To see the other types of publications on this topic, follow the link: Chemically modified electrodes.
Dissertations / Theses on the topic 'Chemically modified electrodes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Chemically modified electrodes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Dicks, J. M. "Amperometric biosensors and chemically modified electrodes." Thesis, Cranfield University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233354.
Full text
2
Xin, Junhua Shannon Curtis. "Chemically modified electrodes a supramolecular assembly approach /." Auburn, Ala, 2008. http://hdl.handle.net/10415/1424.
Full text
3
Przeworski, J. E. "The development of chemically modified electrodes for electrocatalysis." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37822.
Full text
4
Spencer, G. C. W. "The development of conducting polymer electrodes." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239274.
Full text
5
Xu, Shuanghua. "Development and application of chemically modified electrodes for analysis." Thesis, University of Canterbury. Chemistry, 1992. http://hdl.handle.net/10092/8317.
Full textAbstract:
This thesis presents a study on development and application of chemically modified electrodes (CMEs) for analysis, especially for analysis of aluminium(III). A parallel study involved flow injection analysis with indirect amperometric detection.
The electrochemistry was studied for several electroactive ligands which bind strongly to aluminium(III). The effect of pH on redox behaviour was investigated. The complex formation between aluminium(III) and these ligands was examined under different conditions such as pH, electrolyte and temperature. For quantitative determination of aluminium(III), either the increase in peak height due to the redox processes of the formed aluminium(III)-ligand complex, or the decrease of the peak height for free ligand redox processes, was used.
Several CMEs were prepared using polymer coatings, chemisorption and by mixing ligand into the electrode material.
The use of CMEs consisting of charged polymers for preconcentration of analytes was investigated. The accumulation of aluminium(III) in polyxylylviologen coated electrodes as anionic phenolic complexes was studied. The measurement of aluminium(III)(4-nitrocatechol) complexes which have an overall negative charge resulted in a sensitive method for analysis of aluminium(III).
A 1,2-dihydroxyanthraquinone(alizarin)-modified graphite electrode was used in the voltammetric determination of aluminium(III). Alizarin was immobilised on a solid electrode by chemisorption. The electrode was applied in determination of exchangeable aluminium(III) in soils. This provided a simple, rapid method for monitoring aluminium in the environment.
Ligands mixed into electrode materials (carbon paste and graphite epoxy) were studied. Graphite epoxy modified with 4- nitrocatechol showed good results for the determination of aluminium(III).
In CME studies, it was found that the loss of ligand from CMEs due to irreversible oxidation of ligand and other reasons limits electrodes to single-use.
The method for determination of aluminium(III) by adsorptive stripping voltammetry of its SVRS complex was modified by room temperature reaction at a higher pH, followed by accumulation in acidified solution. This method provided good results with high sensitivity and reproducibility and significantly shorter analysis time.
Aluminium(III) was determined in a flow injection system involving the formation of the aluminium(III)-1,2- dihydroxyanthraquinone-3-sulphonic acid (DASA) complex and amperometric measurement of excess DASA at +0.50 V on a gold electrode. Electrode fouling by adsorption of ligand oxidation products was minimized by use of a double pumping system and cathodic/anodic voltage cycling. The method was applied to soil extracts.
A simple flow system for magnesium(II) determination in natural waters and serum was developed. This involved complexation of magnesium(II) with the redox active ligand eriochrome black T (EBT). Analysis of human blood serum samples was effected by two methods: (1) direct injection of serum after dilution and (2) after dialysis to effect separation of magnesium(II) from acidified serum in the flow system. Electrode fouling by adsorption of EBT oxidation products and serum in the flow system was minimized by use of several surfactants and a dialyzer.
6
Lowens, Michael James. "Studies on polypyrrole chemically modified electrodes for analytical voltammetry." Thesis, University of Salford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299127.
Full text
7
Lau, Chung Yin. "Electroanalytical behaviors of chemically modified electrodes bearing complexing ligands." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/833.
Full text
8
Song, Fayi. "Studies on the preparation and electroanalytical applications of chemically modified electrodes." HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/268.
Full text
9
Elhag, Sami. "Chemically Modified Metal Oxide Nanostructures Electrodes for Sensing and Energy Conversion." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134275.
Full textAbstract:
The goal of this thesis is the development of scalable, low cost synthesis of metal oxide nanostructures based electrodes and to correlate the chemical modifications with their energy conversion performance. Methods in energy conversion in this thesis have focused on two aspects; a potentiometric chemical sensor was used to determine the analytical concentration of some components of the analyte solution such as dopamine, glucose and glutamate molecules. The second aspect is to fabricate a photo-electrochemical (PEC) cell. The biocompatibility, excellent electro-catalytic activities and fast electron transfer kinetics accompanied with a high surface area to volume ratio; are properties of some metal oxide nanostructures that of a potential for their use in energy conversion. Furthermore, metal oxide nanostructures based electrode can effectively be improved by the physical or a chemical modification of electrode surface. Among these metal oxide nanostructures are cobalt oxide (Co3O4), zinc oxide (ZnO), and bismuth-zincvanadate (BiZn2VO6) have all been studied in this thesis. Metal oxide nanostructures based electrodes are fabricated on gold-coated glass substrate by low temperature (< 100 0C) wet chemicalapproach. X-ray diffraction, x-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption and photoluminescence were used to investigate the optical properties of the nanostructures. The resultant modified electrodes were tested for their performance as chemical sensors and for their efficiency in PEC activities. Efficient chemically modified electrodes were demonstrated through doping with organic additives like anionic, nonionic or cationic surfactants. The organic additives are showing a crucial role in the growth process of metal oxide nanocrystals and hence can beused to control the morphology. These organic additives act also as impurities that would significantly change the conductivity of the electrodes. However, no organic compounds dependence was observed to modify the crystallographic structure. The findings in this thesis indicate the importance of the use of controlled nanostructures morphology for developing efficient functional materials.
10
Perera, Dingiri Mudiyanselage Neluni T. "Study of permeability changes induced by external stimuli on chemically modified electrodes." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/7030.
Full textAbstract:
Doctor of PhilosophyDepartment of Chemistry
Takashi Ito
This research was focused on understanding how external stimuli affect the permeability of the chemically modified electrodes, and how the materials used in modifying the working electrodes respond to the changes in the surface charge. We adopted a voltammetric type electrochemical sensor to investigate the permeability effects induced by pH and organic solvents. The working electrodes used in this research were chemically modified with thioctic acid self assembled monolayer (TA SAM), track etched polycarbonate membranes (TEPCM) and PS-b-PMMA nanoporous films (polystyrene-block-polymethylmethacrylate). We studied the permeability behavior of each of the material upon application of external stimuli. In chapter 3, the permeability changes induced by change in surface charge of thioctic acid SAM was investigated. The surface charge of the monolayer was tuned by changing pH of the medium, which resulted in decrease of redox current of a negatively charged marker due to deprotonation of the surface –COOH groups of TA SAM. Decrease in redox current reflected a decrease in the reaction rate, and by using closed form equations the effective rate constants at several pKa values were extracted. In chapter 4, permeability changes induced by pH in TEPCM were investigated. We assessed the surface charge of these membranes via cyclic voltammetry generated for neutral and charged redox molecules. Limiting current of charged markers were affected by the surface charge induced by pH, where as the redox current for the neutral marker was not affected. Experimental redox currents were larger than the theoretical current, indicating that redox molecules preferentially distributed in a surface layer on the nanopore. Organic solvent induced permeability changes of PS-b-PMMA nanoporous films were investigated via electrochemical impedance spectroscopy and AFM. Higher response of pore resistance in the presence of organic solvents indicated either swelling of the nanoporous film or partitioning of organic solvents in the pores. However AFM data revealed that the permeability changes are due to partitioning of the solvents rather than swelling of the porous film, since there was no appreciable change if the pore diameter in the presence of solvents.
11
Bin, Hamzah Hairul Hisham. "A study on the estimating DPV surface coverages for chemically modified electrodes." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416440/.
Full textAbstract:
This thesis is about estimating the surface coverages (Г) of immobilised redox molecules at modified electrode surfaces using differential pulse voltammetry (DPV). The cyclic voltammetry (CV) technique less sensitive than DPV technique because of the background current that can obscure the Faradaic current of the attached redox molecules. As a result, CV technique less sensitive for measurements of low surface concentrations of immobilised redox species. This is not the case for DPV. Currently, there is no specific agreed procedure to determine the surface coverages by DPV. Thus to establish the method to determine the surface coverages of immobilised redox molecules at the surface of the electrode by DPV measurement was a prime interest in this research. Secondary to that point, exploring a new strategy in preparing chemically modified electrodes in order to obtain a better surface coverages of covalently immobilised redox molecules at electrode surfaces was also an aim of this thesis. Enhanced DPV currents were obtained when an external resistance (Rext) of suitable magnitude was added in the DPV cell circuit for electrode modified with either for organic, DNA labelled or inorganic redox systems. This motivated us to develop an experimental model for estimating the DPV surface coverages (ГDPV, exp) of attached redox molecules at electrode surfaces at suitable Rext. Moreover, a simple equation for estimating the ΓDPV, exp based on DPV parameters is presented in this study and shown to work well, given several underlying assumptions. Our approach makes use of an additional Rext in the DPV cell circuit and several non-adjustable DPV parameters. Subsequently, the ΓDPV, exp of immobilised redox probes can be estimated by integrating the area under the oxidation peak of the differential pulse voltammograms (DPVs) at a suitable Rext. The experimental approach was verified by numerical modelling using a specially developed DPV simulation in MATLAB. The electrochemical parameters used for the DPV simulation, such as uncompensated solution resistance in an electrochemical cell (Ru), double layer capacitance (Cdl) and electrode kinetics (ks and α) were obtained from cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS) measurements made on the modified electrodes. Good agreement was obtained between the experimental DPV and the simulations. The second part of this thesis was focused on extracting thermodynamic and kinetic parameters such as the standard potential (E°), the diffusion coefficient (Do), surface coverages, the rate constant for adsorption (kA), the rate constant for homogenous reaction (kH), the rate of electron transfer (ks), and the transfer coefficient (α) for the electrochemical grafting of primary amine linkers onto GC electrode surfaces by numerical simulation. These parameters are impossible to access by experimental approaches. The grafting process was performed in two different solvents; by electrochemical grafting from neat ACN and by electrochemical grafting in a mixed solvent of ACN and sodium hydrogen carbonate (NaHCO3). In the case of the mixed-solution method, the ratio of ACN to NaHCO3 was 4:1. The primary amine of the EDA-Boc molecule was studied as an experimental model in this work. Using a specially developed CV simulation for inhibiting species at the surface of the electrode, the experimental CVs for the electrochemical grafting of EDA-Boc in the two solutions were simulated. Good agreement between experimental CV and the simulated CV was obtained. Moreover, this simulation allows us to extract the aforementioned parameters, which are not electrochemically accessible. To investigate the effect of the presence of NaHCO3 on immobilised EDA-Boc at the surface of GC electrodes, the anthraquinone (AQ) was covalently coupled to the grafted EDA (after removal of the Boc group). The CV and DPV surface coverages of covalently attached AQ on the EDA linker based on the two methods of electrografting were compared. The developed DPV simulation was also employed in this work in order to show the utility and flexibility. A good agreement between experimental and simulated DPV was achieved.
12
Han, Qi. "Chemically modified electrodes with inorganic films of noble metal complexes and metal oxides : preparation, characterization and applications /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202002%20HAN.
Full text
13
Lakbub, Jude. "Fabrication of Chemically Modified Nanometer-sized Gold Electrodes and Their Application in Electrocatalysis at Pt Nanoparticles." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1385.
Full textAbstract:
Hydrogen evolution via proton reduction occurs at a high rate at the surface of Pt than at Au electrodes. Using cyclic voltammetry, chemically modified nanometer-sized Au electrodes, prepared by the Laser-Assisted Puller Method, were employed to examine current amplification by electrocalysis at Pt nanoparticles adsorbed on the modified Au electrode surfaces. The electrodes were modified with Self-Assembled Monolayers (SAMs) of cysteamine and soaked in Pt colloid solutions overnight. Monitoring the decrements of the characteristic steady-state catalytic current for proton reduction indicated that aggregates of Pt nanoparticles are adsorbed on the cysteamine monolayers and desorb from them particle by particle. The results also indicate that some particles are strongly attached to the modified electrode surface and do not deplete even after thorough rinsing.
14
Enkhtuvshin, Dorjpalam. "Photoelectrochemical properties of TiO2-based thin film electrodes chemically modified by homogeneous- and sectional-doping processes." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147654.
Full text
15
Shedge, Hemangi Y. "Specific and non-specific binding of proteins and nucleic acids on chemically modified reticulated vitreous carbon electrodes." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1246559605/.
Full text
16
Lima, Phabyanno Rodrigues. "Eletrodo modificado a base de 4-nitroftalonitrila : sensor amperometrico para quantificação de alguns antioxidantes de relevancia biologica." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248416.
