CN113042119B - Annular nano-pore and preparation and test method thereof - Google Patents
Annular nano-pore and preparation and test method thereof Download PDFInfo
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- CN113042119B CN113042119B CN202110214005.4A CN202110214005A CN113042119B CN 113042119 B CN113042119 B CN 113042119B CN 202110214005 A CN202110214005 A CN 202110214005A CN 113042119 B CN113042119 B CN 113042119B
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Abstract
The invention discloses an annular nanometer pore canal and a preparation and test method thereof. Injecting electrolyte solution into the pore channel of the nanopore substrate, placing the nanopore substrate in the same electrolyte solution environment, adjusting the temperature to be below the freezing point of the electrolyte solution, and standing for a certain time to enable the nanopore substrate to be in a completely frozen state so as to fill electrolyte solution ice crystals in the pore channel of the nanopore substrate; and then slowly heating the nanopore substrate in a completely frozen state, detecting current change in the nanopore while heating, and forming a quasi-liquid layer on the contact surface of the electrolyte solution ice crystals and the nanopore substrate when the temperature is raised to a current surge point, wherein the quasi-liquid layer forms the annular nanopore.
Description
Technical Field
The invention belongs to the technical field of nanostructures, and particularly relates to preparation and testing of a novel composite annular nanometer pore canal.
Background
Nanopores, also known as nanopores, nanochannels and the like, can be generally classified into two categories: biological nanopores and solid-state nanopores. Compared with biological nanopores, the solid nanopores have controllable shapes and sizes and high precision. In addition, the solid-state nanometer pore canal has high mechanical strength and strong environmental adaptability, and can be used with a plurality of optical and electronic technologies to solve practical problems. To date, scientists have developed various methods for processing and fabricating artificial solid-state nanopores, such as by focused electron beam, electrochemical etching, and chemical ion track etching, and the prepared nanopores have the advantages of controllable size, designable shape, and low cost. The solid-state nanopores are divided into biological materials, inorganic materials, organic materials and composite materials, the shapes of the solid-state nanopores comprise conical shapes, cylindrical shapes, bullet shapes and the like, related reports exist at present, and different materials are prepared into nanopores with different shapes by using a plurality of physical or chemical methods, but research related to annular nanopores is not deeply developed yet.
The nano-pore device has a nano-porous structure and a surface/interface which is easy to modify, and shows huge application prospects in the aspects of DNA sequencing, single-molecule sensing, energy storage and conversion, voltage-gated ion channels and the like. When the pore size structure, surface charge distribution, bulk electrolyte concentration, etc. of the nano-pore have asymmetry, a unidirectional ion transport characteristic similar to that of a diode, called Ionic Current Rectification (ICR), is generated. The key factors affecting the rectification properties of ionic currents are the surface charge distribution and the asymmetry of the pore structure. Currently, ion rectification has been widely used in the research of microfluidic circuits, nanopore sensors, and energy conversion devices.
CN102320564A discloses a preparation method of a nanopore based on a tungsten needle tip and a thick-wall glass tube. The method adopts a template method to prepare the glass nano-pore, and comprises the following steps: 1) preparing a tungsten needle tip; 2) the glass tube seals the tungsten needle tip to prepare a tungsten nano disk electrode; 3) and etching the encapsulated tungsten needle tip to obtain the glass nanopore. The invention provides a method for preparing nanopores in a system, which has simple procedures and easy operation, but has the defect that the pore diameter of the nanopores is not adjustable after the preparation is finished.
CN110031517A relates to a preparation method of a composite glass nanometer pore canal and application thereof in biomolecule detection, wherein a glass drawing instrument is utilized to draw the glass nanometer pore canal, and then phospholipid inserted with a single-walled carbon nanotube is modified in the glass nanometer pore canal through the capillary phenomenon of the nanometer pore canal. The invention can measure the change of current signals of different biomacromolecules through the specificity of the composite glass nanometer pore, is suitable for detecting other different target molecules, has universality and has the defect that the influence of a low-temperature environment on the detection of the biomolecules by the nanometer pore is not considered.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a circular nanometer pore canal and a preparation and test method thereof.
One of the technical schemes adopted by the invention for solving the technical problems is as follows:
an annular nanopore is characterized in that an electrolyte solution ice crystal is filled in a pore channel of a nanopore substrate, and at a specific temperature, the electrolyte solution ice crystal forms a quasi-liquid layer on a contact surface with the nanopore substrate, and the quasi-liquid layer forms the annular nanopore. Ions can be rapidly transported in the annular nanopores.
