Organic photoelectrochemical transistor DNA sensor based on Schottky structure gate electrode and preparation method thereof

Abstract

The invention discloses an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode and a preparation method thereof.The organic photoelectrochemical transistor DNA sensor comprises an electrolytic tank containing electrolyte, a substrate with one end inserted into the electrolyte and the Schottky structure gate electrode; the Schottky structure gate electrode comprises an n-type doped silicon substrate and two gold plating layers arranged on the surface of the n-type doped silicon substrate in a spaced mode, the gold plating layer close to the bottom of the electrolytic tank is located in the electrolyte in an exposed mode, and the other gold plating layer away from the bottom of the electrolytic tank is coated with light blocking glue and located outside the electrolyte. And the surface of the gold plating layer in the electrolyte is connected with a single-stranded probe DNA for hybridizing with the target DNA to be detected. When the sensor is used for detecting target DNA, dual signal amplification can be achieved through the synergistic effect of charge-barrier regulation and OPECT transconductance amplification, fluorescence or enzyme labeling is not needed in the method, and meanwhile high sensitivity and stability are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photoelectrochemical transistors, and in particular to an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode and a preparation method thereof. Background Art

[0002] DNA detection is of great significance in disease diagnosis, genetic analysis, and environmental monitoring. Existing technologies such as fluorescence, electrochemistry, and surface plasmon resonance (SPR) have the following problems: insufficient sensitivity, with fluorescence susceptible to background interference; complex equipment, with SPR and mass spectrometry requiring expensive instruments and professional operation; and labeling dependency, with most methods requiring fluorescent or enzyme-labeled probes, increasing cost and complexity. Traditional photoelectrochemical (PEC) signal amplification capabilities are insufficient, making it difficult to break through the detection limit. Although organic photoelectrochemical transistors (OPECTs) have signal amplification properties, their gates often rely on modification with photosensitive nanomaterials (such as CdS quantum dots), and the preparation process for such materials is relatively complex.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode and a preparation method thereof, aiming to solve the problem that existing organic photoelectrochemical transistors are difficult to detect the target DNA concentration simply, efficiently and with high sensitivity.

[0005] The technical solutions of the present invention are as follows:

[0006] An organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode comprises an electrolytic cell containing an electrolyte, a substrate with one end inserted into the electrolyte, and a Schottky structure gate electrode. A source electrode and a drain electrode are provided on the substrate, each with one end inserted into the electrolyte and spaced apart. The surfaces of the ends of the source and drain electrodes inserted into the electrolyte are coated with an organic semiconductor film. The Schottky structure gate electrode comprises an n-type doped silicon substrate with one end inserted into the electrolyte and two gold-plated layers spaced apart vertically on the surface of the n-type doped silicon substrate. A gold-plated layer near the bottom of the electrolytic cell is exposed in the electrolyte, while another gold-plated layer away from the bottom of the electrolytic cell is coated with light-blocking adhesive and located outside the electrolyte. A single-stranded probe DNA for hybridizing with a target DNA to be detected is connected to the surface of the gold-plated layer in the electrolyte, and the gold-plated layer outside the electrolyte is electrically connected to a conductive adhesive.

[0007] The organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode, wherein the material of the organic semiconductor film is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrroles, polythiophenes, polyanilines, polycarbazoles and copolymers thereof.

[0008] In the organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, the single-stranded probe DNA is 5'-thiol-modified DNA.

[0009] In the organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, the thickness of the gold plating layer is 15-30 nm.

[0010] In the organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, the surface of the gold plating layer is modified with gold nanoparticles.

