Ion selective electrodes for determination of low and ultra low concentrations of lead (II) in natural waters

Att övervaka förekomsten av giftiga komponenter i naturliga vattendrag är nödvändigt för människans välmående. Eftersom halten av föroreningar i naturens ekosystem bör hållas möjligast låg, pågår en ständig jakt efter kemiska analysmetoder med allt lägre detektionsgränser. I dagens läge görs miljöanalyser med dyr och sofistikerad instrumentering som kräver mycket underhåll. Jonselektiva elektroder har flera goda egenskaper som t.ex. bärbarhet, låg energiförbrukning, och dessutom är de relativt kostnadseffektiva. Att använda jonselektiva elektroder vid miljöanalyser är möjligt om deras känslighetsområde kan utvidgas genom att sänka deras detektionsgränser. För att sänka detektionsgränsen för Pb(II)-selektiva elektroder undersöktes olika typer av jonselektiva membran som baserades på polyakrylat-kopolymerer, PVC och PbS/Ag2S. Fast-fas elektroder med membran av PbS/Ag2S är i allmänhet enklare och mer robusta än konventionella elektroder vid spårämnesanalys av joniska föroreningar. Fast-fas elektrodernas detektionsgräns sänktes i detta arbete med en nyutvecklad galvanostatisk polariseringsmetod och de kunde sedan framgångsrikt användas för kvantitativa bestämningar av bly(II)-halter i miljöprov som hade samlats in i den finska skärgården nära tidigare industriområden. Analysresultaten som erhölls med jonselektiva elektroder bekräftades med andra analytiska metoder. Att sänka detektionsgränsen m.hj.a. den nyutvecklade polariseringsmetoden möjliggör bestämning av låga och ultra-låga blyhalter som inte kunde nås med klassisk potentiometri. Den verkliga fördelen med att använda dessa blyselektiva elektroder är möjligheten att utföra mätningar i obehandlade miljöprov trots närvaron av fasta partiklar vilket inte är möjligt att göra med andra analysmetoder. Jag väntar mig att den nyutvecklade polariseringsmetoden kommer att sätta en trend i spårämnesanalys med jonselektiva elektroder.

Carbon Nanotubes as Material for Supercapacitor Electrodes

Electrochemical double-layer supercapacitors have an intermediate position between rechargeable batteries, which can store high amounts of energy, and dielectric capacitors, which have high output power. Supercapacitors are widely suggested to be used in automobiles (recuperation during braking, facilitate engine starting, electric stabilization of the system), industry (forklifts, elevators), hybrid off-road machinery and also in consumer electronics. Supercapacitor electrodes require highly porous material. Typically, activated carbon is used. Specific surface area of activated carbon is approximately 1000 m2 per gram. Carbon nanotubes represent one of prospective materials. According to numerous studies this material allows to improve the properties of supercapacitors. The task of this Master‘s Thesis was to test multiwalled carbon nanotubes and become confident with the testing methods.

Solid-state reference and ion-selective electrodes : towards portable potentiometric sensing

