Nanomaterials, Volume 13, Issue 14 (July-2 2023) – 123 articles

One of the approaches to manipulate MnBi${}_2$Te${}_4$ properties is the magnetic dilution, which inevitably affects the interplay of magnetism and band topology in the system. In this work, we carried out angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations for analysing changes in the electronic structure of Mn${}_{1-x}$Ge${}_x$Bi${}_2$Te${}_4$ that occur under parameter x variation. We consider two ways of Mn/Ge substitution: (i) bulk doping of the whole system; (ii) surface doping of the first septuple layer. For the case (i), the experimental results reveal a decrease in the value of the bulk band gap, which should be reversed by an increase when the Ge concentration reaches a certain value. Ab-initio calculations show that at Ge concentrations above 50%, there is an absence of the bulk band inversion of the Te $p_z$ and Bi $p_z$ contributions at the $\Gamma$-point with significant spatial redistribution of the states at the band gap edges into the bulk, suggesting topological phase transition in the system. For case (ii) of the vertical heterostructure Mn${}_{1-x}$Ge${}_x$Bi${}_2$Te${}_4$/MnBi${}_2$Te${}_4$, it was shown that an increase of Ge concentration in the first septuple layer leads to effective modulation of the Dirac gap in the absence of significant topological surface states of spatial redistribution. The results obtained indicate that surface doping compares favorably compared to bulk doping as a method for the Dirac gap value modulation. Full article

Due to the unique optical responses induced by vertical atomic asymmetry inside a monolayer, two-dimensional Janus structures have been conceived as promising building blocks for nanoscale optical devices. In this paper, second harmonic generation (SHG) in Janus transition metal chalcogenide oxide monolayers is systematically investigated by the first-principles calculations. Second-order nonlinear susceptibilities are theoretically determined for Janus MXO (M = Mo/W, X = S/Se/Te) monolayers. The calculated values are comparable in magnitude with Janus MoSSe monolayer. X-M-O symmetry breaking leads to non-zero components in vertical direction, compared with the non-Janus structure. Focusing on the SHG induced by incident light at 1064 nm, polarization-dependent responses of six Janus MXO monolayers are demonstrated. The symmetry of p-polarization changes from six-fold to three-fold with acute incidence angle. Moreover, the effects of biaxial strain on band structures and SHG are further investigated, taking MoSO as an exemplary case. We expect these results to bring in recipes for designing nonlinear optical devices based on Janus transition metal chalcogenide oxide monolayers. Full article

Lithium-sulfur technology is a strong candidate for the future generation of batteries due to its high specific capacity (1675 mAh g${}^{-1}$), low cost, and environmental impact. In this work, we propose a facile and solvent-free microwave synthesis for a composite material based on doped (sulfur and nitrogen) reduced graphene oxide embedded with zinc sulfide nanoparticles (SN-rGO/ZnS) to improve the battery performance. The chemical-physical characterization (XRD, XPS, FESEM, TGA) confirmed the effectiveness of the microwave approach in synthesizing the composite materials and their ability to be loaded with sulfur. The materials were then thoroughly characterized from an electrochemical point of view (cyclic voltammetry, galvanostatic cycling, Tafel plot, electrochemical impedance spectroscopy, and Li${}_2$S deposition test); the SN-rGO/ZnS/S${}_8$ cathode showed a strong affinity towards polysulfides, thus reducing their loss by diffusion and improving redox kinetics, allowing for faster LiPSs conversion. In terms of performance, the composite-based cathode increased the specific capacity at high rate (1 C) from 517 to 648 mAh g${}^{-1}$. At the same time, more stable behavior was observed at 0.5 C with capacity retention at the 750th cycle, where it was raised from 32.5% to 48.2%, thus confirming the beneficial effect of the heteroatomic doping process and the presence of zinc sulfide nanoparticles. Full article

