Preparation method of photoelectrochemical sensor based on cadmium sulfide-gallium oxide heterojunction and method for detecting tetracycline by using photoelectrochemical sensor

Abstract

The invention relates to the technical field of photosensitive electrode materials, in particular to preparation of a cadmium sulfide-gallium oxide heterojunction-based photoelectrochemical sensor and a method for detecting tetracycline by using the cadmium sulfide-gallium oxide heterojunction-based photoelectrochemical sensor. A CdS / Ga2O3 composite material is synthesized by adopting a hydro-thermal method and is used as a substrate material for preparing a photoelectrochemical sensor. Ga2O3 with the advantages of good chemical stability, high photoelectric conversion efficiency and the like is compounded with CdS with the problems of high photo-induced electron-hole recombination rate, serious photo-corrosion phenomenon and the like to construct the S-type heterojunction photosensitive composite material, so that the photo-response range is widened, and the light energy utilization rate and the photo-induced carrier separation efficiency are improved. Due to excellent chemical stability and light corrosion resistance of Ga2O3, CdS can be effectively protected, the light corrosion phenomenon is reduced, and the long-term stability of the photoelectrochemical sensor is enhanced. The photoelectrochemical sensor constructed by the invention realizes high-sensitivity detection of tetracycline within a wide linear range of 1 [mu] M to 50 [mu] M, and has the advantages of low preparation cost, stable photoelectric response, good repeatability and the like while the detection limit is as low as 0.045 [mu] M.

Description

[0001] 1. Name

[0002] Method for preparing a photoelectrochemical sensor based on a cadmium sulfide-gallium oxide heterojunction and detecting tetracycline Technical Field

[0003] The present invention belongs to the technical field of preparation of novel composite photoelectric composite materials and tetracycline detection. The present invention first introduces Ga2O3 with a wide bandgap and excellent chemical stability into the field of photoelectrochemical sensor detection to prepare an S-type heterojunction CdS / Ga2O3 composite material. The CdS / Ga2O3 composite material is used as a substrate material and combined with an ITO electrode to obtain a photocurrent. Tetracycline is dissolved in the electrolyte to achieve highly sensitive and wide-range direct detection of tetracycline. Compared with the existing CdS-based photoelectrochemical sensors, when combined with Ga2O3, its heterojunction and energy band complementary structure improve the photoelectric performance of the PEC sensor while enhancing the long-term working stability of the photoelectrochemical sensor. Background Art

[0004] As a widely used antibiotic, tetracycline plays an important role in the fields of medicine, animal husbandry, etc. However, its residue problem has increasingly attracted attention. Tetracycline residues may enter the human body through the food chain, causing health risks such as allergic reactions, and may also cause potential hazards to the ecological environment, such as harming the growth of animals and plants and reducing soil fertility. Traditional detection methods such as high-performance liquid chromatography and liquid chromatography-mass spectrometry, although having high detection sensitivity and strong specificity, are expensive in equipment and complex in operation, and it is difficult to achieve wide and convenient detection applications. Enzyme-linked immunosorbent assay has a fast detection speed, but lower specificity and sensitivity. Capillary electrophoresis and fluorescence spectroscopy are simple in operation, but have limited application ranges. Although surface-enhanced Raman spectroscopy and surface plasmon resonance technology have the advantages of high sensitivity and real-time detection, their quantitative analysis and stability still need to be improved. Therefore, it is very important to develop a tetracycline detection method with high sensitivity and good specificity.

[0005] As an emerging detection method, photoelectrochemical sensing technology has gradually emerged and received extensive attention. This technology cleverly combines photoexcitation with electrochemical detection to achieve sensitive detection of target substances through photoelectric conversion. In principle, the core of photoelectrochemical sensing technology lies in using photoactive materials to generate electron-hole pairs under light illumination, and these photo-generated carriers participate in redox reactions at the electrode / electrolyte interface, thereby generating detectable photoelectric signals. By analyzing the change characteristics of these signals, qualitative identification and quantitative detection of target substances can be achieved, which has significant advantages such as high sensitivity and rapid response compared with traditional detection methods.

