CN110736770B

CN110736770B - N-GQDs modified 3DOM In2O3Composite material and preparation method and application thereof

Info

Publication number: CN110736770B
Application number: CN201910983837.5A
Authority: CN
Inventors: 要红昌; 吕雅坤; 李中军; 潘玉平
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2019-10-16
Filing date: 2019-10-16
Publication date: 2022-04-19
Anticipated expiration: 2039-10-16
Also published as: CN110736770A

Abstract

The invention belongs to the technical field of nano materials, and discloses N-GQDs modified 3DOM In₂O₃Composite material and its preparation method and application. The composite material is composed of 3DOM In₂O₃And N-GQDs uniformly loaded on the surface and in the pore channels. Dispersing N-GQDs In water, adding 3DOM In₂O₃，N₂Bubbling for 1-3 h, then carrying out hydrothermal reaction on the mixture at the temperature of 150-180 ℃ for 4-8 h, naturally cooling to room temperature, and finally carrying out vacuum drying to obtain the N-GQDs modified 3DOM In₂O₃A composite material. Said composite material is in NO₂The application of the gas sensor as a gas sensitive material. The 3DOM In modified by using N-GQDs In the invention₂O₃Effectively overcomes the defect that the two-dimensional graphene can not enter the 3DOM In₂O₃Inside the pore channel, so that an effective heterojunction can not be formed, has good repeatability, selectivity, long-term stability and short response recovery time, can realize the actual detection concentration of 100 ppb, and can be used for NO under ultra-low concentration₂And (5) detecting the content.

Description

N-GQDs modified 3DOM In2O3Composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of nano materials, and particularly relates to N-GQDs modified 3DOM In₂O₃Composite material and its preparation method and application.

Background

Nitrogen dioxide (NO)₂) As air pollutionOne of the main components of the product is mainly derived from automobile exhaust, fossil fuel combustion and the like. The research shows that: long term exposure to concentrations of NO exceeding 1 ppm₂In particular, respiratory diseases and even life-threatening diseases can be caused. In addition, it can form acid rain and contribute to the formation of ozone, a major factor in photochemical smog formation. Therefore, an accurate, selective and rapid detection of NO was developed₂The gas sensor has important significance for monitoring air quality and protecting human health. The resistance type metal oxide semiconductor gas sensor has received wide attention in recent years due to low cost, practicality, convenience and timely feedback. It is known that a three-dimensional ordered macroporous (3 DOM) material with a large specific surface area, high porosity and an open inner surface has more gas adsorption sites, is more favorable for adsorption and desorption of gas, can increase the sensitivity of a sensor and shorten the response recovery time.

In₂O₃As a wide band gap n-type semiconductor, it has been widely used in the field of gas sensors due to its high conductivity and good chemical stability. However, In of single phase₂O₃The gas sensor still has the problems of high working temperature, low response value and the like, and practical application of the gas sensor is limited. Thus, a 3DOM In having a high porosity and a large specific surface area was constructed₂O₃NO for high performance composites₂Detection is very important.

Graphene as a special carbon material has the characteristics of large specific surface area, adjustable band gap, unique gas adsorption capacity and the like, and is proved to be excellent low-temperature NO₂A sensing material. In addition, nitrogen doping in graphene can effectively increase NO₂Adsorbed active sites. However, the single-phase graphene material has a long recovery time and poor selectivity in the gas sensing process, which is not favorable for practical application. Therefore, a nitrogen-doped graphene and 3DOM In are constructed₂O₃The heterojunction material is expected to realize NO with high response value, low working temperature and quick response-recovery time₂And (4) gas sensing.

Disclosure of Invention

The invention aims to provide a 3DOM In modified by N-GQDs₂O₃Composite material and its preparation method and application.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

N-GQDs modified 3DOM In₂O₃A composite material consisting of 3DOM In₂O₃(three-dimensionally ordered macroporous In)₂O₃) And N-GQDs (N-doped graphene quantum dots) uniformly loaded on the surface and in the pore channels.

