Quantitative measurement of scattering and extinction spectra of nanoparticles by darkfield microscopy

We demonstrate a versatile concept for the quasi simultaneous and quantitative measurement of light extinction and scattering cross section spectra of nanoparticles in a darkfield microscope. We validate this method by the analysis of an aqueous suspension of gold nanorods and comparison with both numerical simulations and standard spectrophotometry measurements. Our approach holds the promise to allow one to map the principal optical properties of nanoparticles in a biological sample with m spatial resolution, which is an issue of particular relevance for applications in biomedical optics such as photothermolysis and laser hyperthermia.