Covalent organic framework-silver nanoparticle hybrid modified electrode and photoelectrochemical detection platform and application thereof

Abstract

A covalent organic framework-silver nanoparticle hybrid modified electrode and a photoelectrochemical detection platform and application thereof, using tri(4-aminophenyl)amine and p-phthalaldehyde as monomers to grow covalent organic framework nanosheets in situ on an indium tin oxide substrate, and forming silver nanoparticle-covalent organic framework hybrids with enhanced photocatalytic activity by taking the covalent organic framework nanosheets as nanocarriers. Based on the photocatalytic activity regulation of the covalent organic framework nanosheets and the directional loading strategy of the silver nanoparticles, the amplification output of the photoelectric signal is realized. In order to realize the detection application of pesticides, the amino-modified aptamer is assembled on the surface of the silver nanoparticle-covalent organic framework hybrid, the specific interaction between the aptamer and the target is utilized, the selective capture of the pesticide acetamiprid is realized, the steric hindrance effect of the acetamiprid is utilized to reduce the photoelectric signal output of the electrode, and the high-sensitivity detection of the acetamiprid is realized. The technology improves the photoactivity of the covalent organic framework nanosheet, and provides a new idea for the simple, sensitive and accurate detection of pesticides. The application has potential application in the fields of food safety and environmental monitoring, and has important significance for human health and ecological environment protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical sensing technology, in particular to a covalent organic framework-silver nanoparticle hybrid modified electrode and a photoelectrochemical detection platform and application thereof. BACKGROUND

[0002] The widespread use of pesticides has improved crop yields, but has also led to pesticide residue problems. Therefore, developing simple, sensitive and accurate pesticide residue detection technology is of great significance for food safety and environmental protection. At present, the commonly used detection methods for pesticide residues include gas chromatography, liquid chromatography, enzyme-linked immunosorbent assay, etc. However, the above methods are limited by expensive instruments, complex operation steps and low sensitivity, and it is still necessary to develop more simple and efficient pesticide residue detection technology. Photoelectrochemical sensing analysis is a new type of analysis technology that has attracted much attention, and has the advantages of fast response speed, high sensitivity and good stability. The modification of photoelectric active materials in the photoelectrochemical sensing interface is the key to improving the analysis performance of the sensor. Photoactive covalent organic frameworks are ideal carriers for constructing photoelectrochemical sensing interfaces, which can improve the light absorption performance and photoelectric conversion efficiency of the electrode. Therefore, developing an in-situ synthesis method of photoactive covalent organic framework nanosheets and constructing a high-performance photoelectrochemical sensor for pesticide residue detection is of great significance for food safety monitoring and ecological environment protection. SUMMARY

[0003] In order to solve the technical defects of the poor light absorption performance, mismatched absorption band gap and low photoelectric conversion efficiency of traditional photoactive materials, the present application provides a covalent organic framework-silver nanoparticle hybrid modified electrode and a photoelectrochemical detection platform and application thereof. Covalent organic framework nanosheets are grown in-situ on an indium tin oxide substrate, and the directional loading strategy of silver nanoparticles is used to realize the amplification output of photoelectric signals. Combined with the specific recognition of the target by the aptamer, a high-sensitivity photoelectrochemical sensor is constructed to realize rapid, sensitive and accurate detection of pesticide pollutants.

[0004] The technical solution adopted by the present application is: a covalent organic framework-silver nanoparticle hybrid modified electrode, wherein the covalent organic framework-silver nanoparticle hybrid modified electrode is obtained by in-situ growth of covalent organic framework nanosheets on an indium tin oxide substrate using tri(4-aminophenyl)amine and p-phthalaldehyde as monomers as an electrode carrier and orderly assembling silver nanoparticles.

[0005] The application of a covalent organic framework-silver nanoparticle hybrid modified electrode in the preparation of a photoelectrochemical sensor for detecting pesticide residues, wherein the covalent organic framework-silver nanoparticle hybrid modified electrode is used as a substrate, and an amino-modified aptamer is modified on the substrate as a molecular recognition element.

[0006] The aminoated aptamer is an aminoated aptamer of the pesticide component to be detected.

