Dissertations / Theses on the topic 'Potentiometer'

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
Includes bibliographical references (leaves 43-45).
by Emily Barbara Cooper.
S.B.and M.Eng.

In this paper, four methods to simulate or generate electric resistance at high resolution have been developed, tested and evaluated. Each method is called a Resistor Simulator and are numbered from one to four.  Resistor Simulator one is based upon a set of digital potentiometers configured to achieve increased performance over a single 8-bit potentiometer. There were many issues with calibration and control over the individual potentiometers leading to a decent but uneven characteristic.  Resistor Simulator two tests the setup of an encapsulated LED a photoresistor pair where output resistance is controlled by the light output of the current controlled LED. Although the output was purely resistive, and the resistance was controllable. This method has big issues with non-linearity and very poor repetitivity were the same input could give resistances several kiloOhms apart.  Resistor Simulator three uses an ADC in combination with a DAC to measure the current going through the simulator over a shunt-resistor and regulate the voltage output to match the voltage-drop that the set resistance would generate. There were some issues with working in the extreme ends of the analog electronics in the circuit limiting how low currents that could be properly measured. This problem could be bypassed to evaluate the rest of the system with good results. The limiting factor of the simulator was the resolution of the DAC at high resistances. Resistor Simulator four was the largest and costliest of them all, but performance was also the best. It is built as a resistance ladder with a set of 16 binary matched resistors and bypass switches for each resistance. This way, output resistance is set just like a binary number. The performance of the simulator was equally good throughout the entire resistance span. The only thing that limited performance from great to good was that it was hard to get precisely matched resistors of odd values and low tolerance making for some deviation from the theoretical resistances. All four resistance simulators were realized on a single Arduino shield PCB, designed with Altium Designer and assembled by the student. Although an Arduino was used for this project, any microcontroller could be used as all communication with the PCB is done via SPI.  Resistance performance was evaluated with an automated test system for inaccuracy, resolution and repetitivity. Furthermore, practicality parameters such as size and cost were evaluated to further determine the suitability of each resistor simulator.  The outcome from this work is intended to be used as basis to design systems for test and evaluation of alarm systems.
Denna rapport beskriver fyra metoder för att simulera eller generera elektisk resistans med hög upplösning och noggrannhet. Metoderna har identifierats, utvecklats, testats och utvärderats. Varje metod benämns som en Resistor Simulator och är numrerade från ett till fyra. Resistor Simulator ett bygger på en uppsättning av digitala potentiometrar konfigurerade i en krets för att utöka dess upplösning och prestanda jämfört med en enkel 8-bitars potentiometer. Dock så stöttes en hel del problem på i samband med kalibrering och styrning av de individuella potentiometrarna med hyffsad men ojämn karaktäristik. Resistor Simulator två utvärderar konceptet med en inkapslad LED och fotoresistor där resistansen styrs genom att kontrollera ljusflödet med strömstyrning av dioden. Denna lösning var den enda med rent resistiv utgång och resistansen var kontrollerbar. Dock så har metoden stora problem med icke-linjärt beteende och variationer mellan test där samma styrsignal kan ge resistanser flera kiloOhm från varandra. Resistor Simulator tre använder en ADC tillsammans med en DAC för att mäta strömmen genom simulatorn och reglera spänningen för att motsvara det spänningsfall som den valda resistansen skulle generera. Denna lösning stötte på en del problem med för höga spänningsnivåer på den analoga elektronik som användes vilket begränsade hur låga strömmar som kunde mätas. Detta problem kunde förbigås för att utvärdera resten av systemet med goda resultat. Den begränsande faktorn för simulatorns upplösning låg dock i upplösningen på DAC vid höga resistanser. Resistor Simulator fyra var den största och dyraste av dem alla, men också den som presterade bäst. Den är byggd som en resistorstege med en uppsättning av 16 binärt matchade resistorer som alla försetts med en kortslutande styrbar brytare vilket gör att resistans kan beräknas på samma sätt som ett binärtal räknas. Prestandan var genomgående bra i hela mätområdet med enda baksida att det var svårt att införskaffa resistorer av udda värden med mycket låga toleranser varav mindre avvikelser från den teoretiska upplösningen uppkom. Alla simulatorer realiserades på ett tilläggskort till en Arduino som designats med Altium Designer och byggdes ihop av studenten. Även om en Arduino användes för just detta projekt skulle vilken annan mikrokontroller kunna användas då all kommunikation på kretskortet sker via SPI. Prestandan av simulerad resistans testades med ett automatiskt testsystem och utvärderades för onoggrannhet, upplösning och repeterbarhet. Utöver detta utvärderades praktiska parametrar som storlek och materialkostnad för att kunna utvärdera i vilka sammanhang respektive simulator passar bäst till. Utfallet från detta arbete avser att ligga till grund för utveckling av utrustning för test och utvärdering av larmsystem.

In today’s society, CNC machines are used for various purposes.In this project, a CNC plotter is created to analyzehow the performance of the plotter differs when using twodifferent motors: a DC motor controlled by a potentiometerin the horizontal direction and a stepper motor in thevertical direction. A CNC plotter is built and used to dotests in order to answer the research question. The resultsshow that a DC motor with a potentiometer is more precisethan a stepper motor and the mean value of the relative errorsin the vertical direction is always higher. The valuesdiffer with 1 percentage point to 3 percentage points. Thedifference in the performance of the two motors depend onseveral factors and one of the main factors is considered tobe the fact that the stepper motor sometimes skips steps.
I dagens samhälle används CNC-maskiner för olika ändamål.I detta projekt skapades en CNC-plotter för att analyserahur plotterns prestanda skiljer sig vid användning avtvå olika motorer: en DC motor kontrollerad av en potentiometeri horisontell riktning och en stegmotor i vertikalriktning. En CNC-plotter byggdes och användes för genomförandeav tester för att kunna svara på forskningsfrågan.Resultaten visar att en DC motor med en potentiometer ärmer exakt än en stegmotor och medelvärdet av de relativafelen i vertikala riktningen är alltid högre. Värdena skiljersig från 1 procentenhet till 3 procentenheter. Skillnaden iprestanda för de två motorerna beror på flera faktorer ochen av huvudfaktorerna anses vara det faktum att stegmotornibland hoppar över steg.

This thesis is focused on the microprocessor-controlled frequency filter project. The main goal of the thesis is to present basic terms and principles of frequency filters and active frequency filters for cascading synthesis. Furthermore, the work contains information on digital potentiometers. The thesis includes circuit simulations and a project of connecting with a printed circuit board. The last chapter contains the results of the measurements.

In today’s society, CNC machines are used for various purposes. In this project, a CNC plotter is created to analyze how the performance of the plotter differs when using two different motors: a DC motor controlled by a potentiometer in the horizontal direction and a stepper motor in the vertical direction. A CNC plotter is built and used to do tests in order to answer the research question. The results show that a DC motor with a potentiometer is more precise than a stepper motor and the mean value of the relative errors in the vertical direction is always higher. The values differ with 1 percentage point to 3 percentage points. The difference in the performance of the two motors depend on several factors and one of the main factors is considered to be the fact that the stepper motor sometimes skips steps.
I dagens samhälle används CNC-maskiner för olika ändamål. I detta projekt skapades en CNC-plotter för att analysera hur plotterns prestanda skiljer sig vid användning av två olika motorer: en DC motor kontrollerad av en potentiometer i horisontell riktning och en stegmotor i vertikal riktning. En CNC-plotter byggdes och användes för genomförande av tester för att kunna svara på forskningsfrågan. Resultaten visar att en DC motor med en potentiometer är mer exakt än en stegmotor och medelvärdet av de relativa felen i vertikala riktningen är alltid högre. Värdena skiljer sig från 1 procentenhet till 3 procentenheter. Skillnaden i prestanda för de två motorerna beror på flera faktorer och en av huvudfaktorerna anses vara det faktum att stegmotorn ibland hoppar över steg.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV
Cobham Electronic Systems, Inc. has developed a digital potentiometer circuit to allow for digital compensation of frequency and temperature variations in the VCO/PLL frequency control loop of a telemetry transmitter. The ability to reprogram the RF center frequency of a telemetry transmitter is a useful feature and is required on many telemetry programs. When setting the frequency modulation deviation (FM Modulation Index) of a telemetry transmitter, the exact setting will change with RF center frequency due to the variation of the transfer function of the VCO (Kvco). Typically, a resistor divider is used to set the frequency modulation deviation level by setting the output data signal amplitude. However, since Kvco varies with respect to RF center frequency, a method of adjusting frequency modulation deviation for each frequency setting is required. The shunt resistor in the resistor divider is replaced with a digital potentiometer to provide the necessary adjustment, using the on-board microprocessor to store a look-up table of settings versus frequency. A key feature of the digital potentiometer circuit is a method to increase the frequency bandwidth of the potentiometer. Digital potentiometers typically have frequency bandwidths measured in kiloHertz to MegaHertz, which limits their use in setting the frequency modulation deviation of high data rate telemetry transmitters. The circuit consists of a 256 position digital potentiometer and several resistors that are used to adjust the slope of the resistance vs. digital code curve and to translate the curve up and down along the Y-Axis. Adding external resistors to the digital potentiometer helps to increase the frequency bandwidth of the digital potentiometer. The selection of the maximum resistance range of the digital potentiometer is also important, as the potentiometer bandwidth is greater when a small portion of the total resistance is used. This paper will explore various methods of increasing the effective bandwidth of a digital potentiometer, with the goal of making them suitable for use in dynamically setting the frequency modulation deviation via digital control.

