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  • 1.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lindqvist, Camilla
    INTERACT, Department of Engineering and Physics, Karlstad University, Karlstad, Sweden.
    Musumeci, Chiara
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy2015Manuscript (preprint) (Other academic)
    Abstract [en]

    The nanoscale morphology of the photo-active layer in organic solar cells is critical for device efficiency. The photoactive layer is cast from solution and during drying both the polymer and the fullerene self-assemble to form a blend. Here, we introduce in-situ spectroscopic photoluminescence (PL) combined with laser reflectometry to monitor the drying process of an amorphous polymer:fullerene blend. When casting only the pristine components (polymer or PCBM only), the strength of PL emission is proportional to the solid content of the drying solution, and both kinetics reveal a rapid aggregation onset at the final stage of film drying. On the contrary, when casting polymer:fullerene blends, the strength of PL emission is proportional to the wet film thickness and reveals polymer/fullerene charge transfer (CT) already at the earliest stages of film drying, i.e. in dilute solutions. The proposed method allows to detect polymer/fullerene phase separation during film casting – from a reduction in the PL quenching rate as the film dries. Poor solvents lead to phase separation already at early stages of film drying (low solid content), resulting in a coarse final morphology as confirmed by atomic force microscopy (AFM). We therefore anticipate that the proposed method will be an important tool in the future development of processing inks, not only for solution-cast polymer:fullerene solar cells but also for organic heterojunctions in general.

  • 2.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Abdalla, Hassan
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Lilja, Louise
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, Reykjavik, Iceland.
    Oxidation-induced deep levels in n- and p-type 4H- and 6H-SiC and their influence on carrier lifetime2016In: Physical Review Applied, ISSN 2331-7019, Vol. 6, no 1, p. 1-15, article id 014010Article in journal (Refereed)
    Abstract [en]

    We present a complete analysis of the electron- and hole-capture and -emission processes of the deep levels ON1, ON2a, and ON2b in 4H-SiC and their 6H-SiC counterparts OS1a and OS1b through OS3a and OS3b, which are produced by lifetime enhancement oxidation or implantation and annealing techniques. The modeling is based on a simultaneous numerical fitting of multiple high-resolution capacitance deep-level transient spectroscopy spectra measured with different filling-pulse lengths in n- and p-type material. All defects are found to be double-donor-type positive-U two-level defects with very small hole-capture cross sections, making them recombination centers of low efficiency, in accordance with minority-carrier-lifetime measurements. Their behavior as trapping and weak recombination centers, their large concentrations resulting from the lifetime enhancement oxidations, and their high thermal stability, however, make it advisable to minimize their presence in active regions of devices, for example, the base layer of bipolar junction transistors.

  • 3.
    Cavanillas, Santiago
    et al.
    University of Barcelona, Spain.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    A self-polishing platinum ring voltammetric sensor and its application to complex media2015In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 859, p. 29-36Article in journal (Refereed)
    Abstract [en]

    A self-polishing voltammetric sensor was recently developed and has been applied to samples of urea, milk and sewage water. The polishing device continuously grinds a platinum ring electrode, offering a reproducible and clean electrode surface. Principal component analysis (PCA) and partial least squares (PLS) techniques were applied to interpret the data and to build prediction models. In an evaluation of samples with different urea concentrations, the grinding step allows for repeatable measurements, similar to those after electrochemical cleaning. Furthermore, for the determination of sewage water concentrations in drinking water and for the evaluation of different fat contents in milk samples, the polishing eliminates sensor drift produced by electrode fouling. The results show that the application of a self-polishing unit offers a promising tool for electrochemical studies of difficult analytes and complex media. (C) 2014 Elsevier B.V. All rights reserved.

  • 4.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    3D printed disposable optics and lab-on-a-chip devices for chemical sensing with cell phones2017In: MICROFLUIDICS, BIOMEMS, AND MEDICAL MICROSYSTEMS XV, SPIE-INT SOC OPTICAL ENGINEERING , 2017, Vol. 10061, article id UNSP 100610EConference paper (Refereed)
    Abstract [en]

    Digital manufacturing (DM) offers fast prototyping capabilities and great versatility to configure countless architectures at affordable development costs. Autonomous lab-on-a-chip (LOC) devices, conceived as only disposable accessory to interface chemical sensing to cell phones, require specific features that can be achieved using DM techniques. Here we describe stereo-lithography 3D printing (SLA) of optical components and unibody-LOC (ULOC) devices using consumer grade printers. ULOC devices integrate actuation in the form of check-valves and finger pumps, as well as the calibration range required for quantitative detection. Coupling to phone camera readout depends on the detection approach, and includes different types of optical components. Optical surfaces can be locally configured with a simple polishing-free post-processing step, and the representative costs are 0.5 US$/device, same as ULOC devices, both involving fabrication times of about 20 min.

  • 5. Comina, German
    et al.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    3D Printed Unibody Lab-on-a-Chip: Features Survey and Check-Valves Integration dagger2015In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 6, no 4, p. 437-451Article in journal (Refereed)
    Abstract [en]

    The unibody lab-on-a-chip (ULOC) concept entails a fast and affordable micro-prototyping system built around a single monolithic 3D printed element (unibody). A consumer-grade stereo lithography (SL) 3D printer can configure ULOCs with different forms of sample delivery, transport, handling and readout, while minimizing material costs and fabrication time. ULOC centralizes all complex fabrication procedures and replaces the need for clean room resources, delivering prototypes for less than 1 US$, which can be printed in 10 min and ready for testing in less than 30 min. Recent examples of ULOC integration of transport, chemical sensing for optical readout and flow mixing capabilities are discussed, as well as the integration of the first check-valves for ULOC devices. ULOC valves are strictly unidirectional up to 100 psi, show an exponential forward flow behavior up to 70 psi and can be entirely fabricated with the ULOC approach.

  • 6.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    A 3D printed device for quantitative enzymatic detection using cell phones2016In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 8, no 32, p. 6135-6142Article in journal (Refereed)
    Abstract [en]

    A disposable device for quantitative enzymatic detection capable of coupling illumination and image readouts from cell phones is demonstrated. The device integrates a calibration range for glutamate detection, utilizes the phone screen as a light source, and provides the necessary actuation for autonomous operation. Custom made optics required to couple to the cell phone camera is accomplished using affordable stereolithography (SLA) 3D printers. The described method does not involve polishing, requires only two steps from design to implementation, and can be locally applied to 3D printed lab-on-a-chip (LOC) prototypes, using the same materials. Optical finishing and dimensional variability within 2% were achieved, supporting entirely arbitrary geometries for elements larger than 400 mm in radius. Representative fabrication times and costs were 20 min and $0.50 USD per prototype.

  • 7.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Autonomous Chemical Sensing Interface for Universal Cell Phone Readout2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 30, p. 8708-8712Article in journal (Refereed)
    Abstract [en]

    Exploiting the ubiquity of cell phones for quantitative chemical sensing imposes strong demands on interfacing devices. They should be autonomous, disposable, and integrate all necessary calibration and actuation elements. In addition, a single design should couple universally to a variety of cell phones, and operate in their default configuration. Here, we demonstrate such a concept and its implementation as a quantitative glucose meter that integrates finger pumps, unidirectional valves, calibration references, and focusing optics on a disposable device configured for universal video acquisition.

  • 8.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Low cost lab-on-a-chip prototyping with a consumer grade 3D printer2014In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 14, no 16, p. 2978-2982Article in journal (Refereed)
    Abstract [en]

    Versatile prototyping of 3D printed lab-on-a-chip devices, supporting different forms of sample delivery, transport, functionalization and readout, is demonstrated with a consumer grade printer, which centralizes all critical fabrication tasks. Devices cost 0.57US$ and are demonstrated in chemical sensing and micromixing examples, which exploit established principles from reference technologies.

  • 9.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    PDMS lab-on-a-chip fabrication using 3D printed templates2014In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 14, no 2, p. 424-430Article in journal (Refereed)
    Abstract [en]

    The fabrication of conventional PDMS on glass lab-on-a-chip (LOC) devices, using templates printed with a commercial (2299 US$) micro-stereo lithography 3D printer, is demonstrated. Printed templates replace clean room and photolithographic fabrication resources and deliver resolutions of 50 mu m, and up to 10 mu m in localized hindrances, whereas the templates are smooth enough to allow direct transfer and proper sealing to glass substrates. 3D printed templates accommodate multiple thicknesses, from 50 mu m up to several mm within the same template, with no additional processing cost or effort. This capability is exploited to integrate silicone tubing easily, to improve micromixer performance and to produce multilevel fluidics with simple access to independent functional surfaces, which is illustrated by time-resolved glucose detection. The templates are reusable, can be fabricated in under 20 min, with an average cost of 0.48 US$, which promotes broader access to established LOC configurations with minimal fabrication requirements, relieves LOC fabrication from design skills and provides a versatile LOC development platform.