Full textAbstract:
Orientadores: Lauro Tatsuo Kubota, Marilia Oliveira Fonseca GoulartTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-13T21:41:20Z (GMT). No. of bitstreams: 1 Lima_PhabyannoRodrigues_D.pdf: 3618536 bytes, checksum: e30e8edf8ae8a08c57fdb0a003e8b6fd (MD5) Previous issue date: 2009
Resumo: Neste trabalho descreve-se o desenvolvimento de sensores amperométricos a base de um simples eletrodo de pasta de carbono modificado com um novo mediador redox, a 4-nitroftalonitrila (4-NO2FN), para a determinação de alguns antioxidantes de relevância biológica [L-cisteína (L-CySH), L-glutationa (L-GSH), ácido L-ascórbico (L-AscH2), ácido úrico (AU) e nicotinamida adenina dinucleotídeo (forma reduzida) (NADH)]. Com este propósito, inicialmente, a 4-NO2FN foi ativada in situ, gerando o par redox nitroso/hidroxilamina (4-NOFN/4- NHOHFN) estável na superfície eletródica, o qual apresentou atividade electrocatalítica na oxidação dos analitos estudados. As técnicas empregadas para a realização deste trabalho foram voltametria cíclica e cronoamperometria, as quais foram utilizadas para estudar o comportamento dos eletrodos modificados, para otimização dos parâmetros experimentais, obtenção dos parâmetros cinéticos e caracterização analítica dos sensores. Além disso, os estudos hidrodinâmicos e cronoamperométricos foram realizados com o objetivo de se obter maiores informações sobre os processos de oxidação entre L-AscH2, NADH e os eletrodos modificados. Assim, por meio dos gráficos e equações de Koutech- Levich e Cottrell foi possível obter os valores para o coeficiente de difusão (D) e constante de velocidade da reação (kobs) para L-AscH2 e NADH. Os valores do D e de kobs, determinados para L-AscH2 e NADH, foram de 9,0x10 cm s e 2,4x10 cms, 6,0x10 molL s e 1,0x10 molL s, respectivamente. O aumento na velocidade de reação, tanto para o L-AscH2 quanto para o NADH, foi atribuído à eficiente transferência de elétrons entre estas espécies e o par redox 4-NOFN/4-NHOHFN eletrogerado in situ. Sob condições otimizadas, o sensor amperométrico apresentou uma faixa de resposta linear (mmol L), limite de detecção (mmol L), quantificação (mmol L) e sensibilidade (nA L mmol) para L-CySH (a), L-GSH (b), L-AscH2 (c), AU (d) e NADH (e), os quais apresentaram os valores de (a) 0,8-13,2, 0,25, 0,8, 37,0; (b) 8,0-83,0, 2,7, 8,0, 54,0; (c)5,0-120,0, 1,6, 5,5, 108,0; (d) 5,0- 120,0, 1,3, 4,5, 121,6 e (e) 0,8-8,5, 0,25, 0,82, 500,0, respectivamente. Após a aplicação destes sensores em amostras de interesse, estudos de adição e recuperação dos analitos foram realizados para avaliar a exatidão dos métodos e verificou-se que foi possível uma percentagem de recuperação entre 98,5 e 102,0% para L-CySH, L-GSH, L-AscH2 e AU
Abstract: In this work, the development of amperometric sensors based on a simple carbon paste electrode modified with a new redox ¿mediator¿, 4- nitrophthalonitrile (4-NO2PH), for quantification of some antioxidants of biological relevance (L-cystein (L-CySH), L-glutathione (L-GSH), L-ascorbic acid (L-AscH2), uric acid (UA) and b-nicotinamide adenine dinucleotide (NADH)), is described. For this purpose, initially, 4-NO2PH was activated in situ, generating a stable redox-active nitroso/hydroxylamine system (4- NOPH/4-NHOHPH) on the electrodic surface, which presented electrocatalytic activity towards the oxidation of studied analytes. The techniques used in this work were cyclic voltammetry and cronoamperometry, to study the behavior of the modified electrodes, for the experimental parameters optimization, for the attainment of the kinetic parameters and analytical characterization of the sensors. Hydrodynamic and cronoamperometric studies were carried out with the aim to get information on the reduction processes and oxidation of L-AscH2 and NADH, respectively, on the modified electrodes. Through the Koutech-Levich and Cotrell plots it was possible to obtain the values for the diffusion coefficient (D) and kinetic constant of the reaction (kobs) for the analytes in study. The values of the diffusion coefficient and kobs, determined for L-AscH2 and NADH were 9,0x10 cm s and 2,4x10 cms, 6,0x10 molL s and 1,0x10 molL s, respectively. The increase of the reaction rate for L-AscH2 and NADH was attributed to the efficient electron transfer between the studied species and immobilized electroactive species on the surface of the carbon paste electrode. After optimizing conditions, the sensor provided a linear response range (mmol L), limit of detection (LOD) (mmol L), limit of quantification (LOQ) (mmol L) and sensitivity (nA L mmol) for L-CySH (a), L-GSH (b), L-AscH2 (c), UA (d) e NADH (e) of (a) 0.8-13.2, 0.25, 0.8, 37.0; (b) 8.0-83.0, 2.7, 8.0, 54.0; (c)5.0-120.0, 1.6, 5.5, 108.0; (d) 5.0-120.0, 1.3, 4.5, 121.6 and (e) 0.8- 8.5, 0.25, 0.82, 500.0, respectively. After the application of these sensors in samples of interest, studies of addition and recovery of the analytes were carried out to evaluate the error of the methods and it was verified recovery percentages between 98.5 and 102.0% for L-CySH, L-GSH, L-AscH2 and AU, were obtained
Doutorado
Quimica Analitica
Doutor em Ciências
17
Pires, Bruno Morandi 1989. "Estratégia de modificação de eletrodos com filmes de azul da Prússia a partir de complexo pentacianoferrato." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250677.
Full textAbstract:
Orientador: Juliano Alves BonacinDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-26T03:08:14Z (GMT). No. of bitstreams: 1 Pires_BrunoMorandi_M.pdf: 2407620 bytes, checksum: 2e530d02b80b21bc630f85382a3a4ece (MD5) Previous issue date: 2014
Resumo: Complexos de cianoferratos receberam destaque na década de 70, com a investigação de suas estruturas eletrônicas e reatividade. Estas espécies possuem grande afinidade por compostos N-heterocíclicos, aminoácidos, sulfóxidos, tio éteres e tioamidas. A modificação com diferentes ligantes permite a modulação suas propriedade e reatividade. Esses complexos também podem produzir o azul da Prússia, que é um mimético da enzima peroxidase. Neste trabalho, foi sintetizado o complexo de pentacianoferrato (II) [Fe(CN)5(isn)]4- (isn= 4carboxilatopiridina ou isonicotinato), que devido a sua labilidade, foi utilizado na obtenção filmes de azul da Prússia a partir de deposição sobre eletrodos de carbono vítreo. Os filmes utilizados foram utilizados na determinação eletrocatalítica de ácido ascórbico, que é um analito de interesse biológico e industrial. A caracterização do complexo foi realizada através de espectroscopia eletrônica UV-Vis e espectroscopia vibracional na região do infravermelho, cujo espectro vibracional teórico apresentou grande concordância com os resultados experimentais, o que reforça a identidade do produto obtido. Outra técnica utilizada na caracterização do complexo foi a voltametria cíclica. Experimentos de cinética de substituição do ligante N-heterocíclico mostram que a reação de troca por DMSO ocorre por mecanismo dissociativo, com parâmetros cinéticos e termodinâmicos em concordância com complexos análogos descritos na literatura. A partir do complexo sintetizado foi possível obter filmes finos de azul da Prússia pelo método potenciostático. Esses filmes, estáveis em pH 3,0 e 5,0, foram utilizados na oxidação eletrocatalítica de ácido ascórbico, apresentando resposta linear na determinação deste analito. Também foi observada variação do potencial de pico anódico com o aumento do valor do pH. Com estes resultados, conclui-se que os filmes obtidos por essa metodologia tem grande potencial na construção de sensores eletroquímicos
Abstract: Cyanoferrate complexes have received attention in the 1970¿s, mainly the investigation of their electronic structures and reactivity. These species have a great affinity for N-heterocyclic compounds, amino acids, sulfoxides, thioethers and thioamides. The modification with different ligands allows the modulation of their properties and reactivities. These complexes can also produce Prussian blue, which is a well-known mimetic of peroxidase enzyme. In this work, the pentacyanoferrate (II) complex [Fe(CN)5(isn)]4- (isn = 4-carboxilatepyridine or isonicotinate), which reactivity was used to obtain Prussian blue films deposited on the surface of glassy carbon electrodes. The films were used in the electrocatalytical quantification of ascorbic acid, which is a very important analyte with industrial and biological importance. The characterization of the complex was performed using UV-Vis and infrared spectroscopy, which theoretical calculation showed good agreement with experimental data. Also, cyclic voltammetry was used to determine the electrochemical properties of the complex. Substitution kinetics of the N-heterocyclic ligand indicated that the switch for DMSO occurs by a dissociative mechanism, with kinetic and thermodynamic parameters in agreement with analog complexes described in literature. The synthesized complex was used to obtain thin Prussian blue films by the potentiostatic method. These films, which were stable at pH 3.0 and 5.0, were used in the catalytical electrooxidation of ascorbic acid, showing linear response for the determination of this analyte. Another interesting feature of this system is the variation of the anodic peak potential with pH change. From these results, it was possible to conclude that the films obtained using this methodology have great potential in the construction of electrochemical sensors
Mestrado
Quimica Inorganica
Mestre em Química
18
Deliberto, Laíla Aparecida. "Eletrodos quimicamente modificados com Poli (benzil viologênio): comportamento eletroquímico de fármacos nitroderivados." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-16042013-095504/.
Full textAbstract:
Na área da saúde, destacam-se alguns fármacos amplamente administrados, os quais possuem grupamentos nitro em suas moléculas, como o Clonazepam (CNZ), Nitrazepam (NTZ) e Nimesulida (Nimes). O CNZ e o NTZ são utilizados ilicitamente em coquetéis entorpecentes, fragilizando vítimas. A Nimes é anti-inflamatório amplamente administrado e frequentemente usado sem prescrição médica. As metodologias de detecção e quantificação destes fármacos são, na sua maioria, dispendiosas, desenvolvidas por HPLC, GC, etc. Poucos trabalhos utilizam determinação eletroanalítica e dentre eles, menos ainda utilizam eletrodos quimicamente modificados (EQMs). Os EQMs melhoram a seletividade e sensibilidade das análises. Dentre as formas de modificação, a metodologia de filmes poliméricos é muito versátil e possibilita o desenvolvimento de eletrodos específicos. Uma classe importante de polímeros é a dos derivados de viologênio, como o Poli (benzil viologênio) (PBV). Este polímero é empregado com diferentes finalidades. Possui três estados de oxidação, um deles; o PBV+ atua como mediador redox. E, a partir de experimentos prévios em nosso laboratório demonstrou ainda a possibilidade de atuar na redução de nitrocompostos. Neste sentido, este trabalho determinou as melhores condições experimentais para obtenção de um EQM com o PBV para seu emprego em análise e quantificação de fármacos nitroderivados (CNZ, NTZ e Nimes), bem como em amostras comerciais, utilizando a técnica de voltametria cíclica. Este trabalho contribuiu para o desenvolvimento de uma metodologia eficaz de modificação do eletrodo de carbono vítreo (CV) com o PBV sintetizado. Este método garantiu o controle da cobertura e a linearidade nas análises. Assim, o método foi padronizado com a aplicação de eletrólise por 30 s durante o terceiro ciclo em -0,4 V. A varredura adotada foi 50 mV s-1 de 0 a -0,8 V. Esse padrão forneceu de 2,0 a 3,0 nmol cm-2 de cobertura. O eletrodo CV-PBV não apresentou dificuldades na transferência de carga da superfície do eletrodo para o polímero, apesar do valor de k = 5,2 s-1 em tampão fosfato 0,1 mol L-1 pH 7,0. O valor do coeficiente difusional de cada fármaco foi determinado em tampão fosfato 0,1 mol L-1 pH 7,0. Os estudos de redução dos fármacos em diferentes pHs estão de acordo com o mecanismo descrito na literatura. Além disso, os resultados indicam que o eletrodo modificado diminui a influência do pH sobre a redução dos fármacos. As quantificações dos fármacos foram feitas por curvas padrões com os eletrodos CV e Au, polidos e modificados. As correntes foram lineares até a concentração de 120 mol L-1. A modificação do eletrodo de CV com o PBV diminuiu, no mínimo, em aprox. 80 mV o potencial de redução dos fármacos em pH 7,0 em relação ao eletrodo de CV polido. A exceção foi o eletrodo de ouro modificado (Au-PBV) na análise de Nimes. Pode-se ainda, atribuir à modificação do eletrodo com o PBV o aumento da sensibilidade das análises em comparação aos respectivos eletrodos polidos. Somente a determinação do NTZ não apresentou o mesmo efeito. O eletrodo CV-PBV foi empregado com sucesso na quantificação dos fármacos (NTZ, CNZ e Nimes) em amostras comerciais de Rivotril®, Sonebon® e Nimesulida - medicamento genérico. As quantificações apresentaram aproximadamente 100% de recuperação. A normalização das diferentes análises pelos valores das coberturas dos eletrodos mostrou uma curva analítica com boa correlação linear. Finalmente, os resultados apresentados neste trabalho sugerem a possibilidade de desenvolver eletrodos descartáveis. Estes eletrodos podem ser empregados na análise de substâncias utilizadas de forma ilícitas, neste caso, o coquetel chamado Boa noite Cinderela, para uso da perícia forense em análise amperométrica, no próprio local investigado. Estes eletrodos também podem ser aplicados nas indústrias farmacêuticas, nos setores de controle de qualidade de fármacos e medicamentos.In health care, broadly administered drugs can be highlighted, which possess nitro group moieties within their molecules, such as the Clonazepam (CNZ), Nitrazepam (NTZ), and Nimesulide (Nimes). CNZ and NTZ are illicitly administered as part of narcotics drinks, weakening their victims. Nimes is an anti-inflammatory drug widely administered and often used in self-medication. Detection and quantification methods of these drugs are in the majority of cases costly and involve techniques such as HPLC, gas chromatography, etc. Only few studies have made use of electroanalytical determination, and among them, even fewer have made use of chemically modified electrodes (CME). CMEs improve selectivity and sensitivity of analysis. Among of modification methods, polymeric films are very versatile and make possible the development of specific electrodes. An important type of polymers comprise Viologen derivatives, such as Poly (benzyl viologen) (PBV). This polymer is used serving different purposes. This polymer has three oxidation states; one of them, PBV+, acts as a redox mediator. Also in addition, our group has provided evidence for the possibility of PBV+ to act reducing nitro compounds. In this way, in the present work it was determined the best experimental conditions for developing CME with PBV for further application in analysis and quantification of nitro derivative drugs (CNZ, NTZ and Nimes), as well as commercial samples, through the use of cyclic voltammetry technique. This work has contributed to the development of an effective methodology for the modification of glassy carbon (GC) electrodes with synthesized PBV. This method guaranteed the control of coverage and the linearity of the analysis. In this way, this method was standardized with a potential hold during the third cycle of about -0.4V for 30 sec. Scan rate of potential was 50 mV s-1, from 0 to -0.8 V. This method provided a coverage 2.0 to 3.0 nmol cm-2. The electrode GC-PBV did not show difficulties to charge transfer from the electrode surface to polymer, although the value of k was 5.2 s-1 in 0.1 mol L-1 phosphate buffer solution, pH 7.0. The difusional coefficient value of each drug was determined in 0.1 mol L-1 phosphate buffer solution, pH 7.0. Reduction studies of drugs in different pHs were in agreement with mechanisms described in the literature. Furthermore, results suggest that modified electrode decreased pH influence regarding drug reduction. Drug quantification was achieved from standard curves using GC and gold electrodes, polished and modified. Currents were linear up to 120 mol L-1. GC electrode modification with PBV decreased, at least, in approximately 80 mV, the drug potential reduction at pH 7.0 compared to respective polished electrode. The exception was found for gold modified electrode during Nimes analysis. It can be also attributed to modification with PBV the increase of analysis sensitivity when compared to respective polished electrodes. Only NTZ determination did not show the same effect. The GC-PBV was successfully employed for drug quantification (NTZ, CNZ and Nimes) from commercial samples, such as Rivotril®, Sonebon® and Nimesulide generic medicine. Drug quantification exhibited recovery close to 100%. Standardization of different analysis by electrode coverage value showed good linear correlation. Finally, results suggest the possibility to develop disposable electrodes. These electrodes can be employed to illicit substance analysis, in the present case, the narcotic drinks known in Brazil as Boa noite Cinderela, in addition to use in forensics during amperometic analysis at the site of investigation. Also, such electrodes could be used in pharmaceutical industries, for drug and medicine quality control.
19
Gabriel, Junior Suelino [UNESP]. "Preparação, caracterização e aplicações eletroanalíticas de silsesquioxanos e dendrímeros modificados suportados na superfície da sílica gel." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91960.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0
Previous issue date: 2010-10-01Bitstream added on 2014-06-13T20:14:08Z : No. of bitstreams: 1
gabrieljunior_s_me_ilha.pdf: 1458989 bytes, checksum: 61fbe8b93b56e59134558e478f7ab91e (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O presente trabalho descreve a preparação, caracterização e as aplicações eletroanalíticas de silsesquioxanos e dendrímeros modificados suportados na superfície da sílica gel. A primeira etapa consistiu em ancorar o silsesquioxano ([H2N(CH2)3]8Si8O12) e o dendrímero Hexadecaamino Poli(propileno)imina (DAB-Am- 16) na superfície da 3-cloropropil sílica gel. Os materiais obtidos, SAC e SD, respectivamente, foram caracterizados pelas técnicas de Infravermelho (FTIR), RMN 29Si e 13C no estado sólido e Energia Dispersiva de Raios-X (EDX). A segunda etapa foi interagir o SAC e o SD com íons de Cu2+ e Ni2+ e posterior complexação com substâncias eletroativas, tais como: ferricianeto de potássio e nitroprussiato de sódio formando, dessa forma, os complexos binucleares: CuHCFSAC, NiHCFSAC, CuNPSAC, CuHCFSD, NiHCFSD e CuNPSD que foram caracterizados por Infravermelho (FTIR) e voltametria cíclica (VC). Os espectros na região do Infravermelho dos materiais supracitados exibiram freqüências próximas ou iguais a 2090 cm-1, atribuídas ao estiramento n(C N) característico do hexacianoferrato e nitroprussiato formados na superfície da SAC e SD. Utilizou-se estes materiais na construção do eletrodo de pasta de grafite os quais foram testados na oxidação eletrocatalítica de substâncias biologicamente importantes tais como a dipirona sódica e nitrito de sódio após um rigoroso estudo sobre o comportamento voltamétrico. O eletrodo de pasta de grafite contendo o CuHCFSAC exibiu dois pares redox com potenciais médios (Em) de: (Em)1= 0,29 V e (Em)2= 0,72 V vs Ag/AgCl (KCl =1.0 molL-1; v = 20 mV s-1) ambos atribuídos aos processos redox Cu(I)/Cu(II) e [Fe(II)(CN)6]4- / [Fe(III)(CN)6]3-, respectivamente, valores estes bem próximos para o CuHCFSD. Os eletrodos de NiHCFSAC e NiHCFSD exibiram...
