Flower-like Sn3O4 material modified by CdSe quantum dots, preparation method and application of flower-like Sn3O4 material, n-butyl alcohol gas sensor and preparation method of n-butyl alcohol gas sensor

Abstract

The invention belongs to the technical field of gas sensitive materials, and particularly relates to a CdSe quantum dot modified flower-like Sn3O4 material, a preparation method and application thereof, an n-butyl alcohol gas sensor and a preparation method thereof. In the CdSe quantum dot modified flower-like Sn3O4 material provided by the invention, the flower-like tristannic oxide is formed by self-assembly of nanosheets, and compared with amorphous tristannic oxide or sheet-like tristannic oxide without assembly morphology, the flower-like tristannic oxide has higher specific area and porosity, and promotes diffusion of gas molecules; and on the other hand, the CdSe quantum dots show p-type semiconductor characteristics and can form a heterojunction with n-type stannous oxide, so that the gas-sensitive sensitivity is improved, and the gas-sensitive working temperature of the stannous oxide can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of gas-sensitive materials, and specifically relates to a flower-shaped Sn3O4 material modified by CdSe quantum dots and a preparation method and application thereof, and a n-butanol gas sensor and a preparation method thereof. Background Art

[0002] As a key node and important component of modern sensing technology, gas sensors can convert information data such as gas type, concentration and distribution into electrical signals, thereby realizing environmental detection, monitoring, analysis and alarm. With the advancement of science and technology, timely and accurate detection of flammable, explosive and toxic and harmful gases, supervision of working conditions, and realization of automation and intelligence in industry and agriculture have become important issues that need to be solved in the current process from scientific research to practical application.

[0003] Mixed-valence n-type Sn3O4 is composed of alternating layers of Sn and O atoms, has a layered crystal structure, and has a certain amount of oxygen vacancies. Its band gap is 2.2 to 2.9 eV, and it also contains Sn 2+ and Sn 4+ The two oxidation states have special properties not found in other tin oxide semiconductors and have the potential to be used in gas sensors.

[0004] Some researchers have proposed an Au atom-modified Sn3O4 gas-sensitive material that has a certain selectivity for the target gas, but its response value is too low (S=4.3), which limits its application. Summary of the invention

[0005] The purpose of the present invention is to provide a flower-shaped Sn3O4 material modified by CdSe quantum dots and its preparation method and application, a n-butanol gas sensor and its preparation method. The flower-shaped Sn3O4 material modified by CdSe quantum dots provided by the present invention has a high response value.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The invention provides a flower-shaped Sn3O4 material modified by CdSe quantum dots, comprising flower-shaped tin tetroxide and cadmium selenide quantum dots modified on the surface of the flower-shaped tin tetroxide.

[0008] Preferably, the size of the flower-shaped tin tetroxide is 0.5-2 μm; the flower-shaped tin tetroxide is formed by self-assembly of tin tetroxide nanosheets to form a flower-shaped structure, and the thickness of the tin tetroxide nanosheets is 15-20 nm.

[0009] Preferably, the size of the cadmium selenide quantum dots is 1.8 to 2.5 nm.

[0010] Preferably, the molar ratio of the flower-shaped tin tetraoxide to cadmium selenide quantum dots is 40 to 170:1.

[0011] Preferably, the size of the flower-shaped Sn3O4 material modified by CdSe quantum dots is 1 to 3 μm; the thickness of the nanosheets of the flower-shaped Sn3O4 material modified by CdSe quantum dots is 65 to 70 nm.

[0012] The present invention also provides a method for preparing the flower-shaped Sn3O4 material modified by CdSe quantum dots described in the above scheme, comprising the following steps:

[0013] The cadmium selenide quantum dots are mixed with flower-shaped tin tetroxide and water to obtain the CdSe quantum dot-modified flower-shaped Sn3O4 material.

[0014] Preferably, the preparation method of the flower-shaped tin tetroxide is: a tin source, an oxidant, an alkali and water are mixed to carry out a solvothermal reaction to obtain the flower-shaped tin tetroxide.

[0015] The present invention also provides the application of the flower-shaped Sn3O4 material modified with CdSe quantum dots described in the above scheme or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method described in the above scheme in the field of gas detection.

[0016] The present invention also provides a n-butanol gas sensor, which includes a hollow ceramic tube; the surface of the hollow ceramic tube is covered with a gas-sensitive coating; the raw material of the gas-sensitive coating includes the flower-shaped Sn3O4 material modified with CdSe quantum dots described in the above scheme or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method described in the above scheme.

[0017] The present invention also provides a method for preparing the n-butanol gas sensor described in the above scheme, comprising the following steps:

[0018] The flower-shaped Sn3O4 material modified by CdSe quantum dots and water are mixed to obtain slurry, and the slurry is coated on the surface of the hollow ceramic tube to obtain the n-butanol gas sensor.

[0019] The present invention provides a flower-shaped Sn3O4 material modified by CdSe quantum dots. The flower-shaped Sn3O4 material modified by CdSe quantum dots provided by the present invention (denoted as CdSe Qds / Sn3O4) has a high response value to n-butanol gas and significant selectivity. The flower-shaped tin tetroxide in the flower-shaped Sn3O4 material modified by CdSe quantum dots provided by the present invention has a higher specific area and porosity than amorphous Sn3O4 or sheet-shaped Sn3O4 without assembly morphology, which promotes the diffusion of gas molecules; on the other hand, CdSe quantum dots exhibit p-type semiconductor characteristics and can form a heterojunction with n-type Sn3O4, thereby effectively reducing the Sn3O4 gas-sensitive operating temperature while improving the gas-sensitive sensitivity.

