Ti3C2T X Preparation and Application of (MXene) / Functionalized Graphene Quantum Dot Aerogel Growth of Gold Nanomaterials

Abstract

This invention discloses Ti3C2T x This research focuses on the aerogel growth of gold nanomaterials using (MXene) / functionalized graphene quantum dots and their applications, belonging to the field of organophosphorus pesticide analysis and detection technology. Citric acid, serine, and arginine were dissolved in deionized water and heated to obtain citrate-arginine-serine quantum dots; Ti3A1C2(MAX) was then etched using lithium fluoride and hydrochloric acid to obtain Ti3C2T. x (MXene); To Ti3C2T x A quantum dot solution was added dropwise to generate a microgel; a gold nanoparticle growth solution was added dropwise to the microgel, followed by incubation with chloroauric acid and then a reducing agent. After the reaction was complete, the mixture was centrifuged, washed, and vacuum dried to obtain graphene quantum dot-functionalized gold nanoparticles. This invention utilizes the superior conductivity of Ti3C2T... x Gold nanoparticles were grown on functionalized graphene quantum dot microgels and used as electrocatalytic active materials. An electrochemical sensor was constructed using aptamers as recognition molecules to detect the organophosphorus pesticide methamidophos.

Description

Technical Field

[0001] This invention belongs to the field of organophosphorus pesticide analysis and detection technology, specifically relating to Ti3C2T X Preparation and application of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials. Background Technology

[0002] Organophosphates, as highly effective pesticides for controlling plant diseases, insects, and weeds, are widely used in agricultural production. However, this also leads to varying degrees of pesticide residues in fruits and vegetables, threatening human health. Isocarbophos (O-methyl-O-(2-isopropoxyformylphenyl)thiophosphoramide) is a broad-spectrum insecticide and acaricide characterized by rapid action and a broad insecticidal spectrum. Its main modes of action are stomach poison, contact poisoning, and ovicidal action. Isocarbophos is highly toxic to humans and can enter the body through the intestinal tract, respiratory tract, and skin, causing poisoning. Therefore, a sensitive and rapid detection method is urgently needed to accurately detect methanophos residues in agricultural products.

[0003] Current methods for detecting pesticides and acaricides include fluorescence spectroscopy, high-performance liquid chromatography (HPLC), gas chromatography (GC), and electrochemical methods. However, fluorescence spectroscopy struggles to yield reproducible results in practical sample analysis. HPLC and GC methods often require large and expensive instruments, involve complex sample pretreatment steps, are costly, and require specially trained personnel, making them unsuitable for routine sample analysis and batch screening. Electrochemical sensors, on the other hand, have gained widespread attention and use due to their advantages such as simple operation, high selectivity, high sensitivity, and low testing cost.

[0004] Graphene quantum dots (GQDs) refer to graphene sheets smaller than 100 nm, exhibiting quantum size and edge effects, which endow GQDs with unique optical properties, electrical conductivity, heat resistance, and stability. Various amino acids added during the synthesis process can yield GQDs with different functional groups, allowing for the customization of GQDs with different functional groups to meet specific needs.

[0005] Ti3C2T X Since its introduction in 2011, MXene has been widely used in energy storage, electrochemical sensors, electromagnetic shielding and other fields due to its excellent electrical conductivity, good thermal conductivity and easy processing.

[0006] Gold nanoparticles (AuNPs) have become the preferred material for electrocatalytic activity due to their large specific surface area, ease of functionalization, high chemical stability, excellent electrical conductivity, and high biocompatibility.

[0007] Aptamers are DNA or RNA molecules with specific sequences that can be selected from oligonucleotide libraries using exponential enrichment techniques. Compared to other recognition molecules, aptamers can specifically bind to analytes. Aptamer-based electrochemical sensors offer advantages such as specificity and ease of operation.

