This thesis mainly focuses on the novel structures and characteristics of the iodine molecules confined inside AEL and AFI zeolite crystals.

Firstly, the methods which are used to prepare the pristine AEL and AFI crystals are introduced. The physical diffusion method for intercalating the iodine molecules into the AEL and AFI crystals are also presented. From the size of the molecular surfaces of the nano-channels of AEL and AFI crystals, it is inferred that there will be no favored orientation for iodine molecules inside AFI crystal, but two preferred orientations exist for iodine molecules inside AEL crystal: “standing” inside the channel or “lying” along the channel. The polarized Raman spectroscopy as well as the density functional theory method has been adopted to verify these c...[ Read more ]

This thesis mainly focuses on the novel structures and characteristics of the iodine molecules confined inside AEL and AFI zeolite crystals.

Firstly, the methods which are used to prepare the pristine AEL and AFI crystals are introduced. The physical diffusion method for intercalating the iodine molecules into the AEL and AFI crystals are also presented. From the size of the molecular surfaces of the nano-channels of AEL and AFI crystals, it is inferred that there will be no favored orientation for iodine molecules inside AFI crystal, but two preferred orientations exist for iodine molecules inside AEL crystal: “standing” inside the channel or “lying” along the channel. The polarized Raman spectroscopy as well as the density functional theory method has been adopted to verify these conjectures, it turns out that they are all correct.

Secondly, it is demonstrated that Van der Waals radius of iodine atoms can be determined by Raman spectroscopy. The iodine diatomic molecules are diffused into the nano-channels of AFI and AEL single crystal. Since only the “standing” iodine molecules are concerned, the polarized Raman spectroscopy, which corresponds to iodine molecule’s vibrational motion along the direction of molecular axis, is significantly modified by the interaction between the iodine molecules and the rigid frame of the crystal’s nano-channels. From the number of excitable vibration quantum states of confined iodine molecules and the lifetime of each vibration state determined from Raman spectra as well as the size of the nano-channels, the radius of iodine atom can be determined as 2.10 Å.

Thirdly, the relationship between the rotational energy levels and the fine structures of resonance Raman spectra of iodine gas is discussed. The disappearance of the fine structure in Raman spectra of confined iodine molecules is studied in detail, which reveals that the Van der Waals interaction between the iodine molecules and the framework atoms would destroy the discrete rotational energy levels. The rotational energy level system of a confined diatomic molecule is a continuum.

Finally, the regular iodine chains inside high-density iodine-loaded AEL crystals are investigated by Raman spectroscopy. The structural transformation of iodine molecular chains under heating conditions is observed by in situ polarized Raman spectroscopy. From the comparison between the Raman spectra of high-density and low-density iodine-loaded AFI crystals, it is concluded that no such regular iodine chains exist inside the nano-channels of high-density iodine-loaded AFI crystal. Most of the iodine molecules would maintain the status of isolated state, and only a small number of irregular iodine clusters could exist inside the nano-channels of AFI crystals.