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

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.