Preparation method and application of Bi2MoO6 / CeO2 heterojunction photoelectric material

Abstract

The invention relates to a preparation method and application of a Bi2MoO6 / CeO2 heterojunction photoelectric material, and belongs to the technical field of material preparation and application. The preparation method comprises the following steps: preparing CeO2 nano-particles through hydrothermal reaction and calcination, mixing the CeO2 nano-particles with a Bi2MoO6 precursor solution, and then carrying out hydrothermal reaction to prepare the Bi2MoO6 / CeO2 heterojunction photoelectric material. The invention further provides application of the prepared material in construction of a photoelectrochemical sensor and detection of environmental pollutants. The method for preparing the Bi2MoO6 / CeO2 heterojunction photoelectric material, disclosed by the invention, is simple in preparation steps and environment-friendly; according to the material prepared by the method disclosed by the invention, Bi2MoO6 and CeO2 are compounded to form a type II heterojunction, so that the recombination rate of photo-induced electrons-holes is effectively reduced, and the photoelectrochemical performance is remarkably improved; a sensor constructed by the material has the characteristics of high sensitivity, good selectivity and good stability, and can be widely applied to detection of pollutants in environmental water samples, biological samples and food samples.

Description

Technical Field

[0001] The present invention relates to a Bi 2 MoO 6 / CeO 2 The invention relates to a preparation method and application of a heterojunction photoelectric material, belonging to the technical field of preparation of photoelectric functional materials. Background Art

[0002] Photoelectrochemical sensors are a type of sensor that combines photoelectric materials with commonly used identification methods in analytical detection, and uses the characteristics of photoelectric materials and identification information conversion to detect the chemical information of the target object. Due to its high sensitivity, simple operation, and environmental friendliness, it has been widely used in environmental monitoring, biosensing, and food safety. At present, commonly used photoelectric materials mainly include nanomaterials such as metal sulfides, metal oxides, and graphene-like materials (such as transition metal disulfides); however, for individual photoelectric materials, the excited electron-hole pairs are easy to recombine, the photoelectric conversion efficiency is low, and the photostability is not ideal; therefore, in order to improve the performance of photoelectrochemical sensors, it is necessary to develop photoelectric materials with excellent photoelectrochemical properties, thereby further promoting the transfer rate of photogenerated carriers and effectively improving the photoelectric performance of the system.

[0003] Bi 2 MoO 6 It is a typical layered semiconductor material with excellent photocatalytic performance and chemical stability. However, its high electron-hole recombination rate limits the improvement of its photoelectric performance. 2 It is a wide bandgap semiconductor material with excellent redox properties and electron transport capabilities. 2 MoO 6 and CeO 2 The composite forms a type II heterojunction, which can effectively inhibit the recombination of photogenerated carriers and improve the photoelectrochemical performance.

[0004] At present, there are few studies on the preparation of high-efficiency heterojunction optoelectronic materials. Traditional synthesis methods are mostly for the preparation of single components, which makes it difficult to achieve synergistic effects between different components. 2 MoO 6 / CeO 2 The method of preparing heterojunction photovoltaic materials is cumbersome and requires the use of corrosive and irritating chemical reagents, which is extremely unfriendly to the environment. In order to solve this problem, a product with stable structure, excellent performance, simple preparation steps and environmentally friendly Bi 2 MoO 6 / CeO 2 The preparation method of heterojunction optoelectronic materials is particularly important. Summary of the invention

[0005] In view of some problems existing in the prior art, the present invention provides a Bi 2 MoO 6 / CeO 2 Preparation method and application of heterojunction photoelectric material; The present invention obtains a Bi with excellent photoelectric performance by optimizing the preparation process 2 MoO 6 / CeO 2 Heterojunction photoelectric material, which has good photocurrent response and photostability, can be widely used in photoelectrochemical sensors.

[0006] In order to achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0007] The present invention first provides a Bi 2 MoO 6 / CeO 2 A method for preparing a heterojunction photoelectric material, the method comprising the following steps:

[0008] S1. Dissolve cerium nitrate and urea in deionized water and stir to form a transparent solution; subject the obtained transparent solution to a hydrothermal reaction, cool to room temperature after the reaction, separate the precipitate by centrifugation, wash with deionized water and ethanol in turn, dry and calcine to obtain CeO 2 Nanoparticles.

[0009] Wherein, the dosage of the cerium nitrate, urea and deionized water is 1.08-4.32 g: 0.6-2.4 g: 45-60 mL.

[0010] The hydrothermal reaction is: 96-168° C. for 2.4-4.2 hours.

[0011] The calcination is as follows: calcination at 320-560° C. for 1.6-2.8 hours.

[0012] S2. The CeO obtained in step S1 2 The nanoparticles were dispersed in ethanol and ultrasonicated to form a uniform CeO 2 ethanol solution; dissolve bismuth nitrate and sodium molybdate in ethylene glycol, stir evenly, and mix with CeO 2 The mixed solution was subjected to a hydrothermal reaction, and after the reaction was completed, it was cooled to room temperature, centrifuged to separate the precipitate, and washed with deionized water and ethanol in turn, and dried to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0013] Wherein, the CeO 2The amount of nanoparticles and ethanol used is 0.115-0.172 g: 50-80 mL.

[0014] The dosage ratio of the bismuth nitrate, sodium molybdate and ethylene glycol is 0.485-1.94 g: 0.121-0.484 g: 30 mL.

[0015] The bismuth nitrate and sodium molybdate are dissolved in ethylene glycol to generate Bi 2 MoO 6 , CeO in the mixed solution 2 with Bi 2 MoO 6 The molar ratio is 1:0.5-3.

