A kind of nuclide concentration sensor suitable for hypergravity environment

Abstract

The application discloses a nuclide concentration sensor suitable for a hypergravity environment, which comprises a packaging shell, a thin film sensing layer and a signal processing and transmission unit; the thin film sensing layer comprises a selected ion permeation layer, a sensitive unit layer and a substrate layer which are sequentially connected; a signal acquisition unit connected with the signal processing and transmission unit is arranged between the sensitive unit layer and the substrate layer; carboxylated nanochannels on the selected ion permeation layer, vertical pores on the sensitive unit layer and micropores on the substrate layer are sequentially and mutually communicated; an upper through hole on the packaging shell, an acquisition area of the above-mentioned pores on the thin film sensing layer and a lower through hole on the packaging shell are completely overlapped, so that the acquisition area of the thin film sensing layer is communicated with the outside of the packaging shell, and other parts of the thin film sensing layer and the signal processing and transmission unit are completely sealed in the inside of the packaging shell. The application is of a thin film structure, small in size, capable of meeting the test requirements of a hypergravity model, and realizing rapid detection of nuclide ion concentration in a solution with high detection precision.

Description

Technical Field

[0001] This invention relates to the field of liquid concentration sensor technology, specifically a nuclide concentration sensor suitable for use in hypergravity environments. Background Technology

[0002] The necessity of conducting radionuclide monitoring within geological barriers stems from their crucial role in the safe disposal of nuclear waste and environmental protection. Geological barriers (such as the surrounding rock and engineering barriers of deep-seated repositories) are designed to prevent the migration of radionuclides into the biosphere, but their long-term stability can be affected by complex geological processes such as groundwater activity, tectonic movements, or chemical corrosion. By systematically monitoring the migration behavior, concentration distribution, and barrier integrity of radionuclides (such as uranium, plutonium, and cesium), the barrier's effectiveness can be assessed in real time, potential leakage risks can be warned, and a scientific basis can be provided for the long-term safety of nuclear waste repositories. This monitoring is not only a core requirement of international nuclear safety standards but also an essential technical means to protect public health, maintain the ecological environment, and address future geological changes.

[0003] The multi-scale geometric features of fissures in geological barriers are complex, and conventional methods cannot reproduce the original gradient stress field / hydraulic field. In order to restore, monitor and evaluate the migration law of nuclides in geological barriers over thousands of years, it is proposed to conduct nuclide concentration monitoring in a model test under hypergravity environment.

[0004] In hypergravity environments, the migration of nuclides within fractured geological barriers is extremely slow, resulting in low solution conductivity (for nuclide solutions, including those containing Eu). 2+ I - Re 4+ UO2 2+ The changes in plasma concentration in the solution are extremely subtle (resolution needs to reach 0.01 μS / cm), and the nuclide concentration monitoring accuracy needs to reach 0.01 mol / L. Traditional conductivity sensors generally struggle to maintain accuracy due to mechanical deformation at high g values. Furthermore, the sensor must meet the requirements of miniaturization (sensitive element ≤ 5mm × 5mm, thickness < 0.5mm) and flexibility (fitting a 0.1mm fracture opening), and operate stably for long periods under solution corrosion and radioactive environments. Traditional ion concentration sensors have limited applications in nuclide concentration investigation. In hypergravity model experiments, especially at high g values, the model experiment size is hundreds or thousands of times smaller than in-situ experiments. An excessively large sensor size would affect the flow rate of the nuclide solution in the geological fractures of the model experiment, thus impacting the accuracy of the model experiment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a nuclide concentration sensor suitable for hypergravity environments. The sensing part is a thin-film structure, which is small in size, meets the experimental requirements of hypergravity models, and realizes rapid detection of nuclide ion concentration in solution with high detection accuracy.

[0006] The technical solution of this invention is as follows:

[0007] A nuclide concentration sensor suitable for hypergravity environments includes a package shell, a thin-film sensing layer and a signal processing and transmission unit disposed within the package shell.

[0008] The thin film sensing layer includes a selective ion permeable layer, a sensitive unit layer and a substrate layer connected sequentially from top to bottom. A signal acquisition unit is disposed between the sensitive unit layer and the substrate layer. The electrode wire of the signal acquisition unit passes through the sensitive unit layer and the substrate layer and is connected to the signal processing and transmission unit.

[0009] The selected ion permeation layer is a PI film, and a collection area is provided on the PI film. Carboxylated nanopores are provided on the collection area of ​​the PI film, and each carboxylated nanopore contains a nuclide ion selective molecule.

[0010] The sensitive unit layer is a graphene-MnO2 heterojunction film. A amine oxime group is introduced on the MnO2 surface of the graphene-MnO2 heterojunction film. Vertical channels are etched on the graphene-MnO2 heterojunction film, and the inner wall of each vertical channel is modified with a hydrophilic polymer.

[0011] The substrate layer is a graphene / hexagonal boron nitride heterostructure stacked layer, and a collection area is also provided on the graphene / hexagonal boron nitride heterostructure stacked layer. Micropores are etched on the collection area of ​​the graphene / hexagonal boron nitride heterostructure stacked layer.

[0012] The carboxylated nanopores, vertical pores, and micropores are sequentially interconnected. The top plate of the encapsulation shell has an upper through hole, and the bottom plate of the encapsulation shell has a lower through hole. The upper through hole, the collection area of ​​the aforementioned pores in the thin film sensing layer, and the lower through hole completely overlap, so that the collection area of ​​the thin film sensing layer is connected to the outside of the encapsulation shell, and the other parts of the thin film sensing layer and the signal processing and transmission unit are completely sealed inside the encapsulation shell.

