The Preparation,Characterization And Bioelectrode Application Of CVD-graphene

Chemical vapor deposition(CVD)on Cu foils is a very important method for industrial-scale production,which is capable to provide graphene films with size of up to 300 cm × 30 cm and annual production capacities of 100,000 m2.The structural features of graphene film formed on Cu foils,for instance the coverage,domain size,and layer number dominate the physical properties and the downstream applications.However,the development of preparation process of large-area bi-or multi-layer graphene is not yet mature,which greatly limits its application in many fields.In addition,the current techniques for the characterization of graphene are expensive and inefficient,which limits the industrial-scale preparation and quality control of CVD-graphene.Therefore,both the preparation process of large-area high-quality bilayer graphene film and the rapid,simple and inexpensive characterization method of graphene are urgently needed f-or the industrial-scale production of graphene,which provides technical support and material security so as to expand graphene's application in many fields,such as electronic information,bioscience,aerospace,military defense,etc.In this thesis,CVD graphene on Cu foils was used as the core to develop the preparation process of bilayer graphene,the characterization techques of layer number of multilayer graphene on Cu foil and the bioelectrode application of graphene.The detailed studies are displayed in the following paragraphs.1.The injection of H2O pulses during the growth stage of CVD graphene reduce the growth rate of the first(top)layer graphene by the etching effect H2O at the edges of the growing graphene,and then result in the decouple between graphene and Cu substrate,which promotes the diffusion of carbon atoms in the graphene/Cu interface and leads to the new cleation.By optimizing the CVD process parameters,such as the partial pressures of CH4 and H2O pulse and pulse frequency),a large-area high-quality AB-stacked multilayer graphene film was obtained on the foils,where the bilayer coverage was as high as 77±3.6%.2.O2-plasma etch is able to create structural defects in graphene,and further leads to the oxidation of the copper substrate,which is responsible for the increase of the optical contrast of graphene on Cu foil.The wrinkles,domain sizes of large-area five-layer graphene can be observed with a grayscale increment of?23.4%per one graphene layer after O2-plasma treatment for only 15 s using the optical microscope.The Raman spectroscopy and X-ray photoelectron spectroscopy presents a strong layer number dependence of both the plasma induced graphene defects and Cu oxides,which,as indicated by molecular dynamic simulation,is responsible for the improved image contrast because of the interaction between O-ions and graphene with different layer numbers,as indicated by molecular dynamic simulation.3.Graphene has excellent biocompatibility,transmittance,and conductivity.Based on these advantages,primary culture of neuronal cells was performed,in which the graphene covered PET was used as a substrate.Moreover,graphene is utilized as a bioelectrode to regulate neuronal axon growth through electrical stimulation.The Ca2+imaging results confirmed that the response of neuronal cells to electrical stimulation and the availability of graphene bioelectrode.