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Importance of clean, sustainable and renewable energy sources are increasing gradually because of either being environmental friendly or being alternative for fossil fuels. Hydrogen energy system will let the utilization of alternative energy sources. Fuel cells are the most suitable energy conversion devices while passing through the hydrogen economy. The cost of the fuel cell systems need to be reduced in order to achieve commercialization of these systems. One of the most important cost items is platinum which is used as catalyst both in anode and cathode sides of the proton exchange membrane (PEM) fuel cells. Not only is the cost of the platinum, but also the limited reservoir of the platinum is a handicap. Therefore, the utilization of the cheap replacements of platinum catalysts will accelerate the process of commercialization. Because of their highly conjugated structure and high chemical stability metalo phthalocyanines have been encouraging electrocatalytic activity for oxygen reduction. Therefore, electrocatalytic activity for oxygen reduction in fuel cells was studied with some metalo phthalocyanines and some positive effects have been observed. In this study, phthalocyanines of cobalt, iron and nickel were synthesized via phthalic anhydride-urea method and characterized by IR Spectrophotometry, X-Ray Diffractometry and Thermal Gravimetry (TGA). Catalyst materials were prepared by impregnation method such that they contain either 4% cobalt, 4% or 10% iron or 4% nickel phthalocyanines on carbon black (Vulcan XC72) structure. Impregnated catalysts were pyrolyzed at 600oC or 1000oC and cathode electrodes were prepared by these catalysts as well as unpyrolyzed ones by spraying technique. The impregnated catalysts were characterized by scanning electron microscopy (SEM) and pore structures were analyzed by surface area analyzer (by BET and BJH techniques). All of the anode electrodes were prepared by using 20% Pt containing commercial catalyst by the same technique applied for cathode electrodes. A membrane electrode assembly was also prepared by 20% Pt containing commercial catalyst on the cathode electrode. Performance characteristics of the manufactured membrane electrode assemblies were determined by means of a test station, built in Middle East Technical University Chemical Engineering Department, having a 5 cm2 test cell. The highest performance observed with the commercial membrane electrode assembly was 0.40W/cm2 at 0.5 V. Whereas, the power density obtained from the MEA manufactured at the laboratory having 0.4 mg Pt/cm2 loading both on the anode and cathode was 0.18 W/cm2 at 0.5 V. For the phthalocyanine cathodic MEAs, the highest power reached was 0.04W/cm2 which was obtained from the MEA having a loading of 0.28mg Co/cm2 prepared by using the CoPc/C catalyst pyrolyzed at 1000 oC.

This paper describes the development of an electrochemical sensor glassy carbon modified with gold nanoparticles and a film of multiâwalled carbon nanotube and cobalt phthalocyanine (CoPc-fMWCNTs/AuNp/GCE) for the determination of diethylstilbestrol hormone (DES) in water samples and meat, using a square wave technique voltammetry. (SWV). The electrolyte used was Britton-Robinson buffer (BR) 0.04 mol L-1 pH 10.0. Initially it was studied the electrode configuration to be used for the development work, after the optimization of solution pH, study scan speed to evaluate the charge transfer kinetics in the redox process of the DES, the optimized parameters for SWV, the analytical curve, and finally, applying the methodology developed. The optimized parameters for SWV were f = 5 sâ1, a = 50 mV and ΔEs=1 mV. The CoPc-fMWCNTs/AuNp/GCE was ready to be used for the application since all conditions were optimized. Analytical curves were obtained in the concentration ranged from 7.9365 à 10−7 â 5.6604 à 10−6 mol Lâ1 (R = 0.9996) and there were obtained limits of detection (LOD) and quantification (LOQ) of 