  • 10.
    Comina, German
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering. Not Found:Linkoping Univ, Opt Devices Lab, Dept Phys Chem and Biol IFM, S-58183 Linkoping, Sweden.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Towards autonomous lab-on-a-chip devices for cell phone biosensing2016In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 77, p. 1153-1167Article in journal (Refereed)
    Abstract [en]

    Modern cell phones are a ubiquitous resource with a residual capacity to accommodate chemical sensing and biosensing capabilities. From the different approaches explored to capitalize on such resource, the use of autonomous disposable lab-on-a-chip (LOC) devices conceived as only accessories to complement cell phones underscores the possibility to entirely retain cell phones ubiquity for distributed biosensing. The technology and principles exploited for autonomous LOC devices are here selected and reviewed focusing on their potential to serve cell phone readout configurations. Together with this requirement, the central aspects of cell phones resources that determine their potential for analytical detection are examined. The conversion of these LOC concepts into universal architectures that are readable on unaccessorized phones is discussed within this context. (C) 2015 Elsevier B.V. All rights reserved.

  • 11.
    Ekedahl, Lars-Gunnar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Hydrogen sensing mechanisms of metal insulator interfaces1998In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 31, no 5, p. 249-256Article in journal (Refereed)
    Abstract [en]

    The hydrogen sensitivity of palladium-silicon dioxidesilicon (Pd-MOS) structures was demonstrated about 25 years ago. One of the most interesting features of the Pd-MOS device as a hydrogen sensor is its very large dynamic pressure range. Such devices are now used in several practical applications and in commercially available equipment, both as single sensors and in sensor arrays. We recall that the hydrogen sensitivity of the device occurs due to a hydrogen induced polarization at the Pd-SiO2 interface as schematically shown in Figure 1. During the years, several types of devices have been developed, both with insulators other than silicon dioxide and catalytic metals other than palladium. Furthermore, it has been demonstrated that sensors with thin, discontinuous catalytic metals can detect molecules, like ammonia, which are not detected by sensors with thick continuous palladium gates. 1-3 Although several insulators have been used in hydrogen sensitive Pd-insulator-semiconductor

  • 12.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hydrogen adsorption states at the Pd-SiO2 interface and simulation of the response of a Pd metal-oxide-semiconductor hydrogen sensor1998In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 83, no 8, p. 3947-3951Article in journal (Refereed)
    Abstract [en]

    The response of a Pd–SiO 2 –Si hydrogen sensor depends on the reaction kinetics of hydrogen on the Pd surface and on the hydrogen adsorption states at the Pd/SiO 2 interface. In this work we show that besides the dominating hydrogen adsorption state located on the oxide side of the interface, a second state, resulting in opposite hydrogen polarization, exists. This state is possibly a reminiscence of the hydrogen adsorption state on a clean Pd surface. Taking both states into account, a simulation of the hydrogen response over more than ten decades in hydrogen pressures gives good agreement with published data.

  • 13.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Real time measurements of hydrogen desorption and absorption during CO exposures of Pd: Hydrogen sticking and dissolution1998In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 133, no 1-2, p. 89-97Article in journal (Refereed)
    Abstract [en]

    Combined real time measurements of hydrogen desorption and absorption show that both processes may be induced simultaneously by CO adsorption on a hydrogen-covered Pd surface. The induced absorption is found to be a kinetic effect, where the amount absorbed depends on the hydrogen desorption rate and the CO adsorption rate. In addition to simple site blocking, adsorbed CO induces an increase in the hydrogen desorption energy and an activation barrier for hydrogen dissociation. Both increase linearly with CO coverage for θCO>0.18 ML. Below this coverage, the hydrogen dissociation is non-activated.

  • 14.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Tekniska högskolan.
    The catalytic oxidation of CO on polycrystalline Pd: Experiments and kinetic modelling1998In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 412/413, p. 430-440Article in journal (Refereed)
    Abstract [en]

    The catalytic oxidation of CO on a thin, polycrystalline Pd film has been studied. Even though the Pd film is expected to be dominated by (111) facets, some distinct differences compared to single crystalline Pd(111) are observed. A kinetic model for the CO oxidation reaction is presented. It gives good agreement with experiments, both in terms of CO2 reaction probability and CO coverage during reaction conditions. The model assumes a random distribution of the adsorbates, an activation energy for the reaction that decreases with increasing CO coverage, as well as a CO sticking coefficient that in a temperature dependent fashion depends on the oxygen coverage. Single crystal data available from the literature (initial sticking coefficients and heats of adsorption) were mainly used as input parameters. Thus, the model might also be a useful starting point when modeling the catalytic oxidation of CO on single crystal surfaces.

  • 15.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    The influence of CO on the response of hydrogen sensitive Pd-MOS devices1997In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 42, no 3, p. 217-223Article in journal (Refereed)
    Abstract [en]

    In order to understand and correctly interpret the response of chemical sensors under measurement conditions, detailed studies of molecule—sensor interactions under well-controlled conditions are needed. In this work, the influence of CO on the response of a hydrogen sensitive Pd—metal-oxide-semiconductor (Pd—MOS) device with a dense Pd film is studied in ultrahigh vacuum (UHV). The results show that although CO by itself does not induce any response of the device, CO may have a significant influence on the hydrogen response, especially so in the presence of oxygen. It is also shown that high CO coverages on the Pd surface increases the time needed to obtain equilibrium between the gas phase hydrogen pressure and the response of the Pd—MOS device. This is due to a CO induced increase of the activation energies of the dissociation and association processes for hydrogen. The effect on the hydrogen response is small for CO coverages below 0.2 monolayers and increases dramatically above this coverage.

  • 16.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petersson, Lars-Gunnar
    Tekniska högskolan.
    The water-forming reaction on thin, SiO2 supported, palladium films1990In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 41, no 1-3, p. 137-138Article in journal (Refereed)
    Abstract [en]

    The water-forming reaction has been studied on thin Pd films, evaporated on planar SiO2 substrates. The nominal film thickness varied between 5 and 100 Å. The studies were performed in uhv by means of mass spectrometry, UPS and work function measurements in the temperature range 323–523 K. The film structure was also studied with TEM. The results are compared with previous measurements on 1000 Å, thick, homogeneous Pd films. The structure of the thin Pd films changed dramatically during cyclic H2 and O2 exposures, from that of a continuous film with cracks to that of drop-like metal particles. These structural changes are not observed on the thick (1000 Å) Pd films. Even though there are large structural changes, the water-forming reaction looks qualitatively the same as on a thick Pd film. The total water production however, decreases with decreasing film thickness. We believe that some minor qualitative differences in the water-forming reaction for different nominal Pd film thicknesses, are due to the increasing PdSiO2 boundary as the thickness is reduced.

  • 17.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Iqbal, Zafar
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Two measurement modes for mobile phone optical sensing2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, p. 63-70Article in journal (Refereed)
    Abstract [en]

    The use of a mobile phone for classification and quantification of liquid samples is described. The screen of the phone is used for controlled illumination and the front side camera for imaging. No additional optical equipment is needed. It is shown that there are different regions of the captured image containing different information about the sample. One region contains light that has been specular reflected at the air-liquid interface and one is dominated by light that has propagated through the liquid. The specular reflected light contains information about the refractive index of the liquid sample whereas the transmitted light contains information about color and absorption. It is found that the specular reflectance increases linearly with increasing refractive index, n, in the range 1.33 less than n less than 1.38, as expected from the Fresnel equations. A change of the refractive index of about 0.004 refractive units can be detected. The transmitted light intensity is well described by the Beer-Lambert law over a large absorption range. Light from the two different areas of the image is used to analyze several types of liquid samples. It is shown that a combination of the two measurement modes improves the classification abilities of the mobile phone.

