Publikační záznamy NTC

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Vanadium-Engineered Co2NiSe4 nanomaterial: coupled thermoelectric, piezoelectric, and electronic optimization via DFT+U for advanced energy applications
(2025) Riaz, Ayesha; Azam, Sikander; Rafiq, Qaiser; Khan, Muhammad Tahir; Rahman, Amin Ur; Ahkam, Qazi Muhammad; Hussain, Rafaqat; Khan, Rajwali
The multifunctional potential of quaternary chalcogenides can be dramatically expanded by targeted pointdefect engineering. In this work, we employ density functional theory (DFT) with on-site Coulomb correction (GGA + U) to explore the structural, electronic, optical, thermoelectric, and piezoelectric properties of pristine and dilute vanadium-doped Co2NiSe4 (<= 10 at.%). Our results reveal that V substitution in monoclinic Co2NiSe4 introduces a resonant V d3 impurity level, which simultaneously (i) narrows the electronic band gap from 0.52 eV to 0.30 eV, (ii) lncrease the total spin moment from 3.2 to 3.6 mu B per formula unit, and (iii) triples the density of states at the Fermi level (Ef). These modifications lead to a significant enhancement in electrical conductivity and phonon-defect scattering, collectively boosting the thermoelectric figure of merit (zT) up to approximate to 1.1 at 900 K for 5 at.% V. Concurrently, the dielectric onset red-shifts into the near-infrared, and the dielectric constant and absorption spectrum broaden, enabling broadband light harvesting and potential NIR optoelectronic applications. The piezoelectric modulus e33 also shows a notable 23 % increase, rising to 2.70 C/m2 at 10 % V doping, indicating strong electromechanical coupling driven by lattice distortion and local symmetry breaking. Simulated X-ray absorption spectra at the Co L2,3 edges further reveal redshifted and broadened absorption peaks upon V doping, confirming enhanced Co-V hybridization and an increased unoccupied 3d-state density, which supports improved conductivity and optical response. These mutually reinforcing electronic, vibrational, and electromechanical enhancements position V-doped Co2NiSe4 as a promising multifunctional material platform for integrated heat-to-power conversion, near-infrared photodetection, and spintronic or spin-filter applications. The study highlights how targeted substitutional doping in chalcogenides can unlock simultaneous improvements across energy, sensing, and actuation domains.
Revealing electronic correlations in YNi2B2C using photoemission spectroscopy
(2025) Pulkkinen, Aki Ismo Olavi; Kremer, Geoffroy; Strocov, Vladimir N.; Weber, Frank; Minár, Jan; Monney, Claude
The low-energy electronic structure of materials is crucial to understanding and modeling their physical properties. Angle-resolved photoemission spectroscopy (ARPES) is the best experimental technique to measure this electronic structure, but its interpretation can be delicate. Here we use a combination of density functional theory (DFT) and one-step model of photoemission to decipher the soft x-ray ARPES spectra of the quaternary borocarbide superconductor YNi2B2C. Our analysis reveals the presence of moderate electronic correlations beyond the semilocal DFT within the generalized gradient approximation. We show that DFT and the full potential Korringa-Kohn-Rostoker method combined with the dynamical mean field theory (DFT+DMFT) with average Coulomb interaction U = 3.0 eV and the exchange energy J = 0.9 eV applied to the Ni d-states are necessary for reproducing the experimentally observed SX-ARPES spectra.
Cleaved surfaces and homoepitaxial growth of InBi(001)
(2025) Rehaag, Thomas J.; Mayoh, Daniel A.; Bárta, Tomáš; Slaney-Parker, Freya; Elhoussieny, Ibrahim; Minár, Jan; Bell, Gavin R.
InBi is a semimetal with topologically non-trivial electronic surface states, which is also chemically and structurally compatible with conventional III-V semiconductors. Single crystal InBi has been grown and its (001) cleave surfaces studied. They do not conform to the single Bi-Bi cleave plane previously assumed in band structure studies of the material but instead expose both In- and Bi-terminated surface regions. Crystals cleaved in ultra-high vacuum have been used as substrates for ultra-low temperature homoepitaxy via periodic supply epitaxy (PSE) with alternate Bi and In fluxes. Homoepitaxial growth of good quality InBi was not achieved under these conditions. The 3D and 2D surface structures produced by PSE were studied by reflection high energy electron diffraction and atomic force microscopy. By studying InBi homoepitaxy for the first time, this work highlights the challenge of growing high quality InBi epilayers beyond the ultra-thin heteroepitaxial layers recently demonstrated [Molecules 2024, 29(12), 2825].
