Academic literature on the topic '2-mercaptoethanol'

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-07T11:31:21Z No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5)<br>Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-02T13:29:49Z (GMT) No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5)<br>Made available in DSpace on 2016-07-02T13:29:49Z (GMT). No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5) Previous issue date: 2016-02-29<br>CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Neste trabalho investigou-se a adsorção do triptofano (Trp), seus derivados e do 2-mercaptoetanol (MET) na superfície de nanopartículas metálica de prata ou ouro. Utilizou-se como ferramentas para o estudo, as técnicas espectroscópicas de absorção no ultravioleta e visível (UV-VIS), espalhamento Raman normal e intensificado pela superfície (surface-enhanced Raman scattering – SERS) e cálculos teóricos baseados na teoria do funcional da densidade (density functional theory – DFT). A banda da ressonância do plásmon de superfície localizado (localized surface plasmon resonance – LSPR) foi monitorada nos espectros UV-VIS para a investigação das propriedades eletrônicas das nanopartículas metálicas, envolvidas nas interações com os adsorbatos e nas distribuições de tamanhos. Foram sintetizados nanoprismas de prata estabilizados por citrato de sódio em diferentes condições de temperatura, envolvendo múltiplas etapas de crescimento e usando cobre como dopante indutor de geometria. A inclusão de pequena quantidade de cobre, em relação a prata, levou à maior formação de nanoprismas triangulares que o método original. Estas superfícies foram utilizadas nos estudos da adsorção do MET. Os nanoprismas, dopados ou não, mostraram-se inadequados para uso como substrato SERS de outros adsorbatos que não fossem mercaptanas. Sintetizou-se também nanoesferas de prata ou ouro para o estudo da adsorção do Trp e seus derivados em diferentes ambientes químicos. Os nanoprismas foram utilizados para estudos LSPR na presença do MET em diferentes concentrações, além da obtenção do espectro SERS da molécula. Observou-se que a concentração possui papel determinante na auto-organização de uma monocamada molecular, fazendo com que a conformação predominante se altere na superfície metálica. Os cálculos por DFT permitiram a simulação da adsorção do MET em superfície (111) de prata e obtenção de resultados relacionados às estruturas e estabilidades dos confôrmeros. Teoria e experimento mostraram-se em acordo dentro das condições estudadas e permitindo inferir que a ligação de hidrogênio possui um papel chave nas propriedades da monocamada. Estudou-se a adsorção dos isômeros L-Trp e D-Trp e dos peptídeos Ala-Trp, Trp-Gly, pGlu-Lys-Trp-Ala-Pro e Trp-His-Trp-Leu-Gln-Leu através das espectroscopias SERS e UV-VIS. Em prata, os espectros mostraram que os aminoácidos e os dipeptídeos adsorvem preferencialmente através dos grupos carboxilato e amina. Em ouro, a análise espectral permitiu identificar a adsorção das moléculas de Trp via nitrogênio do anel indólico. Os espectros foram obtidos em concentração de 10-3 mol L-1 nos diferentes metais, contudo a adição de HCl permitiu a obtenção de espectros em 10-5 mol L-1. As diferenças entre os espectros em ouro permitiram concluir que o Trp interage mais intensamente com a superfície na presença de HCl. A partir de todos os resultados obtidos, pode-se sugerir que as nanopartículas de ouro mostram-se úteis para o estudo de estruturas mais complexas por diferencia o triptofano adsorvido à superfície de outros presentes na estrutura de interesse.<br>The adsorption of tryptophan (Trp), his derivatives and 2-mercaptoethanol (MET) on metallic nanoparticle surface had been studied on this thesis. For such investigations it was employed the following tools: ultraviolet and visible absorption spectroscopy (UV-VIS), Raman scattering spectroscopy, surface enhanced Raman spectroscopy (SERS) and density functional theory. The localized surface plasmon resonance (LSPR) band was monitored on UV-VIS spectra to study the electronic properties of metallic nanoparticles involved in the interactions with the adsorbates and the size distributions. Silver nanoplates were synthesized in different conditions of temperature, multiple growing steps and using copper as a stabilizing doping. A small addition of copper, compared to silver, increased the triangular nanoprism yield of the original synthesis. These nanoparticles were used for adsorption study of MET. It was synthesized gold and silver nanospheres for studying Trp adsorption and other peptides on different chemical surroundings. The nanoprisms were utilized for LSPR study in the presence of MET at different concentrations, in addition to SERS spectra of this molecule. It has been observed the molecule concentration has a key role for self-assembled monolayer formation, which changes the most common conformer on the metallic surface. DFT calculation allowed us to simulate MET adsorption on silver surface (111) obtaining results related to the structures and stabilities of the conformers. Theory and experiment showed in agreement in the conditions studied and conclude the hydrogen bond is a key player in the monolayer properties. It was studied the adsorption of the isomers, L-Trp and D-Trp, and the peptides, Ala-Trp, Trp-Gly, pGlu-Lys-Trp-Ala-Pro and Trp-His-Trp-Leu-Gln-Leu, through SERS spectroscopy. In silver, the spectra showed amino acids and dipeptides tend to adsorb by the acid and amine group. In gold, an enhancement and shifting of the bands allowed us to identify the adsorption by the indole ring, specifically by the nitrogen atom. The spectra were obtained at concentration of 10-3mol.L-1 on different metals, however in presence of HCl the molecular concentration was 10-5mol.L-1. When HCl was added, the spectra showed a slightly different pattern, which suggest us that, in this condition, Trp interacts stronger to the surface.