[0013] The method for preparing the selective ion-permeable layer specifically includes the following steps:

[0014] S11. A high-energy heavy ion beam is used to vertically bombard the collection area of ​​the PI film to form a latent track, which penetrates from the incident surface of the PI film to the other side.

[0015] S12. The two sides of the PI film bombarded by high-energy heavy ion beam are irradiated with ultraviolet light respectively.

[0016] S13. Place the PI film irradiated by ultraviolet light in an H-type electrolytic cell, add etching solution to both sides, apply a constant voltage, and control the etching process by monitoring the current change, thereby etching multiple carboxylated nanopores that penetrate both sides of the PI film. After etching, the carboxyl groups on the inner wall of the carboxylated nanopores are retained and stabilized by chemical cleaning.

[0017] S14. Immerse the etched PI film in a mixed solution of EDC and NHSS to activate the carboxyl groups on the inner wall of the nanopores.

[0018] S15. Selective molecular modification of nuclide ions is fixed on the inner wall of carboxylated nanopores to achieve selective affinity of nuclides.

[0019] The high-energy heavy ion beam is selected from either a high-energy xenon ion beam or a high-energy argon ion beam; the ion energy of the high-energy heavy ion beam is 1-10 MeV, and the bombardment density is 10-1. 8 -10 10 ions / cm 2 ;

[0020] The ultraviolet light irradiation has a wavelength of 254 nm and an intensity of 1-5 mW / cm. 2 The irradiation time is 30-60 minutes;

[0021] The etching solutions on both sides of the H-type electrolytic cell are NaOH solution or KOH solution, and the applied constant voltage is 1.0V. The chemical cleaning after etching is performed using HCl solution.

[0022] The radionuclide ion-selective molecules mentioned are azo-G4-DNA molecules, G4-DNA molecules, crown ether molecules, or calixarenes.

[0023] The method for preparing the sensitive unit layer specifically includes the following steps:

[0024] S21. A nanoscale MnO2 layer with a thickness of less than 50 nm was deposited on the surface of graphene using atomic layer deposition.

[0025] S22. A uniform MnO2 layer is further prepared on the graphene surface on which a nano-scale MnO2 layer has been deposited using the sol-gel method, and the heterojunction structure is solidified to form a graphene-MnO2 heterojunction composite layer.

[0026] S23. Modify the surface of the graphene-MnO2 heterojunction composite layer with a amine oxime group;

[0027] S24. Multiple vertical channels are etched on the surface-modified graphene-MnO2 heterojunction composite layer using reactive ion etching or laser ablation. The vertical channels penetrate both sides of the graphene-MnO2 heterojunction composite layer, and the inner wall of each vertical channel is modified with a hydrophilic polymer.

[0028] The specific steps for further preparing a uniform MnO2 layer on the graphene surface after deposition of a nano-sized MnO2 layer using the sol-gel method are as follows: dissolve manganese salt in a solvent to obtain a precursor solution, then drop-coat or spin-coat the precursor solution onto the graphene surface after deposition of the nano-sized MnO2 layer, control the coating thickness to be 50-100 nm, bake the coating at 80-100 °C for 1-2 hours, and then anneal at 200-300 °C for 2-4 hours to convert the gel into crystalline MnO2 with a particle size of 10-20 nm.

[0029] The specific steps for modifying the surface of the graphene-MnO2 heterojunction composite layer with ammonia oxime groups are as follows: First, the surface of the graphene-MnO2 heterojunction composite layer is treated with oxygen plasma to generate hydroxyl groups on the surface of the graphene-MnO2 heterojunction composite layer; then, the graphene-MnO2 heterojunction composite layer is immersed in an ethanol solution containing 3-aminopropyltriethoxysilane and reacted at 60°C for 4-6 hours to form -(CH2)3-NH2 groups on the surface of the graphene-MnO2 heterojunction composite layer; then, the graphene-MnO2 heterojunction composite layer is further modified with ammonia oxime groups. The O2 heterojunction composite layer is immersed in a dimethylformamide solution containing acrylonitrile, a catalyst is added, and the reaction is carried out at 50-70℃ for 6-12 hours to form -(CH2)3-NH-(CH2)2-CN groups. Finally, the graphene-MnO2 heterojunction composite layer with cyano groups on its surface is immersed in a solution containing hydroxylamine hydrochloride and reacted at 60℃ for 4-8 hours to convert the cyano groups into amylopectin groups. After washing with deionized water and ethanol, it is dried at 80℃, thereby modifying the surface of the graphene-MnO2 heterojunction composite layer with amylopectin groups.

[0030] The signal acquisition unit includes a platinum resistance thermometer thin-film temperature sensor disposed between the sensing unit layer and the substrate layer acquisition area, an IrO2-pH electrode unit, an internal electrode pair, and an external electrode pair. The platinum resistance thermometer thin-film temperature sensor and the IrO2-pH electrode unit are respectively connected to the signal processing and transmission unit after passing through the sensing unit layer and the substrate layer through corresponding electrode wires. The inner ends of the internal electrode pair and the external electrode pair are located between the sensing unit layer and the substrate layer acquisition area, and the outer ends of the internal electrode pair and the external electrode pair pass through the outside of the sensing unit layer and the substrate layer acquisition area and are connected to the signal processing and transmission unit. A known current is applied to the internal electrode pair, and the voltage between the external electrode pairs is measured to calculate the solution conductivity.

[0031] The signal processing and transmission unit calculates the real-time ion concentration of the solution using the real-time temperature value collected by the platinum resistance film temperature sensor under hypergravity conditions, the pH value of the solution collected by the IrO2-pH electrode unit, and the calculated solution conductivity.