[0006] Photoelectrochemical (PEC) sensors, with their characteristics such as high sensitivity, provide strong support for fields such as food safety monitoring. However, there are still many technical problems in the actual application process of PEC sensors, such as weak anti-interference ability, high recombination rate of photo-generated carriers, and photo-corrosion phenomenon. These problems seriously restrict the further improvement of their detection performance. Certain improvements are still needed when applying PEC sensing detection to specific tetracycline detection. Starting from the composition structure and working principle of PEC sensors, the optoelectronic material on the working electrode of PEC sensors serves as a "converter" of optoelectronic signals. The selection of optoelectroactive materials directly affects the detection efficiency and analytical performance of PEC sensors. Among many methods to optimize the optoelectronic properties of materials, constructing composite heterojunctions has become a mature and effective method to improve the optoelectronic properties of materials due to its flexible designability and controllability.

[0007] Based on this, selecting and developing optoelectroactive composite materials with high optoelectronic performance to further optimize the performance of photoelectrochemical sensors, so as to achieve efficient and reliable on-site rapid detection of tetracycline in the fields of food safety, environmental pollutant detection, etc. Summary of the Invention

[0008] To solve the above deficiencies of the existing technology, the purpose of the present invention is to provide a method for preparing a photoelectrochemical sensor based on a cadmium sulfide-gallium oxide heterojunction and its detection of tetracycline. By compositing the CdS phase with excellent chemical stability and anti-photo-corrosion properties to form an S-type heterojunction, the advantages and disadvantages of the optoelectronic properties of the two are complementary, and the formed heterojunction can effectively improve the optoelectronic conversion efficiency and long-term stability of the photoelectrochemical sensor. Using the CdS / Ga2O3 composite material as the substrate, a photoelectrochemical sensor with a simple preparation method, good stability, and high sensitivity can be prepared, which can realize simple, efficient, stable, and accurate specific detection of tetracycline.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] 1. Preparation of a photoelectrochemical sensor based on a cadmium sulfide-gallium oxide heterojunction, characterized by including the following steps:

[0011] (1) Preparation of CdS / Ga2O3 heterojunction composite material:

[0012] First, dissolve thiourea in deionized water and stir magnetically until it is completely dissolved. Then, while stirring magnetically, add cadmium nitrate tetrahydrate and gallium oxide respectively to obtain a white suspension. Subsequently, put the well-stirred solution into a high-pressure reaction kettle, react at a certain temperature for a period of time, take it out from the polytetrafluoroethylene inner liner and collect the yellow precipitate. After repeatedly washing to remove impurities, put it into a vacuum oven for drying, and finally obtain the CdS / Ga2O3 heterojunction composite material.

[0013] (2) ITO electrode pretreatment:

[0014] The ITO glass was ultrasonicated in an ultrasonic machine in the order of acetone, anhydrous ethanol, and deionized water, and then dried in an oven.

[0015] (3) Preparation of Ga2O3 / CdS heterojunction sensor:

[0016] A Ga2O3 / CdS suspension was dropped onto the conductive surface of an ITO conductive glass, which was then dried naturally at room temperature to prepare an ITO electrode for detecting tetracycline, and finally a photoelectrochemical sensor was obtained.

[0017] Preferably, the dosage ratio of thiourea, cadmium nitrate tetrahydrate and gallium oxide in step 1 (1) is 0.945 g: 1.2825 g: 0.085 g, the mixed solution is reacted in an oven at a temperature of 180 to 200° C. for 12 to 24 hours, the collected yellow precipitate is washed three times with deionized water and anhydrous ethanol respectively, and finally dried in a vacuum oven at a temperature of 40 to 70° C. for 6 to 12 hours.

[0018] Preferably, the size of the ITO conductive glass in step (2) is 20 * 10 * 1.1mm, and each ultrasonic time is 15min to fully remove the oxide on the ITO surface.

[0019] Preferably, the ITO glass conductive surface described in step (3) is covered with copper tape on half of its area.

