Electrospray-Scanning Mobility Particle Sizer (ES-SMPS) Technique: Superior Sizing and Multimodal Characterization of Colloidal Nanoparticles Compared to NTA and DLS.

Abstract

This study primarily employed three techniques─electrospray-scanning mobility particle sizer (ES-SMPS), nanoparticle tracking analysis (NTA), and dynamic light scattering (DLS)─to assess multimodal samples. For monodisperse particles, both ES-SMPS (all sizes) and NTA (for particles larger than 40 nm) accurately determined the mean size, while DLS overestimated it. The ES-SMPS technique demonstrated precision in particle counting for multimodal samples, with a standard deviation of around 2.5-4%. Conversely, NTA's ability to count particles potentially leads to misinterpretation. The ES-SMPS approach could identify particle peaks in multimodal (bimodal, trimodal, and tetramodal) samples and show the relatively accurate position of the mode diameter. In contrast to ES-SMPS, DLS and NTA have weaknesses in characterizing multimodal samples. While NTA's performance depends on the optical properties of particles and cannot measure silica particles smaller than 30-40 nm, ES-SMPS is independent of light scattering and can handle particles as small as ∼13 nm. The ES-SMPS also excelled in separating particle peaks of the bimodal sample with a size interval gap of 10 nm, whereas NTA needs at least 20-50 nm depending on the particle type. To sum up, the ES-SMPS method performs better and provides more accurate measurements for characterizing multimodal samples compared to NTA and DLS.