Nanotechnology最新文献

Carbon-based nanostructures have unparalleled electronic properties. At the same time, using an allotrope of carbon as the contacts can yield better device control and reproducibility. In this work, we simulate a single-electron transistor composed of a segment of a graphene nanoribbon coupled to carbon nanotubes electrodes. Using the non-equilibrium Green's function formalism we atomistically describe the electronic transport properties of the system including electron-electron interactions. Using this methodology we are able to recover experimentally observed phenomena, such as the Coulomb blockade, as well as the corresponding Coulomb diamonds. Furthermore, we separate the different contributions to transport and show that incoherent effects due to the interaction play a crucial role in the transport properties depending on the region of the stability diagram being considered.

A kind of antistatic coatings which were applied to nonconductive surfaces were prepared with Polytetrafluoroethylene (PTFE) as matrix, modified carbon black (CB) as conductive filler. Compared to sodium dodecyl sulfate, poly(vinyl pyrrolidone), the TMN-10 modified CB has better wettability, dispersion, stability and re-disperse. When CB_TMN-10content is 5 wt.%, the surface resistivity of coating reach to 10⁶Ω*cm, which denotes the coating performance good antistatic behavior. The antistatic coating of 5 wt.% CB_TMN-10content is found to exhibit excellent hydrophobicity and high HV hardness. Meanwhile, the low average friction coefficients and wear rate were achieved in antistatic coating of 5 wt.% CB_TMN-10content. Furthermore, compared to MXene, reduced graphene oxide, carbon nanotube, the modified CB as conductive material in PTFE antistatic materials could be an useful way not only excellent properties but also large-scale production as well as a reduction in unit cost in antistatic materials.

Elongated akaganéite (β-FeOOH) nanoparticles were prepared by a forced hydrolysis route using FeCl₃·6H₂O employing various urea concentrations.β-FeOOH nanoparticles stabilized within the SiO₂matrix were annealed at different temperatures, ranging from 500 °C to 1300 °C. It was observed thatβ-FeOOH underwent a temperature-induced conversion toγ-Fe₂O₃and subsequently toϵ-Fe₂O₃. Due to theϵ-Fe₂O₃phase formation, the coercivity rapidly increased to 16 kOe for samples annealed at 900 °C and reached values up to 21.5 kOe when annealed at 1200 °C. At a higher temperature of 1300 °C, theϵ-Fe₂O₃phase transforms mainly into theα-Fe₂O₃phase, which causes the coercivity to rapidly drop to negligible values.

As a result of enormous progress in nanoscale electronics, interest in artificial intelligence (AI) supported systems has also increased greatly. These systems are typically designed to process computationally intensive data. Parallel processing neural network architectures are particularly noteworthy for their ability to process dense data at high speeds, making them suitable candidates for AI algorithms. Due to their ability to combine processing and memory functions in a single device, memristors offer a significant advantage over other electronic platforms in terms of area scaling efficiency and energy savings. In this study, single-layer and bilayer metal-oxide HfO_xand TiO_ymemristor devices inspired by biological synapses were fabricated by pulsed laser and magnetron sputtering deposition techniques in high vacuum with different oxide thicknesses. The structural and electrical properties of the fabricated devices were analysed using x-ray reflectivity, x-ray photoelectron spectroscopy, and standard two-probe electrical characterization measurements. The stoichiometry and degree of oxidation of the elements in the oxide material for each thin film were determined. Moreover, the switching characteristics of the metal oxide upper layer in bilayer devices indicated its potential as a selective layer for synapse. The devices successfully maintained the previous conductivity values, and the conductivity increased after each pulse and reached its maximum value. Furthermore, the study successfully observed synaptic behaviours with long-term potentiation, long-term depression (LTD), paired-pulse facilitation, and spike-timing-dependent plasticity, showcasing potential of the devices for neuromorphic computing applications.

Despite all the advancements in aqueous synthesis of gold nanoparticles, certain features like one-pot/one-step method with minimal reactants using greener solvents are still demanding. The challenge in the aqueous phase synthesis is to balance the nucleation and precise growth of nanoparticles avoiding aggregation. In this work, we report a unique versatile unexplored molecule aminosalicylate sodium (Na-4-ASA) which functions as a capping, reducing, stabilizing and more interestingly as an encapsulating agent for gold nanoparticles. This multi-faceted molecule showed excellent control in synthesizing monodisperse tunable encapsulated nanoparticles of sizes (60 nm, 53 nm and 12 nm) exhibiting absorbance bands at 560 nm, 540 nm and 520 nm respectively. X-ray diffraction and Fourier Transmission Infra-Red validated crystalline structure and binding of Na-4-ASA onto gold nanoparticles surface respectively. Furthermore, the AuNPs were investigated for their ability to detect metal ions through colorimetric change where purification via centrifugation turned out to be a key parameter in enabling the detection. Selectivity towards Al³⁺was observed with the 12 nm sized nanoparticles at 0.5 ppm metal ion concentration. The AuNPs of sizes 60 nm and 53 nm detected Al³⁺/Cr³⁺/Fe³⁺and Al³⁺/Fe³⁺respectively indicating the impact of size in heavy metal ions detection. The greater the size of AuNPs, lower is the selectivity where detection of three metal ions were observed and vice versa i.e. smaller-sized AuNPs showed high selectivity by detecting single metal ion. Also, the time duration for detection increased with decreasing size of the AuNPs. Finally, LOD for the heavy metal ions Al³⁺, Cr³⁺, and Fe³⁺were calculated as 67 ppb, 78 ppb, 76 ppb respectively.

