Sensor Characterization of Tin Oxide Nanostructures
P. H. Suman1 and M. O. Orlandi1
1
LIEC, IQ, Universidade Estadual Paulista – UNESP, Campus de Araraquara, SP, Brazil
In the last years, nanostructured materials have attracted the attention of researchers especially
since the 1990s with the discovery of carbon nanotubes. Moreover, there is a wide
applicability of these materials in several areas of knowledge, for example, chemicals sensors,
emitters by electric field and microelectronic devices. Tests showed that the use of
nanomaterials may make the device faster, more sensitive and still consume less power. It is
known that different types of nanostructures can be formed by variations in synthesis
conditions such as temperature and pressure of the furnace. Among these nanostructures, we
emphasize the nanobelts that, in general, are made from metal semiconducting oxides, such as
the SnO2. The SnO2 is an interesting material because it can be used since gas sensors until
varistors and electrodes for fuel cells. In this work, nanostructures of tin oxide was
synthesized from the vapor phase by carbothermal reduction method. In this method, the SnO2
is mechanically mixed with a carbon source causing increases of the vapor pressure of the
oxide and thereby the decrease of the synthesis temperature. Previous results showed that
controlling the synthesis atmosphere it is possible to obtain tin oxide nanomaterials grown in
the SnO or the SnO2 phase. The control of oxidation state of the nanostructures was done by
variation of the synthesis atmosphere inside the furnace. The analysis of X-ray diffraction
showed that in atmospheres without oxygen materials grow in the SnO phase, while in
atmospheres with oxygen the materials grow only in the SnO2 phase. The materials grown in
the SnO2 phase have not yet been fully characterized. However, the materials grown in the
SnO phase were characterized morphologically by field emission gun scanning electron
microscope (FEG-SEM; JEOL, model 7500F) and showed that the structures grown are onedimension and have rectangular cross-section, i.e, they are nanobelts. The nanobelts have a
constant width along its length, and have a maximum width frequency in the range of 20 to 40
nm. By SEM images, we can perceive the presence of metallic spheres at one end of the
nanobelts. This fact is related with the mechanism of grown that follows a process vaporliquid-solid (VLS) autocatalytic. Moreover, the sensor responses to gases (CO and CO2) of the
materials were measured and these materials showed good results indicating that they have
sensor properties.
Keywords: Nanomaterials, tin oxide, sensor characterization.
Work supported by CNPq and FAPESP.
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P.H. Suman, M.O. Orlandi, J. Nanopart. Res., manuscript in press.
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