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Film
deposition of TiO2 nanoparticles
Titanium dioxide (TiO2) is one of the most
investigated materials due to its interesting properties such as chemical
stability, non-toxicity, high refractive index, elevate dielectric constant,
anti-fog and self-cleaning abilities to be exploited in a wide range of
applications, e.g. optical coatings, electrical insulation, solar cells,
antibacterial coatings and gas sensors.
In particular, the reduction from bulk to nanostructured
material has been generally recognized as the most efficient strategy to
enhance the sensing properties of metal oxides and especially of titanium
dioxide.
In this respect, a very interesting result was obtained
since the MAPLE technique was employed, for the first time, for the
deposition of colloidal TiO2 nanoparticle thin films. In this way
it was possible to overcome the problems generally presented by the
conventional deposition techniques (spin coating and drop casting) in term
of good film thickness control and uniform coverage of flat and rough
substrates, preserving the colloidal nanoparticles properties.
Structural analyses (FTIR, XRD, EDX) revealed that TiO2
composition and crystalline phase were preserved, while optical
evaluations (UV-Vis absorbance) showed standard
responses, presented also by titania nanostructered films deposited with
other techniques.
Fig. 1: Scanning Electron Microscopy images of the
interdigitated sensor and of the TiO2 film coverage on the Al2O3
grains deposited by MAPLE technique
Uniform coverage of TiO2 nanoparticles
resulted on flat silicon and quartz substrates and on non-planar alumina
substrates (Fig.1), confirming the great potentiality of this technique in
the microsensor field. In fact, these films were successfully employed as
gas detectors and integrated in a reading system. Very interesting sensing
results were achieved in terms of reproducibility and response of the sensor
in the presence of ethanol and acetone vapors.
Works are in progress to improve the thin film properties
in order to enhance the gas sensor responses and to test these devices
towards pollutant gases detection.
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