Langmuir-Blodgett film characterization in air using MP-SPR

Application Note #109

Langmuir-blodgett

"Precise control of Langmuir-Blodgett film thickness"
SPR intensity versus angle curves measured in air for number of LB layers of Stearic Acid on gold.

Creating ordered single or multiple layers of molecules has a multitude of technology applications in biosensor development, displays, and nanoelectronics for instance. LB technique is used to deposit functional molecules, nanoparticles, nanowires etc.

In this experiment, Langmuir-Blodgett deposition was used to form a single and multiple layers of stearic acid on gold. With the use of MP-SPR, a full SPR curve was acquired by measuring the SPR intensity versus angle in air at a single wavelength. This enables determination of layer thickness for each of the layers after deposition. In this case, the film thickness increased linearly with the number of layers.

The thickness of each layer was determined using a literature value for refractive index and by fitting Fresnel equations. With MP-SPR it´s also possible to determine both refractive index and thickness of deposited layer, for more information see Application note AN128.

MP-SPR determined thickness of the LB-deposited stearic acid layer as 2.45 nm, which is in good agreement with literature.

Recommended instrument for this application:

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Further reading

  • If you are interested in the measurement principle of in situ and ex situ deposited layers to enable not only interaction and thickness calculations but also layer refractive index, we recommend AN#128 for further reading.

  • Do you want to find out how to calculate thickness out of MP-SPR measurements? Click here.

  • Do you want to see how MP-SPR instruments range? Click here.

  • Click here to take a look at MP-SPR publications. 

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