Nano-channel film with pH response hydrophilic-hydrophobic conversion and preparation method of nano-channel film

Abstract

The invention discloses a nano-channel film with pH response hydrophilic-hydrophobic conversion and a preparation method thereof. The preparation process of the film comprises the following steps: after carrying out surface treatment on a PET film, etching a nano channel on the surface of the PET film by adopting a chemical etching method; placing the PET film with the nano-channel in a modified MES mixed solution for activating treatment, and then cleaning to obtain a precursor film; and placing the precursor film in a mixed modification solution containing glycine and amylamine to carry out pore channel internal modification, and then cleaning with ultrapure water to obtain the porous carbon film. The carboxyl group of glycine in the film can be used as a protonated or deprotonated trigger group under different pH conditions, the amylamine can effectively prolong the carbon chain length of a modifier and can be used as a hydrophobic chain to adjust the hydrophilicity and hydrophobicity of a nano channel, and based on the synergistic effect between glycine and amylamine, the film can realize the characteristic of hydrophilicity and hydrophobicity conversion under different pH conditions.

Description

Technical Field

[0001] The invention relates to an organic film with nanochannels, in particular to a pH-responsive hydrophilic-hydrophobic conversion nanochannel film and a preparation method thereof, belonging to the technical field of biochemical sensing. Background Art

[0002] In the field of biosensing and molecular detection, nanochannel technology has shown great potential. As a molecular channel, nanochannels can realize material transfer and recognition at the single-molecule level, and they play a key role in biomedical applications such as DNA sequencing and protein analysis. However, traditional unmodified nanochannels have problems such as poor selectivity and sensitivity. In recent years, chemical modification of nanochannels to improve their performance has become a research hotspot. Glycine and pentylamine, as molecules with good biocompatibility and adjustable structure, are widely used in the surface modification of nanochannels to improve the stability and selectivity of the pores. Although studies have shown that glycine and pentylamine modification can significantly enhance the recognition ability of nanochannels for specific molecules, the existing technology still has challenges in modification efficiency, stability and adaptability to complex environments, which limits its effectiveness in practical applications. Therefore, the development of an efficient and stable glycine and pentylamine modified nanochannel technology is of great significance to the promotion of biosensing technology. Summary of the invention

[0003] In view of the problems existing in the prior art, the first object of the present invention is to provide a nanochannel film with pH-responsive hydrophilic-hydrophobic conversion. The film is based on the synergistic effect of glycine and pentylamine on the inner wall of the conical nanochannel, and realizes the characteristics of different pH-responsive hydrophilic-hydrophobic conversion under different total salt concentrations, wherein the carboxyl group of glycine will act as a trigger group for protonation or deprotonation under different pH conditions, and the addition of pentylamine can effectively extend the carbon chain length of the modifier, and as a hydrophobic chain, it regulates the hydrophilicity of the nanochannel, that is, glycine acts as a pH-responsive switch, and pentylamine acts as an amplifier of the hydrophilic-hydrophobic effect, thereby greatly improving the sensitivity and response rate of the hydrophilicity of the film to pH response.

[0004] The second object of the present invention is to provide a method for preparing a pH-responsive hydrophilic-hydrophobic conversion nanochannel film. The method activates the hydroxyl groups on the inner wall surface of the nanochannel by a modified MES mixed solution, so that the amino groups of glycine and pentylamine react with the modified MES mixed solution, and then directly modifies the inner wall of the nanochannel with glycine and pentylamine by an immersion method in a PBS buffer environment; the method has the advantages of simple operation, low cost and environmental friendliness, and is convenient for industrial continuous production.

[0005] In order to achieve the above technical objectives, the present invention provides a method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film, comprising: Step S1, after surface treatment of the PET film, a nanochannel is etched on the surface by chemical etching; Step S2, placing the obtained PET film with nanochannels in a modified MES mixed solution for activation treatment, and then washing it to obtain a precursor film; Step S3, placing the precursor film in a mixed modification solution containing glycine and pentylamine to modify the inside of the pores, and then washing with ultrapure water to obtain; The molar ratio of glycine to pentylamine in the mixed modification solution is 1:2-4.

