M.Tech (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Dithiocarbamate ligands and their complexes has been a subject of interest in various fields but they found much interest in medical applications as potential anti-microbial agents. The dithiocarbamate ligands were used to prepare complexes of copper and zinc. All the prepared ligands and complexes were characterized using techniques such as IR and 13CNMR spectroscopy and thermogravimetric analysis (complexes). The data obtained from the spectroscopies was consistent with the coordination of the ligand to the metal ion through the sulfur atoms of the dithiocarbamate or thioureide moiety. The thermal analysis of the prepared complexes gave a final residue of metal sulfide, thus indicating the potential of the prepared complexes as single molecular precursor for the synthesis of metal sulfide nanoparticles. The prepared complexes were then used to synthesize metal sulfide nanoparticles. The nanoparticles were successfully prepared by thermal decomposition of a single-source precursor (dithiocarbamate complexes) in a solution of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO). The investigated parameters were the capping molecule (HDA and TOPO), and capping molecule concentration (3 g and 6 g) to see their effect on the shape and size of the synthesized nanomaterials. The synthesized metal sulfide nanoparticles were characterized using techniques such as UV-vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The absorption study showed some interesting features in the prepared nanomaterials. The first was the red-shifted spectra of the ZnS nanoparticles which was attributed to the impurities and that assumption was further confirmed by the XRD analysis that showed a sulfur impurity and other amorphous peaks. The second was the localized surface plasmon resonances on the copper sulfide nanoparticles that suggested the formation of electron deficient copper sulfide stoichiometry that was further confirmed by XRD analysis that gave hexagonal phase copper sulfide covellite. The TEM images of the prepared nanoparticles showed that the concentration and the capping molecule has an effect on the size and shape of the synthesized nanoparticles. The increase in capping concentration gave a decrease in particle size in most of the prepared nanoparticles, while they were few exceptions. The capping molecule effect showed that most of the nanoparticles prepared from TOPO were spherical in shape and were well dispersed compared to the mixed morphological nanoparticles prepared from HDA. There were also exceptions of the well dispersed HDA-capped nanoparticles.

Pyrolytic oils produced from poultry litter differ in physico-chemical properties and the chemical composition. The litter is composed of manure and bedding material with traces of spilled feed and feathers. The type and amount of bedding material was varied to investigate its influence on the pyrolysis of layer manure. 400g of each feedstock: manure, wood (pine and oak), and mixtures of manure and wood in proportions (75:25 50:50, and 25:75 w/w %) respectively were subjected to fast pyrolysis at 450oC in a fluidized bed reactor. The total pyrolytic oil yield ranged from 43.3% to 64.5 wt%. The highest bio oil yield and the lowest char yield were obtained from oak wood. The manure oil had the highest HHV of 29.7 MJ/kg, the highest pH (5.89), the lowest density (1.14 g/cm3) and a relatively low viscosity of 130cSt. The oils had relatively high nitrogen content ranging from 5.88wt% to 1.36 wt%; low ash content (approximately <0.07wt %) and low sulfur content (<0.28wt %). FT-IR, 13CNMR, and 1HNMR analysis showed that manure oil was rich in aliphatic hydrocarbon and primary and secondary amides and the addition of wood introduced oxygenated compounds like aliphatic alcohols, phenols, aromatic ethers, and carbonyl/carboxylic groups into the oil. TG/DTG analysis also showed that the thermal decomposition of the oils were different depending on the amount and the type of wood in the manure/wood mixture. The parametric variables used for the mixture of 50% manure and 50% pine wood shavings study were; temperature (400-550°C), nitrogen gas flow rate (12-24 L/min), and feed rate (160-480 g/h). The results showed that the pyrolysis product yields, physical properties and the chemical composition of the oil were influenced by all parameters. Temperature was the most influential factor and its effect on the liquid, char and gas yields were significant. It was evident that depending on the gas flow rate and the feed rate, a maximum oil yield (51.1wt.%) can be achieved between 400-500 oC. Also an increase in temperature significantly increased the oil viscosity and decreased the carbonyl/carboxylic and the primary aliphatic alcohol functional groups in the oil. The study on the influence of wood on the stability of the oils when stored at ambient conditions for 8 months in a 30ml glass bottle showed that the viscosity of the oils increases when stored, however the manure oil was relatively more stable and the oil from the 50/50 mixture for both pine and oak was the least stable. It was found that the stability of the oils from the manure and wood mixtures were dependent on the amount and the type of wood (pine or oak) added to the manure. Also the addition of 10% solvent (methanol/ethanol) to the oil from 50% manure and 50% pine reduced the initial viscosity of the oil and was also beneficial in slowing down the increase in viscosity during storage. / Master of Science

