CN110726759A - Preparation method of tin dioxide quantum dots, gas sensor and preparation method of gas sensor - Google Patents

Abstract

The invention discloses a preparation method of a tin dioxide quantum dot, a gas sensor and a preparation method thereof, and the preparation method of the tin dioxide quantum dot comprises the following steps: sequentially adding CH into a reaction vessel₄N₂S、H₂O and SnCl₂·2H₂O, stirring for 15-30 h at room temperature to obtain SnO₂A quantum dot solution; the obtained SnO₂Carrying out hydrothermal treatment on the quantum dot solution at 125-225 ℃ for 2-20 h. A preparation method of a gas sensor comprises the following steps: SnO after hydrothermal treatment₂Heating and concentrating the quantum dot solution to 15% -25% of the original solution to obtain a concentrated solution; spin-coating the concentrated solution on an alumina substrate attached with a silver electrode, and drying; repeating the spin coating step at least once to obtain coated SnO₂Quantum dot gas sensors. SnO prepared by the invention₂The quantum dots are simple, nontoxic and controllable in particle size, and the manufactured gas sensor is convenient to use and low in cost.

Description

Preparation method of tin dioxide quantum dots, gas sensor and preparation method of gas sensor

Technical Field

The invention belongs to the field of plating of metal materials by inorganic chemistry, and particularly relates to a preparation method of tin dioxide quantum dots, a gas sensor and a preparation method of the gas sensor.

Background

Semiconductor Quantum Dots (QDs) are a very small three-dimensional system with dimensions of a few nanometers. It consists of several hundred atoms, which is much fewer than the number of atoms in a large system. Due to the small volume of the quantum dots, the energy states of electrons, holes and excitons are discrete, which has a high value for producing good electronic devices. Although PbS, ZnO and WO₃The colloidal quantum dots are ideal candidate materials for novel semiconductor gas sensors, but the consumption of toxic organic matters in the manufacturing process of the quantum dots not only brings danger to staff, but also increases the cost of factory environment restoration, is not beneficial to environmental protection from the aspect of environmental friendliness, and especially has aggravated toxicity after the toxic organic matters are accumulated through a food net.

Tin dioxide (SnO)₂) The nanometer material is a typical semiconductor material, has a wider direct band gap of 3.6eV, has the advantages of good chemical stability, no toxicity and low cost, and is suitable for being applied to the field of semiconductor quantum dot preparation.

The gas sensor of semiconductor metal oxide has the advantages of simple synthesis, small volume, low cost, convenient use and the like, and has wide application prospect in the aspects of detecting various flammable, explosive, toxic and polluting gases, controlling and testing various gases and the like. At present, gas detection by gas sensitive elements in the world mainly aims at H₂、H₂S、NO_X、C_XH_YGases such as liquefied petroleum gas, pipeline gas and the like are mostly reducing, combustible and toxic gases, and the gases are mostly applied to semiconductor metal oxide gas-sensitive materials, mainly N-type SnO₂、ZnO、TiO₂And the like, P-type NiO, CuO, and the like, and composite oxide-based solid electrolytes, and the like.

SnO in contrast to other sensitive material types₂The thin film sensor is favored by people because of its advantages of high response, fast reaction, easy compatibility with microelectronic process, etc. However, the particle size of the existing preparation method of the tin dioxide quantum dot is not controllable, and a sensor with the most suitable performance cannot be obtained according to the requirement.

Disclosure of Invention

Aiming at the problems, the invention researches and designs a preparation method of a tin dioxide quantum dot, a gas sensor and a preparation method thereof, and the SnO provided by the invention₂The preparation method of the quantum dots overcomes the defects of complexity and toxicity of the traditional method, and the gas sensor prepared by the SnO2 quantum dot solution overcomes the defects of complexity in manufacturing, large volume, high cost and inconvenience in use. The technical means adopted by the invention are as follows:

a preparation method of tin dioxide quantum dots comprises the following steps:

s1, sequentially adding CH into the reaction vessel₄N₂S、H₂O and SnCl₂·2H₂O, stirring for 15-30 h at room temperature to obtain SnO₂A quantum dot solution;

s2, SnO obtained in step S2₂Carrying out hydrothermal treatment on the quantum dot solution at 125-225 ℃ for 2-20 h.

