Four-Wave-Mixing Approach to <i>In Situ</i> Detection of Nanoparticles

Abstract

Volumetric methods of nanoparticle synthesis (such as arc discharges, flames, and laser ablation) yield a plethora of particle types, but in general we lack a deep understanding of the physical processes behind such synthesis. This is due in part to a lack of diagnostic tools. The authors demonstrate a four-wave-mixing laser technique, termed coherent Rayleigh-Brillouin scattering, for $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ detection of ~5 nm particles produced in an arc discharge, with a spatial resolution of ~150 \ensuremath{\mu}m. By enabling detailed $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ monitoring of nanoparticle nucleation and growth during large-scale synthesis, this approach will advance our physical understanding of the growth mechanisms.