Measurement of the complex dielectric constant of a single gold nanoparticle

Abstract

A differential interference contrast microscopy technique that employs a photonic crystal fiber as a white-light source is used to measure both the real and the imaginary part of the complex dielectric constant of single 10 and $15\mathrm{nm}$ gold nanoparticles over a wavelength range of $480\text{to}610\mathrm{nm}$. Noticeable deviations from bulk gold measurements are observed at short wavelengths and for individual particles even after taking into account finite-size surface damping effects.