The enhancement of superconductivity at surfaces and interfaces, where the order parameter persists at higher temperatures or magnetic fields than in the bulk, is a subtle yet fundamentally important phenomenon in condensed matter physics. In this work, we experimentally investigate the difference between near-surface and bulk superconducting transitions in 160-nm-thick NbN films, a conventional s-wave superconductor, under magnetic fields up to 8 T. To this end, we developed a highly sensitive nonlocal four-probe measurement scheme capable of simultaneously detecting surface and bulk electrical responses. This approach revealed distinct critical temperatures and superconducting transition widths that vary with the orientation of the applied magnetic field, ranging from perpendicular to parallel to the film plane. Our findings are consistent with recent theoretical predictions concerning multiple phase transitions in superconductors with spin-imbalanced fermion populations. The results not only establish a robust methodology for probing boundary-induced superconducting phenomena, but also provide insights relevant to the design of superconducting devices with engineered surface properties.

We report on the fabrication and study of NbN/F/NbN trilayers with NbN films of 80-nm thickness, which is much larger than the coherence length but significantly smaller than the London penetration depth, and 50-nm-thick ferromagnetic (F = Ni or NiCu alloy) interlayers, along with 160-nm-thick single layers of NbN as a reference. The heterostructures were patterned into square shapes to enable nonlocal four-probe resistive measurements. This technique, previously applied to single-layer NbN films, allows for the simultaneous and independent probing of surface and bulk superconducting transitions in one measurement run. By comparing NbN and NbN/F/NbN trilayers, we demonstrate that the inclusion of a ferromagnetic interlayer leads to a significant shift in the onset of the superconducting transition, particularly in the near-surface region of the trilayer, and increases the overall transition width. This behavior is consistent with the concept of the electromagnetic proximity effect, predicted theoretically and, thanks to a new measurement strategy that distinguishes between surface and bulk contributions, provides evidence for its presence. The work provides insights into the delicate interplay between superconductivity and magnetism and opens pathways for engineering related interface-sensitive spintronic devices.

Despite its history of more than a century, the four-probe technique has remained a cornerstone of electrical measurements in thin conductive layers. Its traditional on-sample configuration consists of four electrical contacts arranged along a straight line to measure local sheet resistances. In multilayers, the results of such measurements cannot be interpreted straightforwardly due to their significant dependence on the properties of individual films and contact resistances between them. To address this challenge, we propose a through-sample nonlocal four-terminal method based on the Landauer-Büttiker scattering approach, which has been tested on hybrid all-metallic sandwiches composed of two 80 nm thick NbN films and a 50 nm thick core made of three archetypal ferromagnets, Co, Ni, or NiCu alloy. Results obtained for the trilayers are compared with the corresponding data for single NbN films 160 nm thick. At temperatures above the critical temperature of NbN, we have found negative values of nonlocal resistances which are explained using an equivalent circuit model with six resistances connecting the four probes. The key advantage of the proposed methodology lies in its simple design enabling the detection of subtle physical effects in transversely heterogeneous devices that might otherwise go unnoticed.

Contaminants of emerging concerns, such as sulfonamides, have been frequently discovered in surface water, and the design of biomass-based adsorbents is a promising research direction to remove them from water. In this study, hydrothermal carbonization was utilized to prepare hydrochar (HC) from orange peels along with various activations, including hydrogen peroxide (H2O2) and HCl. The main goals of the present study are (i) to prepare hydrochars that were activated by different chemical methods and (ii) to provide insights into the adsorption mechanism of pollutant removal using sulfamethoxazole (SMX) as a model pharmaceutical pollutant. The H2O2 activated hydrochar (ACHC) exhibited the best adsorption capacity for removal of 40 μM SMX from water, i.e., 1.971 mg g−1 using 0.2 g L−1 ACHC. Scanning electron microscopy (SEM) studies revealed that the ACHC exhibited a coral-like structure and the highest amount of mesopores (74.6 m2 g−1) and BET area of 79.5 m2 g−1. The effects of pH, adsorbent dosage, initial concentration, and adsorption temperature were investigated, and a substantial relationship between porosity and adsorption suggests that mesoporosity played a crucial role in the adsorption process for all the activated hydrochars. The mechanism of SMX adsorption involves reversible chemisorption and retention in the pores of the adsorbent surface. The use of ACHC was also tested in different water matrices to highlight its potential applications in wastewater treatment, and it exhibited an adsorption capacity of 0.598 and 0.429 mg g−1 in tap water and wastewater effluents, respectively.