1.9910 x 10â7 mol Lâ1and 6.6367 x 10â7 mol Lâ1, respectively, being comparable to those reported in the literature. The repeatability and reproducibility of the proposed procedure were evaluated. The relative standard deviation (RSD) were 4.33% and 3.49%, respectively, indicating the precision of the assay. The recovery percentage was 98.56% for the water sample and 94.05% for beef sample (RSD of 0.40 and 1.55% respectively). The modified electrode has developed sensitivity, reproducibility and repeatability appropriate and consistent LOD and LOQ values with those reported in the literature. Moreover, the results obtained by the use of CoPc-fMWCNTs/AuNp/GCE proved very efficient as the detection and DES recovery, being thus a promising device in the detection and quantification of DES in water samples and food. / O presente trabalho descreve o desenvolvimento de um sensor eletroquÃmico de carbono vÃtreo modificado com nanopartÃculas de ouro, nanotubos de carbono de paredes mÃltiplas funcionalizados e ftalocianina de cobalto (CV/NpAu/NTCPMf-FcCo) para a determinaÃÃo do hormÃnio dietilestilbestrol (DES) em amostras de Ãgua e carne, utilizando a tÃcnica de voltametria de onda quadrada (VOQ). O eletrÃlito empregado foi tampÃo BrittonâRobinson (BR) 0,04 mol Lâ1 pH 10,0. Inicialmente estudou-se a configuraÃÃo do eletrodo a ser utilizado para o desenvolvimento do trabalho, depois a otimizaÃÃo do pH do meio, estudo da velocidade de varredura para avaliar a cinÃtica de transferÃncia de carga no processo redox do DES, otimizaÃÃo dos parÃmetros da VOQ, construÃÃo da curva analÃtica e por fim, a aplicaÃÃo da metodologia desenvolvida. Os parÃmetros otimizados para a VOQ foram: f = 5 sâ1, a = 50 mV e ΔEs = 1 mV. De posse de todas as condiÃÃes otimizadas para aplicaÃÃo do CV/NpAu/NTCPMf-FcCo, curvas analÃticas foram obtidas no intervalo de concentraÃÃo de 7,9365 à 10−7 â 5,6604 à 10−6 mol Lâ1 (R = 0,9996) e os limites de detecÃÃo (LD) e de quantificaÃÃo (LQ) calculados foram 1,9910 x 10â7 mol Lâ1 e 6,6367 x 10â7 mol Lâ1, respectivamente, sendo comparÃveis aos citados na literatura. A repetibilidade e a reprodutibilidade do procedimento proposto foram avaliadas. Os valores de desvio padrÃo relativo (DPR) obtidos foram 4,33% e 3,49%, respectivamente, evidenciando a precisÃo da metodologia. O percentual de recuperaÃÃo foi de 98,56% para amostra de Ãgua e 94,05% para amostra de carne bovina (DPR de 0,40 e 1,55% respectivamente). O eletrodo modificado desenvolvido apresentou sensibilidade, reprodutibilidade e repetibilidade adequados, bem como valores de LD e LQ concordantes com os relatados na literatura. Os resultados obtidos pelo emprego do CV/NpAu/NTCPMf-FcCo se mostraram muito eficientes quanto à detecÃÃo e recuperaÃÃo de DES, mostrando-se, desse modo, um dispositivo promissor na detecÃÃo e na quantificaÃÃo de DES em amostras de Ãgua e alimentos.

Made available in DSpace on 2016-08-19T12:56:38Z (GMT). No. of bitstreams: 1 Ilanna Campelo Lopes.pdf: 782855 bytes, checksum: 0cbaabd79c9d12083e00badf326ac1d0 (MD5) Previous issue date: 2006-07-24 / Determination of paraquat (PQ) in watery solutions was investigated with the technique of wave square voltammetry on pyrolytic graphite electrodes (PG) before and after modifications with metal phtalocyanines. The electrode modified with cobalt phthalocyanine (CoPc) presented PQ reduction currents more accented and voltammetrics profiles better with respect to the electrodes unmodified and modified with nickel phthalocyanine (NiPc), iron (FePc), manganese (MnPc) and in the acid form (H2Pc). This sensor presented two reversible peaks for the reduction of PQ next to - 0,71 V (peak 1) and - 1,10 V (peak 2) versus S C E. After optimization of cobalt phthalocyanine concentration and the adsorption time on electrode, the best analysis conditions for the PQ in 0,10 mol L-1 Britton-Robinson buffer solution (pH 7,0) was established: frequency of 100 s-1, wave amplitude of 50 mV and scan increment of 2 mV. In these