Film scale
A film balance (also Langmuir trough or Pockels-Langmuir balance ) is a device for the production and investigation of two-dimensional, insoluble monolayers of amphiphilic molecules ( Langmuir film ).
construction
Film scales with different equipment are commercially available for special applications. The classic film scale consists of the following main components.
trough
The main component of a film balance is the rectangular, temperature-controlled trough filled with a liquid, usually water. As it is highly hydrophobic and chemically inert , polytetrafluoroethylene (PTFE) is usually used as the material for the trough. Glass or metal troughs coated with PTFE are less common.
barrier
Analogously to a two-dimensional compression piston, the area A available for the monolayer is varied via a barrier which touches the liquid / air interface and can be moved along the walls of the trough. Like the trough, this is also mostly made of PTFE.
Pressure sensor
The measurement of the surface tension of the Langmuir layer is usually carried out over a Wilhelmy plate . The ratio of surface tension or film pressure to the area of the monolayer or surface concentration of the monolayer molecules is recorded.
use
The film balance is used to examine the following topics:
- Biomembranes : Monolayers made of various lipids and membrane proteins represent a simplified model for the investigation of the properties of cell membranes .
- Surface chemistry : Adsorption and desorption processes can be examined, biosensors and enzymatic / immunological reactions on surfaces can be monitored.
- Surface coating: Investigation and production of new organic / inorganic surface coatings of, for example, nanotubes , nanowires or graphenes .
- Surfactants and colloids : Investigation of foam formation and stability, emulsion , dispersion and colloid stability .
- Thin film rheology
history
The anomalous behavior of the surface of the washing-up water was observed in 1880 by the then 18-year-old autodidact Agnes Pockels and in 1882 designed a "sliding channel" to investigate this phenomenon. She reported her discovery in 1890 to John William Strutt, 3rd Baron Rayleigh , in a letter that prompted its publication in Nature in 1891 . Pockel's "Schieberinne" expanded and refined Irving Langmuir to the Langmuir balance , who received a Nobel Prize in 1932 "for his discoveries and investigations in surface chemistry".
swell
- Irving Langmuir, Katharine B. Blodgett: On Some New Methods for Examining Monomolecular Films . In: Colloid Journal . tape 73 , no. 3 , December 1935, p. 257-263 , doi : 10.1007 / BF01428777 .
- G. Adam, P. Läuger, G. Stark: Physical chemistry and biophysics . 2nd edition, Springer, Berlin 1988.
Individual evidence
- ↑ Cristiane A. Silva, Thatyane M. Nobre, Felippe J. Pavinatto, Osvaldo N. Oliveira Jr .: Interaction of chitosan and mucin in a biomembrane model environment . In: Journal of Colloid and Interface Science . tape 376 , no. 1 , June 15, 2012, p. 289-295 , doi : 10.1016 / j.jcis.2012.03.027 .