[0011] A method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode as described in the present invention comprises the steps of:

[0012] Prepare a source electrode and a drain electrode on a substrate, and prepare a layer of organic semiconductor thin film on the surface of the source electrode and the drain electrode for later use;

[0013] Using a masking tape to separate the two ends of the smooth surface of the n-type doped silicon substrate, two spaced-apart gold-plated layers are formed on the smooth surface of the n-type doped silicon substrate, one of the gold-plated layers is covered with light-blocking adhesive and led out through conductive adhesive to form a Schottky structure gate electrode;

[0014] The Schottky-structured gate electrode is treated with UV-ozone to remove residual organic matter and activate the exposed gold coating surface to enhance its thiol-binding ability. The exposed gold coating is then placed in a solution of 5'-thiol-modified single-stranded probe DNA to react, promoting the binding of the gold coating and the single-stranded probe DNA through gold-sulfur bonds to form a self-assembled monolayer.

[0015] The substrate and the Schottky structure gate electrode modified with the single-stranded probe DNA are inserted into an electrolytic cell filled with an electrolyte to prepare the organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode.

[0016] The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, wherein the step of preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate comprises:

[0017] The n-type doped silicon substrate is placed in a magnetron sputtering coater, the magnetron sputtering power is set to 70-90 W, the substrate holder rotation speed is set to 15-25 rpm, the vacuum degree is maintained at 0.4-0.6 Pa during operation, and the target material used is gold, until two gold coatings with a thickness of 15-30 nm and spaced apart are prepared on the smooth surface of the n-type doped silicon substrate.

[0018] The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, wherein, after preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate, further comprises the steps of:

[0019] A three-electrode system was constructed using an n-type doped silicon substrate with a gold coating on its surface as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. A mixed solution of chloroauric acid, sulfuric acid, and CTAB was used as the electrolyte.

[0020] The gold was deposited at -0.8 V (vs. Ag / AgCl) for 300 seconds using a constant potential method. CTAB served as a morphology directing agent to guide the growth of gold along the (111) crystal plane, forming uniform gold nanoparticles with a particle size of 50 ± 8 nm on the surface of the gold coating. After deposition, the electrode was rinsed with deionized water and dried with nitrogen, and then annealed in nitrogen at 200 ° C for 30 minutes to eliminate internal stress and improve the conductivity of the particles.

[0021] The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode is characterized in that the step of preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate comprises:

[0022] A single layer of polystyrene nanospheres with a particle size of 300 nm was spin-coated on the surface of an n-type doped silicon substrate, and the polystyrene nanospheres were shrunk to a particle size of 150 nm by oxygen plasma etching to serve as a mask.

[0023] Argon was used as the sputtering gas, the magnetron sputtering power was controlled to be 70-90W, and the deposition rate was The gold coating is sputtered to a thickness of 15-30 nm, and then the polystyrene mask is removed to form a periodic nanopore array gold coating. The gold coating is further annealed to promote the migration of gold atoms, and the pore walls shrink to form a nanoparticle gold coating with a particle size of 50±5 nm.

[0024] Beneficial effects: The organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode provided by the present invention has a gold / silicon (Au / n-Si) Schottky structure gate electrode as the core, and dynamically regulates the metal work function through the change of surface charge density caused by DNA modification, thereby realizing label-free and highly selective detection; the Schottky structure gate electrode is prepared by magnetron sputtering deposition of metallic gold on an n-type silicon substrate. During the deposition process, the gold layer is separated by a mask plate of a certain width, so that the gold plating layers on the upper and lower sides of the n-type silicon substrate are independent of each other, and the gold plating layer on the upper side is coated with light-blocking glue. This design can realize a potential difference through light treatment Generation: Under light conditions, the electrons of the silicon substrate below the unshielded gold layer are excited to jump, break through the Schottky barrier and accumulate on the surface of the gold layer, forming a potential difference compared to the light-shielded part, thereby realizing the photoelectric control function of the photosensitive gate; for the modification and regulation of DNA, the single-stranded probe DNA (ssDNA) is first fixed to the Au surface through a gold-sulfur bond. The probe DNA layer has a negative charge characteristic, which can reduce the Schottky barrier of the gate when in contact with the gold layer, thereby enhancing the efficiency of photogenerated electron transfer; after the target DNA hybridizes with the single-stranded probe DNA, the generated double-stranded DNA (dsDNA) has a higher charge density, further regulating the barrier and amplifying the photocurrent signal. When the DNA sensor of the present invention detects the target DNA, it can achieve dual signal amplification through the synergistic effect of charge-barrier regulation and OPECT transconductance amplification. This method does not require fluorescence or enzyme labeling and has a low background signal. The process is simple and has good sensitivity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode.

