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Liquid metals can play an essential role in the generation of electrically conductive composites for electronic devices and environmental sensing and remediation applications. Here, a method for gr...

Liquid phase exfoliation techniques of layered crystals establish the basis for high yield production of two-dimensional (2D) flakes suspension. However, such techniques generally require a long processing time. The recent demonstration of the piezoelectric phenomenon in noncentrosymmetric layered transition metal dichalcogenides, such as molybdenum disulfide (MoS2), leads to new opportunities for fast and efficient exfoliation processes. Here we use concomitant electric field and mechanical shear force for producing a suspension of MoS2 nanoflakes from exfoliation of their layered bulk powder particles. The electrical and mechanical fields are applied by a surface acoustic wave (SAW) microcentrifugation device. We show that the overall yield per unit of time of 3.816%/h can be achieved, which is at least an order of magnitude larger than previously reported liquid phase exfoliation methods. Simultaneously, the impressive monolayer yield is 58% in an excellent agreement with the computational estimation b...

There is ongoing interest in exploring new two-dimensional materials and exploiting their functionalities. Here, a top-down approach is used for developing a new morphology of ultrathin nanosheets from highly ordered bismuth sulfide crystals. The efficient chemical delamination method exfoliates the bulk powder into a suspension of corrugated ultrathin sheets, despite the fact that the Bi2S3 fundamental layers are made of atomically thin ribbons that are held together by van der Waals forces in two dimensions. Morphological analyses show that the produced corrugated sheets are as thin as 2.5 nm and can be as large as 20 μm across. Determined atomic ratios indicate that the exfoliation process introduces sulfur vacancies into the sheets, with a resulting stoichiometry of Bi2S2.6. It is hypothesized that the nanoribbons were cross-linked during the reduction process leading to corrugated sheet formation. The material is used for preparing field effect devices and was found to be highly p-doped, which is att...

Grinding-assisted sonication exfoliation of stratified materials such as MoS2 is a widely used method for the preparation of their single- and few-layer thick flakes. This work introduces a two-solvent step approach utilizing a separate solvent during the grinding phase, while implementing ethanol during exfoliation. It is found that the grinding solvent played a critical role, determining exfoliation yield, flake dimensions, and morphology, highlighting the importance of such parameters in the process. Furthermore, it is found that the commonly used N-methyl-2-pyrrolidone (NMP) leads to persistent residues on the exfoliated flakes, which may alter the properties of the flakes and interfere with the development of electronic devices and other applications. A solvent residue free exfoliation method is presented herein, which may be advantageous for future studies.

Atomically thin WO3 is fabricated using a three-step process, involving wet-chemical synthesis of hydrated-WO3, mechanical exfoliation of fundamental layers and dehydration by annealing at 300 °C. Atomic force microscopy reveals that the minimum resolvable thickness of the hydrated flakes to be ∼1.4 nm, which corresponds to the unit-cell height. The subsequent annealing temperature determines the degree of dehydration and thereby the crystallographic structure of the resultant WO3. The hydrated and dehydrated flakes are characterized by Raman spectroscopy to reveal spectroscopic fingerprints of flake thickness. Thin flakes are also shown to have higher propensity for lithium intercalation, which is also evidenced in Raman planar peak intensity.