Nanotechnology最新文献

Environmental issues have emerged as a pivotal challenge in the realm of industrial development, rendering the prioritization of renewable energy and sustainable development imperative. Photocatalytic materials should align with these goals by being recyclable and reusable. In this work, spherical nano-Bi₂₄Fe₂O₃₉ was synthesized via a sol-gel method combined with calcination and loaded onto In₂S₃ to construct an S-scheme In₂S₃/Bi₂₄Fe₂O₃₉ heterojunction with superior photocatalytic degradation performance. The composite exhibited an extended light absorption range from 585 nm to 650 nm (IB-30), a narrowed apparent bandgap compared to pure In₂S₃, and significantly improved carrier separation and transfer efficiency. Under the optimal conditions of pH = 7, catalyst dosage = 10 mg, and tetracycline (TC) concentration = 10 mg l^-1, the IB-30 material achieved a removal rate of 85.8% for tetracycline, which is 1.7 times and 2.46 times higher than that of pure In₂S₃ and pure Bi₂₄Fe₂O₃₉, respectively. Driven by the built-in electric field, photogenerated electrons follow an S-scheme pathway for transfer, while・O₂^-(superoxide anion radicals) and h⁺(holes) serve as the primary active species, effectively facilitating the photocatalytic degradation reaction. This study provides new insights into developing efficient and stable visible-light-driven photocatalysts.

Lithium sulfur batteries (LSBs) are regarded as the potential next-generation energy storage system due to their high theoretical energy density and low cost. However, LSBs also face problems such as the dissolution of lithium polysulfide, volume expansion, and the formation of lithium dendrites. Optimizing the design of sulfur cathode materials to tackle these issues at their source is the primary approach to enhancing the performance of LSBs, since the inherent limitations of sulfur are the root cause of the challenges in LSBs. The review covers the latest research on carbon-based sulfur cathode materials of LSBs, including structural design and functional optimization strategies, aiming to prepare multifunctional carbon-based sulfur cathodes by integrating physical confinement, chemical adsorption, and catalytic effect towards lithium polysulfides. The future development directions are prospected, including material design, optimization of reaction mechanisms, and low-cost preparation technologies.

This study investigates the quantum efficiency (QE) and operational lifetime of a negative electron affinity GaAs truncated nanocone array (TNCA) photocathode benchmarked against a conventional flat GaAs photocathode under varying activation temperatures. The TNCA structure demonstrated a QE of up to 13.6% at 590 nm with room temperature (RT) activation-approximately 1.5 times higher than its flat counterpart. This enhancement is due to Mie resonance effects within the nanostructure, as confirmed by finite-difference time-domain simulations. Moreover, the TNCA photocathode exhibits significantly extended charge lifetime, with enhancement factors of ∼6.1 and ∼19.8 under RT and 50 °C activations, respectively. These gains are primarily attributed to increased effective surface area and optimized dipole layer formation at elevated temperatures. In addition, shorter excitation wavelengths further contribute to lifetime improvements. These findings underscore the TNCA GaAs photocathode's potential as a high QE, long lifetime electron source for many large-scale electron accelerators.

In this paper, we present results of x-ray diffraction investigations of GaN micro-pillars grown on GaN template. These rods are special in so far that they have stable a- and m-plane side walls and dodecagonal and not hexagonal shape as usual. Such growth mode is simulated by adding As as surfactant. The work shows the influence of changing the amount of gallium and arsenic and lowering the temperature on the growth of micro-pillars. Changing the growth parameters led to both a change in the density of the growing micro-pillars, their height and width, and their structural parameters, such as a disturbance in the direction of growth of the structures. In order to characterize the studied samples, measurements were carried on the configuration from the surface and from the edge of the sample. This measurements method allowed to visualize the structure in the perpendicular and parallel directions of the micro-pillars growth. In addition, the strain and mosaic analysis showed correlations between the resulting shape and density of the rods and the strain of the GaN-pillar and GaNAs crystalline lattice.

