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

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 degrees 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 (c) 2015 John Wiley & Sons, Ltd.