Method for modifying gold layer in nanochannel

Abstract

The invention discloses a method for modifying a gold layer on the inner surface of a nanochannel. The preparation method comprises the following steps: performing chemical etching on a PET (Polyethylene Terephthalate) film to obtain a conical porous nano-channel with carboxyl anions on the inner surface, and modifying the nano-channel by using L-cysteine through a covalent modification method to obtain an L-cysteine modified nano-channel; and reducing [AuCl4] <-> in the HAuCl4 solution into elemental Au through-SH exposed from L-cysteine, and inducing deposition of the gold layer on the inner surface, thereby constructing the solid-state multi-nano channel with the inner surface modified with the gold layer. The method is easy to operate, low in cost and not prone to blockage, and the gold layer can be evenly and stably deposited on the inner surface of the nanometer channel.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanostructure surface modification and relates to a method for modifying a gold layer in a nanochannel. Background Art

[0002] The deposition of a gold layer on the inner surface of a nanochannel is a key step in various nanotechnologies. After the gold layer deposition is completed, the gold layer in the nanochannel can serve as a substrate for further modification of self-assembled monolayers (SAMs). SAMs can selectively adsorb molecules or ions on the gold layer surface through chemical reactions or physical adsorption to form surface structures with specific functions. Therefore, the process of depositing a gold layer on the inner surface of a nanochannel plays a crucial role in many applications such as biosensors, catalysts, drug delivery, gene detection, etc.

[0003] At present, the deposition of the gold layer on the inner surface of nanochannels mainly adopts methods such as ion sputtering, electrochemical deposition, electroless deposition, or vacuum film plating. Among them, ion sputtering uses a high-energy ion beam to bombard the gold target, causing gold atoms to sputter out and deposit on the inner surface of the nanochannels. Although this method can achieve gold layer deposition to a certain extent, the equipment is expensive and requires professional ion sources and vacuum systems, which greatly increases the production cost. Moreover, in the complex microstructure of nanochannels, it is difficult to precisely control the incident direction of ions, and sputtering dead angles are likely to occur, resulting in uneven deposition of the gold layer on some inner surfaces of the nanochannels and affecting the consistency of device performance. Electrochemical deposition is carried out by using the nanochannels as the cathode in an electrolyte containing gold ions, applying a certain electric field, and causing the gold ions to migrate to the surface of the nanochannels under the action of the electric field and be reduced and deposited to form a gold layer. However, the special microstructure of nanochannels makes the internal electric field distribution extremely uneven, which leads to a large difference in the deposition rate of gold ions at different positions and makes it difficult to obtain a uniform gold layer thickness. At the same time, during the deposition process, side reactions such as hydrogen evolution are likely to occur on the cathode surface. These side reactions not only consume the effective components in the electrolyte, increase the production cost, but may also introduce defects such as pores in the gold layer, reducing the quality and adhesion of the gold layer. Electroless deposition is a method in which, without an external current, suitable reducing agents are used to reduce and deposit the gold ions in the solution on the surface of the catalytically active nanochannels to form a gold layer. The stability of the plating solution in this method is poor, and it is significantly affected by environmental factors such as temperature and pH value. Slight carelessness will cause the plating solution to decompose, which not only wastes raw materials but also interrupts the production process and affects production efficiency. Vacuum film plating is a method in which gold is heated to a high temperature to evaporate, and then it condenses and deposits on the surface of the nanochannels to form a gold layer. This method has extremely high requirements for the vacuum environment and requires high-performance vacuum equipment, which greatly increases the equipment cost and maintenance cost. When depositing on the inner surface of nanochannels, since the movement trajectory of gold atoms is difficult to precisely control, it is difficult to ensure that gold atoms are evenly deposited on all parts of the inner surface in the complex nanochannel structure, and uneven deposition is likely to occur, affecting the performance of nano-devices.

[0004] Therefore, there are still many difficulties in modifying the gold layer on the inner surface of nanochannels, such as: (i) the size of nanochannels is small, and the plating metal is extremely likely to block the nanochannels; (ii) the deposition of the gold layer on the inner surface of nanochannels is uneven. When the nanochannels are deep or have a complex shape, due to changes in current, electrolyte flow, or reaction conditions, the deposition rate of the metal in different regions is different, which may lead to the deposition layer being too thick or too thin in some parts, thus affecting the performance of the final device. In summary, although the existing methods for depositing the gold layer on the inner surface of nanochannels can achieve gold layer deposition to a certain extent, they all have their own defects and problems. Therefore, there is an urgent need in this field for a new method to obtain a gold layer with a uniform surface, low cost, and good stability for modifying the inner surface of nanochannels.

