Academic literature on the topic 'Diffusion - Organic Dyes'

The main aim of doctoral thesis was the study on reactivity, transport and barrier properties of biocolloidal and synthetic polymeric substances by simple diffusion techniques. It was studied mainly the influence of basic physic-chemical parameters (temperature, concentration, pH and modification of material) on the reactivity and barrier ability of chosen compounds. Further substances were chosen as a model compounds: biocolloids (humic acids, alginate, chitosan, hyaluronate) and synthetic polymer (polystyrenesulfonate). Reactivity, barrier and transport properties of chosen substances were studied by interactions with oppositely charged basic organic dyes (methylene blue, rhodamine 6G, amido black 10B respectively) in hydrogels medium based on linear polysaccharide (agarose). The attention was also paid to basic physic-chemical characterisation (infrared spectroscopy, rheology, elemental analysis, thermogravimetry and scanning electron microscopy) of chosen materials and also hydrogels. Key part of the whole doctoral thesis was the optimization of selected diffusion techniques (diffusion cell technique and non-stationary diffusion in cuvettes) designated for the study on reactivity and barrier properties of wide range compounds (optimized method should be used as an universal method for simple and fast determination of reactivity of different compounds at given or changing conditions). The rate of reactivity, transport and barrier properties was determined based on fundamental diffusion parameters such as diffusion coefficients, break-through time so called lag time, interfacial concentration of chosen organic dye, apparent equilibrium constant, tortuosity factor, partition coefficient.

Submitted by OSWALDO NUNES NETO null (netfisic@fc.unesp.br) on 2016-08-13T20:37:55Z No. of bitstreams: 1 Tese_Doutorado_Oswaldo.pdf: 4276326 bytes, checksum: e73a2086ffde0d12d2f5875fb168f8c1 (MD5)<br>Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-08-16T14:27:21Z (GMT) No. of bitstreams: 1 nunesneto_o_dr_bauru.pdf: 4276326 bytes, checksum: e73a2086ffde0d12d2f5875fb168f8c1 (MD5)<br>Made available in DSpace on 2016-08-16T14:27:21Z (GMT). No. of bitstreams: 1 nunesneto_o_dr_bauru.pdf: 4276326 bytes, checksum: e73a2086ffde0d12d2f5875fb168f8c1 (MD5) Previous issue date: 2016-04-28<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Materiais e dispositivos baseados em compostos orgânicos desempenham um importante papel em diversas áreas da aplicação tecnológica devido às suas interessantes propriedades eletro-magneto- ópticas, adicionadas às suas características mecânicas únicas, facilidade de processamento, versatilidade de síntese e baixo custo relativo. Apesar do proeminente campo de aplicação destes materiais, muitos aspectos associados à sua ciência básica são ainda pouco compreendidos. Nesse cenário destaca-se o fenômeno de Magnetoresistência Orgânica (OMAR, da sigla em inglês). Tal fenômeno encontra-se associado a variações significativas da condutividade elétrica de dispositivos orgânicos induzidas por pequenos campos magnéticos externos em temperatura ambiente e tem sido observado em diversificados materiais poliméricos e moleculares. No presente trabalho avaliou-se o fenômeno de OMAR apresentado por um Diodo Emissor de Luz baseado na molécula de Alq3. Medidas de Espectroscopia de Impedância Elétrica na presença de um Campo Magnético estático externo (EIE-CM) foram realizadas sobre o referido dispositivo para diferentes temperaturas. Métodos diferenciados de aquisição e manipulação de dados foram empregados a fim de remover a dependência temporal dos sinais tipicamente observados. Os seguintes Efeitos de Campo Magnético (MFE, da sigla em inglês) foram observados sobre a resposta elétrica do dispositivo: (i) redução de cerca de 1% na