Autor Mária Čaplovičová

GaAs ablation with ultrashort laser pulses in ambient air and water environments

Edgaras Markauskas,  Laimis Zubauskas, Arnas Naujokaitis, Bronislovas Čechavičius, Martynas Talaikis, Gediminas Niaura, Mária Čaplovičová, Viliam Vretenár, Tadas Paulauskas

In: Journal of Applied Physics. Vol. 133, iss. 23 (2023)


Water-assisted ultrashort laser pulse processing of semiconductor materials is a promising technique to diminish heat accumulation and improve process quality. In this study, we investigate femtosecond laser ablation of deep trenches in GaAs, an important optoelectronic material, using water and ambient air environments at different laser processing regimes. We perform a comprehensive analysis of ablated trenches, including surface morphological analysis, atomic-resolution transmission electron microscopy imaging, elemental mapping, photoluminescence, and Raman spectroscopy. The findings demonstrate that GaAs ablation efficiency is enhanced in a water environment while heat-accumulation-related damage is reduced. Raman spectroscopy reveals a decrease in the broad feature associated with amorphous GaAs surface layers during water-assisted laser processing, suggesting that a higher material quality in deep trenches can be achieved using a water environment.

Polycaprolactone–MXene Nanofibrous Scaffolds for Tissue Engineering

Kateryna Diedkova, Alexander D. Pogrebnjak, Sergiy Kyrylenko, Kateryna Smyrnova, Vladimir V. Buranich, Pawel Horodek, Pawel Zukowski, Tomasz N. Koltunowicz, Piotr Galaszkiewicz, Kristina Makashina, Vitaly Bondariev, Martin Sahul, Mária Čaplovičová, Yevheniia Husak, Wojciech Simka, Viktoriia Korniienko, Agnieszka Stolarczyk, Agata Blacha-Grzechnik, Vitalii Balitskyi, Veronika Zahorodna, Ivan Baginskiy, Una Riekstina, Oleksiy Gogotsi, Yury Gogotsi, and Maksym Pogorielov

In: ACS Applied Materials & Interfaces. Vol. 15, iss. 11 (2023)


New conductive materials for tissue engineering are needed for the development of regenerative strategies for nervous, muscular, and heart tissues. Polycaprolactone (PCL) is used to obtain biocompatible and biodegradable nanofiber scaffolds by electrospinning. MXenes, a large class of biocompatible 2D nanomaterials, can make polymer scaffolds conductive and hydrophilic. However, an understanding of how their physical properties affect potential biomedical applications is still lacking. We immobilized Ti3C2Tx MXene in several layers on the electrospun PCL membranes and used positron annihilation analysis combined with other techniques to elucidate the defect structure and porosity of nanofiber scaffolds. The polymer base was characterized by the presence of nanopores. The MXene surface layers had abundant vacancies at temperatures of 305–355 K, and a voltage resonance at 8 × 104 Hz with the relaxation time of 6.5 × 106 s was found in the 20–355 K temperature interval. The appearance of a long-lived component of the positron lifetime was observed, which was dependent on the annealing temperature. The study of conductivity of the composite scaffolds in a wide temperature range, including its inductive and capacity components, showed the possibility of the use of MXene-coated PCL membranes as conductive biomaterials. The electronic structure of MXene and the defects formed in its layers were correlated with the biological properties of the scaffolds in vitro and in bacterial adhesion tests. Double and triple MXene coatings formed an appropriate environment for cell attachment and proliferation with mild antibacterial effects. A combination of structural, chemical, electrical, and biological properties of the PCL–MXene composite demonstrated its advantage over the existing conductive scaffolds for tissue engineering.