[0005] L-cysteine is a non-toxic, water-soluble, biocompatible, naturally occurring proteinogenic amino acid with functional groups of mercapto (-SH), carboxyl (-COOH) and primary amine (-NH2). The amino group of L-cysteine can be modified to the inner surface of the nanochannel by covalently reacting with the carboxyl group in the nanochannel, which provides the possibility for the modification of L-cysteine in the nanochannel in the present invention. L-cysteine can be used as a reducing agent and a stabilizer. During the synthesis of gold nanoparticles, the sulfhydryl group of L-cysteine binds to the surface of the gold nanoparticles to form stable gold-sulfur bonds, enhancing the stability of the gold nanoparticles, which provides the possibility for the deposition of the gold layer in the present invention. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a method for modifying a gold layer on the inner surface of a nanochannel. This method is achieved by modifying L-cysteine molecules to the inner surface of a solid nanochannel and using the sulfhydryl group of L-cysteine to bind to the surface of gold nanoparticles, providing a new method for modifying a gold layer on the inner surface of a nanochannel with simple operation, low cost, not easily blocked, and uniform deposition.

[0007] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0008] A method for modifying a gold layer on the inner surface of a nanochannel, which comprises the following steps:

[0009] Step 1: Clean the surface of the porous PET membrane irradiated by heavy ions;

[0010] Step 2: Etch the nanochannels of the PET membrane obtained in Step 1 by chemical etching to obtain a PET membrane with porous conical nanochannels. The inner surface of the porous conical nanochannels has carboxyl groups and is negatively charged under neutral conditions;

[0011] Step 3: Immerse the PET membrane obtained in Step 2 in a mixed solution of 0.2 mol / mL NHS and 0.1 mol / mL EDC for a period of time, and take it out and rinse with ultrapure water;

[0012] Step 4: Immerse the PET membrane obtained in Step 3 in an aqueous solution of 0.01 mol / mL L-cysteine for a period of time to obtain a PET membrane with porous conical nanochannels modified with L-cysteine;

[0013] Step 5: Immerse the PET membrane obtained in Step 4 in a 0.005 mol / mL HAuCl4 solution for a period of time, and immediately obtain a PET membrane nanochannel with a gold layer modified on its inner surface.

[0014] Further, the structure of the L-cysteine is:

[0015]

[0016] Further, in Step 1, the porous PET membrane irradiated by heavy ions is soaked in ultrapure water for 3 minutes to remove dust and impurities on the membrane surface, dried, and then irradiated on each side under an ultraviolet lamp for 1.5 h for standby.

[0017] Further, in Step 2, the etching channels are carried out as follows: A transmembrane voltage is applied on both sides of the PET membrane obtained in Step 1. An etching solution, i.e., 9 mol / L NaOH solution, is added to one side of the PET membrane, and a blocking solution, i.e., a mixed solution of 1 mol / L HCOOH and KCl, is added to the other side. A current measuring device is used to detect the etching process. Once the ionic current increases by two orders of magnitude, it indicates that the nanochannels have been etched through, and thus a PET membrane with porous conical nanochannels is obtained.

[0018] Further, after obtaining the PET membrane with porous conical nanochannels by chemical etching in Step 2, the method further includes applying a transmembrane voltage on both sides of the obtained PET membrane, adding 0.1 mol / L KCl solution on both sides of the membrane, using a current detection device to detect the rectification process, and proving that the inner surface of the prepared porous conical nanochannels carries negative charges through the rectification effect.

[0019] Further, in Step 3, the PET membrane obtained in Step 2 is soaked in a mixed solution of 0.2 mol / mL NHS and 0.1 mol / mL EDC for 24 h.

[0020] Further, in Step 4, the PET membrane obtained in Step 3 is soaked in a 0.01 mol / mL aqueous solution of L-cysteine for 24 h to obtain an L-cysteine-modified PET membrane with porous conical nanochannels.

[0021] Further, in Step 5, the PET membrane obtained in Step 4 is soaked in a 0.005 mol / mL HAuCl4 solution for 12 h.