[0016] The stirring reaction time is 1 h.

[0017] The conditions of the hydrothermal reaction are: 128-224° C. for 4.8-8.4 h.

[0018] The present invention also provides Bi prepared by the preparation method 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0019] The present invention also provides the Bi 2 MoO 6 / CeO 2 Application of heterojunction optoelectronic materials in constructing photoelectrochemical aptamer sensors or photoelectrochemical detection of environmental pollutants.

[0020] The present invention also provides a method for constructing a photoelectrochemical aptamer sensor, the method comprising:

[0021] S1. The Bi 2 MoO 6 / CeO 2 The heterojunction photoelectric material is dispersed in ethanol and ultrasonically treated to prepare a suspension; the obtained suspension is drop-coated on the surface of an ITO conductive glass electrode and dried at room temperature to obtain a modified electrode.

[0022] Among them, the Bi 2 MoO 6 / CeO 2 The dosage of the heterojunction photoelectric material and ethanol is 0.5-1.5 mg: 1-1.5 mL; the volume of the suspension drop-coated on the surface of the ITO conductive glass electrode is 10-50 μL.

[0023] S2. The aptamer and phosphate buffer solution are mixed to obtain an aptamer solution, and the aptamer solution is dripped onto the surface of the modified electrode obtained in step S1. After incubation at room temperature, the electrode is washed with PBS buffer to obtain a photoelectrochemical aptamer sensor.

[0024] The concentration of the aptamer solution is 0.5-5 μM, preferably 2 μM; the aptamer includes a profenofos aptamer, and the nucleotide sequence of the profenofos aptamer is shown in SEQ ID No: 1.

[0025] The incubation time is 1-3 hours, preferably 2 hours; the concentration of the PBS buffer is 0.01 M, and the pH value is 7.4.

[0026] The present invention also provides a photoelectrochemical aptamer sensor prepared by the construction method of the photoelectrochemical aptamer sensor.

[0027] The present invention also provides application of the photoelectrochemical aptamer sensor in detecting environmental pollutants; the environmental pollutants include propyl bromide.

[0028] The present invention also provides a method for detecting environmental pollutants, wherein the method uses the constructed photoelectrochemical aptamer sensor for detection.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Bi provided by the present invention 2 MoO 6 / CeO 2 The preparation method of heterojunction photoelectric material mainly comprises: 2 MoO 6 Precursor solution and CeO 2 After hydrothermal reaction, calcination is performed to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photoelectric material; the steps are simple, and the preparation process only involves chemical reagents such as ethanol and ethylene glycol, and does not involve corrosive, irritating, and environmentally unfriendly chemical reagents such as concentrated nitric acid and ammonia water required in the prior art, so the preparation method of the present invention is a green and environmentally friendly method.

[0031] (2) Bi prepared by the preparation method of the present invention 2 MoO 6 / CeO 2 Heterojunction optoelectronic materials, compared to Bi alone 2 MoO 6 or CeO 2 , its photoelectrochemical performance is significantly improved, and the experimental verification of the present invention shows that the obtained Bi2 MoO 6 / CeO 2 The heterojunction photoelectric material exhibits a high photocurrent response intensity and excellent light stability, indicating that the Bi 2 MoO 6 / CeO 2 Heterojunction optoelectronic materials have high separation efficiency for photogenerated electron-hole pairs, which is more conducive to the separation of photogenerated charges.

[0032] (3) Bi prepared by the present invention 2 MoO 6 / CeO 2 Heterojunction photoelectric materials can be applied to the field of photoelectrochemical detection; the Bi 2 MoO 6 / CeO 2 The PEC aptamer sensor constructed by the heterojunction photoelectric material achieves high-sensitivity detection of propyl bromide with a detection limit of 33 pg L-1. Moreover, the PEC aptamer sensor constructed by the present invention can detect propyl bromide at high concentrations (1 mg L-1). -1 ) interferences were detected at low concentrations (100 ng / L -1 )'s PFF has strong specificity; and during the continuous irradiation of 500s, after a total of 9 photocurrent test cycles, the photocurrent intensity of the PEC aptamer sensor constructed by the present invention has almost no change, showing strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 CeO 2 (A) Bi 2 MoO 6 (B)Bi 2 MoO 6 / CeO 2 SEM images of heterojunction optoelectronic materials (C) and Bi 2 MoO 6 / CeO 2 Energy dispersion spectrum of heterojunction optoelectronic materials (D).

[0034] Figure 2 (A) X-ray diffraction patterns and (B) FT-IR spectra of different materials.

[0035] Figure 3 To use XPS technology to 2 MoO 6 / CeO 2High-resolution analysis results of the chemical composition and valence state of the Ce element in heterojunction optoelectronic materials, where Figure A is the XPS high-resolution spectrum of Ce 3d, Figure B is the XPS high-resolution spectrum of Mo 3d, Figure C is the XPS high-resolution spectrum of Bi 4f, and Figure D is the full XPS spectrum of each material.

[0036] Figure 4 The photocurrent response results (A) and EIS spectra (B) of each material under different lighting conditions.

[0037] Figure 5 is the UV-visible diffuse reflectance spectrum of each material (A), Bi 2 MoO 6 Tauc curve (B), CeO 2 Tauc curve of material (C), Bi 2 MoO 6 Mott-Schottky curve (D), CeO 2 The Mott-Schottky curve (E) and Bi 2 MoO 6 and CeO 2 Energy level diagram (F).

[0038] Figure 6 Different electrodes BC-1 / ITO (a), aptamer / BC-1 / ITO (b), aptamer / BC-1 / ITO at 10 -5 g -1 PEC response graph (A) and Nyquist plot of EIS (B) after PFF incubation (c).

