Evaluation method for pore size preservation effect of nanoporous membrane and pore size preservation method for nanoporous membrane

Abstract

The present invention relates to a method for evaluating the pore size preservation effect of a nanoporous membrane and a method for preserving the pore size of a nanoporous membrane. The evaluation method comprises the following steps: (1) performing a current-voltage curve test on a nanoporous membrane without pore size preservation to obtain the initial current and initial voltage of the nanoporous membrane; (2) performing pore size preservation on the nanoporous membrane, and then performing a current-voltage curve test on the nanoporous membrane after pore size preservation to obtain the current after preservation and the voltage after preservation of the nanoporous membrane; (3) using an evaluation formula to calculate the preservation effect, and the evaluation formula is that the smaller the ΔD, the smaller the pore size change, and the better the preservation effect. The evaluation method of the present invention is convenient to operate and has high accuracy, and is applicable to the verification of the pore size preservation effect of nanoporous membranes.

Description

Technical Field

[0001] The present invention relates to the technical field of nano - material preparation, and particularly relates to a method for evaluating the pore size preservation effect of a nanoporous membrane and a method for preserving the pore size of a nanoporous membrane. Background Art

[0002] A nanoporous membrane is a thin - film material with nano - scale pores, which is widely used in fields such as medical diagnosis, biological research, and drug development, and has also shown great application prospects in fields such as agriculture and environmental monitoring in recent years. Currently, nanopores are divided into two categories: protein pores embedded in biological membranes and solid - state pores fabricated on an insulating thin - film substrate.

[0003] With the rise of the third - generation sequencing technology, a sequencing device based on protein pores has been successfully commercialized by a foreign company, and the research of this technology has a profound impact on the development of the field of biomolecular sensors and detection. However, solid - state pores have advantages such as low cost, high stability, and easy integration compared with protein pores, and thus have become the recognized next - generation technology in the field of nanopore gene sequencing. The current solid - state nanopore gene sequencing technology is to fabricate nano - scale pore diameters by punching holes in a solid - state thin - film such as a silicon nitride membrane chip, and under the action of voltage, make the DNA chain pass through the solid - state nanopore to obtain the DNA base sequence.

[0004] In the actual process of preparing solid - state pores, due to the extremely small scale of nanopores, extremely high manufacturing precision is often required. However, during the preparation process, active functional groups are usually introduced on the surface of the nanopores, affecting the stability of the pore diameter. The above factors result in the difficulty of maintaining the pore - size stability of solid - state nanopores in practical applications for a long time, restricting their further application and popularization. In addition, the currently commonly used methods for measuring the pore diameter of nanopores are mainly the transmission electron microscope (TEM) measurement method and the atomic force microscope (AFM) measurement method. These two pore - diameter measurement methods are not only costly but also cumbersome, and the time required to obtain an accurate pore diameter is relatively long. Therefore, there is an urgent need to develop a method that can effectively preserve the nanoporous membrane and simply evaluate the preservation effect, so as to optimize the nanoporous membrane preservation process and improve the preservation stability of the nanoporous membrane. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a simple, convenient and highly accurate method for evaluating the pore - size preservation effect of a nanoporous membrane and a method for preserving the pore size of a nanoporous membrane.

[0006] To achieve the above - mentioned purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for evaluating the pore - size preservation effect of a nanoporous membrane includes the following steps:

[0008] (1) Perform current-voltage curve tests on the nanoporous membrane without pore size preservation to obtain the initial current and initial voltage of the nanoporous membrane;

[0009] (2) Preserve the pore size of the nanoporous membrane, and then perform current-voltage curve tests on the nanoporous membrane after pore size preservation to obtain the current after preservation and the voltage after preservation of the nanoporous membrane;

[0010] (3) Use the evaluation formula to calculate the preservation effect, and the evaluation formula is

[0011]

[0012] where ΔD is the absolute value of the dimensionless number describing the pore size preservation effect, I0 is the initial current of the nanoporous membrane, V0 is the initial voltage of the nanoporous membrane, I1 is the current after preservation of the nanoporous membrane, V1 is the voltage after preservation of the nanoporous membrane, and t is the preservation time.

[0013] The smaller the ΔD, the smaller the pore size change and the better the preservation effect.

[0014] Preferably, the nanoporous membrane includes any one or a composite membrane of two or more of a silicon nitride membrane, a silicon dioxide membrane, a silicon membrane, and a silicon carbide membrane.