[0006] The ratio of glycine to pentylamine in the modification solution of the present invention must be strictly implemented in accordance with the above requirements. The ratio of the two inside the nanochannel after modification is positively correlated with the ratio of the two in the modification solution. If the ratio of glycine is too high, the overall hydrophilicity inside the nanochannel will be higher. If the ratio of pentylamine is too high, the overall hydrophobicity inside the nanochannel will be too high, and it will be difficult to achieve a rapid and significant conversion of the hydrophilicity and hydrophobicity of the film.

[0007] As a preferred solution, the surface treatment method in step S1 is: placing the PET film under a UV lamp, irradiating one side for 11 to 13 hours and the other side for 8 to 10 hours.

[0008] As a preferred solution, the chemical etching method is an asymmetric etching method, and the process is: a transmembrane voltage of 1~2V is applied to both sides of the surface-treated PET film, one side of the film contacts the etching solution, and the other side contacts the blocking solution, until the ion current on both sides of the film increases by two orders of magnitude compared with the initial state.

[0009] As a preferred solution, the nanochannel is a conical channel with a large pore diameter of 200-250 nm and a small pore diameter of 10-50 nm.

[0010] As a preferred solution, the etching solution is a NaOH solution with a concentration of 7-10 mol / L.

[0011] As a preferred solution, the blocking liquid is a 1 mol / L mixed solution of acetic acid and KCl, and the volume mass ratio of acetic acid to KCl is 0.5-0.6 ml / g.

[0012] As a preferred solution, ultrapure water is required to be immersed overnight before the activation treatment in step S2; the activation treatment process is: placing the PET film with nanochannels in a MES mixed solution containing EDC and NHS, and immersing for 10 to 20 minutes.

[0013] As a preferred solution, the concentration of MES in the MES mixed solution is 0.08-0.12 mol / L, the concentration of EDC is 40-60 mmol / L, and the concentration of NHS is 20-30 mmol / L.

[0014] Under the catalysis of EDC, NHS reacts with the carboxyl groups on the inner wall of the nanochannel to form a CO-NHS group with high grafting activity, which can react quickly with the amino compound added later to form a CO-NH bond to achieve covalent modification of pentylamine and glycine. If the concentrations of the two are not within the above range, the activation effect of the hydroxyl group will be reduced, or even completely eliminated, which will lead to the inability to effectively carry out the subsequent covalent modification and make it difficult to achieve the hydrophilic-hydrophobic conversion of the film.

[0015] As a preferred solution, the cleaning process in step S2 is: washing the PET film with a neutral PBS buffer until the MES mixed solution is completely removed.

[0016] It should be noted that after the nanochannel is activated with the MES mixed solution, it must be thoroughly cleaned before the subsequent modification steps can be carried out. This is because the glycine in the modification contains a carboxyl group. If it comes into contact with the residual EDC / NHS mixture, it will catalyze the condensation reaction of glycine with glycine, and glycine with pentylamine in the solution, resulting in the inability of glycine and pentylamine to be modified on the inner wall surface of the nanochannel.

[0017] As a preferred solution, the concentration of glycine in the mixed modification solution is 10-20 mmol / L, and the concentration of pentylamine is 40-50 mmol / L.

[0018] As a preferred solution, the time for modifying the interior of the pore is 20 to 50 minutes.

[0019] As a preferred solution, the ultrapure water cleaning method is immersion cleaning for 1 to 3 hours.

[0020] The present invention also provides a pH-responsive hydrophilic-hydrophobic switching nanochannel film obtained by any of the preparation methods described above; the film is hydrophobic under acidic conditions and hydrophilic under alkaline conditions.

[0021] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are: 1) The film provided by the present invention is based on the synergistic effect of glycine and pentylamine on the inner wall of the conical nanochannel, achieving different pH-responsive hydrophilic-hydrophobic conversion characteristics under different total salt concentrations, wherein the carboxyl group of glycine acts as a trigger group for protonation or deprotonation under different pH conditions, and the addition of pentylamine can effectively extend the carbon chain length of the modifier, acting as a hydrophobic chain to regulate the hydrophilicity of the nanochannel, that is, glycine acts as a pH-responsive switch, while pentylamine acts as an amplifier of the hydrophilic-hydrophobic effect, thereby greatly improving the sensitivity and response rate of the film's hydrophilicity to pH response.

