Structure characterization of nanoparticles with optical tweezers using scattering light

Abstract

Here we present and demonstrate a non-contact optical measuring method for the characterization of both the shape and size parameters of nanoparticles using optical tweezers. The measurement relies on the optical polarization and scattering of nanoparticles. For nanoparticles levitated within optical tweezers, the absolute scattering light power in a fixed detection region gives the nanoparticle size, while the scattering light pattern provides insight into the shape of nanoparticles. With prior information on the nanoparticles, particle structures can be derived only through its scattering light. The method is experimentally demonstrated using silica and polystyrene nanoparticles obtaining shape measuring results in consist with the traditional detecting method conducted in a vacuum. Moreover, the radii of the componential nanospheres derived from the method lie within the radii range obtained from electron microscopy imaging results, where the uncertainty is about ±3.5%. This work provides an effective method for the identification and studying of individual nanoparticles, which is attracting growing concerns in areas, such as precise sensing, environment, and health.