Increase of nanodiamond crystal size by selective oxidation

The control of the crystal size in nanodiamond (ND) powder is crucial, since most of its physical and chemical properties are size-related. In this work we demonstrate a simple method for increasing the crystal size of ND powder by selective oxidation in air. We analyze the oxidized powders by high-resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy in order to monitor changes in the average crystal size distribution and identify the limitations of these techniques for crystal size measurements. Our studies show that none of these techniques alone is able to provide sufficiently accurate information on size distributions, but can produce complementary results for better understanding of the properties of ND powder.