  • 18.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lindgren, David
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Bjorklund, Robert
    Linköping University, Department of Physics, Chemistry and Biology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Sundgren, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Drinking water monitoring with voltammetric sensors2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 25, p. 1165-1168Article in journal (Refereed)
    Abstract [en]

    Pulsed voltammetry has been applied to drinking water monitoring. This non-selective technique facilitates detection of several different threats to the drinking water. A multivariate algorithm shows that anomaly detection is possible with a minimum of false alarms. Multivariate analysis can also be used to classify different types of substances added to the drinking water. Low concentrations of sewage water contaminating the drinking water can be detected. A network of such sensors is envisaged to facilitate real-time and on-line monitoring of drinking water distribution networks.

  • 19.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    A model of the Temkin isotherm behaviour for hydrogen adsorption at Pd-SiO2 interfaces1997In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 82, no 6, p. 3143-3146Article in journal (Refereed)
    Abstract [en]

    A simple electrostatic model of the adsorbate–adsorbateinteraction of hydrogen atoms at a Pd–SiO 2 interface is presented. The model predicts a hydrogen adsorption isotherm of the Temkin type. It is found that, in practice, an upper limit for the hydrogen response of a Pd-metal-oxide-semiconductor device exists. The value (in V) is equal to the difference of the initial heats of adsorption (in eV) of the interface and the Pd bulk, respectively. Furthermore, a corresponding maximum hydrogen concentration, at the interface, of 1×10 18  m −2 is predicted. The predictions are in good agreement with previously observed experimental data.

  • 20.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Olsson, Lars
    Linköping University, Department of Medical and Health Sciences.
    Erlandsson, Ragnar
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology.
    Morphology changes of thin Pd films grown on SiO2: influence of adsorbates and temperature1999In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 342, no 1-2, p. 297-306Article in journal (Refereed)
    Abstract [en]

    Under certain conditions morphology changes occur when thin Pd films, grown on SiO2 at room temperature, are subject to elevated temperatures. First holes in the metal are observed, followed by network formation and finally isolation of metal islands. This process is known as agglomeration. The influence of gas exposures on this restructuring process has been studied by following variations in the capacitance of the structure and by atomic force microscopy, transmission electron microscopy and ultraviolet photoelectron spectroscopy. The capacitance measurements show that carbonaceous species have an impeding influence on the rate of agglomeration and may lock the film structure in a thermodynamic non-equilibrium state. By removing these species with oxygen exposure, i.e. by forming volatile CO and CO2, a clean surface is obtained and the agglomeration process can proceed. High oxygen or hydrogen coverages also lower the rate of restructuring, compared to the case of a clean surface. For the clean Pd surface, an apparent activation energy of 0.64 eV is found for the restructuring process.

  • 21.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Petersson, Lars-Gunnar
    Spillover of hydrogen, oxygen and carbon monoxide in oxidation reactions on SiO2 supported Pd1994In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 311, no 1-2, p. 139-152Article in journal (Refereed)
    Abstract [en]

    Oxidation of H2 and CO on large, oxygen preexposed Pd islands supported on SiO2, has been investigated in the temperature range 323 ⩽, T ⩽ 523 K. The results have been compared with the corresponding reactions on a polycrystalline Pd film. A maximum reactive sticking coefficient of 0.9 for H2 and an initial sticking coefficient for O2 of 0.8 on both structures is concluded. The maximum reactive sticking coefficient for CO is 0.85 on the film and apparently larger than unity on the island structure. The results obtained from the island structure can be rationalized if O2 and H2 dissociate on the Pd islands and have the possibility to spillover onto the oxide, while CO adsorbs and reacts both on the Pd islands and on the oxide. Spillover of oxygen occurs in a precursor state and is irreversible with an apparent activation energy of 0.1 eV for the forward reaction.

  • 22.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Diesel detection in surface water in the low ppb range2016In: PROCEEDINGS OF THE 30TH ANNIVERSARY EUROSENSORS CONFERENCE - EUROSENSORS 2016, ELSEVIER SCIENCE BV , 2016, Vol. 168, p. 384-387Conference paper (Refereed)
    Abstract [en]

    A method for diesel detection in surface water in the low ppb range is presented. Even though standard commercial metal oxide gas sensors with detection limits in the ppm range are used, extraction of volatile compounds from the water enables a detection limit of about 2 ppb diesel in the water. The technique can be used for surface water monitoring. The standard technique of ultraviolet fluorescence detection has an interference problem with humic substances. This is not a problem with the suggested technique. Results from lab measurements as well as field tests at a water utility in the Stockholm region in Sweden are presented. (C) 2016 Published by Elsevier Ltd.

  • 23.
    Erlandsson, Ragnar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Elwing, Hans
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Olsson, Lars
    Linköping University, Department of Medical and Health Sciences. Tekniska högskolan.
    Tengvall, Pentti
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wigren, Roger
    Welin Klintström, Stefan
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Scanning force microscopy - examples of applications to surface chemistry1992In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 88, p. 154-161Article in journal (Refereed)
    Abstract [en]

    Some recent results from the scanning force microscopy activity at our laboratory are presented. A brief description of attractive mode force microscopy is followed by a discussion of the following examples: O2/H2-induced morphology changes in thin palladium films, structure of spin cast polysulfone films, fibrinogen adsorption on hydrophobic SiO2, and force measurements on hydrophobic/hydrophilic substrates.

  • 24.
    Erlandsson, Ragnar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Olsson, Lars
    Linköping University, Department of Medical and Health Sciences.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Petersson, Lars-Gunnar
    Gas-induced restructuring of palladium model catalysts studied with atomic force microscopy1991In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 9, no 2, p. 825-828Article in journal (Refereed)
    Abstract [en]

    The structure of thin Pd films evaporated onto planar SiO2 substrates changes dramatically during oxygen/hydrogen exposures in ultrahigh vacuum. In this work we have used an atomic force microscope(AFM), operated in the attractive mode, to obtain the three‐dimensional morphology of the Pd surface for different film thicknesses and treatments, and compared the data with transmission electron microscopy(TEM) micrographs. During restructuring, a 100‐Å film changes from being a smooth continuous film with cracks into metal clusters dispersed on the SiO2 support. In the 5‐Å case the metal films are already well dispersed as fabricated. Here the gas exposure instead results in a clustering effect resulting in larger particles. The AFM gives results which are consistent with TEM micrographs but also gives additional information on metal particle shape which can lead to a further understanding of the restructuring process.

  • 25.
    Fathollahzadeh, Marjam
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering. College of Chemistry, Institute for Advanced Studies in Basic Sciences, Gava Zang, Zanjan, Iran.
    Tyagi, Manav
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Maziz, Ali
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Haghighi,, B
    Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Iran.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Mak, Wing Cheung
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Dynamic gates based on polypyrrole for microfluidic bioanalytical applications2016In: Biosensors 2016 – The World Congress on Biosensors, Gothenburg, Sweden, 25-27 May 2016, Elsevier, 2016Conference paper (Other academic)
  • 26.
    Imar, Shahzad
    et al.
    Dundalk Institute Technology, Ireland.
    Maccato, Chiara
    University of Padua, Italy.
    Dickinson, Calum
    University of Limerick, Ireland.
    Laffir, Fathima
    University of Limerick, Ireland.
    Vagin, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    McCormac, Timothy
    Dundalk Institute Technology, Ireland.
    Enhancement of Nitrite and Nitrate Electrocatalytic Reduction through the Employment of Self-Assembled Layers of Nickel- and Copper-Substituted Crown-Type Heteropolyanions2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 8, p. 2584-2592Article in journal (Refereed)
    Abstract [en]

    Multilayer assemblies of two crown-type type heteropolyanions (HPA), [Cu20Cl(OH)(24)(H2O)(12)(P8W48O184)](25-) and Ni-4(P8W48O148)(WO2)](28-), have been immobilized onto glassy carbon electrode surfaces via the layer-by-layer (LBL) technique employing polycathion-stabilized silver nanoparticles (AgNP) as the cationic layer within the resulting thin films characterized by electrochemical and physical methods. The redox behaviors of both HPA monitored during LBL assembly with cyclic voltammetry and impedance spectroscopy revealed significant changes by immobilization. The presence of AgNPs led to the retention of film porosity and electronic conductivity, which has been shown with impedance and voltammeric studies of film permeabilities toward reversible redox probes. The resulting films have been characterized by physical methods. Finally, the electrocatalytic performance of obtained films with respect to nitrite and nitrate electrocatalytic reduction has been comparatively studied for both catalysts. Nickel atoms trapped inside HPA exhibited a higher specific activity for reduction.