conditions, the modified electrode obtained a linear response range from 5,00 x 10-7 to 2.91 x 10-5 mol L-1 (128,59 to 748,36 x 101 μg L-1) with detection and quantification limits equals to 1,44 x 10-7 mol L-1 (37,03 μg L-1) and 4,79 x 10-7 mol L-1 (123,26 μg L-1)1, respectively. The studied sensor presented values below 5%, in terms of relative standard deviation, for repeatability (0,58% (± 0,27) for N = 10) and reproducibility (1,58% (± 0,74) for N = 5) studies. The sensor was applied in natural water samples and the gotten results was presented recovery averages of 93,14% (± 7,16) and 119,25% (± 5,68) in two water samples analyzed. / A determinação de paraquat (PQ) em soluções aquosas foi investigada com a técnica de voltametria de onda quadrada sobre eletrodos de grafite pirolítico (GP) antes e após modificações com metaloftalocianinas. O eletrodo modificado com ftalocianina de cobalto (CoPc) apresentou correntes de redução do PQ mais acentuadas e melhores perfis voltamétricos em relação ao eletrodo não modificado e modificados com ftalocianina de níquel (NiPc), de ferro (FePc), de manganês (MnPc), e na forma ácida (H2Pc). Este sensor apresentou dois picos reversíveis para redução do PQ em torno de - 0,71 V (pico 1) e - 1,10 V (pico 2) vs E C S. Após otimizações da concentração da ftalocianina de cobalto e do tempo de adsorção no eletrodo, as melhores condições de análise para o PQ em solução tampão Britton- Robinson 0,10 mol L-1 (pH 7,0) estabelecidas foram: freqüência de 100 s-1, amplitude de pulsos de 50 mV e incremento de varredura de 2 mV. Nestas condições, o eletrodo modificado obteve uma resposta linear de 5,00 x 10-7 a 2,91 x 10-5 mol L-1 (128,59 a 748,36 x 101 μg L-1) com limites de detecção e quantificação iguais a 1,44 x 10-7 mol L-1 (37,03 μg L-1) e 4,79 x 10-7 mol L-1 (123,26 μg L-1), respectivamente. O sensor estudado apresentou valores abaixo de 5%, em termos de desvio padrão relativo, para estudos de repetibilidade (0,58% (± 0,27) para N = 10) e reprodutibilidade (1,58% (± 0,74) para N = 5). O sensor foi aplicado em amostras de águas naturais e os resultados obtidos apresentaram médias de recuperação de 93,14% (± 7,16) e 119,25% (± 5,68) em duas amostras de água analisadas.

Made available in DSpace on 2016-08-19T12:56:40Z (GMT). No. of bitstreams: 1 DISSERTACAO ANA PAULA03072012.pdf: 1293829 bytes, checksum: 334feb3233e863de1a2f3bf991a6af4b (MD5) Previous issue date: 2012-07-03 / Lipoic acid, also known as thioctic acid is a compound organosulfur derived from octanoic acid, which is a saturated fatty acid. It is an antioxidant that has the property of suppressing free radicals in both aqueous and lipid environment, which differs from other antioxidants. Nowadays, various techniques are employed for determining the lipoic acid such as capillary electrophoresis, chromatography, high performance liquid chromatography efficiency. However, the electrochemical detection is a promising method, because since it is less labor intensive and can distinguish between the oxidized and reduced form of lipoic acid. A growing number of studies has shown the need for a rapid procedure for evaluating the content of lipoic acid and electrochemical techniques were employed successfully. This study aimed to develop a pyrolytic graphite electrode modified with cobalt metallophthalocyanines for the determination of lipoic acid. The oxidation of lipoic acid has a peak located at approximately 0.8 V vs SCE, being close to the peak potential presented in the literature. The cyclic voltammograms reported in the presence of 1 x 10-3 mol L-1 of lipoic acid in phosphate buffer 0.1 mol L-1 (pH 7.0) to a potential scan rate 25 mV s-1 showed that the electrode modified with 1 x 10-4 mol L-1 CoPc, showed better profiles in relation to the voltammetric electrode unmodified or modified with other metallophthalocyanine. Is then optimized the parameters for the cyclic voltammetry, chronoamperometry and differential pulse. Was then constructed curves for analytical