Friction stir processing (FSP) is an effective method for incorporating ceramic nanoparticles into metal matrix composites. This study investigated the effects of single and multiple additions of BN, VC, and SiC nanoparticles on the microstructure refinement and tribological behavior of an AA2024 alloy-based nanocomposite matrix fabricated by FSP. The results showed that adding ceramic nanoparticles, either singly or in combination, led to significant refinement of grain structure and improved wear resistance of the AA2024 alloy-based nanocomposite matrix. Additionally, the study found that combining BN, SiC, and VC nanoparticles produced the most effective effects on refining and reducing grain size. The microhardness behavior of the composite surface resulting from the hybrid particles showed a significant improvement, reaching 94% more than the base alloy. Overall, these results indicate that the multiple additions of ceramic nanoparticles by FSP are a promising approach to improve aluminum alloys’ tribological behavior and mechanical properties. Full article

This paper presents results of the magnetic dynamics study (the microwave power absorptions at the fixed frequencies during magnetic field sweeping) in samples of Y₃Fe₅O₁₂ single crystals in the form of plates and spheres of various sizes, at frequencies exceeding 30 GHz, in magnetic fields up to 18 kOe, at room temperature, and T = 77 K. It was found that in this case, the inhomogeneity’s of the magnetic state manifested itself in the Y₃Fe₅O₁₂ samples as 2D local phase separation regions. Such 2D phase separation regions formed inside layered domain walls representing superlattices with sizes of 700–900 Å. Depending on the shape and size of the studied plates and spheres, Landau diamagnetism or de Haas–van Alphen oscillations were observed in the 2D phase separation regions at room temperature and T = 77 K. Full article

Dielectric layers are widely used in ferroelectric applications such as memory and negative capacitance devices. The wake-up and the split-up phenomena in the ferroelectric hafnia are well-known challenges in early-stage device reliability. We found that the phenomena even occur in the bilayer, which is composed of the hafnia and the dielectrics. The phenomena are known to be affected mainly by oxygen vacancies of hafnia. Dielectric layers, which are often metal oxides, are also prone to be affected by oxygen vacancies. To study the effect of the dielectric layer on the wake-up and the split-up phenomena, we fabricated ferroelectric thin-film capacitors with dielectric layers of various thicknesses and measured their field-cycling behaviors. We found that the movement of oxygen vacancies in the dielectric layer was predominantly affected by the polarization state of the ferroelectric layer. In addition, the mechanism of the field-cycling behavior in the bilayer is similar to that in ferroelectric thin films. Our results can be applied in ferroelectric applications that use dielectric layers. Full article

Nanoparticles (NP) with optical properties embedded silica particles have been widely used in various fields because of their unique properties. The surfaces of optical NPs have been modified with various organic ligands to maintain their unique optical properties and colloidal stability. Among the surface modification methods, silica encapsulation of optical NPs is widely used to enhance their biocompatibility and stability. However, in the case of NPs with hydrophobic ligands on the surface, the ligands that determine the optical properties of the NPs may detach from the NPs, thereby changing the optical properties during silica encapsulation. Herein, we report a generally applicable silica encapsulation method using trimethoxy(2-phenylethyl)silane (TMPS) for non-hydrophilic optical NPs, such as quantum dots (QDs) and gold NPs. This silica encapsulation method was applied to fabricate multiple silica-encapsulated QD-embedded silica NPs (SiO₂@QD@SiO₂ NPs; QD²) and multiple silica-encapsulated gold NP-embedded silica NPs labeled with 2-naphthalene thiol (SiO₂@Au_2-NT@SiO₂). The fabricated silica-encapsulated NPs exhibited optical properties without significant changes in the quantum yield or Raman signal intensity. Full article

A switchable and tunable terahertz (THz) metamaterial based on photosensitive silicon and Vanadium dioxide (VO₂) was proposed. By using a finite-difference time-domain (FDTD) method, the transmission and reflective properties of the metamaterial were investigated theoretically. The results imply that the metamaterial can realize a dual electromagnetically induced transparency (EIT) or two narrow-band absorptions depending on the temperature of the VO₂. Additionally, the magnitude of the EIT and two narrow-band absorptions can be tuned by varying the conductivity of photosensitive silicon (PSi) via pumping light. Correspondingly, the slow-light effect accompanying the EIT can also be adjusted. Full article