Improved prediction of ultrashort pulse laser ablation efficiency
(2025) Redka, David; Vela, Sergio; Spellauge, Maximilian; Minár, Jan; Morales, Miguel; Molpeceres, Carlos; Huber, Heinz Paul
Achieving maximum efficiency and precision in ultrafast laser ablation is crucial for micromachining applications, where advanced models are pivotal to predict and optimize laser-material interactions. Existing models for predicting laser ablation efficiency assume an equivalence between the threshold fluence determined by ablation depth and diameter. However, experimental measurements have shown this assumption does not hold. In this work, we present a new model for ablation efficiency by introducing a minimum ablation depth (d0) into the ablation depth equation, which accounts for the discrepancy between depth and diameter thresholds. We have designated this framework as the threshold-refined ablation model (TRM). Unlike the Furmanski model, which places the fluence corresponding to maximum ablation efficiency at e2 times the threshold fluence, the TRM predicts this maximum occurs at a lower range (three to five times the threshold fluence), aligning with experimental findings. The new model has been validated against single-pulse experiments for metals, glasses, and dielectrics. For most cases, the TRM demonstrates significantly better agreement with experiments, providing enhanced predictive accuracy for sub-ps and fs pulses.
Spin-orbital mixing in the topological ladder of the two-dimensional metal PtTe2
(2025) Qahosh, M.; Masilamani, M.; Boban, H.; Hou, Xiao; Bihlmayer, G.; Mokrousov, Y.; Karain, W.; Minár, Jan; Reinert, F.; Schusser, Jakub; Schneider, C.M.; Plucinski, L.
We visualize the topological ladder and band inversions in PtTe2 using spin-polarized photoemission spectroscopy augmented by three-dimensional momentum imaging. This approach enables the detection of spin polarization in dispersive bands and provides access to topological properties beyond the reach of conventional methods. Extensive mapping of spin-momentum space reveals distinct topological surface states, including a surface Dirac cone at a binding energy ??∼2.3eV and additional states at ??∼1.6eV, ??∼1.0eV, and near the Fermi level. The electronic structure analysis demonstrates strong hybridization between Pt and Te atomic orbitals, confirming the nontrivial topology of these surface states. Furthermore, by comparison to one-step model photoemission calculations, we identify a robust correlation between the initial-state and measured spin polarizations while revealing asymmetries in specific experimental spin textures. These asymmetries, absent in the initial states due to symmetry constraints, arise from the breaking of time-reversal symmetry during the photoemission process, emphasizing the crucial influence of symmetries on experimental signatures of topology. A phase analysis of ladder states in real space suggests a route to probe them using photoemission, paving the way towards spectroscopic access to the quantum geometric tensor.
Conduction band structure and ultrafast dynamics of ferroelectric α-GeTe(111)
(2025) Kremer, Geoffroy; Nicolai, Laurent Christophe; Chassot, Frédéric; Maklar, Julian; Nicholson, Christopher W.; Dil, J. Hugo; Krempaský, Juraj; Springholz, Gunther; Ernstorfer, Ralph; Minár, Jan; Rettig, Laurenz; Monney, Claude
alpha-GeTe(111) is a noncentrosymmetric ferroelectric (FE) material for which a significative lattice distortion combined with a strong spin-orbit interaction gives rise to giant Rashba split states in the bulk and at the surface, which have been intensively probed in the occupied valence states using static angle-resolved photoemission spectroscopy (ARPES). Nevertheless, its unoccupied conduction band structure remains unexplored, in particular the experimental determination of its electronic band gap across momentum space. Using time-resolved ARPES based on high-repetition rate and extreme ultraviolet femtosecond (fs) laser, we unveil the band structure of alpha-GeTe(111) in the full Brillouin zone, both in the valence and conduction states, as well as the exploration of its out-of-equilibrium dynamics. Our work confirms the semiconducting nature of alpha-GeTe(111) with a 0.85 eV indirect band gap, which provides an upper limit for comparison to density functional theory calculations. We finally reveal the dominant scattering mechanisms of photoexcited carriers during the out-of-equilibrium dynamics under fs light pulses.