[0020] The present invention also provides a method for preparing the flower-shaped Sn3O4 material modified with CdSe quantum dots in the above scheme. The preparation method provided by the present invention has simple steps, and the obtained CdSe Qds / Sn3O4 material has more surface sensitive points, which is conducive to the adsorption and diffusion of n-butanol gas on the surface of the material.

[0021] The present invention also provides the application of the flower-shaped Sn3O4 material modified by CdSe quantum dots described in the above scheme or the flower-shaped Sn3O4 material modified by CdSe quantum dots obtained by the preparation method described in the above scheme in the field of gas detection. The CdSe Qds and Sn3O4 in the CdSe Qds / Sn3O4 material provided by the present invention construct a pn heterojunction at the interface, resulting in the formation of an energy barrier and the adsorption / desorption of gas compounds, providing a material basis for gas detection, and playing a vital role in the performance of the chemiresistor sensor.

[0022] The present invention also provides a n-butanol gas sensor. The n-butanol gas sensor provided by the present invention adopts the CdSe Qds / Sn3O4 material of the present invention, has high sensitivity, good target gas selectivity, and can achieve accurate and effective monitoring of n-butanol gas. The results of the embodiment show that the n-butanol gas sensor prepared using the CdSe Qds / Sn3O4 material of the present invention has a sensitivity of 11.0 to 48.8 to 100ppm triethylamine, which is 1.5 to 12.0 times the sensitivity of the pure Sn3O4-based gas sensor, and the minimum concentration value detected is 100ppb, with a lower limit of detection of ppb order.

[0023] The present invention also provides a method for preparing the n-butanol gas sensor of the above scheme. The preparation method provided by the present invention has simple steps, convenient operation, good feasibility, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 X-ray diffraction patterns of products prepared in Example 2, Example 4, Comparative Example 1 and Comparative Example 2 of the present invention; wherein a is Example 2, Example 4 and Comparative Example 2, and b is Example 4 and Comparative Example 1;

[0026] Figure 2 The electron microscope images of the products prepared in Example 2 and Comparative Example 2 of the present invention; wherein a is the SEM image of Comparative Example 2, b is the SEM image of Example 2, c is the size schematic diagram of Comparative Example 1, and d is the HRTEM image of Example 2;

[0027] Figure 3 The EDS surface scan and electron diffraction ring spectrum of the product prepared in Example 2 of the present invention; wherein a is the EDS surface scan, and b is the electron diffraction ring spectrum;

[0028] Figure 4 The XPS spectra of the products prepared in Example 2 and Comparative Example 2 of the present invention; wherein a is the high-resolution O1s spectrum of Comparative Example 2, b is the high-resolution O1s spectrum of Example 2, c is the high-resolution Sn 3d spectrum of Example 2, and d is the full XPS spectrum of Example 2;

[0029] Figure 5 A schematic diagram of the structure of the n-butanol gas sensor provided by the present invention;

[0030] Figure 6 The gas-sensitive response of the n-butanol gas sensor of the products prepared in Examples 1 to 4 of the present invention and Comparative Example 2 to 100 ppm n-butanol at different temperatures;

[0031] Figure 7 The instantaneous dynamic response recovery curve of the n-butanol gas sensor of the product prepared in Example 2 of the present invention when exposed to n-butanol vapor of different concentrations;

[0032] Figure 8The present invention provides a response recovery curve, transient response curve and long-term stability curve of the n-butanol gas sensor to 100 ppm n-butanol; wherein, a is the response recovery curve of the n-butanol gas sensor prepared by the flower-shaped Sn3O4 material modified with CdSe quantum dots in Example 2 to 100 ppm n-butanol, b is the resistance transient response curve of the n-butanol gas sensor prepared by the flower-shaped Sn3O4 material modified with CdSe quantum dots in Example 2 to multiple 100 ppm n-butanol, and c is the long-term stability curve of the n-butanol gas sensor prepared by the products of Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0033] The invention provides a flower-shaped Sn3O4 material modified by CdSe quantum dots, comprising flower-shaped tin tetroxide and cadmium selenide quantum dots modified on the surface of the flower-shaped tin tetroxide.

[0034] In the present invention, the size of the flower-like tin tetroxide (referring to the size of the overall morphology of the flower-like tin tetroxide, that is, the size of the entire "flower") is preferably 0.5-2 μm, specifically 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm.

[0035] In the present invention, the flower-like tin tetroxide is formed by self-assembly of tin tetroxide nanosheets to form a flower-like structure; the thickness of the tin tetroxide nanosheets is preferably 15 to 20 nm, specifically 15 nm, 16 nm, 17 nm, 18 nm, 19 nm or 20 nm.

[0036] In the present invention, the size (particle diameter) of the cadmium selenide quantum dots is preferably 1.8 to 2.5 nm, specifically 1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm or 2.5 nm.

