A gas sensing material with high adhesion and its use

Abstract

The application discloses a gas sensing material with high adhesion, which comprises at least an adhesion unit and a sensing unit, the adhesion unit is combined with the sensing unit in a coordination bond mode, the adhesion unit comprises a polymer main chain and a functional group at the end of the main chain, the functional group is subjected to a coordination reaction with the sensing unit; the nanobelt array made of the gas sensing material has excellent adhesion on various rigid or flexible substrates, and has excellent responsiveness, selectivity and stability in sensing volatile organic compounds, can rapidly detect organic gas at room temperature, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas sensor, in particular to a gas sensing material with high adhesion, and a gas sensor prepared by using the gas sensing material. BACKGROUND

[0002] Gas sensor is a sensor for detecting gas composition and content, which can be used to detect combustible gas, toxic gas in the environment, and also can be used to detect carbon dioxide, oxygen and other non-toxic gas related to human comfort, so as to be widely used in many fields. The sensitive element made of sensing material is the core of the sensor, and the appropriate sensing material is the guarantee for the optimal performance of the sensor. The selection and optimization of sensing material and the development and application of new sensing material have always been the focus of sensor research.

[0003] The adhesion between the sensing material and the substrate is also crucial, which affects the stability of the sensor. There are mainly two ways to enhance the adhesion strength between the sensing material and the substrate; mechanical bonding and chemical bonding. Mechanical bonding is to introduce inorganic or organic adhesives in the sensing material, so as to adhere to the substrate. For example, Chinese invention patent CN201010160302.7 provides a gas sensor, by properly adjusting the composition of the insulating layer, the reference gas layer and the sensing layer, so as to improve the heterogeneous bonding degree of the reference gas substrate, the insulating layer and the sensing layer, and improve the bonding force between the insulating layer, the reference gas layer and the sensing layer. However, this technology needs to be sintered at high temperature, which is not suitable for organic sensing material and flexible substrate. SUMMARY

[0004] The purpose of the present application is to provide a gas sensing material with high adhesion, which has excellent adhesion performance on various rigid or flexible substrates, and has excellent response, selectivity and stability to volatile organic compounds, and can quickly detect organic gas at room temperature.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a gas sensing material with high adhesion, which comprises at least an adhesion unit and a sensing unit, and the adhesion unit and the sensing unit are combined in a coordination bond mode.

[0007] In the preferred scheme, the nanobelt array made of the gas sensing material can have a normal adhesion strength of not less than 150 N / cm 2 and a shear adhesion strength of not less than 380 N / cm 2 on the silica substrate at 25℃.

[0008] The gas sensing material with high adhesion provided by the present application, wherein the sensing unit is selected from metal organic complex, the metal organic complex has at least one metal center and at least one organic ligand.

[0009] The metal center includes but is not limited to Au (III), Pt (II), Pd (II); the organic ligand includes but is not limited to 6-phenyl-2,2-dipyridine, terpyridine.

[0010] In one preferred scheme, when the two molecular distances of the sensing unit are 0.7 nm, the difference between the super-exchange electron coupling of the sensing unit after adsorbing the gas and the direct electron coupling of the sensing unit without adsorbing the gas is greater than 0, preferably greater than 4.

[0011] The gas sensing material with high adhesion provided by the present application, wherein the adhesion unit includes a polymer main chain and a functional group at the end of the main chain, the functional group can be coordinated with the metal center.

[0012] The polymer main chain includes but is not limited to polydimethylsiloxane, polyethylene glycol, polyethyleneimine and derivatives thereof. The functional group at the end of the main chain includes but is not limited to cyano, alkynyl.

[0013] In one preferred scheme, the number average molecular weight of the polymer main chain is 890-5000 g / mol.

[0014] The present application also provides a gas sensor, which includes a nanobelt array, a support substrate and a detection electrode, the nanobelt array is prepared from the aforementioned gas sensing material with high adhesion, and the nanobelt array includes a plurality of oriented nanobelts.

[0015] In one preferred scheme, the height of each nanobelt is 60-80 nm, the width is 1-2 μm, and the distance between adjacent nanobelts is 9-11 μm.

[0016] In one preferred scheme, the sensor has a detection limit of 50 ppm or less, the response time of the sensor is 11 seconds or less, and the recovery time is 19 seconds or less.

[0017] The present application also provides a use of a gas sensor for detecting gas compounds or volatile organic compounds (VOCs), preferably, the gas compounds or volatile organic compounds include ethanol, methanol, acetone, acetonitrile, dichloromethane, chloroform, tetrahydrofuran, formaldehyde, hexane, diethyl ether.