Further, in step S1, CH₄N₂S and SnCl₂·2H₂The molar ratio of O is (0.8-1.2):10, and the concentration of the quantum dot solution is 0.1-0.5 mol/L.

Further, in step S1, the mode of maintaining the room temperature is water bath.

Further, in step S2, SnO obtained in step S1₂And carrying out hydrothermal treatment on the quantum dot solution for 2 hours.

Further, the gas sensor is SnO prepared by using the preparation method of the tin dioxide quantum dots₂Quantum dots.

Further, a preparation method of the gas sensor comprises the following steps:

s' 1 and SnO prepared by using preparation method₂Heating and concentrating the quantum dot solution to 15% -25% of the original solution to obtain SnO₂A concentrated solution of quantum dots;

s' 2, reacting SnO₂Spin-coating the concentrated solution of quantum dots on the alumina substrate attached with the silver electrode, and drying;

s' 3, repeating the spin coating step at least once to obtain the coated SnO₂Quantum dot gas sensors.

Compared with the prior art, the preparation method of the tin dioxide quantum dot, the gas sensor and the preparation method thereof have the following beneficial effects:

1. SnO of the present invention₂The quantum dots are simple to prepare, and the aqueous solution is used as the main raw material to be added into CH₄N₂Catalyzed by S, by SnCl₂·2H₂Preparation of SnO by hydrolytic oxidation of O₂And (4) quantum dots.

2. SnO prepared by the invention₂The quantum dots have the advantage of no toxicity, do not need toxic organic compounds in the preparation process, and are beneficial to environmental protection.

3. The invention controls SnO by a hydrothermal mode₂The grain size of the quantum dots can be controlled, the grain size of the quantum dots can be controlled through hydrothermal treatment temperature, and the prepared quantum dots are ideal candidate materials for preparing novel semiconductor gas sensors.

4. In the invention, SnO₂The gas sensor prepared from the quantum dot solution has the advantages of simple manufacture, small volume, low cost, convenient use and the like, and has high sensitivity for detecting various flammable, explosive, toxic and polluting gases at room temperature.

5. SnO prepared by the invention₂The quantum dots are well dispersed in the aqueous solution, and under the action of reducing gas, because reducing gas molecules consume adsorbed oxygen on the surfaces of particles, SnO on electrodes₂Reduction of resistance, SnO, of quantum dot films₂Gas transmissionThe performance of the sensor benefits from the structure of the quantum dots.

Drawings

FIG. 1 is prepared SnO observed from transmission electron microscope₂The morphology of the quantum dots;

fig. 2 is an X-ray diffraction pattern of QD0, QD125, and QD225 samples;

fig. 3 is a measured XPS spectrum of a QD0 sample;

fig. 4 is the size distribution of QD0, QD125, and QD225 samples in aqueous solution;

FIG. 5 is SnO prepared at room temperature₂Film for H concentrations of 133ppm and 1333ppm₂The dynamic response of the gas;

above, QD0 is SnCl₂·2H₂SnO prepared by O hydrolysis oxidation₂Quantum dots; QD125 is SnO treated by a 125 ℃ hydrothermal method for 2 hours₂Quantum dots; QD225 is SnO treated by a 225 ℃ hydrothermal method for 2h₂And (4) quantum dots.

Detailed Description

A preparation method of tin dioxide quantum dots is characterized by comprising the following steps: the method comprises the following steps:

s1, sequentially adding CH into the reaction vessel₄N₂S、H₂O and SnCl₂·2H₂O, stirring for 15-30 h at room temperature to obtain SnO₂A quantum dot solution;

s2, SnO obtained in step S2₂Carrying out hydrothermal treatment on the quantum dot solution at 125-225 ℃ for 2-20 h. SnO by controlling temperature of hydrothermal treatment₂The particle size of the quantum dots is controlled according to the needed SnO₂The particle size of the quantum dots, and the temperature and time for hydrothermal treatment are selected.

