Two-dimensional nanomaterials : characterising properties and structures in real environments

Abstract

This thesis discusses studies of several two-dimensional nanomaterials with a view to understanding their behaviour when exposed to environments similar to those they would experience in the laboratory and in applications. Many of these nanomaterials can be exfoliated in large quantities through liquid-phase exfoliation techniques, and they are being researched for their energy storage properties. Exposure to ambient conditions can often result in changes to the materials, and this is expected to be worse when exposed to harsher environments within an energy storage device. Transmission electron microscopy (TEM) has been used to characterise the effect of these environments on the structure of two such materials, titanium disulphide (TiS2) and gallium sulphide (GaS), which were both found to oxidise. However, the nature of the oxidation depended on the particular environment the samples were aged in, namely air, water and heating, and on the length of time for which the ageing took place (up to several weeks). The combination of imaging using TEM and scanning transmission electron microscopy (STEM) with analytical spectroscopy such as energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) enabled us to identify structural and compositional variations within these materials.