title: Controlling nanotube dimensions: correlation between composition, diameter, and internal energy of single-walled mixed oxide nanotubes.
abstract: Control over the diameter of nanotubes is of significance in manipulating their properties, which depend on their dimensions in addition to their structure and composition. This aspect has remained a challenge in both carbon and inorganic nanotubes, since there is no obvious aspect of the formation mechanism that allows facile control over nanotube curvature. Here we develop and analyze a quantitative correlation between the composition, diameter, and internal energy of a class of single-walled mixed oxide aluminosilicogermanate (AlSiGeOH) nanotubes. A series of synthetic AlSiGeOH nanotubes with varying Si/Ge ratio are characterized by X-ray photoelectron spectroscopy, vibrational spectroscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction to relate their compositions and diameters. We then study these nanotubes computationally by first parametrizing and validating a suitable interatomic potential model, and then using this potential model to investigate the internal energy of the nanotube as a function of diameter and composition via molecular dynamics simulations. There are minima in the internal energy as a function of diameter which progressively shift to larger nanotube diameters with increasing Ge content. An approximate analytical theory of nanotube diameter control, which contains a small number of physically significant fitted parameters, well describes the computational data by relating the composition and geometry to the strain energy of bending into a nanotube. The predicted composition-dependent shift in the energetically favored diameter follows the experimental trends. We suggest related methods of controlling nanotube energetics and their role in engineering nanotubes of controlled dimensions by liquid-phase chemistry.
authors.affiliation: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332-0100, USA.
authors.forename: Suchitra
authors.initials: S
authors.lastname: Konduri
authors.forename: Sanjoy
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Sankar
authors.initials: S
authors.lastname: Nair
mesh_terms: D000535:Aluminum / Q000737:chemistry; D005857:Germanium / Q000737:chemistry; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D015203:Reproducibility of Results; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D010087:Oxides; D005857:Germanium; D000535:Aluminum