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In recent years there has been considerable interest in the use of synthetic hydrotalcites as stabilisers for poly(vinyl chloride) (PVC). Hydrotalcites are essentially hydrated magnesium-aluminium-hydroxy-carbonates: a typical formula being Mg6Al2(OH)16CO3.4H2O. Substitution of a divalent by a trivalent cation in the brucite structure creates a positive charge that needs to be counterbalanced by the presence of an anion, and this is usually carbonate. Hence, hydrotalcites are anionic clays, as opposed to the more common montmorillonite-like clays or so called cationic clays. These double-layered hydroxides have the capacity to undergo anion exchange reactions and so the carbonate can be substituted for other anions such as chloride, sulphate or nitrate. The characteristic of anion exchange means that, commercially, synthetic hydrotalcites are used for catalysis, ion scavenging, purification processes and the stabilisation of PVC formulations. This thesis present result of a project to synthesise and modify hydrotalcites to produce ultra-fine particles in recognition of the fact that the benefits of hydrotalcite could be enhanced with smaller particle sizes. The work has proceeded via two routes: firstly, by experiments to modify and intercalate the hydrotalcite with a surfactant in a way analogous to that used to montmorillonite clays, and secondly by novel synthesis methods. Two different synthesis reactions were used: one based on Urea and the second by a controlled pH method. Different drying technologies were used to obtain the optimum particle morphology and size. It was found that ultra-fine hydrotalcite particles gave an improvement in PVC thermal stability, although addition of higher levels of the hydrotalcites caused a reversal in this trend. The Haake Rheometer was used extensively to study the behaviour of the polymer clay nanocomposite formulations and to investigate the pros and cons of the addition of nanometre particles. Further work using an autoclave has resulted in particles of nanometre-sized dimensions with enhanced crystallinity and very high surface area which are promising for future work on PVC clay nanocomposites.

My PhD thesis explores the nature of Nanoscale Science and Technology, in particular how this new and emergent research field is constructed in science practice. I examine the sociotechnological worlds of scientists in NST, in particular their disciplinary identity construction, and their negotiation of NST as a research field. I identify three dimensions of identity here: belonging, practice, and strategy.

Engineered nanoparticles are defined as having at least one dimension between 1 to 100 nm, which are intentionally produced because of specific properties based on shape, size and surface chemistry. The small size of nanomaterials gives them specific and/or enhanced physicochemical properties compared with the same materials at the macroscale, making them of great interest for development of “new” products. Silver nanoparticles (AgNPs) are being increasingly used in consumer products such as ‘stay fresh’ clothing, water purification and household cleaning agents. They are released into the environment in increasing amounts and concerns have been raised about the risk of harmful impact on both the environment and human health. This research used human cells in culture as a model system to investigate the potential toxicity of AgNPs. Early experiments used the MTT assay to define the concentrations of AgNPs and AgNO3 and incubation times that caused an acceptable loss of cell viability (≤ 20% loss). Using these conditions, the Comet method and phosphorylation of gH2AX determined DNA damage by the AgNPs in comparison to AgNO3 on the basis of weight (μg/ml). Epigenetic changes in response to AgNPs and AgNO3 were indicated by measurement of methylation of LINE-1 using pyrosequencing. The effect on oxidative stress was evaluated using a qPCR array platform followed by functional analysis of SOD1. A novel dialysis method was then developed to quantify release of Ag+ ions from the AgNPs that were available to the cells and TEM determined cellular localisation of the AgNPs. In conclusion, this research showed that both AgNPs and AgNO3 caused DNA damage in time and dose response manners by oxidative stress mechanisms, involving inhibition of SOD1. TEM imaging of cells exposed to AgNPs indicated that they were not internalized, but bound to the cell membrane, and from here released Ag+ ions into the cell.

Spontaneous formation of macroscopic hydrogels from small molecule building blocks via self-assembly is a powerful tool for the preparation of novel materials with well defined properties. Peptides are particularly interesting as building blocks for these materials. Self-assembled nanowires, fibres, sheets and tubes from peptide systems have all been described.

There has been a rapid growth of interest in graphene, a strictly two-dimensional material, since its discovery. The exceptionally high crystal and electronic quality of graphene makes it not only an excellent platform to study fundamental physics but also a promising material for future nanoelectronics in post-silicon era. The work presented In this thesis aims to probe into the electronic transport in graphene.

Graphene's discovery adds a new dimension to carbon based nano-science which was originated by nanotubes and fullerenes. Recent advances in graphene research have uncovered unique physical and electronic properties of this material. So much has been the importance of these properties that graphene has become one of the most sought after research materials today. The work presented in this thesis is directed towards new aspects of electronic and spm transport mechanisms in graphene.