No description available.

No description available.

Twenty different materials have been successfully deposited as Langmuir- Blodgett monolayer films. All exhibit second harmonic generation (SHG) when irradiated with laser light at 1064 nm. E-1-docosyl-4-{2-(4-dimethylami nophenyl)ethenyl}quinolinium bromide (C22H45QHBr) and E-1-docosyl-4-{2-(4-dimethy laminonaphthyl)ethenyl}quinolinium bromide (C22H45QNBr) have been deposited separately as multilayer films. They form Y-type structures when deposition is alternated with the material N-docosyl-4- methylquinolinium bromide. The nonlinear responses are quadratic up to 20 and 10 bilayers respectively and the response from the thick films is only 2 orders less than that produced by a Y-cut quartz plate. Similar results were obtained with C22H45QHBr when interleaved with 4,4'-dioctadecyl-3,5,3', 5'- tetra me thyldipyrrylmethenehydrobromide. Ellipsometry studies of the 10 bilayer film of C H45QNBr indicate that the structure is interdigitated. This explains the stability of the film which gave the same SH response up to 6 months after deposition. A 10 bilayer films has also been fabricated using E-1- docosyl-4-{2-(4-{2-(4-dimethylaminophenyl)ethenyl}benzyl)ethenyl}pyridinium bromide (C22H45PBHBr) alternated with E-1-docosy1-4-{2-(4-methylphenyl)ethenyl}pyridinium bromide (C22H45PT). E-1-octadecyl-4-{2-(4-methyloxyphenyl)ethenyl}pyridinium iodide and E-1- methyl-4-{2-(4-octadecyloxyphenyl)ethenyl}pyridinium iodide have been fabricated into monolayer films that are transparent at 1064 and 532 nm, therefore resonant enhancement does not contribute to their nonlinear response which is attributed solely to charge transfer in the molecule. Mixed solutions of E-1-octadecyl-4-{2-(4-methyloxyphenyl)ethenyl}pyridinium iodide and sodium octadecylsulphate (C1SH37OSO3 Na+) have been deposited as very stable monolayers. The nonlinear response from the mixed film offers a significant improvement upon the performance of the film containing pure hemicyanine. Novel zwitterionic materials have been fabricated as LB monolayers that also exhibit SHG.

The work in this thesis can be split into three areas. In the first, inelastic electron tunnelling spectroscopy (IETS) is used to investigate resistive and bias polarity dependent effects on vibrational mode energy in metal - aluminium oxide - metal tunnel junctions. It is shown that even when four point-probe techniques are used the ratio of width to thickness of the electrodes used in IET junctions has an effect on both the breadth and position of spectral lines. A simple treatment based upon work done by Giaever allows for such effects to be corrected. Work done on top metal and polarity effects in undoped IET junctions investigated the effect on the position of the 450 meV mode on reversing the applied bias. The investigation revealed that any dependence on the nature of the top-metal electrode was outside the accuracy of the work. Calculation of q/e for the hydroxyl group on alumina within the tunnel junction has been extended to include other electrode materials. A new and exciting facility within the university provided the impetus for the second area of work. A class 100 clean room housing a Langmuir Blodgett (LB) trough offered the opportunity to produce metal - insulator - Langmuir Blodgett film - metal tunnel junctions. It was realised at the outset that IETS using LB films would be difficult, previous workers had tried using a home-made tank with only limited success. However, the added sophistication of the new tank did not improve matters as was hoped. Although the results were disappointing, only a few junctions had resistances low enough to be usable in the spectrometer, the investigation produced some of the very few IET specra using junctions doped with LB films. The results also revealed the important role that imperfections and pin-holes play in the tunnelling process. The last area used IETS to investigate two commercially important and interesting polymers, hydrogels and polymeric electrolytes. Hydrogel have many applications in the field of implants, prosthetic, and cosmetics and have been studied and developed for many years. Polymeric electrolytes have many commercial applications especially in the field of solid-state batteries and conducting polymers. The way in which hydrogels swell as they absorb water is important, as is the way they adsorb onto a surface and much work has been done to investigate these characteristics using bulk samples. The study done by this group is the first to investigate the swelling and adsorption behaviour of a monolayer of the hydrogel poly 2-hydroxylethyl methacrylate. The results from both investigations indicate that ester cleavage occurs in p-HEMA and that water incorporated within a hydrogel has a limited structure with the first layer being thinner than the second and subsequent layers.