[0008] Ti3C2T X There are two main methods for combining (MXene) and nano-gold (AuNPs), namely Ti3C2T X Direct mixing with AuNPs and Ti3C2T X In-situ synthesis of nano-gold. Elumalai et al. (10.1007 / s00604-019-4018-0) alternately coated Ti3C2T on the electrode surface. X Gold nanoparticles were used to prepare Ti3C2T X Gold film. The insertion of gold nanoparticle layers prevents Ti3C2T X The Ti3C2T film aggregates between different layers. However, Ti3C2T within the same layer... X Gold nanoparticles and flakes often aggregate during use. Yang et al. (10.3390 / molecules27061871) used Ti3C2T X Gold nanocrystals were prepared by reducing HAuCl4 to Ti3C2T. X flakes and AuCl4 - Separation can lead to severe aggregation and result in the formation of large gold nanocrystals. Summary of the Invention

[0009] To address the problems existing in the prior art, the technical problem to be solved by the present invention is to provide a preparation and application of Ti3C2Tx(MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials. The synthesized gold nanomaterials have excellent conductivity. Using the microgel-grown gold nanomaterials as electrocatalytic active substances and aptamers as recognition molecules, an electrochemical sensor can be constructed to detect the organophosphorus pesticide methamidophos.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] Ti3C2T X The preparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials includes the following steps:

[0012] (1) Dissolve citric acid, serine and arginine in deionized water, stir evenly and heat to prepare citric acid arginine serine quantum dots, and adjust the pH of the solution after dissolution.

[0013] (2) Ti3AlC2(MAX) was etched using lithium fluoride and hydrochloric acid. After adjusting the pH of the solution to neutral, Ti3C2T was collected by centrifugation and washing. X (MXene);

[0014] (3) To Ti3C2T X A microgel is generated by adding citrate, arginine, serine, and quantum dot solution dropwise.

[0015] (4) The gold nanoparticle growth solution was added dropwise into the microgel, followed by incubation with chloroauric acid for 30 min, and then ascorbic acid as a reducing agent was added and reacted for 30 min. After the reaction was completed, the product was centrifuged, washed, and vacuum dried to obtain Ti3C2T. X Functionalized graphene quantum dot microgels for growing gold nanomaterials.

[0016] This invention is the first to report Ti3C2T X Arginine and serine functionalized graphene quantum dot (RS-GQD) aerogel (Ti3C2T) X In-situ synthesis of gold nanostars using RS-GQD. Positively charged RS-GQD and negatively charged Ti3C2T X The wafers self-assemble into Ti3C2T through electrostatic adsorption. X / RS-GQD gel. AuCl4- is adsorbed on a newly assembled growth template formed by close contact between the growth solution (CTAC, KBr, KCl, and L-GSH) and Ti3C2TX / RS-GQD. Through in-situ reduction with ascorbic acid, gold nanostars are formed and uniformly dispersed within Ti3C2TX / RS-GQD. CTAC and Ti3C2TX / RS-GQD bind AuCl4- to the gel. - Introduced into the Ti3C2TX / RS-GQD gel structure, halogens act as morphology modifiers, accelerating the absorption of Au. 3+ The reduction rate is high. L-glutathione triggers the asymmetric structural evolution of gold nanocrystals, giving them more exposed high-refractive-index crystal facets. Ti3C2TX / RS-GQD@Au, with its unique structure, exhibits high electrical conductivity, structural stability, and high catalytic activity.

[0017] This invention introduces a Ti3C2TX(MXene) functionalized graphene quantum dot aerogel with a stable three-dimensional structure and excellent conductivity. The catalytic activity is enhanced by combining gold nanoparticles with the aerogel. The aerogel, along with CTAC, halogens, and L-glutathione, assembles into a growth template for gold nanostars, uniformly dispersing the gold nanoparticles while inducing the growth of high-index crystal faces of the gold nanoparticles (i.e., gold nanostars).

[0018] The Ti3C2T XPreparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials, step (1), the molar ratio of citric acid, arginine and serine is 1:0.1-0.5:1; heating at 150-180℃ for 120-200min, and adjusting the pH of the solution to 1-3 with hydrochloric acid solution; preferably, the heating temperature is 180℃, the heating time is 180min, and the pH value is 2.

