Transformations of iodine species inside elliptical channels of AlPO₄ -11 crystals at low temperature: a Raman study

Abstract

Raman spectra of iodine species confined in one‐dimensional elliptical channels of AlPO4‐11 (AEL) crystals have been studied from room temperature down to −196 °C. As temperature decreases, thermal fluctuations of individual iodine molecules confined in AEL channels are slowed down and they prefer to rotate to channel axis direction, which increases the population of iodine molecules along channel axis (i.e., lying molecules and chains). Such temperature‐driven orientation transformation of iodine molecules is found to be reversible upon heating up to room temperature. The experimental observations are in good agreement with our theoretical simulations by molecular dynamics on low density iodine‐filled AEL crystals. We thus provide a new way to modulate the orientation of iodine molecules in nanochannels, which may have implications in low‐temperature‐sensitive nanoscale devices. Copyright © 2015 John Wiley & Sons, Ltd.

Supramolecular Organization in Confined Nanospaces

“…Finally, inclusion in the MFI 3D‐channels resulted in a red‐brown color,, ascribed to stronger halogen interactions . Several studies have then focused on the organization of confined dihalogens, exploring not only the structure of the aggregates, but also how their organization is affected by size and concentration of the guests, structure and composition of the host,, solvation, temperature, and pressure . In general, molecules confined in small cages, like in SOD (Figure ), undergo rotational motion – which may be more frictioned for large guests, but is normally very fast .…”

“…To further explore thermal effects, Chen et al. studied the confinement of iodine molecules in AFI and AEL frameworks down to −196 °C. Combined Raman experiments and molecular dynamics indicated that, upon decreasing temperature, the thermal motion of the confined molecules slowed down, thus inducing a change in orientation.…”

“…The population of I 2 molecules aligned to the channel increased: hence, longer I 2 chains were formed in both hosts, with higher ordering. Nonetheless, such a cooling‐induced order enhancement was not preserved after recovery to room temperature ,…”

Pressure‐induced insertion and transformation of N2 in the cavities of zeolitic imidazolate framework‐8: A Raman study

“…[31,32] As we know, the Raman intensity is closely related to the population of the confined molecules in the confinement environments. [43,44] The weak intensity of the 2,322.5 cm −1 band relative to the 2,328 cm −1 band suggests that a smaller number of nitrogen molecules are on the central site. This is consistent with the results in previous literature, which shows that the nitrogen molecules are not apt to occupy the sites far from the ZIF-8 framework and only 2 out of 52 nitrogen molecules per unit cell occupy in the center of the cavities.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part X

“…The experimental observations were in good agreement with their theoretical simulations by molecular dynamics on low dimension iodine‐filled AEL crystals. They thus provide a new way to modulate the orientation of iodine molecules in nanochannels, which may have implications in low‐temperature‐sensitive nanoscale devices . Goryainov et al .…”