Preparation method of low-dimensional silver nanostructure driven by dynamic polymer hydrogel

Abstract

The invention provides a preparation method of a low-dimensional silver nanostructure driven by dynamic polymer hydrogel, which comprises the following steps: fully mixing an organic electron donor and a steric hindrance stabilizer to form a polymer hydrogel precursor; adding a solution containing a cross-linked metal ion compound into the polymer hydrogel precursor, and stirring to form stable dynamic polymer hydrogel; adding a solution or dispersion liquid containing a silver source into the dynamic polymer hydrogel, stirring, and reacting at 25-85 DEG C for 0.1-12 hours; after the reaction is completed, adding a pH buffer solution to destroy gel of a reaction product in the step S3, then carrying out centrifugal collection, washing a separated substance, and then dispersing the separated substance in ethanol or water for storage or drying. According to the technical scheme, the silver nanoparticles, the silver nanowires or the silver nanoribbons with special shapes can be obtained, the cost is low, the environment is protected, and the problems of high energy consumption and high cost in the current synthesis process of the silver nanowires are solved.

Description

Technical Field

[0001] This invention relates to the field of one-dimensional nanomaterials technology, and in particular to a method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels. Background Technology

[0002] Silver nanowires, with their excellent conductivity, high light transmittance, and good mechanical flexibility, are considered an ideal flexible transparent electrode material to replace traditional indium tin oxide (ITO). Compared with ITO, silver nanowires can be processed using solution methods at a lower cost, and they can overcome the limitations of ITO's brittleness and the scarcity of indium resources, making them particularly suitable for applications requiring large curvature bending, such as flexible displays and wearable devices.

[0003] Currently, the mainstream synthesis method for silver nanowires is still the polyol method, but this method has significant problems such as high reaction temperature, high energy consumption, and numerous side reactions. The synthesis process usually needs to be carried out at a high temperature of 130-170℃, resulting in high energy consumption, and the side reactions lead to low yields. At the same time, the side reactions also generate impurities such as silver nanoparticles, causing the product to have a wide diameter distribution and poor uniformity, which in turn seriously affects the photoelectric properties and overall uniformity of the silver nanowire film.

[0004] In contrast, aqueous green synthesis processes demonstrate great potential due to their mild reaction conditions, environmental friendliness, and lower cost. This method avoids the use of organic solvents during synthesis, aligning with the principles of green chemistry, and is expected to reduce production costs and improve process safety, making it more suitable for future large-scale production. Furthermore, the aqueous method exhibits good process compatibility, potentially overcoming the limitations of existing methods in terms of synthesis efficiency, environmental friendliness, and product quality, providing a reliable pathway for large-scale preparation. Therefore, developing a controllable synthesis process for high-performance, low-dimensional nanostructures using water as a solvent and under low-temperature conditions is not only of significant scientific importance but also possesses substantial application value. Summary of the Invention

[0005] To address the above technical problems, this invention discloses a method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels, which yields silver nanoparticles, silver nanowires, or silver nanoribbons with unique morphologies, solving the problems of high energy consumption and high cost in the current synthesis of silver nanowires.

[0006] The technical solution adopted by this invention is as follows:

[0007] A method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels includes the following steps:

[0008] Step S1: The organic electron donor and the steric hindrance stabilizer are thoroughly mixed to form a polymer hydrogel precursor. At this stage, the hydrogel has low strength and is easily destroyed. The organic electron donor is one or a mixture of two or more of the following: cinnamic acid, chlorogenic acid, phthalic acid, acetophenone, ferulic acid, catechin, p-hydroxybenzoic acid, epicatechin, quercetin, kaempferol, caffeic acid, rutin, hyperoside, digitalis flavonoids, apigenin, p-cresol, gallic acid, genistein, p-methoxybenzoic acid, daidzein, hesperidin, proanthocyanidins, anthocyanins, resveratrol, ellagic acid, epigallocatechin gallate, and ethyl benzoate. The steric hindrance stabilizer is poly(N-vinylcaprolactam), N-vinylpyrrolidone (NVP) copolymer, polyacrylic acid (PAA), or polyvinyl alcohol (PVA). One or a mixture of two or more of the following: polyvinyl caprolactam (PVCL), poly-N-vinyl formamide (PNVF), polyethylene glycol (PEG), hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxymethyl cellulose, sodium hydroxymethyl cellulose, PVP, chitosan, sodium alginate, and gelatin;

[0009] Step S2: Add a solution containing cross-linked metal ion compound to the polymer hydrogel precursor and stir to form a stable dynamic polymer hydrogel, which provides a guarantee for subsequent physical confinement.

[0010] The cross-linked metal ion compound is at least one of lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, ferric chloride, ferrous chloride, copper chloride, nickel chloride, cobalt chloride, lanthanum chloride, ruthenium chloride, chloroplatinic acid, chloroauric acid, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, sodium iodide, potassium iodide, ferric bromide, nickel bromide, cobalt bromide, lanthanum bromide, sodium iodide, sodium iodide, potassium iodide, ferric iodide, nickel iodide, cobalt iodide, and lanthanum iodide.

[0011] Step S3: Add the solution or dispersion containing the silver source to the dynamic polymer hydrogel of step S3 and stir, and react at 25-85℃ for 0.1-12 h; the mass ratio of the organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions is (0.1~50):1:(1~150):(0.02-10); the silver source is at least one of silver fluoride, silver chloride, silver bromide, silver iodide, silver sulfate, silver carbonate, silver nitrite, silver nitrate, silver acetate, silver oxalate, silver chlorate, silver perchlorate, silver perbromate, silver periodate, silver bicarbonate, silver sulfide, silver gluconate, silver cyanate, and silver oxide.

