Capillary-based semiconductor SERS active substrate and preparation process method thereof

Abstract

The invention relates to a capillary-based semiconductor SERS (Surface Enhanced Raman Scattering) active substrate and a preparation process method thereof, and belongs to the technical field of environmental science detection. The invention relates to a capillary-based semiconductor SERS (Surface Enhanced Raman Scattering) active substrate which is a capillary-based semiconductor SERS active substrate based on a semiconductor ZnO (at) ZIF-8. The method comprises the following steps: dispersing ZnO (at) ZIF-8 nanoparticles in an ethanol solution of 4-MBA, stirring, and washing an obtained ZnO (at) ZIF-8 / 4-MBA sample to remove free 4-MBA molecules on the surfaces of the ZnO (at) ZIF-8 nanoparticles; the purified ZnO (at) ZIF-8 / 4-MBA is dispersed in the ethanol solution again; and injecting the solution obtained in the step 1 into a capillary tube, and drying, so that the ZnO (at) ZIF-8 / 4-MBA is attached to the interior of the capillary tube. The operation method is simple and efficient.

Description

Technical Field

[0001] The invention relates to a capillary-based semiconductor SERS active substrate and a preparation process method thereof, belonging to the technical field of environmental science detection. Background Art

[0002] With the continuous development of modern industry and agriculture, a large number of heavy metal-related materials and products (pesticides, fertilizers, gasoline, batteries, etc.) are used in people's daily production and life through various mining, processing and smelting methods. The production and application of heavy metals have brought about the inevitable problem of heavy metal pollution. In addition, the arbitrary discharge of industrial wastewater has made heavy metal ion pollution increasingly serious in recent years, and the health of organisms and the sustainable development of the environment are seriously threatened. The development of economic, fast, highly sensitive and highly specific heavy metal ion detection methods is the key to early warning of heavy metal pollution. At present, the main methods for detecting heavy metals are: atomic absorption spectroscopy, atomic fluorescence spectrophotometry, inductively coupled plasma mass spectrometry and high performance liquid chromatography. These methods generally require expensive and complex instruments, and have the disadvantages of long test cycles and complex analysis steps. Therefore, in order to achieve the sustainable development of human environment and organism health, it is of great significance to develop simple, fast, low-cost, highly sensitive and selective heavy metal ion detection and analysis technologies.

[0003] Surface enhanced Raman scattering (SERS) is a vibrational spectroscopy technique with high sensitivity, strong specificity, short response time, and many inherent advantages such as resistance to photobleaching, high spectral band resolution, and rich spectral fingerprint information. Currently, a variety of methods for heavy metal ion detection using SERS sensing technology have been proposed, and all have obtained good detection results. For example: Publication No. CN114894771B, the invention is named AgNPs-modified dual MOFs-derived semiconductor heterojunction SERS substrate and its preparation and application, which includes the preparation and calcination of ZIF-8, ZIF-8@ZIF-67 crystals, and complex chemical processes such as silver mirror reaction, which are used for on-site trace detection of pesticide residues on the surface of agricultural products, and the preparation process is complicated.

[0004] Therefore, it is urgent to provide a capillary-based semiconductor SERS active substrate and its preparation process to solve the above technical problems. The present invention prepares a capillary-based semiconductor SERS active substrate for metal ion detection and separation, which is simple to prepare and operate. Compared with the above patents, it has better chemical stability and biocompatibility, can be tested stably for a long time in a complex chemical environment, and ensures the reliability of the detection results. Summary of the invention

[0005] In order to solve the above problems, it is necessary to provide a capillary-based semiconductor SERS active substrate and a preparation process thereof. A brief overview of the invention is given below to provide a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive overview of the invention. It is not intended to identify the key or important parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of the present invention:

[0007] A capillary-based semiconductor SERS active substrate, a capillary-based semiconductor SERS active substrate is a capillary-based semiconductor SERS active substrate based on semiconductor ZnO@ZIF-8.

[0008] A method for preparing a capillary-based semiconductor SERS active substrate, used for preparing the capillary-based semiconductor SERS active substrate, comprises the following steps:

[0009] Step 1: Disperse ZnO@ZIF-8 nanoparticles in an ethanol solution of 4-MBA, stir, and rinse the resulting ZnO@ZIF-8 / 4-MBA sample to remove free 4-MBA molecules on the surface of ZnO@ZIF-8 nanoparticles; the purified ZnO@ZIF-8 / 4-MBA is dispersed again in an ethanol solution;

[0010] Step 2: Inject the solution obtained in step 1 into the capillary and dry it to allow ZnO@ZIF-8 / 4-MBA to adhere to the inside of the capillary.

