Interpretation of electrokinetic measurements of nanodiamond particles

The electrophoretic mobility of nanodiamond (ND) particles measured using laser Doppler electrophoresis in LiCl, NaCl, KCl and CsCl aqueous solutions is reported. The nanodiamond samples included porous aggregates of detonation nanodiamond (DND) particles, completely disaggregated single-digit DND and monolithic 50nm particles of static high-pressure high-temperature (HPHT) synthesis. Corresponding values of ζ-potential were calculated as functions of electrolyte concentration using different theory of electrophoresis. The use of the Miller formula, which takes into account the electromigration fluxes of ions and electroosmotic flows of solutions in pores of dispersed particles, was found to provide the most accurate ζ-potential values for DND aggregates, while for monolithic ND particles Ohshima's approximation developed for the arbitrary zeta potential value and the Debye length/particle radius ratio is more appropriate. ► Electrophoretic mobilities of nanodiamond (ND) particles in electrolytes were measured. ► ND particles had different structures: monolithic particles or porous aggregates. ► Validity of different theories of electrophoresis for the ND structures was analyzed. ► Recommendations on calculations of zeta potential for ND are provided.