Adsorption of Pd on<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:mn /><mml:mo>(</mml:mo><mml:mn>1000</mml:mn><mml:mo>)</mml:mo><mml:mo>:</mml:mo></mml:math><i>Ab initio</i>electronic-structure calculations

Fuhr, J. D.; Sofo, Jorge O.; Saúl, Andrés

doi:10.1103/physrevb.60.8343

Cited by 42 publications

(39 citation statements)

References 28 publications

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“…However, such values are in conflict with the published values of surface energy of several hundred mJ/m 2 for TMDs. 47,48 These values were calculated by computation some years ago and we have been unable to find experimentally measured values to benchmark our results against. There is a significant possibility that these published values are simply too high.…”

Section: The Role Of Surface Energymentioning

confidence: 99%

Solvent Exfoliation of Transition Metal Dichalcogenides: Dispersibility of Exfoliated Nanosheets Varies Only Weakly between Compounds

et al. 2012

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Abstract:We have studied the dispersion and exfoliation of four inorganic layered compounds, WS 2 , We found that the dispersed concentration of each material falls exponentially with  as predicted by solution thermodynamics. This work shows that solution thermodynamics and specifically solubility parameter analysis can be used as a framework to understand the dispersion of 2-dimensional materials. Finally, we note that in good solvents such as 2 cyclohexylpyrrolidone, the dispersions are temporally stable with >90% of material remaining dispersed after 100 hours. ToC figOver the last decade, 2-dimensional nanomaterials have become one of the most studied subfields of nanoscience. These developments have been spearheaded by research into graphene, a material that is unique due to its combination of thermal, electronic, optical and mechanical properties. 1-5 However, over the last few years, it has become clear that a range of other inorganic layered compounds can be mechanically exfoliated in small quantities to give 2-dimensional nanosheets with interesting properties. 6-10 For example, exfoliated hexagonal boron nitride has been used as a dielectric support in graphene-based transistors 11 while MoS 2 has been fabricated into sensors 10, 12 , transistors 13-15 and integrated circuits. 16 The availability of a wide range of 2-dimensional materials is important as it allows access to a broad palette of physical and chemical properties. A good example is provided by the family of transition metal dichalcogenides (TMDs). These materials have the chemical composition MX 2 where M is a transition metal (commonly, but not limited to Ti, Nb, Ta, Mo, W) and X is a chalcogen (i.e. S, Se, Te). As in graphite, these atoms are covalently bonded into nanosheets which stack into 3-dimensional crystals by van der Waals interactions. These materials are of particular interest because, depending on the combination of metal and chalcogen, the material can be semiconducting or metallic. 17 In addition, the bandgap can vary from a few hundred meV to a few eV, 17 suggesting these materials have potential as versatile electronic device materials.Furthermore, these materials have interesting electrochemical properties which make them suitable for applications such as battery electrodes. 18,19 As with graphene, many applications will require relatively large quantities of material suggesting that a solution processing route is required. 20 A number of possibilities exist. For example, it has been known for many years that materials such as MoS 2 can be exfoliated by 3 lithium intercalation. 21 However, such a route tends to result in structural deformations in some TMDs leading to considerably altered electronic properties. 22 Alternatively, TMDs can be synthesised in the liquid phase. 7,8 Probably the simplest route to liquid exfoliation of layered compounds is sonication assisted exfoliation in solvents [23][24][25][26][27][28][29] or aqueous surfactant solutions. 19,[30][31][32] Here, sonication results in the exfoliation of the ...

