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This work focuses on the design, synthesis and characterisation of novel ruthenium bipyridyl complexes and their use in dye sensitised solar cells (DSSCs). Four series of dyes have been synthesised with the general formula Ru(R-bpy)2L, where R = H, CO2Et, CO2H and L represents four different bidentate ligands; cyanodithioimidocarbonate (L1), ethyl xanthate (L2), 2,3-bis(2-cyanoethylthio)-6,7-bis(methylthio) tetrathiafulvalene (L3) and Cu(exoO2-cyclam) (L4). These have been chosen to investigate two key aims: firstly, the increase of the light-harvesting ability of the dye and secondly, the retardation of the recombination of the injected electron with the oxidised dye. Each complex was characterised using electrochemistry, absorption spectroscopy, spectroelectrochemistry and hybrid-DFT calculations. In addition the performance of the acid derivatives in a DSSC was also investigated using IPCE and IV measurements, as well as transient absorption spectroscopy. Two different S-donor ligands, L1 and L2, have been used to investigate the effect of these strongly electron-donating systems on the light-harvesting ability of the dye. Complexes utilising the di-anionic L1 were shown to exhibit significantly increased absorption range and higher extinction co-efficients, relative to the high efficiency dye N719. This dye series also showed a large degree of S-donor ligand character to the HOMO, deduced via spectroelectrochemical and computational studies. Despite these advantageous features the dye performed very poorly in a DSSC, which was attributed to fast recombination. This was a result of the cyano group of L1 coordinating to the TiO2 in addition to the acid groups of the bipyridine ligands. The complexes synthesised with the mono-anionic L2 on the other hand showed only a slightly increased lightharvesting ability relative to N719 and no significant ligand character to the HOMO. However, the performance of this dye in a DSSC was more promising, with efficiencies of up to ~ 2 % achieved. The control of the loss mechanism via recombination of the injected electron with the oxidised dye in a DSSC was investigated by incorporating redox-active ligands, L3 and L4. The series of dyes synthesised with L3 showed significant ligand character to the HOMO orbital, as deduced by spectroelectrochemical, emission and computational studies. Upon adsorption of the acid derivative to TiO2 an extremely long-lived chargeseparated state of 20 ms was observed via transient absorption spectroscopy. Despite this unique long-lived charge-separated state, the dye yielded extremely low DSSC efficiencies. This was attributed to the poor regeneration of the neutral dye by iodide, which in turn was thought to be the result of a stable intermediate formation between the dye cation and the iodide anion. The complexes synthesised with L4 showed the highest light-harvesting efficiency of all the series studied with a wide absorption range and large molar extinction co-efficients. Whilst the maximum efficiency of the dye in a DSSC was nearly 3 %, the performance was found to vary under prolonged irradiation. This was attributed to the degradation of the dye by either exchange of the counter ions with the electrolyte or loss of L4.

M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / In 1854 friction over labour practices, land appropriation and inland trade routes led to the simultaneous murder of three groups of Dutch settlers, or Trekkers by the Kekana Ndebele. The Trekkers mounted a retaliatory attack on the Kekana, who retreated into Historic Cave, Limpopo Province. Although the cave had been well stocked prior to the attack, the Kekana were decimated and this event later became known as the Siege of Makapan. Excavations from 2001 uncovered a unique cache of European fabric preserved by the unusually dry conditions in the cave. Within the fluid social and political landscape of the internal frontier of nineteenth century northern Transvaal, European clothing and fabric was a valuable resource that served different functions. Contemporary records from traders, travellers and missionaries indicate that, as a high status item, clothing and fabric was often restricted to elites, was subject to social mores and could be used to signal changing religious or political affiliations. Certain groups, or individuals, also invested fabric with unusual properties. No entire garments were recovered from Historic Cave but some of the fragmentary fabric remains that were revealed indicate their possible use as ritual objects endowed with supernatural qualities. The unique find from Historic Cave allows an opportunity of comparing archaeological remains with historical documents to understand more about fabric use at this time.

