A new approach to the characterisation of detonation nanodiamond (DND) using capillary zone electrophoresis (CZE) is presented in this work. DND has been receiving significant research interest due to its favourable optical and mechanical properties, biocompatibility, and thermal stability and conductivity. DND is a diverse material in terms of its surface properties such as functional groups, impurities, ζ-potentials and tendency to form aggregates, which are highly variable in size. Future applications depend on better understanding and control of surface properties and dispersion stability to ensure a highly reproducible material. CZE offers a rapid, automated and reliable method for the characterisation of DND, with low sample volume requirements. It has previously been employed as a method for the size and surface-charge characterisation of a variety of nano-particles; however, to date no reports have been published related to the use of CZE for DND characterisation.

It is necessary to study and understand the influence of different electrophoretic parameters on DND in order to effectively utilise CZE as a characterisation technique. The influence of background electrolyte conditions on the electro-migration and the separation of nanodiamonds was investigated and compared with ζ-potential and particle size measurements by dynamic light scattering (DLS). The effect of pH and increasing concentrations of sodium phosphate, tris and borate buffers on the electrophoretic profile of single digit DND was compared. This method was subsequently applied to a variety of commercial and non-commercial DND samples which underwent different routes of purification following detonation synthesis. They produced a characteristic peak or series of spikes under the conditions investigated. This study provided a better understanding of the diverse surface properties and dispersion quality of different DND samples.

This research was supported by ARC discovery grant DP110102046.