Sintetizou-se uma nova diimida naftálica difosfônica, a N, N-bis(2-fosfonetil)naftaleno diimida (DPN), pela reação do dianidrido 1,4,5,5-naftálico com o ácido 2-aminoetil-fosfônico. Essa molécula foi caracterizada por H-RMN, micro-análise, titulação potenciométrica e análise de fosfato. Através de estudos fotofísicos e fotoquímicos do DPN em solução verificou-se que essas moléculas encontravam-se na forma monomérica em água e na forma de agregados em solventes orgânicos. Verificou-se que o rendimento quântico de fluorescência Φf dessa molécula é dependente do pH do meio, uma vez que ocorre diminuição do Φf com aumento do pH. Por estudos com fotólise de relâmpago e por experimentos de lente térmica resolvida no tempo, verificou-se que a diminuição do Φf com aumento do pH. Por estudos com fotólise de relâmpago e por experimentos de lente térmica resolvida no tempo, verificou-se que a diminuição Φf é causada principalmente por um aumento no cruzamento intersistema, de singleto a tripleto. Multicamadas à base de zircônio (Mallouk et al. 1987) do DPN foram obtidas substratos como vidro, silício e ouro. O crescimento de filmes em vidro foi acompanhado por espectroscopia de absorção e em filmes sobre o silício por elipsometria. Sobre a superfície de ouro, foram estudadas as propriedades de oxido-redução do filme por voltametria cíclica. Por estudos fotofisicos desses filmes depositados em vidro, verificou-se que os mesmos eram fotoativos, formando produtos fotoquímicos por processos radicalares. Por outro lado, quando se preparou micro-cristais, pricipitando-se o radical do DPN com o zircônio em solução, observou-se por espectroscopia de ressonância de spin eletrônico (EPR) que estas estruturas micro-cristalinas estabilizavam o radical do DPN em presença de ar por vários dias. / The new diimide N, N\' -bis-(2-phosphoethyl)-1,4,5,8-naphtalenediimide (DPN) was synthesized by reaction of 2-aminoethylphosphonic acid with the compound 1,4,5,8-naphatalene tetracarboxylic dianhydride. This molecule was characterized by 1H-RMN, elemental analysis, potentiometric titration and phosphorus analysis. By photophysical and photochemical studies of DPN in solution, it was verified that DPN is in monomeric form in aqueous solution and DPN is in an aggregated state in organic solvents. When the fluorescence spectra in aqueous media show a sharp decrease in the fluorescence quantum yield (Φf) with the increase in pH. By laser flash photolysis and thermal lensing, it was verified that this reduction of Φf with the increase pH can be attributed to an increment in the intersystem crossing processes when the pH increased. The zirconium phosphonate thin films formed from 1,4,5,8-naphtalene diimides were assembled on quartz, borosilicate glass (BK7), silicon or gold. The film growth was followed by absorption spectroscopy on quartz and BK7 and by ellipsometry on silicon substrate. Toe oxidation and reduction properties of the films were studied by cyclic voltammetry of films deposited on gold. Photophysical and photochemical data revealed that the films were photosensitive, giving rise to products derived by radicalar reactions. On the other hand, when the DPN radical was precipitated with Zr4+ in solution, micro-crystals were obtained which stabilized the radical in the presence of air for several days.