碩士<br>國立暨南國際大學<br>應用化學系<br>99<br>We report here the electrochemical determination of 2-mercaptoethanol (2-ME) in alkaline aqueous solution by using cobalt(III) porphyrin/Nafion screen printed carbon electrodes (SPCE). Bare SPCE were electro-activated by potential scans ranging from -0.6 to 1.0 V for 10 cycles in pH 7 buffer solution. Then, a Nafion solution containing cobalt porphyrin was dropped onto the pre-actived electrode surfaces. Cyclic voltammetrograms of 5.0 mM 2-ME was studied in various buffer solutions at the modified electrodes. It was observed that the modified electrodes showed good electrocatalytic activity toward the oxidation of 2-ME. Flow injection amperometry (FIA) was studied in pH 12 buffer solution at the optimized conditions. Good analytical features were obtained, including a wide linear range (1~1000 µM), a low detection limit(0.2 µM) and high sensitivity (0.0093 µAµM-1). In addition, the interferent species, such as uric acid, glutathione and caffeine showed insignificant effect on the detection signals.

碩士<br>國立成功大學<br>化學系碩博士班<br>92<br>The thermal reactions and surface intermediates of HSCH2CH2OH on Cu(100) and Cu(111) under ultra-high vacuum have been studied by temperature-programmed reaction/desorption (TPR/D), X-ray photoelectron spectroscopy (XPS), and reflection-absorption infrared spectroscopy. In the case of Cu(111), -SCH2CH2OH is generated from HSCH2CH2OH dissociative adsorption on Cu(111) below 123K. At lower coverages, -SCH2CH2OH transforms to -SCH2CH2O-, a cyclic intermediate between 223-323K. Above 350K, -SCH2CH2O- decomposes to form carbon-containing products of CH4, C2H4, and CH3CHO. The relative amount of these two intermediates is dependent on temperature and surface coverage. In the case of Cu(100), thermal decomposition of HSCH2CH2OH is similar to Cu(111) and produces intermediates of -SCH2CH2OH, -SCH2CH2O-, and surface species containing C=C=O or C=C=S. Carbon-containing products of CH4, C2H4, and CH3CHO evolve between 300-400K. Desorption of sulfur-containing products are not observed in both cases.