This example uses an aqueous solution as the main starting material in CH₄N₂S catalysis, room temperature by simple SnCl₂·2H₂Preparation of SnO by hydrolytic oxidation of O₂The quantum dots are marked as QD0, the room temperature is 25 +/-5 ℃, and the obtained SnO₂The concentration of the quantum dot solution is 0.1-0.5 mol/L. The obtained SnO₂Putting the quantum dot solution into a polyphenyl autoclave at 125 ℃ and 225 ℃ respectivelyHydrothermal treatment was carried out for 2h, noted as QD125 and QD 225. SnO treated by hydrothermal method₂And drying the quantum dot solution to obtain powder, and performing component characterization and optical characterization.

Due to tautomerism of thiourea and isothiourea in acidic solution, CH₄N₂S acts as a stabilizer and accelerator. Thus, it consumes HCl and accelerates the process of equation (1) and SnO₂And (4) forming quantum dots.

SnCl₂+2H₂O→Sn(OH)₂+2HCl (1)

2Sn(OH)₂+O₂→2SnO₂+2H₂O (2)

SnO₂The preparation of the quantum dot solution is realized by the following technical scheme, and the specific steps are as follows: weighing proper amount of CH according to the molar ratio of 1:10₄N₂S and SnCl₂·2H₂O; sequentially putting CH into a beaker₄N₂S, water and SnCl₂·2H₂O, magnetically stirring, wherein the beaker is a white emulsion; after 24 hours of water bath treatment at room temperature, yellow and clear SnO is obtained₂A quantum dot solution.

For the resultant SnO₂TEM, XRD and DLS observation of quantum dot solution, SnO observation₂Quantum dot morphology.

As shown in FIG. 1, from the TEM analysis result, preparative SnO was observed from transmission electron microscopy₂The morphology of the quantum dots, indicating that the average particle sizes of the QD0, QD125, and QD225 samples were 1.9 ± 0.2nm, 2.7 ± 0.4nm, and 3.9 ± 0.8nm, respectively. The QD0 and QD125 samples dispersed well in aqueous solution, while a small amount of aggregation was found in the QD225 sample. A characteristic spacing of 0.33nm was observed with SnO₂The (110) planes in the rutile phase correspond.

As shown in FIG. 2, the X-ray diffraction patterns and SnO of the QD0, QD125 and QD225 samples were analyzed by XRD₂The standard patterns of the semiconductor are consistent.

As shown in fig. 3, the measured XPS spectra of the QD0 sample indicate the presence of C, O and Sn elements. Two peaks of 487.3eV and 495.6eV, a peak of O1s, were observed in a high-temperature solution pattern of Sn 3dAppeared at 531.5eV, and as a result, it was found that rutile SnO₂The standard patterns of the system are consistent.

Thus, it was confirmed that SnO can be obtained by the production method₂And (4) quantum dots.

The obtained SnO₂The quantum dot solution is placed in a polyphenyl autoclave and is subjected to hydrothermal treatment for 2 hours at 125 ℃ and 225 ℃ respectively.

As shown in fig. 4, the size distribution of QD0, QD125, and QD225 samples in aqueous solution is shown by DLS analysis, in which the three curves correspond to QD0, QD125, and QD225 in order from left to right, in terms of peak positions. The grain size became larger with increasing temperature of the hydrothermal process, and peaks appeared at 4.8nm, 5.6nm and 6.5 nm. The average particle diameters are respectively 5.3 +/-1.1 nm, 5.8 +/-0.9 nm and 8.0 +/-5.9 nm. The analysis results of TEM, XRD and DLS show that the hydrothermal method is used for controlling SnO₂The effective method of the quantum dot grain size can prepare the quantum dot with controllable grain size.