O design de materiais na escala nanométrica está levando a sistemas com novas propriedades e aplicações as mais diversas, como em sistemas de diagnóstico e de tratamento inteligentes e sustentáveis. Melhorar a eficiência dos tratamentos de doenças através do desenvolvimento de fármacos mais eficientes e com menos efeitos colaterais, e agentes de contraste e de diagnóstico mais específicos e sensíveis para monitoramento preventivo precoce, é um dos principais objetivos da Nanomedicina. Todavia, a química de superfície necessária para realizar tais reações de funcionalização/conjugação de moléculas ainda está longe de ser adequadamente controlada, particularmente considerando-se a complexidade das biomoléculas e a estabilidade coloidal. Assim, nesta tese foram desenvolvidos processos de conjugação de nanopartículas de óxido de ferro (SPIONs) com um ou mais agentes co-funcionalizantes, gerando partículas mono, bi e multifuncionalizadas dispersáveis em meio aquoso. Os esforços foram concentrados no desenvolvimento de sistemas de diagnóstico e de entrega de fármacos baseados em nanopartículas, cujas propriedades precisam ser ajustadas pela conjugação de biomoléculas e espécies bioativas em sua superfície, num verdadeiro trabalho de engenharia a nível nanométrico/molecular. De fato, nanopartículas modificadas com moléculas co-funcionalizantes estabilizantes (glicerol-fosfato, glicose-fosfato, fosforiletanolamina, dopamina e tiron), agentes de vetorização que direcionam o nanoconjugado a células-alvo tumorais (ácido fólico e biotina), bem como com fármacos como metotrexato e ibuprofeno foram preparadas, e o efeito das mesmas sobre a eficiência de incorporação por células tumorais (HeLa e MCF-7) estudada. Os estudos de atividade biológica in vitro foram realizados em parceria com o Laboratório de Processos Fotoinduzidos e Interfaces (LPFI-IQUSP). Os resultadosobtidos confirmaram a possibilidade de se controlar a atividade biológica das nanopartículas por meio dos agentes funcionalizantes, abrindo perspectivas interessantes para o desenvolvimento de nanoagentes multifuncionais para teranóstica, conjugados com agentes de vetorização específicos (particularmente anticorpos e aptâmeros), além de agentes de contraste (radiofármacos, fluoróforos, contraste para IRM, etc.) e moléculas terapêuticas (antitumorais, anti-inflamatórios, dentre outros). Entretanto, diversos são os problemas associados aos processos químicos envolvendo a produção e funcionalização desses nanomateriais por processos convencionais em batelada, que tendem a ser demorados e apresentam dificuldade de controle dos parâmetros de reação e baixa reprodutibilidade, dificultando o escalonamento produtivo e a comercialização dos eventuais produtos. Uma estratégia promissora é o uso de reatores microfluídicos com projeto de canais adequado, além de atuadores e sensores que, juntos garantam excelente controle de processos e baixo consumo de energia e de reagentes. Assim, também foram desenvolvidos reatores microfluídicos para produção e funcionalização de nanopartículas de ouro, de forma a tornar os processos químicos programáveis, mais eficientes, controláveis e econômicos, em parceria com o Laboratório de Micromanufatura do Instituto de Pesquisas Tecnológicas (LMI-BIONANO/IPT). Essa parte do desenvolvimento foi realizando empregando a tecnologia de microfabricação em Low Temperature Co-fired Ceramics (LTCC), uma tecnologia versátil que possibilita a produção de dispositivos de diferentes geometrias em materiais cerâmicos de baixa reatividade e de baixo custo. Esses dispositivos podem tornar os processos de produção de nanopartículas multifuncionais dispersáveis suficientemente simples, versáteis e reprodutíveis para atender aos altos padrões de qualidade exigidos para produtos voltados para aplicações biomédicas / Materials design at nanoscale is leading us to intelligent systems with new properties and applications, such as more efficient diagnostic and treatment systems. Improving the treatment of diseases by the development of more specific and efficient drugs, displaying fewer or no side effects, conjugated with sensitive contrast/diagnostic agents for early preventive monitoring and treatment is one of the main goals of the Nanomedicine. However, the knowledge