A self-driven enzyme-free glucose photoelectric sensing electrode and its preparation method

Abstract

The present invention belongs to the field of photoelectric sensing and discloses a self-driven, enzyme-free glucose photoelectric sensor electrode and a method for preparing the same. The electrode comprises a conductive substrate, an n-type titanium dioxide layer disposed on the conductive substrate, a top nanopore array and a bottom nanopore array disposed within the n-type titanium dioxide layer, and an oxide semiconductor nanoparticle layer coating the end faces and inner walls of the top nanopore array and the bottom nanopore array. The oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer form a heterojunction with a type II energy band structure, and the n-type titanium dioxide layer and the conductive substrate form an ohmic contact. The n-type titanium dioxide layer employed in this solution has an extremely large specific surface area, and the introduced oxide semiconductor nanoparticle layer simultaneously coats the end faces and inner walls of the top and bottom nanopore arrays contained in the n-type titanium dioxide layer, resulting in the self-driven, enzyme-free glucose photoelectric sensor electrode having excellent light absorption capacity and a high density of active sites.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric sensing and relates to a self-driven glucose photoelectric sensing electrode and a preparation method thereof. Background Art

[0002] Blood glucose levels are a key indicator of human metabolic capacity and a crucial component of the clinical diagnosis of diabetes. Glucose in the blood is a crucial target for detection in fields such as human health management, pharmaceuticals, and food. Currently, glucose sensing is developing towards real-time, high-sensitivity, and low-detection-limit technologies.

[0003] Depending on whether enzyme modification is used, glucose sensors can be divided into: enzymatic sensors and non-enzymatic sensors, among which non-enzymatic sensors mainly include optical sensors, electrochemical sensors, and photoelectric (or photoelectrochemical) sensors. Enzymatic sensors are based on the specific recognition function of glucose oxidase and can selectively detect glucose. However, this type of sensor has obvious disadvantages, such as: glucose enzyme is easily affected by the environment, the enzyme modification process is complicated and the cost is high. Optical sensors invert the test substance based on changes in spectral information and have high sensitivity, but their selectivity is poor (such as: Zhang et al., Sensors & Actuators: B. Chemical, 2020, 304, 127304). In contrast, non-enzymatic electrochemical sensors based on metal or metal oxide nanostructured modified electrodes are less affected by the test environment and have good stability and selectivity. However, since both the excitation signal and the detection signal are electrical signals, and the preparation process of the metals or metal oxides involved is complicated, the background noise of the electrochemical sensor is large and the lower limit of detection is high, which is not conducive to the integration and miniaturization of the sensor (such as: MA Kachouei et al., Sensors & Actuators: B. Chemical, 2021, 344, 130254). As a new type of sensor, the photoelectric (or photoelectrochemical) sensor uses an optical signal as the excitation source and an electrical signal as the detection source, so that the device has the advantage of low background noise. However, most of the photoelectric (or photoelectrochemical) sensors currently disclosed for glucose detection require an external bias, have low sensitivity, and have a high minimum detection limit (such as: NJ Cory et al., Applied Surface Science, 2022, 576, 151822), which cannot meet the increasingly demanding market requirements. Summary of the Invention

[0004] The present invention aims to solve the problems of existing glucose sensing technologies, such as the need for enzyme modification, external operating voltage, high background noise, low sensor sensitivity, and high minimum detection limit. The technical solution adopted is as follows:

[0005] A self-driven enzyme-free glucose photoelectric sensor electrode comprises: a conductive substrate, an n-type titanium dioxide layer disposed on the upper surface of the conductive substrate, and an insulating and waterproof protective layer disposed on the lower surface of the conductive substrate; the n-type titanium dioxide layer is provided with a top nanopore array, and each nanopore in the top nanopore array is further provided with a plurality of small holes at the bottom thereof facing the conductive substrate; all the small holes constitute a bottom nanopore array; the end faces and inner walls of the top nanopore array and the bottom nanopore array are coated with an oxide semiconductor nanoparticle layer; the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer form a heterojunction with a type II energy band structure, and the n-type titanium dioxide layer is in ohmic contact with the conductive substrate.