This work describes the preparation, characterization and electroanalytical properties of modified silsesquioxanes and dendrimers supported onto the silica gel surface. The first step was to anchor the silsesquioxane [(H2N(CH2)3] 8Si8O12) and dendrimer Hexadecaamino Poly(propylene)imine (DAB-Am-16) onto the 3-chloropropyl silica gel surface. The materials obtained, SAC and SD, respectively, were characterized by infrared (FTIR), 29Si NMR and 13C solid state and Energy Dispersive X-ray (EDX). The second step was interact the SAC and SD with Cu2+ and Ni2+ ions and subsequent complexation with electroactive substances, such as: ferricyanide of potassium and sodium nitroprusside forming binuclear complexes: CuHCFSAC, NiHCFSAC, CuNPSAC, CuHCFSD, NiHCFSD and CuNPSD which were characterized by Infrared (FTIR) and cyclic voltammetry (CV). The spectra in the infrared region of the above materials exhibited frequencies near or equal to 2090 cm-1 assigned to stretching n(C N) characteristic of nitroprusside and hexacyanoferrate formed onto the SD and SAC surface. We used these materials in the construction of carbon paste electrode which were tested in the electrocatalytic oxidation of biologically important substances such as sodium dipyrone and sodium nitrite after a rigorous study about voltammetric behavior. The graphite paste electrode containing CuHCFSAC exhibited two redox couples with midpoint potentials (Em) of: (Em)1 = 0.29 V and (Em)2 = 0.72 V vs. Ag/AgCl (KCl = 1.0 mol L-1, v = 20 mV s-1) both assigned to the redox processes Cu(I)/Cu(II) and [Fe(II)(CN)6]4- / [Fe(III)(CN)6]-3, respectively, values very near to the CuHCFSD. The electrodes of NiHCFSAC and NiHCFSD each exhibited two redox couples with midpoint potentials (Em): (Em)1 = 0.29 V and (Em)2 = 0.51 V vs Ag/AgCl (KCl = 1.0 mol L-1, v = 20 mV s- 1) both... (Summary complete electronic access click below)
20
Menezes, Matheus Manoel Teles de. "Desenvolvimento de sensores voltamétricos e piezelétricos modificados quimicamente com cucurbiturilas para análises de cocaína em amostras de interesse forense." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-13012015-224604/.
Full textAbstract:
Considerando a relevância dos trabalhos onde se utiliza eletrodos quimicamente modificados e o pequeno número de estudos envolvendo cocaína e seus interferentes (cafeína, teobromina e lidocaína), por técnicas eletroquímicas ou piezelétricas, este estudo tem como objetivo o desenvolvimento de eletrodos de ouro e platina quimicamente modificados com compostos da classe das cucurbiturilas (CB[5], CB[6] e CB[7]) para a detecção de cocaína. A técnica de microbalança de cristal de quartzo foi empregada a fim de se estudar cocaína padrão e seus interferentes, em fase gasosa. Os eletrodos de ouro foram quimicamente modificados com cucurbiturilas e o modificador CB[6] apresentou os melhores resultados. Medidas por voltametria cíclica foram realizadas utilizando-se um potenciostato Autolab III acoplado a um computador, com eletrodo de ouro e platina atuando como eletrodo de trabalho, Ag/AgCl como eletrodo de referência e eletrodo espiral de platina como eletrodo auxiliar, com velocidade de varredura de 0,1 V.s-1 (100 mV.s-1). Os parâmetros voltamétricos foram otimizados para tornar as análises mais rápidas e sensíveis sem perda de qualidade ou intensidade do sinal voltamétrico. O eletrodo de platina quimicamente modificado com filme de cucurbit[6]urila apresentou aumento da corrente de pico catódica quando estudado frente à cocaína, teobromina e lidocaína. Análises com eletrodo de platina sem modificador químico apresentaram limite de detecção de 4,14.10-6 mol.L-1 e limite de quantificação de 1,38.10-5 mol.L-1 , para a cocaína, e na presença do modificador químico CB[6] apresentou limite de detecção de 1,36.10-6 mol.L-1 e limite de quantificação de 4,54.10-6 mol.L-1 . Eletrodos de ouro com ou sem a presença de modificadores químicos não apresentaram sinal para nenhum analito.Considering the importance of chemically modified electrodes and the small amount of the cocaine study and their interfering (caffeine, theobromine and lidocaine) using electrochemical and piezoelectric techniques, this study aims to investigate the development of the gold and platinum electrodes chemically modified by cucurbiturils (CB[5], CB[6] and, CB[7]) in order to detect cocaine. The Quartz Crystal Microbalance technique was employed in order to study in gas phase the standard samples of cocaine and their interfering. Gold electrode was chemically modified with cucurbiturils films and the CB[6] modifier showed the best results. The cyclic voltammetric measurements were performed using a Autolab III potentiostat coupled to a computer, being gold and platinum as the working electrode, Ag/AgCl as the reference electrode and platinum wire as counter electrode, using a scan rate of 0,1 V.s-1 (100 mV.s-1). The voltammetric parameters were optimized in order to make the analysis faster and more sensitive without loss of intensity and quality of the voltammetric signal. The platinum electrode modified by cucurbit[6]uril film showed an increase of cathodic current peak when electrode was exposed to cocaine, theobromine and lidocaine. Analysis employed platinum working electrode without chemical modifier showed a detection limit of 4.14 . 10-6 mol.L-1 and quantification limit of 1.38 . 10-5 mol.L-1 for cocaine and with chemical modifier CB[6] showed a detection limit of 1.36 . 10-6 mol.L-1 and quantification limit of 4.54 . 10-6 mol.L-1 . Gold electrodes with or without chemical modifiers showed no response for any analyte.
21
Ribeiro, Maria Fernanda Muzetti. "Desenvolvimento de métodos voltamétricos para a quantificação de LSD utilizando-se o eletrodo de pasta de carbono modificado com complexo de base de Schiff." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-22122015-224845/.
Full textAbstract:
Nos últimos anos, vários métodos eletroanalíticos foram desenvolvidos a fim de tornarem mais práticas e acessíveis às análises químicas de substâncias entorpecentes realizadas pela polícia científica. Com a sensibilidade e seletividade compatíveis com as dos métodos instrumentais convencionais, é a portabilidade da técnica eletroanalítica que se sobressai e tem apresentado grande potencial para tais aplicações. O uso de complexos metálicos com as bases de Schiff como modificadores do eletrodo de trabalho, tornou ainda mais promissora a utilização destes métodos para a detecção e quantificação de entorpecentes. Os eletrodos de pasta de carbono também contribuem para a praticidade da eletroanalítica, uma vez que são produzidos de forma simples e barata. Desta forma, neste projeto foram desenvolvidos métodos voltamétricos para a quantificação da dietilamida do ácido lisérgico (LSD), utilizando-se o eletrodo de pasta de carbono modificado com o complexo [UO2(Ac-ophen)]·H2O. A aplicação do KCl como eletrólito suporte, em solução aquosa, diferencia estes métodos do encontrado na literatura. Nas análises, foram empregadas as técnicas de voltametria cíclica, onda quadrada e de pulso diferencial. A linearidade no aumento da corrente frente às variações da concentração do LSD possibilitou a obtenção das curvas analíticas com desvio padrão e limites de detecção e quantificação de 2,45, 0,62 e 1,02 mol L-1, respectivamente, como melhores resultados. As análises de recuperação das amostras, 103 e 108%, demostra a possibilidade da utilização destas no âmbito forense.The development of electroanalytical methods for forensic science has been growing in recent years by the fact of their practicality and low cost. Once sensibility and selectivity values are compatible to conventional methods, as chromatography and spectrometry, the portability of this system consists on interesting advantages. The simple modification of the carbon paste working electrode with Schiff bases complexes became even more promising to use this method for the detection and quantification of narcotics. The carbon paste electrode itself contributes for the practicality of the analyses, once it is made of simple carbon powder, which can be disposable. This project aimed to develop voltammetric methods for the quantification of the lysergic acid diethylamide (LSD) using a carbon paste electrode modified with the complex [UO2(Ac-ophen)]·H2O. The use of aqueous solution of KCl as supporting electrolyte characterizes a less pollutant methodology, differently of other methods that still use toxic solvents The combination of the differential pulse and square wave voltammetries with the modified carbon paste was crucial for the detection of trace levels of the LSD. The linear response in various concentrations of LSD results on analytical curves with standard deviation, detection, and quantification limits of 2,45, 0,62, 1,02 mol L-1, respectively. And the recovery values of 103 and 108 % indicates the possibility of using this method in the forensic science
22
Gabriel, Junior Suelino. "Preparação, caracterização e aplicações eletroanalíticas de silsesquioxanos e dendrímeros modificados suportados na superfície da sílica gel /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/91960.
Full textAbstract:
Orientador: Devaney Ribeiro do CarmoBanca: Newton Luiz Dias Filho
Banca: André Luís dos Santos
Resumo: O presente trabalho descreve a preparação, caracterização e as aplicações eletroanalíticas de silsesquioxanos e dendrímeros modificados suportados na superfície da sílica gel. A primeira etapa consistiu em ancorar o silsesquioxano ([H2N(CH2)3]8Si8O12) e o dendrímero Hexadecaamino Poli(propileno)imina (DAB-Am- 16) na superfície da 3-cloropropil sílica gel. Os materiais obtidos, SAC e SD, respectivamente, foram caracterizados pelas técnicas de Infravermelho (FTIR), RMN 29Si e 13C no estado sólido e Energia Dispersiva de Raios-X (EDX). A segunda etapa foi interagir o SAC e o SD com íons de Cu2+ e Ni2+ e posterior complexação com substâncias eletroativas, tais como: ferricianeto de potássio e nitroprussiato de sódio formando, dessa forma, os complexos binucleares: CuHCFSAC, NiHCFSAC, CuNPSAC, CuHCFSD, NiHCFSD e CuNPSD que foram caracterizados por Infravermelho (FTIR) e voltametria cíclica (VC). Os espectros na região do Infravermelho dos materiais supracitados exibiram freqüências próximas ou iguais a 2090 cm-1, atribuídas ao estiramento n(C N) característico do hexacianoferrato e nitroprussiato formados na superfície da SAC e SD. Utilizou-se estes materiais na construção do eletrodo de pasta de grafite os quais foram testados na oxidação eletrocatalítica de substâncias biologicamente importantes tais como a dipirona sódica e nitrito de sódio após um rigoroso estudo sobre o comportamento voltamétrico. O eletrodo de pasta de grafite contendo o CuHCFSAC exibiu dois pares redox com potenciais médios (Em) de: (Em)1= 0,29 V e (Em)2= 0,72 V vs Ag/AgCl (KCl =1.0 molL-1; v = 20 mV s-1) ambos atribuídos aos processos redox Cu(I)/Cu(II) e [Fe(II)(CN)6]4- / [Fe(III)(CN)6]3-, respectivamente, valores estes bem próximos para o CuHCFSD. Os eletrodos de NiHCFSAC e NiHCFSD exibiram... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work describes the preparation, characterization and electroanalytical properties of modified silsesquioxanes and dendrimers supported onto the silica gel surface. The first step was to anchor the silsesquioxane [(H2N(CH2)3] 8Si8O12) and dendrimer Hexadecaamino Poly(propylene)imine (DAB-Am-16) onto the 3-chloropropyl silica gel surface. The materials obtained, SAC and SD, respectively, were characterized by infrared (FTIR), 29Si NMR and 13C solid state and Energy Dispersive X-ray (EDX). The second step was interact the SAC and SD with Cu2+ and Ni2+ ions and subsequent complexation with electroactive substances, such as: ferricyanide of potassium and sodium nitroprusside forming binuclear complexes: CuHCFSAC, NiHCFSAC, CuNPSAC, CuHCFSD, NiHCFSD and CuNPSD which were characterized by Infrared (FTIR) and cyclic voltammetry (CV). The spectra in the infrared region of the above materials exhibited frequencies near or equal to 2090 cm-1 assigned to stretching n(C N) characteristic of nitroprusside and hexacyanoferrate formed onto the SD and SAC surface. We used these materials in the construction of carbon paste electrode which were tested in the electrocatalytic oxidation of biologically important substances such as sodium dipyrone and sodium nitrite after a rigorous study about voltammetric behavior. The graphite paste electrode containing CuHCFSAC exhibited two redox couples with midpoint potentials (Em) of: (Em)1 = 0.29 V and (Em)2 = 0.72 V vs. Ag/AgCl (KCl = 1.0 mol L-1, v = 20 mV s-1) both assigned to the redox processes Cu(I)/Cu(II) and [Fe(II)(CN)6]4- / [Fe(III)(CN)6]-3, respectively, values very near to the CuHCFSD. The electrodes of NiHCFSAC and NiHCFSD each exhibited two redox couples with midpoint potentials (Em): (Em)1 = 0.29 V and (Em)2 = 0.51 V vs Ag/AgCl (KCl = 1.0 mol L-1, v = 20 mV s- 1) both... (Summary complete electronic access click below)
Mestre
23
Oliveira, Laura Siqueira de. "Desenvolvimento de um sistema eletroquímico de análise por injeção em fluxo para detecção de cocaína." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-15022012-110539/.