碩士<br>國立暨南國際大學<br>應用化學系<br>100<br>We report here the electrochemical determination of 2-mercaptoethanol (2-ME) in aqueous solution by screen printed carbon electrode (SPCE) modified cobalt(III) porphyrin (Co(TMPyP)), multi-walled carbon nanotubes (MWCNT) and Nafion. Preparation of the modified electrode is easy and quickly, using a mixture of Nafion solution containing cobalt porphyrin and MWCNT.The modified electrode’s were prepared by deposition and dry methode. Cyclic voltammetrograms of 5.0 mM 2-ME was studied in various buffer solutions at the modified electrodes. It was observed that the modified electrodes showed good electrocatalytic activity toward the oxidation of 2-ME. Flow injection amperometry (FIA) was studied in pH 7 buffer solution at the optimized cinditions. Good analytical features were obtained, including a wide linear range (1~1000 µM), a low detection limit(0.93μM) and high sensitivity (6.6512 µAmM-1). In addition, the interferent species, such as glutathione showed insignificant effect on the detection signals.

碩士<br>國立暨南國際大學<br>應用化學系<br>101<br>In this study, we prepared the poly ionic liquid (PIL) and cobalt phthalocyanine (CoPc) modified electrodes, showing characteristics of electrocatalytic oxidation of thiol compounds in aqueous solution. The bi-layer modified electrode (SPCE/PIL/CoPc*) was constructed by polymerization the ionic liquid monomers on the screen-pirnted carbon electrode at 80℃ for 5 hours, casting the CoPc solution on the electrode surface, dried in the oven at 50℃ for 3hrs, then electrochemical pretreatment by potential scanning. The poly ionic liquid layer behaves as a bridge to improve the electode conductivity between SPCE and CoPc. The SPCE/PIL/CoPc* modified electrode showed excellent catalytic activity for the thiols (cysteine, GSH, 2-ME) compounds in pH 7.0 to pH 12.0 buffer solution. The electrochemical behavior of the modified electrode was invstigated using cyclic voltammetry and flow injection analysis methods. By the FIA method, the detection limit is 0.69M for 2-ME.

碩士<br>國立暨南國際大學<br>應用化學系<br>97<br>We prepared a cobalt porphyrin-modified electrode, showing characteristics of electrocatalytic oxidation of 2-mercaptoethanol in aqueous solution.The water-soluble cobalt(III) porphyrin was modified onto gold disk surface through 4-mercaptopyridine as a bridge. The modified electrode showed excellent catalytic activity for the 2-mercaptoethanol oxidation in 0.1M NaOH solution. The electrochemical behavior and stability of the modified electrode were investigated using cyclic voltammetry, UV-Vis and rotating disk electrode methods. The heterogeneous rate constant for the oxidation of 2-mercaptoethanol at the surface of the modified electrode and the diffusion coefficient of 2-mercaptoethanol were determined. Detection of thiols has been an important research subject in the biological and industrial world. The obtained modified electrode in this work was used for detection 2-mercaptoethanol in alkaline solutions. Cyclic votammetric results showed that the modified thin fim can facilitate electron transfer, lower the overpotential required and improve electrochemical behavior of 2-mercaptoethanol oxidation, as compared to the bare gold electrode. The way for the assembly of electrodes was easy, fast and highly stable with enhanced performances toward the electrocatalytic oxidation of 2-mercaptoethanol.

Catalytic activity of cobalt tetra ethoxythiophene and cobalt tetra phenoxypyrrole phthalocyanine complexes towards oxidation of 2-mercaptoethanol, L-cysteine and reduced glutathione is reported. It was found that the activity of the complexes depends on the substitution of the phthalocyanine ring, pH, film thickness and method of electrode modification. The high electrocatalytic activity obtained with adsorbed complexes in alkaline medium clearly demonstrates the necessity of modifying bare carbon electrodes to endow them with the desired behaviour.

Catalytic activity of cobalt tetra ethoxythiophene and cobalt tetra phenoxypyrrole phthalocyanine complexes towards oxidation of 2-mercaptoethanol, L-cysteine and reduced glutathione is reported. It was found that the activity of the complexes depends on the substitution of the phthalocyanine ring, pH, film thickness and method of electrode modification. The high electrocatalytic activity obtained with adsorbed complexes in alkaline medium clearly demonstrates the necessity of modifying bare carbon electrodes to endow them with the desired behaviour.