Effect of laser shock peening on the microstructure of GX4CrNi13-4 martensitic stainless steel
(2025) Bricín, David; Jansa, Zdeněk; Kaufman, Jan; Špirit, Zbyněk; Fulín, Zdeněk; Strejcius, Josef
This study investigates the effect of laser shock peening (LSP) on the microstructure and properties of GX4CrNi13-4 martensitic stainless steel. Three different conditions of surface preparation were examined in this study. First, a control group was left with a ground surface. The two remaining groups were treated with LSP. In one case, a single pass of LSP was applied and in the other case, a double pass of LSP was concerned. The samples were subsequently subjected to corrosion-fatigue testing in a water solution of 0.5 g/l NaCl, metallographic analysis, X-ray diffraction, and microhardness measurements. Experimental results of the corrosion-fatigue test showed that the LSP-treated samples exhibited fatigue cracking at higher force amplitude. Roughness measurements showed that the surface after LSP was rougher compared to the initial ground surface but with a lower proportion of grooves. Greater plastic surface deformation resulted in an increase in microhardness in the near-surface region, which was accompanied by an increase in the calculated density of geometrically necessary dislocations, a decrease in the proportion of retained austenite and coarsening of the martensite phase crystallite.
Emergence of a bandgap in nano-scale graphite: A computational and experimental study
(2025) Chaiyachad, Sujinda; Vo, Phuc; Jindata, Warakorn; Singsen, Sirisak; Eknapakul, Tanachat; Jaisuk, Chutchawan; Fevre, Patrick Le; Bertran, Francois; Lu, Donghui; Huang, Yaobo; Nakajima, Hideki; Liewrian, Watchara; Fongkaew, Ittipon; Minár, Jan; Meevasana, Worawat
Bandgaps in layered materials are critical for enabling functionalities such as tunable photodetection, efficient energy conversion, and nonlinear optical responses, which are essential for next-generation photonic and quantum devices. Gap engineering could form heterostructures with complementary materials like transition metal dichalcogenides or perovskites for multifunctional devices. Graphite, conventionally regarded as a gapless material, exhibits a bandgap of similar to 100 meV in nano-scale patterned highly oriented pyrolytic graphite (HOPG), as revealed by angle-resolved photoemission spectroscopy (ARPES) and Raman measurements. Our state-of-the-art calculations, incorporating photoemission matrix element effects, predict this bandgap with remarkable accuracy and attribute it to mechanical distortions introduced during patterning. This work bridges theory and experiment, providing the direct evidence of a tunable bandgap in HOPG. Beyond its fundamental significance, this finding opens new possibilities for designing materials with tailored electronic properties, enabling advancements in terahertz devices and optoelectronics.
Smart injectable hydrogels for periodontal regeneration: Recent advancements in biomaterials and biofabrication strategies
(2025) Yin, Bohan; Dodda, Jagan Mohan; Wong, Siu Hong Dexter; Deen, G. Roshan; Bate, Jeffrey S.; Pachauri, Abhishek; Shiroud Heidari, Behzad; Kovářík, Tomáš; Luo, Chi-An; Tsai, Shiao-Wen
Periodontitis is a globally prevalent chronic inflammatory disease that leads to periodontal pocket formation and eventually destroys tooth-supporting structures. Hence, the drastic increase in dental implants for periodontitis has become a severe clinical issue. Injectable hydrogel based on extracellular matrix (ECM) is highly biocompatible and tissue-regenerative with tailor-made mechanical properties and high payload capacity for in situ delivery of bioactive molecules to treat periodontitis. This therapeutic tool not only enhances the drug release efficiency and treatment efficacy but also reduces operation time. Nevertheless, it remains challenging to optimize the mechanical properties and intelligent control drug release rate of injectable hydrogels to achieve the highest therapeutic outcome. Literature precedent has shown the modulation of polymer backbones (synthetic polymers, natural polysaccharides, and proteins), crosslinking strategies, other bioactive constituents, and potentially the incorporation of nanomaterials that overall improve the desirable physiochemical and biological performances as well as biodegradability. In this review, we summarize the recent advances in the development, design, and material characterizations of common injectable hydrogels. Furthermore, we highlight cutting-edge representative examples of polysaccharide-, protein- and nanocomposite-based hydrogels that mediate regenerative factors and anti-inflammatory drugs for periodontal regeneration. Finally, we express our perspectives on potential challenges and future development of multifunctional injectable hydrogels for periodontitis.
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.

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