Potentiometric sensors are very attractive tools for chemical analysis because of their simplicity, low power consumption and low cost. They are extensively used in clinical diagnostics and in environmental monitoring. Modern applications of both fields require improvements in the conventional construction and in the performance of the potentiometric sensors, as the trends are towards portable, on-site diagnostics and autonomous sensing in remote locations. The aim of this PhD work was to improve some of the sensor properties that currently hamper the implementation of the potentiometric sensors in modern applications. The first part of the work was concentrated on the development of a solid-state reference electrode (RE) compatible with already existing solid-contact ion-selective electrodes (ISE), both of which are needed for all-solid-state potentiometric sensing systems. A poly(vinyl chloride) membrane doped with a moderately lipophilic salt, tetrabutylammonium-tetrabutylborate (TBA-TBB), was found to show a satisfactory stability of potential in sample solutions with different concentrations. Its response time was nevertheless slow, as it required several minutes to reach the equilibrium. The TBA-TBB membrane RE worked well together with solid-state ISEs in several different situations and on different substrates enabling a miniature design. Solid contacts (SC) that mediate the ion-to-electron transduction are crucial components of well-functioning potentiometric sensors. This transduction process converting the ionic conduction of an ion-selective membrane to the electronic conduction in the circuit was studied with the help of electrochemical impedance spectroscopy (EIS). The solid contacts studied were (i) the conducting polymer (CP) poly(3,4-ethylienedioxythiophene) (PEDOT) and (ii) a carbon cloth having a high surface area. The PEDOT films were doped with a large immobile anion poly(styrene sulfonate) (PSS-) or with a small mobile anion Cl-. As could be expected, the studied PEDOT solid-contact mediated the ion-toelectron transduction more efficiently than the bare glassy carbon substrate, onto which they were electropolymerized, while the impedance of the PEDOT films depended on the mobility of the doping ion and on the ions in the electrolyte. The carbon cloth was found to be an even more effective ion-to-electron transducer than the PEDOT films and it also proved to work as a combined electrical conductor and solid contact when covered with an ion-selective membrane or with a TBA-TBB-based reference membrane. The last part of the work was focused on improving the reproducibility and the potential stability of the SC-ISEs, a problem that culminates to the stability of the standard potential E°. It was proven that the E° of a SC-ISE with a conducting polymer as a solid contact could be adjusted by reducing or oxidizing the CP solid contact by applying current pulses or a potential to it, as the redox state of the CP solid-contact influences the overall potential of the ISE. The slope and thus the analytical performance of the SC-ISEs were retained despite the adjustment of the E°. The shortcircuiting of the SC-ISE with a conventional large-capacitance RE was found to be a feasible instrument-free method to control the E°. With this method, the driving force for the oxidation/reduction of the CP was the potential difference between the RE and the SC-ISE, and the position of the adjusted potential could be controlled by choosing a suitable concentration for the short-circuiting electrolyte. The piece-to-piece reproducibility of the adjusted potential was promising, and the day-today reproducibility for a specific sensor was excellent. The instrumentfree approach to control the E° is very attractive considering practical applications.

Ultrasound-assisted electrochemical treatment of wastewaters containing organic pollutants by using novel Ti/Ta2O5-SnO2 electrodes

Advanced oxidation processes (AOPs) are modern methods using reactive hydroxyl radicals for the mineralization of organic pollutants into simple inorganic compounds, such as CO2 and H2O. Among AOPs electrochemical oxidation (EO) is a method suitable for coloured and turbid wastewaters. The degradation of pollutants occurs on electrocatalytic electrodes. The majority of electrodes contain in their structure either expensive materials (diamond and Pt-group metals) or are toxic for the environment compounds (Sb or Pb). One of the main disadvantages of electrochemical method is the polarization and contamination of electrodes due to the deposition of reaction products on their surface, which results in diminishing of the process efficiency. Ultrasound combined with the electrochemical degradation process eliminates electrode contamination because of the continuous mechanical cleaning effect produced by the formation and collapse of acoustic cavitation bubbles near to the electrode surface. Moreover, high frequency ultrasound generates hydroxyl radicals at water sonolysis. Ultrasound-assisted EO is a non-selective method for oxidation of different organic compounds with high degradation efficiencies. The aim of this research was to develop novel sustainable and cost-effective electrodes working as electrocatalysts and test their activity in electrocatalytic oxidation of organic compounds such as dyes and organic acids. Moreover, the goal of the research was to enhance the efficiency of electrocatalytic degradation processes by assisting it with ultrasound in order to eliminate the main drawbacks of a single electrochemical oxidation such as electrodes polarization and passivation. Novel Ti/Ta2O5-SnO2 electrodes were developed and found to be electrocatalytically active towards water (with 5% Ta content, 10 oxide film layers) and organic compounds oxidation (with 7.5% Ta content, 8 oxide film layers) and therefore these electrodes can be applicable in both environmental and energy fields. The synergetic effect of combined electrolysis and sonication was shown while conducting sonoelectrochemical (EO/US) degradation of methylene blue (MB) and formic acid (FA). Complete degradation of MB and FA was achieved after 45 and 120 min of EO/US process respectively in neutral media. Mineralization efficiency of FA over 95% was obtained after 2 h of degradation using high frequency ultrasound (381, 863, 1176 kHz) combined with 9.1 mA/cm2 current density. EO/US degradation of MB provided over 75% mineralization in 8 h. High degradation kinetic rates and mineralization efficiencies of model pollutants obtained in EO/US experiments provide the preconditions for further extrapolation of this treatment method to pilot scale studies with industrial wastewaters.