[0015] Preferably, the thickness of the nanoporous membrane is 5-20 nm, and more preferably 5-15 nm.

[0016] Preferably, the pore size of the nanoporous membrane is 1-30 nm.

[0017] Preferably, the current-voltage curve test includes immersing the nanoporous membrane in a salt solution, and then applying a voltage of -200 to 200 mV to the nanoporous membrane to obtain a current-voltage curve. Applying a voltage of -200 to 200 mV will not affect the pore size of the nanoporous membrane.

[0018] More preferably, the salt solution is a potassium chloride solution.

[0019] Preferably, the concentration of the salt solution is 0.1-2 mol / L.

[0020] Preferably, the evaluation method further includes the step of washing the nanoporous membrane with deionized water after the current-voltage curve test and / or after the pore size preservation, and then drying the nanoporous membrane.

[0021] In some embodiments, the drying includes air-drying the nanoporous membrane naturally.

[0022] Preferably, the pore size preservation includes contacting the inner surface of the nanoporous membrane with a neutral liquid, an organic solvent or an inert gas to isolate the nanopores of the nanoporous membrane from the external environment.

[0023] In some embodiments, the neutral liquid includes a mixed solution of one or more of lithium chloride, potassium chloride, and sodium chloride and water.

[0024] Preferably, the concentration of the neutral solution is 0.5 to 4.0 mol / L, more preferably 0.5 to 2.0 mol / L, and even more preferably 0.8 to 1.8 mol / L.

[0025] In some embodiments, the organic solvent includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, and isopropanol.

[0026] In some embodiments, the inert gas includes one or more of helium, nitrogen, and argon.

[0027] Preferably, the contact method includes one or more of immersion, spraying, and pouring.

[0028] The present invention also provides a method for preserving the pore size of a nanoporous membrane. The pore size preservation method includes contacting the inner surface of the nanoporous membrane with a neutral liquid, an organic solvent or an inert gas to isolate the nanopores of the nanoporous membrane from the external environment, wherein the neutral liquid includes a mixed solution of one or more of lithium chloride, potassium chloride, and sodium chloride and water, the organic solvent includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, and isopropanol, and the inert gas includes one or more of helium, nitrogen, and argon.

[0029] Preferably, the concentration of the neutral solution is 0.5 to 4.0 mol / L, more preferably 0.5 to 2.0 mol / L, and even more preferably 0.8 to 1.8 mol / L.

[0030] Preferably, the contact method includes one or more of immersion, spraying, and pouring.

[0031] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0032] The evaluation method of the present invention is simple, convenient, and highly accurate, and is applicable to verifying the preservation effect of nanoporous membranes.

[0033] The preservation method of the present invention can improve the storage stability of nanoporous membranes, maintain the pore size of nanoporous membranes, and is simple to operate and low in cost. Description of the Drawings

[0034] Figure 1Variation diagram of the current-voltage (I-V) curve of the first diaphragm in Example 1;

[0035] Figure 2 Variation diagram of the current-voltage (I-V) curve of the second diaphragm in Example 1;

[0036] Figure 3 Variation diagram of the current-voltage (I-V) curve of the third diaphragm in Example 1. Detailed implementation manners

[0037] The present invention will be further described below in conjunction with embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each implementation manner of the present invention can be combined with each other as long as they do not conflict with each other.

[0038] Unless otherwise specified, the raw materials or instruments involved in the following text can be commercially available products or can be prepared with reference to the preparation methods of the prior art. Among them, in order to test the pore size preservation effect of the nanoporous membrane, the inventor obtained nanopores by punching holes in the self-made diaphragm, and verified the accuracy of the evaluation method and the quality of the preservation effect by comparing the pore sizes before and after the nanopore preservation. The punching process can refer to the prior art, such as the dielectric breakdown process.

[0039] The preparation method of the nanoporous membrane diaphragm is as follows: Using a silicon wafer as the substrate, a required nanometer thin film is deposited on the silicon substrate by low-pressure chemical vapor deposition technology (the pressure of vapor deposition is 0.01 - 1 torr, and the temperature is 500 - 1200 °C); subsequently, the thin film is patterned by lithography and etching technologies; finally, the silicon wafer is etched from the back to generate a cavity under the membrane window, thereby forming an independent unsupported nanometer thin film. The nanoporous membrane diaphragm can also be prepared with reference to the prior art or directly obtained by commercial purchase, and the present application does not make specific restrictions.

