Langmuir and Langmuir–Blodgett (LB) Films

An ultrathin, resistant layer can be formed at the air-water interface by spreading a single drop of oil. This phenomenon was discovered centuries ago, but it was Irving Langmuir that in the early twentieth century established sound theoretical and experimental basis for their study (Langmuir 1917). The now-called Langmuir monolayers are formed at air-water interfaces using an experimental system known as Langmuir trough. Basically a solution containing amphiphilic molecules (with both hydrophobic and hydrophilic parts) is spread over at the air-water interface. The hydrophilic parts allow the spreading of the molecules while the hydrophobic parts do not let the molecules dissolve into subphase. Movable barriers are used to compress the monolayer. The presence of the monolayer can be detected easily by measuring the surface pressure (π), which is the decrease in surface tension, as the monolayer is compressed, thus leading to pressure-area isotherms.

In the 1930s, Katharine Blodgett–...