[0026] Figure 2 This is a diagram of the working principle of the Schottky structure gate electrode.

[0027] Figure 3 Schematic diagram of the DNA detection principle based on organic photoelectrochemical transistor DNA sensor.

[0028] Figure 4 To detect different states of DNA process I DS -T curve graph.

[0029] Figure 5 This is a graph showing the relationship between the step current change rate and the target DNA concentration. DETAILED DESCRIPTION

[0030] The present invention provides an organic photoelectrochemical transistor DNA sensor based on a Schottky-structured gate electrode and a method for preparing the same. To clarify the objectives, technical solutions, and advantages of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0031] See also Figure 1 , Figure 1 The present invention provides a schematic structural diagram of an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode. As shown in the figure, the organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode comprises an electrolytic cell 1 filled with an electrolyte 2, a substrate 7 with one end inserted into the electrolyte 2, and a Schottky structure gate electrode. The substrate 7 is provided with a source electrode 9 and a drain electrode 10 with one end inserted into the electrolyte and spaced apart. The surface of the end of the source electrode 9 and the drain electrode 10 inserted into the electrolyte is coated with an organic semiconductor. The body film 8, the Schottky structure gate electrode includes an n-type doped silicon substrate 5 with one end inserted into the electrolyte and two gold-plated layers 6 arranged on the surface of the n-type doped silicon substrate at intervals in the vertical direction, wherein a gold-plated layer close to the bottom of the electrolytic cell is exposed in the electrolyte 2, and the other gold-plated layer away from the bottom of the electrolytic cell is covered with a light-blocking glue 4 and is located outside the electrolyte 2, the surface of the gold-plated layer 6 located in the electrolyte is connected to a single-stranded probe DNA for hybridizing with the target DNA to be tested, and the gold-plated layer 6 located outside the electrolyte is electrically connected to a conductive glue 3.

[0032] The present invention uses a Schottky structure gate electrode (photosensitive gate Au / n-Si) with a simple preparation process to build an organic photoelectrochemical transistor (OPECT). The metal work function is dynamically regulated by the change in surface charge density caused by DNA modification, forming a "charge-barrier-photocurrent" coupling mechanism. Among them, the change in effective work function caused by DNA hybridization can directly amplify the photocurrent signal. At the same time, the OPECT transconductance characteristics can further convert the photocurrent change into a significant response of the channel current, and high-sensitivity detection of DNA can be achieved through dual signal amplification.

[0033] Specifically, the Schottky structure gate electrode is obtained by depositing gold on an n-type silicon substrate by magnetron sputtering to form a gold plating layer. During the deposition process, the gold plating layer is separated by a mask plate of a certain width, so that the gold plating layers on the upper and lower sides of the n-type silicon substrate are independent of each other, and the gold plating layer on the upper side is coated with light-blocking glue. This design can achieve the generation of potential difference through light treatment: under light conditions, the electrons of the silicon substrate under the unshielded gold plating layer are excited to jump, break through the Schottky barrier and accumulate on the surface of the gold layer, forming a potential difference compared to the shielded part, thereby realizing the photoelectric control function of the photosensitive gate; for DNA modification and regulation, the single-stranded probe DNA (ssD NA) is fixed to the Au surface through a gold-sulfur bond. The probe DNA layer has a negative charge characteristic and can reduce the Schottky barrier of the gate electrode when in contact with the gold plating layer, thereby enhancing the efficiency of photogenerated electron transfer. After the target DNA hybridizes with the probe DNA, the generated double-stranded DNA (dsDNA) has a higher charge density, which further regulates the barrier and amplifies the photocurrent signal. Therefore, when the sensor provided in this embodiment detects the target DNA, dual signal amplification can be achieved through the synergistic effect of charge-barrier regulation and OPECT transconductance amplification. This method does not require fluorescence or enzyme labeling and has a low background signal. The process is simple and has good sensitivity and stability.

