Tungsten Oxide Nanoflake Self-assembly Nanosphere and Preparing Method

The tungsten trioxide is a η- type wide band gap semiconductor oxide (band gap of about 2.8eV), since the crystal memory in the atomic or electronic defect, the compound stoichiometry deviation occurs, the charge carrier concentration is mainly determined by the concentration of stoichiometric defects (such as oxygen vacancies), it has excellent catalytic and gas sensing performance. Tungsten oxide based gas sensors for the N02, H2S, 03, and NH3, and many other environmentally harmful gases sensitive response, especially for low concentration of nitrogen oxides show ultra-high sensitivity. In addition, the tungsten oxide also has a photochromic, electrochromic properties, photocatalysis, field emission and solar cells have a wide range of applications.

Tungsten oxide nanosheets self-assembly microsphere preparation, concrete steps are as follows:
(1)In a reaction vessel, the soluble tungsten salt dissolves in deionized water. Dub the concentration of the solution to 0.10~0.80mol L, place 100 ~750W power ultrasonic generator under ultrasonic condition oxalic acid.
(2)0.12~0.47mol of oxalic acid is added, the concentration will be dissolved as 1.00~4.50mol / L  inorganic acid solution.
(3)It was slowly added to the above solution to PH value 0.50~3.50, continued ultrasound 20~150min, the yellow precipitate was washed by centrifugation, and the resulting yellow precipitate was dried at 50~80 °C under 4~20h. Soluble tungsten salt is tungsten hexachloride (WCl₆), sodium tungstate (Na₂WO₄.2H₂O), ammonium metatungstate [(NH₄) 6W₇O₂₄.6H₂O] and paratungstate [5 (NH₄) 20.12W0₃.5H₂O] one; the inorganic acid are sulfuric acid (H₂SO₄) 'hydrochloric acid (HCl) and nitric acid (HNO₃).

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