Full textAbstract:
O aumento nos índices de criminalidade, na maioria das vezes decorrente de atividades ligadas ao tráfico de drogas, afeta drasticamente a qualidade de vida do ser humano. A análise instrumental de entorpecentes é realizada comumente por métodos cromatográficos, oferecendo limites de detecção (LDs) em torno de 1 ng mL-1. As técnicas analíticas como voltametria, amperometria, potenciometria, dentre outras, assemelham-se às técnicas convencionais de análise, pois além de se mostrarem sensíveis para a análise de traços de substâncias orgânicas e inorgânicas, oferecem vantagens operacionais como a compreensão de mecanismos pato-fisiológicos de várias drogas, dentre elas a cocaína e seus metabólitos. Os eletrodos quimicamente modificados (EQMs) com bases de Schiff (grupos funcionais que contém uma ligação dupla carbono-nitrogênio com o átomo de nitrogênio conectado a um grupo arila ou alquila) desenvolvidos para a determinação de cocaína em amostras de interesse forense podem ser empregados em situação de análise por injeção em fluxo (FIA). Cuja metodologia consiste na inserção de uma alíquota de amostra em um fluido carregador que a transporta do ponto de injeção até a unidade de detecção. Atualmente a análise de cocaína está limitada à dosagem posterior de amostras apreendidas, uma vez que não há nenhum dispositivo portátil para a detecção da mesma em local de crime. Assim, este projeto visa desenvolver uma metodologia voltamétrica, por meio de eletrodos quimicamente modificados com bases de Schiff, e da aplicação dos mesmos em FIA para a detecção de cocaína em amostras de interesse forense.The increase in crime occurrences, mostly due to activities linked to drug trafficking, dramatically affects the quality of human life. The instrumental analysis of drugs is commonly performed by chromatographic methods, offering limits of detection (LD) around 1 ng mL-1. Analytical techniques such as voltammetry, amperometry, potentiometry, among others, are similar to conventional analysis techniques, as well as prove sensitive for trace analysis of organic and inorganic substances, provide operational advantages as the understanding of pathophysiological mechanisms of several drugs, among them cocaine and its metabolites. The chemically modified electrodes (CMEs) with Schiff bases (functional groups containing a carbon-nitrogen double bond with the nitrogen atom attached to an alkyl or aryl group) developed for the determination of cocaine in samples of forensic interest can be used in situation of flow injection analysis (FIA). The methodology consists of inserting a sample rate of a carrier fluid that carries the point of injection to the detection unit. The analysis is limited to the dosage cocaine samples seized previously, since there is no portable device for detection in the same scene. Thus, this project aims to develop a voltammetric methodology, by means of chemically modified electrodes with Schiff bases, and applying them in the FIA for the detection of cocaine in samples of forensic interest.
24
Intema, Rolf de Campos. "PREPARAÇÃO E CARACTERIZAÇÃO DE FILMES AUTOMONTADOS CONTENDO POLIELETRÓLITOS INORGÂNICOS E GOMA NATURAL DO CAJUEIRO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2011. http://tede2.uepg.br/jspui/handle/prefix/2096.
Full textAbstract:
Made available in DSpace on 2017-07-24T19:38:05Z (GMT). No. of bitstreams: 1
RolfIntema.pdf: 3696203 bytes, checksum: 9dabc8dc5e71a01ee4c010a743e2f479 (MD5)
Previous issue date: 2011-03-04Nanocomposites in the form of ultrathin films with bilayer and tetralayer structure using the polyelectrolyte chloride 3-n-propyl-1-azonia-4-azabicyclo [2.2.2] octane silsesquioxane (designated as SiDb+Cl-) or polyelectrolyte chloride 3-n-propylpyridinium silsesquioxane (designated as SiPy+Cl-) and tetrasulfonated nickel phthalocyanine (NiTsPc), together with a natural polysaccharide, were produced using the Layer-by-Layer (LbL) technique on a FTO substrate (tin oxide doped with fluorine). The formation of the films was monitored by UV-VIS spectroscopy, accompanying the Q band of phthalocyanine. It was observed that for all the films studied that the absorbance of the Q band at 620 nm linearly increased with the number of bilayers indicating that the same amount of material is adsorbed to each bi/tetralayers prepared. It was also observed that the spectra of the films (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc) and SiDb+Cl /Goma/SiDb+Cl-/NiTsPc), the bands related to the monomeric species were more intense when compared to the films obtained without gum, which s an indication that the inclusion of the gum between the layers of the films can proportionate more organized films with higher interaction between the polymeric species. FTIR spectra showed a shift in the band referring to the NiTsPc sulfonic groups indicating that an electrostatic interaction occurs between NiTsPc and the polycations studied. AFM images showed up the interaction between the polycations of the film, which can be notice by the decrease on the films roughness with the increase of the number of bilayers. In this case, when comparing the SiDb+Cl- containing films with SiPy+Cl- ones, it was observed a more considerable decrease in the rugosity values for the SiPy+Cl- films. Results of cyclic voltammetry carried out with these films with architectures (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc), (SiPy+Cl- /NiTsPc), (SiDb+Cl-/Goma/SiDb+Cl-/NiTsPc) and (SiDb+Cl-/NiTsPc) showed a peak related to the aromatic ring of NiTsPc at 1.4 V. The stability as a function of the number of the voltammetry cycles of the electrodes modified with SiPy+Clwas considerably greater than for the SiDb+Cl- films. These films were sensitive to DA detection at different concentrations in a range of 9.9.10-6 molL-1 to 9.1.10-5 mol L-1 with a detection limit of 7.72.10-6 mol L-1 and 8.34.10-6 molL-1 for architectures (SiPy+Cl-/NiTsPc) and (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc), respectively.
Nanocompósitos na forma de filmes ultrafinos com estrutura em bicamadas e tetracamadas, utilizando o polieletrólito cloreto de 3-n-propil-1- azonia-4-azabiciclo[2.2.2] octano silsesquioxano (designado como SiDb+Cl-) ou o polieletrólito cloreto de 3-n-propilpiridínio silsesquioxano (designado como SiPy+Cl-) e ftalocianina tetrassulfonada de níquel (NiTsPc) juntamente com polissacarídeos naturais, foram produzidos utilizando a técnica Layer-by-Layer (LbL) sobre substrato de FTO (óxido de estanho dopado com flúor. A formação dos filmes foi monitorada por espectroscopia na região do UV-VIS, monitorando a banda Q da ftalocianina. Observou-se que a absorbância da banda Q em 620 nm aumentou linearmente com o número de bicamadas depositadas, para todos os filmes estudados indicando que a mesma quantidade de material é adsorvido a cada bi/tetracamada preparada. Pode ser observado que para os espectros dos filmes (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc) e (SiDb+Cl-/Goma/ SiDb+Cl-/NiTsPc), já nas primeiras tetracamadas, as bandas relativas às espécies monoméricas apresentaram-se mais intensas em relação aos filmes sem goma, o que é uma indicação de que a inclusão da goma pode além de proporcionar, maior organização aos filmes, maior interação entre as espécies poliméricas. Espectros de FTIR demonstraram um deslocamento na banda referente aos grupos sulfônicos da NiTsPc, indicando que ocorre uma interação eletrostática entre a NiTsPc e os policátions estudados. Imagens de AFM evidenciaram essa interação, a qual pode ser constatada a partir da diminuição da rugosidade com o aumento do número de bicamadas. Ao comparar os filmes que contêm o policátion SiDb+Cl- com os filmes contendo SiPy+Clobservou- se que houve uma diminuição mais acentuada da rugosidade para os filmes onde SiPy+Cl- estava presente. Resultados de voltametria cíclica realizados com estes filmes com arquiteturas (SiPy+Cl-/Goma/SiPy+Cl -/NiTsPc)n, (SiPy+Cl-/NiTsPc)n, (SiDb+Cl-/Goma/SiDb+Cl-/NiTsPc)n e (SiDb+Cl- /NiTsPc)n apresentaram um pico referente ao anel aromático da NiTsPc em 1,4 V. Os filmes com a goma apresentaram uma maior estabilidade em função do número de ciclos voltamétricos do que os sem a mesma. Os eletrodos modificados com os filmes foram aplicados para determinação de dopamina em uma faixa de concentração de 9,9.10-6 mol L-1 a 9,09.10-5 mol L-1 com um limite de detecção de 7,72.10-6 mol L-1 e 8,34.10-6 mol L-1 para arquiteturas (SiPy+Cl-/NiTsPc)n e (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc)n, respectivamente.
25
Carvalho, Sâmea Eulles Quixaba de. "Desenvolvimento e aplicação de eletrodos quimicamente modificados com hexacianoferratos dos metais Fe, Ni e Co." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-16092011-155444/.
Full textAbstract:
O presente trabalho descreve o uso de eletrodos de carbono vítreo como eletrodo-base para modificação com hexacianoferratos de Fe (FeHCF), Co (CoHCF) e Ni (NiHCF) por meio da adsorção destes complexos utilizando a técnica de voltametria cíclica. Os eletrodos quimicamente modificados (EQMs) preparados por este método apresentam características diferenciadas tais como robustez e estabilidade ao longo das medidas eletroquímicas, além de boas propriedades redox. Os EQMs com FeHCF e NiHCF foram avaliados em função da sua atividade eletrocatalítica para a reação de oxidação do Ácido Ascórbico em solução de KCl 0,1 mol L-1 (pH 6,6). O EQM com CoHCF foi avaliado nas mesmas condições dos outros filmes, porém não apresentou uma diminuição no sobrepotencial de oxidação do Ácido Ascórbico. Embora não tenha apresentado uma resposta semelhante aos EQMs com FeHCF e NiHCF, o EQM com CoHCF apresentou a melhor sensibilidade da resposta de corrente de pico quando comparado aos demais. A fim de proporcionar a renovação da superfície do eletrodo foi avaliada a utilização de eletrodos de pasta de carbono modificada com FeHCF, CoHCF ou NiHCF. Os parâmetros de composição da pasta, o eletrólito suporte e o pH foram avaliados utilizando o EPCM com FeHCF por meio da técnica de voltametria cíclica e os parâmetros otimizados foram aplicados no uso dos EPCM com CoHCF e NiHCF. Para avaliar a sensibilidade na deteccção da L-Cisteína, do Glifosato e da N-Acetilcisteína, os EPCMs modificados foram submetidos a estudos com a técnica de voltametria de onda quadrada. Todos os analitos apresentaram resposta eletroquímica em todos os EPCMs, porém as melhores respostas foram para o FeHCF na presença de L-Cisteína, CoHCF na presença de Glifosato e NiHCF na presença de N-Acetilcisteína. Na presença de 1 x 10-8 mol L-1 dos analitos os EPCMs com hexacianoferratos apresentaram um boa resposta eletroquímica, embora não tenha sido possível observar uma linearidade entre o aumento da concentração dos analitos propostos e a corrente de pico. Essa sensibilidade demonstrada pelos EPCMs na presença de moléculas com grupos funcionais, como ácidos carboxílicos, aminoácidos e tióis abre novas perspectivas para a análise direta de compostos de interesse clínico, farmacêutico e amostras de interesse ambiental.This work describes the use of glassy carbon electrodes as the base for electrode modification with hexacyanoferrates of Fe (FeHCF), Co (CoHCF) and Ni (NiHCF) through adsorption of these complexes using cyclic voltammetry. The chemically modified electrodes (CMEs) prepared by this method have specific features such as robustness and stability along the electrochemical measurements, and good redox properties. The CME with FeHCF and NiHCF were evaluated take into accounting their electrocatalytic activity for oxidation reaction of Ascorbic Acid in KCl 0.1 mol L-1 (pH 6.6). The CME with CoHCF was evaluated under the same conditions, but did not show a decrease on the overpotential for Ascorbic Acid oxidation. Although the CME with CoHCF has not showed the same behavior presented by CMEs with FeHCF and NiHCF, the CME with CoHCF presented the best sensitivity in order to relationship between peak current and concentration of Ascorbic Acid when compared to CMEs with either. In order to provide the renewal of the electrode surface was evaluated the use of carbon paste electrodes (CPEs) modified with FeHCF, CoHCF and NiHCF. The CPE parameters such as composition, supporting electrolyte and pH were evaluated using the CPE with FeHCF by cyclic voltammetry and these optimized parameters were applied for CPEs with CoHCF and NiHCF. The studies about the sensitivity of the detection for L-Cysteine, glyphosate and N-acetylcysteine using the modified CPEs with hexacyanoferrates were performed by square wave voltammetry. All analytes showed electrochemical response at all CPEs, but the best electrochemical responses were obtained for FeHCF in the presence of L-Cysteine, CoHCF in the presence of glyphosate and NiHCF in the presence of N-acetylcysteine. The CPEs with hexacyanoferrates in the presence of 1 x 10-8 mol L-1 of L-Cysteine, glyphosate or N-acetylcysteine had showed a good electrochemical response, although were not possible to observe a linear correlation between the concentration of analytes and peak current. This sensitivity demonstrated by CPEs with hexacyanoferrates electrodes in presence of specific functional groups such as carboxylic acids, amino acids and thiols opens new perspectives for the direct analysis of compounds with clinical, pharmaceutical and environmental samples.
26
CAMPOS, Rômulo Augusto Lins de. "Eletrodo íon-seletivo de pasta de carbono para determinação de cobre baseado em um novo Lariat-éter coroa." Universidade Federal Rural de Pernambuco, 2011. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/6391.
Full textAbstract:
Submitted by (lucia.rodrigues@ufrpe.br) on 2017-02-16T13:10:45Z
No. of bitstreams: 1
Romulo Augusto Lins de Campos.pdf: 5930168 bytes, checksum: 7553330ff526456aa81970434c7c3475 (MD5)Made available in DSpace on 2017-02-16T13:10:45Z (GMT). No. of bitstreams: 1 Romulo Augusto Lins de Campos.pdf: 5930168 bytes, checksum: 7553330ff526456aa81970434c7c3475 (MD5) Previous issue date: 2011-03-16
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Potentiometric sensors are known for their high sensitivity and selectivity. Such sensors have versatility, low cost and robustness, which ensures their applicability in a wide variety of complex chemical samples. The ion-selective electrodes for polymeric membrane are the best known potentiometric sensors, has by these traits. However, modified carbon paste electrodes have gained prominence due a great advance in their studies. This paper proposes an electrode chemically modified carbon paste for potentiometric determination of copper (II), using a new ionophore lariat-crown ether synthesized from precursor aminopropyl triethoxysilane is a silylating agent known in the literature. Studies were conducted to evaluate the influence of pH on the potential, the best buffer as supporting electrolyte, and the experimental design of mixtures to obtain the best composition of EQMPC. The proposed electrode showed a sensitivity of 38.5 mV/decade of activity with a detection limit of 2.04 x 10-5 mol L-1, and as a supporting electrolyte buffer biftalate/HCl pH = 3.0 proving to be promising for application in the determination of Cu(II). The electrode showed no significant analytical sensitivity to Co(II), Ni(II) and Zn(II) being these their main interferences.
Sensores potenciométricos são conhecidos por sua alta sensibilidade e seletividade. Tais sensores apresentam versatilidade, baixo custo e robustez, o que garante a esses sensores aplicabilidade em uma grande variedade de amostras químicas complexas. Os eletrodos íon-seletivos de membrana polimérica são os sensores potenciométricos mais conhecidos, por possuirem essas características. Contudo, os eletrodos modificados de pasta de carbono têm ganhado forte destaque devido ao avanço em seus estudos. Neste trabalho é proposto um eletrodo quimicamente modificado de pasta de carbono para determinação potenciométrica de cobre (II), utilizando um novo ionóforo lariat-éter coroa sintetizado a partir de precursor aminopropil trietoxisilano que é um agente sililante conhecido na literatura. Foram realizados estudos para avaliar a influência do pH sobre o potencial, o melhor tampão como eletrólito de suporte, além do planejamento experimental de misturas para se obter a melhor composição do EQMPC. O eletrodo proposto apresentou uma sensibilidade de 38,5mV/década de atividade com limite de detecção de 2,04 x 10-5 mol L-1, tendo como eletrólito de suporte um solução-tampão biftalato/HCl pH = 3,0 demonstrando ser promissor para aplicação na determinação de íons Cu(II). O eletrodo não apresentou sensibilidade analítica significativa aos íons Co(II), Ni(II) e Zn(II) sendo esses seus principais interferentes.
27
Turk, Douglas J. "The electrochemical detection of amitriptyline at a chemically modified reticulated vitreous carbon electrode surface /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63368.
Full text
28
Pinczewska, Aleksandra. "High-throughput electrochemistry (HTP) : a new approach to the rapid development of modified carbon electrodes." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/341808/.