[0032] Under hypergravity conditions, the relationship between real-time temperature, pH, solution conductivity, and real-time ion concentration satisfies the following equation (1):

[0033]

[0034] In equation (1), Λ represents the molar conductivity of the solution measured under hypergravity conditions, with units of S·cm. 2 / mol; Λ0 represents the molar conductivity of the solution at infinite dilution, which is a constant; e represents the elementary charge, which is 1.602 × 10⁻⁶. -19 C;z - and z + , representing the charge numbers of the positive and negative ions of the nuclide in the solution, respectively; 3π is a mathematical constant used to describe the resistance to ion migration, with a value of 3 times 3.1415926; b represents the viscosity constant of the solution under hypergravity conditions, b = 1.05 when the hypergravity acceleration is 200g, and b = 1.08 when the hypergravity acceleration is 300g; η represents the viscosity of the solvent, in Pa·s; k1 represents the influence coefficient of pH value on ion migration under hypergravity conditions. pH 测 This represents the pH value of the solution collected by the IrO2-pH electrode unit under hypergravity conditions. 常 The pH value of the solution is measured under constant gravity; N A This represents Avogadro's constant, with a value of 6.022 × 10²³ mol. -1 k2 represents the coefficient of influence of temperature on ion migration. T 测 T represents the real-time temperature value collected by a platinum resistance thermometer thin-film temperature sensor under hypergravity conditions. 常 K represents the temperature of the solution measured under constant gravity. B This represents the Boltzmann constant, with a value of 1.381 × 10⁻⁶. -23 J / K; ε0 represents the vacuum permittivity, which is a constant; ε γ The relative permittivity of the solvent is represented by ; k represents the Debye constant of the solution. I represents the nuclide ion intensity; a represents the effective diameter of the nuclide ion, with a value of 0.3–0.5 nm; k3 represents the influence coefficient of the carboxylated nanopores of the selected ion permeability layer and the vertical channels of the sensitive unit layer on the ion migration rate in the solution, with a value of 0.95; λ + 0 and λ- 0 β represents the limiting molar conductivity of the nuclide positive and negative ions in the solution at infinite dilution, respectively, and is a constant value; β represents the error of the signal acquisition unit in the hypergravity environment, with a value of 0.95 to 1; C represents the real-time ion concentration of the solution in the hypergravity environment.

[0035] The carboxylated nanopores have a pore size of 2-50 nm, and the density of the carboxylated nanopores in the selective ion permeation layer collection region is 10. 5 -10 6 Hole / cm 2 The vertical channels have a diameter of 500-1000 nm, and the density of the vertical channels on the sensitive unit layer is 10. 3 -10 4 Hole / cm 2 The micropores have a pore size of 10-100 μm and a density of 10-1 micropores on the substrate. 2 -10 3 Hole / cm 2 .

[0036] The encapsulation shell is an epoxy resin encapsulation shell. The epoxy resin encapsulation shell encapsulates and seals the thin film sensing layer and the signal processing and transmission unit, and tightly presses together the selective ion permeable layer, the sensitive unit layer, the substrate layer, and the signal acquisition unit of the thin film sensing layer. The edge of the encapsulation shell located on the outer periphery of the upper through hole is sealed to the selective ion permeable layer of the thin film sensing layer, and the edge of the encapsulation shell located on the outer periphery of the lower through hole is sealed to the substrate layer of the thin film sensing layer.

[0037] The signal processing and transmission unit includes a surface-mount processing chip and a surface-mount wireless module that are interconnected. The surface-mount processing chip processes the data collected by the signal acquisition unit to obtain the real-time ion concentration of the solution, and then transmits the real-time ion concentration of the solution to the host computer through the surface-mount wireless module via a wireless communication network.

[0038] Advantages of this invention:

[0039] (1) The acquisition part of the present invention is a thin film sensing layer, the signal processing and transmission unit is a patch structure, and it is sealed with an epoxy resin encapsulation shell. Only the acquisition area of ​​the thin film sensing layer is exposed to allow liquid to enter and exit. The overall structure is small in size, meets the experimental requirements of the hypergravity model, and can work stably for a long time in the environment of solution erosion and radioactivity.

[0040] (2) The present invention has carboxylated nanopores on the collection area of ​​the selective ion permeation layer. Each carboxylated nanopore contains a nuclide ion-selective molecule. The carboxyl group provides an active site for subsequent modification of the nuclide ion-selective molecule and is used to fix the nuclide ion-selective molecule. The specific nuclide ion-selective molecule is selected according to the nuclide molecule to be collected, so that the selective ion permeation layer isolates the influence of large particulate impurities in the solution and has selective permeability to the target nuclide ion, thereby improving the accuracy of nuclide concentration collection and detection.

[0041] (3) The sensitive unit layer of this invention is a graphene-MnO2 heterojunction film, and the high carrier mobility of graphene (>10) 4 cm 2 The pseudocapacitive properties of graphene (V·s) and MnO2 work synergistically to convert changes in ion concentration into high-amplitude electrical signals (such as changes in current or impedance). Furthermore, the Fermi level difference between graphene (metal-like) and MnO2 (semiconductor) at the interface forms a Schottky barrier, leading to charge transfer and barrier formation. This Schottky barrier filters out background interference currents (such as random migration noise from impurity ions in solution), improving the signal-to-noise ratio (SNR>50dB). This significantly enhances nuclide selectivity, conductivity sensitivity (increasing by 2-3 orders of magnitude), and resistance to high-g interference. The high mechanical strength of graphene combined with the toughness of the MnO2 nanolayer ensures stable interfacial contact resistance between the sensitive unit layer and the signal acquisition unit under hypergravity conditions, preventing signal drift caused by mechanical deformation. The introduction of amine oxime groups on the MnO2 surface of the graphene-MnO2 heterojunction film further enhances the effect of amine oxime on UO2. 2+ Nuclide has high affinity, which enhances selective adsorption and significantly increases the local concentration of nuclide ions in the sensitive unit layer (enrichment factor >100 times), thereby amplifying the response signal of the signal acquisition unit electrode. Vertical channels are etched on the graphene-MnO2 heterojunction film, and the inner wall of each vertical channel is modified with a hydrophilic polymer. The vertical channel array is responsible for rapidly transporting the enriched nuclide solution to the electrode layer for signal detection. The hydrophilic polymer enhances the transmission rate of the nuclide solution.

