Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on June 3, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 157-169).

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 18, 2007) Vita. Includes bibliographical references.

Thesis (M.S.)--Baylor University, 2006. / Includes bibliographical references (p. 65-67).

Σε αυτήν την εργασία περιγράφεται αναλυτικά ένα κύκλωμα ανάγνωσης για ηλεκτροχημικό βιοαισθητήρα, καθώς και η κατάλληλη τροποποίησή του ώστε να μπορεί να χρησιμοποιηθεί σε σύστημα χωρητικού βιοαισθητήρα. Βασικός στόχος και στις δύο περιπτώσεις είναι η συμβατότητα των κυκλωμάτων με πλήρως ολοκληρωμένα βιοχημικά μικροσυστήματα, με έμφαση στη μικρή επιφάνεια ολοκλήρωσης και τη χαμηλή κατανάλωση. Κεντρικό στοιχείο των δύο υλοποιήσεων αποτελεί ο χωρητικός ενισχυτής διαντίστασης ο οποίος αναλαμβάνει το ρόλο της μετατροπής της χρήσιμης πληροφορίας, που είναι ένα ρεύμα, σε μία τάση. Αυτή η τάση στη συνέχεια μπορεί να δοθεί για ψηφιακή επεξεργασία, αφού περάσει από έναν ADC . Τα δύο κυκλώματα σχεδιάσθηκαν σε τεχνολογία CMOS της TSMC των 90nm και εμφάνισαν στις εξομοιώσεις ικανοποιητικά χαμηλό θόρυβο. Το κύκλωμα του ηλεκτροχημικού βιοαισθητήρα παρουσίασε καλή γραμμικότητα για ρεύματα από 10nA έως 10uA, ενώ το αντίστοιχο του χωρητικού βιοαισθητήρα είναι δυνατό να μετρήσει χωρητικότητες με μέγιστη απόκλιση 3%. / This paper presents a readout circuit for electrochemical biosensors and the appropriate modification of the circuit to make it compatible with capacitive biosensors. The main goal is to ensure compatibility of the circuits with fully integrated biochemical microsystems and therefore emphasis is placed on achieving small area and low consumption. The fundamental part of the circuits is a Capacitive Transimpedance Amplifier that is responsible for converting the current signal to a voltage. That voltage can then be passed forward to digital processing with the use of an ADC. Both circuits were designed using 90nm TSMC CMOS technology and showed low noise in simulations. The electrochemical biosensor readout circuit achieves good linearity in a range of 10nA to 10uA, while the capacitive biosensor readout circuit is capable of measuring capacitances with a 3% error.

This work describes the development of mediated amperometric biosensors that are able to monitor the metabolic activity of both single and mixed microbial populations, with applications in toxicity assessment and wastewater treatment plant protection. Biosensor systems have been constructed incorporating either the single-species eubacteria Escherichia coli or Pseudomonas putida, Bioseed®, or a mixture of activated sludge organisms from wastewater treatment plants, as the sensing components immobilised on disposable screen printed electrodes in stirred reaction vials. The biosensor approach is generic allowing for a wide range of microbial cell types to be employed. Appropriate bacterial species can be selected for specific sensor applications in order to confer validity and relevance to the test, hence the biosensor can be tailor-made to assess the toxicity in a particular environment and provide diagnostically valid and relevant results. The biosensors have been used to assess the toxicity of a standard toxicant and toxicant formulations and in blind testing of a range of industrial effluents, in parallel with a number of bioassays including Microtox® and activated sludge respiration inhibition. The biosensor results generally show significant correlation to the appropriate conventional toxicity tests. In this study, an activated sludge based biosensor assay was developed and used to assess the toxicity of industrial process and site effluents with the specific purpose of wastewater treatment plant protection. Data generated compared significantly with those from an activated sludge respiration inhibition test, with added advantages of rapidity, safety and ease of use.