[0006] The conductive substrate of the self-driven enzyme-free glucose photoelectric sensor electrode is provided with lead terminals, which are sequentially connected to an ammeter and a counter electrode. During use, the self-driven enzyme-free glucose photoelectric sensor electrode and the counter electrode are placed in a light-transmitting sensing cell; the light-transmitting sensing cell is filled with a background solution containing glucose. When excitation light shines on the surface of the self-driven enzyme-free glucose photoelectric sensor electrode, photogenerated holes in the heterojunction are separated and transported to the surface of the oxide semiconductor nanoparticle layer. The surface charges of the oxide semiconductor nanoparticle layer selectively undergo an oxidation reaction with glucose molecules, while photogenerated electrons in the heterojunction flow through the conductive substrate to the counter electrode, undergoing a corresponding reduction reaction, thereby forming a photocurrent response between the self-driven enzyme-free glucose photoelectric sensor electrode and the counter electrode. The ammeter can monitor the current, and the displayed photocurrent value shows a characteristic of being positively correlated with the glucose concentration to be measured, thereby achieving glucose detection.

[0007] Preferably, the material of the oxide semiconductor nanoparticles includes: copper oxide (CuO x ), nickel oxide (NiO x ), cobalt oxide (CoO x ), iron oxide (FeO x ), manganese oxide (MnO x ), cerium oxide (CeO x ) or a mixture of any one or more of the following.

[0008] Preferably, the nanoparticles in the oxide semiconductor nanoparticle layer have a diameter of 1 to 20 nm, and the nanoparticles are densely distributed but not in a continuous film.

[0009] Preferably, in the n-type titanium dioxide layer, the pores have a diameter of 40 to 100 nm and a depth of 1 to 5 μm; each nanopore in the top nanopore array has a diameter of 100 to 300 nm and a depth of 50 to 1000 nm.

[0010] Preferably, the conductive substrate is a metal titanium sheet with a thickness of 50 to 1000 μm.

[0011] Preferably, the n-type titanium dioxide layer is prepared by performing anodizing treatment on a conductive substrate.

[0012] Preferably, the counter electrode is a platinum electrode.

[0013] Preferably, the excitation light source is any one of sunlight, simulated sunlight and ultraviolet light.

[0014] Preferably, the glucose sensing concentration range of the glucose sensor is 0 to 200 μM.

[0015] In the scheme of the present invention, the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer absorb incident light to generate photogenerated electron-hole pairs. The generated photogenerated electron-hole pairs can be separated under the built-in electric field formed by the heterojunction. The photogenerated holes are transferred to the surface of the oxide semiconductor nanoparticles and selectively undergo an oxidation reaction with glucose molecules. The photogenerated electrons are transferred to the counter electrode through the conductive substrate of the self-driven enzyme-free glucose photoelectric sensor electrode to undergo a corresponding reduction reaction. When the glucose concentration is higher, the oxidation reaction on the surface of the self-driven enzyme-free glucose photoelectric sensor electrode is more intense, and the photocurrent generated is larger. With the generation and transfer of photogenerated holes, the valence of the metal elements in the oxide semiconductor nanoparticles will increase, and the metal ions with increased valence are reduced by glucose molecules. This cyclic process of increase and decrease in metal valence gives the self-driven enzyme-free glucose photoelectric sensor electrode the ability to recognize glucose molecules. Since the n-type titanium dioxide layer is provided with a top layer and a bottom layer of nanopore arrays and has a large specific surface area, the subsequently introduced oxide semiconductor nanoparticle layer is coated on the end faces and inner walls of the top layer and the bottom layer of nanopore arrays, so that the self-driven enzyme-free glucose photoelectric sensing electrode has excellent light anti-reflection performance and a high density of active sites. In addition, since the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer can effectively absorb the incident light, and the band structure of the heterojunction formed is type II (i.e., the conduction band bottom and the valence band top of the oxide semiconductor material are respectively higher than the conduction band bottom and the valence band top of the titanium dioxide material, and the conduction band bottom of the titanium dioxide material is higher than the valence band top of the oxide semiconductor), the self-driven enzyme-free glucose photoelectric sensing electrode can achieve the separation of photogenerated electron-hole pairs under zero bias, and thus can achieve glucose detection under zero bias. Since the external voltage applied to the self-driven enzyme-free glucose photoelectric sensing electrode is zero, the corresponding background current (i.e., dark current) is much lower than other electrochemical, photoelectric (or photoelectrochemical) sensors that require an external working voltage. Since no enzyme modification is involved, the ability to resist interference from the test environment (such as temperature changes) is significantly better than other glucose sensors that use enzyme modification.

