A porous microneedle electrode with nanoparticles embedded in the tip and its preparation and application

Abstract

The present invention relates to the field of electrochemical analysis, and more specifically, to a porous microneedle electrode with nanoparticles embedded in the tip, and its preparation and application. A microneedle electrode body is prepared with a nickel-chromium alloy needle; the tip of the microneedle electrode is electrochemically etched to form closely arranged nanopores at the tip of the microneedle electrode; wherein the nanopores cover the entire tip of the electrode; and metal particles are embedded into the nanopores of the microneedle electrode with closely arranged nanopores at the tip by pulse electrodeposition. The porous structure of the tip of the microneedle electrode described in the present invention can also protect the nanoparticles in the nanopores and prevent the nanoparticles from falling off during the detection process, so that the prepared electrode has good stability and a longer service life, and can be widely used for high-sensitivity and high-stability detection of different pollutants in different samples.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical analysis, and specifically to a porous microneedle electrode with nanoparticles embedded at the tip and its preparation and application. Background Art

[0002] The research on voltammetry-based chemically modified electrodes has always been a hot topic in the research of electrochemical sensors. Electrochemical voltammetry has the advantages of simple instrument equipment, easy operation, high sensitivity, easy miniaturization and automation, etc., and has been widely used in the fields of biomedicine, food, industry and environmental analysis. The core of electrochemical voltammetry is the working electrode. The traditional working electrode is a mercury electrode, but mercury has been listed as an environmentally highly toxic pollutant prohibited from use in many countries, and it has special requirements in terms of production and storage. Therefore, people have paid more and more attention to green and environmentally friendly chemically modified electrodes that can replace mercury.

[0003] In early research, people directly loaded nanomaterials with good electrochemical catalytic performance onto the surfaces of conventional solid electrodes such as glassy carbon electrodes, gold electrodes, platinum electrodes, etc. to prepare chemically modified electrodes to improve the sensitivity of electrode detection. However, it was found that due to the large area of the substrate solid electrode, such electrodes had a large background current and low sensitivity. Later, it was found that by reducing the volume of the substrate solid electrode to prepare a miniaturized electrode, the mass transfer rate of the electrode could be increased, the equilibrium time could be reduced, and the sensitivity of electrode detection could be improved. Therefore, chemically modified electrodes based on miniaturized solid electrodes have attracted extensive attention from researchers in the analysis field. In the existing literature reports, gold wires, iridium wires, carbon fibers, etc. have been widely used as the substrate electrode materials for preparing chemically modified microelectrodes. However, due to the small volume, smooth surface, small specific surface area and few active binding sites of the microelectrode, the modified microelectrodes prepared by currently used direct electrodeposition method, physical sputtering method, etc. can only load a small amount of nanomaterials with excellent performance. To increase the loading amount of nanomaterials on the microelectrode, there has been research on physically sputtering a conductive layer on the surface of the microelectrode, then electro-depositing a metal alloy, and then removing the active metal in the alloy to form a porous metal modified layer to increase the loading amount and reaction area; the above-mentioned loaded microelectrodes can improve the sensitivity of the prepared sensors. However, the surface of the microelectrode is very smooth, lacking sufficient binding sites to load nanomaterials. At the same time, the smooth electrode surface cannot effectively protect the nanomaterials loaded thereon, resulting in the above-mentioned modified nanomaterials being easily detached from the electrode surface during the detection process, causing a decrease in detection performance and poor stability, thus limiting the wide application of the modified microelectrodes.

[0004] Therefore, the research on the surface structure modification of the microelectrode body, while increasing the specific surface area, effectively improving the electrode stability, will open up a new research direction for the development of chemically modified electrodes. Summary of the Invention

[0005] The object of the present invention is to provide a porous microneedle electrode with nanoparticles embedded at the tip, and its preparation and application.

