Dissertations / Theses on the topic 'Gold electrode'
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Iranpour, Bahar. "Gold electrode electrochemistry in protein based solar cells." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42218.
Full textSantana-Aguiar, Francisco Aurelio. "Characterisation of electrode microarrays produced photolithographically and with thiol self-assembled monolayers on gold electrodes." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/45/.
Full textCafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." University of Sydney, 2008. http://hdl.handle.net/2123/3870.
Full textSYNOPSIS OF THIS THESIS The aim of this thesis is to more fully understand and explain the binding mechanism of organic molecules to the Au(111) surface and to explore the conduction of such molecules. It consists of five discreet chapters connected to each other by the central theme of “The Single Molecule Device: Conductance and Binding”. There is a deliberate concentration on azine linkers, in particular those with a 1,10-phenanthroline-type bidentate configuration at each end. This linker unit is called a “molecular alligator clip” and is investigated as an alternative to the thiol linker unit more commonly used. Chapter 1 places the work in the broad context of Molecular Electronics and establishes the need for this research. In Chapter 2 the multiple break-junction technique (using a Scanning Tunnelling Microscope or similar device) was used to investigate the conductance of various molecules with azine linkers. A major finding of those experiments is that solvent interactions are a key factor in the conductance signal of particular molecules. Some solvents interfere with the molecule’s interaction with and attachment to the gold electrodes. One indicator of the degree of this interference is the extent of the enhancement or otherwise of the gold quantized conduction peak at 1.0 G0. Below 1.0 G0 a broad range for which the molecule enhances conduction indicates that solvent interactions contribute to a variety of structures which could bridge the electrodes, each with their own specific conductance value. The use of histograms with a Log10 scale for conductance proved useful for observing broad range features. vi Another factor which affects the conductance signal is the geometric alignment of the molecule (or the molecule-solvent structure) to the gold electrode, and the molecular alignment is explored in Chapters 3 for 1,10-phenanthroline (PHEN) and Chapter 4 for thiols. In Chapter 3 STM images, electrochemistry, and Density Functional Theory (DFT) are used to determine 1,10-phenanthroline (PHEN) structures on the Au(111) surface. It is established that PHEN binds in two modes, a physisorbed state and a chemisorbed state. The chemisorbed state is more stable and involves the extraction of gold from the bulk to form adatom-PHEN entities which are highly mobile on the gold surface. Surface pitting is viewed as evidential of the formation of the adatom-molecule entities. DFT calculations in this chapter were performed by Ante Bilic and Jeffery Reimers. The conclusions to Chapter 3 implicate the adatom as a binding mode of thiols to gold and this is explored in Chapter 4 by a timely review of nascent research in the field. The adatom motif is identified as the major binding structure for thiol terminated molecules to gold, using the explanation of surface pitting in Chapter 3 as major evidence and substantiated by emergent literature, both experimental and theoretical. Furthermore, the effect of this binding mode on conductance is explored and structures relevant to the break-junction experiment of Chapter 2 are identified and their conductance values compared. Finally, as a result of researching extensive reports of molecular conductance values, and having attempted the same, a simple method for predicting the conductance of single molecules is presented based upon the tunneling conductance formula.
Nandhakumar, Iris. "The early stages of CdTe epitaxial growth on gold single crystal electrode surfaces." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242869.
Full textSantos, Vanessa Nascimento dos. "Gold electrode modified with inorganic complexes applied as electrochemical sensors for nitric oxide." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7264.
Full textThe aim of this work is to study the surface modification of gold electrode with the trans-[Ru(NH3)4(tina)(SO4)]+ (Au/trans-[Ru(NH3)4(tina)(SO4)]+) and trans-[Fe(cyclam)(NCS)2]+ (Au/trans-[Fe(cyclam)(NCS)2]+) complexes ion, emplyoing the electrodeposition and self-assembled monolayer techniques, respectively; and evaluate the potentiality of these modified electrodes as electrochemical sensors for detection and quantification of NO. Cyclic voltammetry and electrochemical quartz crystal microbalance results suggest that the deposition of trans-[Ru(NH3)4(tina)(SO4)]+ complex ion on the gold surface. Cyclic voltammetry and surface enhanced raman spectroscopy results confirm the modification of gold electrode surface by the trans-[Fe(cyclam)(NCS)2]+ complex ion. Peak current (Ip) observed in cyclic voltammograms for the oxidation of NO on the modified electrodes were higher than that observed for the unmodified gold electrode, and the modified electrode Au/trans-[Fe(cyclam)(NCS)2]+ showed the highest Ip for the oxidation of NO. The values of detection limit and quantification limit obtained for the electrode Au/trans-[Ru(NH3)4(tina)(SO4)]+ were 7.73 x 10-8 mol L-1 and 2.58 x 10-7 mol L-1, and for the electrode Au/trans-[Fe(cyclam)(NCS)2]+ were 5.15 x 10-8 mol L-1 and 1.72 x 10-7 mol L-1, respectively, being this values smaller by an order of magnitude as the same obtained for the unmodified gold electrode. Computational simulations suggest that the increase in Ip oxidation of NO on the electrode Au/trans-[Fe(cyclam)(NCS)2]+ is due to the interaction energy between molecules of NO and the complex trans-[Fe(cyclam)(NCS)2]+, adsorbed on the gold surface, to be stronger than the energy of interaction of NO with the gold surface. The dopamine and serotonin molecules and the nitrite ion interfere in electrochemical detection of NO and dopamine and serotonin showed greater interference in the detection of NO in relation to the nitrite ion. The electrode Au/trans-[Fe(cyclam)(NCS)2]+ showed the greatest stability when compared to the electrode Au/trans-[Ru(NH3)4(tina)(SO4)]+. The results obtained in this work showed the potentiality of modified electrodes as sensors for deteccion and quantification of NO, among which stands out the electrode Au/trans-[Fe(cyclam)(NCS)2]+ due to the further intensification of the signal current for the oxidation of NO and provided greater stability.
O objetivo deste trabalho à estudar a modificaÃÃo da superfÃcie do eletrodo de ouro com os Ãons complexos trans-[Ru(NH3)4(tina)(SO4)]+ (Au/trans-[Ru(NH3)4(tina)(SO4)]+) e trans-[Fe(cyclam)(NCS)2]+ (Au/trans-[Fe(cyclam)(NCS)2]+), empregando as tÃcnicas de eletrodeposiÃÃo e formaÃÃo de camadas auto-organizadas, respectivamente; e avaliar a potencialidade destes eletrodos modificados como sensores eletroquÃmicos para detecÃÃo e quantificaÃÃo de NO. Os resultados de voltametria cÃclica e de microbalanÃa eletroquÃmica a cristal de quartzo sugerem a deposiÃÃo do Ãon complexo trans-[Ru(NH3)4(tina)(SO4)]+ sobre a superfÃcie de ouro. Os resultados de voltametria cÃclica e de espalhamento raman amplificado por superfÃcie comprovam a modificaÃÃo da superfÃcie do eletrodo de ouro pelo Ãon complexo trans-[Fe(cyclam)(NCS)2]+. As correntes de pico (Ip) observadas nos voltamogramas cÃclicos para a oxidaÃÃo do NO sobre os eletrodos modificados foram maiores que as observadas para o eletrodo de ouro sem modificaÃÃo, sendo que o eletrodo modificado Au/trans-[Fe(cyclam)(NCS)2]+ apresentou a maior Ip para a oxidaÃÃo de NO. Os valores de limite de detecÃÃo e de quantificaÃÃo obtidos para o eletrodo Au/trans-[Ru(NH3)4(tina)(SO4)]+ foram de 7,73 x 10-8 mol L-1 e 2,58 x 10-7 mol L-1, e para o eletrodo Au/trans-[Fe(cyclam)(NCS)2]+ foram de 5,15 x 10-8 mol L-1 e 1,72 x 10-7 mol L-1, respectivamente, sendo estes valores menores em uma ordem de grandeza que os mesmos obtidos para o eletrodo de ouro nÃo modificado. As simulaÃÃes computacionais sugerem que o aumento de Ip da oxidaÃÃo de NO sob o eletrodo Au/trans-[Fe(cyclam)(NCS)2]+ à devido à energia de interaÃÃo entre as molÃculas de NO e o complexo trans-[Fe(cyclam)(NCS)2]+, adsorvido na superfÃcie de ouro, ser mais forte que a energia de interaÃÃo do NO com a superfÃcie de ouro. As molÃculas dopamina e serotonina e o Ãon nitrito interferem na detecÃÃo eletroquÃmica de NO e a dopamina e a serotonina apresentaram maior interferÃncia na detecÃÃo de NO em relaÃÃo ao Ãon nitrito. O eletrodo Au/trans-[Fe(cyclam)(NCS)2]+ apresentou maior estabilidade quando comparado ao eletrodo Au/trans-[Ru(NH3)4(tina)(SO4)]+. Os resultados obtidos neste trabalho demonstram a potencialidade dos eletrodos modificados como sensores para detecÃÃo e quantificaÃÃo de NO, dentre os quais se destaca o eletrodo Au/trans-[Fe(cyclam)(NCS)2]+, devido à maior intensificaÃÃo no sinal de corrente para a oxidaÃÃo de NO e a maior estabilidade apresentada.
Young, Samantha. "Designing the Nanoparticle/Electrode Interface for Improved Electrocatalysis." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23723.
Full text2019-01-27
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 textGibbon-Walsh, Kristopher Bryant. "Speciation of trace metals and metalloids in natural waters using the vibrating gold microwire electrode." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569659.
Full textRemes, Daniel. "Biosensor based on a MOS capacitor with an internal reference electrode." Thesis, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19829.
Full textIn this project a new type of metal oxide semiconductor (MOS) sensor for biosensing was investigated. With the use of a porous gold film as aninternal reference electrode, measurements of pH were performed in liquid. This new approach for liquid measurements demands new methods andstudies to increase the conductivity and adhesion in liquid of the porous gold film. The films have been deposited, either by sputtering orevaporation. Extensive studies included the investigation of depositions parameters on film structure and investigating the film morphology. Thesurface structure was studied with a scanning electron microscope (SEM). pH measurements were preformed with promising results. The adhesionof the electrode was greatly improved by using grains of titanium underneath the gold film. This new approach could lead to new applications anddevices for MOS sensors and its sensor relatives.
