Covalent superlattice material and preparation method and application thereof

Abstract

The invention belongs to the field of semiconductor materials, and relates to a covalent superlattice material and a preparation method and application thereof.The covalent superlattice material comprises an inorganic metal sulfide layer and an organic molecular layer, the organic molecular layer is composed of organic molecules, the inorganic metal sulfide layer comprises a central metal atom A and a coordination atom sulfur, and the central metal atom A is a metal atom. Sulfur atoms are connected with a central metal atom A to form twisted tetrahedral structures, and all the tetrahedral structures are mutually connected in a common-edge and common-vertex manner to form an infinitely extending {AS} n inorganic metal chalcogenide layer; carbon atoms in the organic molecular layer can be covalently connected with sulfur atoms and can be suspended on the two sides of the {AS} n inorganic metal chalcogenide layer to form a structural repeating unit, and the structural repeating units are alternately connected through carbon-sulfur covalent bonds, so that a covalent superlattice structure is formed; the central metal atom A is selected from one or more of Ag, Cu or Pb, and the organic molecule is selected from benzene and / or biphenyl. The preparation method is simple.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials, and relates to a covalent superlattice material, its preparation method, and its application. Background Technology

[0002] The basis of chemiluminescence (CMR) gas sensors lies in the semiconductor properties of the materials. The formula for calculating the gas response of a CMR gas sensor is ΔR / R0. In practical applications, the resistance R0 of a CMR gas sensor changes with the external temperature. Therefore, temperature changes can lead to instability in the response of the CMR gas sensor. This may cause false alarms (incorrectly detecting non-existent gases) or missed alarms (failing to detect present gases) in practical applications. Such CMR gas sensors pose serious safety hazards when used in fields such as safety monitoring and environmental monitoring.

[0003] To mitigate the impact of temperature variations on the performance of chemiluminescence gas sensors, researchers employ various methods, such as temperature compensation techniques, designing sensor structures with temperature-adaptive characteristics, or integrating temperature sensors into the sensor system to monitor and adjust the temperature in real time. While these methods can offset the problems caused by temperature changes, they are complex to implement and costly.

[0004] Therefore, there is an urgent need to develop a simpler technology to eliminate the effects of temperature. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a covalent superlattice material, its preparation method, and its applications.

[0006] In a first aspect, the present invention provides a covalent superlattice material, the material comprising an inorganic metal sulfide layer and an organic molecular layer, wherein the organic molecular layer is composed of organic molecules, and the inorganic metal sulfide layer comprises a central metal atom A and coordinating sulfur atoms, the sulfur atoms being connected to the central metal atom A to form a twisted tetrahedral structure, each tetrahedral structure being interconnected by sharing edges and vertices to form an infinitely extending {AS}. n Inorganic metal sulfide layer; the molar ratio of the central metal atom A to sulfur atoms is 1:1;

[0007] The carbon atoms in the organic molecule can be covalently linked to sulfur atoms and suspended in {AS} n The two sides of the inorganic metal sulfide layer form a repeating structural unit, and the repeating structural units are alternately connected by carbon-sulfur covalent bonds, thus forming a covalent superlattice structure.

[0008] According to an embodiment of the present invention, the central metal atom A is selected from one or more of Ag, Cu or Pb, and the organic molecule is selected from benzene and / or biphenyl.

[0009] As an example, the central metal atom A is Ag, and the organic molecule is benzene.

[0010] According to an embodiment of the present invention, the covalent superlattice material is a crystalline material.

[0011] According to an embodiment of the present invention, the covalent superlattice material is a nanosheet.

[0012] According to an embodiment of the present invention, the thickness of the nanosheet is 3-6 nm, preferably 4-5 nm.

[0013] As an example, the molecular formula of the covalent superlattice material is C0. 12 H8Ag4S4, C 12 H8Ag4S4 crystal belongs to the monoclinic crystal system, and its space group is P21 / c. α=γ=90.0000°, β=104.0200°, Z = 1.