Furthermore, the nanopore substrate is provided with a single nanopore or a plurality of nanopores.
Preferably, the material of the nanopore substrate comprises an inorganic material or an organic polymer material; the inorganic material includes at least one of glass, silicon material, alumina or graphene, for example; the organic polymer material includes, for example, at least one of Polyimide (PI), polyethylene terephthalate (PET), Polycarbonate (PC), polypyrrole, polyaniline, or the like. Namely, the nanopore substrate is, for example, a glass nanopore, a silicon material nanopore, an alumina nanopore, a graphene nanopore or an organic polymer nanopore.
Preferably, the inner surface of the pore of the nanopore substrate is hydrophilic. For example, the inner surface of the channels of the nanopore substrate are hydroxyl-bearing and thus highly hydrophilic, and can be used for subsequent modification. The nanopore substrate with the hydrophilic pore inner surface can be used for covalently modifying the silane coupling agent with the end group carrying charges on the pore inner surface of the nanopore substrate in the later stage, so that the nanopore substrate has obvious asymmetry in both geometric structure and surface charge distribution and shows good ion rectification property.
Preferably, the pore shape of the nanopore substrate comprises a cone shape, a column shape, a bullet shape, an hourglass shape, a cigar shape, a funnel shape or a multi-branch shape.
Preferably, the concentration of the electrolyte solution ranges from 0.1mM to 1M; further preferably, the concentration of the electrolyte solution may be 0.1mM, 1mM, 10mM, 100 mM.
Preferably, the electrolyte solution comprises a metal salt solution, the metal salt comprising at least one of a monovalent metal salt, a divalent metal salt, a trivalent metal salt, or a multivalent metal salt; the electrolyte solution is preferably a monovalent metal salt solution; further preferably, the electrolyte solution includes at least one of a lithium salt solution, a sodium salt solution, a potassium salt solution, or the like.
The second technical scheme adopted by the invention for solving the technical problems is as follows:
a method for preparing a ring-shaped nanopore, comprising the following steps:
1) injecting electrolyte solution with a certain concentration into the pore canal of the nanopore substrate, placing the nanopore substrate in the electrolyte solution with the same type and concentration, adjusting the temperature to be below the freezing point of the electrolyte solution by adopting methods such as program cooling and the like, and standing for a period of time (for example, adjusting the temperature to be below-20 ℃ and standing for more than 8 hours), so that the nanopore substrate is in a completely frozen state, and filling electrolyte solution ice crystals in the pore canal of the nanopore substrate;
2) ensuring that the nanopore substrate filled with the electrolyte solution ice crystals is in a completely frozen state, slowly heating, detecting current change in the pore by using detectors such as Keithley 6487 picoammeter and the like while heating, and obtaining the annular nanopore when the temperature is heated to a current surge point.
The term "standing for a certain time" as used herein refers to a sufficient time of standing to allow the nanopore substrate to be in a fully frozen state, thereby forming electrolyte solution ice crystals within the pores of the nanopore substrate.
The specific temperature refers to the temperature of the electrolyte solution ice crystals when the electrolyte solution ice crystals form a quasi-liquid layer at the contact surface with the nanopore substrate; in the preparation method of the invention, the specific temperature is the temperature corresponding to the current surge point in the temperature rise process. For example, when the electrolyte solution is a 1mM KCl solution, the current is abruptly increased when the temperature is raised to-12.6 ℃, and the temperature corresponding to the abrupt current increase point, i.e., the "specific temperature", is-12.6 ℃, and then a quasi-liquid layer is formed between the inner surface of the channel of the nanopore substrate and the ice crystals of the electrolyte solution and forms the annular nanopore.
Preferably, taking the preparation of a single glass nanopore (i.e., the material of the nanopore substrate is glass, and the nanopore substrate is provided with a single nanopore) as an example, the preparation of the ring-shaped nanopore can be realized based on the good mechanical properties of the single glass nanopore, and the combination of the nanoscale pore of the single glass nanopore and the ice crystals of the electrolyte solution. Wherein the preparation method of the single tapered glass nanopore comprises the following steps: packaging a platinum wire nano tip with the tip length of 60-80 mu m and the cone angle of 12-18 degrees into a glass capillary, polishing to expose the platinum wire nano tip, and removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with the aperture (small-opening end radius) of 10-50 nm. Preferably, the melting point of the platinum wire nanometer tip is 1769 ℃, the melting point of the glass tube is 600-700 ℃, the thermal expansion coefficient of platinum is far smaller than that of glass, and the tip is not easy to deform when the platinum is embedded into the glass.
