Preparation method and application of photoelectrochemical sensor for preparing titanium dioxide / copper oxide heterojunction based on laser induction

Abstract

The invention relates to a preparation method and application of a photoelectrochemical sensor for preparing a titanium dioxide / copper oxide heterojunction based on a laser induction technology. Titanium carbide / binuclear copper-beta-cyclodextrin is used as a precursor material to be coated on the surface of ITO (Indium Tin Oxide) conductive glass, and a precursor is converted into a titanium dioxide / copper oxide heterojunction by utilizing a laser induction technology, so that the photoelectrochemical sensor is constructed. Compared with a traditional preparation method, the laser induction technology not only realizes high-strength combination of the material and the substrate, but also has the advantages of simple and convenient process, environment friendliness, safety, controllability and the like. The obtained heterojunction remarkably improves the interface charge transfer efficiency, and the photoelectric response performance of the heterojunction is improved by about 2.3 times compared with that of commercial TiO2. A simple photoelectric detection system is constructed based on a common glass beaker and self-made LED light sources with different wavelengths, and miniaturization of a detection device and portability of a detection process are realized. The electrochemical sensor is low in cost and simple in process, and a novel heterostructure building strategy and a simple system for detecting ascorbic acid integration scheme are provided.

Description

Technical Field

[0001] The present invention relates to the fields of laser-induced technology and photoelectrochemical sensing technology, and particularly relates to the construction of a photoelectrochemical sensing electrode material by obtaining a titanium dioxide / cupric oxide heterojunction (TiO2@C / CuO@C) through laser induction of titanium carbide / dinuclear copper-β-cyclodextrin (MXene / Cu-β-CD), so as to realize the photoelectrochemical sensing detection of ascorbic acid.

Background Art

[0002] Ascorbic acid (AA) is an important vitamin and antioxidant in the human body. It has functions such as antioxidant damage, delaying cell aging, promoting wound healing, and anti-tumor. The human body cannot synthesize AA independently and can only obtain it from the outside. As an antioxidant, AA can be added to foods rich in polysaccharides, such as fruit juices, beverages, and pasta. Quantitative analysis of the content of AA in items such as foods, cosmetics, health products, and drugs is an important indicator to ensure the quality and safety of foods and supplies. Therefore, it is of great significance to construct a sensing system with portability, low cost, simplicity, and high efficiency.

[0003] Photoelectrochemistry (PEC) is an interdisciplinary field that studies the interaction between light and electrochemical processes, combining photophysics, photochemistry, and electrochemistry. Based on semiconductor materials absorbing photons to generate electron-hole pairs, and separating and transporting these carriers through an external circuit. PEC sensors utilize the response characteristics of photoanode materials to specific analytes for highly sensitive detection, with advantages such as low background noise and fast response speed. However, most photoelectric materials are mainly excited by ultraviolet light, limiting their application scope. Developing photoelectric materials that can be excited by visible light and near-infrared light is of great significance for expanding the applications in this field. Common materials applied to PEC sensors include quantum dots (QDs), metal oxide semiconductors, perovskite materials, and porphyrin derivatives, etc. By constructing heterostructures to form Schottky junctions, it can effectively promote the generation and transport of electron carriers. Titanium dioxide (TiO2) is widely used due to its chemical stability, low cost, and excellent optical properties. However, its wide bandgap (about 3.2 eV) limits its absorption to only ultraviolet light, and ultraviolet light only accounts for 5% of the solar spectrum. Moreover, the low charge separation efficiency is one of the main bottlenecks restricting its performance. Therefore, researchers have turned to two-dimensional titanium carbide (MXene) with a graphene-like structure, in-situ growing TiO2 crystals on its surface and forming a heterojunction with MXene, thus providing new potential for photocatalytic applications due to its high conductivity and high specific surface area. Copper oxide nanoparticles (CuO) have a narrower bandgap (1.2 - 2.0 eV), are more sensitive to visible light, and have advantages such as safety, non-toxicity, and low cost. Utilizing the formation of a heterojunction between CuO and TiO2 can not only broaden the light absorption range but also further improve the charge separation efficiency, overcome the problem of the too-wide bandgap of TiO2, and thus significantly improve the overall performance of PEC sensors.

[0004] The application of laser-induced technology in the field of materials science has developed rapidly, including reaction catalysis, microelectronic component preparation, laser cladding, laser induction, etc. The traditional high-temperature calcination oxidation method for preparing TiO2 and CuO heterojunctions requires cumbersome steps such as inert gas protection and programmed heating. Laser-induced technology has the advantages of high energy density, high precision, fast processing speed, specific area processing, and short processing time. It can achieve the preparation of TiO2 and CuO heterojunctions by instant high-temperature oxidation, and can make the material tightly adhere to the surface of indium tin oxide glass electrode (ITO). Especially, the preparation process is simple, safe, and non-toxic. In the prior (CN117169309A), a spinning solution containing tetrabutyl titanate and copper acetate was prepared, and a precursor nanofiber membrane was obtained through an electrospinning machine. The precursor nanofiber membrane was calcined in a muffle furnace to obtain CuO / TiO2 nanoparticles, and it was modified on ITO conductive glass to prepare a CuO / TiO2 / ITO modified electrode, realizing the effective detection of glucose. In (CN118422242A), ultrathin titanium carbide (Ti3C2 MXene) was spin-coated on a conductive glass substrate by the spin-coating method, iron oxide hydroxide was prepared on the substrate by the hydrothermal method and doped with tin, and titanium dioxide / tin-iron oxide heterojunction rich in Fe 2+ was obtained by high-temperature calcination, that is, TiO2 / Sn-Fe2O 3-x , and a part of the iron oxide was reduced to Fe 2+ , titanium carbide was oxidized to TiO2, which can be applied to fields such as photoelectrocatalytic water splitting, pollutant degradation, and construction of PEC sensors.

