Effect of Rotational Diffusion on Quasi-Elastic Light Scattering from Fractal Clusters
The aggregation of colloids is of substantial interest both fundamentally and practically. The level of interest has risen in recent years with the observation that colloidal aggregates are often well characterized as scale-invariant, or fractal, objects, providing a quantitative description of the structure of these random, irregular clusters.1–4 The consequences of the scale invariance on light scattering from the clusters has been widely exploited. In static light scattering, the dependence of the scattering intensity on the scattering wave vector q allows a convenient way of determining the fractal dimension of the clusters, while Quasi-Elastic Light Scattering (QELS) has proved useful in monitoring the kinetics of the aggregation process. The combination of the scale-invariant structures of the aggregates and the power-law distributions which often occur leads to elegant scaling behavior of the dynamic light scattering.5,6 For the large clusters (qRg ≳1) often found in aggregation, rotational diffusion can play an important role in determining the decay of the autocorrelation of the scattered light measured in QELS. While scaling arguments have been used to account for the contribution of rotational diffusion, it is nonetheless important to determine this effect more quantitatively.
KeywordsFractal Dimension Autocorrelation Function Dynamic Light Scattering Rotational Diffusion Rotational Effect
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- 2.D. A. Weitz, M. Y. Lin, J. S. Huang, T. A. Witten, S. K. Sinha, J. S. Gethner and R. C. Ball, in Scaling Phenomena in Disordered Systems,ed. R. Pynn and A. Skjeltorp (Plenum, New York:1985).Google Scholar
- 5.J. E. Martin, this volume.Google Scholar
- 9.Z. Chen, P. Sheng, D. A. Weitz, H. M. Lindsay, M. Y. Lin and P. Meakin, to be published.Google Scholar
- 10.B. J. Berne and R. Pecora, Dynamic Light Scattering (Wiley, New York:1976).Google Scholar