  • 27.
    Iqbal, Zafar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Classification and quantitative optical analysis of liquid and solid samples using a mobile phone as illumination source and detector2013In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 185, p. 354-362Article in journal (Refereed)
    Abstract [en]

    A mobile phone has been used both as illumination source and image detector for quantitative optical analysis of colored liquid samples (4 different colorants) and solid samples (printed color patterns, plastic beads and colored sand grains). Even though the measurement conditions were far from ideal, because the light source was strongly polychromatic and the illumination was not a collimated light beam with homogeneous light intensity, a logarithmic concentration dependence, in accordance with the Beer-Lambert law, described the data of the colored liquids quite well. By utilizing blue-blue (420-510 nm), green-green (480-590 nm) and red-red (575-695 nm) illumination/detection combinations, each sample could be assigned a unique color signature for classification that agreed with reference absorbance spectra measured with a spectrometer. Quantification of validation samples within a few percent of the actual values was achieved. Also the long-term repeatability of the measurements was investigated and was surprisingly good for such a simple system. Analysis of the colored solid samples was more complex with results being dependent on the morphology and colorimetric properties of the samples.

  • 28.
    Iqbal, Zafar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Optical sensing with a mobile phone applied to liquid solutions2012Manuscript (preprint) (Other academic)
    Abstract [en]

    The use of a mobile phone with a front side camera for the classification of liquid samples is described. The classification is based on the observation that there are different regions of the image captured by the mobile camera, one containing specular reflected light and one due to diffuse reflected light with transmission through the liquid. The specular reflected light contains information about the refractive index of the liquid sample whereas the diffuse light contains information about the color and absorption properties of the liquid. The information in the specular light is first elucidated. It is found that the reflectance of the region with specular reflected light increases linearly with increasing refractive index, n, in the range 1.33 < n < 1.38 as expected from the Fresnel equations. The information in the specular light is then used together with the previously described diffuse light from another region of the image to analyze several types of liquid samples. It is shown that a combination of the two areas of the image improves the classification abilities of the mobile phone.

  • 29.
    Naseer, Rashda
    et al.
    Dundalk Institute Technology, Ireland .
    Sankar Mal, Sib
    Jacobs University, Bremen, Germany .
    Ibrahim, Masooma
    Jacobs University, Bremen, Germany .
    Kortz, Ulrich
    Jacobs University, Bremen, Germany .
    Armstrong, Gordon
    University of Limerick, Ireland .
    Laffir, Fathima
    University of Limerick, Ireland .
    Dickinson, Calum
    University of Limerick, Ireland .
    Vagin, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    McCormac, Timothy
    Dundalk Institute Technology, Ireland .
    Redox, surface and electrocatalytic properties of layer-by-layer films based upon Fe(III)-substituted crown polyoxometalate [P8W48O184Fe16(OH)(28)(H2O)(4)](20-)2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 134, p. 450-458Article in journal (Refereed)
    Abstract [en]

    The electrocatalytic ability of the iron-substituted crown-type polyoxometalate (POM) Li4K16[P8W48O184Fe16(OH)(28)(H2O)(4)]center dot 66H(2)O center dot 2KCl (P8W48Fe16) towards the reduction of both nitrite and hydrogen peroxide reduction has been studied in both the solution and immobilized states for the POM. P8W48Fe16 was surface immobilised onto carbon electrode surfaces through employment of the layer-by-layer technique (LBL) using pentaerythritol-based Ru(II)-metallodendrimer [RuD](PF6)(8) as the cationic layer within the resulting films. The constructed multilayer films have been extensively studied by various electrochemical techniques and surface based techniques. Cyclic voltammetry and impedance spectroscopy have been utilized to monitor the construction of the LBL film after the deposition of each monolayer. The electrochemical behaviour of both a cationic and anionic redox probes at the LBL films has been undertaken to give indications as to the films porosity. The elemental composition and the surface morphology of the LBL films was conifmrde through the employment of AFM, XPS and SEM.

  • 30.
    Preechaburana, Pakorn
    et al.
    Thammasat University, Pathumthani, Thailand.
    Suska, Anke
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Biosensing with cell phones2014In: Trends in Biotechnology, ISSN 0167-7799, E-ISSN 1879-3096, Vol. 32, no 7, p. 351-355Article, review/survey (Refereed)
    Abstract [en]

    Continued progress in cell-phone devices has made them powerful mobile computers, equipped with sophisticated, permanent physical sensors embedded as the default configuration. By contrast, the incorporation of permanent biosensors in cell-phone units has been prevented by the multivocal nature of the stimuli and the reactions involved in biosensing and chemical sensing. Biosensing with cell phones entails the complementation of biosensing devices with the physical sensors and communication and processing capabilities of modern cell phones. Biosensing, chemical-sensing, environmental-sensing, and diagnostic capabilities would thus be supported and run on the residual capacity of existing cell-phone infrastructure. The technologies necessary to materialize such a scenario have emerged in different fields and applications. This article addresses the progress on cell-phone biosensing, the specific compromises, and the blend of technologies required to craft biosensing on cell phones.

  • 31.
    Sekretareva, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Stanford University, CA 94305 USA.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Correspondence on "Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts"2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 5, p. 3591-3593Article in journal (Other academic)
    Abstract [en]

    n/a

  • 32.
    Sekretareva, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Volkov, Anton V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Screen printed microband array based biosensor for water monitoring2015In: The Frumkin Symposium, 2015Conference paper (Refereed)
  • 33.
    Sekretareva, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail Yu
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Volkov, Anton V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony P.F.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Total phenol analysis of water using a laccase-based microsensor array2015In: Program of the XXIII International Symposium on Bioelectrochemistry and Bioenergetics of the Bioelectrochemical Society. 14-18 June, 2015. Malmö, Sweden, Lausanne: Bioelectrochemical Society , 2015, p. 155-155Conference paper (Other academic)
    Abstract [en]

    The monitoring of phenolic compounds in raw waters and wastewaters is of great importance for environmental control. Use of biosensors for rapid, specific and simple detection of phenolic compounds is a promising approach. A number of biosensors have been developed for phenol detection. A general drawback of previously reported biosensors is their insufficient detection limits for phenols in water samples. One way to improve the detection limit is by the use of microelectrodes.

    Microband design of the microelectrodes combines convergent mass transport due to the microscale width and high output currents due to the macroscopic length. Among the various techniques available for microband electrode fabrication, we have chosen screen-printing which is a cost-effective production method.

    In this study, we report on the development of a laccase-based microscale biosensor operating under a convergent diffusion regime. Screen-printing followed by simple cutting was utilized for the fabrication of graphite microbands as a platform for further covalent immobilization of laccase. Numerical simulations, utilizing the finite element method with periodic boundary conditions, were used for modeling the voltammetric response of the developed microband electrodes. Anodization followed by covalent immobilization was used for the electrode modification with laccase. Direct and mediated laccase bioelectrocatalytic oxidation of phenols was studied on macro- and microscale graphite electrodes. Significant enhancement of the analytical performance was achieved by the establishment of convergent diffusion in the microscale sensor. Finally, the developed microsensor was utilized to monitor phenolic compounds in real waste water.

  • 34.
    Sekretaryova, Alina
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Facilitating electron transfer in bioelectrocatalytic systems2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bioelectrocatalytic systems are based on biological entities, such as enzymes, whole cells, parts of cells or tissues, which catalyse electrochemical processes that involve the interaction between chemical change and electrical energy. In all cases, biocatalysis is implemented by enzymes, isolated or residing inside cells or part of cells. Electron transfer (ET) phenomena, within the protein molecules and between biological redox systems and electronics, enable the development of various bioelectrocatalytic systems, which can be used both for fundamental investigations of enzymatic biological processes by electrochemical methods and for applied purposes, such as power generation, bioremediation, chemical synthesis and biosensing.

    Electrical communication between the biocatalyst’s redox centre and an electrode is essential for the functioning of the system. This can be established using two main mechanisms: indirect ET and direct ET. The efficiency of the ET influences important parameters such as the turnover rate of the biocatalyst, the generated current density and partially the stability of the system, which in their turn determine response time, sensitivity, detection limit and operational stability of biosensing devices or the power densities and current output of biofuel cells, and hence should be carefully considered when designing bioelectrocatalytic systems.