[0005] Therefore, the present invention proposes a method for preparing TiO2@C / CuO@C heterojunction by laser induction using MXene / Cu-β-CD as a precursor material, and by building a simple detection device, using an ordinary glass beaker as a photoelectric detection cell and a self-made light-emitting diode (LED) with different wavelengths as a light source to effectively detect AA, providing a new heterostructure construction strategy and a simple system detection AA integration scheme.

Summary of the Invention

[0006] Aiming at the above analysis, the object of the present invention is to solve the problems that most existing optoelectronic materials are limited in their application scope by ultraviolet light excitation and the effective charge separation efficiency of TiO2 is relatively low. It provides a PEC sensor based on laser-induced preparation of TiO2@C / CuO@C heterostructure for detecting AA. In terms of the preparation process flow, it has the advantages of simple preparation process and low cost compared with other commercial products. The constructed PEC sensor shows good stability and reproducibility, and can effectively detect AA. And through a self-made detection device, using an ordinary glass cup as a photoelectric detection cell and a self-made LED detection light source with different wavelength ranges, it can also effectively detect AA compared with other commercial products. At the same time, this preparation method has the advantages of high efficiency, convenience, and low cost.

[0007] Technical solution of the present invention

[0008] The purpose of the first aspect of the present invention is to construct a photoelectrochemical (PEC) sensor. MXene / Cu-β-CD is selected as the precursor material, and TiO2@C / CuO@C heterojunction is prepared by laser induction, and TiO2@C / CuO@C / ITO photoelectrode is constructed as the working electrode using it as the modification material, Ag / AgCl electrode as the reference electrode, and platinum wire electrode as the counter electrode. A PEC sensor for detecting AA is constructed. By building a simple detection device, using a common glass beaker as the photoelectric detection cell and a self-made LED with different wavelengths as the light source, and applying it to the photoelectrochemical detection of AA.

[0009] The purpose of the second aspect of the present invention is to provide a preparation method of the PEC sensor, including the following steps:

[0010] Step 1: Preparation of MXene

[0011] The synthesis of MXene is based on the minimum-intensity delamination method and is placed in a low-temperature environment for protection;

[0012] Using a mixed etching agent of 12M lithium fluoride (LiF) and 9M hydrochloric acid (HCl) solution, hydrogen fluoride (HF) is in-situ generated to selectively etch aluminum titanium carbide to prepare MXene. The reaction is carried out at 55 °C for 24 h. Through centrifugation, the acidic mixture is washed with deionized water for multiple cycles. After each cycle, the acidic supernatant is poured out as waste, and then fresh deionized water is added before another centrifugation cycle. Repeat these washing cycles until the pH value reaches 4 - 5. When pH≥5, a dark green supernatant can be observed, which is stable even when the centrifugation time is increased from 5 min to 60 min. Take out the lower layer precipitate, dissolve it in water, and ultrasonically wash it under nitrogen protection, while keeping the water temperature controlled at low temperature. Then the mixed solution is centrifuged again. At this time, the upper layer solution after centrifugation is an opaque black solution, which is freeze-dried. After grinding and sieving, it is stored at low temperature in a glove box.

[0013] Step 2: Preparation of Cu-β-CD

[0014] To prepare Cu-β-CD, first dissolve 227 mg of β-cyclodextrin (β-CD), 150 mg of copper sulfate pentahydrate (CuSO4·5H2O) and 200 mg of sodium hydroxide (NaOH) in 25 mL of deionized water, and stir and mix for 12 h. Subsequently, sufficient ethanol is added to the solution, and the product is allowed to precipitate by standing. Then, the mixed solution is filtered through a 0.25 μm filter membrane, and the solid precipitate is collected and dried, ground and sieved to finally obtain Cu-β-CD powder.

[0015] Step 3: Preparation of TiO2@C / CuO@C heterojunction PEC sensor

[0016] Step 3-1: Preparation of an electrode suspension containing MXene and Cu-β-CD. Disperse MXene and Cu-β-CD in deionized water to form an MXene / Cu-β-CD suspension, and place it in an ultrasonic bath for ultrasonic treatment for 2 h to ensure sufficient dispersion.

[0017] Step 3-2: Take an ITO electrode, ultrasonically clean it in acetone, absolute ethanol, and ultrapure water for 10 min each in turn, and then dry it in a blast drying oven.