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

[0007] A preparation method of a porous microneedle electrode with nanoparticles embedded at the tip:

[0008] a. Prepare a microneedle electrode body with a nickel-chromium alloy needle;

[0009] b. Through electrochemical etching on the tip part of the above microneedle electrode, form closely arranged nanopores at the tip of the microneedle electrode; wherein, the nanopores cover the entire electrode tip, and the pore diameter is between 300 - 900 nm;

[0010] c. Embed metal particles into the nanopores of the microneedle electrode obtained above with closely arranged nanopores at the tip through pulse electrodeposition.

[0011] In the step b, use a nickel-chromium alloy microneedle electrode as the working electrode and a graphite electrode as the auxiliary electrode. Place the above two electrodes in the etching solution and perform electrochemical etching by the potentiostatic method to form closely arranged nanopores at the tip of the microneedle electrode.

[0012] The etching potential of the electrochemical etching is 1 - 5 V, and the etching time is 30 - 180 s;

[0013] Preferably, the etching potential of the electrochemical etching is 2 V, and the etching time is 120 s.

[0014] The composition of the etching solution is 0.2 - 0.5 wt% ammonium fluoride, 2 - 5 vol% ethylene glycol, and 95 - 98 vol% deionized water.

[0015] Preferably, the composition of the etching solution is 0.3 wt% ammonium fluoride, 2 vol% ethylene glycol, and 98 vol% deionized water.

[0016] The tip of the nickel-chromium alloy microneedle electrode body is the electrode sensing area, the top is the electrode wire, and the rest is coated with an insulating layer; wherein, the length of the tip part is 0.5 - 1 mm, accounting for 0.5% - 1.2% of the length of the microneedle electrode body, and the top is 30% - 50% of the length of the microneedle electrode body.

[0017] In step c, the micro-needle electrode with nanopores closely arranged at the tip is used as the working electrode, and nanoparticles are deposited in the nanopores at the tip of the micro-needle electrode by pulse electrodeposition to obtain a porous micro-needle electrode with nanoparticles embedded at the tip.

[0018] Further, after cleaning the micro-needle electrode with nanopores closely arranged at the tip with deionized water, it is used as the working electrode, combined with a platinum electrode as the auxiliary electrode and silver / silver chloride as the reference electrode, and placed in an electroplating solution of different metal nanoparticles. A three-stage pulse potential and time sequence are cycled to deposit metal nanoparticles in the nanopores closely arranged at the tip. Among them, the size of the metal nanoparticles is between 20 - 500 nm.

[0019] The three-stage pulse potential and time sequence are: -0.5 - 0.6 V, 4 - 6 ms; 0.1 - 0.15 V, 26 - 35 s; 0 - 0.1 V, 900 - 1200 ms; preferably, the three-stage pulse potential and time sequence are: -0.5 V, 4 ms; 0.1 V, 26 s; 0 V, 900 ms.

[0020] The number of cycles of the three-stage pulse potential and time sequence is 9 - 12 times; preferably, the number of cycles of the three-stage pulse potential and time sequence is 9 times.

[0021] The electroplating solution is a solution containing different metal nanoparticle precursors; among them, the ions to be detected are one or more of metal ions (such as copper, lead, cadmium, zinc, iron, chromium, mercury, nickel, etc.), non-metal ions (such as arsenic, selenium, oxygen, etc.), pH, nitrate, nitrite, phosphate, silicate.

[0022] The electroplating solution is obtained by dissolving different metal nanoparticle precursors in water or other organic solutions.

[0023] Then, according to the deposition operation, the deposition conditions are optimized to determine the electroplating solution concentration, etc.

[0024] Still further, the electroplating solution is at least one of chloroauric acid, silver nitrate, copper sulfate, chloroplatinic acid, sodium chloropalladate, bismuth nitrate.

[0025] A prepared porous micro-needle electrode with nanoparticles embedded at the tip, the surface of the tip of the micro-needle body is covered with nanopores closely arranged, and the porous micro-needle electrode with nanoparticles embedded at the tip with metal nanoparticles uniformly deposited in the pores is prepared according to the method.

