Method for detecting trace p-xylene gas based on HKUST-1 modified terahertz metasurface sensor

Abstract

The invention relates to the technical field of terahertz sensing, and discloses a method for detecting trace p-xylene gas based on an HKUST-1 modified terahertz metasurface sensor. The method comprises the following steps: modifying the surface of a sensor with HKUST-1, placing the modified sensor in a gas chamber, testing the terahertz spectrum of the modified sensor in a no-load state, introducing paraxylene gas with different concentrations into the gas chamber, and collecting response spectrums with different concentrations by using a spectrum system; further, comparing the terahertz spectrum in the no-load state with the response spectrum, and establishing a relational expression according to the frequency shift amount of the spectrum; furthermore, according to the operation method, the selectivity of the sensor is verified by comparing response spectrums of the sensor to other types of gas samples with the same concentration. The method for detecting trace p-xylene gas based on the HKUST-1 modified metasurface sensor is simple to operate at room temperature, and has important application value in the field of sensitive and selective p-xylene gas detection.

Description

Technical Field

[0001] The invention relates to the field of terahertz sensing technology, and in particular to a method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1. Background Art

[0002] Terahertz (THz) waves are electromagnetic waves between microwaves and infrared. They have the advantages of wide frequency band (0.1-10THz), low energy, no ionizing radiation, and sensitivity to biomacromolecules. They can be applied to broadband wireless communications, nondestructive testing, biomedical sensing and other fields. Metamaterials are artificially designed new materials with special electromagnetic properties. They can achieve negative refractive index, super-resolution optical imaging and electromagnetic stealth. Two-dimensional metamaterials are also called metasurfaces. Compared with traditional refractive index optical devices, metasurface devices have the characteristics of multi-function, ultra-thinness and easy integration. Combining metasurfaces with terahertz waves is an effective way to improve detection sensitivity. The enhancement of the local electric field on the terahertz metasurface will improve the detection sensitivity because the change of the dielectric constant around the sensor will lead to changes in the resonant frequency and quality factor (Q).

[0003] Many volatile organic compounds are harmful to the human body, such as paraxylene. The National Institute for Occupational Safety and Health (NIOSH) recommends that the long-term exposure limit for paraxylene is 100 ppm. In addition, paraxylene is detected in the exhaled gas and urine volatiles of cancer patients and is an important marker for lung cancer and prostate cancer-related diseases. Therefore, detecting the concentration of paraxylene is of great significance in many fields.

[0004] HKUST-1 is a metal organic framework (MOF) material with the chemical formula of Cu 3 (BTC) 2 BTC stands for 1,3,5-benzenetricarboxylic acid ligand. HKUST-1 is composed of copper ions (Cu 2+ ) units and benzene ring structures. Due to the electrostatic attraction of copper ions and the similar solubility of benzene ring structures, it has a good adsorption effect on p-xylene molecules and is suitable for the adsorption storage and high-sensitivity sensing of p-xylene gas. Summary of the invention

[0005] The purpose of the present invention is to provide a method for detecting trace amounts of p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1, aiming to solve the technical problems of the prior art such as complex operation, harsh detection conditions and low sensitivity.

[0006] To achieve the above object, the present invention adopts a method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1, comprising the following steps:

[0007] HKUST-1 was modified onto the surface of the metasurface sensor;

[0008] Place the modified sensor in the air chamber;

[0009] Test the terahertz spectrum of the modified sensor when it is unloaded;

[0010] Different concentrations of p-xylene gas were introduced into the gas chamber, and the response spectra of different concentrations were collected using a terahertz spectroscopy system;

[0011] The terahertz spectrum of the modified sensor when unloaded is compared with the response spectrum to obtain the frequency shift of each resonance peak, establish a relationship between the frequency shift and the concentration of p-xylene gas, and calculate the concentration of p-xylene gas;

[0012] The sensor was used to test the response spectra of other types of gas samples with the same concentration, and its ability to selectively identify paraxylene gas was verified by comparison.

