This doctorate thesis focuses on investigating the parameter space involved in numerically modeling the bandgap engineering of a GaInP/InGaAs/Ge lattice matched multi-junction solar cell (MJSC) using InAs/InGaAs quantum dots (QDs) in the middle sub-cell. The simulation environment – TCAD Sentaurus – solves the semiconductor equations using finite element and finite difference methods throughout well-defined meshes in the device to simulate the optoelectronic behavior first for single junction solar cells and subsequently for MJSCs with and without quantum dots under concentrated illumination of up to 1000 suns’ equivalent intensity. The MJSC device models include appropriate quantum tunneling effects arising in the tunnel junctions which serve as transparent sub-cell interconnects. These tunneling models are calibrated to measurements of AlGaAs/GaAs and AlGaAs/AlGaAs tunnel junctions reaching tunneling peak current densities above 1000 A/cm^2. Self-assembled InAs/GaAs quantum dots (QDs) are treated as an effective medium through a description of appropriate generation and recombination processes. The former includes analytical expressions for the absorption coefficient that amalgamates the contributions from the quantum dot, the InAs wetting layer (WL) and the bulk states. The latter includes radiative and non-radiative lifetimes with carrier capture and escape considerations from the confinement potentials of the QDs. The simulated external quantum efficiency was calibrated to a commercial device from Cyrium Technologies Inc., and required 130 layers of the QD effective medium to match the contribution from the QD ground state. The current – voltage simulations under standard testing conditions (1 kW/cm^2, T=298 K) demonstrated an efficiency of 29.1%, an absolute drop of 1.5% over a control structure. Although a 5% relative increase in photocurrent was observed, a 5% relative drop in open circuit voltage and an absolute drop of 3.4% in fill factor resulted from integrating lower bandgap nanostructures with shorter minority carrier lifetimes. However, these results are considered a worst case scenario since maximum capture and minimum escape rates are assumed for the effective medium model. Decreasing the band offsets demonstrated an absolute boost in efficiency of 0.5% over a control structure, thus outlining the potential benefits of using nanostructures in bandgap engineering MJSCs.

Philosophiae Doctor - PhD / This study firstly reports the development, characterisation, and application of thick-film acetylcholinesterase (AChE) biosensors based on a gold electrode modified with a mercaptobenzothiazole (MBT) self-assembled monolayer and either poly(omethoxyaniline) (POMA) or poly(2,5-dimethoxyaniline) (PDMA) in the presence of polystyrene(4-sulphonic acid) (PSSA). The Au/MBT/POMA-PSSA/AChE and Au/MBT/PDMA-PSSA/AChE biosensors were then applied to successfully detect standard organophosphorous and carbamate pesticides in a 0.1 M phosphate buffer, 0.1 M KCl (pH 7.2) solution. Secondly, it reports the construction of the Au/MBT/PANI/AChE/PVAc thick-film biosensor for the determination of certain organophosphate and carbamate pesticide solutions in selected aqueous organic solvent solutions. / South Africa

xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Altering and controlling the properties of solid surfaces in aqueous or other liquid phase environments has been a sought after objective for decades. With the discovery of chemisorbed self-assembled monolayers, this dream has become a reality. Oxide and metal surfaces can now be readily coated with an array of commercially available products to produce a desired fnctionality. The presence of these coatings on solid surfaces affects properties of the interfacial region by altering interfacial electrostatic fields, changing the structure of interfacial water molecules and altering the interactions of adsorbed species. This dissertation reports on in situ studies of adsorption at several solid/aqueous interfaces using vibrational sum-frequency spectroscopy, a surface specific technique. These studies are augmented by the use of atomic force microscopy and contact angle goniometry to characterize the prepared surfaces and their interactions with adsorbates. The studies investigate how changes in the surface structure and chemistry, as well as the bulk aqueous phase, affect interfacial structure. The studies within are primarily focused on the interactions of water with bare and functionalized fused silica and the relationship between the aqueous phase composition and the structure of fluorocarbon and hydrocarbon self-assembled monolayers. The variations in aqueous structure are then examined in detail using ionic