Effect of PdO Nanoparticles Decorated with WO
3
Nanorods by the
Precipitation/Impregnation Methods for Ethanol Gas Sensors
S. Kabcum,
a
A. Wisitsora-at,
b
C. Liewhiran,
a
S. Phanichphant,
c,
*
a
Department of Physics and Materials Science, Faculty of Science, Chiang Mai University,
Chiang Mai 50200, Thailand.
b
Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology
Center, Klong Luang, Pathumthani 12120, Thailand.
c
Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai
50200, Thailand.
Fax: +66-53892277, *E-mail:
The ultra-rapid gases sensors based on unloaded and 0.25–2.0 wt% Pd–loaded WO
3
nanoparticles were synthesized by the precipitation method and imgregnated using palladium
acetylacetonate. Unloaded and 0.25–2.0 wt% Pd–loaded WO
3
nanoparticles were
characterized by by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy
dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy
(HRTEM) techniques. The BET surface area (
SSA
BET
) of the nanoparticles was measured by
nitrogen adsorption. The sensing films were prepared by mixing the unloaded and Pd–loaded
WO
3
nanoparticles into an organic paste composed of vehicle ethyl cellulose binder and
–
terpineol solvent to form a viscous paste. The resulting paste was spin–coated onto Al
2
O
3
substrates interdigitated with Au electrodes by spin coating technique to form the sensing
films. All sensors were systematically tested with C
2
H
5
OH gases. The C
2
H
5
OH gas sensing
performances including the change in resistance, sensor response, selectivity, dynamic range,
and enhanced time factors were significantly performed at the different operating
temperatures ranging from 150–350ºC with various C
2
H
5
OH gas concentrations in dry air.
After sensing test, the morphology and the cross–sectional sensing film (3–5
µ
m in thickness)
were analyzed by SEM and EDS analyses. It was found that 1.0 wt% Pd-loaded WO
3
sensing
film showed the highest response of 1.52x10
4
to 2,000 ppm C
2
H
5
OH at 350ºC and the
shortest response time within 3.8 s. Therefore, an operating temperature of 350ºC was
optimal for C
2
H
5
OH detection. The responses of 1.0 wt% Pd–loaded WO
3
sensing film to
other flammable and toxic gases, including CO, NO
2
, NH
3
and H
2
S, demonstrating Pd–
loaded WO
3
sensing film to be highly selective to C
2
H
5
OH.
Keywords:
WO
3
nanoparticles; Precipitation; Impregnation; Pd; Ethanol gas sensors.
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