Nuclide concentration sensor suitable for supergravity environment

Abstract

The invention discloses a nuclide concentration sensor suitable for a supergravity environment. The nuclide concentration sensor comprises a packaging shell, a thin film sensing layer and a signal processing transmission unit, the film sensing layer comprises a selective ion permeation layer, a sensing unit layer and a substrate layer which are sequentially laminated, and a signal acquisition unit connected with the signal processing and transmitting unit is arranged between the sensing unit layer and the substrate layer; the carboxylated nano-pore channel on the selective ion permeation layer, the vertical pore channel on the sensing unit layer and the micro-pore channel on the substrate layer are sequentially communicated with one another, and the upper through hole on the packaging shell, the acquisition area of the pore channels arranged on the thin film sensing layer and the lower through hole on the packaging shell are completely overlapped. The acquisition area of the film sensing layer is communicated with the outside of the packaging shell, and other parts of the film sensing layer and the signal processing and transmitting unit are completely sealed in the packaging shell. The device is of a thin film type structure, is small in size, meets the test requirements of a supergravity model, achieves the rapid detection of the concentration of nuclide ions in a solution, and is high in detection precision.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid concentration sensors, and specifically to a nuclide concentration sensor applicable to a hypergravity environment. Background Art

[0002] The necessity of carrying out nuclide monitoring in geological barriers stems from its crucial role in the safe disposal of nuclear waste and environmental protection. Geological barriers (such as the surrounding rock and engineering barriers of deep geological repositories) are designed to block the migration of radionuclides to the biosphere, but their long-term stability may be affected by complex geological processes such as groundwater activity, tectonic movement, or chemical corrosion. By systematically monitoring the migration behavior, concentration distribution, and barrier integrity of nuclides (such as uranium, plutonium, cesium, etc.), the barrier's blocking efficiency can be evaluated 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. Such monitoring is not only a core requirement of international nuclear safety standards but also a necessary technical means to protect public health, maintain the ecological environment, and respond to future geological environmental changes.

[0003] The multi-scale geometric characteristics of fractures in geological barriers are complex, and conventional means cannot reproduce the original in-situ gradient stress field / hydraulic field. In order to restore, monitor, and evaluate the law of nuclide migration in geological barriers over tens of thousands of years, nuclide concentration monitoring is planned to be carried out in model tests under a hypergravity environment.

[0004] Under a hypergravity environment, the migration process of nuclides in fractured geological barriers is extremely slow, resulting in extremely weak changes in the solution conductivity (nuclide solutions, including solutions containing Eu 2+ , I - , Re 4+ , UO2 2+ and other plasma) (the 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 have difficulty maintaining accuracy due to mechanical deformation under high g-values. In addition, the sensor needs to meet miniaturization (sensitive unit ≤ 5 mm × 5 mm, thickness < 0.5 mm) and flexibility (fitting a fracture aperture of 0.1 mm), and work stably for a long time under solution erosion and radioactive environments. Traditional ion concentration sensors, on the one hand, have less exploration of nuclide concentration. Due to hypergravity model tests, especially under high g-values, the size of the model test is hundreds or thousands of times smaller than that of in-situ experiments. The too large size of the sensor will affect the flow rate of nuclide solutions in geological fractures of the model test and affect 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 applicable to a hypergravity environment. The acquisition and induction part is of a thin-film structure, small in size, meeting the test requirements of the hypergravity model, and realizing the rapid detection of nuclide ion concentration in the solution with high detection accuracy.

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

[0007] A nuclide concentration sensor applicable to a hypergravity environment, comprising a packaging shell, and a thin-film sensing layer and a signal processing and transmission unit disposed within the packaging shell;

[0008] The thin-film sensing layer includes a selective ion permeation layer, a sensitive unit layer, and a base layer connected in sequence from top to bottom. A signal acquisition unit is disposed between the sensitive unit layer and the base layer, and the electrode wires of the signal acquisition unit pass through between the sensitive unit layer and the base layer and are connected to the signal processing and transmission unit;

[0009] The selective ion permeation layer is a PI film, a collection area is provided on the PI film, and carboxylated nanopores are provided on the collection area of the PI film. A nuclide ion-selective molecule is disposed within each carboxylated nanopore;

[0010] The sensitive unit layer is a graphene-MnO2 heterojunction thin film. An amidoxime group is introduced on the surface of MnO2 of the graphene-MnO2 heterojunction thin film, and vertical pores are etched on the graphene-MnO2 heterojunction thin film. The inner wall of each vertical pore is modified with a hydrophilic polymer;

