Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material as well as preparation method and application thereof

Abstract

The invention relates to a Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material and a preparation method and application thereof, and belongs to the technical field of detection material preparation. The preparation method comprises the following steps: firstly preparing Bi2WO6 and g-C3N4, then synthesizing a Z-type heterojunction Bi2WO6 / g-C3N4 composite material, and then carrying out partial in-situ reduction treatment on the prepared Bi2WO6 / g-C3N4 composite material by using a reducing agent NaBH4, thereby obtaining the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material. According to the ternary Z-type heterojunction Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material prepared by the preparation method disclosed by the invention, the problems that a Bi2WO6 / g-C3N4 electron hole pair is easy to block and the electron transfer rate is slow can be solved; the invention also provides a PEC sensor which is constructed by taking the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material as a substrate material and combining with a specific recognition aptamer, and the constructed sensor realizes efficient detection of environmental pollutants, such as CPF.

Description

Technical Field

[0001] The invention relates to a Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material and a preparation method and application thereof, belonging to the technical field of detection material preparation. Background Art

[0002] Organophosphorus pesticides have certain application value in agricultural production, but they are also environmental pollutants that endanger human health; some organophosphorus pesticides do play a key role in pest control, but their potential harm to the environment and human health cannot be ignored. Many studies have clearly pointed out that long-term exposure to the environment of organophosphorus pesticides (such as chlorpyrifos) residues may lead to a series of serious health problems. With the increasing exposure of the risks of organophosphorus pesticides, many researchers have developed a variety of methods for testing organophosphorus pesticides, such as high-performance liquid chromatography, spectrophotometry, gas-liquid chromatography, etc. However, these methods have the disadvantages of expensive equipment, complex sample processing, high detection limits, and susceptibility to interference. Therefore, the development of rapid, reliable, and highly sensitive detection methods is of great significance in the fields of environment, medicine, food, etc.

[0003] Photoelectrochemical (PEC) sensor is a method that uses specific recognition elements and signal conversion components to achieve trace detection of target objects. It has the advantages of high sensitivity, high responsiveness, wide linear range, low detection limit, simple operation, and structural diversity. It has been widely used and expanded in food testing, environmental analysis, medicine and other fields.

[0004] The optoelectronic performance of PEC aptasensors directly depends on the characteristics of the optoelectronic materials themselves. Bi2WO6 is one of the simplest oxides and is widely used in photoresponsive materials. However, bare Bi2WO6 exhibits a fast recombination rate of electron-hole pairs in the visible light region from UV shorter than 450nm, which greatly limits its energy conversion efficiency. In order to change the electronic structure and intrinsic properties of Bi2WO6, metal / non-metal doping and surface modification strategies are often used. In recent years, metallic bismuth (Bi) has been shown to be an ideal substitute for precious metals. It is reported that low-cost metallic bismuth has a direct plasmon resonance effect and can be used as a promising electron mediator to improve the photoelectric response ability of many optoelectronic materials.

[0005] g-C3N4 is a promising photoactive material with a band gap of about 2.7 eV, which can be used for water splitting to produce hydrogen and oxygen under visible light irradiation. In recent years, many new functional g-C3N4 have been developed, such as g-C3N4 thin films, g-C3N4 quantum dots, nitrogen-doped porous carbon g-C3N4, etc. In the system of g-C3N4 / Bi2WO6 composite materials, photoinduced electrons tend to transfer from the CB of g-C3N4 to the CB of Bi2WO6. However, in the visible light region greater than 450nm, Bi2WO6 produces fewer electrons, resulting in a slower electron transfer rate from g-C3N4 to Bi2WO6.

[0006] Therefore, it is necessary to study new materials that are not easily blocked by electron-hole pairs and have fast electron transfer rates, in the hope of further improving the performance of PEC aptamer sensors and thus efficiently detecting pollutants in the environment. Summary of the invention

[0007] In view of some deficiencies in the prior art, the present invention provides a Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material and a preparation method and application thereof, which solve the problem of slow electron transfer rate of g-C3N4 / Bi2WO6 composite materials and realize rapid and sensitive detection of environmental pollutants such as chlorpyrifos.

[0008] In order to achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0009] The present invention first provides a Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material. The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material is a ternary Z-type heterostructure. Metal Bi particles are evenly distributed on the surface of Bi2WO6 / g-C3N4 in the material. The metal Bi particles are in a uniform spherical shape with a diameter of 5-10nm.

[0010] The present invention also provides a method for preparing a Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material, the method comprising:

[0011] Step S1: adding g-C3N4 and Bi2WO6 into ethanol, and ultrasonically obtaining a uniformly dispersed mixed solution; stirring the obtained mixed solution for a period of time until the ethanol is completely evaporated, grinding the obtained product, and calcining to obtain a composite material Bi2WO6 / g-C3N4;

[0012] The dosage of Bi2WO6, g-C3N4 and ethanol is 100 mg: 400-900 mg: 90-110 mL; the ultrasonic time is 1.5-2.5 h, and the stirring time of the mixed liquid is 7-9 h.

[0013] The calcination is carried out at 350-450° C. for 3-5 hours.

[0014] The preparation method of g-C3N4 is as follows:

[0015] Melamine is calcined, and the calcined product is ground. Then, the same calcination method is used again for secondary calcination. The product obtained by the secondary calcination is g-C3N4.

[0016] The conditions for the short calcination are: heating to 520-600°C at a rate of 1-5°C / min and maintaining the constant temperature for 3-5h; and the amount of melamine used is 5-15g.

[0017] The preparation method of Bi2WO6 is as follows:

[0018] After dissolving Na2WO4·2H2O in deionized water, add Bi(NO3)3·5H2O, stir for a certain period of time and adjust the pH value to obtain a mixture; after the obtained mixture is subjected to a hydrothermal reaction, centrifuge, take the precipitate, wash it alternately with distilled water and ethanol, and dry it overnight to obtain Bi2WO6.

