The research into the subject of graphene has soared over the past few years. Due to the exceptional nature of some of its properties, it has become ever popular in the field of nanotechnology. The use of graphene for various electronics applications have been displayed using graphene that can be exfoliated or grown via several techniques. However, the scalability of these methods do not allow for bulk synthesis, known in the case of other graphitic nanomaterials like fullerenes and carbon nanotubes. For realistic applications, graphene has to be made in large quantities at a reasonable cost for use in, for example, solar cells, FETs, chemical sensors and engineering composites. Here successful attempts have been made to synthesise few layer graphene via bulk methodologies commonly used in the manufacture of carbon nanotubes, using relatively inexpensive precursor materials. Spray pyrolysis, a simple and scalable technique for the manufacture of few layer graphene using ethanol and various sodium precursors was demonstrated, which showed polymer composite, electronic device and transparent thin film application. Few layer graphene was grown using a bimetallic catalyst of sodium and cobalt. Addition of the sodium caused a visual decrease in the amount of carbon deposited from ethanol chemical vapour deposition. The product when observed using the scanning and transmission electron microscope was shown to be made up of turbostatic few layer graphene platelets. Growth of single and few layer graphene was demonstrated using copper nanoribbons and cobalt nanosheets as catalyst templates. These when incorporated onto inert support material, produced single and few layer graphene in a process that is deemed scalable and compatible with present industrial CVD reactors used for making carbon nanotubes.

The crystal structures of five hemiadducts of paracetamol with 1,4-dioxane, N-methylmorpholine, morpholine, N,N-dimethylpiperazine and piperazine, and a related 1:1 adduct of paracetamol with 4,4’-bipyridine are described. All structures are characterised by the formation of chains of paracetamol molecules, linked either via OH…O=C interactions [C(9) chains in graph set notation] or NH..O=C interactions [C(4) chains], depending on the presence or absence of substituent groups on the guest molecule. In all cases except for the morpholine and bipyridine adduct these chains are connected by H-bond interactions with the guest molecules residing on crystallographic inversion centres. In the bipyridine adduct this linkage also involves a π-stacking interaction; in the morpholine adduct it is formed between the OH groups of two opposed paracetamol molecules. Most adducts (that with 4,4’-bipyridine is an exception) decompose on heating to give monoclinic paracetamol. This is the first systematic study of a series of co-crystals containing paracetamol. The crystal structures of eight new co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine, 4,4’-bipyridine, N-methylmorpholine and N,N’-dimethylpiperazine are also reported. Quinol forms 1:1 co-crystals with pyrazine, piperazine and N,N’-dimethylpiperazine, but 1:2 co-crystals with morpholine, 4,4’-bipyridine, N-methylmorpholine, pyridine and piperidine. This difference can be rationalised in most cases by the presence of respectively two or one strong H-bond acceptor(s) in the guest molecule. The exception to this generalisation is 4,4’-bipyridine, which forms a 1:2 co-crystal, possibly to optimise crystal packing. All structures are dominated by hydrogen bonding between quinol and the guest molecules. A doubly-bridging motif, which connects pairs of quinol and guest molecules via NH…O or CH…O interactions, is present in all but the sterically-hindered N,N’-dimethylpiperazine and N-methylmorpholine co-crystals. Existing methodologies for crystal structure prediction work tolerably well for small, rigid molecules, prediction tests often appear to fail to predict known polymorphs, even though many hundreds of energetically similar structures may be predicted instead. Many algorithms attempt to maximise density, it is possible that ‘failed’ prediction attempts have in fact yielded polymorphs which are stable at high pressure, but which have not yet been identified experimentally. Crystal structures of all isomers of monofluorophenol and monochlorophenol have been determined both at low temperature and high pressure. All except the 3-subsittued isomers show some degree of polymorphism with applied pressure. 2-chlorophenol, for example, forms H-bonded chains in the solid state; thee are disposed about crystallographic 3₂ screw axes at low temperature, but 2₁ axes at high pressure (0.12 GPa). Previous work on the packing characteristics of alcohols suggests that the chlorophenyl group in this case is behaving as a large group at low temperature, but a small group at high pressure.

No description available.

No description available.