[0018] Step 3-3: Uniformly drop the MXene / Cu-β-CD suspension prepared in Step 3-1 onto the cleaned and dried ITO electrode, and dry it in a blast drying oven at 60 °C to obtain an MXene / Cu-β-CD / ITO electrode.

[0019] Step 3-4: Laser-induced treatment of the MXene / Cu-β-CD / ITO electrode prepared in Step 3-3 by a CO2 laser marking machine to obtain a TiO2@C / CuO@C / ITO photoanode. This process ensures good dispersion and adhesion of the electrode material, providing a high-quality electrode substrate for subsequent photoelectrochemical detection.

[0020] The mass-volume ratio of MXene, Cu-β-CD, and deionized water in Step 3-1 is 2-10 mg: 10 mg: 1 mL; the dropping amount of the MXene / Cu-β-CD suspension on the surface of the ITO electrode: 80-120 μL; the laser-induced power is 1.5-6 W.

[0021] The purpose of the third aspect of the present invention is to build a simple detection device, use a common glass beaker as a photoelectric detection cell and a self-made LED with different wavelengths as a light source, and provide the application of the PEC sensor in detecting AA.

[0022] By preparing a TiO2@C / CuO@C / ITO photoanode, a simple self-made PEC sensor is constructed for detecting AA. The specific electrochemical detection method is as follows:

[0023] Step 1: Plot the standard curve of AA sample concentration and photocurrent.

[0024] Step 1.1: Use AA samples to prepare standard solutions with different concentrations respectively; take the TiO2@C / CuO@C / ITO photo - electrode prepared by the above - mentioned method as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the counter electrode to build a simple detection device. Use a common glass beaker as the photoelectric detection cell and a self - made LED with different wavelengths as the light source, and conduct time - current curve tests in the prepared standard sample solution to obtain the photocurrent magnitude of the sample signal.

[0025] Step 1.2: Draw a standard curve of concentration and photocurrent based on the concentration of the standard sample and the detected photocurrent magnitude.

[0026] Step 2: Use the method in Step 1.1 to detect the sample to be measured, obtain the photocurrent magnitude of the sample to be measured, and calculate the concentration content of AA in the solution to be measured through the standard curve of concentration and photocurrent drawn in Step 1.2 above.

[0027] The concentration range of the standard sample AA is 0.01 - 500 mmol / L; the test time of the time - current curve is 200 s; the test sensitivity of the time - current curve is 10 -6 A; the wavelength range of the self - made LED light source is 420 - 655 nm; the power of the LED light source is 15 W.

[0028] The advantages and beneficial effects of the present invention are as follows: Based on the high - efficiency photocatalytic activity of TiO2 and the narrower bandgap of CuO, the TiO2@C / CuO@C heterojunction is prepared, which can significantly improve the transfer efficiency of photo - generated carriers, the charge separation efficiency, and the photoelectric detection effect. At the same time, it has the advantages of safety, non - toxicity, high efficiency, and low cost. And compared with other methods, the laser - induced technology makes the material adhere tightly to the surface of the ITO electrode. Based on a common glass beaker and a self - made LED light source system with different wavelengths, a simple photoelectrochemical detection system is constructed to realize the miniaturization of the detection device and the portability of the detection process. This PEC sensor has low cost and simple process, providing a new strategy for constructing heterostructures and an integrated scheme for detecting AA with a simple system.

Description of the Drawings

[0029] Figure 1 It is the scanning electron microscope image of TiO2@C / CuO@C, where a is the scanning electron microscope image of TiO2@C / CuO@C, b is the transmission electron microscope image, and c is the energy spectrum image.

[0030] Figure 2 It is the X - ray diffraction pattern of MXene, TiO2@C, Cu - β - CD, CuO@C, and TiO2@C / CuO@C.

[0031] Figure 3Infrared spectrum data of TiO2@C, Cu-β-CD, CuO@C, and TiO2@C / CuO@C.

[0032] Figure 4 Time-current curves for the detection of AA by four photoanodes: MXene / ITO (a), TiO2@C / ITO (b), CuO@C / ITO (c), and TiO2@C / CuO@C / ITO (d).

[0033] Figure 5 Time-current curve for the detection of AA by the TiO2@C / CuO@C / ITO photoanode as the working electrode to construct a PEC sensor.

[0034] Figure 6 Standard curve of concentration and photocurrent plotted for the TiO2@C / CuO@C / ITO photoanode as the working electrode to construct a PEC sensor for different standard sample concentrations of AA and the corresponding detected photocurrent magnitudes.

Detailed implementation manners

[0035] The present invention will be further described below with reference to the accompanying drawings through examples.

[0036] In the present invention, TiO2 is in-situ formed on the surface of MXene. The layered structure of MXene can efficiently transport photo-generated electrons by virtue of its excellent conductivity, thereby greatly improving the separation efficiency of photo-generated carriers, enhancing the overall efficiency of the photocatalytic reaction, and effectively solving the common charge recombination problem in TiO2 materials. Compared with TiO2, CuO has a narrower bandgap (1.2 - 2.0 eV), is more sensitive to visible light, and has the advantages of safety, non-toxicity, and low cost. By combining CuO with TiO2, not only can the light absorption range be broadened, but also the charge separation efficiency can be further improved, overcoming the problem of the too-wide bandgap of TiO2, thereby significantly improving the overall performance of the PEC sensor.