[0019] The stirring time is 50-70 min, the pH value is adjusted to 6.5-7.5, the temperature of the hydrothermal reaction is 140-180° C., and the time of the hydrothermal reaction is 23-25 ​​h; the dosage ratio of Na2WO4·2H2O, Bi(NO3)3·5H2O and deionized water is 0.27-0.37 g: 0.92-1.02 g: 25-35 mL.

[0020] Step S2: Add the composite material Bi2WO6 / g-C3N4 and PVP together into deionized water for ultrasonic treatment, then add NaBH4 solution and stir evenly, let stand at room temperature, centrifuge and separate the precipitation, and dry to obtain Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0021] Among them, the dosage of Bi2WO6 / g-C3N4, PVP and water is 55-65mg: 50-70mg: 50-70mL.

[0022] The amount of the NaBH4 solution is 50-70 mL, and the concentration is 50 mM; the time of adding the NaBH4 solution and stirring is 25-35 min, and the time of standing at room temperature is 25-35 min; the time of the ultrasonic treatment is 20-40 min.

[0023] The present invention also provides the use of the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material in constructing a photoelectrochemical aptamer (PEC) sensor or photoelectrochemical detection of environmental pollutants.

[0024] The present invention also provides a method for constructing a photoelectrochemical aptamer sensor, the method comprising:

[0025] (1) The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material is uniformly dispersed in water by ultrasonic method to obtain a Bi / Bi2WO6 / g-C3N4 suspension, and the Bi / Bi2WO6 / g-C3N4 suspension is drop-coated on the surface of ITO, and after natural drying, a CS solution is drop-coated and dried to obtain Bi / Bi2WO6 / g-C3N4 / ITO.

[0026] (2) The Bi / Bi2WO6 / g-C3N4 / ITO surface obtained in step (1) is coated with an aptamer solution of the target object to be detected, and after incubation and rinsing, a photoelectrochemical aptamer sensor is obtained.

[0027] Wherein, the surface area of ​​the ITO in step (1) is 0.5 cm 2 ; The concentration of the Bi / Bi2WO6 / g-C3N4 suspension is 1-3 mg / mL, and the drop coating amount of the Bi / Bi2WO6 / g-C3N4 suspension is 10-30 μL; the amount of CS solution is 5-15 μL.

[0028] The concentration of the aptamer solution in step (2) is 1-3 μM; the aptamer includes a chlorpyrifos aptamer, and the nucleotide sequence of the chlorpyrifos aptamer is shown in SEQ ID No: 1; and the incubation time is 11-13 hours.

[0029] The present invention also provides a photoelectrochemical aptamer sensor constructed by the method.

[0030] The present invention also provides application of the photoelectrochemical aptamer sensor in detecting environmental pollutants.

[0031] Furthermore, the environmental pollutant includes chlorpyrifos (CPF).

[0032] The present invention also provides a method for detecting environmental pollutants, wherein the method uses the constructed photoelectrochemical aptamer sensor for detection.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention utilizes NaBH4 to partially in situ reduce Bi2WO6 / g-C3N4, and prepares for the first time a ternary Z-type heterostructure functional heterojunction photoelectric material Bi / Bi2WO6 / g-C3N4, which is conducive to the transmission of electrons and solves the problem that the electron-hole pairs of Bi2WO6 / g-C3N4 are easily blocked and the electron transfer rate is slow. The ternary Z-type heterojunction Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material prepared by the present invention is composed of a flower-like hierarchical structure self-assembled by many nanosheets, and has good photoelectric response performance as verified by experiments.

[0035] (2) The present invention further utilizes the obtained Bi / Bi2WO6 / g-C3N4 to construct a highly sensitive self-powered PEC biosensor, thereby realizing specific detection of environmental pollutants. Experimental verification shows that the present invention plays the role of an electron conduction bridge between Bi2WO6 and g-C3N4 by partially reducing the Bi element in situ during the material synthesis process. With the help of its SPR effect and combined with the Z-type heterojunction interaction of the material, the charge transfer is greatly enhanced, the photoelectric conversion efficiency is significantly improved, and excellent PEC activity is exhibited. In the embodiment, taking chlorpyrifos as an example, the PEC sensor constructed by the present invention shows a wide linear detection range (0.01-1000nM) and a low detection limit (3.3pM). Under the interference of the interfering substances PLN, PX, and MP, the sensor only has PEC activity for CPF, exhibiting excellent specificity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 These are scanning electron microscope images of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi2WO6 / g-C3N4 prepared in Example 3, where Figures A and B are scanning electron microscope images of g-C3N4, Figure C is a scanning electron microscope image of Bi2WO6, Figure D is a scanning electron microscope image of Bi2WO6 / g-C3N4, Figure E is a scanning electron microscope image of Bi / Bi2WO6 / g-C3N4, and Figure F is a scanning electron microscope image of pure Bi.

[0037] Figure 2The XPS spectra, XRD spectra and FT-IR spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials obtained in Example 3, wherein Figures A, B, C, E, and F are high-resolution C1s, N 1s, Bi 4f, O 1s, and W 4f spectra of Bi / Bi2WO6 / g-C3N4, respectively, Figure G is the XPS measurement total spectrum of Bi / Bi2WO6 / g-C3N4, Figure D is the XRD spectrum of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4, and Bi / Bi2WO6 / g-C3N4, and Figure H is the FT-IR spectrum of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 samples.

[0038] Figure 3 The UV-visible diffuse reflectance spectra and estimated band gap spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials obtained in Example 3, wherein Figure A is the UV-visible diffuse reflectance spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4, and Figure B is the estimated band gap spectrum.

[0039] Figure 4 These are the photocurrent response (A) and EIS response (B) result graphs of Bi / Bi2WO6 / g-C3N4 / ITO, aptamer / Bi / Bi2WO6 / g-C3N4 / ITO and CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO obtained in Example 3.

