Silver / transition oxometallate heterojunction nano material, preparation method and application

Abstract

The invention relates to the technical field of composite heterojunction materials, and discloses a silver / transition oxometallate heterojunction nanomaterial, the chemical expression of the nanomaterial is Ag / AgxMyOz.nH2O, and the surface of the nanomaterial is modified by silver nanoparticles. The method comprises the following steps: placing silver metal electrode plates on two sides of a reaction container, and placing a transition metal target material in the center of the reaction container; injecting high-purity deionized water into the reaction container until the high-purity deionized water submerges the surface of the target material; the preparation method comprises the following steps: performing liquid-phase laser corrosion reaction on a transition metal target material for 30 minutes under the induction of an electric field to obtain a reaction solution containing the transition metal target material, collecting the reaction solution containing the transition metal target material in a new container, and standing for more than two weeks until white precipitates appear in the reaction solution, thereby obtaining the Ag / AgxMyOz.nH2O heterojunction nano material. The method is simple and convenient to operate, no other chemical reagent needs to be added in the production process, compared with a hydrothermal chemical method, the method is more environment-friendly, simpler and more convenient, and the structural material is obtained through the method for the first time.

Description

Technical Field

[0001] The present invention relates to the technical field of composite heterojunction materials, and particularly relates to a silver / transition metal oxysalt heterojunction nanomaterial, a preparation method and an application thereof. Background Art

[0002] Attaching plasmons to semiconductor materials to construct heterojunctions can improve the optical and electrical properties of materials through mechanisms such as local surface plasmon resonance (LSPR) enhancement of light absorption and scattering, local electromagnetic fields, hot carrier injection, and thermal effects. However, currently, the strategy of attaching plasmons to semiconductor nanostructures is mainly to first prepare semiconductor nanomaterials by wet chemical methods using various chemical reagents, and then add noble metal chemical reagents to the semiconductor suspension to obtain noble metal / semiconductor composite structures. However, hydrothermal reactions usually require the addition of a large amount of chemical reagents, resulting in relatively high pollution and complex operation steps.

[0003] Chinese Invention Patent (Application No.: 202010108449.5) discloses a nano-composite material based on phosphorus molybdenum polyoxometalate, a preparation method thereof, an aptasensor and an electrode thereof. The nano-composite material of the present invention includes carbon, molybdenum disulfide nanosheets and silver-containing nanoparticles; the nano-composite material is obtained by calcining silver-doped phosphorus molybdenum polyoxometalate, wherein the silver-doped phosphorus molybdenum polyoxometalate is obtained by reacting a silver source, phosphomolybdic acid and thioacetamide. The nano-composite material has a relatively high specific surface area and strong biocompatibility. The electrochemical sensor constructed from the nano-composite material has a low detection limit when used for detecting bisphenol A (BPA), and has high selectivity, good stability and reproducibility, excellent renewable performance and applicability in different environments. However, this method first undergoes a hydrothermal reaction and then high-temperature calcination, and the reaction conditions are relatively harsh. The present invention proposes a noble metal / transition metal oxysalt heterojunction nanomaterial and a new method with convenient operation, no need to add chemical reagents, and simple reaction conditions. Using this method, an Ag / Ag x M y O z heterojunction nanostructure is obtained, and it is found that it is a gas-sensitive sensor material with good response to hydrogen. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a silver / transition metal oxysalt heterojunction nanomaterial, a preparation method and an application thereof.

[0005] On the one hand, the present invention provides a silver / transition metal oxysalt heterojunction nanomaterial, and the chemical expression of the nanomaterial is Ag / Ag x M y O z ·nH2 O, the surface of the nanomaterial is modified with silver nanoparticles, where M is a transition metal, x is the number of Ag elements, y is the number of transition metals, z is the number of oxygen elements, and n is the number of water molecules.

[0006] Preferably, the diameter of the nanomaterial is 1 nm - 900 nm, and the length is 1 μm - 1000 μm.

[0007] On the other hand, the present invention provides a method for preparing a silver / transition metal oxalate heterojunction nanomaterial, comprising the following steps: Place silver metal electrode sheets on both sides of the reaction vessel, and place the transition metal target in the center of the reaction vessel; Inject deionized water into the reaction vessel to submerge the surface of the transition metal target; Perform a liquid-phase laser ablation reaction on the transition metal target under the induction of an electric field to obtain a reaction solution containing the transition metal target; Collect the reaction solution containing the transition metal target in a new container and let it stand for more than 2 weeks until white precipitates appear in the reaction solution, thus obtaining the Ag / Ag x M y O z heterojunction nanomaterial.

[0008] Preferably, the purity of the silver metal electrode sheet is 99% - 99.999%, and the purity of the transition metal target is 99% - 99.999%.

