SPR detection of single nanoparticles and viruses
By applying the conventional optical microscopy to detection of particles, which are smaller than the wavelength, scattered light is observed. Since the scattering cross section drops as the sixth power of the size, high illumination intensity and high aperture objective is required. In the present work a new approach for nano particles visualization is suggested.The observation of the particle is based on local increasing of reflection on a surface caused
by a particle bound to the surface. The reflection is observed on a thin metal layer in the Kretschman scheme for surface plasmon resonance measurements. It was shown that the local reflection increasing corresponds to effective scattering cross section which is up to three orders of magnitude larger than by Mie scattering on the same particle.