Nanomaterials最新文献

At an ultra-thin 3 nm SnO₂ channel thickness, a record-high effective mobility (µ_eff) of 301 cm²/V·s, field-effect mobility (µ_FE) of 304 cm²/V·s, and a sharp subthreshold swing (SS) of 201 mV/decade are achieved at a high carrier density (N_e) of 5 × 10¹² cm^-2. These excellent transport properties are attributed to ultraviolet (UV) light annealing. The resulting µ_eff is significantly higher than that of Molybdenum Disulfide (MoS₂) and Tungsten Diselenide (WSe₂), and is more than twice that of single-crystalline Si channel transistors at the same quasi-two-dimensional (2D) thickness of 3 nm (equivalent to five monolayers of MoS₂). UV annealing not only enhances µ_eff and µ_FE but also sharpens the SS, which is crucial for low-power operation. This improved SS is attributed to reduced scattering from charged interface traps, as supported by µ_eff-N_e analysis, thereby increasing the transistor's mobility. The realization of such high-mobility devices at a quasi-2D thickness of only 3 nm is of particular importance for the further downscaling of ultra-thin-body transistors for high-speed computing and monolithic three-dimensional (M3D) integration. Furthermore, the wide bandgap of SnO₂ (3.7 eV) enables operation at relatively high voltages, paving the way for pioneering ternary logic applications.

Thermochromic VO₂ crystalline domains have been formed in amorphous nanocolumnar VO_x films by means of a low-temperature oxidation process. The oxidation of an amorphous film with [O]/[V] below 1.9 favors the formation of VO₂, V₃O₇, and V₂O₅ crystalline domains in the material for temperatures as low as 260 °C, while values above 1.9 lead to the sole formation of the V₂O₅ phase. It is found that the absorption of oxygen also causes a relevant film volume expansion that makes pores shrink. Under some specific conditions, low-temperature oxidation causes the near disappearance of the amorphous regions, clearly improving the overall transparency and optimizing the optical and electrical modulation capabilities associated with the presence of crystalline VO₂ domains. The best thermochromic performance was found when the original stoichiometry was [O]/[V] = 1.5 and the oxidation temperature was 280 °C. These conditions yield a relatively transparent coating in the visible range that presents an optical modulation in the near-infrared range of nearly 50% and a drop of electrical resistivity of more than two orders of magnitude, with a transition temperature of 50.3 °C. A tentative model based on the volume expansion experienced by the film upon oxidation is proposed, which links the structural/chemical features of the material and the formation of the crystalline domains at such relatively low temperatures.

Thorium carbide (ThC2±x) nano-structured thin disc-like pellets were produced from thoria nanoparticles (ThO2-NP) and multi-walled carbon nanotubes (MWCNT). These composites are to be studied as a target material candidate for radioactive ion beam (RIB) production via nuclear reactions upon impact with high-energy proton beams on a stack of solid pellets. The ThO2-NP precursor was produced via precipitation of thorium oxalate from a thorium nitrate solution with oxalic acid and subsequent hydrothermal oxidation of the oxalate, creating the thoria nanoparticles. The ThO2-NP were then mixed with MWCNT in isopropyl alcohol and sonicated by two different methods to create a nanoparticle dispersion. This dispersion was then heated under medium vacuum to evaporate the solvent; the resulting powder was pressed into pellets and taken to an inert-atmosphere oven, where it was heated to 1650 °C and carbothermally reduced to ThC2±x. The resulting pellets were characterized via XRD, SEM-EDS, and Raman spectroscopy. The resulting thorium pellets exhibited, at most, trace levels of the oxide precursor. Furthermore, the nanotube structures were still present in the final product and are expected to contribute positively towards faster radioisotope release times by lowering isotope diffusion times, which is required for the efficient extraction of the shortest-lived (<1 s half-life) radioisotopes.