[0022] 2) In the preparation method provided by the present invention, the hydroxyl groups on the inner wall surface of the nanochannel are activated by a modified MES mixed solution to facilitate the reaction of the amino groups of glycine and pentylamine with the mixed solution, and then the glycine and pentylamine are directly modified on the inner wall of the nanochannel by an immersion method in a PBS buffer environment; the method has the advantages of simple operation, low cost and environmental friendliness, and is convenient for industrial continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the thin film nanochannel modification process in Example 1 of the present invention; Figure 2 is an IV curve diagram of the PET film with nanochannels in Example 1 of the present invention; Figure 3 The IV curves of the PET film with nanochannels before and after modification of glycine and pentylamine in Example 1 of the present invention; Figure 4 Schematic diagram of the pH response hydrophilicity and hydrophobicity conversion process of the film in Example 1 of the present invention; in, Figure 4 (a) is a schematic diagram of the principle of pH-responsive hydrophilicity and hydrophobicity conversion of the film. Figure 4 (b) is the conductivity image of the film in 1MNaCl solution at pH=3 and pH=11. Figure 4 (c) Conductivity images of the film in 0.001M NaCl solution at pH = 3 and pH = 11. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner in conjunction with the accompanying drawings and preferred embodiments of the specification. It should be noted that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a pH-responsive hydrophilic-hydrophobic switching nanochannel film, the preparation process of which is as follows: first, the surface of the PET film is activated by ultraviolet irradiation, then the nanopores are etched by chemical etching, the etched nanopores are soaked in a MES solution mixed with EDC and NHS, then cleaned with water, and then a PBS solution containing glycine and pentylamine is added to obtain a film modified with glycine and pentylamine. The structural formulas of glycine and pentylamine are: Glycine: NH2-CH2-COOH Amylamine: CH3-(CH2)3-NH2

[0026] Example 1 This embodiment provides a pH-responsive hydrophilic-hydrophobic switching nanochannel film, and the specific process is as follows: 1. Preparation of single cone nanochannels on PET film 1) Irradiate the PET film under UV light for 12 hours on one side and 9 hours on the other side, and set aside; 2) Prepare etching solution: 250mL of 9mol / L NaOH solution, of which 90.0g of NaOH is added; prepare blocking solution: 250mL of 1mol / L HCOOH and KCl mixed solution, of which 9.5mL of CH2COOH and 18.6g of KCl are added; 3) Apply a transmembrane voltage at both ends of the film. The side of the film with a longer irradiation time contacts the etching solution, and the other side contacts the blocking solution. At the same time, a current measuring device is used to detect the ion current on both sides of the membrane. When the ion current increases by two orders of magnitude, it indicates that the nanochannel has been opened and the film is removed; 2. Preparation of precursor film 1) Prepare a MES mixed solution according to 0.1 mol / L MES, 50 mmol / L EDC and 25 mmol MES and set aside; 2) Dissolve 2.25g NaCl, 0.0741g NaH2PO4•H2O and 0.7252g Na2HPO4•12H2O in 250ml deionized water to prepare 0.01mol / L PBS buffer for later use; 2) The obtained PET film with nanochannels was immersed in the MES mixed solution for 15 minutes (except for the data that cannot be accurately counted, all the data in the manual should be used as point values), and then washed with PBS buffer for 3 times; 3. Modification of glycine and pentylamine 1) Take 10 ml PBS buffer, add 0.01126 g of glycine and 0.523 ml of pentylamine to prepare a mixed modification solution of 45 mmol / L pentylamine and 15 mmol / L glycine, and set aside; 2) The obtained precursor film is placed in the mixed modification solution and immersed for 30 minutes. After taking it out, it is soaked and cleaned in ultrapure water for 2 hours.

[0027] Comparative Example 1 This comparative example is exactly the same as Example 1, except that only glycine is used to modify the nanochannel. The specific process is as follows: 1) Take 10 ml PBS buffer and add 0.01126 g of glycine to prepare 15 mmol / L glycine modification solution for later use; 2) The obtained precursor film is placed in the mixed modification solution and immersed for 30 minutes. After taking it out, it is soaked and cleaned in ultrapure water for 2 hours.