[0016] The present application also discloses a method for preparing a self-driven enzyme-free glucose photoelectric sensing electrode, comprising the following steps:

[0017] 1) placing the conductive substrate in a mixture of deionized water and hydrofluoric acid for chemical polishing, followed by chemical cleaning;

[0018] 2) using an electrochemical anodization process to prepare an n-type titanium dioxide layer on the upper surface of a conductive substrate, controlling the voltage and time of the electrochemical anodization to introduce a top nanopore array on the upper surface of the n-type titanium dioxide layer; adjusting the voltage and time of the electrochemical anodization to introduce a plurality of small holes at the bottom of each nanopore in the top nanopore array toward the conductive substrate; all the small holes constitute a bottom nanopore array, and the diameter of the nanopores in the top nanopore array is controlled to be larger than the diameter of the small holes;

[0019] 3) heat-treating the n-type titanium dioxide layer comprising the top nanopore array and the bottom nanopore array obtained in step 2) in an air atmosphere;

[0020] 4) Using the n-type titanium dioxide layer obtained in step 3) as a substrate, a layer of metal nanoparticles is coated on the end faces and inner walls of the top nanopore array and the bottom nanopore array by sputtering or evaporation;

[0021] 5) performing a heat treatment in an air atmosphere to convert the metal nanoparticles deposited in step 4) into an oxide semiconductor nanoparticle layer;

[0022] 6) Leading out a wire from the back of the conductive substrate; and sealing the back of the conductive substrate with an insulating waterproof material to form an insulating waterproof protective layer on the lower surface of the conductive substrate.

[0023] Preferably, the metal nanoparticles in the deposited metal nanoparticle layer are distributed discretely and discontinuously.

[0024] Technical Effects

[0025] The solution of this technical invention can detect glucose at low concentrations and with high selectivity under sunlight or ultraviolet light without external bias or enzyme modification. Since the valence state of the metal elements in the oxide semiconductor nanoparticles has a cyclic characteristic of increasing and decreasing during the glucose sensing process, the self-driven enzyme-free glucose photoelectric sensing electrode has specific recognition of glucose molecules and thus has sensing selectivity for glucose. Since the n-type titanium dioxide layer prepared by this solution has an extremely large specific surface area, the subsequently introduced oxide semiconductor nanoparticle layer is simultaneously coated on the end faces and inner walls of the top and bottom nanopore arrays contained in the n-type titanium dioxide layer, so that the self-driven enzyme-free glucose photoelectric sensing electrode has excellent light anti-reflection performance and a high density of active sites. In addition, since both the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer can absorb incident light, and the band structure of the heterojunction formed is type II (i.e., the conduction band bottom and valence band top of the oxide semiconductor are higher than the conduction band bottom and valence band top of the titanium dioxide material, respectively, and the conduction band bottom of the titanium dioxide material is higher than the valence band top of the oxide semiconductor), the self-driven enzyme-free glucose photoelectric sensor electrode can achieve the separation of photogenerated electron-hole pairs under zero bias, and thus can achieve glucose detection under zero bias. Finally, since the self-driven enzyme-free glucose photoelectric sensor electrode forms a semiconductor-solution junction with a rectifying effect with the background solution, and the operating voltage is zero, the dark current between the self-driven enzyme-free glucose photoelectric sensor electrode and the counter electrode is as low as 3nA / cm 2 , which is far lower than electrochemical sensors and photoelectric sensors that require an operating voltage. It should be noted that the self-driven enzyme-free glucose photoelectric sensor electrode has higher sensing sensitivity for glucose concentrations in the range of 0 to 200 μM. However, for glucose solutions with concentrations above 200 μM, although it has a significant photocurrent response, the corresponding sensing sensitivity is lower. Therefore, the self-driven enzyme-free glucose photoelectric sensor electrode is more suitable for detecting low-concentration glucose. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Schematic diagram of the working principle of a self-driven enzyme-free glucose photoelectric sensing electrode;

[0027] Among them: 11 is the oxide semiconductor nanoparticle layer, 12 is the n-type titanium dioxide layer, 13 is the conductive substrate, 14 is the insulating and waterproof protective layer, 15 is the counter electrode, 16 is the light-transmitting sensing cell, 17 is the n-type titanium dioxide layer absorbing incident light to generate electron-hole pairs, and 18 is the oxide semiconductor nanoparticle layer absorbing incident light to generate electron-hole pairs.

