Preparation And Repair Of Graphene Based On Modified Hummers' Method And Its Application In Field Emission

Graphene refers to a single-layer graphite of a two-dimensional honeycomb structure,which is a basic unit constituting fullerenes,carbon nanotubes,and graphite.The liquid phase method is a low-cost and promising method for synthesizing graphene,and is widely used in transparent conductive films,flexible electronic components,and field emission devices.As a common method for preparing graphene in large quantities,this method has been criticized because of the low quality of the prepared graphene.In this paper,a high-quality graphene conductive film is prepared by combining the redox method and the CVD method.In the field of field emission,how to solve the problem that graphene is easy to lie flat has always been the focus of research.In this paper,a simple freeze-drying and hydrothermal self-assembly method is used to prepare a vertical array of graphene with rich tips to improve the field emission properties of graphene.The content of this paper is as follows:1.Graphene oxide(GO)and reduced graphene oxide(RGO)were prepared by modified Hummers'and thermal reduction method.Also,single layer Graphene was prepared by CVD.This work use Raman spectroscopy(RS),scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and other means for analysis of GO,RGO and single-layer Graphene.Through characterization and analysis,the sample prepared by thermal reduction has large yield,but samples are easy to stack and the defects in the structure are obvious.Furthermore,there are many residual oxygen-containing functional groups.The single-layer graphene film grown by CVD has high quality and few defects,which is an ideal transparent film material.2.A method for repairing GO by CVD method based on Langmuir-Blodgett(LB)self-assembly film formation on Cu substrate was proposed.The graphene film material with surface resistivity as low as 0.25k?/?was obtained.The Cu substrate acts as a catalytic metal for graphene growth by CVD,and it has a repairing effect on the structure of graphene either.This high quality and low resistance graphene film provides an excellent film material for applications on conductive films and flexible electronic devices.3.Reduced graphene oxide bundles with sharp tips were fabricated by a simple approach with freeze-drying and hydrothermal reduction,and this approach could modify the surface topography of the field emission cathode and make more graphene bundles sharpen and aligned.This field emission cathode material displayed excellent field emission properties decreased from 2.9 V/?m to a low turn-on field of 0.8 V/?m at the emission current density of 10?A/cm~2.Sharp graphene emitter arrays have sharp protruded tips in abundance,leading to an enlarged field enhancement factor from 1683 to 10182,which was much better than those films prepared by other methods we adopted.It also revealed a good field emission stability with no degradation in the current for 3 h.We believe that this approach can enhance the field emission performance of graphene emitters,which could be widely candidate for various field emission applications.