Publikační záznamy NTC

Permanent URI for this collection

http://hdl.handle.net/11025/59115

Browse

Showing 1 - 20 out of 161 results

Probing the semiconductor-Dirac-semimetal transition in Na-Sb-Bi alloys with x-ray Compton scattering
(2025) Pulkkinen, Aki Ismo Olavi; Kothalawala, Veenavee Nipunika; Suzuki, Kosuke; Barbiellini, Bernardo; Nokelainen, Johannes; Chiu, Wei-Chi; Singh, Bahadur; Lin, Hsin; Pandey, Alok K.; Yabuuchi, Naoaki; Tsuji, Naruki; Sakurai, Yoshiharu; Sakurai, Hiroshi; Minár, Jan; Bansil, Arun
We discuss electron redistribution during the semiconductor-to-Dirac semimetal transition in Na-Sb-Bi alloys using x-ray Compton scattering experiments combined with first-principles electronic structure modeling. A robust signature of the semiconductor-to-Dirac semimetal transition is identified in the spherically averaged Compton profile. We demonstrate how the number of electrons involved in this transition can be estimated to provide a novel descriptor for quantifying the strength of spin-orbit coupling responsible for driving the transition. The associated theoretical deviation of the Born charge of Na in Na3Bi from the expected ionic charge of +1 is found to be consistent with the corresponding experimental value of about 10%. Our study also shows the sensitivity of the Compton scattering technique toward capturing the spillover of Bi 6p relativistic states onto Na sites.
Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2
(2024) Yadav, Radhey Shyam; Kashyap, Diwakar; Pitussi, Itay; Gebru, Medhanie Gebremedhin; Teller, Hanan; Schechter, Alexander; Kornweitz, Haya
The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 degrees C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied-MF, methanol, and formic acid-MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).
Kramers nodal lines in intercalated TaS2 superconductors
(2025) Zhang, Yichen; Gao, Yuxiang; Pulkkinen, Aki Ismo Olavi; Guo, Xingyao; Huang, Jianwei; Guo, Yucheng; Yue, Ziqin; Oh, Ji Seop; Moon, Alex; Oudah, Mohamed; Gao, Xue-Jian; Marmodoro, Alberto; Fedorov, Alexei; Mo, Sung-Kwan; Hashimoto, Makoto; Lu, Donghui; Rajapitamahuni, Anil; Vescovo, Elio; Kono, Junichiro; Hallas, Alannah M.; Birgeneau, Robert J.; Balicas, Luis; Minár, Jan; Hosur, Pavan; Law, Kam Tuen; Morosan, Emilia; Yi, Ming
Kramers degeneracy is one fundamental embodiment of the quantum mechanical nature of particles with half-integer spin under time reversal symmetry. Under the chiral and noncentrosymmetric achiral crystalline symmetries, Kramers degeneracy emerges respectively as topological quasiparticles of Weyl fermions and Kramers nodal lines (KNLs), anchoring the Berry phase-related physics of electrons. However, an experimental demonstration for ideal KNLs well isolated at the Fermi level is lacking. Here, we establish a class of noncentrosymmetric achiral intercalated transition metal dichalcogenide superconductors with large Ising-type spin-orbit coupling, represented by InxTaS2, to host an ideal KNL phase. We provide evidence from angle-resolved photoemission spectroscopy with spin resolution, angle-dependent quantum oscillation measurements, and ab-initio calculations. Our work not only provides a realistic platform for realizing and tuning KNLs in layered materials, but also paves the way for exploring the interplay between KNLs and superconductivity, as well as applications pertaining to spintronics, valleytronics, and nonlinear transport.
Reexamining circular dichroism in photoemission from a topological insulator
(2025) Sidilkover, Ittai; Yen, Yun; Dsouza, Sunil Wilfred; Schusser, Jakub; Pulkkinen, Aki Ismo Olavi; Rotundu, Costel R.; Hashimoto, Makoto; Liu, Donghui; Shen, Zhi-Xun; Minár, Jan; Schüler, Michael; Soifer, Hadas; Sobota, Jonathan A.
