Ethanol - Aqueous Solution Raman Spectra And Molecular Structure Analysis

Ethanol-water has been widely used in medical and health field, food production and industrial solvent field. Its molecular structure, physical and chemical properties, biological significance is greatly concerned. So it has important theoretical significance and applications.Fluorolog3 spectrometer is used in the experiment as well as a laser with a wavelength of 532.0nm. Subtract baseline from the spectral data and smooth the curve, and the Gaussian function is applied to fit local peak area further. We research and analyze Raman structural features corresponding to the three local structure of molecular vibration mode of ethanol and water including the structure of ethanol molecules CH stretching vibration, the structure of water molecules HOH bending vibration and the structure of water molecules HOH stretching vibration mode. The relationship between Raman structural features of the above three vibration modes and ethanol concentration are studied. The results show that:(1) With the increase of ethanol concentration, ethanol molecule CH stretching vibration frequency has "red shift", And there is approximately linear relationship between peak intensity and the concentration of ethanol. This "red shift" property and linear relationship, on one hand, offers an effective method to detect ethanol concentration in solution and this has practical value in applications. On the other hand, the evidence of change in microscopic molecular structure with the increase of ethanol concentration is observed and this can provide the basis for father theoretical study. (2) When the concentration of ethanol-water solution changes, the water molecules HOH bending vibration frequency doesn't change significantly in overall, but it only has a slight fluctuation in the local area. (3) When the concentration of ethanol is from 60% to 90%,the stretching vibration frequency of water molecules HOH is significant in this region, and HOH symmetric stretching vibration frequency pronounces ups and downs obviously. The deep physical mechanism it contained needs further study.The research methods and the corresponding results in this paper can provide valuable reference for the theoretical and application research of water molecules and alcohol clusters.