[0011] The base layer is a graphene / h-BN hetero-stacked layer, and a collection area is also provided on the graphene / h-BN hetero-stacked layer. Micropores are etched on the collection area of the graphene / h-BN hetero-stacked layer;

[0012] The carboxylated nanopores, the vertical pores, and the micropores are vertically and sequentially interconnected. An upper through-hole is provided on the top plate of the packaging shell, and a lower through-hole is provided on the bottom plate of the packaging shell. The upper through-hole, the collection area of the thin-film sensing layer provided with the above-mentioned pores, and the lower through-hole are completely overlapped, so that the collection area of the thin-film sensing layer is communicated with the outside of the packaging shell, and the other parts of the thin-film sensing layer and the signal processing and transmission unit are completely sealed inside the packaging shell.

[0013] The preparation method of the selective ion permeation layer specifically includes the following steps:

[0014] S11. Vertically bombard the collection area of the PI film with a high-energy heavy ion beam to form latent tracks, and the latent tracks penetrate from the incident surface of the PI film to the other surface;

[0015] S12. Perform ultraviolet light irradiation on both sides of the PI film bombarded by the high-energy heavy ion beam;

[0016] S13. Place the PI film after ultraviolet light irradiation in an H-type electrolytic cell, add etching solution to both sides, apply a constant voltage, and control the etching process by monitoring the change of current, so as to etch and form a plurality of carboxylated nanopores penetrating both sides of the PI film. After the etching is completed, the carboxyl groups on the inner wall of the carboxylated nanopores are retained and stabilized through 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 carboxylated nanopores;

[0018] S15. Select a nuclide ion-selective molecule to be immobilized on the inner wall of the carboxylated nanopores to achieve selective affinity for nuclides.

[0019] The high-energy heavy ion beam selected is 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 8 -10 10 ions / cm 2 ;

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

[0021] The etching solution on both sides in the H-type electrolytic cell is selected from NaOH solution or KOH solution, the applied constant voltage is 1.0 V, and the chemical cleaning after the etching is completed is carried out with HCl solution;

[0022] The nuclide ion-selective molecule is an azo-G4-DNA molecule, a G4-DNA molecule, a crown ether molecule or a calixarene molecule.

[0023] The preparation method of the sensitive unit layer specifically includes the following steps:

[0024] S21. Use atomic layer deposition to deposit a nanoscale MnO2 layer with a thickness less than 50 nm on the surface of graphene;

[0025] S22. Use the sol-gel method to further prepare a uniform MnO2 layer on the graphene surface deposited with the nanoscale MnO2 layer, cure the heterojunction structure, and form a graphene-MnO2 heterojunction composite layer;

[0026] S23. Modify the surface of the graphene-MnO2 heterojunction composite layer with amidoxime groups;

[0027] S24. On the surface-modified graphene-MnO2 heterojunction composite layer, use reactive ion etching or laser ablation to etch multiple vertical channels that penetrate both sides of the graphene-MnO2 heterojunction composite layer, and modify hydrophilic polymers on the inner walls of each vertical channel.

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

[0029] The specific steps for modifying amidoxime groups on the surface of the graphene-MnO2 heterojunction composite layer are as follows: first, treat the surface of the graphene-MnO2 heterojunction composite layer with peroxy plasma to generate hydroxyl groups on the surface of the graphene-MnO2 heterojunction composite layer; then immerse the graphene-MnO2 heterojunction composite layer in an ethanol solution containing 3-aminopropyltriethoxysilane and react at 60 °C for 4-6 hours to form -(CH2)3-NH2 groups on the surface of the graphene-MnO2 heterojunction composite layer; then immerse the graphene-MnO2 heterojunction composite layer in a dimethylformamide solution containing acrylonitrile, add a catalyst, and react at 50-70 °C for 6-12 hours to form -(CH2)3-NH-(CH2)2-CN groups; finally, immerse the graphene-MnO2 heterojunction composite layer with cyanide groups on the surface in a solution containing hydroxylamine hydrochloride and react at 60 °C for 4-8 hours to convert the cyanide groups into amidoxime groups, and then wash with deionized water and ethanol and dry at 80 °C to modify amidoxime groups on the surface of the graphene-MnO2 heterojunction composite layer.

[0030] The signal acquisition unit includes a platinum thin-film resistance temperature sensor, an IrO2-pH electrode unit, an internal electrode pair, and an external electrode pair arranged between the sensitive unit layer and the acquisition area of the base layer; the platinum thin-film resistance temperature sensor and the IrO2-pH electrode unit respectively pass through corresponding electrode wires between the sensitive unit layer and the base layer and are connected to the signal processing and transmission unit. The inner ends of the internal electrode pair and the external electrode pair are located between the sensitive unit layer and the acquisition area of the base layer, and the outer ends of the internal electrode pair and the external electrode pair pass out of the sensitive unit layer and the acquisition area of the base layer and are connected to the signal processing and transmission unit. Apply a known current to the internal electrode pair and measure the voltage between the external electrode pairs to calculate the solution conductivity.

