Nanotechnology最新文献

Most previously reported susceptors for microwave welding are in powder form. In this study, a thin-film susceptor was employed due to its uniform heating rate and ease of handling. Silicon carbide nanowhisker (SiCNW) were incorporated into a poly(methyl methacrylate) (PMMA) matrix to create a nanocomposite thin film, which served as the susceptor. The microwave welding process involved three straightforward steps: fabrication of the PMMA/SiCNW nanocomposite thin film, application of the nanocomposite film to the target area, and subsequent microwave heating. Upon cooling, a robust microwave-welded joint was formed. The mechanical properties and microstructure of the welded joints were characterized using single-lap shear tests, three-point bending tests, and scanning electron microscopy. Results demonstrated that the shear strength and elastic modulus of the welded joints were optimized with increased heating time and SiCNW filler loading. This optimization is attributed to the formation of a SiCNW-filled polypropylene (PP) nanocomposite layer of increasing thickness at the welded joint interface. However, the incorporation of SiCNW also constrained the mobility of the PP chains, reducing the joint's flexibility. Furthermore, the welded joint formed with the PMMA/SiCNW nanocomposite thin-film susceptor exhibited an 18.82% improvement in shear strength compared to joints formed with a powdered SiCNW susceptor. This study not only demonstrates the potential of PMMA/SiCNW nanocomposite thin films as efficient susceptors for microwave welding but also paves the way for developing high-performance polymer-based composite joints with improved mechanical properties for applications in the automotive, aerospace, and construction industries.

Large area graphene patterning is critical for applications. Current graphene patterning techniques, such as electron beam lithography and nano imprint lithography, are time consuming and can scale unfavorably with sample size. Resist-based masking and subsequent dry plasma etching can lead to high roughness edges with no alignment to the underlying graphene crystal orientations. In this study, we present hot punching as a novel and feasible method for patterning of chemical vapor deposition (CVD) graphene sheets supported by a polyvinylalcohol (PVA) layer. Additionally, we observe the effect of such hot punching on graphene supported by PVA via optical microscopy, Raman spectroscopy, AFM, and TEM, including wrinkling, strain and the formation of nanoribbons with crystallographically aligned and smooth edges due to fracturing. We present hot punching as a facile technique for the production of arrays of such nanoribbons.

This research investigates the eco-friendly production of iron oxide nanoparticles and their combination with carbon to create the FeC-1 and FeC-2 NPs, using seedless pods ofAcacia nilotica. These pods, rich in tannins and flavonoids, serve as a natural reducing, stabilizing, and carbon source. The study details the synthesis of FeC NPs through a non-toxic, green method and examines the influence of varying concentrations ofA. niloticaextract (ANE) on the electrochemical characteristics of the resulting n FeC-1 and FeC-2 electrodes. Both FeC-1 and FeC-2 NPs were tested extensively using cyclic voltammetry and galvanostatic charge-discharge methods to evaluate their pseudocapacitive properties in a three-electrode setup. The FeC-2 electrodes showed much better performance, achieving a specific capacitance of 482.85 F g^-1, compared to FeC-1's 155.71 F g^-1. This enhanced capacity is attributed to an optimal content that notably boosts conductivity. Additionally, FeC-2 showed impressive cyclic stability, retaining approximately 80% capacity at a constant current density. These findings underscore the potential of using ANE for developing cost-effective and environmentally benign FeC-1 and FeC-2 NPs with promising applications in high-performance supercapacitors.

Sapphire is an attractive material in photonic, optoelectronic, and transparent ceramic applications that stand to benefit from surface functionalization effects stemming from micro/nanostructures. Here we investigate the use of ultrafast lasers for fabricating nanostructures in sapphire by exploring the relationship between irradiation parameters, morphology change, and selective etching. In this approach an ultrafast laser pulse is focused on the sapphire substrate to change the crystalline morphology to amorphous or polycrystalline, which is characterized by examining different vibrational modes using Raman spectroscopy. The irradiated regions are then removed using a subsequent wet etch in hydrofluoric acid. Laser confocal measurements conducted before and after the etching process quantify the degree of selective etching. The results indicate that a threshold laser pulse intensity is required for selective etching to occur. This process can be used to fabricate hierarchical sapphire nanostructures over large areas with enhanced hydrophobicity, which exhibits an apparent contact angle of 140 degrees and a high roll-off angle that are characteristic of the rose petal effect. Additionally, the fabricated structures have high broadband diffuse transmittance of up to 81.8% with low loss, which can find applications in optical diffusers. Our findings provide new insights into the interplay between the light-matter interactions, where Raman shifts associated with different vibrational modes can be used as a predictive measure of selective etching. These results advance the development of sapphire nanostructure fabrication, which can find applications in infrared optics, protective windows, and consumer electronics. .