[0020] 2. The detection steps of tetracycline by a photoelectrochemical sensor based on cadmium sulfide-gallium oxide heterojunction are as follows:

[0021] (1) The electrochemical workstation uses a classic three-electrode system to test the performance of the photoelectrochemical sensor, and Na2SO4 is selected as the experimental electrolyte.

[0022] (2) Using the chronoampere method (IT), a xenon lamp simulates sunlight, the illumination switching cycle is set to T = 40 seconds, and a bias voltage of 0.1 V is applied.

[0023] (3) Place the ITO electrode in the electrolytic cell with the conductive surface facing the xenon lamp and connect it to a computer to record the photoelectric response changes of the ITO working electrode before and after tetracycline is added to the electrolyte.

[0024] (4) Record the photoelectric response changes of the ITO working electrode in the blank control and when adding different concentrations of tetracycline as the analyte, and draw a fitting curve for analysis.

[0025] (5) On the basis of the above experiments, different CdS / Ga2O3 / ITO electrodes of the same batch were selected for optoelectronic performance testing to analyze the performance gap between different ITO electrodes.

[0026] (6) Different interferents were added to the electrolyte, and the changes in the optoelectronic response of the CdS / Ga2O3 / ITO electrode were recorded and compared with the optoelectronic response changes when tetracycline was added in step (4).

[0027] Preferably, the electrochemical workstation described in step (1) uses the CHI660E electrochemical workstation of Shanghai Qihua Instrument Co., Ltd., and an external xenon lamp light source (Solar-500 W, NBET) is used as the excitation source. A silver / silver chloride electrode is used as the reference electrode, a platinum wire electrode is used as the counter electrode, and the prepared CdS / Ga2O3 / ITO electrode is used as the working electrode. The experimental environment is unified, and 50 ml of 0.1 M Na2SO4 containing 0.1 M ascorbic acid (AA) is selected as the experimental electrolyte for the PEC sensor performance test. All experiments are carried out at room temperature of 25 °C.

[0028] Preferably, the xenon lamp simulated light band described in step (2) is 200~1100 nm.

[0029] Preferably, the concentration of tetracycline added to the electrolyte described in step (3) is 1~10 μM. To test the stability of the ITO electrode, the test time of the electrochemical workstation is 1000~1500 s.

[0030] Preferably, in step (4), the detection concentration range of tetracycline is 1 pM~50 μM.

[0031] Preferably, in step (5), to ensure sufficient data collection, at least 5 pieces are selected from the ITO electrodes of the same batch for experimental testing.

[0032] Preferably, in step (6), to test the high selectivity of the optoelectrochemical sensor for tetracycline detection, the concentration of the added interferent is generally 10 times or more of the selected concentration of tetracycline.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention provides a preparation method of an optoelectrochemical sensor based on a cadmium sulfide-gallium oxide heterojunction. The CdS / Ga2O3 composite material is prepared by a one-step hydrothermal method, which reduces the preparation steps. While preparing the composite material at low cost and high efficiency, it is convenient to regulate and optimize the experimental testing.

[0035] 2. For the first time, Ga2O3 with excellent photoelectrochemical stability is applied to the field of photoelectrochemical detection. It is compounded with CdS, and the two have complementary energy band structures. While improving the photoelectric response, CdS is protected to reduce the impact of photo-corrosion on it, and the stability of device operation is improved.

[0036] 3. The photoelectrochemical sensor for tetracycline detection constructed in the present invention has good response time, photoelectric stability, selectivity, repeatability, etc. while the linear detection range is 1 μM - 50 μM and the detection limit is 0.045 μM. Brief Description of the Drawings

[0037] Figure 1 Schematic diagram of the construction process of the photoelectrochemical sensor in Example 1.

[0038] Figure 2 Scanning electron microscope image of the CdS / Ga2O3 composite material prepared in Example 1.

[0039] Figure 3 X-ray photoelectron spectroscopy image of the CdS / Ga2O3 composite material prepared in Example 1.

[0040] Figure 4 Comparison diagram of the photoelectric responses of the CdS / Ga2O3 / ITO electrode, pure CdS, and pure Ga2O3 / ITO electrode prepared in Example 1.