[0007] The aminoated aptamer is an aminoated acetamiprid aptamer

[0008] A preparation method of the photoelectrochemical sensor for detecting pesticide residues comprises the following steps:

[0009] (1) Preparation of photoactive covalent organic framework nanosheet: two monomers of tris (4-aminophenyl) amine and p-xylylene glycol are dissolved in a mixture of mesitylene-acetic acid-ethanol, then mixed, and the above solution is drop-coated on the surface of an indium tin oxide electrode, reacted, washed with ultrapure water, and then covalent organic framework nanosheet is formed on the surface of the electrode;

[0010] (2) Synthesis of silver nanoparticles: citrate solution is mixed with ultrapure water and heated to boiling, then silver nitrate solution is added to the above solution and stirred under reflux, finally, the obtained silver nanoparticles are cooled to room temperature and stored at 4°C for standby;

[0011] (3) Ordered assembly of silver nanoparticles: the modified electrode obtained in step (1) is incubated with the silver nanoparticles obtained in step (2), washed with ultrapure water, and then dried to obtain a covalent organic framework-silver nanoparticle hybrid modified electrode surface;

[0012] (4) Construction of photoelectrochemical sensor: using the aminoated aptamer of the pesticide component to be detected as the molecular recognition element, the modified electrode prepared in step (3) as the substrate, drop-coating the aptamer of the pesticide component to be detected on the surface as the capture probe for assembly, and further assembling mercaptohexanol for surface site blocking, the photoelectrochemical sensor is obtained.

[0013] In step (1), the mass ratio of tris (4-aminophenyl) amine and p-xylylene glycol is 1:1, and after the tris (4-aminophenyl) amine and p-xylylene glycol are dissolved in the mixture of mesitylene-acetic acid-ethanol, the volume ratio of the mixed solvent is adjusted to 5:1:5.

[0014] In step (2), the concentration of citrate is 1%, the concentration of silver nitrate solution is 1%, and the stirring reflux time is 1 hour.

[0015] In step (3), the incubation time of the modified electrode with silver nanoparticles is 12 h, and the incubation temperature is 25°C.

[0016] In step (4), the concentration of aminoated aptamer is 1 μM; the assembly time of the aptamer is 12 hours, the concentration of mercaptohexanol is 1 mM, and the assembly time is 1 hour.

[0017] An electrochemical photoelectric detection platform for acetamiprid pesticide residues, the electrochemical photoelectric detection platform comprises the electrochemical photoelectric sensor.

[0018] The electrode of the electrochemical photoelectric sensor is incubated with different concentrations of acetamiprid at 37 DEG C for 2 hours to achieve specific capture and recognition of acetamiprid.

[0019] The concentration of the phosphate buffer solution is 0.1 mol / L, and the pH is 7.0; the current-time curve scanning voltage is 0V, and the scanning time is 100 s.

[0020] The beneficial effects of the present application are:

[0021] (1) The present application innovatively combines in-situ growth of photoactive covalent organic framework nanosheets and controllable assembly of silver nanoparticles, and utilizes the interaction of the two to improve the photoelectric conversion efficiency of the electrode. By assembling amino-acetylated acetamiprid aptamer on the surface of the silver nanoparticle-covalent organic framework hybrid, specific capture and selective detection of the pesticide acetamiprid is achieved, providing a new strategy for rapid, sensitive and accurate detection of pesticide residues in complex matrices.

[0022] (2) Compared with the hydrothermal synthesis method and the mechanical stirring method, the in-situ assembly strategy of photoactive covalent organic framework has the outstanding advantages of simplicity, rapidness and controllability, and can quickly form a film on the surface of an indium tin oxide electrode.

[0023] (3) Compared with the prior art in which pesticide residue detection relies on large instruments or has poor selectivity, the photoelectrochemical sensing platform of the present application can realize simple, high-sensitivity and selective detection of pesticide residues, and improve the detection efficiency. Compared with the traditional detection method (detection limit ng / mL-μg / mL), the photoelectrochemical sensing platform constructed has a detection limit for acetamiprid as low as 20 pg / mL.

[0024] (4) The high stability of the covalent organic framework gives the sensing platform high reproducibility, and the introduction of the acetamiprid aptamer effectively improves the detection sensitivity and accuracy of the sensing platform, so that the pesticide residues can be detected quickly without complex sample pretreatment steps.

