Langmuir–Blodgett trough

A film balance (also Langmuire trough or Pockels Langmuire - scale ) is a device for the production and study of two-dimensional insoluble monolayers of amphiphilic molecules ( Langmuir film).

Construction

Film scales with different equipment are commercially available for special applications. The classical film balance consists of the following main components.

Trough

Main component of a film balance is the rectangular, tempered and with a liquid, usually water -filled trough. Since highly hydrophobic and chemically inert, polytetrafluoroethylene (PTFE) is commonly used as the material for the trough. Less commonly used are glass or metal troughs are used, which are coated with PTFE.

Barrier

Similar to a two-dimensional compression of the piston, the space available for the single layer area A is varied by a barrier, the liquid / air contacts the boundary surface and can be moved along the walls of the trough. As the trough is this also mostly made ​​of PTFE.

Pressure sensor

Measuring the surface tension of the Langmuir- layer is usually carried out over a Wilhelmy plate. Is taken, the ratio of surface tension and film pressure to the surface of the monolayer or surface concentration of the monolayer molecules.

Use

The film balance is used in the investigation of the following topics:

• Biomembranes: monolayers of various lipids and membrane proteins provide a simplified model for the study of properties of cell membranes dar.
• Surface Chemistry: Adsorption and desorption processes can be studied, biosensors and enzymatic / immunological reactions at surfaces are tracked.
• Surface coating: investigation and preparation of novel organic / inorganic surface coatings, for example, nanotubes, nanowires, or graphene.
• Surfactants and colloids: Investigation of foam formation and stability, emulsion, dispersion and colloidal stability.
• Dünnschichtrheologie

History

The abnormal behavior of the surface of dishwater observed in 1880 the then 18 -year-old self-taught artist Agnes Pockels and designed to study this phenomenon in 1882, a " slide attachments ." About their discovery, they reported in 1890 Lord Rayleigh in a letter which in 1891 led to its publication in the journal Nature. Pockels ' slide Inne "extended and refined to Irving Langmuir Langmuir balance, who received a Nobel Prize " for his discoveries and investigations in surface chemistry " in 1932.

Swell

• Irving Langmuir, Katharine B. Blodgett: About some new methods for the study of monomolecular films. In: Colloids magazine. 73, No. 3, 1935, pp. 257-263, doi: 10.1007/BF01428777.
• G. Adam, P. Läuger, G. Stark: Physical Chemistry and Biophysics. 2nd edition, Springer, Berlin 1988.