CN112683967B - Micro-nano charged electrode, preparation method thereof and enzyme-free biosensor - Google Patents
Micro-nano charged electrode, preparation method thereof and enzyme-free biosensor Download PDFInfo
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Abstract
The invention provides a micro-nano charged electrode, a preparation method thereof and an enzyme-free biosensor. In the preparation method of the micro-nano charged electrode, a 2-allylphenol insulating layer is deposited on a part of the surface of an electrode substrate by electrophoresis, so that the electrode substrate forms a structure with one end coated with the poly 2-allylphenol insulating layer and the other end not coated; fixing the lead at the uncoated end through conductive adhesive, wherein the metal wire of the lead extends out of the substrate; then placing the glass tube into a glass tube with openings at two ends, wherein the end part of one end of the glass tube, which is not bonded with the lead, is flush with the opening at one end of the glass tube, the lead at the other end extends out of the glass tube, and then pouring sealant for encapsulation and solidification; and then, polishing the end face of the non-conducting wire end, forming a Sn film on the polished face, stripping the Sn film, and depositing a metal-containing film to obtain the micro-nano band electrode. The micro-nano charged electrode prepared by the invention can be used for quickly and sensitively detecting H2O2。
Description
Technical Field
The invention relates to the field of electrode materials, in particular to a micro-nano strip electrode, a preparation method thereof and an enzyme-free biosensor.
Background
Microelectrodes are electrodes smaller than 25 μm in at least one dimension (e.g. the radius of the disk or the width of the strip) and have a steady state current density that is better than the current of conventional electrodes under forced convection. The polarized current on the microelectrode reduces the iR drop of the system, so that the system can be used in a high-resistance system, including a low-supporting electrolyte concentration and even a non-supporting electrolyte solution, a gas-phase system, a semi-solid system and an all-solid system, and the characteristics provide a powerful means for people to search the microstructure of a substance. The small RC time constant inherent in microelectrodes makes them useful for studying fast, transient electrochemical reactions. Meanwhile, the steady-state current of the microelectrode can be easily obtained through theoretical calculation and experimental means. The unique capability of microelectrodes greatly expands the range of applications of electrochemical methods, extending them to previously intractable time, medium and space domains. For example, rapid reactions of chemical systems that were previously difficult to study can be studied; can be used in media such as non-aqueous media where electrochemical methods have previously been difficult to use; small volume or small space in vivo assays inaccessible to conventionally sized electrodes can be studied to image surfaces, such as scanning electrochemical microscopy (SECM) and the like.
Although there are many advantages and wide applications, the current detected at the micro-electrode is usually about n A, and in practical applications, the current of the micro-electrode such as a disk is sometimes less than the lower detection limit of a conventional electrochemical instrument, so that the application is limited. The microelectrode can be divided into different types according to the difference of the geometric shapes of the surfaces of the electrodes, wherein the surface of one electrode is a banded micro-nano charged electrode, the width of the micro-nano charged electrode is nano-micron, the length of the micro-nano charged electrode is millimeter or even centimeter, the microelectrode has the characteristics of the microelectrode, the generated current is larger, and a conventional electrochemical instrument can detect the signal, so the microelectrode is favorable for analysis and application.
Ingrid Fritsch [ anal. chem.70,2908,1998] prepares the nano-scale microstrip electrode by photolithography, ion sputtering combined with thermal and chemical deposition, but the required instrument is expensive, the operation is complex and the manufacture is difficult. R.M. Wightman [ anal. chem.57,1984,2101] and A.J.Bard [ anal. chem.59,1987,2101] et al, a layer of gold film with nanometer thickness is evaporated on the surface of mica, and after encapsulation, a nano-scale gold microstrip electrode is prepared. This method is relatively simple and does not require expensive instrumentation, but suffers from the following disadvantages: the mica sheet is thin and fragile, and the electrode is difficult to prepare; the electrode can not be ground, the surface is difficult to be processed cleanly, and the reproducibility is poor; the shape of the electrodes is fixed and can only be linear. Zhumingzhi et al (chemical bulletin of higher school, 2005, 26(5), 838-. The corrosion resistance of the interdigital type ultramicro-band electrode array and the electrochemical characteristics of the ultramicro-electrodes are characterized by cyclic voltammetry. Patent application CN 104132976 a discloses a method for constructing an electrode, which deposits a gold, platinum or silver film on the surface of ITO conductive glass to improve the stability of the electrode.
Hydrogen peroxide (H)2O2) Is one of active oxygen substances, is a raw material and an intermediate product of a plurality of industrial processes, and is a byproduct of oxidase reaction in a plurality of organisms, so that the determination of the content of the active oxygen substances has important significance in industrial, food, clinical, pharmaceutical and environmental analysis. At present, for detecting H2O2There are many methods such as titrimetric analysis, spectroscopic analysis, fluorescence detection and electrochemical detection. Among them, the current enzyme biosensor is widely used for H due to its advantages such as simple preparation method and high sensitivity2O2The measurement of (1). However, enzyme molecules have some weaknesses, such as difficult fixation to the electrode surface, easy inactivation, large relative molecular mass, embedding of active centers in the polypeptide structure, difficult occurrence of direct electron transfer, and the like. Therefore, it is urgent to develop a novel enzyme-free hydrogen peroxide sensor having excellent performance.
Disclosure of Invention
In view of the above, the present invention provides a micro-nano band electrode, a method for preparing the same, and an enzyme-free biosensor. The micro-nano charged electrode provided by the invention can be used for quickly and sensitively detecting H2O2。
The invention provides a micro-nano charged electrode, which comprises:
an electrode substrate; the electrode substrate is divided into a coating area and an uncoated area along the length direction;
a poly 2-allylphenol insulating layer coated on the coating region;
a wire secured to the uncoated region;
the glass tube is sleeved on the periphery of the electrode substrate; the electrode substrate is characterized in that the glass tube is a glass tube with openings at two ends, the end face of the cladding area is flush with the opening at one end of the glass tube, the end face is compounded with a metal-containing film layer, and a lead of the non-cladding area extends out of the opening at the other end of the glass tube;
and the sealant is filled in the glass tube.
Preferably, the electrode substrate is a Sn-containing electrode substrate;
the wire is a metal enameled wire, and two ends of the wire are exposed out of the metal wire;
the lead is a copper wire, a silver wire, an aluminum wire, a gold wire, a nickel wire, a zinc wire or a tin wire;
the conducting wire is fixed on the uncoated area through conductive adhesive.