[0037] In the present invention, the molar ratio of the flower-shaped tin tetraoxide and cadmium selenide quantum dots is 40 to 170:1, specifically 40:1, 60:1, 70:1, 80:1, 100:1, 120:1, 150:1 or 170:1.

[0038] In the present invention, the size of the flower-like Sn3O4 material modified by CdSe quantum dots (the size of the overall morphology of the flower-like Sn3O4 material modified by CdSe quantum dots) is preferably 1 to 3 μm, specifically 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm or 3 μm.

[0039] In the present invention, the thickness of the nanosheets of the flower-shaped Sn3O4 material modified by CdSe quantum dots is preferably 65 to 70 nm, specifically 65 nm, 66 nm, 67 nm, 67.5 nm, 68 nm, 68.5 nm, 69 nm or 70 nm.

[0040] The flower-shaped Sn3O4 material modified with CdSe quantum dots provided by the present invention increases the thickness of tin tetroxide nanosheets and increases the surface sensitive sites on the basis of retaining the layered stacked micro-flower structure of tin tetroxide, and forms a pn heterostructure with CdSe Qds and Sn3O4, thereby improving the gas-sensing performance of the material.

[0041] The present invention also provides a method for preparing the flower-shaped Sn3O4 material modified by CdSe quantum dots described in the above scheme, comprising the following steps:

[0042] The cadmium selenide quantum dots are mixed with flower-shaped tin tetroxide and water (referred to as modified mixing) to obtain the CdSe quantum dot-modified flower-shaped Sn3O4 material.

[0043] In the present invention, the method for preparing cadmium selenide quantum dots is preferably: mixing a cadmium source, a selenium source, a stabilizer, a polyol, a base and water (referred to as aqueous phase mixing to obtain an aqueous phase synthesis solution) for reflux aqueous phase synthesis.

[0044] In the present invention, the cadmium source is preferably a cadmium salt; the cadmium salt is preferably cadmium chloride; and the cadmium chloride is preferably anhydrous cadmium chloride.

[0045] In the present invention, the selenium source is preferably selenite; and the selenite is preferably sodium selenite.

[0046] In the present invention, the molar ratio of the cadmium source to the selenium source is preferably 180-220:40-60, specifically 180:40, 190:40, 200:40, 180:50, 190:50, 200:50, 180:60, 190:60 or 200:60.

[0047] In the present invention, the stabilizer is preferably 3-mercaptopropionic acid.

[0048] In the present invention, the molar ratio of the selenium source to the stabilizer is preferably 40-60:260-320, and can be specifically 40:260, 50:260, 60:260, 40:270, 50:270, 60:270, 40:280, 50:280, 60:280, 40:290, 50:290, 60:290, 40:300, 50:300, 60:300, 40:310, 50:310, 60:310, 40:320, 50:320 or 60:320.

[0049] In the present invention, the polyol is preferably polyethylene glycol; the weight average molecular weight (M w ) is preferably 20000.

[0050] In the present invention, the molar ratio of the stabilizer to the polyol is preferably 260-320:1, specifically 260:1, 265:1, 270:1, 275:1, 280:1, 285:1, 290:1, 295:1, 300:1, 305:1, 310:1, 315:1 or 320:1.

[0051] In the present invention, the alkali is preferably sodium hydroxide.

[0052] In the present invention, the amount of the base added is preferably based on the pH value of the aqueous phase synthesis liquid being ≥ 11; in the present invention, the water is preferably deionized water.

[0053] In the present invention, the mass ratio of the cadmium source to water is preferably 0.036-0.038:187-197, specifically 0.036:187, 0.036:188, 0.0366:190, 0.037:192 or 0.038:197.

[0054] In the present invention, the aqueous phase mixing is preferably: mixing a cadmium source with a stabilizer to obtain a premix, then mixing the premix with water to obtain a premix solution, adjusting the pH value of the premix solution to ≥11 using an alkali, wherein the alkali is used in the form of an alkali solution, then mixing the premix solution with a polyol to obtain a mixed solution, and then mixing the mixed solution with a selenium source, wherein the selenium source is used in the form of a selenium source solution.

[0055] In the present invention, the concentration of the alkali solution is preferably 1-10 mol / L, specifically 5 mol / L or 10 mol / L.

[0056] In the present invention, the method for preparing the sodium selenite solution is preferably: mixing selenium powder and sodium sulfite solution, heating and refluxing, and then diluting.

[0057] In the present invention, the selenium powder is preferably commercial McLean reagent (S817648), and the particle size of the selenium powder is preferably 75 μm; the concentration of the sodium sulfite solution is preferably 1 mol / L; the mass volume ratio of the selenium powder and the sodium sulfite solution is preferably (3.80-4.02) g:(95-105) mL, specifically 3.95 g:100 mL; the heating reflux temperature is preferably 70-120° C., specifically 90° C. or 110° C., the reflux time is preferably 2-6 h, specifically 4 h; the concentration of the sodium selenite solution is preferably 0.005 mol / L.

[0058] In the present invention, the temperature of the reflux water phase synthesis is preferably 130°C, and the insulation synthesis time is preferably 3 to 5 hours, specifically 3 hours, 3.5 hours, 4.0 hours or 4.5 hours; the reflux water phase synthesis is preferably carried out under stirring conditions; the atmosphere of the reflux water phase synthesis is preferably an inert gas; the inert gas is preferably argon.

