CN104085929B - A kind of method of low-temperature growth tungsten oxide nano - Google Patents

Abstract

The invention discloses a method for preparing tungsten oxide nanowires at low temperature, and relates to the field of nanomaterials. The preparation method uses Na ₂ WO ₄ ·2H ₂ O and concentrated hydrochloric acid as raw materials, and adds Na ₂ WO ₄ ·2H ₂ O aqueous solution After the surfactant, add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and when the pH reaches 5, transfer the mixed solution to an ordinary sealed glass bottle, and store it under 100°C and close to normal pressure Tungsten oxide nanowires were synthesized by the hydrothermal method under the conditions. The method for preparing tungsten oxide nanowires at low temperature provided by the present invention has simple process, easy operation, ultra-low reaction temperature, and can greatly shorten the reaction cycle. The requirements for equipment are simple, and ordinary glass containers can be used. Compared with the method The high-pressure reactor with polytetrafluoroethylene lining has lower energy consumption and lower cost.

Description

A method for preparing tungsten oxide nanowires at low temperature

technical field

The invention belongs to the field of nanometer materials, in particular to a method for preparing tungsten oxide nanowires at low temperature.

Background technique

Tungsten oxide is a typical transition metal oxide with a bandgap of 2.4-2.8eV and belongs to a typical n-type semiconductor. In addition to being used as catalysis, electrochromism, battery electrodes, solar energy absorbing materials and invisible materials, tungsten-based oxides also have the properties of semiconductor functional materials such as pressure-sensitive, heat-sensitive, and gas-sensitive. More and more attention has been paid to the application research of tungsten oxide nanocrystalline film in gas sensor, photocatalysis, photoconductivity and other aspects.

Compared with traditional tungsten oxide materials, tungsten oxide nanowires have a larger specific surface area, and have good application prospects in various aspects such as gas sensing, electroluminescence and photoluminescence, conductivity electrodes and photocatalysis, especially In the application field of oxide semiconductor gas sensors, tungsten oxide nanowires not only have a large specific surface area, but also have greater surface activity and stronger adsorption capacity.

The traditional preparation process of tungsten oxide nanowires is complicated and consumes a lot of energy, and the experimental conditions of these methods are demanding. Some hydrothermal temperatures are as high as 200 ° C, and the hydrothermal time is as long as 24 hours or even longer. In the traditional hydrothermal method, the reaction vessels used are high-pressure reactors lined with polytetrafluoroethylene. These preparation methods have high conditions and high energy consumption.

Contents of the invention

The technical problem solved by the present invention: aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing tungsten oxide nanowires at low temperature.

Technical scheme of the present invention: a method for preparing tungsten oxide nanowires at low temperature, the preparation steps are as follows:

(1) Prepare Na ₂ WO ₄ ·2H ₂ O solution with a concentration of 0.001-0.1mol/L;

(2) Add a surfactant to the Na ₂ WO ₄ 2H ₂ O solution in an amount of 0.01-0.1mol/L;

(3) Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution reaches 5;

(4) Put the solution obtained in step (3) at 95° C. for 2-4 hours to react to obtain tungsten oxide nanowires.

As preferably, the dropping speed of concentrated hydrochloric acid is 0.1mL/s.

Preferably, the surfactant is (NH ₄ ) ₂ SO ₄ or NH ₄ Cl.

Preferably, the surfactant is (NH ₄ ) ₂ SO ₄ .

Preferably, the annealed tungsten wire is put into the solution obtained in step (3), and then the solution is placed at 95° C. for 2-4 hours to react to obtain tungsten oxide nanowires.

Beneficial effects: The method for preparing tungsten oxide nanowires at low temperature is based on the principle of chemical reaction of Na ₂ WO ₄ 2H ₂ O and concentrated hydrochloric acid to generate tungsten oxide. Na ₂ WO ₄ 2H ₂ O and concentrated hydrochloric acid are used as Raw materials, and adding appropriate surfactants, synthesize tungsten oxide nanowires by hydrothermal method under the condition of lower than 100°C and close to normal pressure, the reaction time is 2-4h, which is different from the existing preparation method of tungsten oxide nanowire materials In comparison, the process is simple, the operation is simple, the reaction temperature is ultra-low, and the reaction cycle can be greatly shortened. The requirements for the equipment are simple, and ordinary glass containers can be used. Reactor, lower energy consumption and lower cost.

Put the annealed tungsten wire into the solution for reaction, and tungsten oxide grains will be produced on the surface. According to the growth kinetics principle, the further growth of the grains in the solution is conducive to the growth of nanowires along the C axis. The annealed tungsten wire can serve as a substrate and provide crystal nuclei here, so that tungsten oxide nanowires can be arranged in an array on the substrate tungsten wire to achieve better results.

