A Fe2O3 nanotube / zinc ferrite open nanocage superstructure composite material, its preparation method and application

Abstract

The present invention discloses a Fe2O3 nanotube / zinc ferrite open nanocage superstructure composite material, its preparation method and application. The preparation method includes the following steps: preparing a zinc-iron Prussian blue nanocube precursor material, dispersing it in deionized water, and standing and aging at 15-45 °C for 24-120 h to obtain zinc-iron Prussian blue nanocages; dispersing them in deionized water, adding ferrous salts, stirring evenly, standing and reacting at 30-90 °C for 3-24 h, filtering, washing, drying, and then performing heat treatment at 280-520 °C for 1-5 h. The present invention adopts a self-template epitaxial growth strategy combined with a heat treatment process to controllably prepare a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure, and systematically studies the gas-sensing performance of this material, providing a new idea for constructing complex hierarchical nanomaterials and a new choice for high-performance hydrogen sulfide-sensitive materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and particularly relates to an Fe2O3 nanotube / zinc ferrite open nanocage superstructure composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In daily life, gas sensors have been applied in various fields such as environmental monitoring, medical diagnosis, and agriculture. Gas sensors based on semiconductor metal oxides have attracted great interest in the past few decades due to their advantages such as high-performance tunability, simple structure, convenient manufacturing, and intuitive sensing mechanism. Although some novel gas-sensitive materials have been introduced in the application of the sensing field, traditional metal oxides are still general and effective sensing materials.

[0003] As a classical n-type semiconductor material with a band gap of 2.1 eV, Fe2O3 has been widely used in various fields such as biomedicine, cancer targeted therapy, lithium-ion batteries, organic pollutant degradation, catalysis, and gas sensors due to its advantages such as rich resources, high conductivity, and good stability. It is well known that the gas-sensitive performance of metal oxides depends to a large extent on their morphology, such as aspect ratio, size, crystal plane orientation, and crystal density. Therefore, in the past few decades, based on the basic principle of controlling the intrinsic sensing reaction kinetics, various Fe2O3 nanostructures have been synthesized by various strategies, such as nanospindles, nanocubes, nanospheres, nanoflowers, nanotubes, etc. In addition, by changing the intrinsic sensing reaction process, several effective strategies such as noble metal modification, doping with other elements, and composite with other materials have been successfully adopted to improve the sensing performance of Fe2O3. Among these methods, the combination of the chemical functions of complex structures and composite materials is widely regarded as a simple and effective method to achieve high sensing performance. Advantages such as large porosity, high specific surface area, large cavity volume, and highly activated shell structure can effectively promote the adsorption or desorption of gas molecules from the material surface, contribute to the migration of carriers inside the material, and thus improve the gas-sensitive performance of the material.

[0004] In recent years, people have further realized that materials with specific nanostructures can exhibit unique or enhanced properties. Driven by the discovery of carbon nanotubes and fullerenes, scientists have invested a great deal of effort in developing nanomaterials with hollow interiors, such as hollow polyhedra and spheres, tubular, open-cage, and framework-like, which has become an interesting research topic in the past two decades. Prussian blue (PB) is the first artificial coordination polymer (CP) obtained by co-precipitation of Fe III salt and [Fe II (CN)6] 4- in water. The crystal structure has been solved as a face-centered cubic (fcc) unit cell, in which Fe III and FeII Alternately bridged by cyanide ligands. Meanwhile, iron can be replaced by other transition metal elements such as cobalt, nickel, and manganese without disrupting the basic fcc crystal structure, thus producing Prussian blue analogues (PBAs). Due to their unique structural features, the hollow structure endows them with fascinating physicochemical properties and a wide range of applications, especially in electrochemical energy storage and conversion. In recent years, Prussian blue (PB) and its analogue (PBA) related nanomaterials have received extensive attention due to their advantages such as low cost, easy preparation, intrinsic open structure, and adjustable composition.

