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Two-dimensional material-based photodetectors (PDs) show great potential owing to unique optoelectronic characteristics and attract much attention in research. However, poor absorption of two-dimensional material remains a vital restriction. Responsivity improvement by applying Au nanoparticles (NPs) through surface plasmon (SP) is studied both in theory and simulation. The effect of size and NPs distribution density is analyzed concerning absorption promotion and fabrication feasibility. Both absorption spectrum and inner electric field are studied. A novel face-to-face PD is proposed that performs better in visible range. The results can be helpful in two-dimensional material PD design and fabrication where high responsivity is required.

To form a tungsten disulfide film, a tungsten trioxide film is deposited first and then hydrogen sulfide is injected into the furnace tube to sulfide the tungsten trioxide film in a high-temperature environment. Due to the need to accurately control the thickness of tungsten trioxide, the power of the RF sputtering machine was reduced as much as possible in a stable condition in the experiment and the bias voltage during each process was monitored. In this experiment, a sapphire substrate and a silicon substrate with 200nm silicon dioxide are used. Then use optical instruments such as Raman optics, ellipsometers and high-resolution electron transmission microscopes, atomic force microscopes and other instruments for further measurement. The analysis results show that we have successfully made tungsten disulfide films of different thicknesses. Moreover, two-dimensional tungsten disulfide thin film has a response to light, gas and pH and related devices have been successfully fabricated in experiments. Among them, comparing the single-layer film and the double-layer film, the film quality of the double-layer film is better. The quality of the film grown on the sapphire substrate is also better than the quality of the film grown on the silicon dioxide substrate.

We report a systematic study of large-scale growth of high-quality WSe₂ atomic layers directly on SiO₂/Si substrates using a convenient method. Various parameters, especially growth temperatures, flow rate of carrier gas and tube pressure, are investigated in affecting the properties of as-grown WSe₂ flakes in terms of their sizes, shapes and thickness. The pre-annealing step is demonstrated to be a key role in achieving the large-scale growth. Under an optimized condition, the lateral size of triangular single-crystal monolayer WSe₂ is up to 30 $\mu$m and the area of the monolayer thin film can be up to 0.25 mm². And some other interesting features, such as nanoflowers, are observed, which are a promising for catalyzing research. Raman spectrum and microphotoluminescence indicate distinct layer dependent efficiency. Auger electron spectroscopy (AES) studies demonstrate the atomic concentration of the as-grown WSe₂. Electrical transport further shows that the $p$-type WSe₂ field-effect transistors exhibit excellent electrical properties with carrier mobility of $\sim$64 cm${}^2\cdot$V${}^{-1}\cdot$s${}^{-1}$ and current on/off ratio over 10⁵. These results are comparable to the exfoliated materials.

Dopamine (DA) is a crucial molecule for the central nervous system, and the ability to detect it in samples containing molecules such as Ascorbic Acid (AA) and Uric Acid (UA) could facilitate early diagnosis of related disorders. In this work, the interaction of DA, UA, and AA with InBi and Graphene (GR) monolayers under charging was investigated using Density Functional Theory (DFT) calculations with van der Waals (vdW) correction and nonequilibrium Green’s function method for the first time. According to our calculations, the most influential factor in the interaction was observed to arise from the $\pi$–$\pi$ and $\pi$–O interaction between molecules and surfaces. It has been concluded that InBi is a better adsorbent than GR for DA, AA, and UA, where the adsorption energies from the highest to lowest were found as $\mathrm{\text{UA}}>\mathrm{\text{AA}}>\mathrm{\text{DA}}$. Furthermore, the charge transfers between molecules and surfaces were investigated, and it was demonstrated that the molecules on GR act as charge acceptors. In contrast, for InBi–molecule systems, electronic drift from molecules to the InBi surface was observed. The Partial Density of States (P-DOS) plots were examined, and the results were discussed in detail. The consequences of adding/removing charges to/from the systems were also examined, and it was shown that removing $Q=2$e/cell from the GR–molecule systems effectively detected DA molecules from the others. Charging also broke the topological state of InBi, leading to semiconductor to metal, except for the $Q=-2$e/cell case. Finally, the changes in transmittance due to adsorption were simulated, and our results show that InBi is a possible candidate for DA sequencing biosensor applications compared to GR. The findings of this work provide a theoretical framework for the development and creation of highly precise biodevices and biosensors.

Type A molecular sieves have been extensively employed in various fields. It is noteworthy that the direct synthesis of type A molecular sieves from natural kaolin is a common practice among researchers. Traditional type A molecular sieves are characterized by a three-dimensional cubic lattice structure. In this study, our objective is to facilitate the transformation of type A molecular sieves into a two-dimensional layered configuration by employing a two-dimensional layered material as a templating agent. In this research, natural kaolin serves as the primary source material. To eliminate impurities including quartz, illite, and dolomite, an alkali-based solvent extraction method is employed, yielding amorphous silicon and aluminum compounds. Subsequently, a graphene-based templating agent is introduced, and a hydrothermal synthesis process is employed to fabricate two-dimensional type A molecular sieves. The method described herein yields two-dimensional layered type A molecular sieves with a crystallinity exceeding 90%, thereby resulting in a specific surface area that is approximately 11-fold greater compared to their three-dimensional type A counterparts. The applicability of this methodology can be extended to the valorization of low-grade natural mineral resources, optimizing their utility. Furthermore, the approach presented herein for the synthesis of two-dimensional molecular sieves is of a universal nature, offering valuable insights that can serve as a reference for the synthesis of various other categories of two-dimensional molecular sieves.

Herein, we report on a novel two-dimensional (2D) material application, which shows that an accordion-like layered Ti₃C₂ nanomaterial (MXene) with an excellent adsorption capacity of Cr(VI) from aqueous solution was prepared by etching Al layer from Ti₃AlC₂ phase in hydrofluoric acid (HF) solution. Ti₃C₂ nanopowders were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the physical property of as-obtained samples was studied by UV–Vis diffuse reflectance spectra (DRS). After HF treatment, Ti₃AlC₂ not only has a phase transition from one crystal to another, but surprisingly, its microstructure is also undergoing an obvious change. Ti₃C₂ with product of change possesses an accordion-like multilayer structure, and a relatively higher specific surface area (SSA) than untreated Ti₃AlC₂. Then, accordion-like Ti₃C₂ with a high SSA provides abundant active sites for pollutant removal and functionalization. Accordion-like Ti₃C₂ nanomaterial exhibits a stable adsorption capacity, and 1g as-prepared accordion-like Ti₃C₂ powders can remove about 80mg potassium dichromate. Therefore, the results suggest that 2D MXenes are promising as an effective nanoadsorbent in heavy metal removal from the wastewater.

Nanopore-based devices are emerging as unique technique for fast and high-resolution detection of DNA bases. Recently, the two-dimensional (2D) materials have been identified as promising materials for nanopore devices due to its high sensitivity and label-free sensing of DNA bases. It is really challenging to transfer nanoscale film structure onto target substrates to fabricate nanopore devices of 2D materials. Herein, we report a mild and efficient transfer method based on the mediator of poly-propylene carbonate and elastic stamp. Through this method, most of the 2D materials are able to be transferred onto fragile substrates without hurting the substrate. Experimental observation shows that fabricated nanostructures adhere to the surface of substrates closely free of wrinkles and bubbles. Moreover, this method enables the fabrication of multilayered structures of complimentary 2D materials and offers the potential method to fabricate functionalized devices.