Robotic arms and hands come in all shapes and sizes, they can be general purpose or task-specific. They can be pre-programed by a computer or controlled by a human operator. There is a certain subsection of robotic hands which try to mimic the shape, movement and function of the human hand, these are sometimes known as biomimetic robotics. This project explores the human robot interaction by creating an anthropomorphic robotic hand with an accompanying exoskeleton. The hand, which consists of a 3D-printed body and fingers, is connected to a forearm where the servos that control the fingers are housed. The exoskeleton connects to the operator's hand allowing finger tracking through a set of potentiometers. This setup allows the operator to intuitively control a robotic hand with a certain degree of precision. We set out to answer research questions in regard to the form and function of a biomimetic hand and the exoskeleton. Along the way, a multitude of problems were encountered such as budgetary issues resulting in only half the fingers having movement. Despite this, good results were gathered from the functioning fingers and our research questions were answered.
Robotarmar och händer finns många former och storlekar, de kan vara för allmänna ändamål eller uppgiftsspecifika. De kan programmeras av en dator eller styras av en mänsklig operatör. Det finns en viss typ av robothänder som försöker efterlikna formen, rörelsen och funktionen hos den mänskliga handen, och brukar kallas biomimetisk robotik. Detta projekt utforskar interaktionen mellan människa och robot genom att skapa en antropomorf robothand med tillhörande exoskelett. Handen, som består av en 3D-printad kropp och fingrar, är ansluten till en underarm där servormotorerna som styr fingrarna sitter. Exoskelettet ansluts till operatörens hand vilket möjliggör spårning av fingrarnas rörelse genom ett antal potentiometrar. Detta tillåter operatören att intuitivt styra en robothand med en viss grad av precision. Vi valde att besvara ett antal forskningsfrågor med avseende på form och funktion av en biomimetisk hand och exoskelettet. Under projektets gång påträffades en mängd problem såsom budgetproblem som resulterade i att bara hälften av fingrarna kan kontrolleras. Trots detta fick vi bra resultat från de fungerande fingrarna och våra forskningsfrågor kunde besvaras.

The data acquisition system COMET developed by Saab AB contains a unit for signal conditioning and A/D conversion, called KSM. The varieties in signal conditioning constitutes of a number of specific PBAs and maintenance as well as reconfiguration of these are complicated not to mention costly. This thesis has aimed to investigating whether the signal conditioning circuits can be replaced by a general purpose, programmable solution. If so, how can this be done?

The development has been carried out by evaluating ideas through the use of a laboratory environment and has resulted in an analog design for laboratory purpose. A reconfigurable design is the result of this thesis as an alternative to the solution used today. In the proposed design mainly digital otentiometers, switches and MUXes are used. In that way signal path and overall behaviour can be selected. Some extensions have been made in comparison to the current functionality, but additional development is necessary to make the design complete.

Future versions of the COMET system could be significantly improved by considering the result of this thesis when developing the signal conditioning circuitry.

How can we improve the living standards of the visuallyimpaired using an Arduino?Living with visual impairment could potentially be oneof the hardest things one could do. Constantly having toworry about obstacles and carrying a stick to feel your wayforward. In order to combat this difficulty, we have designedVision for the Blind.One of the usages of ultrasonic sensors are to measurethe distance from objects using sound waves. These sensors,in combination with Piezo buzzers, have been used inVision for the Blind to warn the user of incoming obstaclesby emitting sound from the buzzers. The volume of thebuzzers is controlled by using a digital potentiometer andvaries depending on the measured distance. All three areconnected to an Arduino which has been coded to performthe given task.
Hur kan vi öka levnadsstandarden för visuellt nedsattamänniskor med hjälp av en Arduino?Att leva med visuell nedsättning är självklart ett stortproblem som medför svårigheter, att alltid vara orolig överhinder som kan finnas i vägen eller bära en pinne med sigför att hitta sin väg. För att bekämpa de här svårigheternahar vi konstruerat Vision for the Blind.Ultraljudsbaserade sensorer använder ljudvågor för attmäta avstånd från ett objekt. Dessa sensorer har använtsi Vision for the Blind i kombination med Piezo sumrarför att varna användaren om inkommande hinder genomatt emittera ljud från sumrarna. Ljudvolymen kontrollerasmed hjälp av en digital potentiometer och varierar med detuppmätta avståndet. Alla tre är kopplade till en Arduinosom är kodad för att utföra det givna uppdraget.

Detta examensarbete gick ut på att försöka hitta ett sätt att mäta kompo nentkänslighet hos parameteriserbara aktiva vågfilter. Två olika ansatser har gjorts, men bara ett försök har avslutats.

Det första försöket behandlar möjligheten att realisera ett vågfilter med hjälp av standardkomponenter i en kretskortslösning. Detta fungerade inte beroende på att nödvändiga komponenter inte finns på marknaden idag. Komponenterna som finns har för stora parasitkapacitanser. Dessa oönskade parasiter var så stora att de skulle kunna förstöra funktionen och det var således inte värt att fortsätta försöket. De komponenter som undersöktes var resistansstegar och digitala potentiometrar. Den största delen av studierna till det första försöket har bestått i att studera datablad från olika kretstillverkare för att hitta lämpliga komponenter.

Istället startades ett nytt försök som syftade till att undersöka möjligheten att implementera ett aktivt vågfilter i en integrerad krets. I denna rapport presenteras en förstudie till hur en sådan lösning skulle kunna se ut. För att möjliggöra en fortsättning där mitt examensarbete tar slut har arbetet förklarats ingående. Jag har också inkluderat min programkod som bilagor i slutet av rapporten.

The purpose of this thesis was to find a way of measuring the sensitivity of component values for parameterized wave active filters. Two different approaches were made, but only one was finished.

The first approach is about the possibility of making a wave active filter with standard components on a printed circuit board. This did not work though, because of a scarce market of possible components. The compo-nents existing today have too high parasite capacitances. These unwanted parasites are so large in value that they could destroy the functionality and it was therefore not worth continuing the attempt. The components that were investigated as possible on the board were ladder networks and digitally controlled potentiometers. The main part of the studies for the first attempt was to read data sheets from different electronic companies trying to find possible components.

Instead a new approach was made with the purpose of investigating the possibility of making a wave active filter as an integrated circuit. In this report a pilot study for such an attempt is presented. To make it possible to continue work where these studies end, the work has been carefully explained. I have also included the computer programs I have made in the appendix of the report.

I projektet utreds möjligheterna kring att kunna kontrollera en generators reaktiva effektproduktion genom att styra magnetiseringsströmmen från en PLC. Som metod för styrning från PLC beslutades att en signal på 0-5V skulle användas. För att reglera magnetiseringen, och därmed i förlängningen den reaktiva effekten, beslutades att den befintliga manuella potentiometern skulle ersättas med två parallellkopplade digitala potentiometrar av typen MCP4261 som kontrollerades av en mikrokontroller. Att de digitala potentiometrarna skulle parallellkopplas beslutades efter en förstudie som visade på att det skulle resultera i en noggrannare reglering utan någon inskränkning på användbart reglerspann. Praktisk provning av mikrokontroller och digitala potentiometrar gav ett tillfredsställande och bra resultat med god upplösning.
This project investigates the possibilities of being able to control a generators reactive power production by controlling the excitation current from a PLC. As a method for controlling from PLC, it was decided that a signal of 0-5V should be used. In order to regulate the magnetization, and hence in the long term the reactive power, it was decided that the existing manual potentiometer would be replaced by two parallel-connected digital potentiometers of the type MCP4261 controlled by a microcontroller. The fact that the digital potentiometers would be connected in parallel was decided after a feasibility study which showed that in this way it would result in a more accurate regulation without any restriction on the usable control span. Practical testing of microcontrollers and digital potentiometers provided a satisfactory result with a good resolution.

The aim of this work is to design an architecture of the embedded device that will be used for controlling DAW software in recording studio. First of all, attention is given to a brief summary of the necessary knowledge which is needed to design such kind of device. Af- ter that follows short survey of the existing solutions and description of protocols which can be used for communication with the recording software. Then, subsequent part of the thesis builds upon these foundations and further elaborates the device architecture by me- ans of decomposing it into several modules. In fact, two hardware modules are designed and manufactured, when each of them is conceived on a separate PCB with its own microcon- troller. Then the control firmware has been implemented for each of the modules. At the end of the work an aluminium enclosure, which holds both modules, is designed. The result of this work is a functional prototype of the assembled controller which can be used for the purpose of controlling DAW software.

The thesis deals with analyses of the laboratory symmetrical supplies with adjustable output voltage. It also describes different kinds of current cut-out circuits and several most frequent supply connection schemes. Analyses (simulation program OrCAD) show the characteristics and behaviour of the mentioned supplies. To set the output voltage, operational amplifier structures or linear three-terminal voltage regulator are very often used. The suggested supply was tested and its parameters compared with the simulations. The value of output voltage and current can be controlled with a computer with a USB port. For controlling of the output voltage and current the digital potentiometers were used and controlled by I2C bus.

