Reversible Control of the Orientation of Iodine Molecules inside the AlPO₄-11 Crystals

Abstract

We demonstrate a technique of reversible controlling the orientation of iodine molecules embedded in elliptical nanochannels of an AlPO4-11 (AEL) crystal. We find that the interactions between iodine and water molecules can significantly affect the iodine molecular orientation inside the nanochannels. In well-hydrated AEL crystals, all the iodine molecules are standing along major axes of the elliptical cross sections of the channels. As decreasing the density of water molecules in the channels, the iodine molecules rotate to lie along the channels. The experimental results obtained from polarized Raman spectroscopy agree well with the results of molecular dynamics simulations. As a result, we can tune the pressure and temperature, which effectively modifies the water molecule density inside the channels, to set the spatial orientation of the iodine molecules over entire crystal. At last, we demonstrate a reversible local operation using a focused laser spot. This technique may be used for engineering molecular orientation in nanostructured devices.