[0026] Application of the porous micro-needle electrode with nanoparticles embedded at the tip, the application of the porous micro-needle electrode with nanoparticles embedded at the tip in detecting different ions.

[0027] The advantages of the present invention are:

[0028] 1. The microneedle electrode of the present invention forms closely arranged nanopores at its tip through electrochemical etching. This structure can significantly increase the specific surface area of the electrode, increase the active binding sites of the electrode for nanoparticles, enable the electrode to bind more nanoparticles with excellent electrocatalytic performance, make the detection response of the electrode to the analyte more sensitive, and have higher sensitivity and lower detection limit.

[0029] 2. The present invention forms closely arranged nanopores at its tip through electrochemical etching, and then deposits nanoparticles with excellent electrocatalytic performance into the nanopores at the tip of the electrode, obtaining a porous microneedle electrode with nanoparticles embedded at the tip. Compared with the microneedle electrode with a smooth surface without electrochemical etching, the nanoparticles can be deposited in the nanopores at the tip of the microneedle electrode of the present invention, and the nanopores will effectively protect the nanoparticles therein and prevent them from falling off during the detection process, thus having better stability and service life. After physically wiping the nanoparticles on the electrode, it can be clearly seen by testing the residual amount of nanoparticles on the electrode by cyclic voltammetry that the prepared porous microneedle electrode with nanoparticles embedded at the tip has a significantly better effect of preventing nanoparticles from falling off than the unetched electrode and has better stability.

[0030] 3. The porous microneedle electrode with nanoparticles embedded at the tip prepared by the present invention has high sensitivity, good stability and longer service life, and can be used for highly sensitive and highly stable detection of different pollutants in the fields of environmental monitoring, food safety and clinical applications. Description of the Drawings

[0031] Figure 1 Scanning electron microscope images of the tip of the microneedle electrode with closely arranged nanopores prepared by the electrochemical etching method provided in the embodiment of the present invention (left) and the scanning electron microscope image of the tip of the unetched microneedle electrode (right).

[0032] Figure 2 Scanning electron microscope image of the porous microneedle electrode with nanoparticles embedded at the tip provided in the embodiment of the present invention.

[0033] Figure 3 Variation of the characteristic peaks of nanoparticles after the porous microneedle electrode with nanoparticles embedded at the tip (left) and the unetched microneedle electrode directly deposited with nanoparticles (right) provided in the embodiment of the present invention are physically wiped different times in the same way.

[0034] Figure 4The stripping voltammograms and corresponding linear curves of the porous microneedle electrode with gold nanoparticles embedded at the tip provided by the embodiments of the present invention for the detection of copper ions with different concentrations (0.1, 0.3, 0.5, 0.7, 1, 3, 5, 7, 10, 50, 100, 300, 500, 700, 1000 nM) in a buffer solution.

[0035] Figure 5 The change of the current response when the porous microneedle electrode with gold nanoparticles embedded at the tip provided by the embodiments of the present invention continuously detects copper ions 30 times in a buffer solution.

[0036] Figure 6 The current response diagram and corresponding standard working curve of the porous microneedle electrode with gold nanoparticles embedded at the tip provided by the embodiments of the present invention for the detection of heavy metal copper in seawater. Detailed implementation manners

[0037] The following further illustrates the detailed implementation manners of the present invention in combination with examples. It should be noted that the detailed implementation manners described here are only for explaining and interpreting the present invention and are not limited to the present invention.

[0038] The tip porous structure of the microneedle electrode obtained by the present invention can provide a large specific surface area and many active binding sites, so as to be able to bind more nanoparticles with excellent catalytic performance, making the electrode have high sensitivity. More importantly, the tip porous structure of the microneedle electrode can also protect the nanoparticles in the nanopores, preventing the nanoparticles from falling off during the detection process, making the prepared electrode have good stability and a longer service life, and can be widely used for the highly sensitive and highly stable detection of different pollutants in different samples.