Full textAbstract:
The major aim of this project was development of novel covalently modified glassy carbon electrodes for application in NADH-dependent biosensors using combinatorial and high-throughput methods. Studies on transition metal complexes containing redox active 1,1-phenanthroline-5,6-dione (phendione) ligand(s) showed they are effective electrocatalysts for oxidation of NADH. In order to covalently tether the metal complexes at the GC surface, the design of GC electrodes modified with novel metal complexes bearing phendione ligand(s) was proposed based on sequential electrochemical and solid-phase synthesis methods. Initial work involved optimisation of the process for modification of individual GC electrodes. Firstly, following earlier work, the GC electrodes were electrochemically functionalised by primary amines or a diazonium salt bearing Boc-protected amine groups, which allowed introduction of chelating ligands at the GC surface under solid-phase coupling conditions. The final step involved coordination of the bidentate ligand at the GC surface to the metal centre and formation of novel metal complexes under solid-phase coupling conditions. The successfully modified individual electrodes were applied in the design of a library of GC electrodes modified with different linkers, ligands and metal complexes and prepared in a combinatorial and parallel way. The library was electrochemically screened in a high-throughput way using a multichannel potentiostat, which allowed instant comparison of electrochemical and electrocatalytic properties between different members of the library. The experimental data extracted from HTP screening of the library were used for evaluation of a) the surface coverage obtained for different library members; b) the catalytic activity towards NADH oxidation and c) the kinetics parameters kcat and KM for the electrocatalytic oxidation of NADH for all members of the library.
29
Chuang, Janet Duanping. "Electrochemistry of soluble methane monooxygenase on a modified gold electrode : implications for chemical sensing in natural waters." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/31156.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (p. 87-90).
This work explored the possibility of using the soluble methane monooxygenase (MMO) enzyme, a three-component enzyme which catalyzes the oxygenation of methane and other substrates, to design a methane sensor for use in natural waters. Such a sensor would be useful for monitoring lake biogeochemistry, including the potential for lakes to be a source of methane into the atmosphere. An op amp-based potentiostat was constructed, and a LabVIEW program was written to control the instrument and acquire data digitally. Cyclic voltammetry experiments were conducted with both acetonitrile, a liquid substrate, and the natural substrate methane. With the hydroxylase component of the enzyme (MMOH) adsorbed onto a peptide-modified gold electrode, the amount of charge transferred during a scan depended on both substrate and oxygen concentrations. This concentration dependence did not occur when MMOH was not present. In the case of methane, the kinetic limitations of partitioning between gas and liquid phases may have contributed to experimental scatter. These results raise the possibility that MMOH may be used without the other two components to generate a reproducible, concentration-dependent signal. Signal strength was also dependent on the order in which high- and low-concentration trials were conducted. The hydroxylase may be able to store methane and oxygen in a hydrophobic cavity for later use, an observation that has both ecological and sensor-design implications.
by Janet Duanping Chuang.
S.M.
30
Williams, Claire Elizabeth. "Development and investigation of the properties of an electrochemically regenerable chemically modified electrode for chemeluminescence detection of analytes in solution." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/1713.
Full textAbstract:
The aim of this study was to exploit the sensitivity of the chemiluminescent ruthenium tris(2,2'-bipyridme) redox system for analytical purposes by producing electrochemically regenerable electrodes modified with a polymer derivative of this complex. Ruthenium tris(4-meth)i-4' -vinyl-2,2' -bipyridine) bis(hexafluorophosphate) was synthesised and subsequently polymerised onto an electrode surface using the technique of cyclic voltammetry. A potential was applied to the resulting Chemically Modified Electrode (CME) and upon reaction of the ruthenium centres with an analyte in solution, chemiluminescence was observed. Measurement of the emission intensity was used for the determination of the analyte concentration The ruthenium centres were subsequently regenerated by the reversal of the applied potential Very littie environmentally unfriendly and expensive waste results from this process. This is in direct contrast with current methods which traditionally use the ruthenium tris(2,2'-bipyndine) complex either in solution or immobilised within a membrane for analyses of this type. Attention was focused upon detection of the oxalate ion and the ruthenium tris(2,2'-bipyridine)/oxalate redox system reported in the literature was used as a model to investigate the capabilities of the CME's produced. A scan rate of 10 V/s between the potential limits of + 0.5 to + 1.5 V at pH 6.5 was established as the optimum conditions. A linear working range for oxalate was observed from 1.9 x 10'^ M to the limit of detection, 1.1 x 10'^ M. The lifetime of a CME was investigated and although the chemiluminescent signal diminished with time, the electrode was still functioning after 24 weeks, a total of over 200 regenerations. A series of amines and valine were also successfully detected using CME's. In addition, a similar sensor was fabricated from the electropolymerization of a novel ruthenium complex, ruthenium tris(4-methyl-4'-(£-prop-2-enyl>2,2'-bipyridine) bis(hexafluorophosphate). This was also shown to be capable of chemiluminescence emission and was successfully regenerated Two electrochemically regenerable CME's were therefore produced and this research is a valuable advance in the field of chenuluminescent detectors.
31
Niiranen, Pentti. "Electrically Modified Quartz Crystal Microbalance to Study Surface Chemistry Using Plasma Electrons as Reducing Agents." Thesis, Linköpings universitet, Kemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176607.
Full textAbstract:
Metallic films are important in various applications, such as electric devices where it can act as contacts. In electrical devices, the substrate typically consists of silicon dioxide (SiO2) which is a temperature-sensitive substrate. Therefore, plasma enhanced chemical vapor deposition (PECVD) are better suited than thermally activated chemical vapor deposition (CVD). Depositing metallic films with PECVD demands co-reactants that act as reducing agents. However, these are not well-studied and do not always have the power enough to perform the reduction reaction for metals. Recently it has been concluded that electrons can act as reducing agents in the deposition of first row transition metallic films in a PECVD process. By supplying a positive bias to the substrate, the electrons got attracted to the surface of the substrate, which facilitated metal growth. The study concluded that metal growth only occurred at conductive -and semiconductive substrates and that the substrate bias and plasma power affected the metal growth. The process is however not well understood, which causes a knowledge gap, signifying that studies of the surface chemistry are needed. Here a new modified analytical method to study the surface chemistry in the newly developed process mentioned above is presented. The analytical method consists of an electrically modified quartz crystal microbalance (QCM) with gold electrodes as a conductive substrate. This allows the electron current to run through the QCM during the measurement. By supplying a DC-voltage to the front electrode it gets readily biased (negative and positive) and by placing a capacitor in the circuit, it connects the AC-circuit (oscillator circuit) and the DC-circuit (DC-voltage bias circuit). At the same time, it blocks the DC-current from going back to the oscillator but allows the high-frequency signal to pass from the QCM. The results in this thesis concluded that the QCM can be electrically modified to allow an electron flux to the QCM while using it as a substrate when electrons are used as reducing agents. Scanning electron microscopy (SEM) of a QCM crystal revealed that a 2 µm film had been deposited while SEM coupled with energy dispersive X-ray spectroscopy (EDS) showed that the film indeed contained iron. Further analysis was made by high-resolution X-ray photoelectron spectroscopy (HR-XPS) to find the elemental composition of the film, which revealed that the thin film contained 41 at.% iron. In addition, this study investigated if the QCM could be used to study CVD processes where electrons were used as reducing agents. The results indeed revealed that it is possible to study the surface chemistry where electrons are used as reducing agents with the electrically modified QCM to gain knowledge concerning film deposition. Initial results of the QCM showed that film growth could be studied when varying the plasma power between 5 W to 15 W and the QCM bias between -40 V to +40 V. The method generated easily accessible data concerning the process where electrons are used as reducing agents, which gained insight to the method that never has been disclosed before.
32
Soares, Layciane Aparecida. "Propriedades analíticas e eletroanalíticas de um silsesquioxano nanoestruturado organofuncionalizado /." Ilha Solteira : [s.n.], 2011. http://hdl.handle.net/11449/91961.
Full textAbstract:
Orientador: Devaney Ribeiro do CarmoBanca: Newton Luiz Dias Filho
Banca: Regina Massako Takeuchi
Resumo: O presente trabalho apresenta a preparação de um silsesquioxano nanoestruturado, o cloropropilsilsesquioxano (S) que foi organofuncionalizado com os seguintes agentes modificadores: 4-amino-3-hidrazinico-5-mercapto-1,2,4-triazol (Purpald®) e o 4-amino-5-4(piridil)-4H-1,2,4-triazol-3-tiol (APTT), os materiais obtidos dessa funcionalização foram descritos como SP e SA, respectivamente. Os materiais SP e SA foram caracterizados por diversas técnicas espectroscópicas: Espectroscopia na região do infravermelho (FT-IR), Ressonância magnética nuclear 29Si e 13C no estado sólido (RMN), Difração de Raios- X (DRX), Espectroscopia de Energia Dispersiva de Raios X (EDX), Termogravimetria e Análise Térmica Diferencial (TG - DTA). Após a devida caracterização, realizaram-se estudos de adsorção de íons metálicos (Cu2+, Cd2+ e Ni2+) nos sítios ativos do SA, porém, curiosamente não se observou a mesma capacidade de sorção pelo SP. Diferentes meios foram estudados no processo de adsorção dos íons metálicos supracitados: aquoso, etanólico 99% e etanólico 42%, determinando-se o tempo de equilíbrio de adsorção, que para ambos os meios e metais esse tempo máximo foi em média 35 min. Determinado o tempo de equilíbrio de adsorção dos íons metálicos em cada sistema, determinou-se a capacidade específica de sorção (Nfmax) através de isotermas de adsorção. Para o Cu2+, os valores de Nf foram: meio aquoso (3,09 × 10-4 mol g-1), etanólico 42% (1,03 × 10-4 mol g-1) e etanólico 99% (1,86 × 10-4 mol g-1), com concentrações de íons Cu2+ variando de 1,74 a 29,64 mol L-1. Os valores encontrados para o Ni2+ foram: em meio aquoso (2,11 × 10-4 mol g-1), etanólico 42% (0,97 × 10-4 mol g-1) e etanólico 99% (1,05 × 10-4 mol g-1), com concentrações de íons Ni2+ variando de 2,25 a 33,18 mol L-1. Para os íons cádmio não foram... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work presents the preparation of a nanostructured silsesquioxane, the cloropropilsilsesquioxano (S) that was organofunctionalised with the following modifying agents: 4-amino-3-hydrazino 5 - mercapto 1,2,4 triazole (Purpald ®) and 4- amino-5-4 (pyridyl)-4H-1,2,4-triazole-3-thiol (APTT), the materials obtained of the functionalization were described as SP and SA, respectively. The materials SA and SP were characterized by various spectroscopic techniques such as spectroscopy in the region of infrared (FTIR), nuclear magnetic resonance 29Si and 13C solid-state (NMR), X-ray diffraction (XRD), Energy Dispersive Spectroscopy Rays (EDS), Thermogravimetry and Differential Thermal Analysis (TG - DTA). After proper characterization, were carried studies on adsorption of metallic ions such as Cu2+, Ni2+ and Cd2+ in the active sites of SA, but curiously did not observe the same sorption capacity of the SP. Different methods were studied in the adsorption of metal ions above: aqueous, 99% ethanolic and 42% ethanolic, determining the adsorption equilibrium time, which for both means and metals the maximum time averaged 35 min. After determining the adsorption equilibrium time of metal ions in each system, we determined the specific sorption capacity (Nfmax) through adsorption isotherms. For Cu2+, the values of Nf were: aqueous solution (3.09 × 10-4 mol g-1), 42% ethanolic (1.03 × 10-4 mol g-1) and 99% ethanolic (1.86 × 10-4 mol g-1), with Cu2 + ion concentrations ranging from 1.74 to 29.64 mol L-1. The values obtained for the Ni2+ were: aqueous solution (2.11 × 10-4 mol g-1), 42% ethanolic (0.97 × 10-4 mol g-1) and 99% ethanolic (1.05 × 10-4 mol g-1), with Ni2 + ion concentrations ranging from 2.25 to 33.18 mol L-1. For the cadmium ions were not observed saturation of adsorption sites in the concentration range studied, not getting the maximum... (Summary complete electronic access click below)
Mestre
33
Marinho, Maria Inês da Costa. "Desenvolvimento de eletrodo modificado com polímero de azul de metileno para a determinação eletroanalítica de glifosato." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-18032011-153140/.
Full textAbstract:
O presente trabalho descreve o preparo, a caracterização e o uso de eletrodo modificado com polímero de azul de metileno (PMB) imobilizado sobre a superfície de eletrodo de carbono vítreo (GCE-PMB) na análise do herbicida glifosato. O método utilizado para a preparação dos filmes do PMB foi a eletropolimerização. Os filmes preparados por este método apresentam características diferenciadas tais como robustez, estabilidade e propriedade redox satisfatória. As condições experimentais otimizadas foram a velocidade de varredura (50 mV s-1), o intervalo de potencial (-0,4 a +1,2 V), o número de ciclos (30) e o pH da solução do eletrólito suporte (pH 8). A solução de eletrólito suporte foi preparada a partir das soluções de tampão fosfato (0,05 mol L-1) e NaNO3 (0,1 mol L-1), pH 8. A mesma foi utilizada no preparo da solução de azul de metileno (MB) (0,25 x 10-3 mol L-1), no pré-tratamento do eletrodo de carbono vítreo (GC) por voltametria cíclica (CV) e no preparo de soluções para os estudos iniciais com o GCE-PMB. O pré-tratamento da superfície do eletrodo de GC foi realizado aplicando + 0,9 V por 240 s seguido de várias varreduras cíclicas de -0,4 a +1,0 V com velocidade de varredura de 50 mV s-1 até obter um perfil estável do voltamograma do eletrodo. Após o preparo do GCE-PMB, a atividade eletrocatalítica do eletrodo foi investigada para o Ácido Ascórbico (AA) e a L-Cisteína (L-Cys) por CV de -0,4 a +0,6. Foi observado aumento da corrente de pico e diminuição do sobrepotencial em relação ao eletrodo de GC. Nos estudos na presença do glifosato, o GCE-PMB apresentou resposta eletroquímica direta, por voltametria cíclica, para o glifosato (1,0 x 10-3 mol L-1) em solução de KCl 0,1 mol L-1 (pH 5,3) de -0,4 a +0,6 V e velocidade de varredura 50 mV s-1. A resposta voltamétrica apresentou picos anódico e catódico em 0,2 e 0, respectivamente. Para os estudos realizados por meio da técnica de voltametria de onda quadrada (SWV), os parâmetros freqüência, amplitude e incremento de varredura foram otimizados. A partir desses estudos foi possível obter informações relevantes sobre a interação do GCE-PMB com o glifosato. Os resultados mostraram que é possível observar a eletroatividade do herbicida glifosato sobre uma superfície eletródica sem a presença de metais como agentes complexantes.This work describes the preparation, characterization and the use of the modified electrode with methylene blue polymer (PMB) immobilized onto the surface of glassy carbon electrode (GCE-PMB) in the analysis of the herbicide glyphosate. Concerning the methodology aspects, the method used for the preparation of the films PMB was the electropolymerization. The films prepared by this method present a differentiated characteristic such as robustness, stability and good redox properties. The optimized experimental conditions are the scan rate (50 mV s-1), the potential range (-0.4 to +1.2 V), the number of cycles (30) and the pH of the supporting electrolyte (pH 8). The supporting electrolyte solution was prepared from phosphate buffer solutions (0.05 mol L-1) and NaNO3 (0.1 mol L-1), pH 8. The same solution was used to prepare the solution of methylene blue (MB) (0.25 x 10-3 mol L-1), the pretreatment of the GC electrode by cyclic voltammetry (CV). It was also utilized in preparing solutions for the initial studies with GCE-PMB. The pre-treatment of the electrode surface of GC was performed, considering 0.9 V during 240 s, followed by several cyclic scans from -0.4 to 1.0 V (with scan rate of 50 mV s-1) until a stable profile of the voltammogram. After preparing the GCE-PMB, electrocatalytic activity it was investigated for Ascorbic Acid (AA) and L-Cysteine (L-Cys) by CV from -0.4 to +0.6 V. It was observed increase in peak current and decrease the overpotential comparing to glassy carbon electrodes. The GCE-PMB presented direct electrochemical response, for glyphosate (1 x 10-3 mol L-1) in KCl 0.1 mol L-1 (pH 5.3) from -0.4 to +0.6 V and scan rate 50 mV s-1. The voltammetric response showed anodic and cathodic peaks in 0.2 and 0, respectively. Using the square wave voltammetry (SWV), the parameters frequency, amplitude and scan increment were optimized. It was possible to find relevant information about the interaction between GCE-PMB and glyphosate. These results showed that is possible observe the electroactivity of glyphosate on a modified electrodic surface in absence of metals or complexing agents.
