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. Measuring this quantity by conventional methods, however, often proves challenging. We describe a facile approach to determine the molar mass of (soft) nanoparticles via counting their number per volume using a widefield fluorescence microscope. The method is exemplified on a microgel dispersion as a model system, while it is applicable to other types of stainable nanoparticles. For this, covalent labeling or modification of the nanoparticles is not required. The dispersion is simply mixed with a Nile Red solution in a defined ratio and measured in an optical fluorescence microscope accessible to most researchers in the field.