Centrum pre Nanodiagnostiku Materiálov

PAULAUSKAS, Tadas – ACEECHAVIČIUS, Bronislovas – KARPUS, Vytautas – JOČIONIS, Lukas – TUMĖNAS, Saulius – DEVENSON, Jan – PAČ̌EBUTAS, Vaidas – STANIONYTE, Sandra – STRAZDIENE, Viktorija – GEIAUTIS, Andrejus – ČAPLOVIČOVÁ, Mária – VRETENÁR, Viliam – WALLS, Michael G. – KROTKUS, Arunas

In Journal of Applied Physics. Vol. 128, iss. 19 (2020)

https://doi.org/10.1063/5.0030091

ABSTRACT

The GaAs_1–xBi_x semiconductor alloy allows one to achieve large bandgap reduction and enhanced spin–orbit splitting energy at dilute Bi quantities. The bismide is currently being developed for near- to mid-infrared lasers, multi-junction solar cells, and photodetectors. In this structure–property relationship study of GaAsBi alloys, we report polarization dependent photoluminescence that reaches a polarization ratio up to 2.4 at room temperature. Polarization dependence is also presented using transmittance spectra, birefringence, and linear dichroism. The optical anisotropy observations agree with the predictions of point symmetry reduction in the CuPt_B-type ordered GaAsBi phase. The structural ordering is investigated experimentally from the atomic scale in molecular-beam epitaxy (MBE) grown samples on exact and miscut (001) GaAs substrates, as well as on (001) Ge. The latter sample is composed of anti-phase domains in which the ordering axes are rotated by 90° angles. Since the conditions stabilizing the CuPt_B ordered phase fall within the typical MBE growth regime of dilute bismides, the optical anisotropy in GaAsBi alloys is expected to be ubiquitous. These findings are important for the future development of GaAsBi-based optoelectronics and also provide new means to analyze structurally complex bismide alloys.

ABBAS, Somia M. – HASHEM, Ahmed M. – ABDEL-GHANY, Ashraf E. – ISMAIL, Eman H. – KOTLÁR, Mário – WINTER, Martin – LI, Jie – JULIEN, Christian M.

In Energies [Open access]. Vol. 13, iss. 19 (2020)

https://doi.org/10.3390/en13195194

Abstract

In this work, the properties of silver-modified LiMn₂O₄ cathode materials are revisited. We study the influence of calcination atmosphere on the properties of the Ag-coated LiMn₂O₄ (Ag/LMO) and highlight the silver oxidation. The effect of the heat treatment in vacuum is compared with that in air by the characterization of the structure, specific surface area, Li transport properties and electrochemical performance of Ag/LMO composites. Surface analyses (XPS and Raman spectroscopy) show that the nature of the coating (~3 wt.%) differs with the calcination atmosphere: Ag/LMO(v) calcined in vacuum displays Ag nanospheres and minor AgO content on its surface (specific surface area of 4.1 m² g⁻¹), while Ag/LMO(a) treated in air is mainly covered by the AgO insulating phase (specific surface area of 0.6 m² g⁻¹). Electrochemical experiments emphasize that ~3 wt.% Ag coating is effective to minimize the drawbacks of the spinel LiMn₂O₄ (Mn dissolution, cycling instability, etc.). The Ag/LMO(v) electrode shows high capacity retention, good cyclability at C/2 rate and capacity fade of 0.06% per cycle (in 60 cycles).