In this thesis, we establish the foundations on which graphene based chemical sensors can be developed. Graphene combines several ideal characteristics for potentiometry and charge probing at surfaces which are essential for chemical sensing applications. Hitherto, graphene/substrate interactions have masked the response of graphene based chemical sensors. We demonstrate the use of hydrophobic polymers as a substrate for graphene field effect transistors (FETs) as a means to eliminate undesired graphene/substrate interactions. Parylene gated devices exhibit stable neutrality point gate voltage under ambient conditions, higher mobilities (~10,000 cm2/V.s), and less hysteresis than that observed in graphene FETs with a typical silicon oxide gate. We show quantitatively that electrochemistry involving adsorbed water, graphene, and the substrate is responsible for p-doping in silicon oxide gated graphene FETs. We identify the water/oxygen redox couple as the underlying mechanism for this reaction and capture its kinetics.The aforementioned fundamental studies of graphene permit the development of improved graphene FET based chemical sensors in atmosphere and in solution. We demonstrate that large-area, graphene FETs with a passive parylene substrate and a polyethyleneimine (PEI) functional layer have enhanced sensitivity to CO2 gas exposure. The electron doping of graphene, caused by protonated amine groups within the PEI, is modulated by the formation of negatively charged species generated by CO2 adsorption. The charge doping mechanism is general, and quantitative doping density changes can be determined from the graphene FET characteristics. Finally, we investigate the behavior of graphene FETs in a solution. We present electrochemical techniques to probe the graphene's Fermi level position versus changes in pH. We show that bare graphene devices are not sensitive to changes in pH due to the absence of surface sites available to participate in the protonation and deprotonation process necessary for pH sensing. We finally provide a technique to increase the sensitivity of graphene FETs to changes in pH by utilizing a thin Ta2O5 layer on the graphene surface.
Dans cette thèse, nous établissons les bases selon lesquelles les senseurs chimiques à base de graphène pourront être développés. Le graphène combine plusieurs caractéristiques idéales pour la potentiométrie et la sensibilité aux charges en surface. Ces deux caractéristiques sont essentielles pour des applications de senseurs chimiques. Depuis lors, les interactions entre le graphène et le substrat ont masqués la réponse des senseurs chimiques à base de graphène. Nous démontrons l'utilité de polymères hydrophobe comme substrat pour des transistors à effet de champ (FET) à base de graphène afin d'éliminer les interactions entre le substrat et le graphène. Les dispositifs à base de parylène démontrent une stabilité du point de neutralité dans le voltage de grille, des mobilités supérieures (10000 cm2/Vs) ainsi que moins d'hystérèse que les dispositifs avec une grille à base d'oxyde de silicium. Nous démontrons quantitativement que l'électrochimie entre l'eau adsorbée, le graphène et le substrat est responsable du dopage p dans les FETs à base de graphène et d'oxyde de silicium. Nous identifions le couple redox eau/oxygène comme responsable de cette réaction et nous mesurons la cinétique de cette réaction. Les études fondamentales mentionnées ci-haut permettent le développement de senseurs chimiques à base de graphène dans des conditions ambiantes ainsi qu'en solution. Nous démontrons que des échantillons de large taille de FETs à base de graphène avec une couche de parylène passivé et une couche fonctionnelle de polyethyleninine (PEI) augmentent la sensibilité au CO2. Le dopage aux électrons du graphène, causé par la protonation des groupes aminés dans le PEI, est modulé par la formation d'espèces chargées négativement par l'absorption de CO2. Le mécanisme de dopage de charge est général et la densité du dopage peut être déterminée par les caractéristiques des FETs à base de graphène.Finalement, nous investiguons le comportement des FETs à base de graphène en solution. Nous présentons des techniques électrochimiques afin de mesurer la position du niveau de Fermi dans le graphène en fonction de changement du pH. Nous démontrons que des dispositifs sans PEI ne sont pas sensibles aux changements de pH à cause de l'absence de sites en surface capables de participer à la protonation et la dé-protonation nécessaire pour être sensible au pH. Nous présentons finalement une technique pour augmenter la sensitivité des FETs de graphène aux changements de pH en utilisant une fine couche de Ta2O5 sur la surface du graphène.

The specificity of biosensors is achieved by the use of biological probes with affinity to the targets to be detected. The electrochemical transducer converts the biological recognition process into an electrical signal. The resulting electrical signal is the response of the recognition from the biolayer. Potentiometric, amperometric and voltammetric detection are the fundamental electrochemical measurement techniques. In this thesis, direct open circuit potentiometry (OCP) is studied with several types of electrochemical systems. The biological interaction between the probes and the targets are characterised by measuring the variations of the true open circuit potential (OCP) that occurs at the surface of the working electrode when the charge density and the distribution of the immobilised biolayer change upon interactions with the target biomolecules. OCP is a detection technique which measures the recognition electrical signal in real time. With the true OCP measurement system developed in-house, a number of electrochemical systems were studied by looking at the interaction with different biomolecules, to show that a true OCP measurement system could be achieved for biosensor development. The electrochemical systems that have been investigated include DNA – DNA detection with a novel cobalt complex for signal enhancement, PNA – DNA detection with gold nanoparticles for signal enhancement, and protein phosphorylation (for drug discovery applications) with gold nanoparticles for signal enhancement. A comparison with promising biosensing techniques such as electrochemical impedance spectroscopy (EIS) and other techniques is performed to demonstrate the benefits of OCP as a biosensing technique. An easily expandable multichannel OCP biosensor array instrumentation system was developed. The whole instrumentation is built and assembled with a custom designed electronic system, a microfluidic system and its applicability demonstrated for a range of electrochemical systems. Through an investigation of the instrumentation amplifier circuit and the multiplexing technique, and the analysis of experimental data, an optimisation for the OCP measurement system is achieved. This thesis tackles a gap in the literature in terms of studies of OCP as a biosensing technique, providing a number of case studies that can contribute towards the development of potential new low-cost biosensors.

The diploma thesis deals with the modern design of the control circuits for digital potentiometers and their application in analog systems. The concept of the digital control is demonstrated on the electronically controlled active 2-nd order filter and programmable oscillator. The proposed design of the active filter describes a programmable active 2-nd order filter Sallen-Key. In this circuit it is possible independently programme cut-off frequency, Q factor and type of approximation with very good accuracy. The circuits of the designed filter and designed oscillator are simulated in PSpice (OrCAD), parasite effects and effects of the real parts are studied. Properties simulated circuits are compare with experimental results. These results appreciate quality and efficiency of the digitally controlled potentiometers in dependence on variable input circuit parameters. Integral part of this project is author’s universal control program called Digipot and comunications interface for many types of digital potentiometers with I2C, SPI or Up/Down interface. It is possible to use this device for many applications. The constructional details of the filter are presented at the end of this work. The software equipment is availability on enclosed CD.

Subject of the thesis is experimental verification of load capacity of construction for storage coal by using load test. In the first part, the analysis of sorts of load tests is made and its execution in causality with standard regulations. Further possible options of bringing test load are described and also the method of evaluation of static load test. Second part looks into the analysis of means of measurement which can be used to determine required quantity. Final part is dedicated to realization and evaluation of the load test on material construction followed by comparison of experimental values with values established on a model of construction created by using computing program.

