Nanotechnology最新文献

Electron beam lithography is a critical technology for achieving high-precision nanoscale patterning. The presence of resist residues in the structures can significantly affect subsequent processes such as etching and lift-off. However, the evaluation and optimization of resist residues currently relies on qualitative observations like scanning electron microscopy (SEM), necessitating multiple experiments to iteratively optimize exposure parameters, which is not only labor-intensive but also costly. Here, we propose a quantitative method to evaluate resist residues. By processing the obtained SEM images using a threshold segmentation algorithm, we segmented the resist structure region and the residual resist region in the images. The grayscale values of these two regions are identified, and the residues are quantified based on the ratio of these values. Furthermore, a relationship curve between the residue amount and the exposure dose is plotted to predict the optimal exposure dose. To validate this method, we fabricated hydrogen silsesquioxane annular grating structures with 30 nm linewidth and analyzed the residue levels over an exposure dose range of 2000-2500μC cm^-2, predicting the optimal dose to be 1800μC cm^-2and confirming this through experiments. Additionally, we applied the method to polymethyl methacrylate and ZEP-520A structures, achieving similarly accurate results, further confirming the method's general applicability. This method has the potential to reduce experimental costs and improve yield and production efficiency in nano fabrication.

Two-dimensional materials are widely studied due to its unique physical, optical, electrical properties, and good compatibility with various synthesis methods. And among the many fabrication methods, tin disulfide (SnS₂) material, a two-dimensional (2D) material that can be achieved with accurate thickness control using atomic layer deposition (ALD), high uniformity and conformality even at low process temperatures is attracting attention. However, since the crystallinity of the thin film is low at a low process temperature, various post-annealing methods are being studied to compensate for film quality. In this work, we compared the crystal structures, chemical binding energies, and electrical properties of the thin films by post-annealing SnS₂thin films according to the hydrogen sulfide concentrations of 4.00% and 99.99% in the hydrogen sulfide atmospheres. The crystallinity, grain size, and carrier concentrations of the SnS₂thin film were the highest at a post-annealing temperature of 350 °C at a hydrogen sulfide concentration of 99.99%, and the chemical binding energies also corresponded with the standard Sn⁴⁺states, forming a pure 2D-hexagonal SnS₂phase. In addition, SnS₂thin films deposited via ALD showed high uniformity and conformality in large-scale wafers and trench structure wafers.

Investigating high-efficiency oxygen reduction reaction (ORR) catalysts is one of the most effective methods for addressing the sluggish kinetics at the fuel cell cathode. Bimetallic three-dimensional porous materials have garnered significant attention due to their diverse structures, large specific surface area and synergistic catalytic effects. Herein, we synthesized a bimetallic three-dimensional porous dodecahedral structure, Mn/Co-C-N, derived from MOF using a straightforward approach. Experimental reults confirm that the strategic incorporation of Mn enhances the electrocatalytic activity for ORR. Meanwhile, the synergistic effects of Mn and Co, as well as the advantages of the dodecahedral structure for expediting electron transfer, all contribute to the exceptional ORR performance. Arc testing in an alkaline electrolyte reveals that the initial potential (E_onset) and the half-wave potential (E_1/2) are 0.89 V and 0.80 V, closely approximating those of commercial Pt/C (20 wt%). Following 10 000 stability test cycles, the half-wave potential exhibits a mere 8 mV change, confirming its remarkable stability.

Aiming at finding wide-temperature-zone thermoelectric (TE) materials, five kinds of monolayer GeTe allotropes including the newly designedγ-,δ-, andɛ-GeTe monolayers and the usualα- andβ-GeTe ones are constructed. By using the density functional theory and the nonequilibrium Green's function method, all their electronic properties and TE transport properties are comparatively investigated. It is found that the room-temperature figure of meritZTof theγ-GeTe (ɛ-GeTe) along the armchair (zigzag) direction can amount to 4.5 (3.5), which is further increased to 7.15 (5.91) at 700 K. TheseZTvalues are much higher than the other IV-VI compounds usually withZT < 3, indicating that the armchairγ-GeTe and the zigzagɛ-GeTe we designed here can be used as superior wide-temperature-zone and high-performance TE materials in the temperature range from 300 K to 700 K. Moreover, with the increase of temperature, theZTpeaks will become wider in width and move towards the position of zero chemical potential, which will make the GeTe-based TE devices work at low bias voltages more efficiently. This work should be an important reference on the way to the stage ofZT⩾4, which will motivate more explorations into the high-performance TE materials working in a wider temperature scope.

We present a method that uses viscosity-lowering materials to fabricate flexible polydimethylsiloxane-based quantum dot (QD) films with high quantum yield (QY) and improved uniformity. We found that the aggregation of individual QDs was prevented, and the QY improved simultaneously in films that contained surfactants. These films showed an improved absorption of approximately 27% in the near-UV and blue light regions, along with an improved photoluminescence of approximately 18%, indicating improved light conversion from the UV to the visible frequency region.