strength controlled experiments to understand the direct interactions of water hydrophobically coated silica. This analysis is followed by an investigation of the competitive adsorption of methanol and water at fluorocarbon and hydrocarbon monolayers which show spectroscopic signatures of the interaction strength between fluorocarbons and hydrocarbons. Further studies are performed using butylammonium chloride to verify these spectroscopic signatures and reveal different molecular structures of adsorbed species at chemically different hydrophobic surfaces. Lastly, specific ion effects on the CaF 2 /water interface are shown using equilibrium and time-resolved sum-frequency spectroscopy. The results of all these studies have implications for an array of surface chemical applications from mineral flotation to biocompatibility. This dissertation includes previously published co-authored material. / Committee in charge: Thomas Dyke, Chairperson, Chemistry; Geraldine Richmond, Advisor, Chemistry; James Hutchison, Member, Chemistry; Mark Lonergan, Member, Chemistry; Qusheng Jin, Outside Member, Geological Sciences

Este trabalho consistiu de estudos da viabilidade da geração e identificação de radicais livres envolvidos em processos oxidativos avançados por via eletroquímica. Para a geração e identificação de radicais livres em eletrodos modificados com organotióis via eletroquímica, escolheu-se uma técnica pouco aplicada para este fim; a espectroscopia de impedância eletroquímica, e o ajuste dos dados experimentais pela proposta de modelos de circuitos equivalentes. O eletrodo de trabalho utilizado (Au) foi caracterizado em meio ácido e básico e diversas monocamadas auto-organizadas conhecidas foram adsorvidas sobre o mesmo e também caracterizadas por esta técnica. Parâmetros importantes como constante dielétrica, capacitância de uma monocamada livre de defeitos e grau de recobrimento foram determinados com êxito. Também foram empregadas moléculas menos utilizadas como modificadoras de eletrodos (fenotiazinas e derivados). As mesmas foram caracterizadas no sistema Au/adsorvente/NaOH, pois, o pH alto garante a formação do radical superóxido e do ânion hidroperóxido. Os mesmos modelos de circuitos equivalentes puderam ser empregados na obtenção dos parâmetros físicos relativos a essas moléculas no sistema eletroquímico utilizado. Em uma etapa subsequente obteve-se a valiosa informação, se as moléculas adsorvidas sobre Au poderiam ser usadas para a geração de superóxido e outros radicais. As monocamadas de tióis, quando utilizadas para gerar radicais livres, se mostraram aptas a gerar superóxido em meio alcalino saturado com oxigênio molecular. Como se demonstrou na etapa de caracterização, as SAM-3 e SAM-6 não formaram um empacotamento totalmente hidrofóbico. Por este motivo, mesmo que superóxido tenha sido gerado, não pôde ser detectado. Já para a fenotiazina e seu metil-derivado, a cinética de adsorção e a utilização de soluções aquosas impediram a formação de um filme completo e homogêneo, imprescindível para a constituição de uma interface hidrofóbica e isolante. Além disso, possíveis reações de complexação entre as moléculas e superóxido, reações entre a fenotiazina cátion-radical e superóxido fazem necessários mais estudos acerca da natureza eletroquímica do sistema, que já é bastante conhecido fotoquimicamente. Posterior a modificação, todos os eletrodos se mostraram ser bastante sensíveis ao pH e aos eletrólitos utlizados, alterando-se a estrutura interna muito facilmente, o qual implica uma limitação no tempo de uso e reprodutibilidade quando da geração de um radical tão reativo quanto superóxido. / This work consisted in testing the viability of investigations into the electrochemical generation and identification of free radicals involved in advanced oxidative processes. In these studies, a technique which is rarely used for the electrochemical generation and identification of free radicals at organothiole-modified electrodes, electrochemical impedancy spectroscopy, was chosen and the experimental data obtained were fitted by equivalent circuit models. A working electrode (Au) was characterized in both acidic and basic media and several known self-assembled monolayers were adsorbed over this electrode and also characterized using this technique. Important parameters such as dielectric constants, capacitance of the monolayers free of defects and coverage were determined with success. Other lesser-known molecules such as phenothiazines and their derivatives were also used .The modified electrodes were characterized in NaOH solution, since the high pH assures the production of superoxide radicals and hydroperoxylate anions. The equivalent circuit model was employed to obtain