Surface-sensitive infrared probing from corroded metal to biological membranes
Dr. Magnus Johnson, KTH Stockholm
Vibrational spectroscopy can be used in numerous research areas to obtain chemical information under in-situ conditions. In these studies the surface specific laser technique vibrational sum frequency spectroscopy (VSFS) that only probes the top few monolayers of a material, the near-surface technique infrared reflection/absorption spectroscopy (IRRAS), and nano FTIR microscopy to obtain chemical information at the nano scale, have been used to investigate models of biological membranes and atmospheric corrosion processes.
The major constituents of cell membranes are phospholipids, and several important properties of these membranes are determined by how the phospholipids interact with each other and with the surroundings. These interactions are further of importance for how cell membranes respond to pharmaceuticals. In order to shed some light on these issues, VSFS has been used to study model membranes consisting of phospholipid monolayers at a molecular level. We have examined how different phospholipids and other biomolecules such as cholesterol and sphingolipids pack together and interact with surrounding water molecules, as well as how phospholipids of varying degree of unsaturation may oxidize. In addition, the interactions between phospholipid layers and the most widely used anesthetic drug propofol have been studied.
In the field of corrosion science, a multianalytical approach has been used to study the ability of self-assembled thiol and selenol monolayers to protect the industrially important metal copper against atmospheric corrosion. The samples have been exposed to humid air containing formic acid, thus mimicking a typical indoor atmospheric corrosion process. The combination of techniques has allowed examinations of the nature and kinetics of formation of the corrosion products (IRRAS), the mass of the corrosion products (quartz crystal microbalance (QCM), ng/cm2), the spatial distribution of the corrosion products with a resolution of 20 nm (nano FTIR microscopy), and the status (induced disorder, removal) of the corrosion inhibiting monolayer films (VSFS).