CN108828026A - A kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature - Google Patents

Abstract

The invention discloses a method for preparing a gas sensor for detecting nitrogen _dioxide with high sensitivity at room temperature, and relates to a method for preparing a gas sensor for detecting NO2. It is to solve the problem that the existing SnO ₂ semiconductor NO ₂ sensing materials cannot meet the high sensitivity and high selectivity detection of NO ₂ at room temperature. Methods: 1. Preparation of ethylenediamine graphene; 2. Preparation of SnO ₂ /ethylenediamine graphene composite material; 3. Preparation of SnO ₂ /ethylenediamine graphene composite sensing film. The sensor prepared by this method has excellent selectivity to NO ₂ and improves the sensitivity to NO ₂ gas. The invention is used in the technical field of gas detection.

Description

A kind of preparation method of high-sensitivity detection nitrogen dioxide gas sensor at room temperature

technical field

_The invention relates to a preparation method of a gas sensor for detecting NO2.

Background technique

Nitrogen dioxide (NO ₂ ) is a toxic air pollutant. Only 5ppm NO ₂ can damage the lungs and even cause disease. It is also one of the main causes of acid rain and photochemical smog. The main source of NO ₂ is industrial production and automobile exhaust emissions. When detecting NO ₂ concentration, there are a lot of interfering gases in the environment, which will seriously affect the detection precision and accuracy. Therefore, realizing highly selective and sensitive _NO2 gas detection is very important for human health and environmental protection.

SnO ₂ semiconductor material is widely used as a sensitive material to prepare NO ₂ gas sensor because of its low cost and good stability. However, the application of this type of resistive semiconductor sensor is limited because of its high operating temperature (over 200°C), poor selectivity, and low sensitivity. Due to its high conductivity and high carrier mobility, graphene has been widely used in combination with semiconductors in recent years, thereby greatly reducing the operating temperature of semiconductor sensors and realizing _NO detection at room temperature. However, SnO ₂ /graphene is used as a room temperature NO ₂ sensing material. Compared with pure SnO ₂ , the selectivity has not been fully improved, and the improvement of sensitivity is also very limited.

Contents of the invention

The present invention aims to solve the problem that the existing SnO ₂ semiconductor NO ₂ sensing materials cannot meet the high sensitivity and high selectivity detection of NO ₂ at room temperature, and provides a preparation method of a room temperature highly sensitive nitrogen dioxide gas sensor.

The preparation method of the gas sensor for detecting nitrogen dioxide with high sensitivity at room temperature of the present invention comprises the following steps:

One, the preparation of ethylenediamine graphene:

Prepare graphene oxide with Hummer's method, configure graphene oxide into graphene oxide aqueous solution, add ethylenediamine and distilled water to graphene oxide aqueous solution, wherein the volume ratio of graphene oxide aqueous solution, ethylenediamine and distilled water is 6:1 : (13-15), stir evenly, and react at 80-95°C for 8-24h, after the reaction finishes, centrifuge and wash the product with distilled water, then redisperse the product in distilled water, and prepare ethylenediamine graphene aqueous solution;

The concentration of the graphene oxide aqueous solution is 2.5-3.5mg/mL; the concentration of the ethylenediamine graphene aqueous solution is 0.8-1.2mg/mL;

2. Preparation of SnO ₂ /ethylenediamine graphene composite material:

Dissolving tin tetrachloride pentahydrate in water, adding the ethylenediamine graphene aqueous solution and concentrated hydrochloric acid prepared in step 1, stirring at room temperature for 2-3 hours to obtain a mixed solution, placing the mixed solution in a hydrothermal kettle, React at 110-130°C for 12-48h; wash the product with water and ethanol solution to neutrality in turn, and then redisperse the product in ethanol solution to obtain an ethanol solution of SnO ₂ /ethylenediamine graphene composite material;

Wherein the quality of tin tetrachloride pentahydrate and the volume ratio of water are 0.35g: (33-36) mL, the mass ratio of tin tetrachloride pentahydrate and ethylenediamine graphene is 1: (0.0011-0.0034), The volume ratio of the mass of tin tetrachloride pentahydrate to concentrated hydrochloric acid is 0.35g: (1.5-2.5) mL, and the concentration of the ethanol solution of SnO ₂ /ethylenediamine graphene composite material is 37.5-150 mg/mL;

3. Preparation of SnO ₂ /ethylenediamine graphene composite sensing film:

The ethanol solution of the SnO ₂ /ethylenediamine graphene composite material obtained in step 2 is coated on the ceramic sheet with silver-palladium interdigitated electrodes by drop coating or spin coating, and then repeated coating 4-20 times, Then dry in an oven at 60-65° C. for 24h-72h to obtain a NO ₂ gas sensor of SnO ₂ /ethylenediamine graphene composite material.

