We have studied the dynamical and structural properties of dense charge stabilized colloidal suspensions by a combination of small-angle neutron scattering (SANS), 3D dynamic light scattering (3DDLS) and diffusing wave spectroscopy (DWS). SANS and 3DDLS extend static and dynamic light scattering techniques to the regime of opaque samples while DWS additionally provides information on short length scales, typically from 1-50 nm. This offers an increased range of accessible length and time scales perfectly suited for the (non-invasive) investigation of highly concentrated suspensions. Different systems have been examined ranging from hard sphere like suspensions over strongly repulsive charged spheres to colloidal gels. We furthermore present an extended theoretical frame for DWS to characterize the internal dynamics of turbid gels made from nanosized colloidal particles.

Abstract. -Static structure factors S(q) of deionized aqueous suspensions of charged polystyrene particles with similar radii but strongly differing bare charges have been measured for volume fractions 3.5 × 10 −4 ≤ ϕ ≤ 1.55 × 10 −2 , using a cross-correlation light scattering technique which allows for the extraction of single scattered light from highly turbid samples. Measurement of absolute intensities allowed to determine unambiguously normalized values of S(q). With decreasing volume fraction, the amplitude of the first peak of S(q) reflecting the order of the suspension does not monotonically decrease, but rather shows a distinct minimum at ϕ ∼ (5 − 8) × 10 −3 . This reappearance of structure is compared with theoretical predictions on the basis of a jellium model for the effective interparticle potential U eff (r).The forces governing the structure and phase behavior of suspensions of charged colloidal particles are of prime importance for many technological applications, such as ceramic processing, drug delivery or the stability control of paints. In the standard picture of Derjaguin, Landau, Verwey, and Overbeek (DLVO) [1], the electrostatic interaction between two charged colloidal particles in an electrolyte arises from the repulsion of the electric double layers that form due to the competition between configurational entropy of the small ions and their potential energy in the Coulomb field of the macroions with negative charge −Ze 0 , e 0 being the elementary charge. When the bare charge Z is large, a part of the surrounding counterions is strongly bound to the particle and thus reduces the bare charge to an effective chargeZ < Z which then governs the ion distribution at distances comparable to the Debye screening length κ −1 [2]. In contrast to the situation in simple liquids, however, the strength of the effective interparticle potential U eff (r) determined by the effective chargeZ and its range κ −1 does not only depend on the bare charge Z but also on the concentrations of co-and counterions and the particle volume fraction ϕ [3]. This density dependence of the effective potential is reflected by the fact that even at volume fractions as low as 10 −4 strongly charged particles show considerable order, as reflected by the strong first peak in the colloid-colloid structure factor S(q) measured in light scattering experiments from deionized suspensions [4,5]. When, at higher volume fractions, the number of counterions balancing the particle charge becomes larger than the number of excess salt ions, the screening will become dominated by the former,

Abstract. We show that the spectral speckle intensity correlation (SSIC) technique can be profitably exploited to recover the path length distribution of photons scattered in a random turbid medium. We applied SSIC to the study of Teflon slabs of different thicknesses and were able to recover, via the use of the photon diffusion approximation theory, the characteristic transport mean free path * and absorption length s a of the medium. These results were compared and validated by means of complementary measurements performed on the same samples with standard pulsed laser time of flight techniques.

Amyloid-beta peptide (Aβ) aggregation is one of the hallmarks of Alzheimer's disease (AD), and metal ions such as Cu(ii) have been proposed to play a role in amyloid formation and the onset of this progressive neurodegenerative disorder. This study reports the design and characterization of a novel bifunctional non-natural tetrapeptide, Met-Asp-d-Trp-Aib, that is capable of binding copper, competing with Aβ for Cu(ii), and modulating Aβ aggregation. The study of this tetrapeptide provides further insights into the role of Cu(ii) in the Aβ aggregation pathway, and into the design of compounds with therapeutic potential for Alzheimer's disease.

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