The development of an effective and selective catalyst is the key to improving the multi-electron transfer nitrate reduction reaction (NO₃^-RR) to ammonia. Here, we synthesized a coherent NiS₂@SnS₂nanosheet catalyst loaded on carbon cloth via one-step solvothermal method. Experimental data reveals that the integration of NiS₂and SnS₂can enhance the NO₃^-RR performance in terms of high NH₃yield rate of 408.2μg h^-1cm^-2and Faradaic efficiency of 89.61%, as well as satisfying cycling and long-time stability.

Since the sensitivity and accuracy of traditional detection for early gastric cancer diagnosis are still insufficient, it is significant to continuously optimize the optical molecular imaging detection technology based on an endoscopic platform. The signal intensity and stability of traditional chemical fluorescent dyes are low, which hinders the clinical application of molecular imaging detection technology. This work developed a probe based on perovskite quantum dots (PQDs) and peptide ligands. By utilizing CsPbBr₃perovskite PQDs modified by azithromycin (AZI), combined with the specific polypeptide ligand of CD44v6, a gastric cancer biomarker, the perovskite-based probe (AZI-PQDs probe) which can specifically identify gastric cancer tumor was prepared. Owing to the high photoluminescence quantum yield of CsPbBr₃PQDs, the naked eye can observe the imaging under the excitation of the hand-held ultraviolet light source. AZI-PQDs probe can accurately identify gastric cancer cells, tissues, and xenograft models with experiments ofex vivoandin vivofluorescence imaging detection. It also exhibited low toxicity and immunogenicity, indicating the safety of the probe. This work provides a probe combined with cancer specificity and a reliable fluorescent signal that has the potential for application in gastric cancer optical molecular imaging.

Recently, various methods have been developed for synthesizing zinc oxide (ZnO) nanostructures, including physical and chemical vapor deposition, as well as wet chemistry. These common methods require either high temperature, high vacuum, or toxic chemicals. In this study, we report the growth of zinc oxide ZnO nanowires by a new hot water deposition (HWD) method on various types of substrates, including copper plates, foams, and meshes, as well as on indium tin oxide (ITO)-coated glasses (ITO/glass). HWD is derived from the hot water treatment (HWT) method, which involves immersing piece(s) of metal and substrate(s) in hot deionized water and does not require any additives or catalysts. Metal acts as the source of metal oxide molecules that migrate in water and deposit on the substrate surface to form metal oxide nanostructures (MONSTRs). The morphological and crystallographic analyses of the source-metals and substrates revealed the presence of uniformly crystalline ZnO nanorods after the HWD. In addition, the growth mechanism of ZnO nanowires using HWD is discussed. This process is simple, inexpensive, low temperature, scalable, and eco-friendly. Moreover, HWD can be used to deposit a large variety of MONSTRs on almost any type of substrate material or geometry.

Fingerprint patterns (or epidermal ridges) are by far one of the most reliable techniques for individual identification. Fingerprint patterns get deposited on all kinds of solid surfaces due to human transudation or exudation process. Bodily fluids through sweat glands contain moisture, natural oils and proteins. Since latent fingerprint patterns are not readily recognizable they are collected from a crime scene and are further processed physically or chemically. Fingerprints obtained using conventional black and white powders face severe drawbacks including low sensitivity, high background interference from the substrates, involvement of toxic materials, and poor stability. To overcome the above-listed issues, especially for coloured and transparent substrates, luminescent materials have emerged as potential agents for rapid visualization of high-contrast latent fingerprints. This review covers the recent advancements in luminescent nanomaterials of both kinds (up and down conversion) and persistent nanophosphors for developing latent fingerprints. Special emphasis has been given to an unusual class of luminescent materials known as persistent nanophosphors, which do not require a constant excitation, thereby completely eradicating background noise. The review also covers different approaches to gathering fingerprints such as powder dusting, cyanoacrylate fuming, ninhydrin fuming and vacuum metal deposition.

Molybdenum disulfide (MoS₂) is a representative two-dimensional layered transition-metal dichalcogenide semiconductor. Layer-number-dependent electronic properties are attractive in the development of nanomaterial-based electronics for a wide range of applications including sensors, switches, and amplifiers. MoS₂field-effect transistors (FETs) have been studied as promising future nanoelectronic devices with desirable features of atomic-level thickness and high electrical properties. When a naturallyn-doped MoS₂is contacted with metals, a strong Fermi-level pinning effect adjusts a Schottky barrier and influences its electronic characteristics significantly. In this study, we investigate multilayer MoS₂Schottky barrier FETs (SBFETs), emphasizing the metal-contact impact on device performance via computational device modeling. We find thatp-type MoS₂SBFETs may be built with appropriate metals and gate voltage control. Furthermore, we propose ambipolar multilayer MoS₂SBFETs with asymmetric metal electrodes, which exhibit gate-voltage dependent ambipolar transport behavior through optimizing metal contacts in MoS₂device. Introducing a dual-split gate geometry, the MoS₂SBFETs can further operate in four distinct configurations:p - p,n - n,p - n, andn - p. Electrical characteristics are calculated, and improved performance of a high rectification ratio can be feasible as an attractive feature for efficient electrical and photonic devices.