A multi-turn silver nanoring and its preparation method
Multi-turn silver nanorings were prepared by solvothermal reaction and precipitation separation, which solved the problem that existing technologies could not prepare multi-turn silver nanorings. This method achieved high yield and high quality of multi-turn silver nanorings, which is suitable for micro-nano optical waveguides and plamon research.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWEST UNIV
- Filing Date
- 2024-02-07
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies cannot prepare multi-turn silver nanorings, which limits their application in fields such as flexible transparent conductive films, transparent electrode materials, sensors, and micro/nano integrated optoelectronic devices.
Multi-turn silver nanorings were prepared by a solvothermal reaction of polyvinylpyrrolidone, pyridine, sodium halide, silver nitrate and alkali metal nitrate, by controlling the reaction conditions and precipitation separation process.
A simple and easy preparation of multi-turn silver nanorings was achieved with a yield of 40-70%. The nanorings are bent, densely arranged in parallel, and have a perfect circular structure and single-crystal properties, making them suitable for micro-nano optical waveguides and palmon research.
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Figure CN118002793B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal nanomaterial preparation technology, and in particular to a multi-turn silver nanoring and its preparation method. Background Technology
[0002] Noble metal nanowires, due to their electrical and optical properties (including the surface-enhanced Raman effect and the surface plasmon resonance effect), have broad application prospects in flexible transparent conductive thin film materials, transparent electrode materials, sensors, wearable electronic devices (artificial skin, etc.), and micro / nano integrated optoelectronic devices. Nanorings can be viewed as a special growth form of nanowires, namely nanowires with closed ends. Compared with open nanowires, this structure exhibits novel characteristics in terms of material mechanical properties, contact conductivity, and plasmon resonance properties, and is expected to become a fundamental building block for next-generation transparent conductive thin films and nano-sensors.
[0003] Currently, reports on the preparation methods of precious metal gold / silver nanorings can be roughly classified into the following categories: (1) Nanoparticles arranged in a ring shape. This type of structure has a very rough shape and the connection between particles is not tight, which basically cannot meet the aforementioned application scenarios; (2) In the confined microenvironment of "water-in-oil" or "oil-in-water" emulsion, nanowires are bent to form a ring structure. This method has a certain degree of universality, but it has certain limitations in terms of product size, and the bending process will cause damage to the nanowire structure; (3) Template method or printing method, using nanospheres as templates, and through sputtering and electrodeposition, etc. The method of preparing ring structures has good control over sample type, size, morphology and arrangement, but the product is a polycrystalline structure; (4) Chemical growth method, taking silver as an example, is basically a modification of the traditional preparation of silver nanowires. Some adjustments are made to the reactants and reaction conditions to achieve the bending growth of nanowires. This method can obtain single crystal structure or overall twin structure, which has the best conductivity and is suitable for application in conductive films and electrode materials. The geometry of the product is very perfect, the preparation scheme is specific, and there are some natural limitations in terms of material size.
[0004] However, current preparation methods can only prepare single-turn silver nanorings, and there are no reports on how to prepare multi-turn silver nanorings. Summary of the Invention
[0005] The purpose of this invention is to provide a multi-turn silver nanoring and its preparation method, so as to solve the problem that multi-turn silver nanorings cannot be prepared in the prior art.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] This invention provides a method for preparing multi-turn silver nanorings, comprising the following steps:
[0008] (1) Mix the ethylene glycol solution of polyvinylpyrrolidone with pyridine to obtain a mixed solution;
[0009] (2) Mix the mixed solution, sodium halide in ethylene glycol, silver nitrate and alkali metal nitrate, and then carry out solvothermal reaction and precipitation separation in sequence to obtain multi-turn silver nanorings.
[0010] Preferably, in step (1), the concentration of the ethylene glycol solution of polyvinylpyrrolidone is 0.005-0.04 g / mL; the volume ratio of the ethylene glycol solution of polyvinylpyrrolidone to pyridine is 1:0.5-1.5; and the number average molecular weight of polyvinylpyrrolidone is 1,300,000.