[0018] In one preferred scheme, the use of the gas sensor is for wearable devices, indoor toxic gas detection, factory flammable and explosive gas detection, food spoilage or freshness detection.

[0019] The beneficial effects of the present application are:

[0020] (1) The present application innovates in introducing an adhesion unit in the sensing molecule, which enhances the adhesion of the sensing material to the substrate, greatly enhances the mechanical stability of the sensor device, and at the same time ensures excellent gas sensing performance.

[0021] (2) The sensing material of the present application can realize high response recognition of different types of gases through the selection of sensing units, greatly widening the application field of the sensing material.

[0022] (3) The sensing material of the present application can realize adhesion to different types of sensor substrates through the selection of adhesion units, greatly improving the limitation of the sensor substrate material. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 : Infrared spectrum of the gas sensing material prepared in Example 1;

[0024] Figure 2 : Nuclear magnetic resonance hydrogen spectrum of the gas sensing material prepared in Example 1;

[0025] Figure 3 : Scanning electron microscope photo of the gas sensing nanobelt array prepared in Example 1;

[0026] Figure 4 : Shear force and displacement curve of the gas sensing nanobelt array prepared in Example 1 and Comparative Example 1;

[0027] Figure 5 : Normal tensile force and displacement curve of the gas sensing nanobelt array prepared in Example 1 and Comparative Example 1;

[0028] Figure 6 : Response curve of the gas sensing nanobelt array prepared in Example 1 to ethanol gas;

[0029] Figure 7 : Response curve of the gas sensing nanobelt array prepared in Example 1 to ethanol gas of different concentrations;

[0030] Figure 8 : Response comparison of the gas sensing nanobelt array prepared in Example 1 to different gases;

[0031] Figure 9 : Response comparison of the gas sensing nanobelt array prepared in Example 1 and Comparative Example 1 to ethanol gas. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be further described in detail below in combination with specific examples. The following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0033] [super-exchange electron coupling]

[0034] In donor-acceptor polymers, two donor (acceptor) groups are separated by an acceptor (donor) and there is no direct coupling, but the intermediate acceptor (donor) is coupled as a bridge. This coupling is called effective coupling, also called super-exchange coupling. When organometallic ligands adsorb gas, the gas acts as a bridge to form super-exchange coupling. By using density functional theory calculations, the distance between metal organic ligands is changed, and when the intermolecular distance is about 0.7 nm, the system energy reaches a minimum point, and the optimized molecular structure is obtained. Therefore, by using the potential energy correction method and the separation method, under the condition that the minimum intermolecular distance is 0.7 nm, the intermolecular distance is adjusted, and the super-exchange electronic coupling and direct electronic coupling are calculated. We get that the super-exchange electronic coupling after introducing gas is greater than the direct electronic coupling. The mobility is proportional to the square of the electronic coupling, after the gas is introduced, a strong super-exchange electronic coupling is formed, the mobility increases, the conductivity performance is improved, and the gas sensing is realized. (Reference 1. Valeev, E. F.; Coropceanu, V.; da Silva Filho, D. A.; Salman, S.; Bredas, J.-L. Effect of electronic polarization on charge-transport parameters in molecular organic semiconductors. Journal of the American Chemical Society 128, 9882-9886 (2006). 2. Geng, H.; Zheng, X.; Shuai, Z.; Zhu, L.; Yi, Y. Understanding the Charge Transport and Polarities in Organic Donor–Acceptor Mixed-Stack Crystals: Molecular Insights from the Super-Exchange Couplings. Adv. Mater. 27, 1443-1449 (2015). 3. Geng, H.; Zhu, L.; Yi, Y.; Zhu, D.; Shuai, Z. Superexchange Induced Charge Transport in Organic Donor–Acceptor Cocrystals and Copolymers: A Theoretical Perspective. Chem. Mater. 31, 6424-6434 (2019). 4. Guo, Y.Han, G.; Tu, Z.; Yi, Y. Electronic and optical properties of π-bridged perylenediimide derivatives: the role of π-bridges. J. Mater. Chem. A 7, 12532-12537 (2019).5.Ning, L.; Han, G.; Yi, Y. Intra-chain and inter-chains synergistic effect gives rise to high electron mobilities for naphthalenediimide based copolymers. Journal of Materials Chemistry C 8, 16527-16532 (2020).

