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20 results on '"Koleśnik-Gray, Maria"'

1. Unconventional conductivity increase in multilayer black phosphorus

Author

Koleśnik-Gray, Maria, Meingast, Laura, Siebert, Martin, Unbehaun, Tim, Huf, Tobias, Ellrott, Günter, Abellán, Gonzalo, Wild, Stefan, Lloret, Vicent, Mundloch, Udo, Schwarz, Julian, Niebauer, Michael, Szabo, Maximilian, Rommel, Mathias, Hutzler, Andreas, Hauke, Frank, Hirsch, Andreas, and Krstić, Vojislav

Published
2023
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2. Monolayer black phosphorus by sequential wet-chemical surface oxidation

Author

Wild, Stefan, Lloret, Vicent, Vega-Mayoral, Victor, Vella, Daniele, Nuin, Edurne, Siebert, Martin, Koleśnik-Gray, Maria, Löffler, Mario, Mayrhofer, Karl J. J., Gadermaier, Christoph, Krstić, Vojislav, Hauke, Frank, Abellán, Gonzalo, and Hirsch, Andreas

Subjects
Physics - Applied Physics
Abstract

We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent. Moreover, the oxidation process can be stopped at will by two different passivation procedures, namely the non-covalent functionalization with perylene diimide chromophores, which prevents the photooxidation, or by using a protective ionic liquid layer. The obtained flakes preserve their electronic properties as demonstrated by fabricating a BP field-effect transistor (FET). This work paves the way for the preparation of BP devices with controlled thickness

Published
2019
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3. Effect of TCNQ layer cover on oxidation dynamics of black phosphorus

Author

Meingast, Laura, Koleśnik-Gray, Maria, Siebert, Martin, Abellán, Gonzalo, Wild, Stefan, Lloret, Vicent, Mundloch, Udo, Hauke, Frank, Hirsch, Andreas, and Krstić, Vojislav

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

The puckered surface of black phosphorus represents an ideal substrate for an unconventional arrangement of physisorbed species and the resulting specific two-dimensional chemistry of this system. This opens the way to investigate the chemical and physical properties of locally confined areas of black phosphorus without the necessity for further physical downscaling of the material. We have evaporated TCNQ on top of black phosphorus under over-saturation non-equilibrium conditions in vacuum. The evolution of linear density and height of droplets formed through oxidation during exposure to air was studied time-dependently by scanning-force microscopy. Our study suggests that the TCNQ molecules spontaneously arrange in a thin layer of the order of a few nm height, which, however, is fragmented with a periodicity of about 100 nm. It is shown that within the confined space separating the layer fragments the chemical dynamics of the oxidation process is remarkably different than on a bare black phosphorus surface.

Published
2018
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4. Electrically Conductive Collagen‐PEDOT:PSS Hydrogel Prevents Post‐Infarct Cardiac Arrhythmia and Supports hiPSC‐Cardiomyocyte Function

Author

Roshanbinfar, Kaveh, primary, Schiffer, Miriam, additional, Carls, Esther, additional, Angeloni, Miriam, additional, Koleśnik‐Gray, Maria, additional, Schruefer, Stefan, additional, Schubert, Dirk W., additional, Ferrazzi, Fulvia, additional, Krstić, Vojislav, additional, Fleischmann, Bernd K., additional, Roell, Wilhelm, additional, and Engel, Felix B., additional

Published
2024
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7. Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

Author

Vecera, Philipp, Eigler, Siegfried, Koleśnik-Gray, Maria, Krstić, Vojislav, Vierck, Asmus, Maultzsch, Janina, Schäfer, Ricarda A., Hauke, Frank, and Hirsch, Andreas

Subjects
ddc:530, Naturwissenschaftliche Fakultät, Article
Abstract

Covalent functionalisation of graphene is a continuously progressing field of research. The optical properties of such derivatives attract particular attention. In virtually all optical responses, however, an enhancement in peak intensity with increase of sp3 carbon content, and a vanishing of the peak position shift in monolayer compared to few-layer systems, is observed. The understanding of these seemingly connected phenomena is lacking. Here we demonstrate, using Raman spectroscopy and in situ electrostatic doping techniques, that the intensity is directly modulated by an additional contribution from photoluminescent π-conjugated domains surrounded by sp3 carbon regions in graphene monolayers. The findings are further underpinned by a model which correlates the individual Raman mode intensities to the degree of functionalisation. We also show that the position shift in the spectra of solvent-based and powdered functionalised graphene derivatives originates predominantly from the presence of edge-to-edge and edge-to-basal plane interactions and is by large functionalisation independent.

Published
2017
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8. Monolayer black phosphorus by sequential wet-chemical surface oxidation

Author

Wild, Stefan, primary, Lloret, Vicent, additional, Vega-Mayoral, Victor, additional, Vella, Daniele, additional, Nuin, Edurne, additional, Siebert, Martin, additional, Koleśnik-Gray, Maria, additional, Löffler, Mario, additional, Mayrhofer, Karl J. J., additional, Gadermaier, Christoph, additional, Krstić, Vojislav, additional, Hauke, Frank, additional, Abellán, Gonzalo, additional, and Hirsch, Andreas, additional

Published
2019
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19. Spectro‐Spatial Unmixing in Optical Microspectroscopy for Thickness Determination of Layered Materials.

Author

Schwarz, Julian, Niebauer, Michael, Römling, Lukas, Pham, Adrian, Koleśnik‐Gray, Maria, Evanschitzky, Peter, Vogel, Nicolas, Krstić, Vojislav, Rommel, Mathias, and Hutzler, Andreas

Subjects
*SILICA films, *CARBON films, *REFLECTANCE measurement, *OPTICAL measurements, *TRANSFER matrix, *PYROLYTIC graphite
Abstract

Van der Waals materials and devices incorporating them exhibit highly thickness‐dependent properties. The small lateral dimensions of mechanically exfoliated 2D‐layered flakes, however, remarkably complicate their precise thickness determination. Quantitative analysis of reflectance measurements using optical microspectroscopy is proven to be as precise as spectroscopic ellipsometry while providing an easily adaptable and non‐destructive method for thickness determination. The use of magnifying objective lenses allows obtaining the reflectance within a measurement spot of only a few microns in diameter. When the dimensions of exfoliated flakes are even smaller, however, the acquired reflectance is a superposition of those of the material of interest and the subjacent materials. To overcome this limitation, a facile approach to reduce the resolvable structure size by combining the evaluation of the reflectance measurement via transfer matrix method with spatial information extracted from optical micrographs is introduced. The efficacy when characterizing micrometer‐sized flakes is exemplarily demonstrated for thickness determination of highly oriented pyrolytic graphite and a thin film of silicon dioxide. It is shown that a maximum error of less than 10% is achieved even when the flake only covers 20% of the measurement spot. [ABSTRACT FROM AUTHOR]

Published
2024
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20. Substrate-Modulated Reductive Graphene Functionalization.

Author

Schäfer RA, Weber K, Koleśnik-Gray M, Hauke F, Krstić V, Meyer B, and Hirsch A

Abstract

Covalently functionalizing mechanical exfoliated mono- and bilayer graphenides with λ-iodanes led to the discovery that the monolayers supported on a SiO 2 substrate are considerably more reactive than bilayers as demonstrated by statistical Raman spectroscopy/microscopy. Supported by DFT calculations we show that ditopic addend binding leads to much more stable products than the corresponding monotopic reactions as a result of the much lower lattice strain of the reactions products. The chemical nature of the substrate (graphene versus SiO 2 ) plays a crucial role., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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