[0005] With the progress of nanoscience and the in-depth understanding of hollow structures, non-spherical complex structures have been gradually separated from hollow porous structures as a unique and emerging structure. These structures endow them with special performance advantages due to their additional advantages (such as adjustable chemical composition, fully open anisotropic hierarchical structure, etc.). Designing and developing hierarchical structure metal oxide composites with novel structures is expected to bring opportunities for the development of new gas sensors. Summary of the Invention

[0006] The purpose of the present invention is to provide a Fe2O3 nanotube / ZnFe2O4 open nanocage composite material, its preparation method and application; in order to design and synthesize hierarchical structure metal oxide composites with novel structures, the present invention uses a self-template epitaxial growth strategy combined with a heat treatment process to controllably prepare a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure, and systematically studies the gas sensing performance of this material, providing new ideas for constructing complex hierarchical nanomaterials and new options for high-performance hydrogen sulfide sensitive materials.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A preparation method of a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, characterized in that the preparation method comprises the following steps:

[0009] (1) Dissolve a zinc salt in dilute hydrochloric acid, add an aqueous solution of potassium ferrocyanide thereto, stir until the solution becomes a yellow suspension, stand at 10 - 95 °C for 2 - 36 h, filter, wash, and dry to obtain a zinc-iron Prussian blue nanocubic block precursor material, and then disperse it in deionized water, stand and age at 15 - 45 °C for 24 - 120 h, filter, wash, and dry to obtain zinc-iron Prussian blue nanocages;

[0010] (2) Dispersing zinc-iron Prussian blue nanocages in deionized water, adding ferrous salt, stirring evenly, standing at 30-90°C for reaction for 3-24 hours, filtering, washing, and drying, and then heat treating at 280-520°C for 1-5 hours to obtain a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material.

[0011] In step (1), the zinc salt is one or more of zinc chloride, zinc sulfate, zinc acetate and zinc nitrate.

[0012] In step (1), the molar ratio of potassium ferrocyanide to zinc salt is 1:1.

[0013] In step (1), the concentration of the potassium ferrocyanide aqueous solution is 0.1-2.0 mol / L; the concentration of the zinc salt in dilute hydrochloric acid is 0.1-2.0 mol / L; and the concentration of the dilute hydrochloric acid is 0.1-1.2 mol / L.

[0014] In step (1), the standing condition is preferably 60-80° C. for 12-24 h; and the standing aging condition is preferably 20-30° C. for 72-96 h.

[0015] In step (2), the ferrous salt is one or more of ferrous sulfate, ammonium ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0016] In step (2), the mass ratio of the zinc-iron Prussian blue nanocage to the ferrous salt is 1:0.75-2.5.

[0017] In step (2), the concentration of the zinc-iron Prussian blue nanocage in deionized water is 0.0015-0.02 g / mL.

[0018] In step (2), the static reaction condition is preferably 35-50° C. for 10-12 hours.

[0019] In step (2), the heat treatment condition is preferably 340-400° C. for 2-3 hours.

[0020] In step (2), the heating rate to the specified heat treatment temperature is 1 to 5°C / min, preferably 1 to 2°C / min.

[0021] The present invention also provides a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared by the preparation method.

[0022] The present invention also provides the application of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material in a gas sensor, which has a highly sensitive response to hydrogen sulfide gas and good stability.

[0023] In the preparation method disclosed by the present invention, zinc - iron Prussian blue nanocubes which are easy to prepare are used as precursors. Through aging, zinc - iron Prussian blue nanocages are obtained. Through in - situ growth, iron oxyhydroxide tubes / zinc - iron Prussian blue analogue nanocages are obtained. Through heat treatment, Fe2O3 nanotubes / ZnFe2O4 open nanocage superstructure materials are obtained.

[0024] Some of the chemical reaction equations involved in the reaction process are shown as follows:

[0025] 3Zn 2+ +2Fe(CN)6 3- →Zn3[Fe(CN)6]2 (1)

[0026] 4Fe 2+ +O2+4H + →4Fe 3+ +2H2O (2)

[0027] 2Fe 3+ +6Fe 2+ +3Zn3[Fe(CN)6]2→2Fe4[Fe(CN)6]3+9Zn 2+ (3)

[0028] 2Fe 2+ + O2 + 2H2O → 2FeOOH+ 4H + (4)

[0029] 2FeOOH→Fe2O3 + 2H2O (5)

[0030] The present invention adopts a self - template epitaxial growth strategy combined with an annealing process to controllably prepare Fe2O3 nanotubes / ZnFe2O4 open nanocage superstructures, and systematically studies the gas - sensing properties of this material. The results show that the Fe2O3 nanotubes / ZnFe2O4 open nanocage sensor has a relatively low operating temperature, a low detection limit, fast response / recovery times, good reversibility and long - term stability, and significantly better selectivity for H2S than other reducing gases. The Fe2O3 nanotubes / ZnFe2O4 open nanocages exhibit excellent sensitive characteristics to H2S gas, which is mainly attributed to its hierarchical open structure with unobstructed gas diffusion channels, its heterostructure being conducive to interfacial charge transfer, and its abundant oxygen vacancies and adsorption - catalytic reaction sites. The work of the present invention provides new ideas for constructing complex hierarchical nanomaterials and new options for highly sensitive and highly selective detection of hydrogen sulfide gas. Brief Description of the Drawings