[0059] In the present invention, after the reflux water phase synthesis, the first post-treatment of the obtained product is preferably further included; the first post-treatment is preferably: centrifugal washing and drying the obtained product in sequence.

[0060] In the present invention, the number of centrifugal washing is preferably 3 to 6 times, specifically 3 times, 4 times, 5 times or 6 times; the rotation speed of the centrifugal washing is preferably 8000 to 10000 rpm, specifically 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm or 10000 rpm; the time of a single centrifugal washing is preferably 10 to 20 min, specifically 10 min, 12 min, 14 min, 16 min, 18 min or 20 min; the reagent used for the centrifugal washing is preferably alcohol; the alcohol is preferably isopropanol.

[0061] In the present invention, the drying temperature is preferably 60-80°C, specifically 60°C, 65°C, 70°C, 75°C or 80°C; the drying time is preferably 4-8h, specifically 4h, 5h, 6h, 7h or 8h.

[0062] In the present invention, the method for preparing the flower-shaped tin tetraoxide is preferably: mixing a tin source, an oxidant, an alkali and water (referred to as a first mixing to obtain a first mixed solution) and performing a solvothermal reaction.

[0063] In the present invention, the tin source is preferably a tin salt; the tin salt is preferably tin dichloride; and the tin dichloride is preferably tin dichloride pentahydrate.

[0064] In the present invention, the oxidant is preferably trisodium citrate; and the trisodium citrate is preferably trisodium citrate dihydrate.

[0065] In the present invention, the molar ratio of the tin source to the oxidant is preferably 1:2.8-3.5, specifically 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4 or 1:3.5.

[0066] In the present invention, the alkali is preferably sodium hydroxide.

[0067] In the present invention, the molar ratio of the tin source to the base is preferably 1:0.5-1, specifically 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.

[0068] In the present invention, the water is preferably deionized water.

[0069] In the present invention, the mass volume ratio of the tin source and water is preferably (0.85-0.95) g:(22-27) mL, and specifically can be 0.9 g:25 mL.

[0070] In the present invention, the first mixing preferably includes: mixing a tin source and water to obtain a premix, mixing the premix and an oxidant to obtain a mixture, and then mixing the mixture and a base.

[0071] In the present invention, the temperature of the first mixing is preferably room temperature, specifically 20-30° C.; the first mixing is preferably stirring; and the time of the first mixing is preferably 1-3 hours, specifically 2 hours.

[0072] In the present invention, the temperature of the solvent thermal reaction is preferably 160-200° C., specifically 180° C., and the insulation reaction time is preferably 4-8 h, specifically 6 h.

[0073] In the present invention, after the solvothermal reaction, the obtained reaction product is preferably subjected to centrifugal washing and drying in sequence.

[0074] In the present invention, the centrifugal washing preferably includes water washing and alcohol washing in sequence under centrifugal conditions; the water used for the water washing is preferably deionized water; the number of water washings is preferably more than 3 times; the alcohol used for the alcohol washing is preferably anhydrous ethanol; the number of alcohol washings is preferably more than 3 times; the centrifugal washing is preferably stopped when the pH value of the water washing liquid is neutral; the rotation speed of the centrifugal washing is preferably 5000-10000rpm, specifically 5000rpm, 7000rpm, 8500rpm or 10000rpm; the time for a single centrifugal washing is preferably 5-15min, specifically 5min, 7min, 10min, 12min or 15min.

[0075] In the present invention, the drying temperature is preferably 60-80°C, specifically 60°C, 65°C, 70°C, 75°C or 80°C; the drying time is preferably 8-16h, specifically 12h.

[0076] In the present invention, the molar ratio of the flower-shaped tin tetraoxide and cadmium selenide quantum dots is preferably 40 to 170:1, specifically 40:1, 60:1, 70:1, 80:1, 100:1, 120:1, 150:1 or 170:1.

[0077] In the present invention, the water is preferably deionized water.

[0078] In the present invention, the mass ratio of the flower-shaped tin tetraoxide to water is preferably 0.05-0.15:10-30, and specifically may be 0.1:20.

[0079] In the present invention, the modified mixing is preferably stirring mixing; the temperature of the modified mixing is preferably room temperature, specifically 20-30° C.; the total time of the modified mixing is preferably 2-5 h, specifically 2 h or 3 h.

[0080] In the present invention, the modified mixing preferably comprises: premixing the flower-shaped tin tetraoxide and water to obtain a premixed solution, and then mixing the premixed solution with cadmium selenide quantum dots.

[0081] In the present invention, the modified mixing preferably also includes centrifugal washing and then drying the obtained product; the centrifugal washing is preferably performed in sequence under centrifugal conditions with water washing and alcohol washing; the water used for the water washing is preferably deionized water; the number of water washings is preferably more than 3 times; the alcohol used for the alcohol washing is preferably anhydrous ethanol; the number of alcohol washings is preferably more than 3 times.

[0082] In the present invention, the centrifugal speed of the centrifugal washing is preferably 5000-10000 rpm, specifically 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm or 10000 rpm.

[0083] In the present invention, the time for a single centrifugal washing is preferably 5 to 15 minutes, specifically 8 minutes or 12 minutes.