Further, in the first step, the graphene oxide is configured into a graphene oxide aqueous solution by an ultrasonic-assisted method.

Further, in step 1, the product was centrifuged and washed more than 5 times with distilled water.

Beneficial effects of the present invention:

The present invention prepares NO ₂ sensor by compounding SnO ₂ and ethylenediamine graphene. On the one hand, the strong conductivity of graphene is used to detect NO ₂ at room temperature, and on the other hand, the selectivity and sensitivity to NO ₂ are improved by using the adsorption capacity of ethylenediamine groups on NO ₂ .

The present invention carries out ethylenediamine functional modification on graphene, and the ethylenediamine group on the graphene surface modification can improve the selectivity and sensitivity to NO2 gas. _The specific reasons are: first, the N atom on the group contains The lone pair of electrons is an electron-rich region, which can be used as the adsorption site of NO ₂ to improve the selectivity to NO ₂ ; secondly, the ethylenediamine group acts as an electron-donating group, which will reduce the hole concentration on the graphene surface , so that the resistance increases, and then after adsorbing NO ₂ , the ethylenediamine group can be used as the adsorption site to absorb more NO ₂ , so that the resistance of the ethylenediamine graphene decreases, and the resistance ratio before and after the adsorption changes greatly, thus Increased sensitivity to NO ₂ gas.

_The ratio of reduced graphene to 500 ppm NO2 is only 1.05, while the ratio of ethylenediamined graphene to ₅ ppm NO2 is as high as 1.52. This shows that the gas _- sensing performance of ethylenediamine graphene to NO2 has indeed been greatly improved.

The response ratio of SnO ₂ /ethylenediamine graphene to 5 ppm NO ₂ at room temperature of the present invention reaches 5.22, while the response ratio of SnO ₂ and graphene composited to 5 ppm NO ₂ in the prior art is less than 3.

In the present invention, in the range of 0.25-5ppmNO ₂ to SnO ₂ /ethylenediamine graphene, the response magnification to NO ₂ has a linear relationship with the gas concentration, y=0.799x+1.098, R ² =0.988. This indicates that the quantitative detection of _NO2 can be achieved through the measured data relationship. And the detection value can be as low as 0.25ppm, while the detection range of general sensors is higher than 1ppm.

Description of drawings

Fig. 1 is the atomic force diagram of ethylenediamine graphene in embodiment 1;

Fig. 2 is the infrared figure of ethylenediamine graphene in embodiment 1;

Fig. 3 is the transmission electron micrograph of SnO ₂ / ethylenediamine graphene in embodiment 1;

Fig. 4 is to NO under the room temperature of ethylenediamine graphene in embodiment ₁ Response curve;

Fig. 5 is the dynamic response curve of _SnO2 /ethylenediamine graphene to the continuous test of 0.25-5ppm at room temperature in embodiment 1;

Fig. 6 is the linear fitting curve of _SnO2 /ethylenediamine graphene to the continuous test of 0.25-5ppm at room temperature in embodiment 1;

FIG. 7 is a gas selectivity diagram of SnO ₂ /ethylenediamine graphene in Example 6. FIG.

Detailed ways

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Specific embodiment one: the preparation method of the room temperature high-sensitivity detection nitrogen dioxide gas sensor of this embodiment comprises the following steps:

One, the preparation of ethylenediamine graphene:

Graphene oxide is configured into a graphene oxide aqueous solution, and ethylenediamine and distilled water are added to the graphene oxide aqueous solution, wherein the volume ratio of the graphene oxide aqueous solution, ethylenediamine and distilled water is 6:1:(13-15), stirring Uniform, and react at 80-95°C for 8-24 hours. After the reaction is completed, wash the product with distilled water, and then redisperse the product in distilled water to prepare an aqueous solution of ethylenediamine graphene;

The concentration of the graphene oxide aqueous solution is 2.5-3.5mg/mL; the concentration of the ethylenediamine graphene aqueous solution is 0.8-1.2mg/mL;