34
Soares, Layciane Aparecida [UNESP]. "Propriedades analíticas e eletroanalíticas de um silsesquioxano nanoestruturado organofuncionalizado." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/91961.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0
Previous issue date: 2011-01-20Bitstream added on 2014-06-13T18:53:39Z : No. of bitstreams: 1
soares_la_me_ilha.pdf: 1532013 bytes, checksum: 0f4004d265a97a7015b084d2b64eb7b7 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O presente trabalho apresenta a preparação de um silsesquioxano nanoestruturado, o cloropropilsilsesquioxano (S) que foi organofuncionalizado com os seguintes agentes modificadores: 4-amino-3-hidrazinico-5-mercapto-1,2,4-triazol (Purpald®) e o 4-amino-5-4(piridil)-4H-1,2,4-triazol-3-tiol (APTT), os materiais obtidos dessa funcionalização foram descritos como SP e SA, respectivamente. Os materiais SP e SA foram caracterizados por diversas técnicas espectroscópicas: Espectroscopia na região do infravermelho (FT-IR), Ressonância magnética nuclear 29Si e 13C no estado sólido (RMN), Difração de Raios- X (DRX), Espectroscopia de Energia Dispersiva de Raios X (EDX), Termogravimetria e Análise Térmica Diferencial (TG – DTA). Após a devida caracterização, realizaram-se estudos de adsorção de íons metálicos (Cu2+, Cd2+ e Ni2+) nos sítios ativos do SA, porém, curiosamente não se observou a mesma capacidade de sorção pelo SP. Diferentes meios foram estudados no processo de adsorção dos íons metálicos supracitados: aquoso, etanólico 99% e etanólico 42%, determinando-se o tempo de equilíbrio de adsorção, que para ambos os meios e metais esse tempo máximo foi em média 35 min. Determinado o tempo de equilíbrio de adsorção dos íons metálicos em cada sistema, determinou-se a capacidade específica de sorção (Nfmax) através de isotermas de adsorção. Para o Cu2+, os valores de Nf foram: meio aquoso (3,09 × 10-4 mol g-1), etanólico 42% (1,03 × 10-4 mol g-1) e etanólico 99% (1,86 × 10-4 mol g-1), com concentrações de íons Cu2+ variando de 1,74 a 29,64 mol L-1. Os valores encontrados para o Ni2+ foram: em meio aquoso (2,11 × 10-4 mol g-1), etanólico 42% (0,97 × 10-4 mol g-1) e etanólico 99% (1,05 × 10-4 mol g-1), com concentrações de íons Ni2+ variando de 2,25 a 33,18 mol L-1. Para os íons cádmio não foram...
This work presents the preparation of a nanostructured silsesquioxane, the cloropropilsilsesquioxano (S) that was organofunctionalised with the following modifying agents: 4-amino-3-hydrazino 5 - mercapto 1,2,4 triazole (Purpald ®) and 4- amino-5-4 (pyridyl)-4H-1,2,4-triazole-3-thiol (APTT), the materials obtained of the functionalization were described as SP and SA, respectively. The materials SA and SP were characterized by various spectroscopic techniques such as spectroscopy in the region of infrared (FTIR), nuclear magnetic resonance 29Si and 13C solid-state (NMR), X-ray diffraction (XRD), Energy Dispersive Spectroscopy Rays (EDS), Thermogravimetry and Differential Thermal Analysis (TG - DTA). After proper characterization, were carried studies on adsorption of metallic ions such as Cu2+, Ni2+ and Cd2+ in the active sites of SA, but curiously did not observe the same sorption capacity of the SP. Different methods were studied in the adsorption of metal ions above: aqueous, 99% ethanolic and 42% ethanolic, determining the adsorption equilibrium time, which for both means and metals the maximum time averaged 35 min. After determining the adsorption equilibrium time of metal ions in each system, we determined the specific sorption capacity (Nfmax) through adsorption isotherms. For Cu2+, the values of Nf were: aqueous solution (3.09 × 10-4 mol g-1), 42% ethanolic (1.03 × 10-4 mol g-1) and 99% ethanolic (1.86 × 10-4 mol g-1), with Cu2 + ion concentrations ranging from 1.74 to 29.64 mol L-1. The values obtained for the Ni2+ were: aqueous solution (2.11 × 10-4 mol g-1), 42% ethanolic (0.97 × 10-4 mol g-1) and 99% ethanolic (1.05 × 10-4 mol g-1), with Ni2 + ion concentrations ranging from 2.25 to 33.18 mol L-1. For the cadmium ions were not observed saturation of adsorption sites in the concentration range studied, not getting the maximum... (Summary complete electronic access click below)
35
Hsueh, Chang-Jung. "Development of Electrochemical Biosensors for Potential Liver Disease Detections of ALT & AST and Application of Ionic Liquid into Biosensing-Modified Electrodes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364989187.
Full text
36
Sá, Acelino Cardoso de. "Potencialidades eletroanalíticas de complexos binucleares de nitroprussiato de metais de transição suportado em 3-aminopropil sílica /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/91954.
Full textAbstract:
Orientador: Devaney Ribeiro do CarmoBanca: Newton Luiz Dias Filho
Banca: Jeosadaque José de Sene
Resumo: O objetivo deste trabalho esta resumido através de três etapas. 1 - A primeira etapa consistiu em funcionalizar e caracterizar a sílica gel com grupos 3- aminopropiltrietoxisilano. Nesta etapa o material obtido (Si) foi caracterizado por técnicas de Ressonância Magnética Nuclear no estado sólido (24Si e 13C) e espectroscopia vibracional (FTIR). 2- Numa segunda etapa promoveu-se a adsorção de íons de cobre (II) e de cobalto (II) na superfície da sílica (Si). Os materiais obtidos (SiCu e SiCo) foram caracterizados por espectroscopia vibracional e voltametria cíclica. 3- Na terceira etapa reagiu-se os materiais preparados (SiCu e SiCo) com nitroprussiato de sódio para formar os complexos binucleares (SiCuNP e SiCoNP). Estes materiais também foram caracterizados por espectroscopia vibracional e voltametria cíclica. Estes materiais foram utilizados na construção do eletrodo de pasta de grafite e testados na oxidação eletrocatalítica de substâncias biologicamente importantes tais como a hidrazina e N-acetilcisteína sendo empregado para isto a técnica de voltametria cíclica. Observou-se que o eletrodo de SiCuNP apresentam dois pares redox nos potenciais (Em)1 = 0,34 V e (Em)2 = 0,76 V vs Ag/AgCl, O primeiro foi atribuído ao processo de oxidação do par Cu(I)/Cu(II) e o segundo ao processo de oxidação Fe(II)(CN)5NO / Fe(III)(CN)5NO do complexo binuclear. O sistema SiCoNP foram observados dois pares redox distintos com os seguintes potenciais médios (Em); (Em)1 = 0,29 V e (Em)2 = 0,56 V vs Ag/AgCl, o primeiro foi atribuído ao processo redox do par Co(II)/Co(III) e o segundo ao processo redox Fe(II)(CN)5NO / Fe(III)(CN)5NO do complexo binuclear formado. O sistema SiCuNP foi sensível a concentração de hidrazina apresentando um limite de detecção e sensibilidade amperométrica de 3,07×10-4 mol L-1 e 5,84×10-6 A / mol L-1... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The objective of this work is summarized in three stages. 1 - The first stage functionalizes and characterizes the silica gel with 3-aminopropyltriethoxysilane groups. At this stage the material obtained (Si) was characterized by solid state Nuclear Magnetic Resonance techniques (24Si and 13C) and vibrational spectroscopy (FTIR). 2 - The second stage promotes the adsorption of copper (II) and cobalt (II) ions on the surface of the silica (Si). The materials obtained (SiCu and SiCo) were characterized by vibrational spectroscopy and cyclic voltammetry. 3 - The third stage prepares the reaction of the materials (SiCu and SiCo) with sodium nitroprusside to form the binuclear complex (SiCuNP and SiCoNP). These materials were characterized by vibrational spectroscopy and cyclic voltammetry. These materials were used to construct the electrode carbon paste and were tested for electrocatalytic oxidation of biologically important substances such as hydrazine and N-acetylcysteine using the cyclic voltammetry technique. It was observed that the electrode SiCuNP has two redox pairs in the potential (Em)1 = 0.34 V and (Em)2 = 0.76 V vs. Ag/AgCl, the first was attributed to the oxidation process of the pair Cu(I)/Cu(II) and the second to the oxidation process Fe(II)(CN)5NO / Fe(III)(CN)5NO of the binuclear complex. For the SiCoNP system, two distinct redox couples were observed with the following mean potentials (Em); (Em)1 = 0.29 V and (Em)2 = 0.56 V vs Ag/AgCl, the first one was assigned to the redox process of the Co(II)/Co(III) pair and the second one to the redox process Fe(II)(CN)5NO / Fe(III)(CN)5NO of the binuclear complex formed. The SiCuNP system was sensitive to the hydrazine concentration, exhibiting a detection limit and amperometric sensitivity of 3.07×10-4 mol L-1 and 5.84×10-6 A / mol L-1 respectively and was also... (Summary complete electronic access click below)
Mestre
37
Araújo, Kelly Rejane de Oliveira. "Estudo da determinação de ácido ascórbico em solução utilizando eletrodo de carbono vítreo modificado com Nafion®." Universidade Federal de Goiás, 2017. http://repositorio.bc.ufg.br/tede/handle/tede/7112.
Full textAbstract:
Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-04-07T17:50:24Z
No. of bitstreams: 2
Dissertação - Kelly Rejane de Oliveira Araújo - 2017.pdf: 2397939 bytes, checksum: 0dbd2a7c4b642d80fbadf119bba1a9db (MD5)
license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-10T11:23:50Z (GMT) No. of bitstreams: 2 Dissertação - Kelly Rejane de Oliveira Araújo - 2017.pdf: 2397939 bytes, checksum: 0dbd2a7c4b642d80fbadf119bba1a9db (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2017-04-10T11:23:50Z (GMT). No. of bitstreams: 2 Dissertação - Kelly Rejane de Oliveira Araújo - 2017.pdf: 2397939 bytes, checksum: 0dbd2a7c4b642d80fbadf119bba1a9db (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-28
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
This work was developed with the objective of determining the oxidation profile of ascorbic acid in solution using cyclic voltammetry, square wave voltammetry and differential pulse voltammetry, observing the oxidation behavior due to the increase in the concentration of ascorbic acid in solution using In the electrochemical measurements, a carbon-modified glass-carbon electrode and Nafion®, a polymer widely used in electrochemical analysis. The experiments had an emphasy on standard ascorbic acid analysis, but were also performed with vitamin C tablets of different trade marks, obtaining in both a significant increase of the anodic peak currents coming from the oxidation of the ascorbic acid, resulting from a good stability Of the modified working electrode. For comparison purposes with the Nafion®-modified glass carbon electrode, standard ascorbic acid analyzes were also performed with the use of the vitreous carbon electrode. With the results of the analysis it was possible to determine the mass of ascorbic acid found in vitamin C tablets, from the construction of an analytical curve, in which it presented the necessary parameters for this. By varying the scanning velocities of the analyzes by cyclic voltammetry, it was possible to find out when plotting the current x square root velocity graphs by which process the oxidation of ascorbic acid on the electrode surface would occur. The electrochemical experiments with standard ascorbic acid showed the oxidation behavior by varying the pH of the phosphate buffer solution, evidencing the best pH range to work using the Nafion® modified glass carbon electrode. The use of square wave and differential pulse voltammetry techniques allowed to now the profile of the oxidation of ascorbic acid in vitamin C tablets, demonstrating a better sensibility in the peak current signal by the use of differential pulse voltammetry.
Esse trabalho foi desenvolvido com o objetivo de determinar o perfil da oxidação do ácido ascórbico em solução empregando a voltametria cíclica, a voltametria de onda quadrada e a voltametria de pulso diferencial, observando o comportamento da oxidação decorrente do aumento da concentração de ácido ascórbico em solução, usando nas medidas eletroquímicas um eletrodo de carbono vítreo modificado com uma mistura de carbono e Nafion®, um polímero largamente empregado em análises eletroquímicas. Os experimentos tiveram ênfase na análise de ácido ascórbico padrão, mas também foram realizados com comprimidos de vitamina C de marcas comerciais diferentes, obtendo, em ambos, um aumento significativo das correntes de pico anódica provenientes da oxidação do ácido ascórbico, resultante de uma boa estabilidade do eletrodo de trabalho modificado. Para avaliação do eletrodo de carbono vítreo modificado com Nafion® também foram realizadas análises de ácido ascórbico padrão com o uso do eletrodo convencional. Com os resultados das análises foi possível determinar a massa de ácido ascórbico encontrada nos comprimidos de vitamina C, a partir da construção de uma curva analítica, na qual apresentou os parâmetros necessários para tal. Variando as velocidades de varredura das análises, por voltametria cíclica, foi possível descobrir ao plotar os gráficos de corrente versus raiz quadrada da velocidade por qual processo ocorreria a oxidação do ácido ascórbico na superfície do eletrodo. Os experimentos eletroquímicos com ácido ascórbico padrão mostraram o comportamento da oxidação ao variar o pH da solução tampão fosfato, evidenciando a melhor faixa de pH para se trabalhar usando o eletrodo de carbono vítreo modificado com Nafion®. O uso das técnicas de voltametria de onda quadrada e de pulso diferencial possibilitou conhecer o perfil da oxidação do ácido ascórbico nos comprimidos de vitamina C, demonstrando melhor sensibilidade no sinal da corrente de pico pelo uso da voltametria de onda quadrada.
38
Nascimento, Leandro Fontanetti do. "Grafite funcionalizada em condições de Friedel-Crafts mediada por radiação de microondas: novo material para construção de eletrodos de pasta de carbono." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-04072007-151512/.
