Langmuir–Blodgett film

A Langmuir- Blodgett film ( LB film LB film ) is composed of one or more monolayers of organic molecules that have been transferred during immersion and / or withdrawal of a liquid from the interface of the liquid to a solid substrate. An application example, the precipitation of the phthalocyanine in the construction of gas sensors, which respond to reducible gases.

Langmuir-Blodgett layers are named after Irving Langmuir and Blodgett Katherine. In the late 1910s developed Langmuir different techniques for fabrication and investigation of surface films, but he improved including the Pockels trough ( by Agnes Pockels ) for Langmuir- Pockels - scale ( 1917). Based on these later works was a Langmuir Associate Katherine Blodgett method before 1934, with the polymeric monolayers could be manufactured on specially prepared glass surfaces (Langmuir -Blodgett technique ). The technique was developed in the early 1960s by Hans Kuhn and the layers are since then Langmuir -Blodgett -Kuhn - layers ( LBK layers ) or Langmuir- Blodgett -Kuhn films called ( LBK ) films.

Production

At each immersion or withdrawal ( " emersion " ) a monolayer comes to it; thus it can be applied a precisely defined number of monolayers in the ideal case. If the liquid is water and the substrate hydrophilic, when pulling the hydrophilic end of the molecule to the substrate remains attached. In contrast, after immersing the hydrophilic end of the monolayer outside the newly created (that is facing the water ). Often molecules are used that have a hydrophilic and a hydrophobic end; after extraction is then Thus the hydrophobic side out, after immersion (if the pad is hydrophobic), the hydrophobic side inwards.

Are closed and good ordered layers of molecules on the liquid (and hence to the substrate after immersion / extraction ) to obtain the molecular layer is pushed together on the liquid surface by a bar. This so-called film balance holds the (surface) pressure in the layer ( the so-called transfer printing ), and thus the areal density of molecules constant. Nevertheless, the greatest difficulty in coating with the Langmuir -Blodgett method in the lack of mechanical, thermal and chemical stability of the layers ( binding only by physisorption ).