Studies On Spectroscopy Characteristic Of Ethanol-Water Clusters And Its' Structure Inversion

Based on the experimental results of the fluorescence spectrum, the molecularstructure of ethanol-water clusters have been studied by using the theories of quantummechanics and quantum chemistry. The physical model and the structure information of thecluster molecules have been presented and concluded after a detailed discussion on thespatial orientation character, the planar structure feature as well as the change rule ofenergy levels. Furthermore, the cluster molecular structures have been inversed.From the experimental results of fluorescence spectral characteristic of ethanol-watersolutions with different concentrations, a further theoretical study on the quantum yield andlight absorbency give the results of the bonding number n to form MR_n clusters ofethanol and water molecules. It is concluded that there are three possible cluster structures:five ethanol molecules and six water molecules connect with each other to form a ring orchain structures through the hydrogen bond, an ethanol molecule and two water moleculesform the chain structure with hydrogen bond, and an ethanol molecule and five watermolecules link mutually to form a new molecular structure.Based on the polarized fluorescence spectrum of ethanol-water solution, thepolarization degree and molecular anisotropy have been calculated and the molecularspatial orientation behavior has been characterized as well. As a result, it was consideredthat the cluster molecule in the solution has an ordered structure with a fixed orientation toa large extent. The theoretical analysis reveals that the hydrogen bond not only influencesthe spatial structure of cluster, but also affects the molecular energy levels, representing bythe change in the molecular dipole moment and the polarity.It is concluded that the clusters form the excimer by the excited state molecules andthe ground state molecules based on a broad and featureless fluorescent spectrum at longStokes shift. By solving decay process of the fluorescence intensity, the possiblephotophysical process of the excimer formation was analyzed theoretically. Furthermore,all the ground and excited energy levels of water molecule, ethanol molecules and theclusters were calculated by density functional theory (DFT) and the theoretical electrontransition value of the cluster was obtained accordingly. The change process of the energylevels and the luminescence mechanism of the solution have been presented by studying the formation mechanism of the excimer and the collision compound of two clusters in theground state.The structure of ethanol-water cluster molecule was inversed using the quantumchemistry, the quantum mechanics and the time dependent density functional theory(TDDFT). The conclusion is that several ethanol molecules and water molecules haveconnected into ring or chain structure through hydrogen bonds, with inlaid planar structurecharacteristic and a spatial structure characteristic with high degree of order.The research consequences may offer a theoretical and experimental reference tostudy the intermolecular cluster structure, as well as the interaction between ethanolmolecule and biological tissue.