Fe3O4-PEI Nanocomposites for Magnetic Harvesting of Chlorella vulgaris, Chlorella ellipsoidea, Microcystis aeruginosa, and Auxenochlorella protothecoides

GERULOVÁ, Kristína – KUCMANOVÁ, Alexandra – SANNY, Zuzana – GARAIOVÁ, Zuzana – SEILER, Eugen – ČAPLOVIČOVÁ, Mária – ČAPLOVIČ, Ľubomír – PALCUT, Marián

In Nanomaterials. Vol. 12, iss. 11 (2022)


Magnetic separation of microalgae using magnetite is a promising harvesting method as it is fast, reliable, low cost, energy-efficient, and environmentally friendly. In the present work, magnetic harvesting of three green algae (Chlorella vulgaris, Chlorella ellipsoidea, and Auxenochlorella protothecoides) and one cyanobacteria (Microcystis aeruginosa) has been studied. The biomass was flushed with clean air using a 0.22 μm filter and fed CO2 for accelerated growth and faster reach of the exponential growth phase. The microalgae were harvested with magnetite nanoparticles. The nanoparticles were prepared by controlled co-precipitation of Fe2+ and Fe3+ cations in ammonia at room temperature. Subsequently, the prepared Fe3O4 nanoparticles were coated with polyethyleneimine (PEI). The prepared materials were characterized by high-resolution transmission electron microscopy, X-ray diffraction, magnetometry, and zeta potential measurements. The prepared nanomaterials were used for magnetic harvesting of microalgae. The highest harvesting efficiencies were found for PEI-coated Fe3O4. The efficiency was pH-dependent. Higher harvesting efficiencies, up to 99%, were obtained in acidic solutions. The results show that magnetic harvesting can be significantly enhanced by PEI coating, as it increases the positive electrical charge of the nanoparticles. Most importantly, the flocculants can be prepared at room temperature, thereby reducing the production costs.

Contribution of photocatalytic and Fenton-based processes in nanotwin structured anodic TiO2 nanotube layers modified by Ce and V

THIRUNAVUKKARASU,  Guru Karthikeyan – GOWRISANKARAN, Sridhar – ČAPLOVIČOVÁ, Mária – SATRAPINSKYY, Leonid – GREGOR, Maroš – LAVRIKOVA, Aleksandra Y. – GREGUŠ, Ján – HALKO, Radoslav – PLESCH, Gustav – MOTOLA, Martin – MONFORT, Olivier

In Dalton Transactions. Vol. 51, iss. 28 (2022)


In the present work, nanotwin structured TiO2 nanotube (TNT) layers are prepared by the electrochemical anodization technique to form the anatase phase and by surface modification via spin-coating of Ce and V precursors to form Ce-TNT and V-TNT, respectively. The surface and cross-sectional images by SEM revealed that the nanotubes have an average diameter of ∼130 nm and a length of ∼14 μm. In addition, the TEM images revealed the nanotwin structures of the nanotubes, especially the anatase (001) and (112) twin surfaces, that increase the transport of photogenerated charges. The photoinduced degradation of caffeine (CAF) by TNT, Ce-TNT, and V-TNT led to a degradation extent of 16%, 26% and 33%, respectively, whereas it increased to 26%, 38%, and 46% in the presence of H2O2, owing to the involvement of Fenton-based processes (in addition to photocatalysis). The effect of the Fenton-based processes accounts for about 10% of the total degradation extent of CAF. Finally, the mechanism of the photoinduced degradation of CAF was investigated. The main oxidative species were the hydroxyl radicals, and the better efficiency of V-TNT over Ce-TNT and TNT was ascribed to its negative surface, thus improving the interactions with CAF.

Effect of Multiply Twinned Ag(0) Nanoparticles on Photocatalytic Properties of TiO2 Nanosheets and TiO2 Nanostructured Thin Films.

BAKARDJIEVA, Snejana – MAREŠ, Jakub – KOCI, Eva – TOLASZ, Jakub – FAJGAR, Radek – RYUKHTIN, Vasyl – KLEMENTOVÁ, Mariana – MICHNA, Štefan – BIBOVÁ, Hana – HOLMESTAD, Randi – TITORENKOVA, Rositsa – ČAPLOVIČOVÁ Mária

In Nanomaterials. Vol. 12, iss. 5 (2022)


