Characterization of spherical core-shell particles by static light scattering. Estimation of the core- and particle-size distributions

A numerical method is proposed for the characterization of core-shell spherical particles from static light scattering (SLS) measurements. The method is able to estimate the core size distribution (CSD) and the particle size distribution (PSD), through the following two-step procedure: (i) the estimation of the bivariate core-particle size distribution (C-PSD), by solving a linear ill-conditioned inverse problem through a generalized Tikhonov regularization strategy, and (ii) the calculation of the CSD and the PSD from the estimated C-PSD. First, the method was evaluated on the basis of several simulated examples, with polystyrene-poly(methyl methacrylate) core-shell particles of different CSDs and PSDs. Then, two samples of hematite-Yttrium basic carbonate core-shell particles were successfully characterized. In all analyzed examples, acceptable estimates of the PSD and the average diameter of the CSD were obtained. Based on the single-scattering Mie theory, the proposed method is an effective tool for characterizing core-shell colloidal particles larger than their Rayleigh limits without requiring any a-priori assumption on the shapes of the size distributions. Under such conditions, the PSDs can always be adequately estimated, while acceptable CSD estimates are obtained when the core/shell particles exhibit either a high optical contrast, or a moderate optical contrast but with a high 'average core diameter'/'average particle diameter' ratio. (C) 2012 Elsevier Ltd. All rights reserved.