The invention also provides a preparation method of the micro-nano strip electrode in the technical scheme, which comprises the following steps:
a) taking an electrode substrate as a working electrode, taking a 2-allylphenol solution as an electrolyte, and depositing a 2-allylphenol insulating layer on the surface of the electrode substrate by electrophoretic deposition under a three-electrode system to obtain a coating substrate;
the electrode substrate is divided into an upper part and a lower part along the length direction of the electrode substrate, wherein a 2-allyl phenol insulating layer is deposited on one part and is marked as a coated end, and the other part is marked as an uncoated end;
the electrode substrate is an Sn-containing electrode substrate;
b) taking a lead, fixing one end of the lead to the uncoated end of the coated substrate through conductive adhesive, and extending the other end of the lead out of the coated substrate along the direction far away from the coated end to obtain an intermediate body; wherein, one end bonded with the lead is marked as a lead end, and the other end not bonded with the lead is marked as a non-lead end;
c) putting the intermediate body into a glass tube with openings at two ends, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate body is flush with the opening at one end of the glass tube, and the conducting wire extends out of the glass tube;
sealing the opening of the glass tube which is flush with the end part of the non-conducting end of the intermediate body with a sealing film, injecting a sealant from the opening at the other end of the glass tube and curing to obtain a cured packaging body;
d) polishing the end face of the non-conducting wire end in the solidified packaging body to obtain a polished body;
e) and sequentially performing electroreduction on the Sn film, stripping off the Sn film and deposition on a metal-containing film on the polished surface of the polished body to obtain the micro-nano charged electrode.
Preferably, in step a):
the concentration of the 2-allylphenol solution is 0.01-90 mmol/L;
the solvent in the 2-allylphenol solution is one or more of methanol, water, ethanol, acetone and n-hexane;
the pH value of the 2-allyl phenol solution is 9.0-9.2.
Preferably, in step a):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the voltage of the electrophoretic deposition is 0.5-10V, and the time is 1-30 min;
the Sn-containing electrode substrate is an ITO electrode, an FTO electrode or a PET-ITO composite electrode;
the thickness of the Sn-containing electrode substrate is less than or equal to 25 mu m.
Preferably, in the step d), the polishing includes:
s1, polishing the end face of the non-conducting wire end in the solidified packaging body into a mirror surface by using sand paper;
s2, using the electrode obtained in the step S1 as a working electrode, Ag-AgCl as a reference electrode, a Pt sheet as a counter electrode and K3[Fe(CN)6]Testing a scanning cyclic voltammetry curve by taking an aqueous solution as an electrolyte and KCl as a supporting electrolyte; if the obtained cyclic voltammetry curve is S-shaped, judging the cyclic voltammetry curve to be qualified; if the cyclic voltammogram obtained is not S-shaped, polishing with sand paper is continued until the cyclic voltammogram is S-shaped.
Preferably, in step b):
the wire is a metal enameled wire, and two ends of the wire are exposed out of the metal wire;
the lead is a copper wire, a silver wire, an aluminum wire, a gold wire, a nickel wire, a zinc wire or a tin wire;
the conductive adhesive is one or more of conductive silver adhesive, conductive copper adhesive, conductive aluminum adhesive, conductive zinc adhesive, conductive iron adhesive, conductive nickel adhesive and graphite adhesive;
in the step c):
the sealant is epoxy sealant;
the glass tube is filled with the sealant.
Preferably, said step e) comprises:
e1) performing electro-reduction under a three-electrode system by using the polishing body as a working electrode and a phosphate buffer solution as an electrolyte to form an Sn film layer on the polishing surface of the polishing body; then, stripping the Sn film layer to form a stripping surface;
e2) taking the electrode obtained in the step e1) as a working electrode, carrying out electrodeposition under a three-electrode system, and forming a metal-containing film on the stripping surface to obtain the micro-nano charged electrode.
Preferably, in step e 1):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the pH value of the phosphate buffer solution is 6.80-7.40;
the voltage of the electroreduction is-0.5 to-5V, and the time is 60 to 1000 s;
the stripping is carried out by soaking in acid liquor;
in said step e 2):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the electrodeposition is step pulse electrodeposition;
the conditions of the step pulse electrodeposition are as follows: the initial voltage is 0.1-1V, and the pulse time is 0.1-5 s; the termination voltage is-0.02 to-0.5V, and the pulse time is 0.2 to 10 s; the pulse number is 50-300;
the metal-containing film is a metal film, a metal composite salt film or a metal oxide film;
the metal film is a gold film, a platinum film, a silver film, a copper film or a palladium film;
the metal composite salt is Prussian blue;
the metal oxide is titanium dioxide.
The invention also provides an enzyme-free biosensor, which is a three-electrode system formed by taking the micro-nano-electrode as a working electrode, Ag-AgCl as a reference electrode and a Pt sheet as a counter electrode;
the micro-nano charged electrode is the micro-nano charged electrode in the technical scheme or the micro-nano charged electrode prepared by the preparation method in the technical scheme.
The invention provides a preparation method of a micro-nano charged electrode, which comprises the steps of firstly, carrying out electrophoresis deposition on a part of the surface of an electrode substrate to form a 2-allylphenol insulating layer, so that the electrode substrate forms a structure with one end coated with the 2-allylphenol insulating layer and the other end not coated; fixing the lead at the uncoated end through conductive adhesive, wherein the metal wire of the lead extends out of the substrate; then placing the glass tube into a glass tube with openings at two ends, wherein the end part of one end of the glass tube, which is not bonded with the lead, is flush with the opening at one end of the glass tube, the lead at the other end extends out of the glass tube, and then pouring sealant for encapsulation and solidification; and then, polishing the end face of the non-conducting wire end, forming a Sn film on the polished face, stripping the Sn film, and depositing a metal-containing film to obtain the micro-nano strip electrode. The micro-nano charged electrode prepared by the invention can be used for quickly and sensitively detecting H2O2。
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a micro-nano strip electrode provided by the invention;
FIG. 2 is a schematic diagram of a process for preparing a micro-nano strip electrode according to the present invention;
FIG. 3 is a schematic view showing the arrangement of ITO sheets in example 3;
FIG. 4 shows detection of modified electrode pair H in example 72O2Effect diagram of catalysis;
FIG. 5 is a graph showing the effect of linear range and detection limit in example 7; wherein, fig. 5A is a graph of the variation of current with time, and fig. 5B is a graph of the variation of current with concentration;
FIG. 6 is a graph showing the effect of the test on signal interference by the electroactive species in example 7.