[0084] In the present invention, the drying temperature is preferably 60 ～ The temperature may be 80°C, specifically 60°C, 65°C, 70°C, 75°C or 80°C, and the heat preservation and drying time is preferably 8 to 16 hours, specifically 12 hours.

[0085] The present invention also provides the application of the flower-shaped Sn3O4 material modified with CdSe quantum dots described in the above scheme or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method described in the above scheme in the field of gas detection.

[0086] The CdSe Qds and Sn3O4 in the CdSe Qds / Sn3O4 material provided by the present invention construct a pn heterojunction at the interface, resulting in the formation of an energy barrier and the adsorption / desorption of gas compounds, providing a material basis for gas detection and playing a vital role in the performance of the chemiresistor sensor.

[0087] The present invention also provides a n-butanol gas sensor, which includes a hollow ceramic tube; the surface of the hollow ceramic tube is covered with a gas-sensitive coating; the raw material of the gas-sensitive coating includes the flower-shaped Sn3O4 material modified with CdSe quantum dots described in the above scheme or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method described in the above scheme.

[0088] In the present invention, the thickness of the gas-sensitive coating is preferably 30-50 μm, specifically 35 μm, 40 μm or 45 μm.

[0089] In the present invention, the n-butanol gas sensor is preferably a indirectly heated structure; the n-butanol gas sensor preferably also includes a hollow ceramic tube, an electrode, a heating coil, a platinum wire, a heating electrode, a measuring electrode and a base; the hollow ceramic tube is preferably an Al2O3 hollow ceramic tube; the electrode is preferably a gold electrode; the number of the gold electrodes is preferably 2, and the two gold electrodes are preferably arranged parallel to each other at both ends of the outer surface of the hollow ceramic tube; the gas-sensitive coating is preferably covered on the outer surface of the hollow ceramic tube and the electrode; the heating coil is preferably a Ni-Cr heating coil; the heating coil preferably passes through the inside of the hollow ceramic tube; the number of the platinum wires is preferably 4, and every 2 are connected to one of the electrodes; the number of the measuring electrodes is preferably 4, and every 1 is connected to one of the platinum wires; the number of the heating electrodes is preferably 2, and they are respectively connected to both ends of the heating coil; the base is preferably provided with a hollow ceramic tube, a measuring electrode and a heating electrode, respectively.

[0090] The present invention also provides a method for preparing the n-butanol gas sensor described in the above scheme, comprising the following steps:

[0091] The flower-shaped Sn3O4 material modified by CdSe quantum dots and water are mixed to obtain slurry, and the slurry is coated on the surface of the hollow ceramic tube to obtain the n-butanol gas sensor.

[0092] In the present invention, the mass ratio of the flower-shaped Sn3O4 material modified with CdSe quantum dots to water is preferably 1:50-70, specifically 1:50, 1:55, 1:60, 1:65 or 1:70.

[0093] In the present invention, the mixing is preferably ultrasonic mixing; the ultrasonic mixing is preferably carried out in a centrifuge tube; the coating is preferably carried out by taking 5 to 15 μL of slurry with a pipette gun; the coating amount is preferably 33 to 99 μL / cm 2 , specifically 50 μL / cm 2 or 70 μL / cm 2 .

[0094] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0095] Comparative Example 1

[0096] 3.95 g of selenium powder (particle size of about 75 μm) was added to 100 mL of Na2SO3 solution (1 mol / L), and the mixture was stirred at 90 °C for 3 h until the selenium powder was basically dissolved to obtain NaSeSO3 solution; the NaSeSO3 solution obtained above was diluted to 0.005 mol / L; 36.6 mg of anhydrous cadmium chloride and 26 μL of 3-mercaptopropionic acid were added to a three-necked flask and mixed, 190 mL of deionized water was added, and the alkalinity was adjusted to pH ≥ 11 with sodium hydroxide solution (10 mol / L), and then added to a flask. 20mg polyethylene glycol (20000 weight average molecular weight); remove oxygen from the water, fill with argon, repeat 3 times to ensure an anaerobic environment, and finally add 10mL of NaSeSO3 solution (0.005mol / L), maintain reflux at 130℃ for 4h to obtain a yellow-green solution; add isopropanol to the yellow-green solution obtained above, centrifuge at 10000rpm for 15min, and collect the precipitated product; dry the precipitated product at 60℃ in a vacuum for 6h, redissolve it with 20mL of deionized water, and disperse it ultrasonically to obtain a CdSe QDs suspension.

[0097] Comparative Example 2

[0098] 0.9 g of tin dichloride pentahydrate was dissolved in 25 mL of deionized water, and 2.94 g of trisodium citrate Na3C6H5O7·2H2O was slowly added. After mixing, 0.08 g of sodium hydroxide was added, and the mixture was stirred at room temperature for 2 h. The mixture was transferred into a 50 mL polytetrafluoroethylene high-pressure hydrothermal reactor and reacted at 180° C. for 6 h. After the reaction, the temperature was cooled to room temperature. The obtained product was washed with deionized water and ethanol at 7000 rpm by centrifugation until the pH value of the solution was neutral, and the precipitated product was collected. The precipitated product obtained above was dried at 60° C. for 12 h to obtain a flower-like Sn3O4 material.

