1 research outputs found
Facile Synthesis of Titania Nanowires via a Hot Filament Method and Conductometric Measurement of Their Response to Hydrogen Sulfide Gas
Titania nanostructures are of increasing interest for
a variety of applications, including photovoltaics, water splitting,
and chemical sensing. Because of the photocatalytical properties of
TiO<sub>2</sub>, chemical processes that occur at its surface can
be exploited for highly efficient nanodevices. A facile and fast synthesis
route has been explored that is free of catalysts or templates. An
environmental scanning electron microscopy (ESEM) system was employed
to grow titania nanowires (NWs) in a water vapor atmosphere (∼1
mbar) and to monitor the growth in situ. In addition, the growth process
was also demonstrated using a simple vacuum chamber. In both processes,
a titanium filament was heated via the Joule effect and NWs were found
to grow on its surface, as a result of thermal oxidation processes.
A variety of nanostructures were observed across the filament, with
morphologies changing with the wire temperature from the center to
the end points. The longest NWs were obtained for temperatures between
∼730
°C and 810 °C. Typically, they have an approximate thickness
of ∼300 nm and lengths of up to a few micrometers. Cross sections
prepared by focused-ion-beam milling revealed the presence of a porous
layer beneath the NW clusters. This indicates that the growth of NWs
is driven by oxidation-induced stresses in the subsurface region of
the Ti filament and by enhanced diffusion along grain boundaries.
To demonstrate the potential of titania NWs grown via the hot filament
method, single NW devices were fabricated and used for conductometric
sensing of hydrogen sulfide (H<sub>2</sub>S) gas. The NW electric
resistance was found to decrease in the presence of H<sub>2</sub>S.
Its variation can be explained in terms of the surface depletion model