Nanodiamond Size from Low-Frequency Acoustic Raman Modes

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.

Absolute energy levels in nanodiamonds of different origins and surface chemistries

“…41 In monocrystalline HPHT NDs, no signicant shis of diamond Raman peak have been observed down to 2-3 nm. 6,41 Paper Nanoscale Advances…”

“…Diamond nanoparticles, so-called nanodiamonds (NDs), are fascinating carbon-based nanomaterials, characterised by a rigid and stable diamond core and a reactive surface that can host multiple surface functional groups. [1][2][3][4][5] The diamond lattice in the ND core keeps the bulk-like diamond structure down to a few nm, 6 and allows the possibility to host stable colour centres such as nitrogen or silicon vacancies in sub-10 nm NDs. [7][8][9] In contrast, due to the extremely high surface-to-volume ratio, it is the surface chemistry that controls NDs' colloidal and, in particular, electronic properties as well as interactions with other materials including biosystems.…”

Phonon engineering in thermal materials with nano-carbon dopants

“…89 Such resonant modes have been observed in various NPs, including nanodiamond, 90 and are expected to contribute to their thermal properties. [91][92][93] Atoms within a few monolayers of NP surfaces also participate in distinctive vibrational modes, which give rise to an excess of low-energy vibrations over the bulk phonon modes, and also high-energy surface modes above the normal bulk cutoff. [94][95][96] The high surface area offers a host of guest molecules (e.g., H) to form the so-called riding modes, which involve coupling between the particle's normal phonon modes and those of the guest molecule.…”

Surface Tamm States of 2–5 nm Nanodiamond via Raman Spectroscopy

“…To prevent contamination of the surface, the nanodiamond must be dispersed in NaCl after annealing in a vacuum. The saturation of the surface of the diamond nanoparticles with hydrogen, for example, leads to the disappearance of these additional lines [ 6 ].…”