[0011] Preferably: In step 1, 1 mg of ZnO@ZIF-8 nanoparticles is dispersed in 1 mL of 10 -3 M of 4-MBA in ethanol solution, stirred for 2 h, and the obtained ZnO@ZIF-8 / 4-MBA sample was rinsed with ethanol to remove the free 4-MBA molecules on the surface of ZnO@ZIF-8 nanoparticles; the purified ZnO@ZIF-8 / 4-MBA was dispersed again in 1 mL of ethanol solution;

[0012] Preferably, in step 2, 100 μL of the above solution is injected into the capillary using a syringe, and dried in an oven at 60° C. for 2 h, so that ZnO@ZIF-8 / 4-MBA adheres to the inside of the capillary.

[0013] Preferably: in step 1, the synthesis of ZnO nanoparticles comprises the following steps:

[0014] Zinc acetate dihydrate is added to diethylene glycol, and the mixture is slowly heated to a certain temperature, at which it is magnetically stirred to form a turbid colloidal suspension;

[0015] The colloidal suspension was cooled to room temperature and centrifuged, and the supernatant was used as the seed solution for further reactions;

[0016] Zinc acetate dihydrate is dissolved in diethylene glycol, the temperature is raised to a certain temperature, a seed solution is added to the hot solution, the temperature is raised to a set temperature, and magnetic stirring is performed at this temperature to generate submicron spherical ZnO particles;

[0017] The ZnO nanoparticles were collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried in vacuum.

[0018] Preferably: in step 1, 0.01 mol to 0.015 mol zinc acetate dihydrate is added to 100 ml diethylene glycol, the mixture is slowly heated to 160° C. to 170° C., and magnetically stirred at 160° C. to 170° C. for 1 hour to form a turbid colloidal suspension; the colloidal suspension is cooled to room temperature, placed in a centrifuge for centrifugal separation, and the supernatant is used as a seed solution for further reaction; another 0.01 mol to 0.015 mol zinc acetate dihydrate is dissolved in 100 ml diethylene glycol, the temperature is slowly raised to 130° C. to 135° C., 0.3 ml to 0.32 ml seed solution is added to the hot solution, the temperature is quickly raised to 160° C. to 175° C., and magnetically stirred at this temperature for 1 hour to generate submicron spherical ZnO particles; the ZnO nanoparticles are collected by centrifugation, washed with distilled water and anhydrous ethanol, and finally dried at 60° C. for 12 hours in a vacuum dryer before use.

[0019] Preferably: in step 2, the synthesis of ZnO@ZIF-8 nanoparticles comprises the following steps:

[0020] The synthesized ZnO nanoparticles were added into DMF / H2O solution in which 2-methylimidazole was dissolved;

[0021] The mixture was sonicated to disperse the ZnO nanoparticles;

[0022] The mixture was transferred to a preheated oil bath, and ZnO@ZIF-8 nanoparticles were formed after a period of reaction, collected by centrifugation, and washed with DMF and anhydrous ethanol;

[0023] The ZnO@ZIF-8 nanoparticles were dried in vacuum.

[0024] Preferably: in step 2, 0.0204 g to 0.0205 g of the synthesized ZnO nanoparticles are added to a 16 mL DMF / H2O solution in which 0.11 g to 0.115 g of 2-methylimidazole is dissolved; the mixture is ultrasonically treated for 10 min to disperse the ZnO nanoparticles; the mixture is transferred to an oil bath preheated to 70° C., reacted at 70° C. for 3 h to form ZnO@ZIF-8 nanoparticles, which are collected by centrifugation and washed with DMF and anhydrous ethanol; the ZnO@ZIF-8 nanoparticles are dried in a vacuum dryer at 60° C. for 12 h before use.

[0025] Preferably, the method further comprises step 3: detecting metal ions, comprising the following steps:

[0026] Connect the capillary-based semiconductor SERS active substrate prepared in step 2 to the syringe through a Teflon tube and mount it on a microscope glass slide with double-sided tape. Use a syringe to inject the test solution into the capillary, inject air into it through the syringe to push the sample to move, draw a mark every 5 mm on the surface of the microscope slide to determine the position of the moving sample solution, and perform Raman testing.

