Determination of High Frequency Dielectric Constant and Surface Potential of Graphene Oxide and Influence of Humidity by KPFM.

We use Kelvin probe force microscopy (KPFM) and capacitance coupling (dC/dz) to study the electrical properties of graphene oxide (GO). We propose using the dC/dz signal to probe the high frequency dielectric constant of mono- and few-layer GO. Our measurements suggest that the dynamic dielectric constant of GO is on the order of εGO ? 3.0 ε0, in the high frequency limit, and independent of the number of GO layers. The measurements are performed at a humidity controlled environment (5 of humidity). The effects of increasing humidity on both the dC/dz and KPFM measurements are analyzed

Fabrication Of Transparent And Ultraviolet Shielding Composite Films Based On Graphene Oxide And Cellulose Acetate.

Graphene oxide (GO) has been considered a promising filler material for building polymeric nanocomposites because of its excellent dispersibility and high surface area. In this work, we present the fabrication and characterization of transparent and ultraviolet (UV) shielding composite films based on GO and cellulose acetate (CA). GO sheets were found to be well-dispersed throughout the CA matrix, providing smooth and homogeneous composite films. Moreover, the GO sheets were completely embedded within the CA matrix and no presence of this nanomaterial was found at the surface. Nevertheless, CAGO composite films offered an improved high energy light-shielding capacity when compared to pristine CA films. Particularly for UVC irradiation, the CAGO film containing 0.50wt% GO displayed a UV-shielding capacity of 57%, combined with 79% optical transparency under visible light. These CAGO composite films can be potentially applied as transparent UV-protective coatings for packing biomedical, pharmaceutical, and food products.123217-22