Development of advanced silicon radiation detectors for harsh radiation environment

This thesis describes the development of advanced silicon radiation detectors and their characterization by simulations, used in the work for searching elementary particles in the European Organization for Nuclear Research, CERN. Silicon particle detectors will face extremely harsh radiation in the proposed upgrade of the Large Hadron Collider, the future high-energy physics experiment Super-LHC. The increase in the maximal fluence and the beam luminosity up to 1016 neq / cm2 and 1035 cm-2s-1 will require detectors with a dramatic improvement in radiation hardness, when such a fluence will be far beyond the operational limits of the present silicon detectors. The main goals of detector development concentrate on minimizing the radiation degradation. This study contributes mainly to the device engineering technology for developing more radiation hard particle detectors with better characteristics. Also the defect engineering technology is discussed. In the nearest region of the beam in Super-LHC, the only detector choice is 3D detectors, or alternatively replacing other types of detectors every two years. The interest in the 3D silicon detectors is continuously growing because of their many advantages as compared to conventional planar detectors: the devices can be fully depleted at low bias voltages, the speed of the charge collection is high, and the collection distances are about one order of magnitude less than those of planar technology strip and pixel detectors with electrodes limited to the detector surface. Also the 3D detectors exhibit high radiation tolerance, and thus the ability of the silicon detectors to operate after irradiation is increased. Two parameters, full depletion voltage and electric field distribution, is discussed in more detail in this study. The full depletion of the detector is important because the only depleted area in the detector is active for the particle tracking. Similarly, the high electric field in the detector makes the detector volume sensitive, while low-field areas are non-sensitive to particles. This study shows the simulation results of full depletion voltage and the electric field distribution for the various types of 3D detectors. First, the 3D detector with the n-type substrate and partial-penetrating p-type electrodes are researched. A detector of this type has a low electric field on the pixel side and it suffers from type inversion. Next, the substrate is changed to p-type and the detectors having electrodes with one doping type and the dual doping type are examined. The electric field profile in a dual-column 3D Si detector is more uniform than that in the single-type column 3D detector. The dual-column detectors are the best in radiation hardness because of their low depletion voltages and short drift distances.

Tandem-GMA Welding of Low Alloy Structural Steel

The Tandem-GMAW method is the latest development as the consequences of improvements in the welding methods. The twin-wire and then the Tandem-method with the separate power sources has got a remarkable place in the welding of many types of materials with different joint types. The biggest advantage of Tandem welding method is the flexibility of choosing both the electrodes of different types from each other according to the type of the parent material. This is possible because of the feasibility of setting the separate welding parameters for both the wires. In this thesis work the effect of the variation in three parameters on the weld bead in Tandem-GMA welding method is studied. Theses three parameters are the wire feed rate in the slave wire, the wire feed rate in the master wire and the voltage difference in both the wires. The results are then compared to study the behaviour of the weld bead with the change in these parameters.

DSA-elektrodien testaaminen kulumisen arvioimiseksi

Työn tavoitteena oli tutkia eri mittausmenetelmillä metallipinnoitettujen elektrodien kulumista kulumiskokeiden aikana. Mittausmenetelminä olivat käytössä syklinen voltammetria, polarisaatiokäyrän määritys ja sähkökemiallinen impedanssispektrometria, jotka olivat offline-mittausmenetelmiä. Näiden menetelmien avulla pystyttiin seuraamaan yksittäisten elektrodien kulumista ajon aikana. Elektrodin pinnoitteen alkuaineiden pitoisuuksia tutkittiin myös elektronimikroskoopin röntgenspektrometrin avulla. Työn aikana tehdyissä kulumiskokeista havaittiin elektrodin kuluvan sitä nopeammin mitä suurempi on virrantiheys. Työssä tehtyjen elektronimikroskooppikokeiden avulla havaittiin, että harvinaisten metallien seostaminen pinnoitteeseen pidentää metallipinnoitetun elektrodin käyttöikää. Syklisen voltammetrian avulla pystyttiin seuraamaan elektrodin pinta-alan muuttumista ajon aikana. Työssä käytettyjen kulumiskokeiden avulla ei suoranaisesti pystytty määrittämään elektrodin jäljellä olevaa elinikää.