physical parameters for these molecules in the electrochemical systems studied. In a subsequent step, a valuable piece of information was obtained; it was noted that the molecules adsorbed over Au could be used in order to generate superoxide and other radicals. The ability of thiol monolayers used in the generation of free radicals, to produce superoxides in alkaline media saturated with molecular oxygen was demonstrated. However, characterization of the self-assembled monolayers, SAM-3 and SAM-6, revealed that these were not able to pack in a completely hydrophobic manner. This may account for the fact that the superoxide could not be detected even when it was believed to have formed. For the phenothiazine-modified electrodes, the adsorption kinetics and the utilization of aqueous solutions prevented the formation of an intact and homogeneous film, which is essential in establishing a hydrophobic and isolating interface. Furthermore, possible complexation reactions between the molecules and the superoxide and reactions between the phenothiazine cation-radical and superoxide, point to the need for further studies regarding the electrochemical nature of this system, whose photochemical properties are very well known. Following modification, all the electrodes were shown to be too sensitive to pH and to the electrolytes used, since the inner structure was easily modified, which implies that they would have a limited time of use and in addition that the reproducibility of the rate of generation of reactive radical species such as superoxides could be compromised.

Dans le but de développer des matériaux et des dispositifs avec de nouvelles propriétés, l’élaboration de monocouches auto-assemblées (SAM) est un sujet d'intérêt croissant dans le domaine des nanosciences. Les SAM sont des agrégats bidimensionnels formés par des molécules régulièrement espacées sur une surface et liées entre elles par des forces non covalentes. Le domaine des biocapteurs électrochimiques pour la reconnaissance des brins d'ADN est parmi les applications les plus récentes des SAM. Dans ce cadre, nous avons mené une étude théorique des mécanismes fondamentaux engagés lors de l’adsorption de la molécule quinone Jug-C4-thiol sur la surface Au (111). Les résultats ont été confrontés aux mesures expérimentales accessibles réalisées par l’équipe « nano 2D » au laboratoire ITODYS (Université Paris7). Tout d’abord, la théorie de la fonctionnelle de la densité PBE et PBE-D2 a été utilisée pour étudier les mécanismes mis en jeu (physisorption ou chimisorption) lors de l’adsorption de la molécule isolée à la surface de Au (111) et déterminer le site le plus favorable pour chaque mécanisme. La nature de la liaison entre la molécule et la surface de a été finement analysée à l’aide de calculs de densité d’états (DOS) et de différences de densités de charge. Ensuite, l'assemblage de la molécule quinone Jug-C4-thiol sur la surface Au (111) a été étudié. Cet assemblage des molécules a été initié par la formation de configurations de dimère à travers la formation de liaisons intermoléculaires (liaison hydrogène et π-stacking, …). Les spectres infrarouges des configurations les plus stables ont été simulés et confrontés à l’expérience. Et enfin, le mécanisme d’échange entre des molécules « hôtes » (alcanethiols C12H25SH préalablement assemblés sur la surface) et « invitées » (Jug-C4-thiols) a été exploré avec les outils théoriques. L’analyse des résultats a mis en évidence des informations structurales et énergétiques importantes sur la formation de la monocouche moléculaire mixte. / In order to develop materials and devices with new properties, the development of self- In order to develop materials and devices with new properties, the development of self-assembled monolayers (SAM) is a topic of growing interest in the field of nanoscience. SAM are two-dimensional aggregates formed by molecules regularly spaced on a surface and bonded together by non-covalent forces. The field of electrochemical biosensors for DNA strand recognition is among the most recent applications of SAM. In this context, we conducted a theoretical study of the fundamental mechanisms involved in the adsorption of the quinone Jug-C4-thiol molecule on the Au (111) surface. The results were compared to the accessible experimental measurements from the "nano 2D" team at the ITODYS laboratory (Paris 7 University). First, the density functional theory at PBE and PBE-D2 levels was used to study the mechanisms involved (physisorption or chemisorption) during the adsorption of the isolated molecule on the surface of Au (111) and access to the most favorable site for each mechanism. The nature of the binding between the molecule and the surface was