[0028] The conductivity of the obtained film was measured in 1 M NaCl solution or 0.001 M NaCl solution at pH 11 and pH 3, respectively. The conductivity measured in 1 M NaCl solution at pH 11 was 1.02 ± 0.07 nS; the conductivity measured in 1 M NaCl solution at pH 3 was 1.02 ± 0.04 nS, with no significant difference. The conductivity measured in 0.001 M NaCl solution at pH 11 was 0.054 ± 0.009 nS; the conductivity measured in 0.001 M NaCl solution at pH 3 was 0.052 ± 0.005 nS, with no significant difference. This shows that the use of single glycine to modify the nanoporous film has no obvious hydrophilic-hydrophobic conversion effect.

[0029] Comparative Example 2 This comparative example is exactly the same as Example 1, except that only pentylamine is used to modify the nanochannel. The specific process is as follows: 1) Take 10 ml of PBS buffer and add 0.523 ml of pentylamine to prepare 45 mmol / L pentylamine modification solution for later use; 2) The obtained precursor film is placed in the mixed modification solution and immersed for 30 minutes. After taking it out, it is soaked and cleaned in ultrapure water for 2 hours.

[0030] The conductivity of the obtained film was measured in 1 M NaCl solution or 0.001 M NaCl solution at pH 11 and pH 3, respectively. The conductivity measured in 1 M NaCl solution at pH 11 was 0.87 ± 0.02nS; the conductivity measured in 1 M NaCl solution at pH 3 was 0.82 ± 0.01nS, with no significant difference. The conductivity measured in 0.001 M NaCl solution at pH 11 was 0.008 ± 0.002nS; the conductivity measured in 0.001 M NaCl solution at pH 3 was 0.008 ± 0.004nS, with no significant difference. This shows that the nanoporous film modified with single pentylamine has no obvious hydrophilic-hydrophobic conversion effect.

[0031] In order to better illustrate the advantages of the above technical solution, a series of characterizations were performed on the films obtained in the above stages of the present invention.

[0032] First, the present invention carries out electrochemical characterization of a single nanochannel on a PET film having nanochannels, and the results are as follows: Figure 2 As shown, a transmembrane voltage of 1V is applied to both sides of the film, and both sides of the film are in contact with 1 mol / L NaCl solution. The rectification process is detected by a current detection device to obtain its IV curve. From the figure, it can be seen that the single-conical nanopore has a rectification effect under the condition of applied voltage, and the negative current is larger than the positive current. Therefore, it can be proved that the inner surface of the prepared single-conical nanopore carries a negative charge.

[0033] Next, the present invention also conducted electrochemical characterization on unmodified PET film and film modified with glycine and pentylamine, and the results are as follows: Figure 3 As shown, through Figure 3 It can be seen that after the PET film was modified with glycine and pentylamine, the IV curve changed, indicating that the surface charge distribution inside the pores and the hydrophilicity and hydrophobicity changed.

[0034] Furthermore, the present invention also conducted a hydrophilic-hydrophobic conversion test on the film modified with glycine and pentylamine, and the process was as follows: 1) Prepare 1 mol / L NaCl solution and 0.001 mol / L NaCl solution respectively for use, and adjust the pH of the NaCl solution by using caustic soda solution and dilute hydrochloric acid; 2) A transmembrane voltage was applied to the film modified with glycine and pentylamine. Both sides of the film were exposed to a 1 mol / L NaCl solution at pH = 11. The conductivity was detected using an electric current device. The film was then rinsed with a 1 mol / L NaCl solution at pH = 3. Both sides of the film were exposed to a 1 mol / L NaCl solution at pH = 3. The conductivity was detected. The above process was repeated once to obtain the conductivity diagram of the film in a high salt concentration environment and different pH environments. The results are shown in Figure 2. Figure 4 (b) shown.

