Microwave-assisted purification of detonation nanodiamond

• New purification scheme of detonation nanodiamonds is proposed.
• Purification degree of 99.95% is achieved for detonation nanodiamonds.
• Laboratory glassware is identified as a source of substantial contamination of nanodiamonds.

In the present work microwave-assisted purification approaches for detonation nanodiamond (DND) are considered, and the resultant impurity content of purified DND revealed by direct ICP-MS and elemental analysis. A significant reduction in noncarbon contaminants as compared with detonation soot was achieved with resulting purity of 99.95%. Surface characterisation including scanning electronic microscopy, low temperature adsorption of nitrogen, acid–base potentiometric titration, zeta potential measurements and particle size distribution of the DND in suspensions revealed distinctive surface properties for each purified DND sample. Results highlight the suitability of the microwave purification approach using acid reagents, allowing nanodiamonds with different and reproducible surface properties to be produced or modified. Contamination effects from laboratory glassware used to store samples were carefully considered. Refined DND with impurity levels over two orders of magnitude lower than commercially available samples was prepared. The profile and concentration levels of residual impurities in purified samples of nanodiamond are discussed with identification of possible reasons for contamination.