Over the past three decades, the growth of Bi thin films has been extensively explored due to their potential applications in various fields such as thermoelectrics, ferroelectrics, and recently for topological and neuromorphic applications, too. Despite significant research efforts in these areas, achieving reliable and controllable growth of high-quality Bi thin-film allotropes has remained a challenge. Previous studies have reported the growth of trigonal and orthorhombic phases on various substrates yielding low-quality epilayers characterized by surface morphology. In this study, we present a systematic growth investigation, enabling the high-quality growth of Bi epilayers on Bi-terminated Si (111) 1 × 1 surfaces using molecular beam epitaxy. Our work yields a phase map that demonstrates the realization of trigonal, orthorhombic, and pseudocubic thin-film allotropes of Bi. In-depth characterization through X-ray diffraction (XRD) techniques and scanning transmission electron microscopy (STEM) analysis provides a comprehensive understanding of phase segregation, phase stability, phase transformation, and phase-dependent thickness limitations in various Bi thin-film allotropes. Our study provides recipes for the realization of high-quality Bi thin films with desired phases, offering opportunities for the scalable refinement of Bi into quantum and neuromorphic devices and for revisiting technological proposals for this versatile material platform from the past 30 years. Full article

It is of great significance to recycle the silicon (Si) kerf slurry waste from the photovoltaic (PV) industry. Si holds great promise as the anode material for Li-ion batteries (LIBs) due to its high theoretical capacity. However, the large volume expansion of Si during the electrochemical processes always leads to electrode collapse and a rapid decline in electrochemical performance. Herein, an effective carbon coating strategy is utilized to construct a precise Si@C_PPy composite using cutting-waste silicon and polypyrrole (PPy). By optimizing the mass ratio of Si and carbon, the Si@C_PPy composite can exhibit a high specific capacity and superior rate capability (1436 mAh g⁻¹ at 0.1 A g⁻¹ and 607 mAh g⁻¹ at 1.0 A g⁻¹). Moreover, the Si@C_PPy composite also shows better cycling stability than the pristine prescreen silicon (PS-Si), as the carbon coating can effectively alleviate the volume expansion of Si during the lithiation/delithiation process. This work showcases a high-value utilization of PV silicon scraps, which helps to reduce resource waste and develop green energy storage. Full article

Harmful algal blooms impact human welfare and are a global concern. Sargassum spp., a type of algae or seaweed that can potentially bloom in certain regions of the sea around Thailand, exhibits a noteworthy electron capacity as the sole reducing and stabilizing agent, which suggests its potential for mediating nanoparticle composites. This study proposes an eco-friendly microwave-assisted biosynthesis (MAS) method to fabricate silver nanoparticles coated with Sargassum aqueous extract (Ag/AgCl-NPs-ME). Ag/AgCl-NPs-ME were successfully synthesized in 1 min using a 20 mM AgNO₃ solution without additional hazardous chemicals. UV–visible spectroscopy confirmed their formation through a surface plasmon resonance band at 400–500 nm. XRD and FTIR analyses verified their crystalline nature and involvement of organic molecules. TEM and SEM characterization showed well-dispersed Ag/AgCl-NPs-ME with an average size of 36.43 nm. The EDS results confirmed the presence of metallic Ag⁺ and Cl⁻ ions. Ag/AgCl-NPs-ME exhibited significant antioxidant activity against free radicals (DPPH, ABTS, and FRAP), suggesting their effectiveness. They also inhibited enzymes (tyrosinase and ACE) linked to diseases, indicating therapeutic potential. Importantly, the Ag/AgCl-NPs-ME displayed remarkable cytotoxicity against cancer cells (A375, A549, and Caco-2) while remaining non-toxic to normal cells. DNA ladder and TUNEL assays confirmed the activation of apoptosis mechanisms in cancer cells after a 48 h treatment. These findings highlight the versatile applications of Ag/AgCl-NPs-ME in food, cosmetics, pharmaceuticals, and nutraceuticals. Full article