[0035] 3) A transmembrane voltage was applied to the film modified with glycine and pentylamine. Both sides of the film were exposed to a 0.001 mol / L NaCl solution at pH = 11. The conductivity was detected using an electric current device. The film was then rinsed with a 0.001 mol / L NaCl solution at pH = 3. Both sides of the film were exposed to a 0.001 mol / L NaCl solution at pH = 3. The conductivity was detected. The above process was repeated once to obtain the conductivity diagram of the film in a high salt concentration environment and different pH environments. The results are shown in Figure 2. Figure 4 (c) shown.

[0036] pass Figure 4 (b) It can be seen that when the total salt concentration of the solution is ≥0.1 mol / L, the conductivity of the film is proportional to the size of the nanochannel. Under acidic conditions, the carbon chain end of pentylamine folds toward the carboxyl group, making the pore size of the nanochannel larger and showing high conductivity. At this time, the nanoporous film exhibits strong hydrophobicity; under alkaline conditions, the carboxyl group dissociates into carboxylate groups, which repel the carbon chain end of pentylamine, making the pore size of the hydrophilic nanochannel smaller and showing low conductivity. At this time, the nanoporous film exhibits strong hydrophilicity. , while through Figure 4 As shown in (c), when the total salt concentration of the solution is less than 0.01 mol / L, the conductivity is proportional to the surface charge density of the nanopore. Under alkaline conditions, the carboxyl group dissociates into carboxylate groups with negative charges, and the charge density increases, so the nanopore exhibits high conductivity. At this time, the nanopore film exhibits strong hydrophilicity; under acidic conditions, the carboxylate groups are protonated into carboxyl groups, lose negative charges, and the charge density decreases. Therefore, the nanopore exhibits low conductivity. At this time, the nanopore film exhibits strong hydrophobicity.

Claims

1. A method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film, characterized in that: include: Step S1, after surface treatment of the PET film, a nanochannel is etched on the surface by chemical etching; Step S2, placing the obtained PET film with nanochannels in a modified MES mixed solution for activation treatment, and then washing it to obtain a precursor film; Step S3, placing the precursor film in a mixed modification solution containing glycine and pentylamine to modify the inside of the pores, and then washing with ultrapure water to obtain; The molar ratio of glycine to pentylamine in the mixed modification solution is 1:2-4.

2. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: The surface treatment method in step S1 is: placing the PET film under a UV lamp, irradiating one side for 11 to 13 hours and the other side for 8 to 10 hours.

3. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: The chemical etching method is an asymmetric etching method, and the process is as follows: a transmembrane voltage of 1 to 2 V is applied to both sides of the surface-treated PET film, one side of the film contacts the etching solution, and the other side contacts the blocking solution, until the ion current on both sides of the film increases by two orders of magnitude compared with the initial state; the nanochannel is a conical channel, the large pore diameter of which is 200 to 250 nm, and the small pore diameter is 10 to 50 nm.

4. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 3, characterized in that: The etching solution is a NaOH solution with a concentration of 7-10 mol / L; the blocking solution is a mixed solution of acetic acid and KCl with a concentration of 1 mol / L, and the volume mass ratio of acetic acid to KCl is 0.5-0.6 ml / g.

5. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: In step S2, ultrapure water is required to be used for overnight immersion before the activation treatment. The process of the activation treatment is as follows: the PET film with nanochannels is placed in a MES mixed solution containing EDC and NHS and immersed for 10 to 20 minutes.

6. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 5, characterized in that: The concentration of MES in the MES mixed solution is 0.08-0.12 mol / L, the concentration of EDC is 40-60 mmol / L, and the concentration of NHS is 20-30 mmol / L.

7. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: The cleaning process in step S2 is: washing the PET film with a neutral PBS buffer until the MES mixed solution is completely removed.

8. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: The concentration of glycine in the mixed modification solution is 10-20 mmol / L, and the concentration of pentylamine is 40-50 mmol / L.

9. The method for preparing a pH-responsive hydrophilic-hydrophobic switching nanochannel film according to claim 1, characterized in that: The time for modifying the interior of the pores is 20 to 50 minutes; the ultrapure water cleaning method is immersion cleaning, and the time is 1 to 3 hours.

10. A pH-responsive hydrophilic-hydrophobic switching nanochannel film, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9; the film is hydrophobic under acidic conditions; the film is hydrophilic under alkaline conditions.

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