Detailed Description
The invention provides a micro-nano charged electrode, which comprises:
an electrode substrate; the electrode substrate is divided into a coating area and an uncoated area along the length direction;
a poly 2-allylphenol insulating layer coated on the coating region;
a wire secured to the uncoated region;
a glass tube containing the electrode substrate; the electrode substrate is characterized in that the glass tube is a glass tube with openings at two ends, the end face of the cladding area is flush with the opening at one end of the glass tube, the end face is compounded with a metal-containing film layer, and a lead of the non-cladding area extends out of the opening at the other end of the glass tube;
and the sealant is filled in the glass tube.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a micro-nano strip electrode provided by the present invention. Wherein, 1 is an electrode substrate, 2 is a poly 2-allyl phenol insulating layer, 3 is a lead, 4 is a glass tube, 5 is a sealant, 6 is a metal-containing film layer, and 7 is a conductive adhesive.
The electrode substrate 1 is made of a conductive material, in particular to an electrode substrate containing Sn; preferably comprising an ITO conductive glass, an FTO conductive glass or a PET-ITO composite substrate. The electrode substrate 1 is divided into a coated region and an uncoated region along the length direction, that is, the electrode substrate 1 is divided into an upper part and a lower part along the length direction, wherein one part is the coated region, and the other part is the uncoated region. The electrode substrate 1 has a rectangular shape, and in the case of a square shape, the longitudinal direction is also the width direction.
The poly 2-allylphenol insulating layer 2 is coated on the coating area of the electrode substrate 1. The purpose of arranging the 2-allylphenol insulating layer in the coating area is to successfully prepare an impermeable micro-nano charged electrode.
The lead 3 is fixed to the uncoated region of the electrode substrate 1. The conductor 3 is preferably antiparallel to the length of the electrode substrate 1, facing away from the cladding region, and projects beyond the electrode substrate 1 along the unclad region. In the present invention, the lead 3 is preferably fixed to the surface of the electrode substrate 1 by the conductive paste 7.
The glass tube 4 is sleeved on the periphery of the electrode substrate 1; the glass tube 4 is a glass tube with openings at two ends, in the electrode substrate 1, the end face of the cladding area is flush with the opening at one end of the glass tube, and the lead of the non-cladding area extends out of the opening at the other end of the glass tube. Wherein, the end face is also compounded with a metal-containing film layer 6.
The sealing glue 5 is filled in the glass tube 4, and the electrode substrate is fixed in the glass tube through the sealing glue. The sealant is preferably filled in the glass tube. The sealant is preferably an epoxy sealant.
The micro-nano charged electrode provided by the invention can be used for quickly and sensitively detecting H2O2。
The invention also provides a preparation method of the micro-nano strip electrode in the technical scheme, which comprises the following steps:
a) taking an electrode substrate as a working electrode, taking a 2-allylphenol solution as an electrolyte, and depositing a 2-allylphenol insulating layer on the surface of the electrode substrate by electrophoretic deposition under a three-electrode system to obtain a coating substrate;
the electrode substrate is divided into an upper part and a lower part along the length direction of the electrode substrate, wherein a 2-allyl phenol insulating layer is deposited on one part and is marked as a coated end, and the other part is marked as an uncoated end;
the electrode substrate is an Sn-containing electrode substrate;
b) taking a lead, fixing one end of the lead to the uncoated end of the coated substrate through conductive adhesive, and extending the other end of the lead out of the coated substrate along the direction far away from the coated end to obtain an intermediate body; wherein, one end bonded with the lead is marked as a lead end, and the other end not bonded with the lead is marked as a non-lead end;
c) putting the intermediate body into a glass tube with openings at two ends, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate body is flush with the opening at one end of the glass tube, and the conducting wire extends out of the glass tube;
sealing the opening of the glass tube which is flush with the end part of the non-conducting end of the intermediate body with a sealing film, injecting a sealant from the opening at the other end of the glass tube and curing to obtain a cured packaging body;
d) polishing the end face of the non-conducting wire end in the solidified packaging body to obtain a polished body;
e) and sequentially performing electroreduction on the Sn film, stripping the Sn film and depositing a metal film on the polished surface of the polished body to obtain the micro-nano charged electrode.
The method comprises the steps of firstly, electrophoretically depositing a poly (2-allylphenol) insulating layer on a part of the surface of an electrode substrate to form a structure with one end coated with the poly (2-allylphenol) insulating layer and the other end uncoated; fixing the lead at the uncoated end through conductive adhesive, wherein the metal wire of the lead extends out of the substrate; then placing the glass tube into a glass tube with openings at two ends, wherein the end part of one end, which is not bonded with the lead, is flush with the opening at one end of the glass tube, the lead at the other end extends out of the glass tube, and then pouring sealant for curing and packaging; and then, polishing the end face of the non-conducting wire end, forming a Sn film on the polished face, stripping the Sn film, and depositing a metal-containing film to obtain the micro-nano strip electrode. The micro-nano charged electrode prepared by the invention can be used for quickly and sensitively detecting H2O2。
Referring to fig. 2, fig. 2 is a schematic flow chart of the method for preparing the micro-nano strip electrode.
With respect to step a): and (3) taking the electrode substrate as a working electrode and 2-allylphenol solution as electrolyte, and depositing a 2-allylphenol insulating layer on the surface of the electrode substrate by electrophoretic deposition under a three-electrode system to obtain the coated substrate.
In the invention, the electrode substrate is an Sn-containing electrode substrate; preferably comprising an ITO conductive glass, an FTO conductive glass or a PET-ITO composite substrate. The ITO conductive glass is obtained by plating an ITO (indium tin oxide) film on the basis of substrate glass by magnetron sputtering; the other types of conductive glass described above work equally well; the PET-ITO composite substrate is a conductive material obtained by taking PET as a substrate and plating an ITO film. The ITO conductive glass is single-sided ITO conductive glass or double-sided ITO conductive glass. The thickness of the electrode substrate is preferably less than or equal to 25 μm.
