The Influence of Solvents on the Fluorescence Background in Raman Spectroscopy

Abstract

For the purpose of reducing the fluorescence background induced by the laser irradiation in the measurements of Raman spectra, the influence of solvents on the background intensities for three polycyclic aromatic compounds was examined, where the experiments were conducted with typical solvents. It was demonstrated that the behaviors of the fluorescence background against the laser irradiation time were quite different according to the solvents, and that the behaviors could be classified roughly into the three categories. It was proved that when suitable solvents were used, the background intensities could be reduced sufficiently, even for the fluorescent samples such as those treated here; thus, the clear observation of Raman spectra is obtained. As an example of the solvent influence on the Raman spectra, the results of measurements for three separate cases were shown for 1-nitropyrene. The three cases are as follows: first, the Raman bands are masked almost completely by the strong background (solvent: 1,1,2,2-tetrachloroethane); second, though the spectrum can be obtained, its S/N ratio is low because of the relatively large background (solvent: acetonitrile); third, a clear spectrum with excellent S/N ratio can be obtained because the background intensity is low enough (solvent: carbon tetrachloride).