CN105699433A - Graphene quantum dot-ZnO composite gas-sensitive material with high sensitivity to acetic acid gas - Google Patents

Abstract

The invention discloses a graphene quantum dot-ZnO composite gas sensitive material with high sensitivity to acetic acid gas, belonging to the technical field of gas sensitive materials. The gas-sensing material is composed of ZnO and graphene quantum dots, wherein the mass of the graphene quantum dots accounts for 10-20% of the total mass of the gas-sensing material. The side thermal gas sensor made of this material as a sensitive material has a sensitivity to 0.01ppm acetic acid (ratio of element resistance in air to element resistance in measured gas) between 2-2.6 at a working temperature of 300°C. The sensitivity to 1000ppm acetic acid is between 590-620, and the response recovery time is less than 45s, which can realize the rapid detection of the concentration of acetic acid in the air.

Description

A graphene quantum dot-ZnO composite gas-sensing material with high sensitivity to acetic acid gas

technical field

The invention belongs to the technical field of gas-sensing materials, in particular to a graphene quantum dot-ZnO composite gas-sensing material with high sensitivity to acetic acid gas. The gas sensor made of the gas sensitive material has high sensitivity and good selectivity to low concentration acetic acid in the air.

technical background

Acetic acid is a volatile, colorless liquid with a strong pungent smell. It is highly corrosive and can cause skin and mucous membranes to blister, redness, and swelling. When the concentration is high, it can cause rhinitis and bronchitis. In severe cases, acute chemical reactions may occur. pneumonia. At present, acetic acid is widely used in chemical enterprises, and more and more enterprises are involved in monitoring the concentration of acetic acid in environmental impact assessment and acceptance monitoring. The hygienic standard of the United States, Japan and other countries is 25mg/m ³ (about 9.3ppm), and China has not formulated the limit value of acetic acid in the air of the workplace. The current methods for measuring the concentration of acetic acid in the air mainly use gas chromatography and ion chromatography, etc. These methods require relatively expensive instruments and equipment, and sampling and analysis take a long time.

Contents of the invention

In order to overcome the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a gas-sensitive material for detecting acetic acid gas in the air, in order to provide a method for rapidly detecting the concentration of acetic acid gas in the air.

The invention provides a graphene quantum dot-ZnO composite gas-sensing material with high sensitivity to acetic acid gas. The gas-sensing material is composed of ZnO and graphene quantum dots, wherein the mass of the graphene quantum dots accounts for 10% of the total mass of the gas-sensing material. 10-20%; the gas-sensitive material is prepared through the following steps:

1) Preparation of graphene quantum dots: Weigh 2g of citric acid and add it to a 25mL beaker and keep it at 200°C. After the citric acid starts to change from white crystals to orange solution, slowly add 10mg/mL NaOH solution dropwise to the above solution and adjust the pH to 7.0, the resulting solution is the graphene quantum dot solution.

2) Preparation of graphene quantum dots-ZnO composite gas-sensing material: Weigh 2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O and dissolve in 20mL of deionized water, then add 10-20ml of graphene quantum dots prepared in step (1) Slowly add the point solution to the above solution, stir for 30min, and ultrasonically treat the mixed solution to obtain a suspension; then add 1mol/L NaOH solution dropwise to the suspension until the pH of the reaction solution is 7.0; then transfer the reaction solution to a volume of 50mL React in a hydrothermal kettle at 140-200°C for 8-24h. After the reactor is cooled, the product is washed with deionized water and absolute ethanol, and the washed precipitate is put in an oven and dried at 60°C for 24h. obtain the target product.

As an optimization, in the gas-sensitive material preparation step (2), the graphene quantum dot solution added is 20ml.