Blodgassprutor beställs för att undersöka en patients syra-bas-status, laktatkoncentration och elektrolytkoncentration. Några orsaker till balansrubbningar kan vara trauma, syrebrist, infektion, intoxikation eller svält. År 2018 installerades ett nytt rörtransportsystem på Västerviks sjukhus och syftet med studien var att undersöka om det är möjligt att transportera blodgassprutor i det nya rörsystemet utan att provresultat påverkas. Analyser som studerades var pH (power of hydrogen), syretryck, koldioxidtryck, syrgasmättnad, natriumjoner, kaliumjoner, fria kalciumjoner, standardbikarbonat, basöverskott och laktat. Studien omfattade 27 arteriella dubbelprover där det ena provet transporterades i rörtransportsystemet och det andra transporterades manuellt till laboratoriet. Proverna analyserades på instrumentet ABL 800 Flex, inom 30 minuter efter provtagning, med analysmetoderna potentiometri, amperometri och spektrofotometri. Resultaten jämfördes i korrelationsdiagram med en regressionslinje för att påvisa samband mellan proverna. Korrelationsdiagrammen visade positiv linjär korrelation hos samtliga analyser och ett samband kunde påvisas (r = 0,930-0,998). Om resultatet från proverna som transporterats manuellt ökade, ökade även resultatet från proverna som transporterats i rörpost och tvärtom. Ett stapeldiagram skapades för att visualisera skillnader i medelvärde som visade en liten skillnad på basöverskott som ökade efter transport i rörpostsystemet. Ett tvåsidigt parat t-test utfördes för att påvisa om någon signifikant skillnad förelåg mellan analysresultaten. T-testet visade en statistisk signifikant skillnad på syretrycket (p = 0,04), syrgasmättnaden (p = 0,04), basöverskott (p = 0,001) och standardbikarbonat (p = 0,006), då medelvärdet ökade efter transport i rörpost. Medelvärdet för halten natriumjoner minskade efter transport i rörpostsystemet vilket innebar att hemolys inte förekom. Slutsatsen var att det finns en signifikant skillnad mellan blodgassprutor transporterade i rörpostsystem och blodgassprutor transporterade manuellt på vissa analyser, men skillnaden har ingen klinisk betydelse.
Blood gas syringe are ordered to examine the patient´s acid-base status, lactate concentration and electrolyte concentration. Some causes for imbalance could be trauma, lack of oxygen, infection, poisoning or starvation. In 2018, a new pneumatic tube transport system was installed at Västervik´s hostpital and the purpose of this study was to investigate if it is possible to transport samples for blood gas analyses with the new pneumatic tube transport system without affecting the test results. The analyses which were investigated were pH (power of hydrogen), oxygen tension, carbon dioxide tension, saturation, sodium ions, potassium ions, free calcium ions, standard bicarbonate, base excess and lactate. The study included 27 arterial double samples, one samples was transported in the pneumatic tube transport system and the other was manually transported to the laboratory. The samples were analysed within 30 minutes after the sampling, on the ABL 800 Flex instrument, using the methods potentiometry, amperometry and spectrophotometry. The results were compared using a correlation diagram with a regression line to study the relationship between the parameters. The correlation diagram shown a positive linear correlation and a relationship could be demonstrated for all the parameters (r = 0,929-0,998). If the results from the samples transported manually increased, the results also increased from the samples transported in the pneumatic tube transport system and vice versa. A bar chart was created to visualize differences in the mean values. A difference could be seen in base excess and the mean value increased after transport in the pneumatic tube transport. A two-sided paired t-test was performed to demonstrate any significant difference between the parameters. The t-test demonstrated a significant difference in the oxygen tension (p = 0,04), oxygen saturation (p = 0,04), base excess (p = 0,001) and the standard bicarbonate (p = 0,006) and statistically the values was higher after transport with the pneumatic tube transport system. The mean value for sodium ions decreased after transport in the pneumatic tube transport system and that indicate that hemolysis did not occur. The conclusion of the study was that there is a significant difference between blood gas syringes transported with pneumatic tube transport system and blood gas syringes transported manually, but the differences are not clinically relevant.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
No presente trabalho estudo0se o desempenho eletroquímico de sensores a base de óxido de manganês (IV) do tipo espinélio dopado, para determinação potenciométrica de íons lítio. A matriz porosa de óxido de manganês é formada por unidades de blocos de MnO6 octaédricos que podem formar diferentes estruturas cristalinas. O óxido de manganês tipo espinélio apresenta uma estrutura tridimensional com túneis estruturais próprios e adequados para a inserção do íon lítio. Entretanto, o desempenho eletroquímico desse óxido diminui quando submetido a várias ciclagens de inserção e extração do íon lítio na estrutura do óxido, devido ao efeito de Jahn0Teller (distorção de rede cristalina). Para minimizar o efeito Jahn0Teller, a substituição parcial do íon manganês e do oxigênio por cátions de metais de transição e/ou de ânions, respectivamente, tem sido estudado por vários grupos de pesquisa com objetivo de melhorar o desempenho eletroquímico do óxido na construção de baterias recarregáveis. Dessa forma, foi investigado o comportamento potenciométrico de óxidos de manganês dopados e avaliada sua futura aplicabilidade na determinação do cátion lítio. A resposta potenciométrica para esse cátion é baseada no mecanismo de inserção topotática redox pode ser representada por: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) Li2[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) Os óxidos de manganês dopados estudados foram: Li1,05Ga0,02Mn1,98O3,98; Li1,05Ga0,02Mn1,98S0,02O3,98 e Li1,05Ga0,02Mn1,98F0,02O3,98. Estes óxidos mostraram0se promissores para determinação de íons lítio, pois apresentaram uma maior sensibilidade (80,16, 87,02 e 94,39 mV dec01, respectivamente) quando comparados ao óxido de manganês tipo espinélio não dopado, o qual apresentou uma sensibilidade de 78,9 mV dec01 para pH 8,3. Com relação...
The electrochemical performance of the sensors based on doped spinel0type manganese (IV) oxide for lithium ions potentiometric determination was studied in this work. The porous matrix of manganese oxide is formed by MnO6 0 octahedral structure, which may form different crystal structure. The spinel0type manganese oxide has a three0dimensional structure with own structural tunnels and suitable for the insertion of lithium ion. However, the electrochemical performance this oxide decreases when subjected to various cycles of lithium ions insertion and extraction into oxide structure, ascribed to Jahn0Teller effect (crystal lattice distortion). Thus, to minimize the Jahn0 Teller effect, the partial substitution of manganese and oxygen ions by transition metal cations and/or anions, respectively, has been studied by many research groups with the objective of improving the electrochemical performance of oxide in the construction of rechargeable batteries. Accordingly, the potentiometric behavior of the doped manganese oxide and your application in the lithium cation determination were investigated and evaluated. The potentiometric response for lithium cation was based on topotactic insertion mechanism: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) ↔ Li[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) The doped manganese oxide studied were: Li1,05Mn1,98Ga0,02O3,98; Li1,05Mn1,98Ga0,02S0,02O3,98 e Li1,05Mn1,98Ga0,02F0,02O3,98.. This oxides showed promising application, because presented great sensibility (80.16; 87.02 and 94.39 mV/dec, respectively) when compared to undoped spinel0type manganese oxide, before studied by Teixeira and coauthor, which presented a sensibility of 78.9 mV/dec for pH 8.3. In relation to linear range of response, the result were satisfactory for doped oxide (5.96 x 1005 to 1.62 x1003, 3.49 x 1005 to... (Complete abstract click electronic access below)

The role of magnesium is acknowledged in human physiology even though it is incompletely understood,a nd measuremenot f ionized magnesium by ion-selective electrode analysers is becoming commoner as recent research has alerted clinicians to its importance. Standardisation of ionized magnesium in blood samples in the form of a reference method is required. A prototype reference cell, which was developed for the reference method for ionized calcium, has been tested and found to perform well for magnesium. Selectivity coefficients, and the effects of pH and of proteins on various magnesium selective membranes have been determined. None of these membranes showed sufficient selectivity for magnesium over calcium and sodium for use with serum samples without simultaneous measurement of calcium. Knowledgeo f magnesiums peciationis requiredf or a full understanding of its role in physiology. Stability constants for magnesium and calcium with various ligands have been determined by using a new method in which a pH electrode and a Mg (or, Ca) electrode have been employed simultaneously in alkalimetric titrations. The' results were analysed using the program SUPERQUAD. In general, agreement was very good between values obtained from titrations with Mg (or Ca) electrodes and from pH. The protonation constants of the ligands were also determined and agree well with literaturev alues.R esultsf or Mg-citrate,l actate,g lycinate,a spartatea nd glutamatec omplexationc onstantsc omparew ell with recentlyp ublishedd ata. New systems investigated were Mg-pyroglutamate (Mg-5-oxo-2- pyrrolidinecarboxylic acid) and Mg-pyridoxine (Mg-3-hydroxy-4,5- bis(hydroxymethyl)-2-methylpyridine). Also HEPES (N-(2-hydroxyl) piperazine-N-ethanesulfoniacc id), used in calibration standardsa s a pH buffer, was found not to complex magnesium at physiological pH.

Abstract The aims with this report are to document the upgrade and development of new software for the distance laboratory at Blekinge Tekniska Högskola. The work has been focused on implementing the identification number in a microcontroller, to read its data from a so called look-up table and to be able to control digital components through a serial bus (SPI). The look-up table is a list of data from which the software reads data for the different types of printed circuit boards in the hardware component of the distance laboratory is in focus. The results of the report are an implemented, upgraded version of the software and all three aims has been accomplished. Sammanfattning Syftet med detta arbete har varit att utveckla och uppgradera en ny mjukvara till distanslaboaratoriet på Blekinge Tekniska Högskola, genom att implementera adressen till en microcontroller, att läsa dess data från en så kallad look-up table, samt att kunna styra digitala komponenter med en seriell buss (SPI). Fokus i programmeringen har legat på look-up table, vilket är en datalista som mjukvaran läser funktionsdata från för de olika korttyperna i matrisen. Resultatet är en implementerad, uppgraderad version av mjukvaran och alla tre målen har gått att genomföra.

This diploma thesis is focused on complete construction of lab source which is controlled and powered by USB in personal computer. Different types of possible solutions are mentioned and finally one of them has been picked up as a best choice, which is developed in the rest of this thesis. Besides hardware construction there is also shown creation of main program for PIC18F14K50 microcontroller and main application that provides controlling of USB source via personal computer.

