Nanoparticle characterization with photon correlation LDA

A completely new photon correlation Laser Doppler Anemometer system was developed to simultaneous particle number, velocity and size measurements down to the nanometer size range. The backscattering arrangement assures the online, in-situ, non-invasive measurements without further fine tuning. Since the measurements are on-line and in situ the particle synthesis process can be monitored with high temporal and spatial resolution. In this way a nanoparticle generator can be analyzed and, for instance, the source of an unwanted broad size distribution may be identified, or the degree of agglomeration and the related properties can be controlled. The accuracy limits of individual velocity and size estimations were investigated with monodisperse paraffin particles separated by Differential Mobility Analyzer. Although the signal-to-noise ratio decreases for nanoparticles, the particle sizing remains robust due to high power increase of the scattered intensity with the size.