A novel electrode was constructed and tested in a bio-battery. This configuration consisted of a composite electrode with immobilized bacteria (Escherichia coli K-12) in the anode and a composite electrode with immobilized Carbon Nanoparticles (CNP) and algae (Chlorella vulgaris/Scenedesmus sp.) suspended in the cathode. The composite electrode consisted of three parts: a 304L stainless steel mesh base, an electro-polymerized layer of pyrrole, and an electro-polymerized layer of methylene blue. The bacteria were immobilized on the anode electrode using a technique incorporating CNP and a Teflontm emulsion. The anode and cathode electrodes were tested separately in conjunction with chemical cathodes and anodes respectively. The composite electrode with immobilized bacteria was tested in a bioanode setup. The cathode chamber of the cell contained a potassium ferricyanide and buffer solution with a graphite electrode. Factors affecting electrode performance, such as Teflontm and carbon nanoparticle concentration, were investigated to find optimum values. The maximum power density generated by the composite electrode with immobilized bacteria and a chemical cathode was 378 mW/m2. This electrode configuration produced approximately 69% more power density and 53% more current density than composite electrodes with bacteria suspended in solution. Electrochemical Impedance Spectroscopy analysis determined that a significant portion of the bio-battery’s resistance to charge transfer occurred at the surface of the anode and this resistance was significantly lowered when using immobilized bacteria (51% lower than bio-batteries with suspended bacteria). Similarly, biocathodes containing composite electrodes coated with CNP were tested using two algae species, Chlorella vulgaris and Scenedesmus sp., suspended in solution. This electrode configuration was compared with composite electrode without CNP coating. The anode chamber contained potassium ferrocyanide solution with a graphite counter electrode. The composite electrode with CNP produced approximately 23% more current density than composite electrode without CNP. A complete bio-battery was designed using a composite electrode with immobilized bacteria anode and a CNP coated composite electrode with algae suspended in the cathode. EIS analysis showed that the resistance was higher in the biocathode than in the bioanode and a significant portion of the ohmic resistance was contributed by the membrane.

Nanoelectrodes are defined as electrodes which have a critical dimension on the order of nanometres. Due to their smaller dimensions they have a reduced iR drop and enhanced mass transport, which results in the rapid establishment of an enhanced steady-state diffusion profile and a greater Faradaic current density, along with a smaller relative double layer capacitance, which together give a significantly increased signal to noise ratio compared to macroelectrodes. This potentially makes nanoelectrodes better sensors and analytical tools than macroelectrodes in terms of their having lower limits of detection and faster detection times. However, due to difficulties with fabrication most nanoelectrode designs are highly irreproducible which has inhibited their characterisation and commercial development. The Mount group has previously reported the design, fabrication and characterisation of a novel nanoelectrode design in conjunction with Engineers from the Scottish Microelectronic Centre (SMC). Microsquare Nanoband Edge Electrode arrays (MNEEs) consist of an array of cavities with nanoscale Pt bands (formed by sandwiching the metal between insulating layers) exposed around their perimeter. MNEEs are fabricated using a photolithographic process so can be reproducibly made in large quantities to high fidelity. The purpose of this work is to develop our understanding of the fundamental electrochemical behaviour of MNEEs for biosensing. First, a quantitative analysis of the cyclic voltammograms (CVs) and Electrochemical Impedance Spectroscopy (EIS) of macroelectrodes, microelectrodes and MNEE are compared and discussed. Second, their fundamental response is compared in terms of their biosensing properties by using a pre-established impedimetric biosensing protocol developed on macroelectrodes. This protocol uses a PNA probe to detect the mecA cassette of methicillin resistant staphylococcus aureus (MRSA). The procedure has been optimised and compared for macroelectrodes, microelectrodes and MNEE so as to compare their performances as biosensors. It was observed that MNEE’s: (a) form thiol films faster than electrodes with larger dimensions, determined by kinetic studies of 6-mercaptohexan-1-ol film formation (b) form films with different packing structures dependant on the electrode bulk to edge ratio (c) can detect the same concentration of target in less time than larger electrodes because of their increased sensitivity. The film packing has also been quantitatively investigated using EIS and it can be seen that films formed n MNEE were better able to incorporate target DNA into their more splayed out structure. Unique to this project has been the establishment of a protocol to form heterogeneous carbazole-alanine hydrogel matrices on nanoelectrodes, whose polymerisation is initiated by a pH swing at the electrode surface induced by the oxidation of hydroquinone. The gels growth pattern follows the diffusion field at the electrode and can be monitored using EIS. This also gives a measure of the permeability of the gel by fitting to the correct equivalent circuit. The gel structure has been imaged using light microscopy, confocal microscopy and scanning electrochemical microscopy (SEM). The results give a visual demonstration that MNEE has enhanced diffusion at the corners of the cavities, which is in agreement with previously published simulations, and give evidence as to the onset of hemispherical diffusion and the conditions at which the diffusion field between neighbouring electrodes begin to overlap, a phenomenon which can be observed visually and correlated to changes in the EIS data. Hydrogels have been grown chronopotentiometrically at different currents and the permittivity (through the diffusion coefficients) has been measured of redox couples through gels grown at different speeds. It was found that the hierarchical structure of the hydrogels can be tuned; potentially opening the door to a new breed of tuneable, biocompatible anti-biofouling matrices on bio-functionalised electrodes. The system was characterised using the same MRSA detection protocol as optimised for the MNEE and the target DNA was found to be able to permeate through the hydrogels and bind to the probe, which resulted in a significant change in impedance.

