Investigation of Particle Interactions in Concentrated Colloidal Suspensions Using Frequency Domain Photon Migration: Monodisperse Systems

Investigation of structure factors in dense colloidal suspensions using frequency domain photon migration: polydisperse systems

“…The details of FDPM instrumentation and theory are described elsewhere [6,21]. Briefly, the measurements consisted of measuring the phase shift (PS) and attenuation of average of intensity (DC) and amplitude (AC) at 12 different source-detector distances ranging from 7 to Table 1 Particle size information for the polydisperse sample measured by DLS…”

“…By comparing angle-integrated structure factors obtained experimentally with those theoretically predicted, one can examine the model of S i,j in colloidal suspensions. A similar approach has been successfully employed to study structure factors in mono-and bidisperse colloidal suspensions [6,7].…”

“…In previous studies using FDPM, we found that the monodisperse and bidisperse hard sphere Percus-Yevick (HSPY) model are suitable for accounting for the predominant particle interactions in monodisperse [6] and bidisperse [7] suspensions at high volume fractions. For polydisperse systems, Vrij [12] and Blum and Stell [13] independently derived the analytical solutions of the partial structure factor S i,j using the polydisperse HSPY approximation.…”

“…There are three primary advantages of FDPM: (i) since FDPM depends upon multiply scattered light, it is more suitable than light, X-ray, and neutron scattering approaches for assessment of particle interactions within concentrated suspensions; (ii) since FDPM measures time-dependent propagation characteristics rather than the amount of light detected, it is self-calibrating and no external calibration is required; and (iii) since FDPM allows determination of absorption and scattering independently, characterization of colloidal scatters is not biased by changes in the light absorption or color of suspending fluids. Using the FDPM technique, we have successfully studied volume-excluded interactions in monodisperse [5,6] and bidisperse [7] suspensions, as well as depletion interactions in colloid-polymer mixtures [8].…”

Assessment of Small-Angle and Angle-Averaged Structure Factor for Monitoring Electrostatic Colloidal Interactions Using Multiply Scattered Light

“…The FDPM approach is based upon "timeof-flight" measurements of multiply scattered light made in the frequency domain and provides accurate, static light scattering measurement of the isotropic scattering coefficient. Previously we have shown that these measurements can be quantitatively 434 0021-9797/02 $35.00 predicted using models for particle interactions (20,21). Assuming particle interactions are due predominantly to volume exclusion effects, Sun et al employed the hard-sphere Percus-Yevick model to predict light scattering measured by FDPM and to infer particle size in monodisperse (21), binary (22), and polydisperse systems (23).…”