[0031] The described signal processing and transmission unit calculates the real-time ion concentration of the solution based on the real-time temperature value collected by a platinum thin-film resistance temperature sensor, the pH value of the solution collected by an IrO2-pH electrode unit, and the conductivity of the solution collected and calculated under a hypergravity environment;

[0032] Under a hypergravity environment, the relationship between the real-time temperature value, pH value, solution conductivity, and real-time ion concentration of the solution satisfies the following formula (1):

[0033]

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

[0035] The pore diameter of the carboxylated nanopores is 2 - 50 nm, and the density of the carboxylated nanopores in the collection area of the selective ion permeation layer is 10 5 -10 6 pores / cm 2 ; The pore diameter of the vertical pores is 500 - 1000 nm, and the density of the vertical pores on the sensitive unit layer is 10 3 -10 4 pores / cm 2 ; The pore diameter of the microchannels is 10 - 100 μm, and the density of the microchannels on the base layer is 10 2 -10 3 pores / 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 and connects the selective ion permeation layer, the sensitive unit layer, the base layer and the signal acquisition unit of the thin film sensing layer. The edge part of the encapsulation shell located outside the upper through hole is hermetically connected to the selective ion permeation layer of the thin film sensing layer, and the edge part of the encapsulation shell located outside the lower through hole is hermetically connected to the base layer of the thin film sensing layer.

[0037] The signal processing and transmission unit includes a patch-type processing chip and a patch-type wireless module connected to each other. The patch-type processing chip processes the data collected by the signal acquisition unit to obtain the real-time ion concentration of the solution, and then sends the real-time ion concentration of the solution to the host computer through the patch-type wireless module via a wireless communication network.

[0038] Advantages of the present invention:

[0039] (1). The collection part of the present invention is a thin film sensing layer, the signal processing and transmission unit is of a patch type structure, and is sealed with an epoxy resin encapsulation shell. Only the collection area of the thin film sensing layer is exposed for liquid inlet and outlet. The overall structure is small in size, meets the test requirements of the hypergravity model, and can work stably for a long time under solution erosion and radioactive environments.

[0040] (2) A carboxylated nanopore is provided in the collection area of the ion permeable layer of the present invention. A nuclide ion selective molecule is provided inside each carboxylated nanopore. The carboxyl group provides an active site for subsequent modification of the nuclide ion selective molecule to fix the nuclide ion selective molecule. The nuclide ion selective molecule is specifically selected differently according to the nuclide molecule to be collected, so that the ion permeable layer isolates the influence of large particle impurities in the solution and has selective permeability to target nuclide ions, improving the accuracy of nuclide concentration collection and detection.

[0041] (3) The sensitive unit layer of the present invention is a graphene-MnO2 heterojunction thin film. The high carrier mobility of graphene (>10 4 cm 2 / (V·s)) and the pseudocapacitive characteristics of MnO2 act synergistically to convert the change in ion concentration into a high-amplitude electrical signal (such as current or impedance change). Moreover, the Fermi level difference between graphene (metal-like) and MnO2 (semiconductor) at the interface forms a Schottky barrier, resulting in charge transfer and barrier generation. The Schottky barrier can filter out background interference current (such as the random migration noise of impurity ions in the solution), improving the signal-to-noise ratio (SNR>50dB), which can greatly improve nuclide selectivity, conductivity sensitivity (increase by 2-3 orders of magnitude), and anti-high g-value interference ability. The combination of the high mechanical strength of graphene and the toughness of the MnO2 nanolayer ensures the stability of the interfacial contact resistance between the sensitive unit layer and the signal collection unit in the hypergravity environment, avoiding signal drift caused by mechanical deformation; An amidoxime group is introduced on the surface of MnO2 in the graphene-MnO2 heterojunction thin film. The amidoxime group has high affinity for nuclides such as UO2 2+ , enhancing selective adsorption and significantly increasing the local concentration of nuclide ions in the sensitive unit layer (enrichment factor>100 times), thereby amplifying the response signal of the electrodes of the signal collection unit; Vertical pores are etched on the graphene-MnO2 heterojunction thin film, and each inner wall of the vertical pores is modified with a hydrophilic polymer. The vertical pore array is responsible for quickly transporting the enriched nuclide solution to the electrode layer for signal detection, and the hydrophilic polymer enhances the transport 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 through the real-time temperature value collected by the platinum thin film resistance temperature sensor, the pH value of the solution collected by the IrO2-pH electrode unit, and the conductivity of the solution collected by the internal electrode pair and the external electrode pair under the hypergravity environment. The accuracy of the real-time ion concentration of the solution collected and calculated under the hypergravity environment is high, and the detection accuracy is high.