Preferably, a self-made circuit device is adopted when the platinum wire nanometer tip is ground and exposed, the detection limit is as low as 0.1nA, the exposed size of the nanometer disc electrode tip can be accurately controlled, and the purpose of accurate polishing is achieved.
Preferably, the surface of the single glass nanometer pore channel is provided with hydroxyl after being washed by the piranha solution, so that the single glass nanometer pore channel is highly hydrophilic and can be used for subsequent modification. The third technical scheme adopted by the invention for solving the technical problems is as follows:
a testing device for detecting the ion permeability of a nanopore comprises a low-temperature constant-temperature tank, an experiment container, a working electrode, a reference electrode and a current-voltage detector; the experiment container is provided with an interlayer filled with refrigerating fluid, and the refrigerating fluid is driven by the low-temperature tank to circularly flow so as to keep the temperature inside the experiment container stable; the working electrode is a nano-pore channel provided with an Ag/AgCl electrode; the reference electrode is an Ag/AgCl electrode; electrolyte solution is arranged in the experiment container, and the working electrode and the reference electrode are inserted into the electrolyte solution in the experiment container to form a two-electrode system; and detecting and obtaining the electric signal change of the two-electrode system through the current-voltage detector.
Preferably, the test device further comprises a temperature detector for detecting the temperature inside the test vessel.
Preferably, the testing device for detecting the ion permeability of the nanopore can sensitively measure a tiny current of 20fA (including noise) to 20mA at a speed of 1000 readings per second under the low-temperature condition.
The fourth technical scheme adopted by the invention for solving the technical problems is as follows:
the testing method of the annular nanometer pore canal can be carried out by adopting the testing device; the working electrode is a nano-pore substrate provided with an Ag/AgCl electrode; placing the experimental container at a temperature lower than the freezing point of the electrolyte solution and standing for a certain time to enable the nanopore substrate to be in a completely frozen state so as to fill electrolyte solution ice crystals in pores of the nanopore substrate; then heating, detecting the current change in the pore channel while heating, and forming a ring-shaped nanometer pore channel when the temperature is raised to a current surge point; and detecting by the current-voltage detector to obtain an I-V curve of the annular nanometer pore channel.
The invention is based on the following principle: in a typical ice crystal, each water molecule forms a hydrogen bond with 4 adjacent water molecules, whereas on the ice surface, each molecule is hydrogen bonded with two to three water molecules, which are not strongly bonded. When the temperature is gradually increased, molecules with only two hydrogen bonds are gradually increased, and the hydrogen bonds connected with the inner layer ice are broken, so that a quasi-liquid layer (QLL) appears on the surface of the ice to form a nano-scale annular channel.
The equipment, reagents, processes, parameters and the like related to the invention are conventional equipment, reagents, processes, parameters and the like except for special description, and no embodiment is needed.
All ranges recited herein include all point values within the range.
In the present invention,% is mass% and ratio is mass ratio unless otherwise specified.
The invention has the following beneficial effects:
1) the composite annular nanometer pore canal prepared by the invention utilizes a thick-wall glass tube, has good mechanical stability, high preparation success rate, large end surface, small leakage current and high signal-to-noise ratio, and is suitable for researches in the aspects of biosensing, DNA sequencing, drug screening, pore canal protein function and the like.
2) The nanometer pore channel is cleaned and can be modified again to achieve the purpose of recycling.
3) The invention breaks through the defect of certain shape of the solid-state nanometer pore canal, and can realize the design and preparation of the annular nanometer pore canal on nanometer pore canal substrates of different materials and shapes.
4) The invention designs an ion device for detecting metal ions with different valence states based on the ion rectification characteristic, and can be used for detecting the metal ions with different valence states (univalent, bivalent and trivalent).
5) The invention enriches the existing composite nanometer pore canal preparation technology and enlarges the temperature application range.
6) The invention has simple process flow and does not need expensive reagents and large-scale instruments.
Drawings
Fig. 1 is a schematic diagram of a preparation process of a circular nanopore in an embodiment of the invention.
Fig. 2 is a schematic diagram of a mechanism of asymmetric transport of nanopore ions and symmetric transport of ring-shaped nanopore ions.
Fig. 3 is a schematic view of a nanopore ion permeability testing device used in an embodiment of the invention.
Fig. 4 is a schematic diagram of a testing mechanism of the low-temperature condition ion transport performance of the composite annular nano-pore in the embodiment of the invention.
