There are hundreds of companies worldwide claiming to produce "graphene," showing a large variation in its properties. A systematic and reliable protocol is developed to test graphene quality using electron microscopy, atomic force microscopy, Raman spectroscopy, elemental analysis, X-ray photoelectron spectrometry, and scanning and transmission electron microscopy, which is used to study graphene from 60 producers. The statistical nature of the liquid-phase exfoliation of graphite is established. It is shown that the current classification of graphene flakes used in the market is erroneous. A new classification is proposed in terms of distribution functions for number of layers and flake size. It is shown unequivocally that the quality of the graphene produced in the world today is rather poor, not optimal for most applications, and most companies are producing graphite microplatelets. This is possibly the main reason for the slow development of graphene applications, which usually require a customized solution in terms of graphene properties. It is argued that the creation of stringent standards for graphene characterization and production, taking into account both the physical properties, as well as the requirements from the particular application, is the only way forward to create a healthy and reliable worldwide graphene market.
展开▼