[0034] As an example, an OPECT system including a source electrode, a drain electrode, and a Schottky structure gate electrode is first constructed, with 0.1 M phosphate buffer (PBS) as the electrolyte. Figure 1 As shown. 425nm wavelength light is used as the excitation light source; the substrate is soda-lime glass, and the source and drain electrodes are prepared on the substrate by thermal evaporation. A certain gate voltage in the electrolyte can affect the injection of cations in the solution into the organic semiconductor film between the source and drain electrodes, thereby affecting the doping state of the organic semiconductor film, and ultimately achieving the effect of gate voltage change on the channel current I of the OPECT device. DS Regulation; depositing a gold plating layer of about 20nm on the surface of the n-type silicon substrate by magnetron sputtering and a mask plate, the gold plating layer is separated by a mask plate of a certain width during the deposition process, so that the gold plating layers on the upper and lower sides are independent of each other, thereby obtaining the Schottky structure gate electrode; wrapping one end of the gold plating layer with black tape for light blocking treatment, under light conditions, the electrons of the silicon substrate below the unshielded gold layer are excited to jump, break through the Schottky barrier and accumulate on the surface of the gold layer, forming a potential difference compared to the shielded part, and the electrons move directionally from the illuminated end to the shielded end, such as Figure 2 When this Schottky structure gate electrode is used as the gate electrode of OPECT, the potential difference caused by light makes the channel current I DS regulated (e.g. Figure 3 Indication and Figure 4When the single-stranded probe DNA (ssDNA) is further modified on the Au surface of the illuminated side, the negative charge of DNA can reduce the Schottky barrier of the gate when in contact with the gold layer, thereby reducing the work function of the Au surface and enhancing the efficiency of photogenerated electron transfer. DS subject to greater regulation (e.g. Figure 3 Indication and Figure 4 When the target DNA and probe DNA hybridize to form double-stranded DNA (dsDNA), the channel current I DS subject to further regulation (e.g. Figure 3 Indication and Figure 4 As shown in the dsDNA step current. Figure 5 As shown, ΔI / I is the step current change rate. It can be seen that the change rate gradually increases with the increase of target DNA concentration, thereby achieving quantitative detection of DNA.

[0035] In some embodiments, the material of the organic semiconductor film is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrroles, polythiophenes, polyanilines, polycarbazoles and copolymers thereof, but is not limited thereto.

[0036] In some embodiments, the single-stranded probe DNA is 5'-thiol-modified DNA, and the single-stranded probe DNA is fixed to the surface of the gold-plated layer via a gold-sulfur bond.

[0037] In some embodiments, the surface of the gold plating layer is modified with gold nanoparticles. By modifying the surface of the gold plating layer with gold nanoparticles, the light absorption efficiency of the Au / n-Si gate can be further improved, thereby further improving the sensitivity of DNA concentration detection.

[0038] In some embodiments, the thickness of the gold plating layer is 15-30 nm, but is not limited thereto. For example, the thickness of the gold plating layer can be 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, etc.

[0039] The organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode and its preparation method of the present invention are described below by means of specific examples:

[0040] Example 1

[0041] A method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode comprises the following steps:

[0042] 1) Prepare a source electrode and a drain electrode on a substrate, and prepare a layer of organic semiconductor film on the surface of the source electrode and the drain electrode for later use:

[0043] The cut soda-lime glass was ultrasonically cleaned with acetone, ethanol, and water in sequence. A mask with a designed pattern was attached to the glass. 10nm of chromium (Cr) and 100nm of gold (Au) were deposited on the soda-lime glass by thermal evaporation to obtain Au / Cr / glass electrodes. A layer of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS) material containing dimethyl sulfoxide (DMSO) was spin-coated on the electrode. The area outside the Au / Cr electrode was wiped clean, leaving the channel electrode part. The electrode was then annealed at 180°C in a nitrogen atmosphere for 60 minutes to obtain the source and drain electrodes in the OPECT.

