Number of observable features in the acoustic-Raman spectra of nanocrystals

TL;DR

This paper investigates how the size of gold nanocrystals influences their low-frequency Raman spectra, revealing that the number of observable features is limited by the atom count and defining the validity range of elastic models.

Contribution

It provides a comparative analysis of elastic and atomistic models to determine the observable Raman features based on nanocrystal size.

Findings

Number of Raman peaks varies with nanocrystal size.

Atom count limits the maximum observable Raman features.

Elastic approximation validity range is size-dependent.

Abstract

Low-frequency Raman scattering spectra are presented for gold nanocrystals with diameters 3.5 and 13 nm. The frequencies of the Raman peaks but also their number are shown to vary with the nanocrystal size. These results are analyzed using both the continuous elastic medium approximation and an atomistic approach. We show that the number of atoms in the nanocrystal determines an upper limit of the number of observable Raman features. The frequency range in which the continuous elastic medium approximation is valid is defined by comparison with the calculations based on the atomistic approach.