Fig. 5 is an ion transmission performance of a phase transition process of a nanopore in an embodiment of the invention, wherein a left graph is used for explaining a current surge phenomenon occurring in a temperature rise process, that is, existence of an annular nanochannel, and a right graph is used for explaining occurrence and duration of the annular nanochannel.
FIG. 6 shows the specific structural formulas of 3-Aminopropyltriethoxysilane (APTES) and 3-Mercaptopropyltriethoxysilane (MPTES) used in example 2 of the present invention.
Fig. 7 is a graph showing the ion transport performance of the nanopores with different electrical properties on the surface in example 2 of the present invention, where the left graph is used to illustrate the asymmetric transport of the nanopores modified at normal temperature, and the right graph is used to illustrate the initial temperature of the annular nanochannels with different electrical properties on the surface.
Reference numerals: the device comprises a low-temperature constant-temperature tank 1, an experimental container 2, an interlayer lower connector 2-1, an interlayer upper connector 2-2, a temperature detector 3, a working electrode 4, a reference electrode 5, a Keithley 6487 Pian ammeter 6 and a computer terminal 7.
Detailed Description
The invention is further illustrated by the following figures and examples.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "lateral", "vertical", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships that are based on orientations or positional relationships shown in perspective views in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Referring to fig. 3, the apparatus for detecting the low temperature state of the nanopore ion permeability adopted by the embodiment of the invention includes a cryostat 1, the low-temperature constant-temperature tank 1 is used as a cold source to lead the refrigerated refrigerating fluid in the tank to an experimental container 2 outside the machine for cooling, the temperature of the electrolyte solution in the experimental container 2 is very uniform and stable through external circulation, the experimental container 2 is a customized embedded double-layer glass device, an interlayer is formed by an inner-outer double-layer structure, the interlayer is provided with an upper interface and a lower interface, the lower interface 2-1 of the interlayer is connected with a liquid outlet of the low-temperature constant-temperature groove, the upper interface 2-2 of the interlayer is connected with a liquid inlet of the low-temperature constant-temperature groove, the interlayer of the experimental container 2 is ensured to be filled with refrigerating fluid led out from the low-temperature constant-temperature groove 1 as far as possible, the refrigerating fluid in the interlayer of the experiment container 2 is driven to circularly flow by the low-temperature thermostatic bath 1, so that the temperature of the electrolyte solution in the experiment container 2 serving as a detection environment is controlled to be stable.
The cover of the experimental container 2 is made of an acrylic plate, so that on one hand, the thermal insulation effect is achieved, and on the other hand, the freezing of condensed water in air can be prevented, and the experimental result is interfered. Three annular holes with different sizes are carved on an acrylic plate cover of the packaging experiment container 2, one hole is connected with a temperature detector 3, the specific temperature inside the experiment container 2 is detected in real time, a working electrode 4 is placed in the second hole, the working electrode 4 is a glass nanometer pore canal embedded with an Ag/AgCl electrode, a reference electrode 5 is placed in the third hole, and the temperature detector 3, the working electrode 4 and the reference electrode 5 are all fixed by rubber rings to keep the stability of the measuring process. The aperture of the three holes of the cover is as close as possible to the size of the placed electrode or lead, so that the stable distance between the two stable electrode systems can be kept during measurement, and the stability and repeatability of the experimental result can be ensured. Keithley 6487 Pian Meter 6 enables current-voltage (I-V) measurements to be taken and the electrical signals displayed by computer terminal 7.
When the temperature detector is used, the temperature detector 3 is firstly inserted into the experimental container 2, the initial temperature is recorded, the electrolyte solution is filled into the glass nano-pore channel by using the injector, the self-made Ag/AgCl electrode is inserted into the glass nano-pore channel to be used as the working electrode 4, and the other Ag/AgCl electrode is directly placed in the electrolyte solution in the experimental container 2 to be used as the reference electrode 5. The electrolyte-filled solution inside the glass nanopores and the electrolyte solution inside the experimental vessel 2 should remain the same throughout the entire operation. And (3) respectively connecting the upper and lower interfaces of the interlayer of the experimental container 2 with a liquid inlet of the low-temperature constant-temperature tank and a liquid outlet of the low-temperature constant-temperature tank, and setting a voltage interval by using a Keithley 6487 Pian table 6 when the temperature reaches a specified temperature, so as to measure an I-V curve.
In the embodiment, the temperature of the low-temperature constant-temperature bath 1 can be corrected to be +/-0.01 ℃, the highest temperature fluctuation can be +/-0.05 ℃, and the internal temperature of the pore channel can be accurately controlled.