The orbital angular momentum (OAM) of electron states is an essential ingredient for topological and quantum geometric quantities in solids. For example, Dirac surface states with helical spin- and orbital-angular momenta are a hallmark of a 3D topological insulator. Angle-resolved photoemission spectroscopy (ARPES) with variable circular light polarization, known as circular dichroism (CD), has been assumed to be a direct probe of OAM and, by proxy, of the Berry curvature of electronic bands in energy- and momentum-space. Indeed, topological surface states have been shown to exhibit angle-dependent CD (CDAD), and more broadly, CD is often interpreted as evidence of spin-orbit coupling. Meanwhile, it is well-established that CD originates from the photoemission matrix elements, which can have extrinsic contributions related to the experimental geometry and the inherently broken inversion symmetry at the sample surface. Therefore, it is important to broadly examine CD-ARPES to determine the scenarios in which it provides a robust probe of intrinsic material physics. We performed CDARPES on the canonical topological insulator Bi2Se3 over a wide range of incident photon energies. Not only do we observe angle-dependent CD in the surface states, as expected, but we also find CD of a similar magnitude in virtually all bulk bands. Since OAM is forbidden by inversion symmetry in the bulk, we conclude this originates from symmetry-breaking in the photoemission process. Comparison with theoretical calculations supports this view and suggests that "hidden" OAM-localized to atomic sites within each unit cell-contributes significantly. Additional effects, including inter-atomic interference and final-state resonances, are responsible for the rapid variation of the CDAD signal with photon energy.
Layered multiple scattering approach to Hard X-ray photoelectron diffraction: theory and application
(2025) Vo, Phuc; Tkach, Olena; Tricot, Sylvain; Sébilleau, Didier; Braun, Jürgen; Pulkkinen, Aki Ismo Olavi; Winkelmann, Aimo; Fedchenko, Olena; Lytvynenko, Yaryna; Vasilyev, Dmitry; Elmers, Hans-Joachim; Schönhense, Gerd; Minár, Jan
Photoelectron diffraction (PED) is a powerful technique for resolving surface structures with sub-angstrom precision. At high photon energies, angle-resolved photoemission spectroscopy (ARPES) reveals PED effects, often challenged by small cross-sections, momentum transfer, and phonon scattering. X-ray PED (XPD) is not only an advantageous approach but also exhibits unexpected effects. We present a PED implementation for the spin-polarized relativistic Korringa-Kohn-Rostoker (SPRKKR) package to disentangle them, employing multiple scattering theory and a one-step photoemission model. Unlike conventional real-space approaches, our method uses a k-space formulation via the layer-KKR method, offering efficient and accurate calculations across a wide energy range (20-8000 eV) without angular momentum or cluster size convergence issues. Additionally, the alloy analogy model enables simulations of finite-temperature XPD and effects in soft/hard X-ray ARPES. Applications include modeling circular dichroism in angular distributions (CDAD) in core-level photoemission of Si(100) 2p and Ge(100) 3p, excited by 6000 eV photons with circular polarization.
Two-dimensional to bulk crossover of the WSe2 electronic band structure
(2025) Raphaël, Salazar; Jamet, Matthieu; Vergnaud, Céline; Pulkkinen, Aki Ismo Olavi; Bertran, François; Bigi, Chiara; Minár, Jan; Ouerghi, Abdelkarim; Jaouen, Thomas; Rault, Julien; Le Fèvre, Patrick
Transition metal dichalcogenides (TMDs) are layered materials obtained by stacking two-dimensional sheets weakly bonded by van der Waals interactions. In bulk TMD, band dispersions are observed in the direction normal to the sheet plane (z-direction) due to the hybridization of out-of-plane orbitals but no kz-dispersion is expected at the single-layer limit.Using angle-resolved photoemission spectroscopy, we precisely address the two-dimensional to three-dimensional crossover of the electronic band structure of large area epitaxial WSe2 thin films. Increasing number of discrete electronic states appears in given kz-ranges while increasing the number of layers. The continuous bulk dispersion is nearly retrieved for 6-sheet films. These results are reproduced by calculations going from a relatively simple tight-binding model to a sophisticated KKR-Green’s function calculation.
