Preparation method of ITO / Au (at) CdS (at) ALP photoelectrochemical sensor for rapidly detecting organophosphorus pesticide

Abstract

The invention discloses a preparation method of an ITO / Au (at) CdS (at) ALP photoelectrochemical sensor for rapidly detecting organophosphorus pesticides. The method comprises the following steps: preparing Au (at) CdS NPs, and modifying the surface of the Au (at) CdS NPs with alkaline phosphatase to construct the sensor; different from a traditional photoelectrochemical sensor, a target substance is detected by causing change of system impedance or introducing (removing) a photoelectrochemical material, the intensity of a photoelectric signal is changed by changing the content of an electron donor in a system, and the preparation method is simple to operate, does not need a complex modification process, and is suitable for large-scale production. The method has good reproducibility and stability, and can rapidly, sensitively and accurately detect the organophosphorus pesticide.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrochemical detection, and relates to a method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides. Background Art

[0002] Organophosphorus pesticides (OPPs) are commonly used insecticides, fungicides and herbicides for controlling crop pests and weeds. The mechanism of action of organophosphorus pesticides involves the destruction of enzyme systems, especially by inhibiting the activity of acetylcholinesterase, leading to abnormal excitement and paralysis of the nervous system, and ultimately death. However, despite the important role that organophosphorus pesticides play in agricultural production, there are also potential hazards and risks. Organophosphorus pesticides are potentially harmful to human health. Organophosphorus pesticides are effective cholinesterase inhibitors that block the activity of cholinesterase and affect the normal function of the neurotransmitter system. Long-term exposure or contact with organophosphorus pesticides may cause symptoms such as headache, dizziness, muscle cramps, nausea, vomiting, fatigue and other neurological symptoms. In addition, organophosphorus pesticides can damage the respiratory system, reproductive system, endocrine system and immune system, leading to various diseases. In addition, organophosphorus pesticides may also cause environmental hazards, such as residues in farmland soil and water, which have a negative impact on soil ecosystems and aquatic organisms. Therefore, it is crucial to develop a sensitive, rapid and reliable method for detecting organophosphorus pesticides.

[0003] Among the detection methods of organophosphorus pesticides, electrochemiluminescence (ECL) analysis, fluorescence detection, electrochemical methods and photoelectrochemical (PEC) analysis, each has its own unique characteristics. However, ECL analysis, fluorescence detection and electrochemical methods have inherent limitations in some aspects, which restrict their widespread application. Although ECL analysis is highly sensitive, it may be interfered by other chemicals, resulting in false positive or false negative results. Fluorescence detection relies on the specific properties of fluorescent molecules and may not be able to detect certain substances that do not contain fluorescent groups. Electrochemical methods are limited by factors such as electrode selection and stability and electrolyte solution composition. In contrast, PEC analysis has a unique working principle and significant advantages. It is based on the energy conversion between light and electricity, and uses the correlation between the target substance and the photoelectrochemical reaction process to detect the concentration of the target substance. This method has the characteristics of low background signal and ultra-high sensitivity, and can detect organophosphorus pesticides more accurately. In addition, the excitation and detection processes in photoelectrochemical analysis are separated, which reduces the influence of interference factors and improves the accuracy and reliability of detection. Therefore, photoelectrochemical analysis has broad application prospects in the field of organophosphorus pesticide detection.

[0004] Traditional photoelectrochemistry involves detecting target substances by causing changes in system impedance or by introducing (removing) photoelectrochemical materials that change electrical signals. This type of sensing platform is bulky and has too many electrode modification steps, which limits the repeatability of the sensing platform. Photoelectrochemical analysis usually involves a charge transfer process between an electron donor and an electron acceptor, which affects the generation and change of the photoelectric signal. When there is an electron acceptor in the detection solution, electrons flow from the electrode to the solution, and when there is an electron donor in the detection solution, electrons flow from the solution to the electrode. In this process, changes in the content of electron donors or electron acceptors in the system directly affect the intensity of the photoelectric signal. Therefore, if the target substance reacts with the electron donor (acceptor) or inhibits its production, it will cause changes in the content of electron donors or acceptors in the system, thereby affecting the generation and change of the photoelectric signal. This sensing platform is simple to operate, does not require complex modification processes, and has good reproducibility and stability, thereby better meeting the detection needs of different fields.

