A method for specifically detecting samples using terahertz band polyaniline metamaterials

Abstract

The present invention discloses a method for specific detection of samples using terahertz band polyaniline metamaterials. A terahertz band polyaniline metamaterial is prepared, which includes polyaniline, a metal anti-transmission layer, and a silicon substrate from top to bottom; a sample point to be tested is set and a terahertz time domain signal is collected; a sample solution is prepared; the sample solution is dripped onto the sample point to be tested, and the terahertz time domain signal is collected after drying; the terahertz band polyaniline metamaterial is rinsed, and the terahertz time domain signal is collected after drying; the terahertz time domain signal of air is collected; the transmittance change is obtained according to the terahertz time domain signal, and the detection sample is judged according to the transmittance change. The present invention utilizes the interaction between polyaniline and the sample to change the terahertz transmission spectrum of the terahertz band polyaniline metamaterial, thereby amplifying the sample signal. This method can achieve specific detection of the sample to be tested and meet the growing demand for accurate detection.

Description

Technical Field

[0001] The invention relates to a specific detection method for a sample, and in particular to a specific detection method using a terahertz band polyaniline metamaterial. Background Art

[0002] There is an urgent need for a highly sensitive, fast, and non-destructive detection method. Terahertz waves have been widely used in detection due to their unique characteristics, including low photon energy, high signal-to-noise ratio, and obvious response to the rotation and vibration of organic molecules. Terahertz time-domain spectroscopy (THz-TDS) technology has great application potential in anti-terrorism, security inspection, biology, medicine, and other fields that require the detection of trace substances. However, although the metamaterials currently used in sample detection in this discipline can significantly enhance the sample signal, it is difficult to achieve specific detection of the target sample by the metamaterial. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a method for specifically detecting samples of polyaniline metamaterials in the terahertz band. The method should have the characteristics of being able to specifically detect the samples to be tested and being fast and convenient.

[0004] The technical solution adopted by the present invention comprises the following steps:

[0005] 1) Preparation of terahertz band polyaniline metamaterial: preparing a terahertz band polyaniline metamaterial comprising polyaniline, a metal anti-transmission layer, and a silicon substrate from top to bottom, setting a sample point to be tested on the surface of the terahertz band polyaniline metamaterial, and collecting the terahertz time domain signal of the sample point to be tested before adding the sample solution;

[0006] 2) preparing the sample solution to be tested;

[0007] 3) Adding sample solution onto the surface of terahertz band polyaniline metamaterial;

[0008] 4) collecting the terahertz time domain signal of the sample point to be tested after the sample solution is added;

[0009] 5) Rinse the terahertz band polyaniline metamaterial. After the terahertz time domain signal of the terahertz band polyaniline metamaterial is collected, rinse the terahertz band polyaniline metamaterial. After rinsing, collect the terahertz time domain signal of the sample point to be tested:

[0010] 6) Collect the terahertz time domain signal of air as a reference;

[0011] 7) Calculate the terahertz time domain signal obtained from steps 1), 4) to 6), obtain the transmittance change of the transmission spectrum peak of the polyaniline metamaterial in the terahertz band, and judge the detection sample according to the transmittance change.

[0012] In the step 1), the terahertz band polyaniline metamaterial is prepared in the following manner:

[0013] 1.1) Evaporation of metal on silicon wafer surface;

[0014] A silicon wafer was ultrasonically cleaned in acetone, isopropanol and water for 10 min each, dried with nitrogen, and titanium with a thickness of 10 nm and gold with a thickness of 200 nm were successively evaporated on the surface of the silicon wafer;

[0015] 1.2) Electrochemical deposition of polyaniline;

[0016] The silicon wafer with titanium and gold deposited was laid flat in an aniline electrolyte solution, and an oxidative polymerization reaction was carried out through an electrochemical workstation to deposit a 1um thick polyaniline layer on the gold surface;

[0017] 1.3) Finally, a rectangular superstructure is engraved on the polyaniline layer.