[0011] Preferably, in step (2), the mass-to-volume ratio of silver nitrate to the mixed solution is 0.03–0.07 g: 8–15 mL; the mass ratio of silver nitrate to alkali metal nitrate is 3–7: 10–30; and the alkali metal nitrate is sodium nitrate or potassium nitrate.
[0012] Preferably, in step (2), the volume ratio of the mixed solution to the sodium halide ethylene glycol solution is 1 mL: 8-12 μL; and the concentration of the sodium halide ethylene glycol solution is 40-60 mmol / L.
[0013] Preferably, in step (2), the temperature of the solvothermal reaction is 130-150°C and the time of the solvothermal reaction is 22-26 h.
[0014] Preferably, in step (2), the washing solution used during precipitation separation is a saturated nitrate aqueous solution.
[0015] Preferably, in step (2), the precipitation separation step is to allow the product of the solvothermal reaction and the saturated nitrate aqueous solution to stand in separate layers.
[0016] Preferably, in step (2), the volume ratio of the product of the solvothermal reaction to the saturated nitrate aqueous solution is 1:2 to 4.
[0017] Preferably, in step (2), the time for layering and settling is 3 to 5 days.
[0018] The present invention also provides a multi-turn silver nanoring prepared by the above-described preparation method, wherein the multi-turn silver nanoring has a line diameter of 30-60 nm and a diameter of 10-100 μm.
[0019] The beneficial effects of this invention are:
[0020] (1) The key to this invention is the addition of the organic solvent pyridine when preparing multi-turn silver nanorings. The addition of pyridine increases the solubility of silver halide and can change the aggregation form of PVP in the mixed solution of ethylene glycol and pyridine. This has an additional effect on the growth of silver nanowires, causing them to grow in a large bending manner to form multi-turn silver nanorings.
[0021] (2) The preparation method of multi-turn silver nanorings provided by the present invention is simple and easy to implement, with good reproducibility, and the yield of multi-turn silver nanorings can reach 40-70%.
[0022] (3) The multi-turn silver nanorings prepared by the present invention have curved nanowires that tend to be densely arranged in parallel in local areas, and there is no fusion growth between adjacent nano-turns. Due to the support of internal stress, the multi-turn silver nanorings have a near-perfect circle.
[0023] (4) The multi-turn silver nanorings prepared by this invention are a novel nanostructure, which is a nanowire array with richer morphological features and parameters, and has a larger overall aspect ratio (which can exceed 20000). It is an ideal experimental material for research on micro-nano optical waveguides and palmons. Attached Figure Description
[0024] Figure 1 The image shows the XRD pattern of the multi-turn silver nanorings prepared in Example 1.
[0025] Figure 2 The EDS spectrum of the multi-turn silver nanorings prepared in Example 1 is shown.
[0026] Figure 3 The images shown are SEM images of the multi-turn silver nanorings prepared in Example 1, where a is the overall morphology SEM image, b is the SEM image of a single multi-turn silver nanoring, c is a locally magnified SEM image of a single multi-turn silver nanoring, d is the SEM image of a single multi-turn silver nanoring with a diameter of 10 μm, e is the SEM image of a silver nanoring with 22 turns, and f is a locally magnified SEM image of a silver nanoring with 22 turns.
[0027] Figure 4 The images show partial TEM and SAED images of the multi-turn silver nanorings prepared in Example 1, where a is a partial TEM image and b is a SAED image.
[0028] Figure 5 This is a schematic diagram of the precipitation separation process;
[0029] Figure 6 This is a schematic diagram of a multi-turn silver nanoring. Detailed Implementation
[0030] This invention provides a method for preparing multi-turn silver nanorings, comprising the following steps:
[0031] (1) Mix the ethylene glycol solution of polyvinylpyrrolidone with pyridine to obtain a mixed solution;
[0032] (2) Mix the mixed solution, sodium halide in ethylene glycol, silver nitrate and alkali metal nitrate, and then carry out solvothermal reaction and precipitation separation in sequence to obtain multi-turn silver nanorings.
[0033] In this invention, in step (1), the concentration of the ethylene glycol solution of polyvinylpyrrolidone is 0.005-0.04 g / mL, preferably 0.008-0.03 g / mL, and more preferably 0.01-0.02 g / mL; the volume ratio of the ethylene glycol solution of polyvinylpyrrolidone to pyridine is 1:0.5-1.5, preferably 1:0.8-1.2, and more preferably 1:1; the number average molecular weight of polyvinylpyrrolidone is 1,300,000.
