Nanotechnology最新文献

This study investigates the structural and microstructural characteristics of magnetite (Fe₃O₄) and cobalt ferrite (CoFe₂O₄) nanoparticles synthesized via the sol-gel auto-combustion method using ferric nitrate and cobalt nitrate as metal precursors. X-ray diffraction (XRD) analysis confirmed the formation of single-phase crystalline nanoparticles with a cubic inverse spinel structure. Transmission electron microscopy further validated the nanocrystalline nature and morphological uniformity of the particles. To gain deeper insight into the crystallite size and lattice strain, multiple XRD-based analytical approaches Williamson-Hall, size-strain plot, and Halder-Wagner methods were employed. The novelty of this work lies in the first systematic side-by-side comparison of Fe₃O₄and CoFe₂O₄nanoparticles synthesized under identical conditions and evaluated using four complementary XRD models, ensuring cross-validated accuracy. The comparative evaluation of these models revealed slight discrepancies in size estimations, attributed to their varied assumptions regarding strain and instrumental broadening. Notably, CoFe₂O₄nanoparticles exhibited marginally larger crystallite sizes and higher lattice strain compared to Fe₃O₄, imply compositional influence on structural properties. The combined application of these analytical techniques enabled accurate estimation of crystallite size, microstrain, and energy density, providing insights into the mechanical stability and potential functional behavior of the synthesized nanoparticles.

The rapid rise of antibiotic resistance threatens global health, highlighting the need for new antimicrobial strategies. Here, we investigated nitrogen vacancies and Ag nanoparticles decoration in carbon nitride (Ag-g-C₃N₄-V). Nitrogen vacancies optimized the electronic structure, boosting light absorption and charge separation. Ag nanoparticles induced a synergistic effect via localized surface plasmon resonance and the conjugated C₃N₄network, enhancing visible-light photocatalysis. The composite promoted hydrogen peroxide (H₂O₂) generation, a reactive oxygen species with antibacterial activity. The incorporation of Ag synergistically coupled H₂O₂generation with Ag⁺release, leading to enhanced bactericidal performance. Treatment with Ag-g-C₃N₄-V reduces the survival rates ofE. coliandS. aureusby approximately 39% and 58% respectively compared to the control group; under light conditions, Ag-g-C₃N₄-V lowers the survival rates ofE. coliandS. aureusto only 16% and 6%, showing a more remarkable bactericidal effect. This work offers a strategy for designing multifunctional photocatalysts against bacterial infections with potential biomedical applications.

Electric conduction mechanisms in pressed powder samples consisting of molybdenum-disulfide-oxide (MoS_xO_y) nanoflakes depending on their content and structure have been investigated. The MoS_xO_ynanoflakes were synthesized in the temperature range of 130 °C-180 °C by reaction of (NH₄)₆Mo₇O₂₄with 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 into 'nanoflower'-shaped agglomerates forming powder particles. The agglomerates in powders synthesized at different temperatures are shown to consist of MoS₂and molybdenum oxides/sulfoxides whose content ratios differ from each other in powders depending on their synthesis temperature. The current versus 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 theI-Vcharacteristics and a very large difference between the forward and backwardI-Vbranches at small DC biases. However, the samples with low content of these forms have slightly non-linearI-Vcharacteristics, narrower hysteresis loops and the absence of NDC. All samples manifest a long-lasting (tens of seconds) transient charge/discharge process after switching 'on/off' the voltage across the sample and ability of large charge accumulation, with the specific capacitance equal to achieving 12 ÷ 75 F g^-1depending on the powder synthesis temperature. These phenomena provide evidence of the important role of interface charges in the MoS_xO_ypowder electric conduction mechanisms. To describe theoretically the observedI-Vcurves, polar and electric-transport properties of the pressed MoS_xO_ynanoflake 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.