The preparation method comprises the following steps: dispersing N-GQDs In water, adding 3DOM In₂O₃，N₂Bubbling for 1-3 h, then carrying out hydrothermal reaction on the mixture at the temperature of 150-180 ℃ for 4-8 h, naturally cooling to room temperature, and finally carrying out vacuum drying to obtain the N-GQDs modified 3DOM In₂O₃A composite material; wherein the dosage ratio of the raw materials is N-GQDs, water and 3DOM In₂O₃=（0.2~5） mg∶（5~20） mL∶（25~200） mg。

The 3DOM In modified by the N-GQDs₂O₃Composite material in NO₂The application of the gas sensor as a gas sensitive material.

In the invention, 3DOM In₂O₃And N-GQDs can be prepared according to the prior art. NO according to the invention₂Gas sensor made of Al₂O₃Ceramic tube coated with Al₂O₃N-GQDs modified 3DOM In on ceramic tube₂O₃The composite material, the nickel-cadmium heating wire and the hexagonal base. Al (Al)₂O₃The surface of the ceramic tube is provided with two parallel annular gold electrodes and four platinum wires for conducting electricity, and the nickel-cadmium heating wire is used for providing the required working temperature for the sensor. Wherein, Al₂O₃The structure of the ceramic tube and the structure of welding the ceramic tube on the hexagonal base can refer to the attached figure 1 in the Chinese patent CN 201710279627.9.

Has the advantages that:

1. 3DOM In modified by using N-GQDs₂O₃Effective gramTwo-dimensional graphene can not enter 3DOM In₂O₃The inside of the pore channel can not form an effective heterojunction, and the method is not only suitable for 3DOM In₂O₃The method can also be popularized to the modification of other 3DOM and other porous gas-sensitive materials;

2. by using a 3DOM In₂O₃N-GQDs are uniformly loaded on the surface and the inside of the pore channel, so that a large number of effective heterojunction interfaces are formed, and the NO is greatly improved₂The response sensitivity of the sensor reduces the working temperature;

3. nitrogen is introduced into the graphene quantum dots, so that active sites of the material are increased, and NO is facilitated₂The adsorption of (2) provides favorable conditions for subsequent reaction;

4. the obtained indirectly heated sensor has low working temperature, high sensitivity, good repeatability, selectivity, long-term stability and short response recovery time, can realize the actual detection concentration of 100 ppb, and can be used for NO under ultra-low concentration₂Detecting the content; the indirectly heated sensor has the advantages of low price, simple process, small volume, portability, suitability for mass production and important practical value.

Drawings

FIG. 1: scanning electron micrographs of polystyrene microsphere templates and the products prepared in comparative example and example 3.

FIG. 2: transmission electron microscopy and high resolution transmission electron microscopy of the product prepared in example 3.

FIG. 3: products prepared in comparative and examples 1-5 were on 1 ppm NO₂Response value versus operating temperature curve.

FIG. 4: comparative example and products prepared in examples 1-5 for different concentrations of NO at 100 deg.C₂The dynamic response curve of (2).

FIG. 5: the product prepared in the example 3 has the NO content of 100 ppb-3 ppm at 100 DEG C₂The response value of (2).

FIG. 6: the product prepared in example 3 is on 1 ppm NO at 100 deg.C₂、50 ppm CO、50 ppm CH₄、50 ppm NH₃And 50 ppm of formaldehydeResponse values are compared to a graph.

FIG. 7: the product prepared in example 3 is resistant to 0.5 ppm NO at 100 deg.C₂And 1 ppm NO₂Long term stability test of (1).

Detailed Description

The following examples are intended to illustrate the invention in further detail, but are not to be construed as limiting the invention in any way; the materials used in the following examples were obtained from conventional chemical agents companies and raw material suppliers, unless otherwise specified.