[0014] According to an embodiment of the present invention, the C 12 H8Ag4S4 crystal has a unit cell structure as shown in Formula I:

[0015]

[0016] Secondly, the present invention also provides a method for preparing the covalent superlattice material as described above, comprising the following steps:

[0017] The covalent superlattice material is obtained by mixing a salt solution of the central metal atom A with a solution of sulfur-substituted organic molecules and reacting at a temperature of 70–200 °C for 20–100 h.

[0018] According to an embodiment of the present invention, the mixing adopts a mixing method commonly used in the art, such as ultrasonic mixing or stirring mixing.

[0019] According to an embodiment of the present invention, the degree of substitution in the sulfur-substituted organic molecule is 1-3, preferably 1-2.

[0020] According to an embodiment of the present invention, the molar ratio of the central metal atom A to the organic molecule is 1:1-5, preferably 1:1.

[0021] According to an embodiment of the present invention, the reaction temperature is 80 to 160°C, for example, 85°C, 120°C, 150°C, or 160°C.

[0022] According to an embodiment of the present invention, the reaction time is 20 to 90 hours, for example, 24 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, or 96 hours.

[0023] According to an embodiment of the present invention, mixing a salt solution of a central metal atom A with a solution of a sulfur-substituted organic molecule comprises the following steps: dissolving the salt of the central metal atom A in a first solvent to obtain solution a; dissolving the sulfur-substituted organic molecule in a second solvent and then adding it to solution a and mixing.

[0024] According to an embodiment of the present invention, the first solvent is a good solvent of a salt of the central metal atom A, preferably an organic solvent or an inorganic solvent, such as water or N,N-dimethylformamide.

[0025] According to an embodiment of the present invention, the second solvent is a good solvent for sulfur-substituted organic molecules, such as N,N-dimethylformamide.

[0026] As an example, the method for preparing the superlattice crystal includes the following steps:

[0027] s1. Dissolve AX and NX in a first solvent to obtain solution a. Dissolve the sulfur-substituted organic molecule in a second solvent to obtain solution b. Add solution a dropwise to solution b until a transparent solution is obtained. N is an alkali metal element, such as Na or K, and X is a halogen element, such as F, Cl, Br or I.

[0028] s2. Add HX to the transparent solution until it turns into a white turbid liquid. React the white turbid liquid at a temperature of 120-180℃ for 80-100 hours to obtain a covalent superlattice single crystal material.

[0029] According to an embodiment of the present invention, the X in AX and HX may be the same or different, for example, the same.

[0030] According to an embodiment of the present invention, after the reaction in step s2, the following step is further included: cooling the reaction solution to 20-40°C, preferably to 25-30°C.

[0031] According to an embodiment of the present invention, the cooling is performed using programmed cooling, and the rate of programmed cooling is 1 to 10 °C / h, for example, 5 °C / h.

[0032] According to an embodiment of the present invention, after cooling, the following steps are further included: washing the cooled product to obtain a covalent superlattice single crystal material.

[0033] As an example, the preparation method of the nanosheet material includes the following steps:

[0034] The salt of the central metal atom A is dissolved in the first solvent to obtain solution a. The sulfur-substituted organic molecule is dissolved in the second solvent to obtain solution b. Solution b is added to solution a and mixed. The mixture is reacted at a temperature of 80-100℃ for 20-40 hours to obtain covalent superlattice nanosheets.

[0035] According to an embodiment of the present invention, the mixing is ultrasonic mixing, and the ultrasonic mixing time is 10 to 40 minutes, for example, 30 minutes.

[0036] According to an embodiment of the present invention, after the reaction is complete, the following step is further included: rinsing the reaction precipitate with anhydrous ethanol to obtain covalent superlattice nanosheets.

[0037] Thirdly, the present invention also provides an application of the covalent superlattice material as described above in a sensor, the sensor including a chemielectric gas sensor and a photoelectric sensor, for example a chemielectric gas sensor.

[0038] Fourthly, the present invention also provides a resistive gas sensor, the sensor comprising the covalent superlattice material as described above.

[0039] According to an embodiment of the present invention, the sensor includes an electrode coated with a covalent superlattice material nanosheet, preferably the central region of the electrode is coated with a covalent superlattice material.