In this work, copper (II) ions were saturated and copper oxide nanoparticles (CuO NPs) were supported in natural zeolite from Chile; this was achieved by making the adsorbent material come into contact with a copper ion precursor solution and using mechanical agitation, respectively. The kinetic and physicochemical process of the adsorption of copper ions in the zeolite was studied, as well as the effect of the addition of CuO NPs on the antibacterial properties. The results showed that the saturation of copper (II) ions in the zeolite is an efficient process, obtaining a 27 g L⁻¹ concentration of copper ions in a time of 30 min. The TEM images showed that a good dispersion of the CuO NPs was obtained via mechanical stirring. The material effectively inhibited the growth of Gram-negative and Gram-positive bacteria that have shown resistance to methicillin and carbapenem. Furthermore, the zeolite saturated with copper at the same concentration had a better bactericidal effect than the zeolite supported with CuO NPs. The results suggested that the ease of processing and low cost of copper (II) ion-saturated zeolitic material could potentially be used for dental biomedical applications, either directly or as a bactericidal additive for 3D printing filaments. Full article

Developing highly efficient and durable hydrogen evolution reaction (HER) electrocatalysts is crucial for addressing the energy and environmental challenges. Among the 2D-layered chalcogenides, MoSe₂ possesses superior features for HER catalysis. The van der Waals attractions and high surface energy, however, stack the MoSe₂ layers, resulting in a loss of edge active catalytic sites. In addition, MoSe₂ suffers from low intrinsic conductivity and weak electrical contact with active sites. To overcome the issues, this work presents a novel approach, wherein the in situ incorporated diethylene glycol solvent into the interlayers of MoSe₂ during synthesis when treated thermally in an inert atmosphere at 600 °C transformed into graphene (Gr). This widened the interlayer spacing of MoSe₂, thereby exposing more HER active edge sites with high conductivity offered by the incorporated Gr. The resulting MoSe₂-Gr composite exhibited a significantly enhanced HER catalytic activity compared to the pristine MoSe₂ in an acidic medium and demonstrated a superior HER catalytic activity compared to the state-of-the-art Pt/C catalyst, particularly at a high current density beyond ca. 55 mA cm⁻². Additionally, the MoSe₂-Gr catalyst demonstrated long-term electrochemical stability during HER. This work, thus, presents a facile and novel approach for obtaining an efficient MoSe₂ electrocatalyst applicable in green hydrogen production. Full article

Alkaline phosphatase (ALP) is among the most studied enzymes by far, playing an important role in the metabolism of organisms and the regulation of protein activity. Herein, a label-free composite nanoprobe is constructed by combining inorganic nanomaterials and aggregation-induced emission (AIE) molecule to achieve highly sensitive and selective detection of ALP. Negatively charged 9,10-bis [2-(6-sulfonatopropoxyl) naphthylethenyl] anthracene (BSNVA) molecule is synthesized, which has the AIE performance and can be assembled on the surface of amino–SiO₂ nanoparticles through electrostatic interaction for fluorescence enhancement. MnO₂ nanosheets are rich in negative charges, enabling them to be wrapped on the surface of the amino–SiO₂ nanosphere to shield the positive charge on its surface, making it impossible for BSNVA to accumulate on the surface and then weakening the bio-fluorescence of the system. Furthermore, with catalyzed substrates induced by ALP, generating ascorbic acid and the redox reaction between ascorbic acid and MnO₂, the nanoprobe helps in realizing the high-sensitivity detection of ALP with a detection limit of 0.38 mU/mL. The proposed strategy requires no complex cleaning and modification processes and can overcome the quenching effect caused by the aggregation of traditional organic dyes, proving to be a simple, low-cost and “turn-on” fluorescent detection method for ALP. Full article

Neuromorphic computing, reconfigurable optical metamaterials that are operational over a wide spectral range, holographic and nonvolatile displays of extremely high resolution, integrated smart photonics, and many other applications need next-generation phase-change materials (PCMs) with better energy efficiency and wider temperature and spectral ranges to increase reliability compared to current flagship PCMs, such as Ge₂Sb₂Te₅ or doped Sb₂Te. Gallium tellurides are favorable compounds to achieve the necessary requirements because of their higher melting and crystallization temperatures, combined with low switching power and fast switching rate. Ga₂Te₃ and non-stoichiometric alloys appear to be atypical PCMs; they are characterized by regular tetrahedral structures and the absence of metavalent bonding. The sp³ gallium hybridization in cubic and amorphous Ga₂Te₃ is also different from conventional p-bonding in flagship PCMs, raising questions about its phase-change mechanism. Furthermore, gallium tellurides exhibit a number of unexpected and highly unusual phenomena, such as nanotectonic compression and viscosity anomalies just above their melting points. Using high-energy X-ray diffraction, supported by first-principles simulations, we will elucidate the atomic structure of amorphous Ga₂Te₅ PLD films, compare it with the crystal structure of tetragonal gallium pentatelluride, and investigate the electrical, optical, and thermal properties of these two materials to assess their potential for memory applications, among others. Full article