[0039] Example 1

[0040] The specific preparation steps of the porous microneedle electrode with metal nanoparticles embedded at the tip are as follows:

[0041] (1) Preparation of the nickel-chromium alloy microneedle electrode: Select a nickel-chromium alloy needle with a needle body diameter of 0.25 mm and a length of 60 mm. Take 1 mm of the tip part as the electrode sensing area and 25 mm of the top part as the electrode lead wire, and coat the insulation layer on the rest of the needle body to obtain the nickel-chromium alloy microneedle electrode.

[0042] (2) Preparation of nanopore channels at the tip of the microneedle electrode: After cleaning the nickel-chromium alloy microneedle electrode with deionized water and drying it, it was used as the working electrode, and the graphite electrode was used as the auxiliary electrode. They were placed in an etching solution containing 0.3 wt% ammonium fluoride, 2 vol% ethylene glycol, and 98 vol% deionized water. Electrochemical etching was carried out using the potentiostatic technique under the conditions of an etching potential of 2 V and an etching time of 120 s. After etching was completed, it was cleaned with deionized water and dried to obtain a microneedle electrode with nanopore channels closely arranged at the tip. (See Figure 1 )

[0043] It can be seen from Figure 1 that after electrochemical etching, the tip surface of the microneedle electrode is covered with closely arranged nanopore channels, and the entire surface is very rough. The pore diameter is approximately 600 nm; while the tip surface of the unetched microneedle electrode is very smooth.

[0044] (3) Deposition of metal nanoparticles in the nanopore channels at the tip of the microneedle electrode: Using the microneedle electrode with nanopore channels closely arranged at the tip obtained in the above steps as the working electrode, the platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode, they were placed in an electroplating solution containing gold nanoparticle precursors. Under the optimal conditions, that is, a pulse potential and time sequence of -0.5 V, 4 ms; 0.1 V, 26 s; 0 V, 900 ms, it was cycled 9 times to deposit gold nanoparticles in the nanopore channels closely arranged at the tip, and thus a porous microneedle electrode with gold nanoparticles embedded at the tip was obtained. (See Figure 2 )

[0045] The electroplating solution containing gold nanoparticle precursors used in this example was a 1 mM chloroauric acid solution prepared from 0.5 M H 2 SO 4 .

[0046] It can be seen from Figure 2 that after pulse electroplating, the gold nanoparticles are uniformly deposited in the nanopore channels closely arranged at the tip of the microneedle electrode.

[0047] To investigate the protective effect of the nanopore channels closely arranged at the tip of the microneedle electrode on the gold nanoparticles, after physically wiping the porous microneedle electrode with gold nanoparticles embedded at the tip and the unetched microneedle electrode directly deposited with gold nanoparticles different numbers of times, the change in the characteristic peaks of the gold nanoparticles of the two electrodes was tested using cyclic voltammetry (see Figure 3 , left in the figure: the unetched microneedle electrode directly deposited with gold nanoparticles after being physically wiped 1 time and 2 times, right: the porous microneedle electrode with gold nanoparticles embedded at the tip after being physically wiped 1 time, 5 times, 10 times, 15 times, and 20 times).

[0048] Among them, the preparation process of the unetched microneedle electrode directly deposited with gold nanoparticles is as follows: The nickel-chromium alloy microneedle electrode obtained in the above step (1) is directly used as the working electrode, a platinum electrode is used as the auxiliary electrode, and Ag / AgCl is used as the reference electrode, and they are placed in 1 mM chloroauric acid electroplating solution prepared from 2 SO 4 and the cycle is carried out 9 times with a pulse potential and time sequence of -0.5V, 4ms; 0.1V, 26sm; 0V, 900ms to obtain an unetched microneedle electrode directly deposited with gold nanoparticles.