[0018] In the above treatment, titanium forms a metal anti-transmission layer, which can also be replaced by silver, copper, aluminum, titanium, etc. The polyaniline layer can be replaced by a semi-metal, such as tungsten ditelluride.

[0019] The rectangular superstructure is composed of a plurality of rectangular structures arranged in a periodic array, and the length and width of the rectangular structure and the spacing between the rectangular structures are all in the micrometer scale.

[0020] The terahertz band polyaniline metamaterial is carved into a rectangular superstructure using a laser engraving method. The resonant peak resonance frequency of the polyaniline metamaterial prepared in this way is just within the terahertz effective detection band, achieving the effect of material detection.

[0021] In the step 1), during the oxidative polymerization reaction in the electrochemical workstation, the number of cycles is set differently during the deposition process on the electrode surface, so that the polyaniline deposition is uniform and the thickness of the polyaniline is controllable.

[0022] In the steps 4) and 6), the terahertz time domain signal of the sample point to be tested on the polyaniline metamaterial in the terahertz band and the terahertz time domain signal of the air are collected under the condition of zero air humidity and in the spectral bandwidth range of 0.1-1.6 THz.

[0023] In the steps 4) and 6), when collecting the terahertz time domain signal, the detection area of ​​the sample point to be measured is 1 to 2 mm 2 .

[0024] In the step 5), the terahertz band polyaniline metamaterial is rinsed in the following manner: before each drop of the sample solution, the surface of the terahertz band polyaniline metamaterial is rinsed with deionized water until no sample to be tested remains, and then dried with nitrogen.

[0025] The sample solution is a pesticide solution.

[0026] The sample solution is imidacloprid solution.

[0027] The step 7) is specifically as follows:

[0028] All terahertz spectrum time domain signals are converted into frequency domain signals by fast Fourier transform, and the frequency domain signals of the sample points to be tested are calculated with the frequency domain signals of the air as a reference to obtain the transmittance of the sample points to be tested before and after the addition of the sample solution and the transmittance of the sample points to be tested after rinsing, and the following judgment is made: if the transmittance of the sample points to be tested after the addition of the sample solution decreases by more than a preset first threshold value compared with the transmittance of the sample points to be tested before the addition of the sample solution, and the transmittance of the sample points to be tested after rinsing decreases by more than a preset second threshold value compared with the transmittance of the sample points to be tested before the addition of the sample solution, then it is considered to be a sample solution; otherwise, it is not a sample solution.

[0029] Therefore, the present invention proves that polyaniline reacts chemically with the sample to be tested to produce bond bonding based on the difference comparison of the lowest transmittance points before and after flushing, so as to achieve specific detection of the sample to be tested by the terahertz band polyaniline metamaterial, that is, after the sample solution to be tested is added, the lowest transmittance value of the terahertz band polyaniline metamaterial decreases significantly, and the transmittance does not return to the initial peak value after flushing.

[0030] In the specific implementation, sample solutions of different concentrations were added to conduct experiments to obtain the detection limit.

[0031] In the specific implementation, multiple sample solution additions are set up for testing, or multiple sample points to be tested are set up, and the transmittance data of different sample points to be tested with different sample solutions are compared separately. Multiple sets of data are listed in parallel to prove that the terahertz band polyaniline metamaterial can achieve specific detection of the sample to be tested.

[0032] In the specific implementation, in step 2), sample solutions of different concentrations are prepared, and then in step 3), the sample solutions of different concentrations are dripped to the sample points to be tested at different positions, 10ul is dripped each time, and heated and dried on a hot plate after dripping. Then, in steps 4) and 6), the terahertz time domain signal is collected at each sample point to be tested.

[0033] The concentrations of the sample solutions prepared in step 2) are 0.01 ppm, 0.1 ppm, 1 ppm, 10 ppm, and 100 ppm; and 10 μL of the sample solution is added dropwise each time in step 3) to control the experimental variables.

