Sizing colloidal particles from their contribution to the effective refractive index: Experimental results

In this work we assess experimentally a new methodology for sizing non-absorbing colloidal particles in situ. It requires measuring the real and imaginary part of the effective refractive index per unit volume fraction occupied by the particles. The mean size and refractive e index of the particles are determined from a suitable model for the effective refractive index of dilute colloids. We present results of experiments made with polystyrene and silica nano-particles and compare them with dynamic light scattering and electron microscopy measurements.