[0027] The present invention has the following beneficial effects:

[0028] 1. The present invention develops a capillary-based semiconductor SERS active substrate based on semiconductor ZnO@ZIF-8, and the operation method is simple and efficient;

[0029] 2. Capillary-based semiconductor SERS active substrates can detect and separate a variety of metal ions without the need for pretreatment and incubation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The scanning electron microscope image of ZnO nanoparticles obtained in Example;

[0031] Figure 2 This is a scanning electron microscope image of ZnO@ZIF-8 nanoparticles obtained in Example;

[0032] Figure 3 This is a transmission electron microscope image of ZnO@ZIF-8 nanoparticles obtained in Example;

[0033] Figure 4 This is the SERS signal diagram of ZnO@ZIF-8 nanoparticles obtained in Example to 4-mercaptobenzoic acid;

[0034] Figure 5 This is an actual photo of the capillary-based semiconductor SERS active substrate obtained in Example;

[0035] Figure 6Comparison of SERS signals obtained by detecting different metal ions using the capillary-based semiconductor SERS active substrate obtained in the embodiment;

[0036] Figure 7 This is a diagram showing the separation and differentiation of lead ions and ferrous ions by the capillary-based semiconductor SERS active substrate obtained in the example;

[0037] Figure 8 This is a local enlarged view of the separation of lead ions and ferrous ions by the capillary-based semiconductor SERS active substrate obtained in the example. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0039] Specific implementation method 1: Combination Figure 1-8 The present embodiment is described. The present embodiment is a capillary-based semiconductor SERS active substrate. The capillary-based semiconductor SERS active substrate is a capillary-based semiconductor SERS active substrate based on semiconductor ZnO@ZIF-8.

[0040] Specific implementation method 2: Combination Figure 1-8 The present embodiment is described. A method for preparing a capillary-based semiconductor SERS active substrate according to the present embodiment is used to prepare a capillary-based semiconductor SERS active substrate based on semiconductor ZnO@ZIF-8, and includes the following steps:

[0041] Step 1: Disperse ZnO@ZIF-8 nanoparticles in an ethanol solution of 4-MBA, stir, and rinse the resulting ZnO@ZIF-8 / 4-MBA sample to remove free 4-MBA molecules on the surface of ZnO@ZIF-8 nanoparticles; the purified ZnO@ZIF-8 / 4-MBA is dispersed again in an ethanol solution;

[0042] Step 2: Take the solution obtained in step 1 and inject it into the capillary, dry it, and make ZnO@ZIF-8 / 4-MBA adhere to the inside of the capillary; realize the capillary base for separation and detection of multiple metal ions.

[0043] Specific implementation method three: Combination Figure 1-8 The present embodiment is described. In the present embodiment, a method for preparing a capillary-based semiconductor SERS active substrate is as follows: in step 1, 1 mg of ZnO@ZIF-8 nanoparticles is dispersed in 1 mL of a 10 -3 The purified ZnO@ZIF-8 / 4-MBA was dispersed in 1 mL of ethanol solution of 4-MBA and stirred vigorously for 2 h. The obtained ZnO@ZIF-8 / 4-MBA sample was rinsed with ethanol several times to remove the free 4-MBA molecules on the surface of ZnO@ZIF-8 nanoparticles. The purified ZnO@ZIF-8 / 4-MBA was dispersed in 1 mL of ethanol solution again.

[0044] Specific implementation method four: Combination Figure 1-8 The present embodiment is described as a method for preparing a capillary-based semiconductor SERS active substrate. In step 2, 100 μL of the above solution is injected into the capillary using a syringe, and then dried in an oven at 60° C. for 2 h to allow ZnO@ZIF-8 / 4-MBA to adhere to the inside of the capillary.

[0045] Specific implementation method five: Combination Figure 1-8 This embodiment is described. In the preparation process of a capillary-based semiconductor SERS active substrate of this embodiment, in step 1, the synthesis of ZnO nanoparticles includes the following steps:

[0046] Zinc acetate dihydrate is added to diethylene glycol, and the mixture is slowly heated to a certain temperature, at which it is magnetically stirred to form a turbid colloidal suspension;

[0047] The colloidal suspension was cooled to room temperature and centrifuged, and the supernatant was used as the seed solution for further reactions;

[0048] Zinc acetate dihydrate is dissolved in diethylene glycol, the temperature is raised to a certain temperature, a seed solution is added to the hot solution, the temperature is raised to a set temperature, and magnetic stirring is performed at this temperature to generate submicron spherical ZnO particles;

[0049] The ZnO nanoparticles were collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried in vacuum.