[0019] The Ti3C2T X Preparation of (MXene) / functionalized graphene quantum dot aerogel to grow nano-gold materials, step (2), etch Ti3AlC2(MAX) at 35℃ using lithium fluoride and hydrochloric acid for 48h; add deionized water and centrifuge at 3500rpm for 5min to wash away hydrofluoric acid in the solution, and adjust the pH of the solution to 6.

[0020] The Ti3C2T X Preparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials, step (2): repeating the operation of hand-shaking mixing-centrifugation-hand-shaking mixing until the supernatant is a thick black liquid, which is Ti3C2T X (MXene).

[0021] The Ti3C2T X Preparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials, step (3), the amount of citrate arginine serine quantum dots added is 10wt%.

[0022] The Ti3C2T X Preparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials, step (4): the growth solution consists of 0.5424 g cetyltrimethylammonium chloride, 1130 μL of 0.5 mM potassium bromide, 113 μL of 0.5 mM potassium iodide, and 103 μL of 2.5 mM L-glutathione; the concentration of chloroauric acid is 10 mM and the concentration of ascorbic acid is 50 mM.

[0023] The Ti3C2T X Preparation of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials, step (4): centrifugation washing speed is 4240 rpm, centrifugation time is 1 min, washing three times; drying temperature is 50-70℃, drying time is 8-10 h.

[0024] Ti3C2T obtained by the above method X The application of (MXene) / functionalized graphene quantum dot aerogel-grown gold nanomaterials in the fabrication of electrochemical testing sensors is as follows:

[0025] After polishing, ultrasonically washing, and drying the glassy carbon electrode, a graphene quantum dot-functionalized gold nanoparticle solution was dropped onto the electrode surface. After drying, a nucleic acid aptamer solution was dropped onto the electrode and incubated at 37°C for 1-2 hours. Then, a mercaptohexanol solution was dropped onto the electrode surface and incubated for 1-2 hours to block the active sites of the gold nanoparticles. Finally, a complementary chain solution was dropped onto the electrode surface and incubated at 37°C for 1-2 hours to obtain the electrochemical testing sensor.

[0026] In the application described, the sequence of the nucleic acid aptamer is: 5′-AGCTTGCTGCAGCGATTCTTGATCGCCACAGAGCTCAAGCTTTTTTT-(CH2)6-SH-3′; the sequence of the complementary strand is: 5′-bisferrocene-TTGATCGCCACAGAAAAGCTTGAGCTCTGTGGCGATCAAGAATCGCTGCAGCAAGCTTTTCAT-3′.

[0027] The application uses the electrochemical test sensor as the working electrode, Ag / AgCl as the reference electrode, and Pt wire electrode as the counter electrode to construct a three-electrode system; it is used to detect the concentration of methamidophos; the electrochemical window for detection is 0.15-0.45V, and the step size is 50-100mV / s.

[0028] The principle of the electrochemical test sensor of the present invention for detecting methamidophos is as follows: the modified electrode is immersed in PBS solutions of methamidophos at different concentrations. The interaction force between methamidophos and the aptamer is greater than the interaction force between the aptamer and the complementary chain. Therefore, the complementary chain carrying the electrical signal falls off the electrode, which weakens the electrochemical signal.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. In this invention, functionalized graphene quantum dots were prepared by adding arginine and serine, which increased the water solubility of the graphene quantum dots. Furthermore, the functionalized graphene quantum dots can react with Ti3C2T... X (MXene) composite to obtain Ti3C2T X (MXene) functionalized graphene quantum dot microgel material, which has excellent conductivity and more active sites.

[0031] 2. In this invention, Ti3C2T is utilized. X Using MXene-functionalized graphene quantum dot microgels as a substrate, gold nanoparticles with unique morphologies were grown in situ. The resulting gold nanoparticles exhibited good dispersibility, numerous surface active sites, and excellent electrocatalytic performance, making them suitable for constructing electrochemical sensors to detect the organophosphorus pesticide methamidophos.