Zamlynny, Volodymyr. "Electrochemical studies of adsorption of insoluble pyridine surfactants and their mixtures at a gold(111) electrode." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ33292.pdf.
Full textRidley, Paul. "Underpotential deposition of lead on gold and platinum (111) electrode surfaces investigated by scanning tunnelling microscopy." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343615.
Full textWanibuchi, Mizue. "Three-dimensional Structural Effects of Porous Materials on the Direct-electron-transfer-type Bioelectrocatalysis of Bilirubin Oxidase." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263704.
Full textChuang, 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 textIncludes 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.
Zhang, Kun. "Spectroelectrochemical Investigations of the Interaction of Flotation Reagents with Gold Surfaces." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/366588.
Full textThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text
Revesz, Erika. "Second harmonic generation spectroscopy of the potential induced surface reconstruction of the gold(110) electrode in perchloric acid electrolyte." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9925.
Full textMedeiros, Natália Goedtel. "Desenvolvimento de biossensor baseado em tirosinase para determinação de adenosina." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/170374.
Full textIn this work we report for the first time the determination of adenosine by a biosensor based on tyrosinase. The biosensor was developed by modifying a screen-printed carbon electrode (SPE) with gold nanoparticles (AuNPs), tyrosinase (Tyr) and Nafion, denoted as Nafion/Tyr/AuNPs/SPE biosensor. The synthesized AuNPs have a mean diameter of 15.0 ± 1.1 nm and their function is to improve the electron conduction pathway between the enzyme and the electrode. The entrapment with Nafion® film was selected to prevent the enzyme lixiviation from the electrode surface. Immobilized tyrosinase showed good activity with the catechol substrate. It was found that adenosine acts as a non-competitive type inhibitor. The biosensor is stable for at least 45 days. In addition, the electro-oxidation of adenosine was performed for its determination. The biosensor has superior sensitivity compared to SPE, AuNPs/SPE and Nafion/AuNPs/SPE. Calibration curves revealed two linear ranges for adenosine concentrations of 1,010-5 mol L-1 up to 5,010-5 mol L-1 and from 6,010-5 mol L-1 to 1,210-4 mol L-1. The detection limit (3 × (standard deviation + mean of blanks)/slope of the curve) was 7,010-7 mol L-1.
Pouliwe, Antibe. "Electrochemical Studies of The Interaction Between DNA and a Compound Having Anticancer Properties." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1352.
Full textOlowu, Rasaq Adewale. "Impedimetric and electrode kinetic dynamics of DNA aptamer nanobiosensors for estrogeneous endocrine disruptors." University of the Western Cape, 2011. http://hdl.handle.net/11394/8455.
Full textIn this work, DNA aptamer biosensor systems were developed for the detection of l7p-estradiol - an estrogeneous endocrine disrupting chemical (EDC). Endocrine disrupting chemicals are group of compounds that impact negatively on the endocrine system of humans and wildlife. High concentrations of l7p-estradiol in water or food chain disrupts the physiology of the endocrine system of various animal species, leading to feminisation in fish and stimulates the proliferation of cancer cells in humans. Aptasensor systems for the determination of l7pestradiol were prepared with three immobilization platforms: (i) poly(3,4- ethylenedioxythiophene) {PEDOT} doped with gold nanoparticles (AuNPs) to form PEDOTIAuNPs polymeric nanocomposite, (ii) generation 1 poly(propylene thiophenoimine)-copoly( 3 ,4-ethy lenedioxythiophene) dendritic star copolymer (G 1PPT -co-PEDOT), and (iii) generation 2 poly (propylene thiophenoimine)-co-poly(3,4-ethylenedioxythiophene) dendritic star copolymer (G2PPT-co-PEDOT). The morphological properties of the sensor platforms were interrogated by scanning emission microscopy (SEM) and atomic force microscopy (AFM), while their spectroscopic characteristics were studied by Fourier transform infra red spectroscopy (FTIR) and fluorescence spectroscopy. The electrochemical behaviour of the platforms and the aptasensors were studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave voltammetry (SWV). The DNA aptamer developed for detecting 17~-estradiol and which was used in the fabrication of all aptamer biosensors in this study is a 76-mer biotinylated aptamer (5'-BiotinGCTTCCAGCTTATTGAATTACACGCAGAGG TAGCGGCTCTGCGCATTCAATGCTGCGCGCTGAAGCGCGGAAGC-3'). AulPEDOTIAuNPslAptamer (platform 1) was obtained by covalently attaching streptavidin to the polymeric nanocomposite platform using carbodiimide chemistry and the aptamer immobilized via streptavidin-biotin interaction. The electrochemical signal generated from the aptamer-target molecule interaction was monitored electrochemically using cyclic voltammetry and square wave voltammetry in the presence of [Fe(CN)6J 3-/4- as a redox probe. The signal current observed was inversely proportional to the concentration of 17Bestradiol. The aptasensor demonstrated specificity toward 17~-estradiol. The detectable concentration range of the 17B estradiol was 0.01 nM-O .09 nM with a detection limit of 3.2 pM. The 76-mer biotinylated aptamer for 17~-estradiol was incorporated into a generation 1 poly(propylenethiophenoimine )-co-poly(3 ,4-ethylenedioxythiophene) dendritic star copolymer modified Au electrode via biotin-avidin interaction (platform 2). The Bode plot shows that the charge transfer dynamics of the nanoelectrode can be frequency modulated while the AulG 1PPTco- PEDOT nanoelectrode exhibited greater semi-conductor behavior (higher phase angle value) than AulG 1PPT due to the incorporation of charged functionalized dendrimer at low frequencies (100 mHz). The biosensor response to 17~-estradiol was based on the decrease in the SWV current as the EDC binds to the ssDNA aptamer on the biosensor. The dynamic linear range of the sensor was 0.01-0.07 nM with a detection limit of7.27 pM. Synthesis of electro synthetic generation G2PPT-co-PEDOT (platform 3) was performed by copolymerization of PEDOT with G2PPT dendrimer modified electrode immersed in a solution of 0.1 M LiCI04 containing 0.1 M EDOT monomer and 0.1 M sodium dodecyl sulphate (SDS) for ten (10) cycles. The electrochemical behaviour of the dendritic star copolymer was investigated with CV and EIS in LiCI04 and phosphate buffer solutions. The results show that the electrochemical deposition of G2PPT-co-PEDOT on gold electrode decreased the electrochemical charge transfer resistance when compared to AuiPEDOTILiCI04 and AuiLiCI04 interfaces. Bode impedimetric analysis indicates that G2PPT-co-PEDOT is a semiconductor. The fabrication of two novel aptasensors (based on platforms 2 and 3) simultaneously on a screen printed micro array electrode of 96-well multichannel electrochemical robotic sensor testing system for the detection of endocrine disrupting l7~-estradiol, was also carried out. The aptasensors responses to l7~-estradiol, based on the decrease in the SWV current, were evaluated.
Triffaux, Eleonore. "Interfacial study of a sensing platform for MDM2, based on the self-assembly of a p53 peptide on a gold electrode." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/217746.
Full textDoctorat en Sciences
info:eu-repo/semantics/nonPublished
AragÃo, Janmille da Silva. "Electrochemical Determination of diethylstilbestrol at glassy carbon electrode modified with gold nanoparticles and a film of multi-wall carbon nanotubes and cobalt phthalocyanine." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16652.
Full textO presente trabalho descreve o desenvolvimento de um sensor eletroquÃmico de carbono vÃtreo modificado com nanopartÃculas de ouro, nanotubos de carbono de paredes mÃltiplas funcionalizados e ftalocianina de cobalto (CV/NpAu/NTCPMf-FcCo) para a determinaÃÃo do hormÃnio dietilestilbestrol (DES) em amostras de Ãgua e carne, utilizando a tÃcnica de voltametria de onda quadrada (VOQ). O eletrÃlito empregado foi tampÃo BrittonâRobinson (BR) 0,04 mol Lâ1 pH 10,0. Inicialmente estudou-se a configuraÃÃo do eletrodo a ser utilizado para o desenvolvimento do trabalho, depois a otimizaÃÃo do pH do meio, estudo da velocidade de varredura para avaliar a cinÃtica de transferÃncia de carga no processo redox do DES, otimizaÃÃo dos parÃmetros da VOQ, construÃÃo da curva analÃtica e por fim, a aplicaÃÃo da metodologia desenvolvida. Os parÃmetros otimizados para a VOQ foram: f = 5 sâ1, a = 50 mV e ΔEs = 1 mV. De posse de todas as condiÃÃes otimizadas para aplicaÃÃo do CV/NpAu/NTCPMf-FcCo, curvas analÃticas foram obtidas no intervalo de concentraÃÃo de 7,9365 à 10−7 â 5,6604 à 10−6 mol Lâ1 (R = 0,9996) e os limites de detecÃÃo (LD) e de quantificaÃÃo (LQ) calculados foram 1,9910 x 10â7 mol Lâ1 e 6,6367 x 10â7 mol Lâ1, respectivamente, sendo comparÃveis aos citados na literatura. A repetibilidade e a reprodutibilidade do procedimento proposto foram avaliadas. Os valores de desvio padrÃo relativo (DPR) obtidos foram 4,33% e 3,49%, respectivamente, evidenciando a precisÃo da metodologia. O percentual de recuperaÃÃo foi de 98,56% para amostra de Ãgua e 94,05% para amostra de carne bovina (DPR de 0,40 e 1,55% respectivamente). O eletrodo modificado desenvolvido apresentou sensibilidade, reprodutibilidade e repetibilidade adequados, bem como valores de LD e LQ concordantes com os relatados na literatura. Os resultados obtidos pelo emprego do CV/NpAu/NTCPMf-FcCo se mostraram muito eficientes quanto à detecÃÃo e recuperaÃÃo de DES, mostrando-se, desse modo, um dispositivo promissor na detecÃÃo e na quantificaÃÃo de DES em amostras de Ãgua e alimentos.
Arotiba, Omotayo Ademola. "Electrochemical impedance modelling of the reactivities of dendrimeric poly(propylene imine) DNA nanobiosensors." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_7669_1266190932.