[0099] Example 1

[0100] The preparation method of the CdSe QDs suspension in this example is the same as that of Comparative Example 1, and the preparation method of the flower-shaped Sn3O4 material is the same as that of Comparative Example 2.

[0101] 0.1 g of the flower-like Sn3O4 material was dispersed in 20 mL of deionized water. After uniform dispersion, 0.1 mL of the CdSe QDs suspension was slowly added and stirred at room temperature for 2 h to allow full contact. The above mixed solution was centrifuged with deionized water and ethanol, the precipitated product was collected, and dried at 60°C for 12 h to obtain a flower-like Sn3O4 material modified with CdSe quantum dots, which was recorded as CdSeQds / Sn3O4-1.

[0102] Example 2

[0103] The preparation method of the CdSe QDs suspension in this example is the same as that of Comparative Example 1, and the preparation method of the flower-shaped Sn3O4 material is the same as that of Comparative Example 2.

[0104] 0.1 g of the flower-like Sn3O4 material was dispersed in 20 mL of deionized water. After uniform dispersion, 0.2 mL of the CdSe QDs suspension was slowly added and stirred at room temperature for 2 h to allow full contact. The above mixed solution was centrifuged with deionized water and ethanol, the precipitated product was collected, and dried at 60°C for 12 h to obtain a flower-like Sn3O4 material modified with CdSe quantum dots, which was recorded as CdSeQds / Sn3O4-2.

[0105] Example 3

[0106] The preparation method of the CdSe QDs suspension in this example is the same as that of Comparative Example 1, and the preparation method of the flower-shaped Sn3O4 material is the same as that of Comparative Example 2.

[0107] 0.1 g of the flower-like Sn3O4 material was dispersed in 20 mL of deionized water. After uniform dispersion, 0.3 mL of the CdSe QDs suspension was slowly added and stirred at room temperature for 2 h to allow full contact. The mixed solution was centrifuged with deionized water and ethanol, the precipitated product was collected, and dried at 60°C for 12 h to obtain a flower-like Sn3O4 material modified with CdSe quantum dots, which was recorded as CdSeQds / Sn3O4-3.

[0108] Example 4

[0109] The preparation method of the CdSe QDs suspension in this example is the same as that of Comparative Example 1, and the preparation method of the flower-shaped Sn3O4 material is the same as that of Comparative Example 2.

[0110] 0.1 g of the flower-like Sn3O4 material was dispersed in 20 mL of deionized water. After uniform dispersion, 0.4 mL of the CdSe QDs suspension was slowly added and stirred at room temperature for 2 h to allow full contact. The mixed solution was centrifuged with deionized water and ethanol, the precipitated product was collected, and dried at 60°C for 12 h to obtain a flower-like Sn3O4 material modified with CdSe quantum dots, which was recorded as CdSeQds / Sn3O4-4.

[0111] Test Example 1

[0112] The products prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to crystal structure characterization, micromorphology characterization and gas-sensing performance testing. The crystal structure characterization was performed using a powder X-ray diffractometer (X'Pert Pro MPD) produced by PANalytical of the Netherlands, the micromorphology characterization was performed using a field emission scanning electron microscope (FEI Verios G4) produced by FEI of the United States, and the gas-sensing performance test was performed using a WS-30B platform produced by Zhengzhou Weisheng Electronics Co., Ltd.

[0113] X-ray diffraction analysis was performed on the products prepared in Example 2, Example 4, Comparative Example 1 and Comparative Example 2 of the present invention. The structural properties of the flower-shaped Sn3O4 material modified with CdSe quantum dots were analyzed by powder XRD characterization method. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that all diffraction peaks of the pure Sn3O4 powder prepared in Comparative Example 2 can correspond to the Sn3O4 triclinic structure card No. 16-0737 given in JCPDS, indicating that Comparative Example 1 successfully prepared Sn3O4 powder; for CdSe / Sn3O4-2 and CdSe / Sn3O4-4 materials, there are obvious characteristic diffraction peaks corresponding to pure Sn3O4 in the XRD spectrum, that is, triclinic Sn3O4 still exists in the CdSe / Sn3O4-2 and CdSe / Sn3O4-4 materials; in the XRD spectrum of CdSe prepared in Comparative Example 1, it can correspond well to the CdSe card No. 19-0191 given in JCPDS, that is, CdSe is successfully obtained; the grain size analysis combined with HRTEM shows that CdSe quantum dots are successfully obtained.

[0114] The products prepared in Example 2 and Comparative Example 2 of the present invention were analyzed by electron microscope. The results are as follows: Figure 2 As shown. Figure 2It can be seen that in the surface morphology of pure Sn3O4 prepared in comparative example 2, evenly distributed and clearly layered stacked nanoflowers can be observed; the locally enlarged image shows that the pure Sn3O4 microflowers are composed of Sn3O4 nanosheets with a thickness of about 15nm; in the SEM image of the CdSe / Sn3O4-2 material prepared in Example 2, the material has a certain degree of agglomeration, the lamellar structure is stacked, and the distribution of nanoflowers is gradually uneven; the regional enlarged image shows the detailed information of the microflowers of the CdSe / Sn3O4-2 material, and agglomeration is observed. In the present case, the Sn3O4 nanosheets become thicker, generally around 68nm, but there are still a large number of nanosheets that can form larger layered stacked nanoflowers; the CdSe quantum dots prepared in Comparative Example 1 were characterized by high-resolution transmission electron microscopy, with a size of 2.1nm; the lattice fringes of the CdSe / Sn3O4-2 material prepared in Example 2 were photographed by high-resolution transmission electron microscopy, wherein the CdSe quantum dots (220) crystal plane corresponded to lattice fringes with a spacing of 0.215nm, and the Sn3O4 (210) crystal plane corresponded to lattice fringes with a spacing of 0.271nm.