[0043] (5). The base layer of the present invention is a graphene / hBN hetero - stacked layer. Graphene provides electrical conductivity and mechanical support, hBN serves as an insulating layer to achieve ion - selective shielding, and the micro - channels on the graphene / hBN hetero - stacked layer enable the immediate free diffusion of the solution after detection.

[0044] (6). The pore diameters of the carboxylated nano - channels, vertical channels, and micro - channels on the thin - film sensing layer of the present invention increase in sequence, and the arrangement densities decrease in sequence, and they are connected up and down. By capillary action, the solution is driven to flow downward, avoiding liquid retention, and can quickly achieve the purpose of screening ions through the selective ion - permeable layer, transporting the solution through the sensitive unit layer, and rapidly diffusing the solution after detection through the base layer. Brief Description of the Drawings

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

[0046] Figure 2 is a schematic plan view of the selective ion - permeable layer of the present invention.

[0047] Figure 3 is a schematic plan view of the sensitive unit layer of the present invention.

[0048] Figure 4 is a schematic plan view of the signal processing and transmission unit connected below the sensitive unit layer of the present invention.

[0049] Figure 5 is a schematic plan view of the base layer of the present invention.

[0050] Figure 6 is a schematic structural diagram of the carboxylated nano - channels on the selective ion - permeable layer, the vertical channels on the sensitive unit layer, and the micro - channels on the base layer corresponding to each other and being connected of the present invention.

[0051] Reference Numerals: 1 - epoxy resin encapsulation shell, 21 - selective ion - permeable layer, 22 - sensitive unit layer, 23 - signal acquisition unit, 24 - base layer, 31 - patch - type processing chip, 32 - patch - type wireless module, 211 - PI film, 212 - carboxylated nano - channels, 221 - graphene - MnO2 heterojunction thin film, 222 - vertical channels, 231 - platinum resistance thin - film type temperature sensor, 232 - IrO2 - pH electrode unit, 233 - internal electrode pair, 234 - external electrode pair, 241 - graphene / hBN hetero - stacked layer, 242 - micro - channels. Detailed Embodiments

[0052] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] See Figure 1 , a nuclide concentration sensor applicable to a hypergravity environment, including an epoxy resin encapsulation shell 1, and a thin film sensing layer and a signal processing and transmission unit arranged in the epoxy resin encapsulation shell;

[0054] The thin film sensing layer includes a selective ion permeation layer 21, a sensitive unit layer 22, and a base layer 24 connected in sequence from top to bottom. A signal acquisition unit 23 is arranged between the sensitive unit layer 22 and the base layer 24. The signal processing and transmission unit includes a patch-type processing chip 31 and a patch-type wireless module 32 connected to each other. The electrode wires of the signal acquisition unit 23 pass out between the sensitive unit layer 22 and the base layer 24 and are connected to the patch-type processing chip 31. The patch-type processing chip 31 processes the data collected by the signal acquisition unit 23 to obtain the real-time ion concentration of the solution, and then sends the real-time ion concentration of the solution to the upper computer through the patch-type 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 and connects the selective ion permeation layer 21, the sensitive unit layer 22, the base layer 24, and the signal acquisition unit 23 of the thin film sensing layer. An upper through hole 11 is arranged on the top plate of the epoxy resin encapsulation shell 1, and a lower through hole 12 is arranged on the bottom plate of the epoxy resin encapsulation shell 1. The edge part of the epoxy resin encapsulation shell 1 around the upper through hole 11 is hermetically connected to the selective ion permeation layer 21, and the edge part of the epoxy resin encapsulation shell 1 around the lower through hole is hermetically connected to the base layer 24, so that the acquisition area of the thin film sensing layer is communicated with the outside of the epoxy resin encapsulation shell 1, and 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 selective ion permeation layer 21 is a PI film 211. A circular acquisition area is arranged on the PI film 211. Carboxylated nanopores 212 are arranged on the acquisition area of the PI film 211. Nuclide ion selective molecules are arranged inside each carboxylated nanopore 212. The preparation method of the selective ion permeation layer specifically includes the following steps:

[0057] S11. Vertically bombard the acquisition area of the PI film 211 with high-energy heavy ion beams to form latent tracks, and the latent tracks penetrate from the incident surface of the PI film 211 to the other side;