In the present invention, the electrode substrate is preferably pretreated before the operation. The pretreatment comprises the following steps: cutting, cleaning and drying. The cutting is to cut the electrode substrate into electrodes with certain sizes, and the invention has no special limitation on the sizes and is only required to prepare the conventional electrode sizes of the micro-nano charged electrode; in one embodiment of the present invention, the electrode substrate is cut to a size of 3mm in width by 20mm in length. In the invention, the cleaning agent used for cleaning is not particularly limited in type and comprises one or more of acetone, ethanol and water; the cleaning is preferably ultrasonic cleaning. In the present invention, the drying is preferably nitrogen blow drying.
In the invention, 2-allyl phenol solution is used as electrolyte for electrophoretic deposition. In the invention, the concentration of the 2-allyl phenol solution is preferably 0.01-90 mmol/L. The solvent in the 2-allyl phenol solution is preferably one or more of methanol, water, ethanol, acetone and n-hexane. In some embodiments of the invention, the solvent is methanol and water; the mass ratio of the methanol to the water is preferably 1 to (0.2-5).
In the invention, the pH value of the 2-allylphenol solution is preferably 9.0-9.2, if the pH value is too low, the polymerization reaction speed is slow, the formed polymer film is rough and weak, and if the pH value is too high, the polymerization reaction speed is fast, and the polymer film is likely to be cracked. In the invention, the pH value can be regulated and controlled by a pH regulator, namely after the 2-allylphenol solution is prepared, the pH value regulator is added to regulate and control the pH value of the solution; the pH regulator is preferably ammonia water or hydrogen and oxygenOne or more of sodium hydroxide and potassium hydroxide. According to the invention, the 2-allylphenol insulating layer is deposited on the electrode and is combined with the electrode substrate more tightly, the service life of the prepared micro-nano charged electrode is longer, if the poly 2-allylphenol insulating layer is not arranged, the sealing glue of the micro-nano charged electrode is easy to separate from the surface of the electrode substrate, at this time, the electrode is actually an ITO large electrode, the micro-nano charged electrode is not obtained, and the solution is easy to enter the surface of the ITO electrode. Performing H after ITO surface modification of nano material2O2And detection results are poor (such as slow response speed and low detection sensitivity).
In the invention, an electrode substrate is taken as a working electrode, a 2-allyl phenol solution is taken as an electrolyte, and electrophoretic deposition is carried out under a three-electrode system. The reference electrode in the three-electrode system is preferably an Ag-AgCl electrode, and the counter electrode is preferably a Pt electrode. In the invention, a 2-allyl phenol insulating layer is deposited only at one end of the surface of an electrode substrate (see figure 1), and can be controlled during deposition operation, specifically, during deposition, the electrode substrate is vertically immersed into electrolyte, only the lower part of the electrode substrate is immersed into the electrolyte, and the upper part of the electrode substrate extends out of the electrolyte, so that a layer of 2-allyl phenol insulating layer is deposited and coated on the surface of the lower end which is immersed into the electrolyte; wherein, one end of the insulating layer coated with the 2-allylphenol is marked as a coated end, and the other end is marked as an uncoated end.
In the present invention, the condition parameters of the electrophoretic deposition are preferably: the voltage is 0.5-10V and the time is 1-30 min. In some embodiments of the invention, the electrophoretic deposition is performed at a voltage of 4V for a period of 10 min.
In the present invention, after the above electrophoretic deposition, it is preferable to further perform washing and drying. The cleaning is preferably performed by deionized water. The drying temperature is preferably 60-200 ℃, and the drying time is preferably 10-120 min. And (4) obtaining the coated substrate through the treatment.
With respect to step b): and taking a lead, fixing one end of the lead to the uncoated end of the coated substrate through conductive adhesive, and extending the other end of the lead out of the coated substrate along the direction far away from the coated end to obtain an intermediate.
In the invention, the electric conduction is preferably a metal enameled wire, namely a wire which takes a metal wire as a core and is wrapped by an enamel coating on the surface; wherein the wires are exposed at both ends. In the present invention, the conductive wire is preferably a copper wire, a silver wire, an aluminum wire, a gold wire, a nickel wire, a zinc wire, or a tin wire (i.e., the covered metal wire is a metal wire of the above-mentioned kind).
In the invention, after a lead is taken, one end of the lead is placed at the uncoated end of the coated substrate obtained in the step a), the other end of the lead is back to an insulating layer and extends out of the substrate along the length direction of the electrode substrate (see figure 2), then conductive adhesive is bonded to the contact part of the lead and the uncoated end of the substrate, the lead is fixed on the electrode substrate through the conductive adhesive, and specifically, a metal wire with one exposed end of the lead is bonded on the substrate, so that an intermediate is obtained; wherein, one end bonded with the wire is marked as a wire end, and one end not bonded with the wire is marked as a non-wire end.
In the invention, the conductive adhesive is preferably one or more of conductive silver adhesive, conductive copper adhesive, conductive aluminum adhesive, conductive zinc adhesive, conductive iron adhesive, conductive nickel adhesive and graphite adhesive. In the present invention, the form of the conductive adhesive is not particularly limited, and may be conductive paste, conductive adhesive coating, conductive tape, conductive glue, or the like. In the present invention, after the conductive paste is bonded, it is preferable to further perform curing. In the present invention, the curing temperature is not particularly limited, and may be carried out at room temperature. The curing time is preferably 1-24 h.
With respect to step c): putting the intermediate body into a glass tube with openings at two ends, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate body is flush with the opening at one end of the glass tube, and the conducting wire extends out of the glass tube; and sealing the opening of the glass tube which is flush with the end part of the non-conducting end of the intermediate body by using a sealing film, injecting a sealant from the opening at the other end of the glass tube, and curing to obtain a cured packaging body.
In the invention, the glass tube is a glass tube with openings at two ends, and the length of the glass tube is greater than that of the electrode substrate, so that the electrode substrate can be completely contained in the glass tube. In some embodiments of the invention, a glass tube was cut with an inner diameter of 5mm, a wall thickness of 1mm, and a length of 80 mm. In the present invention, before the glass tube is used, it is preferable to further perform washing and drying. Wherein, the cleaning agent adopted for cleaning comprises but is not limited to one or more of acetone, ethanol and water; the cleaning is preferably ultrasonic cleaning. The drying temperature is preferably 40-100 ℃.