[0037] In addition, the TiO2@C / CuO@C heterojunction was prepared by a laser-induced method using MXene / Cu-β-CD as the precursor and used to construct a novel PEC sensor. Compared with other methods, laser induction can make the material tightly adhere to the surface of the ITO electrode. The preparation process is simple, safe, and non-toxic, ensuring the successful preparation of the TiO2@C / CuO@C heterojunction. This heterojunction significantly improves the transfer efficiency of photo-generated carriers and the photoelectric detection effect, enhancing the performance of the PEC sensor. In addition, the PEC sensor exhibits good stability and reproducibility. This method provides new ideas and technical approaches for the development of high-performance PEC sensors.

[0038] Example 1:

[0039] I. Composition of the PEC sensor for detecting AA.

[0040] The PEC sensor is constructed by using a TiO2@C / CuO@C / ITO optoelectrode prepared by laser-induced method with MXen / Cu-β-CD as the precursor material as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, a common beaker as the photoelectrochemical electrolytic cell, preparing a standard AA solution and placing it in the photoelectrochemical electrolytic cell, and performing tests using a time-current curve.

[0041] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0042] Step (1) Preparation of MXene

[0043] MXene is prepared by selectively etching aluminum titanium carbide in situ with HF generated by mixing 12 mol / L LiF and 9 mol / L HCl etching agents, reacting at 55 °C for 24 h, centrifuging, washing the acidic mixture with deionized water, and performing multiple cycles. After each cycle, the acidic supernatant is poured out as waste, and then fresh deionized water is added before another centrifugation cycle. Repeat these washing cycles until the pH value reaches 4–5. When pH ≥ 5, a dark green supernatant can be observed, which is stable even when the centrifugation time is increased from 5 min to 60 min. Take out the lower layer precipitate, dissolve it in water, protect it with nitrogen and ultrasonicate, while keeping the water temperature controlled at a low temperature. Then, centrifuge the mixed solution again. At this time, the upper layer solution after centrifugation is an opaque black solution, which is freeze-dried. After grinding and sieving, it is stored at low temperature in a glove box.

[0044] Step (2) Preparation of Cu-β-CD

[0045] To prepare Cu-β-CD, first dissolve 227 mg of β-CD, 150 mg of CuSO4·5H2O, and 200 mg of NaOH in 25 mL of deionized water, and stir and mix for 12 h. Subsequently, add sufficient ethanol to the solution and let it stand to precipitate the product. Then, filter it through a 0.25 μm filter membrane, collect the solid precipitate, and perform drying, grinding, and sieving to finally obtain Cu-β-CD powder.

[0046] Step (3) Preparation of the TiO2@C / CuO@C heterojunction PEC sensor

[0047] 1) Prepare a material suspension containing MXene and Cu-β-CD. Disperse 6 mg of MXene and 10 mg of Cu-β-CD in 1 mL of deionized water to form an MXene / Cu-β-CD suspension, and place it in an ultrasonic bath for ultrasonic treatment for 2 h to ensure thorough mixing.

[0048] 2) Take the ITO electrode and ultrasonically clean it in acetone, absolute ethanol, and ultrapure water for 10 min each in turn, and then place it in a forced-air drying oven to dry.

[0049] 3) Uniformly drop 100 μL of the MXene / Cu-β-CD suspension prepared in step 1) onto the cleaned and dried ITO conductive glass, and place it in a forced-air drying oven at 60 °C to dry, obtaining an MXene / Cu-β-CD / ITO electrode.

[0050] 4) Subject the MXene / Cu-β-CD / ITO electrode prepared in step 3) to laser-induced treatment using a CO2 laser marking machine under the condition of a power of 3 W to obtain a TiO2@C / CuO@C / ITO optoelectrode. This process ensures good dispersion and adhesion of the electrode material, providing a high-quality electrode substrate for subsequent photoelectrochemical detection.

[0051] 5) Use a 440-nm LED light source as the light source, and perform photoelectrochemical testing using a three-electrode system. Use the prepared TiO2@C / CuO@C / ITO optoelectrode as the working electrode, a platinum wire electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Perform a sensitive test on AA through a time-current curve test, and finally construct a PEC sensor for detecting AA.

[0052] Figure 1 Scanning electron microscope images of TiO2@C / CuO@C, where a is the scanning electron microscope image of TiO2@C / CuO@C, b is the transmission electron microscope, and c is the energy spectrum image.

[0053] Figure 2 X-ray diffraction patterns of MXene, TiO2@C, Cu-β-CD, CuO@C, and TiO2@C / CuO@C.

[0054] Figure 3 Infrared spectrum data of TiO2@C, Cu-β-CD, CuO@C, and TiO2@C / CuO@C.

[0055] Figure 4 Time-current curves of four optoelectrodes, MXene / ITO (a), TiO2@C / ITO (b), CuO@C / ITO (c), and TiO2@C / CuO@C / ITO (d), for detecting AA.