[0058] S12. Ultraviolet light is irradiated on both sides of the PI film 211 after being bombarded by high-energy heavy ion beams. The wavelength of the ultraviolet light irradiation is 254 nm, and the intensity is 1 - 5 mW / cm 2 , and the irradiation time for each side is 30 - 60 minutes;

[0059] S13. The PI film 211 after ultraviolet light irradiation is placed in an H-type electrolytic cell, and an etching solution (NaOH solution or KOH solution) is added to both sides. A constant voltage (1.0 V) is applied, and the etching process is controlled by monitoring the current change, so as to etch and form a plurality of carboxylated nanopores 212 penetrating both sides of the PI film 211. After the etching is completed, the carboxyl groups on the inner wall of the carboxylated nanopores 212 are retained and stabilized through chemical cleaning (HCl solution);

[0060] S14. The etched PI film is immersed 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 nuclide ion molecular modification is fixed on the inner wall of the carboxylated nanopores 212 to achieve selective affinity for nuclides; the nuclide ion selective molecule is azo-G4-DNA molecule, G4-DNA molecule, crown ether molecule or calixarene molecule. The azo group in the azo-G4-DNA molecule can enhance the light responsiveness and is suitable for the selective affinity of uranium ions. The G4-DNA molecule has a high affinity for monovalent cations such as K + , Cs + and other monovalent cations, and is suitable for monitoring nuclides such as cesium; the crown ether molecule or calixarene molecule has optimized selectivity for nuclides such as Pu 4+ , Am 3+ and other nuclides.

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

[0063] S21. Using atomic layer deposition (ALD) to deposit a nanoscale MnO2 layer with a thickness less than 50 nm on the surface of graphene. ALD ensures that MnO2 covers the graphene, forms a high-quality interface, reduces the interference of defect states on the potential barrier, and the charge transfer (electrons transfer from graphene to MnO2) at the interface between MnO2 and graphene directly leads to the generation of the potential barrier;

[0064] S22. Further prepare a uniform MnO2 layer on the surface of graphene deposited with a nanoscale MnO2 layer by sol-gel method to solidify the heterojunction structure and form a graphene-MnO2 heterojunction composite layer. Specifically, first dissolve manganese salt (Mn(CH3COO)2·4H2O, concentration 0.1 - 0.5 M) in a solvent (ethanol or isopropanol), and add a stabilizer (such as urea or citric acid, concentration 0.05 - 0.1 M) to control the MnO2 precipitation rate to obtain a precursor solution. Then, drop-coat or spin-coat (spin-coating speed 2000 - 3000 rpm) the precursor solution on the surface of graphene deposited with a nanoscale MnO2 layer, control the coating thickness to be 50 - 100 nm, and then bake the coating at 80 - 100 °C for 1 - 2 hours to promote sol-gelation and form a MnO2 gel network. Anneal it at 200 - 300 °C for 2 - 4 hours (protected by nitrogen or argon, annealing rate is 5 °C / min to avoid thermal stress damage to the graphene structure) to convert the gel into crystalline MnO2, and the particle size of the crystalline MnO2 is 10 - 20 nm. The sol-gel method increases the thickness of the MnO2 layer and improves the crystal structure, reduces the interface resistance, and enhances the electrical stability of the potential barrier. The annealing process optimizes the interface bonding, reduces trap states, and further stabilizes the potential barrier height;

[0065] S23. Modify amidoxime groups on the surface of the graphene-MnO2 heterojunction composite layer. The specific steps are as follows: First, treat the surface of the graphene-MnO2 heterojunction composite layer with oxygen plasma (power 50 - 100 W, 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 an ethanol solution containing 3-aminopropyltriethoxysilane ((NH2)(CH2)3Si(OCH2CH3)3, abbreviated as APTES, 1 - 5 vol%) and react at 60 °C for 4 - 6 hours to form -(CH2)3-NH2 groups on the surface of the graphene-MnO2 heterojunction composite layer. First, the ethoxy group (-OCH2CH3) of APTES hydrolyzes to generate silanol groups (Si-OH), and then the silanol groups and hydroxyl groups condense. The reaction formula is: (HN2)(CH2)3Si(OH)3 + MnO2-OH → MnO2-O-Si-(CH2)3-HN2 + H2O. Then, immerse the graphene-MnO2 heterojunction composite layer in a DMF solution containing acrylonitrile (0.1 - 0.5 M), add a triethylamine catalyst (0.01 M), and react at 50 - 70 °C 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, immerse the graphene-MnO2 heterojunction composite layer with cyanide groups on the surface in a water / ethanol solution containing hydroxylamine hydrochloride (0.1 - 0.5 M, pH: 6 - 7) and react at 60 °C for 4 - 8 hours to convert the cyanide groups into amidoxime groups (-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, dry at 80 °C to modify amidoxime groups on the surface of the graphene-MnO2 heterojunction composite layer;