Full textIn this thesis, I present the electrochemical studies of three dendrimeric polypropylene imine (PPI) nanomaterials and their applications as a platform in the development of a novel label free DNA nanobiosensor based on electrochemical impedance spectroscopy. Cyclic voltammetry (CV), differentia pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivities of the nanomaterials on glassy carbon electrode (GCE) as the working electrode.
Silva, Vinicius Carlos Costa. "Estudo eletroanalítico da dopamina utilizando eletrodo de pasta de carbono produzidos com pó de grafite recoberto por eletrodepósitos de ouro." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8925.
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Electroanalytical techniques are extensively studied for the quantification of species of biological and pharmacological interest. In general, they present high sensitivity and low costs, which, combined with the possibility of miniaturization and real-time analysis, has generated increasing attention in recent times. This work describes an electroanalytical dopamine research system using voltametric techniques through the application of a modified carbon electrodeposite (EPCM) carbon paste electrode. The electrochemical measurements were performed in a potentiostat using a three electrode system, using a gold electrode as working electrode (EPCM), AgCl electrode as reference and platinum wire as electrode. The kinetics of dopamine oxidation was investigated by cyclic voltammetry and by square wave voltammetry using EPCM in dopamine standard solution, without and with sodium metabisulfite (additive present in the drug). By cyclic voltammetry, different scanning velocities were used as a methodology to identify the type of kinetic control, whereas square wave voltammetry was used, with the use of factorial design, to investigate how the gold electrodeposing variables influence the oxidation of DA. he effect of the pH of the medium was also investigated, using phosphate buffer at different pH. Furthermore, under optimized conditions the effect of various concentrations of DA was investigated in order to obtain an analytical curve. The results show by means of measurements by cyclic voltammetry in solutions of DA with and without metabisulfite, that the anodic current of the DA increases from potentials more positive than +0,225 V, with a peak at +0,320. Factorial design observed that sodium metabisulfite significantly decreased the peak current for oxidation of DA. In quadra wave voltammograms for EPCM in phosphate buffer solutions pH 7 containing dopamine and sodium metabisulfite, it is observed that the peak oxidation of dopamine occurs at +0.195 V, while the oxidation of the metabisulfite occurs at approximately +0.834 V. In the study of the pH effect it is verified that an increase of the current occurs when the pH value is above 6.0, while the oxidation potential of the dopamine shifts to more negative values from pH 2, having a sigmoid relation. In the parameter effect of the concentration it was possible to conclude that using this type of modification (gold electrodeposits) showed an improvement in the peak currents when compared to the unmodified electrode. The linearity ranges obtained using EPCM were 3.17 × 10-5 - 1.06 × 10-4, but it was not possible to obtain an ideal calibration curve for the determination of dopamine.
As técnicas eletroanalíticas são amplamente estudadas para quantificação de espécies de interesse biológico e farmacológico. De modo geral, apresentam alta sensibilidade e baixos custos, o que, aliado à possibilidade de miniaturização e análise em tempo real, tem gerado atenção crescente nos últimos tempos. Este trabalho descreve um sistema eletroanalítico de investigação de dopamina utilizando técnicas voltametricas através da apliacação de um eletrodo de pasta de carbono modificado com eletrodepositos de ouro (EPCM). As medidas eletroquímicas foram realizadas em um potenciostato utilizando um sistema de três eletrodos, empregando eletrodo de ouro como eletrodo de trabalho (EPCM), eletrodo de AgCl como referência e fio de platina como contra eletrodo. A cinética de oxidação de dopamina foi investigada por voltametria cíclica e por voltametria de onda quadrada utilizando o EPCM em solução padrão de dopamina, sem e com metabissulfito de sódio (aditivo presente no medicamento). Por voltametria cíclica foi utilizada diferentes velocidades de varredura como metodologia para identificar o tipo de controle cinético, enquanto que a voltametria de onda quadrada foi empregada, com uso de planejamento fatorial, para investigar como as variáveis de eletrodeposição de ouro influenciam sobre a oxidação de DA. Também foi investigado o efeito do pH do meio, utilizando-se tampão fosfato a diferentes pH. Além disso, sob condições otimizadas foi investigado o efeito de várias concentrações de DA, com a finalidade de se obter uma curva analítica. Os resultados mostram através das medidas por voltametria cíclica em soluções de DA com e sem metabissufito, que a corrente anódica da DA aumenta a partir de potenciais mais positivos que +0,225 V, apresentando um pico em +0,320. Diante do planejamento fatorial observou que o metabissulfito de sódio diminui significativamente a corrente de pico para oxidação da DA. Nos voltamogramas de onda quadra para o EPCM nas soluções tampão fosfato pH 7 contendo dopamina e metabissulfito de sódio, observa-se que o pico de oxidação da dopamina ocorre em +0,195 V, enquanto que a oxidação do metabissulfito ocorre em aproximadamente +0,834 V. No estudo do efeito do pH verifica-se que ocorre um aumento da corrente quando o valor de pH está acima de 6,0, enquanto que o potencial de oxidação da dopamina desloca para valores mais negativos desde o pH 2, tendo uma relação sigmoide. No parâmetro efeito da concentração foi possível concluir que utilizando este tipo de modificação (eletrodepósitos de ouro) mostrou uma melhora no aumento das correntes de pico quando comparado com o eletrodo não modificado. As faixas de linearidade obtidas utilizando o EPCM foram de 3,17 × 10-5 – 1,06 × 10-4, porém não foi possível obter uma curva de calibração ideal para a determinação da dopamina.
Souza, Nyccolas Emanuel de. "Aspectos fundamentais das reações de eletro-oxidação de glicerol e álcoois similares sobre ouro." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-07052015-112646/.
Full textFundamental aspects of glycerol and similar alcohols electrooxidation reactions on gold were studied by comparing with similar alcohols: 1-propanol, 2-propanol, propane-1,2-diol and propane-1,3-diol, and also sorbitol and glucose. Electrochemical measurements were performed in acidic, neutral and alkaline solutions. Moreover, CV tests were performed in alkaline environment with the main possible glycerol oxidation byproducts: dihydroxyacetone, gyceraldehyde, glycerate, hydroxypyruvate, mesoxalate, tartronate, oxalate and formate. Finally, the reaction products were analyzed by in situ FTIR and HPLC. As expected, gold was practically inactive for all alcohols in acidic and neutral conditions, but highly active in alkaline medium. However, RDE data showed that the alkoxide formation is not the responsible for the high activity, as proposed until now. By comparing the glycerol electrooxidation with the other alcohols, it was possible note that the vicinal hydroxyl groups is the key property to yield the high current densities (for alcohols electrooxidation in a general way) seen on gold. It favors the C-C bonding break, that leads to more oxidized products, as seen by FTIR and HPLC data. In addition, FTIR measurements showed that neutralization and even acidification can occur near to the electrode in alkaline medium (if the base concentration is not high enough), due to the formation of acidic byproducts that can also lead to different reaction mechanism. RDE experiments indicated that it is possible to control the selectivity of glycerol and other alcohols electrooxidation products on gold by artificial convection, but control by the potential or concentration are limited, as shown by products analysis. The CV tests with byproducts and products analysis allowed to refine the glycerol electrooxidation reaction pathways.
Zorica, Stojanović. "Elektrohemijsko određivanje histamina." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2011. https://www.cris.uns.ac.rs/record.jsf?recordId=76992&source=NDLTD&language=en.
Full textIn this work, the electrochemical methods for the determination of histamine weredeveloped. All electrochemical investigations were carried out by chronopotentiometry. The research included optimization of the experimental parameters of electroanalytical techniques and comparison of the mechanism of the analytical signal generation by using the different working electrodes. Upon the development of sample preparation procedure, histamine was determined in different food and beverages. The possibility of applying solid gold electrodes, thin film mercury electrode and thin film nickel electrode for electrochemical determination of histamine was examined. The mechanisms of histamine electrooxidation on different working electrodes were explained and elaborated. Optimization of the experimental parameters of electroanalytical techniques included the selection of appropriate supporting electrolyte and its concentration, and investigation of the influence of initial potential and oxidation current on histamine analytical signal. Beside this, for each electrochemical system sensitivity and reproducibility, selectivity as well as linearity range were defined. The use of thin nickel film electrode resulted in adsorptive accumulation, and in that case the effects of accumulation time and medium temperature on histamine analytical signal were defined. On thin film mercury electrode, histamine analytical signal was generateddue to direct oxidation of histamine by a constant current. On other two electrodes, electrode reactions were coupled with chemical reaction, and histamine oxidation was by ECE mechanism (electrode reaction – chemical reaction – electrode reaction). On solid gold electrode histamine was oxidized indirectly by electrogenerated chlorine, while in the case of thin film nickel electrode combination of catalytic and adsorptive chronopotentiomety was responsible for signal generation. Thin film mercury electrode showed good selectivity for histamine and amino acids concentrations below 5 mg/dm3, but higher concentrations caused the overlapping of analytical signals. Other electrochemical systems did not show adequate selectivity. The best sensitivity was achived by thin film nickel electrode (LOD = 0.11 mg/dm3),followed by a solid gold electrode (LOD = 0.27 mg/dm3), and by thin film mercury electrode (LOD = 1.31 mg/dm3). In order to define adequate sample preparation procedure, the efficiency of different extraction techniques and different solvents were tested for histamine extraction from the samples. Appropriate procedures for purification of extracts were defined as well, by applying preparative thin layer and column chromatography. After optimization of the electrochemical methods for histamine determination, as well as the procedure of sample preparation, developed methods were applied for histamine determination in various food and beverages.
Untiveros, Katherine Lozano. "Electrochemical approach and development of an eletrochemical biosensor based on hairpin-DNA modified gold electrode for detection of DNA damage for a new acridine-thiophene cancer drug." Universidade Federal de Alagoas, 2017. http://www.repositorio.ufal.br/handle/riufal/2120.
