Carbon Nanotube Engendered Pseudo-1D Morphologies of Silver Nanowire
Silver nanowires show enhancement in properties due to large surface area and high aspect ratio, which increases the possibility of design and development of many advanced optoelectronic devices. The organization of silver atoms and the morphology of cylindrical nanowires highly influence the desired properties at various physical conditions during applications. Therefore, the synthesis of nanowires with desired atomic organization becomes essential.
A pseudo-1D morphology of silver nanowires, encapsulated into a Single Wall Carbon Nanotubes (SWCNTs), has been investigated by Molecular Dynamics (MD) simulation. At high temperature (T = 1500 K), molten silver encapsulates into a SWCNT attaining a low energy state, followed by restricted thermal motion or vibration. With an increase in SWCNT diameter, various unique pseudo-1D morphologies of encapsulated silver atoms were observed during cooling from 1500 to 10 K. Silver atoms, encapsulated into a SWCNT having a diameter of 10.85 Å, mainly reveal 5-fold symmetrical icosahedral(ico) having pseudo-1D morphology. With a further increase in diameter (d = 40.68 Å) of SWCNT, a decagonal pattern consisting of face centered cubic (fcc), hexagonal closed packed (hcp) and body centered cubic (bcc) evolves due to non-homogenous packing of silver atoms into SWCNT. Simulation results indicate that the diameter of SWCNT is the one of the major factors controlling the pseudo-1D morphology of silver nanowire. The present theoretical investigations provide a guideline and enhance the current understanding related to solid state physical phenomena of metal nanowires synthesis.
Snapshots of phase transition from liquid to crystalline state of silver encapsulated into SWCNT of diameter d = 40.68 Å during cooling from 1500 to 10 K. Blue, red, green, and yellow color atoms pertain to bcc, hcp, fcc, and ico structure, respectively. For clear visualization, atoms with random organization have not been shown in the snapshot. SWCNT has not been shown in right most snapshot due to clear visualization of solidified silver. Red color arrows are indicating the progress of phase transition.
Silver atoms organization into a SWCNT of diameter d = 10.85 Å: (a) snapshot of silver atom encapsulated into SWCNT, (b) magnified view of pseudo 1-D organization of encapsulated silver atoms, and (c) a unit cell consisting of 13 silver atoms organization as 1-5-1-5-1.