[0012] Step S4: After the reaction is complete, add pH buffer to disrupt the gel of the reaction product from step S3, then centrifuge to collect the product, wash the separated product, and then disperse it in ethanol or water for storage, or dry it.

[0013] Using this technique, one, two, or more low-dimensional silver nanostructures, including one-dimensional silver nanowires, silver nanowire particles, and silver nanoribbons, can be prepared. The resulting silver nanoribbons exhibit significant differences in width and thickness, and are generally in the form of quasi-two-dimensional slender rhomboid sheets, with some nanoribbons showing slight bending or twisting.

[0014] The dynamic polymer hydrogel-driven preparation of low-dimensional silver nanostructures in this invention differs from traditional methods for synthesizing silver nanowires, despite using similar raw materials. Traditional polyol-based silver nanowire synthesis primarily involves three steps: reduction, nucleation, and growth. During synthesis, the polyol acts as both a reducing agent and solvent, reducing Ag+ ions in the solution to elemental silver. With PVP acting as a capping agent, this silver selectively adsorbs onto the {100} facets of the silver nanocrystals, initiating the growth of one-dimensional silver nanostructures. In contrast, the dynamic polymer hydrogel in this invention not only serves as an electron donor and spatially confined ligand but also provides a microreaction vessel, enabling confined crystallization and anisotropic growth of silver nanoparticles within the gel network. This hydrogel possesses dynamic and reversible intelligent properties. By controlling various parameters during the reaction process, the morphology of the dynamic polymer hydrogel can be adjusted, thereby synthesizing one, two, or more low-dimensional composite structures within different dimensional nanostructures.

[0015] As a further improvement of the present invention, the steric hindrance stabilizer is polyvinylpyrrolidone PVP-K30 (Mw: 45000~58000).

[0016] As a further improvement of the present invention, the cross-linked metal ion compound is potassium chloride.

[0017] As a further improvement of the present invention, the silver source is silver nitrate.

[0018] As a further improvement of the present invention, mechanical stirring or ultrasonic dispersion is used in step S1.

[0019] As a further improvement of the present invention, in step S2, the stirring is gentle stirring at room temperature or slightly above room temperature.

[0020] As a further improvement of the present invention, step S3 also includes irradiating the reaction solution with ultraviolet light to promote the directional growth of silver nanostructures, which can yield samples with higher crystallinity or specific morphology.

[0021] As a further improvement of the present invention, in step S3, the stirring rate is 50-800 r / min; more preferably, in step S3 the stirring rate is 50-400 r / min.

[0022] As a further improvement of the present invention, in step S3, the reaction temperature is 25-60℃ and the reaction time is 3-6h.

[0023] As a further improvement of the present invention, in step S3, the mass concentration of the solution or dispersion containing the silver source is 0.03-30 g / mL.

[0024] As a further improvement of the present invention, in step S4, the centrifugation speed is 1000-9000 r / min, and the washing is performed by centrifuging with deionized water 1-3 times, followed by centrifugation with anhydrous ethanol 2-4 times. More preferably, the centrifugation speed is 4000-7500 r / min.

[0025] As a further improvement of the present invention, the solvent of the silver source-containing solution or dispersion is water, and the mass concentration of the soluble silver salt is 0.03-30 g / mL.

[0026] As a further improvement of the present invention, in step S4, the drying is natural air drying, oven drying, vacuum drying, spray drying, freeze drying, or supercritical drying.

[0027] As a further improvement of the present invention, vacuum drying is used in step S4, with a vacuum drying temperature of 30-100°C and a vacuum drying time of 3-10 hours. Further, the vacuum drying temperature is 60-80°C.

[0028] As a further improvement of the present invention, in step S4, the pH buffer is at least one of citrate buffer, HEPES buffer, Tris-HCl buffer, PBS buffer, acetate-sodium acetate buffer, borate buffer and Tris-EDTA buffer.

[0029] As a further improvement of the present invention, low-dimensional silver nanostructure powder is obtained by air jet milling after drying.

[0030] As a further improvement of the present invention, the mass ratio of the organic electron donor, the soluble silver salt solution, the steric hindrance stabilizer, and the crosslinked metal ions is (1~10):1:(1~50):(0.02-1). Further, the mass ratio of the organic electron donor, the soluble silver salt solution, the steric hindrance stabilizer, and the crosslinked metal ions is (1~4):1:(6~15):(0.02-0.04).

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] By adopting the technical solution of the present invention,

[0033] First, the technical solution of the present invention uses dynamic polymer hydrogel as a microreactor, and utilizes its synergistic effect of chemical guidance and physical confinement to achieve low-dimensional controllable growth of silver nanostructures.

[0034] Secondly, the technical solution of this invention can not only prepare conventional silver nanowires, but also directionally synthesize one or more low-dimensional silver nanostructures, including one-dimensional silver nanowires, silver nanoparticles, and silver nanoribbons, by precisely controlling reaction parameters. The silver nanoribbons are elongated rhomboid flakes with significant differences in width and thickness, and some exhibit slight bending or twisting, unlike the slender linear morphology. This provides adaptable size and morphology options for diverse applications such as flexible displays and sensors. Especially in the field of conductive pastes, composite low-dimensional silver nanostructure pastes exhibit superior application performance compared to single silver nanowire pastes.

[0035] Third, the technical solution of this invention uses plant extracts as green electron donors and replaces traditional organic solvents with water-based solutions, thereby reducing environmental pollution and wastewater treatment burden from the source. It has less toxicity and is more in line with the requirements of green chemistry and sustainable development.

[0036] Fourth, the technical solution of this invention adopts a one-step reduction process, which eliminates the need for inert gas protection and high-temperature, high-pressure conditions, and avoids the use of harmful organic solvents, thereby significantly simplifying the production process and reducing purification difficulty. This method has high reaction efficiency, low equipment requirements, and simple operation, with a product yield of over 90%. While significantly reducing production costs, it also possesses good potential for large-scale production and has broad application prospects. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the reaction process of the present invention.