Transparent superconductors combined with quantum photonics are in high demand for quantum computing, communication, and sensing. In this work, we report detailed magneto-transport properties of In 2- y Sn y O 3- δ ( y ∼ 0.2) thin films electrochemically reduced in aqueous electrolytes and analyze temperature and angular dependences of the upper critical magnetic field. The relationship between processing parameters and spatial variations of the superconducting properties is examined.

This work is focused on the investigation of three different Bi-based materials, i.e., CaBi2O2(CO3)(2) (CBOC), Ca4Bi6O13 (CBO), and Bi2Ce2O7 (BCO), as photocatalysts in N2O reduction. This study has emphasized the effectiveness of the bismuth ion, irrespective of its presence in different structures with self-regulating electronic and morphological properties, when employed as a photocatalyst. Monophasic CBOC, CBO, and BCO samples have been synthesized by wet-chemical methods, and they exhibit distinct morphological features such as plate-like, dumbbell-shaped, and irregularly shaped crystallites. From the UV-visible diffuse reflectance spectroscopy (DRS) data, CBO exhibits a lower optical band gap of 2.52 eV compared to CBOC (3.95 eV), which CBO is synthesized from. BCO shows the lowest optical band gap of 2.16 eV. CBO exhibits the highest photocurrent generation and the lowest value in work function measurements, following the trend as CBO > CBOC > BCO. The efficiency of the Bi-based materials in photocatalytic decomposition of N2O also follows a similar trend as observed in the photocurrent measurements, wherein the CBO sample exhibits a maximum of 10.4% decomposition of N2O under UV-A in 24 h. Oxygen vacancies in CBO and BCO have been reasoned to play a crucial role in the photocatalytic decomposition of N2O.

In this study, a composite material consisting of MXenes (Ti3C2Tx) and Fe3O4 in the ratio of 70 : 30 w/w% (MXF-30) was synthesized via solvothermal method. The material was characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller measurements (BET) to understand the relationship between the structure and properties for radionuclide removal (Ba-133 and Cs-137). Batch experiments employing Box-Behnken design (BBD) were conducted to investigate the impacts of operating parameters such as initial pH, contact time, and initial concentration of Ba2+ and Cs+ ions (containing radiotracers Ba-133 and Cs-137). The optimized conditions suggested by BBD were found to be pH 5.5, 240 min contact time, and 0.1 mol L-1 radionuclides. Under these conditions, the experimental values and values predicted from the models for maximum adsorption capacity were in agreement, i.e., 4.18 and 4.07 mmol g(-1) for Ba2+ and 6.34 and 6.12 mmol g(-1) for Cs+ ions, respectively. The results of studies in a solution containing a mixture of ions (Na+, K+, Ca2+, Co2+, and Mg2+) confirmed that pH 5.5 and 8.0 are suitable for Cs+ and Ba2+ adsorption, respectively. In addition, MXF-30 showed higher affinity for Cs+ due to increased interlayer spacings via the encapsulation mechanism. The typical mechanism of the adsorption of Ba2+ and Cs+ ions was proposed to be a combination of encapsulation (physisorption) and surface complexation (chemisorption).

The magnetic biochar was prepared using Ulva fasciata marine algae and used to remove Methylene blue (MB) as model organic molecule. A comprehensive characterization was conducted on pristine Ulva fasciata biochar (UFBC) and UFBC modified by Fe3O4 (UFBC-MIO) by using SEM, EDX, FTIR, TEM, BET, and XRD along with the PZC. The adsorption of MB was noted as 20.83 mg g-1 for UFBC and 50.12 mg g-1 for UFBC-MIO, at pH = 9, 2 g L-1 dosage and T = 298 K with approx. 85 mg L-1 MB concentration. The higher performance of UFBC-MIO was explained by formation of higher surface area and pore volume. The mechanism of adsorption depicted as pore-filling and electrostatic interaction was identified as physisorption. The adsorption model followed the Langmuir isotherm and the kinetic studies disclosed pseudo-second-order for both adsorbents. The thermodynamic study revealed that the process is non-spontaneous, decreased in randomness and was exothermic. The UFBC-MIO was easily recovered and regenerated through its magnetic property and exhibited 89% MB removal after 5 cycles at pH = 9, 2 g L-1 dosage and T = 298 K with 86.37 mg L-1 of MB. The magnetic biochar of algae Ulva fasciata is an excellent adsorbent recommended for the removal of cationic dyes from wastewaters.

Even though high-temperature superconductivity in cuprates has been studied for almost 40 years, it remains one of the most puzzling topics in modern physics. It is well known that most of its electrical properties strongly depend on doping and superconducting current is conducted through the CuO2 layers. From a scientific and technological perspective, YBa2Cu3O7−x (YBCO) poses significant challenges due to its low chemical stability, leading to potential alterations in its properties when exposed to various gasses, solvents, and solutions. In our study, we investigated the effects of various solvents on the metal-to-superconductor transition (MST) of YBCO. Additionally, we explored the potential to enhance the MST through exposure to solvents, along with proposing mechanisms to explain this enhancement.

Copper ferrites (CuFe2O4) nanopowder was prepared via hydrothermal method followed by annealing at 500 degrees C, and XRD, SEM, XPS and UPS were employed for its characterization. CuFe2O4 was tested for the catalytic degradation of bisphenol A (BPA) in the dark and under UVA light, both in the presence of peroxymonosulfate (PMS) or peroxydisulfate (PDS) as radical precursor under natural pH of 6.2. While the individual photo-induced processes i.e., photocatalysis (using CuFe2O4 alone) and photolysis of either PMS or PDS, exhibited limited efficiencies in BPA degradation, a significant increase of performance was observed by combining CuFe2O4 and UVA light with either PMS or PDS with a synergy effect of 3.8 and 34.1, respectively. Under the optimal conditions, employing 0.5 g/L of nanopowder, the degradation constant of 25 mu M BPA was 0.211 min(-1) with 2 mM of PMS and 0.018 min(-1) with 2 mM of PDS, and resulted in the complete degradation of BPA within less than 20 min. The activation mechanism of PMS and PDS using CuFe2O4 was elucidated, revealing sulfate radicals as the primary reactive species in PMS-containing systems, whereas a predominantly non-radical pathway was observed in the presence of PDS. Indeed, advanced spectroscopic techniques indicated that surface copper played an important role in the non-radical pathway. Furthermore, the CuFe2O4/PMS/UVA system exhibited high performance in the degradation of different phenolic compounds including BPA, phenol and p-nitrophenol in real water matrices. These achievements were observed across different real water matrices with a particular emphasis on sewage treatment plant water.

The synthesis of high-efficiency TiO2 nanotube (TNT) layers is crucial for achieving photocatalytic caffeine degradation and H2 production. Herein, we successfully used next-generation fluoride-free nitrate-based X(NO3)Y, where X = Na+, K+, Sr2+, Ag+; Y = 1,2) electrolytes to prepare TNT layers via electrochemical anodisation. The prepared TNT layers (approximately 1 μm thick; 20–30 nm in diameter) underwent comprehensive characterisation, encompassing aspects of their morphology, structure, composition, as well as their photoelectrochemical and photocatalytic properties. The results demonstrated that the highest caffeine degradation efficiencies (k = 0.0354 min−1 and k = 0.0346 min−1) were achieved in K− and Ag-based electrolytes, respectively. Additionally, the H2 yields for the photocatalysts obtained after 4 h of irradiation ranged from 1791 to 1507 μmol/gcat. The use of a large surface area of the nanotubes (∼20 cm2), along with the absence of fluoride ions during anodisation, paves the way for potential industrial applications and provides a promising approach for the green synthesis of high-performance and environmentally friendly photocatalysts.

A thin TiO2 semiconductor film embedded between two metal electrodes works as a memristor after being formed by soft breakdown. The forming creates a nano-filament that penetrates through the poorly conducting TiO2 film and connects the electrodes conductively. While previous works characterized the nano-filament properties (shape, composition, and resistivity) by electron microscopy techniques, we present a characterization by electrical measurements. In a typical memristor, both electrodes are made of normal metals. We study the metal/TiO2/metal memristors with a bottom electrode made of a superconducting NbN layer and a top electrode made of a normal (Pt) or superconducting (Nb) metal. The nano-filament connecting the electrodes touches the bottom electrode as a point contact, thus allowing us to perform point-contact Andreev reflection spectroscopy of the NbN superconductor. The spectra, measured below the critical temperature (15 K) of NbN, are analyzed theoretically. The analysis reveals the presence of one nano-filament and determines the nano-filament resistance, Sharvin resistance of the point contact, and Maxwell resistance of the electrodes. Moreover, it shows that the nano-filament is a conical-shaped Ti-like metal point contact with a tip diameter of ∼3–5 nm, Fermi velocity of 2×106m/s, and low-temperature resistivity of ∼10−8–10−7Ωm. Thus, the nano-filament in our device is not the Ti4O7 phase observed in previous works. Remarkably, the point contact spectrum of the superconducting NbN layer shows the Andreev peak typical for ballistic transport. This is because the point contact probes the NbN layer through a thin Al layer that mimics superconductivity of NbN via the proximity effect and eliminates the effects of tunneling and disorder.

TiO2 microflowers, consisting of nanotubes, were generated via potentiostatic anodization in fluoride-free electrolytes infused with metal chlorides. Anodizing titanium foil at 15 V for 10 min in electrolytes containing 0.1 M of FeCl3 center dot 6H2O, CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O yielded nanotubes with outer diameters of approximately 30 nm, 45 nm, 50 nm, and 60 nm, respectively. The introduction of metal chloride to the electrolyte significantly altered the anodization kinetics, facilitating the growth of TiO2 microflowers. These structures consist of nanotube bundles that are of few microns in length with tunable diameters, achieved rapidly within the anodization timeframe. Microflowers formed in FeCl3 center dot 6H2O electrolyte feature high aspect ratio TiO2 nanotube bundles with smaller diameters and higher nucleation density, whereas those developed in CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O electrolytes exhibit less preferable morphology.

Biodielectrics is a subset of biological and/or bioinspired materials that has brought a huge transformation in the advancement of medical science, such as localized drug delivery in cancer therapeutics, health monitoring, bone and nerve repair, tissue engineering and use in other nanoelectromechanical systems (NEMS). While biodielectrics has long been used in the field of electrical insulation for over a century, polar dielectric properties of biological building blocks have not been well understood at the fundamental building block level. In this review article, we provide a brief overview of dielectric properties of biological building blocks and its hierarchical organisations to include polar dielectric properties such as piezo, pyro, and ferroelectricity. This review article also discusses recent trends, scope, and potential applications of these dielectrics in science and technology. We highlight electromechanical properties embedded in rationally designed organic assemblies, and the challenges and opportunities inherent in mapping from molecular amino acid building blocks to macroscopic analogs of biological fibers and tissues, in pursuit of sustainable materials for next-generation technologies.

Ceramic electrolytes based on Yb and Sc stabilized zirconia enable efficient heat transfer and effective ionic conductivity. Here, the design and synthesis of Yb and Sc stabilized zirconia electrolyte is presented for inter-mediate temperature solid oxide fuel cells (SOFCs). Yb0.12Sc0.08Zr0.8O2-8 was synthesized using the sol-gel method, and a thorough characterization of the electrolyte properties was conducted including structural and electrical properties. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) confirmed the composition of the electrolyte. A single-phase cubic structure with a density of 6.7041 +/- 0.0008 g cm-3 was obtained. The thermal expansion coefficient in the temperature range from 25 degrees C to 800 degrees C is equal to 1.17 x 10-6 K-1. The activation energy of 1.06 eV and 1.15 eV was obtained for the bulk and grain boundary conductivity, respectively. The ionic conductivity of approx. 2.10 S m- 1 was achieved at 667 degrees C, thus it is suitable for efficient ionic conduction at intermediate temperatures.

Magneto-transport characteristics of 2D and 3D superconducting layers, in particular, temperature and angular dependences of the upper critical field H c2 , are usually considered to be fundamentally different. In the work, using non-local resistance measurements at temperatures near the normal-to-superconducting transition, we probed an effective dimensionality of nm-thick NbN films. It was found that in relatively thick NbN layers, the thicknesses of which varied from 50 to 100 nm, the temperature effect on H c2 certainly pointed to the three-dimensionality of the samples, while the angular dependence of H c2 revealed behavior typical for 2D samples. The seeming contradiction is explained by an intriguing interplay of three length scales in the dimensionally confined superconducting films: the thickness, the Ginzburg–Landau coherence length, and the magnetic-field penetration depth. Our results provide new insights into the physics of superconducting films with an extremely large ratio of the London penetration depth to the Ginzburg–Landau coherence length exhibiting simultaneously 3D isotropic superconducting properties and the 2D transport regime.

A simple noninvasive measurement method which allows one to determine the trapped charge in a biocompatible hydroxyapatite dielectric is developed. The hydroxyapatite samples are charged by electron beam with energy 30 keV and total irradiated charge ranging from 2 × 10-9 C to 2 × 10-7 C. The value of the trapped charge is determined by analyzing the shape change of a liquid droplet hanging from a needle in proximity of the charged sample surface. The shape change of the pendant drop in the field of gravity is commonly utilized in the measurements of the surface free tension (SFT) of liquids. The external electric field leads to a further modification of the droplet shape and to an effective change of the SFT. The change of the SFT as a function of distance between the droplet and sample and the critical distance at which the droplet detaches from the needle are measured for various values of the irradiated charge. These two quantities are also derived theoretically by considering the trapped charge as a single fitting parameter. We can thus determine the trapped charge in two independent noninvasive ways. It is noteworthy that our method is easily implementable into the standard pendant drop setups. As a practical application of the method, a long-term charge stability of the charged hydroxyapatite is demonstrated, thus paving the way toward quantitative studies of its bioactivity in dependence on the value of the trapped charge.

The effect of the Ti3C2Tx MXene modification of the SnO2 electron transport layer (ETL) was studied for the concentration range 0-7.4 wt% MXene. The electronic properties of the MXene-modified ETL were studied by the electrical conductivity measurements, density of states mapping by the energy-resolved electrochemical impedance spectroscopy, ultraviolet photoelectron spectroscopy, and photoluminescence. The structure and morphology of the MXene-modified ETL and the top perovskite layer were analyzed by the scanning electron microscopy (SEM), scanning transmission electron microscopy, grazing-incidence X-ray diffraction and in situ grazing-incidence wide-angle X-ray scattering (GIWAXS). The increased electrical conductivity and electron selectivity for the MXene-modified SnO2 ETL was confirmed up to 1 wt% MXene. For 7.4 wt% MXene, significant suppression of the hole blocking property of the ETL was found. The in situ GIWAXS was performed during the post-deposition annealing of the perovskite layer. The increased perovskite grain size on the SnO2 ETL modified by MXene compared to the pure SnO2 ETL visible by SEM was confirmed. The uniaxial texture of the perovskite crystals was revealed in both cases with an increased misorientation angle for the MXene-modified ETL. The grain size and misorientation angle do not exhibit any systematic temporal changes during the post-deposition annealing. The increasing number of the grains during the annealing was observed. These results are explained using the nucleation and growth model. The increased power conversion efficiency from 17.4% to 18.3% of the archetypal methylammonium-lead-iodide perovskite solar cell after the modification of the SnO2 ETL with 0.1 wt% MXene is the effect of two contributions -increased electrical conductivity of the ETL and improved crystallinity and larger grain size compared to the pure SnO2 ETL, which lowers the total boundary area and charge recombination at trap states typically formed at grain boundaries.

The four-point probe is a relatively simple method of measuring thin-layer surface resistance using separate pairs of current-carrying and voltage-sensing contacts. This approach makes it possible to measure resistivity regardless of the resistance of the contacts that is especially important when the latter are large and non-ohmic, which makes simpler two contact measurements inapplicable. Nevertheless, its results turn out to be significantly dependent on the sample geometry as well as the position of the probes, leading in some cases, as shown below, to qualitatively incorrect conclusions. We demonstrate this with the example of an anomalous resistance peak at temperatures near the critical one T c , which is often observed in experiments on mesoscopic superconducting samples. Below, with an oversimplified model for nonlocal four-probe measurements, we argue that the anomalous resistance behavior near T c observed in traditional four-probe measurements can arise due to noticeable variations in local T c values (superconducting granularity) and attributed the near- T c anomaly to the current redistribution effect. The model results well explain temperature-dependent resistance data for 50 nm thick NbN films, which exhibited not only the resistance peak but also fundamentally different resistance-vs-temperature behavior depending on the arrangement of the contacts. Nonlocal probing performed for in-plane and out-of-plane magnetic fields clearly demonstrates the interplay of orbital and Zeeman couplings different for the two field orientations. We believe that the anomalous temperature behavior of the four-point resistance near the transition from the normal to superconducting state is sometimes an artifact that, if misinterpreted, can lead to incorrect conclusions. On the other hand, we show that such a nonlocal contact arrangement strongly enhances sensitivity to inhomogeneity factors. This gives grounds for using the corresponding experiments as a method of choice for revealing the spatial distribution of the order parameter in superconducting films.

In this paper, we present the preparation of few-layer MoS2 films on single-crystal sapphire, as well as on heteroepitaxial GaN templates on sapphire substrates, using the pulsed laser deposition (PLD) technique. Detailed structural and chemical characterization of the films were performed using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction measurements, and high-resolution transmission electron microscopy. According to X-ray diffraction studies, the films exhibit epitaxial growth, indicating a good in-plane alignment. Furthermore, the films demonstrate uniform thickness on large areas, as confirmed by Raman spectroscopy. The lateral electrical current transport of the MoS2 grown on sapphire was investigated by temperature (T)-dependent sheet resistance and Hall effect measurements, showing a high n-type doping of the semiconducting films (ns from ~1 × 1013 to ~3.4 × 1013 cm−2 from T = 300 K to 500 K), with a donor ionization energy of Ei = 93 ± 8 meV and a mobility decreasing with T. Finally, the vertical current injection across the MoS2/GaN heterojunction was investigated by means of conductive atomic force microscopy, showing the rectifying behavior of the I-V characteristics with a Schottky barrier height of ϕB ≈ 0.36 eV. The obtained results pave the way for the scalable application of PLD-grown MoS2 on GaN in electronics/optoelectronics.