Controllable preparation method of tin dioxide spiral tube based on modification of ZIF-8 and carbon porous filter layer

Abstract

The invention discloses a controllable preparation method of a SnO2 spiral tube modified based on a ZIF-8 and C porous filter layer, which comprises the following steps: respectively modifying the inside of the SnO2 spiral tube with ZIF-8 and C, and filtering and screening the entered gas by a filter layer before the gas reaches a sensitive layer to react. The SnO2 / ZnO spiral tube composite material is prepared through an atomic layer deposition technology, ZnO in the tube is converted into a ZIF-8 or C porous filter layer, and the MEMS gas sensor which performs screening and response according to the gas molecule dynamic diameter is obtained. The preparation of the ZIF-8 and C porous filter layer modified SnO2 spiral tube is realized, after ZIF-8 and C modification, the selectivity of SnO2 on benzene series is improved, compared with a traditional synthesized porous filter layer and benzene series with similar sizes, the SnO2 spiral tube has excellent selectivity, and has unique value in gas classification and recognition.

Description

Technical Field

[0001] This invention belongs to the field of MOF-derived porous thin film materials technology, specifically relating to a controllable preparation method of SnO2 spiral tubes based on ZIF-8 and C porous filter layer modification. Background Technology

[0002] Tin dioxide (SnO2) is widely used in gas sensors, especially in environmental monitoring and industrial safety, due to its excellent photoelectric properties, chemical stability, and high sensitivity. Despite its advantages such as high sensitivity, fast response, and low cost, practical applications still present challenges, including poor selectivity and high temperature dependence. Therefore, optimizing the nanostructure of SnO2 to improve the sensitivity and selectivity of sensors remains an important research area.

[0003] Metal-organic frameworks (MOFs) possess ultra-high porosity, structural and chemical tunability, structural flexibility, and a large equivalent internal surface area. The abundant micropores in MOFs not only allow gas molecules to penetrate rapidly but also induce surface enrichment effects for trace target molecules. Furthermore, the well-defined pore structure of MOFs can provide a molecular sieving effect. These two effects hold promise for improving sensor response sensitivity and selectivity, enabling selective filtering of similar gas molecules.

[0004] ZIF-8 is a subclass of MOFs with a characteristic pore size of 1.1 nm. A SnO2 gas sensor modified with a ZIF-8 filter layer is a gas sensor that pre-sieves gas molecules using the specific pore size of the ZIF-8 material. This sensor combines the excellent properties of SnO2 with the molecular sieving effect of ZIF-8, significantly improving gas selectivity by controlling the rate at which gas molecules pass through the filter layer. Further high-temperature calcination of ZIF-8 yields a porous C filter layer, which not only retains the porous characteristics of ZIF-8 but also significantly improves the material's conductivity, thus enhancing the sensor's sensitivity. Utilizing ZIF-8 and C porous filter layers to modify the SnO2 sensing material allows for controllable filter layer thickness, enabling differentiated responses based on the differences in the diameters of different gas molecules, thereby improving sensor selectivity. The ZIF-8 and C porous filter layer-modified SnO2 gas sensor also offers advantages in miniaturization and integration, supporting large-scale manufacturing while ensuring device uniformity and reliability.

[0005] Therefore, designing and synthesizing SnO2 with specific functional filter layer modifications provides a new approach to improving the selectivity of gas sensors, which is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a controllable preparation method for SnO2 helical tubes modified with ZIF-8 and C porous filter layers. Based on atomic layer deposition (ALD) technology, SnO2 nano-helical tubes modified with ZIF-8 and C porous filter layers of different thicknesses were prepared. SnO2 gas sensors with different thicknesses of ZIF-8 and C porous filter layers showed different sensing performance for several benzene series gases.

[0007] This invention is achieved through the following technical solution:

[0008] A controllable preparation method for SnO2 spiral tubes modified with ZIF-8 and C porous filter layers is disclosed. SnO2 / ZnO composite materials are prepared by atomic layer deposition. These materials are then reacted with a DMF solution of 2-methylimidazole at 70°C for 5 hours to convert ZnO to ZIF-8. The SnO2 / ZIF-8 is further calcined at 850°C to convert it to SnO2 / C. These materials are then combined with MEMS devices to obtain SnO2 MEMS gas sensors modified with ZIF-8 and C porous filter layers. The specific steps include:

[0009] Step 1: Using CNC as a template, uniformly coat it onto a silicon wafer and place it in an atomic layer deposition (ALD) reactor. Add a Zn source to a raw material bottle, selecting Zn and H2O as precursors for ZnO deposition; add a Sn source to another raw material bottle, selecting Sn and H2O as precursors for SnO2 deposition.

[0010] Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250.

[0011] Step 3: Under light-protected conditions, ZnO is deposited first, followed by SnO2, to obtain a SnO2 / ZnO spiral tube with a specific thickness;

[0012] Step 4: Place the above SnO2 / ZnO in a DMF solution of 2-methylimidazole and react in a water bath at 70°C for 5 hours to obtain a SnO2 / ZIF-8 spiral tube with ZIF-8 as the filter layer.