Photoelectric Measurements and Modeling of Bacteriorhodopsin

Recent technology has provided us with new information about the internal structures and properties of biomolecules. This has lead to the design of applications based on underlying biological processes. Applications proposed for biomolecules are, for example, the future computers and different types of sensors. One potential biomolecule to be incorporated in the applications is bacteriorhodopsin. Bacteriorhodopsin is a light-sensitive biomolecule, which works in a similar way as the light sensitive cells of the human eye. Bacteriorhodopsin reacts to light by undergoing a complicated series of chemical and thermal transitions. During these transitions, a proton translocation occurs inside the molecule. It is possible to measure the photovoltage caused by the proton translocations when a vast number of molecules is immobilized in a thin film. Also the changes in the light absorption of the film can be measured. This work aimed to develop the electronics needed for the voltage measurements of the bacteriorhodopsin-based optoelectronic sensors. The development of the electronics aimed to get more accurate information about the structure and functionality of these sensors. The sensors used in this work contain a thick film of bacteriorhodopsin immobilized in polyvinylalcohol. This film is placed between two transparent electrodes. The result of this work is an instrumentation amplifier which can be placed in a small space very close to the sensor. By using this amplifier, the original photovoltage can be measured in more detail. The response measured using this amplifier revealed two different components, which could not be distinguished earlier. Another result of this work is the model for the photoelectric response in dry polymer films.

Effects of pulp electrochemistry on PGE flotation in sulphide poor ores

This work gives a reader basic knowledge about mineralogy and mineral processing. Main focus of this work was on flotation process and pulp electrochemistry on flotation. Three different sulphide poor ores are examined on experimental part. Platinum and palladium were the noble metals, which were contained into studied ores. Electrochemistry of flotation of PGE minerals on sulphide poor ores has been examined only slightly. Bench scale flotation test was used in this study. Chalcopyrite, nickel-pentlandite, pyrite, platinum and pH electrodes were used to investigation of pulp electrochemistry during flotation tests. Effects of grinding media, carbon dioxide atmosphere in grinding and mixture of carbon dioxide and air as flotation gas to PGE flotation and electrochemistry of flotation were studied. Stainless steel grinding media created more oxidising pulp environment to flotation than mild steel grinding media. Concentrate quality improved also with stainless steel grinding media, but the recovery was remarkably poorer, than with mild steel grinding media. Carbon dioxide atmosphere in grinding created very reducing pulp environment, which caused very good concentrate quality. But the recovery was again poorer than with normal mild steel grinding media. Mixture of carbon dioxide and air as flotation gas improved PGE recovery with some ores, but not always. Effect of carbon dioxide to pulp electrochemistry was detected mainly via pH-value.

Simulations of 3D Stripixel Detectors

Large Hadron Collider (LHC) is the main particle accelerator at CERN. LHC is created with main goal to search elementary particles and help science investigate our universe. Radiation in LHC is caused by charged particles circular acceleration, therefore detectors tracing particles in existed severe conditions during the experiments must be radiation tolerant. Moreover, further upgrade of luminosity (up to 1035 cm-2s-1) requires development of particle detector’s structure. This work is dedicated to show the new type 3D stripixel detector with serious structural improvement. The new type of radiation-hard detector has a three-dimensional (3D) array of the p+ and n+ electrodes that penetrate into the detector bulk. The electrons and holes are then collected at oppositely biased electrodes. Proposed 3D stripixel detector demonstrates that full depletion voltage is lower that that for planar detectors. Low depletion voltage is one of the main advantages because only depleted part of the device is active are. Because of small spacing between electrodes, charge collection distances are smaller which results in high speed of the detector’s response. In this work is also briefly discussed dual-column type detectors, meaning consisting both n+ and p+ type columnar electrodes in its structure, and was declared that dual-column detectors show better electric filed distribution then single sided radiation detectors. The dead space or in other words low electric field region in significantly suppressed. Simulations were carried out by using Atlas device simulation software. As a simulation results in this work are represented the electric field distribution under different bias voltages.