Full textAbstract:
A modificação e/ou a funcionalização de eletrodos têm por objetivos o desenvolvimento de métodos eficazes para a preparação de eletrodos quimicamente modificados (EQMs) que possam aliar melhorias em sua sensibilidade, seletividade e reatividade em relação aos eletrodos base. Entretanto, a estabilidade e a reprodutibilidade dos EQMs quanto ao processo de lixiviação dos modificadores precisam ser melhorados para que se possam obter eletrodos mais robustos com longo tempo de análise. Uma das possibilidades para se obter eletrodos mais estáveis é por meio de uma ligação estável do tipo covalente entre o eletrodo base e o modificador. Desta forma este trabalho tem por objetivo a funcionalização da grafite por meio de uma reação covalente entre os modificadores cloreto de 4-nitrobenzoíla (4-NB), cloreto de 3,4-dihidroxibenzoíla (3,4-DHB) e do cloreto de 2,2?-bipiridina 4,4?-dicarbonílico (2,2-BP) por meio de uma reação de acilação de Friedel-Crafts assistida por radiação de microondas. O material de síntese foi caracterizado por voltametria cíclica, espectroscopia de infravermelho, curvas termogravimétricas e térmicas diferenciais e espectroscopia de impedância eletroquímica em comparação com a mistura física entre a grafite e os modificadores. Além disso, realizou-se uma generalização da síntese de Friedel-Crafts para outros substratos carboníferos eletródicos como os nanotubos e as fibras de carbono, além de algumas aplicações dos materiais funcionalizados, como exemplos, a grafite funcionalizada e as fibras de carbono funcionalizadas com o derivado bipiridínico (GFT-2,2BP e CNF-2,2BP), por meio de uma ligação entre as bipiridinas funcionalizadas covalentemente nos materiais carboníferos e alguns complexos de rutênio tais como [Ru(bpy)2(OH2)2](PF6)2, [RuCl2(PPh3)3] e do precursor RuCl3.3H2O em eletrooxidações de compostos orgânicos. Para a grafite funcionalizada com nitro derivado (GFT-4NB), realizou-se a eletrooxidação de NADH sobre o potencial redox da hidroxilamina/nitroso. Os resultados dos experimentos de EIS demonstram que a grafite funcionalizada possui uma maior resistência que o material obtido por mistura física. Isto seria esperado já que a formação da ligação covalente afeta a deslocalização de elétrons pi. Finalmente esta metodologia seria uma plataforma geral para a preparação de grafite covalentemente modificada com derivados cujas moléculas possui aplicações de interesse. Assim, o material obtido por este método pode ser usado em aplicações como em eletrodos de pasta de carbono, eletrodos impressos, filmes finos e nanocompósitos e mesmo como um catalisador em reações químicas. Desde que a resposta eletroquímica é muito sensível ao eletrólito, este trabalho abriu uma larga variedade de estudos para entender a interação desses materiais no meio aquoso e orgânico.Modification and/or functionalization of eletrodic materials have been investigated in order to improve the application of chemically modified electrode (CME) regards on their sensitivity, selectivity and reactivity comparing with unmodified substrate. However, the stability and reproducibility of these CME are one of the most important goals to achieve mainly regarding on the lixiviation of the modifier molecule. Quimisorption is one way to obtain very stable modified materials, since the redox mediator is attached to the substrate by covalent bound. Still it is very important to study the stability and chemical reactivity of these materials. The aim of this work is to synthesize graphite, carbon nanotube and carbon fiber with 4-nitrobenzoíl chloride (4-NB), 3,4-dihidroxibenzoíl chloride (3,4-DHB) and 2,2-bipyridine- 4,4-dicarbonil chloride (2,2-BP) in Friedel-Crafts condition mediated by microwave radiation. The materials were characterized by cyclic voltammetry (CV), using carbon paste electrode (CPE), infrared spectroscopy (IR), thermo gravimetric (TG) and differential thermal analysis (DTA) and electrochemical impedance spectroscopy (EIS). All of the synthesized graphite derivatives were compared with the respective physical mixtures. Moreover, graphite derivatives with bipyridine were used as a ligand in the synthesis with [Ru(bpy)2(OH2)2](PF6)2, [RuCl2(PPh3)3] and RuCl3.3H2O. These products were used as electrocatalysts to oxidize alcohols in comparison with the complex incorporated in graphite. Graphite obtained from 4-NB reaction was employed to oxidize NADH in the redox potential of hydroxylamine/nitroso derived. Results from EIS measurements have show that graphite functionalized has higher resistance than the material obtained by physical mixture. This would be expected since the covalent bound would affect a pi electron dislocation. In conclusion, this methodology would be a general platform to prepare graphite and derivatives covalently bounded to molecules that have interesting application. In addition, it\'s been shown that the catalytic property of the respective function organic hasn\'s changed after reaction with carbon substrate. Thus the material obtained by this method could be used in applications such as carbon paste electrodes, finger print electrodes, thin films and nanocomposites and even as a catalyst in chemical reaction. Since the electrochemical response is very sensitive regards on the electrolyte, this work opened a wide range of studies to understand the interaction of these materials in aqueous and organic medium.
39
Pereira, Paulo Augusto Raymundo. "Estudo de filmes poliméricos de complexos a base de tiofeno8Schiff na construção de sensores eletroquímicos /." São José do Rio Preto : [s.n.], 2011. http://hdl.handle.net/11449/97756.
Full textAbstract:
Resumo: Os polímeros condutores a Base de Tiofeno-Schiff despontam como materiais alternativos para obtenção de eletrodos modificados com potencial aplicação em sensores químicos devido as excelentes propriedades condutoras e quelantes conferidas pelo poli-tiofeno e pelas Bases de Schiff, respectivamente. Neste trabalho, o complexo Tiofeno-Salen foi sintetizado e caracterizado por UV8Vis e FTIR, em seguida, monômeros complexos metálicos-tiofeno-Schiff foram sintetizados com a complexação de cátions metálicos de transição como Ni2+, Cu2+, VO2+, Fe3+, Ru3+ e Ce4+ e novamente caracterizados por UV8Vis e FTIR para comprovar a formação dos monômeros complexos metálicos-tiofeno-Schiff. Filmes poliméricos desses complexos metálicos foram obtidos pela técnica de eletropolimerização anódica e foram caracterizados eletroquimicamente por voltametria cíclica em solução aquosa. Verificou-se a influência de diversas variáveis experimentais tais como solvente, eletrólito de suporte, intervalo de varredura de potenciais, velocidade de varredura de potenciais, concentração do monômero e número de ciclos durante a etapa de eletropolimerização. Os substratos condutores utilizados na etapa de eletropolimerização foram o eletrodo de platina e o eletrodo de carbono vítreo, demonstrando a influência do substrato condutor na etapa de eletropolimerização e verificou-se que o eletrodo de platina apresentou maior eficiência de transferência eletrônica quando comparado ao eletrodo de carbono vítreo devido a natureza amorfa do carbono vítreo para esses filmes poliméricos estudados. Os eletrodos de platina modificados com esses filmes poliméricos foram também utilizados no estudo das suas propriedades eletroquímicas para a detecção de analitos de interesse analítico como L-dopa, ditionito, piridoxina, sulfito, nitrito, L-tiroxina e ácido gálico.Abstract: Conducting polymers of the Thiophene-Schiff Bases emerge as alternative materials to obtain modified electrodes with potential applications in chemical sensors due to the excellent conductive chelating properties conferred by the poly-thiophene and the Schiff Bases, respectively. In this work, the complex Thiophene-Salen was synthesized and characterized by UV-Vis and FTIR, then monomers complex metals8thiophene8Schiff were synthesized with the complexation of cations of transition metals such as Ni2+, Cu2+, VO2+, Fe3+, Ru3+ and Ce4+ and again characterized by UV-Vis and FTIR to confirm the formation of monomer-metal complexes with thiophene-Schiff. Polymer films of these complexes were obtained by anodic electropolymerization technique and were characterized electrochemically by cyclic voltammetry in aqueous solution. There was the influence of different experimental variables such as solvent, supporting electrolyte, potential scan range, potential scan rate, monomer concentration and number of cycles during the electropolymerization. The conductive substrates used in the electropolymerization were platinum electrode and a glassy carbon electrode, demonstrating the influence of the conductive substrate in the electropolymerization and was found that the platinum electrode showed a higher electron transfer efficiency when compared to the carbon electrode vitreous due to amorphous nature of glassy carbon for these polymer films studied. The platinum modified electrodes with these polymer films were also used to study their electrochemical properties for the detection of analytes of analytical interest as L-dopa, dithionite, pyridoxine, sulphite, nitrite, L-thyroxine and gallic acid presented higher apllication as chemical sensors for these analytes.
Orientador: Marcos Fernando de Souza Teixeira
Coorientador: Luiz Humberto Marcolino Junior
Banca: Lúcio Angnes
Banca: Homero Marques Gomes
Mestre
40
Pereira, Paulo Augusto Raymundo [UNESP]. "Estudo de filmes poliméricos de complexos a base de tiofeno8Schiff na construção de sensores eletroquímicos." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/97756.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:29:06Z (GMT). No. of bitstreams: 0
Previous issue date: 2011-11-28Bitstream added on 2014-06-13T20:48:16Z : No. of bitstreams: 1
pereira_par_me_sjrp.pdf: 2491155 bytes, checksum: 9deb7dfefe2de27d42938548e5d1567a (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Os polímeros condutores a Base de Tiofeno-Schiff despontam como materiais alternativos para obtenção de eletrodos modificados com potencial aplicação em sensores químicos devido as excelentes propriedades condutoras e quelantes conferidas pelo poli-tiofeno e pelas Bases de Schiff, respectivamente. Neste trabalho, o complexo Tiofeno-Salen foi sintetizado e caracterizado por UV8Vis e FTIR, em seguida, monômeros complexos metálicos-tiofeno-Schiff foram sintetizados com a complexação de cátions metálicos de transição como Ni2+, Cu2+, VO2+, Fe3+, Ru3+ e Ce4+ e novamente caracterizados por UV8Vis e FTIR para comprovar a formação dos monômeros complexos metálicos-tiofeno-Schiff. Filmes poliméricos desses complexos metálicos foram obtidos pela técnica de eletropolimerização anódica e foram caracterizados eletroquimicamente por voltametria cíclica em solução aquosa. Verificou-se a influência de diversas variáveis experimentais tais como solvente, eletrólito de suporte, intervalo de varredura de potenciais, velocidade de varredura de potenciais, concentração do monômero e número de ciclos durante a etapa de eletropolimerização. Os substratos condutores utilizados na etapa de eletropolimerização foram o eletrodo de platina e o eletrodo de carbono vítreo, demonstrando a influência do substrato condutor na etapa de eletropolimerização e verificou-se que o eletrodo de platina apresentou maior eficiência de transferência eletrônica quando comparado ao eletrodo de carbono vítreo devido a natureza amorfa do carbono vítreo para esses filmes poliméricos estudados. Os eletrodos de platina modificados com esses filmes poliméricos foram também utilizados no estudo das suas propriedades eletroquímicas para a detecção de analitos de interesse analítico como L-dopa, ditionito, piridoxina, sulfito, nitrito, L-tiroxina e ácido gálico.
Conducting polymers of the Thiophene-Schiff Bases emerge as alternative materials to obtain modified electrodes with potential applications in chemical sensors due to the excellent conductive chelating properties conferred by the poly-thiophene and the Schiff Bases, respectively. In this work, the complex Thiophene-Salen was synthesized and characterized by UV-Vis and FTIR, then monomers complex metals8thiophene8Schiff were synthesized with the complexation of cations of transition metals such as Ni2+, Cu2+, VO2+, Fe3+, Ru3+ and Ce4+ and again characterized by UV-Vis and FTIR to confirm the formation of monomer-metal complexes with thiophene-Schiff. Polymer films of these complexes were obtained by anodic electropolymerization technique and were characterized electrochemically by cyclic voltammetry in aqueous solution. There was the influence of different experimental variables such as solvent, supporting electrolyte, potential scan range, potential scan rate, monomer concentration and number of cycles during the electropolymerization. The conductive substrates used in the electropolymerization were platinum electrode and a glassy carbon electrode, demonstrating the influence of the conductive substrate in the electropolymerization and was found that the platinum electrode showed a higher electron transfer efficiency when compared to the carbon electrode vitreous due to amorphous nature of glassy carbon for these polymer films studied. The platinum modified electrodes with these polymer films were also used to study their electrochemical properties for the detection of analytes of analytical interest as L-dopa, dithionite, pyridoxine, sulphite, nitrite, L-thyroxine and gallic acid presented higher apllication as chemical sensors for these analytes.
41
Sá, Acelino Cardoso de [UNESP]. "Potencialidades eletroanalíticas de complexos binucleares de nitroprussiato de metais de transição suportado em 3-aminopropil sílica." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91954.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0
Previous issue date: 2010-01-26Bitstream added on 2014-06-13T19:12:22Z : No. of bitstreams: 1
sa_ac_me_ilha.pdf: 1061286 bytes, checksum: b370fdf160f4689709efe584af803c2a (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo deste trabalho esta resumido através de três etapas. 1 - A primeira etapa consistiu em funcionalizar e caracterizar a sílica gel com grupos 3- aminopropiltrietoxisilano. Nesta etapa o material obtido (Si) foi caracterizado por técnicas de Ressonância Magnética Nuclear no estado sólido (24Si e 13C) e espectroscopia vibracional (FTIR). 2- Numa segunda etapa promoveu-se a adsorção de íons de cobre (II) e de cobalto (II) na superfície da sílica (Si). Os materiais obtidos (SiCu e SiCo) foram caracterizados por espectroscopia vibracional e voltametria cíclica. 3- Na terceira etapa reagiu-se os materiais preparados (SiCu e SiCo) com nitroprussiato de sódio para formar os complexos binucleares (SiCuNP e SiCoNP). Estes materiais também foram caracterizados por espectroscopia vibracional e voltametria cíclica. Estes materiais foram utilizados na construção do eletrodo de pasta de grafite e testados na oxidação eletrocatalítica de substâncias biologicamente importantes tais como a hidrazina e N-acetilcisteína sendo empregado para isto a técnica de voltametria cíclica. Observou-se que o eletrodo de SiCuNP apresentam dois pares redox nos potenciais (Em)1 = 0,34 V e (Em)2 = 0,76 V vs Ag/AgCl, O primeiro foi atribuído ao processo de oxidação do par Cu(I)/Cu(II) e o segundo ao processo de oxidação Fe(II)(CN)5NO / Fe(III)(CN)5NO do complexo binuclear. O sistema SiCoNP foram observados dois pares redox distintos com os seguintes potenciais médios (Em); (Em)1 = 0,29 V e (Em)2 = 0,56 V vs Ag/AgCl, o primeiro foi atribuído ao processo redox do par Co(II)/Co(III) e o segundo ao processo redox Fe(II)(CN)5NO / Fe(III)(CN)5NO do complexo binuclear formado. O sistema SiCuNP foi sensível a concentração de hidrazina apresentando um limite de detecção e sensibilidade amperométrica de 3,07×10-4 mol L-1 e 5,84×10-6 A / mol L-1...
The objective of this work is summarized in three stages. 1 - The first stage functionalizes and characterizes the silica gel with 3-aminopropyltriethoxysilane groups. At this stage the material obtained (Si) was characterized by solid state Nuclear Magnetic Resonance techniques (24Si and 13C) and vibrational spectroscopy (FTIR). 2 - The second stage promotes the adsorption of copper (II) and cobalt (II) ions on the surface of the silica (Si). The materials obtained (SiCu and SiCo) were characterized by vibrational spectroscopy and cyclic voltammetry. 3 - The third stage prepares the reaction of the materials (SiCu and SiCo) with sodium nitroprusside to form the binuclear complex (SiCuNP and SiCoNP). These materials were characterized by vibrational spectroscopy and cyclic voltammetry. These materials were used to construct the electrode carbon paste and were tested for electrocatalytic oxidation of biologically important substances such as hydrazine and N-acetylcysteine using the cyclic voltammetry technique. It was observed that the electrode SiCuNP has two redox pairs in the potential (Em)1 = 0.34 V and (Em)2 = 0.76 V vs. Ag/AgCl, the first was attributed to the oxidation process of the pair Cu(I)/Cu(II) and the second to the oxidation process Fe(II)(CN)5NO / Fe(III)(CN)5NO of the binuclear complex. For the SiCoNP system, two distinct redox couples were observed with the following mean potentials (Em); (Em)1 = 0.29 V and (Em)2 = 0.56 V vs Ag/AgCl, the first one was assigned to the redox process of the Co(II)/Co(III) pair and the second one to the redox process Fe(II)(CN)5NO / Fe(III)(CN)5NO of the binuclear complex formed. The SiCuNP system was sensitive to the hydrazine concentration, exhibiting a detection limit and amperometric sensitivity of 3.07×10-4 mol L-1 and 5.84×10-6 A / mol L-1 respectively and was also... (Summary complete electronic access click below)
42
Caix, Chrystelle. "Propriétés électrochimiques des complexes du type ((eta5-Me5C5)M(L)Cl)+ (M=Ir(III), Rh(III)) en solution et immobilisés dans des films de polymère : application à l'électrocatalyse." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10154.
