Scattering and absorption cross-section spectral measurements of gold nanorods in water

The usually measured attenuation (extinction) spectra of gold nanorods in water include two unresolving contributions: absorption and scattering. The present study is to separate these two contributions by measuring the total scattering losses as a function of wavelengths. Knowing the total-attenuation spectrum and the scattering-loss spectrum, the pure absorption spectrum can be finally determined for a given sample system. Two approaches are employed for experimentally estimating the pure scattering losses: one is direct measurement using a calibrated large-area photodetector to collect the scattered energy along a certain solid angle; the other is comparison measurement by using polystyrene microspheres in water as a standard sample whose scattering cross section is known well. These two methods have given nearly the same results and are finally compared with the theoretical calculations.