We investigate the electronic properties of nanoribbons made out of monolayer Lieb, transition, and kagome lattices using the tight-binding model with a generic Hamiltonian. It allows us to map the evolutionary stages of the interconvertibility process between Lieb and kagome nanoribbons by means of only one control parameter. Results for the energy spectra, the density of states, and spatial probability density distributions are discussed for nanoribbons with three types of edges: straight, bearded, and asymmetric. We explore for different nanoribbon terminations: (i) the semiconductor-metallic transition due to the interconvertibility of the Lieb and kagome lattices, (ii) the effect of both nanoribbon width and inclusion of the next-nearest-neighbor hopping term on the degeneracy of the quasi-flat states, (iii) the behavior of the energy gap versus the nanoribbon width, (iv) the existence and evolution of edge states, and (v) the nodal spatial distributions of the total probability densities of the non-dispersive states.

In this work, a novel composite anode material was developed, utilizing S-doped graphene oxide (SGO), polypyrrole (PPy), and fumed silica to enhance the performance of lithium-ion batteries (LIBs). The chronoamperometric approach was used to produce SGO, while the chemical method was employed to synthesize PPy. A composite of SGO, PPy, and fumed silica was prepared as an anode for a half-cell, using two samples: one with a high PPy ratio (S1) and the other with a low PPy ratio (S2) and compared the results with bare sample (S0). The S1 sample exhibited a good initial discharge capacity (648 mAh g^-1), with capacities of 207 and 131 mAh g^-1at 5 C and 10 C, respectively. S1 and S2 also demonstrated superior cycling stability at a high current (100 cycles at 10 C), with a retention capacity of 99 and 87%, respectively compared with S0 which retained only 68%. Coin-type full cells with S1 as the anode and LiFePO₄(LFP) as the cathode were assembled and compared with commercial graphite anodes. The S1 full cell showed a high reversible capacity (164 mAh g^-1at 0.1 C), with a capacity retention of 66% after 100 cycles at 10 C. At the same time, the graphite anode exhibited a reversible capacity of 133 mAh g^-1at 0.1 C, with a capacity retention of 58% after 100 cycles at 10 C. The S1 full cell achieved a gravimetric energy density of 164 W h kg^-1at 0.1 C and 49 W h kg^-1at 10 C, which is 25% greater than that of the graphite full cell(39 W h kg^-1) at 10 C. These distinguishing characteristics of S1 make it a viable substitute for graphite as a high-performance anode material in LIBs, opening the possibility for devices with reliable battery systems.

The present work describes the synthesis of WO₃-BiVO₄-nanoflakes heterostructure (NFHs) by a single step hydrothermal method. The analysis of crystalline phases and structural behavior deduced the formation of good crystal quality WO₃-BiVO₄NFHs. Under microscopic observation, the as-prepared WO₃-BiVO₄displayed uniform and conspicuous nanoflakes like structures. The extensive density functional theory was studied to examine the electronic and band structures of as-prepared WO₃-BiVO₄NFHs in terms of formation energy, charge density, density of state and band structures. The synthesized WO₃-BiVO₄NFHs was used as sensing electrode towards the detection of ethylenediamine (EDA) chemical that displayed a good sensitivity of ∼318.52 mA·mM^-1cm^-2, excellent dynamic range of 1μM-1 mM with detection limit of ∼94.51 nM and retention coefficient of ∼0.9929. WO₃-BiVO₄NFHs electrode possessed the good reproducibility, stability, and repeatability towards EDA chemical. To the best of our knowledge, for the first time, the fabricated chemical sensor fabricated with WO₃-BiVO₄NFHs electrode could be promising electrode materials to identify dangerous chemicals at very low concentration in environment. Importantly, the fabricated chemical sensor can be effective for environmental monitoring.