[0115] The product prepared in Example 2 of the present invention was subjected to EDS surface scanning and electron diffraction ring spectrum analysis, and the results are as follows: Figure 3 As shown. Figure 3 It can be seen that the CdSe quantum dots prepared in Comparative Example 1 are dispersed more evenly on the surface of the material and are successfully anchored on the surface of the lamellar Sn3O4; in the electron diffraction pattern of the CdSe / Sn3O4-2 material prepared in Example 2, the diffraction rings of Sn3O4 can be clearly seen, which are (111), (-210), (130), (-1-41), (2-41), (312), and (014), respectively.

[0116] The products prepared in Example 2 and Comparative Example 2 of the present invention were analyzed by XPS spectra. The results are as follows: Figure 4 As shown. Figure 4It can be seen that the material contains O and Sn elements; in the O1s fitting orbit of pure Sn3O4 prepared in comparative example 2, 529.9eV, 531.6eV, and 532.9eV correspond to three oxygen species in different states: lattice oxygen, oxygen vacancy, and chemically adsorbed oxygen, respectively; in the O1s fitting orbit of pure CdSe / Sn3O4-2 prepared in Example 2, 530.26eV, 531.55eV, and 532.82eV correspond to the peak positions of lattice oxygen, adsorbed oxygen, and chemical oxygen, respectively; the oxygen species peak position of CdSe / Sn3O4-2 is similar to that of pure Sn3O4, but the content of different oxygen species varies greatly. In the purer Sn3O4, the content of lattice oxygen increases from 14% to 40%, which may be due to the influence of CdSe quantum dots on the content of lattice oxygen during the polymerization process with Sn3O4; Sn The high-resolution fine spectrum of 3d contains two split peaks, namely 3d 5 / 2 and 3D 3 / 2 , Sn 3d 5 / 2 At 486.17eV and 486.74eV, it can be clearly divided into Sn 2+ and Sn 4+ Two Gaussian-like peaks; Sn 3d 3 / 2 The peak can also be decomposed into Sn 2+ (494.57 eV) and Sn 4+ (495.14eV) two peaks. Sn 2+ and Sn 4+ The content can be approximated by the peak area, which is 43%:57%.

[0117] Application Example 1

[0118] This application example assembles a n-butanol gas sensor with a structure such as Figure 5As shown, it is composed of an Al2O3 hollow ceramic tube, a Ni-Cr heating coil, a gold electrode, a platinum wire, a measuring electrode, a heating electrode, a gas-sensitive coating and a base, and has a indirectly heated device structure; the Ni-Cr heating coil passes through the interior of the Al2O3 hollow ceramic tube; the number of the gold electrodes is 2, which are parallel to each other and surround the two ends of the outer surface of the Al2O3 hollow ceramic tube; the number of the platinum wires is 4, and every 2 are connected to one of the gold electrodes; the number of the measuring electrodes is 4, and each is connected to one of the platinum wires; the number of the heating electrodes is 2, which are respectively connected to the two ends of the Ni-Cr heating coil; the gas-sensitive coating is made of the flower-shaped Sn3O4 material modified by CdSe quantum dots prepared in any one of Examples 1 to 4 or the tin tetroxide prepared in Comparative Example 2 The material is formed and covers the outer surface of the Al2O3 hollow ceramic tube and the gold electrode with a thickness of 40.0μm; the Al2O3 hollow ceramic tube, the measuring electrode and the heating electrode are respectively arranged on the base; the preparation process of the sensor is as follows: 5mg of the product prepared in Examples 1 to 4 or Comparative Example 2 are ultrasonically mixed with 300μL of deionized water in a centrifuge tube to form a uniform slurry; 10μL of the slurry is transferred with a pipette as a raw material for the gas-sensitive sensing coating, and is evenly coated on the Al2O3 hollow ceramic tube to obtain a n-butanol gas sensor; the n-butanol gas sensor is installed on an aging bench and tested after being treated at 160°C for 24h; the n-butanol gas sensor controls the working temperature by applying different working voltages to the Ni-Cr heating coil inside the Al2O3 hollow ceramic tube.

[0119] Test Example 2

[0120] The gas sensitive response recovery performance of the n-butanol gas sensor prepared in Example 1 to 100 ppm n-butanol was tested at different temperatures. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that the n-butanol gas sensor shows excellent reversible recovery characteristics for n-butanol gas of different concentrations, and the gas-sensitive responses of all n-butanol gas sensors show a change trend of "increase-maximum-decrease", which indicates that the optimal operating temperature of the n-butanol gas sensors prepared in Examples 1 to 4 is 200°C, and the corresponding response values ​​are 19.44, 48.79, 11.76 and 6.28, respectively; compared with the n-butanol gas sensor prepared in Comparative Example 2 at the same temperature, it can be seen that the n-butanol gas sensor prepared by the flower-shaped CdSe Qds / Sn3O4 material has a response value improved by 1.5 to 12 times that of the pure Sn3O4 sensor.

