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New structures for sensing of NO2 and CO gases are presented. The first gas is important for detection of explosives like TNT or RDX, the second one in the protection of health. Sensing with metal oxide semiconductors (including Fe3O4 or CoFe2O4) in the form of films was investigated for this purpose because their resistance is modified by ambient gas. At present attention is paid also to sensing by nanoparticle (NP) arrays benefiting from high gas adsorption surface. In this paper the behavior of Fe3O4, CoFe2O4 and Ag+ Fe3O4 NPs is studied. They were synthesized by high-temperature solution phase reaction of metal acetylacetonates (Fe (acac) 3, Co (acac) 2) with 1, 2-hexadecanediol and surfactant creating oleic acid/oleyl amine in phenyl ether at 200oC/30 min plus 265oC/30 min. The product was dissolved in toluen. Ag+ Fe3O4 NPs were prepared by adding AgNO3 to Fe3O4 and by heat treatment as above. NP arrays were deposited by Langmuir-Blodgett technique from the water subphase in the NIMA trough at the surface pressure of 20 mN/m. They were characterized by XRD, SEM and magnetic measurements. NPs are monodomain, superparamagnetic at RT and they form hexagonal like configuration with crystalline structure of inverse spinel group A (B2) O4. 1, 3 or 7 LB layers were formed on the alumina substrates 2x2 mm2 equipped with heating Ti/Pt meander on the back side and by similar interdigitated contacts on the front side. Substrates were soldered onto commercial TO-8 socket. Sensing properties were studied in a testing chamber with the dilution of gases between 5 and 100 ppm in air. Current I was monitored by …
Publication date: 
1 Jan 2010

AP Caricato, A Luches, M Martino, R Rella, L Chitu, M Jergel, S Luby, E Majkova, P Siffalovic

Biblio References: 
Abstracts of the 18th International of Vacuum Congress