[0042] (4) The signal processing and transmission unit of the present invention calculates the real-time ion concentration of the solution by means of the real-time temperature value collected by the platinum resistance film temperature sensor under hypergravity, the pH value of the solution collected by the IrO2-pH electrode unit, and the solution conductivity collected by the internal electrode pair and the external electrode pair. The real-time ion concentration of the solution under hypergravity is highly accurate and has high detection precision.

[0043] (5) The base layer of the present invention is a graphene / hexagonal boron nitride heterostructure stacked layer. Graphene provides conductivity and mechanical support, while hexagonal boron nitride serves as an insulating layer to achieve ion-selective shielding. The micropores on the graphene / hexagonal boron nitride heterostructure stacked layer enable instantaneous free diffusion of the solution after detection.

[0044] (6) The carboxylated nanopores, vertical pores and micropores on the thin film sensing layer of the present invention have progressively larger pore sizes and progressively smaller arrangement densities, and are connected vertically. They drive the solution to flow downward through capillary action, avoiding liquid stagnation. This can quickly achieve the purpose of selective ion permeation layer screening ions, sensitive unit layer transporting solution, and base layer rapidly diffusing the detected solution. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of the present invention.

[0046] Figure 2 This is a schematic diagram of the planar structure of the selective ion permeation layer of this invention.

[0047] Figure 3 This is a schematic diagram of the planar structure of the sensitive unit layer of the present invention.

[0048] Figure 4 This is a schematic diagram of the planar structure of the signal processing and transmission unit of the present invention connected below the sensitive unit layer.

[0049] Figure 5 This is a schematic diagram of the planar structure of the base layer of the present invention.

[0050] Figure 6 This is a schematic diagram of the structure in which the carboxylated nanopores on the selected ion-permeable layer, the vertical pores on the sensitive unit layer, and the micropores on the substrate layer are interconnected.

[0051] Reference numerals: 1-Epoxy resin encapsulation shell, 21-Selective ion permeation layer, 22-Sensitive unit layer, 23-Signal acquisition unit, 24-Base layer, 31-Surface mount processing chip, 32-Surface mount wireless module, 211-PI film, 212-Carboxylated nanopores, 221-Graphene-MnO2 heterojunction film, 222-Vertical pores, 231-Platinum resistance thermometer film-type temperature sensor, 232-IrO2-pH electrode unit, 233-Internal electrode pair, 234-External electrode pair, 241-Graphene / hexagonal boron nitride heterostructure stacked layer, 242-Micropores. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] See Figure 1 A nuclide concentration sensor suitable for hypergravity environments includes an epoxy resin encapsulation shell 1, a thin film sensing layer and a signal processing and transmission unit disposed within the epoxy resin encapsulation shell.

[0054] The thin-film sensing layer includes a selective ion permeable layer 21, a sensitive unit layer 22, and a substrate layer 24 connected sequentially from top to bottom. A signal acquisition unit 23 is disposed between the sensitive unit layer 22 and the substrate layer 24. The signal processing and transmission unit includes a surface-mount processing chip 31 and a surface-mount wireless module 32 connected to each other. The electrode wires of the signal acquisition unit 23 pass through the space between the sensitive unit layer 22 and the substrate layer 24 and are connected to the surface-mount processing chip 31. The surface-mount processing chip 31 processes the data acquired by the signal acquisition unit 23 to obtain the real-time ion concentration of the solution, and then transmits the real-time ion concentration of the solution to the host computer through the surface-mount wireless module 32 via a wireless communication network.

[0055] The epoxy resin encapsulation shell 1 encapsulates and seals the thin-film sensing layer and the signal processing and transmission unit, and tightly presses together the selective ion permeable layer 21, the sensitive unit layer 22, the substrate layer 24, and the signal acquisition unit 23 of the thin-film sensing layer. The top plate of the epoxy resin encapsulation shell 1 is provided with an upper through hole 11, and the bottom plate of the epoxy resin encapsulation shell 1 is provided with a lower through hole 12. The edge of the epoxy resin encapsulation shell 1 located on the outer periphery of the upper through hole 11 is sealed to the selective ion permeable layer 21, and the edge of the epoxy resin encapsulation shell 1 located on the outer periphery of the lower through hole is sealed to the substrate layer 24, so that the acquisition area of ​​the thin-film sensing layer is connected to the outside of the epoxy resin encapsulation shell 1, and the other parts of the thin-film sensing layer and the signal processing and transmission unit are completely sealed inside the epoxy resin encapsulation shell 1.

[0056] See Figure 2 The ion-permeable layer 21 is selected as a PI membrane 211, on which a circular collection area is provided. Carboxylated nanopores 212 are provided in the collection area of ​​the PI membrane 211, and each carboxylated nanopore 212 contains a nuclide ion-selective molecule. The preparation method of the selected ion-permeable layer specifically includes the following steps:

[0057] S11. A high-energy heavy ion beam is used to vertically bombard the collection area of ​​the PI film 211 to form a latent track, and the latent track penetrates from the incident surface of the PI film 211 to the other side.

