Molecular insights into specific ion effects
- Reference number
- FFL12-0119
- Start and end dates
- 140101-191231
- Amount granted
- 9 700 000 SEK
- Administrative organization
- KTH - Royal Institute of Technology
- Research area
- Life Sciences
Summary
The project will provide exciting new insights into the molecular origins of specific ion effects, which have daunted scientists for over a century starting with the pioneering work of Hofmeister in the 1880s. These effects have important implications in an enormous number of fundamental and applied situations, ranging from the solubility of oxygen in salt solutions, to the structure and function of complex biological systems. The project will specifically target the ion behaviour at different model interfaces. This involves identifying which ions tend to preferentially adsorb to particular interfaces, probing the influence of ions on the surface water structure and local functional groups. Moreover, additional studies between two approaching surfaces will determine the influence of confinement on the ion preferential adsorption and provide the means to directly correlate molecular properties with macroscopic force measurements. Finally, with de-icing applications in mind, the influence of ions on the properties of quasiliquid layers at the solid/ice interface will be explored. The molecular information will be obtained using two advanced surface sensitive vibrational spectroscopic techniques, mainly Sum Frequency and TIR Raman. The studies under confinement will be performed in custom-built devices. The information gathered following this unique and novel experimental approach will bring forth understanding from a molecular perspective on how specific ion effects really are.
Popular science description
We all know the importance of water for our survival. Sixty percent of our body weight is actually made out of water. However, if we were in a dessert and had at our disposal just pure water with no salts dissolved, we could still die of dehydration. The importance of salt in our lives cannot be overstated. Without salt, our bodies cannot perform some of the vital functions like regulating blood and body fluids and maintaining nerve signals. Salt deprivation can even prove fatal. Nonetheless, not just any salt would work. For our body to work efficiently it requires certain types and amounts of ions or dissolved salts. Sodium and potassium are the most abundant, but calcium and trace amounts of other metal ions, like magnesium or zinc, are just as important. Each ion plays a crucial role in specific body functions and cannot be easily exchanged. This ion specificity was first study systematically by a german pharmacologist named Hofmeister more than 120 years ago, who rank a series of ions depending on their ability to precipitate an egg protein from solution. The series was later found to be relevant in a large number of systems, triggering an immense research effort that has continued for over a century. Notwithstanding, it was not until the last decade that started emerging new theories trying to take this ion specific effects into account. It is now believed that interfacial effects including specific ion adsorption are the most plausible explanation for the Hofmeister phenomena. Understanding these effects is believed to be as important in the physical chemical sciences as Mendel’s work was for genetics. In order to challenge and extend these theories, direct experimental observations of the molecular structure from ions and water at different interfaces is required. Here it is proposed to use a unique combination of advance techniques to look how different ions interact with interfaces having molecular groups typically found in many biologically relevant systems. The surface molecular information will be obtained using two laser based techniques: VSFS and TIR Raman. Moreover, many ion specific phenomena occur in confined spaces. Here a novel approach will be used to study such a situation using devices designed and built by the applicant. This type of combined studies, though challenging, has never been attempted before and will be world leading with far reaching consequences for many fields of science including physics, chemistry and biology.