11-10-2016 1 1 Monolayers and Langmuir- Blodgett Films Amélia M. P. S. Gonçalves da Silva CENTRO DE QUÍMICA ESTRUTURAL, IST, LISBOA 2 I – Introduction II – Formation and Characterization of LM and LB films III – Experimental studies Monolayers and Langmuir-Blodgett Films
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11-10-2016
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Monolayers and Langmuir-Blodgett Films
Amélia M. P. S. Gonçalves da Silva
CENTRO DE QUÍMICA ESTRUTURAL, IST, LISBOA
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I – Introduction
II – Formation and Characterization of LM and LB films
III – Experimental studies
Monolayers and Langmuir-Blodgett Films
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Monolayers and Langmuir-Blodgett Films
Agnes Pockels1862 – 1935
carried out the first experiences in the
kitchen sink
Irving Langmuir1881 – 1957
Nobel Prize in Chemistry1932
developed the theory and the experimental method that are being
used until nowadays
Katherine Blodgett1898 – 1979
In collaboration with Langmuir developed (1935)
the technique to transfer monolayers onto solid substrates (LB films)
Initiators:
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Relevance:
Fundamental studies
Potential applications
Langmuir Monolayers (LM)
Distinctive characteristics:
• Simple system
• Low thickness
• High molecular order
Out coming information:
• Orientation and packing of molecules
• Molecular interactions
• Two-dimensional (2D) states
• Phase behavior
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Reactions in Monolayers
The monolayer components can react with some species in the subphase
Models in fundamental studies
Biomembranes and liposomes
Lung Surfactants
Development of synthetic lung surfactants
Evaporation Control
Dense monolayers spread on water reservoirs reduce the water evaporation
LB films
Building up of multilayered structures
Applications of Langmuir Monolayers
Langmuir-Blodgett Films
Langmuir monolayer
LB films characteristics
• High molecular order
• Large regions nearly free of defects
• Precise control of thickness
• Active or passive films
Building up of multilayered structures:
Composition and structure
components,
orientation of molecules,
substrate,
number of layers , …
can be adjusted to the expected properties and
function of LB film
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LB films
Solid substrates
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Chemistry and BiochemistryCatalyst; Biocompatible surfaces; biosensors(glucose sensor, for example)
MicroelectronicsFabrication of ultra-miniaturized devices, composed of conductor, semiconductor or insulator layers
Antireflection coatingApplied to glass make an antireflective action, allowing 99% of visible light to pass through.
Protection against corrosion and lubricationCondensed layers of amphiphilic molecules can act as surface coating, preventing erosion and corrosion
Applications of LB Films
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� Materials, method and equipment
� Analysis of π –A isotherms of single and mixed monolayers
� Brewster Angle Microscopy (BAM)
� LB films – dipping method
� General characterization
II – Formation and Characterization of LM and LB films
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Materials
The substances that form stable monolayers at the a ir-water interface are amphiphilic molecules insoluble in the subphase :
� Long-chain fatty substances (classic molecules)
N
N
N
N H H
R
RR
R
� Polycyclic aromatic compounds
loop
tailtail
train
� Amphiphilic polymers and proteins
Non-amphiphilic molecules can also be incorporated in monolayers anchored by the amphiphilic molecules
R = long alkyl chain
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Surface pressure: π = γπ = γπ = γπ = γ0000 – γγγγγ0− surface tension of the air-water interface (pure water ).γ − surface tension of the air-water interface with the film (monolayer )
Wilhelmy Method
π π π π −−−−Α Α Α Α isotherm: measurement of the surface pressure (ππππ) as a function of the surface area (A) at constant temperature during compression
balance
Wilhelmy plate
mobile barrier
water
mobile barrier
trough
� Before the spreading (for pure water): π = γπ = γπ = γπ = γ0000 – γγγγ0000 = = = = 0000