[0025] (5) The application prospect is broad. The technology can be used for rapid and accurate detection of acetamiprid in vegetables, fruits, lake water and other actual samples, and provides a new method for food safety and environmental monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1is the principle diagram of in-situ synthesis of photoactive covalent organic framework nanosheet and pesticide residue detection of the present application: (A) three (4-aminophenyl) amine and p-phenylenedimethanal as monomers are reacted for 10 min at room temperature to synthesize covalent organic framework nanosheet; (B) the step-by-step modification steps of the photoelectrochemical sensor, including the generation of covalent organic framework nanosheet on the electrode surface, the loading of silver nanoparticles, the assembly of amino-derivatized acetamiprid aptamer as capture probe on the surface of silver nanoparticles, and the specific recognition and capture of acetamiprid by the capture probe.

[0027] Figure 2 (a) transmission electron microscopy of photoactive covalent organic framework nanosheet; (b) transmission electron microscopy of silver nanoparticle-covalent organic framework nanosheet hybrid.

[0028] Figure 3 (a) polarization curve of covalent organic framework nanosheet modified electrode (black) and silver nanoparticle-covalent organic framework hybrid modified electrode (red); (b) photocurrent of covalent organic framework nanosheet modified electrode (black) and silver nanoparticle-covalent organic framework hybrid modified electrode (red).

[0029] Figure 4 Feasibility study diagram of photoelectrochemical sensor constructed by silver nanoparticle-covalent organic framework hybrid for acetamiprid detection. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Embodiment 1

[0032] In combination with Figure 1 the present application for in-situ synthesis of photoactive covalent organic framework nanosheet and pesticide residue detection, the following steps are included:

[0033] S1, preparation of photoactive covalent organic framework nanosheet:

[0034] Three (4-aminophenyl) amine and p-phenylenedimethanal two monomers are dissolved in tri-methylbenzene-acetic acid-ethanol mixed solvent according to the mass ratio of 1:1, and the volume ratio of the mixed solvent is adjusted to 5:1:5. After mixing for 5 minutes, 30 μL of the above solution is drop-coated on the surface of an indium tin oxide electrode, reacted for 10 minutes, and then washed with ultrapure water to form covalent organic framework nanosheet on the surface of the electrode;

[0035] S2, synthesis of silver nanoparticles

[0036] Mix 2 mL of citrate solution with 80 mL of ultrapure water and heat to boiling for 15 minutes. Subsequently, add 1.7 mL of silver nitrate solution to the above solution and stir to reflux. Finally, cool the obtained silver nanoparticles to room temperature and store at 4 °C for standby use.

[0037] S3, Silver nanoparticle ordered assembly:

[0038] Incubate the modified electrode obtained in step S1 with 30 μL of silver nanoparticles obtained in step S2, after rinsing with ultrapure water, dry to obtain the covalent organic framework-silver nanoparticle hybrid modified electrode surface;

[0039] S4, Construction of photoelectrochemical sensor

[0040] Adaptors are short-chain nucleic acids obtained by screening through the SELEX technology, with a sequence length mostly between 15-60 bases, which can specifically bind to target substances through secondary bond forces such as hydrogen bonds and electrostatic interactions, and then capture specific target substances, with the advantages of high affinity, easy preparation and modification, low synthesis cost and good stability. Therefore, using acetamiprid adaptor as a molecular recognition element and performing amino modification, the modified electrode obtained in S3 is used as a substrate, 30 μL of amino-modified acetamiprid adaptor is drop-coated on the surface as a capture probe for specific recognition of acetamiprid in complex samples; further assemble 50 μL of mercaptohexanol for surface site blocking;

[0041] S5, Acetamiprid detection:

[0042] Incubate the electrode obtained in S4 with different concentrations of acetamiprid at 37 °C for 2 hours to achieve specific capture and recognition of acetamiprid; use phosphate buffer (pH 7.0) as the base solution, and record the current-time curve of the sensor.