[0013] Step 5: Grind a small amount of SnO2 / ZIF-8 mixed with ethanol into powder, and coat it evenly onto the MEMS sensor to obtain a MEMS sensor suitable for gas detection.

[0014] Furthermore, in step 2, the number of cycles of Zn is set to 20, 30, 40, or 50.

[0015] Furthermore, in step 2, the number of cycles for Sn is set to 100, 150, 200, or 300.

[0016] Furthermore, in step 4, SnO2 / ZIF-8 is calcined at 850°C for 2 hours in a N2 atmosphere to obtain a SnO2 spiral tube with a porous C / N filter layer.

[0017] This invention provides a controllable preparation method for SnO2 spiral tubes based on ZIF-8 and C porous filter layer modification. The principle is as follows: by setting different cycle numbers during ALD deposition, SnO2 / ZnO spiral tubes with ZnO layers of different thicknesses can be prepared; further, SnO2 / ZIF-8 spiral tubes with a certain thickness of porous ZIF-8 filter layer are obtained through water bath reaction; and SnO2 / ZIF-8 is calcined at high temperature to obtain SnO2 / C spiral tubes with a certain thickness of C porous filter layer.

[0018] This invention utilizes ALD technology to prepare SnO2 gas-sensitive materials with filter layers of specific thickness, offering advantages such as a short preparation process, precise thickness control, high uniformity, and good coverage. While SnO2 / ZnO responds to a variety of gases, it is difficult to distinguish between different gas molecules. By converting ZnO into ZIF-8 and C as porous filter layers, the gas is pre-sieved through ZIF-8 before reaching the SnO2 sensitive layer, resulting in different responses based on differences in molecular dynamics diameter. The ZIF-8 and C filter layers do not alter the gas-sensing properties of SnO2 itself; rather, they control the rate at which the target gas reaches SnO2, thereby achieving efficient and rapid selective gas monitoring.

[0019] The present invention provides a controllable preparation method for SnO2 spiral tubes based on ZIF-8 and C porous filter layer modification, which has the following beneficial effects:

[0020] (1) The preparation of ZIF-8 and C filter layers with controllable thickness was achieved.

[0021] (2) After ZIF-8 and C modification, SnO2 significantly improves the selectivity of benzene series compounds. Compared with the traditional post-synthesis modified porous filter layer, the consistency of different regions is good.

[0022] (3) The SnO2 / ZIF-8 and SnO2 / C composite materials have excellent selectivity for benzene compounds with similar molecular properties and sizes.

[0023] (4) SnO2 modified with ZIF-8 and C porous filter layers has unique value in regulating gas selectivity and realizing gas classification and identification. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the process before and after modification of different porous filter layers.

[0025] Figure 2 This is a schematic diagram of the pore analysis of SnO2 / ZIF-8.

[0026] Figure 3 A schematic diagram illustrating the application of SnO2 modified with ZIF-8 and C porous filter layers in the field of gas sensing.

[0027] Figure 4 A schematic diagram of the preparation route of SnO2 modified with ZIF-8 and C porous filter layers. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0029] Example 1

[0030] This embodiment provides a controllable preparation method for SnO2 spiral tubes modified with ZIF-8 and C porous filter layers, specifically including the following steps:

[0031] Step 1: Coat the silicon wafer with the CNC ethanol dispersion evenly and place it in an atomic layer deposition (ALD) reactor. Add a Zn source to the feed bottle and select Zn precursor and H2O as the deposition precursor. Add a Sn source to another feed bottle and select Sn precursor and H2O as the deposition precursor.

[0032] Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250.

[0033] Step 3: Deposit under light-protected conditions to obtain SnO2 / ZnO spiral tube gas-sensitive material;

[0034] Step 4: React SnO2 / ZnO with a DMF solution of 2-methylimidazole in a water bath at 70°C for 5 hours.

[0035] Example 2

[0036] This embodiment provides a controllable preparation method for SnO2 spiral tubes modified with ZIF-8 and C porous filter layers, specifically including the following steps:

[0037] Step 1: Coat the silicon wafer with the CNC ethanol dispersion evenly and place it in an atomic layer deposition (ALD) reactor. Add a Zn source to the feed bottle and select Zn precursor and H2O as the deposition precursor. Add a Sn source to another feed bottle and select Sn precursor and H2O as the deposition precursor.

[0038] Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250.

[0039] Step 3: Deposit under light-protected conditions to obtain SnO2 / ZnO spiral tube gas-sensitive material;

[0040] Step 4: React SnO2 / ZnO with a DMF solution of 2-methylimidazole in a water bath at 70°C for 5 hours to obtain ZIF-8 modified SnO2 spiral tubes;

[0041] Step 5: Calcine SnO2 / ZIF-8 at 850℃ for 2 hours in a N2 atmosphere to obtain a SnO2 spiral tube with a porous C / N filter layer.

