Publication details
Photophysics and Photochemistry of Molecular Species Trapped in Ice: An Overview
| Authors | |
|---|---|
| Year of publication | 2008 |
| Type | Chapter of a book |
| MU Faculty or unit | |
| Citation | |
| Description | Water is an only one material that takes three phases in the environment. Water vapor is a source of OH radicals, which are one of the most important compounds in the atmosphere since they react with various substances to clean up the atmosphere. Water vapor becomes cloud, fog, rain, dew, etc., all of which are liquid, as well as snow, ice, frost, rime, etc., which are solid. Water dissolves various substances and transfers them to other environments. Water vapor or water freezes to be ice in the environment. Generally, it is believed that ice suppresses chemical reactions, prevents decomposition of substances by microorganisms and preserves the past environment within it. Ice is made of a network of strong hydrogen bonds, with one water molecule uniting with four other water molecules. The hydrogen bonds of water are very strong, and other molecules hardly enter the ice crystal lattice. Therefore, when solution freezes, pure ice is generated. The central part of the ice produced at home is white due to the dissolved substances (dissolved gases also) that have been excluded from ice. This is macroscopic freeze-concentration. Here, concentrations increase several times. By the normal freezing method, polycrystalline ice is formed. When each ice crystal of polycrystalline ice grows up, the unfrozen solution is confined in the space of several ice crystals. In addition, the concentration of the confined solution increases more and more as ice crystals grow up. This can be called a microscopic freeze-concentration, and through this, the concentration increases several hundreds to a few thousands times. As a result, it has been known for a long time that the increase in the reaction rate by the freeze-concentration becomes greater than the decrease in the reaction rate as the temperature decreases, and the reaction in ice proceeds faster than that in solution. Furthermore, it has been understood that reactions in ice are promoted by altering the pH without adding acid or base reagent but due to the freezing potential and freeze-concentration. Recently, it was reported that reaction pathways of some reactions in ice are different from those in solution. |
| Related projects: |