[0028] Figure 2 : Schematic diagram of the structure of a self-driven enzyme-free glucose photoelectric sensing electrode;

[0029] Wherein: 21 is the top nanopore array, and 22 is the bottom nanopore array.

[0030] Figure 3 : Scanning electron micrograph of the prepared n-type titanium dioxide layer with top and bottom nanopore arrays.

[0031] Figure 4 : Scanning electron microscopy image of the prepared copper oxide nanoparticles / n-type titanium dioxide layer heterojunction.

[0032] Figure 5 : Photocurrent response curve of the glucose photoelectric sensing electrode based on copper oxide nanoparticles / n-type titanium dioxide layer heterojunction to different concentrations of glucose under zero bias and simulated sunlight.

[0033] Figure 6 : The corresponding relationship between the photocurrent density obtained by the glucose photoelectric sensing electrode based on copper oxide nanoparticles / n-type titanium dioxide layer heterojunction under zero bias and simulated sunlight and the glucose concentration in the range of 0 to 200 μM.

[0034] Figure 7 : The corresponding relationship between the photocurrent density obtained by the glucose photoelectric sensing electrode based on copper oxide nanoparticles / n-type titanium dioxide layer heterojunction under zero bias and simulated sunlight and the glucose concentration in the range of 0-1μM.

[0035] Figure 8 : Selective sensing test curve of glucose photoelectric sensing electrode based on FTO / copper oxide nanoparticles under zero bias and simulated sunlight.

[0036] Figure 9 : Selective sensing test curve of glucose photoelectric sensing electrode based on n-type titanium dioxide layer with top and bottom nanopore arrays under zero bias and simulated sunlight.

[0037] Figure 10 : Selective sensing test curve of glucose photoelectric sensing electrode based on copper oxide nanoparticles / n-type titanium dioxide layer heterojunction under zero bias and simulated sunlight.

[0038] Figure 11 : Comparison of the photocurrent response percentages of the glucose photoelectric sensing electrode based on copper oxide nanoparticles / n-type titanium dioxide layer heterojunction to four typical interfering substances under zero bias and simulated sunlight. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the present technical solution, further description is given below in conjunction with the accompanying drawings and embodiments.

[0040] Example 1

[0041] A self-driven enzyme-free glucose photoelectric sensing electrode, such as Figure 1 and Figure 2 As shown, it includes a conductive substrate 13, an n-type titanium dioxide layer 12 disposed on the upper surface of the conductive substrate, and an insulating and waterproof protective layer 14 disposed on the lower surface of the conductive substrate; the n-type titanium dioxide layer is provided with a top nanopore array 21, and each nanopore in the top nanopore array is further provided with a plurality of small holes at the bottom thereof facing the conductive substrate; all the small holes constitute a bottom nanopore array 22; the end faces and inner walls of the top and bottom nanopore arrays are coated with an oxide semiconductor nanoparticle layer 11; the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer form a heterojunction with a type II energy band structure (i.e., the conduction band bottom and valence band top of the oxide semiconductor material are higher than the conduction band bottom and valence band top of the titanium dioxide material, respectively, and the conduction band bottom of the titanium dioxide material is higher than the valence band top of the oxide semiconductor); the oxide semiconductor nanoparticle layer and the n-type titanium dioxide layer absorb incident light to generate photogenerated electron-hole pairs, which can be effectively separated only under the action of the heterojunction; and the n-type titanium dioxide layer forms an ohmic contact with the conductive substrate.

[0042] When using the self-driven enzyme-free glucose photoelectric sensing electrode, Figure 2 As shown, lead terminals are provided on a conductive substrate 13, and the lead terminals are connected to an ammeter and a counter electrode 15 in sequence; the self-driven enzyme-free glucose photoelectric sensing electrode and the counter electrode are placed in a light-transmitting sensing cell 16; the light-transmitting sensing cell is filled with a background liquid containing glucose; an insulating and waterproof protective layer 14 isolates the conductive substrate and the lead terminals from the background liquid; when excitation light is irradiated onto the surface of the self-driven enzyme-free glucose photoelectric sensing electrode, both the oxide semiconductor nanoparticle layer 11 and the n-type titanium dioxide layer 12 can absorb the incident light; photogenerated electron-hole pairs are generated: the n-type titanium dioxide layer absorbs the incident light to generate electron-hole pairs 17, and the oxide semiconductor nanoparticle layer absorbs the incident light to generate electron-hole pairs 18. Photogenerated electron-hole pairs are separated under the action of the heterojunction, and the photogenerated holes are transported to the surface of the oxide semiconductor nanoparticle layer. The surface charge of the oxide semiconductor nanoparticle layer selectively undergoes an oxidation reaction with glucose molecules, while the photogenerated electrons flow through the conductive substrate to the counter electrode to undergo a corresponding reduction reaction, thereby forming a photocurrent response between the self-driven enzyme-free glucose photoelectric sensor electrode and the counter electrode; the ammeter can monitor current changes, and the displayed photocurrent value shows a characteristic of being positively correlated with the glucose concentration to be measured, thereby realizing glucose detection.