[0042] like Figure 1 The images shown are TEM images of SnO2 / ZnO, SnO2 / ZIF-8, and SnO2 / C prepared in Examples 1 and 2 above. The crystal planes corresponding to the lattice fringes obtained from different examples are the same. The XRD diffraction patterns show that the modification of ZIF-8 does not change the crystal structure of SnO2 itself, and the modification of ZIF-8 and C layers only plays a filtering role.

[0043] like Figure 2 The image shows the SnO2 pore characteristics analysis of the ZIF-8 porous filter layer modified in Example 1 above. It can be seen that ZIF-8 was successfully formed and the pore size is 1.1 nm.

[0044] like Figure 3 The above-mentioned SnO2 / ZIF-8 and SnO2 / C prepared in Examples 1 and 2 are shown to be gas-sensitive tests. The materials have a fast response, the filter layer modification improves the selectivity of SnO2 for different benzene compounds, and they have good stability and repeatability.

[0045] like Figure 4 The diagram shows the synthesis of SnO2 modified with ZIF-8 and C porous filter layers of different thicknesses prepared in Examples 1 and 2 above.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A controllable preparation method for SnO2 spiral tubes modified with ZIF-8 and C porous filter layers, characterized in that, A gas sensor was developed by modifying the interior of a SnO2 spiral tube with ZIF-8 and C, respectively, so that the incoming gas is pre-filtered and sieved by the filter layer before reaching the sensitive layer for reaction. A SnO2 / ZnO spiral tube composite material was prepared using atomic layer deposition (ALD) technology, where the ZnO inside the tube was converted into ZIF-8 or C porous filter layers. These layers were then combined with MEMS devices to obtain a MEMS gas sensor that sieves and responds based on the diameter of gas molecules in dynamical geometry. The specific steps include the following: Step 1: Using CNC as a template, uniformly coat it onto a silicon wafer and place it in an atomic layer deposition (ALD) reactor. Add a Zn source to a raw material bottle, selecting Zn and H2O as precursors for ZnO deposition; add a Sn source to another raw material bottle, selecting Sn and H2O as precursors for SnO2 deposition. Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250. Step 3: Under light-protected deposition conditions, ZnO is deposited first, followed by SnO2, to obtain a SnO2 / ZnO spiral tube with a specific thickness; Step 4: Place the SnO2 / ZnO spiral tube in a DMF solution of 2-methylimidazole and react it in a water bath at 70°C for 5 hours to obtain a SnO2 / ZIF-8 spiral tube with ZIF-8 as the filter layer.

2. The controllable preparation method of SnO2 spiral tube based on ZIF-8 and C porous filter layer modification according to claim 1, characterized in that, In step 2, the number of cycles of Zn is set to 20, 30, 40 or 50.

3. The controllable preparation method of SnO2 spiral tube based on ZIF-8 and C porous filter layer modification according to claim 1, characterized in that, In step 2, the number of cycles for Sn is set to 100, 150, 200, or 300.

4. The controllable preparation method of SnO2 spiral tube based on ZIF-8 and C porous filter layer modification according to claim 1, characterized in that, In step 4, SnO2 / ZIF-8 is calcined at 850°C for 2 hours in a N2 atmosphere to obtain a SnO2 spiral tube with a porous C / N filter layer.

5. The controllable preparation method of SnO2 spiral tube based on ZIF-8 and C porous filter layer modification according to claim 1, characterized in that, Specifically, the steps include the following: Step 1: Coat the silicon wafer with the ethanol dispersion of CNC evenly, place it in the atomic layer deposition (ALD) reactor, add the Zn source to the raw material bottle, and select Zn precursor and H2O as the precursor for deposition. Sn source was added to another raw material bottle, and Sn precursor and H2O were selected as the precursors for deposition. Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250. Step 3: Deposit under light-protected conditions to obtain SnO2 / ZnO spiral tube gas-sensitive material; Step 4: React SnO2 / ZnO with a DMF solution of 2-methylimidazole in a water bath at 70°C for 5 hours.

6. The controllable preparation method of SnO2 spiral tube based on ZIF-8 and C porous filter layer modification according to claim 1, characterized in that, Specifically, the steps include the following: Step 1: Coat the silicon wafer with the ethanol dispersion of CNC evenly, place it in the atomic layer deposition (ALD) reactor, add the Zn source to the raw material bottle, and select Zn precursor and H2O as the precursor for deposition. Sn source was added to another raw material bottle, and Sn precursor and H2O were selected as the precursors for deposition. Step 2: Set the reaction temperature of Zn to 150℃ and the number of cycles to 10; set the reaction temperature of Sn to 85℃ and the number of cycles to 250. Step 3: Deposit under light-protected conditions to obtain SnO2 / ZnO spiral tube gas-sensitive material; Step 4: React SnO2 / ZnO with a DMF solution of 2-methylimidazole in a water bath at 70°C for 5 hours to obtain ZIF-8 modified SnO2 spiral tubes; Step 5: Calcine SnO2 / ZIF-8 at 850℃ for 2 hours in a N2 atmosphere to obtain a SnO2 spiral tube with a porous C / N filter layer.

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