[0034] In the preferred implementation of the imidacloprid of the present invention, imidacloprid with a product number of 37894-100MG produced by Sigma Company can be selected, but it is not limited thereto.

[0035] In the preferred implementation of the aniline of the present invention, the aniline solution with the product number A283803-100ml produced by Aladdin Company can be selected, but it is not limited thereto.

[0036] In the specific implementation, the preferred terahertz time-domain spectroscopy system of the present invention is recommended to adopt the terahertz time-domain spectroscopy system of model z3 produced by Z-omega.

[0037] The terahertz band polyaniline metamaterial of the present invention is a polyaniline-metal anti-transmission layer structure, which meets the chemical bond conjugation matching conditions and can detect specific objects to be detected.

[0038] Although pure metal terahertz band metamaterials have high detection sensitivity, they cannot specifically match the target molecules. In contrast, the outstanding advantage of the present invention is that polyaniline can specifically detect the molecules to be detected, ensuring detection sensitivity while achieving detection specificity.

[0039] The present invention manufactures a terahertz band polyaniline metamaterial by steps such as metal evaporation, electrochemical deposition of polyaniline, and laser engraving of metamaterials, configures a sample (imidacloprid) solution, drips the sample solution on the surface of the terahertz band polyaniline metamaterial, and then dries it through a heating plate, collects the terahertz time domain signal of the sample point to be tested on the surface of the terahertz band polyaniline metamaterial and the air reference, finally rinses the surface of the terahertz band polyaniline metamaterial with ultrapure water until no sample to be tested remains, blows it dry with nitrogen, and collects the terahertz time domain signal of the rinsed terahertz band polyaniline metamaterial. The transmittance spectrum of the sample point to be tested is calculated from the terahertz time domain signal, and the intensity change of the transmission peak is obtained according to the transmittance of the transmission spectrum to judge the detection sample effect.

[0040] The present invention has the following beneficial effects:

[0041] The polyaniline film deposited by the electrochemical method adopted in the present invention utilizes the change of chemical properties caused by the chemical reaction between polyaniline and the sample (polyaniline is oxidized to form a bond with the object to be tested) to amplify the sample signal.

[0042] The present invention utilizes the interaction between polyaniline and the sample to change the absorption peak of the polyaniline metamaterial in the terahertz band, thereby amplifying the sample signal. This method not only has high detection sensitivity, but also can achieve specific detection of the sample to be tested.

[0043] Compared with the metal metamaterial signal amplification method, the polyaniline in the method of the present invention can specifically bind to the analyte to achieve specific detection of the target pesticide molecule; compared with the traditional tablet pressing technology, the method of the present invention greatly improves the detection sensitivity; and the method is fast and simple to operate, which can meet the growing demand for rapid detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic structural diagram of the terahertz band polyaniline metamaterial of the present invention.

[0045] Figure 2 This is the transmission spectrum obtained from the terahertz band polyaniline metamaterial experiment of the present invention.

[0046] Figure 3 It is the transmission spectrum of polyaniline in Example 1 of the present invention in the presence / absence of imidacloprid molecules and after being rinsed with imidacloprid solution. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0048] Embodiments of the present invention are as follows:

[0049] (1) Fabrication of polyaniline metamaterials in the terahertz band;

[0050] Take a 1mm thick high-resistance silicon wafer, ultrasonically clean it in acetone, isopropanol and water for 10 minutes each, blow dry with nitrogen, and evaporate 10nm of titanium as a binder on the surface of the silicon wafer by evaporation, and then evaporate 200nm of gold as an anti-transmission layer. The prepared substrate is laid flat and placed in the aniline electrolyte solution in the electrochemical workstation. The aniline electrolyte solution mainly plays two roles: one is to provide the pH value required by the reaction medium, and the other is to enter the polyaniline molecular chain in the form of a dopant to give it a certain conductivity. After the intrinsic polyaniline is doped with proton acid, its conductivity can be increased by ten orders of magnitude or even higher. The doped polyaniline has reversible redox reaction characteristics. In the electrochemical workstation, the prepared substrate is used as an anode electrode, and a polyaniline film is deposited on the electrode surface through an oxidative polymerization reaction. The thickness of the polyaniline can be controlled by setting the number of cycles in the electrochemical workstation. Blow dry with nitrogen after deposition.