Magister Scientiae - MSc / The focus of this study is to synthesize a novel hinged polymer actuator. The linking molecule (hinge) is phenazine with interconnected dipyrrole units. / South Africa

CAMPOS, Othon Souto. Estudo Mecanístico da Eletrodeposição de Cádmio em Meio de Sulfato Ácido. 2011. 46 f. Dissertação (Mestrado em química)- Universidade Federal do Ceará, Fortaleza-CE, 2011. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-02T19:41:14Z No. of bitstreams: 1 2011_dis_oscampos.pdf: 938891 bytes, checksum: 170c80aaa846defc16b0b360c53792fb (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-07-20T20:01:55Z (GMT) No. of bitstreams: 1 2011_dis_oscampos.pdf: 938891 bytes, checksum: 170c80aaa846defc16b0b360c53792fb (MD5) / Made available in DSpace on 2016-07-20T20:01:55Z (GMT). No. of bitstreams: 1 2011_dis_oscampos.pdf: 938891 bytes, checksum: 170c80aaa846defc16b0b360c53792fb (MD5) Previous issue date: 2011 / This work describes a mechanistical proposition for cadmium electrodeposition in acid sulfate medium on platinum substrate using electrochemical techniques. The cadmium electrodeposition studies were carried in sodium sulfate 1 mol L–1 medium containing cadmium sulfate 10–2 mol L–1, which the pH of the solutions were adjusted with analytical grade sulfuric acid. The pH interval of the work solutions were ranged between 1 and 3. In all studied medium, the potentiostatic polarization curves showed a diffusional plateau which obeys the Levich equation. The interfacial pH studies showed the influence of acid–base equilibrium of bisulfate ion with the formation of a coordination compound Cd(HSO4)+ in platinum electrode. It is proposed that the cadmium ion associated in acid–base equilibrium of bisulfate ion, deposits as cadmium bisulfate at an irreversible step, and followed by a reversible metallic deposition of cadmium with the leaving of bisulfate ion, and this step is slower than the first one. Then, a mathematical model was calculated for the mechanism proposed, and qualitative studies were carried regarding to the polarization curve and electrochemical impedance spectroscopy behavior. / Este trabalho descreve uma proposição mecanística para a deposição de cádmio em meio de sulfato ácido sobre substrato de platina utilizando técnicas eletroquímicas. Os estudos de eletrodeposição de cádmio foram feitas em meio de sulfato de sódio 1 mol L–1 contendo 10–2 mol L–1 de sulfato de cádmio, em que o pH das soluções foi ajustado com ácido sulfúrico PA. O intervalo de pH das soluções de trabalho foi variado entre 1 e 3. Em todos os meios estudados, as curvas de polarização potenciostática mostraram a formação de um patamar difusional que obedece a equação de Levich. Os estudos de pH local revelaram a influência do equilíbrio ácido–base do íon bissulfato com formação de compostos de coordenação Cd(HSO4)+ no eletrodo de platina. Propõe-se que o íon cádmio, associado ao equilíbrio ácido–base do íon bissulfato, deposita como bissulfato de cádmio numa etapa irreversível, e seguida pela deposição de cádmio metálico reversível com a saída do íon bissulfato, sendo esta última etapa mais lenta que a primeira. Desse modo, foi calculado um modelo matemático para o mecanismo proposto, sendo realizados estudos qualitativos em relação ao comportamento da curva de polarização e do espectro de impedância eletroquímica.