[0044] 2) Preparation of Schottky structure gate electrode:

[0045] Specifically, a 5mm*10mm square silicon wafer was cut from an n-type doped silicon substrate, and the cut silicon wafer was respectively placed in anhydrous ethanol and deionized water for cleaning for 15 minutes. After cleaning, it was blown dry with nitrogen. A 0.2mm wide mask tape parallel to the short side was used in the middle of the silicon wafer to separate the two ends of the smooth surface of the silicon wafer. Then, the silicon wafer was placed in a magnetron sputtering coater, the magnetron sputtering power was set to 80W, the substrate holder rotation speed was 20rpm, the vacuum degree was maintained at 0.5Pa during operation, the target material used was gold, and the sputtering time was controlled to finally produce two separated gold coatings with a film thickness of 20nm. One section of the gold coating was wrapped with black tape for light blocking and led out through conductive glue, and the Schottky structure gate electrode was completed.

[0046] 3) Fixation of single-stranded probe DNA on the surface of Schottky structure gate electrode:

[0047] The prepared Schottky-structured gate electrode (20 nm gold layer thickness) was rinsed sequentially with ethanol and deionized water, then dried with nitrogen to remove surface contaminants. Acetone and strong oxidants were avoided to prevent damage to the adhesive tape and conductive adhesive-wrapped areas. After surface pretreatment, UV-ozone treatment (254 nm wavelength, 30 W power, 10 minutes) gently removed residual organic matter and activated the gold surface to enhance thiol binding capacity. A 5'-thiol-modified DNA probe was dissolved in PBS buffer (0.01 M PBS, 10 mM TCEP) at a concentration of 0.1 μM. The prepared DNA solution was incubated at 37°C in a thermostatic shaker for 1 hour. Finally, the exposed gold layer, which had been pretreated and measured for electrical signal, was placed in the probe DNA solution for 12 hours at room temperature to form a self-assembled monolayer (SAM) through Au-S bonds.

[0048] 4) inserting the substrate and the Schottky structure gate electrode modified with the single-stranded probe DNA into an electrolytic cell filled with an electrolyte to prepare the organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode.

[0049] Example 2

[0050] A method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode comprises the following steps:

[0051] 1) Prepare a source electrode and a drain electrode on a substrate, and prepare a layer of organic semiconductor film on the surface of the source electrode and the drain electrode for later use:

[0052] The cut soda-lime glass was ultrasonically cleaned with acetone, ethanol, and water in sequence. A mask with a designed pattern was attached to the glass. 10nm of chromium (Cr) and 100nm of gold (Au) were deposited on the soda-lime glass by thermal evaporation to obtain Au / Cr / glass electrodes. A layer of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS) material containing dimethyl sulfoxide (DMSO) was spin-coated on the electrode. The area outside the Au / Cr electrode was wiped clean, leaving the channel electrode part. The electrode was then annealed at 180°C in a nitrogen atmosphere for 60 minutes to obtain the source and drain electrodes in the OPECT.

[0053] 2) Preparation of Schottky structure gate electrode:

[0054] A 5mm*10mm square silicon wafer was cut from an n-type doped silicon substrate and washed in anhydrous ethanol and deionized water for 15 minutes respectively. After washing, it was blown dry with nitrogen. A 0.2mm wide masking tape parallel to the short side of the middle of the silicon wafer was used to separate the two ends of the smooth surface of the silicon wafer. The silicon wafer was then placed in a magnetron sputtering coater. The magnetron sputtering power was set to 80W, the substrate holder rotation speed was 20rpm, and the vacuum degree was maintained at 0.5Pa during operation. The target material used was gold. The sputtering time was controlled to finally produce two separated gold coatings with a film thickness of 15nm. One section of the gold coating was wrapped with black tape to block light and led out through conductive glue to obtain an Au / n-Si gate.

