- Modification of Monolayers and Their Applications

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Chemically Modified Electrodes (CMEs)
- Modification of Monolayers and Their
Applications
State Key Laboratory of Electroanalytical
Chemistry Changchun Institute of Applied
Chemistry Chinese Academy of Sciences
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Contents

• History and Development of CMEs
• Classification of CMEs
• Orientated Monolayer Classification of
  Kaleidoscopic SAMs
• Several Examples

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Early Studies on CMEs
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Classification of CMEs
Chemically Modified Electrodes (CMEs)
Multilayer
Monolayer
Composite Others
Polymer Thin Film
Adsorption
Vapor Deposition
Underpotential Deposition (UPD)
Monomer
Polymer
LB SA Films
Irreversible Adsorption
Simply by Physical/ Chemical Adsorption
By Chemical Synthesis
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Merit Function Structure - tunable
controllable
Applications
Electrosynthesis Electrocatalysis
ChemiSensors Biosensors
Electroanalysis Electrochemical Detection
Electrolyzing, Electroplating Fuel Cell
The understanding of the interrelationship
between the molecular structure of amphiphiles
and their organization on different surfaces is a
fundamental problem. The packing and orientation
of such molecules affect the surface chemistry of
the monolayer, and play an important role in the
phenomena of boundary lubrication, corrosion
inhibition, adhesion, and catalysis.
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Orientated Monolayer
Origin of the oil-on-water and LB film,
1. Aristotle - spread oil droplets on a water
surface and used the behavior of the film to
foretell the future.
2. 1774, Benjamin Franklin, the first preparation
of LB film, and show the thickness of the oil
layer is a few nanometers.
3. 1891, Agnes Pockels, the first monolayers at
the water-air interface.
4. 1899-1913, Rayleigh, Devaus, and Hardy, the
nature of these layers, and the amphiphilic
structure.
5. 1917, Langmuir, the first systematic study of
monolayers of amphiphilic molecules at the
water-air interface.
6. 1935, Blodgett, the first study on a
deposition of multilayers of long chain
carboxylic acid onto a solid substrate.
Deposition of a monolayer from the water-air
interface to a vertical plate.
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Self-Assembled Monolayers
Classical SAM literatures,
1. Bigelow , W.C. Pickett,D.L. Zisman, W.A. J.
Colloid Interface Sci. 1946, 1, 513. 2. Zisman,
W.A. Adv. Chem. Ser. 1964, 43, 1. 3. Sagiv, J. J.
Am. Chem. Soc. 1980, 102, 92.
Several typical examples of organic monolayers
Organosilicon/Hydroxylated surfaces (SiO2/Si,
Al2O3/Al, Glass, etc.)
Alkanethiols/Au, Ag, Cu
Dialkyl sulfides, dialkyl disulfides/Au
Alcohols, amines, pyridines/Au, Pt
Carboxylic acids/Al2O3, Ag (acid-base
interaction --gt salt)
Self-assembled monolayers are molecular
assemblies that are formed spontaneously by the
immersion of an appropriate substrate into a
solution of an active surfactant in an organic
solvent.
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Self-Assembled Monolayers
Electroactive Groups in SAMs
Ferrocene Viologen Quinone Porphyrin
Bioactive Molecules in SAMs
Electroactive Biomolecules in SAMs
Inorganic composites and particles in SAMs
A schematic view of the forces in a
self-assembled monolayer
Polymers in SAMs
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Extended SAM Systems
Small Organic Molecules -Classical SAMs
Inorganic Ions/Atoms
Metal Atoms
UPD of Ag, Cu, Ni, Pb, etc.
I-/I
Charged negatively, or positively
Neutral
Conjugated Chain
Non-conjugated
Different Headgroups, eg. -SH, Pyridyl, etc.
S2-/Sca.1-
SCN-
NSC-
CN-
(unconventional SAM systems)
Tail group
Bulk Chain
Headgroup