This paper investigates the influence of different abrasive morphology of silicon carbide (SiC) through molecular dynamics simulations on the scratching process, aiming to provide theoretical guidance and process optimization directions for the precision machining of SiC materials. The paper analyzes the differences in contact area, stress distribution, and material deformation mechanisms between sphere, cone, frustum cone, face of a square pyramid and edge of a square pyramid abrasives during the scratching process. It focuses on key characteristics such as scratching force, atom removal, surface topography, amorphous deformation, and subsurface stress distribution. The results show that the morphology of the abrasive significantly affects machining efficiency and surface quality, with sphere abrasives being more prone to plastic deformation and pyramid abrasives tending to cause brittle fracture. Additionally, the interaction between abrasive morphology and SiC crystal orientation also has a significant impact on the scratching process. This paper not only reveals the surface formation mechanisms of SiC under different abrasive morphology but also provides important theoretical and experimental basis for achieving more efficient and precise SiC material machining.

In this work, TiCrC nanocarbide was consolidated via spark plasma sintering (SPS) from TiCrC nanopowder prepared via mechanical alloying (MA). The microstructure, elemental compositions, and morphology of the prepared samples were investigated using x-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The mechanical properties of the sintered (Ti,Cr)C nanocarbide were also studied. XRD studies of the bulk samples show the presence of (Ti,Cr)C and a small amount of Cr₃C₂and graphite. SEM study reveals the presence of transgranular cleavage in fracture surfaces and the shape of grains is partially rounded. TEM analysis shows that the SPS process leads to the increase in grain size with retention of nanoscale. The optimized SPS parameters were a pressure of 80 MPa, a sintering temperature of 1800 °C and a holding time of 5 min. Results reveal that TiCrC nanocarbide also has an excellent mechanical properties achieving microhardness, relative density, fracture toughness, and compressive strength of 28 GPa, 98.51%, 6.5 MPa m^1/2, and 2290 MPa, respectively. Finally, our study shows that the prepared TiCrC nanocarbide can be used for cutting tools without loss of mechanical strength.

This work presents a facile, scalable nanocomposite-based resistive memory device incorporating a 2D hybrid of hydrothermally synthesized and exfoliated tungsten disulfide (E-WS₂) nanosheets embedded in a poly (ethylene oxide) (PEO) matrix for energy efficient neuromorphic applications. WS₂was synthesized via a simple, cost-effective hydrothermal method and subsequently exfoliated via liquid phase exfoliation to obtain few-layer nanosheets with improved surface uniformity and reduced defect density. These nanosheets were integrated into the active layer of an ITO/E-WS₂+ PEO/Cu device fabricated via spin coating and thermal evaporation. The device exhibits reliable bipolar resistive switching with low SET voltages, a high ON/OFF current ratio (∼10⁴), excellent retention (>450 s), and endurance over 70 cycles. The transport mechanism is governed by Ohmic conduction at low voltages, followed by space charge limited current (SCLC) and trap-controlled SCLC (TC-SCLC) mechanisms near-threshold voltages. Energy band analysis indicates that charge trapping and de-trapping at the WS₂/PEO interface plays a critical role in the switching process. Compared to bulk WS₂, exfoliated WS₂offers enhanced interfacial contact, lower resistance pathways, and reduced variability in switching, resulting in improved device performance and stability. It also shows more analog like behavior. Sulfur vacancies in E-WS₂ assist in forming conductive filaments, while the PEO matrix enhances ionic mobility and switching behavior. This work offers a scalable, environmentally benign approach to fabricating 2D material-based resistive memory, establishing solution-processed E-WS₂ nanocomposites as strong candidates for next-generation, scalable, energy-efficient non-volatile memory and neuromorphic technologies.