[0055] To improve the light absorption efficiency of the Au / n-Si gate, gold nanoparticles were deposited on the exposed gold coating surface of the Au / n-Si gate by electrodeposition to increase the light absorption efficiency. Specifically, a three-electrode system was constructed using an n-type doped silicon substrate with a gold coating as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. A mixed solution of chloroauric acid, sulfuric acid, and CTAB was used as the electrolyte of the three-electrode system. The gold was deposited at -0.8V (vs. Ag / AgCl) for 300 seconds using a constant potential method. CTAB was used as a morphology guide to guide the growth of gold along the (111) crystal plane, forming uniform gold nanoparticles with a particle size of 50±8nm on the exposed gold coating surface. After deposition, the electrode was rinsed with deionized water and dried with nitrogen, and then annealed in nitrogen at 200℃ for 30 minutes to eliminate internal stress and improve the conductivity of the particles, thereby preparing a Schottky structure gate electrode.

[0056] 3) Fixation of single-stranded probe DNA on the surface of Schottky structure gate electrode:

[0057] The prepared Schottky-structured gate electrode (20 nm gold layer thickness) was rinsed sequentially with ethanol and deionized water, then dried with nitrogen to remove surface contaminants. Acetone and strong oxidants were avoided to prevent damage to the adhesive tape and conductive adhesive-wrapped areas. After surface pretreatment, UV-ozone treatment (254 nm wavelength, 30 W power, 10 minutes) gently removed residual organic matter and activated the gold surface to enhance thiol binding capacity. A 5'-thiol-modified DNA probe was dissolved in PBS buffer (0.01 M PBS, 10 mM TCEP) at a concentration of 0.1 μM. The prepared DNA solution was incubated at 37°C in a thermostatic shaker for 1 hour. Finally, the exposed gold layer, which had been pretreated and measured for electrical signal, was placed in the probe DNA solution for 12 hours at room temperature to form a self-assembled monolayer (SAM) through Au-S bonds.

[0058] 4) inserting the substrate and the Schottky structure gate electrode modified with the single-stranded probe DNA into an electrolytic cell filled with an electrolyte to prepare the organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode.

[0059] Example 3

[0060] A method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode comprises the following steps:

[0061] 1) Prepare a source electrode and a drain electrode on a substrate, and prepare a layer of organic semiconductor film on the surface of the source electrode and the drain electrode for later use:

[0062] The cut soda-lime glass was ultrasonically cleaned with acetone, ethanol, and water in sequence. A mask with a designed pattern was attached to the glass. 10nm of chromium (Cr) and 100nm of gold (Au) were deposited on the soda-lime glass by thermal evaporation to obtain Au / Cr / glass electrodes. A layer of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS) material containing dimethyl sulfoxide (DMSO) was spin-coated on the electrode. The area outside the Au / Cr electrode was wiped clean, leaving the channel electrode part. The electrode was then annealed at 180°C in a nitrogen atmosphere for 60 minutes to obtain the source and drain electrodes in the OPECT.

[0063] 2) Preparation of Schottky structure gate electrode:

[0064] A 5mm*10mm square silicon wafer was cut from the n-type doped silicon substrate, and the cut silicon wafer was washed in anhydrous ethanol and deionized water for 15 minutes respectively. After washing, it was blown dry with nitrogen. A 0.2mm wide mask tape parallel to the short side was used in the middle of the silicon wafer to separate the two ends of the smooth surface of the silicon wafer. In order to improve the light absorption efficiency of the Au / n-Si gate, magnetron sputtering combined with nanosphere lithography technology was used to optimize the gold layer structure. First, a single layer of polystyrene nanospheres with a particle size of 300nm was spin-coated on the surface of the n-type doped silicon substrate. The polystyrene nanospheres were etched with oxygen plasma to reduce the particle size of 150nm as a mask. Subsequently, argon was used as the sputtering gas (pressure 3mTorr), the power was 80W, and the deposition rate was 2.5~3.5. A gold layer is sputtered to a thickness of 30 nm. The polystyrene mask is then removed, forming a periodic gold layer with a nanopore array. This layer is then annealed to promote the migration of gold atoms, shrinking the pore walls to form a nanoparticle gold layer with a particle size of 50 ± 5 nm, creating a Schottky-structured gate electrode.