[0022] Further, in Step 5, the pH value of the HAuCl4 solution is adjusted to 3.

[0023] In this technical solution, the -NH2 of L-cysteine covalently reacts with -COOH in the nanochannels and is thus modified onto the inner surface of the nanochannels. The -SH contained in L-cysteine adsorbs [AuCl4] - and is reduced to elemental Au, synthesizing stable Au nanoparticles. Au 0 can promote the subsequent [AuCl4] -The dechlorination reduction of Au in the molecule forms gold clusters, and the gold clusters can be combined with -SH groups through Au-S bonds, so that the gold layer is uniformly deposited on the inner surface of the nanochannels.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides a method for modifying the inner surface of a solid multi-nanochannel with a gold layer based on L-cysteine modification. First, the PET membrane is subjected to ion track etching to obtain porous conical nanochannels with carboxyl groups on the inner surface, which are negatively charged under neutral conditions, while L-cysteine has an -NH2, so L-cysteine can be modified to the inner surface of the nanochannels by covalent reaction to obtain L-cysteine-modified nanochannels. The L-cysteine fixed inside the nanochannels exposes -SH, and -SH in-situ reduces [AuCl4] in the solution - to elemental Au, and Au 0 promotes the subsequent dechlorination reduction of [AuCl4] - in the molecule to form gold clusters, and the gold clusters are combined with -SH groups through Au-S bonds, inducing the deposition of the gold layer on the inner surface. Subsequently, functional molecules containing mercapto groups can be modified on the surface of the gold layer to achieve further functionalization of the nanochannels.

[0026] The method of the present invention is simple to operate, low in cost, not easily blocked, and can construct solid multi-nanochannels with a uniformly deposited gold layer on the inner surface. Brief Description of the Drawings

[0027] Figure 1 is a schematic diagram of the principle of the method of the present invention.

[0028] Figure 2 is an I-V curve graph of the electrochemical characterization of the bare conical porous nanochannels, L-cysteine-modified multi-nanochannels, and porous nanochannels with a gold layer modified on the inner surface provided in the examples of the present invention in 0.1M KCl.

[0029] Figure 3 is the XPS data of the Au element of the gold layer modified inside the nanochannels provided in the examples of the present invention.

[0030] Figure 4 is the fluorescence spectrum of the PET membranes with a blank surface, modified with L-cysteine, and modified with a gold layer provided in the examples of the present invention.

[0031] Figure 5 is the EDS data of the gold layer modified inside the nanochannels provided in the examples of the present invention.

[0032] Figure 6 is the contact angle (CA) data of the PET membrane before and after being modified with L-cysteine and a gold layer on the surface provided in the examples of the present invention. Detailed implementation mode

[0033] The present invention provides a method for modifying a gold layer on the inner surface of a nanochannel, and a schematic diagram of its principle is shown in Figure 1 . First, the PET film is chemically etched to obtain a conical porous nanochannel. The inner surface of the nanochannel has carboxyl negative ions. Then, L-cysteine is used to modify the nanochannel by a covalent modification method to obtain an L-cysteine modified nanochannel. The exposed -SH of L-cysteine reduces [AuCl4] in the solution - to elemental Au, inducing the deposition of the gold layer on the inner surface, that is, constructing a solid multi-nanochannel with a gold layer modified on the inner surface.

[0034] The present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings of the specification.

[0035] Example 1 Modifying a gold layer on the inner surface of a nanochannel

[0036] A method for modifying a gold layer on the inner surface of a nanochannel includes the following steps:

[0037] 1) Clean the surface of the porous PET film irradiated by heavy ions

[0038] First, soak the porous PET film irradiated by heavy ions (pore density 7*10 7 / cm 2 , thickness 12 μm, purchased from the Lanzhou Interdisciplinary Heavy Ion Microbeam Laboratory) in ultrapure water for 3 minutes, remove the dust and impurities on the film surface, dry it, and set it aside. Then irradiate each side under ultraviolet light for 1.5 h and set it aside.

[0039] 2) Etch the PET film obtained in step 1 by chemical etching to obtain a PET film with porous conical nanochannels, and the inner surface of the porous conical nanochannels has carboxyl negative ions;

[0040] Prepare 250 mL of 9 mol / L NaOH solution, in which 90.0 g of NaOH is added and stored in a 250 mL volumetric flask, and 250 mL of 1 mol / L HCOOH and KCl mixed solution, in which 9.5 mL of HCOOH and 18.6 g of KCl are added and stored in a 250 mL volumetric flask.