[0050] Specific implementation method six: Combination Figure 1-8The present embodiment is described. The present embodiment is a process for preparing a capillary-based semiconductor SERS active substrate. In step 1, 0.01 mol of zinc acetate dihydrate is added to 100 ml of diethylene glycol, the mixture is slowly heated to 160°C, and magnetically stirred at 160°C-170°C for 1 hour to form a turbid colloidal suspension; the colloidal suspension is cooled to room temperature, placed in a centrifuge for centrifugal separation, and the supernatant is used as a seed solution for further reaction; another 0.01 mol of zinc acetate dihydrate is dissolved in 100 mL of diethylene glycol, the temperature is slowly raised to 130°C, 0.3 mL-0.32 mL of seed solution is added to the hot solution, the temperature is quickly raised to 160°C, and magnetically stirred at this temperature for 1 hour to generate submicron spherical ZnO particles; the ZnO nanoparticles are collected by centrifugation, washed several times with distilled water and anhydrous ethanol, and finally dried at 60°C in a vacuum dryer for 12 hours before use.

[0051] Specific implementation method seven: Combination Figure 1-8 This embodiment is described. In the preparation process of a capillary-based semiconductor SERS active substrate of this embodiment, in step 2, the synthesis of ZnO@ZIF-8 nanoparticles includes the following steps:

[0052] The synthesized ZnO nanoparticles were added into DMF / H2O solution in which 2-methylimidazole was dissolved;

[0053] The mixture was sonicated to disperse the ZnO nanoparticles;

[0054] The mixture was transferred to a preheated oil bath, and ZnO@ZIF-8 nanoparticles were formed after a period of reaction, collected by centrifugation, and washed several times with DMF and anhydrous ethanol;

[0055] The ZnO@ZIF-8 nanoparticles were dried in vacuum.

[0056] Specific implementation method eight: Combination Figure 1-8 The present embodiment is described. A process for preparing a capillary-based semiconductor SERS active substrate according to the present embodiment is as follows: in step 2, 0.0204 g of synthesized ZnO nanoparticles is added to a 16 mL DMF / H2O (volume ratio of 10:1) solution in which 0.11 g of 2-methylimidazole is dissolved; the mixture is ultrasonically treated for 10 min to disperse the ZnO nanoparticles; thereafter, the mixture is transferred to an oil bath preheated to 70°C, and reacted at 70°C for 3 h to form ZnO@ZIF-8 nanoparticles, which are collected by centrifugation and washed several times with DMF and anhydrous ethanol; finally, the ZnO@ZIF-8 nanoparticles are dried in a vacuum dryer at 60°C for 12 h before use.

[0057] Specific implementation method nine: Combination Figure 1-8The present embodiment is described. The preparation process of a capillary-based semiconductor SERS active substrate of the present embodiment further includes step 3: detection of metal ions, including the following steps:

[0058] Connect the capillary-based semiconductor SERS active substrate prepared in step 2 to the syringe through a Teflon tube and mount it on a microscope glass slide with double-sided tape. Use a syringe to inject the test solution into the capillary, inject air into it through the syringe to push the sample to move, draw a mark every 5 mm on the surface of the microscope slide to determine the position of the moving sample solution, and perform Raman testing.

[0059] Embodiment 1:

[0060] A capillary-based semiconductor SERS active substrate for separation and detection of multiple metal ions and a preparation process thereof are specifically carried out in the following steps:

[0061] Step 1: Synthesis of ZnO nanoparticles:

[0062] 0.01 mol zinc acetate dihydrate was added to 100 ml diethylene glycol, heated to 160°C, magnetically stirred for 1 hour, the resulting solution was cooled to room temperature, centrifuged, and the supernatant was used as a seed solution for further reaction; another 0.01 mol zinc acetate dihydrate was dissolved in 100 mL diethylene glycol, heated to 130°C, 0.3 mL seed solution was added to the hot solution, the temperature was raised to 160°C, magnetically stirred for 1 hour, and the generated ZnO nanoparticles were collected by centrifugation, washed several times with distilled water and anhydrous ethanol, and dried in a vacuum dryer at 60°C for 12 hours; Figure 1 This is a scanning electron microscope image of ZnO nanoparticles. It can be seen that the material is a monodispersed spherical particle with uniform size.

