In situ Characterization of Nanoparticles Using Rayleigh Scattering

TL;DR

This paper presents a theoretical analysis demonstrating that Rayleigh scattering can be used to monitor nanoparticle growth in arc discharge conditions, providing insights into particle formation mechanisms.

Contribution

The study introduces a method to use Rayleigh scattering for in situ monitoring of nanoparticle synthesis, including calculations of scattering cross sections and spectral features.

Findings

Rayleigh scattering can detect nanoparticles as small as C60.

Brighter signals from larger asymmetric nanoparticles enable tracking growth.

Spectral features include resonant behavior and shape-dependent depolarization.

Abstract

We report a theoretical analysis showing that Rayleigh scattering could be used to monitor the growth of nanoparticles under arc discharge conditions. We compute the Rayleigh scattering cross sections of the nanoparticles by combining light scattering theory for gas-particle mixtures with calculations of the dynamic electronic polarizability of the nanoparticles. We find that the resolution of the Rayleigh scattering probe is adequate to detect nanoparticles as small as C60 at the expected concentrations of synthesis conditions in the arc periphery. Larger asymmetric nanoparticles would yield brighter signals, making possible to follow the evolution of the growing nanoparticle population from the evolution of the scattered intensity. Observable spectral features include characteristic resonant behaviour, shape-dependent depolarization ratio, and mass-dependent line shape. Direct observation of nanoparticles in the early stages of growth with unobtrusive laser probes should give insight on the particle formation mechanisms and may lead to better-controlled synthesis protocols.