/library/oar/handle/123456789/70980 2025-12-25T21:01:59Z /library/oar/handle/123456789/141614 Title: Molecular logic gates as fluorescent markers and DNA binding agents Abstract: N/A Description: Ph.D.(Melit.) 2023-01-01T00:00:00Z /library/oar/handle/123456789/136794 Title: On folded graphene and its properties : a preliminary study Abstract: Graphene is one of the newly discovered forms of carbon and exists as a single sheet, made from sp2-hybridised carbon atoms, which is flexible enough to be able to adopt a variety of conformations. This material, or its variants, may exhibit wide-ranging properties, including a negative Poisson’s ratio (auxeticity). This property may be imparted to graphene through a process which involves modification through the use of patterned or randomly-placed defects which guide graphene to adopt particular three-dimensional conformations that are amenable to exhibiting negative Poisson’s ratios. This work re-examines and extends recent work which has shown how graphene with defects inserted along equally spaced lines may exhibit giant negative Poisson’s ratios as a result of the corrugated-sheet-like conformation it adopts, which defect lines act as crease lines. It is shown, through a combination of static force-field based simulations using the polymer consistent force-field (PCFF) and more computationally intensive NPT molecular dynamics simulations using the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) force-field that the corrugated forms of graphene which had previously been reported are neither the most stable nor the most auxetic forms that these systems may adopt. In fact, it is shown that unless constrained, the low-density corrugated forms of graphene are likely to fold and adopt much denser forms with graphite-like features that impart added stability, which may or may not be auxetic. It was also shown that other stable variants of the less dense form of the corrugated graphene may exist which may exhibit an even higher extent of auxeticity than what was reported so far. Other anomalous properties, such as negative tangential stiffness or zero Poisson’s ratios for some of these forms are also identified and discussed. Description: B.SC.(HONS) 2018-01-01T00:00:00Z /library/oar/handle/123456789/132575 Title: The synthesis of single-phase materials exhibiting a controlled, isotropic positive or negative thermal expansion Abstract: Thermal expansion is a fundamental physical property of a material and it is considered crucial for some high precision applications. The aim of this project is to synthesise and characterise new single-phase materials which exhibit controlled thermal expansion or zero thermal expansion (ZTE). This idea originated from the fact that in the last decade several materials with negative thermal expansion (NTE) were synthesised. Recent publications showed that this property can be altered through chemical and physical modifications, in such a way that the coefficient of thermal expansion (CTE) is tuned from negative to zero to positive. The projects discussed in this work involved both organic and inorganic frameworks. The metal organic frameworks HKUST-1 and UiO-66 were used, as these are known to contract upon heating. These frameworks were subjected to methods that hinder contracting mechanisms, such as the introduction of guest molecules and functionalized chains and also the introduction of defects. In the case of inorganic frameworks, the family of Prussian blue analogues was chosen. Here a methodology was constructed which involved doping of hexacyanoferrates(III) which exhibit negative thermal expansion with first row transition metals, in an attempt to tune the coefficient of thermal expansion. Powder X-ray diffraction data conducted at room temperature showed structural changes within both metal organic frameworks. This was followed by variable temperature powder X-ray diffraction experiments which concluded that the coefficient of thermal expansion did indeed change. This was observed when toluene and n-pentane were added as guest molecules, when 1,2,4,5-benzene tetracarboxylic was added as a functionalised linker and via introduction of defects using acetic acid, formic acid, oxalic acid and isophthalic acid. In some samples the magnitude of negative thermal expansion was enhanced, in others near-zero thermal expansion was reached, whilst in some samples even positive thermal expansion (PTE) occurred. Similar tuning in the coefficient of thermal expansion was observed in one of the series of doped hexacyanoferrates(III) which involved the Cu/Co metal cations. Description: Ph.D.(Melit.) 2025-01-01T00:00:00Z /library/oar/handle/123456789/120164 Title: Green chemistry alternatives for an established industrial process of an active pharmaceutical ingredient (API) Abstract: In this research, an effort was made to improve the protection of a starting molecule used in the industrial process for the synthesis of an API. Three protecting groups were utilized, 2- (Trimethylsilyl)ethoxymethyl Chloride (SEM-Cl), Di-tert-butyl Dicarbonate (BOC2O), and Pivaloyloxymethyl Chloride (POM-Cl). Trials were conducted with each group, even attempting to optimize the preexisting reactions, however, only the ones for BOC2O gave good results. The optimization attempt for the SEM-Cl protection failed as the catalyst available to us was not strong enough for the reaction, while no optimization was possible for the POM-Cl as the best catalyst was already being used, and no alternative was available. After analyzing all final purified products with 1H-NMR, IR, and GC, it was clear that the optimized BOC2O protections, despite working well, still contained quite some impurities. However, in comparison to the trials with the other protecting groups, the modified BOC2O trials were still the best alternatives out of all. Ultimately, the results gathered during this research gave an insight to potential alternatives to the industrial synthesis of this API. Furthermore, findings from this research could also be utilized in the optimization of other industrial processes that make use of similar reactions. Description: B.Sc. (Hons)(Melit.) 2023-01-01T00:00:00Z