[0040] Unless otherwise specified, the current-voltage curve test in the present invention can refer to the prior art, including placing the diaphragm on the test equipment, connecting one end to the positive electrode and the other end to the negative electrode, and performing voltage scanning at -200 - 200 mV at room temperature (25 ± 5 °C), so as to obtain the curve change of the current-voltage of the diaphragm.

[0041] Unless otherwise specified, the units of I0 and I1 in the formula for evaluating the pore size preservation effect of the present invention are nA, the units of V0 and V1 are V, and the unit of t is days.

[0042] Example 1

[0043] Take three silicon nitride films with a thickness of 12 nm, named the first film, the second film and the third film. The initial pore sizes of the first film, the second film and the third film are measured by TEM measurement method to be 8.5 nm, 8.6 nm and 8.7 nm respectively.

[0044] Immerse the first film, the second film and the third film into 1 mol / L potassium chloride solution respectively for current-voltage (I-V) curve test to obtain the initial current I0 and initial voltage V0 of the nanopores of the three films. After the test, clean the above three films with deionized water and dry them for standby.

[0045] Then, immerse the first film and the second film into the solution containing 1 mol / L potassium chloride solution and dimethyl sulfoxide respectively, and store them at room temperature (25±5 °C) for 1 day. The third film is used as a control and stored at room temperature in the air for 1 day. After storage, clean the film with deionized water and dry it for standby.

[0046] Finally, conduct current-voltage (I-V) curve test on the above first film, second film and third film respectively to obtain the final current I1 and final voltage V1 of the nanopores of the three films. Substitute all parameters into the formula for evaluating the pore size preservation effect:

[0047] The pore size preservation effects ΔD of the first film, the second film and the third film are obtained as 0.20, 0.03 and 0.43 respectively. Among them, the pore size preservation effect ΔD of the second film is the smallest, and that of the first film is the second. That is to say, for the silicon nitride film with a thickness of 12 nm and a pore size of about 8.5 nm, compared with using no preservation means, using 1 mol / L potassium chloride solution or dimethyl sulfoxide has a certain pore size preservation effect, and using dimethyl sulfoxide has a better pore size preservation effect.

[0048] The actual pore sizes of the first film, the second film and the third film after storage are measured by TEM measurement method to be 13 nm, 8 nm and 2 nm respectively. The actual preservation effect is consistent with the evaluation result of the above formula for pore size preservation effect.

[0049] Example 2

[0050] Take three silicon nitride films with a thickness of 11.5 nm, named the first film, the second film and the third film. The initial pore sizes of the first film, the second film and the third film are measured by TEM measurement method to be 3.3 nm, 3.2 nm and 3.4 nm respectively.

[0051] The first diaphragm, the second diaphragm, and the third diaphragm were respectively immersed in 1 mol / L potassium chloride solution for current-voltage (I-V) curve testing to obtain the initial current I0 and initial voltage V0 of the nanopores of the three diaphragms. After the testing, the three diaphragms were cleaned with deionized water and dried for later use.

[0052] Then, the first diaphragm and the second diaphragm were respectively immersed in a solution containing 1 mol / L potassium chloride and isopropanol and stored at room temperature for 1 day. The third diaphragm was used as a control and exposed to air at room temperature for 1 day. After the storage, the diaphragms were cleaned with deionized water and dried for later use.

[0053] Finally, the first diaphragm, the second diaphragm, and the third diaphragm were respectively subjected to current-voltage (I-V) curve testing to obtain the final current I1 and final voltage V1 of the nanopores of the three diaphragms. All parameters were substituted into the formula for evaluating the pore size preservation effect:

[0054] The pore size preservation effects ΔD of the first diaphragm, the second diaphragm, and the third diaphragm were obtained as 0.13, 0.20, and 0.75 respectively. The pore size preservation effect ΔD of the first diaphragm was the smallest, followed by the second diaphragm. That is to say, for the silicon nitride membrane with a thickness of 11.5 nm and a pore size of about 3.3 nm, the potassium chloride solution has a better pore size preservation effect.

[0055] The actual pore sizes of the first diaphragm, the second diaphragm, and the third diaphragm after preservation were measured by TEM measurement method to be 4.2 nm, 4.7 nm, and 10.5 nm respectively. The actual preservation effect was consistent with the evaluation result of the above formula for pore size preservation effect.