Identification of asbestos fibres from soil sediments in the Pilsen region of the Czech Republic and the impact of these minerals on the health of the local population
(2025) Jansová, Štěpánka; Jansa, Zdeněk; Calta, Pavel; Vavruňková, Veronika; Nedvědová, Lucie; Minár, Jan
Asbestos is the term for silicate minerals with a typical fibrous structure that crystallises as separable fibres that can be released into the environment due to natural processes and anthropogenic activities. There is a need to intensify geo-environmental monitoring of the occurrence of natural asbestos on a global scale. The study of this material is essential to clarify the impact of asbestos on public health and to have an accurate knowledge of the requirements for asbestos replacement materials. The technical and ecological reasons for switching to these fibres are complex, as asbestos replacement materials are subject to considerable technological and economicdemands, as well as demands for their biological safety. The main objective of this paper is to establish a suitable methodology for detecting asbestos in soil sediments and accurately identify the different types from a range of samples. Samples were analysed by electron microscopy and X-ray diffraction and compared with standards or available literature. The measurements demonstrated the presence of asbestos in the site sediments and identified specific types of asbestos. The conclusion of this work is confirming the presence of asbestos in all samples, including its most dangerous types, which can cause severe diseases. In this context, the mechanism of asbestos-related diseases will be further addressed, which is linked to the size and shape of the individual fibres, the chemical composition of the asbestos types and the links between their basic structural units.
Efficient electrochemical performance of asymmetric supercapacitor based on nitrogen-doped Nb2CTx MXene in an alkaline electrolyte
(2025) Syed, Arooma; Ali, Irfan; Maqbool, Sana; Yousaf, Muhammad; Hussain, Iftikhar; Zhang, Kaili; Khan, Saleem Ayaz; Rizwan, Syed
The versatile, and tunable surface chemistry of two-dimensional (2D) MXenes coupled with their distinct properties including hydrophilic nature, favorable ion transport and metallic conductivity make them an ideal candidate for energy storage devices. Modifying surface terminations by doping heteroatom is an efficient approach to improve layer spacing and electrochemical active sites of the MXenes. However, nitrogen doping in 2D materials has been an effective way to enhance their electrochemical characteristics. In this study, N-Nb2CTx MXene was synthesized by utilizing the hydrothermal method in which nitrogen doping in MXene was confirmed through several characterization techniques. Tuning of MXene surface by a cost-effective strategy has shown improved performance for energy storage. After doping nitrogen in Nb2CTx MXene, it has shown enhanced pseudocapacitance performance in 1 M potassium hydroxide (KOH), elevating the electrochemical properties. N-Nb2CTx MXene has displayed a better specific capacitance of up to 640 Fg-1 while pristine Nb2CTx MXene has shown 276 Fg-1 from the cyclic voltammogram (CV) at a scan rate of 5 mVs-1. In addition, an asymmetric device of activated carbon/N-Nb2CTx was assembled for real-world applications, it has exhibited refined results. The asymmetric device has shown remarkable cyclic stability of 90% capacity retention at a current density of 5 Ag-1 for 5000 cycles. Additionally, the detailed density functional theory (DFT) calculations support the stability of nitrogen replacing the fluorine functional group, complementing the experiment.
Exploring optoelectronic, optical thin films, mechanical and thermal transport properties of bromide double perovskites Rb2Ag(Ga/In)Br6 for photovoltaic and thermoelectric applications
(2025) Benkaddour, I.; Haddou, A.; Khachai, Y.A.; Baki, N.; Chiker, F.; Khachai, H.; Khenata, R.; Metadjer, N.; Bin-Omran, S.; Shankar, A.; Khan, Saleem Ayaz
Lead-free double halide perovskites like Rb2Ag(Ga/In)Br-6 have demonstrated themselves potential candidates in solar cell research owing to their environmental friendliness, stability, and exceptional performance. This study comprehensively analyzes the structural, mechanical, optoelectronic and optical coating features, as well as thermodynamic and thermoelectric properties of two Rb2AgGaBr6 and Rb2AgInBr6 compounds. Using the Wien2k code with GGA + mBJ exchange-correlation potentials, we confirm their structural stability in cubic phase Fm-3m and identifying them as direct band gap semiconductors (Gamma -> Gamma) of 0.38 eV and 1.0644 eV, respectively. Then, optical analysis reveals broad absorption bands across visible and ultraviolet wavelengths, making them suitable for photovoltaic absorbers. Finally, the thermoelectric investigations under varying temperatures show favourable properties, such as a high Seebeck coefficient with poor electronic thermal conductivity. This also yields exceptional value (0.96 and 0.994 for Rb2AgGaBr6, Rb2AgInBr6, respectively) of figure of merit (ZT) at room temperature and chemical potential mu-mu 0 = - 0.09eV near the Fermi energy level, enhancing their potential for thermoelectric applications. These findings underscore the versatility and promising future of Rb2Ag(Ga/In)Br-6 as important semiconductors processing for optoelectronic, thermoelectric, and mechanical devices.
