Surfaces
Molecular films
Measurement of the complex impedance is a powerful method to probe molecular films such as self-assembled monlayers, polyelectrolytes and proteins at surfaces. Since the impedance is independent of molecular mass but sensitive to structural and chemical properties of a molecular film, impedance measurements give important complementary information to mass-sensitive techniques. The following list gives some examples what kind of information about an adsorbed or grafted film that can be detected using the Z-lab system.
- Structuring or re-structuring among molecules at a surface giving rise to a change of their isolating properties can be seen as a change in surface capacitance. Examples include all kind of self-assembled thiol monolayers as well as adsorption of polyelectrolytes.
- Displacement of charged or polar chemical groups in a film changing the film’s dielectric properties and its interaction with electrolyte can also be seen as a change in capacitance. Examples include chemical reactions and insertion of DNA, phosphorylation etc.
- Hydrophobic (water-excluding) interactions between proteins or peptides and surface layers can be distinguished from more loosely bound (native conformation) proteins and peptides.
- The resistance to charge transfer of a film can easily be detected by applying some suitable redox-probe. The charge-transfer resistance is sensitive to defects and heterogeneity in a film as well as to its conducting properties.
Related products: z-LAB Instrument / z-LAB Sensors
Surface-active molecules
Amphiphilic molecules like surfactants are extremely important in industrial applications and are mayor components of commercial products like detergents, food, paints etc. These kinds of molecules can obtain very distinct phases in solution and on surfaces for example micelles or ordered films. The different structural phases of the molecules are closely related to their function. Complex impedance measurements with the z-LAB technology are well suited to address questions related to surfactants’ interactions and structural properties on different surfaces and can be applied for technical and fundamental research and development.
Related products: z-LAB Instrument / z-LAB Sensors