[0031] Figure 1This is a SEM image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 1;

[0032] Figure 2 This is a SEM image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 2;

[0033] Figure 3 This is a SEM image of the zinc iron Prussian blue nanocube precursor prepared in Example 3;

[0034] Figure 4 This is the XRD pattern of the zinc iron Prussian blue nanocube precursor prepared in Example 3;

[0035] Figure 5 This is a SEM image of the zinc-iron Prussian blue nanocage prepared in Example 3;

[0036] Figure 6 This is the XRD pattern of the nanotube-modified zinc-iron Prussian blue nanocage prepared in Example 3;

[0037] Figure 7 This is a SEM image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 3;

[0038] Figure 8 The XRD pattern of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 3;

[0039] Figure 9 This is the EDS image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 3;

[0040] Figure 10 The BET diagram of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 3;

[0041] Figure 11 This is a SEM image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 4;

[0042] Figure 12 This is a SEM image of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared in Example 5;

[0043] Figure 13 This is a SEM image of the ZnFe2O4 open nanocage superstructure prepared in Comparative Example 1;

[0044] Figure 14XRD pattern of the ZnFe2O4 open nanocage superstructure prepared as Comparative Example 1;

[0045] Figure 15 Response sensitivities of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite prepared in Example 3 and the ZnFe2O4 open nanocage sensor prepared in Comparative Example 1 to 10 ppm H2S and 100 ppm of different kinds of VOCs (including ethanol, isopropanol, acetone, benzene, toluene, n-butanol, methanol, ammonia, etc.) at a working temperature of 140 °C. Detailed Description of the Invention

[0046] The present invention will be described in detail below in conjunction with examples.

[0047] In each example, the reaction vessel used in step (2) is a beaker, and the beaker mouth is covered with plastic wrap during heating.

[0048] Example 1

[0049] A preparation method of an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite, comprising the following steps:

[0050] (1) Dissolve potassium ferricyanide in deionized water to prepare 1000 mL of 0.1 M potassium ferricyanide solution; dissolve zinc chloride in 0.1 M dilute hydrochloric acid to prepare 1000 mL of 0.1 M zinc chloride-hydrochloric acid solution; under magnetic stirring at a rotation speed of 150 rpm, add the above potassium ferricyanide solution to the zinc chloride-hydrochloric acid solution, and then continue to stir at room temperature for 5 min to obtain a mixed suspension. Let it stand at 10 °C for 36 h to obtain a yellow precipitate. Filter and wash the yellow precipitate to obtain a zinc-iron Prussian blue nanocube precursor material, and then disperse it in 50 mL of deionized water. Let it stand and age at 15 °C for 120 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is the zinc-iron Prussian blue nanocage.

[0051] (2) Take 0.2 g of zinc-iron Prussian blue nanocage and disperse it in 15 mL of deionized water. Add 0.15 g of ferrous chloride and stir vigorously for 5 min, then transfer it to an oven at 90 °C and react for 3 h. Wash the yellow precipitate thoroughly with deionized water and ethanol and dry it to obtain zinc-iron Prussian blue nanocage modified with iron oxyhydroxide nanotubes.

[0052] (3) Transfer the obtained zinc-iron Prussian blue nanocage sample modified with iron oxyhydroxide nanotubes to a muffle furnace, and heat it to 280 °C at a heating rate of 5 °C / min and hold for 5 h to obtain an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure. Its SEM image is as Figure 1 shown.

[0053] Example 2

[0054] A preparation method of an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, comprising the following steps:

[0055] (1) Dissolve potassium ferricyanide in deionized water to prepare a 1000 mL 0.4 M potassium ferricyanide solution; dissolve zinc sulfate in 0.3 M dilute hydrochloric acid to prepare a 1000 mL 0.4 M zinc sulfate-hydrochloric acid solution; under magnetic stirring at a rotation speed of 160 revolutions / min, add the above potassium ferricyanide solution to the zinc sulfate-hydrochloric acid solution, and then continue to stir at room temperature for 5 min to obtain a mixed suspension. Let it stand at 30 °C for 30 h to obtain a yellow precipitate. Filter and wash the yellow precipitate to obtain a zinc-iron Prussian blue nanocube precursor material, and then disperse it in 90 mL of deionized water. Let it stand and age at 25 °C for 100 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is the zinc-iron Prussian blue nanocage.