[0039] Figure 7 Optimal parameter verification for sensor construction, where: Figure 7 A is the verification result of the optimal drop volume of the suspension. Figure 7 B is the verification result of the optimal concentration of the aptamer solution.

[0040] Figure 8 The changes with PFF concentration (1 mg L -1 -0.1ng L -1 ), photocurrent response result diagram of aptamer sensor (A); logarithmic linear calibration curve of PEC response versus PFF concentration (B).

[0041] Fig. 9 Figure 2 shows the selectivity of PEC aptasensor for PFF detection.

[0042] Fig.10 This is a graph showing the stability test results of the PEC aptamer 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 bromophos is used as an example to illustrate the function of the photoelectrochemical aptamer sensor constructed by the present invention. The sequence of the aptamer corresponding to bromophos is: 5'-NH 2 -AAG CTT GCT TTATAGCCT GCAGCG ATT CTT GAT CGG AAAAGG CTG AGAGCT ACG C-3' (SEQ ID No: 1); the aptamer solution is prepared by the aptamer and PBS buffer solution.

[0046] Example 1: Bi 2 MoO 6 / CeO 2 Preparation of heterojunction photovoltaic material (BC-0.5)

[0047] Step S1:

[0048] (1) Weigh 1.08 g of cerium nitrate and 0.6 g of urea, dissolve them in 45 mL of deionized water, and stir to form a transparent solution;

[0049] (2) The resulting solution was transferred to a hydrothermal reactor and reacted at 96°C for 2.4 h;

[0050] (3) After the reaction is completed, the mixture is cooled to room temperature, the precipitate is separated, and washed with deionized water and ethanol three times each;

[0051] (4) After drying the washed precipitate, calcined at 320°C for 1.6 h to obtain CeO 2 Nanoparticles.

[0052] Step S2:

[0053] (1) Weigh 0.172 g of CeO obtained in step S1 2 The nanoparticles were added to 50 mL of ethanol and sonicated for 20 min to form a homogeneous solution;

[0054] (2) Weigh 0.485 g of bismuth nitrate and 0.121 g of sodium molybdate respectively, dissolve them in ethylene glycol and stir evenly;

[0055] (3) Mix the mixture of bismuth nitrate and sodium molybdate with CeO 2 The solution was mixed quickly and stirred thoroughly for 1 h;

[0056] (4) The resulting mixed solution was transferred to a hydrothermal reactor and reacted at 128°C for 4.8 hours;

[0057] (5) After the reaction, cool to room temperature, centrifuge and separate the precipitate, and wash with deionized water and ethanol three times in sequence;

[0058] (6) After washing and drying, the precipitate is dried to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0059] The Bi obtained in this embodiment 2 MoO 6 / CeO 2 Bi in heterojunction optoelectronic materials 2 MoO 6 and CeO 2 The molar ratio is 0.5:1, recorded as BC-0.5.

[0060] Example 2: Bi 2 MoO 6 / CeO 2 Preparation of heterojunction photovoltaic material (BC-1)

[0061] Step S1:

[0062] (1) Weigh 2.16 g of cerium nitrate and 1.2 g of urea, dissolve them in 50 mL of deionized water, and stir to form a transparent solution;

[0063] (2) The obtained solution was transferred to a hydrothermal reactor and reacted at 120°C for 3 h;

[0064] (3) After the reaction is completed, the mixture is cooled to room temperature, the precipitate is separated, and washed with deionized water and ethanol three times each;

[0065] (4) After drying the washed precipitate, calcined at 400 °C for 2 h to obtain CeO 2 Nanoparticles.

[0066] Step S2:

[0067] (1) Weigh 0.172 g of CeO obtained in step S1 2 The nanoparticles were added to 60 mL of ethanol and sonicated for 20 min to form a homogeneous solution;

[0068] (2) Weigh 0.97 g of bismuth nitrate and 0.242 g of sodium molybdate respectively, dissolve them in ethylene glycol and stir evenly;

[0069] (3) Mix the mixture of bismuth nitrate and sodium molybdate with CeO 2 The solution was mixed quickly and stirred thoroughly for 1 h;

[0070] (4) The resulting mixed solution was transferred to a hydrothermal reactor and reacted at 160° C. for 6 h;

[0071] (5) After the reaction, cool to room temperature, centrifuge and separate the precipitate, and wash with deionized water and ethanol three times in sequence;

[0072] (6) After washing and drying, the precipitate is dried to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0073] The mixed solution obtained in step (2) in S2 is directly subjected to the operations of steps (4), (5) and (6), and the final material obtained is Bi 2 MoO 6 .

[0074] The Bi obtained in this embodiment 2 MoO 6 / CeO 2 Bi in heterojunction optoelectronic materials 2 MoO 6 and CeO 2 The molar ratio is 1:1, recorded as BC-1.

[0075] Figure 1 The CeO obtained by scanning electron microscopy (SEM) analysis is shown. 2 、Bi 2 MoO 6 and Bi 2 MoO 6 / CeO 2 The microstructure of heterojunction optoelectronic materials. Figure 1 A is CeO 2 SEM image of CeO 2 The particles are in the form of agglomerates and irregular spheres; this morphological feature indicates that CeO 2Nanoparticles have a large specific surface area, which is beneficial to the subsequent heterojunction formation and surface modification process. Figure 1 B is Bi 2 MoO 6 SEM image, in which it can be observed that its structure presents a spherical morphology. Figure 1 C is Bi 2 MoO 6 / CeO 2 SEM image of heterojunction optoelectronic material, showing its layered structure and Bi 2 MoO 6 The structure is similar to that of 2 The nanoparticles were uniformly modified to form a stable composite material. Figure 1 D is Bi 2 MoO 6 / CeO 2 The EDS (energy dispersive spectroscopy) spectrum of heterojunction optoelectronic materials further verifies that Bi 2 MoO 6 / CeO 2 The uniform distribution of Ce, Bi, Mo and O elements in heterojunction optoelectronic materials also indicates that CeO 2 Success in heterojunction surface modification.