on surface chemistry required to perform such molecular functionalization/conjugation reactions still is far from being adequately controlled, particularly considering the complexity of biomolecules and reaching colloidal stability. Thus, in this thesis, processes of conjugation of iron oxide nanoparticles (SPIONs) with one or more co-functionalizing agents have been developed so as to generate mono, bi and multi-particles dispersible in aqueous medium. Efforts were specifically focused on the development of drug delivery and diagnostic systems based on nanoparticles whose properties must be adjusted by the conjugation of biomolecules and bioactive species on their surface, in a truly nano/molecular scale engineering work. In fact, nanoparticles modified with stabilizing co-functionalizing molecules (glycerolphosphate, glucose-phosphate, phosphorylethanolamine, dopamine and tiron), targeting agents (folic acid and biotin) to guide itself and concentrate in specific tumor cells, as well as with drugs such as methotrexate and ibuprofen were prepared, and their effect on the efficiency of uptake by tumor cells (HeLa and MCF-7) studied. In vitro biological activity studies were performed in collaboration with the Laboratory of Photo Induced Processes and Interfaces (LPFI-IQUSP). The results confirmed the possibility of controlling the biological activity of nanoparticles by anchoring suitable functionalizing agents in an additive way, opening interesting new perspectives for the development ofmultifunctional theranostics nanoagents, conjugated with specific vectorization agents (particularly antibodies and aptamers), as well as diagnostic (radiopharmaceuticals, fluorophores, MRI contrast, etc.) and therapeutic agents (antitumor, anti-inflammatory, among others). However, there are several problems associated with the production and functionalization of these nanomaterials by conventional batch processes, which tend to be time consuming and difficult to control, as confirmed by their low reproducibility, making it difficult to produce and commercialize the eventual products. A promising strategy is the use of microfluidic reactors with suitable channel designs, as well as actuators and sensors that, together, ensure excellent process control and low energy and reagent consumption. Thus, microfluidic reactors were also developed for the production and functionalization of gold nanoparticles in order to make chemical processes more predictable, efficient, controllable and economical, in partnership with the Micromanufacturing Laboratory of the Institute of Technological Research (LMI-BIONANO/IPT). This part of the development was accomplished by employing the Low Temperature Co-fired Ceramics (LTCC) microfabrication technology, a versatile technology that enables the production of devices of different geometries in ceramic materials of low reactivity and of low cost. These devices can make the production processes of dispersible multifunctional nanoparticles simple, versatile and reproducible enough to meet the high standards of quality required for products for biomedical applications

Enhancement of mechanical, thermal and hygrothermal properties of carbon fiber/vinyl ester (CFVE) composites through nanoparticle reinforcement has been investigated. CFVE composites are becoming more and more attractive for marine applications due to two reasons : high specific strength and modulus of carbon fiber and low vulnerability of vinyl ester resin to sea water. However, the problem with this composite system is that the fiber matrix (F/M) interface is inherently weak. This leads to poor mechanical properties and fast ingress of water at the interface further deteriorating the properties. This investigation attempts to address these deficiencies by inclusion of nanoparticles in CFVE composites. Three routes of nanoparticle reinforcement have been considered : nanoparticle coating of the carbon fiber, dispersion of nanoparticles in the vinyl ester matrix, and nanoparticle modification of both the fiber and the matrix. Flexural, short beam shear and tensile testing was conducted after exposure to dry and wet environments. Differential scanning calorimetry and dynamic mechanical analysis were conducted as well. Mechanical and thermal tests show that single inclusion of nanoparticles on the fiber or in the matrix increases carbon/vinyl ester composite properties by 11-35%. However, when both fiber and matrix were modified with nanoparticles, there was a loss of properties. / by Felicia M. Powell. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