[0038] Figure 2 and Figure 3 An optical image of the hydrogel prepared in Example 1 of this invention.

[0039] Figure 4 and Figure 5 This is an optical image of Comparative Example 1 of the present invention.

[0040] Figure 6 , Figure 7 The images are scanning electron microscope (SEM) images of the low-dimensional silver nanostructure prepared in Example 2 of this invention at different magnifications.

[0041] Figure 8 The XRD results are for the low-dimensional silver nanostructure prepared in Example 2 of this invention.

[0042] Figure 9 and Figure 10 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 2 of this invention at different magnifications.

[0043] Figure 11 , Figure 12 and Figure 13 SEM images of the low-dimensional silver nanostructure prepared in Example 3 of this invention at different magnifications.

[0044] Figure 14 and Figure 15 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 3 of this invention at different magnifications.

[0045] Figure 16 , Figure 17 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 4 of this invention at different magnifications.

[0046] Figure 18 , Figure 19 and Figure 20 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 5 of this invention at different magnifications.

[0047] Figure 21 The image shows the EDS spectrum of the low-dimensional silver nanostructure prepared in Comparative Example 4 of this invention.

[0048] Figure 22 , Figure 23 and Figure 24 SEM images of the low-dimensional silver nanostructure prepared in Example 4 of this invention at different magnifications.

[0049] Figure 25 and Figure 26 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 6 of this invention at different magnifications.

[0050] Figure 27 The XRD results are shown for the low-dimensional silver nanostructure prepared in Comparative Example 6 of this invention.

[0051] Figure 28 , Figure 29 and Figure 30 These are SEM images of the low-dimensional silver nanostructure prepared in Comparative Example 7 of this invention at different magnifications.

[0052] Figure 31 This is a mechanism diagram of the present invention. Detailed Implementation

[0053] The preferred embodiments of the present invention will be described in further detail below.

[0054] This invention provides a method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels, such as... Figure 1 As shown, it includes the following steps:

[0055] Step S1: Prepare an organic electron donor, a steric hindrance stabilizer, cross-linked metal ions, and a solution or dispersion containing a silver source; the organic electron donor may be one or a mixture of two or more species such as cinnamic acid, chlorogenic acid, phthalic acid, acetophenone, ferulic acid, catechin, p-hydroxybenzoic acid, epicatechin, quercetin, kaempferol, caffeic acid, rutin, hyperoside, digitalis flavonoids, apigenin, p-cresol, gallic acid, genistein, p-methoxybenzoic acid, daidzein, hesperidin, proanthocyanidins, anthocyanins, resveratrol, ellagic acid, epigallocatechin gallate, and ethyl benzoate;

[0056] In step S2, the organic electron donor and steric hindrance stabilizer are mixed and thoroughly stirred or sonicated to form a polymer hydrogel precursor. At this stage, the hydrogel has low strength and is easily destroyed.

[0057] Step S3: Add cross-linked metal ion solution to polymer hydrogel precursor, and let the gel stand or gently stir at room temperature or slightly above room temperature to form a stable dynamic polymer hydrogel, which provides a guarantee for subsequent physical confinement.

[0058] Step S4: Add the silver source-containing solution or dispersion to the dynamic polymer hydrogel of step S3; place the Ag+-loaded hydrogel in a water bath and stir, reacting at 25-85℃ for 0.1-12 h. For samples requiring higher crystallinity or specific morphology, ultraviolet light irradiation for a period of time can be used to promote the directional growth of silver nanostructures. The mass ratio of the organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions is (0.1~50):1:(1~150):(0.02-10).

[0059] Step S5: After the reaction is complete, the gel can be gently destroyed with a specific pH buffer solution, then collected by low-speed centrifugation, and washed with deionized water, ethanol or a mixture thereof. Finally, it can be dispersed in solvents such as ethanol or water for storage, or dried to obtain a powder sample.

[0060] Figure 31 As shown, the specific mechanism is as follows:

[0061] First, a basic hydrogel is constructed by mixing an organic electron donor and a steric hindrance stabilizer. The steric hindrance stabilizer, acting as a long-chain polymer backbone, increases the system's viscosity and provides structural support for crosslinking. The lactam groups on the steric hindrance stabilizer molecular chain form a dense network of hydrogen bonds with the groups of the organic electron donor. Through supramolecular forces such as intermolecular hydrogen bonds, π-π stacking, and hydrophobic interactions, a three-dimensional network structure is formed, creating a dynamic polymer hydrogel. This network, constructed from non-covalent bonds, endows the hydrogel with extraordinary properties. When external stress is applied, non-covalent bonds such as hydrogen bonds can reversibly break and recombine, dissipating energy and thus giving the hydrogel self-healing capabilities and excellent toughness.

[0062] Secondly, the introduction of cross-linked metal ions enhances the stability of dynamic polymer hydrogels. The organic electron donor and the steric hindrance stabilizer are primarily linked by weak non-covalent interactions such as hydrogen bonds. This cannot form a "dynamic hydrogel" with sufficient mechanical strength and a durable three-dimensional network structure. The system may only exhibit as a viscous solution or a highly unstable weak gel, losing its nanoscale spatial confinement ability and failing to guide the directional growth of crystals. The introduction of cross-linked metal ions provides a stable and responsive environment for the subsequent growth of silver nanowires. Furthermore, the groups of the organic electron donor rapidly coordinate with the metal ions, forming dynamic and reversible cross-linking points. These dynamic coordination bonds endow the hydrogel with self-healing capabilities and responsiveness to environmental stimuli such as pH and reactive oxygen species.

