Modification of detonation nanodiamonds by heat treatment in air

In order to readily utilize nanodiamond (ND) particulates produced by detonation synthesis in many nanotechnology applications, it is necessary to modify the surface chemistry and to separate the particles into a more narrow range of particle sizes. Surface functionalization and fractionalization are highly dependent upon the method of ND synthesis and purification. For example, when material purified through the use of strong liquid oxidizers is used to produce hydrosols, they are unstable and difficult to fractionalize. In this study we developed a method of preparation that overcomes these two barriers. ND powder previously purified with a mixture of sulfuric acid and chromic anhydride was treated as follows: annealed in air followed by dispersion in water using a high power sonicator and multi-step ultracentrifugation. This treatment resulted in stable hydrosols formed from the smallest particle-size fractions.