UV-VIS Spectroscopy

Experimental Setup

Fig.1: Setup for transmission experiment
L: Deuterium-Halogen Light Source
F: Optical Fiber
Sm: Sample
Sp: Spectrometer

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.

VIS spectra of gold nanoparticles

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.