[0056] (2) Take 0.2 g of zinc-iron Prussian blue nanocage and disperse it in 50 mL of deionized water. Add 0.25 g of ferrous sulfate and stir vigorously for 5 min, then transfer it to an oven at 70 °C and react for 5 h. Wash the yellow precipitate thoroughly with deionized water and ethanol and dry it to obtain zinc-iron Prussian blue nanocage modified with iron oxyhydroxide nanotubes.

[0057] (3) Transfer the obtained zinc-iron Prussian blue nanocage sample modified with iron oxyhydroxide nanotubes to a muffle furnace, heat it at a heating rate of 4 °C / min to 320 °C, and keep it warm for 4 h to obtain an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure. Its SEM image is as shown in Figure 2 shown.

[0058] Example 3

[0059] A preparation method of an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, comprising the following steps:

[0060] (1) Dissolve potassium ferricyanide in deionized water to prepare a 1000 mL 0.9 M potassium ferricyanide solution; dissolve zinc nitrate in 0.7 M dilute hydrochloric acid to prepare a 1000 mL 0.9 M zinc nitrate-hydrochloric acid solution; under magnetic stirring at a rotation speed of 165 revolutions / min, add the above potassium ferricyanide solution to the zinc nitrate-hydrochloric acid solution, and then continue to stir at room temperature for 6 min to obtain a mixed suspension. Let it stand at 60 °C for 20 h to obtain a yellow precipitate. Filter and wash the yellow precipitate to obtain a zinc-iron Prussian blue nanocube precursor material, and then disperse it in 200 mL of deionized water. Let it stand and age at 30 °C for 72 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is the zinc-iron Prussian blue nanocage. Its SEM image is as shown in Figure 3As shown, it can be seen from the figure that it is a uniform nanocage; its XRD pattern is as Figure 4 shown, and the diffraction pattern proves that the prepared zinc ferrocyanide blue has strong peaks and high purity.

[0061] (2) Take 0.2 g of zinc ferrocyanide blue nanocage and disperse it in 80 mL of deionized water. Add 0.35 g of ferrous sulfate and stir vigorously for 5 min, then transfer it to an oven at 55 °C and react for 18 h. Wash the yellow precipitate thoroughly with deionized water and ethanol and dry it to obtain zinc ferrocyanide blue nanocage modified with iron oxyhydroxide nanotubes. Its SEM image is as Figure 6 shown.

[0062] (3) Transfer the obtained zinc ferrocyanide blue nanocage sample modified with iron oxyhydroxide nanotubes to a muffle furnace, heat it at a heating rate of 3 °C / min to 380 °C and hold for 3 h to obtain a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure. Its SEM image is as Figure 7 shown, which is zinc ferrocyanide blue nanocage modified with Fe2O3 nanotubes. Its XRD is as Figure 8 shown. It can be found that all diffraction peaks can be attributed to two groups, which match well with Fe2O3 (JCPDS No. 33-0664) and ZnFe2O4 (JCPDS No. 22-1012) respectively, and there are no other impurity peaks; the EDS image of the product is as Figure 9 shown. It can be seen that the product contains zinc, iron and oxygen elements, and the silicon element comes from the silicon substrate. Its BET image is as Figure 10 shown, and its specific surface area is 124.30 m 2 g -1 , and the average pore diameter is 2.27 nm, indicating that it is a porous material with a relatively large specific surface area.

[0063] Example 4

[0064] A preparation method of a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, comprising the following steps:

[0065] (1) Dissolve potassium ferricyanide in deionized water to prepare 1000 mL of 1.5 M potassium ferricyanide solution; dissolve zinc acetate in 1.0 M dilute hydrochloric acid to prepare 1000 mL of 1.5 M zinc acetate-hydrochloric acid solution; under magnetic stirring at a rotation speed of 170 rpm, add the above potassium ferricyanide solution to the zinc acetate-hydrochloric acid solution, and then continue to stir at room temperature for 8 min to obtain a mixed suspension. Let it stand at 80 °C for 1 h to obtain a yellow precipitate. Filter and wash the yellow precipitate to obtain a zinc ferrocyanide blue nanocubic precursor material, and then disperse it in 400 mL of deionized water, let it stand and age at 35 °C for 48 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is zinc ferrocyanide blue nanocage.