This research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion. / Their composites displayed poor wetting, high void content, high seawater weight gain, and low swelling. Both fiber treatment types resulted in great improvements in dry transverse tensile strength over the untreated fibers, but the oxidized fiber composites lost strength as the acid treatment time was extended, due to poor wetting. The acid/silane treated composites lost some transverse tensile strength after seawater exposure, but the nitric acid oxidized fiber composites appeared to be more seawater durable. / by Tye A. Langston. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

by Yeung Sau Lai Catherine. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Yeung Sau Lai Catherine. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter Chapter1 --- Introduction to the Study of Chinese antique objects using surface science techniques / Chapter 1.1 --- Surface Science --- p.1 / Chapter 1.2 --- Surface Science Techniques --- p.1 / Chapter 1.3 --- Study of Antiques Objects --- p.2 / Chapter 1.4 --- Chinese Antique --- p.4 / Chapter 1.5 --- Aims of the current study --- p.4 / Chapter 1.6 --- Reference --- p.7 / Chapter Chapter 2 --- Silicon on Chinese Bronze Seals / Chapter 2.1 --- Introduction --- p.8 / Chapter 2.2 --- Basic Principles of the analytical techniques --- p.9 / Chapter 2.2.1 --- Scanning electron microscopy (SEM) --- p.9 / Chapter 2.2.2 --- Energy dispersive x-ray analysis (EDX) --- p.9 / Chapter 2.2.3 --- X-ray Photoelectron spectroscopy (XPS) --- p.13 / Chapter 2.3 --- Sample --- p.16 / Chapter 2.4 --- Experimental --- p.18 / Chapter 2.4.1 --- Instrument --- p.18 / Chapter 2.4.2 --- Sampling --- p.18 / Chapter 2.5 --- Results and Discussion --- p.20 / Chapter 2.5.1 --- Chemical Composition --- p.20 / Chapter 2.5.2 --- Silicon content --- p.21 / Chapter 2.5.3 --- Sources of silicon --- p.21 / Chapter 2.5.4 --- Implication of high silicon content --- p.25 / Chapter 2.6 --- Conclusion --- p.28 / Chapter 2.7 --- Related studies --- p.28 / Chapter 2.8 --- Reference --- p.29 / Chapter Chapter 3 --- Surface analysis of Chinese Jade using Fourier Transform Infrared Spectroscopy with fixed angle reflectance technique / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- principles of FTIR and specular reflectance technique --- p.31 / Chapter 3.2.1 --- General principles --- p.31 / Chapter 3.2.2 --- IR spectrometer --- p.31 / Chapter 3.2.3 --- Specular (External) Reflectance Technique --- p.33 / Chapter 3.2.4 --- Kramers-Kronig Transformation --- p.33 / Chapter 3.3 --- Sample (Chinese Jade from the Liang-zhu Culture) --- p.36 / Chapter 3.3.1 --- Background on use of Jade in China --- p.36 / Chapter 3.3.2 --- Nomenclature --- p.39 / Chapter 3.3.3 --- Mineralogy of Jade --- p.39 / Chapter 3.3.4 --- Liang-zhu Culture --- p.40 / Chapter 3.4 --- Experimental --- p.40 / Chapter 3.4.1 --- Instrument --- p.40 / Chapter 3.4.2 --- Sampling --- p.44 / Chapter 3.4.3 --- Data Treatment --- p.44 / Chapter 3.5 --- Results and Discussion --- p.44 / Chapter 3.5.1 --- Characteristic of Specular reflectance spectrum of Nephrite --- p.44 / Chapter 3.5.2 --- Reflectance spectrum of Liangzhu samples --- p.57 / Chapter 3.5.2.1 --- Comparison within sample --- p.57 / Chapter 3.5.2.2 --- Comparison among sample --- p.57 / Chapter 3.5.3 --- "Reflectance spectrum of heirloom pieces from the Art Museum, CUHK" --- p.58 / Chapter 3.5.4 --- Absorption peaks at 3000-2800cm-1 --- p.58 / Chapter 3.6 --- Conclusion --- p.58 / Chapter 3.7 --- Related studies --- p.61 / Chapter 3.8 --- Reference --- p.61 / Chapter Chapter 4 --- SIMS and TIMS Analysis on Lead Isotopes Ratio in Ancient Chinese Metallic Artifacts / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Background --- p.64 / Chapter 4.2.1 --- Lead isotope --- p.64 / Chapter 4.2.2 --- Aims of this study --- p.66 / Chapter 4.3 --- Basic principle of TIMS and SIMS --- p.67 / Chapter 4.4 --- Experimental --- p.68 / Chapter 4.4.1 --- Sample --- p.68 / Chapter 4.4.2 --- Instrument --- p.68 / Chapter 4.4.2.1 --- Thermal Ionisation mass spectrometry --- p.68 / Chapter 4.4.2.2 --- Secondary ion mass spectroscopy --- p.70 / Chapter 4.5 --- Results and Discussion --- p.72 / Chapter 4.5.1 --- Data Interpretation --- p.72 / Chapter 4.5.2 --- Standard deviation of SIMS data --- p.74 / Chapter 4.5.3 --- Possible use of SIMS data --- p.74 / Chapter 4.6 --- Conclusion --- p.76 / Chapter 4.7 --- References --- p.76 / Chapter Chapter 5 --- Analysis by Particle Induced X-ray emission technique / Chapter 5.1 --- Introduction --- p.79 / Chapter 5.2 --- Basic principle --- p.80 / Chapter 5.2.1 --- General principle --- p.80 / Chapter 5.2.2 --- Fundamental Set up --- p.80 / Chapter 5.2.3 --- Data analysis --- p.82 / Chapter 5.3 --- Experimental --- p.82 / Chapter 5.3.1 --- PIXE --- p.82 / Chapter 5.3.2 --- Sample --- p.82 / Chapter 5.4 --- Result --- p.85 / Chapter 5.5 --- Further studies --- p.85 / Chapter 5.6 --- Reference --- p.85 / Chapter Chapter 6 --- Conclusion / Chapter 6.1 --- Conclusion --- p.88 / Chapter 6.2 --- Further studies --- p.89

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Paul Dudley Hartung. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Robert B. Laughlin. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / Ph.D.

[pt] Polpas concentradas de caulim (70 por cento em peso de sólidos) são utilizadas na Indústria de Papel como cobertura. Durante a aplicação da polpa são alcançadas altas taxas de cisalhamento que, associadas às altas viscosidades de polpas concentradas, provocam dificuldades no movimento da lâmina acarretando riscos, bolhas ou até mesmo rasgando o papel. Para minimizar esse efeito, são adicionados agentes dispersantes que causam a redução nos valores da viscosidade. O presente trabalho teve por finalidade caracterizar fisicamente as amostras beneficiadas do caulim da região do Prado/BA e, utilizando-se da Teoria DLVO Clássica, contribuir para uma melhor compreensão sobre os aspectos fundamentais que norteiam a reologia de polpas concentradas de caulim a partir dos fundamentos de química coloidal. A caracterização tecnológica das amostras foi efetuada pelas técnicas de difratometria de raios-X, medição de alvura, análise granulométrica e análise morfológica (MEV e MET). As amostras analisadas revelaram ser, predominantemente, de caulinita; de alvura adequada a Indústria Papeleira para as amostras Coat 90 e Coat 87; de distribuição bimodal para as amostras Coat 90 e Coat 87 e de formato lamelar de perfil irregular, tendo sido encontradas partículas de perfil hexagonal. Posteriormente, foram apreciadas as propriedades eletrocinéticas das amostras. Foi medido o potencial zeta das amostras na ausência e na presença do dispersante hexametafosfato de sódio em função do pH e da concentração do dispersante em força iônica constante. A análise dos resultados revelou: que as amostras Coat 90 e Coat 87 possuem ponto isoelétrico de 3,5, enquanto o caulim Extra Fino possui ponto isoelétrico de 3,2; que o potencial zeta assume valores mais negativos com o aumento do pH e com o aumento da concentração de dispersante e que o ânion proveniente da dissociação do hexametafosfato de sódio adsorve quimicamente à superfície das amostras. De posse dos dados de potencial zeta, utilizou-se a Teoria DLVO para calcular a energia de interação total existente entre as partículas da amostra de caulim Coat 90. Após a análise dos resultados, ficou evidente que, para valores de pH maiores ou iguais a 5, existe uma barreira energética que aumenta de intensidade com o aumento do pH e da concentração de dispersante onde, com o aumento do pH, houve uma tendência à estabilização e, no caso da concentração, foi obtido um valor máximo em 3kg/t de dispersante (após este valor não houve aumento da barreira energética). Nessas curvas também foi observada a existência de um mínimo secundário que, embora pequeno (~2kT), revelou a possibilidade de adesão reversível. A análise reológica da amostra de caulim Coat 90 foi realizada a partir da comparação das viscosidades aparentes encontradas para taxas de cisalhamento constantes (100s-1 ou 1000s-1) e após a mesma quantidade de tempo (280s) já que as polpas eram