Smart hydrogels for sensing and biosensing - Preparation, smart behaviours, and emerging applications - A comprehensive review
(2025) Revathi, Devulapalli; Panda, Subhasree; Deshmukh, Kalim Abdul Rashid; Khotele, Nisha; Murthy, V.R.K.; Pasha, S.K. Khadheer
Hydrogels are three dimensional (3D) crosslinked hydrophilic polymer network structures with an excellent stimulus sensitivity. 3D networks of hydrogels can absorb high amount of water in their crosslinked structures. In the last few decades hydrogels are successfully gaining attention in tremendous applications by their nature, texture, smart behaviour and a number of developments are taking chance in the field of sensing and bio-sensing applications. Owing to their highly tunable swelling, self-healing, mechanical, porous-structure and conductive properties, the research has been advancing day-by-day in the field of hydrogels and their applications. Hydrogels are soft materials whch are prepared through physical or chemical crosslinking methods weak van der Waals forces, ionic bonds or covalent bonds. A successive progress and recent advancement in hydrogels from simple network to complex double network structure to development of smart hydrogels which is now a trending research area in this field. The versatility and ability of smart materials to responds to various external stimuli make them ideal for detecting and quantifying wide range of analytes. This review widely discusses hydrogel preparation techniques including self-assembly, ionic interaction, freeze-thawing, graft-copolymerization, chemical, electrochemical, radiation, template polymerization, photo crosslinking and by simple chemical interaction. This review also focusses on various types of hydrogel sensors such as, fluorescent, colorimetric, electrochemical, electrochemiluminescence, surface-enhanced Raman scattering along with their sensing mechanisms. In addition, the visco-elastic behaviour empowering the hydrogels to design 3D, 4D printable structures using additive manufacturing techniques for better sensing applications were discussed. Moreover, the review discusses the behaviour of multifunctional hydrogel composites incorporated with carbon-based nanomaterials, metal-oxides and novel 2D materials likeMXene for the development of flexible, and wearable sensors. The review also highlights the physico-chemical and bio-chemical stimuli sensitive mechanisms in response to external smart stimuli for today's cutting-edge applications in sensing and bio-sensing.
Imaging Orbital Vortex Lines in Three-Dimensional Momentum Space
(2025) Figgemeier, T.; Ünzelmann, M.; Eck, P.; Schusser, Jakub; Crippa, L.; Neu, J.N.; Geldiyev, B.; Kagerer, P.; Buck, J.; Kalläne, M.; Hoesch, M.; Rossnagel, K.; Siegrist, T.; Lim, L.-K.; Moessner, R.; Sangiovanni, G.; Di Sante, D.; Reinert, F.; Bentmann, H.
We report the experimental discovery of orbital vortex lines in the three-dimensional (3D) band structure of a topological semimetal. Combining linear and circular dichroism in soft x-ray angle-resolved photoemission (SX-ARPES) with first-principles theory, we image the winding of atomic orbital angular momentum, thereby revealing—and determining the location of—lines of vorticity in full 3D momentum space. We determine the core of the orbital angular momentum vortex to host an almost movable, twofold, spin-degenerate Weyl nodal line, a topological feature predicted to occur in certain nonsymmorphic crystals. These results establish bimodal dichroism in SX-ARPES as a robust approach to trace 3D orbital textures. Our findings constitute the first imaging of nontrivial quantum-phase winding at line nodes and may pave the way to new orbitronic phenomena in quantum materials.