[0066] S24. Etch a plurality of vertical channels 222 on the surface-modified graphene-MnO2 heterojunction composite layer by reactive ion etching or laser ablation methods. The vertical channels 222 penetrate both sides of the graphene-MnO2 heterojunction composite layer, and hydrophilic polymers (such as polyethylene glycol) are modified on the inner walls of each vertical channel 222;

[0067] See Figure 4, the signal acquisition unit 23 includes a platinum thin-film resistance temperature sensor 231, an IrO2-pH electrode unit 232, an internal electrode pair 233 (Au electrode, excellent stability and corrosion resistance), and an external electrode pair 234 (Ti electrode, good stability and corrosion resistance), which are arranged between the sensitive unit layer 22 and the acquisition area of the base layer 24; the platinum thin-film resistance temperature sensor 231 and the IrO2-pH electrode unit 232 respectively pass through the corresponding electrode wires from between the sensitive unit layer 22 and the base layer 24 and are correspondingly connected to the patch processing chip 31 of the signal processing and transmission unit. 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, and the outer ends of the internal electrode pair 233 and the external electrode pair 234 pass out to the outside of the acquisition areas of the sensitive unit layer 22 and the base layer 24 and are connected to the patch processing chip 31 of the signal processing and transmission unit. A known alternating current (frequency 1 - 10 kHz, amplitude 1 - 10 μA) is applied to the internal electrode pair, and the voltage between the external electrode pairs is measured, and the solution conductivity is calculated through Ohm's law and the electrode geometric constant;

[0068] The patch processing chip 31 calculates the real-time ion concentration of the solution through the real-time temperature value collected by the platinum thin-film resistance temperature sensor, the pH value of the solution collected by the IrO2-pH electrode unit, and the solution conductivity collected and calculated under the hypergravity environment;

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

[0070]

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

[0072] See Figure 5 , the base layer 24 is a graphene / hBN heterostacked layer 241, and a circular collection area that completely overlaps with the collection areas of the sensitive unit layer 22 and the selective ion permeation layer 21 is also provided on the graphene / hBN heterostacked layer 241, and micropores 242 are etched on the collection area of the graphene / hBN heterostacked layer 241.

[0073] See Figure 6 , the carboxylated nanopores 212, the vertical pores 222, and the micropores 242 are sequentially connected up and down. The pore diameter of the carboxylated nanopores 212 is 2 - 50 nm, and the density of the carboxylated nanopores 212 in the collection area of the selective ion permeation layer 21 is 10 5 -10 6 pores / cm 2 ; the pore diameter of the vertical pores 222 is 500 - 1000 nm, and the density of the vertical pores 222 on the sensitive unit layer 22 is 10 3 -10 4 pores / cm 2 ; the pore diameter of the micropores 242 is 10 - 100 μm, and the density of the micropores 242 on the base layer 24 is 10 2 -103 holes / cm 2 。

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

Claims

1. A nuclide concentration sensor applicable to the hypergravity environment, characterized in that: It includes a packaging shell, a thin film sensing layer and a signal processing and transmission unit arranged in the packaging shell; The thin film sensing layer includes a selective ion permeable layer, a sensitive unit layer and a base layer connected in sequence from top to bottom. A signal acquisition unit is provided between the sensitive unit layer and the base layer. The electrode line of the signal acquisition unit passes through between the sensitive unit layer and the base layer and is connected to the signal processing and transmission unit. The selective ion permeation layer is a PI membrane, a collection area is provided on the PI membrane, a carboxylated nanopore is provided on the collection area of the PI membrane, and a nuclide ion selective molecule is provided in each carboxylated nanopore; The sensitive unit layer is a graphene-MnO2 heterojunction film, wherein amidoxime groups are introduced onto 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 base layer is a graphene / hexagonal boron nitride heterogeneous stacking layer, a collection area is also provided on the graphene / hexagonal boron nitride heterogeneous stacking layer, and micro-channels are etched on the collection area of the graphene / hexagonal boron nitride heterogeneous stacking layer; The carboxylated nanochannels, vertical channels and microchannels are sequentially interconnected up and down. An upper through hole is provided on the top plate of the packaging shell, and a lower through hole is provided on the bottom plate of the packaging shell. The upper through hole, the collection area of the thin film sensing layer provided with the above-mentioned channels, 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 packaging shell, and the other parts of the thin film sensing layer and the signal processing and transmission unit are completely sealed inside the packaging shell.