[0121] The transient dynamic response recovery performance of the n-butanol gas sensor prepared by using the CdSe Qds / Sn3O4-2 material of Example 2 of the present invention was tested when exposed to n-butanol vapor of different concentrations. The results are as follows: Figure 7 As shown. Figure 7 It can be seen that the sensor exhibits the gas sensing characteristics of an n-type semiconductor sensor; when the sensor is exposed to n-butanol gas, the sensor resistance decreases sharply with almost no lag time; when the sensor is transferred from an n-butanol environment to an air environment, the sensor resistance recovers slowly and returns to near the original value after a period of time; in addition, the sensitivity of the n-butanol gas sensor to 100 ppb of triethylamine is 3.6, indicating that the n-butanol gas sensor prepared by the flower-like CdSe Qds / Sn3O4 material has a lower limit of detection of the ppb order and a low detection limit.

[0122] The response recovery performance, transient response performance and long-term stability of the n-butanol gas sensor prepared by using the CdSe Qds / Sn3O4-2 material of Example 2 of the present invention to 100ppm n-butanol were tested. The results are as follows: Figure 8 As shown. Figure 8 It can be seen that the sensor has a sensing response time of 71s and a recovery time of 378s for 100ppm n-butanol, and CdSe QDs further enhance the sensing ability of the Sn3O4-based sensor to n-butanol; in the response process, due to more gas reactions on the surface of the Sn3O4 material, the resistance changes more dramatically, resulting in a stronger response value, but CdSe QDs themselves have no effect on the recovery ability of the sensor, which ultimately leads to a longer recovery time for the sensor; the sensor was tested three times for 100ppm n-butanol, and the sensor had good repeatability; the test results show that the n-butanol gas sensor of the present invention exhibited good repeatability in each test, and after three cycles, the sensor resistance value in the n-butanol atmosphere can still maintain a nearly consistent reduction range, and the response value is almost equal; in the three tests, the sensor response values ​​to 100ppm n-butanol were 51.1, 50.3 and 49.7, respectively.

[0123] It can be seen from the above embodiments that the CdSe Qds / Sn3O4 material provided by the present invention has a high response value, significant selectivity and ppb-level detection limit for n-butanol gas, and has broad application prospects in the field of n-butanol sensing.

[0124] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A flower-shaped Sn3O4 material modified with CdSe quantum dots, characterized in that: The invention comprises flower-shaped tin tetraoxide and cadmium selenide quantum dots modified on the surface of the flower-shaped tin tetraoxide.

2. The flower-shaped Sn3O4 material modified with CdSe quantum dots according to claim 1, characterized in that: The size of the flower-shaped tin tetroxide is 0.5-2 μm; the flower-shaped tin tetroxide is formed by self-assembly of tin tetroxide nanosheets to form a flower-shaped structure, and the thickness of the tin tetroxide nanosheets is 15-20 nm.

3. The flower-shaped Sn3O4 material modified with CdSe quantum dots according to claim 1, characterized in that: The size of the cadmium selenide quantum dots is 1.8-2.5 nm.

4. The flower-shaped Sn3O4 material modified with CdSe quantum dots according to any one of claims 1 to 3, characterized in that: The molar ratio of the flower-shaped tin tetraoxide to the cadmium selenide quantum dots is 40 to 170:

1.

5. The flower-shaped Sn3O4 material modified with CdSe quantum dots according to claim 1 or 2, characterized in that: The size of the flower-shaped Sn3O4 material modified by the CdSe quantum dots is 1 to 3 μm; the thickness of the nanosheet of the flower-shaped Sn3O4 material modified by the CdSe quantum dots is 65 to 70 nm.

6. The method for preparing the flower-shaped Sn3O4 material modified with CdSe quantum dots according to any one of claims 1 to 5, characterized in that: The following steps are involved: The cadmium selenide quantum dots are mixed with flower-shaped tin tetroxide and water to obtain the CdSe quantum dot-modified flower-shaped Sn3O4 material.

7. The preparation method according to claim 6, characterized in that: The preparation method of the flower-shaped tin tetraoxide is as follows: a tin source, an oxidant, an alkali and water are mixed to carry out a solvent thermal reaction to obtain the flower-shaped tin tetraoxide.

8. Application of the flower-shaped Sn3O4 material modified with CdSe quantum dots according to any one of claims 1 to 5 or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method according to any one of claims 6 to 7 in the field of gas detection.

9. A n-butanol gas sensor, characterized in that: The n-butanol gas sensor comprises a hollow ceramic tube; the surface of the hollow ceramic tube is covered with a gas-sensitive coating; the raw material of the gas-sensitive coating comprises the flower-shaped Sn3O4 material modified with CdSe quantum dots as described in any one of claims 1 to 5 or the flower-shaped Sn3O4 material modified with CdSe quantum dots obtained by the preparation method as described in any one of claims 6 to 7.

10. The method for preparing the n-butanol gas sensor according to claim 9, comprising the following steps: The flower-shaped Sn3O4 material modified by CdSe quantum dots and water are mixed to obtain slurry, and the slurry is coated on the surface of the hollow ceramic tube to obtain the n-butanol gas sensor.

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