Nanodiamond Size from Low-Frequency Acoustic Raman Modes
Aleš Vlk, Martin Ledinský, A. A. Shiryaev, Е. А. Екимов, Štěpán Stehlík
Abstract
Bottom-up high-pressure, high-temperature (BU_HPHT) synthesis of nanodiamonds (NDs) from organic precursors has recently enabled unprecedented control over the ND size down to the phonon confinement region (≤3 nm) of a diamond. This allows us to perform a comprehensive multiwavelength Raman spectroscopy analysis of the Raman spectra and size-related effects in BU_HPHT NDs in the size range from 1.2 to 8 nm. We present and discuss difficulties in ND size determination using the diamond 1332 cm–1 Raman line position. In contrast, we demonstrate the utilization of the low-frequency acoustic Raman modes for this purpose, namely, for quantum-sized sub-3 nm NDs. Using Lamb’s model for these low-frequency acoustic modes, we calculate the ND size and find a remarkable agreement with the size values obtained by the XRD and HRTEM.