Optical Ultramicroscopy of Nanoparticles in Aqueous Solutions Using Elastic Light Scattering: Real-World Capabilities and Comparison with TEM and DLS

An improved optical ultramicroscope is described to be used for visualizing single nanoparticles (NPs) sized over 5–10 nm in aqueous solutions and determining their hydrodynamic radii. The ultramicroscope is based on detection of Brownian motion trajectories of NPs using the elastic light scattering signals of two—laser and nonlaser—sources and their subsequent analysis for determining individual hydrodynamic radii of the detected NPs. The actual capabilities of the developed microscope in studying NPs of a different nature, including biological ones, are demonstrated. The analysis results for silver and silicon dioxide (SiO2) NPs obtained using the developed microscope are compared to those obtained using a transmission electron microscope and a dynamic light scattering microscope (DLS). The developed microscope is shown to hold promise in medical diagnosis applications. Advantages of using a nonlaser source of bright incoherent radiation for analysis of submicron particles larger than 100 nm are demonstrated.