[0049] It can be clearly seen from Figure 3 that after the unetched microneedle electrode directly deposited with gold nanoparticles is physically wiped once, the characteristic peak of the gold nanoparticles at 0.68V completely disappears, while after the porous microneedle electrode with nanoparticles embedded at the tip is physically wiped 20 times, the characteristic peak of the gold nanoparticles hardly decreases. It can be seen that the porous microneedle electrode with nanoparticles embedded at the tip of the present invention has excellent mechanical stability and service life due to the protection of the nanopores for the gold nanoparticles.

[0050] Example 2

[0051] The porous microneedle electrode with gold nanoparticles embedded at the tip obtained in the above example is used to detect heavy metals: taking copper in seawater as an example. The measurement steps are as follows:

[0052] (1) The porous microneedle electrode with gold nanoparticles embedded at the tip prepared according to the above example should be first washed with deionized water and dried before use.

[0053] (2) The electrode cleaned in step (1) and the platinum auxiliary electrode and Ag / AgCl reference electrode form a three-electrode system and are placed in an acetic acid-sodium acetate buffer solution containing a series of different concentrations of copper ions (0.1, 0.3, 0.5, 0.7, 1, 3, 5, 7, 10, 50, 100, 300, 500, 700, 1000 nM). Through an electrochemical workstation, square wave anodic stripping voltammetry is used, with -0.3V as the enrichment potential and 120s as the enrichment time, the stripping peak current of different concentrations of copper ions is measured, and a linear curve of the peak current versus the corresponding ion concentration is plotted (see Figure 4 ).

[0054] From Figure 4 it can be known that for the porous microneedle electrode with gold nanoparticles embedded at the tip obtained, due to the nanopores significantly increasing the specific surface area and active binding sites of the electrode, more gold nanoparticles with excellent electrocatalytic performance can be combined, making the present invention have high sensitivity for copper ion detection, with a linear range of 0.1 - 1000 nM and a detection limit of 0.03 nM.

[0055] Further detection of the stability of the porous microneedle electrode with gold nanoparticles embedded at the tip for continuously detecting copper ions:

[0056] The above three electrodes were placed in an acetic acid - sodium acetate buffer solution containing 50 nM copper ions. Using an electrochemical workstation and square wave anodic stripping voltammetry, with -0.3 V as the enrichment potential and 120 s as the enrichment time, continuous measurements were carried out 30 times. The three electrodes were always placed in the above solution. After each detection, an oxidation potential was applied for potential cleaning. The cleaning potential was 0.4 V and the cleaning time was 30 s (see Figure 5 ).

[0057] From Figure 5 it can be seen that for the porous microneedle electrode with gold nanoparticles embedded at the tip of the present invention, due to the protective effect of the nanopores on the gold nanoparticles, effectively preventing their detachment during the detection process, the present invention has excellent stability, and the RSD for 30 consecutive detections is 1.5%.

[0058] (3) The above three electrodes were placed in standard seawater containing a series of different concentrations (10, 30, 50, 100, 300, 500 nM) of copper ions. Using an electrochemical workstation and square wave anodic stripping voltammetry, with -0.3 V as the enrichment potential and 120 s as the enrichment time, the stripping peak currents of copper ions at different concentrations were measured, and a standard working curve of peak current versus the corresponding ion concentration was plotted (see Figure 6 ).

[0059] From Figure 6 it can be seen that the prepared porous microneedle electrode with silver nanoparticles embedded at the tip also maintains high sensitivity for copper ion detection in seawater medium, reaching 7.65 μA / μM, and can be fully used for the detection of heavy metal copper in seawater.

[0060] Then the above three electrodes were placed in the seawater to be measured, and the stripping peak current of copper ions was measured. By comparing with the standard working curve of stripping peak current - concentration, the determination of the concentration of heavy metal copper in seawater can be achieved, and the concentration of copper ions in this seawater sample was obtained as 23.73 nM.

[0061] Example 3

[0062] The specific preparation steps of the porous microneedle electrode with silver nanoparticles embedded at the tip are as follows:

[0063] The difference from Example 1 is that the metal nanoparticles embedded in the nanopores at the electrode tip are silver nanoparticles.