[0041] Figure 5 Response / recovery time diagram of the CdS / Ga2O3 / ITO electrode prepared in Example 1.

[0042] Figure 6 I-T diagram of the stability experiment of the photoelectrochemical sensing system prepared in Example 1 before and after adding tetracycline.

[0043] Figure 7 Variation diagram of the photocurrent response of the photoelectrochemical sensing system prepared in Example 1 at different tetracycline concentrations

[0044] Figure 8 Linear fitting curve diagram of the change of the photocurrent response of the photoelectrochemical sensing system prepared in Example 1 with the tetracycline concentration.

[0045] Figure 9 Analysis diagram of the performance differences among different products of the same batch of the photoelectrochemical sensing system prepared in Example 1.

[0046] Figure 10 Comparison diagram of the change of the photocurrent response of the photoelectrochemical sensing system prepared in Example 1 to 100 μM of different interfering substances and 10 μM of tetracycline. Detailed Description of the Invention

[0047] To better understand the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments are carried out on the premise of the technical solution of the present invention, and detailed implementation steps and specific operation processes are given. It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention, but does not limit the present invention.

[0048] If the specific experimental conditions are not specified in the embodiments, they are usually in accordance with conventional conditions or the conditions recommended by reagent companies; for the reagents, consumables, etc. used in the following embodiments, unless otherwise specified, they can be obtained through general commercial channels.

[0049] Example 1:

[0050] According to Figure 1 the preparation process described above, this embodiment provides a method for preparing a photoelectrochemical sensor, which specifically includes the following steps:

[0051] (1) Preparation of CdS / Ga2O3 heterojunction composite material:

[0052] First, 0.945 g of thiourea is dissolved in 35 mL of deionized water. Then, 1.2825 g of Cd(NO3)2·4H2O and 0.085 g of Ga2O3 are gradually added under magnetic stirring, and the mixture is stirred thoroughly for 2 h at room temperature.

[0053] Subsequently, the solution is transferred to a high-pressure reaction kettle with a polytetrafluoroethylene lining and reacted at 180 °C for 18 hours.

[0054] After the reaction is completed, after the high-temperature reaction kettle is cooled to room temperature, the solution in the polytetrafluoroethylene lining is taken out, centrifuged at a speed of 9000 rpm with a centrifuge, the supernatant is poured out to obtain a yellow precipitate, and the obtained product is washed alternately with deionized water and absolute ethanol at least three times, and then placed in a vacuum drying oven to dry for 12 h, and finally the CdS / Ga2O3 heterojunction composite material is prepared.

[0055] The morphology of the CdS / Ga2O3 composite material obtained in Example 1 was characterized by a scanning electron microscope, and the characterization results are as Figure 2 shown. Figure 2 The upper right corner is a partial enlarged view of the morphology of the CdS / Ga2O3 composite material. From Figure 2 it can be seen that the prepared CdS / Ga2O3 composite material presents a rod-like structure in the micron order, and particulate matter is attached to the surface. The long rod-like structure has a large specific surface area, which can significantly increase the contact area between the semiconductor and the electrolyte, thereby promoting the separation and transmission of photo-generated carriers and improving the photocurrent response. From Figure 2 the small figure in the upper right corner, it can be seen that the thickness of the particulate matter is less than 100 nm.

[0056] Figure 3 X-ray photoelectron spectroscopy diagram of the CdS / Ga2O3 composite material prepared in Example 1, where the spectrum shows that all expected elements are present in the composite material. Combining Figure 2 and Figure 3 measurement results, it is proved that the CdS / Ga2O3 composite material is successfully prepared.

[0057] (2) Pretreat the ITO electrode:

[0058] Uniformly cut the ITO conductive glass into a size of 20 * 10 * 1.1 mm, and in the order of acetone, absolute ethanol, and deionized water, ultrasonicate in an ultrasonic machine for 15 min each, and dry in an oven at 60 °C. After drying, fix a circular effective area of 0.2826 cm 2 in size on the conductive surface of the ITO through black insulating tape.

