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Title: Scalable Fabrication of Molybdenum Disulfide Nanostructures and their Assembly

Molybdenum disulfide (MoS2) is a multifunctional material that can be used for various applications. In the single‐crystalline form, MoS2shows superior electronic properties. It is also an exceptionally useful nanomaterial in its polycrystalline form with applications in catalysis, energy storage, water treatment, and gas sensing. Here, the scalable fabrication of longitudinal MoS2nanostructures, i.e., nanoribbons, and their oxide hybrids with tunable dimensions in a rational and well‐reproducible fashion, is reported. The nanoribbons, obtained at different reaction stages, that is, MoO3, MoS2/MoO2hybrid, and MoS2, are fully characterized. The growth method presented herein has a high yield and is particularly robust. The MoS2nanoribbons can readily be removed from its substrate and dispersed in solution. It is shown that functionalized MoS2nanoribbons can be manipulated in solution and assembled in controlled patterns and directly on microelectrodes with UV‐click‐chemistry. Owing to the high chemical purity and polycrystalline nature, the MoS2nanostructures demonstrate rapid optoelectronic response to wavelengths from 450 to 750 nm, and successfully remove mercury contaminants from water. The scalable fabrication and manipulation followed by light‐directed assembly of MoS2nanoribbons, and their unique properties, will be inspiring for device fabrication and applications of the transition metal dichalcogenides.

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Award ID(s):
1710922 1563382 1930649
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Materials
Medium: X
Sponsoring Org:
National Science Foundation
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  2. Abstract

    The removal of heavy metal contaminants from water is important for public health, and recently many two-dimensional (2D) materials with high specific surface areas are being studied as promising new active components in water purification. In particular, 2D MoS2nanosheets have been used for the removal of various heavy metals, but usually in either in complex geometries and composites, or in the chemically exfoliated metallic 1T-MoS2phase. However, the interaction of heavy metals dissolved in water with unmodified semiconducting 2H-MoS2is not well studied. In this paper, we report a detailed fundamental investigation of how Pb2+ions interact with 2H-MoS2. We observe small solid clusters that form on the MoS2surfaces after exposing them to Pb(NO3)2aqueous solutions as shown by atomic force microscopy and transmission electron microscopy, and for liquid phase exfoliated MoS2we observe the nanosheets precipitating out of dispersion along with insoluble solid granules. We use a combination of x-ray photoelectron spectroscopy and x-ray diffraction to identify these solid clusters and granules as primarily PbSO4with some PbMoO4. We put forth an interaction mechanism that involves MoS2defects acting as initiation sites for the partial dissolution in aqueous oxygenated conditions which produces MoO42−and SO42−ions to form the solids with Pb2+. These results are an important contribution to our fundamental understanding of how MoS2interacts with metal ions and will influence further efforts to exploit MoS2for water remediation applications.

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  4. Abstract

    In recent years, the excitation of surface phonon polaritons (SPhPs) in van der Waals materials received wide attention from the nanophotonics community. Alpha-phase Molybdenum trioxide (α-MoO3), a naturally occurring biaxial hyperbolic crystal, emerged as a promising polaritonic material due to its ability to support SPhPs for three orthogonal directions at different wavelength bands (range 10–20μm). Here, we report on the fabrication, structural, morphological, and optical IR characterization of large-area (over 1 cm2size)α-MoO3polycrystalline film deposited on fused silica substrates by pulsed laser deposition. Due to the random grain distribution, the thin film does not display any optical anisotropy at normal incidence. However, the proposed fabrication method allows us to achieve a singleα-phase, preserving the typical strong dispersion related to the phononic response ofα-MoO3flakes. Remarkable spectral properties of interest for IR photonics applications are reported. For instance, a polarization-tunable reflection peak at 1006 cm−1with a dynamic range of ΔR= 0.3 and a resonanceQ-factor as high as 53 is observed at 45° angle of incidence. Additionally, we report the fulfillment of an impedance matching condition with the SiO2substrate leading to a polarization-independent almost perfect absorption condition (R< 0.01) at 972 cm−1which is maintained for a broad angle of incidence. In this framework our findings appear extremely promising for the further development of mid-IR lithography-free, scalable films, for efficient and large-scale sensors, filters, thermal emitters, and label-free biochemical sensing devices operating in the free space, using far-field detection setups.

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  5. ABSTRACT Scalable synthesis of two-dimensional molybdenum disulfide (MoS 2 ) via chemical vapor deposition (CVD) is of considerable interests for many applications in electronics and optoelectronics. Here, we investigate the CVD growth of MoS 2 single crystals on sapphire substrates by using thermally evaporated molybdenum trioxide (MoO 3 ) thin films as molybdenum (Mo) source instead of conventionally used MoO 3 powder for co-evaporation synthesis. The MoO 3 thin film source provides uniform Mo vapor pressure in the growth chamber resulting in clean and reproducible MoS 2 triangles without any oxide or oxysulfide species. Scanning electron microscopy, Raman spectroscopy, photoluminescence spectroscopy and atomic force microscopy characterization were performed to characterize the growth results. Very high photoluminescence (PL) response was observed at 1.85 eV which is a good implication of high optical quality of these crystals directly grown on sapphire substrate. 
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