Preparation and Investigation of the Microtribological Properties of Graphene Oxide and Graphene Films via Electrostatic Layer-by-Layer Self-Assembly

Yongshou Hu,Bin Liu,Wei Liu,Qianqian Lin,Hongkun Ma

doi:10.1155/2015/282369

Abstract

Graphene oxide (GO) films with controlled layers, deposited on single-crystal silicon substrates, were prepared by electrostatic self-assembly of negatively charged GO sheets. Afterward, graphene films were prepared by liquid-phase reduction of as-prepared GO films using hydrazine hydrate. The microstructures and microtribological properties of the samples were studied using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, UV-visabsorption spectroscopy, water contact angle measurement, and atomic force microscopy. It is found that, whether GO films or graphene films, the adhesion force and the coefficients of friction both show strong dependence on the number of self-assembled layers, which both allow a downward trend as the number of self-assembled layers increases due to the interlayer sliding and the puckering effect when the tip slipped across the top surface of the films. Moreover, in comparison with the GO films with the same self-assembled layers, the graphene films possess lower adhesion force and coefficient of friction attributed to the difference of surface functional groups.

Highlights

With the rapid development of science and technology, especially of nanotechnology, micromechanical and highdensity magnetic recording systems, the study of microtribology has attracted wide attention
In order to certify that the graphene films with gradually increased thickness can be prepared by repeating the electrostatic layer-by-layer (LBL) self-assembly; reduced graphene oxide (RGO) multilayer films on indium tin oxide (ITO) glass substrates were prepared according to the same LBL self-assembly followed by the hydrazine hydrate reduction
The measured thickness of the RGO sheet is much larger than the theoretical value of graphene layer (0.34 nm), which is due to the fact that a small number of oxygenous groups still remain on the surface of the RGO sheet after chemical reduction

Summary

Introduction

With the rapid development of science and technology, especially of nanotechnology, micromechanical and highdensity magnetic recording systems, the study of microtribology has attracted wide attention. Ren et al [13] prepared a stearic acid and 3aminopropyl triethoxysilane (STA-APS) dual-layer film on a single-crystal silicon substrate via chemical self-assembly, and the tribological experiment showed that the STA-APS film has good adhesive-resistance and friction-reduction in both microscopic and macroscopic levels. A 2-dimensional atomic thin layer of carbon nanostructure, exhibits notable electronic, thermal, chemical, and mechanical properties, as well as unrivaled mechanical stiffness and strength [14] It is considered highly applicable in next-generation electronic devices and MEMs [15, 16]. Ou et al [22] revealed that assembled reduced graphene oxide (RGO) monolayer film on silicon substrate possesses good friction reduction and antiwear abilities due to its intrinsic structure. A facile preparation of graphene multilayer films with controlled layers, deposited on silicon substrates, was realized by electrostatic self-assembly of negatively charged GO sheets followed by liquid-phase reduction using hydrazine hydrate. Comparisons of the microtribological properties between self-assembled GO and RGO multilayer films were carried out as well

Experimental

Results and Discussion

Conclusion

Conflict of Interests