[0043] Example 2 Synthesis of photoactive covalent organic framework nanosheets: (1) Purpose: To achieve the controllable assembly of photoactive covalent organic framework nanosheets on the surface of an indium tin oxide electrode for efficient loading of silver nanoparticles. (2) Solution preparation: Tris(4-aminophenyl)amine solution: Mix 1 mg of tris(4-aminophenyl)amine, 250 μL of mesitylene, 50 μL of acetic acid, and 50 μL of ethanol, and sonicate at a power of 100 W for 3 minutes. p-Phthalaldehyde solution: Mix 1 mg of p-phthalaldehyde, 250 μL of mesitylene, 50 μL of acetic acid, and 50 μL of ethanol, and sonicate at a power of 100 W for 3 minutes. (3) Instruments: Electronic balance (accuracy 0.0001 g); ultrasonic cleaning instrument (power 100 W). (4) Steps: Synthesis of photoactive covalent organic framework nanosheets: Rapidly mix 20 μL of tris(4-aminophenyl)amine solution and 20 μL of p-phthalaldehyde, and drop coat on the surface of an indium tin oxide electrode with an area of 1 cm*1 cm. After reacting for 10 minutes, rinse with ultrapure water 3 times, and naturally dry at room temperature. Example 3 Construction of a high-sensitivity photoelectrochemical detection platform (1) Purpose: To construct a photoelectrochemical sensing platform with high sensitivity, good selectivity, and strong stability, and to achieve simple, accurate, and rapid detection of acetamiprid. (2) Raw materials and equipment: Raw materials: Aminated acetamiprid aptamer (sequence 5'-NH2-(CH2)6-AAAACTGACACCATATTATGAAGA-3'); photoelectrochemical reaction instrument (PEAC 200A); reference electrode (saturated calomel electrode); counter electrode (platinum wire electrode); detection base solution (0.1 mol / L phosphate buffer, pH 7.0). (3) Operation process: Use a silver nanoparticle-covalent organic framework hybrid modified indium tin oxide electrode as a substrate, and after assembling aminated aptamer on the surface thereof, incubate it with different concentrations of acetamiprid at 37 °C for 2 hours. Take it as a working electrode and combine it with a saturated calomel electrode and a platinum wire electrode to construct a three-electrode system. Use 0.1 mol / L phosphate buffer (pH 7.0) as the test base solution, and record the photocurrent signal of the modified electrode. (4) Key parameters: Photocurrent scan voltage: 0 V; scan time: 100 s; scan interval: 1 s.

[0044] Results analysis:

[0045] As Figure 2 (a) The transmission electron microscopy image of the photoactive covalent organic framework nanosheets shows that they exhibit a typical two-dimensional sheet structure; Figure 2 (b) The transmission electron microscopy image of the silver nanoparticle-covalent organic framework nanosheet hybrid shows that spherical silver nanoparticles are uniformly distributed on the surface of the covalent organic framework nanosheets.

[0046] As Figure 3(a) Polarization curves of the ZIF-8 nanosheet modified electrode (black) and the AgNPs-ZIF-8 hybrid modified electrode (red) are shown, and it can be seen that the loading of AgNPs improves the reduction current response of the electrode; Figure 3 (b) The photocurrent curves of the ZIF-8 nanosheet modified electrode (black) and the AgNPs-ZIF-8 hybrid modified electrode (red) are shown, and it can be seen that the AgNPs-ZIF-8 hybrid has a higher photocurrent response, which can improve the detection sensitivity.

[0047] The feasibility study of the photoelectrochemical sensor constructed by the AgNPs-ZIF-8 hybrid for acetochlor detection is shown in Figure 4 As shown, when there is no acetochlor, the sensor has a larger photocurrent response (red curve), and when 100 ng / mL acetochlor is added, the photocurrent response of the sensor is significantly reduced, and the photoelectrochemical sensing platform constructed on the surface can be used for acetochlor detection.

Claims

1. A photoelectrochemical sensor prepared by a covalent organic framework-silver nanoparticle hybrid modified electrode, characterized in that, The covalent organic framework-silver nanoparticle hybrid modified electrode is obtained by in-situ growth of covalent organic framework nanosheets as an electrode carrier and ordered assembly of silver nanoparticles on an indium tin oxide substrate using tri(4-aminophenyl)amine and p-phthalaldehyde as monomers, and the covalent organic framework-silver nanoparticle hybrid modified electrode is used as a substrate and an aminated aptamer modified on the substrate is used as a molecular recognition element.

