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The secondary inner filter effect on the fluorescence excitation spectra of rhodamine 6G aqueous solutions with concentration was demonstrated in this paper. The peak of fluorescence excitation spectrum stays at 525 nm at low concentrations, while it breaks up and turns into valley at high concentrations. The threshold concentration was determined to be 3.16 mg/L by the second derivative spectroscopy. A mathematical model was proposed to explain the inflection point of fluorescence excitation spectrum caused by the secondary inner filter effect. On the basis of it, the threshold concentration was calculated to be 2.86 mg/L, approaching to the experimental result. [ABSTRACT FROM AUTHOR]

The Raman spectra of nine monohydroxy alcohols have been obtained by confocal Raman spectrometer at room temperature. Based on the Raman spectra, the density functional theory was used to analyze the characteristic Raman bands of monohydric alcohols. Through the discussion of the characteristic Raman bands and their corresponding assignment, four major Raman bands were selected to identify nine monohydric alcohols using principal component analysis and Euclidean distance. Finally, nine saturated monohydroxy alcohols can be distinguished exactly, and the recognition rate is 100%. [ABSTRACT FROM PUBLISHER]