[0040] Figure 5 The photocurrent response (A) and EIS response (B) results of g-C3N4 / ITO, Bi2WO6 / ITO, Bi2WO6 / g-C3N4 / ITO, and Bi / Bi2WO6 / g-C3N4 / ITO obtained in Example 3 are shown.

[0041] Figure 6 The photocurrent response results of the photoelectrochemical (PEC) sensor constructed in Example 3 during the condition optimization process are shown in Figure A, where Figure B shows the effect of Bi2WO6 concentration on the photocurrent, Figure C shows the effect of aptamer concentration on the photocurrent, and Figure D shows the effect of incubation temperature on the photocurrent.

[0042] Figure 7The photoelectric chemical (PEC) sensor constructed in Example 3 shows the change in the photocurrent response intensity at different chlorpyrifos concentrations and the stability and specificity of the photoelectric chemical sensor, wherein Figure A is the photocurrent signal of the photoelectric chemical sensor at different chlorpyrifos concentrations: (af are: 0.01, 0.1, 1, 10, 100, 1000 nM, respectively), Figure B is the standard curve of the photoelectric chemical sensor for measuring chlorpyrifos, Figure C shows the stability of the PEC sensor, and Figure D shows the selectivity of the PEC sensor. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred embodiments of the present invention are described in detail below, but the following embodiments do not limit the protection scope of the present invention. Instead, they should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0044] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0045] The photoelectrochemical aptamer sensor constructed by the present invention can detect different environmental pollutants according to different aptamers. In the embodiment, the aptamer corresponding to chlorpyrifos (CPF) is selected as an example to illustrate the effect of the photoelectrochemical aptamer sensor constructed by the present invention. In the following embodiment, the aptamer used to construct the PEC aptamer sensor is the CPF aptamer, and the sequence of the CPF aptamer is: 5'-biotin-CCT GCC ACG CTC CGC AAG CTT AGG GTT ACG CCT GCAGCG ATT CTT GAT CGC GCT GCT GGT AAT CCT TCT TTAAGC TTG GCA CCC GCA TCG T-3' (SEQ ID No: 1); the aptamer solution is prepared by the aptamer and the PBS buffer solution.

[0046] Example 1: Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials and construction of PEC sensors

[0047] S1. Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials:

[0048] (1) Preparation of g-C3N4

[0049] 5g of melamine was placed in a crucible with a lid, and then the crucible was placed in a tube furnace and the temperature was gradually increased to 520°C at a heating rate of 1°C / min, and the temperature was kept constant for 3 hours for calcination. After the reaction was completed, the prepared sample was taken out and ground to obtain a powdered sample; the ground powdered sample was calcined again using the same calcination method; and the desired g-C3N4 powder material was finally obtained.

[0050] (2) Preparation of Bi2WO6

[0051] After dissolving 0.27 g Na2WO4·2H2O in 25 mL deionized water, 0.92 g Bi(NO3)3·5H2O was added and stirred for 50 min to obtain a mixed solution. After adjusting the pH value of the mixed solution to 6.5, it was transferred to a polytetrafluoroethylene stainless steel autoclave and heated to 140°C for 23 h to obtain a solution containing a light yellow product. The solution was collected and centrifuged, washed alternately with distilled water and ethanol, and dried overnight to obtain Bi2WO6.

[0052] (3) Preparation of Bi2WO6 / g-C3N4

[0053] 900 mg and 100 mg of g-C3N4 and Bi2WO6 prepared in step S1 and step S2 were added to 90 mL of ethanol, and ultrasonicated for 1.5 hours to ensure that both were evenly dispersed in ethanol to obtain a mixed solution; the obtained mixed solution was stirred for 7 hours to promote sufficient contact between Bi2WO6 and g-C3N4. After the ethanol was completely evaporated, the obtained product was ground to obtain a powder. Finally, the powder was placed in a muffle furnace and calcined at 350°C for 3 hours to synthesize the Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0054] (4) Preparation of Bi / Bi2WO6 / g-C3N4

[0055] 55 mg of the Bi2WO6 / g-C3N4 heterojunction photoelectric material obtained in step S3 was added to 50 mL of water and ultrasonicated for 20 minutes to obtain a mixture; 50 mL of a 50 mM NaBH4 solution was added to the obtained mixture and stirred for 25 minutes to obtain a mixed solution; the obtained mixed solution was allowed to stand at room temperature for 25 minutes to allow the precipitation to fully form. Then, the precipitate was separated by centrifugation and dried at 50°C overnight to finally obtain the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0056] S2. Construction of photoelectrochemical (PEC) aptasensor:

[0057] The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material was ultrasonically dispersed uniformly in water to obtain a 1 mg / mL Bi / Bi2WO6 / g-C3N4 suspension. 10 μL of the obtained Bi / Bi2WO6 / g-C3N4 suspension was drop-coated on a fixed area (0.5 cm 2 ) on the ITO surface and dried naturally to obtain a modified electrode. After drying, in order to further fix the heterojunction photoelectric material, 5 μL of CS solution (concentration of 0.1%) was added to the modified electrode and dried again to successfully prepare a Bi / Bi2WO6 / g-C3N4 modified ITO electrode, abbreviated as Bi / Bi2WO6 / g-C3N4 / ITO.

[0058] 10 μL of 1 μM CPF aptamer solution (containing 50 mM EDC) was coated on the surface of Bi / Bi2WO6 / g-C3N4 / ITO electrode for aptamer modification; the electrode modified with aptamer was incubated at 0°C for 11 h to ensure that the aptamer fully reacted with the electrode surface. After incubation, the electrode was rinsed with 0.1 M phosphate buffer solution (PBS) with a pH value of 7.4 to remove excess aptamer and impurities, and a PEC aptamer sensor was obtained, which was recorded as aptamer / Bi / Bi2WO6 / g-C3N4 / ITO.

