Measurement of nanoparticle sizes by conventional optical microscopy with standing evanescent field illumination

摘要

The size of a particle smaller than the diffraction limit is measured using a conventional optical microscopenby adopting a standing evanescent field illumination. The scattering intensity from a nanoparticle is peri-nodically modulated by shifting the intensity fringes of the standing evanescent field. By measuring contrastnof scattering intensity variation during one cycle of modulation, particle sizes can be estimated easily. Fur-nthermore, material dependence can be canceled using contrast as an evaluation factor. From the experimen-ntal results, particle sizes ranging from 20 to 250 nm are successfully determined. This technique offers anlow-cost size measurement for nanoparticles. © 2008 Optical Society of America