A method for preparing silver nanocubes
Silver nanocubes were prepared by reacting cationic cell-penetrating peptides with silver salts in an aqueous phase, solving the problem of complex preparation processes under high-temperature organic solvents. This method achieved low-cost and high-efficiency synthesis of nanocubes with good catalytic and antibacterial properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2023-04-25
- Publication Date
- 2026-05-26
AI Technical Summary
Existing methods for preparing silver nanocubes require high-temperature organic solvent environments, which are complex and costly, and the products also require separation and washing.
Silver nanocubes were synthesized under mild conditions by reacting cationic cell-penetrating peptides with silver salts in an aqueous phase, through the coordination and self-reduction of the cell-penetrating peptides, thus avoiding the use of organic polyols and other reducing agents.
The synthesis of silver nanocubes under mild conditions was achieved, simplifying the process and reducing costs. The synthesized nanocubes exhibit good peroxidase activity and antibacterial properties, making them suitable for catalytic, detection, and antitumor applications.
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Figure CN116493599B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing silver nanoparticles, and more particularly to a method for preparing silver nanocubes. Background Technology
[0002] As research into metallic nanostructures deepens, researchers are increasingly able to precisely control the preparation and production of nanoscale metals, further developing emerging applications by fine-tuning their properties. The optical and magnetic properties of metallic nanostructures are highly dependent not only on their size but also on their shape. Among numerous metals, silver is one of the most studied materials for nanostructure research, closely related to its superior performance in applications such as plasma and surface-enhanced Raman scattering (SERS), making it an ideal material for performing high-sensitivity detection. Previously, a series of silver nanostructures with different morphologies have been synthesized, including spheres, disks, triangular sheets, rods, lines, prisms, right-hand bipyramids, and cubes. Among these, the study of silver nanocubes has attracted considerable attention. Silver nanocubes can serve as sacrificial templates, generating gold nanocages with tunable resonance peaks through an electrosubstitution reaction with chloroauric acid, showing great promise in biomedical applications such as enhancing optical imaging contrast and photothermal processing effects. The specific optical characteristics of silver nanoparticles are closely related to their particle size and shape, and cubic silver nanoparticles, compared to other shapes, have an increased effective surface area and stronger catalytic potential. Furthermore, compared to nanospheres, nanocubes exhibit higher antibacterial activity against both Escherichia coli and Staphylococcus aureus, and their synergistic effect with the antibiotic ampicillin is also promising.
[0003] Previously, there were relatively mature methods for preparing silver nanocubes. As early as 2002, Yugang Sun and Younan Xia synthesized silver nanocube particles by reducing silver nitrate with ethylene glycol in the presence of polyvinylpyrrolidone (PVP) (Shape-Controlled Synthesis of Gold and Silver Nanoparticles, Science, 2010, 298(10):2176-2179). Their research results showed that the morphology of the product was greatly affected by reaction conditions such as temperature, AgNO3 concentration, and the molar ratio of PVP to AgNO3. Since then, the synthesis of nanocube silver has mostly adopted polyol processes, using controlled reactions in an organic phase. For example, Im.SH et al. synthesized uniform silver nanocubes by reducing silver nitrate with ethylene glycol at 140 °C in the presence of polyvinylpyrrolidone (PVP) and HCl ("Large-scale synthesis of silver nanocubes: the role of HCl in promoting cube perfection and monodispersity", Angew. Chem., Int. Ed. 2005, 44, 2154–2157); Andrea Tao et al. prepared silver nanocubes using silver nitrate as a precursor, PVP as a capping agent to control the shape, and pentylene glycol as a solvent and reducing agent. The experiment found that a very small amount of chloride ions reduced the solubility of AgCl and precipitated it, preventing the rapid reduction of silver ions and ultimately leading to the formation of silver cubes ("Polyhedralsilver nanocrystals with distinct scattering signatures", Angew. Chem., Int. Ed. 2006, 45(28), 4597–4601).
[0004] However, the above-mentioned silver nanocubes are prepared at high temperatures and in an environment of organic solvents and polyols. The products obtained still need to be separated and washed, which makes the process complex and costly. Summary of the Invention
[0005] Purpose of the invention: The present invention aims to provide a method for preparing silver nanocubes that does not use organic polyols, has mild reaction conditions, and is simple in process.
[0006] Technical solution: The preparation method of silver nanocubes of the present invention includes the following steps:
[0007] (1) Add cationic cell-penetrating peptides to water and stir until completely dissolved to prepare an aqueous solution of cell-penetrating peptides, which is acidic. Then, while continuing to stir, add an alkaline pH adjusting reagent to adjust the pH of the solution to alkaline.