The vacancy generation dynamics in doped semiconductor heterostructures with quantum dots (QD) formed in the cationic and anionic sublattices of AlAs is studied. We demonstrate experimentally that the vacancy-mediated high temperature diffusion is enhanced (suppressed) in n- and p-doped heterostructures with QDs formed in the cationic sublattice, while the opposite behavior occurs in the heterostructures with QDs formed in the anionic sublattice. A model describing the doping effect on the vacancy generation dynamics is developed. The effect of nonuniform charge carrier spatial distribution arisen in heterostructures at high temperatures on the vacancy generation and diffusion is revealed. Full article

This study shows that a hybridized plasmonic mode, represented by an additional transmission peak, in a compound structure consisting of a nanorod embedded in a nanohole can be effectively described as a quasi-dipole oscillator. When two nanorods are introduced into a nanohole, these two quasi-dipoles can couple and hybridize, giving rise to two additional transmission peaks in the enhanced optical transmission spectrum. The relative intensities of these peaks can be controlled by adjusting the incident polarization, while their separations can be tuned by modifying the length of the nanorods. The concept of quasi-dipoles in compound nanohole structures can be further extended to predict the coupling behavior of even more complex compound configurations, such as multiple nanorods within nanoholes, resulting in the generation of multiple hybridization states. Consequently, the shape and response of the transmission peaks can be precisely engineered. This strategy could be used to design nanohole-based metasurfaces for applications such as ultra-thin optical filters, waveplates, polarizers, etc. Full article

Nanometric multilayers composed of immiscible Ag and Ni metals were investigated by means of molecular dynamics simulations. The semi-coherent interface between Ag and Ni was examined at low temperatures by analyzing in-plane strain and defect formation. The relaxation of the interface under annealing conditions was also considered. With increasing temperature, a greater number of atomic planes participated in the interface, resulting in enhanced mobility of Ag and Ni atoms, as well as partial dissolution of Ni within the amorphous Ag. To mimic polycrystalline layers with staggered grains, a system with a triple junction between a silver single layer and two grains of nickel was examined. At high temperatures (900 K and 1000 K), the study demonstrated grain boundary grooving. The respective roles of Ni and Ag mobilities in the first steps of grooving dynamics were established. At 1100 K, a temperature close but still below the melting point of Ag, the Ag layer underwent a transition to an amorphous/premelt state, with Ni grains rearranging themselves in contact with the amorphous layer. Full article

Integrated frequency routers, which can guide light with different frequencies to different output ports, are an important kind of nanophotonic device. However, frequency routers with both a compact size and multiple channels are difficult to realize, which limits the application of these frequency routers in nanophotonics. Here, a kind of bandgap optimization algorithm, which consists of the finite element method and topology optimization, is proposed to design a multi-channel frequency router. Channels supporting photonic edge states with different frequencies are built through the synthetic dimension of translational deformation. Due to the help of the developed optimization algorithms, the number of channels and output ports can be increased up to nine while maintaining ultracompact device size. The device operates within a working band of 0.585–0.665 c/a, corresponding to 1.504–1.709 μm when the lattice constant is set as 1 μm, covering the telecom wavelength of 1.55 μm. The average crosstalk is about −11.49 dB. The average extinction ratio is around 16.18 dB. Because the bus of the device can be regarded as a part of a topological rainbow, the results show that the structure is robust to fabrication errors. This method is general, which can be used for different materials and different frequency ranges. The all-dielectric planar configuration of our router is compact, robust, and easy to integrate, providing a new method for on-chip multi-channel broadband information processing. Full article

