(133a) Characterization of Graphene, Graphene Oxide and Nanographite Dispersions Using NMR Solvent Relaxation

Nanocarbon materials, such as graphene/graphene oxide and graphite, are increasingly attracting much attention owing to their stable physicochemical properties, low cost, excellent chemical stability, wide operating temperature range properties and long cycle life. They are being considered for use in all types of applications to deliver enhanced performance capabilities to products such as reinforced composites the development of new generation supercapacitors, sensors and electrode materials. However, studying these systems in-situ is not straightforward as the formulations are opaque and often highly concentrated dispersions in a variety of aqueous and non-aqueous liquids. The physical characterization of nanoparticulate dispersions poses challenges, especially at high concentrations; techniques are required which can not only identiy their dispersion and surface behavior but also measure the microdynamics of the components in the formulation. NMR solvent relaxation is a non-invasive technique that probes the molecular motions of species adsorbed onto the particle surface and so can be used to characterize the strength of interaction between a liquid (or other additives) and particle surface functional groups. A major advantage of the technique is that measurements can be made at virtually any solids concentration and in almost any fluid media. The ability to distinguish between molecules at the surface and those in the bulk solution can be used to obtain valuable information on the interfacial interactions and structure at industrially relevant concentration without dilution. In any dispersion, the available amount of wetted surface area depends not only on the amount of physical external/internal surface presented but also the physico-chemical nature of the particle-liquid interface (i.e., surface chemistry). In this paper we will show data, obtained using a small bench-top low field NMR device, on dispersions of porous and non-porous nanocarbon materials that illustrates the versatile utility of the technique as a characterization tool.