[0032] 3. This invention utilizes Ti3C2T X (MXene) functionalized graphene quantum dot microgels grow gold nanoparticles. This material exhibits excellent electrical conductivity. An electrochemical sensor built upon this material utilizes aptamers as recognition molecules, achieving a detection limit of 10⁻⁶. -16 The decrease in M,DPV current showed a good linear relationship with the logarithm of methamidophos concentration. Attached Figure Description

[0033] Figure 1 It is Ti3C2T X Scanning electron microscope image of gold nanomaterials grown from (MXene) functionalized graphene quantum dot microgels;

[0034] Figure 2 It is Ti3C2T X XRD patterns of (MXene) functionalized graphene quantum dot microgels growing gold nanomaterials (A) and microgels (B);

[0035] Figure 3 It is Ti3C2T X (MXene) Functionalized graphene quantum dot microgel-grown gold nanomaterials: Response current (A) and linearity (B) of the detection of water, amine, thiophosphate, and phosphorus.

[0036] Figure 4 2×10 -12 The Ip value results for organophosphorus pesticide M are shown in the figure. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] Example 1

[0039] The preparation of gold nanomaterials grown from Ti3C2TX(MXene) / functionalized graphene quantum dot aerogels includes the following steps:

[0040] (1) Preparation of citrate arginine serine quantum dots:

[0041] Citric acid (2g), serine (1.658g), and arginine (0.2g) (molar ratio 1:1:0.2) were added to a beaker, and an appropriate amount of deionized water was added. After stirring thoroughly, the mixture was reacted at 180℃ for 3 hours to obtain citric acid serine arginine quantum dots (Arg-GQD-Ser).

[0042] (2)Ti3C2T x Preparation of (MXene):

[0043] MAX-Ti3AlC2 was etched using lithium fluoride and hydrochloric acid. The specific steps were as follows: 40 mL of 9M hydrochloric acid and 3.2 g of lithium fluoride were added to a Teflon beaker and stirred for 30 min. Then, 2 g of MAX-Ti3AlC2 was slowly added, and the reaction was carried out at 35 °C for 36 h. After the reaction was complete, the mixture was separated at 3500 rpm for 5 min until the pH of the liquid reached 6. Then, 40 mL of ethanol was added to a centrifuge tube for 30 min, centrifuged at 10000 rpm for 10 min, and the lower layer of sediment was collected. Deionized water was added to the centrifuge tube containing the precipitate, the mixture was vortexed, and centrifuged at 3500 rpm for 5 min to collect the dark green upper layer. Repeating this step yielded a larger amount of MXene dispersion.

[0044] (3)Ti3C2T X Preparation of (MXene) functionalized graphene quantum dot microgels:

[0045] A 10% acidified quantum dot solution was added dropwise to a 5 mg / mL MXene aqueous solution and stirred for 5 min to obtain Arg-GQD-Ser / MXene microgels. The formed hydrogel was washed several times in deionized water until the pH was neutral, and then diluted with 20 mL of water to a concentration of 2 mg / mL.

[0046] (4)Ti3C2T X Preparation of gold nanomaterials grown from (MXene) functionalized graphene quantum dot microgels:

[0047] The growth medium consisted of hexadecyltrimethylammonium chloride (0.5424 g), potassium bromide (1130 μL, 0.5 mM), potassium iodide (113 μL, 0.5 mM), and L-glutathione (103 μL, 2.5 mM).

[0048] Add 100 μL of the above microgel dispersion (2 mg / mL) to a 50 mL centrifuge tube; then add 8.85 mL of growth medium, vortex mix, add 700 μL of chloroauric acid, and incubate at 30 °C for 30 min. After incubation, add 475 μL of ascorbic acid (50 mM), and react at 30 °C for 3 min. Centrifuge the obtained product at 4240 rpm for 5 min, repeat three times, and finally vacuum dry at 60 °C for 12 h to obtain Ti3C2T. X (MXene) Functionalized graphene quantum dot microgels for growing gold nanomaterials.

[0049] Figure 1 This is a scanning electron microscope (SEM) image of gold nanoparticles grown from Ti3C2Tx(MXene) functionalized graphene quantum dot microgels. Figure 1 It can be seen that Ti3C2T X / RS-GQD@Au possesses a highly porous three-dimensional structure, with gold nanocrystals uniformly dispersed within Ti3C2T. x On the film, the in-situ grown gold nanocrystals exhibit a star-shaped nanostructure with sharp, pointed corners. This unique structure is primarily attributed to the L-GSH-induced structural evolution of the gold nanocrystals.

