Synthesis of an array of aligned polypyrrole nanotubes Nanostructures and
P R Marcoux*, L Forró
Novel electronic materials
Institute of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
*
[email protected], http://nanotubes.epfl.ch
1. Interesting features of polypyrrole • It can be designed into different shapes (films, • It is conductive
4
and has sensing properties.
1
nanotubes,
2
3. Synthesised nanostructures
nanowires 3).
5
• It can be functionalised. • It is porous (useful for encapsulation
6
for example).
2. Principles of the synthesis • It is done through electrochemical polymerization, in a three electrodes cell, at constant potential : H
H
1. H
H
N
2.
N
H
N
N
N
N
H
H
N
anode
+
+ e H
H
N
N
H
H
N
N
N
N
N
H
H
H
200 nm ∅ tubes, grown 450 s at 0.8 V potential, 6 microns long
400 nm ∅ tubes, grown 500 s at 0.8 V potential, 2.2 microns long
• Nanotubes are made through the membrane-assisted synthesis ( “template method” ). A polycarbonate membrane is used as the work electrode : polycarbonate membrane
4. Perspectives
polypyrrole nanotube dissolution of the template
electropolymerization
gold (50 nm)
We are currently exploring three different processes to functionalize polypyrrole nanotubes : 1. We have synthesised some nanotubes from potential).
N
H
and
N
through electrochemistry (at a 1.0 V
CN
polypyrrole film
• The synthesis conditions are as follows : Ö potential +0.8 V, Ö electrolyte : polystyrenesulfonate 70 000 g/mol (0.1 M compared to the styrene unit) Ö solvent : water with 0.1 M of pyrrole monomer Ö work electrode : polycarbonate membrane with 10 nm, 200 nm or 400 nm ∅ pores
Then the cyanide function will be converted : • into amine function thanks to reduction
7
:
• or into carboxylic acid through oxidation :
N
CN
N
CN
DIBAL (aluminum hydride)
NH 2
N
diethyl oxide KOH water
N
COOH
2. Since polypyrrole nanotubes are conductive, they can in turn be used as a work electrode for the reduction of an aryldiazonium salt : 8 work electrode
+
N2
R
+ e-
R
+
3. Polypyrrole turns out to be reactive towards good nucleophiles RS
H+
N H
References 1 1. 2. 3. 4.
+
H N
H N N H
N2
9
R
such as thiols and amines :
H N
RS
N H
Jérôme et al, Angew. Chem. Int. Ed., 1998, 37, 2488 - 2490. Dumoustier-Champagne et al, Chem. Mater., 1999, 11, 829 - 834. Cosnier et al, Chem. Commun., 2003, 414-415. Lei et al, Synth. Met., 1992, 46, 53-69.
N H
5. 6. 7. 8. 9.
H N
H N N H
H
+
H N
N H
Pernault et al, J. Phys. Chem. B, 2000, 104, 4080 - 4090. Parthasarathy et al, Nature, 1994, 369, 298 - 301. Foulds et al, Anal. Chem., 1988, 60, 2473 - 2478. Delamar et al, J. Am. Chem. Soc., 1992, 114, 5883 - 5884. Bieniarz et al, Macromolecules, 1999, 32, 792 - 795.