[0063] Secondly, a silver source is introduced into the aforementioned dynamic polymer hydrogel. The groups of the organic electron donor have extremely high coordination affinity for silver ions, enabling them to selectively and uniformly immobilize silver ions at specific sites on the network. This is equivalent to pre-planning countless uniformly distributed "seed sites" for the formation of silver atoms, fundamentally ensuring the uniformity of subsequent nucleation and avoiding the formation of aggregates. The organic electron donor coordinates with both crosslinked metal ions and silver ions. This forms a delicate competitive balance. The presence of crosslinked metal ions effectively regulates the reduction rate and coordination strength of silver ions in the dynamic polymer hydrogel, thereby controlling the generation rate of silver atoms and the growth rate of crystal faces, which is crucial for obtaining high-quality low-dimensional structures.

[0064] The core advantage of this invention lies in its precise control over the two key steps of silver nanostructure nucleation and growth, primarily due to the synergistic effect of the organic electron donor and the steric hindrance stabilizer. Through the synergistic effect of the chemical guidance and physical confinement of the dynamic polymer hydrogel, low-dimensional growth of silver nanostructures is achieved. The organic electron donor is not only a component of the gel but also a mild reducing agent. Under appropriate conditions, the organic electron donor can slowly and in situ reduce anchored silver ions to silver atoms. This slow reduction facilitates controllable nucleation and growth. Furthermore, the three-dimensional network of the hydrogel forms nanoscale channels or microregions. These spatial structures physically restrict the diffusion and aggregation paths of silver atoms, forcing silver crystals to oriented and elongate in the gaps of the network or along the polymer chains, further enhancing the formation of low-dimensional structures.

[0065] Ultimately, low-dimensional silver nanostructures are grown in situ and intertwined within the hydrogel network. Disruption of the gel yields one, two, or more stable low-dimensional silver nanostructures, including one-dimensional silver nanowires, silver nanowire particles, and silver nanoribbons. These structures show promising applications in flexible electronics, smart sensing, antibacterial dressings, and conductive pastes.

[0066] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention.

[0067] Example 1

[0068] The first step is to prepare caffeic acid solution with a mass concentration of 10 mg / mL, NVP solution with a mass concentration of 30 mg / mL, and potassium chloride solution with a mass concentration of 2 mg / mL, respectively, and stir and mix them evenly for later use.

[0069] The second step involves mixing 100 mL of NVP solution and 250 mL of caffeic acid solution, with the mass ratio of organic electron donor to steric hindrance stabilizer being 5:6. The mixture is thoroughly stirred or sonicated, and then 10 mL of potassium chloride solution is added. The mixture is allowed to stand or gently stirred at room temperature or slightly above room temperature to form a stable dynamic polymer hydrogel.

[0070] Depend on Figure 2 and Figure 3 A milky white hydrogel is clearly visible, proving that organic electron donors and steric hindrance stabilizers can generate dynamic polymer hydrogels.

[0071] Comparative Example 1

[0072] Based on Example 1, the difference in this comparative example is that the conditions for gel formation are changed.

[0073] The first step is to prepare two sets of caffeic acid solutions with a mass concentration of 10 mg / mL, NVP solutions with a mass concentration of 20 mg / mL, and potassium chloride solutions with a mass concentration of 2 mg / mL. After stirring and mixing evenly, caffeic acid solution 1 and caffeic acid solution 2, NVP solution 1 and NVP solution 2, and potassium chloride solution 1 and potassium chloride solution 2 are obtained.

[0074] The second step is to add a certain amount of KOH to the caffeic acid solution 1 to change its pH value.

[0075] The third step involved mixing 100 mL of NVP solution 1 with 250 mL of caffeic acid solution 1 after pH adjustment, stirring or sonicating thoroughly, and then adding 10 mL of potassium chloride solution 1. The mass ratio of caffeic acid solution 1, NVP solution 1, and potassium chloride solution 1 was 5:6:0.04. After standing or gently stirring at room temperature or slightly above room temperature, no hydrogel was observed.

[0076] Fourth step: Mix 100 mL of NVP solution 2 with 250 mL of caffeic acid solution 2, stir or sonicate thoroughly, and then add 10 mL of potassium chloride solution 2. The mass ratio of caffeic acid solution 2, NVP solution 2 and potassium chloride solution 2 is 5:6:0.04. Let stand or stir gently at room temperature or slightly above room temperature to obtain hydrogel 2.

[0077] Fifth step: Slowly add KOH solution to hydrogel 2. It is observed that hydrogel 2 gradually disappears and becomes a clear and transparent solution.

[0078] Depend on Figure 4 and Figure 5 It is evident that changing the reaction conditions in this comparative example prevented the formation of hydrogel 1 and caused the destruction of hydrogel 2. This is because the organic electron donor and the steric stabilizing agent groups assemble into a three-dimensional network structure through intermolecular forces such as hydrogen bonds, while the coordination of the cross-linked metal ion organic electron donor enhances the strength of the hydrogel. When external stress is applied, non-covalent bonds such as hydrogen bonds can reversibly break and recombine, dissipating energy and thus endowing the hydrogel with self-healing ability and excellent toughness. This structural characteristic endows the dynamic polymer hydrogel with self-healing ability and responsiveness to environmental factors such as pH and reactive oxygen species, while simultaneously constructing a site-rich hydrophilic three-dimensional network.

[0079] Example 2

[0080] A method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels includes the following steps:

[0081] The first step is to prepare solutions of ellagic acid (10 mg / mL), PVP (20 mg / mL), ferric chloride (3 mg / mL), and silver nitrate (10 mg / mL) with mass concentrations of 10 mg / mL, respectively, and mix them thoroughly before use.

