has been observed. In Figure 8.37(a), we show a TEM image, which reveals the
presence of a large number of gold nanowires obtained from the sealed tube reaction. The image clearly shows extensive filling of SWNT bundles. The length of the
gold nanowires is in the range 15–70 nm with diameters in the range 1.0–1.4 nm.
In some of the nanowires, however, the metal is single-crystalline, as revealed by
the HREM image of Figure 8.37(b). This image reveals the resolved lattice of gold
with a spacing of @0.23 nm, corresponding to the (111) planes. Polycrystalline Au
aggregates are transformed into the single crystalline form by annealing. The Au
nanowires are decomposed to nanoparticles by electron-beam damage at a temperature of 300–350
C. Electronic absorption spectra of dispersions of gold nanowires in ethanol show transverse and longitudinal plasmon absorption bands
Fig. 8.36. (a) TEM image of Ag/SiO 2 coaxial
nanocables prepared by coating Ag nanowires
with amorphous silica using the sol–gel
method. (b) TEM image of silica nanotubes
prepared by selectively dissolving Ag cores of
Ag/SiO 2 in ammonia solution (pH 11).
Reproduced from ref. [316a], with permission.
8 Nanotubes and Nanowires
270
presence of a large number of gold nanowires obtained from the sealed tube reaction. The image clearly shows extensive filling of SWNT bundles. The length of the
gold nanowires is in the range 15–70 nm with diameters in the range 1.0–1.4 nm.
In some of the nanowires, however, the metal is single-crystalline, as revealed by
the HREM image of Figure 8.37(b). This image reveals the resolved lattice of gold
with a spacing of @0.23 nm, corresponding to the (111) planes. Polycrystalline Au
aggregates are transformed into the single crystalline form by annealing. The Au
nanowires are decomposed to nanoparticles by electron-beam damage at a temperature of 300–350
C. Electronic absorption spectra of dispersions of gold nanowires in ethanol show transverse and longitudinal plasmon absorption bands
Fig. 8.36. (a) TEM image of Ag/SiO 2 coaxial
nanocables prepared by coating Ag nanowires
with amorphous silica using the sol–gel
method. (b) TEM image of silica nanotubes
prepared by selectively dissolving Ag cores of
Ag/SiO 2 in ammonia solution (pH 11).
Reproduced from ref. [316a], with permission.
8 Nanotubes and Nanowires
270