We demonstrate a new, room-temperature approach to assemble two-dimensional and three-dimensional networks of gold nanowires by agitating nanoparticles in a toluene-aqueous mixture, without the use of templates. The nanowires have a uniform diameter of about 5 nm and consist of coalesced face-centered cubic nanocrystals. Toluene molecules passivate the gold surfaces during nanoparticle coalescence, rendering the nanowires hydrophobic and enabling their transfer into the toluene layer. Such templateless low-temperature assembly of mesostructures from nanoscale building blocks open up new possibilities for creating porous self-supporting nanocatalysts, nanowires for device interconnection, and low-density high-strength nanofillers for composites.

We demonstrate the use of 10 and 30 keV focused beams of Ga+ ions to thin, slice, weld, and alter the structure and composition of multiwalled carbon nanotubes at precise locations along the nanotube axis. This strategy of harnessing ion-beam-induced defect generation and doping could be attractive for modulating chemical and electrical properties along the nanotube length, and fabricate nanotube heterostructures and networks for device applications.

We report the effects of 30 and 50 keV Ga+ ion irradiation on the structure and electrical properties of arc-evaporated multiwalled carbon nanotubes (MWNTs). For 50 keV ions with doses of ∼1013 ions/cm2 the outer shells of the MWNTs remain intact, while the inner layers reorganize into highly ordered pillbox-like ∼5-nm-diam nanocompartments of varying lengths between 2 and 20 nm. Increasing the dose to ∼1014 ions cm−2 results in the gradual disordering of the graphitic shells and destroys the nanocapsules, while at doses of 1015 ions cm−2 the graphitic shells collapse into the hollow, resulting in the formation a homogenous amorphous rod. Irradiating nanotubes with 30 keV ions yields similar results, but at higher doses. Irradiated nanotubes exhibit a decrease in electron activation energy from 194 to 112 meV, while the semiconducting behavior is essentially preserved for ion doses up to 5×1015 ions cm−2. Ion irradiation could be a useful tool to locally modify nanotube structure and tailor properties for device applications.

Articles you may be interested inPhysical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering J. Vac. Sci. Technol. A 31, 061516 (2013); 10.1116/1.4825349 Thermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates Structural and electrical characteristics of W-N thin films prepared by reactive rf sputtering J. Vac. Sci. Technol. A 21, 616 (2003); 10.1116/1.1564029Epitaxial growth of metastable δ-TaN layers on MgO(001) using low-energy, high-flux ion irradiation during ultrahigh vacuum reactive magnetron sputtering Epitaxial Ti 1Ϫx W x N alloys with 0рxр0.6 were grown on MgO͑001͒ substrates at 500°C by ultrahigh vacuum reactive magnetron sputtering from Ti and W targets in pure N 2 . X-ray diffraction, transmission electron microscopy ͑TEM͒, and cross-sectional TEM show that the 0.3-m-thick Ti 1Ϫx W x N(001) alloys are single crystals with the B1-NaCl structure. Rutherford backscattering spectroscopy investigations indicate that alloys with xу0.05 are slightly overstoichiometric with N/(TiϩW)ϭ1.06Ϯ0.05. The alloy lattice parameter a Ќ along the film growth direction is 4.251 Å, irrespective of the WN concentration, for xр0.41 and decreases slightly at higher concentrations. TEM analyses show that Ti 0.5 W 0.5 N(001) alloys have long-range CuPt-type atomic ordering on the cation sublattice. The room-temperature resistivity increases linearly from 13 ⍀ cm for TiN to 287 ⍀ cm for Ti 0.42 W 0.58 N due primarily to alloy scattering while the temperature coefficient of resistivity is positive in Ti 1-x W x N alloys with xр0.21 and negative for xϾ0.21 due to weak charge carrier localization. The superconducting critical temperature T c of Ti 1-x W x N alloys initially increases with x, due to a larger density of states at the Fermi level, consistent with valence band x-ray photoelectron spectroscopy measurements. T c reaches a maximum of 6.67 K at xϭ0.21 and decreases for larger x values.