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Section: The Role Of Surface Energymentioning

confidence: 99%

Solvent Exfoliation of Transition Metal Dichalcogenides: Dispersibility of Exfoliated Nanosheets Varies Only Weakly between Compounds

et al. 2012

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“…Computational studies have estimated this as greater than 250 mJ/m 2 for both MoS 2 and WS 2 ; [26,27] many times greater than that of graphene [28] or BN [29] . We suggest that sonication can be used to exfoliate TMDs in water, so long as a stabiliser is present to prevent rapid reaggregation driven by the large surface energy.…”

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“…We note that the observation of such stable dispersions at relatively low zeta potential suggests that previous estimates of MoS 2 surface energy may be too high. [26,27] It is critical to ascertain the nature of the dispersed MoS 2 . Transmission electron microscope examination of material deposited from the dispersion showed the presence of large quantities of extremely thin 2-dimensional flakes (figures 2 a -c) which we believe to consist of a small number of [20] This is in contrast to ion exfoliated MoS 2 which generally becomes distorted from the bulk 2H structure.…”

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confidence: 99%

“…While BN can be dispersed in water due to sonication-assisted hydrolysis, this method cannot be extended to other layered compounds. [25] The discovery of a facile, scalable method to exfoliate a range of layered materials in water would assist the production and [26,27] many times greater than that of graphene [28] or BN [29] . We suggest that sonication can be used to exfoliate TMDs in water, so long as a stabiliser is present to prevent rapid reaggregation driven by the large surface energy.…”

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Large‐Scale Exfoliation of Inorganic Layered Compounds in Aqueous Surfactant Solutions

et al. 2011

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We have developed methods to exfoliate MoS 2 in large quantities in surfactant-water solutions. This method can be extended to a range of other layered compounds. The layered material tends to be exfoliated as relatively defect free flakes with lateral sizes of 100s of nm. 2With high surface area and novel properties, two-dimensional (2D) materials are potentially useful for a range of applications. In addition to graphene, many 2D compounds exist with BN, MoS 2 and Bi 2 Te 3 generating renewed interest. Such materials are found stacked in layered crystals and can be metals, semiconductors or insulators.[ tend to bond via van der Waals interactions, stacking to form 3D crystals. These materials span the whole gamut of electronic structures from insulator to metal [1] and display interesting properties [6] such as superconductivity, [3] thermoelectricity [2] and topological insulator effects.[4]While micro-mechanically exfoliated [7] single flakes of materials such as MoS 2 are ideal for electronic devices, [8] large scale liquid-phase exfoliation methods will lead to a range of thin film applications such as nano-scale hybrids for use in thermoelectrics, [9] supercapacitors [10] or Li-ion batteries [11] . One advantage of such applications is that, as the electronic properties of TMDs vary relatively slowly with layer number, [12,13] full exfoliation to monolayers is not necessary; dispersed few-layer flakes are sufficient.While a number of layered compounds can be exfoliated by ion intercalation, [14][15][16][17] this method is time consuming, extremely sensitive to environmental conditions and results in structural deformations in some TMDs.[18] Furthermore, removal of the ions results in re-aggregation of the layers.[19] More promisingly, it has recently been shown that both TMDs [20] and BN can be exfoliated in organic solvents. [21][22][23][24] However, for large-scale applications, exfoliation in an aqueous environment would be hugely advantageous. While BN can be dispersed in water due to sonication-assisted hydrolysis, this method cannot be extended to other layered compounds.[25] The discovery of a facile, scalable method to exfoliate a range of layered materials in water would assist the production and 3 characterisation of a range of new materials and greatly facilitate the potential transfer of such technology to industry. In this work we show that a number of layered crystals can be exfoliated in water, resulting in thin flakes stabilised by a surfactant coating. This method is robust, can be carried out in ambient conditions, is scalable and allows the preparation of films, hybrids and composites.One possible reason why ion intercalation has been prevalent for TMDs rather than other liquid based dispersion methods is the relatively high exfoliation (surface) energy of TMDs. Computational studies have estimated this as greater than 250 mJ/m 2 for both MoS 2 and WS 2 ; [26,27] many times greater than that of graphene [28] or BN [29] . We suggest that sonication can be used to exfoliate TMDs in water,...

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“…[4][5][6][7] The value of e vdW was taken as twice the measured surface energy of MoS 2 . [17] The difference between the numbers of atoms N j and N jÀ1 for two shells of a multilayer nanooctahedron can be determined from the lattice constants a and c of bulk…”

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confidence: 99%