[0040] Fifthly, the present invention provides an application of the above-mentioned chemical resistance gas sensor in gas detection.

[0041] According to an embodiment of the present invention, the gas is selected from NO2, acetone, or H2S, for example, NO2.

[0042] A method for detecting gas using a chemiluminescence resistivity gas sensor includes the following steps:

[0043] A voltage is applied to the sensor and the gas to be measured is introduced, and the change in the sensor's current is detected.

[0044] According to an embodiment of the present invention, before introducing the gas to be measured into the sensor, the following steps are further included: after stabilizing the current in an air atmosphere at different temperatures, the gas to be measured with a determined concentration is introduced into the sensor, and the corresponding current is tested. After the current stabilizes again, the photocurrent signal in the gas atmosphere is tested under a certain light intensity. Then, the light source is removed and air is introduced to restore the baseline, forming a ratio test cycle, wherein the ratio is Ratio gas / light =I g / Ip , where I g It is the current I when exposed to the gas being measured. p It is the electric current under light.

[0045] According to an embodiment of the present invention, after detecting the current change of the sensor, the method further includes the following step: calculating the ratio of the sensor.

[0046] Beneficial effects

[0047] 1) This invention obtains a covalent superlattice material by mixing a salt solution of the central metal atom A with a solution of sulfur-substituted organic molecules and reacting at a temperature of 70–200°C for 20–100 h. The preparation method is relatively simple, and the obtained covalent superlattice material has semiconductor properties and different responsiveness to different gases, such as good selectivity for nitrogen dioxide.

[0048] 2) This invention first proposes the concept of ratio gas sensing, which is the I obtained from the gas sensing response. g Value and photoelectric response value I under atmospheric conditions p The influence of baseline current is eliminated by phase division. This reduces the problem of large coefficient of variation (CV) caused by different operating temperatures. We used AgBDT, a covalent superlattice material with excellent photoelectric response and ultra-high sensitivity to NO2, as the sensing material and tested the CV value for 10ppm NO2 at different temperatures. We found that from 25 to 65 degrees Celsius, the CV value of its gas-sensing response decreased from 21.81% to 7.81% for ratiometric gas sensing. This meets the requirement of a CV value of less than 10% in practical applications. Attached Figure Description

[0049] Figure 1 The image shows the crystal structure of the covalent superlattice single crystal prepared in Example 1.

[0050] Figure 2 Scanning electron microscope image of the covalent superlattice nanosheets prepared in Example 2.

[0051] Figure 3 An atomic force microscope image of the covalent superlattice nanosheets prepared in Example 2.

[0052] Figure 4 The PXRD pattern of the covalent superlattice nanosheets prepared in Example 2.

[0053] Figure 5 These are IV curves at different temperatures in Example 3.

[0054] Figure 6 This is a comparison chart of the sensor's response values ​​to different atmospheres in Example 4.

[0055] Figure 7 This is the It curve of the sensor for nitrogen dioxide at different concentrations in Example 4.

[0056] Figure 8 This is the IV curve of the test sample in Example 5 under light and dark conditions.

[0057] Figure 9 This is the It curve of the sensor in Example 5.

[0058] Figure 10 The response graphs are for the ratio gas sensitivity test of 10 ppm nitrogen dioxide at different temperatures in Example 6. Detailed Implementation

[0059] The method and application of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0060] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0061] Example 1

[0062] This embodiment provides a method for synthesizing a covalent superlattice crystal material, the specific steps of which are as follows:

[0063] The preparation of covalent superlattice (AgBDT, BDT = 1,4-benzenedithiol) crystal materials includes the following steps:

[0064] a. Take 3 mL of N,N-dimethylformamide, then dissolve 0.2490 g KI and 0.1175 g AgI in the solvent, and stir with a magnetic stirrer for 30 min at room temperature until completely dissolved;

[0065] b. Take 2 mL of N,N-dimethylformamide, then dissolve 0.2130 g of BDT in the solvent, and sonicate for 5 min to completely dissolve it to obtain a BDT solution;

[0066] c. Add the BDT solution from step b dropwise to the solution in step a while stirring, to obtain a clear solution;

[0067] d. Transfer the solution from step c to a glass bottle, and add 0.5 mL of hydroiodic acid dropwise while stirring. The transparent solution gradually turns into a white turbid liquid. Place it in a convection oven at 150°C and react for 96 h. Then, use a programmed cooling method to reduce the temperature to 30°C at a rate of 5°C / h before removing it.

