We will develop simple, scalable methods to exfoliate layered compounds into monolayer nanosheets. These materials have exciting properties. Recently, graphene has taken the nanomaterials community by storm. However graphene is only one branch of a family of two dimensional layered compounds. Other examples include hexagonal BN, metal dichalcoginides such as MoS2 and metal oxides such as MnO2. We propose that all layered compounds can be exfoliated in certain solvents by the addition of ultrasonic energy. Such a method has not been demonstrated because the vast majority of solvents are unsuitable for this. We propose that suitable solvents can be identified by matching their surface energy to that of the nano crystal, rendering the exfoliation process energy neutral. This will open the gate to a wide range of nano-materials science and makes possible experiments that have been impossible using standard techniques. We will pick a set of layered compounds such as the semiconductors; hexagonal BN, MoS2 and TaO3 and the metals TaS2 and MnO2. We will learn to exfoliate these materials, studying the physics and chemistry of the solvent-nanosheet interaction. Once we can generate large volumes of highly exfoliated few-layer nanosheets at high concentration, we will study the physics of these materials. We will prepare free standing films of restacked sheets and polymer-sheet composites for mechanical applications. Thin films can also be studied as transparent conductors and capacitor dielectrics. Hybrid films can be used to devices such as photodetectors. Much more challenging will be the production of large quantities of monolayer nanosheets. We will learn to deposit nanosheets on substrates and measure their thickness and size with AFM. Semiconducting monolayers will be characterised by photoluminescence spectroscopy leading to a spectroscopic metric for monolayer population. By optimising the link between exfoliation procedure and monolayer population, we will develop methods to produce monolayer enriched samples. This will pave the way to nanostructured devices such as light emitting diodes.
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