Putting the intermediate obtained in the step b) into a glass tube, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate is flush with an opening at one end of the glass tube, and the conducting wire bonded at the conducting wire end of the intermediate extends out of the glass tube (see figure 2). The opening of the glass tube at the flush end is sealed with a sealing film to prevent leakage of the uncured sealant injected in the subsequent step, and the sealant is injected into the opening at the other end of the glass tube, preferably to fill the entire glass tube (see fig. 2).
The sealant is preferably an epoxy sealant, and more preferably a two-component epoxy sealant. The use mode is preferably as follows: transferring the A, B components into a centrifugal tube, mixing uniformly, centrifuging at high speed, and sucking the sealant by a liquid transfer gun and injecting into a glass tube. After the sealant is injected, curing is performed. In the present invention, the curing temperature is not particularly limited, and may be carried out at room temperature. The curing time is preferably 12-48 h. And curing to obtain the cured packaging body. In the present invention, after curing, it is preferable to remove the sealing film sealing the orifice of the glass tube and perform the subsequent steps.
With respect to step d): and polishing the end face of the non-conducting wire end in the solidified packaging body to obtain a polished body.
In the present invention, the polishing preferably comprises:
s1, polishing the end face of the non-conducting wire end in the solidified packaging body into a mirror surface by using sand paper;
s2, using the electrode obtained in the step S1 as a working electrode, Ag-AgCl as a reference electrode, a Pt sheet as a counter electrode and K3[Fe(CN)6]Testing a scanning cyclic voltammetry curve by taking an aqueous solution as an electrolyte and KCl as a supporting electrolyte; if the obtained cyclic voltammetry curve is S-shaped, judging the cyclic voltammetry curve to be qualified; if the cyclic voltammogram is not S-shaped, polishing with sand paper is continued,until the cyclic voltammogram is sigmoidal.
In step S1, it is preferable to sequentially polish the end surfaces of the non-lead terminals (i.e., the electrode end surfaces) in the cured package with 180-mesh, 600-mesh, 1000-mesh, 2000-mesh, 3000-mesh, 5000-mesh, and 7000-mesh sandpaper until the end surfaces are mirror surfaces. In the present invention, after the above polishing, it is preferable to further perform cleaning; the cleaning agent used for cleaning preferably comprises ethanol and/or water; the cleaning is preferably ultrasonic cleaning.
In the step S2, K is3[Fe(CN)6]The concentration of the aqueous solution is preferably 0.1 to 45 mmol/L. The concentration of the KCl supporting electrolyte in an electrolyte system is preferably 0.1-2 mol/L. Step S2, testing a scanning cyclic voltammetry curve in a three-electrode system, and judging the cyclic voltammetry curve to be qualified if the obtained cyclic voltammetry curve is in a standard S shape; if the obtained cyclic voltammetry curve is not in the standard S shape, polishing by using sand paper until the cyclic voltammetry curve is in the standard S shape; the further polishing with sandpaper is preferably performed with 7000-mesh sandpaper. The conditions of the cyclic voltammetric scan are preferably: the potential range is 0-0.6V, and the sweep rate is preferably 5-100 mV/s. In the present invention, after the polishing is continued, it is preferable to further perform washing to restore the clean state of the electrode itself, and the electrode can be reused by polishing.
Through the steps S1-S2, the micro-nano charged electrode can be successfully prepared, if the monitoring of the step S2 is not carried out, the cyclic voltammetry curve does not reach the standard S shape, the prepared electrode is not the micro-nano charged electrode, and at the moment, the subsequent steps are carried out, so that the H can be obviously reduced2O2The detection sensitivity of (3).
With respect to step e): and sequentially performing electroreduction on the Sn film, stripping off the Sn film and deposition on a metal-containing film on the polished surface of the polished body to obtain the micro-nano charged electrode.
In the present invention, said step e) preferably comprises:
e1) performing electro-reduction under a three-electrode system by using the polishing body as a working electrode and a phosphate buffer solution as an electrolyte to form an Sn film layer on the polishing surface of the polishing body; then, stripping the Sn film layer to form a stripping surface;
e2) taking the electrode obtained in the step e1) as a working electrode, carrying out electrodeposition under a three-electrode system, and forming a metal-containing film on the stripping surface to obtain the micro-nano charged electrode.
In said step e 1): the pH value of the phosphate buffer solution is preferably 6.80-7.40. The reference electrode of the three-electrode system is preferably an Ag-AgCl electrode, and the counter electrode is preferably a Pt electrode. The invention inserts the working electrode, the reference electrode and the counter electrode into the electrochemical detection cell of the phosphate buffer solution, connects each electrode on the electrochemical workstation, and selects the current-time curve method to carry out the electroreduction. Wherein the conditions of the electroreduction are preferably as follows: the voltage is-0.5 to-5V, and the time is 60 to 1000 s. And forming a Sn film layer on the polishing surface of the polishing body through the treatment.
In the present invention, after the above treatment, the Sn film is peeled off. In the present invention, the peeling is preferably acid dip peeling. The acid solution is preferably sulfuric acid solution, hydrochloric acid solution, nitric acid solution or aqua regia. After stripping, a stripping surface is formed.
In said step e 2): the reference electrode of the three-electrode system is preferably an Ag-AgCl electrode, and the counter electrode is preferably a Pt electrode. The electrodeposition is preferably step pulse electrodeposition. The conditions for the step pulse electrodeposition are preferably: the initial voltage is 0.1-1V, and the pulse time is 0.1-5 s; the termination voltage is-0.02 to-0.5V, and the pulse time is 0.2 to 10 s; the number of pulses is 50 to 300.
After the electrodeposition treatment, a metal-containing film layer is deposited on the stripping surface. The metal-containing film is a metal film, a metal composite salt film or a metal oxide film. Wherein, the metal film is preferably a gold film, a platinum film, a silver film, a copper film or a palladium film; the metal composite salt is preferably Prussian blue; the metal oxide is preferably titanium dioxide. For example, a metal salt solution is used as an electrolyte for depositing the metal film, wherein the metal salt is preferably chlorate (such as chloroplatinic acid, chloroauric acid or ferrite). The concentration of the metalate solution is preferably 1-20 mmol/L; wherein the iron-based acid salt solution is K3[Fe(CN)6]With FeCl3A hydrochloric acid solution; in some embodiments of the invention, theThe HCl concentration in the iron-based acid salt solution is 0.1mol/L, FeCl3The concentration is 2.5mol/L, K3[Fe(CN)6]The concentration was 2.5 mol/L.