2. Preparation of SnO ₂ /ethylenediamine graphene composite material:

Dissolving tin tetrachloride pentahydrate in water, adding the ethylenediamine graphene aqueous solution and concentrated hydrochloric acid prepared in step 1, stirring at room temperature for 2-3 hours to obtain a mixed solution, placing the mixed solution in a hydrothermal kettle, React at 110-130°C for 12-48h; wash the product with water and ethanol solution to neutrality in turn, and then redisperse the product in ethanol solution to obtain an ethanol solution of SnO ₂ /ethylenediamine graphene composite material;

Wherein the quality of tin tetrachloride pentahydrate and the volume ratio of water are 0.35g: (33-36) mL, the mass ratio of tin tetrachloride pentahydrate and ethylenediamine graphene is 1: (0.0011-0.0034), The volume ratio of the mass of tin tetrachloride pentahydrate to concentrated hydrochloric acid is 0.35g: (1.5-2.5) mL, and the concentration of the ethanol solution of SnO ₂ /ethylenediamine graphene composite material is 37.5-150 mg/mL;

3. Preparation of SnO ₂ /ethylenediamine graphene composite sensing film:

The ethanol solution of the SnO ₂ /ethylenediamine graphene composite material obtained in step 2 is coated on the ceramic sheet with silver-palladium interdigitated electrodes by drop coating or spin coating, and then repeated coating 4-20 times, Then dry in an oven at 60-65° C. for 24h-72h to obtain a NO ₂ gas sensor of SnO ₂ /ethylenediamine graphene composite material.

Specific embodiment two: the difference between this embodiment and specific embodiment one is: in step one, graphene oxide is prepared by Hummer's method. Others are the same as in the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that in step 1, the graphene oxide is configured into a graphene oxide aqueous solution by an ultrasonic-assisted method. Others are the same as in the first or second embodiment.

Embodiment 4: This embodiment differs from Embodiment 1 to Embodiment 3 in that: in step 1, the product is centrifuged and washed with distilled water for more than 5 times. Others are the same as those in the first to third specific embodiments.

Embodiment 5: This embodiment differs from Embodiment 1 to Embodiment 4 in that: in step 1, the concentration of the graphene oxide aqueous solution is 2.3-3.3 mg/mL. Others are the same as one of the specific embodiments 1 to 4.

Embodiment 6: This embodiment differs from Embodiment 1 to Embodiment 5 in that: in step 1, the concentration of the aqueous solution of ethylenediamine graphene is 0.9-1.1 mg/mL. Others are the same as one of the specific embodiments 1 to 5.

Embodiment 7: This embodiment differs from Embodiment 1 to Embodiment 6 in that: in step 2, the concentration of the ethanol solution of the SnO ₂ /ethylenediamine graphene composite material is 50-100 mg/mL. Others are the same as one of the specific embodiments 1 to 6.

Embodiment 8: This embodiment differs from Embodiments 1 to 7 in that the mass ratio of tin tetrachloride pentahydrate to ethylenediamine graphene in step 2 is 1:0.002-0.003. Others are the same as one of the specific embodiments 1 to 7.

Embodiment 9: This embodiment is different from Embodiment 1 to Embodiment 8 in that: the mass concentration of concentrated hydrochloric acid in step 2 is 37%-37.5%. Others are the same as one of the specific embodiments 1 to 8.

Embodiment 10: This embodiment is different from Embodiment 1 to Embodiment 8 in that: the mass concentration of concentrated hydrochloric acid in step 2 is 37%. Others are the same as one of the specific embodiments 1 to 8.

The following examples of the present invention are described in detail, and the following examples are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1:

The preparation method of the high-sensitivity detection nitrogen dioxide gas sensor at room temperature in this embodiment comprises the following steps:

One, the preparation of ethylenediamine graphene:

Graphene oxide was prepared by the Hummer's method, and the graphene oxide was prepared into a 3 mg/mL graphene oxide aqueous solution by an ultrasonic-assisted method, and 30 mL of graphene oxide aqueous solution, 5 mL of ethylenediamine and 70 mL of distilled water were added to a 250 mL three-necked bottle, and stirred Uniform, and react at 95 ° C for 24h. After the reaction, the product was centrifuged and washed more than 5 times with distilled water, and then the product was redispersed in distilled water to prepare a 1 mg/mL aqueous solution of ethylenediamine graphene.