[0065] 3) Fixation of single-stranded probe DNA on the surface of Schottky structure gate electrode:

[0066] The prepared Schottky-structured gate electrode (20 nm gold layer thickness) was rinsed sequentially with ethanol and deionized water, then dried with nitrogen to remove surface contaminants. Acetone and strong oxidants were avoided to prevent damage to the adhesive tape and conductive adhesive-wrapped areas. After surface pretreatment, UV-ozone treatment (254 nm wavelength, 30 W power, 10 minutes) gently removed residual organic matter and activated the gold surface to enhance thiol binding capacity. A 5'-thiol-modified DNA probe was dissolved in PBS buffer (0.01 M PBS, 10 mM TCEP) at a concentration of 0.1 μM. The prepared DNA solution was incubated at 37°C in a thermostatic shaker for 1 hour. Finally, a bare gold electrode, which had already been measured and pretreated, was placed in the probe DNA solution for 12 hours at room temperature to form a self-assembled monolayer (SAM) through Au-S bonds.

[0067] 4) inserting the substrate and the Schottky structure gate electrode modified with the single-stranded probe DNA into an electrolytic cell filled with an electrolyte to prepare the organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode.

[0068] Application Example 1

[0069] Detection method of organic photoelectrochemical transistor DNA sensor based on Schottky structure gate electrode:

[0070] The Au / n-Si gate electrode immobilized with 0.1 μM ssDNA probes from the organic photoelectrochemical transistor DNA sensor of Example 1 was immersed in target DNA at different concentrations and hybridized in a constant temperature shaker at 37°C with gentle shaking (50 rpm) to promote specific binding of complementary sequences. The hybridized gate electrode was exposed to light and the I values after hybridization reaction with target DNA at different concentrations were measured. DS -T curve, such as Figure 4 By calculating the rate of change of the step current, we can find its relationship with the target DNA concentration, that is, the size of the step current change rate ΔI / I gradually increases with the increase of the target DNA concentration, as shown in Figure 5 In this example, the gate electrode's I DS The -T curve was measured in 0.1M PBS solution. During the measurement, the excitation wavelength of the light was 425nm. Therefore, the concentration of the target DNA to be tested can be quantitatively measured according to the size of the step current. Figure 5 It can be seen that the minimum detection limit of this embodiment can reach 10 -12 M.

[0071] In summary, the organic photoelectrochemical transistor DNA sensor of the present invention can directly regulate the work function of the Au / n-Si gate through the negative charge characteristics of DNA, replacing the modification of traditional photosensitive materials (such as CdS quantum dots), and combining the transconductance amplification characteristics of OPECT to achieve dual signal amplification; based on the Au-S bond, the ssDNA probe is directionally fixed, and the electric dipole layer is formed by the negative charge of its phosphate backbone, thereby reducing the effective work function and Schottky barrier of the gate electrode; the present invention can further design the gold plating layer into a nanoparticle array, and utilize the increased light capture surface area of the gold plating layer to enhance the light absorption efficiency; the signal is directly output through the charge density change caused by DNA hybridization, avoiding complex labeling steps.

[0072] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode, characterized in that: The invention comprises an electrolytic cell filled with an electrolyte, a substrate with one end inserted into the electrolyte, and a Schottky structure gate electrode, wherein a source electrode and a drain electrode with one end inserted into the electrolyte and spaced apart are provided on the substrate, the surfaces of the ends of the source electrode and the drain electrode inserted into the electrolyte being coated with an organic semiconductor film, and the Schottky structure gate electrode comprises an n-type doped silicon substrate with one end inserted into the electrolyte and two gold-plated layers spaced apart in a vertical direction on the surface of the n-type doped silicon substrate, wherein a gold-plated layer near the bottom of the electrolytic cell is exposed in the electrolyte, and another gold-plated layer away from the bottom of the electrolytic cell is coated with light-blocking glue and is located outside the electrolyte, a single-stranded probe DNA for hybridizing with a target DNA to be detected is connected to the surface of the gold-plated layer located in the electrolyte, and the gold-plated layer located outside the electrolyte is electrically connected to a conductive glue.