[0064] The preparation of the nickel - chromium alloy microneedle electrode and the preparation of the nanopores at the tip of the microneedle electrode were carried out according to steps (1) and (2) of Example 1 respectively.

[0065] Deposition of silver nanoparticles in the nanopores of the tip of the microneedle electrode: Using a microneedle electrode with nanopores closely arranged at the tip as the working electrode, a platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode, and placing them in an electroplating solution containing silver nanoparticle precursors, performing 9 cycles with a pulse potential and time sequence of -0.5V, 4ms; 0.1V, 26sm; 0V, 900ms, depositing silver nanoparticles in the nanopores closely arranged at the tip, thus obtaining the prepared porous microneedle electrode with silver nanoparticles embedded at the tip.

[0066] The electroplating solution containing silver nanoparticle precursors is an aqueous solution of 10 mM silver nitrate.

[0067] Example 4

[0068] The specific preparation steps of the porous microneedle electrode with copper nanoparticles embedded at the tip are as follows:

[0069] The difference from Example 1 is that the metal nanoparticles embedded in the nanopores at the tip of the electrode are copper nanoparticles.

[0070] The preparation of the nickel-chromium alloy microneedle electrode and the preparation of the nanopores at the tip of the microneedle electrode are carried out according to steps (1) and (2) of Example 1 respectively.

[0071] Deposition of copper nanoparticles in the nanopores of the tip of the microneedle electrode: Using a microneedle electrode with nanopores closely arranged at the tip as the working electrode, a platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode, and placing them in an electroplating solution containing copper nanoparticle precursors, performing 9 cycles with a pulse potential and time sequence of -0.5V, 4ms; 0.1V, 26sm; 0V, 900ms, depositing copper nanoparticles in the nanopores closely arranged at the tip, thus obtaining the prepared porous microneedle electrode with copper nanoparticles embedded at the tip.

[0072] The electroplating solution containing copper nanoparticle precursors is 0.5 M CuSO 4 aqueous solution.

[0073] Example 5

[0074] The specific preparation steps of the porous microneedle electrode with platinum nanoparticles embedded at the tip are as follows:

[0075] The difference from Example 1 is that the metal nanoparticles embedded in the nanopores at the tip of the electrode are platinum nanoparticles.

[0076] The preparation of the nickel-chromium alloy microneedle electrode and the preparation of the nanopores at the tip of the microneedle electrode are carried out according to steps (1) and (2) of Example 1 respectively.

[0077] Deposition of platinum nanoparticles in the nanopores at the tip of the microneedle electrode: Using a microneedle electrode with nanopores closely arranged at the tip as the working electrode, a platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode, place them in an electroplating solution containing platinum nanoparticle precursors. Perform 9 cycles with a pulse potential and time sequence of -0.5V, 4ms; 0.1V, 26sm; 0V, 900ms to deposit platinum nanoparticles in the nanopores closely arranged at the tip, and thus obtain the prepared porous microneedle electrode with platinum nanoparticles embedded at the tip.

[0078] The electroplating solution containing platinum nanoparticle precursors is an aqueous solution of 10 mM chloroplatinic acid.

[0079] Example 6

[0080] Detecting nutrients with the porous microneedle electrode with copper nanoparticles embedded at the tip of the present invention: Taking nitrate in river water as an example. The measurement steps are as follows:

[0081] (1) The obtained porous microneedle electrode with copper nanoparticles embedded at the tip should be washed with deionized water and dried before use.

[0082] (2) The cleaned electrode, together with the platinum auxiliary electrode and the Ag / AgCl reference electrode, forms a three-electrode system and is placed in a sodium sulfate solution with a pH of 2 containing nitrate at different concentrations (0.02 - 6 mM). Using a electrochemical workstation and differential pulse voltammetry, with -0.3V as the initial potential and -0.8V as the termination potential, measure the reduction peak current of nitrate ions at different concentrations and plot the standard response curve of peak current versus the corresponding ion concentration. The linear range for the detection of nitrate ions by the porous microneedle electrode with copper nanoparticles embedded at the tip of the present invention is 0.02 - 6 mM, and the detection limit is 8 μM.