We used capacitance–voltage (C–V), conductance–voltage (G–V), and noise measurements to examine the carrier trap mechanisms at the surface/core of an AlGaN/GaN nanowire wrap-gate transistor (WGT). When the frequency is increased, the predicted surface trap density promptly drops, with values ranging from 9.1 × 10¹³ eV⁻¹∙cm⁻² at 1 kHz to 1.2 × 10¹¹ eV⁻¹∙cm⁻² at 1 MHz. The power spectral density exhibits 1/f-noise behavior in the barrier accumulation area and rises with gate bias, according to the 1/f-noise features. At lower frequencies, the device exhibits 1/f-noise behavior, while beyond 1 kHz, it exhibits 1/f²-noise behavior. Additionally, when the fabricated device governs in the deep-subthreshold regime, the cutoff frequency for the 1/f²-noise features moves to the subordinated frequency (~10² Hz) side. Full article

The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO₂ and PVP-Ir/IrO₂ types, as well as non-coated Ir/IrO₂ nanoparticles, are synthesized using different synthetic protocols and characterized in terms of their chemical composition and morphology via X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM), respectively. Furthermore, their nonlinear optical (NLO) response and optical limiting (OL) efficiency are studied by means of the Z-scan technique, employing 4 ns laser pulses at 532 and 1064 nm. The results demonstrate that the PVP-Ir/IrO₂ and Ir/IrO₂ systems exhibit exceptional OL performance, while PVP-IrO₂ presents very strong saturable absorption (SA) behavior, indicating that the present Ir-based nanohybrids could be strong competitors to other nanostructured materials for photonic and optoelectronic applications. In addition, the findings denote that the variation in the content of IrO₂ nanoparticles by using different synthetic pathways significantly affects the NLO response of the studied Ir-based nanohybrids, suggesting that the choice of the appropriate synthetic method could lead to tailor-made NLO properties for specific applications in photonics and optoelectronics. Full article

In the XXI century, application of nanostructures in oral medicine has become common. In oral medicine, using nanostructures for the treatment of dental caries constitutes a great challenge. There are extensive studies on the implementation of nanomaterials to dental composites in order to improve their properties, e.g., their adhesive strength. Moreover, nanostructures are helpful in dental implant applications as well as in maxillofacial surgery for accelerated healing, promoting osseointegration, and others. Dental personal care products are an important part of oral medicine where nanomaterials are increasingly used, e.g., toothpaste for hypersensitivity. Nowadays, nanoparticles such as macrocycles are used in different formulations for early cancer diagnosis in the oral area. Cancer of the oral cavity—human squamous carcinoma—is the sixth leading cause of death. Detection in the early stage offers the best chance at total cure. Along with diagnosis, macrocycles are used for photodynamic mechanism-based treatments, which possess many advantages, such as protecting healthy tissues and producing good cosmetic results. Application of nanostructures in medicine carries potential risks, like long-term influence of toxicity on body, which need to be studied further. The introduction and development of nanotechnologies and nanomaterials are no longer part of a hypothetical future, but an increasingly important element of today’s medicine. Full article

This work presents the effect of monovalent (Ag⁺, Na⁺), divalent (Ca²⁺, Cd²⁺), and trivalent (La³⁺) metal ion doping and annealing temperature (500, 800, and 1200 °C) on the structure, morphology, and magnetic properties of MnFe₂O₄/SiO₂ ceramic nanocomposites synthesized via sol–gel method. Fourier-transform infrared spectroscopy confirms the embedding of undoped and doped MnFe₂O₄ nanoparticles in the SiO₂ matrix at all annealing temperatures. In all cases, the X-ray diffraction (XRD) confirms the formation of MnFe₂O₄. In the case of undoped, di-, and trivalent metal-ion-doped gels annealed at 1200 °C, three crystalline phases (cristobalite, quartz, and tridymite) belonging to the SiO₂ matrix are observed. Doping with mono- and trivalent ions enhances the nanocomposite’s structure by forming single-phase MnFe₂O₄ at low annealing temperatures (500 and 800 °C), while doping with divalent ions and high annealing temperature (1200 °C) results in additional crystalline phases. Atomic force microscopy (AFM) reveals spherical ferrite particles coated by an amorphous layer. The AFM images showed spherical particles formed due to the thermal treatment. The structural parameters calculated by XRD (crystallite size, crystallinity, lattice constant, unit cell volume, hopping length, density, and porosity) and AFM (particle size, powder surface area, and thickness of coating layer), as well as the magnetic parameters (saturation magnetization, remanent magnetization, coercivity, and anisotropy constant), are contingent on the doping ion and annealing temperature. By doping, the saturation magnetization and magnetocrystalline anisotropy decrease for gels annealed at 800 °C, but increase for gels annealed at 1200 °C, while the remanent magnetization and coercivity decrease by doping at both annealing temperatures (800 and 1200 °C). Full article