[0056] The TiO2@C / CuO@C heterojunction was observed to be uniformly composite by scanning electron microscopy and transmission electron microscopy, and the uniform distribution of different elements could be observed in energy spectrum analysis; the functional groups of TiO2 and CuO could be clearly observed in the infrared spectrum, as well as the crystal structures of TiO2 and CuO in the X-ray diffraction pattern.

[0057] Detection showed that the prepared TiO2@C / CuO@C / ITO optoelectrode had a significantly better photoelectrochemical response signal to AA than the other three modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0058] III. The PEC sensor prepared by the present invention is applied to the detection of AA, and the specific sensing detection method is as follows:

[0059] Standard solutions with different concentrations were prepared using AA samples, where the concentrations of the AA samples were 0.01, 0.05, 0.1, 0.5, 1, 10, 20, 50, 100, 200, and 500 mmol / L.

[0060] The prepared TiO2@C / CuO@C / ITO optoelectrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, a self-made LED light source was used as the light source, and a common beaker was used as the photoelectrochemical electrolytic cell. The time-current curve test was carried out in the above-prepared standard sample solution to obtain the photocurrent magnitude of the sample;

[0061] Figure 5 The time-current curve graph of the PEC sensor constructed with the TiO2@C / CuO@C / ITO optoelectrode as the working electrode for AA.

[0062] A standard curve was plotted according to the standard sample concentration and the detected photocurrent magnitude, as Figure 6 shown.

[0063] The sample to be tested was detected, and the concentration of the sample was calculated through the standard curve. The detection range of the PEC sensor constructed with the TiO2@C / CuO@C / ITO optoelectrode as the working electrode provided in this example for AA was 0.01 - 500 mmol / L, and the detection limit was 1.83 μM. By comparison, the PEC sensor provided in this example had higher sensitivity and lower detection limit.

[0064] Example 2:

[0065] I. The composition of the PEC sensor for detecting AA was the same as the method in Example 1.

[0066] II. The preparation method of the PEC sensor for detecting AA included the following steps:

[0067] Step (1) Preparation of MXene, with the specific method the same as that in Example 1.

[0068] Step (2) Preparation of Cu-β-CD, with the specific method the same as that in Example 1.

[0069] Step (3) Preparation of TiO2@C / CuO@C heterojunction PEC sensor.

[0070] Disperse 10 mg of MXene and 10 mg of Cu-β-CD in 1 mL of deionized water, and the other steps are the same as those in Example 1.

[0071] Detection shows that the prepared TiO2@C / CuO@C / ITO photoanode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0072] III. Application of the PEC sensor prepared by the present invention in detecting AA. Take the above-prepared TiO2@C / CuO@C / ITO photoanode as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, and a common beaker as the photoelectrochemical electrolytic cell. Place it in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample; detect the sample to be tested, and calculate the concentration content of the sample through the standard curve. The detection range of AA by the TiO2@C / CuO@C / ITO photoanode as the working electrode to construct the PEC sensor provided in this example is 0.01 - 400 mmol / L, and the detection limit is 2.56 μM.

[0073] Example 3:

[0074] I. Composition of the PEC sensor for detecting AA, with the specific method the same as that in Example 1.

[0075] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0076] Step (1) Preparation of MXene, with the specific method the same as that in Example 1.

[0077] Step (2) Preparation of Cu-β-CD, with the specific method the same as that in Example 1.

[0078] Step (3) Preparation of TiO2@C / CuO@C heterojunction PEC sensor.

[0079] Disperse 2 mg of MXene and 10 mg of Cu-β-CD in 1 mL of deionized water, and the other steps are the same as those in Example 1.

[0080] The detection shows that the prepared TiO2@C / CuO@C / ITO optoelectrode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0081] III. Application of the PEC sensor prepared by the present invention in detecting AA. Take the above-prepared TiO2@C / CuO@C / ITO optoelectrode as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, and a common beaker as the photoelectrochemical electrolytic cell. Place it in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. Detect the sample to be tested, and calculate the concentration content of the sample through the standard curve. The detection range of AA by using the TiO2@C / CuO@C / ITO optoelectrode prepared in this example as the working electrode to construct a PEC sensor is 0.01 - 300 mmol / L, and the detection limit is 3.45 μM.

[0082] Example 4:

[0083] I. Composition of the PEC sensor for detecting AA, and the specific method is the same as that in Example 1.

[0084] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0085] Step (1) Preparation of MXene, and the specific method is the same as that in Example 1.

[0086] Step (2) Preparation of Cu-β-CD, and the specific method is the same as that in Example 1.

[0087] Step (3) Preparation of the TiO2@C / CuO@C heterojunction PEC sensor.

[0088] Change the laser-induced power to 6 W, and the other steps are the same as those in Example 1.

