Long-term evolution of the chemical and structural stability of graphene oxide after storage as solid and as aqueous dispersion

Artikel i vetenskaplig tidskrift, 2021

Nanomaterials are intended for industrial applications, for that purpose scalability needs to be addressed, therefore an important issue comes to the picture: storage. Graphene oxide (GO) is of great interest for practical applications in optoelectronics, chemical sensors, supercapacitor electrodes, among others. GO properties are related to its O/C ratio and its precise control allows fine tuning of properties such as conductivity, chemical reactivity and band gap. Nevertheless, GO has a critical storage restriction, due to its chemical self-reduction, that is, the oxygen loss not only alters its properties, but also promotes aggregation through time. In this work, the impact of storage conditions on GO properties was studied by comparing two systems: a solid sample and a liquid dispersion, which were analyzed during the course of 3 years. For this purpose, stability, O/C ratio and optical band-gap of the stored samples were analyzed through time by means of zeta potential, X-ray photoelectron spectroscopy (XPS) and UV-Vis. Results show the difference in stability between the samples due to oxygen loss in the GO structure, confirmed by XPS. Moreover, optical band-gap shows that the solid sample decreases its value around 64% compared to the liquid dispersion.