Full textA interação de drogas com DNA é uma característica significativa na farmacologia e desempenha um papel vital na concepção de drogas mais eficientes e especificamente direcionadas. O conceito de hibridização de duas moléculas bioativas leva ao aumento da atividade devido aos efeitos sinérgicos de drogas híbridas anticâncer com o uso dos farmacóforos importantes: Acridina e Tiofeno. Estes dois sítios ativos foram amplamente estudados como agentes antitumorais, antiparasitários e antibacterianos. Suspeitamos que um conjugado, composto por dois farmacóforos com diferentes mecanismos de ação antiproliferativa, pode resultar em danos ao DNA. Estudos eletroquímicos em meios prótico e aprótico, biossensor de DNA eletroquímico em eletrodo de carbono vítreo, Hairpin DNA em eletrodo de ouro (SL-DNA/GE), modelagem molecular e Espectroscopia UV-Vis foram usados para determinar os danos causados ao DNA por seis conjugados de Acridina-Tiofeno. Neste trabalho, relatamos o estudo de seis intercaladores de DNA com base na acridina ligada a conjugados de tiofeno (7CNAC01, 6CNAC01, 7ESTAC01, 6ESTAC01, ACS6CN e ASC5CN). As propriedades redox da 7CNAC01, 6CNAC01, 7ESTAC01 e 6ESTAC01 envolvem processo quase-reversível com corrente controlada por difusão. As propriedades redox desses compostos foram investigadas usando voltametrias cíclica e de pulso diferencial (VPD) em eletrodo de carbono vítreo e eletrodo de ouro. Foi desenvolvido um novo e eficiente biossensor eletroquímico baseado no Hairpin DNA (SL-DNA/GE) imobilizado e funcionalizado na superfície do eletrodo de ouro para detectar danos oxidativos da guanina através da interação com 7ESTAC01. Os biosensores SL-DNA e dsDNA foram testados com conjugados de acridina-tiofeno reduzidos, apresentando melhor sensibilidade o sensor SLDNA na detecção de danos ao DNA. Além disso, os resultados de modelagem molecular mostraram predominantemente interação hidrofóbica e uma alta constante de ligação. Já os resultados de espectroscopia de absorção no UV-Vis mostraram a presença de ponto isosbéstico com dsDNA, para os conjugados 7ESTAC01, 6ESTAC01, ACS6CN, ACS5CN. Nossos resultados indicaram que três compostos de acridina-tiofeno reduzidos (7CNAC01, 6CNAC01 e ACS5CN) causaram danos direto ao dsDNA, e os seis compostos híbridos reduzidos, causaram danos ao DNA de cadeia simples. Finalmente, propusemos pela primeira vez uma correlação direta entre constante de ligação (Kb) e potencial de meia onda (E1 / 2) para quatro derivados de acridina-tiofeno (7ESTAC01, 6ESTAC01, ACS6CN e ASC5CN). Além disso, o biosensor eletroquímico de SL-DNA/GE mostrou-se bastante sensível para a detecção dos danos causados ao DNA, através da interação entre o DNA e os compostos estudados.
Joca, Jhonny Frank Sousa. "Determinação de manganês em amostras de cimento e clínquer por voltametria de redissolução catódica empregando eletrodos de ouro." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-31082011-160037/.
Full textThis work describes the development and application of a new alternative method for determination of manganese in cement and clinker samples by square wave cathodic stripping voltammetry using gold electrodes. After exploratory studies on the electrochemical behavior of manganese in H3BO3 0.20 mol L-1 / KCl 0.10 mol L-1 supporting electrolyte at pH 6.5 and the optimization of operating parameters for the square wave voltammetry, excellent results were obtained for determination of manganese in the samples analyzed. Most notable are the excellent linearity, verified in two distinct concentration bands and the low limits of detection and quantification obtained (3,1 x 10-8 mol L-1 e 9,8 x 10-8 mol L-1, respectively), in addiction to the concordance between the obtained results by the electroanalytical technique when compared to the provided by the flame atomic absorption spectrometry. For samples treatment were tested the efficiency of the ultrasound-assisted extraction. Were evaluated individually mineral acids (HCl, H2SO4 and HClO4 at different concentrations) in a mixture or associated with H2O2. the best results were obtained using a 3 mol L-1 HCl solution, which extracted manganese quantitatively from the analysed samples, in comparison to the standard method for extraction, targeting a later atomic absorption flame spectrometry analysis, which uses the plate heating and the same extracting solution. The obtained results for the analysed samples agrees with the cement and clinker samples of the used literature
Doneux, Thomas. "Caractérisation par électrochimie et spectroscopie infrarouge in situ d'une électrode d'or (111) modifiée par du 2-mercaptobenzimidazole." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210969.
Full textL’étude des modifications de surfaces, et plus particulièrement des matériaux d’électrodes est un domaine en plein essor. Les modifications d’électrodes par voie organique ont des applications potentielles dans des domaines aussi variés que l’inhibition de la corrosion, l’électronique moléculaire, l’optoélectronique ou encore les biosenseurs.
Dans ce travail, nous nous sommes intéressés à l’électrode d’Au (111) modifiée par du 2-mercaptobenzimidazole.
Dans un premier temps, l’adsorption du MBI sur électrode d’Au (111) sous contrôle du potentiel a été examinée par des mesures de capacité, de voltampérométrie cyclique, de chronocoulométrie et de spectroscopie SNIFTIR in situ.
Les mesures de capacité révèlent qu’en milieu neutre, la molécule de MBI s’adsorbe en un film compact à des potentiels supérieurs à -0,3 V (vs. ECS). En deçà de cette valeur, le film se dilue progressivement lorsque le potentiel est rendu plus négatif, jusqu’à une valeur de -0,9 V où les molécules de MBI sont totalement désorbées de la surface.
La morphologie des voltampérogrammes subit des variations significatives au cours du temps. Ces changements montrent que l’adsorption du MBI s’accompagne d’une levée de reconstruction de la surface, qui passe d’une structure initiale (√3 x 22) à une structure (1 x 1). Une estimation de la quantité de MBI adsorbée est obtenue par intégration des courbes de densité de courant.
La courbe de densité de charge interfaciale a été extraite des mesures de chronocoulométrie. Cette courbe de densité de charge fournit des informations quant à l’évolution de l’excès superficiel en fonction du potentiel.
La qualité des spectres infrarouges relevés in situ nous a permis d’effectuer des analyses qualitatives et quantitatives. Celles-ci montrent une bonne corrélation avec les résultats électrochimiques et apportent une signature moléculaire du film adsorbé et des espèces issues de sa désorption. Des calculs basés sur la Théorie de la Fonctionnelle de la Densité (DFT) ont permis une bonne interprétation des spectres infrarouges du MBI et de certains de ses dérivés. En outre, nous avons pu déterminer l’orientation des molécules à la surface, et montré que celle-ci varie peu avec le potentiel.
Dans un second temps, nous nous sommes focalisés sur les propriétés de la monocouche auto-assemblée de MBI sur électrode d’Au (111), déterminées par voltampérométrie cyclique et spectroscopie infrarouge in situ. La monocouche est stable lorsque le potentiel est maintenu dans un domaine d’environ 800 mV. La monocouche auto-assemblée de MBI subit un processus de désorption réductive, influencé par le temps d’immersion de l’électrode dans la solution de surfactant ainsi que par le pH du milieu. Deux mécanismes de désorption réductive sont proposés, l’un valable en milieu neutre et basique, l’autre en milieu acide. Les résultats des mesures de spectroscopie infrarouge in situ apportent une preuve moléculaire de la validité des mécanismes proposés sur base des résultats électrochimiques.
Un rapide examen des potentialités de cette monocouche a été réalisé à l’aide de réactions sondes.
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Abstract
Studies on surface modifications, and particularly of electrode material, are a growing field of interest. Organic modifications of electrode surfaces have potential applications in domains such as corrosion inhibition, molecular electronics, optoelectronics or biosensors.
In the present work, we focussed on the modification of Au(111) electrodes by 2-mercaptobenzimidazole (MBI).
In the first part, the adsorption, under potential control, of the MBI molecule onto the Au(111) electrode was studied by means of capacitance measurements, cyclic voltammetry, chronocoulometry and in-situ SNIFTIR spectroscopy.
Capacitance measurements indicate that in neutral solution, the MBI molecule is adsorbed as a compact film at potentials higher than -0.3 V (vs. SCE). Below this value, the film becomes progressively less dense when the potential is made more negative, until a value of -0.9 V where MBI molecules are totally desorbed from the surface.
The shape of the voltammograms evolves significantly with time. These changes show that a lift of the surface reconstruction occurs concomitantly to the adsorption of MBI. The initial (√3 x 22) reconstructed structure is lifted to the (1 x 1) unreconstructed one. The amount of adsorbed MBI is estimated by integration of the current density curves.
The interfacial charge density curve was obtained by chronocoulometry measurements. This curve provides useful data regarding the evolution of the surface concentration with the potential.
The quality of the infrared spectra obtained in situ allowed us to perform quantitative as well as qualitative analyses of the results. These analyses show a good correlation with the electrochemical results and provide molecular information on the adsorbed layer and on the species formed during the desorption process. Density Functional Theory (DFT) calculations were helpful in the interpretation of the infrared spectra of MBI and some of its derivatives. Additionally, we were able to determine the orientation of the molecules on the surface, and demonstrated that this orientation is slightly affected by the potential.
In the second part of the work, we investigated the properties of the self-assembled monolayer of MBI on Au(111) electrode by cyclic voltammetry and in situ infrared spectroscopy. The monolayer is stable within an 800 mV potential range. The self-assembled monolayer undergoes a reductive desorption process, which is affected by the pH of the medium and by the immersion time of the electrode into the surfactant solution. Two mechanisms were proposed for the reductive desorption, one being valid in neutral and basic media, the other in acidic conditions. The in situ infrared spectroscopic results provide molecular evidences supporting the mechanisms proposed on an electrochemical basis.
An exploratory examination of the potentialities of the monolayer is made by means of electrochemical probe reactions.
Doctorat en sciences, Spécialisation chimie
info:eu-repo/semantics/nonPublished
DIAS, Ana Carolina Matos da Silva. "Desenvolvimento de plataformas sensoras para detecção eletroquímica do antígeno NS1 do vírus da dengue." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17374.