[0013] The HKUST-1 serves as a bridge between the terahertz metasurface sensor and the paraxylene gas, providing highly sensitive quantitative analysis through the terahertz metasurface sensor and providing selective identification capability through HKUST-1; the HKUST-1 modified on the sensor surface is used to capture the paraxylene gas molecules, thereby causing the frequency shift of the sensor's response spectrum; the frequency shift of the resonance peak is obtained by comparing the terahertz spectrum of the modified sensor when unloaded and the response spectrum of paraxylene gas of different concentrations, a relationship between the frequency shift and the concentration of paraxylene gas is established, and the concentration of paraxylene gas is calculated. The response spectra of other types of gas samples of the same concentration are tested with the sensor, and it is verified by comparison that it can selectively identify paraxylene gas. The method for detecting trace amounts of paraxylene gas based on a terahertz metasurface sensor modified with HKUST-1 is a method for detecting trace amounts of paraxylene gas with simple operation, high sensitivity and selectivity at room temperature. Among them, the process of modifying HKUST-1 to the surface of the metasurface sensor includes the following steps:

[0014] Before modification, the surface of the metasurface sensor was ultrasonically cleaned with anhydrous ethanol for 5 min and then dried with nitrogen;

[0015] The APTES solution was added dropwise onto the surface of the dried metasurface sensor using a micropipette and allowed to stand at room temperature for 20 minutes to activate it;

[0016] The HKUST-1 suspension was dropped onto the activated metasurface sensor surface using a micropipette and then dried in a constant temperature drying oven at 100°C for 30 minutes.

[0017] In the process of modifying HKUST-1 onto the surface of the supersurface sensor, the volume ratio of APTES to anhydrous ethanol is 2%, and the amount used is 25 μl.

[0018] In the process of modifying HKUST-1 onto the surface of the metasurface sensor, the amount of HKUST-1 suspension is 60 μl, and the preparation steps of the suspension are as follows:

[0019] 0.5 mg of HKUST-1 powder was added to 0.5 ml of methanol and allowed to stand for 20 minutes;

[0020] Add 0.5 ml of deionized water to the above mixture;

[0021] The suspension was prepared after 10 minutes of ultrasonic shaking.

[0022] In the process of placing the modified sensor in the air chamber, the air chamber is set in the optical path of the terahertz time-domain spectroscopy system. The air chamber has an air inlet and an air outlet. The gas flow rate is controlled by a gas flow controller (MFC) at a flow rate of 0.8L / minute.

[0023] Wherein, in the process of testing the terahertz spectrum and of the modified sensor when unloaded, their terahertz time domain spectrum is first tested, and then the corresponding frequency domain spectrum is obtained by fast Fourier transform.

[0024] Among them, different concentrations of p-xylene gas are introduced into the gas chamber, and the response spectra of different concentrations are collected by a terahertz spectroscopy system. The concentration of p-xylene gas is set to six concentration gradients of 1ppm, 10ppm, 30ppm, 50ppm, 70ppm, and 100ppm.

[0025] The method of comparing the terahertz spectrum of the modified sensor when unloaded with the response spectrum to obtain the frequency shift of each resonance peak and then establishing a relationship between the frequency shift and the concentration of p-xylene gas comprises the following steps:

[0026] The terahertz frequency domain spectrum of each concentration is subtracted from the terahertz frequency domain spectrum of the sensor when it is unloaded, and the frequency shift of the resonance peak corresponding to the different concentrations of p-xylene gas is obtained;

[0027] A relationship between the frequency shift and the concentration of p-xylene gas is established, and the concentration of p-xylene gas is calculated using the relationship.

[0028] The sensor was used to test the response spectra of other types of gas samples of the same concentration, and its ability to selectively identify paraxylene gas was verified by comparison. The other types of gas samples were ethylbenzene, ethanol, acetone, hexanal, and ethyl acetate, and the concentration of the gas samples was 100 ppm.

[0029] The present invention provides a method for detecting trace amounts of paraxylene gas based on a terahertz metasurface sensor modified with HKUST-1, which detects trace amounts of paraxylene gas with high specificity and high sensitivity by modifying a metal organic framework material HKUST-1 on the surface of a high-sensitivity terahertz metasurface sensor. First, HKUST-1 is modified onto the surface of the metasurface sensor; then, the modified sensor is placed in an air chamber provided in an optical path system, and the terahertz spectrum of the modified sensor when unloaded is tested as a reference; HKUST-1 is used as a specific adsorption layer to specifically capture paraxylene gas molecules, and by increasing the concentration of paraxylene gas, the frequency shift of the spectrum changes, thereby judging the concentration of paraxylene gas. By comparing the terahertz spectrum of the modified sensor when unloaded with the response spectrum, the frequency shift of each resonance peak is obtained.