Altermagnetic materials are a new type of magnetic materials that have recently garnered significant attention due to their exceptional properties, while the Rashba-Edelstein effect (REE) serves as a crucial charge-to-spin conversion mechanism. In this study, we explore the commonalities in symmetry dependence between altermagnetic materials and the occurrence of the REE. Utilizing a self-developed program for quantifying the REE, we calculate the REE intensity of altermagnetic materials after breaking symmetry constraints via twisting. By comparing the REE intensities between altermagnetic materials with weak spin-orbit coupling (SOC) and transition metal dichalcogenides with strong-SOC following symmetry breaking through twisting, it is found that efficient REE can be achieved in weak-SOC altermagnetic materials through symmetry regulation. This result breaks the traditional reliance of the REE on strong-SOC materials, providing theoretical support for the material design and functional optimization of next generation spintronic devices.

Tellurium (Te), a typical p-type elemental semiconductor, exhibits exceptional properties including environmental stability, high carrier mobility, and superior optical responsiveness, demonstrating significant application potential in next-generation optoelectronic devices. This review provides a systematic overview of the crystal structures and optoelectronic properties of Te, along with the research progress in the field of Te-based photodetectors. Firstly, the crystal structures and band characteristics of Te are elucidated, with its optical and electrical properties analyzed in depth to lay a theoretical foundation for subsequent research. On this basis, the photoelectric performance and operating mechanisms of photodetectors based on individual Te nanomaterials are explored, encompassing one-dimensional Te nanowires, nanoribbons, nanocoils, and two-dimensional Te nanosheets and nanofilms. Furthermore, the structural designs and application potential of Te nanomaterial heterostructure photodetectors based on different band alignment types are elaborated in detail. Finally, the current bottlenecks encountered by Te-based materials in the field of photoelectric detection are synthesized, and perspectives on future research directions within this field are delineated. We believe that that frontier explorations of Te-based materials will yield significant breakthroughs, and such research will offer highly valuable industrial references for the commercialization of nanodevices.

Employing amorphous superconductors, such as type-II molybdenum silicide (MoSi), instead of crystalline materials significantly simplifies the material deposition and scalable nanoscale prototyping, beneficial for quantum electronic and photonic device fabrication. In this work, deposition of amorphous superconductive MoSi thin films on flat and nanowire (NW) substrates was demonstrated via pulsed direct-current magnetron co-sputtering from molybdenum and silicon targets in an argon atmosphere. MoSi films were deposited on oxidized silicon wafers and Ga₂O₃NWs with 6 nm Al₂O₃insulating shell, grown around the NWs using atomic layer deposition, and studied using scanning and transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Four-point Cr/Au electrical contacts were defined on the thin films and on individual Ga₂O₃-Al₂O₃-MoSi core-shell NWs using lithography for low-temperature electrical measurements. By controlling the sputtering power of the targets and thus adjusting the molybdenum-to-silicon ratio in the MoSi films, their properties were optimized to achieve critical temperatureT_cof 7.25 K. Such superconducting shell NWs could provide new avenues for fundamental studies and interfacing with other materials for quantum device applications.