After electrodeposition, a corresponding metal film is formed. And (4) obtaining the micro-nano charged electrode through the treatment.
The invention also provides the micro-nano charged electrode prepared by the preparation method in the technical scheme.
The invention also provides an enzyme-free biosensor, which is a three-electrode system formed by taking the micro-nano charged electrode as a working electrode, Ag-AgCl as a reference electrode and a Pt sheet as a counter electrode in the technical scheme.
According to the preparation method, the micro-nano charged electrode is successfully prepared, the surface of a metal film in the prepared micro-nano charged electrode is rough, and the constructed H2O2The enzyme-free biosensor has a large electrochemical active area and can obviously improve H2O2The detection sensitivity of (3).
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
Example 1 preparation of one-sided ITO Linear modified NanoTab electrode
S1, cutting an ITO electrode (thickness is 1.1mm) with the width of 3mm multiplied by the length of 20mm by a flat glass cutter, respectively ultrasonically cleaning the ITO electrode for 20min by acetone, ethanol and water, and drying the ITO electrode by nitrogen. Cutting a glass tube with an inner diameter of 5mm, a wall thickness of 1mm and a length of 80mm by using a glass cutter, respectively ultrasonically cleaning the glass tube for 20min by using acetone, ethanol and water, and drying the glass tube in an oven at 60 ℃.
S2, adding 2-allylphenol into a methanol aqueous solution (mass ratio of water to methanol is 1: 1) to enable the concentration of 2-allylphenol to be 0.90mmol/L, and adjusting the pH of the system to be 9.0-9.2 by ammonia water to obtain a 2-allylphenol solution. Then, the ITO electrode obtained in step S1 was vertically inserted into a 2-allylphenol solution (half of the ITO electrode was immersed in the solution and the other half was protruded out of the solution along the length direction), and electrodeposition was performed for 10min at a constant potential of 4V using Ag-AgCl as a reference electrode and a Pt plate as a counter electrode, to deposit a 2-allylphenol insulating layer on the surface of the bottom half of the ITO electrode. Then, the mixture is taken out and washed clean by deionized water, and is put into an oven at 150 ℃ for drying for 30 min. A coated substrate is obtained.
S3, cutting a copper enameled wire with the length of 100mm, exposing copper wires at two ends, bonding one end of the copper enameled wire to the uncoated end of the coated substrate obtained in the step S1 by using conductive silver adhesive according to the scheme shown in figure 1, and curing for 24h at room temperature. Then, the glass tube is placed into a glass tube, the end face of the non-conductive end is flush with the opening at one end of the glass tube, the opening is sealed by a sealing film, then epoxy sealant is injected into the opening at the other end of the glass tube, the whole glass tube is filled, and the glass tube is cured for 24 hours at room temperature. And obtaining the solidified packaging body.
The epoxy sealant is an epoxy potting sealant purchased from Oersbang (China) Co., Ltd, the component A and the component B are put into a 50mL centrifuge tube according to the mass ratio of 2: 1 to be uniformly mixed, the mixture is centrifuged at a high speed (10000rpm) for 10min, and then the epoxy potting sealant is absorbed by a pipette and is injected into a glass tube.
And S4, polishing the end face of the electrode, flush with the opening of the glass tube, in the cured packaging body obtained in the step S3 to a mirror surface by using 180-mesh, 600-mesh, 1000-mesh, 2000-mesh, 3000-mesh, 5000-mesh and 7000-mesh sandpaper in sequence, and then respectively ultrasonically cleaning the electrode three times by using ethanol and ultrasonically cleaning the electrode three times by using deionized water for 30S each time.
S5, using the polished body obtained in the step S4 as a working electrode, Ag-AgCl as a reference electrode, Pt as a counter electrode and K3[Fe(CN)6]Scanning a cyclic voltammetry curve (the potential range is 0-0.6V, and the scanning speed is 50mV/s) in the three-electrode system by taking an aqueous solution (the concentration is 3mM) as an electrolyte and KCl as a supporting electrolyte (the concentration in the electrolyte is 1M); if the obtained cyclic voltammetry curve is in a standard S shape, judging the curve to be qualified; and if the obtained cyclic voltammetry curve is not in the standard S shape, polishing by 7000-mesh sand paper, and ultrasonically cleaning by using ethanol and secondary deionized water after each polishing until the cyclic voltammetry curve is in the standard S shape. And after the completion, washing the surface of the electrode by using deionized water, and recovering the cleaning state of the electrode.
And S6, taking the electrode obtained in the step S5 as a working electrode, Ag-AgCl as a reference electrode and Pt as a counter electrode, jointly inserting the electrodes into an electrochemical detection cell containing phosphate buffer (pH 7.0), connecting the electrodes to an electrochemical workstation, selecting a current-time curve method, setting the potential to be-1.15V, electrically reducing the ITO nano-band electrode for 200S, and generating a Sn film on the end face flush with the opening of the glass tube.
S7, the electrode obtained in the step S6 is immersed in a sulfuric acid solution for 10 seconds at room temperature, and then the Sn film is peeled off.
S8, taking the stripped electrode as a working electrode, Ag-AgCl as a reference electrode and Pt as a counter electrode, jointly inserting the electrodes into a chloroauric acid solution (the concentration is 10mmol/L), and selecting a step pulse method, wherein the parameters are set as follows: initial potential 0.5V, pulse time 0.5s, end potential-0.1V, pulse time 1s, pulse number 200. And after scanning, forming a layer of gold film on the stripping surface of the ITO nano-belt electrode to obtain the nano-belt electrode.
Example 2 preparation of double-sided ITO Linear modified NanoTab electrode
The preparation process of the embodiment 1 is carried out, except that the conductive material is replaced by double-sided ITO, and 2-allyl phenol electrophoretic deposition is carried out for 15 min; the electrodeposited solution was changed from chloroauric acid to chloroplatinic acid (concentration 10 mmol/L).
