Fig.1: Setup for transmission experiment
L: Deuterium-Halogen Light Source
F: Optical Fiber
Fig. 1 shows a typical transmission experiment: Light of the deuterium-halogen light source is led to the sample through an optical fiber. The sample can be solid or fluid. Another optical fiber leads the light to the spectrometer.
Fig. 2: VIS spectra of gold nanoparticles in water
The optical properties of gold nanoparticles have been investigated more than 100 years ago by Faraday and Mie. Typically, the spectra of non-interacting spherical gold nanoparticles show one broad absorption peak in the visible range. Fig. 2 shows absorption spectra of spherical gold nanoparticles (d ≅ 15nm) in water. The reference spectrum was taken with water in the cuvette. The different spectra correspond to different concentrations of gold nanoparticles in water. The highest concentration (1012 particles/ml) leads to the spectrum with the lowest transmittance. The lower the concentration of gold nanoparticles, the more light is transmitted, and finally one gets a 100% line, when the concentration of gold nanoparticles becomes zero.