[0076] Example 3: Bi 2 MoO 6 / CeO 2 Preparation of heterojunction photovoltaic material (BC-2)

[0077] Step S1:

[0078] (1) Weigh 3.24 g of cerium nitrate and 1.8 g of urea, dissolve them in 55 mL of deionized water, and stir to form a transparent solution;

[0079] (2) The resulting solution was transferred to a hydrothermal reactor and reacted at 144°C for 3.6 hours;

[0080] (3) After the reaction is completed, the mixture is cooled to room temperature, the precipitate is separated, and washed with deionized water and ethanol three times each;

[0081] (4) After the washed precipitate is dried, it is calcined at 480°C for 2.4 h to obtain CeO 2 Nanoparticles.

[0082] Step S2:

[0083] (1) Weigh 0.129 g of CeO obtained in step S1 2 The nanoparticles were added to 70 mL of ethanol and sonicated for 20 min to form a homogeneous solution;

[0084] (2) Weigh 1.455 g of bismuth nitrate and 0.363 g of sodium molybdate respectively, dissolve them in ethanol and stir evenly;

[0085] (3) Mix the mixture of bismuth nitrate and sodium molybdate with CeO 2 The solution was mixed quickly and stirred thoroughly for 1 h;

[0086] (4) The resulting mixed solution was transferred to a hydrothermal reactor and reacted at 192°C for 7.2 h;

[0087] (5) After the reaction, cool to room temperature, centrifuge and separate the precipitate, and wash with deionized water and ethanol three times in sequence;

[0088] (6) After washing and drying, the precipitate is dried to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0089] The Bi obtained in this embodiment 2 MoO 6 / CeO 2 Bi in heterojunction optoelectronic materials 2 MoO 6 and CeO 2 The molar ratio is 2:1, recorded as BC-2.

[0090] Example 4: Bi 2 MoO 6 / CeO 2 Preparation of heterojunction photovoltaic material (BC-3)

[0091] Step S1:

[0092] (1) Weigh 4.32 g of cerium nitrate and 2.4 g of urea, dissolve them in 60 mL of deionized water, and stir to form a transparent solution;

[0093] (2) The resulting solution was transferred to a hydrothermal reactor and reacted at 168°C for 4.2 h;

[0094] (3) After the reaction is completed, the mixture is cooled to room temperature, the precipitate is separated, and washed with deionized water and ethanol three times each;

[0095] (4) After drying the washed precipitate, calcined at 560°C for 2.8 h to obtain CeO 2 Nanoparticles.

[0096] Step S2:

[0097] (1) Weigh 0.115 g of CeO obtained in step S1 2The nanoparticles were added to 80 mL of ethanol and sonicated for 20 min to form a homogeneous solution;

[0098] (2) Weigh 1.94 g of bismuth nitrate and 0.484 g of sodium molybdate, dissolve them in ethanol and stir evenly;

[0099] (3) Mix the mixture of bismuth nitrate and sodium molybdate with CeO 2 The solution was mixed quickly and stirred thoroughly for 1 h;

[0100] (4) The resulting mixed solution was transferred to a hydrothermal reactor and reacted at 224°C for 8.4 h;

[0101] (5) After the reaction, cool to room temperature, centrifuge and separate the precipitate, and wash with deionized water and ethanol three times in sequence;

[0102] (6) After washing and drying, the precipitate is dried to obtain Bi 2 MoO 6 / CeO 2 Heterojunction photovoltaic materials.

[0103] The Bi obtained in this embodiment 2 MoO 6 / CeO 2 Bi in heterojunction optoelectronic materials 2 MoO 6 and CeO 2 The molar ratio is 3:1, recorded as BC-3.

[0104] Figure 2 A shows the Bi characterized by XRD (X-ray diffraction) technique 2 MoO 6 、CeO 2 and Bi 2 MoO 6 / CeO 2 The crystal structure of heterojunction optoelectronic materials (including BC-0.5, BC-1, BC-2 and BC-3). The results show that Bi 2 MoO 6 and CeO 2 The XRD spectra of orthorhombic Bi 2 MoO 6 (JCPDS No.21-0102) and cubic fluorite structure CeO 2 (JCPDF No.43-1002) matches well. Among them, CeO 2 The diffraction peaks of Bi appear at 28.6°, 33.1°, 47.6° and 56.4°, corresponding to the (111), (200), (220) and (311) crystal planes, respectively; 2 MoO6 The diffraction peaks appear at 28.3°, 32.5°, 46.7°, 55.4° and 58.5°, corresponding to the (131), (200), (202), (331) and (262) crystal planes, respectively. 2 MoO 6 / CeO 2 XRD spectrum of heterojunction optoelectronic materials, which shows CeO 2 and Bi 2 MoO 6 All characteristic diffraction peaks of CeO are detected, and no additional impurity diffraction peaks are detected. 2 and Bi 2 MoO 6 Some diffraction peaks are close to that of CeO 2 When the content is low, the XRD spectrum will be closer to Bi 2 MoO 6 ; With CeO 2 The increase of CeO content 2 and Bi 2 MoO 6 The diffraction peaks of Bi 2 MoO 6 / CeO 2 Heterojunction formation.