2. Preparation of SnO ₂ /ethylenediamine graphene composite material:

One-step synthesis of SnO ₂ /ethylenediamine graphene composite material by hydrothermal method, specifically dissolving 0.35g of tin tetrachloride pentahydrate in 35mL of water as raw material, and adding 0.8mL of ethylenediamine graphite prepared in step 1 Alkene aqueous solution and 2 mL of concentrated hydrochloric acid, and the mixture was stirred at room temperature for 2 h to obtain a mixed solution. The mixed solution was placed in a 50mL hydrothermal kettle and reacted at 120°C for 24h. The obtained product was washed once with distilled water, and then washed with ethanol solution until the solution was neutral, and then the product was redispersed in 2 mL of ethanol solution to obtain an ethanol solution of SnO ₂ /ethylenediamined graphene composite material.

3. Preparation of SnO ₂ /ethylenediamine graphene composite sensing film:

Take 10 μ L of step 2 to obtain the ethanol solution of SnO ₂ /ethylenediamine graphene composite material, drop-coat the solution on a ceramic sheet (7mm×14mm) with an interdigitated electrode of silver palladium, repeat the coating 4 times, and then Dry in an oven at 60°C for 72h to obtain a NO ₂ gas sensor of SnO ₂ /ethylenediamine graphene composite. Then the gas sensing performance test is carried out, at room temperature, 0.25-5ppm of NO ₂ is introduced.

Fig. 1 is the atomic force diagram of the ethylenediamine graphene in the present embodiment. This figure shows that the synthesized ethylenediamine graphene has a sheet structure with a thickness of 0.81 nm and is a single-layer graphene.

Figure 2 is an infrared image of ethylenediamine graphene. This figure shows that ethylenediamine graphene is compared with the spectrum of graphene oxide. The characteristic peak of 1737cm ^-1 carboxyl group disappears, and the characteristic peak of the amide I band of 1639cm ^-1 appears newly, which shows that ethylenediamine and graphite oxide The carboxyl group on the alkenes undergoes a condensation acylation reaction. Besides, 2927cm ^-1 and 2856cm ^-1 are attributed to CH stretching vibration. It proves that ethylenediamine graphene is prepared successfully.

Fig. 3 is a transmission electron microscope image of SnO ₂ /ethylenediamine graphene. The figure shows that the prepared SnO ₂ is spherical in shape, the particle size is about 3-5nm, and is evenly distributed on the graphene surface, and the two are well combined.

Figure ₄ is the response curve of ethylenediamine graphene to NO at room temperature. It can be seen from the figure that the ratio of prepared ethylenediamine graphene to ₅ ppm NO2 can reach 1.52, while the ratio of reduced graphene to 500 ppm _NO2 is only 1.05. By comparison, it can be found that the gas _- sensing performance of ethylenediamine graphene to NO2 has indeed been greatly improved.

Fig. 5 is the dynamic response curve of SnO ₂ /ethylenediamine graphene to the continuous test of 0.25-5ppm at room temperature. It can be seen from the figure that when the composite material is continuously tested, the response rate increases with the increase of the concentration, and the recovery performance is good, which meets the needs of continuous detection.

Fig. 6 is a linear fitting curve of continuous testing of SnO ₂ /ethylenediamine graphene at room temperature to 0.25-5ppm. It can be seen from the figure that within the range of 0.25-5ppm, the two have a linear relationship, y=0.799x+1.098, R ² =0.988. This shows that during the measurement process, we can detect the concentration of _NO2 gas according to the measured data relationship, which has practical application value and can realize quantitative detection.

Example 2:

The difference between this example and Example 1 is that the reaction temperature in step 1 is 80°C. Other steps and parameters are the same as in Example 1.

Example 3:

The difference between this embodiment and Example 1 is that the 1mg/ml ethylenediamine graphene aqueous solution added in step 2 is 1.2ml, and the mass ratio of tin tetrachloride pentahydrate and ethylenediamine graphene is 1 : 0.0034. Other steps and parameters are the same as in Example 1.

Example 4:

The difference between this example and Example 1 is that: in step 2, the centrifuged and washed solution is re-dispersed in 4 ml of ethanol solution. Other steps and parameters are the same as in Example 1.

Example 5:

The difference between this embodiment and Example 1 is that in step 3, 10 μl of the solution is all coated on a ceramic sheet (7mm×14mm) with silver-palladium interdigitated electrodes by spin coating, and then repeatedly coated for 20 Second-rate. Other steps and parameters are the same as in Example 1.