[0066] (2) Disperse 0.2 g of zinc - iron Prussian blue nanocages in 90 mL of deionized water, add 0.42 g of ferrous nitrate, stir vigorously for 5 min, and then transfer it to an oven at 80 °C for reaction for 8 h. Wash the yellow precipitate thoroughly with deionized water and ethanol, and dry it to obtain zinc - iron Prussian blue nanocages modified with iron oxyhydroxide nanotubes.

[0067] (3) Transfer the obtained zinc - iron Prussian blue nanocages modified with iron oxyhydroxide nanotubes to a muffle furnace, heat it at a heating rate of 2 °C / min to 450 °C, and keep it at this temperature for 2 h to obtain an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure. Its SEM image is as Figure 11 shown, zinc - iron Prussian blue nanocages modified with Fe2O3 nanotubes.

[0068] Example 5

[0069] A preparation method of an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, comprising the following steps:

[0070] (1) Dissolve potassium ferricyanide in deionized water to prepare a 1000 mL 2.0 M potassium ferricyanide solution; dissolve zinc chloride in 1.2 M dilute hydrochloric acid to prepare a 1000 mL 2.0 M zinc chloride - hydrochloric acid solution; under magnetic stirring at a rotation speed of 180 r / min, add the above - mentioned potassium ferricyanide solution to the zinc chloride - hydrochloric acid solution, and then continue to stir at room temperature for 10 min to obtain a mixed suspension. Let it stand at 95 °C for 2 h to obtain a yellow precipitate. Filter and wash the yellow precipitate to obtain a zinc - iron Prussian blue nanocubic precursor material, and then disperse it in 500 mL of deionized water, let it stand and age at 45 °C for 24 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is zinc - iron Prussian blue nanocages.

[0071] (2) Disperse 0.2 g of zinc - iron Prussian blue nanocages in 120 mL of deionized water, add 0.5 g of ferrous sulfate, stir vigorously for 5 min, and then transfer it to an oven at 90 °C for reaction for 3 h. Wash the yellow precipitate thoroughly with deionized water and ethanol, and dry it to obtain zinc - iron Prussian blue nanocages modified with iron oxyhydroxide nanotubes.

[0072] (3) Transfer the obtained zinc - iron Prussian blue nanocages modified with iron oxyhydroxide nanotubes to a muffle furnace, heat it at a heating rate of 1 °C / min to 520 °C, and keep it at this temperature for 1 h to obtain an Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure. Its SEM image is as Figure 12 shown, zinc - iron Prussian blue nanocages modified with Fe2O3 nanotubes.

[0073] Comparative Example 1

[0074] A preparation method of a ZnFe2O4 open nanocage superstructure composite material, comprising the following steps:

[0075] (1) Dissolve potassium ferricyanide in deionized water to prepare 1000 mL of 0.9 M potassium ferricyanide solution; dissolve zinc nitrate in 0.7 M dilute hydrochloric acid to prepare 1000 mL of 0.9 M zinc nitrate-hydrochloric acid solution; under magnetic stirring at a rotation speed of 165 revolutions / min, add the above potassium ferricyanide solution to the zinc nitrate-hydrochloric acid solution, and then continue to stir at room temperature for 6 min to obtain a mixed suspension. Let it stand at 60 °C for 20 h to obtain a yellow precipitate. Filter and wash the yellow precipitate. Disperse the obtained zinc-iron Prussian blue nanocubes in 200 mL of deionized water, let it stand and age at 30 °C for 72 h, and then wash it thoroughly with absolute ethanol and dry it. The obtained product is zinc-iron Prussian blue nanocages.

[0076] (2) Transfer the obtained zinc-iron Prussian blue nanocage sample to a muffle furnace and heat-treat it at 380 °C for 3 h with a heating rate of 3 °C / min to obtain a ZnFe2O4 open nanocage superstructure. Its SEM image is as shown in Figure 13 shown, and it can be seen that the morphology of the product is nanocage-like. Its XRD is as shown in Figure 14 shown, and it can be seen that all diffraction peaks match those of ZnFe2O4 (JCPDS No. 22-1012) and there are no other impurity peaks.