Sewage Sludge Electro-Dewatering

Original sludge from wastewater treatment plants (WWTPs) usually has a poor dewaterability. Conventionally, mechanical dewatering methods are used to increase the dry solids (DS) content of the sludge. However, sludge dewatering is an important economic factor in the operation of WWTPs, high water content in the final sludge cake is commonly related to an increase in transport and disposal costs. Electro‐dewatering could be a potential technique to reduce the water content of the final sludge cake, but the parameters affecting the performance of electro‐dewatering and the quality of the resulting sludge cake, as well as removed water, are not sufficiently well known. In this research, non‐pressure and pressure‐driven experiments were set up to investigate the effect of various parameters and experimental strategies on electro‐dewatering. Migration behaviour of organic compounds and metals was also studied. Application of electrical field significantly improved the dewatering performance in comparison to experiments without electric field. Electro‐dewatering increased the DS content of the sludge from 15% to 40 % in non‐pressure applications and from 8% to 41% in pressure‐driven applications. DS contents were significantly higher than typically obtained with mechanical dewatering techniques in wastewater treatment plant. The better performance of the pressure‐driven dewatering was associated to a higher current density at the beginning and higher electric field strength later on in the experiments. The applied voltage was one of the major parameters affecting dewatering time, water removal rate and DS content of the sludge cake. By decreasing the sludge loading rate, higher electrical field strength was established between the electrodes, which has a positive effect on an increase in DS content of the final sludge cake. However interrupted voltage application had anegative impact on dewatering in this study, probably because the off‐times were too long. Other factors affecting dewatering performance were associated to the original sludge characteristics and sludge conditioning. Anaerobic digestion of the sludge with high pH buffering capacity, polymer addition and freeze/thaw conditioning had a positive impact on dewatering. The impact of pH on electro‐dewatering was related to the surface charge of the particles measured as zeta‐potential. One of the differences between electro‐dewatering and mechanical dewatering technologies is that electro‐dewatering actively removes ionic compounds from the sludge. In this study, dissolution and migration of organic compounds (such as shortchain fatty acids), macro metals (Na, K, Ca, Mg, Fe) and trace metals (Ni, Mn, Zn, Cr) was investigated. The migration of the metals depended on the fractionation and electrical field strength. These compounds may have both negative and positive impacts on the reuse and recycling of the sludge and removed water. Based on the experimental results of this study, electro‐dewatering process can be optimized in terms of dewatering time, desired DS content, power consumption and chemical usage.

Electrocoagulation in the treatment of industrial waters and wastewaters

Chemical coagulation is commonly used in raw water and wastewater treatment plants for the destabilisation of pollutants so that they can be removed in the subsequent separation processes. The most commonly used coagulation chemicals are aluminium and iron metal salts. Electrocoagulation technology has also been proposed for the treatment of raw waters and wastewaters. With this technology, metal cations are produced on the electrodes via electrolysis and these cations form various hydroxides in the water depending on the water pH. In addition to this main reaction, several side reactions, such as hydrogen bubble formation and the reduction of metals on cathodes, also take place in the cell. In this research, the applications of electrocoagulation were investigated in raw water treatment and wastewater applications. The surface water used in this research contained high concentrations of natural organic matter (NOM). The effect of the main parameters – current density, initial pH, electric charge per volume, temperature and electrolysis cell construction – on NOM removal were investigated. In the wastewater treatment studies, the removal of malodorous sulphides and toxic compounds from the wastewaters and debarking effluents were studied. Also, the main parameters of the treatment, such as initial pH and current density, were investigated. Aluminium electrodes were selected for the raw water treatment, whereas wastewaters and debarking effluent were treated with iron electrodes. According to results of this study, aluminium is more suitable electrode material for electrocoagulation applications because it produces Al(III) species. Metal ions and hydroxides produced by iron electrodes are less effective in the destabilisation of pollutants because iron electrodes produce more soluble and less charged Fe(II) species. However, Fe(II) can be effective in some special applications, such as sulphide removal. The resulting metal concentration is the main parameter affecting destabilisation of pollutants. Current density, treatment time, temperature and electrolysis cell construction affect the dissolution of electrodes and hence also the removal of pollutants. However, it seems that these parameters have minimal significance in the destabilization of the pollutants besides this effect (in the studied range of parameters). Initial pH and final pH have an effect on the dissolution of electrodes, but they also define what aluminium or iron species are formed in the solution and have an effect on the ζ-potential of all charged species in the solution. According to the results of this study, destabilisation mechanisms of pollutants by electrocoagulation and chemical coagulation are similar. Optimum DOC removal and low residual aluminium can be obtained simultaneously with electrocoagulation, which may be a significant benefit of electrocoagulation in surface water treatment compared to chemical coagulation. Surface water treatment with electrocoagulation can produce high quality water, which could be used as potable water or fresh water for industrial applications. In wastewater treatment applications, electrocoagulation can be used to precipitate malodorous sulphides to prevent their release into air. Technology seems to be able to remove some toxic pollutants from wastewater and could be used as pretreatment prior to treatment at a biological wastewater treatment plant. However, a thorough economic and ecological comparison of chemical coagulation and electrocoagulation is recommended, because these methods seem to be similar in pollutant destabilisation mechanisms, metal consumption and removal efficiency in most applications.

