Contributions to Science, 4-2 : Nanoscience and nanotechnology research in Catalonia : Special Issue / N. Ferrer-Anglada, Guest editor

Transparent, flexible electrodes and sensors based on carbon nanotube thin films

Jordi Pérez-Puigdemont, Núria Ferrer Anglada, Bernat Terrés, Martti Kaempgen, Siegmar Roth


We obtained thin films of single-walled carbon nanotubes
(CNTs), which may be used as transparent, flexible electrodes
in electronic devices, on a substrate using a very simple method.
In order to construct reproducible devices with similar
properties, in particular with similar impedance Z(ω), it is important
to associate the electrical properties with the number of
CNTs in a network. We prepared thin CNT networks on transparent,
flexible substrates (PPC, polypropylene carbonate) with
different CNT densities. The number of CNTs was estimated
using a mathematical method based on the data obtained from
thermo-gravimetric analysis (TGA). We were able to estimate
the relative number of CNTs using optical absorption spectroscopy.
These two methods are in good agreement. We also
analysed the various samples using electrical impedance
measurements at frequencies of up to 110 MHz. Low-density
networks are semiconductors, whilst high-density networks
behave like metals and are sufficiently good conductors to be
used as working electrodes in electrochemical processes. It is
thus possible to obtain CNT polymer and metal composite
conductors electrochemically.
With sensor applications in mind, we used CNT thin films as
a working electrode to obtain a composite CNT-conducting
polymer. This was performed by electrochemically depositing a
conducting polymer — polypyrrole or polyaniline — on the
electrode. The pH dependence of the device was measured by
recording its open circuit potential in various buffer solutions.
This enabled us to analyse the properties of the device as an
electrochemical sensor. The results showed a good sensitivity,
linearity and stability in both cases. Thus, the CNT/polypyrrole
and CNT/polyaniline devices could have applications as solidstate
gas sensors or biosensors when they are deposited on
transparent and flexible surfaces of any shape.

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ISSN: 2013-410X (electronic edition); 1575-6343 (print edition)