[0077] Application Example 1

[0078] Application of Fe2O3 nanotubes / ZnFe2O4 open nanocage superstructure composite material in gas sensors

[0079] Disperse the Fe2O3 nanotubes / ZnFe2O4 open nanocage superstructure composite material prepared in Example 3 and the ZnFe2O4 open nanocages prepared in Comparative Example 1 in absolute ethanol respectively, and then evenly coat them on a ceramic tube with electrodes to make a gas sensor. Dry it at 50 °C for 2 h, and then heat-treat it at 200 °C for 2 h. Then, put a small nickel-chromium alloy coil into the tube as a heater to provide the working temperature for the sensor. Age the sensor at 300 °C for 48 h, and then test different volatile organic gases at the working temperature. The specific test operation steps are as follows: Inject a certain amount of organic vapor into the sensor test chamber with a syringe. Wait for about 2 minutes. After the sensor output response value is stable, then introduce dry air into the test chamber, and the sensor output response gradually recovers. Use an electrochemical workstation and a computer to test and record the output response values of the sensor in dry air and in the presence of the target gas. The gas response sensitivity of the sensor is defined as S = R a / R g (reducing gas), R ais the resistance of the sensor in dry air, R g is the resistance of the sensor in the test gas.

[0080] Figure 15 For the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite prepared in Example 3 and the ZnFe2O4 open nanocage sensor prepared in Comparative Example 1, the response sensitivities to 10 ppm H2S and 100 ppm different kinds of VOCs (including ethanol, isopropanol, acetone, benzene, toluene, n-butanol, methanol, ammonia, etc.) were measured at a working temperature of 140 °C. The research shows that the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite prepared in Example 3 has good sensitive responses to common toxic and harmful organic gases in the air, and its sensitive performance is significantly better than that of the ZnFe2O4 open nanocage material, such as Figure 15 shown. As can be seen from the figure, the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite prepared by this method shows good selectivity to hydrogen sulfide compared with different kinds of VOCs (including ethanol, isopropanol, acetone, benzene, toluene, n-butanol, methanol, ammonia, etc.). Therefore, it is appropriate to select the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure as the sensitive material for H2S gas.

[0081] The above detailed description of a Fe2O3 nanotube / zinc ferrite open nanocage superstructure composite and its preparation method and application with reference to the embodiments is illustrative rather than restrictive. Several embodiments can be listed within the defined scope. Therefore, changes and modifications within the general concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material, characterized in that: The preparation method comprises the following steps: (1) dissolving a zinc salt in dilute hydrochloric acid, adding an aqueous solution of potassium ferrocyanide thereto, stirring until the solution becomes a yellow suspension, standing at 10 to 95° C. for 2 to 36 hours, filtering, washing, and drying to obtain a zinc iron Prussian blue nanocube precursor material, and then dispersing the precursor material in deionized water, standing at 15 to 45° C. for aging for 24 to 120 hours, filtering, washing, and drying to obtain a zinc iron Prussian blue nanocage; (2) Dispersing zinc-iron Prussian blue nanocages in deionized water, adding ferrous salt, stirring evenly, standing at 30-90°C for reaction for 3-24 hours, filtering, washing, and drying, and then heat treating at 280-520°C for 1-5 hours to obtain a Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material.

2. The preparation method according to claim 1, characterized in that: In step (1), the zinc salt is one or more of zinc chloride, zinc sulfate, zinc acetate and zinc nitrate.

3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of potassium ferrocyanide to zinc salt is 1:

1.

4. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the potassium ferrocyanide aqueous solution is 0.1 to 2.0 mol / L; the concentration of the zinc salt in dilute hydrochloric acid is 0.1 to 2.0 mol / L; The concentration of the dilute hydrochloric acid is 0.1-1.2 mol / L.

5. The preparation method according to claim 1, characterized in that: In step (2), the ferrous salt is one of ferrous sulfate, ferrous chloride and ferrous nitrate.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the zinc-iron Prussian blue nanocage to the ferrous salt is 1:0.75-2.

5.

7. The preparation method according to claim 1, characterized in that: In step (2), the concentration of the zinc-iron Prussian blue nanocage in deionized water is 0.0015-0.02 g / mL.

8. The preparation method according to claim 1, characterized in that: In step (2), the heating rate to the specified heat treatment temperature is 1 to 5°C / min.

9. The Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Fe2O3 nanotube / ZnFe2O4 open nanocage superstructure composite material as claimed in claim 9 in a gas sensor.

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