[0082] The second step involves mixing 50 mL of PVP solution and 25 mL of ellagic acid solution, stirring or sonicating thoroughly to prepare a polymer hydrogel precursor.

[0083] The third step is to add 1 mL of cross-linked metal ion solution to the polymer hydrogel precursor and let it stand or stir gently at room temperature or slightly above room temperature to form a stable dynamic polymer hydrogel.

[0084] Fourth, 10 mL of silver nitrate solution was added to the dynamic polymer hydrogel. The mass ratio of organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 2.5:1:10:0.03. The Ag+-loaded hydrogel was placed in a water bath and reacted at 35 °C for 12 h. Stirring was carried out at 350 r / min.

[0085] Fifth step: After the reaction is complete, the gel can be gently destroyed with PBS buffer, then collected by centrifugation at 4000 r / min, and washed alternately with deionized water and ethanol, and finally dispersed in ethanol or water for storage.

[0086] Depend on Figure 6 as well as Figure 7 It is evident that the sample contains a large number of low-dimensional nanostructures, primarily silver nanoribbons. The structures exhibit relatively uniform widths and lengths ranging from hundreds of nanometers to several micrometers, demonstrating a high aspect ratio. The structures have clear, sharp edges and smooth surfaces, indicating good crystal growth and high crystallinity. The structures are randomly interwoven and stacked, forming a loose, multi-layered network.

[0087] Depend on Figure 8 It can be seen that the sample is a highly crystalline, high-purity elemental silver. All its diffraction peaks precisely match the standard spectrum (PDF#04-0783) of face-centered cubic silver, with no impurity peaks. The diffraction peak intensity of the (111) crystal plane is significantly dominant in the spectrum, showing a strong preferred orientation. This crystallographic feature directly confirms from the structural level that the sample is mainly composed of silver nanoribbons with the silver (111) crystal plane as the base plane, thus corroborating the low-dimensional morphology observed in previous SEM images.

[0088] Comparative Example 2

[0089] Based on Example 2, this comparative example differs in that silver nanowires were synthesized using a traditional polyol system to demonstrate the innovation of this preparation method.

[0090] First, weigh 5 g of PVP and measure 40 mL of ethylene glycol solution. Mix the two together and stir evenly to ensure the solution is fully integrated. Then, remove the solution and cool it to room temperature to obtain reducing agent solution A.

[0091] The second step is to weigh 1.2 g AgNO3 and measure 10 mL of ethylene glycol solution, and stir at 1000 r / min until AgNO3 is completely dissolved to obtain solution B.

[0092] Third, add 1.2 mL of 0.625 mol / L sodium chloride in ethylene glycol solution and 1.2 mL of 0.25 mol / L sodium bromide in ethylene glycol solution to solution B, and stir at 800 r / min for 30 min.

[0093] Fourth step: Pour solution A and solution B into a flask and stir for 1 h to obtain a mixture. Place the mixture in an oil bath at 170 °C for 70 min.

[0094] Fifth, at the end of the oil bath, remove the flask and stopper it, then quickly place it in ice water until it cools to room temperature, thus obtaining the silver nanowire stock solution. Collect the silver nanowire stock solution by low-speed centrifugation, and wash it alternately with deionized water and ethanol, finally dispersing it in ethanol or water for storage.

[0095] Depend on Figure 9 , Figure 10 It can be seen that the samples in the traditional system are typical silver nanowires, with relatively uniform diameter and an overall slender fibrous morphology, lacking silver nanoribbons. Figure 6 , Figure 7 Significant structural differences exist between the two systems. This is because, although the raw materials are similar, their mechanisms of action are almost entirely different. In the comparative sample, no dynamic polymer hydrogel was formed during synthesis. The polyol acted as both a reducing agent and a solvent, reducing Ag+ in the solution to elemental silver. In the presence of PVP as a capping agent, this silver selectively adsorbed onto the {100} facets of the silver nanocrystals, initiating the growth of one-dimensional silver nanostructures. Therefore, it was impossible to synthesize composite products with low-dimensional nanostructures such as silver nanoribbons. In contrast, the formation of a dynamic polymer hydrogel through organic electron donors and steric hindrance stabilizers leads to significant differences in the morphology of the products from the two systems. Through the synergistic effect of the chemical guidance and physical confinement of the dynamic polymer hydrogel, the low-dimensional growth of silver nanostructures is achieved.

[0096] Example 3

[0097] A method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels includes the following steps:

[0098] The first step is to prepare solutions of epigallocatechin gallate (10 mg / mL), PVA (30 mg / mL), ferric bromide (4 mg / mL), and silver nitrate (10 mg / mL) with mass concentrations of 10 mg / mL, respectively, and mix them thoroughly for later use.

[0099] The second step involves mixing 50 mL of PVA solution and 10 mL of epigallocatechin gallate solution, stirring or sonicating thoroughly to prepare a polymer hydrogel precursor.

[0100] The third step is to add 1 mL of cross-linked metal ion solution to the polymer hydrogel precursor and let it stand or stir gently at room temperature or slightly above room temperature to form a stable dynamic polymer hydrogel.

[0101] In the fourth step, 10 mL of silver nitrate solution was added to the dynamic polymer hydrogel. The mass ratio of organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 1:1:15:0.04. The hydrogel loaded with Ag+ was placed in a water bath and reacted at 30 °C for 12 h. The mixture was stirred at a low speed of 325 r / min.

[0102] Fifth step: After the reaction is complete, the gel can be gently broken down with borate buffer, then collected by centrifugation at 4000 r / min, and washed alternately with deionized water and ethanol, and finally dispersed in ethanol or water for storage.