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FACEPE
A infecção pelo vírus dengue (DENV) é uma das doenças tropicais mais negligenciadas e de maior importância de saúde pública no mundo. Novos métodos de diagnóstico da doença têm sido estudados através da detecção da proteína NS1 do DENV. O antígeno NS1 é um importante marcador precoce da fase aguda da dengue, secretado em altas concentrações pelo vírus no sangue de pessoas infectadas logo nos primeiros dias, porém, não é muito utilizado na rotina laboratorial para diagnóstico da doença devido ao alto custo dos ensaios. A presente tese descreve o desenvolvimento de duas plataformas sensoras eletroquímicas baseadas em eletrodos impressos (EIs) modificados com nanomateriais para detecção do antígeno NS1 do DENV. Os EIs foram confeccionados utilizando-se a impressão de tinta de carbono sobre o polietileno tereftalato (PET), suporte para impressão dos moldes. Inicialmente, foram estudados os efeitos de nanotubos de carbono e sua contribuição na transferência de elétrons, condutividade e aumento de área eletroativa da plataforma sensora. O estudo foi baseado na incorporação de nanotubos de carbono funcionalizados com grupos carboxílicos à tinta de carbono. Para detecção do NS1, um imunoensaio do tipo “sanduíche” foi realizado, no qual a captura específica do NS1 pôde ser avaliada através das reações redox da enzima peroxidase conjugada ao anticorpo. Uma faixa linear entre 0,04 g/mL e 2 g/mL de NS1 foi obtida, indicando boa performance analítica do imunossensor, com coeficiente de correlação linear de 0,996 (p<0.0001, n=8) e limite de detecção de 0,012 g/mL de NS1. Posteriormente, foi investigada a contribuição de nanopartículas metálicas no desenvolvimento de sensores eletroquímicos livres de marcação. Foram utilizadas nanopartículas de ouro (NPsAu) funcionalizadas com grupos amina para a imobilização covalente de anticorpos. Na síntese das NPsAu, foi utilizado o polietilenoimina como agente redutor e funcionalizante para promover uma ligação amida com o anticorpo anti-NS1. O imunossensor desenvolvido mostrou curva de calibração com faixa de concentração linear entre 0,1 g/mL e 2 g/mL de NS1 (r = 0,995, p<0.0001, n=7) e limite de detecção de 0,03 g/mL de NS1. A contribuição dos nanomateriais para as plataformas sensoras desenvolvidas mostrou-se efetiva na sensibilidade analítica, devido ao aumento de área eletroativa e maior quantidade de anticorpos imobilizados. A aplicação destes nanomateriais nos imunossensores proporciona novas alternativas de diagnóstico para detecção da proteína NS1 do DENV.
Infection by Dengue Virus (DENV) is one of the most neglected tropical diseases and of higher importance of public health worldwide. New methods of diagnosis of the disease have been studied through the detection of NS1 protein of DENV. NS1 antigen is an important early marker of acute dengue infection secreted in high concentrations by the virus in the blood of infected people in first days, however it is not widely used in the laboratory routine for diagnosis of the disease due to high cost of assays. The present thesis describes the development of two electrochemical sensor platforms based on screen-printed electrodes (SPEs) modified with nanomaterials for detection of NS1 antigen of DENV. SPEs were prepared using carbon ink printing on the polyethylene terephthalate (PET), support for molds printing. Initially, the effects of carbon nanotubes and their contribution to the electron transfer, conductivity and increase of electroactive area of the sensor platform were studied. The study was based on the incorporation of carbon nanotubes functionalized with carboxylic groups to the carbon ink. For NS1 detection, a sandwich-type immunoassay was carried out, wherein the specific capture of NS1 may be assessed by redox reactions of peroxidase enzyme conjugated to the antibody. A linear range between 0.04 g/mL and 2 g/mL NS1 was obtained, indicating good analytical performance of the immunosensor, with linear correlation coefficient of 0.996 (p<0.0001, n=8) and limit of detection of 0.012 g/mL NS1. Subsequently, the contribution of metal nanoparticles in the development of label-free electrochemical sensors was investigated. Gold nanoparticles (AuNPs) functionalized with amine groups were used for covalent immobilization of antibodies. In the synthesis of AuNPs, polyethyleneimine was used as a reducing and functionalizing agent to promote an amide bond with anti-NS1 antibody. The developed immunosensor showed calibration curve with linear concentration range between 0.1 g/mL and 2 g/mL NS1 (r = 0.995, p<0.0001, n = 7) and limit of detection of 0.03 g/mL NS1. The contribution of nanomaterials for the sensor platforms developed proved effective in the analytical sensitivity due to the increase of electroactive area and larger amount of immobilized biomolecules. The application of these nanomaterials in immunosensors provides new alternatives of diagnosis for detection of NS1 protein of DENV.
Mossanha, Rosana. "PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2011. http://tede2.uepg.br/jspui/handle/prefix/2093.
Full textIn this work were studied investigated different types of modifiers for the formation of self-assembled monolayers on the gold surface. The monolayers used were formed by different structural arrangements, alkyl chains and functional groups. The thiols groups used were: 3-mercaptopropionic acid (MPA), thiolactic acid (TLA), cystamine (CYS) and 11-mercaptoundecanoic acid. The electroactivity of films of different thiols was assessed by the probe molecule, Fe(CN)63-/4-. It was possible to observe through the cyclic voltammetry technique, the formation and organization of the films, monitoring the behavior of the redox couple. The voltammograms showed a decrease in the faradaic current response with the increase of immersion time of the gold substrate in ethanolic solution of thiols, suggesting that the process of electron transfer occurs through the pinholes of the electrodes surface and tunneling. The monolayers of 3-mercaptopropionic acid (MPA) and thiolactic acid (TLA) had a better coating of the surface in immersion time of 3 hours. While the 11-mercaptopropionic acid (MUA) and cystamine (CYS) needed more time to organize the monolayer, 24 hours, because the MUA is a long chain molecule and CYS because the cleavage of S-S. The size of thiol chain influenced the surface organization, short-chain thiols tend to form monolayers with a considerable amount of defects, leading to a lower coating on the electrode surface. Indeed, the MUA that contains a high number of carbons in the chain showed a higher surface coverage, which caused loss of voltammetric response. The electrode surface roughness and the active area, calculated by the voltammetric data, showed a decrease with the formation of the monolayers on gold surface. Aiming to estimate the amount of molecules immobilized on the surface, it was calculated the superficial excess ) by voltammetric charge obtained from the reductive desorption. The obtained values were of 1.88x10-10 for Au-CYS, 5.03x10-10 to Au-MPA, 1.06x10-8 for Au-MUA and 1.35x10-10 mol.cm-2 for the Au-TLA, demonstrating an almost complete coverage of active sites on the surface. By the electrochemical impedance spectroscopy technique, it was possible to determine the kinetic parameters of the SAMs, which were consistent with those obtained by cyclic voltammetry. Analyzing the performance of sensors for dopamine determination through the VC, it was found that the SAM formed by TLA presented the most satisfactory results regarding the sensitivity and selectivity compared to the analyte DA. Studies at different scan rates for the electrodes, Au-MPA, Au-TLA and Au-CYS in the presence of the analite showed that the anodic peak current linearly increases with the square root of scan rate, indicating that the electron transfer process is controlled by diffusion of species to the electrode surface. Dopamine was quantified by CV and SWV technique, in the linear range from 1.1 to 6.6x10-7 mol L-1 with detection limits of 1,42x10-7 mol L-1 and 4,77x10-8 mol L-1, respectively. Using the technique of VOQ, TLA-Au electrode was able to distinguish between AA and DA, when present in the same solution, with a potential difference of approximately 340 mV.
Neste trabalho foram investigados diferentes tipos de modificadores para a formação de monocamadas auto-organizadas sobre a superfície do ouro. As monocamadas utilizadas foram formadas por diferentes arranjos estruturais, tamanho da cadeia carbônica e grupos funcionais. Os tióis utilizados foram: ácido 3- mercaptopropiônico (MPA), ácido tioláctico (TLA), cistamina (CYS) e o ácido 11-mercaptoundecanóico. A eletroatividade dos filmes dos diferentes tióis foi avaliada pela molécula sonda, Fe(CN)6]3-/4-. Foi possível constatar através da técnica de voltametria cíclica, a formação e a organização dos filmes, monitorando o comportamento do par redox. Os voltamogramas mostraram um decréscimo nas respostas da corrente faradaica com o aumento do tempo de imersão do substrato ouro na solução etanólica dos tióis, sugerindo que o processo de transferência de elétrons ocorre através dos pinholes da superfície e por tunelamento. Os eletrodos com as monocamadas de ácido 3-mercaptopropiônico (MPA) e o ácido tioláctico (TLA) obtiveram melhor recobrimento da superfície no tempo de imersão de 3 horas. Enquanto que o ácido 11-mercaptopropiônico (MUA) e a cistamina (CYS) necessitaram de maior tempo de imersão para organização da monocamada, de 24 horas, devido o MUA ser uma molécula de cadeia longa e a CYS devido a quebra da ligação S-S. O tamanho da cadeia do tiol influenciou no empacotamento da superfície, tióis de cadeia curtas tendem a formar monocamadas com uma quantidade de defeitos considerável, levando ao um menor recobrimento na superfície eletródica. O MUA que contém um número elevado de carbonos na cadeia apresentou um maior recobrimento da superfície, o que ocasionou perda da resposta voltamétrica. A rugosidade e a área ativa dos diferentes eletrodos, calculadas a partir dos voltamogramas, diminuíram com a formação das monocamadas sobre a superfície do ouro. Com o objetivo de estimar a quantidade de moléculas imobilizadas sobre a superfície, foram calculados os excessos superficiais por meio da carga voltamétrica obtida da dessorção redutiva. Os valores obtidos foram de = 1,88x10-10 para Au-CYS, 5,03x10-10 para Au-MPA, 1,06x10-8 para Au-MUA e 1,35x10-10 mol.cm-2 para o Au-TLA, demonstrando uma cobertura quase completa dos sítios ativos da superfície. Pela técnica de espectroscopia de impedância eletroquímica foi possível determinar os parâmetros cinéticos das SAMs, os quais foram consistentes com os obtidos pelos voltamogramas cíclicos. Analisando o desempenho dos sensores para a determinação de dopamina (DA) através da VC, verificou que a SAM formada pelo TLA foi a que apresentou resultados mais satisfatórios quanto a sensibilidade e seletividade em relação a este analito. Estudos em diferentes velocidades de varredura para os eletrodos Au-MPA, Au-TLA e Au-CYS na presença do analito mostraram que a corrente de pico anódica aumenta linearmente com a raiz quadrada da velocidade de varredura, indicando que o processo de transferência de elétrons é controlado pela difusão das espécies à superfície do eletrodo. A dopamina foi quantificada pela técnica de VC e VOQ, na faixa linear de 1,1 a 6,6x10-7 mol L-1 com limites de detecção de 1,42x10-7 mol L-1e 4,77x10-8 mol L-1, respectivamente. Utilizando-se a técnica de VOQ, o eletrodo Au-TLA foi capaz de distinguir o ácido ascórbico (AA) e DA quando presentes na mesma solução, com uma diferença de potencial de aproximadamente 340 mV.