finely analyzed using density of states (DOS) calculations and differences in charge densities.Then, the assembly of the quinone Jug-C4-thiol molecule on the Au (111) surface was studied. This assembly of molecules was initiated by the formation of dimer configurations through the formation of intermolecular bonds (hydrogen bonding and π-stacking, etc.). The infrared spectra of the most stable configurations were simulated and compared with the experiment. And finally, the mechanism of exchange between "host" molecules (C12H25SH alkanethiols previously assembled on the surface) and "invited" molecules (Jug-C4-thiols) was explored with the theoretical tools. The analysis of the results revealed important structural and energetic informations on the formation of the mixed molecular monolayer.

O transistor de efeito de campo de porta estendida e separada (SEGFET) é um dispositivo alternativo ao tradicional transistor de efeito de campo seletivo a íons (ISFET). A grande vantagem desse dispositivo se refere ao seu fácil processamento, ou seja, se restringe somente a manipulação do eletrodo de porta, evitando processos convencionais de microeletrônica. Neste sentido, sensores iônicos e biossensores podem ser facilmente implementados combinando materiais de reconhecimento químico e/ou biológico. Por sua vez, a técnica de fabricação de filmes finos camada por camada (layer-by-layer, LbL) se mostra versátil para manipulação de diversos tipos de materiais em nível molecular. Materiais orgânicos e inorgânicos podem ser automontados em substratos sólidos por meio da simples adsorção eletrostática formando compósitos com propriedades únicas com o objetivo de serem aplicados em sensores ou biossensores. Neste trabalho, o conceito de dispositivo SEGFET foi combinado com a técnica LbL por meio da manipulação de materiais orgânicos (polieletrólitos, dendrímeros e polianilina) e inorgânicos (TiO2 e V2O5) nanoparticulados a fim de se obter novos sensores de pH e biossensores para a detecção de glicose e uréia, dois importantes analitos de interesse clínico. Numa primeira etapa, diferentes filmes LbL foram produzidos, caracterizados e testados como camada sensível (porta estendida) em dispositivos SEGFETs. Todos os sistemas estudados se mostraram promissores como sensores de pH, ou seja, com uma sensibilidade próxima do valor teórico sugerido pela equação de Nernst (59,15 mV.pH-1). Esses resultados podem ser atribuídos à natureza anfotérica do material da última camada no filme LbL. Numa segunda etapa, as enzima glicose oxidase (GOx) e urease foram convenientemente imobilizadas nos filmes LbL. Pelo fato dessas enzimas gerarem ou consumirem prótons durante a catálise da reação, os filmes LbL modificados enzimaticamente foram utilizados em biossensores de glicose e uréia, apresentando eficiente detecção. Assim, a união de dispositivos SEGFET com a técnica de automontagem se mostrou promissora para construção de sensores e biossensores eficientes e de baixo custo. / Separative extended gate field-effect transistor (SEGFET) device is an alternative to the conventional ion-sensitive field-effect transistor (ISFET). The great advantage of SEGFET refers to its easy processing, i.e., it is limited under only manipulation of the gate electrode, avoiding the conventional microelectronic processes. In this way, ion sensors and biosensors can be easily implemented combining chemical and/or biological recognition materials. In turn, the layer-by-layer (LbL) technique shows be versatile for handling various types of materials at molecular level. In this thesis, the concept of SEGFET device was combined with the LbL technique through the manipulation of organic (polyelectrolytes, dendrimers and poly (aniline)) and inorganic materials (TiO2 and V2O5 nanoparticles) in order to get new pH sensors and biosensors for the detection of glucose and urea, two important analytes of clinical interest. In a first step, different LbL films were produced, characterized and tested as the sensitive layer (extended gate) in SEGFETs devices. All studied systems were promissing as pH sensors, i.e., with a sensitivity close to the theoretical value suggested by Nernst equation (59.15 mV.pH-1). These results can be attributed to the amphoteric nature of the material in the last layer of the LbL films. In a second step, glucose oxidase (GOx) and urease enzymes were conveniently immobilized onto LbL films. Because these enzymes generate or consume protons during catalysis of the reaction, the enzymatically modified LbL films were used in biosensors for glucose and urea, with efficient detection. Thus, the union of SEGFET devices with the LbL technique is promising to building up efficient and low-cost sensors and biosensors.

