Liter-Scale Precision Synthesis and Measurement of Nano-to-Micrometer Scale PSNPs with Graphene Liquid Cells

Monodisperse polystyrene nanoparticles (PSNPs) have great potential as standard materials in various fields, including environmental analysis, biological research, and instrumental calibration. However, reproducible liter-scale synthesis of PSNPs with controlled sizes across the nano-to-micrometer size range remains challenging because particle nucleation, growth, and colloidal stability are highly sensitive to polymerization conditions. In addition, particle size measurements often vary depending on the analytical method used. In this study, we report a robust liter-scale synthetic protocol for highly monodisperse PSNPs with controlled diameters of 50, 100, 200, and 1000 nm by optimizing key synthetic parameters. The synthesized PSNPs were benchmarked against commercial PSNP standards using transmission electron microscopy (TEM), dynamic light scattering, scanning mobility particle sizing, and static light scattering. Conventional dry-grid TEM yielded smaller apparent particle sizes than the particle size analyzers, indicating that drying and electron-beam exposure can influence the measured dimensions of soft polymer nanoparticles. To further evaluate the PSNP morphology under liquid-confined conditions, graphene liquid cell (GLC)-based solution-phase TEM was employed as a complementary characterization method.