This thesis investigates the electronic structure of iron phthalocyanine (Fe(II)Pc) andiron phthalocyanine chloride (Fe(III)PcCl) immobilized on surfaces. For this purposetwo different deposition methods are used and compared: smearing the molecularpowder under atmosphere condition and evaporation of a molecular layer inultra-high vacuum. The electronic states of FePc and FePcCl are probed withphotoelectron spectroscopy (PES) and compared in relation to the ionic state of thecentral metal (Fe). The PE spectra show that evaporation of FePcCl at around 350°Cresults in dissociation of the chlorine from the FePc molecule, which is stable at thistemperature. Mass spectroscopic measurements during heating of FePcCl in ultra-highvacuum (UHV) show a clear Cl signal for temperature still below 250°C. Theoreticalcalculations of the binding energy for Cl in FePcCl seem to indicate dissociation of theCl from the molecules.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-02T19:09:40Z No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) / Made available in DSpace on 2017-06-02T19:09:40Z (GMT). No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) Previous issue date: 2016-07-25 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / A novel platform for electroanalysis of isoniazid based on multi-walled carbon nanotube oxide and graphene oxide composite as support to iron phthalocyanine (MWCNTO-GO/FePc) has been developed. The FePc/MWCNTO-GO modified electrode is sensible for isoniazid, decreasing substantially its oxidation potential to + 200 mV vs. Ag/AgCl. Electrochemical and electroanalytical properties of the FePc/MWCNTO-GO modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy, and amperometry. The sensor presents better performance in 0,1 mol L-1 phosphate buffer at pH 7,4. Under optimized conditions, a linear response range from 5 μmol L-1 to 476 µmol L-1 was obtained with a sensitivity of 0,0225 μA L μmol-1. The limits of detection and quantification for isoniazid determination were 0,56 μmol L-1 and 1,88 μmol L-1, respectively. The relative standard deviation for 10 determinations of 100 μmol L-1 isoniazid was 2,5%. The sensor was successfully applied for isoniazid determination in artificial body fluids. / No presente trabalho é apresentado o desenvolvimento de uma nova plataforma para eletroanálise de isoniazida baseada em (MWCNTO-GO/FePc). O eletrodo modificado com FePc/MWCNTO-GO diminuiu sensivelmente o potencial de oxidação da isoniazida para +200 mV vs. Ag/AgCl. As propriedades eletroquímicas e eletroanalíticas do eletrodo modificado com FePc/MWCNTO-GO foram investigadas por voltametria cíclica, espectroscopia de impedância eletroquímica, microscopia eletroquímica de varredura, e amperometria. O sensor apresentou melhor desempenho em tampão fosfato 0,1 mol L-1 com pH 7,4. Sob condições otimizadas uma faixa de resposta linear de 5 μmol L-1 a 476 µmol L-1 foi obtida com uma sensibilidade de 0,0225 μA L μmol-1. O limite de detecção e quantificação para a isoniazida foram determinados como sendo 0,56 μmol L-1 e 1,88 μmol L-1, respectivamente. O desvio padrão relativo para 10 determinações de 100 μmol L-1 de isoniazida foi de 2,5%. O sensor foi aplicado com sucesso para determinação de isoniazida em fluidos corporais artificiais.

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.

Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields. Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films. We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature. Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K.

The Phthalocyanines (Pc’s) are a group of macro-cyclic molecules, widely investigated due to the possibility to use them in a variety of applications. Electronic and geometrical structure investigations of molecular model systems of Pc’s adsorbed on surfaces are important for a deeper understanding of the functionality of different Pc-based devices. Here, Pc’s monolayers and films, deposited on different surfaces, were investigated by X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS) and Scanning Tunneling Microscopy (STM). In addition Density Functional Theory (DFT) simulations were performed. For molecular films of Metal-free (H2Pc) and Iron (FePc) Pc’s, on surfaces, it is found that the intermolecular interaction is weak and the molecules arrange with their molecular plane mainly perpendicular to the surface. Several monolayer systems were characterized, namely H2Pc and FePc adsorbed on Graphite, ZnPc on InSb(001)-c(8x2), H2Pc on Al(110) and on Au(111). For all the studied monolayers it was found that the molecules are oriented with their molecular plane parallel to the surface. The electronic structure of the molecules is differently influenced by interaction with the surfaces. For H2Pc adsorbed on Graphite the nearly negligible effect of the surface on the molecular electronic structure allowed STM characterization of different molecular orbitals. A strong interaction is instead found in the case of H2Pc on Al(110) resulting in molecules strongly adsorbed, and partly dissociated. Modifications of the electronic and geometrical structure induced by alkali doping of H2Pc films and monolayers were characterized. It is found both for the H2Pc film on Al(110) and monolayer adsorbed on Au(111), that the molecular arrangement is changed upon doping by Potassium and Rubidium, respectively. Potassium doping of the H2Pc films results in a filling of previously empty molecular orbitals by a charge transfer from the alkali to the molecule, with significant modification of the molecular electronic structure.