[0058] S12. The two sides of the PI film 211 after being bombarded by a high-energy heavy ion beam are irradiated with ultraviolet light at a wavelength of 254 nm and an intensity of 1-5 mW / cm. 2 The irradiation time for each side is 30-60 minutes;

[0059] S13. Place the PI film 211 after UV irradiation in an H-type electrolytic cell, add etching solution (NaOH solution or KOH solution) to both sides, apply a constant voltage (1.0V), and control the etching process by monitoring the current change, thereby etching multiple carboxylated nanopores 212 that penetrate both sides of the PI film on the PI film 211. After etching, the carboxyl groups on the inner wall of the carboxylated nanopores 212 are retained and stabilized by chemical cleaning (HCl solution).

[0060] S14. Immerse the etched PI film in a mixed solution of EDC and NHSS to activate the carboxyl groups on the inner wall of the carboxylated nanopores 212.

[0061] S15. Selective ion-selective molecular modification and fixation are performed on the inner wall of carboxylated nanopores 212 to achieve selective affinity of nuclides. The nuclide-selective molecules are azo-G4-DNA molecules, G4-DNA molecules, crown ether molecules, or calixarenes. The azo group in the azo-G4-DNA molecule can enhance photoresponsiveness and is suitable for selective affinity of uranium ions. The G4-DNA molecule contains K+ ions. + Cs + Monovalent cations have high affinity, making them suitable for monitoring nuclides such as cesium; crown ether molecules or calixarenes have high affinity for Pu. 4+ Am 3+ Nuclide selection is optimized.

[0062] See Figure 3 The sensitive unit layer 22 is a circular graphene-MnO2 heterojunction film that completely overlaps with the collection area of ​​the PI film 211. Amine oxime groups are introduced onto the MnO2 surface of the graphene-MnO2 heterojunction film to generate a surface-modified graphene-MnO2 heterojunction composite layer 221. Vertical channels 222 are etched on the graphene-MnO2 heterojunction film 221, and the inner wall of each vertical channel 222 is modified with a hydrophilic polymer. The preparation method of the sensitive unit layer 22 specifically includes the following steps:

[0063] S21. A nanoscale MnO2 layer with a thickness of less than 50 nm is deposited on the surface of graphene using atomic layer deposition (ALD). ALD ensures that MnO2 covers the graphene, forming a high-quality interface and reducing the interference of defect states on the potential barrier. Charge transfer (electrons from graphene to MnO2) at the interface between MnO2 and graphene directly leads to the generation of the potential barrier.

[0064] S22. A uniform MnO2 layer is further prepared on the graphene surface with a deposited nano-sized MnO2 layer using the sol-gel method, and the heterojunction structure is solidified to form a graphene-MnO2 heterojunction composite layer. Specifically, manganese salt (Mn(CH3COO)2·4H2O, concentration 0.1-0.5M) is first dissolved in a solvent (ethanol or isopropanol), and a stabilizer (such as urea or citric acid, concentration 0.05-0.1M) is added to control the precipitation rate of MnO2 to obtain a precursor solution. Then, the precursor solution is drop-coated or spin-coated (spin-coating speed 2000-3000 rpm) onto the graphene surface with the deposited nano-sized MnO2 layer. On the surface, the coating thickness is controlled to be 50-100 nm, and then the coating is baked at 80-100℃ for 1-2 hours to promote sol-gelation and form a MnO2 gel network. Then, it is annealed at 200-300℃ for 2-4 hours (under nitrogen or argon protection, annealing rate of 5℃ / min to avoid thermal stress damaging the graphene structure) to convert the gel into crystalline MnO2 with a particle size of 10-20 nm. The sol-gel method increases the thickness of the MnO2 layer and improves the crystal structure, reduces the interfacial resistance, and improves the electrical stability of the barrier. The annealing process optimizes the interfacial bonding, reduces trapped states, and further stabilizes the barrier height.

[0065] S23. Modify the surface of the graphene-MnO2 heterojunction composite layer with a amine oxime group. The specific steps are as follows: First, treat the surface of the graphene-MnO2 heterojunction composite layer with oxygen plasma (power 50-100W, treatment time 5-10 minutes) to generate hydroxyl groups on the surface of the graphene-MnO2 heterojunction composite layer. The reaction formula for the generation of hydroxyl groups is: Mn-O· + H2O → Mn-OH + OH·; Then, immerse the graphene-MnO2 heterojunction composite layer in 3-aminopropyltriethoxysilane ((NH2)(CH2)3Si(O) In a 1-5 vol% ethanol solution of APTES (CH2CH3)3, reacted at 60°C for 4-6 hours, -(CH2)3-NH2 groups are formed on the surface of the graphene-MnO2 heterojunction composite layer. First, the ethoxy group (-OCH2CH3) of APTES hydrolyzes to generate a silanol group (Si-OH). Then, the silanol group and hydroxyl group condense, with the reaction formula: (HN2)(CH2)3Si(OH)3 + MnO2-OH → MnO2-O-Si-(CH2)3-HN2 + H2O. Then, graphene... The MnO2 heterojunction composite layer is immersed in a DMF solution containing acrylonitrile (0.1-0.5M), and a triethylamine catalyst (0.01M) is added. The reaction is carried out at 50-70℃ for 6-12 hours to form -(CH2)3-NH-(CH2)2-CN groups. The reaction formula is: MnO2-O-Si-(CH2)3-HN2 + CH2=CHCN → MnO2-O-Si-(CH2)3-HN-(CH2)2CN. Finally, the graphene-MnO2 heterojunction composite layer with cyano groups on its surface is immersed in a solution containing hydroxylamine hydrochloride. In a 0.1-0.5M, pH: 6-7 water / ethanol solution, the reaction was carried out at 60℃ for 4-8 hours to convert the cyano group into a amine oxime group (-C(NH2)=NOH). The reaction formula is: MnO2-O-Si-(CH2)3-HN-(CH2)2CN+NH2OH→MnO2-O-Si-(CH2)3-HN-(CH2)2C-(NH2)=NOH. After washing with deionized water and ethanol, the product was dried at 80℃, thereby modifying the surface of the graphene-MnO2 heterojunction composite layer with amine oxime groups.