Example 1

N-GQDs modified 3DOM In₂O₃The preparation method of the composite material comprises the following steps:

(1) synthesizing N-GQDs by a one-step hydrothermal method, which comprises the following specific steps: mixing 10 mg of graphene oxide (synthesized by a modified Hummers method) with 18 mL of secondary water and 2.0 mL of ammonia water (28wt%), carrying out ultrasonic treatment for 30 min, transferring the mixture into a reaction kettle with a polytetrafluoroethylene lining, carrying out solvent heating at 180 ℃ for 12 h, naturally cooling to room temperature, filtering the mixed solution with a 25 nm microporous membrane to remove black precipitates, carrying out rotary evaporation concentration on a golden yellow filtrate, further purifying in a 1000da dialysis bag for 1 day to remove excessive ammonia, and carrying out vacuum drying to obtain N-GQDs;

(2) synthesizing 3DOM In by an immersion-calcination method₂O₃The method comprises the following specific steps:

(2a) preparing a polystyrene microsphere template: 7.5 mL of purified styrene and 0.14 g K₂S₂O₈Adding 200 mL of secondary water in N₂Mechanically stirring at the speed of 6 rpm for 12 hours under protection, and centrifuging the polystyrene microsphere suspension at 1000 rpm for 24 hours after the reaction is finished to obtain a polystyrene microsphere template;

(2b) 3.82 g of In (NO)₃)₃·4.5H₂O and 2.25 g of anhydrous citric acid are mixed In 5 mL of methanol and subjected to ultrasonic treatment for 30 min to obtain In₂O₃A precursor solution; immersing polystyrene microsphere template into In₂O₃Vacuum filtering the precursor solution for 4 h to make the precursor solution enter the gaps of the polystyrene microsphere template; then removing excess precursor by filtrationDraining, drying at 60 deg.C for 12 hr, and heating to 1 deg.C/min in muffle furnace^-1Heating to 550 ℃ at the heating rate, and keeping the temperature for 3 hours to obtain 3DOM In₂O₃；

(3) 0.2 mg of N-GQDs was dispersed In 10 mL of secondary water, and 100 mg of 3DOM In was added₂O₃，N₂Bubbling for 2 h, then pouring the mixture into a 25 mL reaction kettle, carrying out hydrothermal treatment at 150 ℃ for 4 h, naturally cooling to room temperature, and then carrying out vacuum drying at 60 ℃ to obtain the target product.

Example 2

The difference from example 1 is that: the N-GQDs in step (1) was 0.5 mg.

Example 3

The difference from example 1 is that: the N-GQDs in step (1) was 1.0 mg.

Example 4

The difference from example 1 is that: the N-GQDs in step (1) was 3.0 mg.

Example 5

The difference from example 1 is that: the N-GQDs in step (1) was 5.0 mg.

Comparative example

The difference from example 1 is that: no use of N-GQDs for 3DOM In₂O₃The modification was carried out by omitting step (3) In example 1, and the obtained product was 3DOM In₂O₃。

FIG. 1 is a scanning electron micrograph of a polystyrene microsphere template obtained in a comparative example, a product obtained in a comparative example, and a product obtained in example 3. As can be seen from fig. 1: the prepared polystyrene microsphere template is formed by arranging polystyrene microspheres with the diameter of 200 nm in a hexagonal way; the comparative example is a three-dimensional ordered macroporous structure with the pore diameter of about 130 nm, and the example 3 can still keep a good three-dimensional ordered macroporous structure after being modified by N-GQDs.

FIG. 2 shows TEM and TEM photographs of the product obtained in example 3. As can be seen from fig. 2: the uniform black dots In the white circles indicate that the N-GQDs are uniformly deposited In 3DOM In₂O₃A surface. Furthermore, In high resolution TEM, the lattice spacings of 0.292 nm and 0.253 nm correspond to 3DOM In₂O₃The (222) and (400) planes of (1), and the lattice spacing of 0.214 nm corresponds to the (100) plane of N-GQDs. This result further indicates that: N-GQDs were successfully deposited In 3DOM In₂O₃A surface.