Electrospinning is a widely used technique for fabricating nanomaterials with tailored morphology and functional properties. This study investigates how two fundamental process parameters-applied voltage and needle tip-to-collector distance-affect the spatial geometry and deposited mass of electrospun nanofiber mats in a top-down vertical electrospinning setup using a 10% (w/v) PVA solution prepared in deionized water. To support this hypothesis, both experimental measurements and 3D geometric modeling were performed to evaluate the area, perimeter, and deposited mass under different parameter combinations. Digital image analysis and cross-sectional reconstruction were applied to model nanofiber deposition. Regression and ANOVA analyses reveal that the tip-to-collector distance has a statistically significant impact on both area and perimeter of the electrospun nanofiber mat, while the applied voltage in the tested range (15-20 kV) has no significant effect. Interestingly, the total deposited mass shows no clear dependence on either parameter, likely due to startup irregularities or solution droplets.

Electric-field-sensitive dielectrics play a crucial role in electric field induction sensing and related capacitive conversion, with interfacial polarization and charge accumulation largely determining the signal output. This paper introduces graphene/transition metal dichalcogenide (TMD) (MoSe₂, MoS₂, and WS₂) heterojunctions as functional fillers to enhance the dielectric response and electric-field-induced voltage output of flexible polydimethylsiloxane (PDMS) composites. Density functional theory (DFT) calculations were used to evaluate the stability of the heterojunctions and interfacial electronic modulation, including binding behavior, charge redistribution, and Fermi level-referenced band structure/total density of states (TDOS) characteristics. The calculations show that the graphene/TMD interface is primarily controlled by van der Waals forces, exhibiting negative binding energy and significant interfacial charge rearrangement. Based on these theoretical results, graphene/TMD heterojunction powders were synthesized and incorporated into polydimethylsiloxane (PDMS). Structural characterization confirmed the presence of face-to-face interfacial contacts and consistent elemental co-localization within the heterojunction filler. Dielectric spectroscopy analysis revealed an overall improvement in the dielectric constant of the composite materials while maintaining a stable loss trend within the studied frequency range. More importantly, calibrated electric field induction tests (based on pure PDMS) showed a significant enhancement in the voltage response of all heterojunction composite materials, with the WS₂-G/PDMS system exhibiting the best performance, exhibiting an electric-field-induced voltage amplitude 7.607% higher than that of pure PDMS. This work establishes a microscopic-to-macroscopic correlation between interfacial electronic modulation and electric-field-sensitive dielectric properties, providing a feasible interface engineering strategy for high-performance flexible dielectric sensing materials.

This study investigates Metal-Organic Vapor Phase Epitaxy (MOVPE)-grown AlGaN/GaN and AlN/GaN heterostructures using high-temperature thermal annealing and Secondary Ion Mass Spectrometry (SIMS). By fitting experimental diffusion coefficients (DAl) to the Arrhenius equation, two crucial kinetic parameters were found: the activation energy (E_a) and the pre-factor (D₀). In the AlGaN/GaN structure, the dominating out-diffusion of Al has a large D₀ = 4.03 × 10^-5 cm² s^-1 and a low activation energy in the range of [2.1-2.4 eV]. A substitutional diffusion mechanism in the crystal lattice mediated by defects is closely linked to the low E_a. Significantly higher activation energies (E_a) of 3.66 and 4.59 eV, respectively, control both in- and out-diffusion processes in the AlN/GaN structure. The better intrinsic thermal stability of the pure AlN layer, whose stability is attained by a strong energy barrier, is confirmed by the increase of more than 1.2 eV in E_a.