Full textAbstract:
Ce memoire est consacre a l'evaluation des possibilites offertes par les complexes de coordination de rhodium (iii) et d'iridium (iii) du type (#5-me#5c#5)m(l)x#+ en electrocatalyse. Nous nous sommes plus particulierement interesses a leur application (en phase homogene ou immobilises a la surface d'une electrode sous forme de films polypyrroliques) a l'electroreduction catalytique des protons en hydrogene moleculaire, a l'hydrogenation electrocatalytique de substrats organiques insatures, et a la reduction electrocatalytique du dioxyde de carbone. Une partie de ce travail a consiste a etudier en detail les proprietes electrochimiques des complexes chlorure d'iridium et de rhodium du type (#5-me#5c#5)m(l)cl#+ et a determiner les conditions permettant d'electrogenerer quantitativement les complexes hydrure correspondants, intermediaires proposes dans de nombreux processus catalytiques. Une etude similaire a ete conduite sur des electrodes modifiees par electropolymerisation de ces complexes, et de nouveaux materiaux moleculaires d'electrodes contenant les complexes hydrure ont ainsi ete realises. Ces complexes hydrure ont ete caracterises, en particulier pour l'iridium, par differentes methodes spectroscopiques, aussi bien en solution que sur electrodes modifiees. Enfin ces complexes et plus specialement ceux du rhodium se sont averes etre de bons catalyseurs pour l'electroreduction des protons appliquee ou non a l'hydrogenation de substrats organiques insatures et a l'electrocatalyse de la reduction du co#2 en ions formiate en milieu hydroorganique. Nous avons montre par ailleurs que, pour ces deux dernieres applications, l'immobilisation du complexe dans un film de polymere defavorise la reaction d'insertion du substrat ou du co#2 dans la liaison metal-hydrure au profit de la reduction des protons
43
Daire, Fabrice. "Etude d'electrodes modifiees par fixation de composes de coordination sur un support conducteur du type polypyrrole : application en electrosynthese organique." Paris 6, 1988. http://www.theses.fr/1988PA066176.
Full textAbstract:
Proprietes electrochimiques des complexes co-l, cu-l, ni-l (ou l=methyl-4, bipyridine-2,2', derive du pyrrole) dans l'acetonitrile. Polymerisation electrolytique de ces complexes sur des electrodes d'or, platine et carbone. Proprietes electrochimiques du polymere co-bipyridyl-polypyrrole; utilisation dans la reduction catalytique des derives allyliques
44
Dunand-Sauthier, Marie-Noe͏̈lle. "Propriétés électrochimiques et photochimiques de complexes mono(2,2'-bipyridine) carbonyle de ruthénium (II) : applications à la réduction électrocatalytique du CO2 et à la photoimagerie." Grenoble 1, 1993. http://www.theses.fr/1993GRE10105.
Full textAbstract:
Ce memoire est consacre a l'etude des proprietes electrochimiques, photochimiques et aux applications dans le domaine de la photoimagerie et de la reduction electrocatalytique du dioxyde de carbone d'une serie de complexes monobipyridine carbonyle de ruthenium en phase homogene ou immobilises a la surface d'une electrode sous forme de films polymeriques. Nous avons tout d'abord demontre que le complexe considere dans la litterature comme etant cisru(bpy)(co)#2cl#2 (bpy=2,2-bipyridine) est en realite constitue d'un melange de ru(bpy)(co)#2cl#2 et de ru(bpy)(co)cl#3, ce dernier a pu etre isole sous sa forme reduite par une methode electrochimique originale. L'etude electrochimique detaillee de ces complexes a ete realisee et il a ete montre que l'electroreduction de certains de ces complexes permet de preparer un nouveau type d'electrodes modifiees par des polymeres inorganiques (appeles film bleu: fb). Ce travail s'est poursuivi par la mise en evidence de phenomenes de substitution de ligands par des molecules de solvant lorsque ces complexes sont irradies par la lumiere visible. Lorsque ces complexes sont immobilises a la surface d'une electrode par l'intermediaire de films polypyrroliques fonctionnalises, leurs proprietes photochimiques sont conservees et ces phenomenes ont permis l'utilisation de ces films en photoimagerie. Enfin, ces films (fb et polypyrroliques) se sont averes etre d'excellentes cathodes moleculaires pour la reduction electrocatalytique du co#2, avec la formation quasi quantitative de co meme dans des electrolytes purement aqueux
45
Coche, Liliane. "Préparation et étude électrochimique d'électrodes modifiées par des films de polymères rédox : application à la catalyse électrochimique rédox." Grenoble 1, 1987. http://www.theses.fr/1987GRE10046.
Full textAbstract:
Preparation d'electrodes de platine, palladium et rhodium modifiees par des films de polypyrrole et de poly (pyrrole-crologene). Application a la reduction electrochimique en milieu acetonitrile du dibromo-1,2 diphenyl-1,2 ethane
46
Zsoldos, Daniela. "Complexes mono et bis bipyridine carbonyle de ruthénium(II), précurseurs de polymères organométalliques : propriétés électrochimiques et applications à l'électrocatalyse de la réduction du CO2 en milieu aqueux." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10027.
Full textAbstract:
Ce memoire est consacre a l'etude de l'electrocatalytique de la reduction du co#2 par des complexes mono et bis bipyridine bis carbonyle de ru(ii), en phase homogene ou supportee (electrodes modifiees). Une partie de ce travail traite des proprietes electrochimiques des complexes trans-(cl)-cis-(co)-ru(l)(co)#2cl#2 (l = 2,2'-bipyridine substituee ou non ou 1,10-phenanthroline) et cis-(bpy)-cis-(co)-ru(bpy)#2(co)#2#2#+, precurseurs de polymeres du type ru(l)(co)#2#n, espece electrocatalytique clees. Le mecanisme d'electrogeneration de ces polymeres organometallique a pu etre determine, grace en particulier a l'etude des complexes stereoisomeres cis-(cl)-cis-(co)-ru(l)(co)#2xy#n#+(x = cl#- ; y = cl#- ou c(o)och#3#-). Ceux-ci ont un comportement electrochimique different des complexes equivalents trans-(cl)-cis-(co) et conduisent exclusivement a des dimeres. Tous ces complexes se sont averes etre d'excellents catalyseurs pour l'electroreduction du co#2 en milieu hydro-organique en phase homogene ou supportee. Par ailleurs, le probleme de l'instabilite a l'oxygene des electrodes modifiees par les films de ru(l)(co)#2#n a ete contourne grace a l'utilisation d'un autre type de cathodes moleculaires. Ces dernieres ont ete realisees par immobilisation, a la surface d'electrodes, des complexes precurseurs, dans des films de polypyrrole fonctionnalises. Une etude detaillee des differents parametres influencant l'orientation de la reaction de reduction du co#2 vers la production d'ions formiate (en particulier la substitution du ligand bipyridine) dans un electrolyte purement aqueux, a permis d'etablir les conditions optimales pour l'obtention de rendements electriques quasi quantitatifs.
47
Poltorak, Sergej. "Amperometrinio biojutiklio su chemiškai modifikuotu elektrodu vykstančių reakcijos-difuzijos procesų kompiuterinis modeliavimas ir tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2011~D_20140627_170922-37372.
Full textAbstract:
Magistrinio darbo tikslas yra sukurti kompiuterinį amperometrinio biojutiklio su chemiškai modifikuotu elektrodu modelį ir ištirti jo savybes. Modelis papildo egzistuojančius modelius mediatoriaus sluoksniu. Mediatoriaus koncentracija sluoksnyje nėra konstanta, tirpsta biojutiklio veikimo eigoje. Darbe apžvelgiama medžiaga apie amperometrinius biojutiklius, biojutiklio modeliavimo aspektus, mediatoriaus tirpimo priežastis ir veikimo principus. Vėliau suformuluojamas pasirinkto biojutiklio matematinis modelis. Matematiniame modelyje pateikiamos diferencialinės lygtys su dalinėmis išvestinėmis, aprašančios biojutiklyje vykstančias reakcijas ir difuzijas. Pagal matematinį modelį yra sudaromas skaitinis modelis. Pagal žinomus analizinius sprendimus modelis yra ratifikuojamas. Remiantis skaitiniu modeliu buvo sukurta programinė įranga įgyvendinanti diferencialinių lygčių su dalinėmis išvestinėmis sprendimo metodą (išreikštinę baigtinių skirtumų schemą) ir simuliuojanti biojutiklio veikimą. Programinė įranga yra karkasas, leidžiantis nagrinėti sumodeliuoto biojutiklio savybes bei charakteristikas. Buvo ištirtos substrato ir mediatoriaus koncentracijų, mediatoriaus, fermento, difuzijos sluoksnių, bei mediatoriaus sluoksnio difuzijos koeficiento įtakos biojutiklio generuojamos srovės tankiui. Be to gauti dviejų modelių palyginimo rezultatai parodė sumodeliuoto biojutiklio modelio skirtumus ir panaudojimo prasmingumą.The aim of master thesis is to model amperometric biosensor with chemically modified electrode, introducing into existing model one more additional mediator layer. Mediator concentration inside the layer is changing during the biosensor action. Master thesis content consists of: enzyme kinetics introduction, biosensor modeling peculiarities exploration, chemically modified electrode information, biosensor action aspects description. Following chapter concentrates on mathematical modeling of particular biosensor type. Mathematical model represents differential equations with partial derivatives describing the reactions and diffusion inside biosensor. Next, numerical model is formulated. The explicit method technique was used. Based on numerical model software was made and validated. Using software the biosensor action was simulated in order to investigate biosensor properties and characteristics. In this work several properties were analyzed: impact of substrate and mediator concentrations, size of mediator, enzyme and diffusion layers, mediator layer diffusion coefficient on biosensor response. This model was compared with previous introduced model and it was shown that there is some difference between them and there is a reason to use new model.
48
Bedioui, Fethi. "Etude électrochimique de complexes de métaux de transition (bases de Schiff et porphyrines) en solution et sous forme d'électrodes modifiées : application à la catalyse électroassistée de réactions organiques." Paris 6, 1986. http://www.theses.fr/1986PA066338.
Full textAbstract:
Les propriétés électrochimiques des complexes co-base de Schiff (phenylene-bis(salicylideneiminoto)-co, ou Co(II)saloph, et n-methylenepropylene-bis-(salicylideneiminoto)-co, ou co-selnmedpt) et de tetraphenylporphine-co, ou CoTPP, sont utilisées pour étudier la réduction électroassistée d'halogénures organiques, Rx, avec un catalyseur fixe sur support conducteur, en milieu organique. On étudie: 1) la réduction du chlorure de benzyle électrocatalysée par des électrodes de graphite modifiées par du co-saloph et 2) l'oxydation par l'oxygène moléculaire du di-tert-butylphenol, électrocatalysée par des films de polypyrrole contenant la porphyrine mntcpp.
49
Ourari, Ali. "Étude de deux réactions d'électrocatalyse : hydrogénation électrocatalytique sur des films de polymères contenant des microparticules de métaux nobles et activation de l'oxygène par des complexes Mn(III) - bases de Schiff." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10171.
Full textAbstract:
Ce travail est relatif a l'etude de deux reactions d'electrocatalyse. La premiere partie concerne la mise au point de cathodes moleculaires, realisees par l'inclusion de microparticules de metaux nobles dans des films de polypyrrole fonctionnalise et a leur application en hydrogenation electrocatalytique. L'etude de l'hydrogenation de deux substrats test, le limonene et la carvone, a montre qu'il est possible d'orienter la selectivite de ces electrodes modifiees selon la nature du metal incorpore (pt, pd ou rh). Le resultat le plus significatif est que l'incorporation dans le meme film de polymere de deux metaux d'activite catalytique differente (pt + pd ou rh + pd) conduit a des cathodes dont l'efficacite et la selectivite sont largement superieures a celle des cathodes basees sur un seul metal. La deuxieme partie de ce travail est consacree a l'etude de l'activation electrochimique de l'oxygene par des complexes mn (iii) - bases de schiff. Il apparait que le complexe mn (ii) - salen substitue en 5,5 par des atomes de chlore est le catalyseur le plus stable et le plus efficace pour la reaction test d'epoxydation du cyclooctene. D'autre part, la rigidification du complexe par l'utilisation d'un pont 1,2-cyclohexylidene ou 1,2-phenylene reliant les deux motifs salicylaldehyde du ligand, a la place du groupe ethylidene ligand salen, entraine une forte diminution de l'activite catalytique des complexes correspondants. Ce systeme electrocatalytique a egalement ete applique a l'oxydation de la tetraline et de la triphenylphosphine
50
Ni, Ching-Long. "Electrocatalytic Reduction of Dioxygen at Chemically Modified Electrodes." Thesis, 1987. https://thesis.library.caltech.edu/9057/1/Ni_CL.pdf.
Full textAbstract:
The kinetics of the reduction of O2 by Ru(NH3)6+2 as catalyzed by cobalt(II) tetrakis(4-N-methylpyridyl)porphyrin are described both in homogeneous solution and when the reactants are confined to Nafion coatings on graphite electrodes. The catalytic mechanism is determined and the factors that can control the total reduction currents at Nafion-coated electrodes are specified. A kinetic zone diagram for analyzing the behavior of catalyst-mediator-substrate systems at polymer coated electrodes is presented and utilized in identifying the current-limiting processes. Good agreement is demonstrated between calculated and measured reduction currents at rotating disk electrodes. The experimental conditions that will yield the optimum performance of coated electrodes are discussed, and a relationship is derived for the optimal coating thickness.
The relation between the reduction potentials of adsorbed and unadsorbed cobalt(III) tetrakis(4-N-methylpyridyl)porphyrin and those where it catalyzes the electroreduction of dioxygen is described. There is an unusually large change in the formal potential of the Co(III) couple upon the adsorption of the porphyrin on the graphite electrode surface. The mechanism in which the (inevitably) adsorbed porphyrin catalyzes the reduction of O2 is in accord with a general mechanistic scheme proposed for most monomeric cobalt porphyrins.
Four new dimeric metalloporphyrins (prepared in the laboratory of Professor C. K. Chang) have the two porphyrin rings linked by an anthracene bridge attached to meso positions. The electrocatalytic behavior of the diporphyrins towards the reduction of O2 at graphite electrodes has been examined for the following combination of metal centers: Co-Cu, Co-Fe, Fe-Fe, Fe-H2. The Co-Cu diporphyrin catalyzes the reduction of O2 to H2O2 but no further. The other three catalysts all exhibit mixed reduction pathways leading to both H2O2 and H2O. However, the pathways that lead to H2O do not involve H2O2 as an intermediate. A possible mechanistic scheme is offered to account for the observed behavior.