Graphene is essentially a monolayer of sp2 bonded carbon atoms, arranged in a honeycomb lattice. Graphene has in recent years attracted phenomenal interest from researchers in materials science, condensed matter physics, and electronics since its first demonstration in 2004. The importance of graphene research was epitomised by the Nobel prize for physics being awarded to pioneers of the field in 2010. The main topic of this research was the development of epitaxial graphene on silicon carbide (SiC) substrates. The substrate inferred processability of epitaxial graphene enables graphene devices to be fabricated on full wafers using standard semiconductor processing techniques. Biosensor research is a rapidly expanding field. The major driver comes from the healthcare industry but there are also applications for biosensors in the food quality appraisal and environmental monitoring industries. The key advantages of electrochemical biosensors over competing sensor technologies are the low cost of mass production, and ability to make sensors into small compact systems. Smaller, portable sensors allow for the development of point-ofcare medical devices, which can be crucial in fast diagnosis and long-term monitoring of diseases. Graphene channel resistor devices have been fabricated using electron beam lithography and a successfully developed contact metallisation scheme - using Titanium / Gold contacts. The metal-graphene contacts have been characterised using XPS and electrical current-voltage measurements. The graphene channel device has been used as the basis of an electrochemical sensor for human chorionic gonadotropin (hCG), an indicator of pregnancy - which has also been linked to increased risk of several cancers. The immunosensor developed is a promising tool for point-of-care detection of hCG, due to its excellent detection capability, simplicity of fabrication, low-cost, high sensitivity and selectivity.

abstract: Analysing and measuring of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. Point of care diagnostic system, composing of biosensors, have promising applications for providing cheap, accurate and portable diagnosis. Owing to these expanding medical applications and advances made by semiconductor industry biosensors have seen a tremendous growth in the past few decades. Also emergence of microfluidics and non-invasive biosensing applications are other marker propellers. Analyzing biological signals using transducers is difficult due to the challenges in interfacing an electronic system to the biological environment. Detection limit, detection time, dynamic range, specificity to the analyte, sensitivity and reliability of these devices are some of the challenges in developing and integrating these devices. Significant amount of research in the field of biosensors has been focused on improving the design, fabrication process and their integration with microfluidics to address these challenges. This work presents new techniques, design and systems to improve the interface between the electronic system and the biological environment. This dissertation uses CMOS circuit design to improve the reliability of these devices. Also this work addresses the challenges in designing the electronic system used for processing the output of the transducer, which converts biological signal into electronic signal. / Dissertation/Thesis / M.S. Electrical Engineering 2014

Orientador: Lauro Tatsuo Kubota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-08T22:44:52Z (GMT). No. of bitstreams: 1 Kisner_Alexandre_M.pdf: 3973690 bytes, checksum: 2810b47ecfaaac028a1bf271a3fc25a0 (MD5) Previous issue date: 2007 / Conjuntos de transistores de efeito de campo sensíveis a íons (ISFETs) foram desenvolvidos no presente trabalho. Implementou-se durante a fabricação destes uma etapa adicional de anodização que possibilitou a formação de uma fina camada de alumina porosa sobre suas portas. Esta serviu como dielétrico e também molde para o crescimento de nanocristais de Ag e Au sobre os dispositivos. Os transistores desenvolvidos foram divididos em dois conjuntos, onde as dimensões de porta de cada conjunto foram de 10 x 50 mm e 50 x 50 mm. Utilizando-se um processo simples de anodização, obteve-se sobre a porta dos transistores uma fina camada de alumina de aproximadamente 60 nm de espessura, contendo uma alta densidade de poros (~ 10 poros/cm) com diâmetro médio de 30 + 6 nm e distribuídos de forma regular. A implementação desta possibilitou não só um aumento significativo na área de porta, bem como molde para o crescimento de nanoestruturas de Ag e Au sobre os transistores, atuando assim como nanoeletrodos de porta. Os testes destes como sensores para soluções com diferentes valores de pH, mostraram que os dispositivos apresentam um curto tempo de resposta (t < 30 s) e que as nanoestruturas metálicas são capazes de aumentar a sensibilidade dos dispositivos em relação àqueles formados apenas por alumina. Os primeiros testes para a detecção de moléculas como glutationa, demonstraram que os ISFETs fabricados são capazes de detectar esta, mesmo sendo uma espécie com baixa densidade de carga, em concentrações submicromolares / Arrays of ion-sensitive field effect transistors (ISFETs) were developed in this work. An additional step in the fabrication process was employed to implement a thin film of porous anodic alumina on the gate. This porous layer works as dielectric and template to the vertical growth of Ag and Au nanocrystals on the gate. The produced ISFETs were divided in two groups, which the gate dimensions were 10 x 50 mm and 50 x 50 mm. Using a simple anodizing process, a 60 nm thickness porous anodic alumina was developed on the gate. This porous film presented a high density porosity (~ 10 pores/cm) with an average pore diameter of 30 + 6 nm and a regular distribution on the gate of those ISFETs. This porous film lead to a significant increase in the gate area and also worked as a template to the growth of Ag and Au nanocrystals, which were used as gate nanoelectrodes. The results of such sensors to detect different pH of the solutions showed that the produced ISFETs present a short response time (t < 30 s). Moreover, the presence of such Ag and Au nanostructures increased the sensors sensitivity in comparison to those observed without nanoelectrodes. The first results to detect species such as glutathione, indicated that the ISFETs are even sensitive to detect small charged species in a submicromolar concentration range / Mestrado / Quimica Analitica / Mestre em Química