resistência, efeito praticamente constante para todo o espectro de frequência e; (ii) variações significativas na capacitância, com intensificação do efeito de Capacitância Negativa em baixas frequências. Como suporte para a interpretação dos resultados experimentais foram realizadas simulações empregando-se duas abordagens: Circuitos Equivalentes e Análise de perturbações de pequenos sinais (em inglês, Small Signal Analysis ) via soluções numéricas das equações de transporte de Boltzmann numa aproximação por Drift-Diffusion empregando-se dispositivos simplificados. As análises sugerem que os MFE evidenciados podem estar associados a um aumento da mobilidade efetiva dos portadores de carga e a uma redução na taxa de recombinação bimolecular no dispositivo. Os resultados foram interpretados em termos dos modelos atualmente aceitos para o fenômeno de OMAR. Esta tese também apresenta um estudo de processos de geração e transferência de carga em corantes Cianinas, materiais promissores para aplicações em células solares com absorção no infravermelho. Técnicas de Ressonância de Spin Eletrônico induzida por Luz foram empregadas em blendas destes corantes com o polímero MEH-PPV e com o fulereno (C60) a fim de avaliar, respectivamente, o caráter aceitador e doador de elétrons das Cianinas.<br>Materials and devices based on organic compounds play an important role in various technological applications, mainly due to their interesting electrical-magneto-optical properties combined with their unique mechanical properties, easy processing, versatility of synthesis and relatively low cost. Despite the prominent application field of these materials many aspects associated with their basic science are still not well understood. In this context the Organic Magnetoresistance phenomenon (OMAR) deserves to be highlighted. This phenomenon is associated with significant changes in the electrical conductivity of organic devices induced by the presence of small external magnetic fields at room temperature, being observed in various polymeric and molecular materials. In this study we have investigated the OMAR phenomenon in Alq3-based OLEDs. Electrical impedance spectroscopy technique in the presence of an external static magnetic field (EIS-MF) was employed in the experiments; distinct temperatures were considered. Differentiated methods of acquisition and data manipulation were employed to remove the typically observed signal time dependence. The following magnetic field effects (MFE) were observed on the electrical response of the device: (i) a constant reduction of around 1% in the resistance over the entire frequency spectrum and; (ii) significant changes in the capacitance followed by an intensification of the negative capacitance effect at low frequencies. Simulations employing two different approaches were carried out for the interpretation of the experimental results: (i) Equivalent Circuits and (ii) Small Signal Analysis via numerical solutions of the Boltzmann transport equations by Drift-Diffusion approach. The results suggest that the observed MFE can be associated with an increase in the effective mobility of the charge carriers and a reduction in the bimolecular recombination rate in the device. The results were interpreted in terms of the currently accepted models for the OMAR phenomenon. This thesis also presents a study about generation and charge transfer processes in cyanine dyes (near infrared absorbing compounds) which are promising materials for applications in solar cells. Light induced Electron Spin Resonance (L-ESR) technique was employed to study the presence/formation of paramagnetic centers in blends of these dyes with MEH-PPV polymer and fullerene (C60) to evaluate, respectively, the electron acceptor and donor character of cyanine dyes.<br>FAPESP: 2011/21830-6<br>CNPq: 204432/2013-8

