Quantitative Measurements of Individual Gold Nanoparticle Scattering Cross Sections

Dark field microspectroscopy is a powerful tool for studying plasmon resonances of noble metal nanoparticles and for developing their applications in sensing and imaging. Here we calibrate a dark field microspectrometer with measurements on gold nanospheres in a uniform dielectric medium to yield quantitative spectral scattering cross sections for elongated nanoparticle shapes. Gold bipyramids, 135 nm in length, were found to have a peak differential cross section of 1.2 × 10−16 m2. Measurements of a small ensemble of gold nanorods, 13 nm in diameter and 45 nm in length on average, were found to have a peak differential cross section of only 1 × 10−18 m2. For the smaller gold nanorods, approximate expressions for the total scattering cross section may be used to indicate their scattering signal in microscopy applications.