BODÍK, Michal – DEMYDENKO, Maksym – SHABELNYK, Tetiana – HALAHOVETS, Yuriy – KOTLÁR, Mário – KOSTIUK, Dmytro – SHAJI, Ashin – BRUNOVÁ, Alica – VEIS, Pavel – JERGEL, Matej – MAJKOVÁ, Eva – ŠIFFALOVIČ, Peter

In Journal of Physical Chemistry C. Vol. 124, iss. 29 (2020)

https://doi.org/10.1021/acs.jpcc.0c02365

Abstract

Recent advances in the liquid-phase exfoliation enabled large-scale production of two-dimensional (2D) materials, including few-layer graphene and transition metal dichalcogenides. The exfoliated flakes of 2D materials allow cost-effective deposition of continuous films for various applications ranging from optoelectronics to lubrication technology. The self-assembly of 2D materials on water subphase and subsequent transfer of such a Langmuir film onto a solid substrate offers an unprecedented layer quality in terms of spatial homogeneity as it proceeds in thermodynamic equilibrium. However, while the formation of conventional organic molecular Langmuir films has been widely studied, the application of the Langmuir technique to rigid inorganic 2D materials is still rather unexplored. Here, we study the underlying mechanism behind the formation and collapse at the critical surface pressure of the Langmuir film composed of few-layer MoS₂ flakes. The in situ wide-angle X-ray scattering measured in real time and other supportive techniques applied ex situ after the film transfer onto a Si/SiO₂ substrate were employed. We identify all principal compression stages up to the Langmuir monolayer collapse and beyond, relying on the texture, surface pressure, and elastic modulus temporal evolution. The results obtained and the conclusions drawn can be extended to a large family of the inorganic Langmuir films of other 2D materials to optimize the deposition process for envisaged application.

MARIYCHUK, Ruslan – PORUBSKÁ, Jana – OSTAFIN, Marek – ČAPLOVIČOVÁ, Mária – ELIÁŠOVÁ, Adriana

In Applied Nanoscience. Vol. 10, iss. 12 (2020)

https://doi.org/10.1007/s13204-020-01324-y

Abstract

In the present work, we report, for the first time, the production of stable nanocolloids of highly monodisperse silver and gold nanoparticles (AgNPs and AuNPs) using phytosynthesis approach. With the aim to eliminate misinterpretations associated with the use of usually applied crude plant extracts, the presented study was focused on the use of polyphenolic fraction isolated from elderberry fruits (Sambucus nigra L.) for the synthesis. Obtained AgNPs and AuNP were characterized by UV–Vis and FTIR spectroscopy, DLS and TEM. We observed unexpectedly high capability of the natural polyphenols not only to form monodisperse nanoparticles but also to stabilise the concentrated nanocolloids (539 mg/L AgNPs and 739 mg/L AuNPs) for at least two years. Moreover, AgNPs showed strong antibacterial properties against pathogenic bacterial strains Staphylococcus aureus and Escherichia coli (inhibited after 15 min and totally stopped growth after 3 and 5 h at 3.125 mg/L concentration).

KÁLOSI, Anna – LABUDOVÁ, Martina – ANNUŠOVÁ, Adriana – BENKOVIČOVÁ, Monika – BODÍK, Michal – KOLLÁR, Jozef – KOTLÁR, Mário – KASAK, Peter – JERGEL, Matej – PASTOREKOVÁ, Sylvia – ŠIFFALOVIČ, Peter – MAJKOVÁ, Eva

In Biomaterials Science. Vol. 8, iss. 7 (2020)

https://doi.org/10.1039/C9BM01975H

Abstract

We evaluate the application of surfactant-free liquid-phase exfoliated MoS₂ nanosheets as a nanoplatform for a cancer detection and treatment system equipped with an antibody–antigen based recognition element. Employing antigen–antibody binding, we increased the probability of the endocytosis of MoS₂ nanosheets into CAIX expressing cells by 30%. The nanosheets are functionalized with a specific antibody M75, which forms an antigen–antibody complex with CAIX. The bioconjugation of MoS₂ nanosheets involves biocompatible components with low cytotoxicity, verified in the tested cell lines by fluorescence-based cell viability assay. The cellular internalization is quantified by flow cytometry, while the internalization is confirmed by label-free confocal Raman imaging. Raman measurements show increased lysosomal activity in the proximity of the internalized nanoplatforms.