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Your search keyword '"Matisen, Leonard"' showing total 134 results
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134 results on '"Matisen, Leonard"'

1. The optical properties of transferred graphene and the dielectrics grown on it obtained by ellipsometry

Author

Kasikov, Aarne, Kahro, Tauno, Matisen, Leonard, Kodu, Margus, Tarre, Aivar, Seemen, Helina, and Alles, Harry

Subjects
Condensed Matter - Materials Science
Abstract

Graphene layers grown by chemical vapour deposition (CVD) method and transferred from Cu-foils to the oxidized Si-substrates were investigated by spectroscopic ellipsometry (SE), Raman and X-Ray Photoelectron Spectroscopy (XPS) methods. The optical properties of transferred CVD graphene layers do not always correspond to the ones of the exfoliated graphene due to the contamination from the chemicals used in the transfer process. However, the real thickness and the mean properties of the transferred CVD graphene layers can be found using ellipsometry if a real thickness of the SiO2 layer is taken into account. The pulsed layer deposition (PLD) and atomic layer deposition (ALD) methods were used to grow dielectric layers on the transferred graphene and the obtained structures were characterized using optical methods. The approach demonstrated in this work could be useful for the characterization of various materials grown on graphene., Comment: 8 pages, 8 figures, 2 tables, presented on "Solid State Surfaces and Interfaces", November 2016 Piestany, Slovakia

Published
2018
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2. Nanosecond laser treatment of graphene

Author

Kiisk, Valter, Kahro, Tauno, Kozlova, Jekaterina, Matisen, Leonard, and Alles, Harry

Subjects
Condensed Matter - Materials Science
Abstract

Laser processing of graphene is of great interest for cutting, patterning and structural engineering purposes. Tunable nanosecond lasers have the advantage of being relatively widespread (compared to e.g. femtosecond or high-power continuous wave lasers). Hereby we have conducted an investigation of the impact of nanosecond laser pulses on CVD graphene. The damage produced by sufficiently strong single shots (pulse width 5 ns, wavelength 532 or 266 nm) from tunable optical parametric oscillator was investigated by the methods of scanning electron microscopy and optical microspectroscopy (Raman and fluorescence). Threshold of energy density for producing visible damage was found to be ~200 mJ/cm2. For UV irradiation the threshold could be notably less depending on the origin of sample. Surprisingly strong fluorescence signal was recorded from damaged areas and is attributed to the residues of oxidized graphene.

Published
2013
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22. Pt coated Cr2O3 thin films for resistive gas sensors

Author

Kasikov Aarne, Gerst Alar, Kikas Arvo, Matisen Leonard, Saar Agu, Tarre Aivar, and Rosental Arnold

Subjects
semiconductor gas sensors, epitaxial chromia, platinum nanoislands, atomic layer deposition (ald), x-ray photoelectron spectroscopy (xps), 07.07.df, 79.60.jv, 81.07.-b, 81.15.ef, 81.15.kk, Physics, QC1-999
Published
2009
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29. Oxygen Electroreduction on Pt Nanoparticles Deposited on Reduced Graphene Oxide and N‐doped Reduced Graphene Oxide Prepared by Plasma‐assisted Synthesis in Aqueous Solution

Author

Hussain, Sajid, primary, Erikson, Heiki, additional, Kongi, Nadezda, additional, Treshchalov, Alexey, additional, Rähn, Mihkel, additional, Kook, Mati, additional, Merisalu, Maido, additional, Matisen, Leonard, additional, Sammelselg, Väino, additional, and Tammeveski, Kaido, additional

Published
2018
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30. Oxygen Reduction on Catalysts Prepared by Pyrolysis of Electrospun Styrene–Acrylonitrile Copolymer and Multi-walled Carbon Nanotube Composite Fibres

Author

Mooste, Marek, primary, Kibena-Põldsepp, Elo, additional, Matisen, Leonard, additional, Merisalu, Maido, additional, Kook, Mati, additional, Kisand, Vambola, additional, Vassiljeva, Viktoria, additional, Krumme, Andres, additional, Sammelselg, Väino, additional, and Tammeveski, Kaido, additional

Published
2018
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39. Oxygen Reduction on Graphene-Based Materials of Different Origin

Author

Kibena-Põldsepp, Elo, primary, Lilloja, Jaana, additional, Merisalu, Maido, additional, Rauwel, Protima, additional, Matisen, Leonard, additional, Niilisk, Ahti, additional, Cardoso, Eduardo S.F., additional, Maia, Gilberto, additional, Kook, Mati, additional, Joost, Urmas, additional, Sammelselg, Väino, additional, and Tammeveski, Kaido, additional

Published
2016
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43. Oxygen Reduction on Anthraquinone Diazonium Compound Derivatised Multi-walled Carbon Nanotube and Graphene Based Electrodes.

Author

Mooste, Marek, Kibena‐Põldsepp, Elo, Matisen, Leonard, and Tammeveski, Kaido

Subjects
ANTHRAQUINONES, OXYGEN reduction, DIAZONIUM compounds, MULTIWALLED carbon nanotubes, GRAPHENE, CARBON electrodes, X-ray photoelectron spectroscopy
Abstract

In this work, graphene and multi-walled carbon nanotubes were derivatised with anthraquinone (AQ) groups using spontaneous or electrochemical grafting of Fast Red AL salt. Glassy carbon (GC) electrodes were coated with AQ-modified carbon nanomaterials to study the oxygen reduction reaction (ORR). These nanomaterials were characterised by X-ray photoelectron spectroscopy and multilayer formation of AQ on the electrografted electrodes was observed. All the modified electrodes showed enhanced electrocatalytic activity towards the ORR in alkaline media. High AQ loading on the electrodes was found and the number of electrons transferred per O2 molecule was between 2 and 4. In addition, the stability testing of AQ-derivatised carbon nanomaterial-coated GC electrodes was performed. [ABSTRACT FROM AUTHOR]

Published
2017
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48. Oxygen Reduction on Silver Nanoparticles Supported on Carbide-Derived Carbons

Author

Mart, Jonas, Erikson, Heiki, Merisalu, Maido, Matisen, Leonard, Kaarik, Maike, Leis, Jaan, Sammelselg, Vaino, Aruvali, Jaan, Kaljuvee, Tiit, and Tammeveski, Kaido

Abstract

In this work carbide-derived carbons (CDC) are used as support for silver nanoparticles. The catalysts are studied by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and the electrocatalytic activity of Ag/CDC catalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction in alkaline solution is investigated using the rotating disk electrode (RDE) method. The SEM analysis revealed that the average Ag particle size is 15 nm and these are uniformly distributed over the catalyst material. TGA measurements show that the metal content in the catalyst is close to the nominal value of 40 wt%. The RDE results revealed that the ORR proceeds via a four-electron pathway to form OH[?]. The analysis of RDE data revealed that the mass-activity of Ag/CDC was about twice higher than that of Ag catalysts supported on Vulcan carbon. The Tafel analysis suggests that the slow transfer of the first electron to O2 molecule is the rate determining step for the ORR. The prepared Ag/CDC materials are also efficient catalysts for peroxide electroreduction.

Published
2018

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