乙醇-水溶液中团簇分子的基元荧光光谱研究

Study on the Elements of the Fluorescence Spectra Emitted from Ethanol-Water Mixture

采用高斯分解法对236nm的紫外光激发乙醇体积浓度为10%～95%的乙醇-水二元混合物产生的荧光光谱进行分解,得到了荧光谱线里面所包含的基元峰,发现每种浓度溶液的谱线都是由8个基元高斯峰组成的,并获得了每个基元谱线的相对强度、峰值位置数据。对这些高斯峰及相应参数进行分析,并结合乙醇-水混合物的荧光发射机理得到了各种发光团簇的相对大小以及构象信息,进一步计算了它们各自的荧光主发射跃迁能。另外,还对高斯峰半高宽与溶液中分子间缔合形态之间的联系做了初步探讨。研究结果可为进一步研究乙醇-水二元混合物的微观结构和特性提供理论和实验依据。

The 236 nm UV-light was adopted to excite the 10 ethanol-water mixture samples in which the volume percent of ethanol ranges from 10% to 95%, and the Gaussian decomposition method was used to decompose the fluorescence spectra obtained above to Gaussian curves,where every Gaussian curve can be attributed to the fluorescence emission of a certain kind of luminescent ethanol-water cluster, which is formed by the association between water molecules and ethanol molecules. It was found that every spectrum of the certain binary mixture contains 8 Gaussian elements, and the emission density and peak wavelength of each element were also obtained. The authors studied the mechanism of the fluorescence emission of the mixtures based on the structural characters of fluorescence substances and concluded that the water molecules play an important role in the fluorescence emission： they enlarge the conjugate system as the electron donors; they bridge the ethanol molecules to form 8 kinds of new clusters at the same time, and the conformation of the clusters is rings and chains composed by several rings. Through the peak wavelengths of the Gaussian elements decomposed from the certain concentration spectrum the authors got the information about the relative size of the new clusters, i.e. the clusters are bigger or show chain structures when the peak wavelength of the Gaussian curves is located at the longer positions. The emission transition energies of the 8 kinds of new clusters were also calculated. In addition, it was found that there was a certain relation between the half-width and the association situation. The research contributes to the study of ethanol-water cluster structures and their physical and chemical characteristics.