[0059] 10 μL of 2 μM CPF solution (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was added to the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO surface and incubated for 50 min. After the incubation, the electrode was rinsed with PBS to remove the unbound CPF, and the PEC aptamer sensor bound to CPF was obtained, which was recorded as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, and then the photoelectrochemical performance was tested.

[0060] Example 2: Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials and construction of PEC sensors

[0061] S1. Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials:

[0062] (1) Preparation of g-C3N4

[0063] 15g of melamine was placed in a crucible with a lid, and then the crucible was placed in a tube furnace and the temperature was gradually increased to 600°C at a heating rate of 5°C / min, and the temperature was kept constant for 5 hours for calcination. After the reaction was completed, the prepared sample was taken out and ground to obtain a powdered sample; the ground powdered sample was calcined again using the same calcination method; and the desired g-C3N4 powder material was finally obtained.

[0064] (2) Preparation of Bi2WO6

[0065] After dissolving 0.37 g Na2WO4·2H2O in 35 mL deionized water, 1.02 g Bi(NO3)3·5H2O was added and stirred for 70 min to obtain a mixed solution. After adjusting the pH value of the mixed solution to 7.5, it was transferred to a polytetrafluoroethylene stainless steel autoclave and heated to 180°C for 25 h to obtain a solution containing a light yellow product. The solution was collected and centrifuged, washed alternately with distilled water and ethanol, and dried overnight to obtain Bi2WO6.

[0066] (3) Preparation of Bi2WO6 / g-C3N4

[0067] Take 400 mg and 100 mg of g-C3N4 and Bi2WO6 prepared in step S1 and step S2, respectively, and add them to 110 mL of ethanol. Ultrasonicate for 2.5 hours to ensure that both are evenly dispersed in ethanol to obtain a mixed solution; stir the obtained mixed solution for 9 hours to promote sufficient contact between Bi2WO6 and g-C3N4. After the ethanol is completely evaporated, grind the obtained product to obtain a powder. Finally, place the powder in a muffle furnace and calcine at 450°C for 5 hours to synthesize the Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0068] (4) Preparation of Bi / Bi2WO6 / g-C3N4

[0069] 65 mg of the Bi2WO6 / g-C3N4 heterojunction photoelectric material obtained in step S3 was added to 70 mL of water and ultrasonicated for 40 min to obtain a mixture; 70 mL of a 50 mM NaBH4 solution was added to the obtained mixture and stirred for 35 min to obtain a mixed solution; the obtained mixed solution was allowed to stand at room temperature for 35 min to allow the precipitation to fully form. Then, the precipitate was separated by centrifugation and dried at 70°C overnight to finally obtain the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0070] S2. Construction of PEC aptasensor

[0071] The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material was ultrasonically dispersed uniformly in water to obtain a 3 mg / mL Bi / Bi2WO6 / g-C3N4 suspension. 30 μL of the obtained Bi / Bi2WO6 / g-C3N4 suspension was drop-coated on a fixed area (0.5 cm 2 ) on the ITO surface and dried naturally to obtain a modified electrode. After drying, in order to further fix the heterojunction photoelectric material, 15 μL of CS solution (concentration of 0.1%) was added to the modified electrode and dried again to successfully prepare a Bi / Bi2WO6 / g-C3N4 modified ITO electrode, abbreviated as Bi / Bi2WO6 / g-C3N4 / ITO.

[0072] 30 μL of 3 μM aptamer solution was coated on the surface of Bi / Bi2WO6 / g-C3N4 / ITO electrode for aptamer modification; the electrode modified with aptamer was incubated at 0°C for 13 h to ensure that the aptamer fully reacted with the electrode surface. After incubation, the electrode was rinsed with 0.1 M phosphate buffer solution (PBS) with a pH value of 7.4 to remove excess aptamer and impurities, and a PEC aptamer sensor was obtained, which was recorded as aptamer / Bi / Bi2WO6 / g-C3N4 / ITO.

[0073] 30 μL of 2 μM CPF solution was added to the surface of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO electrode and incubated for 70 min. After incubation, the electrode was rinsed with PBS to remove unbound CPF, and the PEC aptamer sensor bound to CPF was obtained, which was recorded as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, and then the photoelectrochemical performance was tested.

[0074] Example 3: Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials and construction of PEC sensors

[0075] S1. Preparation of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials:

[0076] (1) Preparation of g-C3N4

[0077] 10g of melamine was placed in a crucible with a lid, and then the crucible was placed in a tube furnace and the temperature was gradually increased to 550°C at a heating rate of 2°C / min, and the temperature was kept constant for 4 hours for calcination. After the reaction was completed, the prepared sample was taken out and ground to obtain a powdered sample; the ground powdered sample was calcined again using the same calcination method; and the desired g-C3N4 powder material was finally obtained.

[0078] Figure 1 A and Figure 1 B is a scanning electron microscope image of g-C3N4 powder material at different magnifications. It can be seen from the image that the g-C3N4 powder material has a layered nanosheet structure.

[0079] (2) Preparation of Bi2WO6

[0080] After dissolving 0.32 g Na2WO4·2H2O in 30 mL deionized water, 0.97 g Bi(NO3)3·5H2O was added and stirred for 60 min to obtain a mixed solution. After adjusting the pH value of the mixed solution to 7, the solution was transferred to a polytetrafluoroethylene stainless steel autoclave and heated to 160°C for 24 h to obtain a solution containing a light yellow product. The solution was collected and centrifuged, washed alternately with distilled water and ethanol, and dried overnight to obtain Bi2WO6.

[0081] Figure 1 C is the scanning electron microscope image of Bi2WO6, which appears as irregular, aggregated microspheres.

