The goal of this master's thesis was to examine the possibility of oxidation of seven selected bile acids and evaluate whether such processes are suitable for analytical purposes. The secondary goal was to describe the oxidation products of bile acid electrolysis. The experiments were carried out in a non-aqueous medium of acetonitrile and in a mixed medium of acetonitrile:water using linear sweep and cyclic voltammetry. The working electrode materials employed for voltammetric experiments were: highly oriented pyrolytic graphite, -cyclodextrin modified glassy carbon and boron doped diamond. Preparative electrolysis was carried out on a platinum electrode in the non-aqueous medium of acetonitrile. Experiments have shown that neither the highly oriented pyrolytic graphite electrode nor the -cyclodextrin modified glassy carbon electrode are suitable for analytical purposes under conditions used. The results achieved on the boron doped diamond electrode, on the other hand, have not yet been described in the literature. Primary bile acids cholic and chenodeoxycholic were oxidized at approximately 0.5 V lower potential in the mixed medium of acetonitrile:water than in the papers using carbon electrodes published until now. Products of oxidation on the platinum electrode were separated by TLC and...

Presented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of...

Microbial electrosynthesis (MES) has recently emerged as a novel biotechnology platform for value-added product generation from waste CO2 stream. Integrating MES technology with renewable energy sources for both CO2 valorization and renewable energy storage is regarded as one type of artificial photosynthesis and a perfect example of circular bioeconomy. However, several challenges remain to be addressed to scale-up MES as a feasible process for chemical production, which include enhanced production rate, reduced energy consumption and excellent resistance to external fluctuations. To fill these knowledge gaps, different in-depth approaches were proposed in this dissertation by optimizing the cathode architecture, CO2 flow rates and utilizing efficient photoelectrode to improve MES performance and stability. A novel cathode design, made of conductive hollow fiber membrane, was developed in this dissertation to improve CO2 availability at MES cathode surface via direct CO2 delivery to chemolithoautotrophs through the pores in the hollow fibers. By modifying the hollow fiber surface with carbon nanotubes (CNTs), higher bioproduct formation was achieved with excellent faradaic efficiencies, which could be attributed to the improved surface area for bacterial adhesion and the reduction of cathodic electron transfer resistance. Since CO2 flow rate from industrial facilities typically varies over time, this hollow-fiber architecture was also applied to test the resistance of MES systems to CO2 flow rate fluctuation. Stepwise increase of CO2 flow rates from 0.3 ml/min to 10 ml/min was tested and the effect of CO2 flow rate fluctuations was evaluated in terms of biochemical generation and microbial community. MES was further integrated with renewable energy supply for both energy storage and CO2 transformation into biofuels and biochemicals. Stable MES photoanode, based on molybdenum-doped bismuth vanadate deposited on fluorine-doped tin oxide glass (FTO/BiVO4/Mo), was prepared for efficient solar energy harvesting and overpotential reduction for oxygen evolution reaction (OER), which contributed to one of the highest solar-to-biochemical conversion efficiencies ever reported for photo-assisted MES systems. The applied nature of this dissertation with fundamental insights is of great importance to bring MES one step closer to full-scale applications and enable MES technology to be economically more viable for renewable energy storage and CO2 valorization.

>Magister Scientiae - MSc / This work reports the use of a pencil graphite electrode (PGE) as inexpensive and sensitive electrochemical sensing platform fabricated by using electrochemically reduced graphene oxide (ERGO) in conjunction with an in-situ plated thin mercury film. For the first time the ERGOHgF-PGE sensor is proposed for simultaneous detection of cadmium (Cd2+), copper (Cu2+), lead (Pb2+) and zinc (Zn2+) using N-Nitroso-N-phenylhydroxylamine (cupferron) as complexing agent by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is based on the adsorption of cupferron- metal ion complexes onto the surface of the ERGO-HgFPGE at 0.1 V for 60 s carried out in 0.1 M acetate buffer solution (pH 4.6). The synthesized graphene oxide (GO) and graphene nanosheets (GNs) were characterized using different analytical techniques such as FT-IR which confirms the presence of oxygen moieties embedded in the graphitic structure and further demonstrated by UV-Vis, validating the synthesis of GO / 2023