[0008] (2) Under the condition of continuous stirring of the aqueous solution of cell-penetrating peptide prepared in step (1), soluble silver salt solution is slowly added dropwise and the reaction is kept warm to obtain silver nano cubes.
[0009] In step (2), the solution changes from colorless to yellow-green during the heat preservation reaction process. Preferably, in step (2), the heat preservation reaction temperature is 30-40°C, and the heat preservation time is 8-72 hours.
[0010] Preferably, in step (1), the cationic cell-penetrating peptide is TAT (CCYRGRKKRRQRRR), Penetratin (RQIKIWFQNRRMKWKK), or Polyarginine (R12). The cationic cell-penetrating peptides TAT, Penetratin, and Polyarginine were all purchased from Shanghai Qiangyao Biotechnology Co., Ltd.
[0011] Preferably, in step (1), the pH value of the solution is adjusted to an alkaline pH of 9 to 12.
[0012] Preferably, in step (2), the cell-penetrating peptide reacts with Ag in the silver salt. + The molar ratio is 1:20–30. When the proportion of cell-penetrating peptides increases, the size of the synthesized silver cube decreases; Ag + As the ratio increases, the size of the synthesized silver cube increases.
[0013] Preferably, in step (1), the concentration of cell-penetrating peptide in the cell-penetrating peptide solution is 0.053 mM to 0.106 mM.
[0014] Preferably, in step (2), the Ag in the soluble silver salt solution + The concentration ranges from 1.25 mM to 1.8544 mM.
[0015] Preferably, in step (2), the soluble silver salt is silver nitrate or silver acetate.
[0016] The silver nanocube has a cubic silver core inside and a cell-penetrating peptide membrane on the surface; the side length of the silver nanocube is 50-200 nm.
[0017] Preferably, in step (1), the alkaline pH adjusting reagent refers to NaOH, KOH or ammonia.
[0018] Mechanism of invention: Cationic cell-penetrating peptides (such as TAT-type cell-penetrating peptides) are composed of short peptides rich in arginine, lysine, and histidine, which can bind with Ag. + An interaction occurs, and Ag is adsorbed. + On a specific crystal plane, the reducing groups inherent in the crystal can, under appropriate adjustment, reduce Ag... + The silver atoms are reduced to silver atoms and then grow into silver nanoparticles. Because the cell-penetrating peptides are adsorbed on specific crystal surfaces of the silver particles, the growth rate of the Ag particles toward certain crystal surfaces is limited, and they eventually grow into a stable nanocube structure protected by the cell-penetrating peptides.
[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) Based on the coordination and self-reduction of cell-penetrating peptides to silver ions, the method can synthesize silver nanocubes under mild reaction conditions without the need for additional reducing agents or various organic reagents commonly used in the current method of synthesizing silver nanocubes; (2) The method has multiple advantages such as low carbon and environmental protection, safety and reliability, simple method and good economy; (3) The silver nanocubes synthesized by the method also have good peroxidase activity and can be used for catalysis, detection, antibacterial, antitumor and other purposes, showing the functional effects of the material. Attached Figure Description
[0020] Figure 1 This is a TEM image of the silver nanocube synthesized using TAT cell-penetrating peptide as a ligand in Example 1.
[0021] Figure 2 A magnified TEM image of a single silver nanocube prepared in Example 1;
[0022] Figure 3 The peroxidase activity spectrum characterization diagram of the silver nanocubes prepared in Example 1;
[0023] Figure 4 This is a schematic diagram showing the reaction of silver nanocubes prepared in Example 1 catalyzing the oxidation of TMB by hydrogen peroxide;
[0024] Figure 5 The image shown is a TEM image of silver nanocubes prepared in Example 2 by changing the concentration and ratio based on Example 1.
[0025] Figure 6 This is a TEM image of silver nanocubes synthesized in Example 3 by increasing the pH value based on Example 1;
[0026] Figure 7 This is a statistical diagram showing the side length distribution of silver nanocubes synthesized in Example 4 by changing the reaction temperature based on Example 1.
[0027] Figure 8 The images shown are bright-field and dark-field TEM images of the silver nanocubes synthesized in Example 5 by delaying the heat preservation time based on Example 1.
[0028] Figure 9 This is a TEM image of silver nanoparticles synthesized in the organic phase DMF for Comparative Example 2. Detailed Implementation
[0029] The technical solution of the present invention will be further described below with reference to the embodiments.