[0034] In this invention, the addition of pyridine not only ensures the generation of silver nanowires, but also enables the silver nanowires to grow in a large-scale bending manner to form multi-turn silver nanorings.
[0035] In this invention, in step (2), the mass-to-volume ratio of silver nitrate to the mixed solution is 0.03–0.07 g: 8–15 mL, preferably 0.04–0.06 g: 9–14 mL, and more preferably 0.05 g: 10–12 mL; the mass ratio of silver nitrate to alkali metal nitrate is 3–7: 10–30, preferably 4–6: 15–25, and more preferably 5:20; the alkali metal nitrate is sodium nitrate or potassium nitrate, preferably sodium nitrate.
[0036] In this invention, silver nitrate is used as the silver source, ethylene glycol is used as the reducing agent and provides a liquid-phase reaction environment, and polyvinylpyrrolidone and sodium halide guide the growth of silver nanowires. The addition of pyridine causes the silver nanowires to bend and grow to form a ring structure.
[0037] In this invention, a low concentration of silver nitrate will result in a significant decrease in the yield of multi-turn silver nanorings, mainly because nucleation is difficult in the initial stage. A high concentration of silver nitrate will result in an increase in the diameter of the multi-turn silver nanorings, thus reducing the yield of multi-turn silver nanorings.
[0038] In this invention, the alkali metal nitrate is soluble in the reaction system and does not react with silver nitrate. The addition of the alkali metal nitrate provides a liquid-phase non-aqueous reaction environment filled with positive and negative ions, altering the transport characteristics of silver ions and affecting the microstructure of the multi-turn silver nanorings. Furthermore, the addition of the alkali metal nitrate can reduce the reaction temperature from the original 160–170°C to 130–150°C.
[0039] In this invention, in step (2), the volume ratio of the mixed solution to the sodium halide ethylene glycol solution is 1 mL: 8-12 μL, preferably 1 mL: 9-11 μL, and more preferably 1 mL: 10 μL; the concentration of the sodium halide ethylene glycol solution is 40-60 mmol / L, preferably 45-55 mmol / L, and more preferably 50 mmol / L.
[0040] In this invention, sodium halide is preferably sodium chloride or sodium bromide, and more preferably sodium chloride. The role of sodium halide is to reduce the diameter of the multi-turn silver nanorings.
[0041] In this invention, in step (2), the temperature of the solvothermal reaction is 130-150°C, preferably 125-135°C, and more preferably 130°C; the time of the solvothermal reaction is 22-26h, preferably 23-25h, and more preferably 24h.
[0042] In this invention, the washing solution used in step (2) during precipitation separation is a saturated nitrate aqueous solution.
[0043] In this invention, the precipitation separation step (2) is as follows: the product of the solvothermal reaction and the saturated nitrate aqueous solution are allowed to stand in layers.
[0044] In this invention, in step (2), the volume ratio of the product of the solvothermal reaction to the saturated nitrate aqueous solution is 1:2 to 4, preferably 1:3.
[0045] In this invention, the saturated nitrate aqueous solution is a saturated sodium nitrate aqueous solution or a saturated potassium nitrate aqueous solution, preferably a saturated sodium nitrate aqueous solution.
[0046] In this invention, in step (2), the time for layering and settling is 3 to 5 days, preferably 3 days, 4 days or 5 days, and more preferably 5 days.
[0047] In this invention, a special precipitation separation method is employed to first transfer the multi-turn silver nanorings from the reacted ethylene glycol / pyridine mixed solution to a saturated nitrate aqueous solution before washing the transferred sample with deionized water. Existing technologies generally use deionized water or anhydrous ethanol as the washing solution, which can clean ordinary silver nanowires but cannot be directly used to clean these ring-shaped structures. This is because such treatment introduces small-scale turbulence when different solutions are mixed, which can twist the silver nanowires / rings and form bundles, similar to single cotton / wool fibers twisting together to form yarn. For ordinary nanowires, the bundles can be untangled by appropriate ultrasonic vibration, but for nanorings, this twisting will completely destroy their unique structure. Therefore, this invention employs a special precipitation separation step to weaken and minimize the influence of this turbulence.