Orientador: Marcos Fernando de Souza Teixeira
Banca: Silvio Rainho Teixeira
Banca: Éder Tadeu Gomes Cavalheiro
Resumo: No presente trabalho estudo0se o desempenho eletroquímico de sensores a base de óxido de manganês (IV) do tipo espinélio dopado, para determinação potenciométrica de íons lítio. A matriz porosa de óxido de manganês é formada por unidades de blocos de MnO6 octaédricos que podem formar diferentes estruturas cristalinas. O óxido de manganês tipo espinélio apresenta uma estrutura tridimensional com túneis estruturais próprios e adequados para a inserção do íon lítio. Entretanto, o desempenho eletroquímico desse óxido diminui quando submetido a várias ciclagens de inserção e extração do íon lítio na estrutura do óxido, devido ao efeito de Jahn0Teller (distorção de rede cristalina). Para minimizar o efeito Jahn0Teller, a substituição parcial do íon manganês e do oxigênio por cátions de metais de transição e/ou de ânions, respectivamente, tem sido estudado por vários grupos de pesquisa com objetivo de melhorar o desempenho eletroquímico do óxido na construção de baterias recarregáveis. Dessa forma, foi investigado o comportamento potenciométrico de óxidos de manganês dopados e avaliada sua futura aplicabilidade na determinação do cátion lítio. A resposta potenciométrica para esse cátion é baseada no mecanismo de inserção topotática redox pode ser representada por: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) Li2[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) Os óxidos de manganês dopados estudados foram: Li1,05Ga0,02Mn1,98O3,98; Li1,05Ga0,02Mn1,98S0,02O3,98 e Li1,05Ga0,02Mn1,98F0,02O3,98. Estes óxidos mostraram0se promissores para determinação de íons lítio, pois apresentaram uma maior sensibilidade (80,16, 87,02 e 94,39 mV dec01, respectivamente) quando comparados ao óxido de manganês tipo espinélio não dopado, o qual apresentou uma sensibilidade de 78,9 mV dec01 para pH 8,3. Com relação... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The electrochemical performance of the sensors based on doped spinel0type manganese (IV) oxide for lithium ions potentiometric determination was studied in this work. The porous matrix of manganese oxide is formed by MnO6 0 octahedral structure, which may form different crystal structure. The spinel0type manganese oxide has a three0dimensional structure with own structural tunnels and suitable for the insertion of lithium ion. However, the electrochemical performance this oxide decreases when subjected to various cycles of lithium ions insertion and extraction into oxide structure, ascribed to Jahn0Teller effect (crystal lattice distortion). Thus, to minimize the Jahn0 Teller effect, the partial substitution of manganese and oxygen ions by transition metal cations and/or anions, respectively, has been studied by many research groups with the objective of improving the electrochemical performance of oxide in the construction of rechargeable batteries. Accordingly, the potentiometric behavior of the doped manganese oxide and your application in the lithium cation determination were investigated and evaluated. The potentiometric response for lithium cation was based on topotactic insertion mechanism: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) ↔ Li[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) The doped manganese oxide studied were: Li1,05Mn1,98Ga0,02O3,98; Li1,05Mn1,98Ga0,02S0,02O3,98 e Li1,05Mn1,98Ga0,02F0,02O3,98.. This oxides showed promising application, because presented great sensibility (80.16; 87.02 and 94.39 mV/dec, respectively) when compared to undoped spinel0type manganese oxide, before studied by Teixeira and coauthor, which presented a sensibility of 78.9 mV/dec for pH 8.3. In relation to linear range of response, the result were satisfactory for doped oxide (5.96 x 1005 to 1.62 x1003, 3.49 x 1005 to... (Complete abstract click electronic access below)
Mestre

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

This master´s thesis deals with the design of the control circuits for digital potentiometers and their application in analog systems. Digital potentiometers are three-terminal resistors with an adjustable center connection. The digital potentiomneters enable to drive logic gates, LED drivers, LCD drivers, analog switches etc. Controlling of these mentioned devices is possible by the I2C 2- wire serial bus (invented by Philips). The digital potentiometers are used to control of the primary parameters like cut-off frequency and quality factor in the state variable filter and cut-off frequency in a passive filter. Both filters are simulated in PSpice and then compared with the measured results. Next parts of this master's thesis are a computer program and a exemplary protocol.

Two objectives are achieved in this thesis: (1) to develop a new method to measure the pH-dependent net surface charge of soils and (2) to determine if, by a combination of the surface charge evaluated by potentiometric titration and ion adsorption, we can separate the permanent charge, generated by the isomorphous substitution, from the variable charge. First, a laboratory procedure, using backtitration, was developed for the measurement of the pH-dependent net surface charge. This method was tested on ten soil horizons from Gleysols and Podzols. It appears that the pH-dependent net surface charge, measured by this technique, shows good agreement with that measured by ion adsorption. It is also possible, with this method, to identify some plateaus and inflection points in the backtitration curve associated with protonation/deprotonation reactions of specific soil components. Secondly, it was demonstrated that it is possible to increase the surface charge of montmorillonite with Al-oxide coatings under specific conditions.

No presente trabalho comprova-se o efeito prejudicial do oxalato, utilizado para a separação prévia de cálcio e magnésio, na determinação complexométrica deste último com EDTA em águas, usando-se em titulação visual o indicador Negro de Eriocromo T e, em titulação potenciométrica, o sistema indicador Hg/Hg-EDTA. Comprovou-se, também, a viabilidade de se usar como titulante uma solução de EDTA \"tetraneutralizado\", em titulações potenciométricas com medidas de pH através de eletrodo de vidro combinado. Neste caso o ponto final é obtido através da hidrólise da espécie Y4-, após o ponto de equivalência. Assim evidenciou-se a viabilidade de um novo método para a determinação da mistura de cálcio e magnésio, pelo uso EDTA \"tetraneutralizado\" e separação prévia dos dois cátions através da adição de oxalato. A detecção do ponto final nestas titulações com EDTA \"tetraneutralizado\" pode também ser feita visualmente com fenolftaleína. O efeito de volume em titulações potenciométricas em geral, num certo nível de concentração, foi objeto de análises diversas inclusive por cálculo computacional de curvas derivativas. Comprovou-se que quanto menor o volume do titulado maior é o salto potenciométrico obtido, caracterizando-se o que se denominou de \"paradoxo potenciométrico\", pois uma menor massa de substância pode ser titulada com, teoricamente, o mesmo erro relativo que para uma massa maior de substância.
Alternative method for the complexometric determination of magnesium. Influence of volume on potentiometric titrations. Keywords: Potentiometry, Magnesium, EDTA. Present paper has been found the negative effect of oxalate, used to the previous separation of calcium and magnesium in a complexometric determination of this last with EDTA in waters, using at visual titration Eriochrome black T as indicator and at potentiometric titration the indicator system Hg/Hg-EDTA. It has been found, also, the viability in the use as titrant a \"tetraneutralized\" EDTA solution, in potentiometric titration with measurements of pH with the glass electrode. In this case the end point is obtained on basis of hydrolysis of Y4- species, after the equivalent point. So it has been displayed the viability of a new method to the determination of the mixture calcium and magnesium by the use of \"tetraneutralized\" EDTA and previous separation of both cations by addition of oxalate. The end point detection can be visually found, in these titrations with \"tetraneutralized\" EDTA, by using of phenolphthalein. The effect of volume in potentiometric titration in general, at a defined concentration level, was subject of several analysis incluse using the compute calculation of derivative curves. It has been found that as smaller volume of titrated performes a higher potentiometric jump, this effect was called for us \"potentiometric paradox\", since an smaller weight of substance can be titrated, with theoretically, the same relative error that to a greater weight of substance.

Разработана методика определения степени дехлорирования пестицидов в почве и воде. Она заключается в том, что после инкубирования образцов с пестицидом сравнивают содержание хлор-ионов в опыте и контроле. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/19010

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016.
Boron concentration analysis is an important and critical analysis performed by the Analytical Chemistry Laboratory at Koeberg Nuclear Power Station (KNPS), because boron controls reactivity and the concentration determination is a Technical Specification Parameter (safety parameter). Hence accurate, precise results for boron concentration produced by laboratories and on-line analysers are important because of their operational implications associated with reactivity control and also for nuclear safety. The project focused on comparing the quality of chemical analysis results of boron produced by analysis techniques/ methods used at Koeberg Nuclear Power Station namely; Potentiometric Titration, Atomic Absorption Spectrophotometry (Flame) and UV-VIS Azomethine-H method. The methods were described, optimised, evaluated and compared in terms of uncertainty of measurement, accuracy, precision, analysis range, limitations, appropriateness and applicability for boron analysis in 2500 mg B/kg concentration range. For Potentiometric Titration method, the measurement uncertainty = 2500 ±16 mg B/kg, accuracy= 0.2%, precision= 0.08% the range of analysis= 5-800 mg B/kg. For Atomic Absorption Spectrophotometry (Flame) the measurement uncertainty= 2500 ±51 mg B/kg, accuracy= 0.12%, precision= 0.44% the range of analysis= 0 -500 mg B/kg. For UV-VIS Azomethine-H the measurement uncertainty= 2500 ±72 mg B/kg, accuracy= 0.08%, precision= 0.44% the range of analysis= 0 -10 mg B/kg. The INPOs 95% accuracy and precision criteria for boron is ± 1%. So these techniques could be used for boron analysis in PWR. Based on the evaluation and assessments mentioned above; the Potentiometric Titration was found to be the most preferred method for boron analysis for Pressurised Water Reactors followed by Atomic Absorption Spectrophotometry (Flame) that can be of good use in determining boron especially in waste samples and samples with complex matrices. The UV-VIS Azomethine-H methods can only be used when it is really necessary to determine very low levels of boron between 0- 10mg B/kg of which it was never required before. Since it is specifically the B-10 isotope that is responsible for the ability to control reactivity, the implementation of isotopic boron analysis (by Inductively Coupled Plasma – Mass Spectrometry) at KNPS is explained and the advantage of the programme is illustrated. Although the current state of instrumental capabilities is adequate for 10B isotope determination, further work of optimising the methodology for even better results is recommended.

