Dynamic and static light scattering is applied to concentrated suspensions of silica nanoparticles with surface functionalizations causing highly charged or hard sphere interaction potentials, respectively. The index of refraction of the dispersion medium was matched to that of the particles using a mixture of water/glycerol for the charged particles and toluene/ethanol for the hard spheres. The static structure factors correspond to the appropriate theoretical models, Percus–Yevick and rescaled mean spherical approximation. At volume fractions φ=0.18 a glass transition for the charged systems and at φ=0.53 for the hard spheres can be observed, as evident from the nondecaying components of the intermediate scattering functions. In the glassy state the experimental correlation functions agree with the predictions of the mode-coupling theory over several orders of magnitude in time. Using the fitted experimental structure factors as input for the mode-coupling theory we find good agreement between the theoretical nonergodicity parameters and the measured Debye–Waller factors. In the liquid state close to the glass transition the experimental intermediate scattering functions and the predictions of the mode-coupling theory for the α and β relaxation are compared within a large Q range. Using an exponent parameter λ=0.74 for the charged particles and λ=0.76 for the hard spheres a good agreement between theory and experiment can be obtained, both for the liquidlike and the glassy state.

Using the hydrolysis of appropriate alkoxide mixtures in water-in-oil microemulsions, nanocrystalline BaTiO3 has been prepared in the form of nonaggregated, cube-shaped crystals at room temperature without any sintering process as is demonstrated by means of x-ray diffractograms and transmission electron micrographs. By variation of the length of the hydrophilic part of the surfactant molecules, the diameter of the water droplets in the microemulsions could be tuned to values between 8 and 55 nm as determined by dynamic light scattering. The size of the resulting nano-BaTiO3 (6 nm ≤ 〈d〉vol ≤ 17 nm) was evaluated from the line broadening of x-ray reflections and correlates to the droplet size. The particle size distribution is very narrow, and in some cases nearly monodisperse.

We present evidence for long-range correlations C 2 (t) in temporal intensity fluctuations of multiply scattered visible light. The time autocorrelation function of the angular-averaged light intensity transmitted through a thin slab containing particles undergoing Brownian motion was determined for a series of different sample thicknesses, beam spot sizes at the sample surface, and optical transport mean free paths l*. The results for both the amplitude ͑i.e., the inverse conductance 1/g͒ as well as the time (t) dependence of the correlation function C 2 (t) are in good overall agreement with theory. Significant deviations are found, however, when correlations generated in a layer of 1l* to 2l* adjacent to the incoming surface become important. In particular the predicted t Ϫ1/2 long-time tail of C 2 (t) was not observed. A physical explanation of these deviations is given based on the argument that at least one scattering event is required before long-range correlations C 2 (t) can develop. ͓S0163-1829͑97͒08341-0͔

The density of dependence of the static structure factor S(Q) of liquid-like ordered colloidal suspensions is investigated by light scattering techniques. We found that variation of the particle number density even by a factor of 8 produced only a modest change of the height of the first peak of S(Q). In order to obtain a consistent theoretical description of S(Q) at various particle number densities, the effective charge Z*p of the particles and the Debye screening parameter κ* were calculated on the basis of the Poisson–Boltzmann–Cell (PBC) model and the Poisson–Boltzmann–Jellium (PBJ) model, respectively. The resulting Z*p and κ* values were used to calculate S(Q) via the rescaled mean spherical approximation (RMSA). It is found that a consistent description of the density dependence of S(Q) is possible with the PBC model. By contrast, the PBJ model predicts too weak a liquid-like order than observed experimentally.

The glass transition dynamics of polymer micronetwork colloids. A mode coupling analysis Dynamic and static light scattering is applied to concentrated suspensions of a new species of charged colloidal suspensions with a low refractive index. The polymer colloids which were obtained by polymerizing perfluorobutylacrylate could be index matched in a water/glycerol mixture. At volume fractions ⌽ greater than 0.22 a glass transition can be observed, which is manifested by the nondecaying components of the intermediate scattering functions. The intermediate scattering functions for a supercooled liquid sample and the predictions of the mode-coupling theory for the ␤ relaxation are compared over a large Q range. By using an exponent parameter ϭ0.76 a good agreement between theory and experiment can be obtained.