Nanoscale Interfacial Interactions of Graphene with Polar and Nonpolar Liquids
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- 作者：Benjamin J. Robinson ; Nicholas D. Kay ; Oleg V. Kolosov
- 刊名：Langmuir
- 出版年：2013
- 出版时间：June 25, 2013
- 年：2013
- 卷：29
- 期：25
- 页码：7735-7742
- 全文大小：341K
- 年卷期：v.29,no.25(June 25, 2013)
- ISSN：1520-5827
文摘
While mechanical and frictional properties of graphene in air have been extensively studied, graphene鈥檚 nanomechanical behavior in liquids, vital for its operation in rechargeable batteries, supercapacitors, and sensors, is still largely unexplored. In this paper, we investigate the nanomechanics of normal (adhesive and elastic) and tangential (friction) forces between a stationary, moving, and ultrasonically excited nanoscale atomic force microscope (AFM) tip and exfoliated few layer graphene (FLG) on SiO2 substrate as a function of surrounding media鈥攁ir, polar (water), and nonpolar (dodecane) liquids. We find that, while the friction coefficient is significantly reduced in liquids, and is always lower for FLG than SiO2, it is higher for graphene in nonpolar dodecane than highly polar water. We also confirm that in ambient environment the water meniscus dominates high adhesion for both hydrophobic FLG and the more hydrophilic SiO2 surface, with the lowest adhesion observed in liquids, in particular for FLG in dodecane, reflecting the low interface energy of this system. By using nanomechanical probing via ultrasonic force microscopy (UFM), we observed a profound reduction of graphene rippling and increase of graphene鈥搒ubstrate contact area in liquid environment. Friction force dependence on ultrasonic modulation amplitude suggests that dodecane at the graphene interface produces a solid-like 鈥渃ushion鈥?of approximately 2 nm thickness, whereas, in water immersion, the same dependence shows a remarkable similarity with the ambient environment, confirming the presence of a water meniscus in air, and suggesting negligible thickness of a similar water 鈥渃ushion鈥?on graphene. Dependence of friction on local environment opens new pathways for friction management in microfluidic and micro- and nanoelectromechanical systems.