O presente estudo procura dar continuidade a um dos ramos de pesquisa desenvolvidos na área de Analítica do Instituto de Química da USP, onde se procura estudar a química de complexos formados entre diferentes metais e o ânion azoteto, N-3. O cátion índio(III), à semelhança do que ocorre com o ferro (III), complexa com o ânion azoteto em meio aquoso. Este poder de complexação foi constatado em estudos polarográficos do sistema In N3+ / N-3 ora em desenvolvimento. A obtenção das constantes de estabilidade dos complexos formados entre o In3+ e o ligante azoteto, por via potenciométrica, baseia-se na alteração do pH do tampão formado por N-3 e o ácido fraco HN3, quando se adicionam íons In3+. O acompanhamento da variação da concentração hidrogeniônica foi f.eito com o auxílio do eletrodo de vidro combinado. A concentração de N-3 de equilíbrio variou de valores próximos de zero a 90 mM, para que se obtivessem dados na mais larga faixa de concentraç6es de ligante. Manteve-se a força iônica das soluções em 2,00OM (NaCI04) e trabalhou-se a 25,0οC. A análise dos dados experimentais e tratamento matemático dos mesmos, evidenciaram a formação de complexos mononucleares e os valores das constantes globais encontrados foram: β1 = (2,0 ± 0,1) x 103M-1 β2 = (7 ± 3) x 105M-2 β3 = (5 ± 1) x 107M-3 β4 = (7 ± 3) x 108M-4
The present study is a branch of the main work concerned with the complex formation between several metal cations and azide anion in aqueous media. Indium (III) was selected, in analogy to iron (III), because forms complexes with azide in aqueous media. Polarographic studies in development showed the tendency of these complexation. To determine the stability constants of complexes was used potentiometric method using glass e1ectrode. The main advantage is based on pH modification of the buffer solution constituted by azide and hidrazoic acid (N-3;/HN3) when indium (III) cations are added in the buffer. The azide concentration was a1tered from near zero to 90 mM, the ionic strenght he1d at 2,000 M with sodium perchlorate and the temperature kept constant at 25,0°C. The evaluation of experimental data shawed mononuclear species and the global constants found were: β1 = (2,0 ± 0,1) x 103M-1 β2 = (7 ± 3) x 105M-2 β3 = (5 ± 1) x 107M-3 β4 = (7 ± 3) x 108M-4

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In this paper, we propose the determination of lansoprazole content, selective inhibitor of H + / K + -ATPase gastric using titration based on digital image (Digital Image-Based Titration). The DIB system uses a webcam to acquisition of digital images based on the color system RGB (Red-Green-Blue). During the titration procedure the method was applied to the acid-base titration of the drug lansoprazole with hydrochloric acid. The titration was performed by the DIB, and by potentiometry. In DIB methodology for each volume of titrant added an image was captured and manipulated to obtaining the standard values (N=√R̅2+G̅2+B̅2). The spent volume of titrant to reach the equivalence point was obtained from the second derivative of the titration curve. The results of the samples showed no statistically significant differences at the 95% confidence level was observed after applying the paired t test (tcalculado = 0,439 e tcrítico = 2,353). The relative standard deviations using the DIB methodology with the exception of Sample C, was below 1.0%.
Neste trabalho, propõe-se a determinação do teor de lansoprazol, agente inibidor seletivo da H+/K+-ATPase gástrica, utilizando titulação baseada em imagem digital (Digital Image-Based Titration). O sistema DIB utiliza uma webcam para aquisição das imagens digitais com base no sistema de cor RGB (Red-Green-Blue). Durante o procedimento de titulação o método foi aplicado na titulação ácido-base do fármaco lansoprazol com o ácido clorídrico. A titulação foi realizada por DIB e por potenciometria. Na metodologia DIB para cada volume do titulante adicionado uma imagem era capturada e manipulada para obtenção dos valores da norma (N=√R̅2+G̅2+B̅2). O volume gasto de titulante para atingir o ponto de equivalência, foi obtido a partir da segunda derivada da curva de titulação. Os resultados obtidos das amostras não apresentaram nenhuma diferença estatística significativa no nível de confiança de 95 % que foi verificada após aplicar o teste t emparelhado (tcalculado = 0,439 e tcrítico = 2,353). Os desvios padrão relativos utilizando a metodologia DIB, com exceção da amostra C, ficaram abaixo de 1,0 %.

The aim of this thesis is the development of solid contact ion selective electrodes, ISEs, where the transducer layer is made of a network of carbon nanotubes.

Potentiometric classical ion selective electrodes (ISEs) have been used for analytical applications since the beginning of 1900's. Determination of pH by a glass membrane ion selective electrode emerged at the beginning, being the first ISEs developed. pH glass electrode is still one the most useful and robust sensors for routine measurements both in laboratories and industries.

Throughout the years, new technologies, ideas and designs have been developed and incorporated successfully in the potentiometric fields so as to provide answers to the new society's needs. Therefore, the ion selective electrodes developed in this thesis are a step further in the progress of ISEs and must be considered as products of the scientific envisioning, growth, and interdisciplinary cooperation of many research teams over many years of continuous efforts.

The sensing part can be regarded nowadays as well developed, although it has been during only the last few years when considerable improvements have taken place in the development of new polymeric membranes, ionophores and lipophilic ions. Moreover, the understanding of the theoretical sensing mechanism has been a powerful solid backbone in the rise of ISEs.

Miniaturization of classical ISEs requires making all solid contact electrodes to avoid the intrinsic drawbacks of the inner solution. In this manner, the transduction layer has been the focus of attention for the two last decades. New solid contact transducers having the capacity to convert an ionic current into an electronic current have been emerging. Within them, conducting polymers have played an important role in the transduction of the potentiometric signal, being the most used in solid contact ion selective electrodes (SC-ISEs) up to now. However, the behaviour of conducting polymers can be further improved. For instance, their sensitivity to light one of main operational issues yet to be solved.

In the present context of searching for new materials able to transduce potentiometric signals we selected and tested carbon nanotubes (CNTs). CNTs, which were rediscovered by Ijima in 1991, display excellent electronic properties in terms of signal transduction. In addition, due to their chemical reactivity CNTs can be easily functionalized with receptors or other functional groups. In fact, depending on the type of functionalization the macroscopic and microscopic properties of CNTs can be drastically changed. This nanostructured material had not been used previously as a solid contact material in ISEs.

The main aim of this thesis is to demonstrate that CNTs can act as a clean and efficient transducer in SC-ISEs overcoming the drawbacks displayed by the previously assayed solid contact materials. The developed electrodes were used in different conditions to determine several ions in different sample types, demonstrating the capabilities of this nanostructured material.
The thesis has been structured in different chapters, each one containing the following information:

· Chapter 1 provides a short historical overview of potentiometric ISEs. The evolution from the "classical ISEs" to the SC-ISEs is briefly illustrated. Once the motivation for thesis is described, the general and specific objectives of the thesis are reported.
· Chapter 2 reports the scientific foundations of the developed electrodes. All components of the ISE, sensing layer, transducers and detection systems are introduced. Analytical performance characteristics of ISEs are also described.
· Chapter 3 corresponds to the experimental part. Reagents, protocols, procedures and instruments used in the thesis are reported.
· Chapter 4 provides the demonstration that CNTs can act as a transducer layer in SC-ISEs. The first SC-ISEs based on CNTs are characterized by electrochemical and optical techniques.
· Chapter 5 contains the experimental results that lead to the elucidation of the possible transduction mechanism of CNTs in SC-ISEs. Electrochemical impedance spectroscopy (EIS) is employed as the main characterization technique.
· Chapter 6 is composed of four sections reporting different analytical applications. In the first section, the common pH electrode is developed using a solid contact technology based on CNTs. In the second section, the development of SC-ISEs based on a new synthetic ionophore selective to choline, and CNTs as transducers is shown. In the third section, watertight and pressure-resistant SC-ISEs based on CNTs are developed and tested in aquatic research to obtain information about the gradient profiles along the depth of the lakes. In the fourth section, SC-ISEs based on CNTs are adapted for the on-line control of a denitrification catalytic process.
· Chapter 7 reports the possibilities of miniaturization of the SC-ISEs based on CNTs to reach a nanometric electrode. Potentiometric and optical characterizations are described in this section. Moreover, a discussion about the limitations of the real miniaturization in potentiometry is undertaken.
· Chapter 8 points out the conclusions of the thesis. In addition, future prospects are suggested.
· Finally, several appendices are added to complete the doctoral thesis.
El principal objetivo de esta tesis es el desarrollo de electrodos selectivos de iones de contacto sólido, ESIs-CS, utilizando como capa transductora una red compuesta de nanotubos de carbono.

Los electrodos potenciométricos selectivos de iones han sido utilizados en aplicaciones analíticas desde comienzos de 1900. La determinación de pH mediante electrodos de vidrio selectivo de iones fue el primer ESI desarrollado. Hoy en día, el electrodo de vidrio para la determinación de pH es todavía uno de los más útiles y robustos sensores utilizados en mediciones rutinarias tanto en laboratorios como en industrias.

A lo largo de los años, nuevas tecnologías, ideas y diseños han sido desarrollados e incorporados satisfactoriamente en el campo potenciométrico proporcionando soluciones a las necesidades en continua evolución de la sociedad. De esta manera, los electrodos selectivos de iones desarrollados en esta tesis son un paso más en el progreso de los ESIs y deben ser considerados como el producto de una sólida base científica, del crecimiento y de la cooperación interdisciplinaria de diversos grupos de investigación durante varios años.