Neste trabalho foi utilizada Espectroscopia Vibracional por Geração de Soma de Freqüências, uma técnica óptica não-linear que é sensível à conformação molecular em interfaces e superfícies, para caracterizar o ordenamento molecular de filmes poliméricos automontados de polieletrólitos durante todos os passos do processo de fabricação, tendo como modelo o par de polieletrólitos PAH (poli(cloreto de alilamina)) / PSS (poli(estireno sulfonato de sódio)). Os espectros SFG permitiram verificar que durante o mergulho (in situ) do substrato na solução de polieletrólitos, estes adsorvem, mas se encontram numa configuração desordenada. Observou-se também que a secagem dos filmes pela ação de jato de nitrogênio produz filmes menos homogêneos do que por secagem espontânea, e às vezes até destruindo completamente o ordenamento molecular. Além disso, verificou-se também que camadas de polieletrólitos adsorvidas influenciam o ordenamento das camadas previamente adsorvidas. Com base nos resultados, modelos para a representação das estruturas desses filmes de polieletrólitos in situ e ex situ foram propostos. / In this work, Sum-Frequency Vibrational Spectroscopy, a nonlinear optical technique that is sensitive to molecular conformation at interfaces and surfaces, was used to characterize the molecular ordering of self-assembled films during all steps of self-assembly, having as model poly(allylamine hydrochloride) (PAH) / poly(styrene sulfonate) (PSS) polyelectrolyte assemble. SFG spectra showed that during immersion (in situ) of substrate in polyelectrolytes solutions, adsorption occurs but the molecules are in a disordered configuration. It was observed that the films drying by nitrogen flow are more inhomogeneous than those dried by spontaneous water evaporation. In some cases, dried films by nitrogen flow are quite disordered. Furthermore, it was observed that polyelectrolytes layers affect the ordering of the previously adsorbed layers. Based on our results, models were proposed to represent the structure of polyelectrolytes films in both: in situ and ex situ.