Description of drawings

Fig. 1 is a scanning electron microscope image of tungsten oxide nanowires prepared by selecting different surfactants in a method for preparing tungsten oxide nanowires at low temperature according to the present invention. Where (a) is the scanning electron micrograph of the tungsten oxide nanowires prepared in Example 1, and the selected surfactant is (NH ₄ ) ₂ SO ₄ ; (b) is the scanning electron micrograph of the tungsten oxide nanowires prepared in Example 2 , the selected surfactant is NH ₄ Cl; (c), (d) are the partially enlarged SEM images of (a) and (b), respectively.

Fig. 2 is a scanning electron microscope image of tungsten oxide nanowires prepared by selecting different concentrations of Na ₂ WO ₄ ·2H ₂ O in a method for preparing tungsten oxide nanowires at low temperature according to the present invention. Wherein (a) is the scanning electron micrograph of the tungsten oxide nanowires prepared in Example 3, and the selected Na ₂ WO ₄ ·2H ₂ O concentration is 0.001mol/L; (b) is the oxidized nanowires prepared in Example 4. The scanning electron microscope image of the tungsten nanowire, the concentration of Na ₂ WO ₄ ·2H ₂ O is 0.1 mol/L.

Fig. 3 is a scanning electron microscope image of tungsten oxide nanowires prepared with different reaction times in a method for preparing tungsten oxide nanowires at low temperature according to the present invention. Where (a) is the scanning electron micrograph of the tungsten oxide nanowire prepared in Example 5, and the hydrothermal reaction time is 2 h; (b) is the scanning electron micrograph of the tungsten oxide nanowire prepared in Example 6, and the hydrothermal reaction time is 4h.

Fig. 4 is a scanning electron micrograph of tungsten oxide nanowires prepared by adding surfactants with different concentrations of substances in a method for preparing tungsten oxide nanowires at low temperature according to the present invention. Where (a) is the scanning electron micrograph of the tungsten oxide nanowires prepared in Example 7, and the concentration of the added surfactant (NH ₄ ) ₂ SO ₄ is 0.01mol/L; (b) is prepared in Example 8 The scanning electron microscope image of the tungsten oxide nanowires, the concentration of the added surfactant (NH ₄ ) ₂ SO ₄ is 0.05mol/L.

Fig. 5 is a scanning electron micrograph of tungsten oxide nanowires prepared according to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention in Example 9, wherein the concentration of surfactant (NH ₄ ) ₂ SO ₄ is 0.01 mol/ L.

Fig. 6 is a scanning electron micrograph of tungsten oxide nanowires prepared according to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention in Example 10, wherein the concentration of surfactant (NH ₄ ) ₂ SO ₄ is 0.1 mol/ L, (b) is a partial enlarged view of (a).

detailed description

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than limiting the claims of the present invention.

Example 1

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.01mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, the surfactant is (NH ₄ ) ₂ SO ₄ , and the amount added to the solution is 0.66g; under the condition of magnetic stirring, 0.1ml/ Add concentrated hydrochloric acid drop by drop to the Na ₂ WO ₄ 2H ₂ O solution at a speed of s until the pH value of the solution is adjusted to 5, then stop the dropwise addition; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven stable At 95°C, place the glass bottle in a constant temperature drying oven and react for 3 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and then put it in an oven and dry it at 60°C for 1 hour. The obtained tungsten oxide It is a nanowire structure with a diameter of about 10nm and a length of 200-300nm. The scanning electron microscope is shown in Figure 1 (a) and (c).

Example 2

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.01mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, choose NH ₄ Cl as the surfactant, and add 0.26g in the solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ ·2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and when the temperature of the drying oven is stable at 95°C , put the glass bottle in a constant temperature drying oven, and react for 3 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and put it in an oven to dry at 60°C for 1 hour. The prepared tungsten oxide is nanowire structure, with a diameter of about 20nm and a length of about 500nm, as shown in Fig. 1(b) and (d) by SEM.

Example 3

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.001mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, add 0.66g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven at 95°C , place the glass bottle in a constant temperature drying oven, and react for 3 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and put it in an oven to dry at 60°C for 1 hour, and the obtained tungsten oxide is composed of nanorods. The cluster structure of the rods is about 50nm in diameter and about 400-500nm in length, and its scanning electron microscope is shown in Fig. 2(a).

Example 4

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.1mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, add 0.66g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven at 95°C Place the glass bottle in a constant temperature drying oven and react for 3 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and then put it in an oven and dry it at 60°C for 1 hour. The obtained tungsten oxide is flake and The short rod structure, in which the diameter of the rod is about 50nm, the length is 100-200nm, and the thickness of the sheet is about 50nm, its scanning electron microscope is shown in Figure 2(b).

Example 5

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.01mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, add 0.66g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven at 95°C Place the glass bottle in a constant temperature drying oven and react for 2 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and put it in an oven to dry at 60°C for 1 hour. The obtained tungsten oxide is nanometer Wire structure, the diameter of tungsten oxide nanowire is about 10nm, the length is 200-300nm, and its scanning electron microscope is shown in Fig. 3(a).