[0005] Based on this, there is an urgent need to develop a target-triggered detection mode for changes in electron donor (acceptor) content for highly sensitive detection of organophosphorus pesticides. This sensing platform is simple to operate, does not require complex modification processes, and has good reproducibility and stability, so as to better meet the detection needs of different fields. Summary of the invention

[0006] In view of the above technical problems, the present invention aims to provide a method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides. The method sequentially comprises the steps of preparing Au@CdS NPs and modifying the surface of Au@CdS NPs with alkaline phosphatase to construct a sensor. The present invention is different from traditional photoelectrochemical sensors that detect target substances by causing changes in system impedance or by introducing (removing) photoelectrochemical materials. Instead, the intensity of the photoelectric signal is changed by changing the electron donor content in the system. The sensor is simple to operate, does not require a complicated modification process, has good reproducibility and stability, and can detect organophosphorus pesticides quickly, sensitively and accurately.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides is carried out in the following steps:

[0009] (1) Preparation of Au NPs

[0010] Chloroauric acid was placed in a three-necked flask, heated to boiling, and sodium citrate was quickly added, boiled for 15 min, and cooled to room temperature to obtain Au NPs;

[0011] (2) Preparation of Au@CdS NPs

[0012] The prepared Au NPs were transferred to a three-necked round-bottom flask, and sodium citrate solution, cadmium chloride solution and thiourea solution were added to the flask respectively, and then 0.15 mL of ammonia water was added to adjust the pH of the solution to 9-11, and heated and stirred at 70 °C for 24 h to obtain Au@CdS NPs;

[0013] (3) Preparation of ITO / Au@CdS@ALP electrode

[0014] 10 μL Au@CdS NPs were dropped on the pretreated ITO electrode surface and air-dried to obtain an ITO / Au@CdS electrode. The ITO / Au@CdS electrode was incubated in an alkaline phosphatase solution (ALP) for 5 min, taken out, and rinsed with deionized water to remove excess alkaline phosphatase on the surface to obtain an ITO / Au@CdS@ALP electrode.

[0015] As a limitation of the preparation method of the present invention, in step (1), the molar ratio of chloroauric acid to sodium citrate is 1:4.

[0016] As another limitation of the preparation method of the present invention, in step (2), the molar ratio of the sodium citrate solution, the chromium chloride solution and the thiourea solution is 30:25:26.

[0017] As a third limitation of the preparation method of the present invention, in step (2), the mass ratio of Au NPs to sodium citrate solution is 2:1.

[0018] As a fourth limitation of the preparation method of the present invention, in step (2), the mass fraction of the ammonia water is 25 wt.%.

[0019] As a fifth limitation of the preparation method of the present invention, in step (3), the concentration of the alkaline phosphatase is 0.1 U / mL.

[0020] As a sixth limitation of the preparation method of the present invention, in step (3), the surface pretreatment of the ITO electrode is carried out in the following order:

[0021] S1. Cut the ITO electrode into a 1×5 cm rectangle, wash the ITO electrode with detergent, secondary water, and anhydrous ethanol for 3-5 times, and then dry it with nitrogen for 10-12 minutes;

[0022] S2. Add the dried ITO electrode to a potassium alcohol solution formed by isopropanol and potassium hydroxide and boil it for 15 minutes. After ultrasonically cleaning the boiled ITO electrode with deionized water and anhydrous ethanol for 20 minutes, immerse the ITO electrode in an ethanol solution containing 3-aminopropyltriethylsilane at room temperature overnight, and then store it in the ethanol solution for later use.

[0023] As a further limitation of the ITO electrode surface pretreatment of the present invention, in step S2, the volume mass ratio of isopropanol to potassium hydroxide is 100:11.2 mL / g; the volume ratio of 3-aminopropyltriethylsilane to ethanol is 1:99.

[0024] The Au@CdS NPs prepared by the present invention are spherical nanoparticles with Au nanoparticles as cores and CdS nanoparticles as shells. This special morphology can, on the one hand, ensure that alkaline phosphatase is uniformly adsorbed on the surface of Au@CdS NPs, and on the other hand, due to the surface plasma effect of the noble metal, the material can have higher light absorption efficiency and charge separation efficiency.

[0025] Alkaline phosphatase can catalyze ascorbic acid 2-phosphate to generate ascorbic acid. It acts as an electron donor in photoelectrochemistry. When organophosphorus pesticides are present, the activity of alkaline phosphatase can be inhibited, resulting in a decrease in ascorbic acid content and a weakening of the photoelectric signal. The results show that with the increase in the content of organophosphorus pesticides, the photoelectric signal tends to gradually decrease. The concentration of organophosphorus pesticides and the signal difference show a good linear relationship. This method is fast, sensitive and accurate and can be widely used in the detection and analysis of organophosphorus pesticides.