S1P n.m.r. spectroscopy was used to investigate the mechanism and kinetics of hydrolysis of zinc (II) O,O'-dialkyl dithiophosphates (ZDTP's) in aqueous 1,2-dimethyoxyethane solution at 85°C. All the major intermediates and products were identified and the relative reaction rates of the key steps in the hydrolysis determined. Diethyl ZDTP was found to be hydrolysed (k= 2.35 x 10~4 s"1) to phosphoric acid via O,O'-diethyl dithiophosphoric acid 9ktyj = 1.35 x 10~2 s"1) and thiophosphoric acid (kfcyj = 0.78 x 10~6 s"1); O-ethyl dithiophosphoric acid and dithiophosphoric acid were found to be intermediates; O-elhyl, O,O'-diethyl thiophosphoric and O-ethyl phosphoric acids were produced as by-products of the reaction. From a study of the order of appearance of the intermediates and products, a detailed mechanism for the hydrolysis of ZDTP's has been proposed. The relationship between the 'normal' salt of a ZDTP and its 'basic' form was also studied and the isopropyl derivative was found to dissociate in a variety of organic solvents (including xylene, toluene, diethyl ether, chloroform, 1,2-dimethoxy ethane, acetone, dimethyl formamide and dimethyl sulphoxide) via a facile equilibrium into its 'normal' salt and zinc (II) oxide. The dissociation was promoted by increasing temperature and solvent polarity and by increasing the water content in aqueous 1,2-dimethoxy-ethane. This equilibrium in favour of the 'normal' salt and zinc (II) oxide was also acid-catalysed. Zinc (II) oxide arising from the dissociation of the 'basic' form was found to inhibit the hydrolysis of 'normal' zinc (II) O,O'-diisopropyl dithiophosphate by reaction with its primary hydrolysis product, O,O'-diisopropyl dithiophosphoric acid. Eventual hydrolysis occurred after all the zinc (II) oxide was consumed.

No description available.

Three separate systems have been investigated. Firstly, the electrochemical reduction of some cyclic immonium salts has been examined by means of polarography, cyclic voltammetry, coulometry and preparative electrolysis using aprotic solvents (CH3CN and DM1') as the medium. The immonium salts were reduced to their two-electron reduction products but only one electron per mol was exchanged. The observation of the corresponding enamine among the products led to an investigation of the mechanism by linear sweep voltammetry and stereochemical analysis. This showed that the immonium cations were reduced to neutral radicals which underwent a radical-radical disproportionation reaction involving hydrogen-atom transfer. The effects of proton donors, ion-pairing and adsorption were also investigated. The second study concerned the reduction of acetophenone and 3-methylcinnamonitrile in dry (ca. 100ppm H20) CH 3CN. Products resulting from attack of the conjugate base of the solvent upon the substrate, 3-hydroxy-3-phenylbutanenitrile and 3-methyl-3-phenylglutaronitrile among others, were observed in addition to the usual dimerization products. The residual water in the solvent has been shown to play a crucial role, the participation of OH- ions being implicated in the formation of _CH2CN ions which then form an adduct with the depolariser. It has been proposed that the residual water affects the stereochemistry of the dimers and that dimerization takes place in solution. Evidence for adsorption has been presented but this does involve the dimerization process. The third study involved the reductive cleavage of the cyclopropyl ring in certain 1-cyclopropyl yylidenemalononitriles in aprotic solvents. Linear sweep voltammetry and stereochemical analysis have shown that the cleavage proceeds via a radical-ion and that the cleavage mechanism is radical in character. The cleavage reaction has been shown to be reversible for 2,2-di-alkylsubstituted cyclopropyl rings and irreversible for less substituted rings.

Molecular modelling and crystallographic techniques have been applied to the study of organic molecules used as friction modifiers and metal salt transport reagents. The accuracy of several empirical force fields has been evaluated by calculating low energy conformations of 3-(4-methylbenzoyl) propionic acid and tri acetyl glycerol. These were compared with the crystal structures of related molecules obtained from the Cambridge Structural Database, which contained either the 4-keto-carboxylate moiety or were tri esters of glycerol. Further validation has been carried out by comparing the force field predicted low energy conformations of propionic acid and ethylene glycol with the results of <i>ab initio </i>calculations either obtained from the literature or performed in house. Liquid phase molecular dynamics calculations have been carried out under conditions of constant volume and temperature and of constant temperature and pressure in order to investigate structure – activity relationship in films of physisorbed friction modifiers based on fatty esters of glycerol. We are able to make proposals about how the varying efficacy of mono, di and tri esters of glycerol arises from their structure. The crystal structures of novel complexes of model extractants for salts of base metals have been determined and analysed. These complexes fall into one of four classes: 1) Complexes containing salicylaldoxime ligands; 2) Complexes based on hexadentate tris-salicylaldimine ligands; 3) Complexes based on bipodal hexadentate ligands salicylaldimine ligands; 4) Complexes based on coordination of two tridentate salicylaldimine ligands. For classes 3) and 4) we have investigated the possibility of isomerism using the results of our structure determination and structures obtained from the Cambridge Structural Database. We have also investigated the possibility of a combined molecular dynamics/mechanics approach to asses the efficiency of phase transfer for this type of complex.

No description available.

No description available.