Raman investigation of hydration structure of iodide and iodate*

Abstract

In the troposphere, the destruction of ozone and the formation of new particles are closely related to the iodine content, which mainly comes from iodide (I−) and iodate ( IO 3 − ) in the seawater. Therefore, understanding the interactions between I−, IO 3 − and water molecules plays a certain role in alleviating the destruction of the ozone layer. Raman spectroscopy is commonly used to obtain the information of the interaction between I−, IO 3 − and water molecules quickly and accurately. Herein, the effect of I− and IO 3 − on the change in Raman band characteristics of water is investigated to reflect the associated intermolecular interactions change. With the addition of the two ions, the Raman band corresponding to OH stretching vibration moves towards the high wavenumber, indicating the formation of hydration structure. The narrowing of the Raman band from OH stretching vibration under weak hydrogen bond agrees well with the hydrogen bond variation, while the abnormal broadening of the Raman band from OH stretching vibration under strong hydrogen bond indicates the formation of H-down structure. With the increase of ions concentration, the frequency shift of the Raman band from OH stretching vibration under both weak and strong hydrogen bonds becomes more apparent. Meanwhile, the frequency shift of I− is more obvious than that of IO 3 − , which indicates that I− is more likely to form the hydration structure with water than IO 3 − . These results contribute to analyzing the different interactions between I−–water and IO 3 − –water, then helping to prevent ozone depletion.