

Gold nanowires were synthesized at 150 K by electron beam thinning of a gold thin foil in an UHV electron microscope. The gold nanowires were found to have a helical multishell structure (HMS). One particular nanowire, which was thinner than the 7-1 HMS nanowire, was found to have a tubular structure. The gold single wall nanotube is composed of five atomic rows that coil about the tube axis. The diameter was 0.4 nm and the pitch was 11 nm. The stability of the (5,3) nanotube was discussed in terms of the shear deformation of the triangular network of gold atoms.

Geometrical and electronic structures of the (5, 3) single-walled gold nanotube from first-principles calculations

“…The obtained fully relaxed structure parameters are shown in Table I too, and from it we can find that the diameter of the shear-strain deformed SWGT (5, 3) is only slightly larger than that of the perfect one. But its binding energy per gold atom is smaller than that of perfect tube by 0.008 eV, which means it is more stable than the perfect tube, being consistent with the experimentally observed result [11]. Its calculated electronic band structures and DOSs are shown in Fig.…”

“…It is found that the inner and outer shells always have even-odd or odd-even coupling, and the difference (n − n ′ ) between their number of atomic row is equal to seven (a single atom chain is regarded as "0"-membered in this discussion). Nanowires with n ≤ 6 had been supposed to have only a single-walled shell [7], called as SWGT, which has recently been synthesized experimentally at 150 K in an UHV-TEM [11]. The thinnest SWGT, 4 A in diameter, was found to be the (5, 3), composed of five atomic rows coiled round the tube axis.…”

“…However, the practical SWGTs have the finite length of usual several nanometers (Ref. 11), and so it is necessary to study the finite length effect on the physical properties of SWGT. Our numerical calculation indicates that the SWGT (5, 3) with a length of 4.15 nm (about two times larger than the perfect tube period) shows the characteristic of the semiconductor with its gap of 0.11 eV.…”

Scaling of the conductance in gold nanotubes

“…Recent experiments [1][2][3][4] indicate that gold nanowires exhibit fascinating ordered structures that resemble those of the by now well-known carbon nanotubes ͑CNTs͒. 5 High resolution microscope images show that these wires consist of coaxial nanotubes of helical atom rows coiled around the wire axis.…”

“…So single-walled nanotubes should exist with six or less atom rows, and actually one single-walled tube with five atom rows has been observed. 3 With seven or more atom rows a double-walled tube should be seen, which becomes a triple-walled nanotube when more than fourteen rows are present, and so on. The good reproducibility of these wires, and their stability, [6][7][8][9] which is better for those with outer tubes with an odd number of atom rows, makes them promising candidates for future applications.…”