Ag-decorated TiO2 nanostructured materials are promising photocatalysts. We used non-standard cryo-lyophilization and ArF laser ablation methods to produce TiO2 nanosheets and TiO2 nanostructured thin films decorated with Ag nanoparticles. Both methods have a common advantage in that they provide a single multiply twinned Ag(0) characterized by {111} twin boundaries. Advanced microscopy techniques and electron diffraction patterns revealed the formation of multiply twinned Ag(0) structures at elevated temperatures (500 °C and 800 °C). The photocatalytic activity was demonstrated by the efficient degradation of 4-chlorophenol and Total Organic Carbon removal using Ag-TiO2 nanosheets, because the multiply twinned Ag(0) served as an immobilized photocatalytically active center. Ag-TiO2 nanostructured thin films decorated with multiply twinned Ag(0) achieved improved photoelectrochemical water splitting due to the additional induction of a plasmonic effect. The photocatalytic properties of TiO2 nanosheets and TiO2 nanostructured thin films were correlated with the presence of defect-twinned structures formed from Ag(0) nanoparticles with a narrow size distribution, tuned to between 10 and 20 nm. This work opens up new possibilities for understanding the defects generated in Ag-TiO2 nanostructured materials and paves the way for connecting their morphology with their photocatalytic activity.

Structural Breakdown of Natural Epidote and Clinozoisite in High-T and Low-P Conditions and Characterization of Its Products

Kozáková, P.; Miglierini, M.; Čaplovičová, M.; Škoda, R.; Bačík, P.

Minerals 202212, 238


A heat treatment was performed on selected epidote and clinozoisite crystals to establish the nature of any changes in the optical and crystal-chemical properties and to identify a breakdown product using a wide spectrum of analytical methods. Natural samples were heated from 900 to 1200 °C under atmospheric pressure in ambient oxidation conditions for 12 h. Epidote and clinozoisite were stable at 900 °C; those heated at 1000 °C, 1100 °C, and 1200 °C exhibited signs of breakdown, with the development of cracks and fissures. The average chemical composition of epidote is Ca2.000Al2.211Fe0.742Si2.994O12(OH), while that of clinozoisite is Ca2.017A12.626Fe0.319Si3.002O12(OH). The breakdown products identified by electron microanalysis, powder X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy were anorthite, pyroxene compositionally close to esseneite, and wollastonite. The decomposition of the epidote-clinozoisite solid solution is controlled by the following reaction: 4 epidote/clinozoisite → 2 pyroxene + 2 wollastonite + 4 anorthite + 2 H2O. Pyroxene likely contains a significant proportion of tetrahedral Fe3+ as documented by the Mössbauer spectroscopy. Moreover, the presence of hematite in the Mössbauer spectrum of the clinozoisite sample heated at 1200 °C can result from the following reaction: 4 epidote → pyroxene + 3 wollastonite + 4 anorthite + hematite + 2 H2O. 

Catalytic graphitization of single-crystal diamond

Catalytic graphitization of single-crystal diamond

SemirTulić, ThomasWaitz, MáriaČaplovičová, GerlindeHabler, ViliamVretenár, TomaSusi, VieraSkákalová

Carbon, Volume 185, 2021, 300-313


Diamond and graphene are carbon allotropes with starkly different physical characteristics. Their combination into graphene-on-diamond heterostructures could benefit from the complementary properties of both components. Graphitization of single-crystalline diamond surfaces is a promising synthesis route, but a clear understanding of the growth of graphene or graphite from solid carbon sources is so far missing. Using aberration-corrected transmission electron microscopyRaman spectroscopy, and electrical transport measurements, we provide detailed insight in the mechanisms of structural changes of nickel-catalyzed graphitization of diamond. We propose competing atomistic processes occurring at contact sites of diamond and Ni, depending on diamond surface terminations. One-dimensional etching process dominates on (111) diamond surfaces that remain almost atomically flat during graphitization. Two-dimensional etching of (110) and (100) diamond surfaces results in Ni drilling into the diamond substrate. Our findings also provide evidence on the reaction rates of the catalysis. The most reactive diamond surface in the (100) orientation is covered with the largest amount of well-crystallized graphite, whereas the (111) surface shows the highest stability against catalytic etching. In the latter case, only a thin disordered graphite layer is formed, yielding the lowest electric conductance. By clarifying these etching mechanisms, our results can improve the synthesis of graphene-on-diamond heterostructures.