The work presented in this thesis has two parts. The first part deals with methodological developments in the area of solid-state NMR, relevant to the study of partially ordered systems. Liquid crystals are best examples of such partially ordered systems and they are easily oriented by the magnetic field used for the NMR study. They provide spectra rich in information useful for the study of structure and dynamic s of the oriented molecule. Dipolar couplings and anisotropic chemical shifts are relatively easy to obtain for these systems. However, the methodologies used for extracting the required information are constantly undergoing change, with newer ideas being used for optimal use of the technique and increasing the sensitivity of the methodology. In this thesis, existing methods used for obtaining dipolar couplings from oriented liquid crystalline samples are examined in detail and conditions for optimal use of the methods are investigated. Different approaches for enhancing the sensitivity of the techniques are also proposed. Estimation of chemical shift anisotropy of carbons for a molecule that is used as a building block for several mesogens has been obtained and its utility for estimating the order parameters of the system have been examined. The second part of the thesis deals with the application of solid state NMR methods to the study of a number of novel liquid crystalline systems and for the estimation of dynamics, order and orientation of the mesogenic molecules in the magnetic field. Chapter-2 deals with a detailed and systematic study to improve the sensitivity of cross-polarization based separated local field (SLF) NMR spectroscopy techniques such as PISEMA(Polarization Inversion Spin Exchange at the Magic Angle) and PDLF(Pro-ton Detected Local Field). The chapter has been further divided into three sections. Section-A describes the optimization procedure for cross-polarization period for reducing zero-frequency peaks in SLF experiments. Polarization Inversion(PI) is one of the important components of PISEMA and plays a crucial role in enhancing the dipolar cross-peaks and suppressing the axial-peaks. Shortening this period has the advantage of less r.f. power input into the system, thus less susceptibility to sample heating. Therefore it is crucial to arrive at the optimum condition for which maximum sensitivity and resolution are obtained. A detailed experimental investigation of the role of the initial po1arization period has been carried out for two different samples of static oriented liquid crystalline material at two different temperatures and a contact time of 2ms has been found to be optimal for such samples. Insection-B of this chapter, the initial preparation period of the experiment is considered as a possible means of increasing the sensitivity of the experiment. Thus the use of cross-polarization via the dipolar bath by the use of a diabatic demagnetization in the rotating frame(ADRF-CP) has been proposed to be incorporated into PISEMA. To understand the CP dynamics, magnetization in double-and zero-quantum reservoirs of an ensemble of spin-1/2 nuclei and their role in determining the sensitivity the experiments have been theoretically examined. Experimentally, a modification incorporating ADRF-CP is shown to result in enhancement of signal-to-noise by as much as 90% in the case of rigid single crystals of a model peptide and up to 50% in non-rigid, partially ordered liquid crystalline systems. In section-C another useful SLF technique known as PDLF spectroscopy has also been examined. In this case a sweep of one of the r.f. amplitudes(RAMP-CP),rather than ADRF is found to work well. The reason for the different behaviours has been discussed. Chapter-3 highlights two experimental approaches used to extract the chemical shift anisotropy(CSA) tensor information from rotating solids. Section-A is devoted to the measurement of the CSA values of thiophene by using MAS side band analysis, by extracting the principal values from the intensities of just a few spinning side bands. Experiments have been performed on thiophene-2 carboxylic acid and thiophene-3 carboxylic acid samples and the carbon CSA values have been obtained. In section-B, CSA values of carbons of the core unit of the liquid crystal4- hexyloxybenzoic acid (HBA) have been obtained by using the recoupling pulse sequence SUPER(Separation of Undistorted Powder patterns by Effortless Recoupling).HBA belongs to an important class of thermotropic liquid crystals which are structurally simple and often used as starting materials for many novel mesogens. As this molecule could serve as an ideal model compound, high resolution13C NMR studies of HBA in solution, solid and liquid crystalline phases have been also undertaken. The CSA values obtained from the 2D SUPER experiment showed good agreement to those computed by DFT calculations. The CSA values were used for obtaining the order parameter of the system at different temperatures. These matched well the order parameter obtained from the 13C-1 H dipolar couplings in the nematic phase determined by SLF spectroscopy at various temperatures. A knowledge of the CSA of the carbons is thus very useful, as they can be used for gaining knowledge about the system from the chemical shifts obtained from a simple 1D spectrum. In chapter-4, 1-and 2-dimensional13CNMR techniques have been utilized to obtain extensive information about some novel mesogenic molecules. Four molecules of different structure and topology have been taken up for study. These molecules have the following features. Mesogen-1 has a terminal hydroxyl group. Such systems with further modification can result in mesogenic monomers for side chain liquid crystalline polymers. Mesogen-2 has a dimethyl amino group at one end and has three phenyl groups connected by appropriate linking units that form the core. In the third case, mesogen-3, the terminal hydroxyl group of mesogen-1 is replaced with a hydrogen such that13C-1 H dipolar couplings provide directly information on molecular ordering and orientation. In the fourth case, mesogen-4, the core is built with four phenyl rings. Here the fourth ring is linked to other three rings via a flexible chain unit. In each of these cases the 2DSLFNMR experiments have been carried out where13C-1 H dipolar couplings as well as13C chemical shifts were used for obtaining the order parameters of various segments of the molecule. The data provide useful insight into the phase behaviour, ordering and orientation of the molecules. Chapter-5 discusses the applications of the natural abundance 13CNMR techniques to thiophene based mesogens, that have the potential for use in molecular electronics material. Typically, these molecules consist of phenyl rings appropriately connected by linking units with thiophene. Different core units as well as different linking units to thiophene have been considered. The six mesogens thus obtained have been investigated in detail using 1D and 2D NMR methods.13C-1 H dipolar couplings have been used to obtain ordering information, that show interesting correlation to the molecular orientation and dynamics.