[0056] Example 3

[0057] Three silicon nitride membranes with a thickness of 11.5 nm were taken and named the first diaphragm, the second diaphragm, and the third diaphragm. The initial pore sizes of the first diaphragm, the second diaphragm, and the third diaphragm were measured by TEM measurement method to be 5 nm, 4.9 nm, and 4.8 nm respectively.

[0058] The first diaphragm, the second diaphragm, and the third diaphragm were respectively immersed in 1 mol / L potassium chloride solution for current-voltage (I-V) curve testing to obtain the initial current I0 and initial voltage V0 of the nanopores of the three diaphragms. After the testing, the three diaphragms were cleaned with deionized water and dried for later use.

[0059] Then, the first diaphragm and the second diaphragm were respectively immersed in a solution containing 1.56 mol / L potassium chloride and N-methylpyrrolidone and stored at room temperature for 2 days. The third diaphragm was used as a control and exposed to air at room temperature for 2 days. After the storage, the diaphragms were cleaned with deionized water and dried for later use.

[0060] Finally, the above-mentioned first diaphragm, second diaphragm, and third diaphragm were respectively subjected to current-voltage (I-V) curve tests to obtain the final current I1 and final voltage V1 of the nanopores of the three diaphragms. All parameters were substituted into the formula for evaluating the pore size preservation effect:

[0061] The pore size preservation effects ΔD of the first diaphragm, second diaphragm, and third diaphragm were obtained as 0.09, 0.06, and 0.24 respectively. Among them, the pore size preservation effect ΔD of the second diaphragm was the smallest. That is to say, for a silicon nitride membrane with a thickness of 11.5 nm and a pore size of about 5 nm, N-methylpyrrolidone has a better pore size preservation effect.

[0062] The actual pore sizes of the first diaphragm, second diaphragm, and third diaphragm after preservation were measured by TEM measurement method to be 6.1 nm, 5.6 nm, and 7.8 nm respectively. The actual preservation effect was consistent with the evaluation result of the above formula for pore size preservation effect.

[0063] Example 4

[0064] Three silicon nitride membranes with a thickness of 11.5 nm were taken and named the first diaphragm, second diaphragm, and third diaphragm. The initial pore sizes of the first diaphragm, second diaphragm, and third diaphragm were measured by TEM measurement method to be 2.8 nm, 2.7 nm, and 2.9 nm respectively.

[0065] The first diaphragm, second diaphragm, and third diaphragm were respectively immersed in 1 mol / L potassium chloride solution for current-voltage (I-V) curve tests to obtain the initial current I0 and initial voltage V0 of the nanopores of the three diaphragms. After the test, the above three diaphragms were washed clean with deionized water and dried for standby.

[0066] Then, the first diaphragm and second diaphragm were respectively immersed in a solution containing 1 mol / L lithium chloride and dimethyl sulfoxide and stored at room temperature for 4 days. The third diaphragm was used as a control and exposed to air at room temperature for 4 days. After the storage, the diaphragms were washed clean with deionized water and dried for standby.

[0067] Finally, the above-mentioned first diaphragm, second diaphragm, and third diaphragm were respectively subjected to current-voltage (I-V) curve tests to obtain the final current I1 and final voltage V1 of the nanopores of the three diaphragms. All parameters were substituted into the formula for evaluating the pore size preservation effect:

[0068] The pore size preservation effects ΔD of the first diaphragm, second diaphragm, and third diaphragm were obtained as 0.04, 0.03, and 0.86 respectively. Among them, the pore size preservation effect ΔD of the second diaphragm was the smallest. That is to say, for a silicon nitride membrane with a thickness of 11.5 nm and a pore size of about 2.8 nm, dimethyl sulfoxide has a better pore size preservation effect.

[0069] The actual pore diameters of the first diaphragm, the second diaphragm, and the third diaphragm after preservation were measured by TEM measurement method to be 3 nm, 2.6 nm, and 13.3 nm respectively, and the actual preservation effect was consistent with the formula evaluation result of the above pore diameter preservation effect.

[0070] Example 5

[0071] Three silicon nitride membranes with a thickness of 7.5 nm were taken and named the first diaphragm, the second diaphragm, and the third diaphragm. The initial pore diameters of the first diaphragm and the second diaphragm were both measured to be 3 nm by TEM measurement method, and the initial pore diameter of the third diaphragm was 3.1 nm.

