Fei verios 460

The SEM analysis was conducted according to the method described by Tanpichai et al. [25 (link)] with minor modifications. Briefly, raw materials and papery food dried through vacuum freeze drying were glued on the sample holder using conductive adhesive and then coated with a thin gold layer using an ion sputtering instrument (JYSC-100, Guangzhou Jingying Scientific Instrument Co., Ltd., Guangzhou, China). Microscopic images of the samples’ surface were observed under a high-resolution field emission scanning electron microscope (FEI Verios 460, FEI company, Hillsboro, USA, OSU) at a magnification of 5000× and an acceleration voltage of 5 kV [26 (link)].

Two electron microscopy studies were undertaken. The first study was a bright field transmission electron microscopy (TEM) investigation of the size, shape and topography of the various GO and RGO powder samples. The study was carried out using a Tecnai G2, FEI, (Electron Optics, USA) microscope operating at 100 kV. The second study used a high resolution field emission scanning electron microscope (FESEM: FEI-Verios 460) operating at 5 kV, with 0.10 nA current and operating under secondary electron mode. The FESEM was also used to examine the physical structure and topography of the GO and RGO powder samples. Prior to analysis, dried powder samples were deposited on carbon tape covered SEM holders and then sputter coated (E5000, Polaron Equipment Ltd.) with a 2 nm layer of platinum to prevent charge build up.