Nanoparticle size analysis with relaxation of induced grating by dielectrophoresis

We propose an alternative approach to the use of dynamic light scattering (DLS) for the analysis of particle sizes ranging from 5 nm to 100 nm. This approach employs a combination of 1) diffusion, 2) density grating, and 3) dielectrophoresis (DEP), and measures the diffusion coefficient from the decay rate of the diffracted light intensity in the relaxation process of particle density modulation generated by DEP. Both the experiments and the theoretical analysis confirm the reliable determination of particle size independently of the refractive index. The new method records a decay signal directly without an autocorrelator and is expected to have a less extreme sensitivity dependence on particle size than DLS. (c) 2006 Optical Society of America.