Compared with the prior art, the present invention has the following technical effects:

The present invention mixes graphene quantum dots in ZnO to make a composite material through a hydrothermal reaction method, and uses the material as a sensitive material to make a side thermal gas sensor, which has a sensitivity of 0.01ppm acetic acid at a working temperature of 300°C (The ratio of the element resistance in the air to the element resistance in the measured gas) is between 2-2.6, the sensitivity to 1000ppm acetic acid is between 590-620, and the response recovery time is less than 45s, which can realize the rapid detection of the concentration of acetic acid in the air.

detailed description

The material of the present invention can be used as the sensitive material of the acetic acid gas sensitive element, and the method for utilizing the material to make the side-heating type gas sensitive element is as follows: 0.1 gram of material and 0.5 gram of terpineol are mixed and ground to make a slurry, and the slurry is brushed with a small brush. The material is applied to the surface of the alumina ceramic tube; the dimensions of the alumina ceramic tube are: length 6 mm, inner diameter 1.6 mm, outer diameter 2 mm, gold medals are used as electrodes at both ends of the alumina tube, and gold wires are welded on the electrodes as leads , the distance between the electrodes is 1 mm; a nickel-chromium alloy wire is placed in the alumina tube as a heating wire, and the temperature of the sensitive material on the surface of the alumina tube can be controlled by controlling the current flowing through the heating wire and the voltage across the heating wire; The aluminum oxide tube of the sensitive material slurry is dried under an infrared lamp to obtain a side-heated gas sensor. The sensitivity of the element to a certain gas is the ratio of the resistance of the element in the air to the resistance of the element in the measured gas at the working temperature.

The present invention is described in detail below in conjunction with specific examples, but the present invention is not limited to the following examples.

Example 1

2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O was weighed and dissolved in 20mL of deionized water, 10ml of graphene quantum dot solution was slowly added to the above solution, stirred for 30min, and the mixed solution was sonicated to obtain a suspension. Then 1 mol/L NaOH solution was added dropwise to the suspension until the pH of the reaction solution was 7.0. Subsequently, the reaction solution was transferred to a hydrothermal kettle with a volume of 50 mL and reacted at 140°C for 8 hours. After the reaction kettle was cooled, the product was washed with deionized water and absolute ethanol several times, and the washed precipitate was put into an oven at 60 Bake at ℃ for 24 hours to obtain a graphene quantum dot-ZnO composite material. The material was analyzed by thermogravimetric analysis, and in the composite material, the content of graphene quantum dots was 10%.

The material is made into a side-heated element, and the highest sensitivity of the element to 0.01, 0.1, 1, 10, 100, and 1000ppm acetic acid gas at a working temperature of 300°C is measured to be 2.0, 3.0, 12.1, 45.8, 300.5, and 590.0, respectively. The response time and recovery time for 0.01-1000pp acetic acid are not more than 20 seconds and 45 seconds.

Example 2

2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O was weighed and dissolved in 20mL of deionized water, 15ml of graphene quantum dot solution was slowly added to the above solution, stirred for 30min, and the mixed solution was ultrasonically treated to obtain a suspension. Then 1 mol/L NaOH solution was added dropwise to the suspension until the pH of the reaction solution was 7.0. Subsequently, the reaction solution was transferred to a hydrothermal kettle with a volume of 50 mL and reacted at 180° C. for 12 hours. After the reaction kettle was cooled, the product was washed with deionized water and absolute ethanol several times, and the washed precipitate was put into an oven at 60 Bake at ℃ for 24 hours to obtain a graphene quantum dot-ZnO composite material. The material was analyzed by thermogravimetric analysis, and in the composite material, the content of graphene quantum dots was 15%.

The material was made into a side-heating element, and the highest sensitivity of the element to 0.01, 0.1, 1, 10, 100, and 1000ppm acetic acid gas at a working temperature of 300°C was measured to be 2.2, 3.4, 14.1, 51.8, 311.5, and 609.0, respectively. The response time and recovery time for 0.01-1000pp acetic acid are not more than 20 seconds and 42 seconds.