[0048] The present invention also provides a multi-turn silver nanoring prepared by the above-described preparation method, wherein the multi-turn silver nanoring has a line diameter of 30-60 nm and a diameter of 10-100 μm.
[0049] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0050] Chemical reagents used in Examples 1-4 of this invention:
[0051] Silver nitrate, analytical grade AR, purchased from Guangdong Guanghua Technology Co., Ltd.;
[0052] Ethylene glycol, analytical grade AR, purchased from Aladdin Reagent Company;
[0053] Polyvinylpyrrolidone, with an average molecular weight of 1,300,000, was purchased from Shanghai Xianding Biotechnology Co., Ltd.
[0054] Pyridine, analytical grade AR, purchased from Aladdin Reagents Company;
[0055] Sodium nitrate, analytical grade AR, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.
[0056] Sodium chloride / sodium bromide, analytical grade AR, purchased from Tianjin Jindong Tianyuan Fine Chemical Reagent Co., Ltd.
[0057] Example 1
[0058] 1 g of polyvinylpyrrolidone (average molecular weight 1,300,000) was dissolved in 100 mL of ethylene glycol to obtain a polyvinylpyrrolidone ethylene glycol solution with a concentration of 0.01 g / mL; sodium chloride was dissolved in ethylene glycol to obtain a sodium chloride ethylene glycol solution with a concentration of 50 mmol / L.
[0059] 5 mL of polyvinylpyrrolidone in ethylene glycol solution and 5 mL of pyridine were mixed to obtain a mixed solution. 0.05 g of silver nitrate and 0.2 g of sodium nitrate were added to the mixed solution and stirred at 300 rpm to dissolve. During stirring, 100 μL of sodium chloride in ethylene glycol solution was slowly added dropwise using a micro-injector. After the addition was complete, the mixture was stirred for another 10 min to obtain a clear solution. The clear solution was then transferred to a hydrothermal reactor and reacted at 130 °C for 24 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and removed to obtain a light yellow turbid solution (the product of the solvothermal reaction).
[0060] Add 30 mL of saturated sodium nitrate solution (density 1.16 g / mL) to a 100 mL test tube. Then, slowly pour 10 mL of the above light yellow turbid solution into the test tube containing the saturated sodium nitrate solution using a pipette. The light yellow turbid solution will cover the saturated sodium nitrate solution. Let the test tube stand and wait for the multi-turned silver nanorings to precipitate. The multi-turned silver nanorings will slowly pass through the gradually blurring solution interface and sink to the bottom of the test tube. The standing time is 5 days.
[0061] After the precipitation process, the upper mixed solution was removed with a pipette, and deionized water (with a volume ratio of deionized water to the remaining solution of 3:1) was slowly added to the remaining solution. The test tube was gently shaken to disperse the multi-turned silver nanorings in the diluted solution, and then allowed to stand for precipitation again. This process of "removing the upper solution - diluting with deionized water - allowing to stand for precipitation" was repeated 5 times. Finally, unreacted salt and polyvinylpyrrolidone were removed to obtain multi-turned silver nanorings with a linear diameter of 30-60 nm and a diameter of 10-100 μm, and a yield of 70%.
[0062] Example 2
[0063] 0.5 g of polyvinylpyrrolidone (average molecular weight 1,300,000) was dissolved in 100 mL of ethylene glycol to obtain a polyvinylpyrrolidone ethylene glycol solution with a concentration of 0.005 g / mL; sodium chloride was dissolved in ethylene glycol to obtain a sodium chloride ethylene glycol solution with a concentration of 40 mmol / L.
[0064] 5 mL of polyvinylpyrrolidone in ethylene glycol solution and 7.5 mL of pyridine were mixed to obtain a mixed solution. 0.07 g of silver nitrate and 0.3 g of sodium nitrate were added to the mixed solution and stirred at 300 rpm to dissolve. During stirring, 120 μL of sodium chloride in ethylene glycol solution was slowly added dropwise using a micro-injector. After the addition was complete, the mixture was stirred for another 10 min to obtain a clear solution. The clear solution was then transferred to a hydrothermal reactor and reacted at 140 °C for 22 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and removed to obtain a light yellow turbid solution (the product of the solvothermal reaction).
