A preparation method of an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides

Abstract

The application discloses a preparation method of an ITO / Au@CdS / ALP photoelectrochemical sensor for rapidly detecting organophosphorus pesticides, which comprises the following steps: preparing Au@CdS NPs, and modifying alkaline phosphatase on the surface of the Au@CdS NPs to construct the sensor; the application is different from traditional photoelectrochemical sensors, which detect target substances by causing changes in system impedance or by introducing (removing) photoelectrochemical materials, but changes the intensity of photoelectric signals by changing the content of electron donors in the system; the preparation method is simple in operation, does not need a complex modification process, has good reproducibility and stability, and can rapidly, sensitively and accurately detect organophosphorus pesticides.

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] Organophosphate pesticides (OPPs) are commonly used insecticides, fungicides, and herbicides for controlling crop pests, diseases, and weeds. Their mechanism of action involves disrupting enzyme systems, particularly by inhibiting acetylcholinesterase activity, leading to abnormal nervous system excitation and paralysis, ultimately causing death. However, despite their important role in agricultural production, OPPs also present potential hazards and risks. OPPs pose potential risks to human health. OPPs are potent cholinesterase inhibitors, blocking cholinesterase activity and affecting the normal function of the neurotransmitter system. Long-term exposure or contact with OPPs can cause symptoms such as headaches, dizziness, muscle twitching, nausea, vomiting, fatigue, and other neurological symptoms. OPPs can also damage the respiratory, reproductive, endocrine, and immune systems, leading to various diseases. Furthermore, OPPs can pose environmental risks, such as residues in agricultural soil and water, negatively impacting soil ecosystems and aquatic life. Therefore, the development of sensitive, rapid, and reliable methods for detecting OPPs is crucial.

[0003] Among the methods for detecting organophosphorus pesticides, electrochemiluminescence (ECL), fluorescence detection, electrochemical methods, and photoelectrochemical (PEC) analysis each have their own unique characteristics. However, ECL, fluorescence, and electrochemical methods have inherent limitations that restrict their widespread application. Although highly sensitive, ECL analysis can be subject to interference from other chemicals, resulting in false-positive or false-negative results. Fluorescence detection relies on the specific properties of fluorescent molecules and may not detect certain substances that do not contain fluorescent groups. Electrochemical methods are limited by factors such as electrode selection and stability, as well as electrolyte solution composition. In contrast, PEC analysis has a unique operating principle and significant advantages. It is based on the energy conversion between light and electricity, exploiting the correlation between the target substance and the photoelectrochemical reaction process to detect the concentration of the target substance. This method has low background signal and ultrahigh sensitivity, enabling more accurate detection of organophosphorus pesticides. Furthermore, the excitation and detection processes in photoelectrochemical analysis are separated, reducing the influence of interfering factors and improving detection accuracy and reliability. 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 the impedance of the system or by introducing (removing) photoelectrochemical materials that change the electrical signal. 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 a complex modification process, 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, thereby better meeting the detection needs of different fields. Summary of the Invention

[0006] In response to 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 preparation of Au@CdS NPs and the modification of the Au@CdS NPs surface with alkaline phosphatase to construct a sensor. Unlike traditional photoelectrochemical sensors that detect target substances by causing changes in system impedance or by introducing (removing) photoelectrochemical materials, the present invention changes the intensity of the photoelectric signal by changing the electron donor content in the system. This sensor is simple to operate, does not require a complex 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 order:

[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. The mixture was allowed to boil for 15 minutes and then 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. Then, 0.15 mL of ammonia water was added to adjust the pH of the solution to 9-11. The mixture was 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 of Au@CdS NPs was dropped onto the pretreated ITO electrode surface and air-dried to obtain an ITO / Au@CdS electrode. The ITO / Au@CdS electrode was incubated in alkaline phosphatase solution (ALP) for 5 min, taken out, and rinsed with deionized water to remove excess alkaline phosphatase on the surface, thereby obtaining 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 3-5 times in sequence, and then dry it with nitrogen for 10-12 minutes;

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

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

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

[0025] Alkaline phosphatase catalyzes the conversion of ascorbic acid 2-phosphate to ascorbic acid, acting as an electron donor in photoelectrochemical analysis. The presence of organophosphorus pesticides inhibits alkaline phosphatase activity, leading to a decrease in ascorbic acid content and a weakening of the photoelectric signal. Results showed that the photoelectric signal gradually decreased with increasing organophosphorus pesticide concentration. A good linear relationship was observed between organophosphorus pesticide concentration and the signal difference. This method is rapid, sensitive, and accurate, and can be widely used for the detection and analysis of organophosphorus pesticides.

[0026] The above technical solution of the present invention is taken as a whole, and the various steps are closely related and influence 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, composite materials of noble metals and semiconductor quantum dots can have higher light absorption efficiency and charge separation efficiency due to the surface plasma effect of noble metals.

[0029] 2. Ultra-sensitive detection of organophosphorus pesticides is achieved by suppressing electron donors. In the presence of organophosphorus pesticides, the activity of alkaline phosphatase is 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 and high repeatability, which is convenient for promotion and 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 with reference to 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 graph showing the response of the photoelectric sensor prepared in Example 1 of the present invention to organophosphorus pesticides at 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 merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection 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, unless otherwise specified, are all conventional methods in the art.