    This thesis focuses on approaches that facilitate ET in bioelectrocatalytic systems based on indirect and direct ET mechanisms. Both fundamental aspects of ET in bioelectrocatalytic systems and applications of such systems for biosensing and power generation are considered. First, a new hydrophobic mediator for oxidases – unsubstituted phenothiazine and its improved ET properties in comparison with commonly used mediators are discussed. Application of the mediator in electrochemical biosensors is demonstrated by glucose, lactate and cholesterol sensing. Utilisation of mediated biocatalytic cholesterol oxidation, as the anodic reaction for the construction of a biofuel cell acting as a power supply and an analytical device at the same time, is investigated to deliver a selfpowered biosensor. Also the enhancement of mediated bioelectrocatalysis by employment of microelectrodes as a transducer is examined. The effect of surface roughness on the current response of the microelectrodes under conditions of convergent diffusion is considered. The applicability of the laccase-based system for total phenol analysis of weakly supported water is demonstrated. Finally, a new electrochemical approach derived from collision-based electrochemistry applicable for examination of the ET process of a single enzyme molecule is described.

    All together, the results presented in this thesis contribute to the solution of the ‘electronic coupling problem’, arising when interfacing biomolecules with electronics and limiting the performance of bioelectrocatalytic systems in specific applications. The developed methods to facilitate ET will hopefully promote future biosensing devices and biofuel cells. I believe the new approach for investigation of ET processes at a single enzyme molecule will complement existing single molecule techniques, giving further insights into enzymatic ET mechanisms at the molecular level and filling the gap between fundamental understanding of biocatalytic processes and their potential for bioenergy production.

    List of papers
    1. Bioelectrocatalytic systems for health applications
    Open this publication in new window or tab >>Bioelectrocatalytic systems for health applications
    2016 (English)In: Biotechnology Advances, ISSN 0734-9750, E-ISSN 1873-1899, Vol. 34, no 3, p. 177-197Article, review/survey (Refereed) Published
    Abstract [en]

    We present a brief overview of bioelectrocatalytic devices for in vitro health applications, including food safety and environmental analysis, focusing on microelectrode- and microfluidic-based biosensors, paper-based point-of-care devices and wearable biosensors. The main hurdles and future perspectives are discussed. We then consider the role of electron transfer between a biocatalyst and an electrode in biosensor design. Brief descriptions of indirect, direct and mediated mechanisms are given. The principal strategies, as well as recent developments for modulation of electron transfer in biocatalytic systems are summarised. In conclusion, we highlight some of the challenges associated with improving these redox systems.

    Place, publisher, year, edition, pages
    Elsevier, 2016
    Keywords
    Direct electron transfer; Mediated electron transfer; Immobilisation; Microbiosensor; Nanobiosensor; Paper-based biosensor; Wearable biosensor; Self-powered biosensor
    National Category
    Bioinformatics and Systems Biology
    Identifiers
    urn:nbn:se:liu:diva-123688 (URN)10.1016/j.biotechadv.2015.12.005 (DOI)000375500700004 ()26724183 (PubMedID)
    Available from: 2016-01-08 Created: 2016-01-08 Last updated: 2017-12-01Bibliographically approved
    2. Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
    Open this publication in new window or tab >>Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
    Show others...
    2012 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 3, p. 1220-1223Article in journal (Refereed) Published
    Abstract [en]

    Wiring glucose oxidase in the membrane with an immobilized mediator is possible due to the diffusion ability of the latter, if the enzyme containing membrane is formed according to the proposed protocol, including exposing proteins to water–organic mixtures with the high content of organic solvent. In the course of the study, the new glucose oxidase mediator, unsubstituted phenothiazine, was discovered. The diffusion coefficient of the mediator in the resulting membrane is independent of the presence of enzyme. The cyclic voltammograms of the enzyme electrode after appearance of the only glucose in solution obtain a well-defined catalytic shape, which is normally observed for both the enzyme and the mediator in solution. Analytical performances of the resulting biosensor are comparable to the advanced second generation ones, which, however, require covalent linking of the mediator either to the membrane forming polymer or to the enzyme. Even without such covalent linking, the reported biosensor is characterized by an appropriate long-term operational stability allowing reagentless sensing.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2012
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-112343 (URN)10.1021/ac203056m (DOI)22206508 (PubMedID)
    Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-12-05Bibliographically approved
    3. Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
    Open this publication in new window or tab >>Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
    Show others...
    2014 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 53, p. 275-282Article in journal (Refereed) Published
    Abstract [en]

    The mediation of oxidases glucose oxidase (GOx), lactate oxidase (LOx) and cholesterol oxidase (ChOx) by a new electron shuttling mediator, unsubstituted phenothiazine (PTZ), was studied. Cyclic voltammetry and rotating-disk electrode measurements in nonaqueous media were used to determine the diffusion characteristics of the mediator and the kinetics of its reaction with GOx, giving a second-order rate constant of 7.6×103–2.1×104 M−1 s−1 for water–acetonitrile solutions containing 5–15% water. These values are in the range reported for commonly used azine-type mediators, indicating that PTZ is able to function as an efficient mediator. PTZ and GOx, LOx and ChOx were successfully co-immobilised in sol–gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively, which were then optimised in terms of stability and sensitivity. The electrocatalytic oxidation responses showed a dependence on substrate concentration ranging from 0.6 to 32 mM for glucose, from 19 to 565 mM for lactate and from 0.015 to 1.0 mM for cholesterol detection. Oxidation of substrates on the surface of electrodes modified with PTZ and enzyme membrane was investigated with double-step chronoamperometry and the results showed that the PTZ displays excellent electrochemical catalytic activities even when immobilised on the surface of the electrode.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Phenothiazine; Electron transfer mediator; Enzyme biosensor; Glucose oxidase; Lactate oxidase; Cholesterol oxidase
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-100391 (URN)10.1016/j.bios.2013.09.071 (DOI)000329881100044 ()
    Available from: 2013-11-05 Created: 2013-11-05 Last updated: 2017-12-06Bibliographically approved
    4. Cholesterol Self-Powered Biosensor
    Open this publication in new window or tab >>Cholesterol Self-Powered Biosensor
    Show others...
    2014 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 19, p. 9540-9547Article in journal (Refereed) Published
    Abstract [en]

    Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilized in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalyzed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M-1 cm(-2)), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol. Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.

    Place, publisher, year, edition, pages
    American Chemical Society, 2014
    National Category
    Physical Sciences Biological Sciences
    Identifiers
    urn:nbn:se:liu:diva-112176 (URN)10.1021/ac501699p (DOI)000343017100031 ()25164485 (PubMedID)
    Note

    Funding Agencies|Swedish research council Formas; research centre Security Link; Swedish Institute

    Available from: 2014-11-18 Created: 2014-11-18 Last updated: 2017-12-05
    5. Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
    Open this publication in new window or tab >>Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
    Show others...
    2014 (English)In: ChemElectroChem, ISSN 2196-0216, Vol. 1, no 4, p. 755-762Article in journal (Refereed) Published
    Abstract [en]

    Arrays of microband electrodes were developed by screen printing followed by cutting, which enabled the realization of microband arrays at the cut edge. The microband arrays of different designs were characterized by physical and electro-chemical methods. In both cases, the methods showed that the microband width was around 5 mm. Semi-steady-state cyclic voltammetry responses were observed for redox probes, and chronocoulometric measurements showed the establishment of convergent diffusion regimes characterized by current densities similar to those of a single microelectrode. The analytical performance of the electrode system and its versatility were illustrated with two electrochemical assays: detection of ascorbic acid through direct oxidation and a mediated glucose biosensor fabricated by dip coating. Due to convergent mass transport, both systems showed an enhancement in their analytical characteristics. The developed approach can be adapted to automated electrode recovery.

    Place, publisher, year, edition, pages
    Wiley, 2014
    Keywords
    graphite screen printing; microarrays; microband; sensors; voltammetry
    National Category
    Physical Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-109289 (URN)10.1002/celc.201300204 (DOI)000338296100010 ()
    Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2017-11-03Bibliographically approved
    6. Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currents
    Open this publication in new window or tab >>Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currents
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Two methods to estimate the electrochemically active surface area (EASA) of microelectrodes were compared. One is based on electrocapacitive measurements and the other on faradaic measuements. A systematic study revealed a strong influence of the surface roughness and the electrolyte concentration on the EASA of microelectrodes estimated from the electrocapacitive measurements, yielding a lack of reliability compared to the faradaic method.