Example 1
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Ultrasonically cleaning the solution and deionized water for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, a chronopotentiometric method is adopted, a cathode is a platinum sheet electrode, an anode is a silver wire to be plated, and the anode current is 1.26 multiplied by 10-4A, anode time is 10800s, chooseThe anode is of initial polarity and the selection time takes precedence.
And secondly, obtaining a platinum wire nano tip by an electrochemical etching method, wherein the length of the tip is 60-80 mu m, the taper angle is 12-18 degrees, then packaging the platinum wire tip into a glass capillary by a glass packaging method, polishing and exposing the platinum wire nano tip, measuring the aperture of a platinum disk electrode by adopting limit steady-state current, and finally removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with a small end radius of 10-50 nm (as shown in figure 1).
And thirdly, mixing concentrated sulfuric acid and a hydrogen peroxide solution (30%) according to a volume ratio of 3:1 to prepare piranha washing liquor, injecting and washing the inside of a single conical glass nano-pore for 30min, and then respectively ultrasonically washing the inside of the single conical glass nano-pore for 5min by using water and ethanol. The inside of the cell was filled with the corresponding electrolyte solution and placed in an environment of the same solution, and the I-V relationship within the cell was measured using the Keithley 6487 Pian meter. At the moment, because a large number of hydroxyl groups are arranged on the inner wall of the glass nanometer pore canal, the extreme end in the nanometer pore canal is negatively charged after the hydroxyl groups are partially dissociated in the electrolyte solution, and K in the electrolyte solution+When the nano-porous channel passes through the nano-porous channel, the nano-porous channel is influenced by the static electricity of the negative charges on the nano-porous channel, so that the detected current is small under the voltage of +1V, and the nano-porous channel shows cation selectivity, such as asymmetric transportation shown in figure 2.
In a fourth step, the single tapered glass nanopore was placed in the device as shown in FIG. 3, into which a self-made Ag/AgCl electrode and a thermometer (as shown in FIG. 3) were inserted, respectively. The experimental device is frozen at the temperature of minus 20 ℃ for 8 hours to ensure that the initial state of the glass nanometer pore channel is a complete icing state, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated to the temperature for 20min, the temperature is maintained for 30min, and the I-V curve in the pore channel is measured after the current in the pore channel is stable. Other temperature control operations are the same. And applying a-1V field sweeping voltage through the electrode to measure the ionic current of the nano-pore channel in KCl solutions with different concentrations.
At different temperatures, with the change of the ice crystal state of the electrolyte solution in the glass nanometer pore channel, the channel in the pore channel is changed, which shows different ion currents. Taking the example of injecting 1mM KCl solution into the pore channel, the phase change of the nanometer pore channel is undergone during the temperature rising process, and the process is shown in figure 4. In the temperature range of-20.0 ℃ to-12.6 ℃, the nano-pore canal is in a completely frozen state, the inside of the pore canal is completely filled with the electrolyte solution ice crystals, the current is extremely low, and rectification is not carried out; in the range of more than-12.6 ℃, as the temperature gradually rises, molecules containing 2 hydrogen bonds on the surface layer of the ice crystals of the electrolyte solution begin to increase, and a quasi-liquid layer is formed on the contact surface of the ice crystals of the electrolyte solution and the single tapered glass nano-pore channel, so that an annular nano-pore channel is formed between the single tapered glass nano-pore channel and the ice crystals of the electrolyte solution in the single tapered glass nano-pore channel, at the moment, the current is obviously increased, and the size of the obtained annular channel is smaller than 1nm by combining with the calculation of related theories, and the result is shown in fig. 5.
Example 2
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Ultrasonically cleaning the solution and deionized water for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, a chronopotentiometric method is adopted, a cathode is a platinum sheet electrode, an anode is a silver wire to be plated, and the anode current is 1.26 multiplied by 10-4And A, anode time is 10800s, the anode is selected to be in the initial polarity, and the selection time is prior.
And secondly, obtaining a platinum wire nano tip by an electrochemical etching method, wherein the length of the tip is 60-80 mu m, the taper angle is 12-18 degrees, then packaging the platinum wire tip into a glass capillary by a glass packaging method, polishing and exposing the platinum wire nano tip, measuring the aperture of a platinum disk electrode by adopting limit steady-state current, and finally removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with a small end radius of 10-50 nm (as shown in figure 1).