[0103] Depend on Figure 11 , Figure 12 and Figure 13 It is evident that the low-dimensional nanostructure exhibits multi-dimensional composite characteristics, but is dominated by silver nanoribbons. These nanoribbons are slender with clear edges, nanometer-scale thickness, and significantly larger in length and width than in thickness. Some exhibit parallel or small-angle staggered arrangements, demonstrating high structural anisotropy. Meanwhile, the silver nanoparticles are much smaller than nanosheets, exhibiting irregular spherical shapes and densely clustered together, distributed in the gaps or on the surface of the nanosheets. The absence of obvious agglomeration in the figure indicates that the groups of the organic electron donor have extremely high coordination affinity for silver ions, selectively and uniformly fixing them at specific sites within the network. This is equivalent to pre-planning countless uniformly distributed "seed sites" for the formation of silver atoms, fundamentally ensuring the uniformity of subsequent nucleation and preventing the formation of agglomerates.

[0104] Comparative Example 3

[0105] Based on Example 3, the difference in this comparative example is that no steric hindrance stabilizer is added, so that the gel cannot be formed.

[0106] The first step is to prepare solutions of epigallocatechin gallate (10 mg / mL), ferric bromide (4 mg / mL), and silver nitrate (10 mg / mL) with different mass concentrations, and then mix them thoroughly for later use.

[0107] The second step is to add 1 mL of cross-linked metal ion solution to 10 mL of epigallocatechin gallate solution, and let it stand or stir gently at 30 °C to obtain mixed solution 2.

[0108] Third, 10 mL of soluble silver salt solution was added to mixed solution 2, and the reaction was carried out at 30 °C for 12 h. The mass ratio of organic electron donor, soluble silver salt solution, and crosslinked metal ions was 1:1:0.04, and the mixture was stirred at a low speed of 275 r / min.

[0109] Fourth step: After the reaction is complete, collect the sample by low-speed centrifugation at 4000 r / min, wash with deionized water and ethanol alternately, and finally disperse in ethanol or water for storage.

[0110] Depend on Figure 14 and Figure 15 It is evident that while the low-dimensional nanostructure exhibits some morphology of silver nanoribbons, and these nanoribbons are relatively small in size, they are short and thick despite their ribbon-like structure, and coexist with the bulk structure. This is because the organic electron donor can selectively adsorb onto specific crystal planes to form the low-dimensional nanostructure, but its crystal plane-selective adsorption effect is weak, resulting in minimal differences in crystal growth rates across different directions. The sample exhibits significant agglomeration, which is attributed to the absence of a steric hindrance stabilizer in this comparative example, preventing hydrogel formation and hindering the effective fixation of silver ions in different regions. This may lead to over-enrichment in certain areas, resulting in extremely high-density silver atom clusters during reduction.

[0111] Comparative Example 4

[0112] Based on Example 3, the difference in this comparative example is that no organic electron donor is added, so that the gel cannot be formed.

[0113] The first step is to prepare PVA solution with a mass concentration of 30 mg / mL, ferric bromide solution with a mass concentration of 4 mg / mL and silver nitrate solution with a mass concentration of 10 mg / mL, respectively, and stir and mix them evenly for later use.

[0114] The second step is to add 1 mL of cross-linked metal ion solution to 50 mL of PVA, and let it stand or stir gently at 30 °C to obtain mixed solution 1.

[0115] Third, 10 mL of soluble silver salt solution was added to mixed solution 1, and the reaction was carried out at 30 °C for 12 h. The mass ratio of soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 1:15:0.04, and the mixture was stirred at 350 r / min.

[0116] Fourth step: After the reaction is complete, collect the sample by low-speed centrifugation at 4000 r / min, wash with deionized water and ethanol alternately, and finally disperse in ethanol or water for storage.

[0117] Depend on Figure 16 and Figure 17 It is evident that no dominant, clear low-dimensional linear structure was observed in the sample. Instead, only long, loosely aggregated, mottled, strip-shaped structures, consisting of numerous tiny silver halide particles, existed as the main body. The randomly distributed particles of varying sizes in the image indicate asynchronous and uneven nucleation. This comparative example did not contain an organic electron donor, yet the microstructure exhibited by the sample differed significantly from the expected high-quality, uniform, high aspect ratio low-dimensional silver nanostructure. This suggests that the organic electron donor is an indispensable and crucial component.

[0118] Comparative Example 5

[0119] Based on Example 3, the difference in this comparative example is that no cross-linking metal ions are added, so that a stable gel cannot be formed.

[0120] The first step is to prepare solutions of epigallocatechin gallate (10 mg / mL), PVA (30 mg / mL), and silver nitrate (10 mg / mL) with different mass concentrations, and mix them thoroughly before use.

[0121] The second step involves mixing 50 mL of PVA solution and 10 mL of epigallocatechin gallate solution, stirring or sonicating thoroughly to form polymer hydrogel precursor 1.

[0122] Third, 10 mL of soluble silver salt solution was added to polymer hydrogel precursor 1. The mass ratio of organic electron donor, soluble silver salt solution, and steric hindrance stabilizer was 1:1:15. The reaction was carried out at 30 °C for 12 h with low-speed stirring.

[0123] Fourth step: After the reaction is complete, collect the sample by low-speed centrifugation at 4000 r / min, wash with deionized water and ethanol alternately, and finally disperse in ethanol or water for storage.

[0124] Depend on Figure 18 , Figure 19 as well as Figure 20It is evident that the sample contains a large number of spherical or near-spherical particles with diameters of approximately 100-300 nm, aggregated into a loose cluster. The particle surface is slightly rough, with visible fine crystal faces. Silver ions are rapidly reduced, generating a large number of silver atoms. These atoms, unable to arrange themselves orderly onto the crystal lattice, accumulate randomly or form numerous small crystal nuclei that fuse, resulting in a rough surface and porous structure. In the dynamic polymer hydrogel, the organic electron donor coordinates with both silver ions and cross-linked metal ions. This creates a delicate competitive balance. The presence of cross-linked metal ions effectively modulates the reduction rate and coordination strength of the organic electron donor for silver ions, thereby controlling the generation rate of silver atoms and the growth rate of crystal faces, which is crucial for obtaining high-quality low-dimensional structures.