[0051] (2) Fabrication of polyaniline metamaterials in the terahertz band with pattern shapes;

[0052] Draw the shape of the terahertz band polyaniline metamaterial that needs to be laser engraved. In this embodiment, it is a rectangular structure with a short side of 30um, a long side of 150um, a horizontal axis spacing of 70um, and a vertical axis spacing of 50um. Use a laser engraving method to engrave the terahertz band polyaniline metamaterial into a short rod structure; the laser engraving machine used in this embodiment is the protolaser produced by LPKF, and the laser power is 0.4w. Use a laser engraving machine to engrave a rectangular structure. Terahertz band polyaniline metamaterial such as Figure 1 shown.

[0053] (3) Randomly select the sample points of the polyaniline metamaterial in the terahertz band to be tested, and collect the terahertz time domain signal before adding the imidacloprid solution;

[0054] At room temperature, the terahertz time-domain spectroscopy system is filled with nitrogen until the humidity is 0. The laser is preheated for half an hour before measurement can be carried out; the terahertz band polyaniline metamaterial is placed in the transmission light path, and the sample point to be measured is located at the focal position of the transmission light path, and the detection area is 2mm 2 Measure the sample points to be tested and the air reference one by one, and save the corresponding terahertz time-domain spectrum data.

[0055] (4) Preparation of imidacloprid solution;

[0056] Five imidacloprid solutions with concentration gradients were prepared respectively, which were 0.01ppm, 0.1ppm, 1ppm, 10ppm and 100ppm in this embodiment.

[0057] (5) adding an imidacloprid solution to the surface of the terahertz band polyaniline metamaterial and collecting the terahertz time domain signal after the imidacloprid solution is added;

[0058] Take a 0.01ppm imidacloprid solution, drip it on the sample point to be tested on the surface of the terahertz band polyaniline metamaterial, drip 10ul to each sample point to be tested, dry it on a hot plate after dripping, and collect the terahertz time domain spectrum of the sample point to be tested of the terahertz band polyaniline metamaterial after dripping the imidacloprid solution;

[0059] (7) Calculate the transmittance corresponding to all time domain signals;

[0060] The terahertz spectrum time domain signal of the sample is converted into a frequency domain signal using fast Fourier transform, and the transmittance of the sample point to be measured is calculated using the frequency domain signal using the following formula:

[0061] T=(E (sample) / E (reference) ) 2

[0062] In the above formula, T represents the transmittance of polyaniline metamaterial in the terahertz band, E (sample) represents the frequency domain signal of the sample point to be measured in the transmission mode, E (reference) Frequency domain signal representing air in transmission mode.

[0063] The transmission spectrum obtained from the terahertz band polyaniline metamaterial experiment is as follows Figure 2 shown.

[0064] Find the transmittance corresponding to the maximum value of the transmission spectrum peak. The transmission spectrum of polyaniline metamaterial in the terahertz band with and without imidacloprid molecules is as follows: Figure 3 shown.

[0065] From the above implementation, it can be seen that the present invention proves that polyaniline and the sample to be tested undergo chemical reaction to produce bond bonding based on the difference comparison of the minimum transmittance before and after washing, and uses the interaction between polyaniline and the sample to change the resonance peak intensity of the terahertz band polyaniline metamaterial to achieve specific detection of the sample to be tested by the terahertz band polyaniline metamaterial, that is, after the sample solution to be tested is added, the minimum transmittance value of the terahertz band polyaniline metamaterial decreases significantly, and the transmittance does not rise back to the initial peak after washing. This method can not only amplify the detection signal for the sample to be tested, but also achieve specific detection of the sample to be tested.