[0065] Add 40 mL of saturated sodium nitrate solution (density 1.16 g / mL) to a 100 mL test tube. Then, slowly pour 10 mL of the above light yellow turbid solution into the test tube containing the saturated sodium nitrate solution using a pipette. The light yellow turbid solution will cover the saturated sodium nitrate solution. Let the test tube stand and wait for the multi-turned silver nanorings to precipitate. The multi-turned silver nanorings will slowly pass through the gradually blurring solution interface and sink to the bottom of the test tube. The standing time is 4 days.
[0066] After the precipitation process, the upper mixed solution was removed with a pipette, and deionized water (with a volume ratio of deionized water to the remaining solution of 3:1) was slowly added to the remaining solution. The test tube was gently shaken to disperse the multi-turned silver nanorings in the diluted solution, and then allowed to stand for precipitation again. This process of "removing the upper solution - diluting with deionized water - allowing to stand for precipitation" was repeated 5 times. Finally, the unreacted salt and polyvinylpyrrolidone were removed to obtain multi-turned silver nanorings with a linear diameter of 30-60 nm and a diameter of 10-100 μm, and a yield of 40%.
[0067] Example 3
[0068] 2g of polyvinylpyrrolidone (average molecular weight 1,300,000) was dissolved in 100mL of ethylene glycol to obtain a polyvinylpyrrolidone ethylene glycol solution with a concentration of 0.02g / mL; sodium chloride was dissolved in ethylene glycol to obtain a sodium chloride ethylene glycol solution with a concentration of 60mmol / L.
[0069] 5 mL of polyvinylpyrrolidone in ethylene glycol solution and 3 mL of pyridine were mixed to obtain a mixed solution. 0.03 g of silver nitrate and 0.1 g of potassium nitrate were added to the mixed solution and stirred at 300 rpm to dissolve. During stirring, 80 μL of sodium chloride in ethylene glycol solution was slowly added dropwise using a micro-injector. After the addition was complete, the mixture was stirred for another 10 min to obtain a clear solution. The clear solution was then transferred to a hydrothermal reactor and reacted at 150 °C for 24 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and removed to obtain a light yellow turbid solution (the product of the solvothermal reaction).
[0070] Add 50 mL of saturated sodium nitrate solution (density 1.16 g / mL) to a 100 mL test tube. Then, slowly pour 10 mL of the above light yellow turbid solution into the test tube containing the saturated sodium nitrate solution using a pipette. The light yellow turbid solution will cover the saturated sodium nitrate solution. Let the test tube stand and wait for the multi-turned silver nanorings to precipitate. The multi-turned silver nanorings will slowly pass through the gradually blurring solution interface and sink to the bottom of the test tube. The standing time is 5 days.
[0071] After the precipitation process, the upper mixed solution was removed with a pipette, and deionized water (with a volume ratio of deionized water to the remaining solution of 3:1) was slowly added to the remaining solution. The test tube was gently shaken to disperse the multi-turned silver nanorings in the diluted solution, and then allowed to stand for precipitation again. This process of "removing the upper solution - diluting with deionized water - allowing to stand for precipitation" was repeated 5 times. Finally, unreacted salt and polyvinylpyrrolidone were removed to obtain multi-turned silver nanorings with a linear diameter of 30-60 nm and a diameter of 10-100 μm, with a yield of 55%.
[0072] Example 4
[0073] The difference from Example 1 is that 4g of polyvinylpyrrolidone (average molecular weight 1,300,000) was dissolved in 100mL of ethylene glycol to obtain a polyvinylpyrrolidone ethylene glycol solution with a concentration of 0.04g / mL. All other conditions were the same, and the yield of the multi-turned silver nanorings was 50%.
[0074] Comparative Example 1
[0075] The difference from Example 1 is that the reaction temperature was 180°C, while all other conditions were the same, and the yield of the multi-turn silver nanorings was 30%.
[0076] Figure 2 The image shows the EDS spectrum of the multi-turn silver nanorings prepared in Example 1. The C and O elements in the EDS spectrum are derived from polyvinylpyrrolidone, which is because the outer layer of the multi-turn silver nanorings is covered with a cross-linked PVP layer with a thickness of only atomic level.
