Formation and Growth Mechanisms of Single-Walled Metal Oxide Nanotubes

Abstract

Metal oxide nanotubes have emerged as an important class of ‘building block’ materials for molecular recognition-based applications in catalysis, separations, sensing, and molecular encapsulation due to their well-defined wall structure and porosity, tunable dimensions, and chemically modifiable interior and exterior surfaces. However, their widespread application will depend on the development of synthesis processes that can yield structurally and compositionally well-controlled nanotubes. To this end, we have investigated the mechanisms of formation and growth of single-walled metal oxide nanotubes at multiple length scales, from the molecular scale to the micron-scale. We show how a wide range of quantitative and qualitative information regarding nanotube formation and growth can be obtained by nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, transmission electron microscopy (TEM), and solvated density functional theory (DFT) calculations. Integration of all this information leads to the construction of the first ‘design rules’ of single-walled metal oxide nanotube formation and growth.