[0105] Figure 2 B shows the CeO characterized by FT-IR (Fourier transform infrared spectroscopy) technique. 2 、Bi 2 MoO 6 and BC-1 heterojunction photoelectric materials at 4000-400cm -1 FT-IR spectrum in the range. Pure CeO 2 Typical vibration at 1527cm -1 、1060cm -1 and 1000cm -1 Below, all absorption peaks appear at the appropriate positions. 2 MoO 6 In the FT-IR spectrum, 846 and 723 cm -1 The absorption peak of MoO 6 The stretching vibration of the Mo-O bond in the octahedron is related to the 553 cm -1 The absorption peak near may be related to the stretching vibration of Bi-O bond. In addition, the synthesized BC-1 heterojunction photoelectric material shows similarity to CeO 2 and Bi 2 MoO 6 The characteristic peaks consistent with the2 MoO 6 / CeO 2 Bi 2 MoO 6 / CeO 2 Successful preparation of materials.

[0106] Figure 3 The high-resolution analysis results of the chemical composition and valence state of Ce element in BC-1 heterojunction optoelectronic material using XPS (X-ray photoelectron spectroscopy) technology are presented. Figure 3 (AC) is CeO 2 、Bi 2 MoO 6 High-resolution XPS spectra of Ce 3d, Mo 3d and Bi 4f in BC-1 heterojunction photovoltaic materials; Figure 3 A shows that the XPS signal intensity of Ce in BC-1 is higher than that of pure CeO 2 At the same time, the high-resolution XPS spectrum of Ce 3d in BC-1 detected 6 signal peaks, which are consistent with the CeO 2 3d 5 / 2 and Ce 3d 3 / 2 This indicates that BC-1 mainly contains Ce 4+ , indicating that the structure of BC-1 was not destroyed due to the preparation process; Figure 3 B shows the high-resolution Mo 3d orbital spectrum. The two individual peaks centered at 235.51 eV and 232.36 eV can be assigned to Mo 3d with an oxidation state of +5. 3 / 2 and Mo 3d 5 / 2 orbital, corresponding to the oxidation state of molybdenum; Figure 3 As shown in C, the binding energy signals at 159.15 eV and 164.40 eV are respectively attributed to Bi 4f 7 / 2 and Bi 4f 5 / 2 The binding energy of Ce 3d in BC-1 heterojunction photoelectric material is higher than that of pure CeO 2 , and the Bi 4f and Mo 3d in the BC-1 heterojunction photoelectric material are also higher than those of pure Bi 2 MoO 6 The binding energy of Figure 3 D, in Bi 2 MoO 6 、CeO 2 The XPS spectra of BC-1 and BC-1 are complete, and the above results show that Bi 2 MoO 6 / CeO 2 Successful preparation of heterojunction optoelectronic materials.

[0107] Example 5: Bi 2 MoO 6 / CeO 2 、CeO 2 and Bi 2 MoO 6 Performance Testing

[0108] (1) Weigh 0.5 mg of CeO 2 、Bi 2 MoO 6 , BC-0.5, BC-1, BC-2, or BC-3 were dispersed in 1 mL of ethanol and ultrasonicated for 15 min to prepare a suspension;

[0109] (2) Take 10 μL of the suspension and evenly apply it on the surface of the ITO conductive glass electrode;

[0110] (3) Dry naturally at room temperature to obtain the modified electrode.

[0111] Figure 4 A is the PEC signal of different modified electrodes in PBS buffer under illumination. 2 and Bi 2 MoO 6 The photocurrent response intensity of the material is low, indicating that the separation efficiency of photogenerated electron-hole pairs is poor. 2 MoO 6 / CeO 2 The photocurrent response intensity of the heterojunction photoelectric material is significantly higher than that of the two individual units, indicating that Bi 2 MoO 6 and CeO 2 The combination of CeO and BC-1 is beneficial to the separation of photogenerated charges. It is worth noting that the photocurrent intensity of the BC-1 heterojunction photoelectric material is the strongest, indicating that the electron-hole recombination rate is the lowest. In addition, the EIS curve also found a consistent trend, which is consistent with the CeO 2 and Bi 2 MoO 6 In comparison, Bi 2 MoO 6 / CeO 2 The radius of the heterojunction photoelectric material on the EIS curve decreases, among which the BC-1 heterojunction photoelectric material shows a significantly smaller radius than CeO on the EIS curve. 2 and Bi 2 MoO 6 The radius ( Figure 4 B), indicating that it has a higher charge transfer efficiency. These results show that Bi 2 MoO 6 / CeO 2The construction of heterojunction in heterojunction photoelectric materials successfully suppressed the recombination of photogenerated electron-hole pairs, thereby improving their photoelectric performance, among which BC-1 heterojunction photoelectric material has the best performance.

