To characterize the structural and dynamic properties of (soft) materials, information on the relevant mesoscopic length scales is required. Such information is often obtained from traditional static and dynamic light scattering (SLS/DLS) experiments in the single scattering regime [1]. In dense systems, such as colloidal suspensions and gels, however, these powerful techniques frequently fail due to strong multiple scattering of light. Here we review some of the recent advances in light scattering from turbid fluid- and solid-like media that include 3D cross-correlation experiments to suppress multiple scattering [2] and echo diffusing wave spectroscopy [3] to access dynamic and static properties of extremely turbid media. We in particular focus on a novel multi-angle light scattering instrument that fully implements the 3D cross correlation scheme and thus allows for time-resolved measurements on turbid suspensions. We show that this technique provides access to the initial stage of aggregation and cluster formation in concentrated and turbid destabilized colloidal suspensions.

References: [1] F. Scheffold and P. Schurtenberger, “Light scattering probes of viscoelastic fluids and solids”, Soft Materials 1, 139-165, (2003) [2] Frank Scheffold, Andrey Shalkevich, Ronny Vavrin, Jérome Crassous, and Peter Schurtenberger, “PCS Particle Sizing in Turbid Suspensions: Scope and Limitations”, "Particle Sizing and Characterization", ACS Symposium Series 881, T. Provder and . Texter, Eds., pp 3 - 32 (2004) [3] P. Zakharov, F. Cardinaux and F. Scheffold, "Multi-speckle diffusing wave spectroscopy with a single mode detection scheme", Phys. Rev. E, 73, 011413, 2006