[0041] Next, the nanochannels are etched by chemical etching. The preparation of the porous conical nanochannels uses an asymmetric etching method: that is, a transmembrane voltage is applied on both sides of the irradiated thin film. An etching solution, namely 9 mol / L NaOH solution, is added to one side of the thin film, and a blocking solution, namely a mixed solution of 1 mol / L HCOOH and KCl, is added to the other side. An electric current measuring device is used to detect the etching process. Once the ionic current increases by two orders of magnitude, it indicates that the nanochannels have been etched through. At this time, PET porous conical nanochannels are obtained, preparing for the modification experiment.

[0042] 3) Electrochemical characterization of the porous nanochannels of the PET membrane

[0043] Due to the asymmetry of the structure of the porous conical nanochannels and the presence of carboxylate anions on the inner surface of the nanochannels, there is a rectification effect under an applied voltage. Therefore, the rectification effect of the etched porous conical nanochannels is detected.

[0044] Prepare 100 mL of 0.1 mol / L KCl solution, in which 0.74 g of KCl is added and stored in a 100 mL volumetric flask. A transmembrane voltage is applied on both sides of the PET thin film, and 0.1 mol / L KCl solution is added to both sides of the thin film. An electric current detection device is used to detect the rectification process. It can be seen from the I-V curve data that the single conical nanochannels have a rectification effect under an applied voltage, and the negative current is larger than the positive current. Therefore, it can be proved that the inner surface of the prepared conical nanochannels is negatively charged.

[0045] Figure 2 The I-V curve graphs of the electrochemical characterization of the bare conical porous nanochannels, L-cysteine modified multi-nanochannels, and porous nanochannels with a gold layer modified on the inner surface in 0.1 M KCl are shown. The electrochemical characterization of the unmodified porous conical nanochannels is to prove that the etched nanochannels have a rectification effect and the inner surface has carboxylate anions. The electrochemical characterization of the L-cysteine modified nanochannels is to prove that the effective charge on the inner surface of the modified nanochannels is reduced and the inner surface still has a negative charge. The electrochemical characterization of the porous nanochannels with a gold layer modified on the inner surface is to prove that the limited space inside the nanochannels is reduced after the gold layer is modified.

[0046] 4) Modify L-cysteine on the inner surface of the nanochannels

[0047] Prepare 0.01 mol / mL aqueous solution of L-cysteine hydrochloride, in which 6.70 mg of L-cysteine hydrochloride is added and 50 mL of ultrapure water is stored in a centrifuge tube for later use.

[0048] Prepare 100 mL of 0.1 mol / L EDC solution, with 1.55 g of EDC added, and store it in a 100 mL volumetric flask. Prepare 100 mL of 0.2 mol / L NHS solution, with 2.3 g of NHS added, and store it in a 100 mL volumetric flask.

[0049] Mix 10 mL of 0.1 mol / L EDC solution and 10 mL of 0.2 mol / L NHS solution evenly in a 25 mL beaker. Then place the etched porous conical nanochannels into the beaker and let it stand for 24 h. Take it out, rinse with ultrapure water, and dry for later use. Then place 10 mL of 0.01 mol / mL L-cysteine hydrochloride aqueous solution in a 25 mL beaker, place the porous conical nanochannels into the beaker, and let it stand for 24 h. Take it out, rinse with ultrapure water, and dry for later use.

[0050] 5) Modify the inner surface of the nanochannels in the PET membrane with a gold layer

[0051] Prepare 0.005 mol / mL HAuCl4 solution, with 16.98 mg of HAuCl4 powder added and 10 mL of ultrapure water. Adjust the pH to 3 and store it in a centrifuge tube in the dark for later use. Immerse the conical nanochannel film modified with L-cysteine in the HAuCl4 solution and let it stand for 12 h. Take it out, rinse with ultrapure water, and dry. Thus, a gold layer is modified on the inner surface of the nanochannels in the PET membrane.