[0030] The relationship between the frequency shift and the concentration of p-xylene gas is established, and the concentration of p-xylene gas is calculated. Finally, the sensor is used to test the response spectra of other types of gas samples with the same concentration, and the comparison verifies that it can selectively identify p-xylene gas. This method has the advantages of simple and convenient operation, high sensitivity and good specificity, and solves the problems of complex operation and low sensitivity in the existing p-xylene gas detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a schematic diagram of the detection principle of a method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1 according to the present invention;

[0033] Figure 2 This is a specific operation flow chart of a method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1 according to the present invention;

[0034] Figure 3 is a schematic diagram of a gas detection spectrum system in a specific embodiment of the present invention;

[0035] Figure 4 is a response spectrum diagram of the sensor to different p-xylene gas concentrations in a specific embodiment of the present invention;

[0036] Figure 5 is a fitting diagram for calculating the concentration of p-xylene in a specific embodiment of the present invention;

[0037] Figure 6 It is a response spectrum diagram of the sensor to other gases of the same concentration in a specific embodiment of the present invention.

[0038] Numbers in the figure: 1. metasurface sensor, 2. gas chamber, 3. gas flow controller (MFC), 4. paraxylene gas sample, 5. other types of gas samples, 6. gas recovery device, 7. terahertz transmitting end, 8. terahertz detecting end, 9. lens, 10. control end. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0040] See also Figure 2 The present invention provides a method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1, comprising the following steps:

[0041] S11: Modification of HKUST-1 onto the surface of metasurface sensor;

[0042] S12: placing the modified sensor in the air chamber;

[0043] S13: Test the terahertz spectrum of the modified sensor when it is unloaded;

[0044] S14: passing p-xylene gas of different concentrations into the gas chamber, and collecting response spectra of different concentrations using a terahertz spectroscopy system;

[0045] S15: comparing the terahertz spectrum of the modified sensor when unloaded with the response spectrum to obtain the frequency shift of each resonance peak, establishing a relationship between the frequency shift and the concentration of p-xylene gas, and calculating the concentration of p-xylene gas;

[0046] S16: Use the sensor to test the response spectra of other types of gas samples of the same concentration, and verify through comparison that it can selectively identify p-xylene gas.

[0047] The process of modifying HKUST-1 onto the surface of the metasurface sensor comprises the following steps:

[0048] S21: Before modification, the surface of the metasurface sensor was ultrasonically cleaned with anhydrous ethanol for 5 minutes and then dried with nitrogen;

[0049] S22: using a micropipette, 25 μl of the APTES solution is added dropwise onto the surface of the dried metasurface sensor, and the solution is left to stand at room temperature for 20 minutes to activate the sensor;

[0050] S23: Use a micropipette to drop 60 μl of HKUST-1 suspension onto the activated metasurface sensor surface, and then dry it in a constant temperature drying oven at 100°C for 30 minutes.

[0051] In the process of modifying HKUST-1 onto the surface of the metasurface sensor, it is necessary to first prepare an APTES solution and a HKUST-1 suspension, wherein the volume ratio of APTES to anhydrous ethanol is 2%.

[0052] In the process of modifying HKUST-1 onto the surface of the metasurface sensor, it is necessary to first prepare an APTES solution and a HKUST-1 suspension, wherein the steps for preparing the HKUST-1 suspension are as follows:

[0053] S101: 0.5 mg of HKUST-1 powder was added to 0.5 ml of methanol and allowed to stand for 20 minutes;

[0054] S102: Add 0.5 ml of deionized water to the mixture of HKUST-1 and methanol;

[0055] S103: After ultrasonic vibration for 10 minutes, the preparation of HKUST-1 suspension is completed.

[0056] The process of placing the modified sensor in the air chamber includes the following steps:

[0057] S31: placing the gas cell on the optical path of the terahertz time-domain spectroscopy system;

[0058] S32: The gas chamber is provided with an air inlet and an air outlet, and the sample gas is introduced from the air inlet to purge the surface of the sensor fixed in the gas chamber and then flows out from the air outlet;

[0059] S33: Control the flow rate of the sample gas with a gas flow controller (MFC) to a flow rate of 0.8 L / min. The process of testing the terahertz spectrum of the modified sensor when it is unloaded includes the following operations:

[0060] S41: Test their terahertz time-domain spectroscopy.

[0061] S42: Obtain the corresponding frequency domain spectrum through fast Fourier transform.

[0062] Among them, different concentrations of p-xylene gas are introduced into the gas chamber, and the response spectra of different concentrations are collected by a terahertz spectroscopy system, wherein the concentration of p-xylene gas is set to six concentration gradients of 1ppm, 10ppm, 30ppm, 50ppm, 70ppm, and 100ppm.

