Nanodiamond Size from Low-Frequency Acoustic Raman Modes

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 tothe phonon confinement region (<= 3 nm) of a diamond. This allows us to perform a comprehensivemultiwavelength Raman spectroscopy analysis of the Raman spectra and size-related effects inBU_HPHT NDs in the size range from 1.2 to 8 nm. We present and discuss difficulties in ND sizedetermination using the diamond 1332 cm-1Raman line position. In contrast, we demonstrate theutilization of the low-frequency acoustic Raman modes for this purpose, namely, for quantum-sizedsub-3 nm NDs. Using Lamb's model for these low-frequency acoustic modes, we calculate the ND sizeandfind a remarkable agreement with the size values obtained by the XRD and HRTEM

Automated summary

The bottom-up high-pressure, high-temperature synthesis method allows for unprecedented control over the size of nanodiamonds. In this study, nanodiamonds with sizes ranging from 1.2 to 8 nm were analyzed using multiwavelength Raman spectroscopy. The low-frequency acoustic Raman modes were utilized to determine the size of quantum-sized sub-3 nm nanodiamonds, showing remarkable agreement with other measurement methods such as XRD and HRTEM.