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A Combined Fluorescence and Raman Study on Hydrogen Bonding and Cluster Structure of Ethanol-water Solution

Author: WuBin
Tutor: LuJian；LuoXiaoSen
School: Nanjing University of Technology and Engineering
Course: Optical Engineering
Keywords: Hydrogen bonding Cluster structure Fluorescence spectroscopy Raman spectroscopy Ethanol molecules Water molecules
CLC: O621.13
Type: PhD thesis
Year: 2011
Downloads: 74
Quote: 1
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Abstract


In this paper, a method of combining fluorescence analysis and Raman analysis, from experimental and theoretical studies of ethanol - aqueous solution intermolecular hydrogen bonding and structural characteristics of the formation of molecular clusters. Based on the structural characteristics of the molecules of the fluorescent substance, theoretically clarify the physical mechanism of the ethanol - aqueous solution, the emission fluorescence, and then get a structural model of ethanol - water clusters. Derivative fluorescence theory on the fluorescence spectra of the ethanol - water analysis, the results showed that ethanol and water molecules in the solution formed by the hydrogen bond of the eight kinds of fluorescence cluster structure, access to the various clusters fluorescence emission wavelength and the number of clusters. with the variation of the concentration of the solution, and then get a specific concentration of the solution of the internal molecular structure and morphology of the clusters. Using the Gaussian decomposition decomposition fluorescence spectra of different concentration solution, 8 molecular clusters for each primitive fluorescence spectrum and the spectrum of each primitive central wavelength, full width at half maximum (FWHM), and then calculated according to the Franck-Condon principle electronic energy difference of the cluster structure the binding molecule structure theory is the relative size of the clusters; through research semi high width with the change in the concentration of the solution to obtain the relevant information of the cluster component. Ethanol - the effect of the temperature of the aqueous solution of Clusters. By analyzing the fluorescence spectra of ethanol - aqueous solution of 5 ~ 55 ℃ range, it is found that the temperature rise will result in specific bands of fluorescence emission enhanced accordingly studied the influence of temperature on ethanol - aqueous solution intermolecular hydrogen bonding and association morphology. The results showed that: there exists a threshold value, is located between 15 ~ 25 ℃ when the temperature is above this threshold will cause the cluster structure of the rearrangement and the formation of larger molecular clusters. Also found that the fluorescence spectrum of the low-concentration solution varies with temperature showing specificity analysis of its causes, and to determine the emission wavelength fluorescent clusters located in two clusters of 355nm and 377nm closed cage structure. Based on the hydrogen bond theory, the range of a concentration of 10% to 100% by volume solution of the hydrogen-bonding interactions as well as the corresponding structure and morphology of the molecular clusters. Different volume ratio of ethanol - aqueous solution Raman spectroscopy analysis found that, with the dilution of the solution, the ethanol molecules CH group stretching vibration frequency is blue-shifted CO group stretching vibration frequency of the red shift. Obtained in the study on the basis of the frequency shift causes the shape of the form and the cluster structures of different concentration ranges in solution hydrogen bonding interactions. Furthermore, based on symmetric CH2 telescopic superimposed peaks and CH3 asymmetric stretching vibration and CH3 symmetric stretching vibration of the vibration peak of the frequency shift of the same concentration of ethanol having a linear correlation characteristics of the experimental results, the use of binary linear regression to the establishment of the determination of the concentration of ethanol model; experimental tests: The results show that the present method has higher accuracy compared with the conventional parameters of the model based on the Raman peak intensity characterized. Through the OH stretching vibration spectrum of the hydrogen bond and cluster structure in the range of concentration of 0-10% by volume solution. The results show that: after a small amount of ethanol molecules are added to the water, the water molecules gather around the hydrophobic groups of the ethanol molecules to form a hydrated layer, while water molecules mesh hydrogen system has been expanded; molecular aggregation occurs gradually with increasing concentration of the solution, ethanol, and the water molecular envelope in ethanol molecules aggregate formed around the structure of the vesicle; aggregation of ethanol molecules will eventually lead to the weakening of the hydrophobic hydration, and thus the periphery of the water molecules of the hydrophobic hydration layer from the hydrogen bond structure of water reticulation and the formation of small self-association aggregate clusters present in the solution. The results of this study for ethanol - water clusters structure and its physical and chemical characteristics of the research and application of theoretical and experimental basis.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Theory of organic chemistry,physical organic chemistry > Organic Chemistry Structure Theory
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