[0026] The above technical solution of the present invention is taken as a whole, and each step is closely related and influences each other, which jointly determine the morphological characteristics and performance of the product.

[0027] The above technical solution has the following advantages or beneficial effects:

[0028] 1. Compared with simple semiconductor quantum dots, the composite materials of precious metals and semiconductor quantum dots can have higher light absorption efficiency and charge separation efficiency due to the surface plasma effect of precious metals.

[0029] 2. Ultrasensitive detection of organophosphorus pesticides is achieved by inhibiting electron donors. When organophosphorus pesticides are present, the activity of alkaline phosphatase can be inhibited, resulting in a decrease in ascorbic acid content and a weakening of the photoelectric signal. -9 The linear relationship was good in the range of -1.0μg / mL, and the detection limit was 0.272×10 -9 μg / mL; this method is rapid, sensitive and accurate, and can be widely used in the detection and analysis of organophosphorus pesticides.

[0030] 3. The photoelectrochemical sensor prepared by the present invention is fast, sensitive and accurate, and can be widely used in the detection and analysis of organophosphorus pesticides. It has mild reaction conditions, simple preparation process, low cost, high repeatability, and is easy to promote industrial application.

[0031] The invention is suitable for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides.

[0032] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 TEM image of Au@CdS NPs prepared in Example 1 of the present invention;

[0034] Figure 2 This is the XRD pattern of Au@CdS NPs prepared in Example 1 of the present invention;

[0035] Figure 3 This is a feasibility test diagram of the photoelectric sensor prepared in Example 1 of the present invention;

[0036] Figure 4 This is a response diagram of the photoelectric sensor prepared in Example 1 of the present invention to organophosphorus pesticides of different concentrations;

[0037] Figure 5 This is a stability test diagram of the photoelectric sensor prepared in Example 1 of the present invention;

[0038] Figure 6 This is a selectivity test diagram of the photoelectric sensor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0040] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0041] Example 1

[0042] In this embodiment, an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides is prepared, and the preparation process and steps are as follows:

[0043] (1) Preparation of Au NPs

[0044] Chloroauric acid was placed in a three-necked flask, heated to boiling, and sodium citrate was quickly added (the molar ratio of chloroauric acid to sodium citrate was 1:4), boiled for 15 min, and cooled to room temperature to obtain Au NPs;

[0045] (2) Preparation of Au@CdS NPs

[0046] The prepared Au NPs (the molar ratio of Au NPs to sodium citrate solution is 2:1) were transferred to a three-necked round-bottom flask, and sodium citrate solution, cadmium chloride solution and thiourea solution (the molar ratio of sodium citrate solution, cadmium chloride solution and thiourea solution is 30:25:26) were added to the flask respectively, and then 0.15 mL of 25 wt.% ammonia water was added, and the pH of the solution was adjusted to 10. The mixture was heated and stirred at 70 °C for 24 h to obtain Au@CdS NPs with a core-shell structure.

[0047] (3) Preparation of ITO / Au@CdS@ALP electrode

[0048] 10 μL Au@CdS NPs were dropped on the pretreated ITO electrode surface and air-dried to obtain an ITO / Au@CdS electrode. The ITO / Au@CdS electrode was incubated in a 0.1 U / mL alkaline phosphatase solution for 5 min, then taken out and rinsed with deionized water to remove excess alkaline phosphatase on the surface to obtain an ITO / Au@CdS@ALP electrode.

[0049] The ITO electrode pretreatment process is as follows:

[0050] S1. Cut the ITO electrode into a 1×5 cm rectangle, wash the ITO electrode three times with detergent, secondary water, and anhydrous ethanol, and then dry it with nitrogen for 10 minutes;

[0051] S2. Add the dried ITO electrode to a potassium alcohol solution formed by 100 mL of isopropanol and 11.2 g of potassium hydroxide and boil it for 15 minutes. After ultrasonically cleaning the boiled ITO electrode with deionized water and anhydrous ethanol for 20 minutes, immerse the ITO electrode in an ethanol solution containing 3-aminopropyltriethylsilane (the volume ratio of 3-aminopropyltriethylsilane to ethanol is 1:99) at room temperature overnight, and then store it in the ethanol solution for later use.