No campo da eletroanalítica existe uma intensa atividade de pesquisa sobre eletrodos de pasta de carbono. As principais vantagens da pasta de carbono são a rapidez e a simplicidade do processo de preparação, e a possibilidade de renovação da superfície do eletrodo a cada nova medida. Isso é possível devido à modificação interna do material eletródico, em que o modificador escolhido está diretamente relacionado com o analito de interesse a ser determinado. Os biossensores de pasta de carbono são muito utilizados na determinação de pesticidas da classe dos organofosforados e carbamatos pelo processo de inibição enzimática. Um dos principais problemas na determinação de substâncias utilizando eletrodos de pasta de carbono e biossensores de pasta de carbono é o seu alto limite de detecção, que dificulta a análises traços de substâncias. Uma opção que há décadas vem sendo adotada é a utilização dos eletrodos de nanotubos de carbono, funcionalizados ou não, na elaboração da pasta. Estes sensores, juntamente com os biossensores de pasta de nanotubos de carbono, possuem propriedades catalíticas e estruturais que fornecem um menor limite de detecção e quantificação na determinação de várias substâncias associadas. Estas características são singulares e inerentes à conformação dos nanotubos de carbono, sendo a elevada área ativa e poder eletrocatalítico umas das propriedades destes nanomateriais mais relatadas na literatura. Diante da falta de trabalhos que descrevam, paralelamente, o desempenho destes biossensores na determinação de carbamatos, neste trabalho objetivou-se explorar comparativamente o comportamento eletroquímico de biossensores de pasta de carbono e de pasta de nanotubos de carbono modificados com a enzima acetilcolinesterase para a determinação dos pesticidas carbaril e metomil. Estes nanotubos foram purificados em meio ácido e caracterizados por microscopia eletrônica de varredura e por voltametria cíclica. Parâmetros cinéticos da enzima acetilcolinesterase como a constante de Michaelis-Menten e velocidade máxima de hidrólise do substrato acetiltiocolina foram obtidos e analisados pelo método espectrofométrico. Os biossensores confeccionados tiveram seus parâmetros eletródicos de operação otimizados e foram utilizados na determinação do pesticida carbaril em amostra fluvial. Os biossensores de pasta de carbono e de pasta de nanotubos de carbono modificados com a enzima acetilcolinesterase apresentaram uma repetibilidade com desvio padrão relativo de 2,44% e 1,77%, respectivamente. A reprodutibilidade dos biossensores elaborados apresentou um desvio padrão relativo de 6,60% e 4,13%, respectivamente. Na determinação do pesticida carbaril, os biossensores de pasta de carbono e de pasta de nanotubos de carbono modificados com a enzima acetilcolinesterase apresentaram um limite de detecção de 0,0389 e 0,0163 &micro;mol L-1, respectivamente. Na determinação do pesticida metomil, os biossensores de pasta de carbono e de pasta de nanotubos de carbono modificados com a enzima acetilcolinesterase apresentaram um limite de detecção de 0,0398 e 0,0083 &micro;mol L-1, respectivamente. Em ambas as determinações, o biossensor elaborado com os nanotubos funcionalizados apresentou maior sensibilidade. Quando comparado com o biossensor de pasta de carbono frente à determinação do carbaril, o biossensor de pasta de nanotubos apresentou um limite de detecção aproximadamente 2,4 vezes menor e, quando comparado com o biossensor de pasta de carbono na determinação do pesticida metomil, o biossensor de pasta de nanotubos apresentou um limite de detecção aproximadamente 5 vezes menor. Os limites de quantificação dos biossensores de pasta de carbono e de pasta de nanotubos de carbono modificados com a enzima acetilcolinesterase, para os pesticidas carbaril e o metomil, foram de 0,1297 e 0,0542 &micro;mol L-1 e de 0,1323 e 0,0277 &micro;mol L-1, respectivamente. O biossensor de pasta de nanotubos de carbono modificado com a enzima acetilcolinesterase foi aplicado na determinação de carbaril em amostra de água de rio e ácido húmico, fornecendo um LD de 0,0722 e 0,0704 &micro;mol L-1, respectivamente. Comparado com a curva original realizada em tampão fosfato, este biossensor apresentou um limite de detecção