[0089] The detection shows that the prepared TiO2@C / CuO@C / ITO optoelectrode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0090] III. Application of the PEC sensor prepared by the present invention in detecting AA. Take the above-prepared TiO2@C / CuO@C / ITO photoanode as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, and a common beaker as the photoelectrochemical electrolytic cell. Place it in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. Detect the sample to be tested. The photocurrent signal of the TiO2@C / CuO@C / ITO photoanode provided in this example as the working electrode to construct the PEC sensor for AA is the highest compared with other photoanodes. It can be seen by comparison that the PEC sensor provided in this example has higher sensitivity. Detect the sample to be tested, and calculate the concentration content of the sample through the standard curve. The detection range of the TiO2@C / CuO@C / ITO photoanode provided in this example as the working electrode to construct the PEC sensor for AA is 0.01 - 300 mmol / L, and the detection limit is 4.47 μM.

[0091] Example 5:

[0092] I. Composition of the PEC sensor for detecting AA, and the specific method is the same as that in Example 1.

[0093] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0094] Step (1) Preparation of MXene, and the specific method is the same as that in Example 1.

[0095] Step (2) Preparation of Cu-β-CD, and the specific method is the same as that in Example 1.

[0096] Step (3) Preparation of the TiO2@C / CuO@C heterojunction PEC sensor.

[0097] Change the laser-induced power to 1.5 W, and other steps are the same as those in Example 1.

[0098] Detection shows that the prepared TiO2@C / CuO@C / ITO photoanode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0099] III. Application of the PEC sensor prepared by the present invention in detecting AA. Take the above-prepared TiO2@C / CuO@C / ITO optoelectrode as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, and an ordinary beaker as the photoelectrochemical electrolytic cell. Place it in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. Detect the sample to be tested. The photocurrent signal of the TiO2@C / CuO@C / ITO optoelectrode provided in this example as the working electrode for constructing the PEC sensor for AA is the highest compared with other optoelectrodes. It can be seen by comparison that the PEC sensor provided in this example has higher sensitivity. Detect the sample to be tested, and calculate the concentration content of the sample through the standard curve. The detection range of the TiO2@C / CuO@C / ITO optoelectrode provided in this example as the working electrode for constructing the PEC sensor for AA is 0.01 - 400 mmol / L, and the detection limit is 3.23 μM.

[0100] Example 6:

[0101] I. Composition of the PEC sensor for detecting AA, and the specific method is the same as that in Example 1.

[0102] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0103] Step (1) Preparation of MXene, and the specific method is the same as that in Example 1.

[0104] Step (2) Preparation of Cu-β-CD, and the specific method is the same as that in Example 1.

[0105] Step (3) Preparation of the TiO2@C / CuO@C heterojunction PEC sensor.

[0106] Uniformly drop 80 μL of the MXene / Cu-β-CD suspension, select an LED with a wavelength of 420 nm as the light source, and the other steps are the same as those in Example 1.

[0107] Detection shows that the prepared TiO2@C / CuO@C / ITO optoelectrode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0108] III. Application of the PEC sensor prepared by the present invention in detecting AA. Take the above-prepared TiO2@C / CuO@C / ITO photoanode as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, a self-made LED light source as the light source, and an ordinary beaker as the photoelectrochemical electrolytic cell. Place it in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. Detect the sample to be tested. The TiO2@C / CuO@C / ITO photoanode provided in this example has the highest photocurrent signal for AA when used as the working electrode to construct a PEC sensor. By comparison, it can be seen that the PEC sensor provided in this example has higher sensitivity. Detect the sample to be tested, and calculate the concentration of the sample through the standard curve. The detection range of the TiO2@C / CuO@C / ITO photoanode provided in this example for AA when used as the working electrode to construct a PEC sensor is 0.01 - 400 mmol / L, and the detection limit is 3.75 μM

[0109] Example 7:

[0110] I. Composition of the PEC sensor for detecting AA. The specific method is the same as that in Example 1.

[0111] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0112] Step (1) Preparation of MXene. The specific method is the same as that in Example 1.

[0113] Step (2) Preparation of Cu-β-CD. The specific method is the same as that in Example 1.

[0114] Step (3) Preparation of the TiO2@C / CuO@C heterojunction PEC sensor.

[0115] Uniformly drop 120 μL of the MXene / Cu-β-CD suspension, select an LED with a wavelength of 655 nm as the light source, and the other steps are the same as those in Example 1.

[0116] Detection shows that the prepared TiO2@C / CuO@C / ITO photoanode can have a significantly better photoelectrochemical response signal to AA than the other four modified electrodes, significantly enhancing the sensitivity of the PEC sensor.

[0117] III. Application of the PEC sensor prepared by the present invention in detecting AA. The prepared TiO2@C / CuO@C / ITO optoelectrode is used as the working electrode, the Ag / AgCl electrode is used as the reference electrode, the platinum wire electrode is used as the counter electrode, the self-made LED light source is used as the light source, and the ordinary beaker is used as the photoelectrochemical electrolytic cell. It is placed in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. For the detection of the sample to be tested, the TiO2@C / CuO@C / ITO optoelectrode provided in this example has the highest photocurrent signal for AA when used as the working electrode to construct the PEC sensor. By comparison, it can be seen that the PEC sensor provided in this example has higher sensitivity. For the detection of the sample to be tested, the concentration of the sample is calculated through the standard curve. The TiO2@C / CuO@C / ITO optoelectrode provided in this example has a detection range of 0.01 - 300 mmol / L for AA when used as the working electrode to construct the PEC sensor, and the detection limit is 5.65 μM.

