Deaggregation of diamond nanoparticles studied by NMR

Nanodiamond (ND) particles are usually bound in aggregates that are difficult to separate into a single nanoparticle form, which restrains their applications. Recently, a stable suspension of deaggregated NDs [1] has been prepared using annealed ND samples. We discuss the mechanism of deaggregation of these NDs based on our NMR data. We show that in contrast with the spectra of the initial sample, those of the annealed sample evidence fast proton exchange between the surface carboxyl groups and adsorbed water molecules and the formation of charged ND-COO--H3O+ structures, which results in repulsion of ND particles and yields a stable aqueous suspension of isolated NDs. (C) 2012 Elsevier B.V. All rights reserved.