abstract: Commercial Li-ion cells (18650: Li4Ti5O12 anodes and LiCoO2 cathodes) were subjected to simulated Electric Vehicle (EV) conditions using various driving patterns such as aggressive driving, highway driving, air conditioning load, and normal city driving. The particular drive schedules originated from the Environment Protection Agency (EPA), including the SC-03, UDDS, HWFET, US-06 drive schedules, respectively. These drive schedules have been combined into a custom drive cycle, named the AZ-01 drive schedule, designed to simulate a typical commute in the state of Arizona. The battery cell cycling is conducted at various temperature settings (0, 25, 40, and 50 °C). At 50 °C, under the AZ-01 drive schedule, a severe inflammation was observed in the cells that led to cell failure. Capacity fading under AZ-01 drive schedule at 0 °C per 100 cycles is found to be 2%. At 40 °C, 3% capacity fading is observed per 100 cycles under the AZ-01 drive schedule. Modeling and prediction of discharge rate capability of batteries is done using Electrochemical Impedance Spectroscopy (EIS). High-frequency resistance values (HFR) increased with cycling under the AZ-01 drive schedule at 40 °C and 0 °C. The research goal for this thesis is to provide performance analysis and life cycle data for Li4Ti5O12 (Lithium Titanite) battery cells in simulated Arizona conditions. Future work involves an evaluation of second-life opportunities for cells that have met end-of-life criteria in EV applications. / Dissertation/Thesis / Masters Thesis Engineering 2018

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-09-01T18:02:01Z No. of bitstreams: 0 / Made available in DSpace on 2015-09-01T18:02:01Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

abstract: Monitoring complex diseases and their comorbidities requires accurate and convenient measurements of multiple biomarkers. However, many state-of-the-art bioassays not only require complicated and time-consuming procedures, but also measure only one biomarker at a time. This noncomprehensive single-biomarker monitoring, as well as the cost and complexity of these bioassays advocate for a simple, rapid multi-marker sensing platform suitable for point-of-care or self-monitoring settings. To address this need, diabetes mellitus was selected as the example complex disease, with dry eye disease and cardiovascular disease as the example comorbidities. Seven vital biomarkers from these diseases were selected to investigate the platform technology: lactoferrin (Lfn), immunoglobulin E (IgE), insulin, glucose, lactate, low density lipoprotein (LDL), and high density lipoprotein (HDL). Using electrochemical techniques such as amperometry and electrochemical impedance spectroscopy (EIS), various single- and dual-marker sensing prototypes were studied. First, by focusing on the imaginary impedance of EIS, an analytical algorithm for the determination of optimal frequency and signal deconvolution was first developed. This algorithm helped overcome the challenge of signal overlapping in EIS multi-marker sensors, while providing a means to study the optimal frequency of a biomarker. The algorithm was then applied to develop various single- and dual-marker prototypes by exploring different kinds of molecular recognition elements (MRE) while studying the optimal frequencies of various biomarkers with respect to their biological properties. Throughout the exploration, 5 single-marker biosensors (glucose, lactate, insulin, IgE, and Lfn) and one dual-marker (LDL and HDL) biosensor were successfully developed. With the aid of nanoparticles and the engineering design of experiments, the zeta potential, conductivity, and molecular weight of a biomarker were found to be three example factors that contribute to a biomarker’s optimal frequency. The study platforms used in the study did not achieve dual-enzymatic marker biosensors (glucose and lactate) due to signal contamination from localized accumulation of reduced electron mediators on self-assembled monolayer. However, amperometric biosensors for glucose and lactate with disposable test strips and integrated samplers were successfully developed as a back-up solution to the multi-marker sensing platform. This work has resulted in twelve publications, five patents, and one submitted manuscripts at the time of submission. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2018