Kriegisch, Volker. "Electron transfer processes between organic redox centres and electrodes via active bridges in self-assembled monolayers." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978743814.
Full textSivasubramaniam, Prabalini. "Gold based electro catalysts." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/193147/.
Full textPiatnicki, Slawomir. "Lixiviation de minerais aurifères et électrolyse directe des solutions diluées sur une cathode volumique poreuse percolée pulsée : application aux petits gisements d'or." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL040N.
Full textSaheb, Amir Hossein. "Sensing materials based on ionic liquids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24789.
Full textCommittee Chair: Janata, Jiri; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Josowicz, Mira; Committee Member: Kohl, Paul.
Kynclová, Hana. "Charakterizace nanostrukturovaných elektrod pro elektrochemické biosenzory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219511.
Full textGama, Elter Gouveia. "Desenvolvimento de um eletrodo de pasta de carbono modificado com eletrodepósito de ouro obtido in situ." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6941.
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The present paper concern to the electrochemical characterization of the gold electrodeposition process into a carbon paste (CP) to produce graphite powder covered by gold. This electrode also was used to study the voltammetric features of dopamine oxidation. The voltammetric study of gold electrodeposition process indicated that for MCPE-oily, the reduction of AuCl4 - occurs from potentials more negative than ~+0.60 V (peak at ~+0.35 V) and gold oxidation from potential more positive than ~+0.40 V (peak at +0.65 V). For MCPE-aqueous, without and with glycerol, the reduction of AuCl4 - occurred from potentials more negative than ~+0.73 V (peak at ~0.40 V) and the gold oxidation from more positive potentials than ~ +0.25 V (peak at +0.57 V). These processes were dependents on the gold ion concentration into the CP. It was also verified that the Au(III) reduction probably occurred throughout of the MCP volume, but not homogeneously. It was verified that the reduction process takes place preferably in the MCP interface/aqueous NaCl solution and decreased toward the interior of the PC. In addition, it was observed that the process of gold electrodeposition on the MCPE behaves as a quasi-reversible system, thereby indicating that the system has a strong dependence on the mass transport (diffusion and migration) and electron transfer. In addition, it was found that the cathodic peak currents for MCPE-aqueous were higher than the MCPE-oily, indicating that the reduction kinetics in aqueous medium is highest, probably due to the increase in the mass transport rate in aqueous solution. Studies using factorial design with the oily and aqueous MCPE indicated that the factors: HAuCl4 concentration in the PC, deposition charge and the additive presence affected the performance of the MCPEs in ferrocyanide solution. Micrographs obtained by scanning electron microscopy (SEM) for oily and aqueous MCPE indicated that the gold electrodeposit occurred on some graphite flakes with an homogeneous layer of gold. The TEM images of the graphite powder with gold electrodeposit for MCPE-oily showed gold particles with dimensions of 52.1 nm to 281.5 nm distributed evenly over the graphite flake. X-ray diffraction analisys indicated that the gold electrodeposit was polycrystalline. The dopamine (DA) oxidation was dependenting on the electrodeposition parameters and DA solution composition. The analytical curve for the DA oxidation in NaCl/NaS2O5 did not provide adequate linearity, being influenced by the DA/NaS2O5 ratio and acidity solution.
O presente trabalho trata da caracterização eletroquímica do processo de eletrodeposição de ouro dentro de uma pasta de carbono (PC) para produzir pó de grafite recoberto com ouro. Este eletrodo também foi utilizado para estudar o perfil voltamétrico da oxidação de dopamina. O estudo voltamétrico do processo de eletrodeposição indicou que para o EPCM-oleoso a redução de AuCl4 - ocorre a partir de potenciais mais catódicos que ~+0,60 V (pico em +0,35 V), e a oxidação de ouro a partir de potenciais mais anódicos que ~+0,40 V(pico em +0,65 V). Para o EPCM-aquoso sem e com glicerol a redução de AuCl4 - ocorreu a partir de potenciais mais negativos que ~+0,73 V (pico em ~0,40 V) e oxidação de ouro ocorre a partir de potenciais mais positivos que ~+0,25 V (pico em +0,57 V). Estes processos foram dependentes da concentração de íons ouro na PC. Verificouse também, que a redução do Au3+ provavelmente ocorre em todo o volume da PCM, porém não homogeneamente. Quanto a extensão da eletrodeposição, observou-se que o para os EPCMs oleosos e aquosos o processo de redução ocorre preferencialmente na interface PCM/solução aquosa de NaCl e diminuiu em direção ao interior da PC. Ademais foi observado que o processo de eletrodeposição de ouro no EPCM comporta-se como um sistema quase-reversível, indicando com isso que o sistema tem uma forte dependência do transporte de massa (migração e difusão) e transferência de elétrons. Ademais, observou-se que as correntes de pico catódico para os EPCMs aquoso foram maiores do que os EPCMs oleoso, indicando que a cinética de redução em meio aquoso é maior possivelmente devido a maior velocidade no transporte de massa no meio aquoso. Estudo por planejamento fatorial realizado com EPCM oleoso e aquoso indicou que os fatores (concentração de HAuCl4 na PC, carga de deposição e presença de aditivo) afetaram a performance dos EPCMs em solução de ferrocianeto. Micrografias obtidas por microscopia eletrônica de varredura (MEV) para o EPCM oleoso e aquoso indicaram que a eletrodeposição de ouro ocorreu sobre algumas placas de grafite com uma camada homogênea de ouro. As imagens de MET do pó de grafite com ouro eletrodepositado para o EPCM oleoso mostraram partículas de ouro com dimensões de 52,1 nm a 281,5 nm, distribuídas sobre as placas de grafite. Análise por difração de raios X, indicou que houve eletrodeposição de ouro policristalino no pó de grafite. A oxidação de dopamina foi dependente dos parâmetros de eletrodeposição e da composição da solução de DA. A curva analítica para a oxidação DA em NaCl/Na2S2O5 não apresentou linearidade adequada, sendo influenciada pela razão DA/ Na2S2O5 e acidez da solução.
Cuynet, Stéphane. "Etude des conditions d’élaboration d’électrodes de pile à combustible PEMFC par procédés plasma." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2027/document.
Full textFrom a collaboration between the CNRS laboratory of the CEA and GREMI Ripault, the objective of this thesis is to conduct a complete study on the conditions for producing electrodes of PEM fuel cell by plasma processes in order to improve the electro-catalytic activity of the catalyst (Pt). The platinum atoms on its support appears to be a one of the most important factor determining the performance delivered by the PEMFCs. From this observation, several lines of research have been proposed and each of them has yielded new results. The High Power Impulse Magnetron Sputtering (HiPIMS) process is studied in case of depositions of noble materials (Pt, Au, Pd) and alloy (Pt5Pd95 and Pt50Pd50) and revealed an ionized metal vapor consequent upon deposition (10 % to 90 % depending of the element). The results obtained on the HIPIMS process have allowed a change in the distribution of a small fixed amount of Pt (20 μg.cm−2) deposited on the depth of the gas diffusion layer (GDL), incidentally improving the performance of PEMFCs (+80% at 0.65 V, the voltage at rated power). This result is complemented by those obtained on the development of allied catalysts, especially with the arrangement of the catalytic material on the aggregates structure (+93 % at 0.65 V for Pt5Pd95 in successive deposits). In order to modify the Pt atoms distribution on the membrane support, another study has been realized. The surface of the proton exchange membrane has been structurated before the Pt deposition. Such structuration have shown an increase of the overall performance of PEMFCs in the case of CCB (Catalyst Coated Backing) and CCM (Catalyst Coated Membrane) architecture with an improvement factor of 1.3 up to 12, respectively
Paixão, Thiago Regis Longo Cesar da. "Utilização de eletrodos de Cu e Au em eletroanalítica: detecção amperométrica de etanol em ar exalado e outras aplicações." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-14062007-160003/.
Full textA copper disc working electrode in alkaline solutions was demonstrated to act as a suitable amperometric sensor for ethanol determination at +0.6 V vs Ag/AgCl. The participation of free-soluble Cu(III) species in the electrocatalytic process involving the anodic oxidation of ethanol has been demonstrated by rotating ring-disc electrode voltammetry. The influence of the pretreatment potential on the anodic signal was investigated and a correlation with the morphology of the electrode surface characterized by Energy Dispersive X-Ray Spectroscopy (EDS) indicated that the Cu(III) species is originated from the oxidation of a CuO layer. Ethanol measurements were performed in the amperometric mode at 0.6 V (vs Ag/AgCl). The repeatability of the measurements for a 0.05 % aqueous ethanol solution was estimated as 3 %, and the detection and quantification limits were determined as 0.005 % and 0.01 %, respectively. At the optimum experimental conditions, the amperometric sensor was used to monitor the concentration of ethanol in breath (BrAC), which was conveniently collected in a rubber air balloon (volume = 3 L) and introduced in a 1 mol L-1 NaOH working solution (volume = 10 mL). The sensor can measure a person\'s breath ethanol over the concentration range 0.26 - 130 mg L-1 by operating it according to an established protocol, of which the analytical parameters are specified by the Brazilian Legislation for BrAC measurements in drivers. The rate of ethanol degradation in the body was followed, and the results agree with predictions in the literature. Methodologies for the determination of dipyrone, glucose and ascorbic acid were also developed by using Cu and Au electrodes. Features of a dual-band electrochemical cell were investigated towards the development of a generator-collector system, which was employed in titrations with electrogenerated iodine.