[0041] Example 1

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

[0043] (1) Preparation of Au NPs

[0044] AuCl2 was placed in a three-necked flask and heated to boiling. Then, sodium citrate was quickly added (the molar ratio of auCl2 to sodium citrate was 1:4). The mixture was allowed to boil 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 was 2:1) were transferred to a three-necked round-bottom flask, and sodium citrate solution, cadmium chloride solution, and thiourea solution were added to the flask (the molar ratio of sodium citrate solution, cadmium chloride solution, and thiourea solution was 30:25:26), respectively. 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 of Au@CdS NPs was dropped onto the surface of the pretreated ITO electrode 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 minutes, then removed and rinsed with deionized water to remove excess alkaline phosphatase on the surface, obtaining 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 it 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 for 15 minutes. Ultrasonic clean the boiled ITO electrode with deionized water and anhydrous ethanol for 20 minutes in sequence. Then, 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 future 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 the 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 were 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 the Au@CdS NPs are successfully prepared.

[0055] To characterize the feasibility of the sensing platform, all photoelectric signal detection was carried out in PBS detection solution (containing 200mM ascorbic acid 2-phosphate) at a voltage of 0V, 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 only dissolved oxygen is present in the test solution, with O2 acting as an electron acceptor, resulting in a cathode photocurrent. In the presence of ascorbic acid 2-phosphate, alkaline phosphatase catalyzes the conversion of ascorbic acid 2-phosphate to ascorbic acid, which acts as an electron donor, converting the signal into an anodic photocurrent, as shown in Figure b. The presence of organophosphorus pesticides inhibits alkaline phosphatase activity, resulting in reduced ascorbic acid production and a weakening of the anodic photocurrent, as shown in Figure c. These results demonstrate 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 electrodes were 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 electrodes were then rinsed three times with deionized water for photocurrent detection.

[0057] like Figure 4The figure shows the response of the sensing platform to different concentrations of acephate solution. As can be seen from the figure, in the absence of acephate solution (curve a), alkaline phosphatase catalyzes ascorbic acid 2-phosphate to produce ascorbic acid. Ascorbic acid acts as an electron donor in the reaction, generating 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 generating 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 example 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. As can be seen from the figure, 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] Examples 2-4

[0064] In Examples 2-4, an ITO / Au@CdS@ALP photoelectrochemical sensor for rapid detection of organophosphorus pesticides was prepared. The preparation process was similar to that of Example 1, with the only difference being 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] In this comparative example, a photoelectrochemical sensor similar to that in Example 1 was prepared. The only difference was that the nanomaterial of the photoelectrochemical sensor was not Au@CdS NPs but CdS QDs. The remaining steps were the same as in Example 1. The specific preparation steps of CdS QDs were as follows:

[0071] CdS QDs were prepared by an aqueous phase synthesis method. 250 μL of thioglycolic acid was added to a CdCl2 solution (50 mL, 0.01 M), and then nitrogen was passed through for 30 min to deoxygenate. The pH of the solution was adjusted to 11 with 1.0 M NaOH. Subsequently, 5.0 mL of 0.1 M Na2S solution was quickly added to the reaction system. The reaction temperature was then 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, the detection limit was 3.85×10 -9 μg / mL, and its selectivity and stability were inferior to the sensor prepared in Example 1.

[0073] Comparative Example 2

[0074] In this comparative example, a photoelectrochemical sensor similar to that in Example 1 was prepared, with the only difference being that, in step (3), the ITO / Au@CdS electrode solution was incubated for 2 min. The remaining steps were the same as those in Example 1.

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

[0076] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are 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 will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within 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 detecting 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. The mixture was allowed to boil for 15 min and then cooled to room temperature to obtain Au NPs. The molar ratio of chloroauric acid to sodium citrate is 1:4; (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, followed by 0.15 mL of ammonia water. The pH of the solution was adjusted to 9-11, and the mixture was heated and stirred at 70°C for 24 h to obtain Au@CdS NPs with a core-shell structure. The Au@CdS NPs are spherical nanomaterials with Au nanoparticles as the core and CdS nanoparticles as the shell. The Au NPs have a diameter of 20 nm and a shell thickness of 12 nm. The molar ratio of the sodium citrate solution, the cadmium chloride solution and the thiourea solution is 30:25:26; The mass ratio of the Au NPs to the sodium citrate solution is 2:1; (3) Preparation of ITO / Au@CdS@ALP electrode 10 μL of Au@CdS NPs was dropped onto 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, obtaining an ITO / Au@CdS@ALP electrode.

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

3. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for detecting 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 3-5 times in sequence, and then dry it with nitrogen for 10-12 minutes. S2. Add the dried ITO electrode to a potassium alcohol solution formed by isopropyl alcohol and potassium hydroxide and boil it for 15 minutes. Ultrasonic clean the boiled ITO electrode with deionized water and anhydrous ethanol for 20 minutes in sequence. Then, immerse the ITO electrode in an ethanol solution containing 3-aminopropyltriethylsilane at room temperature overnight and then store it in the ethanol solution for future use.

4. The method for preparing an ITO / Au@CdS@ALP photoelectrochemical sensor for detecting organophosphorus pesticides according to claim 3, characterized in that: In step S2, the volume mass ratio of isopropyl alcohol to potassium hydroxide is 100:11.2 mL / g; and the volume ratio of 3-aminopropyltriethylsilane to ethanol is 1:99.

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