[0063] The step of comparing the terahertz spectrum of the modified sensor when it is unloaded with the response spectrum to obtain the frequency shift of each resonance peak, and then establishing a relationship between the frequency shift and the concentration of p-xylene gas, comprises the following steps:

[0064] S51: subtract the terahertz frequency domain spectrum of the sensor when it is unloaded from the terahertz frequency domain spectrum of each concentration to obtain the frequency shift of the resonance peak corresponding to the p-xylene gas with different concentrations;

[0065] S52: Establish a relationship between the frequency shift and the concentration of p-xylene gas, and use the relationship to calculate the concentration of p-xylene gas.

[0066] The sensor was used to test the response spectra of other types of gas samples of the same concentration, and its ability to selectively identify paraxylene gas was verified by comparison. The other types of gas samples were ethylbenzene, ethanol, acetone, hexanal, and ethyl acetate, and the concentration of the gas samples was 100 ppm.

[0067] The HKUST-1 is used as a bridge to connect the terahertz metasurface sensor and p-xylene gas, and the terahertz metasurface sensor provides highly sensitive quantitative analysis, and the HKUST-1 provides the sensor with selective identification capability; the HKUST-1 modified on the sensor surface is used to capture p-xylene gas molecules, thereby causing the sensor's response spectrum frequency shift; the frequency shift of the resonance peak is obtained by comparing the terahertz spectrum of the modified sensor when it is unloaded and the response spectrum of different p-xylene gas concentrations, and a relationship is established to calculate the concentration of p-xylene gas. The sensor is used to test the response spectra of other types of gas samples of the same concentration, and it is verified by comparison that it can selectively identify p-xylene gas. This method uses a metasurface sensor modified by HKUST-1, and by adsorbing p-xylene gas molecules on the sensor surface, amplifies the frequency shift of the resonance peak, and can detect trace amounts of p-xylene gas with high sensitivity and selectivity.

[0068] The present invention also proposes a specific embodiment:

[0069] A method for detecting trace amounts of p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1 in this embodiment comprises the following specific steps:

[0070] (1) The metasurface sensor was ultrasonically cleaned with anhydrous ethanol for 5 minutes and then dried with nitrogen.

[0071] (2) Preparation of HKUST-1 suspension: 0.5 mg of HKUST-1 powder was added to 0.5 ml of methanol and allowed to stand for 20 minutes; then 0.5 ml of deionized water was added to the mixture; and finally, the suspension was prepared after ultrasonic vibration for 10 minutes.

[0072] (3) Modifying HKUST-1 onto the sensor surface: using a micropipette, drop the APTES solution onto the above-mentioned dried metasurface sensor surface, and let it stand at room temperature for 20 minutes to activate it; using a micropipette, drop the HKUST-1 suspension onto the activated metasurface sensor surface, and then dry it in a constant temperature drying oven at 100°C for 30 minutes.

[0073] (3) Please refer to Figure 3 The modified sensor is placed in the air chamber shown in Figure 2. The air chamber is set in the optical path of the terahertz time-domain spectroscopy system. The spectroscopy system is composed of a terahertz transmitting end 7, a terahertz detection end 8, a lens 9, and a control end 10 as shown in the figure. The air chamber has an air inlet and an air outlet. The flow rate of the gas is controlled by a gas flow controller (MFC) 3 shown in the figure, and the flow rate is 0.8L / minute.

[0074] (4) Test the terahertz spectrum of the modified sensor when it is unloaded: The spectral signal is collected by Figure 3 As shown in 10, the control end controls, firstly tests its terahertz time domain spectrum, and then obtains the corresponding frequency domain spectrum through fast Fourier transform.

[0075] (5) Please refer to Figure 4 , p-xylene gas with six concentration gradients of 1ppm, 10ppm, 30ppm, 50ppm, 70ppm, and 100ppm was introduced into the gas chamber, and the response spectra of different concentrations were collected by the terahertz spectroscopy system. The terahertz spectrum of the sensor when it was unloaded was compared with the obtained response spectrum. Figure 4 Shown

[0076] (6) Please refer to Figure 5 , the terahertz spectrum of the modified sensor when unloaded is compared with the response spectrum to obtain the frequency shift of each resonance peak, and then establish a relationship between the frequency shift and the concentration of p-xylene gas; according to different p-xylene gas concentrations, the relationship between the frequency shift and the frequency shift is established as follows: Figure 5 As shown; the relationship obtained by linear fitting is: F = 0.0811 * C + 5.7170, R 2 = 0.9888, where F is the shift of the resonance frequency, C is the concentration of p-xylene gas, R 2 is a linear correlation.