Orientador: Celia Marina de A. Freire / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-29T00:11:40Z (GMT). No. of bitstreams: 1 Beserra_AntonioAdelmoFreire_D.pdf: 6476925 bytes, checksum: 51577bdfab4d41fd0bb2c35bf250bfc2 (MD5) Previous issue date: 2001 / Resumo: O revestimento de Al55-Zn apresenta uma resistência à corrosão atmosférica em média doze vezes superior à do revestimento galvanizado. Entretanto, após deformação mecânica, o revestimento de Al55-Zn apresenta microtrincas que comprometem a sua resistência à corrosão. Neste trabalho estudou-se a variação na resistência à corrosão do revestimento de Al55-Zn após deformação sob tração ou dobramento e a influência de tratamentos térmicos a '200 GRAUS' e a '360 GRAUS' durante 16h na resistência à corrosão do revestimento antes e depois das deformações. Para isso, um grupo de amostras do material foi deformado sob tensão de tração até 10% ou 15% de seu comprimento inicial e outro grupo foi dobrado até '90 GRAUS' ou '180 GRAUS'. A variação na resistência à corrosão do revestimento foi analisada através das técnicas de extrapolação de Tafel e de espectroscopia de impedância eletroquímica. Como resultado, observou-se que tanto a deformação axial quanto o dobramento do material reduzem a sua resistência à corrosão. Após o tratamento térmico a '360 GRAUS' as amostras deformadas até 10% ou 15% recuperaram a sua resistência à corrosão, entretanto, as amostras dobradas até '90 GRAUS' ou '180 GRAUS' apresentaram apenas uma recuperação parcial na sua resistência à corrosão após os tratamentos térmicos / Abstract: The atmospheric corrosion resistance of 55%Al-Zn alloy coating on average is twelve times that of an equal thickness of galvanized coating. However, it has been shown that microcracks were observed at all levels of strain under simple uniaxial tension. Our research has been focused on determining the degree of corrosion experienced by these coatings after deformation under simple tension or bending and how much the heat treatment at '200 DEGREES' or '360 DEGREES' for 16h can influence the corrosion resistance of the coating. The coated sheet samples were strained to 10% or 15% engineering strain while another group of samples was bent to bend angles of '90 DEGREES' or '180 DEGREES'. The corrosion resistance of the samples was evaluated trhough Tafel extrapolation and electrochemical impedance spectroscopy methods. As a result, it was observed that both the straining and the bending of the coating reduces its corrosion resistance. After the heat treatment at '360 DEGREES' the samples strained to 10% or 15% recover their corrosion resistance, but the specimens bended to '90 DEGREES' or '180 DEGREES' recuperate only partially the corrosion resistance after the heat treatments / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Orientador: Celia Marina de Alvarenga Freire / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-28T23:57:37Z (GMT). No. of bitstreams: 1 Silva_JoseRochaAndradeda_M.pdf: 3642803 bytes, checksum: e91a23ef6d38a032df085e07b32843f1 (MD5) Previous issue date: 2000 / Resumo: Os acumuladores de energia estacionários devem ser periodicamente avaliados quanto à sua capacidade de carga, visando assegurar que sua energia acumulada poderá ser prontamente utilizada, quando das falhas do sistema de alimentação convencional. Normalmente, essas avaliações são realizadas através dos testes de capacidade, que apresentam como principais desvantagens, o fato do banco de baterias permanecer indisponível, durante a realização do teste, e o desperdício da energia acumulada nas baterias. Neste trabalho á avaliada a potencialidade do método de espectroscopia de impedância eletroquímica como ferramenta na determinação do estado-de-carga de baterias chumbo-ácidas, através da análise das relações dos seus parâmetros eletroquímicos e sua quantidade de carga armazenada / Abstract: Stationary lead-acid batteries must have their charge capacity periodically evaluated in order to assure that they are ready to supply energy during conventional supplier faults. Normally, these evaluations are conduct by capacity tests, which present these main disadvantages: batteries remain unavailable while tests are conducted and total energy accumulated in batteries is dissipate during the tests. In this work electrochemical impedance spectroscopy is evaluated as a tool to assess the lead., acid batteries¿ state-of-charge, by analysing the co-relations between battery electrochemical parameters and its stored energy / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-09-01T18:02:01Z No. of bitstreams: 0 / Made available in DSpace on 2015-09-01T18:02:01Z (GMT). No. of bitstreams: 0 / As indústrias que desenvolvem motores de combustão interna têm como preocupação atual prover motores que sejam cada vez menos poluentes, uma vez que a preocupação com a preservação do meio ambiente é intensa em todo o mundo. No entanto, com o desenvolvimento de novas tecnologias destinadas à redução das emissões, a condensação dos gases, provenientes da combustão, está sendo promovida dentro das câmaras de combustão dos veículos. Ácidos, como sulfúrico e nítrico, são gerados pela condensação destes gases. Esta condensação está associada às altas taxas de recirculação de gases de escape, conhecido como EGR, (termo em inglês para Exhaust Gas Recirculation). Consequentemente, problemas de corrosão nos componentes do motor estão aumentando, especialmente em camisas de cilindro em ferro fundido. Neste estudo, foi investigada a resistência à corrosão de dois ferros fundidos, um de microestrutura perlítica e o outro com microestrutura bainítica, em soluções de condensado natural e sintético de motores movidos a diesel. Os resultados foram associados às microestruturas e as composições químicas dos materiais estudados. Resultados de testes de imersão e ensaios de espectroscopia de impedância eletroquímica, bem como de curvas de polarização potenciodinâmicas, indicaram que os dois materiais não apresentam resistência à corrosão nos meios de ensaio adotados. O ataque intenso da matriz observado em ambos os materiais observado pelos ensaios de imersão, mostraram a atuação do mecanismo eletroquímico de corrosão por grafitização. Este mecanismo causa o ataque localizado e destrutivo da matriz de ferrita (-Fe), que funciona como anodo enquanto as grafitas atuam como áreas catódicas. Enquanto em meio ácido não foi possível observar uma diferenciação entre os dois tipos de ferros fundidos estudados, em meio neutro e aerado, o ferro fundido bainítico mostrou resistência à corrosão superior à do ferro fundido perlítico. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP