Search Results (228)

Chromium–aluminum nitride (CrAlN) coatings were deposited on polished H13 tool steel substrates using direct current (DC) magnetron sputtering. The Cr/Al composition in the target was varied by inserting either four or eight chromium (Cr) plugs into cavities machined into an aluminum (Al) plate target. Nitrogen was introduced as a reactive gas to facilitate the formation of the nitride phase. Coatings were deposited at substrate bias voltages of −30 V, −50 V, and −60 V to study the combined effects of composition and ion energy on coating properties. Compositional analysis of coatings deposited at a −50 V bias revealed Cr/Al ratios of approximately 0.8 and 1.7 for the 4- and 8-plug configurations, respectively. This increase in the Cr/Al ratio led to a 2.6-fold improvement in coating hardness. Coatings produced using the eight-Cr-plug target exhibited a nearly linear increase in hardness with increasing substrate bias voltage. Cross-sectional scanning electron microscopy revealed a uniform bilayer structure consisting of an approximately 0.5 µm metal interlayer beneath a 2–3 µm CrAlN coating. Surface morphology analysis indicated the presence of coarse microdroplets in coatings with the lower Cr/Al ratio. These microdroplets were significantly suppressed in coatings with higher Cr/Al content, especially at increased bias voltages. This suppression is likely due to enhanced ion bombardment associated with the increased Cr content, attributed to Cr’s relatively higher atomic mass compared to Al. Coatings with lower hardness exhibited greater scratch resistance, likely due to the influence of residual compressive stresses. The findings highlight the critical role of both Cr/Al content and substrate bias in tailoring the tribo-mechanical performance of PVD CrAlN coatings for wear-resistant applications. Full article

Cell-free biosensors harness the selectivity of cellular machinery without living cells’ constraints, offering advantages in environmental monitoring, medical diagnostics, and biotechnological applications. This review examines recent advances in cell-free biosensor development, highlighting their ability to detect diverse analytes including heavy metals, organic pollutants, pathogens, and clinical biomarkers with high sensitivity and specificity. We analyze technological innovations in cell-free protein synthesis optimization, preservation strategies, and field deployment methods that have enhanced sensitivity, and practical applicability. The integration of synthetic biology approaches has enabled complex signal processing, multiplexed detection, and novel sensor designs including riboswitches, split reporter systems, and metabolic sensing modules. Emerging materials such as supported lipid bilayers, hydrogels, and artificial cells are expanding biosensor capabilities through microcompartmentalization and electronic integration. Despite significant progress, challenges remain in standardization, sample interference mitigation, and cost reduction. Future opportunities include smartphone integration, enhanced preservation methods, and hybrid sensing platforms. Cell-free biosensors hold particular promise for point-of-care diagnostics in resource-limited settings, environmental monitoring applications, and food safety testing, representing essential tools for addressing global challenges in healthcare, environmental protection, and biosecurity. Full article

Spin transport behaviors in heavy metal/ferromagnetic insulator (HM/FI) bilayers have attracted considerable attention due to various novel phenomena and applications in spintronic devices. Herein, we investigate the planar Hall effect (PHE) in Pt/Tm₃Fe₅O₁₂ (Pt/TmIG) heterostructures at low temperatures; moment switching in the ferrimagnetic insulator TmIG is detected by using electrical measurements. Double switching hysteresis PHE curves are found in Pt/TmIG bilayers, closely related to the magnetic moment of Tm³⁺ ions, which makes a key contribution to the total magnetic moment of TmIG film at low temperature. More importantly, a magnetoresistance (MR) curve with double switching is found, which has not been reported in this simple HM/FI bilayer, and the sign of this MR effect is sensitive to the angle between the magnetic field and current directions. Our findings of these effects in this HM/rare earth iron garnet (HM/REIG) bilayer provide insights into tuning the spin transport properties of HM/REIG by changing the rare earth. Full article

The separation of particles smaller than 1 µm either by composition or by size is still a challenge. For the separation of SiO₂ and SnO₂, the creation of a selective separation feature and the specific adsorption of salts and surfactants were investigated. The adsorption of various salts, e.g., AlCl₃, ZnCl₂, MnCl₂ and MgCl₂ were therefore analyzed, and the necessary concentration for the charge reversal of the material was determined. It was noticed that the investigated materials differ in their isoelectric point (IEP) and therefore in their adsorption behavior because only ZnCl₂ and MgCl₂ are suitable for a charge reversal of both metal oxides. The phase transfer of the pure material at different pH values with ZnCl₂ or MgCl₂ and sodium dodecyl sulfate (SDS) revealed that the adsorption behavior of the particle has an influence on the phase transfer. As a result, the phase transfer of SiO₂ is pH dependent, whereas the phase transfer of SnO₂ operates over a wider pH range. This allowed the separation of SiO₂ and SnO₂ to be controlled by the salt and surfactant concentration as well as pH. The separation of SiO₂ and SnO₂ was investigated for various parameters such as salt and surfactant concentration, particle concentration and composition of the mixture. Also, pH 8, where a selective phase transfer for SiO₂ occurs, and pH 6, where the greatest difference between the materials exists, were also investigated. By comparing the parameters, it was found that the combination of ZnCl₂/SDS and MgCl₂/SDS enables a selective separation of the materials. Furthermore, it was also found that the concentration of SDS has a significant effect on the separation, as the formation of a bilayer structure is important for the separation, and therefore, higher SDS concentrations are required at higher particle concentrations to increase the separation efficiency. Full article

To enhance interaction with the host tissue and protect the metal surface, various surface treatments can be applied to dental implants. This study aimed to produce layer-by-layer (LbL) films by alternated immersion of the titanium sample into polyacrylic acid (PAA) and chitosan solutions, obtaining a PAA/chitosan bilayer architecture, seeking to improve the corrosion resistance. For this purpose, 03 experimental groups (n = 05) were performed: Ti-Cp (as control), Ti-Cp+8 bilayers PAA/chitosan, and Ti-Cp+12 bilayers PAA/chitosan. The corrosion behavior was assessed by using open-circuit potential (OCP), potentiodynamic polarization curves (PPcs) and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9 wt% NaCl solution at a controlled temperature of 25 ± 1 °C. The samples were characterized morphologically and structurally by atomic force microscope (AFM), scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) techniques before and after the corrosion tests. The electrochemical results significantly highlight the beneficial influence of coatings based on PAA/chitosan in enhancing the corrosion resistance of titanium. These findings not only corroborate the feasibility of using alternative materials for the protection of titanium but also open new possibilities for the development of innovative coatings that can be applied within the biomedical sector, serving as mediators for medicinal purposes, particularly in osteoconductive interventions. Full article

The N₂ reduction reaction (NRR) under ambient conditions is highly desirable because of its potential to replace the energy-consuming Haber-Bosch process for ammonia production. In recent years, much attention has been devoted to transition metal-based catalysts. However, the development of metal-free electrocatalysts remains a great challenge. Here, the electrocatalytic performance of bilayer borophene is systematically studied based on first-principles calculations. It was found that bilayer borophene has high activity with an overpotential of 0.21 V via the enzymatic mechanism. Bond elongations of nitrogen bond are observed in end-on and side-on patterns, where the bond lengths are stretched to 1.13 and 1.21 Å, respectively. Around 0.36 e⁻ is transferred to the adsorbed N₂ with the contribution of bottom boron atoms. Our results propose bilayer borophene as a novel metal-free catalyst for nitrogen reduction, thus providing an avenue to explore highly efficient electrocatalysts for ammonia production under ambient conditions. Full article

A polymer optical fiber SPR sensor for detecting Cu²⁺ ion concentration in water is proposed. The sensor employs a simple side-polish structure and realizes the detection of Cu²⁺ ion concentration by employing the chitosan (CS)/polyacrylic acid (PAA) bilayer film on the gold film of the optical fiber surface. The structure of the fiber probe is optimized, and the sensing performances for the Cu²⁺ ion detection are analyzed experimentally. The experimental results demonstrate that the sensor exhibits a high sensitivity of 465.539 nm/ppm for the Cu²⁺ ion detection in the concentration range of 0–0.04 ppm. And it has a fast response speed and good selectivity for Cu²⁺ ions. The sensor has the advantages of simple structure and low cost, and has potential applications in the field of heavy metal detection. Full article

This work systematically analyses the electrical and structural properties of a bilayer gate dielectric composed of Sm₂O₃ and ZrO₂ on a 4H-SiC substrate. The bilayer thin film was fabricated using a sputtering process, followed by a dry oxidation step with an adjusted oxygen-to-nitrogen (O₂:N₂) gas concentration ratio. XRD analysis validated formation of an amorphous structure with a monoclinic phase for both Sm₂O₃ and ZrO₂ dielectric thin films. High-resolution transmission emission (HRTEM) analysis verified the cross-section of fabricated stacking layers, confirmed physical oxide thickness around 12.08–13.35 nm, and validated the amorphous structure. Meanwhile, XPS confirmed the presence of more stoichiometric dielectric oxide formation for oxidized/nitrided O₂:N₂-incorporated samples, and more sub-stochiometric thin films for samples only oxidized in ambient O₂. The oxidation/nitridation processes with N₂ incorporation influenced the band offsets and revealed conduction band offsets (CBOs) ranging from 2.24 to 2.79 eV. The affected charge movement and influenced electrical performance where optimized samples with gas concentration ratio of 90% O₂:10% N₂ achieved the highest electrical breakdown field of 10.1 MV cm⁻¹ at a leakage current density of 10⁻⁶ A cm⁻². This gate stack also improved key parameters such as the effective dielectric constant ($k_{eff}$) up to 29.75, effective oxide charge ($Q_{eff}$), average interface trap density ($D_{it}$), and slow trap density (STD). The bilayer gate stack of Sm₂O₃ and ZrO₂ revealed potential attractive characteristics as a candidate for high-k gate dielectric applications in metal-oxide-semiconductor (MOS)-based devices. Full article

The integration of various transition metal oxides into tungsten oxide (WO₃) has been widely investigated to enhance its electrochromic (EC) performance. This approach aims to address the inherent limitations of individual metal oxides, such as poor durability, inadequate color neutrality, and restricted coloring efficiency and optical properties. The use of mixed metal oxides has emerged as a promising strategy, enabling a synergistic effect that optimizes EC performance and expands the material’s functional capabilities. In this study, we compare single-layer WO₃ films with bilayer WO₃/cobalt oxide (CoO) (denoted as W@C) composite films, focusing on their structural, morphological, and electrochromic properties. Both films were fabricated using the electrodeposition technique, with a consistent number of deposition cycles. Field emission scanning electron microscopy (FESEM) analysis revealed that the WO₃ film presented a tightly packed arrangement of nanogranules. In contrast, the bilayer W@C composite thin film exhibited a highly interconnected and porous granular structure, with morphology evolving into larger spherical aggregates. The optimized bilayer W@C composite demonstrated exceptional electrochromic performance, achieving an optical modulation of 85.0% at 600 nm and a significantly improved coloration efficiency of 96.07 cm²/C. Stability tests confirmed its remarkable durability, showing only a 1.05% decrease in optical contrast after 5000 s of operation. Additionally, a prototype electrochromic device based on the W@C film demonstrated an optical modulation of 52.13% and outstanding long-term stability, with minimal degradation in performance. Full article

An electric field applied to the Bernal-stacked bilayer graphene opens an energy gap; its reversal in some regions creates domain walls and leads to the appearance of one-dimensional chiral gapless states localized at the walls. Here, we investigate the energy structure of bilayer graphene with superlattice potential defined by an external electric field. The calculations are performed within an atomistic π-electron tight-binding approximation. We study one-dimensional and two-dimensional superlattices formed by arrays of electric-field walls in the zigzag and armchair directions and investigate different field polarizations. Chiral gapless states discretize due to the superlattice potential and transform into minibands in the energy gap. As the main result, we show that the minibands can cross at the Fermi level for some field polarizations. This leads to a new kind of two-dimensional gapless states of topological character that form Dirac-like cones at the crossing points. This also has application potential: changing the field polarization can close the energy gap and change the character of the superlattice from semiconducting to metallic. Full article

The fast development of portable electronics demands electrodes for supercapacitors that are compatible with miniaturized device applications. In this study, an orderly aligned coaxial bilayer nanotube array made of transition metal/transition metal oxides was adopted as a nanostructure-integrated electrode for applications as miniaturized micro-supercapacitors. Using Ni and NiO as our model materials, the corresponding Ni/NiO-CBNTA electrodes were fabricated using templated growth and post-thermal oxidation. The Ni shells served as parts of the 3D nano-architectured collector, providing a large specific surface area, and the pseudocapacitive NiO layers were directly attached and electrically connected to the collector without any additives. The vertical growth of orderly aligned Ni/NiO-CBNTAs successfully avoided the underutilization of capacitive nanomaterials and allowed the electrolyte to be fully accessed, which manifested full charge storage capabilities under the miniaturizing. It was demonstrated that Ni/NiO-CBNTAs can serve as miniaturized electrodes with an improved specific capacitance of 1125 F/g ≅ 3 A/g, which is comparable to that obtained in a massive load electrode prepared by the conventional slurry-coating technique. Full article

Metallosurfactants combine the unique soft-matter properties of surfactants with magnetic functionalities of metal ions. The inclusion of iron-based species, in particular, can further boost the functionality of the material, owing to iron’s ability to adopt multiple oxidation states and form both high-spin and low-spin complexes. Motivated by this, a series of hybrid inorganic-organic dodecylpyridinium metallosurfactants with iron-containing counterions was developed. It was established that using either divalent or trivalent iron halides in a straightforward synthetic procedure yields C₁₂Py-metallosurfactants with distinct complex counterions: (C₁₂Py)₂[Fe₂X₆O] and (C₁₂Py)[FeX₄] (X = Cl or Br), respectively. A combination of techniques—including conductometry, dynamic and electrophoretic light scattering, single-crystal and thermogravimetric analysis, and magnetic measurements—provided in-depth insights into their solution and solid-state properties. The presence of different iron-based counterions significantly influences the crystal structure (interdigitated vs. non-interdigitated bilayers), magnetic properties (paramagnetic vs. nonmagnetic singlet ground state), and self-assembly (vesicles vs. micelles) of the dodecylpyridinium series. To our knowledge, this is the first report on the synthesis and characterization of hybrid organic-inorganic metallosurfactants containing the μ-oxo-hexahalo-diferrate anion. Full article

Hexagonal BCN (h-BCN), an isoelectronic counterpart to graphene, exhibits chirality and offers the distinct advantage of optical activity in the vacuum ultraviolet (VUV) region, characterized by significantly higher wavelengths compared to graphene nanoflakes. h-BCN possesses a wide bandgap and demonstrates desirable semiconducting properties. In this study, we employ Density Functional Theory (DFT) calculations to investigate the proximity effects of adsorbed h-BCN flakes on two-dimensional (2D) substrates. The chosen substrates encompass monolayers of 3D transition metals and WSe₂, as well as a bilayer consisting of WSe₂/Ni. Notably, the hydrogen-terminated h-BCN nanoflakes retain their planar configuration following adsorption. We observe a strong interaction between h-BCN and fcc-based monolayers such as Ni(111), resulting in the closure of the optical bandgap, while the adsorption energy on WSe₂ is significantly weaker, preserving an approximate 1.1 eV bandgap. Furthermore, we demonstrate the magnetism induced by the proximity of adsorbed chiral h-BCN molecules, and the chiral-induced spin selectivity within the proposed systems. Full article

As a typical heavy metal pollutant discharged from industrial activities, nickel ions are highly bioaccumulative and carcinogenic, and low concentrations (>0.5 mg/L) can disrupt the balance of aquatic ecosystems and pose a threat to human health. In this study, a bifunctional adsorbent based on a carboxymethyl cellulose/boron nitride hydrogel was prepared for the treatment of nickel-containing wastewater with a high adsorption capacity of Ni²⁺ (800 mg/L, 344 mg/g), and after adsorption, the waste gel was converted into nickel-doped porous carbon material through carbonization and used as a bilayer capacitor electrode to achieve a specific capacitance of 40.6 F/g at a current density of 1 A/g. The capacity retention rate was >98% after 150 cycles. This strategy simultaneously solves the problems of nickel-containing wastewater purification (the adsorption method is applicable to medium- and high-concentration heavy-metal wastewater) and environmental pollution caused by waste adsorbents, and provides a new paradigm of the “adsorption-resourcing” closed-loop treatment of heavy-metal pollutants. Full article

The development of functional materials and the use of nanotechnology are ongoing projects. These fields are closely linked, but there is a need to combine them more actively. Nanoarchitectonics, a concept that comes after nanotechnology, is ready to do this. Among the related research efforts, research into creating functional materials through the formation of thin layers on surfaces, molecular membranes, and multilayer structures of these materials have a lot of implications. Layered structures are especially important as a key part of nanoarchitectonics. The diversity of the components and materials used in layer-by-layer (LbL) assemblies is a notable feature. Examples of LbL assemblies introduced in this review article include quantum dots, nanoparticles, nanocrystals, nanowires, nanotubes, g-C₃N₄, graphene oxide, MXene, nanosheets, zeolites, nanoporous materials, sol–gel materials, layered double hydroxides, metal–organic frameworks, covalent organic frameworks, conducting polymers, dyes, DNAs, polysaccharides, nanocelluloses, peptides, proteins, lipid bilayers, photosystems, viruses, living cells, and tissues. These examples of LbL assembly show how useful and versatile it is. Finally, this review will consider future challenges in layer-by-layer nanoarchitectonics. Full article