An Effective Method for the Fabrication of Few‐Layer‐Thick Inorganic Nanosheets

Zeng, Zhiyuan; Sun, Tongming; Zhu, Jixin; Huang, Xiao; Yin, Zongyou; Lü, Gang; Fan, Zhanxi; Yan, Qingyu; Hng, Huey Hoon; Zhang, Hua

doi:10.1002/anie.201204208

Cited by 562 publications

(428 citation statements)

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“…An alternative method of lithiation that is faster and more controllable uses an electrochemical cell with a lithium foil anode and TMDC-containing cathode, as recently demonstrated by Zeng et al 50,57 . Because the intercalation occurs while a galvanic discharge is occurring in the electrochemical cell, the degree of lithiation can be monitored and controlled.…”

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confidence: 99%

“…The main advantage of ion exfoliation is that it gives a high yield of monolayers 49 , and improvements in Li intercalation by an electrochemical method have made the process faster and more controllable 50,57 . But the flammability of the Li compounds under ambient conditions requires the work to be carried out under inert gas, and Li is an increasingly expensive resource, so there is incentive to find alternative intercalants.…”

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

et al. 2012

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699M any two-dimensional (2D) materials exist in bulk form as stacks of strongly bonded layers with weak interlayer attraction, allowing exfoliation into individual, atomically thin layers 1 . The form receiving the most attention today is graphene, the monolayer counterpart of graphite. The electronic band structure of graphene has a linear dispersion near the K point, and charge carriers can be described as massless Dirac fermions, providing scientists with an abundance of new physics 2,3 . Graphene is a unique example of an extremely thin electrical and thermal conductor 4 , with high carrier mobility 5 , and surprising molecular barrier properties 6,7 .Many other 2D materials are known, such as the TMDCs 8,9 , transition metal oxides including titania-and perovskite-based oxides 10,11 , and graphene analogues such as boron nitride (BN) 12,13 . In particular, TMDCs show a wide range of electronic, optical, mechanical, chemical and thermal properties that have been studied by researchers for decades 9,14,15 . There is at present a resurgence of scientific and engineering interest in TMDCs in their atomically thin 2D forms because of recent advances in sample preparation, optical detection, transfer and manipulation of 2D materials, and physical understanding of 2D materials learned from graphene.The 2D exfoliated versions of TMDCs offer properties that are complementary to yet distinct from those in graphene. Graphene displays an exceptionally high carrier mobility exceeding 10 6 cm 2 V -1 s -1 at 2 K (ref. 16) and exceeding 10 5 cm 2 V -1 s -1 at room temperature for devices encapsulated in BN dielectric layers 5 ; because pristine graphene lacks a bandgap, however, fieldeffect transistors (FETs) made from graphene cannot be effectively switched off and have low on/off switching ratios. Bandgaps can be engineered in graphene using nanostructuring [17][18][19] , chemical functionalization 20 and applying a high electric field to bilayer graphene 21 , but these methods add complexity and diminish mobility. In contrast, several 2D TMDCs possess sizable bandgaps around 1-2 eV (refs 9,14), promising interesting new FET and optoelectronic devices.TMDCs are a class of materials with the formula MX 2 , where M is a transition metal element from group IV (Ti, Zr, Hf and so on), group V (for instance V, Nb or Ta) or group VI (Mo, W and so on), and X is a chalcogen (S, Se or Te). These materials form layered structures of the form X-M-X, with the chalcogen atoms in two hexagonal planes separated by a plane of metal atoms, as shown in Fig. 1a. Adjacent layers are weakly held together to form the bulk crystal in a variety of polytypes, which vary in stacking orders and metal atom coordination, as shown in Fig. 1e. The overall symmetry of TMDCs is hexagonal or rhombohedral, and the metal atoms have octahedral or trigonal prismatic coordination. The electronic properties of TMDCs range from metallic to semiconducting, as summarized in Table 1. There are also TMDCs that exhibit exotic behaviours such as charge density waves ...

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

et al. 2012

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“…Insufficient insertion of Li leads to ineffective exfoliation while excess Li-insertion leads to the decomposition of the crystal. Zeng et al [41] have optimized the cut-off voltage and discharge current needed for the optimum Li-intercalation necessary for preparation of few-layer BN, NbSe 2 , WSe 2 , Sb 2 Se 3 and Bi 2 Te 3 .…”

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confidence: 99%

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

Jana¹,

Rao²

2016

Phil. Trans. R. Soc. A.

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The discovery of graphene marks a major event in the physics and chemistry of materials. The amazing properties of this two-dimensional (2D) material have prompted research on other 2D layered materials, of which layered transition metal dichalcogenides (TMDCs) are important members. Single-layer and few-layer TMDCs have been synthesized and characterized. They possess a wide range of properties many of which have not been known hitherto. A typical example of such materials is MoS 2 . In this article, we briefly present various aspects of layered analogues of graphene as exemplified by TMDCs. The discussion includes not only synthesis and characterization, but also various properties and phenomena exhibited by the TMDCs.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'.

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“…Single-layer or few-layer nanosheets can be obtained from bulk TMCs by several exfoliation techniques such as dry mechanical cleavage with Scotch tape 10,11 or solution-based exfoliation processes [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] . Intercalation of alkali metals by using elemental metals 12,13 (for example, potassium) or organo-alkali compounds (for example, butyllithium [14][15][16] and more recently sodium naphthalenide 17 ) has been a widely used method for the exfoliation of layered materials.…”

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“…Although quite effective, the use of reactive chemicals during exfoliation conditions and H 2 generation through multiple exfoliation processes has drawbacks 17 . While the electrochemical exfoliation method has been developed as a faster and controllable exfoliation protocol, complicated electrochemical set-ups present challenges for the mass production of single-layer nanosheets [18][19][20][21] . Alternatively, a sonication method in the presence of solvents 22,23 such as N-methyl-pyrrolidone has been demonstrated for the successful exfoliation of wide range of TMCs, but the products are often mixed with single-and multi-layer TMCs with potential degradation of samples due to the harsh sonication conditions required to overcome the interlayer interactions [24][25][26] .…”

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Tandem intercalation strategy for single-layer nanosheets as an effective alternative to conventional exfoliation processes

et al. 2015

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Simple and effective generation of transition metal chalcogenides (TMCs) in a single-layer form has been a challenging task. Here we present a tandem molecular intercalation (TMI) as a new exfoliation concept for producing single-layer TMCs from multi-layer colloidal TMC nanostructures in solution phase. TMI requires tandem Lewis base intercalates, where short 'initiator' molecules first intercalate into TMCs to open up the interlayer gap, and the long 'primary' molecules then bring the gap to full width so that a random mixture of intercalates overcomes the interlayer force. Spontaneous exfoliation then yields single-layer TMCs. The TMI process is uniquely advantageous because it works in a simple one-step process under safe and mild conditions (that is, room temperature without sonication or H 2 generation). With the appropriate intercalates, we have successfully generated single-layer nanostructures of group IV (TiS 2 , ZrS 2 ), group V (NbS 2 ) and VI (WSe 2 , MoS 2 ) TMCs.

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An Effective Method for the Fabrication of Few‐Layer‐Thick Inorganic Nanosheets

Cited by 562 publications

References 41 publications

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

Tandem intercalation strategy for single-layer nanosheets as an effective alternative to conventional exfoliation processes

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