[0068] e. The product in the glass bottle from step d is washed three times with anhydrous ethanol by centrifugation to remove unreacted ligands, yielding granular single crystals (AgBDT).

[0069] Example 2

[0070] The example provides a method for synthesizing covalent superlattice (AgBDT) nanosheets, comprising the following steps:

[0071] a. First, weigh 0.0568g of BDT, then dissolve it in 15mL of N,N-dimethylformamide and sonicate for 2 minutes to dissolve it completely;

[0072] b. Weigh out 0.017g AgNO3 and dissolve it in 15mL of deionized water;

[0073] Add the solution from step b to step a, and sonicate for 30 minutes to mix thoroughly, resulting in a yellow suspension. After sonication, place the suspension in an 85°C oven for 24 hours. After the reaction, wash the precipitate with anhydrous ethanol; a distinct silky appearance can be observed. The scanning electron microscope (SEM) image is shown below. Figure 2 As shown, thin nanosheets can be observed; their atomic force microscopy (AFM) measurements are as follows: Figure 3 As shown, the AgBDT nanosheets dispersed in ethanol have a thickness of approximately 4-5 nm, meeting the requirements for ultrathin nanosheets. Their PXRD (powder X-ray diffraction) pattern is shown below. Figure 4 As shown, this proves that AgBDT was successfully synthesized.

[0074] In Examples 3-6 below, the nanosheets prepared in Example 2 were used as powder samples to prepare sensors.

[0075] Example 3

[0076] This embodiment provides a method for testing the semiconductor performance of a covalent superlattice material, including the following steps:

[0077] a. The conductivity of the powder tablets was tested using a two-electrode method. Before testing the conductivity of AgBDT, the powder sample was first pressed into a circular tablet with a diameter of 2.50 mm. The thickness of the tablet was controlled by the amount of sample added. Then, the sample was placed in a plastic sealing tape, and the thickness of the tablet was recorded after the tape was peeled off using vernier calipers. Silver paste and gold wire (50 μm in diameter) were used as electrodes. The sample was removed and fixed on a glass slide to prevent the electrodes from falling off.

[0078] b. The IV curves of the sample at different temperatures were measured using a Keithley 4200, and the test results are as follows: Figure 5 As shown.

[0079] Figure 5The test measured the current-voltage (IV) plots at different temperatures. The resistance at different temperatures can be calculated using the IV plots. The results show that the resistance decreases as the temperature increases, indicating that the material exhibits semiconductor properties.

[0080] Example 4

[0081] This invention uses the covalent superlattice material prepared in Example 2 to fabricate a chemielectric gas sensor and performs gas-sensing testing. The specific preparation and detection methods are as follows:

[0082] a. Place 10 mg of AgBDT nanosheet powder from Example 2 in a mortar, add isopropanol and grind the sample into a suspension;

[0083] b. Using a pipette, drop the AgBDT suspension from step a onto the central region of a silver-palladium interdigitated electrode based on Al2O3. Connect the two ends of the interdigitated electrode with gold wires using silver paste, and then place it in a vacuum oven at 60°C overnight to dry for gas detection.

[0084] c. Connect the sensor to the Keithley power meter. During testing, apply a DC voltage to the sensor using the power meter and collect the current changes in real time.

[0085] d. First, dry air is purged to remove impurities and other potentially adsorbed gas molecules from the material surface; different gases (NO2, EtOH, acetone, ET3N, C6H6, C2H2, CH4, NH3, C2H4, H2, CO, CO2, H2S) are introduced into the device, and the changes in current signals under different atmospheres are recorded. The response value is then calculated using the formula: Reply = I g / I0–1 calculates the response under different atmospheres. For example... Figure 6 As shown, the material exhibits good selectivity for nitrogen dioxide.

