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Cattelan, M., Vagin, M., Fox, N. A., Ivanov, I. G., Shtepliuk, I. & Yakimova, R. (2019). Anodization study of epitaxial graphene: insights on the oxygen evolution reaction of graphitic materials. Nanotechnology, 30(28), Article ID 285701.
Open this publication in new window or tab >>Anodization study of epitaxial graphene: insights on the oxygen evolution reaction of graphitic materials
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2019 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 28, article id 285701Article in journal (Refereed) Published
Abstract [en]

The photoemission electron microscopy and x-ray photoemission spectroscopy were utilized for the study of anodized epitaxial graphene (EG) on silicon carbide as a fundamental aspect of the oxygen evolution reaction on graphitic materials. The high-resolution analysis of surface morphology and composition quantified the material transformation during the anodization. We investigated the surface with lateral resolution amp;lt;150 nm, revealing significant transformations on the EG and the role of multilayer edges in increasing the film capacitance.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
epitaxial graphene; anodization; OER; PEEM; XPS
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-156886 (URN)10.1088/1361-6528/ab1297 (DOI)000465983900001 ()30901765 (PubMedID)2-s2.0-85065346689 (Scopus ID)
Note

Funding Agencies| [EP/K035746/1]; [EP/M000605/1]

Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-06-04Bibliographically approved
Santangelo, F., Shtepliuk, I., Filippini, D., Puglisi, D., Vagin, M., Yakimova, R. & Eriksson, J. (2019). Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection. Sensors, 19(10), Article ID 2393.
Open this publication in new window or tab >>Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection
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2019 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, no 10, article id 2393Article in journal (Refereed) Published
Abstract [en]

In this work, we investigated the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb and Cd), showing fast and stable response and low detection limit. The sensing platform proposed includes 3D-printed microfluidic devices, which incorporate all features required to connect and execute lab-on-chip (LOC) functions. The obtained results indicate that EG exhibits excellent sensing activity towards Pb and Cd ions. Several concentrations of Pb2+ solutions, ranging from 125 nM to 500 mu M, were analyzed showing Langmuir correlation between signal and Pb2+ concentrations, good stability, and reproducibility over time. Upon the simultaneous presence of both metals, sensor response is dominated by Pb2+ rather than Cd2+ ions. To explain the sensing mechanisms and difference in adsorption behavior of Pb2+ and Cd2+ ions on EG in water-based solutions, we performed van-der-Waals (vdW)-corrected density functional theory (DFT) calculations and non-covalent interaction (NCI) analysis, extended charge decomposition analysis (ECDA), and topological analysis. We demonstrated that Pb2+ and Cd2+ ions act as electron-acceptors, enhancing hole conductivity of EG, due to charge transfer from graphene to metal ions, and Pb2+ ions have preferential ability to binding with graphene over cadmium. Electrochemical measurements confirmed the conductometric results, which additionally indicate that EG is more sensitive to lead than to cadmium.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
heavy metals detection; epitaxial graphene; high sensitivity; 3D-printed flow cell; reusable lab-on-chip
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-158818 (URN)10.3390/s19102393 (DOI)000471014500180 ()31130608 (PubMedID)2-s2.0-85066922488 (Scopus ID)
Note

Funding Agencies|Swedish Foundation for Strategic research (SSF) [GMT14-0077, RMA15-024]; Angpanneforeningens Forskningsstiftelse [16-541]

Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2019-08-14Bibliographically approved
Ibupoto, Z. H., Tahira, A., Tang, P., Liu, X., Morante, J. R., Fahlman, M., . . . Vomiero, A. (2019). MoSx@NiO Composite Nanostructures: An Advanced Nonprecious Catalyst for Hydrogen Evolution Reaction in Alkaline Media. Advanced Functional Materials, 29(7), Article ID 1807562.
Open this publication in new window or tab >>MoSx@NiO Composite Nanostructures: An Advanced Nonprecious Catalyst for Hydrogen Evolution Reaction in Alkaline Media
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2019 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 7, article id 1807562Article in journal (Refereed) Published
Abstract [en]

The design of the earth-abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of renewable energies. A heterostructured system composed of MoSx deposited on NiO nanostructures (MoSx@NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS2 in alkaline media. Both NiO and MoS2@NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge-like morphology and are completely covered by the sheet-like MoS2. The NiO and MoS2 exhibit cubic and hexagonal phases, respectively. In the MoSx@NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm(-2) current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS2-based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost-effective, and environmentally friendly methodology can pave the way for exploitation of MoSx@NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
alkaline media; electrolysis; MoSx@NiO composites
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-155574 (URN)10.1002/adfm.201807562 (DOI)000459719800018 ()2-s2.0-85059344786 (Scopus ID)
Note

Funding Agencies|Knut and Alice Wallenberg Foundation; Kempe Foundation; LTU Lab fund program; Generalitat de Catalunya [2017 SGR 327, JRM 2017 SGR 1246]; Spanish MINECO project [ENE2017-85087-C3]; Severo Ochoa Programme (MINECO) [SEV-2013-0295-17-1]; CERCA Programme/Generalitat de Catalunya

Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-03-28Bibliographically approved
Wijeratne, K., Ail, U., Brooke, R., Vagin, M., Liu, X., Fahlman, M. & Crispin, X. (2018). Bulk electronic transport impacts on electron transfer at conducting polymer electrode-electrolyte interfaces.. Proceedings of the National Academy of Sciences of the United States of America (7), 11899-11904
Open this publication in new window or tab >>Bulk electronic transport impacts on electron transfer at conducting polymer electrode-electrolyte interfaces.
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2018 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, no 7, p. 11899-11904Article in journal (Refereed) Epub ahead of print
Abstract [en]

Electrochemistry is an old but still flourishing field of research due to the importance of the efficiency and kinetics of electrochemical reactions in industrial processes and (bio-)electrochemical devices. The heterogeneous electron transfer from an electrode to a reactant in the solution has been well studied for metal, semiconductor, metal oxide, and carbon electrodes. For those electrode materials, there is little correlation between the electronic transport within the electrode material and the electron transfer occurring at the interface between the electrode and the solution. Here, we investigate the heterogeneous electron transfer between a conducting polymer electrode and a redox couple in an electrolyte. As a benchmark system, we use poly(3,4-ethylenedioxythiophene) (PEDOT) and the Ferro/ferricyanide redox couple in an aqueous electrolyte. We discovered a strong correlation between the electronic transport within the PEDOT electrode and the rate of electron transfer to the organometallic molecules in solution. We attribute this to a percolation-based charge transport within the polymer electrode directly involved in the electron transfer. We show the impact of this finding by optimizing an electrochemical thermogalvanic cell that transforms a heat flux into electrical power. The power generated by the cell increased by four orders of magnitude on changing the morphology and conductivity of the polymer electrode. As all conducting polymers are recognized to have percolation transport, we believe that this is a general phenomenon for this family of conductors.

Place, publisher, year, edition, pages
National academy of sciences, 2018
Keywords
conducting polymer, electron transfer, thermogalvanic cell
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-152759 (URN)10.1073/pnas.1806087115 (DOI)000450642800036 ()30397110 (PubMedID)
Note

Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University Faculty Grant [SFO-Mat-LiU 2009-00971]

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2019-03-21
Che, C., Vagin, M., Wijeratne, K., Zhao, D., Warczak, M., Jonsson, M. & Crispin, X. (2018). Conducting Polymer Electrocatalysts for Proton-Coupled Electron Transfer Reactions: Toward Organic Fuel Cells with Forest Fuels. Advanced Sustainable Systems, 317
Open this publication in new window or tab >>Conducting Polymer Electrocatalysts for Proton-Coupled Electron Transfer Reactions: Toward Organic Fuel Cells with Forest Fuels
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2018 (English)In: Advanced Sustainable Systems, ISSN 2366-7486, Vol. 317Article in journal (Refereed) Epub ahead of print
Abstract [en]

Lignin is one of the most abundant biopolymers, constituting 25% of plants. The pulp and paper industries extract lignin in their process and today seek new applications for this by-product. Here, it is reported that the aromatic alcohols obtained from lignin depolymerization can be used as fuel in high power density electrical power sources. This study shows that the conducting polymer poly(3,4-ethylenedioxythiophene), fabricated from abundant ele-ments via low temperature synthesis, enables efficient, direct, and reversible chemical-to-electrical energy conversion of aromatic alcohols such as lignin residues in aqueous media. A material operation principle related to the rela-tively high molecular diffusion and ionic conductivity within the conducting polymer matrix, ensuring efficient uptake of protons in the course of proton-coupled electron transfers between organic molecules is proposed.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-148575 (URN)10.1002/adsu.201800021 (DOI)
Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-06-26
Shtepliuk, I. I., Vagin, M., Ivanov, I. G., Iakimov, T., Yazdi, G. & Yakimova, R. (2018). Lead (Pb) interfacing with epitaxial graphene. Physical Chemistry, Chemical Physics - PCCP, 20(25), 17105-17116
Open this publication in new window or tab >>Lead (Pb) interfacing with epitaxial graphene
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2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 25, p. 17105-17116Article in journal (Refereed) Published
Abstract [en]

Here, we report the electrochemical deposition of lead (Pb) as a model metal on epitaxial graphene fabricated on silicon carbide (Gr/SiC). The kinetics of electrodeposition and morphological characteristics of the deposits were evaluated by complementary electrochemical, physical and computational methods. The use of Gr/SiC as an electrode allowed the tracking of lead-associated redox conversions. The analysis of current transients passed during the deposition revealed an instantaneous nucleation mechanism controlled by convergent mass transport on the nuclei locally randomly distributed on epitaxial graphene. This key observation of the deposit topology was confirmed by low values of the experimentally-estimated apparent diffusion coefficient, Raman spectroscopy and scanning electron microscopy (SEM) studies. First principles calculations showed that the nucleation of Pb clusters on the graphene surface leads to weakening of the interaction strength of the metal-graphene complex, and only spatially separated Pb adatoms adsorbed on bridge and/or edge-plane sites can affect the vibrational properties of graphene. We expect that the lead adatoms can merge in large metallic clusters only at defect sites that reinforce the metal-graphene interactions. Our findings provide valuable insights into both heavy metal ion electrochemical analysis and metal electroplating on graphene interfaces that are important for designing effective detectors of toxic heavy metals.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-149854 (URN)10.1039/c8cp01814f (DOI)000436571800024 ()29896595 (PubMedID)
Note