[0043] It should be noted that the n-type titanium dioxide layer comprises a bottom nanopore array and a top nanopore array structure, resulting in a large specific surface area. Furthermore, as a substrate for growing the oxide semiconductor nanoparticle layer, the resulting oxide semiconductor nanoparticle layer / n-type titanium dioxide layer heterojunction possesses a high density of active sites for catalyzing glucose oxidation. Both the oxide semiconductor nanoparticles and the n-type titanium dioxide layer efficiently absorb incident light. Furthermore, the heterojunction formed by the oxide semiconductor nanoparticles and the n-type titanium dioxide layer exhibits a type II band structure, enabling effective separation of photogenerated carriers solely under the influence of the built-in electric field generated by the heterojunction (i.e., without the need for an external bias), thereby ensuring that the photoelectric sensing electrode exhibits a significant photocurrent response at zero bias. As photogenerated holes are generated and transferred within the heterojunction, the valence of the metal elements in the oxide semiconductor nanoparticles increases, and the metal ions with increased valence are then reduced by glucose molecules. This cyclical process of metal valence increase and decrease enables the self-driven, enzyme-free glucose photoelectric sensing electrode to recognize glucose molecules. Furthermore, glucose molecules are able to pass through the top nanopore array and into the underlying titanium dioxide nanopores, ensuring that all active glucose oxidation sites are functional. Because the applied voltage to the self-driven, enzyme-free glucose photoelectric sensor electrode is zero, the corresponding background current (i.e., dark current) is much lower than that of other electrochemical, photoelectric (or photoelectrochemical) sensors that require an applied operating voltage. Because there is no enzyme modification involved, the sensor's resistance to interference from the test environment (such as temperature changes) is significantly better than that of other enzyme-modified glucose sensors.

[0044] In view of the above characteristics, the photoelectric sensing electrode can detect glucose with low detection limit, high sensitivity and high selectivity under zero bias and without enzyme modification.

[0045] Example 2

[0046] A method for preparing a self-driven enzyme-free glucose photoelectric sensing electrode, the preparation process comprising:

[0047] 1) Using a 0.25 mm thick titanium sheet as a conductive substrate, chemically polish it in a mixture of water and hydrofluoric acid for 15 to 30 seconds, and then chemically clean it;

[0048] 2) using a mixture of ethylene glycol, ammonium fluoride, and deionized water as an electrolyte, the conductive substrate treated in step 1) as an anode, and a platinum mesh as a cathode, and performing electrochemical anodic oxidation at a DC voltage of 80 V for 20 minutes;

[0049] The treated conductive substrate was ultrasonically treated in deionized water to obtain a top layer of nanopore arrays;

[0050] Using a mixture of ethylene glycol, ammonium fluoride, and deionized water as an electrolyte, a conductive substrate containing a top nanopore array as an anode, and a platinum mesh as a cathode, electrochemical anodic oxidation was performed at a 60V DC voltage for 10 minutes. After treatment, a plurality of small holes were introduced at the bottom of each nanopore in the top nanopore array toward the conductive substrate. All the small holes formed a bottom nanopore array, and the diameter of the nanopores in the top nanopore array was controlled to be larger than the diameter of the small holes.

