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Physics Research Experience for Undergraduates 2010
This program is funded by the National Science Foundation through grant number PHY-0851599.

Langmuir-Blodgett Film Low and High Pressure Study of Trioctylphosphine oxide (TOPO), Dipalmitoylphosphatidylcholine (DPPC) and Colloidal Gold Nanoparticles coated in Dodecanethiol (DDT)

Sam Stites
(supervisor: Bret Flanders)

Text Box: Other Links:
Vassar College
Kansas State University 
KSU Physics Department  
REU Program Homepage
KSU Condensed Matter Group
Wikipedia: Langmuir-Blodgett films
Sponsored by:
The National Science Foundation
Dr. Bret Flanders
Sam Stites
KSU’s REU Program

      This summer I am working with Langmuir-Blodgett methods to produce and study single-molecule thick layers. These layers can be suspended between two liquids or, as in my case, between a liquid and an air surface. In essence these layers only consist of two dimensions and the layers produced will exhibit gas-like, liquid-like and solid-like states. I intend to study these layers by looking at the relations between surface tension and area of surface, look at what happens when two different molecules are combined into a single layer and look into just how rigorously the ideal gas law applies to these monolayers. These films are used to make glasses anti-reflective and have possible applications in molecular electronics, applied optics, mechanical filters, sensors and more.

On the Langmuir-Blodgett method

The Langmuir-Blodgett method centers around the use of a trough which contains compressible barriers which allow the manual manipulation of area (in the units of cm2 or Ĺ2) and a Wilhelmy plate which will allow for the measure of surface pressure (or tension – measured in mN/m). The molecule of choice is mixed in a solution of chloroform which has a high evaporation rate and, after the solution is placed on the surface of the deionized water, will evaporate from the surface -homogeneously distributing the surfactant on the water. The trough is also equipped with a dipping mechanism which allows a sample of the monolayer to be put onto a slide and observed under the florescence microscopy. The barriers can be configured in such a way that they will then compress to a desired pressure and maintain this pressure as the dipper raises a slide from the surface of the water with the surfactant distributed evenly upon it. Although the Langmuir-Blodgett field is the study of monolayers and contains many more aspects, I will be using these specified methods in my project.


The goals of this project are to look at the interactions of mixed DPPC and TOPO layers and to compare DPPC’s “gas” state to that of a metallic gold nanoparticle. If the latter part of this goal goes well and the trend of a metallic nanoparticle and a phospholipid is comparable to that of the ideal gas law, then it can be assumed that the ideal gas law is comparable and applicable for all molecules in a monolayer at this phase.


First I will look at pure DPPC and TOPO layers’ pressure-area isotherms and mix them in 75%, 65%, 50%, 35% and 25% differences by volume to make sure that the layers are behaving as desired. To look at the layer’s interaction at these mixed solutions I will fluoresce the DPPC and observe these layers under an inversion microscope with florescence capabilities. Finally I will analyze the layers between the pressures of 0 and .5 mN/m by plotting them against a theoretical model for a “gaseous” DPPC molecule and a “gaseous” colloidal gold nanoparticle.


I have recorded a day-by-day summary which can be found here

About me

This summer I am a rising junior at Vassar College. I am a physics and mathematics double major planning on pursing physics or engineering in my graduate studies. When I am out of Vassar’s library you can find me juggling on the quad or singing with my a capella group.