[0077] Figure 3 The images show SEM images of the multi-turn silver nanorings prepared in Example 1. Image a is an overall morphology SEM image, showing that the prepared multi-turn silver nanorings contain a large number of ring structures with a nearly perfect circular shape. Images b and c show non-strictly closed 3-4 turn silver nanorings. Image c shows the state of the endpoints of a single multi-turn silver nanoring, which is not completely closed. Image d shows a multi-turn silver nanoring with a diameter of 10 μm, indicating that the lower limit of the diameter of multi-turn silver nanorings that can be prepared so far is 10 μm. Images e and f show silver nanorings with 22 turns, which are the silver nanorings with the most turns detected so far, and their overall aspect ratio is 30000.
[0078] Figure 4 The images show partial TEM and SAED images of the multi-turn silver nanorings prepared in Example 1. The partial TEM images show that the rings of the multi-turn silver nanorings are arranged in parallel and are neatly arranged with fine gaps between the rings. The SAED images show that the multi-turn silver nanorings have a single-crystal structure.
[0079] The precipitation process in Examples 1-4 of this invention is as follows: Figure 5 As shown.
[0080] Figure 6 This is a schematic diagram of a multi-turn silver nanoring, where D is the diameter of the multi-turn silver nanoring and d is the line diameter of the multi-turn silver nanoring.
[0081] As shown in the above embodiments, this invention provides a multi-turn silver nanoring and its preparation method. First, a solution of polyvinylpyrrolidone in ethylene glycol and pyridine are mixed to obtain a mixed solution. Then, the mixed solution, a sodium halide solution in ethylene glycol, silver nitrate, and sodium nitrate are mixed, followed by a solvothermal reaction and precipitation separation in sequence to obtain multi-turn silver nanorings. The method for preparing multi-turn silver nanorings according to this invention is simple and easy to implement, has good reproducibility, and a high yield. During the preparation process, the addition of the organic solvent pyridine enables the silver nanowires to bend and grow significantly to form multi-turn silver nanorings.
[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing multi-turn silver nanorings, characterized in that, Includes the following steps: (1) Mix the ethylene glycol solution of polyvinylpyrrolidone with pyridine to obtain a mixed solution; (2) Mix the mixed solution, sodium halide in ethylene glycol, silver nitrate and alkali metal nitrate, and then carry out solvothermal reaction and precipitation separation in sequence to obtain multi-turn silver nanorings; In step (1), the concentration of the ethylene glycol solution of polyvinylpyrrolidone is 0.005~0.04 g / mL; the volume ratio of the ethylene glycol solution of polyvinylpyrrolidone to pyridine is 1:0.5~1.5; and the number average molecular weight of polyvinylpyrrolidone is 1,300,000. In step (2), the mass-to-volume ratio of silver nitrate to the mixed solution is 0.03~0.07g:8~15mL; the mass ratio of silver nitrate to alkali metal nitrate is 3~7:10~30; and the alkali metal nitrate is sodium nitrate or potassium nitrate.
2. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of the mixed solution to the sodium halide ethylene glycol solution is 1 mL: 8~12 μL; the concentration of the sodium halide ethylene glycol solution is 40~60 mmol / L.
3. The preparation method according to claim 1 or 2, characterized in that, In step (2), the temperature of the solvothermal reaction is 130~150℃ and the time of the solvothermal reaction is 22~26h.
4. The preparation method according to claim 3, characterized in that, In step (2), the washing solution used during precipitation separation is a saturated nitrate aqueous solution.
5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the precipitation separation step is to separate the product of the solvothermal reaction and the saturated nitrate aqueous solution into layers and allow them to stand.
6. The preparation method according to claim 5, characterized in that, In step (2), the volume ratio of the product of the solvothermal reaction to the saturated nitrate aqueous solution is 1:2~4.
7. The preparation method according to claim 6, characterized in that, In step (2), the time for layering and settling is 3 to 5 days.
8. The multi-turn silver nanorings prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The multi-turn silver nanorings have a wire diameter of 30~60nm and a diameter of 10~100μm.