[0050] Figure 2 It is Ti3C2T X (MXene) Functionalized graphene quantum dot microgels growing gold nanomaterials and XRD patterns of the microgels. Figure 2 It can be concluded that the peak at 5.98° belongs to Ti3C2T. X The (002) crystal plane, because Ti3C2T X Aerogel formation and Ti3C2T X This peak exhibits lower diffraction intensity and a smaller 2θ value. The peaks at 38.18°, 44.36°, 64.61°, 77.47°, 81.72°, 110.82°, and 115.32° correspond to the (111), (200), (220), (311), (222), (310), and (420) crystal planes of the fcc gold nanocrystal (NO. JCPDS 4-0784). This demonstrates the in-situ synthesis of gold and the formation of gold nanostars with high-index crystal planes.

[0051] Example 2

[0052] The construction of an electrochemical sensor includes the following steps:

[0053] 1) Polish the glassy carbon electrode with 0.5 μm Al2O3 powder, then ultrasonically wash it with ethanol and ultrapure water for 5 min each, and air dry it at room temperature.

[0054] 2) Drop 10 μL of Ti3C2T onto the electrode surface. X (MXene) / functionalized graphene quantum dot aerogel solution for growing gold nanoparticles (5 mg / mL), dried and ready for use;

[0055] 3) Pipette 10 μL of nucleic acid aptamer solution onto the electrode and incubate at 37 °C for 2 h. The aptamer is linked to Au NPs via a thiol group. The sequence of the nucleic acid aptamer is: 5′-AGCTTGCTGCAGCGATTCTTGATCGCCACAGAGCTCAAGCTTTTTTT-(CH2)6-SH-3′;

[0056] 4) Apply 10 μL (10 mM) mercaptohexanol (MCH) solution to the electrode surface and incubate for 2 h to block the active sites of AuNPs.

[0057] 5) Add a complementary chain (10 μL, 5 μM) solution to the electrode surface and incubate at 37 °C for 2 h. The sequence of the complementary chain is 5′-bisferrocene-TTGATCGCCACAGAAAAGCTTGAGCTCTGTGGCGATCAAGAATCGCTGCAGCAAGCTTTTCAT-3′. The complementary chain of the nucleic acid aptamer forms a double helix through base complementarity. Because one end of the complementary chain is modified with ferrocene molecules, after the double helix is ​​formed, the ferrocene molecules approach the electrode surface, which enhances the electrochemical signal.

[0058] 6) Immerse the modified electrode in different concentrations (concentrations are: 8×10⁻⁶). -16 M, 1×10 -15 M, 2×10 -15 M, 1×10 -14 M, 2×10 -14 M, 1×10 -13 M, 2×10 -13 M, 1×10 -12 M, 2×10 -12 M and 1×10 -11 Incubate in PBS solution of M) methamidophos for 30 min.

[0059] 7) A three-electrode system was used, with the modified glassy carbon electrode as the working electrode and Ag / AgCl as the reference electrode. A Pt wire electrode was used as the counter electrode. Blank PBS buffer was used as the supporting electrolyte. The electrochemical window was 0.15-0.4 V, with a step size of 50 mV / s. Differential pulse voltammetry (DPV) was used to record the response current. Figure 3 A).

[0060] Analysis performance test

[0061] The modified electrodes were incubated in PBS solutions of different concentrations for 30 minutes before being used for DPV testing.

[0062] Test results show that the decrease in electrode DPV current has a good linear relationship with the logarithm of chlorpyrifos concentration, and the linear equation is: Ip(hA)=235.96×LOG[C ISO [M]+3549.4, detection limit is 2.9×10 -16 M( Figure 3 B).

[0063] Interference test

[0064] The modified electrodes were incubated for 30 min in PBS solutions containing chlorpyrifos (CHL), omethoate (OME), carbendazim (CAR), phoxim (PHO), imidacloprid (IMI), abamectin (AVE), acetaminophen (ACE), and methamidophos (ISO), respectively. The concentration of each organophosphorus pesticide was 2 × 10⁻⁶. -12 M is the response current of the DPV test electrode.