Using SnO₂The gas sensor prepared from the quantum dot solution is realized by the following technical scheme, and the method comprises the following specific steps: SnO obtained by the steps₂Heating and concentrating the quantum dot solution to 15-25% of the original solution volume to obtain SnO with higher concentration₂A quantum dot solution; deposition of SnO on alumina substrate with silver electrode attached by spin coating₂Quantum dot solution, and drying; repeating the spin coating step for a plurality of times to obtain the coated SnO₂Quantum dot gas sensors.

And placing the obtained gas sensor in a specific test system for dynamic response test. The test system is coated with SnO connected on an alumina substrate₂The silver electrode of the quantum dot solution tests the voltammetry performance in real time by changing the concentration of the gas to obtain SnO₂Gas sensitive properties of quantum dots.

The gas sensors prepared from quantum dots with different particle sizes have different response degrees to hydrogen. The gas sensors were prepared and tested using 200 ℃ hydrothermal solutions for 4h and 8h, and the responses were 316.7895 and 200.9858, respectively.

As shown in fig. 5, in which the sensor response (S) is defined as nullThe ratio of the in-gas sheet resistance (Ra) to the in-reducing gas sheet resistance (Rg) (s: Ra/Rg). In this example, SnO was prepared at room temperature₂Film for H concentrations of 133ppm and 1333ppm₂The dynamic response of the gas is 16.1 and 35.5 respectively. Namely SnO prepared by adopting a spin coating method₂Thin film resulting gas sensor, the gas sensor pair H₂Shows good selectivity and high sensitivity.

The invention utilizes the deposition of SnO on an alumina substrate to which a silver electrode is attached₂The quantum dot solution is used for preparing a gas sensor, and gas sensitivity research is carried out on the gas sensor. The sensor is a gas sensor for measuring gas concentration by measuring the resistance of gas-sensitive material, for H₂Shows good selectivity and high sensitivity. The sensor has the advantages of high sensitivity and good selectivity to specific gas molecules, and is simple in structure and capable of being used at normal temperature, so that the defects of other gas sensors can be overcome.

The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.

Claims (6)

1. A preparation method of tin dioxide quantum dots is characterized by comprising the following steps: the method comprises the following steps:

s1, sequentially adding CH into the reaction vessel₄N₂S、H₂O and SnCl₂·2H₂O, stirring for 15-30 h at room temperature to obtain SnO₂A quantum dot solution;

s2, SnO obtained in step S2₂Carrying out hydrothermal treatment on the quantum dot solution at 125-225 ℃ for 2-20 h.

2. The method for preparing the tin dioxide quantum dot according to claim 1, wherein the method comprises the following steps: in step S1, CH₄N₂S and SnCl₂·2H₂The molar ratio of O is (0.8-1.2):10, and the concentration of the quantum dot solution is 0.1-0.5 mol/L.

3. The method for preparing the tin dioxide quantum dot according to claim 1, wherein the method comprises the following steps: in step S1, the room temperature is maintained by a water bath.

4. The method for preparing the tin dioxide quantum dot according to claim 1, wherein the method comprises the following steps: in step S2, SnO obtained in step S1₂And carrying out hydrothermal treatment on the quantum dot solution for 2 hours.

5. A gas sensor, characterized by: SnO produced by the production method according to any one of claims 1 to 4₂Quantum dots.

6. A method for manufacturing a gas sensor is characterized in that: the method comprises the following steps:

s' 1, SnO prepared by the preparation method of any one of claims 1 to 4₂Heating and concentrating the quantum dot solution to 15% -25% of the original solution to obtain SnO₂A concentrated solution of quantum dots;

s' 2, reacting SnO₂Spin-coating the concentrated solution of quantum dots on the alumina substrate attached with the silver electrode, and drying;

s' 3, repeating the spin coating step at least once to obtain the coated SnO₂Quantum dot gas sensors.

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