Light-Scattering Sizing of Single Submicron Particles

The rapid detection of the particle size of a single submicron particle (100-1000 nm) is critical for the quality control of particulate matter, biomedical research, environmental research, and the development of drug delivery systems. Although the direct detection of elastically scattered light of a single submicron particle is the simplest way to measure particle size, the low sensitivity of detection instruments and the complex relationship between particle scattered light intensity and particle size make it a great challenge.

In this study, the high-level sensitivity of the Flow NanoAnalyzer is combined with the side scattering (SSC) detection of single nanoparticles, providing the first comparison of experimentally measured versus Mie theory calculated SSC light intensity of single submicron particles. Good consistency was observed between silica microspheres and polystyrene microspheres in both vertical and parallel polarization directions of the incident laser beam. Compared with vertical polarization, parallel polarization could be better resolved the microspheres of different sizes because the scattering intensity increases with the increase of particle size.

The prediction ability of the simple numerical model established in this work can be used to predict the scattering behavior of the Flow NanoAnalyzer. More importantly, using the linear relationship between the measured and the calculated scattering intensity, the researchers developed a method capable of measuring submicron particle sizes with the precision and accuracy of Mie theory, rather than a calibration curve fitted by several sparsely separated particle size reference standards. Therefore, this method has great potential in guiding the accurate measurement of submicron particle size.

Figure 1. Nano-flow cytometry detectors measure with perpendicular or parallel polarization of the laser. 

Mixture of commercially available fluorescent polystyrene microspheres from 100-900 nm

Figure 2. A new method for size measurement of Staphylococcus aureus 

based on nano-flow cytometry and Mie scattering calculations

Using the linear relationship between a particle's scattering intensity measured by the Flow NanoAnalyzer detector and the calculated scattering intensity, a method capable of measuring submicron particle size with the precision and accuracy of Mie theory was developed.

Anal. Chem., 2018, 90, 12768-12775.