[0063] Step 2, Synthesis of ZnO@ZIF-8 Nanoparticles:

[0064] 0.0204 g ZnO nanoparticles were added to 16 mL DMF / H2O (volume ratio 10:1) solution in which 0.11 g 2-methylimidazole was dissolved; ultrasonic treatment was performed for 10 min; the mixture was transferred to an oil bath and reacted at 70 °C for 3 h, and the ZnO@ZIF-8 nanoparticles were collected by centrifugation and washed several times with DMF and anhydrous ethanol. Finally, the mixture was dried in a vacuum dryer at 60 °C for 12 h; Figure 2 This is the scanning electron microscopy image of ZnO@ZIF-8 nanoparticles, and it can be seen that the surface is covered with sharp edges that are characteristic of ZIF-8; Figure 3 This is the transmission electron microscopy image of ZnO@ZIF-8 nanoparticles. It can be seen that there is a clear boundary between the ZnO core and the ZIF-8 shell, indicating that ZnO is successfully converted into ZIF-8;

[0065] Step 3: Preparation of capillary-based semiconductor SERS active substrate:

[0066] 1 mg of ZnO@ZIF-8 nanoparticles was dispersed in 1 mL of 10 -3 M of 4-MBA in ethanol solution, stirred vigorously for 2 h, rinsed with ethanol several times and dispersed again in 1 mL of ethanol solution; 100 μL of the above solution was injected into the capillary with a syringe and dried in an oven at 60 °C for 2 h; Figure 4 This is the SERS signal diagram of ZnO@ZIF-8 nanoparticles to 4-mercaptobenzoic acid. It can be seen that ZnO@ZIF-8 nanoparticles have strong SERS ability; Figure 5 Actual photo of the capillary-based semiconductor SERS active substrate;

[0067] Step 4: Detection of metal ions:

[0068] The prepared capillary-based semiconductor SERS active substrate was connected to a syringe using a Teflon tube and mounted on a microscope glass slide using double-sided tape; different metal ion solutions were prepared using deionized water as a solvent, the silver and mercury ion solutions were prepared using nitrates, and the remaining metal ion solutions were prepared using metal chlorides; 10 μL of the metal ion solution was injected into the capillary using a syringe, and air was injected into it through the syringe to push the sample to move, and Raman testing was performed; the data acquisition time was 30 s, accumulated once, and the power was 40 mW; the instrument used was a confocal micro-Raman spectrometer (RTS2-301-DL) purchased from Beijing Zhuoli Hanguang Instrument Co., Ltd.; Figure 6 Comparison of SERS signals obtained by detecting different metal ions using the capillary-based semiconductor SERS active substrate obtained in the embodiment;

[0069] Draw a mark every 5 mm on the surface of the microscope slide to determine the position of the moving sample solution; take equal volumes of equimolar lead ion and ferrous ion solutions, mix them evenly, use a syringe to extract 3 μL and inject it near the entrance of the capillary, inject air into the capillary through the syringe, move the sample to the initial point at "0 mm" in the capillary, and record the SERS spectrum. The data acquisition time is 30 s, accumulated once, and the power is 40 mW. Then move the sample to a position about 10 mm away from the initial point, and record the SERS spectrum again. Repeat this process until the SERS band of the benzene ring C=C breathing vibration mode corresponds to only one of the two metal ions determined in the above experiment; Figure 7 This is the separation and differentiation diagram of lead ions and ferrous ions by the capillary-based semiconductor SERS active substrate. Figure 8This is a local enlarged picture of the separation of lead ions and ferrous ions by the capillary-based semiconductor SERS active substrate. It can be seen that when the liquid column moves in the capillary to 90 mm away from the initial point, the SERS band of the benzene ring C=C breathing vibration mode only corresponds to one of the ions. Lead ions and ferrous ions can be distinguished based on the change in the SERS signal; the parameters in this embodiment are the optimal parameters.

[0070] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A capillary-based semiconductor SERS active substrate, characterized in that: A capillary-based semiconductor SERS active substrate is a capillary-based semiconductor SERS active substrate based on semiconductor ZnO@ZIF-8.