[0051] 3) The conductive substrate obtained in step 2) was annealed at 480°C in air for 3 hours to obtain an n-type titanium dioxide layer comprising a top nanopore array and a bottom nanopore array, the microscopic morphology of which is as follows: Figure 3 As shown;

[0052] 4) Using the n-type titanium dioxide layer prepared in step 3) as a substrate, magnetron sputtering a 10 nm thick discontinuous copper nanoparticle layer on the end faces and inner walls of the top nanopore array and the bottom nanopore array;

[0053] 5) The n-type titanium dioxide layer coated with the copper nanoparticle layer obtained in step 4) is annealed at 180°C in air for 30 minutes to obtain a copper oxide nanoparticle layer / n-type titanium dioxide layer heterojunction, the microstructure of which is as follows: Figure 4 As shown;

[0054] 6) Leading out external wires from the back of the conductive substrate, and sealing the back of the conductive substrate with an insulating waterproof material, forming an insulating waterproof protective layer on the lower surface of the conductive substrate, and only exposing the heterojunction on the front.

[0055] from Figure 3 It can be seen that the prepared n-type titanium dioxide layer contains two layers of nanopore arrays, and the diameter of the nanopores in the top layer is larger than that in the bottom layer. Figure 3 and Figure 4 It can be seen that after the treatment in steps 3) and 4), the end surface of the titanium dioxide nanopore array changed from its original smooth surface to a nanoparticle texture. This significant change in surface morphology demonstrates the successful introduction of the oxide semiconductor nanoparticle layer. Using an electrochemical workstation as the measuring instrument, a solar simulator as the light source, and Ag / AgCl as the reference electrode to control the operating potential of the photoelectric sensor electrode, a quartz glass cup as the sensing cell, a platinum mesh electrode as the counter electrode, and a 0.1M NaOH solution as the background solution, a glucose detection experiment was conducted.

[0056] First, the copper oxide nanoparticle layer / n-type titanium dioxide layer heterojunction photoelectric sensing electrode was tested for glucose detection. Its working potential was set to 0V relative to the reference electrode. Different concentrations of glucose were introduced into the background solution, and current density-time (Jt) tests were performed with and without light. Figure 5As shown, the corresponding dark current is as low as 3nA / cm 2 After illumination, the photocurrent corresponding to the background solution without glucose was significantly lower than that in the presence of glucose. Furthermore, as the glucose concentration increased from 5 nM to 200 μM, the photocurrent density gradually and steadily increased. This indicates that the detection limit of this glucose sensing system is as low as 5 nM.

[0057] Furthermore, the sensitivity, selectivity and low detection limit of the copper oxide nanoparticle layer / n-type titanium dioxide layer heterojunction photoelectric sensing electrode were tested for glucose concentrations of 0 to 200 μM. Figure 6 and 7 As shown in Figure 2, the photocurrent response of the photoelectric sensor electrode shows a linear relationship in the two concentration ranges of 20-200 μM and 0.1-1 μM, respectively, and the corresponding sensing sensitivities are 66 μA mM -1 cm -2 、5020μA mM -1 cm -2 . Glucose, sodium chloride, uric acid, sucrose, and ascorbic acid were added to the NaOH background solution in sequence, and the sensor's anti-interference and sensing selectivity were evaluated by observing and analyzing the changes in the photocurrent. In addition, two groups of comparative samples were introduced: one was a photoelectric sensing electrode based on an n-type titanium dioxide layer comprising a top nanopore array and a bottom nanopore array (i.e., no oxide semiconductor nanoparticle layer modification), and the other was a photoelectric sensing electrode based on a copper oxide nanoparticle layer grown on an FTO substrate. Figure 8 The photoresponse of the photoelectric sensing electrode constructed with a copper oxide nanoparticle layer on an FTO substrate shows only a weak photocurrent response to glucose. Figure 9 This is the photocurrent response of the photoelectric sensing electrode (without oxide semiconductor nanoparticle layer modification) containing an n-type titanium dioxide layer with top and bottom nanohole arrays. It can show a certain photocurrent response to glucose, sucrose and ascorbic acid, but the photocurrent response amplitude to sucrose and ascorbic acid is significantly smaller than that to glucose. Figure 10 It is shown that the copper oxide nanoparticle layer / n-type titanium dioxide layer heterojunction photoelectric sensing electrode prepared by the scheme of the present invention has the most significant photocurrent response to glucose solution, has a weaker photocurrent response to sucrose and ascorbic acid, and has almost no response to uric acid and sodium chloride. Figure 11 The photocurrent responses of the copper oxide nanoparticle layer / n-type titanium dioxide layer heterojunction photoelectric sensing electrode prepared by the present invention to sodium chloride, uric acid, sucrose, and ascorbic acid were normalized and compared (relative to glucose). It can be seen that the photocurrent responses generated by sodium chloride and uric acid are less than 2% of that of glucose, while the photocurrent responses generated by sucrose and ascorbic acid are less than 35% of that of glucose.