O intuito do desenvolvimento de biomateriais potencialmente aplicáveis como implantes de substituição óssea é sintetizar superfícies que induzam respostas biológicas positivas quando em contato com o tecido hospedeiro. Para isso, faz-se necessário não somente estudos de composição química, mas também é importante buscar compreender propriedades físicas e estruturais dos sistemas que estes materiais irão substituir. O osso natural é constituído por compostos orgânicos, especialmente proteínas como o colágeno, reforçado com minerais, tais como hidroxiapatita. O processo pelo qual ocorre a formação do componente inorgânico é chamado biomineralização. Uma maneira de introduzir macromoléculas em sistemas modelo para estudos de biomineralização é a formação de monocamadas Langmuir, que são camadas monomoleculares altamente organizadas de moléculas anfifílicas na interface líquido-ar. Essas monocamadas podem ser transferidas para suportes sólidos formando filmes de Langmuir-Blodgett. Neste estudo, foi investigado a incorporação de colágeno tipo-I em monocamadas insolúveis contendo os fosfolipídeos 1,2-dipalmitoil-sn-glicero-3-fosfatidilcolina (DPPC) ou ácido octadecilfosfônico (OPA), bem como a transferência dessas monocamadas para suportes de titânio por meio da técnica de Langmuir-Blodgett. Estes filmes foram utilizados como matrizes para o crescimento de hidroxiapatita biomimética após a exposição dos discos de titânio modificados a uma solução que simula a concentração de íons e pH do plasma sanguíneo humano. As amostras foram caracterizadas por microscopia eletrônica de varredura (MEV), microscopia de força atômica (AFM), espectroscopia vibracional na região do infravermelho (FTIR) e difração de raios-X (DRX). A razão molar Ca/P foi determinada por espectroscopia de dispersão de energia de raios-X (EDX). Propriedades dos biomateriais como molhabilidade, rugosidade e energia livre de superfície também foram estudadas. A biocompatibilidade das amostras foi investigada in vitro utilizando-se ensaios de viabilidade de osteoblastos. O colágeno interage com os fosfolipídios na interface água/ar, como evidenciado pelas isotermas de pressão de superfície, obtidas na presença da proteína. Além disso, a estabilidade das monocamadas de Langmuir foi aumentada devido à presença de colágeno na subfase. A incorporação de colágeno e fosfolipídios em filmes Langmuir-Blodgett sobre as superfícies de titânio são fatores determinantes para a formação de filmes inorgânicos altamente organizado, contínuos e uniformes, compostos por nanopartículas de hidroxiapatita biomimética, semelhante à encontrada no osso natural. As modificações nas superfícies aumentaram a proliferação de osteoblasto no titânio indicando que este material não é tóxico a este tipo de célula. / The development potential of biomaterials for bone replacement is guided by the necessity to provide a surface that induces positive biological responses when the material is in contact with the host tissue. For this, it is necessary the study of the chemistry and surface composition and also to understand the physical properties and the structural organization of the natural system which is in contact with the biomaterial. Natural bone is composed by organic compounds, especially protein like collagen, reinforced with minerals, such as hydroxyapatite. The process by which the formation of the inorganic component takes place is named biomineralization. One way to introduce macromolecules in model systems for biomineralization studies is the formation of Langmuir monolayers, which are highly organized monomolecular layers of amphiphilic molecules adsorved at the liquid-air interface. These monolayers can be transferred to solid substrate to form the Langmuir-Blodgett films. In this study, it was investigated the incorporation of type-I collagen in insoluble Langmuir monolayers containing either 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) or octadecylphosphonic acid (OPA) and their transference to titanium supports using the Langmuir-Blodgett technique. These films were used as matrices to the growth of biomimetic hydroxyapatite by the exposure of the modified titanium discs to a solution that mimics the ions concentration and pH of the human blood plasma. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), vibrational spectroscopy in the infrared region (FTIR), and X-ray diffraction (XRD). The Ca/P molar ratio was determined by energy dispersive X-ray spectroscopy (EDS). The properties of the biomaterials as wettability, roughness, and surface free energy were also studied. The biocompatibility of the samples was studied in vitro using osteoblasts viability assays. The collagen interacts with the phospholipids at air/water interface as evidenced by the pressure surface-surface area isotherms obtained in the presence of the protein. Moreover, the stability of the Langmuir monolayers was increased when collagen is present at the subphase. The incorporation of collagen and phospholipids on the titanium surfaces is important to the formation of organized, continuous and uniform inorganic films composed by biomimetic hydroxyapatite nanoparticles, similar to that found in the natural bone. These films are not toxic to osteoblasts as evidenced by the stimulation of their proliferation on the titanium-modified samples.

Proefschrift Rijksuniversiteit Groningen. / Met lit.opg. - Met samenvatting in het Nederlands.

