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Sizing Nanoparticles by Means of Elliptically Polarized Scattered Light: A suggested method
Author(s) -
Bohren Craig F.
Publication year - 1990
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19900070120
Subject(s) - spheres , optics , polarization (electrochemistry) , azimuth , scattering , wavelength , mie scattering , light scattering , ellipse , circular polarization , sizing , elliptical polarization , nanoparticle , physics , materials science , molecular physics , linear polarization , nanotechnology , chemistry , laser , organic chemistry , astronomy , microstrip
Given the paucity of optical methods for sizing nanoparticles (those between 1 and 100 nm), more methods are needed if, as has been predicted, such particles have a bright future. Linearly polarized light is transformed into elliptically polarized light upon scattering by small spheres at 90°. The resulting circular polarization increases as the fifth power of particle diameter and the shift of the azimuth of the vibration ellipse from the vertical increases as the square if the particles are negligibly absorbing. Titanium dioxide spheres (in air) with diameters between 20 and 120 nm give circular polarizations between about 10 −5 and 10 −1 for incident light of wavelength 450 nm. The corresponding azimuth shifts (in radians) lie between about 10 −2 and 1. These values are within reach of experimental techniques based on polarization modulation. Metallic spheres yield much larger circular polarizations and azimuth shifts (with signs opposite those for negligibly absorbing spheres), both of which increase approximately as the square of particle diameter.