Example 6

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.01mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, add 0.66g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven at 95°C , put the glass bottle in a constant temperature drying oven and react for 4 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and then put it in an oven and dry it at 60°C for 1 hour. The obtained tungsten oxide is nanometer The wire structure, the diameter of tungsten oxide is about 20-30nm, the length is about 100-200nm, and its scanning electron microscope is shown in Figure 3(b).

Example 7

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50mL of 0.01mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution, add 0.066g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution is adjusted to 5; transfer the obtained mixed solution into a sealed glass bottle, and keep the temperature of the drying oven at 95°C Place the glass bottle in a constant temperature drying oven and react for 3 hours; wash the precipitate obtained after the reaction twice with water and ethanol, and then put it in an oven and dry it at 60°C for 1 hour. The obtained tungsten oxide is nanometer Rod structure, the diameter of the rod is about 50nm, the length is about 500nm, its scanning electron microscope is shown in Figure 4(a).

Example 8

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50 mL of 0.01 mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution. Add 0.33g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ ·2H ₂ O solution at a speed of 0.1ml/s under magnetic stirring conditions, When the pH value of the solution is adjusted to 5, stop the dropwise addition; transfer the obtained mixed solution into a sealed glass bottle, and when the temperature of the drying oven is stable at 95°C, place the glass bottle in a constant temperature drying oven and react for 3 hours; after the reaction The obtained precipitate was washed twice with water and ethanol respectively, and then dried in an oven at 60°C for 1 hour. The obtained tungsten oxide was in the form of flakes and short rods. The thickness is about 100nm, and its scanning electron microscope is shown in Fig. 4(b).

Example 9

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50 mL of 0.01 mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution. Add 0.066g of surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ ·2H ₂ O solution at a speed of 0.1ml/s under the condition of magnetic stirring, When the pH value of the solution is adjusted to 5, stop the dropwise addition; transfer the obtained mixed solution into a sealed glass bottle, put the annealed (600°C for 1h) tungsten wire into the bottle, and keep the temperature of the drying oven at 95°C , put the glass bottle in a constant temperature drying oven, after 2 hours of reaction, take out the tungsten wire, wash it twice with water and ethanol, put it in an oven and dry it at 60°C for 1 hour, the obtained tungsten oxide has a nanorod structure , the diameter of the rod is about 100-200nm, the length is about 200-500nm, and its scanning electron microscope is shown in Figure 5.

Example 10

According to the method for preparing tungsten oxide nanowires at low temperature provided by the present invention, tungsten oxide nanowires are prepared, and the preparation steps are as follows:

First prepare 50 mL of 0.01 mol/L Na ₂ WO ₄ ·2H ₂ O aqueous solution. Add 0.66g surfactant (NH ₄ ) ₂ SO ₄ to the reactant solution; add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ ·2H ₂ O solution at a speed of 0.1ml/s under the condition of magnetic stirring, When the pH value of the solution is adjusted to 5, stop the dropwise addition; transfer the obtained mixed solution into a sealed glass bottle, put the annealed (600°C for 1h) tungsten wire into the bottle, and keep the temperature of the drying oven at 95°C , put the glass bottle in a constant temperature drying oven, after reacting for 2 hours, take out the tungsten wire, wash it twice with water and ethanol, put it in an oven and dry it at 60°C for 1 hour, the obtained tungsten oxide has a nanowire structure , with a diameter of about 100-200nm, a length of up to 20um, and an aspect ratio of 50-100. Its scanning electron microscope is shown in Figure 6.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (3)

1. A method for preparing tungsten oxide nanowires at low temperature, characterized in that the preparation steps are as follows: (1) Prepare Na ₂ WO ₄ ·2H ₂ O solution with a concentration of 0.001-0.1mol/L; (2) Add a surfactant to the Na ₂ WO ₄ ·2H ₂ O solution in an amount of 0.01-0.1 mol/L, wherein the surfactant is (NH ₄ ) ₂ SO ₄ or NH ₄ Cl; (3) Add concentrated hydrochloric acid dropwise to the Na ₂ WO ₄ 2H ₂ O solution, and stop the dropwise addition when the pH value of the solution reaches 5; (4) Put the solution obtained in step (3) at 95° C. for 2-4 hours to react to obtain tungsten oxide nanowires. 2. The method for preparing tungsten oxide nanowires at low temperature according to claim 1, characterized in that the dropping rate of concentrated hydrochloric acid is 0.1mL/s. 3. The method for preparing tungsten oxide nanowires at low temperature according to claim 1, characterized in that annealed tungsten wire is placed in the solution obtained in step (3), and then the solution is placed at 95°C for 2-4 Hours, tungsten oxide nanowires were obtained.