[0059] (3) Preparation of the CdS / Ga2O3 / ITO electrode:

[0060] Dissolve the CdS / Ga2O3 heterojunction prepared in step (1) in deionized water to prepare a mixed solution with a concentration of 2 mg / mL, and take 10 μL of the mixed solution and drop it within the circular effective area of the ITO electrode pretreated in step (2), and dry naturally to obtain a CdS / Ga2O3 / ITO photoelectrochemical sensor for detecting tetracycline.

[0061] Example 2:

[0062] Perform photoelectrochemical detection of tetracycline on the CdS / Ga2O3 / ITO photoelectrochemical sensor prepared in Example 1

[0063] Prepare a 50 ml Na2SO4 electrolyte with a concentration of 0.1 mol / L containing 0.1 mol / L ascorbic acid; take the CdS / Ga2O3 / ITO prepared in Example 1 as the working electrode, a platinum wire as the counter electrode, and silver / silver chloride as the reference electrode. Insert the ITO electrode into the electrolytic cell, apply a bias voltage of 0.1 V with an electrochemical workstation, use a 500 W xenon lamp as the light source, face the conductive surface towards the xenon lamp, and connect to a computer to record the photoelectric response changes of the working electrode under blank control and in the presence of different concentrations of the analyte under a xenon lamp "on-off" cycle with a period of 40 seconds.

[0064] From Figure 4It can be seen that the bare ITO and Ga2O3 / ITO electrodes hardly generate photocurrent, while the CdS / ITO electrode shows significant photoelectric response. Further, after the combination of Ga2O3 and CdS, the photocurrent response of its ITO electrode is significantly enhanced, reaching the maximum value in the figure, which is 6 times that of the CdS / ITO electrode and even 500 times that of the Ga2O3 / ITO electrode. This significant improvement is attributed to the heterojunction formed between CdS and Ga2O3.

[0065] From Figure 5 It can be seen that the response time of the CdS / Ga2O3 / ITO electrode is 0.14 s and the recovery time is 0.18 s, indicating that the prepared photoelectrochemical sensor has fast response / recovery time.

[0066] From Figure 6 It can be seen that after 1200 seconds of "on-off" cycling, the photoelectric response loss rates of the photoelectrochemical sensor before and after adding tetracycline are 3.12% and 1.67% respectively. This indicates that even under long-term rapid repeated light "on-off" operations, the photoelectrochemical sensor still exhibits excellent chemical and optical stability.

[0067] From Figure 7 It can be seen that in the concentration range of 0 pM to 50 μM of tetracycline, the photocurrent of the photoelectrochemical sensor is very sensitive to the change of tetracycline concentration, and the magnitude of its photocurrent decreases with the increase of tetracycline concentration.

[0068] From Figure 8 It can be seen that in the concentration range of 0 pM to 50 μM, the change of photocurrent and the concentration of tetracycline show a good linear relationship. The linear equation is y = 0.1778 + 0.04733LgC, and the correlation coefficient R 2 = 0.99785, and the calculated detection limit is 0.045 pM.

[0069] From Figure 9 It can be seen that by detecting the photocurrent responses of five independent CdS / Ga2O3 / ITO electrodes, the performance gap between different batches of individuals of the same sensor is shown. The photoelectric response test shows that the relative standard deviation (RSD) is 0.359%, indicating that the influence of different batches of individuals on the concentration detection results is small in the detection of tetracycline concentration by this sensor.

[0070] From Figure 10 It can be seen that various interfering substances with a concentration of 100 μM are added to the electrolyte solution, including oxytetracycline, chlortetracycline hydrochloride, doxycycline hydrochloride, Na + , K + , Fe 3+ and Zn 2+etc. have little effect on the photoelectric response of the photoelectrochemical sensor. Compared with tetracycline at a concentration of 10 μM alone, the change in the photocurrent response of the photoelectrochemical sensor to tetracycline is significantly higher than that of other interfering substances, indicating its excellent selectivity.