[0058] The above test data fully demonstrate that the glucose sensor prepared by this scheme can effectively sense glucose in the range of 0 to 200 μM without bias and enzyme modification, and has high sensing sensitivity and good sensing selectivity.

Claims

1. A self-driven enzyme-free glucose photoelectric sensing electrode, characterized in that include: A conductive substrate, an n-type titanium dioxide layer disposed on the upper surface of the conductive substrate, and an insulating and waterproof protective layer disposed on the lower surface of the conductive substrate; a top nanopore array is disposed within the n-type titanium dioxide layer, and a plurality of small holes are disposed at the bottom of each nanopore in the top nanopore array toward the conductive substrate; all the small holes constitute a bottom nanopore array; the small holes in the n-type titanium dioxide layer have a diameter of 40 to 100 nm and a depth of 1 to 5 μm; each nanopore in the top nanopore array has a diameter of 100 to 300 nm and a depth of 50 to 1000 nm; the top nanopore array The end faces and inner walls of the top and bottom nanopore arrays are coated with oxide semiconductor nanoparticle layers; the oxide semiconductor nanoparticle layer forms a type II heterojunction with the n-type titanium dioxide layer, and the n-type titanium dioxide layer is in ohmic contact with the conductive substrate; the nanoparticles in the oxide semiconductor nanoparticle layer have a diameter of 1 to 20 nm, and the nanoparticles are spatially distributed densely but not in a continuous film; the glucose sensing concentration range is 0 to 200 μM; glucose molecules pass through the top nanopore array and enter the small pores of the bottom titanium dioxide nanopore array, thereby ensuring that all glucose oxidation active sites are functional.

2. The self-driven enzyme-free glucose photoelectric sensing electrode according to claim 1, characterized in that: The material of the oxide semiconductor nanoparticle layer includes: a mixture of any one or more of copper oxide, nickel oxide, cobalt oxide, iron oxide, manganese oxide, and cerium oxide.

3. The self-driven enzyme-free glucose photoelectric sensing electrode according to claim 1, characterized in that: The conductive substrate is a metal titanium sheet with a thickness of 50 to 1000 μm.

4. The self-driven enzyme-free glucose photoelectric sensing electrode according to claim 1, characterized in that: The n-type titanium dioxide layer is prepared by performing anodizing treatment on a conductive substrate.

5. The self-driven enzyme-free glucose photoelectric sensing electrode according to claim 1, characterized in that: A lead terminal is arranged on the conductive substrate, and the lead terminal is connected to the ammeter and the counter electrode in sequence.

6. The self-driven enzyme-free glucose photoelectric sensing electrode according to claim 5, characterized in that: The counter electrode is a platinum electrode.

7. A method for preparing the self-driven enzyme-free glucose photoelectric sensor electrode according to claim 1, characterized in that include: 1) placing the conductive substrate in a mixture of deionized water and hydrofluoric acid for chemical polishing, followed by chemical cleaning; 2) using an electrochemical anodization process to prepare an n-type titanium dioxide layer on the upper surface of a conductive substrate, controlling the voltage and time of the electrochemical anodization to introduce a top nanopore array on the upper surface of the n-type titanium dioxide layer; adjusting the voltage and time of the electrochemical anodization to introduce a plurality of small holes at the bottom of each nanopore in the top nanopore array toward the conductive substrate; all the small holes constitute a bottom nanopore array, and the diameter of the nanopores in the top nanopore array is controlled to be larger than the diameter of the small holes; 3) heat-treating the n-type titanium dioxide layer comprising the top nanopore array and the bottom nanopore array obtained in step 2) in an air atmosphere; 4) Using the n-type titanium dioxide layer obtained in step 3) as a substrate, a layer of metal nanoparticles is coated on the end faces and inner walls of the top nanopore array and the bottom nanopore array by sputtering or evaporation; the metal nanoparticles in the deposited metal nanoparticle layer are discretely and discontinuously distributed; 5) performing a heat treatment in an air atmosphere to convert the metal nanoparticles deposited in step 4) into an oxide semiconductor nanoparticle layer; 6) Leading out a wire from the back of the conductive substrate; and sealing the back of the conductive substrate with an insulating waterproof material to form an insulating waterproof protective layer on the lower surface of the conductive substrate.

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