2. The organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 1, characterized in that: The material of the organic semiconductor film is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrroles, polythiophenes, polyanilines, polycarbazoles and copolymers thereof.

3. The organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 1, characterized in that: The single-stranded probe DNA is 5'-thiol-modified DNA.

4. The organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 1, characterized in that: The thickness of the gold plating layer is 15-30 nm.

5. The organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 1, characterized in that: The surface of the gold plating layer is modified with gold nanoparticles.

6. A method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to any one of claims 1 to 5, characterized in that: Including steps: Prepare a source electrode and a drain electrode on a substrate, and prepare a layer of organic semiconductor thin film on the surface of the source electrode and the drain electrode for later use; Using a masking tape to separate the two ends of the smooth surface of the n-type doped silicon substrate, two spaced-apart gold-plated layers are formed on the smooth surface of the n-type doped silicon substrate, one of the gold-plated layers is covered with light-blocking adhesive and led out through conductive adhesive to form a Schottky structure gate electrode; The Schottky-structured gate electrode is treated with UV-ozone to remove residual organic matter and activate the exposed gold coating surface to enhance its thiol-binding ability. The exposed gold coating is then placed in a solution of 5'-thiol-modified single-stranded probe DNA to react, promoting the binding of the gold coating and the single-stranded probe DNA through gold-sulfur bonds to form a self-assembled monolayer. The substrate and the Schottky structure gate electrode modified with the single-stranded probe DNA are inserted into an electrolytic cell filled with an electrolyte to prepare the organic photoelectrochemical transistor DNA sensor based on the Schottky structure gate electrode.

7. The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 6, characterized in that: The step of preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate comprises: The n-type doped silicon substrate is placed in a magnetron sputtering coater, the magnetron sputtering power is set to 70-90 W, the substrate holder rotation speed is set to 15-25 rpm, the vacuum degree is maintained at 0.4-0.6 Pa during operation, and the target material used is gold, until two gold coatings with a thickness of 15-30 nm and spaced apart are prepared on the smooth surface of the n-type doped silicon substrate.

8. The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 7, characterized in that: After preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate, the method further comprises the following steps: A three-electrode system was constructed using an n-type doped silicon substrate with a gold coating on its surface as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. A mixed solution of chloroauric acid, sulfuric acid, and CTAB was used as the electrolyte. The gold was deposited at -0.8 V (vs. Ag / AgCl) for 300 seconds using a constant potential method. CTAB served as a morphology directing agent to guide the growth of gold along the (111) crystal plane, forming uniform gold nanoparticles with a particle size of 50 ± 8 nm on the surface of the gold coating. After deposition, the electrode was rinsed with deionized water and dried with nitrogen, and then annealed in nitrogen at 200 ° C for 30 minutes to eliminate internal stress and improve the conductivity of the particles.

9. The method for preparing an organic photoelectrochemical transistor DNA sensor based on a Schottky structure gate electrode according to claim 6, characterized in that: The step of preparing two spaced-apart gold plating layers on the smooth surface of the n-type doped silicon substrate comprises: A single layer of polystyrene nanospheres with a particle size of 300 nm was spin-coated on the surface of an n-type doped silicon substrate, and the polystyrene nanospheres were shrunk to a particle size of 150 nm by oxygen plasma etching to serve as a mask. Argon was used as the sputtering gas, the magnetron sputtering power was controlled to be 70-90W, and the deposition rate was The gold coating is sputtered to a thickness of 15-30 nm, and then the polystyrene mask is removed to form a periodic nanopore array gold coating. The gold coating is further annealed to promote the migration of gold atoms, and the pore walls shrink to form a nanoparticle gold coating with a particle size of 50±5 nm.

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