Raman and Thermoluminescence Studies of HPHT Synthetic Nanodiamond Powders

Nanocrystalline diamond has received increasing attention because of its unique perspectives in biomedical applications. In this work, Raman and thermoluminescence (TL) properties of commercial synthetic high pressure-high temperature (HPHT) nanodiamond powders with mean size of 60, 140, 380, and 660 nm purchased from PlasmaChem GmbH, Germany are presented. The Raman spectra exhibit a diamond peak related to the C-C sp(3) chemical bond and a number of additional bands that could be assigned to G-band, O-H and C(sic)O groups and some intrinsic point defects. The position of the diamond peak does not depend on nanoparticle size when it is monitored with low power laser. The use of a laser with increased power leads to uncontrolled heating of the nanopowders that is manifested as a broadening and down-shifting of the 1332 cm(-1) line. After exposure to beta radiation, all the powders exhibit a main broad TL peak with maxima between 320 and 380 degrees C and a weaker low temperature TL. The dose response is linear at the doses of less than 10 Gy for all the powders. At higher doses a supralinear behavior is observed.