Nano Tungsten Trioxide Preparation by Sol-gel Method

The preparation of core-shell nanocomposites is mainly divided into several methods, such as interface polymerization, condensed phase separation, drying bath and sol-gel method.

Among them, the sol-gel method is a low-cost method, which can chemically bond a layer of polymer on the surface of the tungsten trioxide nanospheres, and then form the tungsten trioxide polymer nanospheres with the core of the nanospheres and the shell of the polymer. The process of this method is as follows:

(1)0.5-5g tungstic acid and 1.26-12.6g citric acid were prepared into water solution at the molar ratio of 3:1. Under the condition of continuous agitation and 55-70 ℃, the pH of the solution was adjusted to 8-12 with ammonia water to form tungsten trioxide / citric acid chelate solution. The solution was heated at 45-100 ℃ for 8-36 hours to form gel like precursor, and burned at 500-900 ℃ for 1-12 hours to form nano tungsten trioxide precursor powder;

(2)Weigh 0.1-1.5g of nano tungsten trioxide nano powder and disperse it in 10-50ml of anhydrous ethanol, add 5-50ml of 0.025g/ml of coupling agent solution drop by drop, react for 30-40h in water bath at 30-40 ℃ and dry in vacuum at 25-45 ℃ for more than 12h to obtain the coupling agent treated nano tungsten trioxide powder;

(3)In a three port flask equipped with a reflux condensing device, 0.5-5g of the above-mentioned coupling agent treated tungsten trioxide nano powder is ultrasonically dispersed in 10-50ml of anhydrous ethanol, and 0.1-1.0g of buffer, 0.05-0.5g of emulsifier and 50-250ml of deionized water are added at the same time. After the ultrasonic dispersion is uniform, 5-25ml of monomer is added. After 0.5-4h of pre emulsification at 45-60 ℃, the temperature rises to 75-85 ℃, and drops are made. The aqueous solution of persulfate with a concentration of 5 to 50ml was added for 6~24 hours after dropping. After that, the white emulsion was stopped. The emulsion was centrifugally filtered and purified, then washed with toluene to remove homopolymer. After 60~100 hours of vacuum drying for more than 12 hours, the tungsten trioxide polymer nano core shell particles were obtained. At the same time, 0.012g/ml was obtained.

Coating polymer materials on the surface of tungsten trioxide nanoparticles can prevent the interaction between the external environment and the nanoparticles, change the optical, thermal, electrical or surface activity of the nanoparticles, improve the dispersion of the nanoparticles, improve their affinity with organic solvents, polymers, etc., and transfer the nanoparticles. With other organic semiconductors for effective composite modification, improve its photoelectric performance or processing performance, so that it can meet a variety of special needs, so it has high application value.

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