And thirdly, mixing concentrated sulfuric acid and a hydrogen peroxide solution (30%) according to a volume ratio of 3:1 to prepare piranha washing liquor, injecting and washing the inside of a single conical glass nano-pore for 30min, and then respectively ultrasonically washing the inside of the single conical glass nano-pore for 5min by using water and ethanol. APTEAnd injecting an S ethanol solution (5%) into the nano-pore for reaction for 1h, washing for 3 times by using ethanol, and drying the obtained nano-pore for 1h at 110 ℃. The same operation is suitable for MPTES, and the modified inner wall of the duct is respectively provided with-NH2and-SH, respectively, as cation selectivity and anion selectivity, the specific structures of APTES and MPTES are shown in FIG. 6.
In a fourth step, the single tapered glass nanopore was placed in the device as shown in FIG. 3, into which a self-made Ag/AgCl electrode and a thermometer (as shown in FIG. 3) were inserted, respectively. The experimental device is placed at the temperature of minus 20 ℃ for freezing for 8 hours, the initial state of the glass nanometer pore channel is ensured to be a complete icing state, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated for 20min and maintained at the temperature for 30min, and after the current in the pore channel is stable, the I-V curve in the pore channel is measured by utilizing a Keithley 6487 Pian table. Other temperature control operations are the same. Ion currents of nanopores (with positive charges and negative charges) with different surface charge properties in KCl solution are measured by applying a-1V field sweeping voltage through the electrodes (as shown in FIG. 7).
The result shows that compared with an unmodified nanopore, the ion current in the glass nanopore after the APTES and the MPTES are modified is remarkably improved, the phase change point of the nanopore after the APTES is modified is-12.4 ℃, the temperature inflection point of a ring-shaped passage formed in the nanopore after the MPTES is modified is-12.4 ℃, and the result shows that the forming temperature of the ring-shaped nanopore has universality and the influence on the surface charge property of the nanopore is small.
Example 3
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Ultrasonically cleaning the solution and deionized water for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, a chronopotentiometric method is adopted, a cathode is a platinum sheet electrode, an anode is a silver wire to be plated, and the anode current is 1.26 multiplied by 10-4And A, anode time is 10800s, the anode is selected to be in the initial polarity, and the selection time is prior.
And secondly, obtaining a platinum wire nano tip by an electrochemical etching method, wherein the length of the tip is 60-80 mu m, the taper angle is 12-18 degrees, then packaging the platinum wire tip into a glass capillary by a glass packaging method, polishing and exposing the platinum wire nano tip, measuring the aperture of a platinum disk electrode by adopting limit steady-state current, and finally removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with a small end radius of 10-50 nm (as shown in figure 1).
And thirdly, mixing concentrated sulfuric acid and a hydrogen peroxide solution (30%) according to a volume ratio of 3:1 to prepare piranha washing liquor, injecting and washing the inside of a single conical glass nano-pore for 30min, and then respectively ultrasonically washing for 5min by using water and ethanol. The inside of the cells was injected with the corresponding electrolyte solution and placed in the same solution environment, and the I-V relationship within the cells was measured using a Keithley 6487 Pian meter.
In a fourth step, the single tapered glass nanopore was placed in the device as shown in FIG. 3, into which a self-made Ag/AgCl electrode and a thermometer (as shown in FIG. 3) were inserted, respectively. The experimental device is frozen at the temperature of minus 20 ℃ for 8 hours to ensure that the glass nano-pore channel is completely frozen in the initial state, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated to the temperature for 20min, the temperature is maintained for 30min, and the I-V curve in the pore channel is measured after the current in the pore channel is stable. Other temperature control operations are the same. And applying a-1V field sweeping voltage to the electrodes to measure the ionic current of the nanopores with different apertures (the aperture of the small end of the original pore is 30nm, 50nm and 100nm respectively) in the KCl solution.
Example 4
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Ultrasonically cleaning the solution and deionized water for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, and a chronopotentiometric method is adopted, wherein the cathode is a platinum sheet electrode, the anode is a wire to be plated with silver, and the anode current is 1.26 × 10-4And A, anode time is 10800s, the anode is selected to be in the initial polarity, and the selection time is prior.
And secondly, obtaining a platinum wire nano tip by an electrochemical etching method, wherein the length of the tip is 60-80 mu m, the taper angle is 12-18 degrees, then packaging the platinum wire tip into a glass capillary by a glass packaging method, polishing and exposing the platinum wire nano tip, measuring the aperture of a platinum disk electrode by adopting limit steady-state current, and finally removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with a small end radius of 10-50 nm (as shown in figure 1).