La parte del sensor donde tiene lugar el reconocimiento químico y donde se genera el potencial dependiente de la muestra en estudio en los ESIs se puede considerar, en estos días, ampliamente desarrollada, aunque considerables mejoras han tenido lugar durante los últimos años, especialmente en el desarrollo de nuevas membranas poliméricas, ionóforos e iones lipofílicos. Sobretodo, el estudio y la comprensión del mecanismo teórico del sensor ha sido muy importante en el crecimiento y desarrollo de los ESIs.

El concepto de electrodos selectivos de iones de estado sólido surge como requisito vital para evitar las intrínsecas desventajas de la solución interna, en el proceso de miniaturización de los ESIs clásicos. De esta forma, la capa transductora ha sido el principal punto de atención durante dos décadas. Así, nuevos transductores de contacto sólido con la capacidad de convertir una corriente iónica en una corriente electrónica han sido desarrollados. Entre ellos, los polímeros conductores han jugado un importante papel en la transducción de la señal potenciométrica, siendo éstos los más empleados en los electrodos selectivos de iones de contacto sólido (ESIs-CS). Sin embargo el comportamiento de los polímeros conductores puede ser mejorado. Por ejemplo, la sensibilidad hacia la luz de estos materiales es un inconveniente todavía no resuelto.

En este contexto de investigación de nuevos materiales capaces de actuar como transductor de una señal potenciométrica, se han escogido y estudiado los nanotubos de carbono (NTCs) como transductores. Los NTCs fueros redescubiertos por Ijima en 1991, y muestran excelentes propiedades electrónicas en términos de traducción de señal. Además, debido a su reactividad química, los NTCs pueden ser fácilmente funcionalizados con receptores u otros grupos funcionales. De hecho, sus propiedades macroscópicas y microscópicas pueden ser afectadas drásticamente dependiendo del tipo y grado de funcionalización. Este material nanoestructurado no había sido previamente utilizado como transductor en ISEs.

El principal propósito de esta tesis es demostrar que los nanotubos de carbono pueden actuar de forma eficiente como transductor en electrodos selectivos de iones de estado sólido logrando vencer las desventajas de los transductores previamente mencionados. Los electrodos desarrollados fueron usados en diferentes condiciones para determinar distintos iones en diversos tipos de sistemas, demostrando las extraordinarias capacidades de este material nanoestructurado.


Esta tesis ha sido estructurada en capítulos que contienen la siguiente información:

· El Capítulo 1 proporciona una breve visión histórica de lo electrodos potenciométricos selectivos de iones. Se ilustra la evolución desde los "clásicos ESIs" hasta los actuales "ESIs-CS". Además se señalan en esta sección los objetivos generales y específicos.
· El Capitulo 2 contiene las bases científicas de los electrodos desarrollados. Se introducen todos los componentes que integran un ESI, tales como: capa reconocedora, capa transductora y sistema de detección. A continuación se describen los parámetros analíticos de calidad de los ESIs.

· El Capitulo 3 describe la parte experimental. Se recogen los reactivos, protocolos, procedimientos e instrumentos usados a lo largo de la tesis.
· El Capitulo 4 provee de la demostración de que los NTCs pueden actuar eficientemente como capa transductora en SC-ISEs. Se caracteriza el primer ESI-CS integrado por NTCs mediante técnicas ópticas y electroquímicas.
· El Capitulo 5 contiene los resultados experimentales que permiten la posible elucidación del mecanismo de transducción de los NTCs en los ESIs-CS. La Espectroscopia de Impedancia Electroquímica (ESI) es utilizada como la principal técnica de caracterización.
· El Capitulo 6 está integrado por cuatro secciones con diferentes aplicaciones analíticas. En la primera sección, se desarrolla un electrodo de pH que usa NTCs como nueva tecnología transductora en ESIs-CS. En la segunda sección se muestra el desarrollo de un ESI-CS integrado por un ionóforo sintético selectivo a colina, y NTCs como transductores. En la tercera sección, ESIs-CS basados en NTCs, resistentes a altas presiones y totalmente herméticos, se desarrollan y prueban en investigaciones acuáticas con la finalidad de obtener información sobre los gradientes de concentración de iones en función de la profundidad de un lago. En la cuarta sección ESIs-CS basados en NTCs se adaptan para el control on-line de un proceso catalítico de desnitrificación.
· El Capitulo 7 presenta la posibilidad de la miniaturización de los ESIs-CS basados en NTCs logrando obtener un electrodo nanométrico. Se muestran en esta sección la caracterización óptica y potentiométrica. Además, se discuten las limitaciones de la miniaturización real de los ESIs en potenciometría.
· El Capitulo 8 contiene las conclusiones de la tesis. Adicionalmente, se sugieren las perspectivas futuras del trabajo presentado.
· Finalmente, se añaden algunos apéndices como complemento de la tesis doctoral.

The importance of porous materials has risen substantially in the last few decades due to their ability to reduce the size and cost of bioanalytical devices and fuel cells. First, this work aims to describe the fabrication of nanoporous gold (NPG) electrodes that are resistant to electrode passivation due to fibrinogen biofouling in redox solutions. The effect on potentiometric and voltammetric experiments was seen as a deviation from ideal behavior on planar gold electrodes, whereas NPG electrodes were consistently behaving in a Nernstian fashion at low concentrations of ferri-ferrocyanide (£100 mM). An improvement in electrode behavior on NPG electrodes versus planar gold was seen in solutions containing ascorbic acid as well as blood plasma. Second, cost effective NPG electrodes were fabricated using a glass substrate to test the response in the presence of a variety of redox molecules. The optical transparency of these electrodes allowed for microdroplet measurements to be made using an inverted microscope in several redox solutions for validation and subsequent biological applicability. Nernstian behavior was demonstrated for all one- and two-electron transfer systems in both poised and unpoised solutions. All experiments were conducted using volumes between 280 and 1400 pL producing rapid results in less than one minute. Third, in order to decrease the requirement for complex instrumentation, microdroplet fabrication technique was used to create mini-nanoporous gold (mNPG) electrodes on glass capillary tubes. The cylindrical shape of the electrodes allowed for testing in sample volumes of 100 mL. The response to ferri-ferrocyanide, ascorbic acid, cysteine, and uric acid was then investigated with Nernstian behavior shown. However, the mNPG electrodes were insensitive to glucose and hydrogen peroxide. In order to increase the sensitivity of the electrodes, a minimal amount of platinum was electrodeposited onto the NPG surface using a low concentration of platinum salt (0.75 mM) for a short deposition time (2 seconds) producing a Nernstian response to both glucose and hydrogen peroxide. Lastly, to test the viability of crossover applications, the platinum incorporated NPG electrode was employed as a fuel cell anode material, testing their oxidation capability with methanol, ethanol, and formic acid.

A construção de sensor potenciométrico, utilizando Nióbio acoplado a eletrodo de referência de prata/cloreto de prata num mesmo instrumento, possibilita o acompanhamento da variação de potencial que ocorre durante uma reação ácido-base em meio aquoso. Foi utilizado eletrodo de vidro combinado, cuja membrana de vidro foi danificada fisicamente, porém com sua referência interna em pleno funcionamento. O eletrodo de Nióbio foi confeccionado com metal polido ou então com a superfície modificada com óxido eletrodepositado. O crescimento de óxido sobre o Nióbio foi obtido por eletrólise em meio a H3PO4 diluído. O metal ou o par metal/óxido foi fixado no eletrodo de vidro contendo uma solução eletrolítica. O eletrodo de Nióbio não apresenta boa sensibilidade quando utilizado como indicador em potenciometria direta, mas é sensível às variações de potenciais que ocorrem em titulações ácido-base. O eletrodo de Nióbio metálico pode substituir o eletrodo de vidro combinado na determinação do teor de acidez de vinagres.
The construction of potentiometric sensors, using Niobium combined with the reference electrode silver / silver chloride in a single instrument, allows the variation of potential monitoring that occurs during an acid-base reaction in aqueous media. It was used a combined electrode glass, whose glass membrane was damaged physically, but with the internal reference in full operation. The Niobium electrode was made with polished metal or with the surface modified by electrodeposited oxide. The oxide growth was obtained by electrolysis in the H3PO4 diluted media. The metal or metal/oxide was fixed in glass electrode containing a electrolyte solution. The Niobium electrode doesn\'t show sensitivity when used as an indicator in direct potentiometry, but is sensitive to changes of potential that occur in acid-base titrations. The electrode of Niobium metal can replace the glass electrode combined in determining the level of acidity of vinegar.

