| 1. |
- Sekretareva, Alina, et al.
(författare)
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Total phenol analysis of water using a laccase-based microsensor array
- 2015
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Ingår i: Program of the XXIII International Symposium on Bioelectrochemistry and Bioenergetics of the Bioelectrochemical Society. 14-18 June, 2015. Malmö, Sweden. - Lausanne : Bioelectrochemical Society. ; , s. 155-155
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
- Sekretaryova, Alina N., et al.
(författare)
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Electrocatalytic Currents from Single Enzyme Molecules
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:8, s. 2504-2507
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Sekretaryova, Alina N., et al.
(författare)
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Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currents
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 4. |
- Sekretaryova, Alina, et al.
(författare)
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Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
- 2016
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 907, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Vagin, Mikhail, et al.
(författare)
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Potential-modulated Electrocapacitive Properties of Soft Microstructured Polypyrrole
- 2017
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Ingår i: Electroanalysis. - : WILEY-V C H VERLAG GMBH. - 1040-0397 .- 1521-4109. ; 29:1, s. 203-207
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Tidskriftsartikel (refereegranskat)abstract
- Microstructured materials are becoming important for high performance electrochemical device especially for energy storage due to their advantageous diffusion and flux properties. Utilizing a rationally designed hollow structured polypyrrole microparticles (PPyMPs) with controllable wall thicknesses of -110 to 340 nm, we observed a significant morphological effect on electrocapacitive kinetics of the PPyMPs modulated by the voltammetric potential window and scan rate. The thinhollow architecture of PPyMPs revealed significant enhancement of charge storage performance (up to 447%), high retention at high scan rate and faster charge/dis-charge kinetics compared to the thick-hollow PPyMPs due to the larger accessible surface area and decrease of diffusion length. These findings demonstrated the electrocapacitive kinetics performance of microstructured soft materials related to morphological effect modulated by operational conditions. Our study provides new insight on electrochemistry of soft electrode materials with controlled nanostructured morphology for understanding the mechanism of charge insertion and mass diffusion for the future development of high performance porous electrode material.
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| 6. |
- Vagin, Mikhail Yu, et al.
(författare)
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Direct bioelectrocatalysis on anodized epitaxial graphene
- 2015
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Ingår i: Program of the XXIII International Symposium on Bioelectrochemistry and Bioenergetics of the Bioelectrochemical Society14-18 June, 2015Malmö, Sweden. - Lausanne : Bioelectrochemical Society. ; , s. 170-170
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Graphene as a nanomaterial consisting of a single layer sheets of atoms of carbon in hexagonal arrangement is making a significant impact in variety of technologies such as energy storage and chemical analysis. The significant attention paid to this thinnest nanomaterial resulted in thousands of patent applications is due to its staggering properties. Due to the planar conjugation of the sp2bonds in graphene, two-dimensional electrical conduction is highly efficient. On the contrary, the efficiency of electron exchange at the out-of-plane of the graphene sheet is small. The significant difference of the densities of electronic states at in-plane and out-of-plane of graphene sheet determines two distinct structural contributions (basal and edge plane respectively) to the behavior of all graphitic materials yielding the chemical and electrochemical anisotropy. Being the simplest building block of graphitic materials, graphene offers the possibility to study the behavior on the simplest level of structural organization. However, the major effort of the recent electrochemical studies of graphene were done using a bulk materials based on graphene flakes possessing the domination of edges of high reactivity. The planar orientation of graphene sheets with controllable exposure of basal plane is achievable via the growth by chemical vapor deposition or by epitaxial flash annealing on crystalline structures of silicon carbide. The slow growth of graphene onto crystalline support during annealing in the inert atmosphere results in a development of a high quality graphene monolayer attached to the solid insulating support. The creation of sp3-type reactive defects on the basal plane of graphite can be achieved by anodization at high anodic potentials.We developed the procedure for the real-time monitoring of epitaxial graphene anodization. The changes of electrochemical properties of graphene monolayer with anodization have been comparatively investigated by electrochemical methods. The estimation of specific capacitance in pure electrolyte and in conditions of Faradaic process has been carried out. Finally, the direct electrocatalysis of laccase (Trametes versicolor) has been used as an electrode reaction to probe the reactivities of anodized epitaxial graphene and conventional carbon materials.
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| 7. |
- Vagin, Mikhail Yu., et al.
(författare)
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Water-processable polypyrrole microparticle modules for direct fabrication of hierarchical structured electrochemical interfaces
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 190, s. 495-503
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
- Wannapob, Rodtichoti, et al.
(författare)
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Printable Heterostructured Bioelectronic Interfaces with Enhanced Electrode Reaction Kinetics by Intermicroparticle Network
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:38, s. 33368-33376
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Tidskriftsartikel (refereegranskat)abstract
- Printable organic bioelectronics provide a fast and cost-effective approach for the fabrication of novel biodevices, while the general challenge is to achieve optimized reaction kinetics at multiphase boundaries between biomolecules and electrodes. Here, we present an entirely new concept based on a modular approach for the construction of heterostructured bioelectronic interfaces by using tailored functional "biological microparticles" combined with "transducer micro particles" as modular building blocks. This approach offers high versatility for the design and fabrication of bioelectrodes with a variety of forms of interparticle spatial organization, from layered structures to more advance bulk heterostructured architectures. The heterostructured biocatalytic electrodes delivered twice the reaction rate and a six-fold increase in the effective diffusion kinetics in response to a catalytic model using glucose as the substrate, together with the advantage of shortened diffusion paths for reactants between multiple interparticle junctions and large active particle surface. The consequent benefits of this improved performance combined with the simple means of mass production are of major significance for the emerging printed electronics industry.
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| 10. |
- Zhybak, Mykhailo T., et al.
(författare)
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Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode
- 2016
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Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 183:6, s. 1981-1987
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Tidskriftsartikel (refereegranskat)abstract
- We describe a composite material for use in electrochemical oxygen reduction. A screen-printed electrode (SPE) was consecutively modified with electrodeposited copper, a Nafion membrane and electropolymerized polyaniline (PANi) to give an electrocatalytic composite of type PANi/Nafion/Cu2O/SPE that displays good electrical conductivity at neutral pH values. It is found that the presence of ammonia causes complex formation with Cu(I), and this causes electroreduction of oxygen to result in an increased cathodic current. The finding was applied to the quantification of ammonium ions in the 1 to 1000 μM concentration range by amperometry at −0.45 V (vs. Ag/AgCl). This Faradaic phenomenon offers the advantage of direct voltammetric detection, one of the lowest known limits of detection (0.5 μM), and high sensitivity (250 mA∙M−1∙cm−2). It was applied to the determination of ammonium ion in human serum where it compared well with the photometric routine approach for clinical analysis using glutamate dehydrogenase. [Figure not available: see fulltext.]
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