[0112] Compare 2 MoO 6 , BC-0.5, BC-1, BC-2, BC-3, CeO 2 Test the light absorption ability and band structure. The test results are as follows: Figure 5 As shown; among them, Figure 5 In A, the absorption band edge is visible near 460nm. 2 MoO 6 CeO 2 Has stronger absorption and will Bi 2 MoO 6 With CeO 2 After compounding, all 2 MoO 6 Bi with similar absorption band edge 2 MoO 6 / CeO 2 The samples have stronger absorption capacity for visible light, indicating that Bi 2 MoO 6 With CeO 2 In addition, according to the Kubelka-Munk equation, Bi 2 MoO 6 ( Figure 5 B) and CeO 2 ( Figure 5 C) are about 2.32eV and 2.83eV respectively. Further analysis of the Mott-Schottky (MS) curve determines the electron density and conduction band potential of the semiconductor. The results are as follows Figure 5 D and 5E: The positive slope of the MS curve indicates that Bi 2 MoO 6 and CeO 2 They are all typical n-type semiconductors, and the obtained Bi 2 MoO 6 and CeO 2The flat band potentials (Efb) of n-type semiconductors are -0.78 and -0.70 eV vs SCE, respectively. According to the relevant literature (Chen F, et al. Novelternary heterojunction photcocatalyst of Ag nanoparticles and g-C3N4 nanosheets co-modified BiVO4 for wider spectrum visible-light photocatalytic degradation of refractory pollutant [J]. Applied Catalysis B: Environmental, 2017, 205: 133-147.), the flat band potential (Efb) of n-type semiconductors is 0-0.2 eV higher than the conduction band (CB) potential, and the flat band potential (Efb) of p-type semiconductors is 0-0.2 eV lower than the valence band (VB) potential. Therefore, assuming a difference of 0.1 eV, the corresponding Bi 2 MoO 6 and CeO 2 The conduction band (CB) potentials of Bi 2 MoO 6 and CeO 2 The corresponding valence band potentials (VB) are 1.68 eV and 2.27 eV, respectively, which further indicates that Bi 2 MoO 6 With CeO 2 Close interaction to form a heterojunction ( Figure 5 F).

[0113] Example 6: Bi prepared in Example 2 2 MoO 6 / CeO 2 Heterojunction Photoelectric Material (BC-1) Construction of Photoelectrochemical Aptamer Sensor (PEC Aptamer Sensor)

[0114] Step S1:

[0115] (1) Weigh 0.5 mg of Bi obtained in Example 2 2 MoO 6 / CeO 2 The heterojunction photovoltaic material (BC-1) was dispersed in 1 mL of ethanol and ultrasonicated for 15 min to prepare a suspension;

[0116] (2) taking 30 μL of the suspension obtained in step (1) and evenly applying it on the surface of the ITO conductive glass electrode;

[0117] (3) Dry naturally at room temperature to obtain the modified electrode.

[0118] Step S2:

[0119] (1) Add a 0.5 μM aptamer solution to the surface of the modified electrode obtained in step S1 and incubate at room temperature for 1 h;

[0120] (2) After incubation, the electrode surface was washed with 0.01 M PBS buffer at a pH of 7.4;

[0121] (3) The electrode cleaned in step (2) is combined with the target substance propylbromide (PFF) to construct a photoelectrochemical aptamer sensor (PEC aptamer sensor).

[0122] In order to verify the feasibility of the preparation of PEC aptamer sensor and the effectiveness of the construction, the current intensity of the product obtained in each step of the preparation process was tested. Figure 6 As shown in Figure A, when BC-1 was introduced into the ITO conductive glass electrode, the initial photocurrent intensity obtained was about 176nA (curve a). When the aptamer was introduced onto the BC-1 / ITO electrode, the charge transfer of the aptamer was relatively weak, and the steric hindrance of the aptamer seriously hindered the transfer of electrons on the electrode surface (curve b). Finally, the modified electrode was incubated with PFF, and the PEC aptamer sensor was obtained by combining the aptamer with PFF (curve c). These results verified the feasibility of the preparation of the PEC aptamer sensor and the effectiveness of the construction.

[0123] To further verify the successful construction of the PEC aptasensor, Figure 6 B compares the charge transfer resistance of the electrodes during the construction of the PEC aptamer sensor. After BC-1 was modified on the ITO electrode, the BC-1 / ITO electrode had the smallest charge transfer resistance (curve a), which was due to the effective inhibition of charge recombination by the composite material and the increase of the photocurrent intensity. Subsequently, the aptamer was modified on the BC-1 / ITO electrode, and its introduction inhibited the migration of charges on the electrode surface, and the resistance increased (curve b). Finally, PFF was modified on the electrode, and the charge transfer resistance decreased (curve c), which was due to the oxidation of the PFF molecules captured by the aptamer by the photoinduced holes in the presence of PFF, so the resistance value decreased. Figure 6 The electrochemical impedance spectrum shown in B is consistent with the transient photocurrent response results, once again demonstrating the successful construction of the stepwise modified PEC aptamer sensor.

[0124] Example 7: Bi prepared in Example 2 2 MoO 6 / CeO 2 Heterojunction Photoelectric Material (BC-1) Construction of Photoelectrochemical Aptamer Sensor (PEC Aptamer Sensor)

[0125] Step S1:

[0126] (1) Weigh 1 mg of Bi obtained in Example 2 2 MoO 6 / CeO 2 The heterojunction photovoltaic material (BC-1) was dispersed in 1.2 mL of ethanol and ultrasonicated for 15 min to prepare a suspension;

[0127] (2) taking 10 μL of the suspension obtained in step (1) and evenly applying it on the surface of the ITO conductive glass electrode;

[0128] (3) Dry naturally at room temperature to obtain the modified electrode.

[0129] Step S2:

[0130] (1) Add a 2 μM aptamer solution to the surface of the modified electrode obtained in step S1 and incubate at room temperature for 2 h;

[0131] (2) After incubation, the electrode surface was washed with 0.01 M PBS buffer at a pH of 7.4;

[0132] (3) The electrode cleaned in step (2) is combined with the target substance propylbromide (PFF) to construct a photoelectrochemical aptamer sensor (PEC aptamer sensor).

