Preparation Of Transparent Conductive Films Of The Liquid Phase Of Graphene Research

In this study, graphite powder was sonicated in organic solvents such as N,N-Dim-ethylformamide (DMF) and solution of a perfluorosulfonated cation-exchange polymer (Nafion), respectively, to produce high quality graphene dispersion. This process avoided complicated oxidation and reduction. Graphene dispersion was diluted by deionized water and vacuum filtered to prepare transparent, conductive films. And the properties of graphene films were investigated with different treatments.Graphene prepared by liquid-phase sonication of graphite, was investigated by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the as-prepared graphene had few defects and was not heavily oxided. Settlement experiments revealed that graphene in DMF and Nafion solution was well dispersed and quite stable.Graphene films, deposited by vacuum filtration, were characterized by optical microscope, field emission scanning electronic microscopy (FESEM), UV-Vis spectroscopy and Four-Probe instruments. It was found that these thin films were homogeneous and dense. With the increase of the volume of graphene dispersion, the transparency and sheet resistivity of films decreased. In order to improve films'properties, graphene films were treated by nitric acid, vacuum-annealed, air-annealed and acid-treated & air-annealed, respectively. After the first two treatments, graphene films's performance were not obviously enhanced. While the latter two treatments had significant efffect on improving films'transparency and reducing their sheet resistance. Finally, graphene films with a sheet resistance between 2 KΩ/sq～3 KΩ/sq and transparency above 80% at 550 nm were achieved.