Effect of colloidal nanoparticle concentration on sizing analysis with an electrospray scanning mobility particle sizer

Precise measurement of the size and size distribution of colloidal nanoparticles are an important component of evaluating nanoparticle safety. However, size measurements become increasingly difficult to perform as particle size decreases. The sizes and size distributions of nanoparticles can be determined using a variety of techniques. In this study, we used an electrospray scanning mobility particle sizer (ES-SMPS) to investigate the effect of nanoparticle concentration on the size and size distribution measurements of 20 nm and 50 nm silica nanoparticles. To calculate the size of the water droplets in the electrospray, the droplet size distribution in sucrose solutions was determined at various sucrose concentrations. The average water droplet diameter was ~ 697.5 nm, regardless of sucrose concentration. Based on these results, we estimated the appropriate nanoparticle concentration ranges for the ES-SMPS size determination of 20-nm and 50-nm silica nanoparticles. Reliable measurements of the 20- and 50-nm silica nanoparticles could be performed at concentrations of < 0.01 wt% and < 0.1 wt%, respectively.