Example 3

2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O was weighed and dissolved in 20mL of deionized water, 15ml of graphene quantum dot solution was slowly added to the above solution, stirred for 30min, and the mixed solution was ultrasonically treated to obtain a suspension. Then 1 mol/L NaOH solution was added dropwise to the suspension until the pH of the reaction solution was 7.0. Subsequently, the reaction solution was transferred to a hydrothermal kettle with a volume of 50 mL and reacted at 180° C. for 16 hours. After the reaction kettle was cooled, the product was washed with deionized water and absolute ethanol several times, and the washed precipitate was put into an oven at 60 Bake at ℃ for 24 hours to obtain a graphene quantum dot-ZnO composite material. The material was analyzed by thermogravimetric analysis, and in the composite material, the content of graphene quantum dots was 15%.

The material is made into a side-heating element, and the highest sensitivity of the element to 0.01, 0.1, 1, 10, 100, and 1000ppm acetic acid gas at a working temperature of 300°C is measured to be 2.5, 3.9, 16.1, 57.8, 319.5, and 615.4, respectively. The response time and recovery time for 0.01-1000pp acetic acid are not more than 20 seconds and 40 seconds.

Example 4

2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O was weighed and dissolved in 20mL of deionized water, 20ml of graphene quantum dot solution was slowly added to the above solution, stirred for 30min, and the mixed solution was ultrasonically treated to obtain a suspension. Then 1 mol/L NaOH solution was added dropwise to the suspension until the pH of the reaction solution was 7.0. Subsequently, the reaction solution was transferred to a hydrothermal kettle with a volume of 50 mL and reacted at 200°C for 24 hours. After the reaction kettle was cooled, the product was washed with deionized water and absolute ethanol several times, and the washed precipitate was put into an oven at 60 Bake at ℃ for 24 hours to obtain a graphene quantum dot-ZnO composite material. The material was analyzed by thermogravimetric analysis, and in the composite material, the content of graphene quantum dots was 20%.

The material is made into a side-heating element, and the highest sensitivity of the element to 0.01, 0.1, 1, 10, 100, and 1000ppm acetic acid gas at a working temperature of 300°C is measured to be 2.6, 3.5, 16.4, 53.6, 314.6, and 620.0, respectively. The response time and recovery time for 0.01-1000pp acetic acid are not more than 20 seconds and 45 seconds.

Claims (2)

1. A graphene quantum dot-ZnO composite gas sensitive material highly sensitive to acetic acid gas, it is characterized in that, this gas sensitive material composition is ZnO and graphene quantum dot, wherein the quality of graphene quantum dot accounts for the total amount of gas sensitive material 10-20% of the mass; the gas-sensitive material is prepared through the following steps: 1) Preparation of graphene quantum dots: Weigh 2g of citric acid and add it to a 25mL beaker and keep it at 200°C. After the citric acid starts to change from white crystals to orange solution, slowly add 10mg/mL NaOH solution dropwise To the above solution and adjust the pH to 7.0, the resulting solution is the graphene quantum dot solution; 2) Preparation of graphene quantum dots-ZnO composite gas-sensing material: Weigh 2.22g of Zn(NO ₃ ) ₂ ·6H ₂ O and dissolve in 20mL of deionized water, then add 10-20ml of graphene quantum dots prepared in step (1) Slowly add the point solution to the above solution, stir for 30min, and ultrasonically treat the mixed solution to obtain a suspension; then add 1mol/L NaOH solution dropwise to the suspension until the pH of the reaction solution is 7.0; then transfer the reaction solution to a volume of 50mL React in a hydrothermal kettle at 140-200°C for 8-24h. After the reactor cools down, wash the product with deionized water and absolute ethanol. Put the washed precipitate in an oven and dry it at 60°C for 24h. . 2. a kind of graphene quantum dot-ZnO composite gas sensitive material to acetic acid gas high sensitivity as claimed in claim 1, is characterized in that, in the described gas sensitive material preparation step (2), the graphene quantum dot added The solution is 20ml.