Bulk Mn₄Si₇is a metallic ferromagnet with a weak magnetic momentµ= 0.012µ_B/Mn below its Curie temperatureT_C∼40 K. Here we report results from magnetic and electron spin resonance (ESR) studies in two samples of nanoparticles (NPs) of Mn₄Si₇prepared by high-energy ball milling for 40 h (B40) and 50 h (B50). Williamson-Hall analysis of the linewidths of various x-ray diffraction (XRD) lines of the two samples yielded average particle diameter <D>= 123 nm with strainη= 1.45 × 10^-2for B40 and <D>= 43 nm withη= 1.22 × 10^-2for B50. Using transmission electron microscopy, a near symmetrical log-normal distribution of particle sizes was found for B40 with <D>= 95 nm whereas for B50, <D>= 10.7 nm was found with the distribution highly skewed towards larger sizes. The larger 〈D〉 from XRD is explained on the basis of this size distribution. Both samples show hysteresis loops in the magnetizationMvsHdata at 340 K as well as at 3 K with coercivityH_C∼ 1 kOe (0.5 kOe) for B50 (B40) at 3 K. TheMvsTvariations for the field-cooled (FC) and zero-field-cooled (ZFC) cases withH= 500 Oe along with that of ΔM=M(FC)-M(ZFC) shows blocking temperatureT_B∼ 30 K with ΔMbeing positive at 300 K for both samples signifyingT_C> 300 K. ESR spectroscopy at 300 K yielded spectra characteristic of Mn²⁺ions with zero field splitting and effective spinS= 5/2 andg∼ 2.0. It is argued that the observed room temperature ferromagnetism is due to these strain-stabilized Mn²⁺ions present on the surface of the NPs in the reduced coordination environment of atoms on the surface of NP. The enhanced magnetization and ESR in the smaller B50 NP vis-a-vis larger B40 NP supports this conclusion.

Silicon nanowire (SiNW) arrays present a promising platform for high-performance hydrovoltaic devices (HDs). However, charge extraction from the SiNW tips remains a key challenge. This work introduces a silver wire (AgW) network as a conjoint top electrode to enable high-efficiency charge collection. Thein-situassembled AgWs form a conformal conductive network that bridges numerous SiNW tips in parrel, effectively interconnecting independent SiNW hydrovoltaic microunits and facilitating efficient charge transport to grid electrodes. Systematic optimization reveals that an AgW areal density of 0.050 mg cm^-2leads to a significant performance boost of SiNW HDs, achieving a 101% increase in output power density compared to reference devices. Furthermore, the AgW conjoint top electrode exhibits good stability under hydrodynamic flushing (13.5 m min^-1), with only an initial 12% performance decay due to the removal of loosely bound nanowires, followed by consistent output over repeated flushing cycles. This work demonstrates a simple yet effective strategy for enhancing charge collection in SiNW HDs, offering a practical pathway toward new-type silicon-based energy harvesting systems.

This study investigates the damage mechanisms induced by HPM stress in GaN HEMTs using Sentaurus TCAD numerical simulations and proposes corresponding multi-scale protection strategies. A comprehensive simulation model of a depletion-mode GaN HEMT was established. The analysis of the evolution of internal electric field, current density, and temperature profiles under HPM stress reveals that the failure mechanism is primarily attributed to an electro-thermal positive feedback loop between the gate and source, leading to thermal accumulation and eventual thermal breakdown when the lattice temperature reaches the melting point of GaN. Based on this understanding, protection strategies were developed through structural optimization. The results demonstrate that moderately increasing the gate length (0.25-0.3μm), extending the field plate length (1.85-2.25μm), and optimizing the channel layer thickness (0.4-0.6μm) effectively reduce the internal electric field and current density, thereby mitigating thermal accumulation and enhancing HPM resilience without significantly compromising DC performance.

To address the increasingly severe ecological degradation, photocatalytic technology has attracted significant attention due to its pollution-free nature and the abundance of renewable resources. Numerous semiconductor photocatalysts have been developed. However, their performance has long been constrained by the rapid recombination of photogenerated electron-hole pairs. In this study, the In 2 O 3 nanorods loaded with graphene structure has been fabricated, where In₂O₃ nanorods were prepared using the glancing angle deposition technique. The research aims to suppress the recombination of photogenerated carriers in In₂O₃ by leveraging the high electron mobility of graphene, thereby enhancing its photocatalytic performance. Under the optimal graphene loading conditions, the photocurrent density of In₂O₃/graphene is as high as 0.6 mA/cm². The photocurrent density and degradation efficiency has been improved by 81.82% and 33.5% compared to pure In₂O₃ nanorods, respectively. This enhancement can be attributed to the built-in electric field formed between graphene and In₂O₃, which facilitates rapid electron transfer and effectively suppresses charge recombination, thereby improving the overall photocatalytic performance.