    Keywords
    Electrochemically active surface area, microelectrode, microband, roughness, capacitive process, faradaic process
    National Category
    Chemical Sciences Chemical Engineering Chemical Process Engineering
    Identifiers
    urn:nbn:se:liu:diva-125240 (URN)
    Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2017-11-03Bibliographically approved
    7. Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
    Open this publication in new window or tab >>Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
    Show others...
    2016 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 907, p. 45-53Article in journal (Refereed) Published
    Abstract [en]

    The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M−1 cm−2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.

    Place, publisher, year, edition, pages
    Elsevier, 2016
    Keywords
    Laccase; microelectrode; microband; electrochemical modeling; total phenol analysis; wastewater
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-123677 (URN)10.1016/j.aca.2015.12.006 (DOI)000368422900005 ()
    Note

    Funding agencies: Swedish research council Formas [245-2010-1062]; research centre Security Link [VINNOVA 2009-00966]; Norrkopings fond for Forskning och Utveckling; VINNOVA

    Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2017-12-01Bibliographically approved
    8. Electrocatalytic Currents from Single Enzyme Molecules
    Open this publication in new window or tab >>Electrocatalytic Currents from Single Enzyme Molecules
    2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 8, p. 2504-2507Article in journal (Refereed) Published
    Abstract [en]

    Single molecule enzymology provides an opportunity to examine details of enzyme mechanisms that are not distinguishable in biomolecule ensemble studies. Here we report, for the first time, detection of the current produced in an electrocatalytic reaction by a single redox enzyme molecule when it collides with an ultramicroelectrode. The catalytic process provides amplification of the current from electron-transfer events at the catalyst leading to a measurable current. This new methodology monitors turnover of a single enzyme molecule. The methodology might complement existing single molecule techniques, giving further insights into enzymatic mechanisms and filling the gap between fundamental understanding of biocatalytic processes and their potential for bioenergy production.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2016
    National Category
    Chemical Sciences Chemical Engineering Chemical Process Engineering
    Identifiers
    urn:nbn:se:liu:diva-125241 (URN)10.1021/Jacs.5b13149 (DOI)000371453700011 ()
    Note

    Funding agencies:  Swedish research council Formas [245-2010-1062]; research center Security Link (VINNOVA ) [2009-00966]; Centre in Nano Science and Technology (CeNano, Linkoping University)

    Vid tiden för dispuation förelåg publikationen endast som manuskript

    Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2017-11-30Bibliographically approved
  • 35.
    Sekretaryova, Alina
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Novel reagentless electrodes for biosensing2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Analytical chemical information is needed in all areas of human activity including health care, pharmacology, food control and environmental chemistry. Today one of the main challenges in analytical chemistry is the development of methods to perform accurate and sensitive rapid analysis and monitoring of analytes in ‘real’ samples. Electrochemical biosensors are ideally suited for these applications.

    Despite the wide application of electrochemical biosensors, they have some limitations. Thus, there is a demand on improvement of biosensor performance together with a necessity of simplification required for their mass production. In this thesis the work is focused on the development of electrochemical sensors with improved performance applicable for mass production, e.g. by screen printing.

    Biosensors using immobilized oxidases as the bio-recognition element are among the most widely used electrochemical devices. Electrical communication between redox enzymes and electrodes can be established by using natural or synthetic electron carriers as mediators. However, sensors based on soluble electronshuttling redox couples have low operational stability due to the leakage of water-soluble mediators to the solution. We have found a new hydrophobic mediator for oxidases – unsubstituted phenothiazine. Phenothiazine and glucose oxidase, lactate oxidase or cholesterol oxidase were successfully co-immobilized in a sol-gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively. All elaborated biosensors with phenothiazine as a mediator exhibited long-term operational stability. A kinetic study of the mediator has shown that phenothiazine is able to function as an efficient mediator in oxidase-based biosensors.

    To improve sensitivity of the biosensors and simplify their production we have developed a simple approach for production of graphite microelectrode arrays. Arrays of microband electrodes were produced by screen printing followed by scissor cutting, which enabled the realization of microband arrays at the cut edge. The analytical performance of the system is illustrated by the detection of ascorbic acid through direct oxidation and by detection of glucose using a phenothiazine mediated glucose biosensor. Both systems showed enhanced sensitivity due to improved mass transport. Moreover, the developed approach can be adapted to automated electrode recovery.

    Finally, two enzyme-based electrocatalytic systems with oxidation and reduction responses, respectively, have been combined into a fuel cell generating a current as an analytical output (a so-called self-powered biosensor). This was possible as a result of the development of the phenothiazine mediated enzyme electrodes, which enabled the  construction of a cholesterol biosensor with self-powered configuration. The biosensor generates a current when analyte (cholesterol) is added to the cell. The biosensor has been applied for whole plasma analysis.

    All developed concepts in the thesis are compatible with a wide range of applications and some of them may even be possible to realize in a fully integrated biosensor unit based on printed electronics.

    List of papers
    1. Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
    Open this publication in new window or tab >>Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
    Show others...
    2012 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 3, p. 1220-1223Article in journal (Refereed) Published
    Abstract [en]

    Wiring glucose oxidase in the membrane with an immobilized mediator is possible due to the diffusion ability of the latter, if the enzyme containing membrane is formed according to the proposed protocol, including exposing proteins to water–organic mixtures with the high content of organic solvent. In the course of the study, the new glucose oxidase mediator, unsubstituted phenothiazine, was discovered. The diffusion coefficient of the mediator in the resulting membrane is independent of the presence of enzyme. The cyclic voltammograms of the enzyme electrode after appearance of the only glucose in solution obtain a well-defined catalytic shape, which is normally observed for both the enzyme and the mediator in solution. Analytical performances of the resulting biosensor are comparable to the advanced second generation ones, which, however, require covalent linking of the mediator either to the membrane forming polymer or to the enzyme. Even without such covalent linking, the reported biosensor is characterized by an appropriate long-term operational stability allowing reagentless sensing.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2012
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-112343 (URN)10.1021/ac203056m (DOI)22206508 (PubMedID)
    Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-12-05Bibliographically approved
    2. Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
    Open this publication in new window or tab >>Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
    Show others...
    2014 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 53, p. 275-282Article in journal (Refereed) Published
    Abstract [en]

    The mediation of oxidases glucose oxidase (GOx), lactate oxidase (LOx) and cholesterol oxidase (ChOx) by a new electron shuttling mediator, unsubstituted phenothiazine (PTZ), was studied. Cyclic voltammetry and rotating-disk electrode measurements in nonaqueous media were used to determine the diffusion characteristics of the mediator and the kinetics of its reaction with GOx, giving a second-order rate constant of 7.6×103–2.1×104 M−1 s−1 for water–acetonitrile solutions containing 5–15% water. These values are in the range reported for commonly used azine-type mediators, indicating that PTZ is able to function as an efficient mediator. PTZ and GOx, LOx and ChOx were successfully co-immobilised in sol–gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively, which were then optimised in terms of stability and sensitivity. The electrocatalytic oxidation responses showed a dependence on substrate concentration ranging from 0.6 to 32 mM for glucose, from 19 to 565 mM for lactate and from 0.015 to 1.0 mM for cholesterol detection. Oxidation of substrates on the surface of electrodes modified with PTZ and enzyme membrane was investigated with double-step chronoamperometry and the results showed that the PTZ displays excellent electrochemical catalytic activities even when immobilised on the surface of the electrode.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Phenothiazine; Electron transfer mediator; Enzyme biosensor; Glucose oxidase; Lactate oxidase; Cholesterol oxidase
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-100391 (URN)10.1016/j.bios.2013.09.071 (DOI)000329881100044 ()
    Available from: 2013-11-05 Created: 2013-11-05 Last updated: 2017-12-06Bibliographically approved
    3. Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
    Open this publication in new window or tab >>Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
    Show others...
    2014 (English)In: ChemElectroChem, ISSN 2196-0216, Vol. 1, no 4, p. 755-762Article in journal (Refereed) Published
    Abstract [en]

    Arrays of microband electrodes were developed by screen printing followed by cutting, which enabled the realization of microband arrays at the cut edge. The microband arrays of different designs were characterized by physical and electro-chemical methods. In both cases, the methods showed that the microband width was around 5 mm. Semi-steady-state cyclic voltammetry responses were observed for redox probes, and chronocoulometric measurements showed the establishment of convergent diffusion regimes characterized by current densities similar to those of a single microelectrode. The analytical performance of the electrode system and its versatility were illustrated with two electrochemical assays: detection of ascorbic acid through direct oxidation and a mediated glucose biosensor fabricated by dip coating. Due to convergent mass transport, both systems showed an enhancement in their analytical characteristics. The developed approach can be adapted to automated electrode recovery.