[0052] Example 2 Electrochemical Characterization of Layer-by-Layer Modified Nanochannels

[0053] Add 0.1 mol / L KCl solution on both sides of the etched porous conical nanochannel PET membrane, apply a transmembrane voltage of +1 to -1 across the membrane, and use a current detection device to detect the rectification process, as shown by the bare nanochannel indication line in Figure 2 As shown in step 4) of Example 1, modify L-cysteine in the nanochannels. Apply a transmembrane voltage of +1 to -1 across the PET membrane with porous conical nanochannels modified with L-cysteine, as shown by the modified L-cysteine indication line in Figure 2 As can be seen from Figure 2 compared with before modification (bare nanochannel indication line), the current decreases, indicating that L-cysteine is modified onto the inner surface of the nanochannels, reducing the effective charge on the inner surface of the nanochannels. As shown in step 5) of Example 1, modify a gold layer on the inner surface of the nanochannels. Then add 0.1 mol / L KCl on both sides of the PET membrane with porous conical nanochannels modified with gold, and apply a transmembrane voltage across the PET membrane, as shown by the modified L-cysteine-Au indication line in Figure 2 As can be seen from Figure 2It can be seen that the current decreases significantly compared with that after modification (naked nanochannel indicating lines, modified L-cysteine indicating lines), which indicates that the effective charge and effective space on the inner surface of the nanochannel are reduced.

[0054] XPS Characterization of Nanochannels after Modifying the Gold Layer in Example 3

[0055] The cleaned PET membrane was immersed in a 9 mol / L NaOH solution and heated at 50 °C for 20 min. Then, L-cysteine and the gold layer were modified according to the methods shown in steps 4) and 5) of Example 1. The PET membrane was taken out, washed, and dried. The above-treated PET membrane was cut into small pieces of 0.5×0.5 mm and subjected to XPS testing.

[0056] Figure 3 The XPS data of the Au element in the nanochannel with the modified gold layer are shown. The XPS data of N and S elements before and after the gold layer modification are used to prove the presence of Au on the surface. The peak signals of N and S atoms are weak because they are buried by the deposited AuNPs. It can be seen from the XPS data that two peaks (84.72 and 81.09 eV) are clearly observed after the deconvolution of the Au 4f peak in the Au 4f region of the PET membrane modified with the gold layer, and the Au 4f peak proves the presence of Au on the surface. A clear N peak can be seen in the N1S region (397.3 eV) of the PET membrane modified with L-cysteine, and a clear S peak can be seen at 160.7 eV in the S2P region (160.7 eV), proving the presence of N and S elements on the surface of the nano-thin film and the successful modification of L-cysteine in the nanochannel. No obvious N peak was observed at 397.3 eV and no obvious S peak was observed at 160.7 eV in the PET membrane modified with the gold layer, proving that the weak S and N peak signals are due to the coverage of the gold layer.

[0057] Fluorescence Characterization of Nanochannels before and after Modification in Example 4

[0058] Three PET membranes without heavy ion bombardment were respectively immersed in a 9 mol / L NaOH solution and heated at 50 °C for 20 min, and then two of them were modified according to the methods shown in steps 4) and 5) of Example 1. The unmodified, L-cysteine-modified, and AuNPs-modified PET membranes were respectively placed in a cuvette and subjected to fluorescence testing under an excitation light source of 480 nm. Figure 4 The fluorescence spectra of the PET thin films with a blank surface, modified with L-cysteine, and modified with the gold layer are shown. It can be seen from the data that the PET membrane modified with the gold layer has obvious fluorescence signal peaks, and the PET membrane modified with gold nanoparticles (blue) emits obvious fluorescence signals (L-cysteine and HAuCl4 themselves have no fluorescence signals), proving the 0 presence of Au on the membrane surface.

[0059] EDS Characterization of Nanopores after Modifying the Gold Layer in Example 5

[0060] The PET membrane without heavy ion bombardment was immersed in 9 mol / L NaOH solution and heated at 50 °C for 20 min, and then modified according to the methods shown in steps 4) and 5) of Example 1 above to obtain a PET membrane with AuNPs modified on its surface. The sample was placed under a scanning electron microscope (SEM) and subjected to X-ray energy spectrum analysis. Figure 5 The EDS data of the gold layer modified in the nanopores are shown. The results show that the PET membrane contains Au elements and is uniformly distributed on the surface of the PET membrane.