tixotrópicas. Esses dados revelaram que, com o aumento do pH, as polpas atingem valores mínimos de viscosidade, onde para cada concentração de dispersante foi atingido um patamar diferente. O menor valor de viscosidade foi obtido em 3kg/t de dispersante, onde a partir desse ponto a viscosidade passou a aumentar levemente. Finalmente, os dados reológicos foram confrontados com os calculados pela Teoria DLVO Clássica, onde foi revelada a existência de um valor de energia de interação total (~400kT) comum a todas as concentrações de dispersante que indica um grau máximo de estabilidade da polpa, isto é, as partículas encontram-se tão afastadas umas das outras que o movimento relativo entre elas durante o cisalhamento não é mais afetado. Concluiu-se que, apesar das interações interparticulares serem de natureza microscópica e a viscosidade uma medida macroscópica, a Teoria DLVO foi capaz de explicar qualitativamente o compor / [en] Concentrated kaolin pulps (70 percent solid weight) are utilized as coatings in the paper industry. During the pulp application, high shear rates are obtained. Shear rates associated to high viscosities incite difficulties on the lamina movement generating risks, bubbles or even tearing the paper. To minimize this effect dispersant agents are added. The aim of the present work was to characterize physically the Prado region (Bahia State) kaolin particles and, using the DLVO theory, contribute for a better understanding about the fundamental aspects of kaolin concentrated pulps rheology via colloidal chemistry. Sample technological characterization was carried out with X-Ray difractometry technique, brightness measurements, size measurements, particle distribution and morphological analysis (MEV and MET). Samples were, predominantly, of kaolinite; samples Coat 90 and Coat 87 were of adequate brightness for Paper Industry and presented two peaks and all samples were platelike with irregular edges where hexagonal particles were found. Sample electrokinetic properties were appreciated afterwards. Zeta potential measurements were taken in the absence and in the presence of sodium hexametaphosphate dispersing agent as a function of pH and dispersant concentration using constant ionic strength. Result analysis revealed: Coat 90 and Coat 87 samples had 3,5 of isoelectric point, while Extra Fino sample had 3,2 of isoelectric point; zeta potential values became more negative with pH and dispersant concentration rising and the anion of sodium hexametaphosphate dissolution chemically adsorbs to sample surfaces. Zeta potential values were used to obtain total interparticular interaction energy by means of DLVO theory. These procedures were done only for Coat 90 sample. It became clear that, for pH values equals or higher than 5, exists an energy barrier whose values rise as pH and dispersant concentration increases. It has been noted that for pH increase, the tendency of energy barrier was to stabilize. In the case of dispersant concentration increase, was obtained maximum value (3kg/t). By data observation, a secondary minimum was noted. However the secondary minimum is low (~2kT), it revealed the possibility of reversible adhesion. The rheological analysis of Coat 90 kaolin sample was realized by comparison of apparent viscosities found on constant shear rates (100s-1 and 1000s- 1) and after the same time (280s) because pulps were thixotropic. The investigation showed that with pH increase, pulps had their viscosity reduced. Each dispersant concentration value generates a different viscosity, where the smallest viscosities were achieved in 3kg/t. Within the increase of dispersant concentration, viscosity had its values improved. Finally, rheological data were coordinated with those calculated from DLVO theory. It was observed that there is a total interaction energy value (~400kT) common to all dispersant concentrations. This point means that pulp stability is maximum, in other words, particles are so far from each other that relative movement among them is not affected anymore. The conclusion of this work is that, however interparticular forces are of microscopic nature and viscosity is a macroscopic measure, DLVO theory was able to explain qualitatively the rheological behavior of kaolin concentrated pulps.