    Place, publisher, year, edition, pages
    Wiley, 2014
    Keywords
    graphite screen printing; microarrays; microband; sensors; voltammetry
    National Category
    Physical Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-109289 (URN)10.1002/celc.201300204 (DOI)000338296100010 ()
    Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2017-11-03Bibliographically approved
    4. Cholesterol Self-Powered Biosensor
    Open this publication in new window or tab >>Cholesterol Self-Powered Biosensor
    Show others...
    2014 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 19, p. 9540-9547Article in journal (Refereed) Published
    Abstract [en]

    Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilized in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalyzed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M-1 cm(-2)), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol. Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.

    Place, publisher, year, edition, pages
    American Chemical Society, 2014
    National Category
    Physical Sciences Biological Sciences
    Identifiers
    urn:nbn:se:liu:diva-112176 (URN)10.1021/ac501699p (DOI)000343017100031 ()25164485 (PubMedID)
    Note

    Funding Agencies|Swedish research council Formas; research centre Security Link; Swedish Institute

    Available from: 2014-11-18 Created: 2014-11-18 Last updated: 2017-12-05
  • 36.
    Sekretaryova, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Karyakin, Arkady A.
    Moscow MV Lomonosov State University, Russia.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Vagin, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Cholesterol Self-Powered Biosensor2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 19, p. 9540-9547Article in journal (Refereed)
    Abstract [en]

    Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilized in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalyzed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M-1 cm(-2)), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol. Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.

  • 37.
    Sekretaryova, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Vagin, Mikhail Y
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    A highly sensitive and self-powered cholesterol biosensor2014In: 24th Anniversary World Congress on Biosensors – Biosensors 2014, Elsevier, 2014Conference paper (Other academic)
    Abstract [en]

    Blood cholesterol is a very important parameter for the assessment of atherosclerosis and other lipid disorders. The total cholesterol concentration in human blood should be less than 5.17 mM. Concentrations in the range 5.17 – 6.18 mM are considered borderline high risk and levels above 6.21 mM, high risk. Cholesterol determination with high accuracy is therefore necessary in order to differentiate these levels for medical screening or diagnosis. Several attempts to develop highly sensitive cholesterol biosensors have been described, but, to the best of our knowledge, this is the first report of a self-powered cholesterol biosensor, i.e. a device delivering the analytical information from the current output of the energy of the biocatalytic conversion of cholesterol, without any external power source. This is particularly relevant to the development of inexpensive screening devices based on printed electronics.

     

    We present two complementary bioelectrocatalytic platforms suitable for the fabrication of a self-powered biosensor. Both are based on cholesterol oxidase (ChOx) immobilisation in a sol-gel matrix, as illustrated in Fig. 1 [1]. Mediated biocatalytic cholesterol oxidation [2] was used as the anodic reaction and electrocatalytic reduction of hydrogen peroxide on Prussian Blue (PB) as the cathodic reaction. Due to a synergistic effect in the self-powered cholesterol biosensor, the analytical parameters of the overall device exceeded those of the individual component half-cells, yielding a sensitivity of 0.19 A M-1 cm-2 and a dynamic range that embraces the free cholesterol concentrations found in human blood.

     

    Thus, we have demonstrated the novel concept of highly sensitive cholesterol determination using the first self-powered cholesterol biosensor. This configuration is particularly promising for incorporation in emerging plastic- and paper-based analytical instruments for decentralised diagnostics and mobile health.

     

  • 38.
    Sekretaryova, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Bioelectrocatalytic systems for health applications2016In: Biotechnology Advances, ISSN 0734-9750, E-ISSN 1873-1899, Vol. 34, no 3, p. 177-197Article, review/survey (Refereed)
    Abstract [en]

    We present a brief overview of bioelectrocatalytic devices for in vitro health applications, including food safety and environmental analysis, focusing on microelectrode- and microfluidic-based biosensors, paper-based point-of-care devices and wearable biosensors. The main hurdles and future perspectives are discussed. We then consider the role of electron transfer between a biocatalyst and an electrode in biosensor design. Brief descriptions of indirect, direct and mediated mechanisms are given. The principal strategies, as well as recent developments for modulation of electron transfer in biocatalytic systems are summarised. In conclusion, we highlight some of the challenges associated with improving these redox systems.

  • 39.
    Sekretaryova, Alina N
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Karyakin, Arkady A
    Moscow State University, Russia.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Vagin, Mikhail Y
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Novel single-enzyme based self-powered biosensor2014In: 15th International Conference on Electroanalysis (ESEAC), 2014Conference paper (Other academic)
  • 40.
    Sekretaryova, Alina N
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Vagin, Mikhail Y
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    A screen-printed microband array biosensor for water monitoring2014In: 15th International Conference on Electroanalysis (ESEAC), 2014Conference paper (Other academic)
  • 41.
    Sekretaryova, Alina N.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail Yu.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currentsManuscript (preprint) (Other academic)
    Abstract [en]

    Two methods to estimate the electrochemically active surface area (EASA) of microelectrodes were compared. One is based on electrocapacitive measurements and the other on faradaic measuements. A systematic study revealed a strong influence of the surface roughness and the electrolyte concentration on the EASA of microelectrodes estimated from the electrocapacitive measurements, yielding a lack of reliability compared to the faradaic method.

  • 42.
    Sekretaryova, Alina N.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail Yu.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony P.F.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Electrocatalytic Currents from Single Enzyme Molecules2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 8, p. 2504-2507Article in journal (Refereed)
    Abstract [en]

    Single molecule enzymology provides an opportunity to examine details of enzyme mechanisms that are not distinguishable in biomolecule ensemble studies. Here we report, for the first time, detection of the current produced in an electrocatalytic reaction by a single redox enzyme molecule when it collides with an ultramicroelectrode. The catalytic process provides amplification of the current from electron-transfer events at the catalyst leading to a measurable current. This new methodology monitors turnover of a single enzyme molecule. The methodology might complement existing single molecule techniques, giving further insights into enzymatic mechanisms and filling the gap between fundamental understanding of biocatalytic processes and their potential for bioenergy production.

  • 43.
    Sekretaryova, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Collision-based Electrochemistry for Investigation of Direct Electron Transfer of a Single Enzyme Molecule2017In: 26th Anniversary World Congress on Biosensors (Biosensors), Elsevier, 2017, p. 238-239Conference paper (Refereed)
    Abstract [en]

    Eldectron transfer between a biorecognition element and an electrode is an essential element of bioelectrocatalytic systems, such as biosensors and biofuel cells. The number of working systems based on direct electron communication is limited and detailed investigations of the mechanism of the process are still required. Here, we present the use of a novel approach of collision-based bioelectrocatalysis to monitor electrocatalytic currents from individual redox enzyme molecules. This approach allowed us to calculate the individual turnover rates of these molecules and investigate the influence of the applied potential, pH and additions of inhibitor on the observed rates of direct electron transfer.

  • 44.
    Sekretaryova, Alina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Volkov, Anton V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail Yu
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Total phenol analysis of weakly supported water using a laccase-based microband biosensor.2016In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 907, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M−1 cm−2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.

  • 45.
    Vagin, Mikhail
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Sekretareva, Alina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Department of Chemistry, Stanford University, Stanford, USA.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Håkansson, Anna
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Graphensic AB, Teknikringen 1F, Linköping, Sweden.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Monitoring of epitaxial graphene anodization2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 238, p. 91-98Article in journal (Refereed)
    Abstract [en]

    Anodization of a graphene monolayer on silicon carbide was monitored with electrochemical impedance spectroscopy. Structural and functional changes of the material were observed by Raman spectroscopy and voltammetry. A 21 fold increase of the specific capacitance of graphene was observed during the anodization. An electrochemical kinetic study of the Fe(CN)(6)(3) (/4) redox couple showed a slow irreversible redox process at the pristine graphene, but after anodization the reaction rate increased by several orders of magnitude. On the other hand, the Ru(NH3) (3+/2+)(6) redox couple proved to be insensitive to the activation process. The results of the electron transfer kinetics correlate well with capacitance measurements. The Raman mapping results suggest that the increased specific capacitance of the anodized sample is likely due to a substantial increase of electron doping, induced by defect formation, in the monolayer upon anodization. The doping concentration increased from less than 1 x 10(13) of the pristine graphene to 4-8 x 10(13) of the anodized graphene. (C) 2017 Elsevier Ltd. All rights reserved.

