Fabrication and demonstration of quantitative dispersibility evaluation system for graphene oxide

The dispersibility of graphene oxide (GO) in a solvent is an interesting and important property. However, all the reported evaluations of the dispersibility of GO and GO-related materials have been performed by the naked eye. Therefore, objective and quantitative dispersibility evaluation has not yet been achieved. We have proposed objective quantitative dispersibility evaluation systems based on light transparency with an LED light source. This system is newly improved by using laser light as the light source. The time dependence of dispersibility was revealed by the fabricated quantitative dispersibility evaluation system. Furthermore, different dispersibility curves were obtained for different light sources. The dispersibility curve obtained by the LED light irradiation decreased as a stretched exponential function. On the other hand, the dispersibility curve obtained by the laser light irradiation stepwisely decreased. These differences were caused by the variation in the intensity of the convection flow owing to the difference in received heat. To discuss the difference in the dispersibility with the GO particle size distribution, a size separation and dispersibility evaluation was conducted. It was elucidated that the distinct decrease in dispersibility in the early stage was mainly caused by the large GO particles, and the subsequent gradual decrease was attributed to medium-size and small GO particles.