Uncertainty analysis of measurements of the size of nanoparticles in aqueous solutions using dynamic light scattering

One of the standard methods used to measure the size of nanoparticles in aqueous solutions in situ is dynamic light scattering (DLS). The principle of this technique used to measure the real size of nanoparticles in a solution is the use of a procedure that extrapolates the apparent diffusion coefficients at different scattering angles and the sample concentration to infinite conditions. The uncertainty in the measurement is related to the extrapolating procedure used, and we have evaluated this for nanoparticles with diameters in the range 20 nm to 100 nm using the methods described in the ISO Guide to the Expression of Uncertainty in Measurement. The size of nanoparticles measured using DLS was compared with that obtained using a microscopic method, a cryo-transmission electron microscope, to check the reliability of the results obtained from the DLS measurements, which showed good agreement within the uncertainty levels evaluated.