Leopold, Michael Christofi. "Interfacial Investigations of a Biological Electron Transfer Model: Cytochrome c Adsorbed on Gold Electrodes Modified with Self-Assembled Monolayers." NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000713-192513.
Full textInterfacial investigations of a protein monolayer electrochemical system, cytochrome c (cyt c) adsorbed to a carboxylic acid (COOH) terminated self-assembled monolayer (SAM) were undertaken. Previous research suggested that anomalous peak broadening observed in the voltammetry of cyt c may be the manifestation of surface effects at the SAM/solution interface (heterogeneous adsorption sites). To examine this matter further, research was directed at 1) deciphering the role of the gold substrate's topography in both SAM formation and cyt c voltammetry; 2) understanding the protein binding interactions at the SAM/solution interface that influence cyt c adsorption and electrochemical response, and 3) investigating the microscopic properties of all the surfaces involved. Electrochemical and scanning probe microscopy techniques were used to explore the influence of gold topography in cyt c / COOH SAM / Au systems. COOH SAMs (11-mercaptoundecanoic acid and 14-mercaptotetradecanoic acid) were prepared and characterized on a variety of gold surfaces including evaporated, bulk, single crystal, and expitaxially grown on mica gold substrates. Each type of gold surface exhibited specific topographical features and characteristic roughness. SAMs were found to have a decreasing number of defects as the topography of the gold became smoother, as evidenced by an increased ability to block solution probe molecules. As the SAMs become less defective on the smoother gold, the extent of adsorption and the magnitude of the electrochemical response of adsorbed cyt c decreased significantly. These results show cyt c adsorption and electrochemistry to be intimately related to the density of defects in the SAM, which, in turn, are heavily influenced by the gold topography. Additionally, as the gold roughness decreased, the double layer capacitance of the films was observed to increase. A physical model was proposed in which the structure and properties of COOH SAMs are dictated by significant endgroup interactions in addition to chain-chain interactions. The model illustrates how gold topography plays an intricate role in determining the structure and application of COOH terminated SAMs. Research was also performed on the SAM/solution interface by thermally healing SAMs on gold and utilizing SAMs on Ag-UPD modified gold. Thermal healing, by reducing the number of defects in the SAMs, was also found to affect both SAM structural properties and cyt c adsorption. SAMs that had been thermally healed exhibited a lower density of defects while, at the same time, supported lower electroactive cyt c coverage. Ag UPD layers were tested as a means of creating more stable, less defective COOH SAMs for cyt c immobilization and possibly allowing for more ideal voltammetry of the proteins. Preliminary research has shown that SAMs with Ag-UPD layers have fewer defects and greater inherent stability. Finally, scanning probe microscopy techniques were employed to investigate the structure of the gold substrate, the SAM/solution interface, and adsorbed cyt c. In addition to cyt c / SAM / Au research, results from the following investigations are presented: electrochemistry of adsorbed cyt c at indium tin oxide electrodes and the electron transfer (ET) properties of iron-sulfur metallodendrimers. The metallodendrimers exhibited attenuated ET properties with increasing generations of dendritic ligands in a solventless, polymeric media. The electrochemistry of Cu(II) in physiological pathways that may be related to neurological and ocular diseases was also explored. Research on these systems revealed that the reduction of Cu(II) by certain peptides and catabolites may play a vital role in the development of these diseases.
Oliveira, TÃlio Ãtalo da Silva. "Desenvolvimento de sensores eletroquÃmicos para detecÃÃo de molinato e Ãxido nÃtrico." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10071.
Full textO presente trabalho ilustra o desenvolvimento de uma rota sintÃtica para a obtenÃÃo de uma meso-metaloporfirina, a partir de uma meso-porfirina base livre, macromolÃcula derivada do LÃquido da Casca da Castanha de Caju (LCC), subproduto do agronegÃcio do caju. A obtenÃÃo dessas espÃcies seguida de estudos preliminares da modificaÃÃo da superfÃcie do eletrodo de ouro com a meso-metaloporfirina de cobre com aplicaÃÃo para sensor de NO (Ãxido NÃtrico) tambÃm compÃe os objetivos desse trabalho. A partir do processo de metalaÃÃo,foi sintetizada uma meso-metaloporfirina utilizando Cu (II) como centro metÃlico, a partir da macromolÃcula base livre, e testes voltamÃtricos foram realizados utilizando o eletrodo de ouro, em meio de diclorometano e PTBA 0,1 mol L-1, obtido a 100 mV s-1.Estudos foram realizados a cerca do comportamento eletroquÃmico dos filmes formados em presenÃa de NO em meio aquoso de Na2SO4 0,5 mol L-1 obtendo o voltamograma cÃclico para o eletrodo de ouro modificado com a porfirina de cobre(II) na detecÃÃo de NO e foi observado no voltamograma para NO sobre uma intensidade de corrente 7,6 vezes maior comparada à do pico observado para o mesmo processo do NO na superfÃcie de ouro nÃo modificado demonstrando elevado potencial para aplicaÃÃo como sensor eletroquÃmico. Outra metodologia eletroanalÃtica foi desenvolvida para a obtenÃÃo de um biossensor, baseado em uma enzima, glutationa-S-transferase (GST), para determinaÃÃo do pesticida molinato, um herbicida prÃ-emergente, em amostras reais de Ãgua de campos de arrozais da cidade do Porto, em Portugal. A construÃÃo deste biossensor baseou-se a imobilizaÃÃo de GST em um eletrodo de carbono vÃtreo (GCE), atravÃs da ligaÃÃo covalente glutaraldeÃdo-amino-silano (APTES/GA). O princÃpio deste biossensor consistiu no processo de inibiÃÃo da GST promovida pelo molinato. A curva de calibraÃÃo foi obtida por meio da tÃcnica de voltametria de pulso diferencial (VPD) variando a concentraÃÃo do pesticida entre 1,01x10-6 â 4,20x10-5 mol L-1 apresentando um limite de detecÃÃo (LD) de 0,064 mg L-1. O biossensor baseado na GST foi aplicado para quantificar o molinato nas amostras de Ãgua das lavouras de arrozais. Os resultados obtidos com este biossensor foram comparados com aqueles obtidos por HPLC e nÃo houve diferenÃas estatisticamente significativas comprovando, entÃo, que a metodologia desenvolvida foi precisa no nÃvel de concentraÃÃo estudada.
This study illustrates the development of synthetic route will be obtaining meso-metalloporphyrin, from porphyrin meso-free base macromolecule derived from Shell Liquid Cashew Nut (CNSL), byproduct of cashew agribusiness. Obtaining these species followed by preliminary studies of surface modification of gold electrode with copper meso-metalloporphyrin with application to sensor of NO (Nitric Oxide) also composed the objectives of this work. From metalation process, was synthesized by meso-metalloporphyrin using Cu (II) the a metal to center, from the macromolecule free base, and voltametric tests were carried out using the gold electrode in the middle of dichloromethane and TBAP 0,1 mol L-1, obtained at 100 mV s-1. Studies have been conducted about the electrochemical behavior of the films formed in the presence of NO in aqueous Na2SO4 0,5 mol L-1 the cyclic voltammogram obtained will be the gold electrode modified with porphyrin to copper (II) the detection of NO and voltammogram was observed in about one NO to current intensity 7,6 times larger compared to the peak observed for the same process of NO in unmodified gold surface showing high potential for application as an electrochemical sensor. Electroanalytical another methodology was developed will be obtaining the biosensor, based on an enzyme, glutathione-S-transferase (GST), will be determining the pesticide molinate, the real daily pre-emergent herbicide in samples of to water of paddy fields City Porto, in Portugal. The construction of this biosensor was based on the immobilization of GST in glassy carbon electrode (GCE) by covalent glutaraldehyde-amino-silane (APTES/GA). The principle of this biosensor consisted of the process promoted by inhibition of GST molinate. The calibration curve was obtained by the technique of differential pulse voltammetry (DPV) varying the concentration of the pesticide between 1,01 x10-6 to 4,20 x10-5 mol L-1 having a limit of detection (DL) of 0,064 mg L-1. The biosensor based on GST was applied to quantify the molinate in water samples of paddy crop. The results obtained with this biosensor were compared with those obtained by HPLC and no statistically significant differences proving therefore that the developed methodology has been studied in terms of concentration.
Mashazi, Philani Nkosinathi. "Study of metallophthalocyanines attached onto pre-modified gold surfaces." Thesis, Rhodes University, 2007. http://eprints.ru.ac.za/868/.
Full textChen, Chen-Yin, and 陳貞吟. "Anti-fouling Nano-porous Gold Electrode Sensors." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/et5cam.
Full text國立交通大學
材料科學與工程學系奈米科技碩博士班
108
When developed country has become more industrialization and its citizens’ life expectancy is increasing, civil diseases like diabetes also have emerged and the related biomedical materials have gradually gained the attention of the world. The biomedical materials studied in this research can be divided into two parts. The first part is Comparison and study of increasing the surface area of gold electrode by etching and electrochemical methods.The other is the study of Nanoporous gold surface modified by anti-fouling material for Blood glucose sensing application. The first part is to use etching and electrochemical methods to increase the surface area of the materical. The etching uses iodine to make its Roughness increase via chemical action.When using electrochemical methods, the most important thing is to use chloride ions at a certain voltage. It will carry out the process of electrolysis, electrodissolution, disproportion and deposition of Au In this research, we focus on the interaction between KCl concentration and pH value, the standardized area of gold electrode and the optimized potential of anodizing in order to find the best condition for preparing nanoporous gold and analyze its surface structure. The second part study uses nanoporous gold as electrode made in the previous study in order to test which oxidation current for glucose is largr and find applied voltage at maximized current signal in a mixed of glucose with interferent solution. Then we synthesizes PFB-CK and PFB-CK salt; the latter has zwitterion properties. And then; we combine PFB-CK and PFB-CK salt with nanoporous gold made in the first part in sulfur-gold bond by using self-assembly respectively. Next, we measure the related current signal experiments of the electrode in the glucose solution, such as detection limit and linear range and then undergo the anti-cell fouling test, bradford protein assay and MTT assay. It has been confirmed by experiments that the modified electrode has anti-cell and protein fouling and high biocompatibility, and its long-term stability is better than the electrode made of bare nanoporous gold.