[0072] The first diaphragm, the second diaphragm, and the third diaphragm were respectively immersed in a 1 mol / L potassium chloride solution for current-voltage (I-V) curve testing to obtain the initial current I0 and the initial voltage V0 of the nanopores of the three diaphragms. After the test, the above three diaphragms were cleaned with deionized water and dried for standby.

[0073] Then, the first diaphragm and the second diaphragm were respectively immersed in a solution containing 1 mol / L lithium chloride and dimethyl sulfoxide and stored at room temperature for 5 days. The third diaphragm was used as a control and exposed to air at room temperature for 5 days. After the preservation, the diaphragms were cleaned with deionized water and dried for standby.

[0074] Finally, the above first diaphragm, the second diaphragm, and the third diaphragm were respectively subjected to current-voltage (I-V) curve testing to obtain the final current I1 and the final voltage V1 of the nanopores of the three diaphragms. All parameters were substituted into the formula for evaluating the pore diameter preservation effect:

[0075] The pore diameter preservation effects ΔD of the first diaphragm, the second diaphragm, and the third diaphragm were obtained to be 0.06, 0.03, and 0.60 respectively. Among them, the pore diameter preservation effect ΔD of the second diaphragm was the smallest. That is to say, for a silicon nitride membrane with a thickness of 7.5 nm and a pore diameter of about 3 nm, dimethyl sulfoxide has a better pore diameter preservation effect.

[0076] The actual pore diameters of the first diaphragm, the second diaphragm, and the third diaphragm after preservation were measured by TEM measurement method to be 3.5 nm, 3.2 nm, and 10.1 nm respectively, and the actual preservation effect was consistent with the formula evaluation result of the above pore diameter preservation effect.

[0077] Example 6

[0078] Three silicon nitride membranes with a thickness of 11.5 nm were taken and named the first diaphragm, the second diaphragm, and the third diaphragm. The initial pore diameters of the first diaphragm and the second diaphragm were both measured to be 3.6 nm by TEM measurement method, and the initial pore diameter of the third diaphragm was 3.5 nm.

[0079] The first diaphragm, the second diaphragm and the third diaphragm were respectively immersed in 1 mol / L potassium chloride solution for current-voltage (I-V) curve test to obtain the initial current I0 and initial voltage V0 of the nanopores of the three diaphragms. After the test, the three diaphragms were cleaned with deionized water and dried for standby.

[0080] Then, the first diaphragm and the second diaphragm were respectively immersed in a solution containing 1 wt% sodium hypochlorite and dimethyl sulfoxide and stored at room temperature for 3 days. The third diaphragm was used as a control and exposed to air at room temperature for 3 days. After the storage, the diaphragms were cleaned with deionized water and dried for standby.

[0081] Finally, the first diaphragm, the second diaphragm and the third diaphragm were respectively subjected to current-voltage (I-V) curve test to obtain the final current I1 and final voltage V1 of the nanopores of the three diaphragms. All parameters were substituted into the formula for evaluating the pore size preservation effect:

[0082] The pore size preservation effects ΔD of the first diaphragm, the second diaphragm and the third diaphragm were obtained as 2.33, 0.03 and 0.33 respectively. Among them, the pore size preservation effect ΔD of the second diaphragm was the smallest. That is to say, for a silicon nitride membrane with a thickness of 11.5 nm and a pore size of about 3.6 nm, dimethyl sulfoxide has a better pore size preservation effect.

[0083] The actual pore sizes of the first diaphragm, the second diaphragm and the third diaphragm after preservation were measured by TEM measurement method as 43.8 nm, 3.4 nm and 1.8 nm respectively. The actual preservation effect was consistent with the evaluation result of the above formula for pore size preservation effect. Sodium hypochlorite would cause the pore size to increase sharply and was not suitable for the pore size preservation of nanoporous membranes.

[0084] Example 7

[0085] Three silicon nitride membranes with a thickness of 11.5 nm were taken and named the first diaphragm, the second diaphragm and the third diaphragm. The initial pore sizes of the first diaphragm and the second diaphragm were both measured as 5.8 nm by TEM measurement method, and the initial pore size of the third diaphragm was 5.9 nm.

[0086] The first diaphragm, the second diaphragm and the third diaphragm were respectively immersed in 1 mol / L potassium chloride solution for current-voltage (I-V) curve test to obtain the initial current I0 and initial voltage V0 of the nanopores of the three diaphragms. After the test, the three diaphragms were cleaned with deionized water and dried for standby.