[0035] [Sensor unit]

[0036] The sensor unit is selected from metal organic complex, which has at least one metal center and at least one organic ligand. Specifically, for example, the following can be mentioned:

[0037] The metal center includes but is not limited to Au (III), Pt (II), Pd (II); the organic ligand includes but is not limited to 6-phenyl-2,2-dipyridine, terpyridine. The preparation of the metal organic complex can refer to the literature Lu W, Chen Y, Roy VAL, Chui SS-Y, Che C-M. Supramolecular Polymers and Chromonic Mesophases Self-Organized from Phosphorescent Cationic Organoplatinum (II) Complexes in Water. Angewandte Chemie International Edition 48, 7621-7625 (2009). The full text of the above-mentioned document can be referred to in the present application.

[0038] [Adhesion unit]

[0039] The adhesion unit includes a polymer main chain and a functional group at the end of the main chain, and specifically, for example, the following can be mentioned:

[0040] The polymer main chain is selected from polymers with adhesive properties, such as polydimethylsiloxane (PDMS), polyethylene glycol (PEG), polyethyleneimine (PEI). By selecting an appropriate main chain, the adhesion of the gas sensing material of the present application to the surface of a substrate of different materials can be adjusted.

[0041] The functional group at the end of the main chain is selected from functional groups that can coordinate with metal atoms, such as cyano. The functional group can be modified according to the end group of the main chain of the polymer raw material by organic reactions known in the art. Specific examples are as follows:

[0042] When the end of the polymer main chain is an amino group, a cyano group is obtained by a two-step reaction, i.e. the reaction of an amino group with an acid anhydride to form an amide, and then the reaction of the amide with POCl3 to form a cyano group. These reactions are known to those skilled in the art.

[0043] [Gas sensing material]

[0044] The adhesion unit and the sensing unit are combined by coordination bonding to form the gas sensing material of the present application. Specifically, the preparation method of the gas sensing material is as follows:

[0045] The sensing unit and the adhesion unit are dissolved in a suitable organic solvent to obtain a sensing unit solution and an adhesion unit solution; the sensing unit solution and the adhesion unit solution are mixed in a certain ratio, stirred at room temperature for 2-12 hours, and then impurities are removed and dried to obtain the gas sensing material of the present application.

[0046] Preferably, the organic solvent is selected from dichloromethane, methanol or a mixture thereof.

[0047] Preferably, the molar ratio of the sensing unit to the adhesion unit is 2:1-3:1.

[0048] [Gas sensor]

[0049] The gas sensor comprises a detector and a nanobelt array formed on the surface of the detector substrate.

[0050] The substrate can be selected from a flexible substrate or a rigid substrate. Preferably, the flexible substrate is selected from a polydimethylsiloxane substrate (PDMS), a polyethylene terephthalate substrate (PET), a polyethylene naphthalate substrate (PEN), and a polyimide substrate (PI); the rigid substrate is selected from a silicon dioxide substrate, a quartz substrate, and a glass substrate.

[0051] In the present application, the nanobelt array can be prepared by liquid bridge-induced self-assembly, inkjet printing, soft lithography, nanoimprinting, solution shearing, laser pulse deposition, and 3D printing.

[0052] In one preferred embodiment, the nanobelt array is prepared by a liquid bridge induced self-assembly method, which comprises the following steps:

[0053] (1) Dissolve the gas sensing material completely in an organic solvent to form a uniform solution;

[0054] (2) Clean and dry the substrate;

[0055] (3) Drop the solution in step (1) on the surface of the substrate, then cover and fix it with a silicon column template to form a "sandwich" system;

[0056] (4) After vacuum drying the "sandwich" system in step (3), remove the silicon column template to obtain the nanobelt array.

[0057] Preferably, the concentration of the solution in step (1) is 5-10 mg mL -1 .

[0058] The implementation process of the present application is illustrated by specific examples and comparative examples, and the implementation effect is fully evaluated. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0059] Example 1:

[0060] Dissolve potassium tetrachloroplatinate (0.54 g) in a mixed solvent of acetonitrile and water, stir under nitrogen atmosphere, add 6-phenyl-2,2-dipyridine (0.29 g), react at 100°C for 24 h to obtain a red solution, rotary evaporate, wash with ethanol and water, filter to obtain the product, and dry in an oven to obtain the organometallic ligand.