[0030] Example 1
[0031] (1) Add TAT cell-penetrating peptide to deionized water and stir continuously until completely dissolved to prepare a TAT cell-penetrating peptide aqueous solution with a concentration of 0.053 mM. The solution is acidic. Under the condition of continuous stirring of the above TAT cell-penetrating peptide aqueous solution, slowly add NaOH solution to adjust the pH value of the reaction solution to 9.
[0032] (2) Prepare a 1.25 mM silver nitrate aqueous solution for later use;
[0033] (3) Under the condition of continuous stirring of TAT cell-penetrating peptide solution, according to TAT:Ag + Silver nitrate solution was slowly added dropwise to the TAT cell membrane-penetrating peptide aqueous solution at a molar ratio of 1:20 until all the solution was added. The reaction was then carried out at 30°C for 24 hours to obtain the synthesized material.
[0034] The synthesized material was characterized by transmission electron microscopy, and the results are shown in [Figure number missing]. Figure 1 and Figure 2 .Depend on Figure 1 It can be seen that the prepared silver nanoparticles have a silver nanocube structure, with the side length mainly distributed in the range of 50 nm to 100 nm. Figure 2 It can be seen that the interior of the silver nanocube is a cubic silver core, and the surface is a TAT cell-penetrating peptide ligand.
[0035] To test whether the synthesized silver nanocubes possessed peroxidase activity, the following solutions were prepared: (I) 10 mM TMB solution, (II) 10 mM H2O2 solution, (III) a mixed solution of 10 mM TMB and 10 mM H2O2, and (IV) a mixed solution of 0.075 mM silver nanocubes, 10 mM TMB, and 10 mM H2O2. The pH of the system was adjusted to 4 using an acetate-sodium acetate buffer solution. After reacting at room temperature for 3 hours, the UV-Vis spectra at 500–800 nm were measured. The test results are shown below. Figure 3 and 4 .
[0036] Figure 3The image shows the peroxidase activity spectrum of the silver nanocubes prepared in Example 1. Figure 3 It can be seen that no characteristic absorption peaks appeared in solutions I, II, and III after standing for 3 hours. Only the buffer solution containing silver nanocubes, TMB, and H2O2 showed a significant absorption peak at 652 nm after 3 hours of reaction. This is the characteristic absorption peak of TMB oxide oxTMB.
[0037] Figure 4 This is a diagram showing the reaction of silver nanocubes prepared in Example 1 catalyzing the oxidation of TMB with hydrogen peroxide. Figure 4 The appearance of the characteristic absorption peak of oxTMB and the blue color of the solution further confirm that the prepared silver nanocubes can catalyze the oxidation of the reduced-state substrate TMB by H2O2 and have peroxidase catalytic activity.
[0038] Example 2
[0039] Based on Example 1, the concentration of the TAT aqueous solution was 0.106 mM, the concentration of the silver nitrate aqueous solution was 1.8544 mM, and the TAT:Ag ratio was... + The molar ratio is 1:30, and all other conditions remain unchanged.
[0040] Figure 5 TEM images of silver nanocubes prepared for this embodiment, by Figure 5 It is known that the side length is 100–150 nm, indicating that changing the concentration and ratio can alter the side length of the synthesized silver nanocubes without affecting their shape. This demonstrates that the size of the aqueous silver nanocubes can be controlled by adjusting the concentration and ratio. With a fixed TAT content, increasing the Ag content in the reactants… + The appropriate ratio of ingredients is beneficial for growing larger silver cubes.
[0041] Example 3
[0042] Based on Example 1, the pH of the AT cell membrane-penetrating peptide solution in step (1) was changed to 12, while the other conditions remained unchanged.
[0043] Figure 6 TEM images of the silver nanocubes prepared for this example show that the average side length of the prepared silver nanocubes is 100–120 nm, which is larger than that of Example 1. This may be due to the fact that increasing pH changes the conformation of the transmembrane peptides and promotes the reduction and growth of the silver nanocubes.
[0044] Example 4
[0045] Based on Example 1, the heat preservation reaction temperature was changed to 40°C, while the other conditions remained unchanged.
[0046] Figure 7The silver nanocubes prepared under these conditions have a main size distribution of 70–130 nm, slightly larger than those in Example 1. This is consistent with the general principle that increasing the reaction temperature is beneficial for grain growth.
[0047] Example 5
[0048] Based on Example 1, the heat preservation reaction time was changed to 72 hours, while the other conditions remained unchanged.