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A multifunctional diagnosis and treatment carrier, ZIF-8@CDs, based on carbon quantum dots (CDs) and the zeolitic imidazolate framework-8 (ZIF-8) metal-organic framework which serves as a core structure for constructing the responsive delivery platform, is developed in this paper. The anticancer drug doxorubicin (DOX) and Survivin oligo (siRNA) are loaded to form a ZIF-8@CDs/DOX@siRNA dual loading platform. CDs of 5-10 nm are synthesized by the solvent method and combined with ZIF-8. Electron microscopy shows that the composites are nearly spherical particles of approximately 200 nm, and the surface potential decreases from +36 mV before loading CDs to +25.7 mV after loading. The composite system shows unique advantages: (1) It has Fenton-like catalytic activity, catalyzes H₂O₂ to generate hydroxyl radicals, and consumes glutathione in the tumor microenvironment. The level of reactive oxygen species (ROS) in the ZIF-8@CDs group is significantly higher than that in the control group. (2) To achieve visual diagnosis and treatment, its fluorescence intensity is superior to that of the traditional Fluorescein isothiocyanate (FITC)-labeled vector; (3) It has a high loading capacity, with the loading amount of small nucleic acids reaching 36.25 μg/mg, and the uptake rate of siRNA by liver cancer cells is relatively ideal. The ZIF-8@CDs/DOX@siRNA dual-loading system is further constructed. Flow cytometry shows that the apoptosis rate of HepG2 cells induced by the ZIF-8@CDs/DOX@siRNA dual-loading system is 49%, which is significantly higher than that of the single-loading system (ZIF-8@CDs/DOX: 34.3%, ZIF-8@CDs@siRNA: 24.2%) and the blank vector (ZIF-8@CDs: 12.6%). The platform provides a new strategy for the integration of tumor diagnosis and treatment through the multi-mechanism synergy of chemical kinetic therapy, gene silencing and chemotherapy.

Exploiting the atomistic tight-binding theory with the sp-d exchange term, the electronic and magnetic characteristics of CdSe nanoparticles embedded with Mn, Fe and Co are determined as a function of external magnetic fields to realize the sp-d exchange interactions. The transition metal species and applied magnetic fields are powerful factors to manipulate the electronic and magnetic characteristics of doped CdSe nanoparticles. With growing applied fields, the energies of spin splitting, Zeeman splitting and magnetic polaron improve and are assumed to reach saturation at high fields. All g-factor values are boosted in the presence of the external field and then fade with increasing applied fields. The electron spin-splitting energies and electron g values are ordered as Fe:CdSe > Mn:CdSe > Co:CdSe. The single-particle gaps, hole spin-splitting energies, Zeeman splitting energies and hole g values follow the order Co:CdSe > Fe:CdSe > Mn:CdSe.

Corrosion in harsh environments causes global economic losses exceeding 3 trillion US dollars annually. Traditional silicone epoxy (SE) coatings are prone to failure due to insufficient physical barrier properties and lack of active protection. In this study, cerium dioxide (CeO₂) was in situ grown on the surface of hexagonal boron nitride (h-BN) mediated by polydopamine (PDA) to prepare BN-PDA-CeO₂ ternary nanocomposites, which were then incorporated into SE coatings to construct a multi-scale synergistic corrosion protection system. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) confirmed the successful preparation of the composites, where PDA inhibited the agglomeration of h-BN and CeO₂ was uniformly loaded. Electrochemical tests showed that the corrosion inhibition efficiency of the extract of this composite for 2024 aluminum alloy reached 99.96%. After immersing the composite coating in 3.5 wt% NaCl solution for 120 days, the coating resistance (Rc) and charge transfer resistance (Rct) reached 8.5 × 10⁹ Ω·cm² and 1.2 × 10¹⁰ Ω·cm², respectively, which were much higher than those of pure SE coatings and coatings filled with single/binary fillers. Density functional theory (DFT) calculations revealed the synergistic mechanisms: PDA enhanced interfacial dispersion (adsorption energy of -0.58 eV), CeO₂ captured Cl^- (adsorption energy of -4.22 eV), and Ce³⁺ formed a passive film. This study provides key technical and theoretical support for the design of long-term corrosion protection coatings in harsh environments such as marine and petrochemical industries.