Image of the Week - 23 September 2008

This dark-field image was formed by accumulations of colloidal gold nanoparticles (40 nm diameter) on a coverslip. The green color comes from the resonance Rayleigh scattering of single gold nanoparticles due to surface plasmon resonance excitation. Because the wavelength of the surface plasmon resonance associated with the nanoparticles is dependent on particle size, shape, and local dielectric environment, the dark-field image exhibits different colors. This image, which measures 30 x 30 microns, was acquired using a color CCD camera attached to our reflected light microscope.