[0066] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for specifically detecting samples using terahertz band polyaniline metamaterials, characterized in that The method comprises the following steps: 1) Fabrication of terahertz-band polyaniline metamaterials: fabricating a terahertz-band polyaniline metamaterial that includes polyaniline, a metal anti-transmission layer, and a silicon substrate from top to bottom, setting a sample point to be tested on the surface of the terahertz-band polyaniline metamaterial, and collecting the terahertz time domain signal of the sample point to be tested; In the step 1), the terahertz band polyaniline metamaterial is prepared in the following manner: 1.1) Evaporation of metal on silicon wafer surface; Take the silicon wafers which have been ultrasonically cleaned in acetone, isopropanol and water, blow dry them with nitrogen, and deposit titanium and gold on the surface of the silicon wafers in sequence; 1.2) Electrochemical deposition of polyaniline; The silicon wafer with titanium and gold deposited on it is laid flat in an aniline electrolyte solution, and an oxidative polymerization reaction is carried out through an electrochemical workstation to deposit a polyaniline layer on the gold surface; 1.3) Finally, a rectangular superstructure is engraved on the polyaniline layer; 2) Prepare sample solution; The sample solution is imidacloprid solution; 3) Add sample solution onto the surface of polyaniline metamaterial in the terahertz band; 4) Collecting the terahertz time domain signal of the sample point to be tested after adding the sample solution; 5) Rinse the terahertz band polyaniline metamaterial, and then collect the terahertz time domain signal of the sample point to be tested; 6) Collect the terahertz time domain signal of air as a reference; 7) Calculate the terahertz time domain signal obtained from steps 1), 4) to 6), obtain the transmittance change of the transmission spectrum peak of the polyaniline metamaterial in the terahertz band, and judge the test sample according to the transmittance change; The step 7) is specifically as follows: All terahertz spectrum time domain signals are converted into frequency domain signals by fast Fourier transform, and the frequency domain signals of the sample points to be tested are calculated with the frequency domain signals of the air as a reference to obtain the transmittance of the sample points to be tested before and after the addition of the sample solution and the transmittance of the sample points to be tested after rinsing, and the following judgment is made: if the transmittance of the sample points to be tested after the addition of the sample solution decreases by more than a preset first threshold value compared with the transmittance of the sample points to be tested before the addition of the sample solution, and the transmittance of the sample points to be tested after rinsing decreases by more than a preset second threshold value compared with the transmittance of the sample points to be tested before the addition of the sample solution, then it is considered to be a sample solution; otherwise, it is not a sample solution.

2. The method for specific detection of samples using terahertz band polyaniline metamaterial according to claim 1, characterized in that: The rectangular superstructure is composed of a plurality of rectangular structures arranged in a periodic array.

3. The method for specific detection of samples using terahertz band polyaniline metamaterial according to claim 1, characterized in that: In the step 1), during the oxidative polymerization reaction in the electrochemical workstation, the number of cycles during the deposition process on the electrode surface is set differently, so that the polyaniline is deposited evenly.

4. The method for specific detection of samples using terahertz band polyaniline metamaterial according to claim 1, characterized in that: In the steps 4) and 6), the terahertz time domain signal of the sample point to be tested on the polyaniline metamaterial in the terahertz band and the terahertz time domain signal of the air are collected under the condition of zero air humidity and in the spectral bandwidth range of 0.1-1.6 THz.

5. The method for specific detection of samples using terahertz band polyaniline metamaterial according to claim 1, characterized in that: In the step 5), the terahertz band polyaniline metamaterial is rinsed in the following manner: before each drop of the sample solution, the surface of the terahertz band polyaniline metamaterial is rinsed with deionized water until no sample to be tested remains, and then dried with nitrogen.

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