Effect of Sub-Zero Treatments and Tempering on Corrosion Behaviour of Vanadis 6 Tool Steel

Peter Jurči, Aneta Bartkowska, Mária Hudáková, Mária Dománková, Mária Čaplovičová, Dariusz Bartkowski

Materials (Basel). 2021 Jul; 14(13): 3759

doi: 10.3390/ma14133759


Sub-zero treatment of Vanadis 6 steel resulted in a considerable reduction of retained austenite amount, refinement of martensite, enhancement of population density of carbides, and modification of precipitation behaviour. Tempering of sub-zero-treated steel led to a decrease in population density of carbides, to a further reduction of retained austenite, and to precipitation of M3C carbides, while M7C3 carbides precipitated only in the case of conventionally quenched steel. Complementary effects of these microstructural variations resulted in more noble behaviour of sub-zero-treated steel compared to the conventionally room-quenched one, and to clear inhibition of the corrosion rate at the same time.

Substrate dependent epitaxy of superconducting niobium nitride thin films grown by pulsed laser deposition

T. Roch, M. Gregor, S. Volkov, M. Čaplovičová, L. Satrapinskyy, A. Plecenik

Applied Surface Science, Volume 551, 2021, 149333


Niobium nitride (NbN) has suitable mechanical properties for application as protective coatings in mechanical engineering, and also its superconductivity can be utilized in thin film devices for sensorics or in combination with ferromagnet in spintronics. Long-range superconducting proximity effect at the heterostructures with a weak ferromagnet can be used for generation of spin-polarized current. For any operational heterostructure application the high quality NbN thin films need to be prepared. In this work we have investigated impact of the substrates on the structure and preferential orientation of niobium nitride thin films fabricated by pulsed laser deposition at 600 °C on Si (0 0 1), MgO (0 0 1), C-plane and R-plane Al2O3 substrates. Growth parameters have been tuned in order to obtain single superconducting δ-NbN phase. Microstructure was analyzed by X-ray diffraction and transmission electron microscopy. Si substrate does not induce the film preferential orientation. Films on MgO are epitaxial (0 0 1) oriented. Films on R-Al2O3 show (1 3 5) orientation with twinned crystallites on the lower symmetry substrate surface. The (1 1 1) epitaxial growth with the largest crystallites and their smallest tilting was achieved on C-Al2O3 substrate leading to the best superconducting properties.

Incorporation mechanism of tungsten in W-Fe-Cr-V-bearing rutile

MAJZLAN, Juraj – BOLANZ, Ralph – GÖTTLICHER, Jörg – MIKUŠ, Tomáš – MILOVSKÁ, Stanislava – ČAPLOVIČOVÁ, Mária – ŠTEVKO, Martin – RÖSSLER, Christiane – MATTHES, Christian

In American Mineralogist. Vol. 106, (2021)


Rutile is a common mineral in many types of ore deposits and can carry chemical or isotopic information about the ore formation. For closer understanding of this information, the mechanisms of incorporation of minor elements should be known. In this work, we have investigated natural rutile crystals with elevated concentrations of WO3 (up to 17.7 wt%), Cr2O3,tot (7.5), V2O3,tot (4.1), FeOtot (7.3), and other metals. X-ray absorption spectroscopy (XAS) of rutile at the Fe K, Cr K, V K, and W L1 and L3 edges shows that all cations are coordinated octahedrally. The average oxidation state of V is +3.8, and that of Cr is near +4. Shell-by-shell fitting of the W L3 EXAFS data shows that W resides in the rutile structure. Raman spectroscopy excludes the possibility of hydrogen as a charge-compensating species. High-resolution TEM and electron diffraction confirm this conclusion as the entire inspected area consists of rutile single crystal with variable amounts of metals other than Ti. Our results show that rutile or its precursors can be efficient vehicles for tungsten in sedimentary rocks, leading to their enrichment in W and possibly later fertility with respect to igneous ore deposits. Leucoxene, a nanocrystalline mixture of Ti and Fe oxides, is an especially suitable candidate for such a vehicle.