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Sensors 2007, 7(7), 1159-1184; doi:10.3390/s7071159

Effects of Palladium Loading on the Response of Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor

1 and 2,*
1 Department of Physics, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand 2 Nanoscience Research Laboratory, Department of Chemistry, Faculty of Science, Chiang Mai 50200, Thailand
* Author to whom correspondence should be addressed.
Received: 6 June 2007 / Accepted: 9 July 2007 / Published: 26 July 2007
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ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in asingle step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II)acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect ofPd loading on the ethanol gas sensing performance of the ZnO nanoparticles and thecrystalline sizes were investigated. The particle properties were analyzed by XRD, BET,AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorptionmeasurements. A trend of an increase in specific surface area of samples and a decrease inthe dBET with increasing Pd concentrations was noted. ZnO nanoparticles were observed asparticles presenting clear spheroidal, hexagonal and rod-like morphologies. The sizes ofZnO spheroidal and hexagonal particle crystallites were in the 10-20 nm range. ZnOnanorods were in the range of 10-20 nm in width and 20-50 nm in length. The size of Pdnanoparticles increased and Pd-dispersion% decreased with increasing Pd concentrations.The sensing films were produced by mixing the particles into an organic paste composedof terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed ontoAl2O3 substrates interdigitated with Au electrodes. The film morphology was analyzed bySEM and EDS analyses. The gas sensing of ethanol (25-250 ppm) was studied in dry air at400°C. The oxidation of ethanol on the sensing surface of the semiconductor wasconfirmed by MS. A well-dispersed of 1 mol%Pd/ZnO films showed the highest sensitivityand the fastest response time (within seconds).
Keywords: Flame spray pyrolysis; ZnO; Palladium; Ethanol sensor. Flame spray pyrolysis; ZnO; Palladium; Ethanol sensor.
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Liewhiran, C.; Phanichphant, S. Effects of Palladium Loading on the Response of Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor. Sensors 2007, 7, 1159-1184.

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