[0049] Figure 8 In this embodiment, TEM bright-field and dark-field images of silver nanocubes were prepared. The side length of the nanocubes was approximately 110 nm, which is slightly larger than that of Example 1. This is consistent with the general principle that prolonged holding time is beneficial for grain growth.
[0050] Example 6
[0051] Based on Example 1, the cell-penetrating peptide TAT was replaced with Penetratin, while all other conditions remained unchanged.
[0052] This change does not affect the experimental results; the prepared silver nanocubes are basically consistent with those in Example 1.
[0053] Example 7
[0054] Based on Example 1, silver nitrate was replaced with silver acetate, while all other conditions remained unchanged.
[0055] This change did not affect the synthesis results, and the prepared silver nanocubes were essentially consistent with those in Example 1. This indicates that soluble silver salts, silver nitrate and silver acetate, can both be used to synthesize aqueous silver nanocubes using this method.
[0056] Example 8
[0057] Based on Example 1, sodium hydroxide was replaced with potassium hydroxide, while all other conditions remained unchanged.
[0058] This change did not affect the synthesis results; the prepared silver nanocubes were essentially consistent with those in Example 1. Surface NaOH, KOH, etc., can be used as pH adjustment reagents in this method.
[0059] Comparative Example 1
[0060] Based on Example 1, TAT aqueous solution was added dropwise to silver nitrate aqueous solution, with all other conditions remaining unchanged.
[0061] Aqueous silver nanocubes could not be synthesized successfully. Changing the order of silver nitrate and TAT addition failed to yield silver nanocubes. This may be because when silver nitrate solution was added to the TAT aqueous solution, the excess TAT immediately coordinated with silver ions to form a good specific crystal facet protection, which was beneficial for controlling the growth of the seed crystals into cubic silver crystals during the subsequent heat-preserving reaction. However, when TAT was added to the silver nitrate solution, the initial amount of TAT was too small to form sufficient coordination protection with the silver ions, thus ultimately failing to restrict the growth of the silver seed crystals into a cubic structure.
[0062] Comparative Example 2
[0063] At 37℃, 10 mL of a 4 mM AgNO3 DMF solution was added dropwise to 10 mL of a 4 mM TAT transmembrane peptide DMF solution, and the reaction was stirred vigorously for 72 h to obtain non-cubic silver nanoparticles. Dialysis converted the TAT-functionalized silver nanoparticles synthesized in the DMF solvent into an aqueous phase. The synthesized silver nanoparticles are shown below. Figure 9 As shown.
[0064] Depend on Figure 9 It can be seen that, using DMF as solvent and TAT membrane-penetrating peptide as ligand in a process similar to that in the examples, the synthesized product is irregularly shaped silver nanoparticles, and silver nanocubes cannot be generated. This indicates that the membrane-penetrating peptide can only play its role as a suitable ligand in the synthesis of silver cubes in water.
Claims
1. A method for preparing silver nanocubes, characterized in that, Includes the following steps: (1) Add cationic cell-penetrating peptides to water and stir until completely dissolved to prepare an aqueous solution of cell-penetrating peptides, which is acidic. Then, while continuing to stir, add an alkaline pH adjusting reagent to adjust the pH of the solution to alkaline. (2) Under the condition of continuous stirring of the aqueous solution of cell-penetrating peptide prepared in step (1), soluble silver salt solution is slowly added dropwise and the reaction is kept warm to obtain silver nano cubes; The cationic cell-penetrating peptide is TAT, Penetratin, or Polyarginine.
2. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (2), the heat preservation reaction temperature is 30~40℃ and the heat preservation time is 8~72 hours.
3. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (1), the pH value of the solution is adjusted to an alkaline pH of 9-12.
4. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (2), the cell-penetrating peptide reacts with Ag in the silver salt. + The molar ratio is 1:20~30.
5. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (1), the concentration of cell-penetrating peptide in the cell-penetrating peptide solution is 0.053 mM to 0.106 mM.
6. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (2), the Ag in the soluble silver salt solution + The concentration ranges from 1.25 mM to 1.85 mM.
7. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (2), the soluble silver salt is silver nitrate or silver acetate.
8. The method for preparing silver nanocubes according to claim 1, characterized in that, The silver nanocube has a cubic silver core inside and cell-penetrating peptides on the surface; the side length of the silver nanocube is 50~200 nm.
9. The method for preparing silver nanocubes according to claim 1, characterized in that, In step (1), the alkaline pH adjusting reagent refers to NaOH, KOH or ammonia.