[0071] Note: The above preferred embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, modifications or reasonable substitutions can be made to the invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a photoelectrochemical sensor based on a cadmium sulfide-gallium oxide heterojunction, characterized in that, It includes the following steps: (1) Prepare the CdS / Ga2O3 heterojunction composite material; First, dissolve thiourea in deionized water and stir magnetically until it is completely dissolved. Then, while stirring magnetically, add cadmium nitrate tetrahydrate and gallium oxide respectively to obtain a white suspension. Subsequently, place the well-stirred solution in a high-pressure reactor, react at a certain temperature for a period of time, take it out from the polytetrafluoroethylene inner liner and collect the yellow precipitate. After washing repeatedly to remove impurities, put it into a vacuum oven for drying to finally obtain the CdS / Ga2O3 heterojunction composite material. (2) Pretreatment of the ITO electrode: Ultrasonically clean the ITO glass in an ultrasonic machine in the order of acetone, absolute ethanol, and deionized water, and dry it in an oven. (3) Preparation of the Ga2O3 / CdS heterojunction sensor: Take the Ga2O3 / CdS suspension and drop it onto the conductive surface of the ITO conductive glass, and let it dry naturally at room temperature; prepare an ITO electrode for detecting tetracycline, and finally obtain a photoelectrochemical sensor.

2. The preparation method according to claim 1, characterized in that, In step (1), the dosage ratio of thiourea, cadmium nitrate tetrahydrate, and gallium oxide is 0.945 g: 1.2825 g: 0.085 g. The reaction temperature of the mixed solution in the oven is 180 - 200 °C, and the time is 12 - 24 hours. The collected yellow precipitate should be washed three times with deionized water and absolute ethanol respectively. Finally, the drying temperature in the vacuum oven is 40 - 70 °C, and the time is 6 - 12 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the size of the ITO conductive glass is: 20 * 10 * × 1.1 mm, and the ultrasonic time each time is 15 min to fully remove the oxides on the surface of ITO.

4. The preparation method according to claim 1, wherein In step (3), half of the area of the conductive surface of the ITO glass should be covered with copper tape. Subsequently, dissolve the CdS / Ga2O3 composite material in deionized water and prepare a mixed solution with a concentration of 2 mg / mL by ultrasonic dispersion, and finally evenly drop it on the ITO conductive area.

5. The photoelectrochemical sensor based on the cadmium sulfide-gallium oxide heterojunction prepared by the preparation method according to claims 1-4 is used for detecting tetracycline, characterized in that, Its detection steps are as follows: (1) Use the CHI660E electrochemical workstation to perform the performance test of the photoelectrochemical sensor with a classic three-electrode system. Use the silver / silver chloride electrode as the reference electrode, the platinum wire electrode as the counter electrode, and the prepared CdS / Ga2O3 / ITO electrode as the working electrode. Unify the experimental environment, and select 50 ml of 0.1 M Na2SO4 containing 0.1 M ascorbic acid (AA) as the experimental electrolyte for the PEC sensor performance test. (2) Use chronoamperometry (I-T), and simulate full-band irradiation with a xenon lamp: 200 - 1100 nm. Set the light-on switch cycle to T = 40 seconds and apply a bias voltage of 0.1 v. (3) Place the ITO electrode in the electrolytic cell, then face the conductive surface towards the xenon lamp, and connect the computer to record the photoelectric response changes of the ITO working electrode in the electrolyte before and after adding tetracycline with a concentration of 10 μM for 1000 - 1500 s. (4) Record the photoelectric response changes of the ITO working electrode under the conditions of blank control and adding tetracycline analytes with a concentration range of 1 μM - 50 μM, and draw a fitting curve for analysis. (5) On the basis of the above experiments, select 5 different CdS / Ga2O3 / ITO electrodes of the same batch for photoelectric performance testing, and analyze the performance gap between different ITO electrodes. (6) Different interferents were added to the electrolyte, and the changes in the photoelectric response of the CdS / Ga2O3 / ITO electrode were recorded and compared with the changes in the photoelectric response when tetracycline was added in step (4).

6. The use according to claim 5, characterized in that, In step (6), to test the high selectivity of the photoelectrochemical sensor for the detection of tetracycline, the concentration of the added interferent was generally 10 times or more of the selected concentration of tetracycline.

Images