2. The use of the photoelectrochemical sensor prepared by the covalent organic framework-silver nanoparticle hybrid modified electrode of claim 1 in the preparation of a photoelectrochemical sensor for detecting pesticide residues, characterized in that, The covalent organic framework-silver nanoparticle hybrid modified electrode is used as a substrate, and an aminated aptamer modified on the substrate is used as a molecular recognition element.

3. Use according to claim 2, characterized in that, The aminated aptamer is an aminated aptamer of a pesticide component to be detected.

4. Use according to claim 3, characterized in that, The aminated aptamer is an aminated acetamiprid aptamer.

5. A method for preparing a photoelectrochemical sensor for detecting pesticide residues in the use according to claim 2, characterized in that, The method comprises the following steps: (1) Preparation of photoactive covalent organic framework nanosheets: tri(4-aminophenyl)amine and p-phthalaldehyde monomers are dissolved in a mixture of mesitylene-acetic acid-ethanol, and then mixed to obtain a mesitylene-acetic acid-ethanol mixed solution containing tri(4-aminophenyl)amine and p-phthalaldehyde, and the mesitylene-acetic acid-ethanol mixed solution containing tri(4-aminophenyl)amine and p-phthalaldehyde is drop-coated on the surface of an indium tin oxide electrode for reaction, and then washed with ultrapure water to form covalent organic framework nanosheets on the surface of the electrode; (2) Synthesis of silver nanoparticles: citrate solution is mixed with ultrapure water and heated to boiling, then silver nitrate solution is added and stirred under reflux, finally the obtained silver nanoparticles are cooled to room temperature and stored at 4°C for standby; (3) Ordered assembly of silver nanoparticles: the modified electrode obtained in step (1) is incubated with the silver nanoparticles obtained in step (2), and then washed with ultrapure water and dried to obtain a covalent organic framework-silver nanoparticle hybrid modified electrode surface; (4) Construction of a photoelectrochemical sensor: an aminated aptamer of a pesticide component to be detected is used as a molecular recognition element, and the modified electrode prepared in step (3) is used as a substrate, and an aminated aptamer of a pesticide component to be detected is drop-coated on the surface of the substrate as a capture probe for assembly, and mercaptohexanol is further assembled to block the surface sites, thereby obtaining the photoelectrochemical sensor.

6. The production method according to claim 5, wherein In step (1), the mass ratio of tri(4-aminophenyl)amine and p-phthalaldehyde monomers is 1:1, and the tri(4-aminophenyl)amine and p-phthalaldehyde are dissolved in a mixture of mesitylene-acetic acid-ethanol, and then the volume ratio of the mixed solvent is adjusted to 5:1:

5.

7. The preparation method according to claim 5, characterized in that, In step (2), the concentration of citrate is 1%, the concentration of silver nitrate solution is 1%, and the stirring and reflux time is 1 hour.

8. The production method according to claim 5, characterized by, In step (3), the incubation time of the modified electrode with silver nanoparticles is 12 h, and the incubation temperature is 25°C.

9. The production method according to claim 5, characterized by, In step (4), the concentration of the aminated aptamer is 1 μM, the assembly time of the aptamer is 12 hours, the concentration of mercaptohexanol is 1 mM, and the assembly time is 1 hour.

10. A photoelectrochemical detection platform for acetamiprid pesticide residues, characterized in that, The photoelectrochemical detection platform comprises the photoelectrochemical sensor of claim 2.

11. The photoelectrochemical detection platform of claim 10, wherein, The electrode of the photoelectrochemical sensor is incubated with different concentrations of acetamiprid at 37 °C for 2 hours to achieve specific capture and recognition of acetamiprid, and the current-time curve of the sensor is recorded in a phosphate buffer solution as a base solution.

12. The photoelectrochemical detection platform of claim 11, wherein, The phosphate buffer solution has a concentration of 0.1 mol / L and a pH of 7.0; the current-time curve scanning voltage is 0 V, and the scanning time is 100 s. The phosphate buffer solution has a concentration of 0.1 mol / L and a pH of 7.0; the current-time curve scanning voltage is 0 V, and the scanning time is 100 s.

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