[0133] Example 8: Bi prepared in Example 2 2 MoO 6 / CeO 2 Heterojunction Photoelectric Material (BC-1) Construction of Photoelectrochemical Aptamer Sensor (PEC Aptamer Sensor)

[0134] Step S1:

[0135] (1) Weigh 1.5 mg of Bi obtained in Example 2 2 MoO 6 / CeO 2 The heterojunction photovoltaic material (BC-1) was dispersed in 1.5 mL of ethanol and ultrasonicated for 15 min to prepare a suspension;

[0136] (2) taking 50 μL of the suspension obtained in step (1) and evenly applying it on the surface of the ITO conductive glass electrode;

[0137] (3) Dry naturally at room temperature to obtain the modified electrode.

[0138] Step S2:

[0139] (1) Add a 5 μM aptamer solution to the surface of the modified electrode obtained in step S1 and incubate at room temperature for 3 h;

[0140] (2) After incubation, the electrode surface was washed with 0.01 M PBS buffer at a pH of 7.4;

[0141] (3) The electrode cleaned in step (2) is combined with the target substance propylbromide (PFF) to construct a photoelectrochemical aptamer sensor (PEC aptamer sensor).

[0142] In order to explore the effect of suspension drop volume on the performance of PEC aptamer sensor, five experimental groups with drop volume of 10, 20, 30, 40 and 50 μL were set up. The effect of drop volume on the performance of PEC aptamer sensor was reflected by the photocurrent response intensity of PEC aptamer sensor. The results are shown in Figure 2. Figure 7 As shown in A, when the drop volume of the suspension on the ITO surface increased from 10 μL to 30 μL, the photocurrent of the constructed PEC aptamer sensor showed an upward trend. However, when the drop volume of the suspension continued to increase, the photocurrent response of the PEC aptamer sensor decreased slightly. This may be due to the increase in the drop volume of the suspension, which caused the Bi on the ITO surface to 2 MoO 6 / CeO 2 The thickness of the heterojunction photoelectric material is too high, which hinders the electron transmission and accelerates the recombination process of electron-hole pairs. Therefore, it can be found through experimental research that the drop coating volume of the suspension is preferably 30μL.

[0143] In order to explore the effect of aptamer solution concentration on the performance of PEC aptamer sensor, five aptamer concentration experimental groups of 0.5, 1.0, 1.5, 2.0, and 2.5 μM were set up. The photocurrent response intensity of the PEC aptamer sensor was used to reflect the effect of aptamer solution concentration on the performance of the PEC aptamer sensor. The results are shown in Figure 2. Figure 7 As shown in Figure B, as the aptamer concentration increases from 0.5 μM to 2 μM, the photocurrent intensity of the constructed PEC aptamer sensor decreases with the increase of the aptamer concentration. When the aptamer concentration increases further, the photocurrent intensity remains basically unchanged. This is because the amount of aptamers fixed on the surface of the PEC aptamer sensor has reached saturation, and excess aptamers cannot be successfully assembled. Therefore, it can be found through experimental research that the concentration of the aptamer solution is preferably 2 μM.

[0144] Example 9: Performance verification of photoelectrochemical aptamer sensor

[0145] (1) Sensitivity verification

[0146] Based on the PEC aptamer sensor constructed in Example 6, the -1 -0.1ng L -1PFF standards within the range of 1.5 wt % (purchased from Sangon Biotech (Shanghai) Co., Ltd.) were used. Each concentration group was repeated three times and the average value was taken to reduce the error. The relationship between the photocurrent response of the PEC aptamer sensor and the PFF concentration was recorded.

[0147] The results are as follows Figure 8 As shown, from Figure 8 As can be seen in A, the photocurrent increases proportionally with the increase of PFF concentration, indicating that at a PFF concentration of 1 mg L -1 -0.1ng L -1 (The ah in the figure are 1 mg L -1 , 0.1mg L -1 , 0.01mg L -1 , 1μg L -1 , 0.1 μg L -1 , 0.01 μg L -1 1ng L -1 , 0.1ng L -1 ), the ratio of the photocurrent intensity to the logarithm of the PFF concentration has a good linear relationship. Figure 8 As shown in B, the corresponding linear regression equation is I(nA)=-7.979LogC PFF -143.343(R 2 =0.999), the detection limit of the PEC aptamer sensor was as low as 33 pg L -1 (S / N=3). These results further verified the convenience and sensitivity of the established PEC aptasensor in detecting bromophos, and depending on the different aptamers, the PEC aptasensor established in the present invention is expected to detect other organophosphorus pesticide (OPs) molecules besides bromophos.

[0148] (2) Specificity verification

[0149] In order to verify the specificity of the constructed sensor, the sensor obtained in Example 6 was used to detect different interfering substances and mixtures of interfering substances and PFF to explore the specificity of the PEC aptamer sensor. Fig. 9 As shown, the sensor obtained in Example 6 has a detection concentration of 100 ngL -1 When the PFF was 0.1%, the photocurrent intensity changed significantly, and at the detection concentration of 1 mg L -1 When the other organophosphorus pesticides were detected, the photocurrent intensity did not change significantly; and the photocurrent intensity change of the sensor in the mixture of interfering substances and PFF was similar to that in the detection concentration of 100ngL -1 This result fully demonstrates that the sensor constructed by the present invention has a high specificity for detecting PFF.

[0150] (3) Stability verification

[0151] The results are as follows Fig.10 As shown, the sensor obtained in Example 6 was continuously irradiated for 500 seconds, during which 9 photocurrent test cycles were passed. During the continuous test cycles, the photocurrent intensity hardly changed, which indicates that the sensor has excellent stability.

[0152] Example 10: Actual sample testing

[0153] (1) Sample preparation

[0154] Water sample: collected from the middle layer of the Yangtze River at the Jiaoshan section in Zhenjiang.