Example 3 preparation of one-sided ITO Linear modified array NanoTab electrode
The procedure is as in example 1, except that 3 sheets of ITO electrophoretically deposited with 2-allylphenol are placed simultaneously in a glass tube and cured with a sealant; the method for converting the electrodeposition liquid chloroauric acid into an iron-based acid salt solution comprises the following steps: 0.1mol/L HCl, 2.5mol/L FeCl3，2.5mol/L K3[Fe(CN)6]。
Wherein, the arrangement mode of 3 pieces of ITO is as follows: are arranged in parallel at equal intervals; referring to FIG. 3, FIG. 3 is a schematic diagram showing the arrangement of ITO sheets in example 3.
Example 4 preparation of Single-sided FTO Linear modified NanoTab electrode
The procedure of example 1 was followed except that the conductive material was replaced with single-sided FTO, 2-allylphenol electrophoretic deposition for 20 min.
Example 5 preparation of curved PET-FTO Linear modified Nanotband electrode
The preparation process of example 1 was followed, except that the conductive material was replaced with a PET-based FTO composite and bent into a curved surface to increase the electrode area, and 2-allylphenol electrophoretic deposition was performed for 30 min; the electrodeposited solution was changed from chloroauric acid to chloroplatinic acid (concentration 10 mmol/L).
Example 6 preparation of curved PET-FTO Linear modified Nanotband electrode
The preparation process of example 1 was followed, except that the conductive material was replaced with a PET-based FTO composite material and it was curled for a plurality of turns to increase the electrode area; the method for converting the electrodeposition liquid chloroauric acid into an iron-based acid salt solution comprises the following steps: 0.1mol/L HCl, 2.5mol/L FeCl3，2.5mol/L K3[Fe(CN)6]。
Example 7
1.1 preparation of enzyme-free Sensors
And a three-electrode system which is formed by taking the micro-nano-electrode as a working electrode, Ag-AgCl as a reference electrode and a Pt sheet as a counter electrode is the enzyme-free sensor.
1.2H2O2Detection of (2)
Detecting an object: h2O2；
Detection method and conditions: a three-electrode system was installed in a beaker containing 10mL of 0.1mol/L phosphoric acid buffer solution of pH 6.0 at room temperature with a stirring speed of 300 r/min: electrochemical detection is carried out on a CHI 832B electrochemical workstation by taking the micro-nano charged electrode prepared in the example 3 as a working electrode, Ag-AgCl as a reference electrode and a Pt sheet as a counter electrode. Sequentially adding 10 μ L of H with different concentrations by using a pipettor2O2Dilute the solution to obtain H in the sensor pair system while keeping the effect on buffer volume small2O2Current response to concentration change. The electrochemical workstation records the current variation with time by using a current meter time method, and generates the current and H2O2Linear relationship of concentration, linear range, detection limit, sensitivity, response time, etc. A nitrogen atmosphere was maintained throughout the electrochemical test.
And (3) displaying a detection result: modified electrode pair H opposite to bare electrode2O2The redox reaction is catalyzed (see FIG. 4, FIG. 4 shows the detection of modified electrode pair H in example 72O2Effect diagram of catalytic action). The linear range of detection is 0.012-0.97 mmol/L, and the detection limit is 0.0082mmol/L (see FIG. 5, FIG. 5 is an effect graph of the linear range and the detection limit in example 7, wherein FIG. 5A is a graph of the change of current and time, and FIG. 5B is a graph of the change of current and concentration).
In electrochemical detection of H2O2In the process, the electroactive substances sodium chloride (NaCl), glucose (Glu), Ascorbic Acid (AA), Dopamine (DA) and Uric Acid (UA) with 100 times concentration are added respectively, and the current response of the sensor is found to be hardly interfered, which indicates that the sensor can effectively avoid the signal interference of the above electroactive substances at the working potential (see fig. 6, and fig. 6 is a test effect graph of the electroactive substances in example 7 on the signal interference).
The detection result shows that the response time is relatively fast, and the time required for the reduction current to reach 95% of the steady-state current value is less than 5 s. The detection sensitivity is 1.149 mu A (mmol/L)-1. The same enzyme-free sensor is used for 10H with the concentration of 0.1mmol/L2O2The samples were tested with a standard deviation of 3.5%. After the micro-nano charged electrode is stored in a buffer solution at 4 ℃ for 3 weeks, the reduction peak current is only reduced by 5.2%. The above results indicate that the enzyme-free biosensor has good reproducibility and stability.
The micro-nano charged electrode prepared in other embodiments is detected, the result is similar to the effect of the micro-nano charged electrode obtained in embodiment 3, and the obtained micro-nano charged electrode has an electrode pair H2O2The redox has catalytic action, sensitive detection, good reproducibility and stability, and can effectively avoid the interference of other electroactive substances.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A micro-nano charged electrode, comprising:
an electrode substrate; the electrode substrate is divided into a coating area and an uncoated area along the length direction;
a poly 2-allylphenol insulating layer coated on the coating region;
a wire secured to the uncoated region;
the glass tube is sleeved on the periphery of the electrode substrate; the electrode substrate is characterized in that the glass tube is a glass tube with openings at two ends, the end face of the cladding area is flush with the opening at one end of the glass tube, the end face is compounded with a metal-containing film layer, and a lead of the non-cladding area extends out of the opening at the other end of the glass tube;
the sealant is filled in the glass tube;
the micro-nano strip electrode is prepared by the following preparation method:
a) taking an electrode substrate as a working electrode, taking a 2-allylphenol solution as an electrolyte, and depositing a 2-allylphenol insulating layer on the surface of the electrode substrate by electrophoretic deposition under a three-electrode system to obtain a coating substrate;
the electrode substrate is divided into an upper part and a lower part along the length direction of the electrode substrate, wherein a 2-allyl phenol insulating layer is deposited on one part and is marked as a coated end, and the other part is marked as an uncoated end;
the electrode substrate is an Sn-containing electrode substrate;
the pH value of the 2-allylphenol solution is 9.0-9.2;
b) taking a lead, fixing one end of the lead to the uncoated end of the coated substrate through conductive adhesive, and extending the other end of the lead out of the coated substrate along the direction far away from the coated end to obtain an intermediate body; wherein, one end bonded with the lead is marked as a lead end, and the other end not bonded with the lead is marked as a non-lead end;
c) putting the intermediate body into a glass tube with openings at two ends, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate body is flush with the opening at one end of the glass tube, and the conducting wire extends out of the glass tube;
sealing the opening of the glass tube which is flush with the end part of the non-conducting end of the intermediate body with a sealing film, injecting a sealant from the opening at the other end of the glass tube and curing to obtain a cured packaging body;
d) polishing the end face of the non-conducting wire end in the solidified packaging body to obtain a polished body;
e) and sequentially performing electroreduction on the Sn film, stripping off the Sn film and deposition on a metal-containing film on the polished surface of the polished body to obtain the micro-nano charged electrode.