Electro-Oxidation Treatment of Pulp and Paper Mill Circulating Waters and Wastewaters

Interest in water treatment by electrochemical methods has grown in recent years. Electrochemical oxidation has been applied particularly successfully to degrade different organic pollutants and disinfect drinking water. This study summarizes the effectiveness of the electrochemical oxidation technique in inactivating different primary biofilm forming paper mill bacteria as well as sulphide and organic material in pulp and paper mill wastewater in laboratory scale batch experiments. Three different electrodes, borondoped diamond (BDD), mixed metal oxide (MMO) and PbO2, were employed as anodes. The impact on inactivation efficiency of parameters such as current density and initial pH or chloride concentration of synthetic paper machine water was studied. The electrochemical behaviour of the electrodes was investigated by cyclic voltammetry with MMO, BDD and PbO2 electrodes in synthetic paper mill water as also with MMO and stainless steel electrodes with biocides. Some suggestions on the formation of different oxidants and oxidation mechanisms were also presented during the treatment. Aerobic paper mill bacteria species (Deinococcus geothermalis, Pseudoxanthomonas taiwanensis and Meiothermus silvanus) were inactivated effectively (>2 log) at MMO electrodes by current density of 50 mA/cm2 and the time taken three minutes. Increasing current density and initial chloride concentration of paper mill water increased the inactivation rate of Deinococcus geothermalis. The inactivation order of different bacteria species was Meiothermus silvanus > Pseudoxanthomonas taiwanensis > Deinococcus geothermalis. It was observed that inactivation was mainly due to the electrochemically generated chlorine/hypochlorite from chloride present in the water and also residual disinfection by chlorine/hypochlorite occurred. In real paper mill effluent treatment sulphide oxidation was effective with all the different initial concentrations (almost 100% reduction, current density 42.9 mA/cm2) and also anaerobic bacteria inactivation was observed (almost 90% reduction by chloride concentration of 164 mg/L and current density of 42.9 mA/cm2 in five minutes). Organic material removal was not as effective when comparing with other tested techniques, probably due to the relatively low treatment times. Cyclic voltammograms in synthetic paper mill water with stainless steel electrode showed that H2O2 could be degraded to radicals during the cathodic runs. This emphasises strong potential of combined electrochemical treatment with this biocide in bacteria inactivation in paper mill environments.

Modelling of potentiometric ion sensors

Potentiometric ion sensors are a very important subgroup of electrochemical sensors, very attractive for practical applications due to their small size, portability, low-energy consumption, relatively low cost and not changing the sample composition. They are investigated by the researchers from many fields of science. The continuous development of this field creates the necessity for a detailed description of sensor response and the electrochemical processes important in the practical applications of ion sensors. The aim of this thesis is to present the existing models available for the description of potentiometric ion sensors as well as their applicability and limitations. This includes the description of the diffusion potential occurring at the reference electrodes. The wide range of existing models, from most idealised phase boundary models to most general models, including migration, is discussed. This work concentrates on the advanced modelling of ion sensors, namely the Nernst-Planck-Poisson (NPP) model, which is the most general of the presented models, therefore the most widely applicable. It allows the modelling of the transport processes occurring in ion sensors and generating the potentiometric response. Details of the solution of the NPP model (including the numerical methods used) are shown. The comparisons between NPP and the more idealized models are presented. The applicability of the model to describe the formation of diffusion potential in reference electrode, the lower detection limit of both ion-exchanger and neutral carrier electrodes and the effect of the complexation in the membrane are discussed. The model was applied for the description of both types of electrodes, i.e. with the inner filling solution and solidcontact electrodes. The NPP model allows the electrochemical methods other than potentiometry to be described. Application of this model in Electrochemical Impedance Spectroscopy is discussed and a possible use in chrono-potentiometry is indicated. By combining the NPP model with evolutionary algorithms, namely Hierarchical Genetic Strategy (HGS), a novel method allowing the facilitation of the design of ion sensors was created. It is described in detail in this thesis and its possible applications in the field of ion sensors are indicated. Finally, some interesting effects occurring in the ion sensors (i.e. overshot response and influence of anionic sites) as well as the possible applications of NPP in biochemistry are described.

