Microwave properties of nanodiamond particles

The dielectric properties of nanodiamond powders were characterised at microwave frequencies using a cavity perturbation technique, and results were compared with UV Raman spectroscopy. Surface sp2 hybridisation in the nanodiamond samples was varied by subsequent oxygenation and hydrogenation. Dielectric polarisation and loss increased as the sp2 hybridisation was increased. The sensitivity to surface bound sp2 carbon obtained by the microwave cavity technique far exceeds that of comparable techniques (such as Raman spectroscopy) and is much more convenient in practice, lending itself to studies of real-time modification of such powders by external influences (such as temperature and chemical functionalisation).