Emerging Techniques for Submicrometer Particle Sizing Applied to Stober Silica

The accurate characterization of submicrometer and nano-meter sized particles presents a major challenge in the diverse applications envisaged for them including cosmetics, biosensors, renewable energy, and electronics. Size is one of the principal parameters for classifying particles and understanding their behavior, with other particle characteristics usually only quantifiable when size is accounted for. We present a comparative study of emerging and established techniques to size submicrometer particles, evaluating their sizing precision and relative resolution, and,demonstrating the variety of physical principles upon which they are based, with the aim of developing a framework in which they can be compared. We used in-house synthesized Stober silica particles between 100 and 400 nm in diameter as reference materials for this study. The emerging techniques of scanning ion occlusion sensing (SIOS), differential centrifugal sedimentation (DCS), and nanoparticle tracking analysis (NTA) were compared to the established techniques of transmission electron microscopy (TEM), scanning mobility particle sizing (SMPS), and dynamic light scattering (DLS). The size distributions were described using the mode, arithmetic mean, and standard deviation. Uncertainties associated with the six techniques were evaluated, including the statistical uncertainties in the mean sizes measured by the single-particle counting techniques. Q-Qplots were used to analyze the shapes of the size distributions. Through the use of complementary techniques for particle sizing, a more complete characterization of the particles was achieved, with additional information on their density and porosity attained.