Novel approach to Raman spectra of nanoparticles

TL;DR

This paper introduces a new combined theoretical approach, DMM-BPM, for accurately modeling Raman spectra of nanoparticles, especially small nanodiamonds, outperforming existing models like PCM.

Contribution

The paper develops a novel DMM-BPM method that effectively describes Raman spectra of nanoparticles, bridging numerical and analytical solutions for different particle sizes.

Findings

DMM-BPM fits experimental data better than PCM for small nanoparticles.

The approach provides both numerical and analytical tools for Raman spectra prediction.

Application to nanodiamond powders demonstrates improved accuracy.

Abstract

In crystalline nanoparticles the Raman peak is downshifted with respect to the bulk material and has asymmetric broadening. These effects are straightly related to the finite size of nanoparticles, giving the perspective to use the Raman spectroscopy as the size probe. By combining the dynamical matrix method (DMM) and the bond polarization model (BPM), we develop a new (DMM-BPM) approach to the description of Raman spectra for random arrays of nanoparticles. The numerical variant of this approach is suitable for the description of small particles, whereas its simplier to implement analytical version allows to obtain the Raman spectra of arbitrary sized particles. Focusing on nanodiamond powders, the DMM-BPM theory is shown to fit the most recent experimental data much better than the commonly used phonon confinement model (PCM), especially for small enough nanoparticles.