techniques mentioned. For the cyclic voltammetry technique limits of detection and quantification are 8.7 × 10-8 mol L-1 and 2.9 x10-7 mol L-1 for the technique of chronoamperometry 9.8 x 10-8 mol L-1 and 3.2 x 10-7 mol L-1 and differential pulse voltammetry are 3.4 x 10-9 mol L-1 and 1.2 x 10-8 mol L-1 respectively. / O ácido lipóico, também conhecido como ácido tióctico, é um composto organosulfurado derivado do ácido octanóico, que é um ácido graxo saturado. É um antioxidante que apresenta a propriedade de reprimir radicais livres tanto em meio lipídico quanto aquoso, o que o diferencia dos demais antioxidantes. Atualmente, diferentes técnicas são empregadas para a determinação do ácido lipóico tais como eletroforese capilar, cromatografia gasosa, cromatografia liquida de alta eficiência. Contudo a detecção eletroquímica é um método promissor, pois uma vez que é menos trabalhosa e pode distinguir entre o oxidado e a forma reduzida de ácido lipóico. Um número crescente de estudos vem mostrando a necessidade de um procedimento rápido para a avaliação do teor de ácido lipóico e técnicas eletroquímicas foram empregadas com sucesso. Este trabalho teve por objetivo desenvolver um eletrodo de grafite pirolítico modificado com metaloftalocianinas de cobalto para a determinação de ácido lipóico. A oxidação do ácido lipóico apresenta um pico localizado em torno de 0,8V vs ECS, estando próximo dos potenciais de pico apresentado na literatura. Os voltamogramas cíclicos registrados na presença de 1 x 10-3 mol L-1 de ácido lipóico em solução tampão fosfato 0,1 mol L-1 (pH 7,0), para uma velocidade de varredura do potencial de 25 mV s-1, mostraram que o eletrodo modificado com 1 x 10-4 mol L-1 CoPc , apresentou perfis voltamétricos melhores em relação ao eletrodo não modificado ou modificado com outras metaloftalocianinas. Aperfeiçoou-se então os parâmetros para as técnicas de voltametria cíclica, pulso diferencial e cronoamperometria. Construíram-se então as curvas analíticas para as técnicas citadas. Para a técnica de voltametria cíclica os limites de detecção e de quantificação são 8,7x10-8 mol L-1 e 2,9x10-7 mol L-1 para a técnica de cronoamperometria 9,8 x 10-8 mol L-1 e 3,2x 10-7 mol L-1 e para voltametria pulso diferencial são 3,4 x 10-9 mol L-1 e 1,2 x 10-8 mol L-1 respectivamente.

In this licentiate thesis, organic molecules, namely Cobalt Phthalocyanine (CoPc) and Biphenylene, have been studied by means of synchrotron radiation-based spectroscopic methods (Photoemission Spectroscopy (PES) and X-ray Absorption Spectroscopy (XAS) in combination with Density Functional Theory (DFT) calculations. Paper I is a combined experimental and theoretical investigation of electronic structure of CoPc. addressing the atomic character of the Highest Occupied Molecular Orbital (HOMO) and the electronic configuration of the molecular ground state. Both these aspects are still under discussion since different experimental and theoretical studies have given controversial results. Previous works have indicated the CoPc ground state to either be described by the 2A1g or 2Eg, or by a mix of the two electronic configurations. Regrading the debated the atomic character of the HOMO of CoPc, it has been suggested to be either metal 3d-like and localized on the central Co atom or originating in the organic ligand of the molecule. In this thesis the valence photoemission results for CoPc in gas phase and as adsorbed films on Au(111) together with the DFT simulations, consistently indicate that the HOMO is derived only by the organic ligand, with mainly contribution from the carbon atoms with no metal character. Moreover, the good agreement between the experimental and theoretical results, confirms that the ground state of CoPc is correctly described by the 2A1g configuration. In Paper II, PES and XAS have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, XAS measurements allowed the characterizion of the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction.