Lin, I.-Hsiu, and 林怡秀. "Studied on the Analytical Applications of Porous Gold Electrode." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/76719482940990660643.
Full text國立成功大學
化學系專班
94
There are three parts in this study : the first part is using nanoporous-Au electrodes and Osteryoung square wave voltammetry to determinate L-cysteine and glutathione in aqueous solution, individually. In the case of L-cysteine, if preconcentration time is 10 mins,the linear dynamic range is 15-160 μM, and the detection limit is 0.1 μM(3s). For the determination of glutathione, with a preconcentration time is 5 mins, and the linear dynamic range is 0.5-25 μM, and the detection limit of < 0.5μM. The second part of this study, use the GSH/nenoporous-Au electrode to determinate the copper ion in aqueous solution. If preconcentration time is 5 mins, the linear dynamic range is 0.79-315 nM, and the detection limit is < 0.79 nM. In the third part, a nanoporous-Au electrode and electrochemical catalytic reaction were employed for the determination of Se(IV) in aqueous solution. Good sensitivity was achieved through the catalytic process between selenium and bromate. Follow potentiostat, linear calibration graph was obtained over the range 20-2000 ppb of Se(IV), with a detection limit (3 x blank signal) of 2.4 ppb.
Hsin-Chun, Ko, and 柯昕君. "Surfactant-Directed Synthesis of Gold Nanostructure on Carbon Electrode." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/22224332353159941955.
Full text國立交通大學
應用化學系所
95
In this study, novel nanostructures of metal gold were discovered, including sheet, flower, wire and coralloid shapes. We demonstrated the synthesis of gold nanostructures via Galvanic displacement reaction. We found that cetyltrimethylammonium chloride (CTAC) played an important role to affect the morphology of the products. Au nanosheets, nanoflowers and nanowires were derived by using Cu metal as the reductant in the presence of CTAC on carbon electrodes. The diameters of single crystal Au nanowires, reducted from HAuCl4 by Cu metal, were 15-25 nm, and the lengths were 300-500 nm. Each nanowire exhibited single crystallinity with the growth in [110] orientation. In addition, Au nanowires, diameters 50-100 nm and lengths up to several tens μm, were prepared by reacting HAuCl4(aq) with Sn metal and CTAC on a carbon electrode. Furthermore, surface-enhance Ramen scattering (SERS) spectra of P-NTP (p-nitrothiophenol) on the as-prepared carbon electrode with gold nanowires was measured. We also used electrochemical synthesis method to produce gold nanocoralloid.
Huang, Shi Jie, and 黃士杰. "Anodic Behaviors of Gold Electrode in Direct Borohydride Fuel Cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/46171038312912785345.
Full text長庚大學
化工與材料工程學系
98
The anodic behaviors of gold electrode as anode catalyst using in direct borohydride fuel cells were investigated to collect the parameters for single cell measurements. To avoid the hydrolysis reaction of sodium borohydride in producing hydrogen and to promote the direct electrochemistry reaction of borohydride to 8 electrons transfer are the key issues of DBFC. The by-product (hydrogen) of sodium borohydride can be measured in the half-cell measurements and single cell measurements were controlled by using the parameters taken in half-cell measurements. Carbon supported gold electrocatalysts were used in DBFC single cell measurements and the half-cell measurements indicate the gold electrode area promote anode electrochemical reactions. The rotating disk electrodes measurements may provide the flow rates parameters for DBFC single cell operations and the anode flow rate of 80ml/min was taken.
Tsai, Cheng Ta, and 蔡承達. "Glucose biosensor with gold electrode produced by electroless plating method." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/94879172909137068941.
Full text國立中央大學
化學工程與材料工程學系
104
With the rapid development of technology, biosensors have been used extensively in medical detecting. Glucose biosensors, which have become the convenient and mature product, have great economic value because of huge consume in the world. In this study, in order to prepare lower cost gold electrode glucose biosensors, the screen printed substrate which contained palladium catalyst was prepared. The effects of contents of palladium on the performance of biosensor was investigated. A reactor for electroless plating was designed. Nickel, palladium and gold were deposited on the substrate in order to increase the conductivity of electron passed through the sample. The operating parameters such as temperature, time, hardness and thickness were changed to study their effects on the stability of product. The samples were then doped by the enzyme to check the performance of glucose biosensors. The samples were characterized by focused ion beam (FIB), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results illustrated that the better operating conditions of electroless reactors for nickel, palladium and gold was at the region of temperature and dipping time.
Chang, Jing-shun, and 張景順. "Application of porous gold enzyme electrode in electrochemical Flow injection analysis." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/48835495278193093271.
Full textFish and 洪筱瑜. "Immobilization of Oligonucleotide Probes to Gold Electrode of Voltammetric Electrochemical Sensor." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/22068578109356503929.
Full textLu, Chih-Lun, and 呂志倫. "Glucose sensor based on chitosan assistant gold nanoparticles modified ITO electrode." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/27318228093081479416.
Full text國立交通大學
應用化學系所
97
It has been paid much attention to develop nonenzymatic glucose electrochemical sensor by inorganic metal、metal oxid or alloy nanometerial, which would eliminate the instability problem of enzymatic glucose sensor. In this study, A disposable gold nanoparticles (AuNPs) modified ITO electrode, which the effect area was fixed by photolithography and etching technique, has been developed only with single step electrodeposition for glucose sensing. The AuNPs film on the electrode was formed by dipping the ITO electrode into the mixed solution containing 400 mg/L HAuCl4 and 0.01% chitosan and giving a reduction potential at -0.8 V (vs. Ag/AgCl) for 60 minute. The layer of the stacked AuNPs on the ITO surface was very stable and the nanostructure of this AuNPs modified sensor was performed by field-emission scanning electron microscope (SEM). After eliminating common interferences by Nafion�� covering, the analytical performance of the electrode for glucose detection was investigated. The sensitivity and the detection limit of the electrode were 107.7 µA/mMcm2 and 1.46 µM respectively in amperometric glucose sensing in 0.1 M NaOH solution. Linear range was from 5 µM to 2.3 mM (R2 = 0.9991). Since the ITO glass was obtained by low cost industrial production with stable quality, this substrate can be used as disposable material of sensor fabrication.
Wei, Fan-Ya, and 魏凡雅. "Synthesis of 1D gold nanowire electrode for the Study of Biological Sensors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/uz7fb8.
Full text中原大學
奈米科技碩士學位學程
98
Gold nanowires were successfully fabricated by electrochemical deposition using polycarbonate membranes (PC) as the growing templates. The Au nanowire electrodes were modified by three methods which enhanced the response of sensibility in different ways. The nanowire electrode was employed to be the support matrix for the immobilization of hemoglobin (Hb).. Therefore, the Hb-modified Au nanowire electrode could be used as a biosensor with high sensitivity for Hb. The 3D electrode has a larger surface area than that of flat electrode and the sensitivity of electrode for hemoglobin (Hb) was enhanced. The electrode of gold nanowires modified by glucose oxidase (GOD) is suitable for application as a glucose sensor. The cyclic voltammorgrams (CV) demonstrated that the response current of glucose was enhanced by using GOD-modified Au nanowires working electrode. Enhanced cyclic voltammorgrams were also obtained using Fe3O4 nanoparticals modified gold nanowires as the working electrode. It is thought that the electron transfer between Fe2 + and Fe3 + ions helped the activity of ferricyanide.
WANG, YI-CHEN, and 王怡珍. "The Electrochemical Characteristics of Alkyl Thiol Self-Assembly Monolayers on Gold Electrode." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/06551144520601042869.
Full text國立臺灣大學
化學工程學研究所
91
In the thesis, alkyl thiols are used to form oriented self-assembly monolayers. Oriented monolayers offer the possibility of precise control of spacing and orientation on a molecular level. It was reported that self-assembly monolayers formed from alkyl thiols are remarkably stable in aqueous solution. This research is mainly carried out by electrochemical analysis techniques, trying to find out the effect of electron transfer by tunneling across the monolayers. The rotating disk system was applied to study the electrochemical reaction mechanisms. Furthermore, the distribution morphology of alkyl thiols on gold was observed by atomic force microscopy (AFM). The cleansing condition of gold surface affects electrochemical reactions seriously. It is essential to clean electrodes completely before electrochemical experimental analysis. Three different alkyl thiols R-SH(R=CnH2n+1,n=4、8、12)were used in this study. And because alkyl thiol can’t take redox reactions, redox species are added into the electrolyte. Then the effect of different chain length to redox reactions can be discussed. One of the redox species in the study is ferricyanide-ferrocyanide couple that is often used in the previous studies; another redox specie cobalt bipyridine Co(bpy)33+is synthesized in this study. As the alkyl chain length of thiols on gold electrode increases, the conductivity of gold electrode will decrease, the redox reaxtion will derivate from reversible reaction more and more obviously. The inhibition of thiol modified gold electrode to the diffusivities of Fe(CN)63-/4- and Co(bpy)33+/2+ couples are also discussed in the thesis. For 1-octanethiol modified gold electrode, the diffusivity of Fe(CN)63- decreases from 7.25×10-6 cm2/s to 5.70×10-6 cm2/s, and the diffusivity of Co(bpy)33+ decreases from 1.52×10-6 cm2/s to 7.56×10-7 cm2/s. As the alkyl chain length of thiols on gold electrode increases, the reaction rate constants decrease at the same time. Especially for the dodecanethiol modified gold electrode, the thickness of self-assembly monolayer is larger, and molecule will arrange much closer. As a result, the redox couples are almost kept out of the gold surface. For dodecanethiol modified gold electrode, the rate constant of 1mM Fe(CN)63- decreases from1.39×10-1 s-1 to 7.40×10-4 s-1, and the rate constant of 1mM Co(bpy)33+ decreases from 2.49×10-2 s-1 to 2.15×10-3 s-1.It was found that the current and the reaction rate of thiol modified gold electrode in Co(bpy)33+ solution are both decrease linearly with alkyl chain length. Therefore, it is more correct to determine the alkyl chain length from voltammograms. However, it is much more convenient to observe the current and reaction rate differences between thiol modified gold electrode and gold electrode in Fe(CN)63-/4- solution.