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As an emerging class of two-dimensional (2D) layered nanomaterial, MXene exhibits a number of intriguing properties, such as good electrical conductivity and high elastic modulus, and has witnessed continued growth in related device research. However, nanoscale MXene devices which leverage both the intrinsic electrical and mechanical properties of these 2D crystals have not been experimentally studied. Here we demonstrate nanoelectromechanical resonators based on 2D MXene crystals, where Ti3C2Tx drumheads with a wide range of thickness, from more than 50 layers all the way down to a monolayer, exhibit robust nanomechanical vibrations with fundamental-mode frequency f0 up to >70 MHz in the very high frequency (VHF) band, a displacement noise density down to 52 fm/Hz1/2, and a fundamental-mode frequency-quality factor product up to f0 × Q ≈ 6.85 × 109 Hz. By combining experimental results with theoretical calculations, we independently derive the Young's modulus of 2D Ti3C2Tx crystals to be 270-360 GPa, in excellent agreement with nanoindentation measurements, based on which we elucidate frequency scaling pathways toward microwave frequencies. We further demonstrate electrical tuning of resonance frequency in MXene resonators and frequency-shift-based MXene vacuum gauges with responsivity of 736%/Torr and detection range down to 10-4 Torr. Our study can lead to the design and creation of nanoscale vibratory devices that exploit the intrinsic electrical and mechanical properties in 2D MXene crystals.

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Nanomechanical resonators based on atomic layers of tungsten diselenide (WSe2) offer intriguing prospects for enabling novel sensing and signal processing functions. The frequency scaling law of such resonant devices is critical for designing and realizing these high-frequency circuit components. Here, we elucidate the frequency scaling law for WSe2 nanomechanical resonators by studying devices of one-, two-, three-, to more than 100-layer thicknesses and different diameters. We observe resonant responses in both mechanical limits and clear elastic transition in between, revealing intrinsic material properties and devices parameters such as Young's modulus and pretension. We further demonstrate a broad frequency tuning range (up to 230%) with a high tuning efficiency (up to 23% V-1). Such tuning efficiency is among the highest in resonators based on two-dimensional (2D) layered materials. Our findings can offer important guidelines for designing high-frequency WSe2 resonant devices.

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In-plane anisotropy in 2D rhenium disulfide (ReS2 ) offers intriguing opportunities for designing future electronic and optical devices, and toward such applications, it is crucial to identify the crystal orientation in such 2D anisotropic materials. Existing spectroscopy or electron microscopy methods for determining the crystalline orientation often require complicated sample preparing procedures and specialized equipment, which could sometimes limit their application. In this work, a dichromatic polarized reflectance method is demonstrated, which can quickly and accurately resolve the crystal orientation (Re-Re chain) in 2D ReS2 crystals with different thicknesses. Furthermore, it can be readily extended to multi-chromatic schemes to achieve greater measurement capability and can be easily tailored to work for different 2D materials. The method offers a simple and effective approach for studying anisotropy in 2D materials.

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RESUMEN

In order to explore the efficacy of nanoantibiotics in rats with sepsis based on MicroRNA-195 and TGF-ß1/Smads signaling pathway, a total of 160 Wistar rats with sepsis were selected and randomly divided into 4 groups of general antibiotics (GA) treatment group and nanoantibiotics treatment (NT) group, MicroRNA-195 treatment (MT) group and TGF-ß1/Smads (TS) treatment group with 40 sepsis rates in each group. After each group was treated for 24 hours, the supernatant was centrifuged, the enzyme-labeled reagent was added to sample wall, the absorbance value of each well in sequence was measured, and the linear regression equation of the standard curve was calculated based on the concentration and absorbance value of the standard. Before and after the experiment, the changes in body weight, mental state, activity, respiration, and abdominal cavity of species rats in each group were observed and measured; the expression of Interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), TGF-ß1, Smad2, Smad3, Smad7 were recorded and analyzed. The results showed that the expression levels of IL-1, TNF-α, TGF-ß1, Smad2, Smad3 and Smad7 in sepsis rats in GA group were higher than those in the NT group (P < 0.05); the myocardial cells in MT group were significantly smaller and the cell arrangement was tighter and more orderly than those in TS group; and the expression levels of TNF-α, IL-6, TGF-ß1, Smad2, Smad3, and Smad7 were significantly reduced (P < 0.05). In summary, the MicroRNA-195 and TGF-ß1/Smads may promote cardiac remodeling in sepsis rats by up-regulating the nanoantibiotics signaling transduction pathway, thereby having objective curative effect on sepsis rats. The study results of this paper provide a reference for further research on the efficacy of nanoantibiotics in sepsis rats based on MicroRNA-195 and TGF-ß1/Smads signaling pathway.

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