[0086] g. Connect the chemiluminescence resistive sensor to a power source and apply a 5V voltage to detect nitrogen dioxide at different concentrations. Test the changes in the current signal under different concentrations of nitrogen dioxide atmosphere, such as... Figure 7 As shown, when the concentration of nitrogen dioxide is 10 ppm, the response value to nitrogen dioxide is as high as 14055%.

[0087] Example 5

[0088] This embodiment provides a covalent superlattice material for photoelectric testing, and the specific steps are as follows:

[0089] a. The electrode was prepared using the same method as in step ab of Example 4;

[0090] b. Before performing the photoelectric test, transfer the electrodes to the probe stage, press the two probes onto the two ends of the interdigital electrode respectively, set the voltage range for measurement to -5V to 5V, and the measurement results are as follows. Figure 8 As shown, the current and voltage exhibit a linear relationship under both light and dark conditions, indicating that the contact between the sample and the electrode is an ohmic contact.

[0091] c. Connect the electrodes to a Keithley source meter and test using a constant voltage of 5V, while simultaneously acquiring real-time current changes. Infrared light is filtered out during the test, and the light source is switched on and off every 30 seconds. The sensor's It curve is shown below. Figure 9 As shown, at a power of 55mW / cm 2 Under light irradiation at a wavelength of 475nm, the photocurrent on / off ratio is 1756.

[0092] Example 6

[0093] This embodiment provides a covalent superlattice material for ratio gas sensing, and the specific steps are as follows:

[0094] a. Place 10 mg of AgBDT nanosheet powder from Example 2 in a mortar, add isopropanol and grind the sample into a suspension;

[0095] b. Drop the suspension onto the silver-palladium interdigitated electrode, connect the two ends of the interdigitated electrode with gold wire using silver paste, and then place it in a vacuum oven at 60°C overnight to dry for gas detection.

[0096] c. Connect the electrodes to a Keithley source meter. During testing, apply a DC voltage to the device using the source meter and collect the current changes in real time. First, purge with dry air to remove impurities and other gas molecules that may be adsorbed onto the material surface;

[0097] d. Connect the chemical resistance gas sensor to a power source and apply a constant voltage of 5V. Detect 10ppm nitrogen dioxide at different temperatures. The testing principle is as follows: first, stabilize the current in an air atmosphere; then, introduce nitrogen dioxide gas and, after the current stabilizes again, turn on the xenon lamp and test the photocurrent signal under the nitrogen dioxide atmosphere; finally, turn off the xenon lamp and introduce air to restore the baseline to its original level. This constitutes a complete cycle for ratio testing.

[0098] The definition of a ratio is Ratio gas / light =I g / I p , where I g It is the current I when exposed to a gaseous analyte. p It is the electric current under light;

[0099] e. The response of the device to a ratiometric gas sensor at 10 ppm nitrogen dioxide was tested at different temperatures, such as... Figure 10 As shown, the CV value of the ratio gas sensor is only 7.81% compared to the CV value of the gas-sensitive response (21.81%).

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A covalent superlattice material, characterized in that, The material comprises an inorganic metal sulfide layer and an organic molecular layer. The organic molecular layer is composed of organic molecules. The inorganic metal sulfide layer includes a central metal atom A and coordinating sulfur atoms. The sulfur atoms are connected to the central metal atom A to form a twisted tetrahedral structure. Each tetrahedral structure is interconnected by sharing edges and vertices to form an infinitely extending {AS}. n Inorganic metal sulfide layer; The carbon atoms in the organic molecule can be covalently linked to sulfur atoms and suspended in {AS} n The inorganic metal sulfide layer has a repeating structural unit on both sides, and the repeating structural units are alternately connected by carbon-sulfur covalent bonds to form a covalent superlattice structure; the central metal atom A is selected from one or more of Ag, Cu or Pb, and the organic molecule is selected from benzene and / or biphenyl.