And thirdly, mixing concentrated sulfuric acid and a hydrogen peroxide solution (30%) according to a volume ratio of 3:1 to prepare piranha washing liquor, injecting the piranha washing liquor into the interior of a single conical glass nano-pore, respectively washing for 30min, 60min, 90min, 180min and 270min, and then respectively ultrasonically washing for 5min by using water and ethanol. The inside of the cell was filled with the corresponding electrolyte solution and placed in an environment of the same solution, and the I-V relationship within the cell was measured using the Keithley 6487 Pian meter.
In a fourth step, the single tapered glass nanopore was placed in the device as shown in FIG. 3, into which a self-made Ag/AgCl electrode and a thermometer (as shown in FIG. 3) were inserted, respectively. The experimental device is frozen at the temperature of minus 20 ℃ for 8 hours to ensure that the glass nano-pore channel is completely frozen in the initial state, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated to the temperature for 20min, the temperature is maintained for 30min, and the I-V curve in the pore channel is measured after the current in the pore channel is stable. Other temperature control operations are the same. And applying a-1V field sweeping voltage through the electrodes to measure the ionic current of the nano-pore channels with different surface charge densities in the KCl solution.
Example 5
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Ultrasonically cleaning the solution and deionized water for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, a chronopotentiometric method is adopted, a cathode is a platinum sheet electrode, an anode is a silver wire to be plated, and the anode current is 1.26 multiplied by 10-4And A, anode time is 10800s, the anode is selected to be in the initial polarity, and the selection time is prior.
And secondly, obtaining a platinum wire nano tip by an electrochemical etching method, wherein the length of the tip is 60-80 mu m, the taper angle is 12-18 degrees, then packaging the platinum wire tip into a glass capillary by a glass packaging method, polishing and exposing the platinum wire nano tip, measuring the aperture of a platinum disk electrode by adopting limit steady-state current, and finally removing the platinum wire by a aqua regia etching method to obtain a single conical glass nano pore channel with a small end radius of 10-50 nm (as shown in figure 1).
And thirdly, mixing concentrated sulfuric acid and a hydrogen peroxide solution (30%) according to a volume ratio of 3:1 to prepare piranha washing liquor, injecting and washing the inside of a single conical glass nano-pore for 30min, and then respectively ultrasonically washing the inside of the single conical glass nano-pore for 5min by using water and ethanol. The corresponding electrolyte solution is injected into the interior of the pore channel and placed in the same solution environment.
In a fourth step, the single tapered glass nanopore was placed in the device as shown in FIG. 3, into which a self-made Ag/AgCl electrode and a thermometer (as shown in FIG. 3) were inserted, respectively. The experimental device is placed at the temperature of minus 20 ℃ for freezing for 8 hours, the initial state of the glass nanometer pore channel is ensured to be completely frozen, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated to the temperature for 20min, the temperature is maintained for 30min, and after the current in the pore channel is stable, the I-V curve in the pore channel is measured by utilizing a Keithley 6487 Pian table. Other temperature control operations are the same. The metal salt solution (such as Li) with different valence states is measured by applying a-1V sweep field voltage through the electrodes+、Mg2+、Ca2+、Zn2+、Fe3+、Cr3+) Ionic current in the nanopores.
Subsequently, small molecules with different functional groups can be introduced through chemical modification, and the pore channel can respond to metal ions with various valence states by utilizing different affinities between metal ions with different valence states and groups. Through the expression of the rectification characteristic of the annular channel, the metal ions with different valence states are distinguished.
Example 6
Firstly, polishing 0.5mm silver wires by using 1000-mesh sand paper, removing oxides on the surfaces of the silver wires, and then sequentially using acetone and 3M HNO3Solution, deionized waterUltrasonically cleaning for 5min, and preparing the Ag/AgCl electrode by using a CHI660E electrochemical workstation and adopting an anodic oxidation method. The specific parameters are as follows: the solution is 0.1M HCl solution, a chronopotentiometric method is adopted, a cathode is a platinum sheet electrode, an anode is a silver wire to be plated, and the anode current is 1.26 multiplied by 10-4And A, anode time is 10800s, the anode is selected to be in the initial polarity, and the selection time is prior.
And secondly, firstly, carrying out ultraviolet radiation on the PET film for 30min for pretreatment so as to ensure that the aperture of the nano-pores obtained after chemical etching is uniform. Etching the PET film by using 9M NaOH solution etching solution, preventing the solution from being 1M HCOOH +1M KC1 mixed solution, detecting the change of current by using a picoammeter, applying 1V bias voltage on two sides of the channel, and stopping etching when the current reaches the current with the required aperture size. The PET film was repeatedly washed with high-purity water for 3 times, and then placed in high-purity water overnight for use.