Nanoscale materials tend to have a single crystal domain, leading to not only size dependence but also orientation dependence of their mechanical properties. Recently, we developed a microscopic nanomechanical measurement method (MNMM), which enabled us to obtain equivalent spring constants (force gradients) of nanocontacts (NCs) while observing their atomic structures by transmission electron microscopy (TEM). Therein, we evaluated Young's modulus based on a model that a newly introduced layer at the thinnest section of a NC determined the change in the measured equivalent spring constant, and discussed their size dependence. However, this model is not general for other nanomaterials that do not exhibit the introduction of a new atomic layer while stretching. In this study, using MNMM, we propose a new analytical method to directly retrieve the local Young's modulus of nanomaterials by measuring initial lattice spacing and its displacement of a local region in the TEM image during the stretching of the NC. This reveals the size dependence of local Young's modulus at various positions of the NC at once. As a result, our estimated Young's modulus for a gold [111] NC showed a size dependence similar to the one previously reported. This indicates that this analytical method benefits in revealing the mechanical properties of not only nanomaterials but also structurally heterogeneous materials such as high-entropy alloys.

Using a first-principles approach, this study delves into the effects of strain and electrostatic doping on the electronic and magnetic properties of the GaN/VTe₂van der Waals (vdW) heterostructure. The results reveal that when the GaN/VTe₂vdW heterostructure is doped with 0.1h/0.2hof electrostatic charge, its magnetization direction undergoes a remarkable reversal, shifting from out-of-plane orientation to in-plane direction. Therefore, we conduct a thorough investigation into the influence of electron orbitals on magnetic anisotropy energy. In addition, as the strain changes from -1% to 1%, the 100% spin polarization region of the GaN/VTe₂vdW heterostructure becomes smaller. It is worth noting that at a doping concentration of 0.1h, the GaN/VTe₂vdW heterostructure has a Curie temperature of 30 K above room temperature. This comprehensive study provides valuable insights and provides a reference for analyzing the electronic and magnetic properties of low-dimensional systems.

To address the issue of low yield in the preparation of nanofiber materials using single-needle electrospinning technology, multi-needle electrospinning technology has emerged as a crucial solution for mass production. However, the mutual interference of multiple electric fields between the needles can cause significant randomness in the morphology of the produced nanofibers. To better predict the influence of electric field distribution on nanofiber morphology, simulation analysis of the multi-needle arrangement was conducted using finite element analysis (FEA) software. Nanofiber-coated yarn was produced continuously with the core yarn rotating. The water bath was utilized as the receiver of nanofibers on self-made water bath electrospinning equipment. The electric field distribution and mutual interference under seven different needle arrangements was simulated and analyzed by FEA software ANSYS Maxwell. The results indicated that when the needles were arranged diagonally in a staggered pattern and directly above the core yarn, the simulated electric field distribution was relatively uniform, with less mutual interference. The produced nanofibers exhibited a finer diameter and the diameter distribution was more concentrated. In addition, the nanofiber coating showed higher crystallinity and better mechanical properties.

In this paper, we present the design and fabrication of a plasmonic metasurface based on titanium dioxide (TiO₂) nanowire arrays integrated with plasmonic layers. The structure is engineered to produce Fano resonances within the visible spectrum, resulting from the coupling of localized surface plasmon resonances, lattice modes, and nanowire's optical modes. Experimentally, we show that by tuning the geometrical features of the metasurface, such as the length, diameter, and period of the nanowires, a high-quality factor single peak can be achieved in the reflection spectra, resulting in vivid structural colors in bright field. To our knowledge, this is the first demonstration of such vivid colors with nanowire arrays in bright field reflections. When characterized by refractive index fluids around the refractive index of water, the plasmonic metasurface also showed great potential for biochemical colorimetric sensing. The best design demonstrated a bulk sensitivity of 183 nm/RIU with high Q resonance features and linear changes in color values using image processing.

We have studied the impact of nanowire alignment and measurement direction at the percolation threshold on the effective resistance (R) of two-dimensional (2D) films. This helps us to analyze the effect of anisotropy on the conductivity and transmittance of the nanowire-based network characterized by the disorder parameter (s). These optoelectronic properties are determined for systems with monodisperse and bimodal length distribution (a combination of two fixed lengths of nanowires). The 2D systems simulated using our computational approach are assumed to be transparent and conductive in which percolative transport is the primary conduction mechanism. We obtain our results numerically using a computational and geometrical approach, i.e. a Discrete (grid) method that is advantageous in algorithm speed. For a particular disorder parameters, the conductivity and transmittance increase as the length fraction (LF) increases for the bimodal distribution of the length of nanowires in networks. We have observed the maximum conductivity when the nanowires are highly aligned along the measurement direction of percolation, in contrast to the isotropic arrangement of nanowires. Significantly, alignment introduced in nanowires leads to a higher percolation threshold which leads to a decrease in the transmittance of the network. We show that the resistivity of the monodisperse network in the direction parallel (perpendicular) to the alignment decreases (increases) with the disorder parameter and scales ass(s²). This scaling holds true for the bimodal distribution of nanowires as well. For a particularLF, the electrical anisotropy increases withs. The anisotropy is maximum for nearly aligned nanowires in a bimodal network with the highest proportion of the longest wire considered. For the maximally aligned wires and highestLF, we obtained an approximately 50%enhancement in the figure of merit, denoted byφ. Hence, incorporating longer-length wires and increasing the alignment in nanowire networks can increase the conductivity, anisotropy, and figure of merit which may benefit a vast range of applications.