[0083] (3) Place the above three-electrode system in the river water sample to be measured. Using a electrochemical workstation and differential pulse voltammetry, with -0.3V as the initial potential and -0.8V as the termination potential, measure the reduction peak current of nitrate ions. Then add a certain amount of standard nitrate ion solution to the sample and measure the reduction peak current of nitrate ions again. Perform the addition of standard and measurement three times, and obtain the concentration of nitrate in the river water sample through the standard addition method.

Claims

1. A method for preparing a porous microneedle electrode with nanoparticles embedded in the tip, characterized in that: a. Prepare the microneedle electrode body with nickel-chromium alloy needle; b. The tip of the microneedle electrode is electrochemically etched to form closely arranged nanopores at the tip of the microneedle electrode; wherein the nanopores cover the entire tip of the electrode and the diameter of the pores is between 300-900 nm; c. embedding metal particles into the nanopores of the microneedle electrode having a closely arranged nanopore tip by pulse electrodeposition; In the step b, a nickel-chromium alloy microneedle electrode is used as a working electrode and a graphite electrode is used as an auxiliary electrode. The two electrodes are placed in an etching solution and electrochemically etched by a constant potential method to form closely arranged nanopores at the tip of the microneedle electrode; The electrochemical etching has an etching potential of 1-5 V and an etching time of 30-180 s; The etching solution composition is 0.2-0.5 wt% of ammonium fluoride, 2-5 vol% of ethylene glycol and 95-98 vol% of deionized water; After the microneedle electrode with closely arranged nanopores at the tip is cleaned with deionized water, it is used as a working electrode, combined with a platinum electrode as an auxiliary electrode and silver / silver chloride as a reference electrode, placed in an electroplating solution of different metal nanoparticles, and cycled with a three-stage pulse potential and time sequence to deposit metal nanoparticles in the closely arranged nanopores at the tip, wherein the size of the metal nanoparticles is between 20-500nm.

2. The method for preparing a porous microneedle electrode with nanoparticles embedded in the tip according to claim 1, characterized in that: The tip of the nickel-chromium alloy microneedle electrode body is the electrode sensing area, the top end is the electrode wire, and the rest of the body is coated with an insulating layer; the tip portion is 0.5-1mm long, accounting for 0.5%-1.2% of the length of the microneedle electrode body, and the top end is 30%-50% of the length of the microneedle electrode body.

3. The method for preparing a porous microneedle electrode with nanoparticles embedded in the tip according to claim 1, characterized in that: The three pulse potentials and time series are: -0.5-0.6 V, 4-6 ms; 0.1-0.15 V, 26-35 ms; 0-0.1 V, 900-1200 ms; The number of cycles of the three-segment pulse potential and time sequence is 9-12 times.

4. The method for preparing a porous microneedle electrode with nanoparticles embedded in the tip according to claim 1, characterized in that: The electroplating solution is a solution containing different metal nanoparticle precursors; wherein the ions to be detected are one or more of metal ions, non-metal ions, pH, nitrate, nitrite, phosphate, and silicate.

5. The method for preparing a porous microneedle electrode with nanoparticles embedded in the tip according to claim 4, characterized in that: The metal ions are copper, lead, cadmium, zinc, iron, chromium, mercury or nickel; the non-metal ions are arsenic, selenium or oxygen.

6. A porous microneedle electrode with nanoparticles embedded in the tip prepared according to claim 1, characterized in that: According to the method of claim 1, a porous microneedle electrode is prepared in which the surface of the tip of the microneedle electrode body is covered with closely arranged nanopores, and metal nanoparticles are uniformly deposited in the pores and the tip is embedded with nanoparticles.

7. The use of the porous microneedle electrode with nanoparticles embedded in the tip according to claim 6, characterized in that: The porous microneedle electrode with embedded nanoparticles at the tip is used for detecting different ions.

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