Paper for printed electronics and functionality

Mass-produced paper electronics (large area organic printed electronics on paper-based substrates, “throw-away electronics”) has the potential to introduce the use of flexible electronic applications in everyday life. While paper manufacturing and printing have a long history, they were not developed with electronic applications in mind. Modifications to paper substrates and printing processes are required in order to obtain working electronic devices. This should be done while maintaining the high throughput of conventional printing techniques and the low cost and recyclability of paper. An understanding of the interactions between the functional materials, the printing process and the substrate are required for successful manufacturing of advanced devices on paper. Based on the understanding, a recyclable, multilayer-coated paper-based substrate that combines adequate barrier and printability properties for printed electronics and sensor applications was developed in this work. In this multilayer structure, a thin top-coating consisting of mineral pigments is coated on top of a dispersion-coated barrier layer. The top-coating provides well-controlled sorption properties through controlled thickness and porosity, thus enabling optimizing the printability of functional materials. The penetration of ink solvents and functional materials stops at the barrier layer, which not only improves the performance of the functional material but also eliminates potential fiber swelling and de-bonding that can occur when the solvents are allowed to penetrate into the base paper. The multi-layer coated paper under consideration in the current work consists of a pre-coating and a smoothing layer on which the barrier layer is deposited. Coated fine paper may also be used directly as basepaper, ensuring a smooth base for the barrier layer. The top layer is thin and smooth consisting of mineral pigments such as kaolin, precipitated calcium carbonate, silica or blends of these. All the materials in the coating structure have been chosen in order to maintain the recyclability and sustainability of the substrate. The substrate can be coated in steps, sequentially layer by layer, which requires detailed understanding and tuning of the wetting properties and topography of the barrier layer versus the surface tension of the top-coating. A cost competitive method for industrial scale production is the curtain coating technique allowing extremely thin top-coatings to be applied simultaneously with a closed and sealed barrier layer. The understanding of the interactions between functional materials formulated and applied on paper as inks, makes it possible to create a paper-based substrate that can be used to manufacture printed electronics-based devices and sensors on paper. The multitude of functional materials and their complex interactions make it challenging to draw general conclusions in this topic area. Inevitably, the results become partially specific to the device chosen and the materials needed in its manufacturing. Based on the results, it is clear that for inks based on dissolved or small size functional materials, a barrier layer is beneficial and ensures the functionality of the printed material in a device. The required active barrier life time depends on the solvents or analytes used and their volatility. High aspect ratio mineral pigments, which create tortuous pathways and physical barriers within the barrier layer limit the penetration of solvents used in functional inks. The surface pore volume and pore size can be optimized for a given printing process and ink through a choice of pigment type and coating layer thickness. However, when manufacturing multilayer functional devices, such as transistors, which consist of several printed layers, compromises have to be made. E.g., while a thick and porous top-coating is preferable for printing of source and drain electrodes with a silver particle ink, a thinner and less absorbing surface is required to form a functional semiconducting layer. With the multilayer coating structure concept developed in this work, it was possible to make the paper substrate suitable for printed functionality. The possibility of printing functional devices, such as transistors, sensors and pixels in a roll-to-roll process on paper is demonstrated which may enable introducing paper for use in disposable “onetime use” or “throwaway” electronics and sensors, such as lab-on-strip devices for various analyses, consumer packages equipped with product quality sensors or remote tracking devices.