[0077] (8) Please refer to Figure 6, the sensor was used to test the response spectra of other types of gas samples with the same concentration, where the other types of gas samples are: ethylbenzene, ethanol, acetone, hexanal, ethyl acetate, and the concentration of the gas samples is 100ppm. The obtained response spectrum is similar to the response spectrum of p-xylene gas at the same concentration. Figure 6 As shown, it is verified by comparison that it can selectively identify p-xylene gas.

[0078] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for detecting trace p-xylene gas based on a terahertz metasurface sensor modified with HKUST-1, characterized in that: The following steps are involved: HKUST-1 was modified onto the surface of the metasurface sensor; Place the modified sensor in the air chamber; Test the terahertz spectrum of the modified sensor when it is unloaded; Different concentrations of p-xylene gas were introduced into the gas chamber, and the response spectra of different concentrations were collected using a terahertz spectroscopy system; The terahertz spectrum of the modified sensor when unloaded is compared with the response spectrum to obtain the frequency shift of each resonance peak, establish a relationship between the frequency shift and the concentration of p-xylene gas, and calculate the concentration of p-xylene gas; The sensor was used to test the response spectra of other types of gas samples with the same concentration, and its ability to selectively identify paraxylene gas was verified by comparison.

2. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified by HKUST-1 according to claim 1, characterized in that: The process of modifying HKUST-1 onto the surface of the metasurface sensor comprises the following steps: Before modification, the surface of the metasurface sensor was ultrasonically cleaned with anhydrous ethanol for 5 min and then dried with nitrogen; The APTES solution was added dropwise onto the surface of the dried metasurface sensor using a micropipette and allowed to stand at room temperature for 20 minutes to activate it; The HKUST-1 suspension was dropped onto the activated metasurface sensor surface using a micropipette and then dried in a constant temperature drying oven at 100°C for 30 minutes.

3. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified by HKUST-1 according to claim 1, characterized in that: In the process of modifying HKUST-1 onto the surface of the supersurface sensor, the volume ratio of APTES to anhydrous ethanol is 2%, and the amount used is 25 μl.

4. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified by HKUST-1 according to claim 1, characterized in that: In the process of modifying HKUST-1 onto the surface of the metasurface sensor, the amount of HKUST-1 suspension is 60 μl, and the preparation steps of the suspension are as follows: 0.5 mg of HKUST-1 powder was added to 0.5 ml of methanol and allowed to stand for 20 minutes; Add 0.5 ml of deionized water to the above mixture; The suspension was prepared after ultrasonic shaking for 10 minutes.

5. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified by HKUST-1 according to claim 1, characterized in that: When the modified sensor is placed in the gas chamber, the gas chamber is set in the optical path of the terahertz time-domain spectroscopy system. The gas chamber has an air inlet and an air outlet. The flow rate of the gas is controlled by a gas flow controller (MFC) at a flow rate of 0.8 L / min.

6. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified by HKUST-1 according to claim 1, characterized in that: In the process of testing the terahertz spectrum of the modified sensors when unloaded, their terahertz time domain spectrum is first tested, and then the corresponding frequency domain spectrum is obtained by fast Fourier transform.

7. The method for detecting trace p-xylene gas based on HKUST-1 modified terahertz metasurface sensor according to claim 1, characterized in that: The p-xylene gas of different concentrations is introduced into the gas chamber, and the response spectra of different concentrations are collected by a terahertz spectroscopy system, wherein the concentration of the p-xylene gas is set to six concentration gradients of 1ppm, 10ppm, 30ppm, 50ppm, 70ppm, and 100ppm.

8. The method for detecting trace p-xylene gas based on HKUST-1 modified terahertz metasurface sensor according to claim 1, characterized in that: The method comprises comparing the terahertz spectrum of the modified sensor when it is unloaded with the response spectrum to obtain the frequency shift of each resonance peak, and then establishing a relationship between the frequency shift and the concentration of p-xylene gas, including the following steps: The terahertz frequency domain spectrum of each concentration is subtracted from the terahertz frequency domain spectrum of the sensor when it is unloaded, and the frequency shift of the resonance peak corresponding to the different concentrations of p-xylene gas is obtained; A relationship between the frequency shift and the concentration of p-xylene gas is established, and the concentration of p-xylene gas is calculated using the relationship.

9. The method for detecting trace p-xylene gas based on the terahertz metasurface sensor modified with HKUST-1 according to claim 1, characterized in that: The sensor was used to test the response spectra of other types of gas samples of the same concentration, and the sensor was verified by comparison to be capable of selectively identifying p-xylene gas, wherein the other types of gas samples were ethylbenzene, ethanol, acetone, hexanal, and ethyl acetate, and the concentration of the gas samples was 100 ppm.

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