[0066] S24. Multiple vertical channels 222 are etched on the surface-modified graphene-MnO2 heterojunction composite layer using reactive ion etching or laser ablation. The vertical channels 222 penetrate both sides of the graphene-MnO2 heterojunction composite layer, and the inner wall of each vertical channel 222 is modified with a hydrophilic polymer (such as polyethylene glycol).

[0067] See Figure 4The signal acquisition unit 23 includes a platinum resistance thermometer thin-film temperature sensor 231 disposed between the acquisition area of ​​the sensitive unit layer 22 and the substrate layer 24, an IrO2-pH electrode unit 232, an internal electrode pair 233 (Au electrode, with excellent stability and corrosion resistance), and an external electrode pair 234 (Ti electrode, with good stability and corrosion resistance). The platinum resistance thermometer thin-film temperature sensor 231 and the IrO2-pH electrode unit 232 pass through the sensitive unit layer 22 and the substrate layer 24 through corresponding electrode wires and are then connected to the patch-type interface of the signal processing and transmission unit. The chip 31 is connected accordingly. The inner ends of the internal electrode pair 233 and the external electrode pair 234 are located between the acquisition areas of the sensitive unit layer 22 and the base layer 24. The outer ends of the internal electrode pair 233 and the external electrode pair 234 extend out to the outside of the acquisition areas of the sensitive unit layer 22 and the base layer 24 and are connected to the surface-mount processing chip 31 of the signal processing and transmission unit. A known alternating current (frequency 1-10kHz, amplitude 1-10μA) is applied to the internal electrode pair, the voltage between the external electrode pair is measured, and the solution conductivity is calculated by Ohm's law and the electrode geometric constant.

[0068] The surface-mount processing chip 31 calculates the real-time ion concentration of the solution by using the real-time temperature value collected by the platinum resistance film temperature sensor under hypergravity, the pH value of the solution collected by the IrO2-pH electrode unit, and the collected and calculated solution conductivity.

[0069] Under hypergravity conditions, the relationship between real-time temperature, pH, solution conductivity, and real-time ion concentration satisfies the following equation (1):

[0070]

[0071] In equation (1), Λ represents the molar conductivity of the solution measured under hypergravity conditions, with units of S·cm. 2 / mol; Λ0 represents the molar conductivity of the solution at infinite dilution, which is a constant; e represents the elementary charge, which is 1.602 × 10⁻⁶. -19 C;z - and z + , representing the charge numbers of the positive and negative ions of the nuclide in the solution, respectively; 3π is a mathematical constant used to describe the resistance to ion migration, with a value of 3 times 3.1415926; b represents the viscosity constant of the solution under hypergravity conditions, b = 1.05 when the hypergravity acceleration is 200g, and b = 1.08 when the hypergravity acceleration is 300g; η represents the viscosity of the solvent, in Pa·s; k1 represents the influence coefficient of pH value on ion migration under hypergravity conditions. pH 测 This represents the pH value of the solution collected by the IrO2-pH electrode unit under hypergravity conditions. 常The pH value of the solution is measured under constant gravity; N A This represents Avogadro's constant, with a value of 6.022 × 10²³ mol. -1 k2 represents the coefficient of influence of temperature on ion migration. T 测 T represents the real-time temperature value collected by a platinum resistance thermometer thin-film temperature sensor under hypergravity conditions. 常 K represents the temperature of the solution measured under constant gravity. B This represents the Boltzmann constant, with a value of 1.381 × 10⁻⁶. -23 J / K; ε0 represents the vacuum permittivity, which is a constant; ε γ The relative permittivity of the solvent is represented by ; k represents the Debye constant of the solution. I represents the nuclide ion intensity; a represents the effective diameter of the nuclide ion, with a value of 0.3–0.5 nm; k3 represents the influence coefficient of the carboxylated nanopores of the selected ion permeability layer and the vertical channels of the sensitive unit layer on the ion migration rate in the solution, with a value of 0.95; λ + 0 and λ - 0 β represents the limiting molar conductivity of the nuclide positive and negative ions in the solution at infinite dilution, respectively, and is a constant value; β represents the error of the signal acquisition unit in the hypergravity environment, with a value of 0.95 to 1; C represents the real-time ion concentration of the solution in the hypergravity environment.

[0072] See Figure 5 The substrate 24 is a graphene / hexagonal boron nitride heterostructure stacked layer 241. A circular collection area is also provided on the graphene / hexagonal boron nitride heterostructure stacked layer 241, which completely overlaps with the collection area of ​​the sensitive unit layer 22 and the selected ion permeation layer 21. Micropores 242 are etched on the collection area of ​​the graphene / hexagonal boron nitride heterostructure stacked layer 241.

[0073] See Figure 6 Carboxylated nanopores 212, vertical pores 222, and micropores 242 are sequentially interconnected. The pore size of the carboxylated nanopores 212 is 2-50 nm, and the density of the carboxylated nanopores 212 in the selective ion permeation layer 21 collection area is 10. 5 -10 6 Hole / cm 2 The pore size of the vertical channel 222 is 500-1000 nm, and the density of the vertical channel 222 on the sensitive unit layer 22 is 10. 3 -10 4 Hole / cm 2 The pore size of microchannel 242 is 10-100 μm, and the density of microchannel 242 on the substrate layer 24 is 10. 2 -103 Hole / cm 2 .