[0052] The performance of the photoelectrochemical sensor prepared in this example was tested, and the specific test results are as follows:

[0053] from Figure 1 It can be seen from the TEM image that the core-shell Au@CdS NPs prepared in this embodiment are spherical nanomaterials with Au nanoparticles as the core and CdS nanoparticles as the shell. The diameter of Au NPs is 20 nm and the shell thickness is 12 nm.

[0054] The core-shell Au@CdS NPs prepared in this example were subjected to XRD test, and the results are as follows: Figure 2 As shown, it can be seen that five sharp peaks are observed at 26.20°, 38.2°, 44.3°, 64.5° and 77.4° for the core-shell Au@CdS NPs, corresponding to the (002) plane of CdS and the (111), (200), (220) and (311) planes of Au, respectively. These results indicate that Au@CdS NPs are successfully prepared.

[0055] To characterize the feasibility of the sensing platform, all photoelectric signal detections were performed in a PBS detection solution (containing 200 mM ascorbic acid 2-phosphate) at a voltage of 0 V, and the excitation light source was blue light. The photoelectric signals at different electrode modification stages were tested, such as Figure 3 Curve a represents the material signal when there is only dissolved oxygen in the test liquid, where O 2 As an electron acceptor, the material presents a cathode photocurrent. In the presence of ascorbic acid 2-phosphate, alkaline phosphatase catalyzes ascorbic acid 2-phosphate to produce ascorbic acid, and ascorbic acid acts as an electron donor to convert the signal into an anodic photocurrent, as shown in Figure b. When organophosphorus pesticides are present, the activity of alkaline phosphatase is inhibited, resulting in a reduction in the production of ascorbic acid and a weakening of the intensity of the anodic photocurrent, as shown in Figure c. The results show that the sensing platform can effectively detect organophosphorus pesticides.

[0056] The sensor prepared in this example was applied to the detection of organophosphorus pesticides. The specific detection process was as follows: ITO / Au@CdS@ALP electrodes were placed at different concentrations (a: 0, b: 1×10 -9 μg / mL, c:1×10 -5 μg / mL, d:1×10 -4 μg / mL, e:1×10 -2 The electrode was incubated in a solution of acephate (1 μg / mL, f: 1 μg / mL) for 5 min to allow the acephate solution to bind to alkaline phosphatase and inhibit its activity. The electrode was then rinsed three times with deionized water for photocurrent detection.

[0057] like Figure 4As shown in the figure, it is the response of different concentrations of acephate solution to the sensing platform. It can be seen from the figure that in the absence of acephate solution (curve a), alkaline phosphatase catalyzes ascorbic acid 2-phosphate to produce ascorbic acid, and ascorbic acid acts as an electron donor in the reaction to produce a strong photoelectric signal. However, the presence of acephate solution in the platform inhibits the activity of alkaline phosphatase, resulting in a decrease in the amount of ascorbic acid produced by ascorbic acid 2-phosphate catalyzed by alkaline phosphatase, thereby producing a weaker photoelectric signal. As the concentration of acephate solution increases, the inhibitory effect on alkaline phosphatase becomes more obvious, accompanied by a corresponding downward trend in the photoelectric signal. At 1×10 -9 A good linear relationship was observed in the range of -1.0 μg / mL, and the detection limit was 0.272×10 -9 μg / mL.

[0058] The sensor prepared in this embodiment was used to detect different types of organophosphorus pesticides. The detection process was consistent with the above-mentioned detection process of acephate. The specific test data are shown in the following table:

[0059] Types of organophosphorus pesticides Acephate Dichlorvos Oxydemeton-methyl Phoxim concentration 0.1 μg / mL 0.1 μg / mL 0.1 μg / mL 0.1 μg / mL Signal drop (△I) 1.75μA 1.68μA 1.55μA 1.68μA

[0060] The stability and selectivity of the sensor prepared in this example were tested. Figure 5 and Figure 6 shown.

[0061] Figure 5 This is a stability test of the sensor platform. It can be seen from the figure that within the 500s time frame, the photoelectric signal of the platform did not drop significantly, indicating that it has good stability.

[0062] Figure 6 To test the selectivity of the sensor platform, under the same experimental conditions, only the target substance was changed, and the response of the sensor platform to different pesticides was tested. As can be seen from the figure, the sensor platform only showed a good response to organophosphorus pesticides.

[0063] Embodiment 2-4

[0064] In Examples 2-4, an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides was prepared respectively. The preparation process was similar to that of Example 1, except that the parameters in the preparation process were different, as shown in the following table:

[0065]

[0066] The photoelectrochemical sensor prepared in Example 2-4 detects organophosphorus pesticides quickly, sensitively and accurately, has mild reaction conditions and a simple preparation process.