[0087] Then, immerse the first diaphragm and the second diaphragm in deionized water and dimethyl sulfoxide respectively, and store them at room temperature for 10 days. The third diaphragm is used as a control and exposed to air at room temperature for 10 days. After the storage is completed, dry the first diaphragm for later use, wash the diaphragm with deionized water, and dry it for later use.

[0088] Finally, perform current-voltage (I-V) curve tests on the above-mentioned first diaphragm, second diaphragm, and third diaphragm respectively to obtain the final current I1 and final voltage V1 of the nanopores of the three diaphragms. Substitute all parameters into the formula for evaluating the pore size preservation effect:

[0089] The pore size preservation effects ΔD of the first diaphragm, second diaphragm, and third diaphragm are 1.01, 0, and 0.68 respectively. Among them, the pore size preservation effect ΔD of the second diaphragm is the smallest. That is to say, for a silicon nitride membrane with a film thickness of 11.5 nm and a pore size of about 5.8 nm, dimethyl sulfoxide has a better pore size preservation effect.

[0090] The actual pore sizes of the first diaphragm, second diaphragm, and third diaphragm after storage are measured by TEM measurement method to be 33.3 nm, 5.8 nm, and 22.1 nm respectively. The actual preservation effect is consistent with the evaluation result of the above formula for pore size preservation effect. Deionized water will cause the pore size to increase sharply and is not suitable for the pore size preservation of nanoporous membranes.

[0091] Example 8

[0092] Take two silicon nitride membranes with a thickness of 11.5 nm, named the first diaphragm and the second diaphragm. The initial pore sizes of the first diaphragm and the second diaphragm are measured by TEM measurement method to be 5.7 nm and 5.8 nm respectively.

[0093] Immerse the first diaphragm, second diaphragm, and third diaphragm in 1 mol / L potassium chloride solution respectively, and perform current-voltage (I-V) curve tests to obtain the initial current I0 and initial voltage V0 of the nanopores of the two diaphragms. After the test is completed, wash the above two diaphragms with deionized water, and dry them for later use.

[0094] Then, expose the first diaphragm to air at room temperature for 2 days, immerse the second diaphragm in dimethyl sulfoxide, and store it at room temperature for 2 days. After the storage is completed, wash the stored diaphragm with deionized water, and dry it for later use.

[0095] Finally, perform current-voltage (I-V) curve tests on the above-mentioned first diaphragm and second diaphragm respectively to obtain the final current I1 and final voltage V1 of the nanopores of the diaphragm. Substitute all parameters into the formula for evaluating the pore size preservation effect:

[0096] The pore size preservation effects ΔD of the first diaphragm, the second diaphragm, and the third diaphragm are 0.50 and 0.01 respectively. Among them, the pore size preservation effect ΔD of the second diaphragm is the smallest. That is to say, for the silicon nitride film with a film thickness of 11.5 nm and a pore size of about 5.8 nm, dimethyl sulfoxide has a better pore size preservation effect.

[0097] The actual pore sizes of the first diaphragm and the second diaphragm after preservation measured by TEM measurement method are 1.6 nm and 5.7 nm respectively. The actual preservation effect is consistent with the formula evaluation result of the above pore size preservation effect.

[0098] The above has described the present invention in detail, aiming to enable those skilled in this field to understand the content of the present invention and implement it. However, it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preserving the pore size of a nanoporous membrane, characterized in that: The nanoporous membrane is a silicon nitride membrane, and the pore size preservation method includes contacting the inner surface of the nanoporous membrane with a neutral liquid or an organic solvent to isolate the nanopores of the nanoporous membrane from the external environment. Among them, the neutral liquid includes a mixed solution of one or more of lithium chloride and potassium chloride and water. The organic solvent includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, and isopropyl alcohol.

2. The method for preserving the pore size of the nanoporous membrane according to claim 1, wherein: The contact method includes one or more of immersion, spraying, and spin coating.

3. The pore size preservation method of the nanoporous membrane according to claim 1, characterized in that: The thickness of the nanoporous membrane is 7.5 - 12 nm.

4. The method for preserving the pore size of the nanoporous membrane according to claim 1 or 3, characterized in that: The pore size of the nanoporous membrane is 2.7 - 8.7 nm.

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