Orientador: Maria Valnice Boldrin / Banca: Humberto Márcio Santos Milagre / Banca: Daniela Pereira dos Santos / Resumo: O presente trabalho investigou a degradação fotoquímica do corante tartrazina, amplamente empregado na indústria de alimentos, utilizando métodos espectrofométricos e de cromatografia líquida com detecção de arranjo de diodos (CLAE-DAD) e detecção por espectroscopia de massas (LC-MS/MS). Além disso, através do Teste de Ames, avaliou-se também o caráter mutagênico do corante e de seus subprodutos de fotodegradação. Os estudos de fotólise foram conduzidos utilizando radiação UV e solar, observando-se maior velocidade de degradação sob luz artificial e em solução de pH ácido. A descoloração total de solução 1x10-5 mol L-1 de tartrazina foi obtida após 30 min de exposição à luz UV 125 W, demandando uma dose de energia de 37,8 J cm-2. Os resultados obtidos mostraram a geração de 5 subprodutos, oriundos da abertura do anel de cinco membros, identificados por análises de LC-MS/MS. A análise destes dados permitiu a proposição de uma rota de degradação para o corante tartrazina. O teste de Ames foi realizado para o corante em uma concentração de 5,34 mg/placa e para as soluções obtidas após exposição à radiação UV, e mostrou que a tartrazina não possuí propriedades mutagênicas frente às linhagens TA98 e TA100 de S. typhimurium, com e sem metabolização exógena (fração S9). Na segunda etapa do trabalho, investigou-se a lixiviação dos corantes Reativo Verde 19, Direto Azul 86 e Direto Vermelho 81, empregados na tintura de algodão, quando em contato com suor sintético. Os tecidos tingidos foram submetidos à ação de soluções de suor, mimetizando diferentes valores de pH, composição, temperatura e tempo de contato entre o tecido tingido e o suor. A lixiviação destes corantes na solução foi monitorada utilizando as técnicas de espetrofotometria na região UV-Vís, cromatografia em camada delgada (CCD) e LC-MS/MS. Espectros de massas e os cromatogramas do padrão e das amostras obtidas... / Abstract: This work investigated the photochemical degradation of the dye tartrazine, widely used in food industry, using spectrophotometric methods and liquid chromatography coupled with diode array (HPLC-DAD) and mass spectrometry (LC-MS/MS) detection. Furthermore, through the Ames test, was studied the mutagenicity of the dye and it's photodegradation by-products. The photolysis studies were conducted under UV and sunlight, with a more pronounced dye degradation achieved under artificial light in a solution of acidic pH. Total discoloration of a 1x10-5 mol L-1 tartrazine solution was obtained after 30 min of exposure to 125 W UV light, demanding an energy dose of 37.8 J cm-2. The results showed the generation of 5 by-products, derived from the opening of the five-membered ring, identified by LC-MS/MS analysis. The analysis of these data enabled the proposition of a degradation pathway for the dye tartrazine. The Ames test, using Salmonella/microsome, was conducted for the dye at a concentration of 5.34 mg / plate and for the solutions obtained after exposure to UV irradiation, showing that the dye does not possess mutagenic properties for strains TA98 and TA100 of S. typhimurium, with and without exogenous metabolization (S9). In the next step, it was investigated the leaching of dyes Reactive Green 19, Direct Blue 86, Direct Red 81 applied to dye cotton fabrics, when in contact with synthetic sweat. The dyed fabrics were exposed to the synthetic sweat mimicking different pH values, composition, temperature and contact time between the dyed fabric and sweat. The releasing of these dyes in the solutions was monitored using the techniques of UV-Vis spectrophotometry, thin layer chromatography (TLC) and LC-MS/MS. Mass spectra and chromatograms of the Reactive Green 19 standard solution and the samples showed that the dye is extracted from the fabric, by sweat solutions, in all situations tested, and the lower concentrations were found... / Mestre

The Guest Host Mode of LCD is doped the dichroic dyes in liquid crystal and it have anisotropic absorbefacient. This operation mode can produce dark or brightness to achieve display target by the electric field and this can operate in the non-polarizer type to achieve high reflectance. Because of market requirement in the e-paper display, so the reflective LCD by the guest host mode is a focal once again. In this study, we will doped the black dichroic dyes in liquid crystal and than we fill into the homogenous alignment cell by difference rubbing direction and homeotropic alignment cell to investigate the optical-electric characteristic in the non-polarizer and polarizer type, because in the difference alignment condition can influence the behavior of dichroic dyes, and we fabricate the double cell to improve the optical-electric characteristic. The reflective type guest host display still have many research space, like dope the dichroic dye in PDLC(polymer dispread liquid crystals) or cholesteric liquid crystal to achieve flexible and bistable characteristic.

Thesis (Honors)--Liberty University Honors Program, 2008. / Includes bibliographical references.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 185-202). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Spyros G. Pavlostathis. / Vita. Includes bibliographical references (leaves 332-345).