Funding Agencies|VR grant [621-2014-5805]; SSF [SSF GMT14-0077, SSF RMA15-0024]; Angpanneforeningens Forskningsstiftelse [16-541]

Available from: 2018-08-02 Created: 2018-08-02 Last updated: 2018-08-20
Zhybak, M., Beni, V., Vagin, M., Dempsey, E., Turner, A. & Korpan, Y. (2016). Creatinine and urea biosensors based on a novel ammonium ion-selective copper-polyaniline nano-composite. Biosensors & bioelectronics, 77, 505-511
Open this publication in new window or tab >>Creatinine and urea biosensors based on a novel ammonium ion-selective copper-polyaniline nano-composite
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2016 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 77, p. 505-511Article in journal (Refereed) Published
Abstract [en]

The use of a novel ammonium ion-specific copper-polyaniline nano-composite as transducer for hydrolase-based biosensors is proposed. In this work, a combination of creatinine deaminase and urease has been chosen as a model system to demonstrate the construction of urea and creatinine biosensors to illustrate the principle. Immobilisation of enzymes was shown to be a crucial step in the development of the biosensors; the use of glycerol and lactitol as stabilisers resulted in a significant improvement, especially in the case of the creatinine, of the operational stability of the biosensors (from few hours to at least 3 days). The developed biosensors exhibited high selectivity towards creatinine and urea. The sensitivity was found to be 85±3.4 mA M−1 cm−2 for the creatinine biosensor and 112±3.36 mA M−1 cm−2 for the urea biosensor, with apparent Michaelis–Menten constants (KM,app), obtained from the creatinine and urea calibration curves, of 0.163 mM for creatinine deaminase and 0.139 mM for urease, respectively. The biosensors responded linearly over the concentration range 1–125 µM, with a limit of detection of 0.5 µM and a response time of 15 s.

The performance of the biosensors in a real sample matrix, serum, was evaluated and a good correlation with standard spectrophotometric clinical laboratory techniques was found.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Creatinine; Urea; Amperometric ammonium detection; Copper polyanilinecomposite
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-123681 (URN)10.1016/j.bios.2015.10.009 (DOI)000366766900073 ()26457736 (PubMedID)
Projects
SMARTCABCERSENS
Funder
EU, FP7, Seventh Framework Programme, PIRSES-GA-2012-318053
Note

Funding agencies: SMARTCANCERSENS

Available from: 2016-01-08 Created: 2016-01-08 Last updated: 2017-12-01Bibliographically approved
Zhybak, M. T., Vagin, M. Y., Beni, V., Liu, X., Dempsey, E., Turner, A. P. F. & Korpan, Y. I. (2016). Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode.. Microchimica Acta, 183(6), 1981-1987
Open this publication in new window or tab >>Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode.
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2016 (English)In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 183, no 6, p. 1981-1987Article in journal (Refereed) Published
Abstract [en]

A novel electrocatalytic material for oxygen reduction, based on polyaniline in combinationwith copper, was developed and utilised for the direct voltammetric quantification of ammonium ions. Consecutive electrode modification by electrodeposited copper, a Nafion membrane and electropolymerised polyaniline resulted in an electrocatalytic composite material which the retained conductivity at neutral pH. Ammonia complex formation with Cu (I) caused the appearance of oxygen electrocatalysis, which was observed as an increase in cathodic current. This Faradaic phenomenon offered the advantage of direct voltammetric detection and was utilised for ammonium electroanalysis. The developed quantification protocol was applied for ammonium assay in human serum and compared with the routine approach for clinical analysis.

Keywords
Conductive polymer, Nanocomposite, Amperometry, Electrochemical impedance spectroscopy, SEM, EDX, XPS, Serum analysis
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:liu:diva-128192 (URN)10.1007/s00604-016-1834-3 (DOI)000376600300021 ()
Funder
EU, FP7, Seventh Framework Programme, PIRSES
Available from: 2016-05-20 Created: 2016-05-20 Last updated: 2018-03-23
Sekretaryova, A. N., Vagin, M. Y., Turner, A. P. .. & Eriksson, M. (2016). Electrocatalytic Currents from Single Enzyme Molecules. Journal of the American Chemical Society, 138(8), 2504-2507
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
Sekretaryova, A., Volkov, A. V., Zozoulenko, I. V., Turner, A., Vagin, M. Y. & Eriksson, M. (2016). Total phenol analysis of weakly supported water using a laccase-based microband biosensor.. Analytica Chimica Acta, 907, 45-53
Open this publication in new window or tab >>Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
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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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8478-4663

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