[0125] Without cross-linked metal ions, the organic electron donor and the steric hindrance stabilizer are primarily linked by weak non-covalent interactions such as hydrogen bonds. This fails to form a "dynamic hydrogel" with sufficient mechanical strength and a durable three-dimensional network structure. The system may only exhibit as a viscous solution or a highly unstable weak gel, losing its nanoscale spatial confinement capability and failing to guide the directional growth of crystals through physical confinement. In this comparative example, no cross-linked metal ions were added, and silver ions were rapidly reduced to particles. The "anchoring" effect of the organic electron donor may have facilitated relatively uniform nucleation, but the absence of cross-linked metal ions prevented its "selective adsorption" and "mild reduction" functions from effectively dominating the subsequent growth process, leading to uncontrolled growth direction.

[0126] Example 4

[0127] A method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels includes the following steps:

[0128] The first step is to prepare solutions of resveratrol (5 mg / mL), poly(N-vinylcaprolactam) (20 mg / mL), sodium chloride (3 mg / mL), and silver nitrate (5 mg / mL) with mass concentrations of 5 mg / mL, respectively, and mix them thoroughly before use.

[0129] The second step involves mixing 50 mL of poly-N-vinylcaprolactam solution and 50 mL of resveratrol solution, stirring thoroughly or sonicating, to prepare a polymer hydrogel precursor.

[0130] The third step is to add 1 mL of cross-linked metal ion solution to the polymer hydrogel precursor and let it stand or stir gently at 40 °C to form a stable dynamic polymer hydrogel.

[0131] Fourth, 25 mL of silver nitrate solution was added to the dynamic polymer hydrogel. The mass ratio of organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 2:1:8:0.024. Ag-loaded hydrogels were then added.+ The hydrogel was placed in a water bath and reacted at 40 °C for 12 h with stirring at 300 r / min.

[0132] Fifth step: After the reaction is complete, the gel can be gently disrupted with Tris-EDTA buffer, then collected by low-speed centrifugation at 4500 r / min, and washed alternately with deionized water and ethanol, and finally dispersed in ethanol or water for storage.

[0133] Depend on Figure 22 , Figure 23 as well as Figure 24 It is evident that the sample contains a large number of low-dimensional nanostructures, exhibiting a multi-dimensional nanostructure composite morphology. The nanoribbons have relatively smooth surfaces, clear edge contours, and good overall morphological regularity, with well-defined ribbon-like structural characteristics. The nanoribbons are randomly stacked and do not exhibit directional alignment; a small number of fine granular structures are visible locally, but no obvious aggregation is observed.

[0134] Example 5

[0135] Based on Example 4, this comparative example differs in that the parameters in the formation process of the dynamic polymer hydrogel are adjusted to control the final product to exist mainly in the form of silver nanowires.

[0136] The first step is to prepare solutions of resveratrol (2.5 mg / mL), poly(N-vinylcaprolactam) (35 mg / mL), sodium chloride (4 mg / mL), and silver nitrate (5 mg / mL) with mass concentrations of 2.5 mg / mL, respectively, and mix them thoroughly before use.

[0137] The second step involves mixing 50 mL of poly-N-vinylcaprolactam solution and 50 mL of resveratrol solution, stirring thoroughly or sonicating, to prepare a polymer hydrogel precursor.

[0138] The third step is to add 1 mL of cross-linked metal ion solution to the polymer hydrogel precursor and let it stand or stir gently at 35 °C to form a stable dynamic polymer hydrogel.

[0139] In the fourth step, 25 mL of silver nitrate solution was added to the dynamic polymer hydrogel. The mass ratio of organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 1:1:14:0.032. The hydrogel loaded with Ag+ was placed in a water bath and reacted at 35 °C for 12 h with stirring at 400 r / min.

[0140] Fifth step: After the reaction is complete, the gel can be gently disrupted with Tris-EDTA buffer, then collected by low-speed centrifugation at 4500 r / min, and washed alternately with deionized water and ethanol, and finally dispersed in ethanol or water for storage.

[0141] Depend on Figure 25 , Figure 26 It can be seen that the sample is mainly composed of silver nanowires, exhibiting a slender linear one-dimensional structure with a relatively uniform diameter. The overall shape is a slender fiber, with some nanowires showing slight bending and twisting, and local "nodular" protrusions are visible.

[0142] Depend on Figure 27 It can be seen that the diffraction peak intensity of the (111) crystal plane is much higher than that of other crystal planes, and the relative intensity significantly exceeds the random orientation ratio of standard polycrystalline silver, indicating that the silver nanostructure has a clear preferred orientation of the (111) crystal plane. This feature also corresponds to the selective adsorption of the organic electron donor on specific crystal planes of silver and the inhibition of its growth, thereby driving the crystal to preferentially extend along the (111) crystal plane, and finally forming a one-dimensional nanostructure. In this comparative example, the three-dimensional structure of the hydrogel is controlled by changing the concentration and temperature during the formation process of the dynamic polymer hydrogel, thereby obtaining a low-dimensional composite silver nanostructure dominated by silver nanowires.

[0143] Example 6

[0144] Based on Example 4, this comparative example differs in that the parameters in the formation process of the dynamic polymer hydrogel are adjusted to control the final product to exist mainly in the form of silver nanoparticles.