A density functional theory study of magnetic transition in MnO2 adsorbed vanadium carbide (V2C) MXene
(2025) Fatima, Mahjabeen; Khan, Saleem Ayaz; Rizwan, Syed
The work reports nonmagnetic behavior (0.04 mu B) in two-dimensional (2D) V2C-OF MXene and ferromagnetism in MnO2 adsorbed V2C-OF MXene. The density functional theory (DFT) calculations were carried out to study the magnetic moments of V2C-OF and MnO2@V2C-OF MXene. The MXene, which is derived from the exfoliation of its parent V2AlC MAX phase, shows a good potential to be a ferromagnetic when MnO2 is adsorbed on it. The V2C MXene and MnO2 adsorbed V2C MXene were successfully synthesized, as characterized using X-ray diffraction, showing an increased c-lattice parameter from 22.6 & Aring; to 27.2 & Aring; after MnO2 adsorption. The DFT study confirmed that MnO2 adsorbed V2C MXene changed from nonmagnetic (in V2C MXene) to a strong ferromagnetic with a magnetic moment of 4.48 mu B for Mn adsorbed V2C-OF MXene. The current work is a step-forward towards understanding of magnetism in two-dimensional materials for future 2D spintronics.
Approaching Hypothetical RbTl in Experiments and Theory - X-ray Structure Determination of Cs1-xRbxTl (x = 0.18, 0.42) and a Solid Solution K1-xRbxTl (x ≤ 0.69)
(2025) Schwinghammer, Vanessa F.; Khan, Saleem Ayaz; Tiefenthaler, Susanne M.; Kovářík, Tomáš; Minár, Jan; Gärtner, Stefanie
Although the binary alkali metal thallides ATl with A = Li, Na, K, and Cs have been reported in the literature, binary RbTl at ambient pressure is still missing. Experiments with a 1:1 ratio of Rb:Tl, either according to Zintl’s procedure in low-temperature experiments in liquid ammonia or classical solid-state synthesis at high temperature, did not result in the desired product. Therefore, several ternary compositions with mixtures of K/Rb and Cs/Rb have been prepared. For K/Rb mixtures, a solid solution in the KTl structure type, up to a proportion of 69% rubidium, could be obtained. Site occupancy preferences for rubidium on the alkali metal sites in the KTl type are observed in experiments and supported by theoretical calculations. In contrast to Rb/K mixtures being realizable in the KTl structure type, Rb/Cs mixtures did not allow for the isolation of materials according to the CsTl structure type. Instead, two new monoclinic compounds could be isolated (Cs0.82Rb0.18Tl: C2/c, a = 14.4136(4) Å, b = 11.1678(3) Å, c = 40.8013(11) Å, β = 96.353(2)°, V = 6527.4(3) Å3; Cs0.58Rb0.42Tl: C2/c, a = 14.2610(3) Å, b = 11.1116(2) Å, c = 27.5589(7) Å, β = 104.056(2)°, V = 4236.30(17) Å3). Detailed DFT calculations on both binary and mixed cation systems were performed and support the experimental results.
Unveiling the structural, optical coating and thermoelectric characteristics of kesterite-quaternary chalcogenides Ag2InGaX4 (X = S, Se, Te) via DFT study
(2025) Bourahla, C.; Chiker, F.; Khachai, H.; Khenata, R.; Bouhemadou, A.; Singh, Devraj; Bin-Omran, S.; Eithiraj, R.D.; Jappor, Hamad R.; Khan, Saleem Ayaz
This study explores the distinctive features of novel kesterite-type chalcogenide semiconductor materials through a new scheme designated as I2-III-III-VI4, focusing on Ag2InGaX4 (X = S, Se, Te). The investigation employs density functional theory (DFT) using the advanced all-electron full potential linear augmented plane wave(FPLAPW) method. The exchange-correlation potential is assessed through the Perdew-Burke-Ernzerhof (PBE) parameterization, complemented by the Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential estimation.Furthermore, thermodynamic parameters are analyzed in relation to temperature and pressure for the selected materials, utilizing the quasi-harmonic model. The electronic structure analysis reveals that Ag2InGaX4 (X = S, Se, Te) materials display semiconducting behavior, with direct band gaps measured at 1.9 eV, 1.1 eV, and 0.86 eV, respectively.Moreover, the predicted refractive index, absorption coefficient, dielectric function, absorbance, transmittance and reflectance revealed that Ag2InGaX4 (X = S, Se, Te) are promising materials for photovoltaic and optoelectronic devices. Furthermore, the analysis of thermoelectric properties considering the Seebeck coefficient, thermal conductivity, electronic conductivity, and highly valued figures of merit showed that the studied kesterite-type compounds have strong potential for applications in the fields of thermoelectric power energy.Finally, all these results are considered favorable and appropriate as per the characteristics mentioned earlier, and their potential advantages and applications in advanced hybrid photovoltaic and thermoelectric systems have been highlighted. It has been declared that this study's attained results were considered a prediction in this kesterite family.