O intuito do desenvolvimento de biomateriais potencialmente aplicáveis como implantes de substituição óssea é sintetizar superfícies que induzam respostas biológicas positivas quando em contato com o tecido hospedeiro. Para isso, faz-se necessário não somente estudos de composição química, mas também é importante buscar compreender propriedades físicas e estruturais dos sistemas que estes materiais irão substituir. O osso natural é constituído por compostos orgânicos, especialmente proteínas como o colágeno, reforçado com minerais, tais como hidroxiapatita. O processo pelo qual ocorre a formação do componente inorgânico é chamado biomineralização. Uma maneira de introduzir macromoléculas em sistemas modelo para estudos de biomineralização é a formação de monocamadas Langmuir, que são camadas monomoleculares altamente organizadas de moléculas anfifílicas na interface líquido-ar. Essas monocamadas podem ser transferidas para suportes sólidos formando filmes de Langmuir-Blodgett. Neste estudo, foi investigado a incorporação de colágeno tipo-I em monocamadas insolúveis contendo os fosfolipídeos 1,2-dipalmitoil-sn-glicero-3-fosfatidilcolina (DPPC) ou ácido octadecilfosfônico (OPA), bem como a transferência dessas monocamadas para suportes de titânio por meio da técnica de Langmuir-Blodgett. Estes filmes foram utilizados como matrizes para o crescimento de hidroxiapatita biomimética após a exposição dos discos de titânio modificados a uma solução que simula a concentração de íons e pH do plasma sanguíneo humano. As amostras foram caracterizadas por microscopia eletrônica de varredura (MEV), microscopia de força atômica (AFM), espectroscopia vibracional na região do infravermelho (FTIR) e difração de raios-X (DRX). A razão molar Ca/P foi determinada por espectroscopia de dispersão de energia de raios-X (EDX). Propriedades dos biomateriais como molhabilidade, rugosidade e energia livre de superfície também foram estudadas. A biocompatibilidade das amostras foi investigada in vitro utilizando-se ensaios de viabilidade de osteoblastos. O colágeno interage com os fosfolipídios na interface água/ar, como evidenciado pelas isotermas de pressão de superfície, obtidas na presença da proteína. Além disso, a estabilidade das monocamadas de Langmuir foi aumentada devido à presença de colágeno na subfase. A incorporação de colágeno e fosfolipídios em filmes Langmuir-Blodgett sobre as superfícies de titânio são fatores determinantes para a formação de filmes inorgânicos altamente organizado, contínuos e uniformes, compostos por nanopartículas de hidroxiapatita biomimética, semelhante à encontrada no osso natural. As modificações nas superfícies aumentaram a proliferação de osteoblasto no titânio indicando que este material não é tóxico a este tipo de célula. / The development potential of biomaterials for bone replacement is guided by the necessity to provide a surface that induces positive biological responses when the material is in contact with the host tissue. For this, it is necessary the study of the chemistry and surface composition and also to understand the physical properties and the structural organization of the natural system which is in contact with the biomaterial. Natural bone is composed by organic compounds, especially protein like collagen, reinforced with minerals, such as hydroxyapatite. The process by which the formation of the inorganic component takes place is named biomineralization. One way to introduce macromolecules in model systems for biomineralization studies is the formation of Langmuir monolayers, which are highly organized monomolecular layers of amphiphilic molecules adsorved at the liquid-air interface. These monolayers can be transferred to solid substrate to form the Langmuir-Blodgett films. In this study, it was investigated the incorporation of type-I collagen in insoluble Langmuir monolayers containing either 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) or octadecylphosphonic acid (OPA) and their transference to titanium supports using the Langmuir-Blodgett technique. These films were used as matrices to the growth of biomimetic hydroxyapatite by the exposure of the modified titanium discs to a solution that mimics the ions concentration and pH of the human blood plasma. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), vibrational spectroscopy in the infrared region (FTIR), and X-ray diffraction (XRD). The Ca/P molar ratio was determined by energy dispersive X-ray spectroscopy (EDS). The properties of the biomaterials as wettability, roughness, and surface free energy were also studied. The biocompatibility of the samples was studied in vitro using osteoblasts viability assays. The collagen interacts with the phospholipids at air/water interface as evidenced by the pressure surface-surface area isotherms obtained in the presence of the protein. Moreover, the stability of the Langmuir monolayers was increased when collagen is present at the subphase. The incorporation of collagen and phospholipids on the titanium surfaces is important to the formation of organized, continuous and uniform inorganic films composed by biomimetic hydroxyapatite nanoparticles, similar to that found in the natural bone. These films are not toxic to osteoblasts as evidenced by the stimulation of their proliferation on the titanium-modified samples.

No description available.

No description available.