2. A method for preparing a capillary-based semiconductor SERS active substrate, characterized in that: The method for preparing a capillary-based semiconductor SERS active substrate according to claim 1 comprises the following steps: Step 1: Disperse ZnO@ZIF-8 nanoparticles in an ethanol solution of 4-MBA, stir, and rinse the resulting ZnO@ZIF-8 / 4-MBA sample to remove free 4-MBA molecules on the surface of ZnO@ZIF-8 nanoparticles; the purified ZnO@ZIF-8 / 4-MBA is dispersed again in an ethanol solution; Step 2: Inject the solution obtained in step 1 into the capillary and dry it to allow ZnO@ZIF-8 / 4-MBA to adhere to the inside of the capillary.

3. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 2, characterized in that: In step 1, 1 mg of ZnO@ZIF-8 nanoparticles was dispersed in 1 mL of 10 -3 The purified ZnO@ZIF-8 / 4-MBA was dispersed in 1 mL of ethanol solution.

4. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 3, characterized in that: In step 2, 100 μL of the above solution was injected into the capillary using a syringe and dried in an oven at 60° C. for 2 h to allow ZnO@ZIF-8 / 4-MBA to adhere to the inside of the capillary.

5. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 4, characterized in that: In step 1, the synthesis of ZnO nanoparticles includes the following steps: Zinc acetate dihydrate is added to diethylene glycol, and the mixture is slowly heated to a certain temperature, at which it is magnetically stirred to form a turbid colloidal suspension; The colloidal suspension was cooled to room temperature and centrifuged, and the supernatant was used as the seed solution for further reactions; Zinc acetate dihydrate is dissolved in diethylene glycol, the temperature is raised to a certain temperature, a seed solution is added to the hot solution, the temperature is raised to a set temperature, and magnetic stirring is performed at this temperature to generate submicron spherical ZnO particles; The ZnO nanoparticles were collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried in vacuum.

6. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 5, characterized in that: In step 1, 0.01 mol to 0.015 mol zinc acetate dihydrate is added to 100 ml diethylene glycol, the mixture is slowly heated to 160° C. to 170° C., and magnetically stirred at 160° C. to 170° C. for 1 hour to form a turbid colloidal suspension; the colloidal suspension is cooled to room temperature, placed in a centrifuge for centrifugal separation, and the supernatant is used as a seed solution for further reaction; another 0.01 mol to 0.015 mol zinc acetate dihydrate is dissolved in 100 ml diethylene glycol, the temperature is slowly raised to 130° C. to 135° C., 0.3 ml to 0.32 ml seed solution is added to the hot solution, the temperature is quickly raised to 160° C. to 175° C., and magnetically stirred at this temperature for 1 hour to generate submicron spherical ZnO particles; the ZnO nanoparticles are collected by centrifugation, washed with distilled water and anhydrous ethanol, and finally dried at 60° C. for 12 hours in a vacuum dryer before use.

7. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 5 or 6, characterized in that: In step 2, the synthesis of ZnO@ZIF-8 nanoparticles includes the following steps: The synthesized ZnO nanoparticles were added into DMF / H2O solution in which 2-methylimidazole was dissolved; The mixture was sonicated to disperse the ZnO nanoparticles; The mixture was transferred to a preheated oil bath, and ZnO@ZIF-8 nanoparticles were formed after a period of reaction, collected by centrifugation, and washed with DMF and anhydrous ethanol; The ZnO@ZIF-8 nanoparticles were dried in vacuum.

8. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 7, characterized in that: In step 2, 0.0204 g to 0.0205 g of the synthesized ZnO nanoparticles are added to a 16 mL DMF / H2O solution in which 0.11 g to 0.115 g of 2-methylimidazole is dissolved; the mixture is ultrasonically treated for 10 min to disperse the ZnO nanoparticles; the mixture is transferred to an oil bath preheated to 70° C., and reacted at 70° C. for 3 h to form ZnO@ZIF-8 nanoparticles, which are collected by centrifugation and washed with DMF and anhydrous ethanol; the ZnO@ZIF-8 nanoparticles are dried in a vacuum dryer at 60° C. for 12 h before use.

9. The method for preparing a capillary-based semiconductor SERS active substrate according to claim 2, characterized in that: The method further comprises step 3: detecting metal ions, comprising the following steps: Connect the capillary-based semiconductor SERS active substrate prepared in step 2 to the syringe through a Teflon tube and mount it on a microscope glass slide with double-sided tape. Use a syringe to inject the test solution into the capillary, inject air into it through the syringe to push the sample to move, draw a mark every 5 mm on the surface of the microscope slide to determine the position of the moving sample solution, and perform Raman testing.

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