2. The nuclide concentration sensor applicable to the hypergravity environment according to claim 1, characterized in that: The method for preparing the selective ion permeable layer specifically comprises the following steps: S11, vertically bombarding the collection area of the PI film with a high-energy heavy ion beam to form a latent track, and the latent track runs from the incident surface of the PI film to the other surface; S12, irradiating both sides of the PI film bombarded by the high-energy heavy ion beam with ultraviolet light; S13, placing the PI film after UV irradiation in an H-type electrolytic cell, adding etching solution on both sides, applying a constant voltage, and controlling the etching process by monitoring the current change, thereby etching a plurality of carboxylated nanopores penetrating both sides of the PI film. After the etching is completed, the carboxyl groups on the inner wall of the carboxylated nanopores are retained and stabilized by chemical cleaning; S14, immersing 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; S15. Select the nuclide ion selective molecule to be modified and fixed on the inner wall of the carboxylated nanopore to achieve selective affinity of the nuclide.

3. The nuclide concentration sensor suitable for use in a hypergravity environment according to claim 2, characterized in that: The high energy heavy ion beam is selected from high energy xenon ion beam or 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 8 -10 10 ions / cm 2 ; The wavelength of the ultraviolet light irradiation is 254 nm, and the intensity is 1 - 5 mW / cm 2 , and the irradiation time is 30 - 60 minutes; The etching solution on both sides of the H-type electrolytic cell is selected from NaOH solution or KOH solution, the constant voltage applied is 1.0V, and the chemical cleaning after etching is completed is HCl solution; The nuclide ion selective molecule is an azo-G4-DNA molecule, a G4-DNA molecule, a crown ether molecule or a calixarene molecule.

4. The radionuclide concentration sensor suitable for use in a hypergravity environment according to claim 2, characterized in that: The method for preparing the sensitive unit layer specifically includes the following steps: S21, depositing a nano-scale MnO2 layer with a thickness of less than 50 nm on the graphene surface by atomic layer deposition; S22, further preparing a uniform MnO2 layer on the graphene surface on which the nano-scale MnO2 layer has been deposited by a sol-gel method, and solidifying the heterojunction structure to form a graphene-MnO2 heterojunction composite layer; S23, modifying the surface of the graphene-MnO2 heterojunction composite layer with amidoxime groups; S24. Reactive ion etching or laser ablation is used to etch a plurality of vertical channels on the surface-modified graphene-MnO2 heterojunction composite layer, wherein 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. The nuclide concentration sensor applicable to the hypergravity environment according to claim 4, wherein: The specific steps of using the sol-gel method to further prepare a uniform MnO2 layer on the graphene surface after the nano-scale MnO2 layer is deposited are: dissolving a manganese salt in a solvent to obtain a precursor solution, then drop-coating or spin-coating the precursor solution on the graphene surface on which the nano-scale MnO2 layer is deposited, controlling the coating thickness to be 50-100nm, then baking the coating at 80-100°C for 1-2 hours, and annealing at 200-300°C for 2-4 hours to convert the gel into crystalline MnO2, wherein the particle size of the crystalline MnO2 is 10-20nm.

6. The nuclide concentration sensor applicable to the hypergravity environment according to claim 4, wherein: The specific steps of modifying the amidoxime group on the surface of the graphene-MnO2 heterojunction composite layer are as follows: first, treating the surface of the graphene-MnO2 heterojunction composite layer with oxygen plasma to generate hydroxyl groups on the surface of the graphene-MnO2 heterojunction composite layer; then immersing the graphene-MnO2 heterojunction composite layer in an ethanol solution containing 3-aminopropyltriethoxysilane, reacting at 60°C for 4-6 hours, forming -(CH2)3-NH2 groups on the surface of the graphene-MnO2 heterojunction composite layer; and then treating the graphene-MnO2 heterojunction composite layer with 3-aminopropyltriethoxysilane. 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°C for 6-12 hours to form -(CH2)3-NH-(CH2)2-CN groups; finally, the graphene-MnO2 heterojunction composite layer containing cyano groups on the surface is immersed in a solution containing hydroxylamine hydrochloride, and the reaction is carried out at 60°C for 4-8 hours to convert the cyano groups into amidoxime groups. After washing with deionized water and ethanol, the layer is dried at 80°C, thereby modifying the amidoxime groups on the surface of the graphene-MnO2 heterojunction composite layer.