[0009] Preferably, the deionized water submerges the surface of the transition metal target by 2 mm - 15 mm.

[0010] Preferably, the conductivity of the deionized water is 15 MΩ - 30 MΩ.

[0011] Preferably, the parameters of the laser ablation are: wavelength is 355 nm or 532 nm, frequency is 1 Hz - 10 Hz, and energy is 50 mJ - 850 mJ / pulse.

[0012] Preferably, the reaction time is 30 min - 2 h.

[0013] Preferably, the voltage of the electric field is 5 V - 180 V.

[0014] On yet another aspect, the present invention also discloses the application of the above silver / transition metal oxalate heterojunction nanomaterial in a gas sensor.

[0015] A silver / transition metal oxalate heterojunction nanomaterial, a preparation method and an application thereof according to the present invention have the advantages that the method of the present invention is simple and convenient to operate, no other chemical reagents need to be added during the production process, and it is more environmentally friendly and simple compared with the hydrothermal chemical method. Moreover, Ag / Ag is synthesized in one step by laser ablation. x M y O z ·nH 2 O. The reaction steps are concise, and this is the first time to obtain this type of structural material by using this method. This method is a general method, and the target can be replaced with other metal targets to obtain noble metal / transition metal oxalate heterojunction micro-nano structural materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the SEM image of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial prepared in Example 1 of the present invention; Figure 2 is the TEM image of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial prepared in Example 1 of the present invention and the corresponding element distribution maps of Ag, Mo, and O; Figure 3 is the XRD pattern of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial prepared in Example 1 of the present invention; Figure 4 is the photocurrent test pattern of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial prepared in Example 1 of the present invention; Figure 5 is the structural diagram of the preparation device of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] As Figures 1-3 shown, this embodiment discloses a silver / transition metal oxalate heterojunction nanomaterial, and the chemical expression of the nanomaterial is Ag / Ag x M y O z·nH 2 O, the surface of the nanomaterial is modified with silver nanoparticles, where M is a transition metal, x is the number of Ag, y is the number of transition metals, z is the number of O, and n is the number of H 2 O. The diameter of the nanomaterial is 2 nm - 900 nm, and the length is 2 μm - 1000 μm.

[0018] In the present invention, M can represent other transition metal targets such as molybdenum, vanadium, tungsten, niobium, tantalum, titanium, etc., that is, the obtained nanomaterial can be Ag / Ag x Mo y O z ·nH 2 O, Ag / Ag x V y O z ·nH 2 O, Ag / Ag x W y O z ·nH 2 O, Ag / Ag x Nb y O z ·nH 2 O, Ag / Ag x Ti y O z ·nH 2 O, etc.

[0019] Taking the molybdenum target as an example, Ag / Ag x Mo y O z ·nH 2 O heterojunction nanomaterials are prepared. Among them, the values of x, y, z, and n will vary slightly according to different card libraries and laser parameters. See the following examples for details. Example 1

[0020] As Figure 5 shown, this example provides a method for preparing a silver / transition metal oxalate heterojunction nanomaterial, including the following steps: S1: Place silver metal electrode sheets (purity 99.99%) on both sides of the reaction vessel, and place a molybdenum target (purity 99.99%) in the center of the reaction vessel; S2: Inject high-purity deionized water (conductivity 18 MΩ) into the reaction vessel and submerge the surface of the molybdenum target by 2 mm; S3: Turn on the laser and the DC reaction power supply, and perform a liquid-phase laser ablation reaction on the molybdenum target for 30 min under electric field induction (voltage 5V) to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 532 nm, frequency 10 Hz, and energy 600 mJ / pulse; S4: Collect the reaction solution containing molybdenum target in a new container and let it stand for 2 weeks until white precipitates appear in the reaction solution, then Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterials. No additional chemical reagents need to be added in the whole synthesis method, and no multi-step reactions are required, which is more convenient and environmentally friendly than the existing methods.

[0021] Figure 1 The SEM morphology of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterials in this example is shown. Figure 1 The left figure in the middle is the low-magnification SEM morphology of the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterials, and the right figure is the high-magnification one. It can be seen from the left figure that the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterials are fibrous, and high-density dislocations form a dislocation network. It can be seen from the right figure that the surface of the nanomaterials is modified with Ag particle materials.

[0022] Fibrous nanomaterials have extremely high specific surface areas, which means they can provide more gas adsorption sites. When gas molecules adsorb on the material surface, they will have physical or chemical interactions with the material, thus changing the electrical properties of the material (such as resistance or capacitance). The high specific surface area enables fibrous nanomaterials to more effectively adsorb target gas molecules, thereby improving the sensitivity of the sensor.