Filmes de Langmuir e Langmuir-Blodgett (LB) de ligninas extraídas do bagaço de cana-de-açúcar, via processo organossolve, foram fabricados. As isotermas de pressão revelaram uma área para a seção média da lignina em torno de 100 &#197 para a monocamada condensada, enquanto a modelagem a partir dos espectros elipsométricos indicou uma espessura por camada de cerca 60 &#197 para os filmes LB. Porém a deposição não se mostrou homogênea sobre toda a superfície do substrato como observado pelas medidas de microscopia de força atômica (AFM), de forma que filmes mais homogêneos foram obtidos a partir de uma solução mista de Iignina com estearato de cádmio. A área por molécula, calculada com base no número de moléculas de ácido esteárico sobre a subfase, aumenta com a quantidade de lignina na solução mista, indicando a presença de ambos os componentes também na monocamada. Os espectros de infravermelho com transformada de Fourier (FTIR) mostraram que tanto a lignina quanto o estearato de cádmio são transferidos e os espectros de ultravioleta visível (UV-vis) indicaram que esta deposição é homogênea até a 20&#170 camada. Os difratogramas de raios-X e as medidas de AFM mostram que a deposição de lignina e estearato de cádmio ocorre em domínios separados. As medidas de AFM revelaram ainda um aumento da rugosidade do filme com o aumento do número de camadas depositadas e com a maior irregularidade do substrato utilizado. Vale destacar que os filmes de lignina pura mostraram-se mais homogêneos que os filmes mistos, apesar da maior estabilidade destes sobre a subfase. A uniformidade macroscópica dos filmes LB foram confirmadas por medidas de potencial de superfície. Um estudo comparativo de filmes de Langmuir de ligninas extraídas por diferentes processos e de diferentes fontes (madeira mole, madeira dura e cana-de- açúcar) foi realizado. Destacou-se a importância dos grupos funcionais nas medidas de pressão e potencial de superfície, sendo que a área molecular média mostrou-se aumentar com a massa molar das ligninas em questão. A observação de uma inversão nos valores do potencial de superfície para filmes LB de lignina de cana e de pinus abriu caminho para uma investigação mais detalhada dos fatores que contribuem para o potencial de superfície dos filmes LB. Além da Iignina, filmes LB de polianilina e estearato de cádmio também foram estudados. Os resultados revelaram que os valores do potencial de superfície para estes filmes podem ser melhor compreendidos levando-se em consideração modelos teóricos que tratam tanto da contribuição dipolar das moléculas que constituem o filme como da contribuição da interface filme/substrato, a qual geralmente é negativa e se dá pela injeção de cargas. No caso dos filmes LB de estearato de cádmio o potencial é positivo para um número ímpar de camadas e negativo para um número par / Langmuir monolayers and Langmuir-Blodgett (LB) films were produced from lignins extracted from sugar cane bagasse, via the organosolv process The surface pressure isotherms revealed an area per molecule of 100 &#197 for a condensed monolayer, and the modelling of ellipsometric data led to a thickness of 60 &#197 per layer for the LB films. The latter were not homogeneous, as demonstrated by atomic force microscopy (AFM) studies, and therefore mixed monolayers of Iignin and cadmium stearate were transferred with the aim of achieving more homogeneous films. The area per molecule, based on the number of stearic acid molecules on the airlwater interface, increased with the lignin contents in the mixed monolayers, thus confirming the presence of both components in the Langmuir monolayer. Fourier transform infra-red (FTIR) spectroscopy of LB films indicated that cadmium stearate as well as lignin were transferred onto the substrate. An equal amount of material was transferred in each deposition step, as demonstrated by the linear increase in UV-vis absorbance with the number of deposited layers up to the 20&#170 layer. Lignin and cadmium stearate are transferred in separate domains, which was indicated in X-ray diffraction measurements and AFM images. The latter also reveal that the roughness increases with the number of layers and may depend upon the substrate. Interestingly, films of pure lignin were more homogeneous than mixed films with cadmium searate, in spite of the higher stability and transterability of the mixed monolayers. Surface potential measurements showed a unitorm profile when the probe was scanned across an LB film, which may be taken as demonstration of uniformity at least at the macroscopic levei, though the film comprises domains and is usually rough for a molecular film. A comparative study was made ot monolayer characteristics for lignins obtained trom different sources and using different extracting procedures. The importance of functional groups was highlighted in these measurements, in which the area per molecule increased with the molecular weight ot the material. The observation that LB films from pinus and sugar cane bagasse exhibit surface potentials ot inverted sign has prompted us to investigate the possible contributions to such surface potentials. In addition to Iignins, in this study cadmium stearate and polyaniline LB films were also used. The overall conclusion was that the surface potential depends on the dipole moment of the monolayer-torming molecules, but is also affected substantially by the contribution from the substrate/film interface. The latter arises from charge injection from the electrode and is generally negative. For simple cadmium stearate LB films, the surface potential is positive for an odd number of layers, but negative for even numbers, since the dipole contribution is cancelled out