Langmuir-Blodgett layer

from Wikipedia, the free encyclopedia
Langmuir film consisting of complex phospholipids in a liquid aqueous sub-phase.

A Langmuir-Blodgett layer (LB layer, LB film) consists of one or more monolayers of organic molecules that were transferred from the interface of the liquid to a solid substrate when immersed and / or withdrawn from a liquid . One application is, for example, the deposition of phthalocyanine in the construction of gas sensors that react to reducible gases . Langmuir-Blodgett strata are named after Irving Langmuir and Katherine Blodgett . Already at the end of the 1910s Langmuir developed various techniques for the production and investigation of surface films, among other things he improved the Pockels trough (from Agnes Pockels ) to the Langmuir-Pockels balance (1917). Based on this work, Langmuir's future colleague, Katherine Blodgett, presented a method in 1934 with which polymer monolayers could be produced on specially prepared glass surfaces (Langmuir-Blodgett technique). The technology was further developed by Hans Kuhn at the beginning of the 1960s and the layers have also been called Langmuir-Blodgett-Kuhn layers (LBK layers) or Langmuir-Blodgett-Kuhn films (LBK films) since then.

Manufacturing

A monolayer is added with each immersion or extraction ("immersion"); In the ideal case, therefore, a precisely defined number of monolayers can be applied. If the liquid is water and the backing is hydrophilic , the hydrophilic end of the molecules will stick to the backing when pulled out. On the other hand, after immersion, the hydrophilic end of the newly created monolayer is on the outside (i.e. facing the water). Often, molecules are used which have a hydrophilic and a hydrophobic end; so after pulling out the hydrophobic side is on the outside, after immersion (if the base is hydrophobic) the hydrophobic side is on the inside.

In order to obtain closed and well-ordered layers of the molecules on the liquid (and thus on the substrate after immersion / extraction), the molecule layer is pushed together on the liquid surface by a bar. This so-called film balance keeps the (surface) pressure in the layer (the so-called transfer pressure) and thus the surface density of the molecules constant. Nevertheless, the greatest difficulties in coating with the Langmuir-Blodgett method are the lack of mechanical, thermal and chemical stability of the layers (bonding only through physisorption ).

Individual evidence

  1. ^ I. Langmuir: The constitution and fundamental properties of solids and liquids. II. Liquids. 1 . In: Journal of the American Chemical Society . tape 39 , no. 9 , 1917, pp. 1848–1906 , doi : 10.1021 / ja02254a006 .
  2. ↑ Katharine B. Blodgett: Monomolecular films of fatty acids on glass . In: Journal of the American Chemical Society . tape 56 , no. 2 , 1934, p. 495 , doi : 10.1021 / ja01317a513 .
  3. ^ Katharine B. Blodgett: Films Built by Depositing Successive Monomolecular Layers on a Solid Surface . In: Journal of the American Chemical Society . tape 57 , no. 6 , 1935, pp. 1007-1022 , doi : 10.1021 / ja01309a011 .
  4. ↑ Gerhard Lagaly, Oliver Schulz, Ralf Zimehl: dispersions and emulsions . Birkhäuser, 1997, ISBN 978-3-7985-1087-6 , pp. 530 .