This master's thesis was focused on the study of interaction of some organic azo dyes (model diffusion probes) with cationic biopolymer chitosan. This interactions were realized via diffusion processes in hydrogel media based on thermoreversible agarose. The main aim was study of influence of pH of solution on the diffusion process. Interactions of used dyes are based on electrostatic character. The aminogroup of chitosan interacts with the functional group of chosen dyes (anionic sulfonic group) and thus affects the process of diffusion. The model diffusion compounds were chosen organic anionic dyes Chicago sky blue 6B (C.I. 24 410), Sirius red (C.I. 35 780) and Reactive blue 49 (C.I. 621 526). The important content of this diffusion method is a monitoring of the time progression of diffusion profile by UV-VIS spectrophotometry. The presented work follows the bachelor thesis and shows comprehensive view of the reactivity of chitosan and its behavior in different systems. Unsteady diffusion in cuvettes appears to be a universal method for the study of reactivity of biopolymers and for the study of transport processes in hydrogel media. The diffusion method is universal, easy and cheap.

Even though titanium dioxide photocatalysis has been promoted as a leading green technology for water purification, many issues have hindered its application on a large commercial scale. For the materials scientist the main issues have centred the synthesis of more efficient materials and the investigation of degradation mechanisms; whereas for the engineers the main issues have been the development of appropriate models and the evaluation of intrinsic kinetics parameters that allow the scale up or re-design of efficient large-scale photocatalytic reactors. In order to obtain intrinsic kinetics parameters the reaction must be analysed and modelled considering the influence of the radiation field, pollutant concentrations and fluid dynamics. In this way, the obtained kinetic parameters are independent of the reactor size and configuration and can be subsequently used for scale-up purposes or for the development of entirely new reactor designs. This work investigates the intrinsic kinetics of phenol degradation over titania film due to the practicality of a fixed film configuration over a slurry. A flat plate reactor was designed in order to be able to control reaction parameters that include the UV irradiance, flow rates, pollutant concentration and temperature. Particular attention was paid to the investigation of the radiation field over the reactive surface and to the issue of mass transfer limited reactions. The ability of different emission models to describe the radiation field was investigated and compared to actinometric measurements. The RAD-LSI model was found to give the best predictions over the conditions tested. Mass transfer issues often limit fixed film reactors. The influence of this phenomenon was investigated with specifically planned sets of benzoic acid experiments and with the adoption of the stagnant film model. The phenol mass transfer coefficient in the system was calculated to be km,phenol=8.5815x10-7Re0.65(ms-1). The data obtained from a wide range of experimental conditions, together with an appropriate model of the system, has enabled determination of intrinsic kinetic parameters. The experiments were performed in four different irradiation levels (70.7, 57.9, 37.1 and 20.4 W m-2) and combined with three different initial phenol concentrations (20, 40 and 80 ppm) to give a wide range of final pollutant conversions (from 22% to 85%). The simple model adopted was able to fit the wide range of conditions with only four kinetic parameters; two reaction rate constants (one for phenol and one for the family of intermediates) and their corresponding adsorption constants. The intrinsic kinetic parameters values were defined as kph = 0.5226 mmol m-1 s-1 W-1, kI = 0.120 mmol m-1 s-1 W-1, Kph = 8.5 x 10-4 m3 mmol-1 and KI = 2.2 x 10-3 m3 mmol-1. The flat plate reactor allowed the investigation of the reaction under two different light configurations; liquid and substrate side illumination. The latter of particular interest for real world applications where light absorption due to turbidity and pollutants contained in the water stream to be treated could represent a significant issue. The two light configurations allowed the investigation of the effects of film thickness and the determination of the catalyst optimal thickness. The experimental investigation confirmed the predictions of a porous medium model developed to investigate the influence of diffusion, advection and photocatalytic phenomena inside the porous titania film, with the optimal thickness value individuated at 5 ìm. The model used the intrinsic kinetic parameters obtained from the flat plate reactor to predict the influence of thickness and transport phenomena on the final observed phenol conversion without using any correction factor; the excellent match between predictions and experimental results provided further proof of the quality of the parameters obtained with the proposed method.

Nous avons construit des lasers qui ont servi a des experiences de melange a quatres ondes (reseau transitoire). Nous avons d'abord etudie la reponse non lineaire du troisieme ordre lorsque le milieu presente un continuum large d'etats (colorants). Le signal obtenu sur le cresyl-violet en film mince de colle cellulosique a ete analyse. La technique du reseau transitoire a ete ensuite utilisee pour caracteriser la dynamique de molecules dans un milieu poreux (vycor) et etudier la geometrie des connexions entre pores. Nous avons etudie la rotation de l'azobenzene en solution soit libre soit contenue a l'interieur de l'espace poreux. Ces experiences peuvent etre realisees sur des echelles allant de la femtoseconde a la seconde, permettant ainsi l'etude tant du temps de coherence que des proprietes de diffusion des materiaux

Étude des structures tautomériques du (bromo-5 pyridyl-2-azo)-2 diethylamino-5 phénol par spectrométrie ir, visible, d'émission visible et de diffusion raman de résonance. Attribution des transitions électroniques et vibrationnelles principales. Seules les structures quinoniques sont observées, la forme azo n'apparaissant pas en quantité détectable

碩士<br>國立臺灣大學<br>光電工程學研究所<br>88<br>Organic light emitting devices (OLEDs) based on molecular organic materials or polymer materials have been extensively studied because of their various merits suitable for flat panel display applications. The capability of solution processing of polymers leads to manufacturing advantage for large-area coating. However, it is found difficult to integrate multicolor polymer materials or devices for full-color displays by conventional coating and sequential photolithography steps. To resolve this issue, printing approaches have been aggressively pursued recently. In this thesis, we propose finite-source dye-diffusion thermal transfer (FS-D2T2) for performing controllable doping of polymer films in OLEDs. In this process, the polymer receiver film is placed in direct contact with the dye-dispersed polymer donor film to permit direct dye-diffusion thermal transfer. We perform a series of experiments of dye diffusion in the poly(N-vinylcarbazole) (PVK) or the poly (N-vinylcarbazole): 2-(4—biphenyl)-5-(4-tert- butylphenyl)-1,3,4-oxadiazole (PVK: PBD) matrix systems and show that it can be modeled by Fick’s diffusion theory. Using this doping process, we demonstrated color tuning & color integration of OLEDs.