Preparation Of Highly Active Facet ?-Fe 2 O 3 Nanomaterials And Their Enhanced Sensing Properties

nanocubes with exposed{012},{102}and{112} faces, two dimensional ?2D? porous ?-Fe₂O₃ nanosheets and three dimensional ?3D? network a-Fe₂O₃ structures assembled by nanosheets with{114} facets exposed, were synthesized through a simple hydrothermal method or solution fast thermal method. Morphologies and structures of these products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, absorption desorption porosimetry and X-ray photoelectron spectra. The gas sensing properties of as obtained a-Fe₂O₃ structures with various morphologies were studied, and the relations between morphology, exposed facets and properties were investigated. Specific research results as follows:?1? a-Fe₂O₃ nanocubes with exposed{012},{102} and{112} facets were synthesized by the way of hydrothermal reaction of FeCl₃ and NaOH. The Cl- ion capped a-Fe₂O₃ nanocubes were soaked by AgNO3 and NH₃·H₂O solutions to obtain a-Fe₂O₃ nanocubes with clean facets, and their gas sensing performances were studied. It is found that gas sensing performances of the Cl-ion capped a-Fe₂O₃ nanocubes were activated by treatment of AgNO3 and NH₃H₂O solutions. This enhanced response performance originated ?012?, ?102? and ?112? surface strong adsorption oxygen ability. The enhancing sensing mechanism of ?-Fe₂O₃ nanocubes exposed{012},{102} and {112} faces with clean surfaces was explained.?2? The three dimensional ?3D? network a-Fe₂O₃ structures were synthesized by heating iron nitrate PVP mixture solution at 650 ? on Si substrate. The effects of different dosage of iron salt or PVP and the reaction temperature on the morphology of the products were studied, and the growth mechanism of the three dimensional ?3D? network a-Fe₂O₃ structure was proposed. The gas sensing performance of the as prepared three dimensional ?3D? network a-Fe₂O₃ structures was investigated at different temperatures. It was found that the detection limit of three dimensional ?3D? network a-Fe₂O₃ structures towards ethanol and triethylamine in the working temperature of 300 ? can reach ppb level. This enhanced response performance originated ?114? surface strong adsorption oxygen ability. The Co₃O₄, NiO, CuO, ZnO and ZnFe₂O₄ structures can also be synthesized by the method that is similar to a-Fe₂O₃ structure.?3? The FeySg nanosheets precursor was prepared by hydrothermal method in the aqueous system of ferrous sulfate, thiourea and hydrazine, and 2D porous a-Fe₂O₃ nanosheets were obtained by calcinated the precursor at 500 ?. The gas sensing performance of the 2D porous ?-Fe₂O₃ nanosheets was investigated towards ethanol and triethylamine. It was found that 2D porous ?-Fe203 nanosheets show superior gas sensing performances compared with commercial powder.