A técnica de Microbalança de Cristal de Quartzo (QCM) tem sido utilizada para a aplicação em biossensores. Esta técnica consiste no monitoramento da freqüência de oscilação do cristal de quartzo e a variação de freqüência está relacionada com a variação de massa na superfície do cristal por meio da equação de Sauerbrey. Porém, sabe-se que há discrepância entre a massa calculada pela equação de Sauerbrey e a massa real aderida na superfície do cristal de quartzo, sendo tal discrepância causada por fatores tais como a viscoelasticidade, o que é especialmente observado para macromoléculas e sistemas biológicos. Com a técnica de Admitância Eletroacústica (AE) é possível analisar a massa real devido à análise em separado dos parâmetros que compõem o circuito equivalente do cristal de quartzo e também inferir informações sobre a estrutura das monocamadas montadas sobre a superfície do cristal de quartzo. Neste trabalho foi utilizada técnica de AE para se potencializar e detalhar o estudo da formação de monocamadas automontadas e interações entre diferentes proteínas e carboidratos. Em muitos casos verificou-se que durante a formação de determinadas monocamadas, grande parte da variação de massa estava relacionada a interações fracas e não-específicas. Também durante a formação das monocamadas de tióis de cistamina, verificou-se que a estrutura da monocamada é extremamente dependente das concentrações iniciais de cistamina utilizadas para formar a monocamada. As interações entre proteínas e carboidratos foram realizadas após formação de multicamadas nas quais as proteínas eram imobilizadas para depois estudar-se, então, sua interação com carboidratos específicos. No caso da Jacalina, um tipo de lectina, observou-se interações bastante específicas com a fetuína e interações fracas com a alfa-lactose. A atividade da enzima GumH também foi testada com sucesso utilizando a técnica de AE. / The Quartz Crystal Microbalance (QCM) has been largely used for biosensor applications. This technique consists on monitoring quartz crystal oscillation frequency. The relationship of quartz crystal frequency variation with mass deposited on the crystal surface is described by Sauerbrey´s equation. However, the relationship is not directly inferred and discrepancy exists caused mainly by viscoelasticity features of mass adsorbed on the quartz crystal surface. The viscoelastic influence is very common to be observed especially for macro-molecules and biological systems. By using Electroacoustic Admittance (EA) technique it is possible to calculate and separate the real mass deposited over the quartz crystal from other contributions. Therefore, the EA was used to infer about self-assembly monolayer structure being deposited over the quartz crystal. In this work EA technique was used to study details of self-assembled monolayer formation and specific interactions between different proteins and carbohydrate molecules. It was observed that during monolayer formation the majority of mass variation was related to non-specific interactions. For instance, regarding cystamine monolayer formation it was observed that the monolayer structure is dependent on the cystamine concentrations in the liquid medium. The study of interactions between proteins and carbohydrates was conducted by means of multilayers approach in which the proteins are immobilized previously to study the interaction between its active sites and carbohydrates. In the specific case of Jacalin, a type of lectin, it was observed a large formation of specific bonding between this protein and alpha-lactose or fetuin. The GumH enzyme activity was also tested successfully by using of EA technique.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Este trabalho teve como objetivo a preparaÃÃo de nanopartÃculas de derivados da galactomanana. O polissacarÃdeo (galactomanana) foi extraÃdo de sementes da Dimorphandra gardneriana com rendimento de 29Â3% e razÃo manose/ galactose (M:G) de 1,93Â0,02. A galactomanana foi modificada por reaÃÃo de sulfataÃÃo (FDS), oxidaÃÃo (FDO) e por acilaÃÃo com anidrido acÃtico (FDAc) e com anidrido propiÃnico (FDPr). Os derivados foram utilizados no desenvolvimento de nanopartÃculas por interaÃÃo com a quitosana via complexaÃÃo polieletrolÃtica, por formaÃÃo de base de Schiff, e por auto-organizaÃÃo. Os derivados