Confocal Depolarized Dynamic Light Scattering: a Novel Technique for the Characterization of Nanoparticles in Complex Fluids

Abstract

We present Confocal Depolarized Dynamic Light Scattering as a novel optical method for the characterization of nanoparticles in solution. The method is validated in conditions of biological interest where traditional optical methods fail. As a test case we study highly concentrated, strongly scattering, samples of thermosensitive core-shell particles constituted by a spherical PMMA core surrounded by a PNIPAM network and, follow the kinetics of the processes induced by temperature changes. We prove that through the confocal optical scheme, the multiple scattering contribution is reduced by orders of magnitude.Moreover, the method allows the efficient characterization of NPs with a superior accuracy in particle size determination. Low degrees of polydispersity can be easily characterized through an adapted cumulant method.

Light extinction and scattering from aggregates composed of submicron particles

“…Although the models for turbidity and the scattering amplitude stem from two different standpoints, the formal results are the same. This correspondence reveals a peculiarity of the relationship between scattering and extinction, as in Rayleigh and Rayleigh-Gans scattering (Van de Hulst 1981;Bohren and Huffman 2008;Potenza and Milani 2014;Potenza et al 2015b): the structure factor S(q) and C sca (λ) can be simply obtained by summing up the fields radiated by each monomer, whereas evaluating the extinction requires to introduce the second-order correlations. For non-dielectric materials, where C sca (λ) ≠ C ext (λ), these two models are not the same.…”