2. The micro-nano strip electrode according to claim 1, wherein the electrode substrate is a Sn-containing electrode substrate;
the wire is a metal enameled wire, and two ends of the wire are exposed out of the metal wire;
the lead is a copper wire, a silver wire, an aluminum wire, a gold wire, a nickel wire, a zinc wire or a tin wire;
the conducting wire is fixed on the uncoated area through conductive adhesive.
3. The preparation method of the micro-nano strip electrode as claimed in any one of claims 1-2, characterized by comprising the following steps:
a) taking an electrode substrate as a working electrode, taking a 2-allylphenol solution as an electrolyte, and depositing a 2-allylphenol insulating layer on the surface of the electrode substrate by electrophoretic deposition under a three-electrode system to obtain a coating substrate;
the electrode substrate is divided into an upper part and a lower part along the length direction of the electrode substrate, wherein a 2-allyl phenol insulating layer is deposited on one part and is marked as a coated end, and the other part is marked as an uncoated end;
the electrode substrate is an Sn-containing electrode substrate;
the pH value of the 2-allylphenol solution is 9.0-9.2;
b) taking a lead, fixing one end of the lead to the uncoated end of the coated substrate through conductive adhesive, and extending the other end of the lead out of the coated substrate along the direction far away from the coated end to obtain an intermediate body; wherein, one end bonded with the lead is marked as a lead end, and the other end not bonded with the lead is marked as a non-lead end;
c) putting the intermediate body into a glass tube with openings at two ends, wherein the coating substrate is completely contained in the glass tube, the end part of the non-conducting end of the intermediate body is flush with the opening at one end of the glass tube, and the conducting wire extends out of the glass tube;
sealing the opening of the glass tube which is flush with the end part of the non-conducting end of the intermediate body with a sealing film, injecting a sealant from the opening at the other end of the glass tube and curing to obtain a cured packaging body;
d) polishing the end face of the non-conducting wire end in the solidified packaging body to obtain a polished body;
e) and sequentially performing electroreduction on the Sn film, stripping off the Sn film and deposition on a metal-containing film on the polished surface of the polished body to obtain the micro-nano charged electrode.
4. The method of claim 3, wherein in step a):
the concentration of the 2-allylphenol solution is 0.01-90 mmol/L;
the solvent in the 2-allyl phenol solution is one or more of methanol, water, ethanol, acetone and n-hexane.
5. The method of manufacturing according to claim 3 or 4, wherein in step a):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the voltage of the electrophoretic deposition is 0.5-10V, and the time is 1-30 min;
the Sn-containing electrode substrate is an ITO electrode, an FTO electrode or a PET-ITO composite electrode;
the thickness of the Sn-containing electrode substrate is less than or equal to 25 mu m.
6. The method of claim 3, wherein the polishing in step d) comprises:
s1, polishing the end face of the non-conducting wire end in the solidified packaging body into a mirror surface by using sand paper;
s2, using the electrode obtained in the step S1 as a working electrode, Ag-AgCl as a reference electrode, a Pt sheet as a counter electrode and K3[Fe(CN)6]Testing a scanning cyclic voltammetry curve by taking an aqueous solution as an electrolyte and KCl as a supporting electrolyte; if the obtained cyclic voltammetry curve is S-shaped, judging the cyclic voltammetry curve to be qualified; if the cyclic voltammogram obtained is not S-shaped, polishing with sand paper is continued until the cyclic voltammogram is S-shaped.
7. The method of claim 3, wherein in step b):
the wire is a metal enameled wire, and two ends of the wire are exposed out of the metal wire;
the lead is a copper wire, a silver wire, an aluminum wire, a gold wire, a nickel wire, a zinc wire or a tin wire;
the conductive adhesive is one or more of conductive silver adhesive, conductive copper adhesive, conductive aluminum adhesive, conductive zinc adhesive, conductive iron adhesive, conductive nickel adhesive and graphite adhesive;
in the step c):
the sealant is epoxy sealant;
the glass tube is filled with the sealant.
8. The method of claim 3, wherein step e) comprises:
e1) performing electro-reduction under a three-electrode system by using the polishing body as a working electrode and a phosphate buffer solution as an electrolyte to form an Sn film layer on the polishing surface of the polishing body; then, stripping the Sn film layer to form a stripping surface;
e2) taking the electrode obtained in the step e1) as a working electrode, carrying out electrodeposition under a three-electrode system, and forming a metal-containing film on the stripping surface to obtain the micro-nano charged electrode.
9. The method for preparing according to claim 8, wherein in step e 1):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the pH value of the phosphate buffer solution is 6.80-7.40;
the voltage of the electroreduction is-0.5 to-5V, and the time is 60 to 1000 s;
the stripping is carried out by soaking in acid liquor;
in said step e 2):
the reference electrode of the three-electrode system is an Ag-AgCl electrode, and the counter electrode is a Pt electrode;
the electrodeposition is step pulse electrodeposition;
the conditions of the step pulse electrodeposition are as follows: the initial voltage is 0.1-1V, and the pulse time is 0.1-5 s; the termination voltage is-0.02 to-0.5V, and the pulse time is 0.2 to 10 s; the pulse number is 50-300;
the metal-containing film is a metal film, a metal composite salt film or a metal oxide film;
the metal film is a gold film, a platinum film, a silver film, a copper film or a palladium film;
the metal composite salt is Prussian blue;
the metal oxide is titanium dioxide.
10. The enzyme-free biosensor is characterized in that the sensor is a three-electrode system which is formed by taking a micro-nano charged electrode as a working electrode, Ag-AgCl as a reference electrode and a Pt sheet as a counter electrode;
the micro-nano charged electrode is the micro-nano charged electrode as defined in any one of claims 1 to 2 or the micro-nano charged electrode prepared by the preparation method as defined in any one of claims 3 to 9.
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