da galactomanana foram caracterizados por espectroscopia na regiÃo do infravermelho (IV), por ressonÃncia magnÃtica nuclear, por anÃlise elementar, por cromatografia de permeaÃÃo em gel e por viscosidade intrÃnseca. O grau de substituiÃÃo para reaÃÃo de sulfataÃÃo foram 0,32 e 0,42. A razÃo de unidades glicosÃdicas/unidades oxidadas para os derivados oxidados foram 10:2; 10:4 e 10:8. Os derivados hidrofÃbicos foram confirmados pelo aparecimento de uma nova absorÃÃo em 1740 cm-1 no IV, atribuÃda ao estiramento C=O e a insolubilidade em Ãgua. NanopartÃculas com perfil unimodal foram obtidas nas trÃs rotas estudadas. As partÃculas de quitosana e galactomanana sulfatada foram obtidas por complexaÃÃo polieletrolÃtica com diÃmetros variando de 10Â6 a 377Â29 nm, Ãndice de polidispersividade de 0,11Â0,02 a 0,5Â0,1 e potencial zeta de â28Â2 a 59Â4 mV. Para as de quitosana e galactomanana oxidada obtidas via base de Schiff com diÃmetros variando de 8Â2 a 20Â9 nm, Ãndice de polidispersividade de 0,36Â0,04 a 0,57Â0,08 e potencial zeta de 0,4Â0,5 a 14Â1 mV. PartÃculas de galactomanana modificadas hidrofobicamente foram obtidas via auto-organizaÃÃo com diÃmetros variando de 35,3Â0,6 a 213Â28 nm, Ãndice de polidispersividade de 0,093Â0,003 a 0,9Â0,1 e potencial zeta de â26,3Â0,9 a â3Â2 mV. O diÃmetro, potencial zeta e Ãndice de poidispersividade sÃo influenciados pela metodologia e derivado utilizado, mas para todos os derivados da galactomanana obteve-se, em pelo menos uma condiÃÃo, nanopartÃculas compatÃveis para um potencial uso como carreadores de fÃrmacos. Fatores como: grau de modificaÃÃo, razÃo, ordem de adiÃÃo e concentraÃÃo dos polissacarÃdeos, pH e a adiÃÃo de fÃrmaco influenciaram no tamanho, Ãndice de polidispersividade, potencial zeta e estabilidade em soluÃÃo das partÃculas. / This work aimed the preparation of nanoparticles galactomannan derivatives. The polysaccharide (galactomannan) was from seeds of Dimorphandra gardneriana with yield of 29Â3% and mannose/galactose ratio (M:G) of 1.93Â0.02. The galactomannan was modified by sulfation raction (FDS), oxidation (FDO) and by acylation with acetic anhydride (FDAc) and proponic (FDPr) and derivates were used in the developmentof nanoparticles by interaction with chitosan by polyelectrolyte complexes, Schiff base formation and by self-assembled. Galactomannan derivatives were characterized by infrared spectroscopy (IR), nuclear magnetic resonance, elemental analysis, gel permeation chromatography and intrinsic viscosity. The degree of substitution for sulfataion reaction were 0.32 and 0.42; the ratio of glycosidic/oxidized units in oxidized derivatives was 10:2; 10:4 and 10:8. The hydrophobic derivatives were confirmed by the appearance of new absorption at 1740 cm-1 in IR, assigned to C=O stretching and water insolubility. Nanoparticles with unimodal profile were obtained on three routes studied. The particles of chitosan and sulfated galactomannan were obtained by complexation polyelectrolytic with diameters ranging from 10Â6 to 377Â29 nm, polydispersity index from 0.11Â0.02 to 0.5Â0.1 and zeta potential of â28Â2 to 59Â4 mV. For chitosan and oxidized galactomannan nanoparticles, obtained by Schiff base, diameters ranging from 8Â2 to 20Â9 nm, polydispersity index from 0.36Â0.04 to 0.57Â0.08 and zeta potential of 0.4Â0.5 to 14Â1 mV were obatined. Hydrophobically modified galactomannan particles were obtained by self-assembled with diameters ranging from 35.3Â0.6 to 213Â28 nm, polydispersity index from 0.093Â0.003 to 0.9Â0.1 and zeta potential of â26.3Â0.9 to â3Â2 mV. The diameter, zeta potential and polydispersity index are influenced by the methodology and derived used, but for all derivatives of galactomannan at least one condition shows nanoparticles compatible for potential use as drug carriers. Factors such as degree of modification, ratio, order of addition and concentration of polysaccharides, pH and addition of drug have influence on size, polydispersity index, zeta potential and solution stability of the particles.

Orientador: Lauro Tatsuo Kubota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-06T00:45:50Z (GMT). No. of bitstreams: 1 Carvalhal_RafaelaFernanda_M.pdf: 708037 bytes, checksum: ed89f8b11b63131a7f452b5191b27432 (MD5) Previous issue date: 2005 / Mestrado / Quimica Analitica / Mestre em Química