Template and template-free preparation of one-dimensional metallic nanostructures

In this article, we have studied and developed two approaches for organizing metallic nanoparticles into one-dimensional assemblies. The first uses DNA as a ‘template’ and allows the preparation of various silver nanostructures (‘beads-on-a-string’ or rod-like wires). The conductance of such nanostructures was demonstrated by employing a powerful technique, Electrostatic Force Microscopy (EFM). This technique gave us ‘contactless’ information about the electrical properties of silver nanostructures, aligned on a SiO₂/Si surface. Additionally, I–V characteristics of a single silver nanowire crossing two microelectrodes were recorded. The nanowire resistivity was estimated at 1.46 × 10⁻⁷ Ω m (at 300 K), which is one order of magnitude higher than that of bulk silver (1.6 × 10⁻⁸ Ω m). The second approach is a ‘template-free’ one, and exploits the binding ability of l-arginine, which favours the self-assembling of capped gold nanoparticles into gold nanochains. The results suggest that gold nanochains were formed due to dipole–dipole interaction between adjacent nanoparticles, which fuse together through an oriented attachment mechanism. Atomic force microscopy, TEM, UV–vis spectroscopy and X-ray diffraction were used to characterize the morphological, optical and structural properties of these metallic nanostructures.