And thirdly, placing the porous PET nanometer pore channel in a glass electrolytic tank, and respectively inserting a self-made Ag/AgCl electrode and a thermometer into the device. The experimental device is placed at the temperature of minus 20 ℃ for freezing for 8 hours, the initial state of the porous PET nanometer pore channel is ensured to be completely frozen, then the temperature is raised by 1 ℃ each time, the temperature is set to be heated to the temperature for 20min, the temperature is maintained for 30min, and after the current in the pore channel is stable, the I-V curve in the pore channel is measured by utilizing a Keithley 6487 Pian table. Other temperature control operations are the same. And applying a-1V field sweeping voltage through the electrodes to measure the ionic current in the nanometer pore canal.
While particular embodiments of the present invention have been described in the foregoing specification, various modifications and alterations to the previously described embodiments will become apparent to those skilled in the art from this description without departing from the spirit and scope of the invention.
Claims (9)
1. An annular nanopore, comprising: filling electrolyte solution ice crystals in a pore channel of a nanopore substrate, heating the nanopore substrate, detecting current change in the pore channel while heating, and forming a quasi-liquid layer on the contact surface of the electrolyte solution ice crystals and the nanopore substrate when the temperature is raised to a current surge point, wherein the quasi-liquid layer forms the annular nanopore; the electrolyte solution ice crystals are formed by complete freezing of the electrolyte solution below its freezing point.
2. The ringlike nanopore according to claim 1, characterized in that: the nanopore substrate is provided with a single nanopore or a plurality of nanopores.
3. The ringlike nanopore according to claim 1, characterized in that: the material of the nanometer pore canal substrate comprises an inorganic material or an organic polymer material; the inorganic material comprises at least one of glass, silicon material, aluminum oxide or graphene; the organic polymer material comprises at least one of polyimide, polyethylene terephthalate, polycarbonate, polypyrrole or polyaniline.
4. The ringlike nanopore according to claim 1, characterized in that: the inner surface of the pore of the nanopore substrate has hydrophilicity.
5. The ringlike nanopore according to claim 1, characterized in that: the pore channel shape of the nanopore substrate comprises a conical shape, a cylindrical shape, a bullet shape, an hourglass shape, a funnel shape or a multi-branch shape.
6. The ringlike nanopore according to claim 1, characterized in that: the concentration range of the electrolyte solution is 0.1 mM-1M.
7. The ringlike nanopore according to claim 1, characterized in that: the electrolyte solution includes at least one of a monovalent metal salt solution, a divalent metal salt solution, or a trivalent metal salt solution.
8. A method of making the cyclic nanopore of any of claims 1-7, comprising:
1) injecting electrolyte solution into the pore channel of the nanopore substrate, placing the nanopore substrate in the same electrolyte solution, adjusting the temperature to be below the freezing point of the electrolyte solution, and standing for a certain time to enable the nanopore substrate to be in a completely frozen state so as to fill electrolyte solution ice crystals in the pore channel of the nanopore substrate;
2) heating the nanopore substrate in the completely frozen state obtained in the step 1), detecting the current change in the nanopore while heating, and obtaining the annular nanopore when the temperature is raised to a current surge point.
9. A test method of a ring-shaped nanometer pore canal is characterized in that: the adopted testing device comprises a low-temperature constant-temperature tank, an experimental container, a working electrode, a reference electrode and a current-voltage detector; the experiment container is provided with an interlayer filled with refrigerating fluid, and the refrigerating fluid is driven by the low-temperature constant-temperature tank to circularly flow so as to keep the temperature in the experiment container stable; the working electrode is a nano-pore channel substrate provided with an Ag/AgCl electrode; the reference electrode is an Ag/AgCl electrode; electrolyte solution is arranged in the experiment container, and the working electrode and the reference electrode are inserted into the electrolyte solution in the experiment container to form a two-electrode system; detecting and obtaining the electric signal change of the two-electrode system through the current and voltage detector; placing the experimental container at a temperature lower than the freezing point of the electrolyte solution and standing for a certain time to enable the nanopore substrate to be in a completely frozen state so as to fill electrolyte solution ice crystals in pores of the nanopore substrate; heating, detecting the current change in the pore channel while heating, and forming an annular nanometer pore channel when the temperature is raised to a current surge point; the annular nanometer pore channel is obtained by the detection of the current voltage detectorI-VA curve.
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