e quantificação de aproximadamente 4,32 e 4,43 vezes maior no procedimento utilizando ácido húmico e água fluvial, respectivamente. / There in the field of electroanalytical an intense research activity on carbon pastes electrodes. The main advantages of carbon paste are the speed and simplicity of the preparation process, and the possibility of renewing the electrode surface with each new measure. This is possible due to the internal modification of the electrode material, in which the modifier selected is directly related to the analytes to be determined. The carbon paste biosensors are widely used in determining the class of pesticides organophosfates and carbamates by enzyme inhibition process. A major obstacle to the determination of substances with a carbon paste electrode and carbon nanotubes paste biosensors is its high detection limit, which complicates the analysis of trace substances. One option that has for decades been adopted is the use of electrodes of carbon nanotubes, functionalized or otherwise, in elaboration of the paste. These sensors, together with the carbon paste nanotubes biosensors, have structural and catalytic properties that provide a lower limit of detection and quantitation in the determination of several related substances. These characteristics are natural and inherent in the arrangement of carbon nanotubes, the high electrocatalytic active area and catalytic power properties of these nanomaterials are most often reported in the literature. Given the lack of studies that describe, in parallel, the performance of these biosensors in the determination of carbamates, this study aimed, comparatively, to explore the electrochemical behavior of carbon paste and carbon nanotubes paste biosensors modified with enzyme acetylcholinesterase to determine pesticide carbaryl and methomyl in distillated and river water. These nanotubes were purified in acidic medium and characterized by scanning electron microscopy and cyclic voltammetry. The kinetic parameters of acetylcholinesterase as the Michaelis-Menten constant and Maximum Velocity of hydrolysis of acetylthiocholine were obtained and analyzed by spectrophotometric method. Biosensors fabricated electrodes had their parameters optimized operation and were used in the determination of carbaryl pesticide in a sample fluvial. Carbon paste and carbon nanotubes paste biosensors modified with enzyme acetylcholinesterase showed a repeatability wih relative standard deviation of 2.44% and 1.77%, respectively. The reproducibility of the biosensor developed showed a relative standard deviation of 6.60% and 4.13%, respectively. In determining the pesticide carbaryl, the carbon paste and carbon nanotubes paste biosensors modified with enzyme acetylcholinesterase showed a detection limit of 0.0389 and 0.0163 &micro;mol L-1, respectively. In determining the pesticide methomyl, the carbon paste and carbon nanotubes paste biosensors modified with enzyme acetylcholinesterase showed a detection limit of 0.0398 and 0.0083 &micro;mol L-1, respectively. In both determinations, the biosensor prepared with functionalized nanotubes showed higher sensitivity. Compared with the carbon paste biosensor in the determination of carbaryl, the nanotubes paste biosensor showed a detection limit of approximately 2.4 times lower and, when compared with the carbon paste biosensor in the determination of the pesticide methomyl, the biosensor elaborated with nanotubes showed a detection limit of approximately five times lower. The limits of quantification of carbon paste and carbon nanotubes paste biosensors modified with enzyme acetylcholinesterase, in the determination of carbaryl and methomyl pesticides, were 0.1297 and 0.0542 &micro;mol L-1, and 0.1323 and 0.0277 &micro;mol L-1, respectively. The carbon nanotubes biosensor modified with the enzyme acetylcholinesterase was applied to the determination of carbaryl in the sample of river water and humic acid, giving a detection limit of 0.0722 and 0.0704 mol L-1, respectively. Compared with the original curve performed in phosphate buffer, the biosensor showed a detection an quantification limit of approximately 4.32 and 4.43 times higher in the procedure using humic acid and fluvial water, respectively.