Chapter1 gives an overview of the basic principles of electrochemistry. A rigorous electrochemical study on the solution phase and solid phase cobalt phthalocyanine (CoPC) is presented in chapter2. The formof CoPC on carbon electrodes was characterized by scanning electron microscope (SEM). The use of CoPC modified edge plane pyrolytic graphite (CoPC-EPPG) for sensing nitrite (NO₂⁻) was also investigated. It was found that the claimed mediator CoPC has no influence on the process. A bare glassy carbon (GC) electrode was successfully applied for the quantitative determination of nitrite as a simple alternative to the modified electrodes reported in the literature (chapter3). Chapter4 compares the voltammetric responses of an edge plane pyrolytic graphite electrode covalently modifed with 2-anthraquinonyl groups (EPPG-AQ2) and solution phase anthraquinone monosulphonate (AQMS) in the presence of a limited concentration of protons. The solution phase and surface bound species show analogous responses resulting in split waves. Digisim™ simulation of the AQMS voltammetry have shown that the pH adjacent to the electrode may be altered by up to 5-6 pH units in low buffered solutions; this is caused by the consumption of protons during the electrochemical reaction. Chapters5 and 6 compare the electrochemical properties of 2-anthraquinonyl groups covalently attached to an edge plane pyrolytic graphite (EPPG) and to a gold electrode. In both cases simulations using newly developedMarcus-Hush-Chidsey theory for a 2e⁻ process assuming a uniform surface did not achieve a good agreement between theory and experiment. Subsequently two models of surface inhomogeneity were investigated: a distribution of formal potentials, E^Ө, and a distribution of electron tunneling distances, r₀. For both EPPG-AQ2 and Au-AQ2 modified electrodes the simulation involving E^Ө distribution turned out to be the most adequate. This is the first time that Marcus-Hush-Chidsey theory has been applied to a 2e⁻ system. Chapter7 briefly summarizes the obtained results.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-20T12:39:54Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Diego_Ricardo_daSilva_Leite_DISSERTAÇÃO.pdf: 2264802 bytes, checksum: 0e31f6102f6a8c9b24148d435e822ef1 (MD5) / Made available in DSpace on 2016-09-20T12:39:54Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Diego_Ricardo_daSilva_Leite_DISSERTAÇÃO.pdf: 2264802 bytes, checksum: 0e31f6102f6a8c9b24148d435e822ef1 (MD5) Previous issue date: 2016-02-04 / CAPES / Atualmente, têm-se buscado métodos que viabilizem um diagnóstico eficaz, prático, rápido e de baixo custo na detecção de doenças que se revelem atrativos para os serviços de saúde pública. Nesse contexto, os imunossensores têm apresentado respostas promissoras, revelando-se como métodos analíticos práticos, rápidos e econômicos. Recentemente, a utilização de nanomateriais de alótropos de carbono, destacando-se os nanotubos de carbono (NTC), têm resultado em melhoria na sensibilidade por aumentar transferência eletrônica, sobretudo quando aliados a polímeros condutores. O objetivo deste trabalho foi desenvolver plataforma nanoestruturada para aplicação em imunossensores. Como objeto de estudo, foi detectado anticorpos contra o nucleocapsídeo do vírus da hepatite B (HBV), visto que este marcador é o mais importante no controle e vigilância de bolsas de sangue em serviços hemoterápicos. No presente trabalho, eletrodos de tinta de carbono serigrafados sobre substrato de politileno tereftalato (PET) foram modificados por 0,0063% de nanotubos de carbono (NTC-COOH) e 6% em concentração de ftalocianina de cobalto (CoPc) que foram recobertos com filmes de polipirrol (PPi). O filme foi obtido por cronoamperometria (0,8V, 80s) usando soluções de 0,1 M de pirrol (Pi) em meio ácido. Foi observada uma boa reprodutibilidade e estabilidade dos eletrodos sobretudo pós-inserção do filme quando caracterizado eletroquimicamente. Além disso, as imagens de microscopia eletrônica mostraram uma baixa produção de pirroles. Os sensores desenvolvidos com a associação de nanotubos de carbono funcionalizados apresentaram melhor desempenho analítico em relação ao controle (sem NTC). A imobilização do antígeno do núcleo capsídeo da hepatite B (HBc-Ag) foi confirmada por decréscimo da área eletroativa dos voltamogramas cíclicos. A resposta aos anticorpos anti-HBc foi evidenciada por técnica de voltametria de onda quadrada, mostrando que a plataforma desenvolvida é promissora para aplicação em sensor para hepatite. / Currently, they have been sought methods that enable effective diagnosis, practical, fast and low-cost in detecting diseases that may prove attractive to public health services. In this context, immunosensors have shown promising responses, revealing himself as analytical methods of practical, fast and economical. Recently, the use of carbon allotropes of nanomaterials, highlighting carbon nanotubes (CNT), have resulted in improved sensitivity by increasing wire transfer, especially when combined with conductive polymers. The aim of this study was to develop nanostructured platform for immunosensors application. As study object was detected antibodies against the nucleocapsid of hepatitis B virus (HBV), as this marker is the most important in the control and surveillance of blood bags in haemotherapic services. In this study, carbon ink electrodes screen printed on the substrate polythene terephthalate (PET) have been modified for 0.0063% of carbon nanotubes (CNT-COOH) and 6% concentration of cobalt phthalocyanine (CoPc) were coated with polypyrrole films (PPy). The film was obtained by chronoamperometry (0.8 V, 80 s) using 0.1 M solution of pyrrole (Py) in acidic. Was observed a good reproducibility and stability particularly after insertion of the film electrode when electrochemically characterized. Furthermore, electron microscopy images showed a low production pyrroles. The sensors developed in association with functionalized carbon nanotubes showed better analytical performance compared to the control (without NTC). The immobilization of the capsid antigen hepatitis B core (HBc-Ag) was confirmed by decreasing the area of the electroactive cyclic voltammograms. The response to anti-HBc antibody was evidenced by technical square wave voltammetry, showing that the platform is developed promising for application to sensor hepatitis.

Made available in DSpace on 2016-08-19T12:56:48Z (GMT). No. of bitstreams: 1 Dissertacao LAISE NAYRA DOS SANTOS PEREIRA.pdf: 1329578 bytes, checksum: bb0923e1ddc2d57bb73b2390b4ceb375 (MD5) Previous issue date: 2014-07-18 / FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO / This work describes the development of electroanalytical procedures for α-lipoic acid (ALA) determination in dietary supplement using a pyrolitic graphite electrode (PG) modified with cobalt phthalocyanine (CoPc) from electrochemical techniques and by Batch Injection Analysis (BIA). Cyclic voltammograms of ALA oxidation on the PG/ CoPc electrode presented an irreversible peak ~+0.85 V vs Ag/ AgCl, a value about 100 mV to less positive potential, well as a significant increase in the magnitude of peak current compared to the PG electrode unmodified. The analytical curves obtained with cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry showed good linearity and sensitivity. The DPV technique showed the best values of limit of detection (LOD) and quantification (LOQ) 3.4 x 10ˉ⁹ mol Lˉ¹ and 1.2 x 10ˉ⁸ mol Lˉ¹, respectively. Therefore was chosen for determination of ALA on technique. Voltammetric response of ALA was also evaluated in PG electrode unimodified and modified in hydrodynamic conditions. The modification of the PG/ CoPc electrode produced an increase of 2.33 times compared to the PG electrode. The analytical method was then proposed using the PG/ CoPc electrode for detection of ALA by BIA. The method showed a good linear range between (1.0 x 10ˉ⁶ to 1.0 x 10ˉ⁴ mol Lˉ¹), values of LOD and LOQ of 1.5 × 10ˉ⁸ mol Lˉ¹ and 5.0 × 10ˉ⁸ mol L-1, respectively, with analytical frequency of 208 injections/ hour. The quantification of ALA in dietary supplement showed concordant results with those obtained by chromatographic method, with a confidence level of 95%. Recovery tests were performed added a concentration of ALA in a sample of synthetic urine, where the recovery values were in the range 98 - 107%. / O presente trabalho descreve o desenvolvimento de procedimentos eletroanalíticos para determinação de ácido α-lipóico (ALA) em suplemento dietético utilizando eletrodo de grafite pirolítico (GP) modificado com ftalocianina de cobalto (CoPc) a partir de técnicas eletroquímicas e pela Análise por Injeção em Batelada (BIA). Os voltamogramas cíclicos da oxidação de ALA sobre o eletrodo GP/ CoPc apresentaram um pico irreversível com potencial ~ +0,85 V vs. Ag/ AgCl, mostrando um deslocamento do início da corrente de oxidação em cerca de 100 mV para potenciais menos positivos, bem como um aumento significativo na magnitude da corrente de pico, quando comparados ao eletrodo não modificado GP. As curvas analíticas obtidas com as técnicas de voltametria cíclica (VC), voltametria de pulso diferencial (VPD) e cronoamperometria apresentaram boa linearidade e sensibilidade. A técnica de VPD apresentou os melhores valores de limite de detecção (LD) e de quantificação (LQ), 3,4 x 10ˉ⁹ mol Lˉ¹ e 1,2 x 10ˉ⁸ mol Lˉ¹, respectivamente. Portanto foi a técnica escolhida para determinação de ALA. Resposta voltamétrica do ALA também foi avaliada no eletrodo GP não modificado e modificado em condições hidrodinâmicas. A modificação do eletrodo GP/ CoPc produziu um aumento de 2,33 vezes comparado com o eletrodo GP. O método analítico foi então proposto usando o eletrodo GP/ CoPc para detecção de ALA por BIA. O método apresentou uma boa faixa linear compreendida entre (1 x 10ˉ⁶ a 1 x 10ˉ⁴ mol Lˉ¹); valores de LD e LQ de 1, 5 x 10ˉ⁸ mol Lˉ¹ e 5, 0 x 10ˉ⁸ mol Lˉ¹, respectivamente, com frequência analítica de 208 injeções/ hora. A quantificação de ALA em suplemento dietético apresentou resultados concordantes com os obtidos pelo método cromatográfico, apresentando um nível de confiança de 95%. Testes de recuperação foram feitos adicionados uma concentração de ALA em amostra de urina sintética, onde os valores de recuperação foram na faixa de 98 a 107%.