Performance testing

The products prepared in examples 1 to 5 and comparative example were ground to powder in a mortar, and the powder and isopropyl alcohol were mixed to be pasty at a mass ratio of 0.5: 1.0, and then uniformly applied to commercially available Al with a brush pen₂O₃Coating sample on ceramic tube (with two parallel annular gold electrodes on its outer surface; two platinum wire leads from each gold electrode) to completely cover the two parallel gold electrodes, and coating Al₂O₃Drying the ceramic tube at 80 deg.C for 6 h, and passing nickel-cadmium heating wire through Al₂O₃Inside the ceramic tube, Al is added₂O₃And welding four platinum wires and nickel-cadmium heating wires on the ceramic tube on the side-heating hexagonal base to obtain the sensor.

Performance testing was performed using the resulting sensors. The gas sensitive test instrument is a Weisheng WS30A type gas sensitive element tester, and the test method is a static test method.

FIG. 3 is a graph of the product prepared in comparative example and examples 1-5 vs. 1 ppm NO₂Response value versus operating temperature curve. As can be seen in fig. 3: after modification of N-GQDs, the working temperatures of the examples were all reduced from 160 ℃ to 100 ℃ as compared to the comparative examples, and the performance was improved, wherein example 3 was performed at 100 ℃ for 1 ppm NO₂The response value of (a) was 82, which is 9.1 times that of the comparative example.

FIG. 4 shows the results of comparative examples and examples 1 to 5 at 100 ℃ for different concentrations of NO₂The dynamic response curve of (2). As can be seen in fig. 4: all samples showed a fast recovery rate of response at different concentrations, indicating that the sample has good reproducibility, and example 3 shows that the sample has good reproducibility for different concentrations of NO₂All showed the highest response value.

FIG. 5 shows that the product prepared in example 3 has 100 ppb-3 ppm NO at 100 ℃₂The response value of (2). As can be seen from fig. 5: example 3 for different concentrations of NO₂The response value of (2) shows substantially linear correlation, and furthermore, example 3 shows a linear correlation with respect to a low concentration of NO of 100 ppb₂Still, a response value of 4.1 could be exhibited.

FIG. 6 shows the product of example 3 at 100 ℃ for 1 ppm NO₂、50 ppm CO、50 ppm CH₄、50 ppm NH₃And 50 ppm formaldehyde. As can be seen in fig. 6: example 3 for 1 ppm NO at 100 deg.C₂Can reach 82, but has no response to other gas of 50 ppm.

FIG. 7 shows the results of example 3 at 100 ℃ for 0.5 ppm NO₂And 1 ppm NO₂Time-response plots for 60 days of continuous testing. As can be seen from FIG. 7, example 3 is on 0.5 ppm and 1 ppm NO in the test lasting 60 days₂The response value of (a) is kept substantially constant and fluctuates only within a range of 7%. This result shows that example 3 is for NO₂The sensing has better long-term stability.

Claims

1. N-GQDs modified 3DOM In₂O₃The preparation method of the composite material is characterized by comprising the following steps: the composite material is composed of 3DOM In₂O₃And N-GQDs uniformly loaded on the surface and in the pore channel; the preparation method comprises the following steps: dispersing N-GQDs In water, adding 3DOM In₂O₃，N₂Bubbling for 1-3 h, then carrying out hydrothermal reaction on the mixture at the temperature of 150-180 ℃ for 4-8 h, naturally cooling to room temperature, and finally carrying out vacuum drying to obtain the N-GQDs modified 3DOM In₂O₃A composite material; wherein the dosage ratio of the raw materials is N-GQDs, water and 3DOM In₂O₃=（0.2~5） mg∶（5~20） mL∶（25~200） mg。