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nuclide concentration sensor suitable for use in hypergravity environments, characterized in that: It includes a package housing, and a thin-film sensing layer and a signal processing and transmission unit disposed within the package housing; The thin film sensing layer includes a selective ion permeable layer, a sensitive unit layer and a substrate layer connected sequentially from top to bottom. A signal acquisition unit is disposed between the sensitive unit layer and the substrate layer. The electrode wire of the signal acquisition unit passes through the sensitive unit layer and the substrate layer and is connected to the signal processing and transmission unit. The selected ion permeation layer is a PI membrane, and a collection area is provided on the PI membrane. Carboxylated nanopores are provided on the collection area of ​​the PI membrane. Each carboxylated nanopore contains a nuclide ion-selective molecule, which is an azo-G4-DNA molecule, a G4-DNA molecule, a crown ether molecule, or a calixarene molecule. The sensitive unit layer is a graphene-MnO2 heterojunction film. A amine oxime group is introduced on the MnO2 surface of the graphene-MnO2 heterojunction film. Vertical channels are etched on the graphene-MnO2 heterojunction film, and the inner wall of each vertical channel is modified with a hydrophilic polymer. The substrate layer is a graphene / hexagonal boron nitride heterostructure stacked layer, and a collection area is also provided on the graphene / hexagonal boron nitride heterostructure stacked layer. Micropores are etched on the collection area of ​​the graphene / hexagonal boron nitride heterostructure stacked layer. The carboxylated nanopores, vertical pores, and micropores are sequentially interconnected. The top plate of the encapsulation shell has an upper through hole, and the bottom plate of the encapsulation shell has a lower through hole. The upper through hole, the collection area of ​​the aforementioned pores in the thin film sensing layer, and the lower through hole completely overlap, so that the collection area of ​​the thin film sensing layer is connected to the outside of the encapsulation shell, and the other parts of the thin film sensing layer and the signal processing and transmission unit are completely sealed inside the encapsulation shell.

2. The nuclide concentration sensor suitable for use in hypergravity environments according to claim 1, characterized in that: The method for preparing the selective ion-permeable layer specifically includes the following steps: S11. A high-energy heavy ion beam is used to vertically bombard the collection area of ​​the PI film to form a latent track, which penetrates from the incident surface of the PI film to the other side. S12. The two sides of the PI film bombarded by high-energy heavy ion beam are irradiated with ultraviolet light respectively. S13. Place the PI film irradiated by ultraviolet light in an H-type electrolytic cell, add etching solution to both sides, apply a constant voltage, and control the etching process by monitoring the current change, thereby etching multiple carboxylated nanopores that penetrate both sides of the PI film. After etching, the carboxyl groups on the inner wall of the carboxylated nanopores are retained and stabilized by chemical cleaning. S14. Immerse the etched PI film in a mixed solution of EDC and NHSS to activate the carboxyl groups on the inner wall of the nanopores. S15. Selective molecular modification of nuclide ions is fixed on the inner wall of carboxylated nanopores to achieve selective affinity of nuclides.

3. A radionuclide concentration sensor suitable for use in hypergravity environments according to claim 2, characterized in that: The high-energy heavy ion beam is selected from either a high-energy xenon ion beam or a high-energy argon ion beam; the ion energy of the high-energy heavy ion beam is 1-10 MeV, and the bombardment density is 10-1. 8 -10 10 ions / cm 2 ; The ultraviolet light irradiation has a wavelength of 254 nm and an intensity of 1-5 mW / cm. 2 The irradiation time is 30-60 minutes; The etching solutions on both sides of the H-type electrolytic cell are NaOH solution or KOH solution, and the applied constant voltage is 1.0V. The chemical cleaning after etching is performed using HCl solution.

4. A radionuclide concentration sensor suitable for use in hypergravity environments according to claim 2, characterized in that: The method for preparing the sensitive unit layer specifically includes the following steps: S21. A nanoscale MnO2 layer with a thickness of less than 50 nm was deposited on the surface of graphene using atomic layer deposition. S22. A uniform MnO2 layer is further prepared on the graphene surface on which a nano-scale MnO2 layer has been deposited using the sol-gel method, and the heterojunction structure is solidified to form a graphene-MnO2 heterojunction composite layer. S23. Modify the surface of the graphene-MnO2 heterojunction composite layer with a amine oxime group; S24. Multiple vertical channels are etched on the surface-modified graphene-MnO2 heterojunction composite layer using reactive ion etching or laser ablation. The vertical channels penetrate both sides of the graphene-MnO2 heterojunction composite layer, and the inner wall of each vertical channel is modified with a hydrophilic polymer.

5. A nuclide concentration sensor suitable for use in hypergravity environments according to claim 4, characterized in that: The specific steps for further preparing a uniform MnO2 layer on the graphene surface after deposition of a nano-sized MnO2 layer using the sol-gel method are as follows: dissolve manganese salt in a solvent to obtain a precursor solution, then drop-coat or spin-coat the precursor solution onto the graphene surface after deposition of the nano-sized MnO2 layer, control the coating thickness to be 50-100 nm, bake the coating at 80-100 °C for 1-2 hours, and then anneal at 200-300 °C for 2-4 hours to convert the gel into crystalline MnO2 with a particle size of 10-20 nm.