[0082] (3) Preparation of Bi2WO6 / g-C3N4

[0083] 566.7 mg and 100 mg of g-C3N4 and Bi2WO6 prepared in step S1 and step S2 were added to 100 mL of ethanol, and ultrasonicated for 2 hours to ensure that both were evenly dispersed in ethanol to obtain a mixed solution; the obtained mixed solution was stirred for 8 hours to promote sufficient contact between Bi2WO6 and g-C3N4. After the ethanol was completely evaporated, the obtained product was ground to obtain a powder. Finally, the powder was placed in a muffle furnace and calcined at 400°C for 4 hours to synthesize the Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0084] Figure 1 D is the scanning electron microscope image of Bi2WO6 / g-C3N4, from which it can be seen that Bi2WO6 / g-C3N4 is composed of a flower-like hierarchical structure self-assembled by many nanosheets.

[0085] (4) Preparation of Bi / Bi2WO6 / g-C3N4

[0086] 60 mg of the Bi2WO6 / g-C3N4 heterojunction photoelectric material obtained in step S3 was added to 60 mL of water and ultrasonicated for 30 min to obtain a mixture. 60 mL of a 50 mM NaBH4 solution was added to the mixture and stirred for 30 min to obtain a mixed solution. The mixed solution was allowed to stand at room temperature for 30 min to allow precipitation to form fully. Then, the precipitate was separated by centrifugation and dried at 60°C overnight to finally obtain the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material.

[0087] Figure 1 E is the scanning electron microscope image of Bi / Bi2WO6 / g-C3N4. It can be clearly seen that many fine particles with diameters ranging from 5 to 10 nm are evenly distributed on the surface of Bi / Bi2WO6 / g-C3N4. These particles are Bi nanoparticles.

[0088] Figure 1 F is the SEM image of pure Bi, showing the uniform spherical morphology of metallic Bi, and its particle size is also in the range of 5 to 10 nm. This result supports Figure 1 E shows that the fine particles with a diameter of 5 to 10 nm existing on the surface of Bi / Bi2WO6 / g-C3N4 are metallic Bi.

[0089] S2. Characteristic analysis of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 heterojunction optoelectronic materials

[0090] In this embodiment, the XPS spectra, XRD spectra, FT-IR spectra, UV-visible diffuse reflectance spectra or estimated band gap spectra of the materials g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials are further analyzed, and the analysis results are as follows:

[0091] Figure 2 The XPS spectrum, XRD spectrum and FT-IR spectrum of the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material prepared in this embodiment are shown in FIG. Figure 2 A, 2B, 2C, 2E, and 2F are the high-resolution C1s, N 1s, Bi4f, O1s, and W 4f XPS spectra of Bi / Bi2WO6 / g-C3N4, respectively. Figure 2 G is the total XPS spectrum of Bi / Bi2WO6 / g-C3N4, Figure 2 H is the FT-IR spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 samples. For C1s spectra ( Figure 2 A) The two strong peaks at 286.1 and 288.3 eV belong to the sp 2 CC key and sp 2 Hybridized carbon. Fitting peak of N 1s spectrum ( Figure 2 B) are located at 398.4, 400.1 and 402.0 eV respectively, which can be attributed to the sp 2Hybridized nitrogen, tertiary nitrogen N-(C)3 groups and π excitation. Bi / Bi2WO6 / g-C3N4 shows a shift of about 0.6 eV to higher binding energy N1s compared to pure g-C3N4. This may be due to the hybridization of Bi2WO6 with g-C3N4, which leads to the inward shift of N1s. The peak of carbon 15 has only a slight change. High-resolution Bi 4f XPS spectra such as Figure 2 C. Bi 4f 7 / 2 and Bi 4f 5 / 2 The binding energies of the two strong peaks are 158.0 and 163.4 eV, which are the Bi 3+ In addition to the two main characteristic peaks, two small peaks at 159.8 and 165.2 eV were found. This can be attributed to the metallic Bi on the surface of Bi2WO6. This phenomenon may be due to the Bi 3+ The amount of metal Bi reduced is very small. Figure 2 In E, the O1s spectra of Bi / Bi2WO6 / g-C3N4 at 531.1 and 534.4 eV are attributed to the Bi-O bond and hydroxyl group, respectively. Figure 2 F is the XPS spectrum of W 4f region, W 4f 7 / 2 The binding energy of W 4f is 35.1eV. 5 / 2 The binding energy of W is 37.5 eV, indicating that W 6+ The chemical state exists; Figure 2 G represents the presence of C, N, W, O and Bi elements in Bi / Bi2WO6 / g-C3N4, and the binding energy is assigned to C1s, N 1s, W 4f, Bi 4f, W 4d, O 1s and Bi 4p. The above results indicate that metallic Bi coexists with g-C3N4-modified Bi2WO6, that is, the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material is successfully synthesized.

[0092] Figure 2D is the XRD pattern of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4, and Bi / Bi2WO6 / g-C3N4. It can be seen from the figure that Bi2WO6 and Bi / Bi2WO6 / g-C3N4 heterojunction optoelectronic materials exhibit similar diffraction patterns. The peaks at 28.3°, 32.79°, 47.1°, 55.8°, 58.5°, 68.8°, 75.9° and 78.4° at 2θ belong to the (131), (200), (202), (331), (262), (400), (193) and (402) crystal planes of orthorhombic Bi2WO6 (JCPDS, No. 39-0256). The two characteristic peaks of g-C3N4 correspond to the (100) plane and (002) plane of g-C3N4, respectively. The typical diffraction peaks of Bi2WO6 and g-C3N4 appear in the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material, indicating that there are two materials, Bi2WO6 and g-C3N4, in the heterojunction photoelectric material. Figure 2 H is the FT-IR spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 samples. The Bi2WO6 sample has a wavelength of 400-800 cm -1 The main absorption ranges are shown at 1247, 1329, 1569, and 1636 cm-1, which are due to Bi-O, WO stretching, and WOW bridging stretching modes. -1 Several typical absorption peaks at 808 cm-1 correspond to the bending vibration of CN groups. -1 The sharp peak at 3100~3300cm belongs to the breathing mode of triazine unit. -1 The strong bands correspond to the stretching modes of primary and secondary amines and their intermolecular hydrogen bonding interactions. Since metallic Bi has no typical absorption peaks in the FT-IR spectrum, there is no obvious difference between Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials. All characteristic absorption bands of g-C3N4 and Bi2WO6 appear in the spectrum of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials, indicating that g-C3N4 and Bi2WO6 coexist in Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials.