    The full text will be freely available from 2019-04-04 13:36
  • 46.
    Vagin, Mikhail
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Sekretareva, Alina
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Sanchez, Rafael
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform2014In: ChemElectroChem, ISSN 2196-0216, Vol. 1, no 4, p. 755-762Article in journal (Refereed)
    Abstract [en]

    Arrays of microband electrodes were developed by screen printing followed by cutting, which enabled the realization of microband arrays at the cut edge. The microband arrays of different designs were characterized by physical and electro-chemical methods. In both cases, the methods showed that the microband width was around 5 mm. Semi-steady-state cyclic voltammetry responses were observed for redox probes, and chronocoulometric measurements showed the establishment of convergent diffusion regimes characterized by current densities similar to those of a single microelectrode. The analytical performance of the electrode system and its versatility were illustrated with two electrochemical assays: detection of ascorbic acid through direct oxidation and a mediated glucose biosensor fabricated by dip coating. Due to convergent mass transport, both systems showed an enhancement in their analytical characteristics. The developed approach can be adapted to automated electrode recovery.

  • 47.
    Vagin, Mikhail Y
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Boron-doped diamond microelectrode arrays for electrochemical monitoring of antibiotics contamination in water2014In: 15th International Conference on Electroanalysis (ESEAC), 2014Conference paper (Other academic)
    Abstract [en]

    The improvement of water management and increasing the access to safe drinking water can develop the quality of life for millions of people world-wide and reduce child mortality due to water-borne diseases [1]. Sweden was recently affected by the lack of appropriate water management which resulted in microbial contamination and tens of thousands of people falling ill [2]. Pollution with chemical compounds is also a waterworks concern. The appearance of pharmaceuticals such as antibiotics in raw water affects the cleaning processes at waterworks [3]. Substances which are not, or are only partly, eliminated in the sewage treatment plant will reach the surface water where they may affect organisms of different trophic levels and cause, for example, the of antibiotics resistance [4]. The inhibition of bacteria of waste water plants by antibiotics may seriously affect organic matter degradation. The efficiency of nitrification as an important step in waste water purification, can be decreased by antibiotics inhibition [5]. Boron-doped diamond (BDD) is an advanced electrode material that possesses the combination of good electrical conductivity achieved via film doping and the extreme chemical inertness of diamond, which gives rise to a number of highly desirable properties of BDD as electrode material: a wide potential window in aqueous media allows electrochemical measurements at both extreme anodic and cathodic potentials, very low capacitive currents leads to a sensitivity increase and extreme chemical and structural inertness prevents electrode fouling [6]. Usage of a microelectrode array as the working electrode offers a variety of benefits for electroanalysis: an improvement of the analytical performance in comparison with macroelectrodes under planar diffusion, higher signal-to-noise ratios due to low capacitive currents at the small surface area, shorter response times and less sensitivity to variations in the water flow rate. The BDD arrays of this work contain 2900 microelectrodes (10 mm diameter each) and have been used for the detection of antibiotics (ofloxacine and canamycin A) in water with high amplitude pulse voltammetry processed by multivariate data analysis. The detection limits observed in monitoring mode were comparable with the characteristics of standard protocols of antibiotics detection, which opens the possibility for continuous monitoring of water.

    [1] The United Nations, World Water Development Report 4, 2012; [2] Lindberg, A. et al.,

    FOI-R--3376--SE, 2011; Dryselius, R.; National Food Agency, Sweden, 2012; [3] Kummerer

    K. Chemosphere, 2009, 75, 417; [4] Kummerer K. Chemosphere, 2009, 75, 435; [5]

    Dokianakis, S.N. et al., Water Sci. Technol. 50, 341; [6] Goeting, C. et al.,

    NewDiam.Front.C.Tech. 1999, 9, 207; Compton, R. et al., Electroanal. 2003, 15, 1349.

     

  • 48.
    Vagin, Mikhail Y
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Sekretaryova, Alina N
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Reategui, Rafael Sanchez
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Screen-printed graphite microbands as a versatile biosensor platform2014In: 24th Anniversary World Congress on Biosensors – Biosensors 2014, Elsevier, 2014Conference paper (Other academic)
    Abstract [en]

    The use of extremely small working electrodes offers a variety of benefits for electroanalysis. The enhanced mass transport as a result of convergent diffusion is the most important advantage of microdimensional electrodes and results in improved of analytical performance The low detectable-currents problem can be solved by single microelectrode multiplication into an array, thus combining the advantages of enhanced mass transport and high output signals. The microband is one of the most cost-effective and easy-fabricated geometries for microelectrodes. The microband width is a critical microscopic dimension of the electrode, which maintains the dominance of convergent diffusion, whereas the microband length is macroscopic and ensures registration of high currents.

    Graphite screen-printing on a plastic support is a standard technology for large-scale production of low cost electrochemical devices. This has been combined with simple guillotine cutting to fabricate of microband arrays for autonomous environmental and clinical monitoring.

    Single-layer and multilayer microband arrays of different band lengths were produced and characterised using optical and electrochemical methods. The critical dimension for the microband width to facilitate convergent diffusion was assessed electrochemically and found to be in the order of 5 microns. The developed electrode structures were used as a versatile platform for the manufacture of model electroanalytical systems. Direct oxidation of ascorbic acid was explored at the microband arrays and a glucose biosensor based on mediated and immobilised glucose oxidase was fabricated. Both examples yielded significant enhancement of the analytical performance.

    A: the layout of the screen-printed graphite microband array of 5 electrode layers. B: voltammmetric responses obtained at the microband arrays.

    Acknowledgement: Formas and Security Link for financial support; David Nilsson (Acreo) for screen-printing.

  • 49.
    Vagin, Mikhail Y
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Sekretaryova, Alina N
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Reategui, Rafael Sanchez
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Screen-printed graphite microbands for electroanalysis2014In: 15th International Conference on Electroanalysis (ESEAC), 2014Conference paper (Other academic)
  • 50.
    Vagin, Mikhail Yu.
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems.
    Jeerapan, Itthipon
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Hat Yai, Songkla, Thailand.
    Wannapob, Rodtichoti
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering. Hat Yai, Songkla, Thailand.
    Thavarungkul, Panote
    Hat Yai, Songkla, Thailand.
    Kanatharana, Proespichaya
    Hat Yai, Songkla, Thailand.
    Anwar, Nargis
    Dublin Road, Dundalk, County Louth, Ireland.
    McCormac, Timothy
    Dublin Road, Dundalk, County Louth, Ireland.
    Eriksson, Mats
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems.
    Turner, Anthony P.F
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Jager, Edwin W.H.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Wing Cheung, Mak
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Water-processable polypyrrole microparticle modules for direct fabrication of hierarchical structured electrochemical interfaces2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 190, p. 495-503Article in journal (Refereed)
    Abstract [en]

    Hierarchically structured materials (HSMs) are becoming increasingly important in catalysis, separation and energy applications due to their advantageous diffusion and flux properties. Here, we introduce a facile modular approach to fabricate HSMs with tailored functional conducting polypyrrole microparticles (PPyMP). The PPyMPs were fabricated with a calcium carbonate (CaCO3) template-assisted polymerization technique in aqueous media at room temperature, thus providing a new green chemistry for producing water-processable functional polymers. The sacrificial CaCO3 template guided the polymerization process to yield homogenous PPyMPs with a narrow size distribution. The porous nature of the CaCO3 further allows the incorporation of various organic and inorganic dopants such as an electrocatalyst and redox mediator for the fabrication of functional PPyMPs. Dawson-type polyoxometalate (POM) and methylene blue (MB) were chosen as the model electrocatalyst and electron mediator dopant, respectively. Hierarchically structured electrochemical interfaces were created simply by self-assembly of the functional PPyMPs. We demonstrate the versatility of this technique by creating two different hierarchical structured electrochemical interfaces: POM-PPyMPs for hydrogen peroxide electrocatalysis and MB-PPyMPs for mediated bioelectrocatalysis. We envision that the presented design concept could be extended to different conducting polymers doped with other functional organic and inorganic dopants to develop advanced electrochemical interfaces and to create high surface area electrodes for energy storage.

12 1 - 50 of 53
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