Strong quantum-size effects in a layered semiconductor:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MoS</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>nanoclusters

Wilcoxon, J. P.; Samara, G. A.

doi:10.1103/physrevb.51.7299

Cited by 223 publications

(151 citation statements)

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“…In addition, the blue shift observed in these peaks is consistent with the smaller lateral flake size following DGU (See Supplementary Fig. 9) [38][39][40][41] , and the strong absorption o400 nm is attributed to the density gradient medium (that is, iodixanol).…”

Section: ]supporting

confidence: 68%

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Kang¹,

Seo²,

et al. 2014

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Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS 2 ) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS 2 samples exhibit strong photoluminescence without further chemical treatment.

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Section: ]supporting

confidence: 68%

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Kang¹,

Seo²,

et al. 2014

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“…The exciton separation is due to the spin-orbit splitting of the valence band at the K point. Above a particle size of 8 -10 nm, the peaks are at bulk values [30]. This agrees with the transmission electron microscopy (TEM) measurements (see following text).…”

Section: Methodssupporting

confidence: 88%

Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS₂ nanoflakes

Singh

Pradeep

Bhattacharjee

et al. 2007

J. Am. Soc. Mass Spectrom.

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The Mo 13 clusters we previously reported were derived from MoS 2 flakes prepared from bulk MoS 2 , although the nature of the precursor species was not fully understood. The existence of the clusters in the condensed phase was a question. Here we report the preparation of MoS 2 nanoflakes from elemental precursors using the sonochemical method and study the gas-phase clusters derived from them using mass spectrometry. Ultraviolet-visible (UV-vis) spectrum of the precursor is comparable to nano MoS 2 derived from bulk MoS 2 . High-resolution transmission electron microscopy (HRTEM) revealed the formation of nanoflakes of MoS 2 with 10-to 30-nm length and 3-to 5-nm thickness. Laser desorption ionization mass spectrometry (LDI-MS) confirmed the formation of Mo 13 clusters from this nanomaterial. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) points to the existence of Mo 13 clusters in the condensed phase. The clusters appear to be stable because they do not fragment in the mass spectrometer even at the highest laser intensity. Computational analysis based on generalized Wannier orbitals is used to understand bonding and stability of the clusters. These clusters are highly stable with a rich variety in terms of centricity and multiplicity of MoOMo There are several synthetic approaches such as gas-phase deposition [5,6], laser ablation [7,8], electron irradiation [9], and high-temperature chemical routes [10,11] for the synthesis of clusters. Nano forms of these materials have their own advantages over the corresponding bulk materials. Electrochemical deposition [12] and sonochemical routes [13,14] are some other methods adapted for the synthesis of nanostructured materials. Electrochemical methods result in the formation of nanomaterials as a film, whereas sonochemical methods produce free-standing nanoflakes of metal chalcogenides with controlled size.

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“…The particle size and morphology of MoS 2 crystals can be tailored through controlling the micelle size, which can be easily achieved by changing the emulsifier/water ratio. For example, Wilcoxon et al [13,14] synthesized the nanosized MoS 2 crystals as small as 2.5 and 4 nm in EHAB/hexanol/octane and TDAB/hexanol/octane micelle solutions. Chikan et al [15] obtained MoS 2 nanocrystals with the size of 3.5, 4.5 and 8 nm in DDAB/hexanol/ octane and TDAI/hexanol/octane ternary micelles, respectively.…”

mentioning

confidence: 99%

Synthesis of chain-like MoS2 nanoparticles in W/O reverse microemulsion and application in photocatalysis

Liu

et al. 2012

Chin. Sci. Bull.

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Chain-like MoS 2 assemblies consisting of hexagonal MoS 2 nanoparticles (20-60 nm) have been successfully synthesized in a Triton X-100/cyclohexane/hexanol/water W/O reverse microemulsion in the presence of (NH 4 ) 2 MoS 4 as the molybdenum source and NH 2 OH·HCl as the reducing agent. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance absorption spectra. The influence of synthetic parameters such as acidity, water/oil ratio ( 0 ), aging time and annealing temperature on the formation of MoS 2 assemblies was investigated. TEM analysis showed that these synthetic factors played important roles in controlling the size of MoS 2 nanoparticles and the length of the chain-like MoS 2 assemblies. XRD analysis indicated that the well-crystallized MoS 2 nanoparticles could be obtained by annealing the precursors at 700C for 2 h under a flow of N 2 atmosphere. In addition, the as-prepared chain-like MoS 2 nanoparticles exhibited excellent photocatalytic H 2 activity in Ru ( The family of layered transition metal chalcogenides, such as MoS 2 , WS 2 , has aroused considerable interest during the past decade because of their unique properties and potential applications in hydrodesulfurization, Mg 2+ and Li + batteries, and solar photocells [1][2][3][4]. Increasing attention is now being focused on their potential applications as promising candidates for Pt, a co-catalyst and as well as a catalyst in photocatalytic H 2 production [5,6]. As it is well known, MoS 2 is an indirect, narrow band gap semiconductor (E g =1.0-1.2 eV, covering the range of solar spectrum energy) with high stability against photocorrosion in solution [7]. The band gap of MoS 2 depends on its crystallinity, size and shape due to the quantum confinement effect. Therefore, considerable effort has been made to the synthesis of MoS 2 nanomaterials with desired size and morphology. This material can be prepared under hydrothermal, solvothermal, sonolysis, inverse micelle, and -irradiation conditions [8][9][10][11][12]. Among the methods, the inverse micelle synthesis has been proven to be a convenient, effective and promising method to regulate the size and morphology of MoS 2 . In this approach, particles are grown inside inverse micelle cages dispersed in non-aqueous solvents. The particle size and morphology of MoS 2 crystals can be tailored through controlling the micelle size, which can be easily achieved by changing the emulsifier/water ratio. For example, Wilcoxon et al. [13,14] synthesized the nanosized MoS 2 crystals as small as 2.5 and 4 nm in EHAB/hexanol/octane and TDAB/hexanol/octane micelle solutions. Chikan et al. [15] obtained MoS 2 nanocrystals with the size of 3.5, 4.5 and 8 nm in DDAB/hexanol/ octane and TDAI/hexanol/octane ternary micelles, respectively. Osseo-Asare and co-workers [11] got MoS 2 nanoparticles ranging 10-80 nm in NP-5/cyclohexane/water microemulsion system. Xie and co-workers [16] fabricated necklace-shaped assembly of fullerene-like Mo...

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Strong quantum-size effects in a layered semiconductor:MoS2nanoclusters

Cited by 223 publications

References 13 publications

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS₂ nanoflakes

Synthesis of chain-like MoS2 nanoparticles in W/O reverse microemulsion and application in photocatalysis

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Strong quantum-size effects in a layered semiconductor:MoS2nanoclusters

Cited by 223 publications

References 13 publications

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS2 nanoflakes

Synthesis of chain-like MoS2 nanoparticles in W/O reverse microemulsion and application in photocatalysis

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Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS₂ nanoflakes