[0093] Figure 3 UV-visible diffuse reflectance spectra and estimated band gap spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4 materials, where Figure 3 A is the UV-visible diffuse reflectance spectra of g-C3N4, Bi2WO6, Bi2WO6 / g-C3N4 and Bi / Bi2WO6 / g-C3N4, Figure 3 B is the estimated bandgap spectrum, from Figure 3 A and Figure 3 It can be seen in B that the absorption edge of Bi2WO6 is about 450nm, and the band gap energy of Bi2WO6 is estimated to be 2.70eV. For g-C3N4, its absorption edge occurs at a wavelength of 470nm, and the corresponding band gap is 2.70eV. Compared with Bi2WO6, the absorption of Bi2WO6 / g-C3N4 in the 450-480nm region increases, and the absorption edge appears at a wavelength of 465nm, which is due to the presence of g-C3N4 on the Bi2WO6 microspheres. The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material exhibits obvious visible light absorption than Bi2WO6 / g-C3N4, which can be attributed to the SPR effect of Bi loading.

[0094] S3. Construction of PEC aptasensor:

[0095] The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material obtained in step S1 was ultrasonically dispersed uniformly in water to obtain a 2 mg / mL Bi / Bi2WO6 / g-C3N4 suspension. 20 μL of the obtained Bi / Bi2WO6 / g-C3N4 suspension was drop-coated on a fixed area (0.5 cm 2 ) on the ITO surface and dried naturally to obtain a modified electrode. After drying, in order to further fix the heterojunction photoelectric material, 10 μL of CS solution (concentration of 0.1%) was added to the modified electrode, and dried again to successfully prepare a Bi / Bi2WO6 / g-C3N4 modified ITO electrode, abbreviated as Bi / Bi2WO6 / g-C3N4 / ITO. Using a similar experimental process, different types of electrode materials such as Bi2WO6 / ITO, g-C3N4 / ITO and Bi2WO6 / g-C3N4 / ITO were prepared in this embodiment as controls.

[0096] 20 μL of 2 μM CPF aptamer solution was coated on the surface of Bi / Bi2WO6 / g-C3N4 / ITO electrode for aptamer modification; the electrode modified with aptamer was incubated at 0°C for 12 h to ensure that the aptamer fully reacted with the electrode surface. After incubation, the electrode was rinsed with 0.1 M phosphate buffer solution (PBS) with a pH value of 7.4 to remove excess aptamer and impurities, and a PEC aptamer sensor was obtained, which was recorded as aptamer / Bi / Bi2WO6 / g-C3N4 / ITO.

[0097] 20 μL of 2 μM CPF solution was added to the surface of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO and incubated for 60 min. After the incubation, the electrode was rinsed with PBS to remove the unbound CPF, and the PEC aptamer sensor bound with CPF was obtained, which was recorded as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO.

[0098] Furthermore, in order to verify the detection effectiveness of the PEC aptamer sensor (denoted as aptamer / Bi / Bi2WO6 / g-C3N4 / ITO) constructed in this example, the photocurrent response and EIS response capabilities of Bi / Bi2WO6 / g-C3N4 / ITO, aptamer / Bi / Bi2WO6 / g-C3N4 / ITO and CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO were analyzed. The analysis results are shown in Figure 2. Figure 4 As shown:

[0099] Figure 4 A is the photocurrent response of Bi / Bi2WO6 / g-C3N4 / ITO, the photocurrent response of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO and the photocurrent response of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO. The PEC signal of Bi / Bi2WO6 / g-C3N4 / ITO is as high as 1.25μA. The main reason is that the Z-type heterojunction forms a synergistic SPR effect of Bi, which enhances the light absorption ability and thus greatly enhances the photoresponse current. However, after the aptamer is incubated on Bi / Bi2WO6 / g-C3N4 / ITO, the obtained The photocurrent of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO dropped significantly to 0.15μA. The possible reason is that the incubation of aptamer on the electrode increased the steric hindrance, hindered the electron transfer, and made the current smaller. The detected substance CPF was combined with aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, and the photocurrent intensity of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO became 1.15μA. This is because CPF combined with the aptamer to form a complex that detached from the electrode surface, reduced the steric hindrance, increased the separation efficiency of photogenerated carriers, and increased the current. Figure 4B is the EIS response. It can be seen that the interface resistance (Ret) of Bi / Bi2WO6 / g-C3N4 / ITO is 75Ω, and the Ret value of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO increases significantly to 237Ω. This change indicates that the aptamer has been successfully bound to the electrode, increasing the steric hindrance. The Ret value of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO decreases to 142Ω, which is attributed to the CPF-aptamer complex. The formation may be separated from the ITO electrode, reducing the steric hindrance; through the results of the photocurrent response and EIS response of Bi / Bi2WO6 / g-C3N4 / ITO, aptamer / Bi / Bi2WO6 / g-C3N4 / ITO and CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, it can be found that the PEC sensor constructed by the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material provided by the present invention can effectively detect CPF.