Full and partial restorations in dentistry must replicate the characteristics of the patient’s natural teeth. Materials must have good mechanical properties and be non-toxic and biocompatible. Microbes, which can form biofilms, are constantly in contact with restorations. In this study, we investigate how well Candida albicans adheres to a polymethyl methacrylate (PMMA) resin base with gold (Au) nanoparticles. We synthesized Au nanoparticles and characterized them. The average size of Au nanoparticles embedded in PMMA was 11 nm. The color difference ΔE between PMMA and PMMA/Au composites was 2.7 and was still esthetically acceptable to patients. PMMA/Au surfaces are smoother and more hydrophilic than pure PMMA surfaces, and the isoelectric point of both types of surfaces was 4.3. Above the isoelectric point, PMMA/Au surfaces are more negatively charged than PMMA surfaces. The added Au nanoparticles decreased the tensile strength, while the hardness did not change significantly. Adhesion measurements showed that PMMA surfaces modified with Au nanoparticles reduced the extent of microbial adhesion of Candida albicans. Full article

Gate-all-around (GAA) structures are important for future logic devices and 3D-DRAM. Inner-spacer cavity etching and channel release both require selective etching of Si_0.7Ge_0.3. Increasing the number of channel-stacking layers is an effective way to improve device current-driving capability and storage density. Previous work investigated ICP selective etching of a three-cycle Si_0.7Ge_0.3/Si multilayer structure and the related etching effects. This study focuses on the dry etching of a 15-cycle Si_0.7Ge_0.3/Si multilayer structure and the associated etching effects, using simulation and experimentation. The simulation predicts the random effect of lateral etching depth and the asymmetric effect of silicon nanosheet damage on the edge, both of which are verified by experiments. Furthermore, the study experimentally investigates the influence and mechanism of pressure, power, and other parameters on the etching results. Research on these etching effects and mechanisms will provide important points of reference for the dry selective etching of Si_0.7Ge_0.3 in GAA structures. Full article

Modern heat-conducting materials require special attention to analyze their thermophysical properties. Compared to classical methods, thermal lens spectrometry (TLS) has advantages due to its high sensitivity to physical and chemical composition. To avoid a systematic error in the analysis of complex systems, it is necessary to realize the limits of the applicability of the method. This study considers the features of thermal-diffusivity measurements by TLS in the stationary state for dispersed systems with absorbances up to 0.05. The limits of applicability of the method in analyzing heterogeneous systems are shown, and a mathematical apparatus is proposed for indicating a systematic error in finding thermal diffusivity that does not exceed 1%. Graphene oxide (GO), which has attractive physicochemical properties, was used as the object of analysis. GO belongs to 2D objects, the study of which requires highly sensitive methods and special attention when discussing the results. The thermophysical properties of aqueous dispersions of graphene oxide in a wide range of concentrations (up to 2 g/L) and lateral sizes (up to 4 µm) were studied by TLS. It has been found that with increasing nanophase concentration, the thermal diffusivity of graphene oxide dispersions passes through a minimum, which can be used in solving thermal insulation problems. It has been established that prolonged laser irradiation of the dispersion leads to a change in thermal diffusivity, which indicates the photochemical reduction of graphene oxide. Full article