[0061] A mixture of acetic anhydride (2.00 mL, 21.20 mmol) and formic acid (1.60 mL, 42.40 mol) was stirred under nitrogen atmosphere and heated at 60 °C for 4 h to form formic acid acetic anhydride. Then, polydimethylsiloxane with amino end groups (PDMS-NH2, 1.00 g, 2.25 mmol Si-NH2, Mn = 890 g / mol, purchased from Gelest) was dissolved in a small amount of CH2Cl2solvent and added dropwise to the in situ formed formic acid acetic anhydride. The reaction mixture was stirred at 60 °C for 24 h and the mixture gradually turned yellow. Then, the mixture was cooled to room temperature, quenched with 10% aqueous Na2CO3solution and extracted with 50 mL CH2Cl2three times. The combined dichloromethane extracts were washed with 100 mL brine and dried over anhydrous Na2SO4. The yellow solution was filtered to remove the drying agent and the filtrate was concentrated on a rotary evaporator. PDMS-NHCOH (0.94 g, 94.0% yield) was obtained as a viscous light yellow oil which was used in the next step without purification.

[0062] The prepared PDMS-NHCOH (0.94 g) was dissolved in anhydrous CH2Cl2(10 mL) and triethylamine (11.10 mL, 80.16 mmol) was added. The mixture was stirred at room temperature under nitrogen atmosphere for 30 min. Then, neat POCl3(2.10 mL, 22.61 mmol) was slowly added to the mixture. The resulting chestnut-colored mixture was stirred at room temperature for 4 h and then quenched with 100 mL of 10% aqueous Na2CO3solution. The organic part was separated and the aqueous solution was extracted with another 50 mL CH2Cl2three times. All the organic extracts were combined with the organic part and the resulting solution was washed with 100 mL brine, dried over Na2SO4, filtered and concentrated on a rotary evaporator. PDMS-NC was obtained as a chestnut-colored and transparent viscous oil (0.70 g, 74.5% yield).

[0063] The sensing unit (0.46 g, 1 mmol) was dissolved in a mixture of dichloromethane and methanol and then PDMS-NC (0.40 g, 0.45 mmol) dissolved in CH2Cl2was added. The mixture was stirred at room temperature for 2 h and the mixture gradually turned black. The black reaction solution was evaporated to dryness under reduced pressure. The resulting solid was dissolved in CH3OH, the solution was filtered and concentrated on a rotary evaporator to obtain the gas sensing material of the present application (0.9 g, 96.77% yield). Figure 1 and 2 The successful synthesis of the gas sensing material was confirmed.

[0064] The gas sensing material prepared above was dissolved in dimethyl sulfoxide, and then ultrasonically treated for 10 minutes to form a uniform solution, to prepare a solution with a concentration of 5 mg / mL. The SiO2 / Si substrate was sequentially cleaned with ethanol, acetone and isopropanol, and then dried using nitrogen. To manufacture the nanobelt array, 10 μL of the foregoing solution was dropped onto the SiO2 / Si substrate, and then covered with a silicon column template to form a "sandwich-like" system. After drying in a vacuum oven at 60 °C for 12 hours, the gas sensing nanobelt array (denoted as PDMS-Pt-L nanobelt array) was successfully obtained on the SiO2 / Si substrate after removing the microcolumn template. Figure 3 A scanning electron microscope (SEM) photo of the gas sensing nanobelt array prepared for Example 1 was obtained by SEM and AFM (atomic force microscope), and the height of the nanobelt array was 60-80 nm, the width was 1-2 μm, and the distance between adjacent nanobelts was 9-11 μm.

[0065] Example 2:

[0066] The nanobelt array was prepared according to the same method as in Example 1, except that the PDMS-NH2 was replaced with PDMS-NH2 with a number average molecular weight of 1743 g / mol.

[0067] Example 3:

[0068] The nanobelt array was prepared according to the same method as in Example 1, except that the PDMS-NH2 was replaced with PDMS-NH2 with a number average molecular weight of 5000 g / mol.

[0069] Comparative Example 1:

[0070] The small molecule sensing unit was dissolved in deionized water, and ultrasonically treated for 10 minutes to form a uniform solution, to prepare a solution with a concentration of 5 mg mL -1 . The SiO2 / Si substrate was sequentially cleaned with ethanol, acetone and isopropanol, and then dried using nitrogen. To manufacture the nanobelt array, 10 μL of the foregoing solution was dropped onto the SiO2 / Si substrate, and then covered with a silicon column template to form a "sandwich-like" system. After drying in a vacuum oven at 60 °C for 12 hours, the small molecule nanobelt array (denoted as Pt-L nanobelt array) was successfully obtained on the SiO2 / Si substrate after removing the silicon column template.