[0100] In this example, the photocurrent response and EIS response of Bi / Bi2WO6 / g-C3N4 / ITO, g-C3N4 / ITO, Bi2WO6 / ITO and Bi2WO6 / g-C3N4 / ITO were analyzed. The analysis results are shown in Figure 5 As shown:

[0101] Figure 5 A is the photocurrent response of g-C3N4 / ITO, Bi2WO6 / ITO, Bi2WO6 / g-C3N4 / ITO, and Bi / Bi2WO6 / g-C3N4 / ITO. It can be seen that g-C3N4 / ITO and Bi2WO6 / ITO have weak PEC signals. When the performance of Bi / Bi2WO6 / g-C3N4 / ITO is deeply explored, it shows a significant photocurrent response characteristic, and the specific value reaches 0.75μA; compared with the single component g- The photocurrent response values ​​of C3N4 / ITO, Bi2WO6 / ITO and their composite components Bi2WO6 / g-C3N4 / ITO and Bi / Bi2WO6 / g-C3N4 / ITO increased by 10.4 times, 5.2 times and 3.4 times respectively. This significant improvement is due to the synergistic effect of surface plasmon resonance and the effective formation of Z-type heterojunction, which significantly enhances the photoelectric response ability of Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric materials, making them show more superior performance. Figure 5B is the EIS response of g-C3N4 / ITO, Bi2WO6 / ITO, Bi2WO6 / g-C3N4 / ITO, and Bi / Bi2WO6 / g-C3N4 / ITO. It can be seen that the g-C3N4 / ITO electrode presents a relatively high electron transfer impedance (Ret) value. In contrast, the Ret values ​​of the Bi2WO6 / ITO electrode and the Bi2WO6 / g-C3N4 / ITO electrode are 221Ω and 195Ω, respectively. This change indicates that the introduction of the heterojunction plays a positive role in the charge migration process. The Bi / Bi2WO6 / g-C3N4 / ITO electrode shows the lowest Ret value of only 75Ω. This significant change fully proves that through the in-situ reduction of NaBH4, Bi2WO6 / g-C3N4 is partially successfully converted into Bi / Bi2WO6 / g-C3N4. This conversion not only greatly improves the conductivity of the material, but also promotes the efficient migration of charge carriers.

[0102] Example 4: Parameter optimization during the construction of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO

[0103] The parameters in the process of constructing aptamer / Bi / Bi2WO6 / g-C3N4 / ITO in Example 3 are the optimal parameters. Therefore, in this example, 2 μM CPF solution is dropped on aptamer / Bi / Bi2WO6 / g-C3N4 / ITO obtained at different Bi2WO6 concentrations, drop-coated Bi / Bi2WO6 / g-C3N4 concentrations, aptamer concentrations or incubation temperatures, and the photocurrent response intensity of the PEC aptamer sensor (CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO) combined with CPF is tested to verify the optimal parameters.

[0104] (1) Optimization of Bi2WO6 content

[0105] The preparation method is the same as that in Example 3, except that the amount of Bi2WO6 is changed, and the Bi2WO6 content is set to 1%, 5%, 10%, 15% and 20% by mass to prepare aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, respectively. It is further combined with CPF (denoted as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO), and the response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO is detected. The results are as follows Figure 6 As shown in A, it can be found that when the content of Bi2WO6 in Bi / Bi2WO6 / g-C3N4 is 15%, the response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO reaches its maximum.

[0106] (2) Concentration optimization of Bi / Bi2WO6 / g-C3N4 suspension

[0107] The concentration of Bi / Bi2WO6 / g-C3N4 suspension drop-coated on the ITO surface was set to 0, 1, 2, 3, and 4 mg / mL, and the other conditions were the same as in Example 3 to prepare aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, which was further combined with CPF (denoted as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO). The response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO was detected. The results are shown in FIG. Figure 6 As shown in Figure B, it can be observed that when the concentration of Bi / Bi2WO6 / g-C3N4 is 2 mg / mL, the response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO reaches the maximum.

[0108] (3) Optimization of aptamer concentration

[0109] The aptamer concentration was set to 0, 1, 2, 3, and 4 μM, and the other conditions were the same as in Example 3 to prepare aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, and the response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO was further detected in combination with CPF (denoted as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO). The results are shown in FIG. Figure 6 As shown in Figure C, it can be observed that as the aptamer concentration gradually increases from 0 μM to 4 μM, the photocurrent also shows a trend of first increasing and then decreasing, and gradually stabilizes after the aptamer concentration reaches 2 μM.

[0110] (4) Optimization of incubation temperature

[0111] The incubation temperature was set to -20, -10, 0, 10, and 20°C, and the other conditions were the same as in Example 3 to prepare aptamer / Bi / Bi2WO6 / g-C3N4 / ITO, which was further combined with CPF (denoted as CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO). The response intensity of the photocurrent of CPF / aptamer / Bi / Bi2WO6 / g-C3N4 / ITO was detected. The results are as follows Figure 6 As shown in D, it can be observed from the figure that when the incubation temperature increases from -20℃ to 20℃, the photocurrent first increases and then decreases, and reaches a maximum value at 0℃.

[0112] Therefore, when the content of Bi2WO6 in Bi / Bi2WO6 / g-C3N4 is preferably 15%, the concentration of Bi / Bi2WO6 / g-C3N4 is preferably 2 mg / mL, the aptamer concentration is preferably 2 μM, and the incubation temperature is preferably 0°C, the photocurrent response intensity of the prepared PEC aptamer sensor reaches the best.

[0113] Example 5: Verification of the application effect of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO constructed in Example 3

[0114] This example verifies the application effect of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO constructed in Example 3, mainly verifying whether there is a linear relationship between the concentration of chlorpyrifos and the photocurrent loudness intensity of the aptamer sensor, as well as the stability and specificity of the aptamer sensor.

[0115] (1) Linear relationship verification

[0116] The CPF standard (Shanghai Sangon Biotech Co., Ltd.) was diluted to obtain different concentrations of CPF: 0.01, 0.1, 1, 10, 100 and 1000 nM; the experiment was carried out using the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO prepared in Example 3.

[0117] By detecting the photocurrent response intensity of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO after binding to CPF, it is verified whether there is a linear relationship between the concentration of chlorpyrifos and the photocurrent intensity of the aptamer sensor. The verification results are as follows: Figure 7 As shown in A, it can be observed that the corresponding intensity of the photocurrent after aptamer / Bi / Bi2WO6 / g-C3N4 / ITO combined with chlorpyrifos increases with the increase of CPF concentration.

