TY - JOUR
T1 - Direct exfoliation of layered materials in low-boiling point solvents using weak acid salts
AU - Arao, Yoshihiko
AU - Tanks, Jonathon D.
AU - Kubouchi, Masatoshi
AU - Ito, Akira
AU - Hosoi, Atsushi
AU - Kawada, Hiroyuki
N1 - Funding Information:
This work was supported by Hosokawa Powder Technology Foundation . We acknowledge the Center for Advanced Materials Analysis in Tokyo Institute of Technology for the TEM and Raman analysis.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/2
Y1 - 2019/2
N2 - The method for mass production of nanosheets is essential for fully realizing their commercial use. Direct exfoliation of layered materials in liquid is the simplest and low-cost technique for exfoliation without introducing defects in basal plane. However, the technique requires toxic and high-boiling point solvents, which makes it difficult for further processing. In addition, solvent exchange involves time-consuming processes such as filtering and redispersion. A breakthrough is necessary to make 2D-crystal-based functional dispersions. Here, we find a new method to directly exfoliate layered materials in low-boiling point solvents. Addition of small amounts of salt prevents reaggregation of exfoliated nanosheets and improves electrical repulsion. In this process, the mechanical force applied by sonication generates active carbon species at the fractured surfaces, leading to a reaction between the active carbon and the salt in liquid. High concentration graphene dispersions (1 g/L) can be obtained in isopropanol with only 5 min of sonication. We also confirm salt-assisted exfoliation is effective for the other 2D crystals such as MoS2 and boron nitride in a wide variety of polar solvents. Direct exfoliation in processable solution opens up a range of large-area applications such as high performance nanocomposites and coatings.
AB - The method for mass production of nanosheets is essential for fully realizing their commercial use. Direct exfoliation of layered materials in liquid is the simplest and low-cost technique for exfoliation without introducing defects in basal plane. However, the technique requires toxic and high-boiling point solvents, which makes it difficult for further processing. In addition, solvent exchange involves time-consuming processes such as filtering and redispersion. A breakthrough is necessary to make 2D-crystal-based functional dispersions. Here, we find a new method to directly exfoliate layered materials in low-boiling point solvents. Addition of small amounts of salt prevents reaggregation of exfoliated nanosheets and improves electrical repulsion. In this process, the mechanical force applied by sonication generates active carbon species at the fractured surfaces, leading to a reaction between the active carbon and the salt in liquid. High concentration graphene dispersions (1 g/L) can be obtained in isopropanol with only 5 min of sonication. We also confirm salt-assisted exfoliation is effective for the other 2D crystals such as MoS2 and boron nitride in a wide variety of polar solvents. Direct exfoliation in processable solution opens up a range of large-area applications such as high performance nanocomposites and coatings.
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U2 - 10.1016/j.carbon.2018.10.063
DO - 10.1016/j.carbon.2018.10.063
M3 - Article
AN - SCOPUS:85055970203
VL - 142
SP - 261
EP - 268
JO - Carbon
JF - Carbon
SN - 0008-6223
ER -