La gran demanda de información en tiempo real, in situ y de calidad, para llevar a cabo el control y la monitorización de múltiples parámetros (bio)químicos en ámbitos como el aeroespacial, medioambiental, industrial, alimentario o biomédico, ha fomentado en los últimos años el desarrollo de instrumentación analítica con un alto nivel de integración, miniaturización y automatización. De esta manera, han aparecido los denominados microsistemas de análisis total (µTAS) o Lab-on-a-Chip (LOC). Así, el trabajo realizado en esta tesis tiene como objetivo principal el desarrollo de microanalizadores automatizados, usando las tecnologías LTCC y de polímeros, para la determinación, mediante medidas potenciométricas y ópticas, de diversos parámetros químicos, en aplicaciones seleccionadas, donde la miniaturización es condición indispensable para poder abordar el problema. Para ello, se han diseñado, construido y evaluado microsistemas donde se han integrado diferentes operaciones unitarias del procedimiento analítico, imprescindibles para la realización de este. Así, en primer lugar se presentan tres dispositivos analíticos desarrollados en el marco de dos proyectos financiados por la Agencia Espacial Europea (ESA) con el objetivo de desarrollar analizadores para monitorizar el proceso de reciclado de agua, y la calidad de esta, en misiones espaciales tripuladas de larga duración. El primero de ellos es un microanalizador potenciométrico robusto, basado en la tecnología LTCC, para monitorizar simultáneamente la presencia de iones potasio y nitrato usando la técnica FIA. El microdispositivo integra, monolíticamente, la microfluídica y el sistema de detección, basado en dos ESIs de membrana polimérica, uno para potasio y otro para nitrato, y un electrodo de referencia de Ag/AgCl serigrafiado. El segundo de ellos, mejora las prestaciones del primero y consiste en un microanalizador, fabricado en COC, para la monitorización simultánea de iones potasio, cloruro y nitrato. Este nuevo dispositivo minimiza la interferencia de cloruro sobre el electrodo de nitrato y miniaturiza y automatiza el sistema de gestión de fluidos incorporando microbombas y microválvulas. El último de ellos es un microanalizador potenciométrico robusto y altamente selectivo fabricado en COC para la determinación de ión amonio. Este integra la microfluídica, un módulo de difusión gaseosa y el sistema de detección en un único sustrato monolítico. El módulo de difusión gaseosa lo compone una membrana hidrófoba de PVDF y el sistema de detección potenciométrico está formado por un electrodo selectivo de ión amonio de membrana polimérica y un electrodo de referencia de Ag/AgCl serigrafiado. También se ha aplicado este último dispositivo al análisis de amonio en muestras acuosas de diversa procedencia (agua de red de distribución y aguas residuales de EDARs, tanto urbanas como industriales) y en muestras de sangre y plasma de pacientes diagnosticados de desordenes en el ciclo de la urea. Otro de los microsistemas analíticos desarrollados, fabricado en COC, incorpora una etapa de difusión gaseosa para la determinación espectrofotométrica de CO2 utilizando un indicador ácido-base colorimétrico. El tamaño reducido del microsistema analítico, unido al tamaño reducido y a la simplicidad del sistema de detección, dotan al equipo global de una gran portabilidad. Se ha aplicado al análisis de CO2 en vino y cervezas y para la monitorización de la acidificación oceánica. Por último, se ha desarrollado un microsistema analítico autónomo y automatizado para la determinación espectrofotométrica de fosfato en aguas residuales. El microanalizador, fabricado en COC, integra un sistema de detección óptica miniaturizado y un sistema de gestión de fluidos automático que le dota de portabilidad y capacidad de funcionamiento autónomo. Todos los microsistemas desarrollados han mostrado unas características analíticas excelentes, cumpliendo los requisitos de las aplicaciones para las que fueron diseñados y demostrando la potencialidad de la miniaturización en los sistemas analíticos.
The high demand for real-time, on-site and quality information to monitor multiple (bio)chemical parameters in areas such as aerospace, environmental, industrial, food or biomedical has promoted the development of an analytical instrumentation with a high level of integration, miniaturization and automation. In this way, the so-called total analysis microsystems (μTAS) or Lab-on-a-Chip (LOC) have appeared. Thus, the main objective of this thesis is the development of automated microanalyzers, using LTCC and polymer technologies, for the determination, using potentiometric and optical measurements, of different chemical parameters in selected applications, where miniaturization is a must to address the problem. For this purpose, different analytical microsystems have been designed, constructed and evaluated where different essential unit operations to carry out the analytical procedure have been integrated. First of all, three analytical devices have been developed in the framework of two projects funded by the European Space Agency (ESA) with the aim of developing analyzers to monitor the water recycling process and its quality in long-term manned space missions. The first one is a robust potentiometric microanalyzer, based on LTCC technology, to simultaneously monitor the presence of potassium and nitrate ions using the FIA ​​technique. The microdevice monolithically integrates the microfluidics and the detection system, based on two ISEs, one for potassium and the other one for nitrate, and a screen-printed Ag/AgCl reference electrode. The second one improves the performance of the first device and consists of a microanalyzer, made of COC, for the simultaneous monitoring of potassium, chloride and nitrate ions. This new device minimizes the chloride interference on the nitrate electrode and miniaturizes and automates the fluid management system incorporating micropumps and microvalves. The last one is a robust and highly selective potentiometric microanalyzer fabricated in COC for the determination of ammonium ion. It integrates the microfluidics, a gas-diffusion module and the detection system into a single monolithic substrate. The gas-diffusion module is composed of a hydrophobic PVDF membrane and the potentiometric detection system consists of an ammonium ion selective electrode and a screen-printed Ag/AgCl reference electrode. The latter device has also been applied to the analysis of ammonia in aqueous samples of diverse origin (drinking water and wastewater from WWTPs, both urban and industrial) and in blood and plasma samples of patients diagnosed with disorders in the urea cycle. Another developed analytical microsystem, made of COC, incorporates a gas-diffusion step for the spectrophotometric determination of CO2 using a colorimetric acid-base indicator. The small size of the device, coupled with the reduced size and simplicity of the detection system, give a high portability to the overall system. It has been applied to CO2 analysis in wine and beers and for the monitoring of ocean acidification. Finally, an autonomous and automated analytical microsystem has been developed for spectrophotometric determination of phosphate in wastewater. The microanalyzer, made of COC, integrates a miniaturized optical detection system and an automatic fluid management system that give it portability and autonomous operation capacity. All microsystems developed have shown excellent analytical features, fulfilling the requirements of the applications for which they were designed and demonstrating the potential of miniaturization in analytical systems.

Dentre as formas alotrópicas do carbono, o grafeno merece destaque. Este material consiste de uma monocamada atômica de carbono sp2 disposta em uma rede bidimensional cristalina hexagonal tipo favo de mel. Uma das formas de se obter o grafeno é pela esfoliação química, que consiste da oxigenação do grafite policristalino em um ambiente altamente oxigenado, formando um produto intermediário chamado de grafeno oxidado (GO). Por este método, gera-se um produto altamente estável e solúvel em água, podendo ser utilizado na construção de filmes ultrafinos. Uma das aplicações possíveis do grafeno oxidado é em sensores e biossensores, área de aplicações de novos materiais que viabilizem o diagnostico rápido, preciso, seletivo e de baixo custo, principalmente os do tipo, point-of-care. O grafeno é um forte candidato, nessa área, devido a sua alta performace e seu baixo custo de processamento. Neste trabalho, a técnica de automontagem eletrostatic layer-by-layer (ELBL) foi utilizada na construção de filmes de grafeno oxidado, juntamente com o policátion dendritico poli(amido amina) geração 4 (PAMAM-G4) em uma plataforma potenciométrica, utilizando um amplificador de instrumentação comercial AD620 como transdutor em um sensor de pH para caracterização da sensibilidade do dispositivo. Diversas técnicas espectroscópicas, óticas e morfológicas foram utilizadas para caracterizar a esfoliação química do grafite e dos filmes automontados. Através destas caracterizações mostrou-se que a esfoliação ocorreu satisfatoriamente concordando com resultados já existentes na literatura. A construção dos filmes ultrafinos ocorreu pela rápida adsorção do GO em camadas alternadas de PAMAM-G4, e o monitoramento do crescimento dos filmes foi realizado utilizando espectroscopia no UV-Vis, onde o crescimento é linear a partir da décima camada. Por microscopia de força atômica, mostrou-se que a adsorção das folhas de grafeno se dá primeiramente pelas folhas de menor número de camada (1 e 2 camadas) de GO e para camadas de número superior tem-se uma morfologia totalmente diferente da primeira. Por espectroscopia no infravermelho, mostrou-se a interação entre os dois polieletrólitos, onde há formação de ligações do tipo cross-linking entre as camadas. Medidas de potenciometria indicam a sensibilidade máxima em torno de 57 mV/pH em um substrato de ouro( sensibilidade Nerstiana), o que evidencia a sua aplicabilidade em sensoriamento e também a sua aplicação em biossensores.
Among the allotropic forms of carbon, graphene deserves special attention. This material consists of one atomic monolayer of sp2 carbon arranged in a two-dimensional hexagonal lattice type, namely \"honeycomb\". One common method to obtain graphene is -=by chemical exfoliation, which consists of oxygenation of polycrystalline graphite in a highly oxygenated medium, forming an intermediate product namely graphene oxide (GO). This method generates a highly stable and water soluble GO that can be used in the fabrication of ultrathin films. Graphene is a strong candidate for sensing, due to its high performance and low cost processing. In this dissertation, GO was obtained via chemical routs and processed in the form of ultrathin films in conjunction with polyamidoamine dendrimer (PAMAM G4) in a layered fashion using the Electrostatic Layer-by-Layer (ELBL). The GO/PAMAM films were deposited on potentiometric platforms and used as pH sensors using a commercial amplifier AD620 instrumentation as the detection technique. GO and the LbL films were characterized via spectroscopic, optical and morphological techniques. Film growth was monitored via UV-Vis spectroscopy and revealed a linear adsorption up to the tenth GO/PAMAM bilayer. AFM analyses revealed that graphene sheets containing 1 or 2 layers occurred adsorbed first on the substrates. Potentiometric measurements indicated a maximum sensitivity of ca. 57 mV/pH for GO/PAMAM films deposited on gold substrates (Nernstian Sensitivity), which demonstrates the applicability of the films in sensing and biosensing.