Die Raman-Spektroskopie ist eine der nützlichsten optischen Methoden zur Untersuchung der Phononen organischer und anorganischer Materialien. Mit der fortschreitenden Miniaturisierung von elektronischen Bauelementen und der damit einhergehenden Verkleinerung der Strukturen von der Mikrometer- zur Nanometerskala nehmen das Streuvolumen und somit auch das Raman-Signal drastisch ab. Daher werden neue Herangehensweisen benötigt um sie mit optischer Spektroskopie zu untersuchen. Ein häufig genutzter Ansatz um die Signalintensität zu erhöhen ist die Verwendung von Resonanz-Raman-Streuung, das heißt dass die Anregungsenergie an die Energie eines optischen Überganges in der Struktur angepasst wird. In dieser Arbeit wurden InAs/Al(Ga)As-basierte Multilagen mit einer Periodizität unterhalb des Beugungslimits mittels Resonanz-Mikro-Raman-Spektroskopie und Raster-Kraft-Mikroskopie (AFM) den jeweiligen Schichten zugeordnet. Ein effizienterer Weg um die Raman-Sensitivität zu erhöhen ist die Verwendung der oberflächenverstärkten Raman-Streuung (SERS). Sie beruht hauptsächlich auf der Verstärkung der elektromagnetischen Strahlung aufgrund von lokalisierten Oberflächenplasmonenresonanzen in Metallnanostrukturen. Beide oben genannten Signalverstärkungsmethoden wurden in dieser Arbeit zur oberflächenverstärkten Resonanz-Raman-Streuung kombiniert um geringe Mengen organischer und anorganischer Materialien (ultradünne Cobalt-Phthalocyanin-Schichten (CoPc), CuS und CdSe Nanokristalle) zu untersuchen. Damit wurden in beiden Fällen Verstärkungsfaktoren in der Größenordnung 103 bis 104 erreicht, wobei bewiesen werden konnte, dass der dominante Verstärkungsmechanismus die elektromagnetische Verstärkung ist. Spitzenverstärkte Raman-Spektroskopie (TERS) ist ein Spezialfall von SERS, bei dem das Auflösungsvermögen von Licht unterschritten werden kann, was zu einer drastischen Verbesserung der lateralen Auflösung gegenüber der konventionellen Mikro-Raman-Spektroskopie führt. Dies konnte mit Hilfe einer Spitze erreicht werden, die als einzelner plasmonischer Streuer wirkt. Dabei wird die Spitze in einer kontrollierten Weise gegenüber der Probe bewegt. Die Anwendung von TERS erforderte zunächst die Entwicklung und Optimierung eines AFM-basierten TERS-Aufbaus und TERS-aktiver Spitzen, welche Gegenstand dieser Arbeit war. TERS-Bilder mit Auflösungen unter 15 nm konnten auf einer Testprobe mit kohlenstoffhaltigen Verbindungen realisiert werden. Die TERS-Verstärkung und ihre Abhängigkeit vom Substratmaterial, der Substratmorphologie sowie der AFM-Betriebsart wurden anhand der CoPc-Schichten, die auf nanostrukturierten Goldsubstraten abgeschieden wurden, evaluiert. Weiterhin konnte gezeigt werden, dass die hohe örtliche Auflösung der TERS-Verstärkung die selektive Detektion des Signals weniger CdSe-Nanokristalle möglich macht.