6. A nuclide concentration sensor suitable for use in hypergravity environments according to claim 4, characterized in that: The specific steps for modifying the surface of the graphene-MnO2 heterojunction composite layer with ammonia oxime groups are as follows: First, the surface of the graphene-MnO2 heterojunction composite layer is treated with oxygen plasma to generate hydroxyl groups on the surface of the graphene-MnO2 heterojunction composite layer; then, the graphene-MnO2 heterojunction composite layer is immersed in an ethanol solution containing 3-aminopropyltriethoxysilane and reacted at 60°C for 4-6 hours to form -(CH2)3-NH2 groups on the surface of the graphene-MnO2 heterojunction composite layer; then, the graphene-MnO2 heterojunction composite layer is further modified with ammonia oxime groups. The O2 heterojunction composite layer is immersed in a dimethylformamide solution containing acrylonitrile, a catalyst is added, and the reaction is carried out at 50-70℃ for 6-12 hours to form -(CH2)3-NH-(CH2)2-CN groups. Finally, the graphene-MnO2 heterojunction composite layer with cyano groups on its surface is immersed in a solution containing hydroxylamine hydrochloride and reacted at 60℃ for 4-8 hours to convert the cyano groups into amylopectin groups. After washing with deionized water and ethanol, it is dried at 80℃, thereby modifying the surface of the graphene-MnO2 heterojunction composite layer with amylopectin groups.

7. A nuclide concentration sensor suitable for use in hypergravity environments according to claim 4, characterized in that: The signal acquisition unit includes a platinum resistance thermometer thin-film temperature sensor disposed between the sensing unit layer and the substrate layer acquisition area, an IrO2-pH electrode unit, an internal electrode pair, and an external electrode pair. The platinum resistance thermometer thin-film temperature sensor and the IrO2-pH electrode unit are respectively connected to the signal processing and transmission unit after passing through the sensing unit layer and the substrate layer through corresponding electrode wires. The inner ends of the internal electrode pair and the external electrode pair are located between the sensing unit layer and the substrate layer acquisition area, and the outer ends of the internal electrode pair and the external electrode pair pass through the outside of the sensing unit layer and the substrate layer acquisition area and are connected to the signal processing and transmission unit. A known current is applied to the internal electrode pair, and the voltage between the external electrode pairs is measured to calculate the solution conductivity. The signal processing and transmission unit calculates the real-time ion concentration of the solution using the real-time temperature value collected by the platinum resistance film temperature sensor under hypergravity conditions, the pH value of the solution collected by the IrO2-pH electrode unit, and the calculated solution conductivity. Under hypergravity conditions, the relationship between real-time temperature, pH, solution conductivity, and real-time ion concentration in the solution satisfies the following equation (1): （1）； In equation (1), This represents the molar conductivity of the solution collected and measured under hypergravity conditions, expressed in S·cm² / mol. The molar conductivity, representing the infinite dilution of the solution, is a constant. Represents the elementary charge, with a value of 1.602 × 10⁻⁶. -19 C; and These represent the charge numbers of the positive and negative ions of the nuclide in the solution, respectively; The mathematical constant used to describe the resistance to ion migration is 3 times 3.1415926; This represents the viscosity constant of the solution under hypergravity conditions, when the hypergravity acceleration is 200g. When the acceleration due to gravity is 300g, ; The viscosity of the solvent is expressed in Pa·s. This represents the influence coefficient of pH value on ion migration under hypergravity conditions. , This represents the pH value of the solution collected by the IrO2-pH electrode unit under hypergravity conditions. This represents the pH value of the solution measured under constant gravity. This represents Avogadro's constant, with a value of 6.022 × 10²³ mol. -1 ; The coefficient representing the effect of temperature on ion migration. , This represents the real-time temperature value collected by a platinum resistance thermometer thin-film temperature sensor under hypergravity conditions. This represents the temperature of the solution measured under constant gravity. This represents the Boltzmann constant, with a value of 1.381 × 10⁻⁶. -23 J / K; Represents the vacuum permittivity, which is a constant. Represents the relative permittivity of the solvent; The Debye constant representing the solution. , The intensity of nuclide ions; The effective diameter of the nuclide ion is represented by a value of 0.3~0.5 nm. The coefficient representing the influence of the carboxylated nanopores of the selective ion-permeable layer and the vertical channels of the sensitive unit layer on the ion migration rate in the solution is λ, with a value of 0.

95. + 0 and λ − 0 These represent the limiting molar conductivity of the radionuclide positive and negative ions in the solution at infinite dilution, and are constant values. This represents the error in signal acquisition and detection by the signal acquisition unit under hypergravity conditions, with a value ranging from 0.95 to 1. This represents the real-time ion concentration of the solution under hypergravity conditions.

8. A radionuclide concentration sensor suitable for use in hypergravity environments according to claim 6, characterized in that: The carboxylated nanopores have a pore size of 2-50 nm, and the density of the carboxylated nanopores in the selective ion permeation layer collection region is 10. 5 -10 6 Hole / cm 2 The vertical channels have a diameter of 500-1000 nm, and the density of the vertical channels on the sensitive unit layer is 10. 3 -10 4 Hole / cm 2 The micropores have a pore size of 10-100 μm, and the density of the micropores on the substrate is 10. 2 -10 3 Hole / cm 2 .

9. A radionuclide concentration sensor suitable for use in hypergravity environments according to claim 6, characterized in that: The encapsulation shell is an epoxy resin encapsulation shell. The epoxy resin encapsulation shell encapsulates and seals the thin film sensing layer and the signal processing and transmission unit, and tightly presses together the selective ion permeable layer, the sensitive unit layer, the substrate layer, and the signal acquisition unit of the thin film sensing layer. The edge of the encapsulation shell located on the outer periphery of the upper through hole is sealed to the selective ion permeable layer of the thin film sensing layer, and the edge of the encapsulation shell located on the outer periphery of the lower through hole is sealed to the substrate layer of the thin film sensing layer.

10. A radionuclide concentration sensor suitable for use in hypergravity environments according to claim 7, characterized in that: The signal processing and transmission unit includes a surface-mount processing chip and a surface-mount wireless module that are interconnected. The surface-mount processing chip processes the data collected by the signal acquisition unit to obtain the real-time ion concentration of the solution, and then transmits the real-time ion concentration of the solution to the host computer through the surface-mount wireless module via a wireless communication network.

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