[0065] Test results show that the electrochemical sensor using gold nanoparticles as the electrocatalytic active material only responds to the organophosphorus pesticide methamidophos, and has a very low response to other organophosphorus pesticides (such as...). Figure 4 (As shown).

Claims

1. Ti3C2T X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Includes the following steps: (1) Citric acid, serine and arginine were dissolved in deionized water, stirred evenly and heated to prepare citric acid arginine serine quantum dots. The pH of the solution was adjusted after dissolution. (2) Ti3C2 was obtained by etching Ti3AlC2 with lithium fluoride and hydrochloric acid, adjusting the pH of the solution to neutral, centrifuging and washing. X ; (3) To Ti3C2T X A microgel is generated by adding citrate, arginine, serine, and quantum dot solution dropwise. (4) The gold nanoparticle growth solution was added dropwise into the microgel, followed by incubation with chloroauric acid and then the reducing agent ascorbic acid was added for reaction. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain Ti3C2T. X Graphene quantum dot functionalized gold nanoparticles; the gold nanoparticle growth solution consists of 0.5424 g cetyltrimethylammonium chloride, 1130 μL of 0.5 mM potassium bromide, 113 μL of 0.5 mM potassium iodide, and 103 μL of 2.5 mM L-glutathione.

2. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Step (1): The molar ratio of citric acid, arginine and serine is 1:0.1-0.5:1; heat at 150-180℃ for 120-200 min, and adjust the pH of the solution to 1-3 using hydrochloric acid solution.

3. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Step (2): Etch Ti3AlC2 at 35°C using lithium fluoride and hydrochloric acid for 48 h; add deionized water and centrifuge at 3500 rpm for 5 min to wash away hydrofluoric acid in the solution, and adjust the pH of the solution to 6.

4. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Step (2): Repeat the process of hand-shaking, centrifugation, and hand-shaking until the supernatant is a thick black liquid. This solution is Ti3C2T. X .

5. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Step (3), the amount of citrate arginine serine quantum dots added is 10 wt%.

6. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... In step (4), the concentration of chloroauric acid is 10 mM and the concentration of ascorbic acid is 50 mM.

7. The Ti3C2T according to claim 1 X The preparation of functionalized graphene quantum dot aerogel-grown gold nanomaterials is characterized by... Step (4): The centrifugation speed is 4240 rpm, the centrifugation time is 1 min, and the washing is repeated three times; the drying temperature is 50-70℃, and the drying time is 8-10 h.

8. Ti3C2T obtained by any of the preparation methods described in claims 1-7 X The application of functionalized graphene quantum dot aerogel-grown gold nanomaterials in the fabrication of electrochemical testing sensors is characterized by... Specifically, after polishing, ultrasonically washing, and drying the glassy carbon electrode, a graphene quantum dot-functionalized gold nanoparticle solution is dropped onto the electrode surface. After drying, a nucleic acid aptamer solution is dropped onto the electrode and incubated. Then, a mercaptohexanol solution is placed on the electrode surface and incubated to block the active sites of the gold nanoparticles. Then, a complementary chain solution is dropped onto the electrode surface and incubated to obtain the electrochemical testing sensor.

9. The application according to claim 8, characterized in that, The sequence of the nucleic acid aptamer is: 5´-AGCTTGCTGCAGCGATTCTTGATCGCCACAGAGCTCAAGCTTTTTTT-(CH2)6-SH-3´; the sequence of the complementary strand is: 5´-bisferrocene-TTGATCGCCACAGAAAAGCTTGAGCTCTGTGGCGATCAAGAATCGCTGCAGCAAGCTTTTCAT-3´.

10. The application according to claim 8, characterized in that, A three-electrode system was constructed using the electrochemical sensor as the working electrode, Ag / AgCl as the reference electrode, and a Pt wire electrode as the counter electrode; it was used to detect the concentration of methamidophos; the electrochemical window for detection was 0.15-0.45V, and the step size was 50-100mV / s.

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