Computational study of magnetic behaviour in Ni-adsorbed Nb2C-OF MXene using density functional theory
(2025) Khan, Zarah; Khan, Saleem Ayaz; Zaheer, Ayesha; Rizwan, Syed
Magnetic 2D materials have achieved significantly consideration owing to their encouraging applications. A variation of these 2D materials by occurrence of defects, by the transition-metal doping or adsorption or by the surface functionalization can initiate both the spin-polarization and magnetic properties in these materials. Density functional theory (DFT) is used to determine the electric, magnetic properties along with the electronic structures and stability of synthesized two-dimensional materials. This work describes the magnetic properties of Ni-ad-Nb2C-OF MXene. The study focuses on the computational approach based first principal calculation providing insight onto the magnetic properties of adsorbed compound and comparing it with pristine Nb2C-OF MXene. The pristine Nb2C-OF and Ni-ad-Nb2C-OF structures are simulated and optimized using Wien2k software. Using exchange-correlational functionals; spin-GGA and spin-GGA + U (for Nickel U = 6 eV), Ni-ad-Nb2C-OF electronic band structure is found to be metallic having magnetic moment calculated + 1.01516 μβ showing its non-superconducting and ferromagnetic properties. Owing to this magnetic properties, this 2D compound holds potential for emerging applications in spintronics and nanoscale magnetic data storage technologies.
Engineering advanced mesoporous nanomaterials for high performance supercapacitors: A review
(2025) Pandey, Mayank; Deepthi, Jayan K.; Deshmukh, Kalim Abdul Rashid; Nalini, V.; Manobalan, S.; Sumangala, T. P.; Pore, O. C.; Lohar, G. M.
Mesoporous nanomaterials refer to a class of materials that possess a well-defined porous structure at the nanometer scale. These materials exhibit a substantial surface area and an orderly arrangement of interconnected pores, typically ranging in diameter from 2 to 50 nanometers. The pore size of mesoporous nanomaterials falls between the microporous range (less than 2 nanometers) and the macroporous range (greater than 50 nanometers). On the other hand, The exceptional characteristics of mesoporous nanomaterials enable rapid ion diffusion, a substantial specific surface area, and enhanced sites for adsorption and reactions. Consequently, they offer a promising solution for the fabrication of high-performance electrode and catalyst materials for nextgeneration energy storage and conversion devices. This review primarily offers a brief discussion about various mesoporous nanomaterials and their recent advancements in supercapacitor applications. Secondly, the review discusses various methods of synthesizing mesoporous nanomaterials with a particular focus on templatebased, template-free, and chemical approaches. Lastly, it explores the applications of mesoporous nanomaterials and their recent developments in cutting-edge supercapacitors, followed by a discussion of the key challenges and future prospects of these nanomaterials in energy storage field.
Nickel-cobalt spinel-based oxygen evolution electrode for zinc-air flow battery
(2025) Richtr, Přemysl; Hnát, Jaromír; Charvát, Jiří; Bureš, Martin; Pocedič, Jaromír; Paidar, Martin; Kosek, Juraj; Mazúr, Petr
Zinc-air flow battery (ZAFB) represents a candidate for safe, cheap and non-toxic stationary energy storage, however, uneven zinc deposition and low efficiency of oxygen reactions on positive electrode still obstruct its commercialization. In our contribution, we address the latter challenge by performance enhancement of electrode for oxygen evolution reaction (OER) from highly alkaline electrolyte. This was achieved by applying a NiCo 4 electro-catalytic layer onto the selected 3D nickel-based substrates via electrochemically-assisted deposition followed by calcination. The detailed physico-chemical characterization of the electrodes (specific surface area, conductivity, EDS, SEM + EDS, XRD) confirmed spinel structure of the prepared catalyst and its homogeneous deposition over the substrate. The electrochemical characterization of the electrodes was performed in three different set-ups using a complex methodology incl. voltammetry techniques, electrochemical impedance spectroscopy, galvanostatic load and charge-discharge cycling in the developed 3-electrodes 3- compartments battery full-cell. For both Ni substrates the deposited NiCo 2 O 4 catalytic layer effectively lowered the OER overpotential due to significantly enlarged specific surface area. This effect was more pronounced for the foam substrate with more compact structure. The developed ZAFB with the optimized OER electrode achieved stable and efficient performance at high current densities of 100 mA cm 2 (which is the highest reported one for cycling experiments) in a broad SoC range (0–80 %) with energy efficiency of 42.1 % and no decay of capacity utilization.