A series of Ti₂O₃@TiO₂ core-shell heterojunction composite photocatalysts with different internal electric fields were synthesized using simple heat treatment methods. The synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites were characterized by means of SEM, XRD, PL, UV–Vis, BET, SPV, TEM and other related analytical techniques. Tetracycline (TC) was used as the degradation target to evaluate the photocatalytic performance of the synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites. The relevant test results show that the photocatalytic performance of the optimized materials has been significantly enhanced compared to Ti₂O₃, while the photocatalytic degradation rate has increased from 28% to 70.1%. After verification via several different testing and characterization techniques, the excellent catalytic performance is attributed to the efficient separation efficiency of the photogenerated charge carriers derived from the built-in electric field formed between Ti₂O₃ and TiO₂. When the recombination of electrons and holes is occupied, more charges are generated to reach the surface of the photocatalyst, thereby improving the photocatalytic degradation efficiency. Thus, this work provides a universal strategy to enhance the photocatalytic performance of Ti₂O₃ by coupling it with TiO₂ to build an internal electric field. Full article

In this work, the SET and RESET processes of bipolar resistive switching memories with silicon nanocrystals (Si-NCs) embedded in an oxide matrix is simulated by a stochastic model. This model is based on the estimation of two-dimensional oxygen vacancy configurations and their relationship with the resistive state. The simulation data are compared with the experimental current-voltage data of Si-NCs/Si${\mathrm{O}}_2$ multilayer-based memristor devices. Devices with 1 and 3 Si-NCs/Si${\mathrm{O}}_2$ bilayers were analyzed. The Si-NCs are assumed as agglomerates of fixed oxygen vacancies, which promote the formation of conductive filaments (CFs) through the multilayer according to the simulations. In fact, an intermediate resistive state was observed in the forming process (experimental and simulated) of the 3-BL device, which is explained by the preferential generation of oxygen vacancies in the sites that form the complete CFs, through Si-NCs. Full article

Nitrogen is commonly implanted in silicon to suppress the diffusion of self-interstitials and the formation of voids through the creation of nitrogen–vacancy complexes and nitrogen–nitrogen pairs. Yet, identifying a specific N-related defect via spectroscopic means has proven to be non-trivial. Activation energies obtained from deep-level transient spectroscopy are often assigned to a subset of possible defects that include non-equivalent atomic structures, such as the substitutional nitrogen and the nitrogen–vacancy complex. Paramagnetic N-related defects were the object of several electron paramagnetic spectroscopy investigations which assigned the so-called SL5 signal to the presence of substitutional nitrogen (N${}_{\mathrm{Si}}$). Nevertheless, its behaviour at finite temperatures has been imprecisely linked to the metastability of the N${}_{\mathrm{Si}}$ center. In this work, we build upon the robust identification of the SL5 signature and we establish a theoretical picture of the substitutional nitrogen. Through an understanding of its symmetry-breaking mechanism, we provide a model of its fundamental physical properties (e.g., its energy landscape) based on ab initio calculations. Moreover by including more refined density functional theory-based approaches, we calculate EPR parameters ($\underset{g}{\leftrightarrow }$ and $\underset{A}{\leftrightarrow }$ tensors), elucidating the debate on the metastability of N${}_{\mathrm{Si}}$. Finally, by computing thermodynamic charge transition levels within the GW method, we present reference values for the donor and acceptor levels of N${}_{\mathrm{Si}}$. Full article

The hydrogen evolution reaction (HER) is a remarkable mechanism which yields the production of hydrogen through a process of water electrolysis. However, the evolution of hydrogen requires highly conductive and stable catalysts, such as the noble metal platinum (Pt). However, the problem lies in the limitations that this catalyst and others of its kind present. Due to limited availability, as well as the costs involved in acquiring such catalysts, researchers are challenged to manufacture catalysts that do not present these limitations. Carbon nanotubes (CNTs), which are nanomaterials, are known to have a wide range of applications. However, specifically, the pristine carbon nanotube is not suitable for the HER due to the binding free energy of its positive H-atoms. Hence, for the first time, we demonstrated the use of the proposed aryl-functionalised catalysts, i.e., Aryl-L@SWCNT (L = Br, CCH, Cl, CO₂CH₃, F, I, NO₂, or t-butyl), along with the effect of the sp2–sp3 hybridised interface through the density functional theory (DFT). We performed calculations of single-walled carbon nanotubes with multiple aryl functional groups. By employing the DFT calculations, we proved that the curvature of the nanotubes along with the proposed aryl-functionalised catalysts had a noteworthy effect on the performance of the HER. Our study opens the door to investigating a promising group of catalysts for sustainable hydrogen production. Full article