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Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation.

ABSTRACT: Layered materials must be exfoliated and dispersed in solvents for diverse applications. Usually, highly energetic probe sonication may be considered to be an unfavourable method for the less defective exfoliation and dispersion of layered materials. Here we show that judicious use of ultrasonic cavitation can produce exfoliated transition metal dichalcogenide nanosheets extraordinarily dispersed in non-toxic solvent by minimising the sonolysis of solvent molecules. Our method can also lead to produce less defective, large graphene oxide nanosheets from graphite oxide in a short time (within 10 min), which show high electrical conductivity (>20,000 S m(-1)) of the printed film. This was achieved by adjusting the ultrasonic probe depth to the liquid surface to generate less energetic cavitation (delivered power ~6 W), while maintaining sufficient acoustic shearing (0.73 m s(-1)) and generating additional microbubbling by aeration at the liquid surface.

SUBMITTER: Han JT

PROVIDER: S-EPMC4038810 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation.

Han Joong Tark JT Jang Jeong In JI Kim Haena H Hwang Jun Yeon JY Yoo Hyung Keun HK Woo Jong Seok JS Choi Sua S Kim Ho Young HY Jeong Hee Jin HJ Jeong Seung Yol SY Baeg Kang-Jun KJ Cho Kilwon K Lee Geon-Woong GW

Scientific reports 20140530

Layered materials must be exfoliated and dispersed in solvents for diverse applications. Usually, highly energetic probe sonication may be considered to be an unfavourable method for the less defective exfoliation and dispersion of layered materials. Here we show that judicious use of ultrasonic cavitation can produce exfoliated transition metal dichalcogenide nanosheets extraordinarily dispersed in non-toxic solvent by minimising the sonolysis of solvent molecules. Our method can also lead to p ...[more]

PMID: 24875584

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Project description:In this work, we have computed the exfoliation energy (the energy required to separate a single layer from the bulk structure), the interlayer distance, and the thermodynamic state functions for representative layered inorganic minerals such as Brucite, Portlandite, and Kaolinite, while leaving the more classical 2D transition-metal dichalcogenides (like MoS2) for future work. Such materials are interesting for several applications in the field of adsorption and in prebiotic chemistry. Their peculiar features are directly controlled by the exfoliation energy. In materials without cations/anions linking different layers, the interactions keeping the layers together are of weak nature, mainly dispersion London interactions and hydrogen bonds, somehow challenging to deal with computationally. We used Hartree-Fock (HF) and density functional theory (DFT) approaches focusing on the role of dispersion forces using the popular and widespread Grimme's pairwise dispersion schemes (-D2 and -D3) and, as a reference method, the periodic MP2 approach based on localized orbitals (LMP2). The results are highly dependent on the choice of the scheme adopted to account for dispersion interactions. D2 and D3 schemes combined with either HF or DFT lead to overestimated exfoliation energies (about 2.5 and 1.7 times higher than LMP2 data for Brucite/Portlandite and Kaolinite) and underestimated interlayer distances (by about 3.5% for Brucite/Portlandite). The reason is that D2 and D3 corrections are based on neutral atomic parameters for each chemical element which, instead, behave as cations in the considered layered material (Mg, Ca, and Al), causing overattractive interaction between layers. More sophisticated dispersion corrections methods, like those based on nonlocal vdW functionals, many body dispersion model, and exchange-hole dipole moment not relying on atom-typing, are, in principle, better suited to describe the London interaction of ionic species. Nonetheless, we demonstrate that good results can be achieved also within the simpler D2 and D3 schemes, in agreement with previous literature suggestions, by adopting the dispersion coefficients of the preceding noble gas for the ionic species, leading to energetics in good agreement with LMP2 and structures closer to the experiments.

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Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation.

Publications

Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation.

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