2. The covalent superlattice material according to claim 1, characterized in that, The molar ratio of the central metal atom A to sulfur atoms is 1:

1.

3. The covalent superlattice material according to claim 1, characterized in that, The molecular formula of the covalent superlattice material is Ci 12 H8Ag4S4, C 12 H8Ag4S4 crystal belongs to the monoclinic crystal system, and its space group is P21 / c. α=γ=90.0000°, β=104.0200°, Z = 1. Preferably, the C 12 H8Ag4S4 crystal has a unit cell structure as shown in Formula I:

4. A method for preparing a covalent superlattice material according to any one of claims 1-3, characterized in that, The method includes the following steps: The covalent superlattice material is obtained by mixing a salt solution of the central metal atom A with a solution of sulfur-substituted organic molecules and reacting at a temperature of 70–200 °C for 20–100 h. Preferably, the degree of substitution in the sulfur-substituted organic molecule is 1-3.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the central metal atom A to the organic molecule is 1:1-5. Preferably, the reaction temperature is 80–160°C, and the reaction time is 20–90 h. Preferably, mixing the salt solution of the central metal atom A with the solution of the sulfur-substituted organic molecule comprises the following steps: dissolving the salt of the central metal atom A in a first solvent to obtain solution a; dissolving the sulfur-substituted organic molecule in a second solvent and then adding it to solution a and mixing.

6. The preparation method according to claim 4, characterized in that, The method for preparing the superlattice crystal includes the following steps: s1. Dissolve AX and NX in a first solvent to obtain solution a. Dissolve the sulfur-substituted organic molecule in a second solvent to obtain solution b. Add solution a dropwise to solution b until a transparent solution is obtained. N is an alkali metal element, such as Na or K, and X is a halogen element, such as F, Cl, Br or I. s2. Add HX to the transparent solution until it turns into a white turbid liquid. React the white turbid liquid at a temperature of 120-180℃ for 80-100 hours to obtain a covalent superlattice single crystal material. Preferably, after the reaction in step s2, the reaction solution is further cooled to 20–40°C. Preferably, the cooling process uses programmed cooling, and the rate of programmed cooling is 1 to 10 °C / h. According to an embodiment of the present invention, after cooling, the following steps are further included: washing the cooled product to obtain a covalent superlattice single crystal material.

7. The preparation method according to claim 4, characterized in that, The method for preparing the superlattice crystal includes the following steps: The salt of the central metal atom A is dissolved in the first solvent to obtain solution a. The sulfur-substituted organic molecule is dissolved in the second solvent to obtain solution b. Solution b is added to solution a and mixed. The mixture is reacted at a temperature of 80-100℃ for 20-40 hours to obtain covalent superlattice nanosheets. Preferably, the mixing is ultrasonic mixing, and the ultrasonic mixing time is 10 to 40 minutes.

8. A resistive gas sensor, the sensor comprising the covalent superlattice material according to any one of claims 1-3 or the covalent superlattice material prepared by the method according to any one of claims 4-7. Preferably, the sensor includes an electrode coated with a covalent superlattice material nanosheet, and more preferably, the central region of the electrode is coated with a covalent superlattice material.

9. An application of the chemical resistance gas sensor of claim 8 in gas detection. Preferably, the gas is selected from NO2, acetone, or H2S, for example, NO2.

10. A method for detecting gas using a chemiluminescence resistivity gas sensor, comprising the following steps: A voltage is applied to the sensor as described in claim 8, and the gas to be measured is introduced to detect the change in the sensor's current. Preferably, before introducing the gas to be measured into the sensor, the following steps are further included: after stabilizing the current in an air atmosphere at different temperatures, a gas of a determined concentration is introduced into the sensor to test the corresponding current. After the current stabilizes again, the photocurrent signal in the gas atmosphere is tested under a certain light intensity. Then, the light source is removed and air is introduced to restore the baseline, forming a ratio test cycle, wherein the ratio is Ratio gas / light =I g / I p ,in, I g It is the current I when exposed to the gas being measured. p It is the electric current under light. Preferably, after detecting the current change of the sensor, the method further includes the following step: calculating the sensor ratio.

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