Electric conduction mechanisms in the pressed powder samples consisting of the molybdenum-disulfide-oxide (MoS_xO_y) nanoflakes depending on their content and structure have been investigated. The MoSxOy nanoflakes were synthesized in the temperatures range of 130 to 180^oC by reaction of (NH₄)₆Mo₇O24 with thiourea in aqueous solution followed by aerial oxidation. The chemical composition and structure of the powders have been determined by means of XPS, EDS and Raman spectroscopy. The obtained nanoflakes are 10-20 nm thick and self-assembled in the "nanoflower"-shape agglomerates forming powder particles. The agglomerates in powders synthesized at different temperatures are shown to consist of MoS2 and molybdenum oxides/sulfoxides which content ratio differs from each other in powders depending on their synthesis temperature. The current vs voltage (I-V) dependences of the pressed powder films manifest a hysteresis-like behavior with substantial dependence on this ratio. For the samples with the highest content of the Mo oxide/sulfoxide nanoflake forms (>50 %) one observes the negative differential conductivity (NDC) in the I-V characteristics and very large difference between the forward and backward I-V branches at small DC biases. Unlike, the samples with low content of these forms have slightly non-linear I-V characteristics, narrower hysteresis loop and absence of NDC. All samples manifest long-lasting (tens second) transient charge/discharge process after switching "on/off" the voltage across the sample, and ability of large charge accumulation with the specific capacitance equal achieving 12-75 F/g depending on the powder synthesis temperature. These phenomena give evidence of the important role of interface charges in the MoSxOy powder electric conduction mechanisms. To describe theoretically the observed I-V curves, polar and electric-transport properties of the pressed MoSxOy nanoflake films, the Landau-Cahn-Hilliard approach considering flexo-chemical field has been used. The revealed features of electric conduction and charge accumulation look interesting for possible applications in nanoelectronics and charge storage devices.

As silicon-based FETs face scaling limits, two-dimensional (2D) material emerge as promising alternatives with potential to suppress short-channel effects and reduce power consumption. We present a comprehensive investigation of the novel 2D bismuth carbide (Bi₂C₃) semiconductor using first-principles density functional theory (DFT) calculations combined with non-equilibrium green's function (NEGF) quantum transport simulations. Electronic band structure calculations indicate that monolayer Bi₂C₃possesses a moderate direct bandgap, a sharp conduction band, and a low electron effective mass (0.48m₀). Device simulations reveal outstanding performance: a Bi₂C₃FET with a 10 nm channel length achieves an ultra-high on-state current (I_on) of 2540μAμm^-1while maintaining a high on/off current ratio (exceeding 10⁴), satisfying the requirements of the international technology roadmap for semiconductors (ITRS) for high-performance (HP) applications. Furthermore, scaling the channel length down to 5 nm still yields device performance compliant with ITRS specifications. Crucially, devices across different channel lengths exhibit fast switching speeds, low power-delay (τ), power-delay product, and excellent energy-delay product, fully meeting the ITRS HP targets. This study, for the first time, systematically evaluates the application potential of Bi₂C₃in MOSFETs via DFT-NEGF. Its excellent comprehensive performance metrics demonstrate that monolayer Bi₂C₃is a highly competitive candidate channel material for future HP integrated circuits.

A ternary stepped heterojunction of PbS/CdS/TiO₂was fabricated using the successive ionic layer adsorption and reaction method, which significantly enhanced the photocathodic protection performance of TiO₂. The experimental results demonstrate the superiority of the dual-loading modification over its single-loading counterparts. The co-loading of CdS and PbS resulted in a TiO₂nanocomposite with a reduced bandgap of 1.0 eV, a further extended light absorption range, and enhanced visible light utilization efficiency. The PbS/CdS/TiO₂electrode exhibited a photogenerated current density of 6.46 mA cm^-2, which is 1.6 times and 22.1 times higher than that of PbS/TiO₂and pure TiO₂, respectively. The dual loading of metal sulfide semiconductors markedly improved the photoelectrochemical properties of TiO₂and its corresponding photocathodic protection effect.