[0023] Fibrous nanomaterials usually have good electrical properties, such as high conductivity and low resistance. This enables them to quickly respond to electrical changes during gas adsorption and desorption processes, thus achieving rapid detection. The surface chemical properties of fibrous nanomaterials can be regulated by various methods, such as doping, surface modification or composite with other materials. These methods can change the selectivity of the material to specific gases, thereby improving the detection accuracy of the sensor. Decorating silver nanoparticles on the surface of metal oxide nanofibers can significantly improve their gas detection performance.

[0024] In summary, due to their unique physical and chemical properties, the fibrous nanomaterials prepared in this example have important application values in gas sensors, can significantly improve the sensitivity, selectivity and stability of the sensors, and at the same time reduce the working temperature and energy consumption.

[0025] Figure 2 shows Ag / Ag in this embodiment 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial TEM image and the corresponding Ag, Mo, O element distribution maps. In the figure, (1) the figure on the left is a single Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial TEM morphology image. It can be seen from the figure that there are many particulate materials modifying the surface of the nanomaterial. The three figures on the right of (1) in the figure are the corresponding Ag, Mo, O element distribution maps. Thus, it can be seen that the long nanowires have Ag, Mo, O elements, and the particulate substances only contain Ag elements and do not contain O elements, which are silver nanoparticles. Therefore, the obtained structure is Ag 2 Mo 3 O 10 ·1.8H 2 O nanostructure.

[0026] Figure 3 shows Ag / Ag in this embodiment 2 Mo 3 O 10 ·1.8H 2 O heterojunction nanomaterial XRD pattern. It can be seen from the figure that there are 7 peaks in the XRD pattern. Except for the peak with the highest diffraction intensity which is the peak of the silicon substrate, the other 6 diffraction peaks are respectively at 11.25̊, 13.40̊, 28.26̊, 35.15̊, 38.07̊, 46.26̊, corresponding to Ag 2 Mo 3 O 10 ·1.8H 2 O (JCPDS No.39-0045) (101), (200), (103), (501), (230), (404) crystal planes. Example 2

[0027] This embodiment provides a preparation method of a silver / transition metal oxoacid heterojunction nanomaterial, including the following steps: Place silver metal electrode sheets (purity 99.9%) on both sides of the reaction vessel, and place a molybdenum target (purity 99.9%) in the center of the reaction vessel; Inject high-purity deionized water (conductivity 15 MΩ) into the reaction vessel and submerge the surface of the molybdenum target by 5 mm; Turn on the laser and the DC reaction power supply. Under the induction of an electric field (voltage 150 V), perform a liquid-phase laser ablation reaction on the molybdenum target for 50 min to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 355 nm, frequency 1 Hz, and energy 50 mJ / pulse; Collect the reaction solution containing the molybdenum target in a new container and let it stand for 3 weeks until white precipitates appear in the reaction solution, thus obtaining Ag / Ag 2 Mo 5 O 14 ·2H 2 O heterojunction nanomaterials. Example 3

[0028] This example provides a method for preparing silver / transition metal oxalate heterojunction nanomaterials, which includes the following steps: Place silver metal electrode sheets (purity 99.0%) on both sides of the reaction container, and place the molybdenum target (purity 99.0%) in the center of the reaction container; Inject high-purity deionized water (conductivity 18 MΩ) into the reaction container and submerge the surface of the molybdenum target by 10 mm; Turn on the laser and the DC reaction power supply. Under the induction of an electric field (voltage 50 V), perform a liquid-phase laser ablation reaction on the molybdenum target for 1 h to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 355 nm, frequency 5 Hz, and energy 300 mJ / pulse; Collect the reaction solution containing the molybdenum target in a new container and let it stand for 4 weeks until white precipitates appear in the reaction solution, thus obtaining Ag / Ag 3 Mo 6 O 18 ·5H 2 O heterojunction nanomaterials. Example 4

[0029] This example provides a method for preparing silver / transition metal oxalate heterojunction nanomaterials, which includes the following steps: Place silver metal electrode sheets (purity 99.9%) on both sides of the reaction container, and place the molybdenum target (purity 99.9%) in the center of the reaction container; Inject high-purity deionized water (conductivity 18 MΩ) into the reaction container and submerge the surface of the molybdenum target by 8 mm; Turn on the laser and the DC reaction power supply. Under the induction of an electric field (voltage 50 V), perform a liquid-phase laser ablation reaction on the molybdenum target for 1 h to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 532 nm, frequency 6 Hz, and energy 350 mJ / pulse; Collect the reaction solution containing the molybdenum target in a new container and let it stand for 4 weeks until white precipitates appear in the reaction solution, thus obtaining Ag / Ag3 Mo 5 O 16 ·3H 2 O Heterojunction Nanomaterials. Example 5

