Particle sizing in highly turbid dispersions by Photon Density Wave spectroscopy

Photon Density Wave (PDW) spectroscopy is presented as a fascinating technology for the independent determination of scattering (μ′s) and absorption (μa) properties of highly turbid liquid dispersions. The theory is reviewed introducing new expressions for the PDW coefficients kI and kΦ. Furthermore, two models for dependent scattering, namely the hard sphere model in the Percus-Yevick Approximation (HSPYA) and the Yukawa model in the Mean Spherical Approximation (YMSA), are experimentally examined. On the basis of the HSPYA particle sizing is feasible in dispersions of high ionic strength. It is furthermore shown that in dialyzed dispersions or in technical copolymers with high particle charge only the YMSA allows for correct dilution-free particle sizing.

► Theory of modern Photon Density Wave (PDW) spectroscopy is presented in a concise form. ► New expressions for the PDW coefficients are derived. ► Two different models for dependent light scattering are experimentally examined. ► Successful particle sizing at volume fractions >40% is presented for technical copolymers.