Coherent control of plasmons in nanoparticles with nonlocal response

We discuss a scheme for the coherent control of light and plasmons in nanoparticles that have nonlocal dielectric permittivity and contain nonlinear impurities or color centers. We consider particles which have a response to light that is strongly influenced by plasmons over a broad range of frequencies. Our coherent control method enables the reduction of absorption and/or suppression of scattering

Structure and electronic properties of porous manganese oxides.

Manganese oxides with varying pore sizes from ~2 to ~7 have been prepared by standard solid-state techniques and by low temperature hydrothermal methods. These materials have an open framework composed exclusively of manganese oxide, which in simple tunnel and layered structures is built up exclusively of edge and corner shared MnO6 octahedra. In more complex structures, such as that exhibited by Na0.44MnO2, this framework is built up of MnO6 octahedra and MnO5 square pyramids, where Mn3+ and Mn4+ are ordered on crystallographically distinct sites. The size of the tunnels or layer gap is dependent on the size of the cation used as a template. This thesis shows that it is possible to remove the 'template' ion from within many framework materials without destroying the structural integrity, this is due primarily to the ready conversion between the various manganese oxidation states to maintain charge balance. This makes it possible to tune the properties by incorporating varying amounts of foreign cations and/or small molecules into the vacant pore sites. These intercalation reactions result in small changes in the average manganese oxidation state, which in turn leads to differences in the thermal stability, observed magnetic and transport properties. We have also shown that it is possible to intercalate conducting polymers into the framework of some layered materials. Whilst the mechanism is not known, it can be seen that the oxidation state of the framework plays an important part in the ordering of the monomer/polymer units within the layers. Incorporation of these polymers leads to large changes in the magnitude of the observed magnetic moment as well as in the magnetic ordering. This work shows that these materials have a versatile framework, which leads to the real possibility of tuning the properties of a material to achieve desired effects leading to many possible uses for these types of materials

Synthesis and characterisation of molecularly imprinted nanoparticles with enzyme-like catalytic activity for the Kemp elimination

PhDThe development of new efficient catalysts with more economical processes and lower environmental impact has now become a major challenge in chemical research. Although it is now well-established that catalysis employs nanoscale processes, the concept of using nanomaterials as new potential catalysts is very recent. This new area of research has today found its place as nanocatalysis. The global aim of this work is to generate synthetic materials capable of behaving like enzymes, with high catalytic efficiency and good selectivity. These materials would supplement enzymes in conditions where these natural catalysts are not utilisable. Our focus is on the synthesis of molecularly imprinted nanogels with catalytic activity for hydrolytic and carbon-carbon bond formation reactions. The advantages of using nanogels as polymer matrix for the generation of catalytic imprinted polymers have been intensively studied and proven in our group and led to two major publications. However, since the dimensions of the nanogels prepared are over the length scale of a single active site, it is essential to investigate the impact of their size, their morphology along with their behaviour in different solvent systems as these parameters will have an effect on their catalytic efficiency and selectivity. The knowledge gained from these studies will lead us to the generation of tailor-made imprinted nanogels with more understanding of their dynamic nature. This thesis has focussed on the rationalisation of the effects of different experimental parameters on the catalytic activity and imprinting efficiency of molecularly imprinted nanogels, using the Kemp elimination as a model reaction. The correlation between the morphology and the structure of the particles and their catalytic behaviour was investigated. This consisted of altering polymerization parameters such as initiator content and monomer-template ratio, and also external stimuli such as organic solvent content, surfactants and temperature alterations, that can play a role in the swelling of the particles. Page | iii The non-covalent complex formation between the functional monomer (4- vynilpiridine) and the template (indole) was studied 1H-NMR. The optimal interaction between both molecules is found to be in non-polar solvents. Soluble nanogels synthesized in a suitable solvent using high dilution radical polymerization, were obtained with a good yield. The size of the particles was characterized by dynamic light scattering nm and Electronic Microscopy and was found to be around 15 nm. The number of the active sites was determined by an acid-base titration of pyridine moieties inside the polymer, allowing an accurate determination of the kinetic parameters such as kcat and KM. The imprinted nanoparticles show significant catalytic activity with 617-fold enhancement over the background reaction. The use of surfactant shows a significant improvement of the catalytic activity, imprinting efficiency and affinity of the polymers towards the substrate. This is in correlation with the effect of surfactant in the size of the nanogels that is decreased from 15 nm to 7 nm. The imprinted nanoparticles also display good selectivity properties when using different substrates.European Union Marie Curie Actio

Quantitative cone-beam computed tomography reconstruction for radiotherapy planning

Radiotherapy planning involves the calculation of dose deposition throughout the patient, based upon quantitative electron density images from computed tomography (CT) scans taken before treatment. Cone beam CT (CBCT), consisting of a point source and flat panel detector, is often built onto radiotherapy delivery machines and used during a treatment session to ensure alignment of the patient to the plan. If the plan could be recalculated throughout the course of treatment, then margins of uncertainty and toxicity to healthy tissues could be reduced. CBCT reconstructions are normally too poor to be used as the basis of planning however, due to their insufficient sampling, beam hardening and high level of scatter. In this work, we investigate reconstruction techniques to enable dose calculation from CBCT. Firstly, we develop an iterative method for directly inferring electron density from the raw X-ray measurements, which is robust to both low doses and polyenergetic artefacts from hard bone and metallic implants. Secondly, we supplement this with a fast integrated scatter model, also able to take into account the polyenergetic nature of the diagnostic X-ray source. Finally, we demonstrate the ability to provide accurate dose calculation using our methodology from numerical and physical experiments. Not only does this unlock the capability to perform CBCT radiotherapy planning, offering more targeted and less toxic treatment, but the developed techniques are also applicable and beneficial for many other CT applications