[0030] This example provides a method for preparing silver / transition metal oxalate heterojunction nanomaterials, which includes the following steps: Place silver metal electrode sheets (purity 99.99%) on both sides of the reaction vessel, and place a molybdenum target (purity 99.99%) in the center of the reaction vessel; Inject high-purity deionized water (conductivity 30 MΩ) into the reaction vessel and submerge the surface of the molybdenum target by 12 mm; Turn on the laser and the DC reaction power supply, and perform a liquid-phase laser ablation reaction on the molybdenum target for 1.5 h under the induction of an electric field (voltage 100 V) to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 532 nm, frequency 3 Hz, and energy 400 mJ / pulse; Collect the reaction solution containing the molybdenum target in a new container and let it stand for 5 weeks until white precipitates appear in the reaction solution, thus obtaining Ag / Ag 3 Mo 3 O 12 ·4H 2 O Heterojunction Nanomaterials. Example 6

[0031] This example provides a method for preparing silver / transition metal oxalate heterojunction nanomaterials, which includes the following steps: Place silver metal electrode sheets (purity 99.999%) on both sides of the reaction vessel, and place a molybdenum target (purity 99.999%) in the center of the reaction vessel; Inject high-purity deionized water (conductivity 20 MΩ) into the reaction vessel and submerge the surface of the molybdenum target by 15 mm; Turn on the laser and the DC reaction power supply, and perform a liquid-phase laser ablation reaction on the molybdenum target for 2 h under the induction of an electric field (voltage 180 V) to obtain a reaction solution containing the molybdenum target. The parameters of the laser ablation are: wavelength 532 nm, frequency 8 Hz, and energy 850 mJ / pulse; Collect the reaction solution containing the molybdenum target in a new container and let it stand for 6 weeks until white precipitates appear in the reaction solution, thus obtaining Ag / Ag 4 Mo 5 O 18 ·3H 2 O Heterojunction Nanomaterials.

[0032] Application Example 1 Ag / Ag prepared in Example 1 2 Mo 3O 10 ·1.8H 2 Application of O heterojunction nanomaterials in gas sensors.

[0033] Ag / Ag 2 Mo 3 O 10 ·1.8H 2 An O heterojunction is made into a gas sensor, and the sensor is connected to an external circuit to capture signal changes in current or resistance. The current response is tested in environments with different hydrogen concentrations to obtain Figure 4 data. Experiments show that the Ag / Ag 2 Mo 3 O 10 ·1.8H 2 O heterojunction has an obvious current signal response to hydrogen. The detection limit of this gas sensor for hydrogen is 10 ppm at 350 degrees Celsius.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by orientation words such as "front, back, up, down, left, right", "lateral, vertical, horizontal" and "top, bottom", etc. are usually based on the orientation or positional relationships shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary instructions, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the protection scope of the present invention.

[0035] For those skilled in the art, various corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A silver / transition metal oxoate heterojunction nanomaterial, characterized in that: The chemical expression of the nanomaterial is Ag / Ag x M y O z ·nH2O, the surface of the nanomaterial is modified with silver nanoparticles, wherein M is a transition metal, x is the number of Ag elements, y is the number of transition metals, z is the number of oxygen elements, and n is the number of water molecules.

2. The silver / transition metal oxoate heterojunction nanomaterial according to claim 1, characterized in that: The diameter of the nano material is 1nm-900nm, and the length is 1μm-1000μm.

3. A method for preparing a silver / transition metal oxoate heterojunction nanomaterial, characterized in that: The following steps are involved: Place silver metal electrodes on both sides of the reaction container and place the transition metal target in the center of the reaction container; Injecting deionized water into the reaction container so as not to cover the surface of the transition metal target; Performing a liquid phase laser ablation reaction on the transition metal target under electric field induction to obtain a reaction solution containing the transition metal target; The reaction solution containing the transition metal target is collected in a new container and allowed to stand for more than 2 weeks until a white precipitate appears in the reaction solution to obtain Ag / Ag x M y O z ·nH2O nanomaterials.

4. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 3, characterized in that: The purity of the silver metal electrode sheet is 99% to 99.999%, and the purity of the transition metal target material is 99% to 99.999%.

5. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 3, characterized in that: The deionized water covers the surface of the transition metal target by 2 mm to 15 mm.

6. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 3, characterized in that: The conductivity of the deionized water is 15MΩ-30MΩ.

7. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 3, characterized in that: The parameters of the laser ablation are: wavelength of 355nm or 532nm, frequency of 1Hz~10Hz, and energy of 50mJ~850mJ / pulse.

8. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 7, characterized in that: The reaction time is 30min-2h.

9. The method for preparing the silver / transition metal oxoate heterojunction nanomaterial according to claim 3, characterized in that: The voltage of the electric field is 5V-180V.

10. Use of the silver / transition metal oxoate heterojunction nanomaterial according to any one of claims 1 to 2 in a gas sensor.

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