[0145] The first step is to prepare solutions of resveratrol (10 mg / mL), poly(N-vinylcaprolactam) (15 mg / mL), sodium chloride (5 mg / mL), and silver nitrate (5 mg / mL) with mass concentrations of 10 mg / mL, respectively, and mix them thoroughly for later use.

[0146] The second step involves mixing 50 mL of poly-N-vinylcaprolactam solution and 50 mL of resveratrol solution, stirring thoroughly or sonicating, to prepare a polymer hydrogel precursor.

[0147] The third step is to add 1 mL of cross-linked metal ion solution to the polymer hydrogel precursor and let it stand or stir gently at 40 °C to form a stable dynamic polymer hydrogel.

[0148] In the fourth step, 25 mL of silver nitrate solution was added to the dynamic polymer hydrogel. The mass ratio of organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions was 4:1:6:0.04. The hydrogel loaded with Ag+ was placed in a water bath and reacted at 40 °C for 12 h with stirring at 300 r / min.

[0149] Fifth step: After the reaction is complete, the gel can be gently disrupted with Tris-EDTA buffer, then collected by low-speed centrifugation at 4500 r / min, and washed alternately with deionized water and ethanol, and finally dispersed in ethanol or water for storage.

[0150] Depend on Figure 28 , Figure 29 as well as Figure 30 It can be seen that the sample is mainly composed of polyhedral silver nanoparticles, which exhibit irregular polyhedral crystal forms with relatively clear crystal face outlines and a certain degree of surface roughness. This comparative example modulates the three-dimensional structure of the hydrogel by changing the concentration during the dynamic polymer hydrogel formation process, thereby obtaining a low-dimensional composite silver nanostructure dominated by silver nanoparticles.

[0151] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels, characterized in that: Includes the following steps: Step S1: The organic electron donor and the steric hindrance stabilizer are thoroughly mixed to form a polymer hydrogel precursor; the organic electron donor is cinnamic acid, chlorogenic acid, phthalic acid, acetophenone, ferulic acid, catechin, p-hydroxybenzoic acid, epicatechin, quercetin, kaempferol, caffeic acid, rutin, hyperoside, digitalis flavonoids, apigenin, p-cresol, gallic acid, genistein, p-methoxybenzoic acid, daidzein, hesperidin, proanthocyanidins, anthocyanins, and resveratrol. The steric hindrance stabilizer is one or a mixture of two or more of the following: ellagic acid, epigallocatechin gallate, and ethyl benzoate; the steric hindrance stabilizer is one or a mixture of two or more of the following: poly(N-vinylcaprolactam), N-vinylpyrrolidone copolymer, polyacrylic acid, polyvinyl alcohol, polyvinylcaprolactam, poly(N-vinylformamide), polyethylene glycol, hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxymethyl cellulose, sodium hydroxymethyl cellulose, PVP, chitosan, sodium alginate, and gelatin. Step S2: Add a solution containing a crosslinked metal ion compound to the polymer hydrogel precursor and stir to form a stable dynamic polymer hydrogel; the crosslinked metal ion compound is at least one selected from lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, ferric chloride, ferrous chloride, copper chloride, nickel chloride, cobalt chloride, lanthanum chloride, ruthenium chloride, chloroplatinic acid, chloroauric acid, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, sodium iodide, potassium iodide, ferric bromide, nickel bromide, cobalt bromide, lanthanum bromide, sodium iodide, potassium iodide, ferric iodide, nickel iodide, cobalt iodide, and lanthanum iodide. Step S3: Add the silver-containing solution or dispersion to the dynamic polymer hydrogel of step S3 and stir, reacting at 25-85℃ for 0.1-12 h; the mass ratio of the organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and crosslinking metal ions is (0.1~50):1:(1~150):(0.01-10). The silver-containing source is at least one of silver fluoride, silver chloride, silver bromide, silver iodide, silver sulfate, silver carbonate, silver nitrite, silver nitrate, silver acetate, silver oxalate, silver chlorate, silver perchlorate, silver perbromate, silver periodate, silver bicarbonate, silver sulfide, silver gluconate, silver cyanate, and silver oxide. Step S4: After the reaction is complete, add pH buffer to disrupt the gel of the reaction product from step S3, then centrifuge to collect the product, wash the separated product, and then disperse it in ethanol or water for storage, or dry it.

2. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: Step S3 also includes irradiating the reaction solution with ultraviolet light to promote the directional growth of silver nanostructures.

3. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: Step S3: Stirring rate is 50-800 r / min, reaction temperature is 25-60℃, and reaction time is 3-6 h.

4. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: In step S4, the centrifugation speed is 1000-9000 r / min, and the washing is performed by centrifuging with deionized water 1-3 times, followed by centrifugation with anhydrous ethanol 2-4 times.

5. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: The solvent of the silver source-containing solution or dispersion is water, and the mass concentration of the soluble silver salt is 0.03-30 g / mL.

6. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: In step S4, the drying process includes natural air drying, oven drying, vacuum drying, spray drying, freeze drying, and supercritical drying; wherein, the temperature of vacuum drying is 30-100℃, and the vacuum drying time is 3-10h.

7. The method for preparing low-dimensional silver nanostructures driven by dynamic polymer hydrogels according to claim 1, characterized in that: In step S4, the pH buffer is at least one of citrate buffer, HEPES buffer, Tris-HCl buffer, PBS buffer, acetate-sodium acetate buffer, borate buffer, and Tris-EDTA buffer.

8. The method for preparing the low-dimensional silver nanostructure driven by the dynamic polymer hydrogel according to any one of claims 1 to 7, characterized in that: The mass ratio of the organic electron donor, soluble silver salt solution, steric hindrance stabilizer, and cross-linked metal ions is (1~10):1:(1~50):(0.02-1).

Images