Embodiment 6:

The difference between this embodiment and the embodiment 1 is that in the third step, when the gas sensitivity performance test is performed, the gases introduced are 5 ppm NO ₂ , 5 ppm H ₂ S, 100 ppm NH ₃ , 100 ppm CH ₄ , and 100 ppm CO. Other steps and parameters are the same as in Example 1.

FIG. 7 is a gas selectivity diagram of SnO ₂ /ethylenediamine graphene in Example 6. FIG. It is found that the response rate of the material to 5ppm NO ₂ is 5.22 at the highest, and the response rate to the same concentration of H ₂ S is 1.57, and the response rate of 100ppm NH ₃ , CO, CH ₄ is only 1.22, 1.02, 1.28, which means that the material It has excellent selectivity to NO ₂ , and this good characteristic can make the sensor be applied in a relatively complex gas environment, and the sensing characteristics of the material will not be affected, and it can play a good role in detecting NO ₂ .

Claims (9)

1. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature, it is characterised in that this method includes following Step：

One, the preparation of ethylenediamine graphite alkene：

Graphene oxide is configured to graphene oxide water solution, ethylenediamine and distillation are added into graphene oxide water solution Water, wherein the volume ratio of graphene oxide water solution, ethylenediamine and distilled water is 6:1:(13-15), stirs evenly, and in 80- At 95 DEG C reaction 8~for 24 hours, to after reaction, with distilled water centrifuge washing product, product is then dispersed in distilled water again In, it is configured to ethylenediamine graphite aqueous solution；

The graphene oxide water solution concentration is 2.5-3.5mg/mL；The concentration of ethylenediamine graphite aqueous solution is 0.8- 1.2mg/mL；

Two, SnO₂The preparation of/ethylenediamine graphite alkene composite material：

Stannic chloride pentahydrate is dissolved in water, and the ethylenediamine graphite aqueous solution and concentrated hydrochloric acid of step 1 preparation is added, 2-3h is stirred at room temperature, obtains mixed solution, mixed solution is placed in water heating kettle, reacts 12-48h at 110-130 DEG C； Product is successively cleaned with water and ethanol solution to neutrality, then product is re-dispersed into ethanol solution, obtains SnO₂/ second The ethanol solution of diamines graphite alkene composite material；

Wherein the quality of stannic chloride pentahydrate and the volume ratio of water are 0.35g：(33-36) mL, stannic chloride pentahydrate and ethylenediamine The mass ratio of graphite alkene is 1：(0.0011-0.0034), the quality of stannic chloride pentahydrate and the volume ratio of concentrated hydrochloric acid are 0.35g：(1.5-2.5) mL, SnO₂The concentration of the ethanol solution of/ethylenediamine graphite alkene composite material is 37.5-150mg/mL；

Three, SnO₂The preparation of/ethylenediamine graphite alkene composite sensing film：

Step 2 is obtained into SnO₂The ethanol solution of/ethylenediamine graphite alkene composite material is coated in a manner of drop coating or spin coating On the potsherd of the interdigital electrode with silver-colored palladium, repetitive coatings 4-20 times later is then dry at 60-65 DEG C in an oven - 72h for 24 hours obtains SnO₂The NO of/ethylenediamine graphite alkene composite material₂Gas sensor.

2. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 1, special Sign is in step 1 prepared by graphene oxide Hummer ' s method.

3. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 1 or 2, It is characterized in that in step 1 that graphene oxide is configured to graphene oxide water solution using ultrasonic wave added method.

4. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is in step 1 with distilled water centrifuge washing product 5 times or more.

5. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is in step 1 that graphene oxide water solution concentration is 2.3~3.3mg/mL.

6. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is that the concentration of ethylenediamine graphite aqueous solution in step 1 is 0.9~1.1mg/mL.

7. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is SnO in step 2₂The concentration of the ethanol solution of/ethylenediamine graphite alkene composite material is 50~100mg/mL.

8. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is in step 2 that the mass ratio of stannic chloride pentahydrate and ethylenediamine graphite alkene is 1：0.002~0.003.

9. a kind of preparation method of the highly sensitive detection nitrogen dioxide gas sensor of room temperature according to claim 3, special Sign is that the mass concentration of concentrated hydrochloric acid in step 2 is 37%~37.5%.