Visualizing the macroscale dispersion of graphene based sheets in epoxy anticorrosive coatings by fluorescence quenching

Abstract

Graphene-based sheets have garnered significant interest due to their exceptional thermal, mechanical, and barrier properties. A general and straightforward visualization approach that facilitates the rapid observation and quantification of the macroscale dispersion of graphene within a polymer matrix would be advantageous, as it can elucidate the intrinsic relationship between macroscale dispersion and the corrosion resistance of composites. In this work, we propose a fast, simple, and efficient strategy to directly observe and quantitatively evaluate the macroscale three-dimensional spatial dispersion of graphene oxide (GO) in epoxy coatings. This is achieved by quenching the emission from the intrinsic luminescent epoxy coatings, as observed in confocal laser scanning microscopy (CLSM), in conjunction with the Morisita index and particle spacing probability density theory. Statistical analysis revealed that the content of 0.1 ∼ 0.25 wt% represents the threshold for uniform dispersion of GO, attributed to the interactions of inter-particle van der Waals forces and physical entanglement. The dispersion of GO in epoxy coatings with a content below this threshold gradually improves during the immersion process, whereas the dispersion of GO at a content above the threshold significantly deteriorates. The electrochemical results are consistent with the findings obtained through direct observation and quantitative evaluation using CLSM, indicating that the epoxy composite coating containing 0.1 ∼ 0.25 wt% GO exhibits long-term protective performance due to its favorable dispersion state. This study presents a valuable opportunity and inspiration for the quantitative evaluation of nanoparticle dispersion within coatings. It also serves as a reference for establishing a relationship between the dispersion state of two-dimensional nanomaterials in coatings and the corrosion resistance of those coatings.