Particle Size Measurement for Nanoparticles by Induced Grating Method Applied Dielectrophoresis

摘要

An important method of conducting the particle size analysis of nanoparticles (NPs) in liquid phase relies on the principle of light scattering, such as dynamic light scattering, laser diffraction, and particle tracking analysis. The intensity of scattered light by NPs, however, sharply declines with decreasing particle size; it becomes difficult to measure with accuracy the size below a few tens of nanometer. To overcome this limitation, an alternative approach has been proposed; the method is called Induced Grating (IG). In principle, NPs tend to accumulate near an electrode array by dielectrophoresis when the electric field is applied, and it is inducing the density grating of NPs. Diffracted light due to NPs density grating can then be detected by the sensor. When the electric field is turned off, the diffraction intensity starts to decline due to the NPs diffusion from the accumulated position. During this relaxation time, the diffusion coefficient of NPs is to be obtained from the decay curve of the diffraction intensity and is converted to particle diameter using the Stokes-Einstein equation. In this study, we evaluate the performance of a new system named IG-1000 (Shimadzu) based on this IG principle against various NPs, such as polystyrene latex, colloidal silica and zinc sulfide NPs.