[0071] Test conditions:

[0072] [Adhesion test]

[0073] The fully dried "sandwich" system prepared by the above embodiments, with an overlap area of ​​1 cm × 1 cm, was used for adhesion force testing, and then measured on a force gauge at a tensile speed of 10 mm / min. The direction of the overlap shear measurement was parallel to the direction of the designed array. The adhesion force at tensile fracture provides the maximum adhesive strength. At least 3-5 samples were measured and the average value was calculated.

[0074] [Sensor Performance Test]

[0075] The gas sensor was fabricated by depositing Cr / Au (10 / 100 nm) electrodes onto a prepared nanoribbon array with a copper mesh template. Current-time measurements were performed at room temperature using a Keithley 4200 semiconductor characterization system with a Lake Shore manual probe station.

[0076] According to the above test conditions, the gas sensing nanobelt arrays prepared in the examples and comparative examples were tested for normal adhesion strength, shear adhesion strength and sensing performance, respectively. The test results are shown in Table 1.

[0077] Table 1. Performance of Examples 1-3 and Comparative Example 1

[0078]

[0079] Appendix Figure 4 and 5 Shear force and normal tensile force tests were conducted on the sensing materials prepared in Example 1 and Comparative Example 1, respectively. The results show that, for both shear force and normal tensile force, the adhesion strength of the nanoribbon array with introduced adhesion units is significantly higher than that of the small molecule nanoribbon array in Comparative Example 1. Figures 6-8 The results show the sensing performance test results of the gas sensing material prepared in Example 1. The results indicate that the gas sensing material prepared in Example 1 exhibits excellent responsiveness and selectivity to ethanol gas, with a fast response speed of approximately 10.75 s. Furthermore, within a certain concentration range, the responsiveness is linearly correlated with the ethanol gas concentration. (Appendix) Figure 9 This is a comparison of the responses of the gas-sensing nanobelt arrays prepared in Example 1 and Comparative Example 1 to ethanol gas. The results show that the sensing performance of the sensing material after the introduction of the adhesion units is not affected by the adhesion units.

[0080] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A gas sensing material with high adhesion, characterized in that, The gas sensing material comprises at least an adhesion unit and a sensing unit, wherein the adhesion unit and the sensing unit are combined by coordinate bonds. The adhesion unit includes a polymer backbone and functional groups located at the ends of the backbone, and the functional groups undergo a coordination reaction with the sensing unit. The sensing unit is selected from organometallic complexes; the organometallic complex has at least one metal center and at least one organic ligand; the metal center is selected from Au(III), Pt(II), and Pd(II), and the organic ligand is selected from 6-phenyl-2,2-dipyridine and terpyridine; When the distance between two molecules in the sensing unit is 0.7 nm, the difference between the superexchange electron coupling of the sensing unit after adsorbing gas and the direct electron coupling of the sensing unit without adsorbing gas is greater than 0. The functional group undergoes a coordination reaction with the metal center of the sensing unit; the polymer backbone is selected from one or more combinations of polydimethylsiloxane, polyethylene glycol, and polyethyleneimine; the functional group located at the end of the backbone is selected from cyano or alkynyl; the number average molecular weight of the polymer backbone is 890-5000 g / mol.

2. The gas sensing material with high adhesion according to claim 1, characterized in that, When the distance between the two molecules of the sensing unit is 0.7 nm, the difference between the superexchange electronic coupling of the sensing unit after adsorbing gas and the direct electronic coupling of the sensing unit without adsorbing gas is greater than 4.

3. A gas sensor, comprising a nanoribbon array, a supporting substrate, and a detection electrode, characterized in that, The nanoribbon array is prepared from the highly adhesive gas sensing material as described in any one of claims 1-2.

4. The gas sensor according to claim 3, characterized in that, The nanoribbon array comprises multiple oriented nanoribbons, each nanoribbon having a height of 60-80 nm, a width of 1-2 μm, and a distance of 9-11 μm between adjacent nanoribbons.

5. The gas sensor according to any one of claims 3-4, characterized in that, The sensor has a detection limit of 50 ppm or lower, a response time of 11 seconds or lower, and a recovery time of 19 seconds or lower.

6. The use of the gas sensor according to any one of claims 3-5, characterized in that, This is used to detect volatile organic compounds, including ethanol, methanol, acetone, acetonitrile, dichloromethane, chloroform, tetrahydrofuran, formaldehyde, hexane, and diethyl ether.

7. The use of the gas sensor according to claim 6, characterized in that, Used for indoor toxic gas detection, factory flammable and explosive gas detection, and food spoilage or freshness detection.

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