[0118] Comparative Example 1:

[0119] I. Composition of the PEC sensor for detecting AA.

[0120] The PEC sensor is formed by using the TiO2@C / ITO electrode prepared by laser-induced using MXene as the precursor material as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire electrode as the counter electrode. It is placed in the prepared AA solution for time-current curve testing to form a PEC sensor.

[0121] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0122] Step (1) Preparation of MXene, the specific method is the same as that in Example 1.

[0123] Step (2) Preparation of the TiO2@C heterojunction PEC sensor.

[0124] 1) Preparation of the MXene material suspension. 6 mg of MXene is dispersed in 1 mL of deionized water to form the MXene / suspension, and it is placed in an ultrasonic bath for ultrasonic treatment for 2 h to ensure sufficient dispersion.

[0125] 2) The ITO electrode is ultrasonically cleaned in acetone, absolute ethanol, and ultrapure water for 10 min each in turn, and then placed in a blast drying oven for drying.

[0126] 3) The MXene suspension prepared in step 1) is evenly drop-coated on the cleaned and dried ITO conductive glass, and then placed in a blast drying oven at 60 °C for drying to obtain the MXene / ITO electrode.

[0127] 4) The MXene / ITO electrode prepared in step 3) was subjected to laser induction by a CO2 laser marking machine under the condition of a power of 3 W to obtain a TiO2@C / ITO photoanode. This process ensured the good dispersion and adhesion of the electrode material, providing a high-quality electrode substrate for subsequent photoelectrochemical detection.

[0128] III. Application of the PEC sensor prepared in this comparative example in the detection of AA. The prepared TiO2@C / ITO photoanode was used as the working electrode, an Ag / AgCl electrode was used as the reference electrode, a platinum wire electrode was used as the counter electrode, a self-made LED light source was used as the light source, and a common beaker was used as the photoelectrochemical electrolytic cell. It was placed in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. The sample to be tested was detected, and the concentration content of the sample was calculated through the standard curve. The detection range of AA by the TiO2@C / ITO electrode provided in this comparative example as the working electrode to construct a PEC sensor was 0.1 - 200 mmol / L, and the detection limit was 11.53 μM. Compared with Example 1, the detection limit and detection range of Comparative Example 1 were significantly lower, and Example 1 had higher sensitivity.

[0129] Comparative Example 2:

[0130] I. Composition of the PEC sensor for detecting AA.

[0131] The PEC sensor commercially purchased TiO2 to prepare a TiO2 / ITO electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the counter electrode. It was placed in the prepared AA solution for time-current curve testing to form a PEC sensor.

[0132] II. Preparation method of the PEC sensor for detecting AA, including the following steps:

[0133] 1) Prepare a suspension containing commercially available TiO2 material. 1 mg of TiO2 was dispersed in 1 mL of deionized water to form a TiO2 suspension, and it was placed in an ultrasonic bath and ultrasonically treated for 2 h to ensure sufficient dispersion.

[0134] 2) The ITO electrode was ultrasonically cleaned in acetone, absolute ethanol, and ultrapure water for 10 min each in turn, and then placed in a blast drying oven to dry.

[0135] 3) The TiO2 suspension prepared in step 1) was evenly drop-coated on the cleaned and dried ITO conductive glass, and then placed in a blast drying oven at 60 °C to dry to obtain a TiO2 / ITO electrode.

[0136] 4) Using an LED light source as the light source, a three-electrode system was employed for photoelectrochemical testing. The prepared TiO2 / ITO photoanode was used as the working electrode, a platinum wire electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. AA was sensitively tested through time-current curve testing, and finally a PEC sensor for detecting AA was constructed.

[0137] The detection showed that the prepared TiO2 / ITO electrode had an obvious photoelectrochemical response signal for the detection of AA, significantly enhancing the sensitivity of the PEC sensor.

[0138] III. The PEC sensor prepared in this comparative example was applied to the detection of AA. The above-prepared TiO2 / ITO electrode was used as the working electrode, an Ag / AgCl electrode as the reference electrode, a platinum wire electrode as the counter electrode, and a self-made LED light source as the light source. A common beaker was used as the photoelectrochemical electrolytic cell, which was placed in the above-prepared standard sample solution for time-current curve testing to obtain the photocurrent magnitude of the sample. The sample to be tested was detected, and the concentration of the sample was calculated through the standard curve. The detection range of the PEC sensor constructed with the TiO2 / ITO electrode provided in this comparative example for AA was 0.2 - 300 mmol / L, and the detection limit was 7.89 μM. Compared with Example 1, the detection limit and detection range of Comparative Example 2 were significantly lower, and Example 1 had higher sensitivity.