La problématique de l’accès potable est très aiguë dans plusieurs pays en développement. Entre les années 1999 et 2004, un programme d’approvisionnement en eau de consommation a été mis en œuvre au profit des populations de la région Nord du Burkina Faso à travers la réalisation de forages. Au cours de son application, ce programme a malheureusement rencontré un problème, lié à la contamination des eaux souterraines par l’arsenic, naturellement relargué à partir des roches en contact avec la nappe aquifère. Dans le cadre de ce travail, nos études conduites par la suite dans la zone nous ont permis de mettre en évidence des teneurs élevées et parfois excessives dans certaines eaux souterraines. Le contrôle chimique et microbiologique régulier de la qualité de l’eau apparaît comme un moyen primordial de prévention des risques sanitaires liés à la consommation de ces eaux. A cet effet, deux outils électroanalytiques de suivi des teneurs en arsenic et en mercure dans les eaux souterraines ont été développé. La méthode conçue sur la base du premier dispositif utilise une électrode de pâte de carbone modifiée par des nanoparticules d’or et recouverte d’une monocouche auto-assemblée de glutathion. Elle est caractérisée par une large gamme de travail comprise entre 3 et 1498 µg/L, une répétabilité de l’ordre de 5%, une exactitude de 3,5 % et une limite de détection estimée à 0,9 µg/L. Cette méthode a été appliquée avec succès à une étude de spéciation sur site. Il ressort de ces investigations que 40% des échantillons d’eaux analysés ont une prévalence relative en arsenic (III) supérieure à 50%, et 60% des échantillons ont une prévalence relative en arsenic (V) supérieure à 50%. Le second dispositif électroanalytique, développé pour la surveillance des teneurs en ions mercuriques dans les eaux souterraines, est basé sur une électrode sérigraphiée de carbone modifiée par des nanoparticules d’or. La méthode mise en œuvre à l’aide de ce transducteur est caractérisée par une gamme de travail comprise entre 1 et 100 µg/L, une répétabilité de 5%, une exactitude de 0,4% et une limite de détection estimé à 1 µg/L. L’application à l’analyse d’une série d’échantillons d’eau souterraine a révélé une teneur cinq fois supérieure à la norme pour un échantillon d’eau et des teneurs proches de la limite de quantification pour 2 échantillons. Les méthodes développées sont aisées à mettre en œuvre, elles offrent des caractéristiques de performances comparables à celles des méthodes de références pour un coût d’investissement très abordable. Elles sont bien adaptées aux mesures de suivi et des analyses sur terrain. Elles pourraient constituer pour un pays comme le Burkina Faso, une alternative très intéressante aux méthodes de spectrophotométrie atomique coûteuses et difficilement accessibles. / Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie) / info:eu-repo/semantics/nonPublished