Ti and TiAlV foils enhanced with PLD and flash-deposited carbon: On cytocompatibility and antibacterial activity
(2025) Slepička, Petr; Hurtuková, Klaudia; Rimpelová, Silvie; Trhoňová, Šárka; Martan, Jiří; Procházka, Michal; Švorčík, Václav; Slepičková Kasálková, Nikola
In this study, we investigated the effects of carbon layer deposition on titanium (Ti) and titanium alloy (TiAlV) substrates using "flash" vaporization and pulsed laser deposition (PLD) techniques. Raman spectroscopy revealed that the PLD method produced a higher sp3 carbon bond content than the evaporation method (61 vs. 47 %). Atomic force microscopy and surface wettability analyzes showed differences in surface roughness and contact angle, with PLD-deposited samples exhibiting enhanced hydrophilicity and wrinkled morphology. Subsequent laser annealing optimized surface properties by increasing hydrophobicity, which is critical for cell adhesion. Surface chemistry analysis via scanning electron microscopy and energy dispersive spectroscopy demonstrated significant carbon enrichment in the PLD-deposited samples, mainly for TiAlV substrate. Cytocompatibility tests using human osteosarcoma cells (U-2 OS) revealed varying cell adhesion and proliferation based on surface modification, with PLD-deposited layers promoting better cell interaction. Both carbon deposition techniques enhanced antibacterial effect. This suggests the potential of PLD-deposited carbon layers for biomedical applications, particularly in enhancing implant surfaces for improved cell growth and adhesion, and reduce bacteria, the nanostructured substrates may serve also for subsequent replication process into polymer.
Multiphase PtPdSb nanoparticles for direct electrochemical energy conversion using hydrogen-rich dimethyl ether
(2025) Gebru, Medhanie Gebremedhin; Pitussi, Itay; Teller, Hanan; Marammurian Chathoth, Achyuth; Kornweitz, Haya; Medlín, Rostislav; Bělský, Petr; Subramanian, Palaniappan; Schechter, Alexander
Dimethyl ether (DME) is a promising next-generation renewable fuel for polymer electrolyte membrane fuel cells (PEMFC) because of its high energy density, ease of handling and supply, nontoxicity, reduced crossover, and ability to be obtained from a wide range of renewable sources. However, its commercialization has not yet been realized, owing to the low activity of state-of-the-art catalysts. We have synthesized a novel Genkenite ternary metal catalyst, PtxPdySbz/C, with varying metal compositions and tested its activity towards DME oxidation in both three-electrode flooded cell and in single fuel cell configurations. Some important insights into the DME reaction mechanism were gleaned using ex-situ Fourier transform infrared spectroscopy and were supported by density functional theory (DFT) computations. A direct DME fuel cell constructed with 1.2 and 3.1 mgPGM cm􀀀 2 loading of Pt5PdSb4/C and Pt/C as anode and cathode catalysts, respectively, operating at 65 ◦C temperature and no back pressure delivered a peak power density of 180 mW cm􀀀 2 and one of the highest reported current density of 360 mA cm􀀀 2 at 0.5 V. Moreover, the catalyst provided the highest PGM (Pt+Pd) mass normalized power density of 150 mW mg􀀀PG1M.
Počítačové modelování maximálního stresu pánevních struktur během porodu hlavičky - vliv práce nedominantní ruky - Abstrakt
(Urogynekologická společnost České republiky, 2022) Jansová, Magdalena; Čechová, Hana; Havelková, Linda; Hynčík, Luděk; Kališ, Vladimír; Rušavý, Zdeněk; Krofta, Ladislav; Ismail, Khaled M.
Počítačové modelování maximálního stresu pánevních struktur během porodu hlavičky - vliv práce nedominantní rukyPráce se zabývá vlivem nedominantní ruky na napětí pánevních struktur během porodu hlavičky.

Browse

Recent Submissions