[0155] Milk sample: Commercially available Yili pure milk (250mL)

[0156] Vegetable samples: Commercially available cabbage (purchased from Zhenjiang Jimailong Supermarket)

[0157] (2) Sample processing

[0158] Water sample: After standing for 30 minutes, centrifuge and filter to remove impurities.

[0159] Milk sample: Milk, 10% trichloroacetic acid by mass, and deionized water were mixed in a mass ratio of 2:2:1, and the mixture was subjected to ultrasonic treatment and centrifuged to obtain the supernatant.

[0160] Vegetable samples: mince 1 g of vegetables, mix with 1 mL of acetone and 9 mL of PBS buffer, and centrifuge. Dilute the supernatant with PBS at a ratio of 1:2 for later use.

[0161] (3) Test results

[0162] According to the process of constructing the sensor in Example 6, propyl bromide (PFF) in the pretreated sample is used as the target, and the modified electrode is immersed in a solution containing the target to construct a photoelectrochemical aptamer sensor (PEC aptamer sensor). The PFF concentration in the sample is calculated by the standard addition method by detecting the change in current.

[0163] The calculation formula is: I (nA) = -7.979Log C PFF -143.343(R 2 =0.999)

[0164] In order to test the practicality of the prepared sensor, the application of the sensor in the detection of actual samples was used as an important part of evaluating its analytical performance. The standard addition method was used to comprehensively evaluate its practicality and accuracy in Yangtze River water, canal water, milk and cabbage samples, where three replicates (n=3) were set for each sample, and the results were averaged. The results are shown in Table 1.

[0165] Table 1. Recovery test of PEC aptamer sensor for PFF in different samples (n=3)

[0166]

[0167] Table 1 shows that the recovery rate of the PEC aptamer sensor obtained by the present invention for PFF is 97.33% to 109.67%, and the RSD is 0.8% to 4.3%, indicating that the Bi 2 MoO 6 / CeO 2 The PEC aptamer sensor constructed by heterojunction optoelectronic materials has a good effect on measuring PFF in actual samples.

[0168] 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 method for preparing Bi2MoO6 / CeO2 heterojunction photoelectric material, characterized in that: The method comprises: S1. Dissolve cerium nitrate and urea in deionized water and stir to form a transparent solution; subject the obtained transparent solution to a hydrothermal reaction, cool to room temperature after the reaction, separate the precipitate by centrifugation, wash with deionized water and ethanol in turn, dry and calcine to obtain CeO2 nanoparticles; S2. Disperse the CeO2 nanoparticles obtained in step S1 in ethanol, and perform ultrasonic treatment to form a uniform CeO2 ethanol solution; dissolve bismuth nitrate and sodium molybdate in ethylene glycol, stir evenly, mix with the CeO2 ethanol solution, and stir to react to obtain a mixed solution; subject the mixed solution to a hydrothermal reaction, and after the reaction is completed, cool to room temperature, separate the precipitate by centrifugation, wash with deionized water and ethanol in turn, and dry to obtain Bi2MoO6 / CeO2 heterojunction photoelectric material.

2. The preparation method according to claim 1, characterized in that: In step S1, the dosage of cerium nitrate, urea and deionized water is 1.08-4.32 g: 0.6-2.4 g: 45-60 mL; the hydrothermal reaction is: 96-168° C. reaction for 2.4-4.2 h; and the calcination is: 320-560° C. calcination for 1.6-2.8 h.

3. The preparation method according to claim 1, characterized in that: In step S2, the amount of CeO2 nanoparticles and ethanol is 0.115-0.172 g: 50-80 mL; the amount of bismuth nitrate, sodium molybdate and ethylene glycol is 0.485-1.94 g: 0.121-0.484 g: 30 mL; the stirring reaction time is 1 hour; the hydrothermal reaction is: 128-224°C reaction for 4.8-8.4 hours.

4. The Bi2MoO6 / CeO2 heterojunction photoelectric material prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the Bi2MoO6 / CeO2 heterojunction photoelectric material prepared by the preparation method according to any one of claims 1 to 3, or the Bi2MoO6 / CeO2 heterojunction photoelectric material according to claim 4 in constructing a photoelectrochemical aptamer sensor or photoelectrochemical detection of environmental pollutants.

6. A method for constructing a photoelectrochemical aptamer sensor, characterized in that: The method comprises: S1. Disperse and dissolve the Bi2MoO6 / CeO2 heterojunction photoelectric material prepared by the preparation method of any one of claims 1 to 3, or the Bi2MoO6 / CeO2 heterojunction photoelectric material according to claim 4 in ethanol, and prepare a suspension by ultrasonic treatment; drop-coat the obtained suspension on the surface of the ITO conductive glass electrode, and dry at room temperature to obtain a modified electrode; S2. Mix the aptamer and phosphate buffer solution to obtain an aptamer solution, and drop the aptamer solution onto the surface of the modified electrode obtained in step S1. After incubation at room temperature, wash with PBS buffer to obtain a photoelectrochemical aptamer sensor.

7. The method according to claim 6, characterized in that The dosage of the Bi2MoO6 / CeO2 heterojunction photoelectric material and ethanol in step S1 is 0.5-1.5 mg: 1-1.5 mL; the volume of the suspension drop-coated on the surface of the ITO conductive glass electrode is 10-50 μL.

8. The method according to claim 6, characterized in that The concentration of the aptamer solution in step S2 is 0.5-5 μM, preferably 2 μM; the aptamer includes a profenofos aptamer, and the nucleotide sequence of the profenofos aptamer is shown in SEQ ID No: 1; the incubation time is 1-3 h, preferably 2 h; the concentration of the PBS buffer is 0.01 M, and the pH value is 7.

4.

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 profenofos.

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.

Images