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- Title
High-concentration dispersions of exfoliated MoS sheets stabilized by freeze-dried silk fibroin powder.
- Authors
Sim, HeungBo; Lee, JiYong; Park, Byeongho; Kim, Sun; Kang, Shinill; Ryu, WonHyoung; Jun, Seong
- Abstract
Liquid-phase exfoliation (LPE) is an attractive method for the scaling-up of exfoliated MoS sheets compared to chemical vapor deposition and mechanical cleavage. However, the MoS nanosheet yield from LPE is too small for practical applications. We report a facile method for the scaling-up of exfoliated MoS nanosheets using freeze-dried silk fibroin powders. Compared to MoS dispersion in the absence of silk fibroin powder, sonicated MoS dispersions with silk fibroin powder (MoS/Silk dispersion) show noticeably higher exfoliated MoS nanosheet yields, with suspended MoS concentrations in MoS/Silk dispersions sonicated for 2 and 5 h of 1.03 and 1.39 mg·mL, respectively. The MoS concentration in the MoS/Silk dispersion after centrifugation above 10,000 rpm is more than four times that without the silk fibroin. The size of the dispersed silk fibroin is controlled by the change of centrifugation rate, showing the removal of silk fibroin above tens of micrometers in size after centrifugation at 2,000 rpm. Size-controlled silk fibroin biomolecules combined with MoS nanosheets are expected to increase the practical use of such materials in fields related to tissue engineering, biosensors and electrochemical electrodes. Atomic force microscopy and Raman spectroscopy provide the height of the MoS nanosheets spin-cast from MoS /Silk dispersions, showing thicknesses of 3-6 nm. X-ray photoelectron spectroscopy and X-ray diffraction indicate that the outermost surface layer of the hydrophobic MoS crystals interact with oxygen-containing functional groups that exist in the hydrophobic part of silk fibroins. The amphiphilic properties of silk fibroin combined with the MoS nanosheets stabilize dispersions by enhancing solvent-material interactions. The large quantities of exfoliated MoS nanosheets suspended in the as-synthesized dispersions can be utilized for the fabrication of vapor and electrochemical devices requiring high MoS nanosheets contents.
- Publication
Nano Research, 2016, Vol 9, Issue 6, p1709
- ISSN
1998-0124
- Publication type
Article
- DOI
10.1007/s12274-016-1065-2