Performance degradation of lithium-ion batteries (LIBs) from in-service abuse was analyzed using novel dynamic abuse tests and sensor-based in-situ monitoring of battery state of health (SOH). The relation between dynamic impact and structure changes of LiCoO₂ (LCO) electrode was analyzed through a nano-impact test directly applied to the electrode and Raman imaging. After the electrode structure damage induced by the dynamic loading was analyzed, the performance of the LIBs with the abused electrodes was evaluated to establish the relation between the number of impact cycles and LIB performance degradation. The mechanism of impact related LIB capacity decrease was analyzed, and the capacity change can be predicted based on the impact abuse history using this approach. In order to provide more detailed information on the battery performance degradation caused by the in-service dynamic loads, a dynamic aging testing platform was designed to simulate in-service vibration and impact experienced by the LIBs. Based on the lessons learned, a sensor network was constructed to provide a comprehensive in-situ evaluation of the SOH of commercial batteries. Mechanisms of LIB capacity fade, temperature increase, and cell deformation from cycling in representative dynamic environments were analyzed and correlated with theoretical predictions. Difference between the aging of a battery pack and that of a single cell was also investigated, which presented the influence of current imbalance on the SOH decay of battery packs. SEM imaging, Raman imaging, and electrochemical impedance spectroscopy (EIS) analysis were also applied to support the sensor network measurements.<br><div> In order to provide an early detection of catastrophic LIB failure such as thermal runaway, an internal resistance temperature detector (RTD) based electrode temperature monitoring approach was developed. By embedding the RTD into LIBs with 3D printing technique, electrode temperature can be collected during ordinary cycling and electrical abuse of LIBs, such as external short circuit and overcharge. The internal RTD presented high measuring efficiency, while there was no interference between the sensor measurement and battery operation. The internal RTD detected the short circuit event and overcharge failure prior of time: the efficiency of the internal RTD was 6-10 times higher than the external RTD in the short circuit test. This provided the chance for early detection and prevention of catastrophic LIB failures. Besides, with the detailed information on electrode temperature evolution during LIB thermal runaway available, the internal RTD also provided the chance to enhance the understanding of the thermal runaway mechanism.</div>

This project aims to investigate a variety of electrodes for ECG (electrocardiogram) measurements and find suitable ones for burn wounded skin in association with the Burn center in Uppsala University Hospital.   To this purpose, the electrical properties (in particular, electrical impedance and equivalent circuit) of electrodes and the influence of the skin on the electrical properties are looked into, and various common artefacts in ECG measurements are investigated, such as wandering baseline (caused by perspiration, respiration, patient movement and poor electrode contact), muscle tremor artefact, 50-60 Hz power line interference and measurement noise.   Simulation of a burn wound was done by putting Ringer’s acetate between two electrodes gel to gel. Six different electrodes made with either a solid or wet gel for the electrolyte were tested, three of which (Ambu Bluesensor L-00-S/25, Ambu Bluesensor R-00-S/25, Milmedtek T-VO01) have wet gel, and three of which (3M 2670-5, Medtronic Arbo, and Ambu Whitesensor WSP30-00-S/50) have solid gel.   The tests showed that the impedance of the electrodes changed as expected and was in almost all cases lowered. An increase in phase shift was also observed with burn wound simulation but could not be proven to relate with increased polarization.   The results showed its wet gel and adhesive developed for sweaty/wet skin, Ambu Bluesensor R-00-S/25 is recommended.   Suggestions for further investigation would be to see if the interference could be solved by impedance balancing the electrodes or to investigate if there is a greater coupling between the wet burn wounds and the main 230V 50Hz network causing higher currents and voltage drops in the body increasing the risk of common mode to differential mode conversion.

The near future will put a lot of demand on the increasing need for energy production and storage. Issues regarding the modern-day battery technology’s environmental benignity, safety and cost to sustain such demands thus serve as a huge bottleneck, necessitating the research into alternative electrochemical energy storage solutions. Conducting redox polymers are a class of materials which combines the concepts of conducting polymers and redox active molecules to work as fully organic electrode materials. In this work three conducting redox polymers based on 3,4-ethylenedioxythiopene and 3,4-propylenedioxythiopene (EPE) with hydroquinone, catechol and quinizarin pendant groups were investigated. The polymers were electrochemically characterized with regards to their ability to cycle protons (aqueous electrolyte) and cations (non-aqueous electrolyte), their kinetics and charge transport and as cathodes in a battery. In non-aqueous electrolyte, hydroquinone and catechol did not exhibit redox activity in a potential region where the backbone was conducting as they were not redoxmatched. Quinizarin showed redox-matching as concluded by in situ conductance and UV-vis measurements when cycling Na+, Li+, Ca2+ and Mg2+-ions in acetonitrile. Comparison of the kinetics revealed that the rate constant for Ca2+-ion cycling was several magnitudes larger than the rest, and galvanostatic charge/discharge showed that 90% of the polymer capacity was attainable at 5C. An EPE-Quinizarin cathode and metallic calcium anode coin cell assembly displayed output voltages of 2.4 V, and the presented material thus shows promising and exciting properties for future sustainable battery chemistries.

