Standards Development

Scope

This document describes methods for measuring the lateral size and thickness of graphene oxide (GO) flakes using scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively, incl uding sample pre-treatments, measurement procedures and data analysis. It is applicable to the characterization of graphene oxide in powder and liquid dispersion forms.

Purpose

Graphene oxide (GO) is an oxidized form of graphene, laced with oxygen -containing groups. It is a single layer two-dimensional material with a carbon to oxide ratio of approximately 2, which is prepared by oxidation and exfoliation of graphite, causing extensive oxidative modification of the basal plane. This material has been used in many fields such as catalysts, supercapacitors, Li -ion batteries, nanofluids, composites, etc. GO comes in many different sizes and shapes, which affects their material properties as they may behave differently in a matrix, which can lead to a degree of engineering freedom not possible for other graphene forms. For example, lateral flake size has a significant influence on mechanical properties and corrosion protection, when GO are mixed in composite materials. Generally, larger flakes should be used to make graphene-based three-dimensional networks, conductive films and 2D layered architectures because of fewer connection points leading to a lower overall contact resistance. The small flakes are more suitable for sensing and biological applications because of outstanding biocompatibility and electrochemical activity. Moreover, therm al and electrical conductivity also have a great relationship withsize, as larger flakes have been proven to have excellent thermal conductivity and electromagnetic interference shielding effectiveness. So the thickness and lateral size of a flake are indicative of the number of layers and size which will affect the properties of product.

SEM is a key technique for the measurement of flake image and size as well. However, the sample pre - treatment, the characterization parameter and procedures for the parame ter calculation require a standardized method to ensure the consistency and reliability of reported material properties. AFM is a powerful technique for the measurement of features at the nanoscale. For graphene oxide, this includes flake thickness and lateral size. However, although the theoretical value of single -layer graphene oxide is known, in reality uncertainties due to contaminants and instrument noise can be large, therefore the thickness may not be accurately measured by either point-to-point or a smoothed lines method. Therefore, it is highly desirable to standardize a method to ensure the consistency and reliability of measurement results.

This document shows the methodology for measuring the thickness of graphene oxide (GO) fl akes using SEM and AFM. It aims to provide a reliable measurement methodology for determining GO thickness and lateral size, that can be used by the graphene oxide supply chain