Zinc deficient soils, or soils with low Zn bioavailability, are widespread, which exacerbates Zn deficiency in human as crops grown on these soils have low Zn content. Often crop yields are also compromised. Fertilizers based on soluble Zn salts often have limited efficacy in such soils. In this research, we evaluate the performance of polymer coated and bare ZnO nanoparticles (NPs) in an attempt to overcome limitations of soluble Zn salts in alkaline soils. We first synthesized 20-30 nm bare ZnO NPs with different surface chemistries to impart colloidal stability to the particles. Bare ZnO were treated in phosphate solution under certain conditions leading to the formation of a core made of ZnO NPs that is covered by a shell of amorphous Zn3(PO4)2 (core-shell NPs). This confers a negative charge to the particles over a wide pH range. The addition of nonionic (neutral dextran) and polyelectrolyte (negatively charged dextran sulfate (DEX(SO4)) during the synthesis resulted in the formation of DEX and DEX(SO4) ZnO NPs. Dextran has a minimal effect on the surface charge of ZnO but dextran sulfate confers a net negative charge. Bare and core-shell ZnO NPs were both electrostatically stabilized whereas DEX and DEX(SO4) ZnO NPs were sterically and electrosterically stabilized, respectively. We investigated the effect of treating seeds with ZnO NPs on the growth and accumulation of Zn in wheat (Triticum aestivum) seedlings in comparison to ZnSO4. All ZnO NPs stimulated seedling growth. Seedlings accumulated higher Zn concentrations when treated with ZnO NPs than with ZnSO4. Zinc sulfate was toxic even at the lower exposure concentrations, which was demonstrated by significantly lower germination success and seedling growth. In the second experiment, we investigated the effect of pH on the attachment and dissolution of ZnO NPs in soil, as compared to ZnSO4. Soil pH was adjusted to 6 and 8, then the soil was spiked with 100 mg Zn/kg soil in the form of ZnSO4, bare, DEX, DEX(SO4), and core-shell ZnO NPs. The results showed that DEX and core-shell ZnO NPs had significantly higher total Zn in soil solution compared to ZnSO4 at pH 8, with little dissolution. Dissolved Zn was similar among treatments except ZnSO4 at pH 6, indicating little dissolution of the ZnO NPs at either pH value. We also found that the engineered coatings dictate the behavior of the particles in simple aqueous systems, but their properties are altered in natural soil solutions because of the dominant effect of natural organic matter (NOM) on their surface chemistry. Based on the outcomes of the previous two experiments, we selected DEX and bare ZnO NPs to test the efficacy of ZnO NPs in delivering Zn to the grain of wheat under greenhouse conditions. We performed two independent studies where seeds were either treated with the NPs or grown in a soil spiked with Zn at pH 6 and 8 and spiked with Zn treatments (nano and ionic). We found that treating seeds with bare ZnO NPs significantly enhanced grain Zn concentrations as compared to the control, DEX-ZnO NPs, and ZnSO4. There were no differences in grain Zn concentration of plants treated with ionic or nano Zn treatments regardless of the soil pH. This work has elucidated important principles which will help carry forward efforts at developing effective ZnO NP-based fertilizers. It also suggests that treatment of seeds with ZnO NPs is more effective than amending soil or treating seeds with ZnSO4.