[0139] The TiO2@C / CuO@C heterojunction was prepared by a laser-induced carbonization method using MXene / Cu-β-CD as the carbon precursor material and was used to construct a novel PEC sensor. Compared with other methods, laser-induced carbonization can make the material tightly adhere to the surface of ITO conductive glass. The preparation process is simple, safe, and non-toxic, ensuring the successful preparation of the TiO2@C / CuO@C heterojunction. This heterojunction significantly improves the transfer efficiency of photogenerated carriers and the photoelectric detection effect, enhancing the performance of the PEC sensor. In addition, this PEC sensor exhibits good stability, reproducibility, and a low detection limit. This method provides new ideas and technical approaches for the development of high-performance PEC sensors.

Claims

1. A photoelectrochemical (PEC) sensor based on laser-induced titanium dioxide / copper oxide (TiO2@C / CuO@C) heterojunction is constructed. The TiO2@C / CuO@C heterojunction obtained by laser induction of titanium carbide / binuclear copper-β-cyclodextrin (MXene / Cu-β-CD) as a carbon precursor is used as a modification material to prepare a TiO2@C / CuO@C heterojunction photoelectrode. Ag / AgCl electrode is used as a reference electrode and a platinum wire electrode is used as a counter electrode to construct a PEC sensor for detecting ascorbic acid (AA). MXene / Cu-β-CD effectively forms a TiO2@C / CuO@C heterojunction through a laser-induced preparation method. By building a simple detection device, using an ordinary glass beaker as a photoelectric detection cell and homemade light-emitting diodes (LEDs) of different wavelengths as light sources, ascorbic acid (AA) can be effectively detected.

2. The method for preparing the photoelectrochemical sensor according to claim 1, characterized in that: The following steps are involved: Step 1: Preparation of MXene The synthesis of MXene is based on the minimum strength layered separation method and is placed in a low temperature environment for protection; Step 2: Preparation of Cu-β-CD β-cyclodextrin and copper sulfate pentahydrate sodium hydroxide were dissolved in deionized water and stirred, and ethanol was added to the solution to stand for precipitation of Cu-β-CD crystals; Step 3: Preparation of TiO2@C / CuO@C heterojunction PEC sensor Step 3-1, preparing an electrode suspension containing MXene and Cu-β-CD, dispersing MXene and Cu-β-CD in deionized water to form a MXene / Cu-β-CD suspension, and ultrasonically treating the suspension; Step 3-2, taking an indium tin oxide (ITO) photoelectrode, ultrasonically cleaning it in acetone, anhydrous ethanol and ultrapure water in sequence, and then drying it in a blast oven; Step 3-3, evenly drop the MXene / Cu-β-CD suspension prepared in step 3-1 on the cleaned and dried ITO electrode, and dry it in a forced air drying oven to obtain MXene / Cu-β-CD / ITO; Step 3-4, the MXene / Cu-β-CD / ITO prepared in step 3-3 is subjected to laser induction by a CO2 laser marking machine to prepare a TiO2@C / CuO@C / ITO photoelectrode; Step 3-5, using a homemade LED light source with different wavelengths as the light source, an ordinary glass beaker as the photoelectric detection cell, and a three-electrode system for photoelectrochemical testing. The TiO2@C / CuO@C / ITO photoelectrode prepared in step 3-4 is used as the working electrode, the platinum wire electrode is used as the counter electrode, and the Ag / AgCl electrode is used as the reference electrode. The AA is sensitively tested by the time-current curve test method, and finally a PEC sensor for detecting AA is constructed.

3. The method for preparing the photoelectrochemical sensor according to claim 2, characterized in that: The mass volume ratio of MXene, Cu-β-CD and deionized water in step 3-1 is 2-10 mg: 10 mg: 1 mL; the drop coating amount of MXene / Cu-β-CD suspension on the ITO electrode surface is 80-120 μL; the laser induced power is 1.5-6 W.

4. The method for preparing the photoelectrochemical sensor according to claim 2, characterized in that: In step 3-5, the wavelength range of the LED light source is 420-655nm; the power of the LED light source is 15W; the sensitivity of the time-current curve test is 10 -6 A, detection time is 200s.

5. An application of the photoelectrochemical sensor for detecting AA according to claim 1, characterized in that: The detection method is as follows: Step 1: Draw the standard curve of AA sample concentration and photocurrent; Step 1.1, using AA samples, respectively, to prepare standard solutions of different concentrations; using the TiO2@C / CuO@C / ITO photoelectrode prepared according to the method of claim 2 as the working electrode, using the Ag / AgCl electrode as the reference electrode, using the platinum wire electrode as the counter electrode, using a homemade LED light source as the light source, and using an ordinary beaker as a photoelectrochemical electrolytic cell, placing it in the prepared standard sample solution for time-current curve testing, and obtaining the photocurrent size of the sample signal by switching the LED light source on and off at the moment; Step 1.2: Draw a concentration and photocurrent standard curve based on the concentration of the standard sample and the detected photocurrent; Step 2: Use the method in step 1.1 to detect the sample to be tested, obtain the photocurrent of the sample to be tested, and calculate the concentration of AA in the solution to be tested using the concentration and photocurrent standard curve drawn in step 1.2 above.

6. The use according to claim 5, characterized in that: The AA concentration range is 0.01~500mmol / L, and the detection limit is: 1.83μM.

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