Tungsten trioxide (WO₃) is a kind of importantηtype semiconductor oxides with varieties of crystal structure, and has been applied in fields of electrochromic, photochromic, sensing, and catalysis. The size of quasi-spherical and spherical tungsten trioxide is respectively 100nm-700nm and 20-200nm. These two kinds of WO₃ can used as precursor for synthesing nanosize tungsten carbide; the length of diagonal of octahedral tungsten trioxide is less than 1μm, used as gas sensing to produce gas sensor because of the high sensitive; the length of diagonal of WO₃ with irregular polyhedral angle is about 10nm-2μm, and it can be used to adsorb organic molecules, or used to photodegradate organic material. The more fine particles the WO₃ is, the more superior property the subsequent products. Therefore, reducing size of WO₃  is the best way to further utilize the excellent properties of WO₃ and broaden its application field.



Vapor Deposition Method is one of the most effective methods to prepare nano structure, and a variety forms of particles produced by the technology of vapor deposition, such as thin films, whiskers and particles ect.. And the Vapor Deposition Method can produce product with high purity from the low concentration of reactants. But the disadvantage of conventional Vapor Deposition Method is the limited yield; and it can’t achieve producing continuously because of products collected in the environment of high vacuum or temperature. This paper presents a method that can produce polymorphic nanosize tungsten trioxide continuously, take APT.XH₂O as raw material, innovatively combine Vapor Deposition Method with calcination, take argon as carrier gas, collect the products in the area of low temperature, and then achieve the goal of producing polymorphic nanosize tungsten trioxide continuously.

Tungsten trioxide (WO₃) is yellow powder, a kind of important tungsten oxide, also known as yellow tungsten oxide. At present, it’s mainly used in the manufacture of tungsten powder (W) and tungsten carbide powder (WC). The main final products of WO₃ are tungsten rod, tungsten wire and tungsten carbide and so on. In order to obtain WO₃ with better chemical activity, and meet the demand of special alloy with superior properties, we propose a new method--Electro-Pyrolytic to prepare nanosize tungsten trioxide.

Equipment: electromagnetic stirrer; evaporator; drying equipment; grinding equipment; crucible.
Reaction materials: high purity of ammonium paratungstate (APT) with size about 5 μm, purity greater than 99.9%; distilled water; citric acid; ammonia; oxygen.

Specific steps as follows:
1. Adding distilled water into the reaction vessel, and use electromagnetic stirrer for mixing, adding citric acid solution with stirring;
2. When the citric acid solution and distilled water are mixed evenly, adding high purity of APT with stirring, the molar ratio of APT and citric acid is 1:3;
3. Adding ammonia with concentration of 30% to APT solution, stirring at the speed of 180-200r/min;
4. Place the reaction solution in the evaporator to concentrate, drying the concentrated liquid in the drying equipment at the temperature of 150~160°C, and then get the precursor;
5. Precursor grinded in the grinding equipment, heating it in a crucible with oxygen, finally gets nanosize tungsten trioxide. Calculate the flow of oxygen at each gram of precursor for 50-60ml/min, heating temperature for 500~520 °C, time for 1.2~1.5h.

Spectrophotometry is qualitative and quantitative analysis method for the substance by measuring the absorbance or emission intensity of the test substance in a specific wavelength or range of wavelengths of light. When the solution is a bunch of intensity I0 monochromatic vertical irradiation of a substance, due to the portion of the light is absorbed by the system, thus the intensity of the transmitted light is reduced to I, T is the light transmittance of the solution is: according to Lambert (Lambert) - Beer (Beer) Law: A = abc. Where A is the absorbance, b is the thickness of the solution layer (cm), c is the concentration of the solution (g / dm ^ 3), a is the extinction coefficient. There are relationships between the absorption coefficient of the nature of the solution, temperature and wavelength and other factors. Solutions of other components (solvents, etc.) are available to deduct by blank liquid absorption of light ion.

From the above equation, when the thickness of the solution layer b and a are fixed a, which can show a linear relationship in the concentration of the solution and the absorbance A. When we have quantitative analysis, determine a solution for absorption of different wavelengths of light (absorption spectrum) is needed, which determines the maximum absorption wavelength. We take this wavelength of light as the light source, a series of known concentrations measured absorbance c solution A, and making A ~ c curve. In the analysis of an unknown solution that is based on the measured absorbance A, checking the working curve we can determine the corresponding concentrations. This is the basic principle of spectrophotometry measurement of concentration.

We find the stability enables the method sensitivity, contrast and enhanced complex improving in the test of 5-Br-PADAP-Pe (Ⅱ) system that adding non-ionic surfactant emulsifier OP and ethanol. In the conditions of 5-Br-PADAP-Fe (Ⅱ) complex formation emulsifier OP pluralism, and in the presence of ethanol and an emulsifier OP, pH3.5-10H Ac-NaAc buffer medium, Fe (Ⅱ) with 5-Br -PADAP generates purple complex at a wavelength of 558nm, the Fe content in the 0-60μg / 50ml law is obeyed in the range, the complex apparent molar absorption coefficient is 7.64 × 10 ~ 4. Color remains completely within five minutes, the absorbance is stable within 24 hours at room temperature, this method has good selectivity.