Electrospinning is a useful technique that can generate micro- and nano-meter sized fibers from polymer materials. Modification of the electrospinning parameters and apparatus can generate nanofibers for use in diverse applications ranging from tissue engineering to nanocomposite fabrication; however, electrospun fibers are typically collected in a random orientation and over large areas limiting their applications.  Here we present several methods to control the deposition of electrospun nanofibers, such as the use of a single auxiliary electrode ring and a negatively charged collector substrate to control the deposition area and the construction of a parallel electrode collector known as the triple electrode setup to control the uniaxial alignment of nanofibers. The numerous constructed setups were advanced by the use of electric field computations to assess the distribution of the electric field and its effect on the deposition behavior and morphology of the electrospun nanofibers. The electrostatic force imposed by the auxiliary electrodes provides converged electric fields that direct the nanofibers to their desired deposition targets. Here it is shown that the use of the auxiliary electrode ring dramatically decreased the deposition area of nanofibers, the negatively charged substrate yielded more uniform nanofibers and the triple electrode setup is a viable method to achieve uniaxially aligned nanofiber mats.    The electrospinning of copolymers appears as an attractive option for enhancing the overall properties of nanofibers as it offers possibility of an intrinsic control of the polymeric material itself. The poly(methyl methacrylate)-graft-poly(dimethylsiloxane) graft copolymer  (PMMA-g-PDMS) is considered to be an organic-inorganic hybrid material with much potential in its use in nanocomposites, and in this work has been successfully synthesized and electrospun via the various constructed electrospinning setups.   In the final elements of this work, the triple electrode setup is used in combination with a dynamic rotating collector to yield a novel collector and has been successfully used to produce PMMA-g-PDMS nanofiber sheets that were further incorporated in a PDMS matrix to yield nanocomposite sheets. A variant of the triple electrode setup with partially insulated electrodes is devised in combination with a methodology to remove the nanofibers from the collector. The nanofibers once removed and dried were incorporated in a PDMS matrix to yield nanocomposites. The preferential dissolution of the fibers from the matrix rendered the fibers to templates and a final porous material with uniaxial nanochannels could be obtained.   This work is believed to be able to lead to a better understanding of the mechanisms of nanofiber deposition and alignment, and should be of help to the design of more practical collecting structures, hence promoting the applications of the electrospinning technique.

This thesis concerns the development and the study of Iron-based water oxidation catalysts (WOCs) and how to immobilize them onto the hydrophobic surface of a carbon paste electrode. In the introductory chapter a general background of the field of water splitting and this thesis is given. In the second chapter, experimental performance is described from synthesis to measurements of a complete complex-doped electrode. The third chapter deals with the results and the discussion of the performed experiments. In chapter four, a descriptive conclusion of the obtained data is held. / Det här arbetet berör studien och utvecklingen utav järnbaserade katalysatorer, speciellt framtagna för för delning utav vatten. Utöver detta undersöks även om dessa katalysatorer (WOCs) kan immobiliseras på den hydrofoba ytan hos elektroder gjorda på kol-pasta. I det inledande kapitlet ges en generell bakgrund till området som berör delning utav vatten. I det andra kapitlet presenteras det experimentella utförandet utav synteser samt elektrokemiska mätningar som berörts under arbetets gång i jakten på en komplexdopad elektrod. I det tredje kapitlet diskuteras resultaten från mätningarna samt möjliga framtidsutsikter. I det fjärde kapitlet presenteras slutsatserna utav studien.