Surface-induced crystallization/amorphization of a Germanium-antimony-tellurium nanolayer is investigated using the phase field model. A Ginzburg-Landau (GL) equation introduces an external surface layer (ESL) within which the surface energy and elastic properties are adequately distributed. Next, the coupled GL and elasticity equations for the crystallization/ amorphization are solved. For the initial surface crystalline nucleus, unphysical crystallization along the ESL appears for the ESL widthΔξ⩾2nmwhile oval growth occurs forΔξ⩽1nm. The ESL results in a faster surface nucleus growth than the sharp surface model but does not affect the crystallization rate inside the bulk. Initial homogeneous conditions cause a simultaneous crystallization in the bulk and later in the ESL. The ESL effect on amorphization is studied to determine the ESL width more precisely. For both the initial amorphous nucleus and homogenous conditions, the amorphization temperature shows a reduction from the sharp surface model to the ESL model withΔξ=0.5nmand then remains almost constant for largerΔξ. Combining the above results gives0.5⩽Δξ⩽1nmas a proper range for the ESL width. The ratio of the effective ESL width to the interface width (Δsat/Δη) and the ratio of the difference between the surface energies of transforming phases to the surface energy of the initial phase (Δγ/γin) are considered crucial parameters in determining the ESL effect on the phase transformation and a linear relation asΔsat/Δη≅6.235Δγ/γinis found based on current and previous works, which can help estimate the effective ESL width for any surface-induced transformations.

Anti-ambipolar transistors (AAT) are considered as a breakthrough technology in the field of electronics and optoelectronics, which is not only widely used in diverse logic circuits, but also crucial for the realization of high-performance photodetectors. The anti-ambipolar characteristics arising from the gate-tunable energy band structure can produce high-performance photodetection at different gate voltages. As a result, this places higher demands on the parametric driving range (ΔVg) and peak-to-valley ratio (PVR) of the AAT. Here, we demonstrate a high-performance photodetector with anti-ambipolar properties based on a van der Waals heterojunction of MoTe2/MoS2. Flexible modulation of carrier concentration and transport by gate voltage achieves a driving voltage range ΔVg as high as 38.4 V and a peak-to-valley ratio PVR of 1.6 × 102. Most importantly, MoTe2/MoS2 exhibits a pronounced gate-tunable photoresponse, which is attributed to the modulation of photogenerated carrier transport by gate voltage. The MoTe2/MoS2 heterojunction photodetector exhibits excellent performance, including an impressive responsivity of 17 A/W, a high detectivity of 4.2 × 1011 cm Hz1/2 W-1, an elevated external quantum efficiency of 4 × 103 %, and a fast response time of 21 ms. Gate-tunable photodetectors based on MoTe2/MoS2 heterostructures AAT have potential to realize optoelectronic devices with high performance, providing a novel strategy to achieve high-performance photodetection.

Accurate and rapid diagnosis of traumatic brain injury (TBI) is essential for high-quality medical services. Nonetheless, the current diagnostic platform still has challenges in rapidly and accurately analysing clinical samples. Here, we prepared a highly stable, repeatable and sensitive gold-plated silver core-shell nanowire (Ag@AuNWs) for surface-enhanced Raman spectroscopy (SERS) metabolic fingerprint diagnosis of TBI. The core-shell structure significantly enhanced SERS intensity and enables the direct detection of 10 μL serum within seconds. The principal component analysis-linear discriminant analysis (PCA-LDA) and partial least squaresdiscriminant analysis (PLS-DA) are used to evaluate the classification effect of this technology on TBI, respectively. The diagnosis accuracy rate of PCA-LDA and PLS-DA is 73.3% and 86.7% for diagnosing TBI, respectively. Consequently, the PLS-DA model is the optimal selection for distinguishing between the TBI and sham groups. This research will facilitate the application-oriented creation of novel materials with tailored structural designs and the formulation of innovative precision medical protocols in the imminent future. .