7. The nuclide concentration sensor suitable for use in a hypergravity environment according to claim 4, characterized in that: The signal acquisition unit includes a platinum thermal resistor thin film temperature sensor, an IrO2-pH electrode unit, an internal electrode pair, and an external electrode pair, which are arranged between the sensitive unit layer and the base layer acquisition area. The platinum thermal resistor thin film temperature sensor and the IrO2-pH electrode unit are respectively connected to the signal processing and transmission unit after passing through the space between the sensitive unit layer and the base layer via corresponding electrode wires. The inner ends of the internal electrode pair and the external electrode pair are located between the sensitive unit layer and the base layer acquisition area, and the outer ends of the internal electrode pair and the external electrode pair pass through the outside of the sensitive unit layer and the base 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 pair is measured to calculate the conductivity of the solution. The signal processing and transmission unit calculates the real-time ion concentration of the solution based on the real-time temperature value collected by the platinum thin-film resistance temperature sensor, the pH value of the solution collected by the IrO2-pH electrode unit, and the conductivity of the solution collected and calculated under the hypergravity environment. Under the hypergravity environment, the relationship between the real-time temperature value, pH value, solution conductivity, and real-time ion concentration of the solution satisfies the following formula (1): In formula (1), Λ represents the molar conductivity of the measured solution under hypergravity conditions, with the unit of S·cm 2 / mol; Λ0 represents the molar conductivity at infinite dilution of the solution, which is a constant value; e represents the elementary charge, with a value of 1.602×10 -19 C; z - and z + represent 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 ion migration resistance, with a value of 3 times 3.1415926; b represents the viscosity coefficient constant of the solution under hypergravity conditions. When the hypergravity acceleration is 200g, b = 1.05, and when the hypergravity acceleration is 300g, b = 1.08; η represents the viscosity of the solvent, with the unit of Pa·s; k1 represents the influence coefficient of pH on ion migration under hypergravity conditions, pH 测 represents the pH value of the solution collected by the IrO2-pH electrode unit under hypergravity conditions, pH 常 represents the pH value of the solution measured under normal gravity; N A represents Avogadro's constant, with a value of 6.022×1023mol -1 ; k2 represents the influence coefficient of temperature on ion migration, T 测 represents the real-time temperature value collected by the platinum thin-film thermoresistance temperature sensor under hypergravity conditions, T 常 represents the temperature value of the solution measured under normal gravity; k B represents Boltzmann's constant, with a value of 1.381×10 -23 J / K; ε0 represents the vacuum permittivity, which is a constant value; ε γ represents the relative dielectric constant of the solvent; k represents the Debye constant of the solution, I is the ionic strength of the nuclide; a represents the effective diameter of the nuclide ion, with a value ranging from 0.3 to 0.5 nm; k3 represents the influence coefficient of the carboxylated nanopores in the selective ion permeation layer and the vertical pores in the sensitive unit layer on the ion migration rate of the solution, with a value of 0.95; λ + 0 and λ - 0 respectively represent the limiting molar conductivities of the positive and negative nuclide ions in the solution at infinite dilution, which are fixed values; β represents the error in signal acquisition and detection by the signal acquisition unit under the hypergravity environment, with a value ranging from 0.95 to 1; C represents the real-time ion concentration of the solution under the hypergravity environment.

8. A nuclide concentration sensor applicable to a hypergravity environment according to claim 6, characterized in that: The pore diameter of the carboxylated nanopores is 2 - 50 nm, and the density of the carboxylated nanopores in the collection area of the ion-selective permeable layer is 10 5 -10 6 pores / cm 2 ; The pore diameter of the vertical pores is 500 - 1000 nm, and the density of the vertical pores on the sensitive unit layer is 10 3 -10 4 pores / cm 2 ; The pore diameter of the microchannels is 10 - 100 μm, and the density of the microchannels on the substrate layer is 10 2 -10 3 pores / cm 2 .

9. The nuclide concentration sensor suitable for use in a hypergravity environment 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 and connects the selective ion permeation layer, sensitive unit layer, substrate layer, and signal acquisition unit of the thin-film sensing layer. The edge part of the encapsulation shell located on the outer periphery of the upper through-hole is hermetically connected to the selective ion permeation layer of the thin-film sensing layer, and the edge part of the encapsulation shell located on the outer periphery of the lower through-hole is hermetically connected to the substrate layer of the thin-film sensing layer.

10. The nuclide concentration sensor suitable for use in a hypergravity environment according to claim 7, characterized in that: The signal processing and transmission unit includes a patch-type processing chip and a patch-type wireless module that are connected to each other. The patch-type processing chip processes the data collected by the signal acquisition unit to obtain the real-time ion concentration of the solution, and then sends the real-time ion concentration of the solution to the upper computer through the patch-type wireless module via a wireless communication network.

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