[0067] Comparative Example

[0068] In order to explore the effects of different nanomaterials and the modification time of alkaline phosphatase on the performance of the product of the present invention during the preparation process of the present invention, the following comparative experiments were conducted. Different photoelectrochemical sensors were prepared in the following comparative examples, as follows:

[0069] Comparative Example 1

[0070] This comparative example prepares a photoelectrochemical sensor similar to that of Example 1, except that the nanomaterial of the photoelectrochemical sensor is not Au@CdS NPs, but CdS QDs. The remaining steps are the same as those of Example 1. The specific preparation steps of CdS QDs are as follows:

[0071] CdS QDs were prepared by aqueous synthesis method. 250 μL of thioglycolic acid was added to CdCl 2 The solution (50 mL, 0.01 M) was then deoxygenated by nitrogen gas for 30 min, the pH of the solution was adjusted to 11 with 1.0 M NaOH, and then 5.0 mL 0.1 M Na 2 The S solution was quickly added into the reaction system, and then the reaction temperature was heated to boiling and refluxed for 4 h to obtain TGA-CdS QDs.

[0072] The photoelectrochemical sensor prepared in this comparative example was tested. -8 -1.0μg / mL range, the detection limit is 3.85×10 -9 μg / mL, and its selectivity and stability are inferior to those of the sensor prepared in Example 1.

[0073] Comparative Example 2

[0074] In this comparative example, a photoelectrochemical sensor similar to that in Example 1 is prepared, except that in step (3), the ITO / Au@CdS electrode solution is incubated for 2 minutes. The remaining steps are the same as those in Example 1.

[0075] The photoelectrochemical sensor prepared in this comparative example was tested. -9 -0.1μg / mL range, the detection limit is 0.756×10 -9 μg / mL, and its selectivity and stability are inferior to those of the sensor prepared in Example 1.

[0076] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides, characterized in that: Follow the steps below in order: (1) Preparation of Au NPs Chloroauric acid was placed in a three-necked flask, heated to boiling, and sodium citrate was quickly added, boiled for 15 min, and cooled to room temperature to obtain Au NPs; (2) Preparation of Au@CdS NPs The prepared Au NPs were transferred to a three-necked round-bottom flask, and sodium citrate solution, cadmium chloride solution and thiourea solution were added to the flask respectively, and then 0.15 mL of ammonia water was added to adjust the pH of the solution to 9-11, and heated and stirred at 70 °C for 24 h to obtain Au@CdS NPs; (3) Preparation of ITO / Au@CdS@ALP electrode 10 μL of Au@CdS NPs was dropped on the pretreated ITO electrode surface and air-dried to obtain the ITO / Au@CdS electrode; The ITO / Au@CdS electrode was incubated in an alkaline phosphatase solution for 5 min, then taken out and rinsed with deionized water to remove excess alkaline phosphatase on the surface, thereby obtaining an ITO / Au@CdS@ALP electrode.

2. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (1), the molar ratio of chloroauric acid to sodium citrate is 1:

4.

3. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (2), the molar ratio of the sodium citrate solution, the chromium chloride solution and the thiourea solution is 30:25:

26.

4. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (2), the mass ratio of Au NPs to sodium citrate solution is 2:

1.

5. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (2), the mass fraction of the ammonia water is 25wt.%.

6. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (3), the concentration of alkaline phosphatase is 0.1 U / mL.

7. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides according to claim 1, characterized in that: In step (3), the ITO electrode surface pretreatment is carried out in the following order: S1. Cut the ITO electrode into a 1×5 cm rectangle, wash the ITO electrode with detergent, secondary water, and anhydrous ethanol for 3-5 times, and then dry it with nitrogen for 10-12 minutes; S2. Add the dried ITO electrode to a potassium alcohol solution formed by isopropanol and potassium hydroxide and boil it for 15 minutes. After ultrasonically cleaning the boiled ITO electrode with deionized water and anhydrous ethanol for 20 minutes, immerse the ITO electrode in an ethanol solution containing 3-aminopropyltriethylsilane at room temperature overnight, and then store it in the ethanol solution for later use.

8. The ITO electrode surface pretreatment according to claim 7, characterized in that: In step S2, the volume mass ratio of isopropanol to potassium hydroxide is 100:11.2 mL / g; the volume ratio of 3-aminopropyltriethylsilane to ethanol is 1:99.

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