[0118] Furthermore, the standard curve is plotted with the concentration lg value of chlorpyrifos as the horizontal axis and the corresponding intensity of the photocurrent as the vertical axis. Figure 7 As shown in B, after data fitting, the regression equation I = 0.066lgC (nM) -0.052 was obtained, and the correlation coefficient (R 2 ) is as high as 0.997, indicating the accuracy and reliability of this linear relationship.

[0119] (2) Stability

[0120] The stability of the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO prepared in Example 3 was tested by irradiating the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO for 600 seconds. The stability of the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO was determined by observing the change in the corresponding intensity of the photocurrent of the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO. The results are as follows: Figure 7 As shown in B, the photocurrent intensity of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO did not fluctuate significantly within 200 to 600 seconds, showing excellent stability, which fully confirms that the PEC aptamer sensor constructed by the method described in the present invention has excellent stability.

[0121] (3) Specificity

[0122] 100 nM solutions of phosalone PLN, phoxim PX, methyl parathion MP and chlorpyrifos CPF were prepared respectively with PBS buffer solution.

[0123] Then, the aptamer / Bi / Bi2WO6 / g-C3N4 / ITO obtained in Example 3 was immersed in PLN, PX, MP, CPF solutions and PLN, PX, MP, CPF mixed solutions respectively, and the specificity of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO was determined by observing the changes in the corresponding intensity of the photocurrent of aptamer / Bi / Bi2WO6 / g-C3N4 / ITO. The results are as follows: Figure 7 As shown in D, it can be observed from the figure that after aptamer / Bi / Bi2WO6 / g-C3N4 / ITO is immersed in PLN, PX, and MP solutions, the photocurrent response intensity does not change significantly, while when immersed in CPF solution and the solution after PLN, PX, MP, and CPF are mixed, the change in the corresponding intensity of the photocurrent is consistent, indicating that the PEC aptamer sensor constructed by the method described in the present invention exhibits excellent specificity in detecting CPF.

[0124] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although the present invention has been described in detail in this specification with reference to the above embodiments, it should be understood by those skilled in the art that the present invention may still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material, characterized in that: The Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material is a ternary Z-type heterostructure, and metal Bi particles are evenly distributed on the surface of Bi2WO6 / g-C3N4 in the material; the metal Bi particles are in a uniform spherical shape.

2. The method for preparing the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material according to claim 1, characterized in that: The method comprises: Step S1: adding g-C3N4 and Bi2WO6 into ethanol, and ultrasonically obtaining a uniformly dispersed mixed solution; stirring the obtained mixed solution for a period of time until the ethanol is completely evaporated, grinding the obtained product, and calcining to obtain a composite material Bi2WO6 / g-C3N4; Step S2: Add the composite material Bi2WO6 / g-C3N4 and PVP together into deionized water for ultrasonic treatment, then add NaBH4 solution and stir evenly, let stand at room temperature, centrifuge and separate the precipitation, and dry to obtain Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material.

3. The preparation method according to claim 2, characterized in that: In step S1, the dosage of Bi2WO6, g-C3N4 and ethanol is 100 mg: 400-900 mg: 90-110 mL; the ultrasonic time is 1.5-2.5 h, and the stirring time of the mixed liquid is 7-9 h; the calcination is carried out at 350-450°C for 3-5 h.

4. The preparation method according to claim 2, characterized in that: The amount of Bi2WO6 / g-C3N4, PVP and deionized water in step S2 is 55-65 mg: 50-70 mg: 50-70 mL; the amount of NaBH4 solution is 50-70 mL and the concentration is 50 mM; the time for adding NaBH4 solution and stirring is 25-35 min, and the time for standing at room temperature is 25-35 min; the time for ultrasonic treatment is 20-40 min.

5. Use of the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material according to claim 1 or the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material prepared by any preparation method of claims 2-4 in constructing photoelectrochemical aptamer sensors or photoelectrochemical detection of environmental pollutants.

6. A method for constructing a photoelectrochemical aptamer sensor, characterized in that: Here are the steps: (1) Ultrasonically uniformly dispersing the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material according to claim 1 or the Bi / Bi2WO6 / g-C3N4 heterojunction photoelectric material prepared by any one of the preparation methods of claims 2 to 4 in water to obtain a Bi / Bi2WO6 / g-C3N4 suspension, drop-coating the Bi / Bi2WO6 / g-C3N4 suspension on the surface of ITO, naturally drying it, drop-adding a CS solution, and drying it to obtain Bi / Bi2WO6 / g-C3N4 / ITO; (2) The Bi / Bi2WO6 / g-C3N4 / ITO surface obtained in step (1) is coated with an aptamer solution of the target object to be detected, and after incubation and rinsing, a photoelectrochemical aptamer sensor is obtained.

7. The construction method according to claim 6, characterized in that: In step (1), the concentration of the Bi / Bi2WO6 / g-C3N4 suspension is 1-3 mg / mL, the drop coating amount of the Bi / Bi2WO6 / g-C3N4 suspension is 10-30 μL; the amount of CS solution is 5-15 μL.

8. The construction method according to claim 6, characterized in that: In step (2), the concentration of the aptamer is 1-3 μM; the target to be detected includes chlorpyrifos, and the nucleotide sequence of the aptamer is shown in SEQ ID No: 1; and the incubation time is 11-13 hours.

9. The photoelectrochemical aptamer sensor constructed by the method according to any one of claims 6 to 8.

10. Use of the photoelectrochemical aptamer sensor constructed by the method according to any one of claims 6 to 8, or the photoelectrochemical aptamer sensor according to claim 9 in detecting environmental pollutants.

11. The use according to claim 10, characterized in that: The environmental pollutants include chlorpyrifos.

12. A method for detecting environmental pollutants, characterized in that: The method is to use the photoelectrochemical aptamer sensor constructed by the method described in any one of claims 6 to 8, or the photoelectrochemical aptamer sensor described in claim 9 for detection.

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