A facile method to determine the molar mass of soft nanoparticles

Abstract

The determination of the molar mass of soft nanoparticles is essential to estimate their (molar) concentration in dispersions. Methods to measure this quantity are, however, challenging. We describe a facile way to determine the molar mass of (soft) nanoparticles via counting their amount per volume using a widefield fluorescence microscope. As model system we applied it to microgels, but it is applicable to other types of stainable nanoparticles. The method does not require covalent labeling or modification of the nanoparticles. The dispersion is simply mixed with a Nile Red solution in a defined ratio and measured in an optical fluorescence microscope to which most researchers in the field have access.