[0061] Contact Angle (CA) Characterization of Nanopores before and after Modification in Example 6

[0062] Three cleaned PET membranes were immersed in 9 mol / L NaOH solution and heated at 50 °C for 20 min, then taken out, washed and dried. Then two of them were taken out and modified with L-cysteine and gold layer according to the methods shown in steps 4) and 5) of Example 1. The above three PET membranes were respectively subjected to CA tests. Figure 6 The contact angle (CA) data of the PET membrane before and after being modified with L-cysteine and gold layer are shown. These CA data prove that due to the hydrophilic -SH functional group, the surface of the nanopores after L-cysteine modification is more hydrophilic than that before modification, and gold has hydrophobicity, so the surface of the nanopores after gold layer modification is more hydrophobic than that after L-cysteine modification. From the CA data of the three, it can be seen that the contact angle of the PET membrane after L-cysteine modification is smaller than that of the unmodified PET membrane, and the contact angle increases after gold layer modification, which indicates that the inner surface of the solid multi-nanopores is successfully modified with a gold layer.

[0063] The method of the present invention well overcomes the problems existing in the prior art, such as the small size of nanopores, the easy blockage of nanopores by the plating metal, and the uneven deposition of the gold layer on the inner surface of nanopores, which affects the performance of the final device. It successfully constructs a solid multi-nanopore with a gold layer modified on its inner surface, which has a uniform surface, low cost and good stability, filling the research gap in the method of modifying the inner surface of such nanopores with a gold layer.

[0064] It should be noted that the above embodiments are only the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several modifications, improvements and equivalent replacements can be made to the present invention, and these modifications, improvements and equivalent replacements are also regarded as falling within the protection scope of the claims of the present invention.

Claims

1. A method for modifying a gold layer on the inner surface of a nanochannel, characterized in that: include: Step 1: Clean the surface of the porous PET film irradiated with heavy ions; Step 2: etching nanochannels on the PET film obtained in step 1 by chemical etching to obtain a PET film having porous conical nanochannels, wherein the inner surface of the porous conical nanochannels has carboxyl groups and carries a negative charge under neutral conditions; Step 3: Soak the PET film obtained in step 2 in a mixture of 0.2 mol / mL NHS and 0.1 mol / mL EDC for a period of time, and then take it out and rinse it with ultrapure water; Step 4: Soak the PET film obtained in step 3 in a 0.01 mol / mL L-cysteine ​​aqueous solution for a period of time to obtain a PET film with L-cysteine-modified porous conical nanochannels; Step 5: Soak the PET film obtained in step 4 in a 0.005 mol / mL HAuCl4 solution for a period of time to obtain a PET film nanochannel with a gold layer modified on the inner surface.

2. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: The L-cysteine ​​structure is:

3. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 1, the porous PET membrane irradiated with heavy ions is immersed in ultrapure water for 3 minutes to remove dust and impurities on the surface of the membrane, and then dried, and then irradiated under ultraviolet light for 1.5 hours on each side for standby use.

4. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 2, the channel is etched as follows: a transmembrane voltage is applied to both sides of the PET film obtained in step 1, an etching solution, i.e., a 9 mol / L NaOH solution, is added to one side of the PET film, and a blocking solution, i.e., a 1 mol / L HCOOH and KCl mixed solution, is added to the other side, and a current measuring device is used to detect the etching process. Once the ion current increases by 2 orders of magnitude, it means that the nanochannel has been etched through, and a PET film with porous conical nanochannels is obtained.

5. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: The method also includes applying a transmembrane voltage on both sides of the obtained PET film after the PET film with porous conical nanochannels is obtained by chemical etching in step 2, adding 0.1 mol / L KCl solution on both sides of the film, using a current detection device to detect the rectification process, and proving through the rectification effect that the inner surface of the prepared porous conical nanochannel has a negative charge.

6. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 3, the PET film obtained in step 2 was immersed in a mixture of 0.2 mol / mL NHS and 0.1 mol / mL EDC for 24 h.

7. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 4, the PET film obtained in step 3 is immersed in a 0.01 mol / mL L-cysteine ​​aqueous solution for 24 hours to obtain an L-cysteine-modified PET film having porous conical nanochannels.

8. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 5, the PET film obtained in step 4 was immersed in a 0.005 mol / mL HAuCl4 solution for 12 h.

9. The method for modifying the inner surface of a nanochannel with a gold layer according to claim 1, characterized in that: In step 5, the pH value of the HAuCl4 solution was adjusted to 3.

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