A recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material and a preparation method and application thereof

Abstract

The application relates to a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material and a preparation method and application thereof. 2+ The application discloses a novel silver nanoparticle composite catalytic material which is prepared by using a metal nanocluster-based hydrogel as a template to in-situ generate Ag NPs. The three-dimensional framework of the hydrogel plays a good dispersion and fixing role on the Ag NPs, and to a great extent, avoids the agglomeration of the Ag NPs in a catalytic reaction, so that the Ag NPs have good stability. The silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material is used in a model reaction of catalytic reduction of 4-NP, and after 8 working cycles, the composite catalytic material can still maintain 80% of the catalytic efficiency.

Description

Technical Field

[0001] This invention relates to a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material, its preparation method and application, belonging to the fields of nanomaterials technology and catalyst technology. Background Technology

[0002] As a typical metallic nanomaterial, silver nanoparticles possess excellent thermal and electrical conductivity, leading to their wide application in antibacterial, surface-enhanced Raman scattering, and catalysis. In catalysis, silver nanoparticles exhibit high reactivity due to their small size and large specific surface area. Furthermore, because the bond and electronic states on the surface of silver nanoparticles differ from those inside, most electrons or holes generated during catalytic reactions do not recombine before reaching the particle surface. This results in excellent catalytic effects in processes such as catalytic hydrogenation reduction and coupling reactions. Compared to other noble metal nanomaterials such as gold and platinum, silver nanoparticles are more widely available and less expensive, making them more advantageous in practical applications.

[0003] Currently, Ag nanoparticles are mainly prepared using hydrothermal synthesis, photodeposition, and electrodeposition methods. For example, patent document CN 117483746 A discloses a silver nanoparticle solution and its preparation method. Using silver nitrate as the silver source and sodium alginate as the reducing agent, silver nanoparticles with a spherical structure and good stability in solution are synthesized through ultraviolet light irradiation and auxiliary heating. Another example is patent document CN 116555807 A, which discloses a cross-shaped silver nanoparticle, its preparation method, and its application. A cross-shaped silver nanoparticle is prepared in a silver electroplating solution using an electrodeposition method, wherein a rotating working electrode is used as the cathode and an inert electrode is used as the anode. This specific morphology of the cross-shaped silver nanoparticle has exposed (110) crystal planes and exhibits good selectivity for ethylene glycol in the catalytic oxidation of ethylene.

[0004] However, free silver nanoparticles, due to their high surface energy, are prone to aggregation, leading to a decrease in catalytic activity. Furthermore, they are difficult to recycle and reuse. Generally, loading silver nanoparticles onto mesoporous silica or polymer matrices can prevent aggregation during catalysis, enhance their stability, and facilitate recycling. Patent document CN 107185591 A discloses a method for preparing recyclable cellulose paper-based silver nanoparticle catalytic materials and their applications. Cellulose paper is used as a support, and its surface is modified to chelate with silver ions. Silver nanoparticles loaded on the cellulose paper are then prepared under the action of a reducing agent. However, the processing and preparation procedures for these supports are relatively cumbersome. Exploring a simple, readily available, non-aggregating, and easily recyclable silver nanoparticle material has significant practical value.

[0005] Metal nanoclusters (typically gold, silver, or copper nanoclusters) are a novel class of nanomaterials, consisting of ultrasmall nanoparticles composed of tens to hundreds of atoms, exhibiting great application potential in fields such as electronics, optics, and catalysis. Due to their rich and tunable surface chemical environments, they can act as gelling agents in the formation of three-dimensional network structures in hydrogels. Patent document CN 115197694 A discloses a method for preparing a fluorescent gold nanocluster composite hydrogel. A composite hydrogel was prepared using bovine serum albumin (BSA) as a crosslinking agent with gold nanoclusters, significantly increasing the aggregation degree of the gold nanoclusters and thus significantly enhancing the fluorescence intensity. Furthermore, this composite gel possesses a stable structure and excellent water solubility.

[0006] For example, patent document CN 114958344 A discloses a method for preparing gold nanocluster luminescent hydrogels and their application in information encryption. The luminescent hydrogel is prepared using the combined action of DPT (4,6-diamino-2-mercaptopyrimidine), chloroauric acid, and water. The fluorescence is switched on and off in the presence or absence of water molecules, thus demonstrating potential application value in the field of information security.

[0007] Hydrogels, with their rich three-dimensional networks and large specific surface areas, can be used as matrices for supporting silver nanoparticles to improve the stability of silver nanoparticle catalysts. However, research on the use of metal nanocluster-based hydrogels for catalysis is currently scarce. Furthermore, methods for preparing recyclable, easily recoverable, and in-situ generated silver nanoparticle catalytic materials on hydrogel fibers using silver nanoclusters are rarely reported. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material, its preparation method, and its application.

[0009] Terminology Explanation:

[0010] Ag9 is a nine-core silver nanocluster with 4-mercaptobenzoic acid as its outer ligand.

[0011] This invention is achieved through the following technical solution:

[0012] The first objective of this invention is to provide a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0013] A recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material, wherein the hydrogel composite catalytic material is composed of Ag9 and Ba 2+ Through self-assembly, it exhibits a nanofiber-like microstructure, with silver nanoparticles loaded in situ on the nanofibers of the hydrogel.

[0014] According to the present invention, preferably, the hydrogel composite catalytic material maintains 80% catalytic efficiency after 8 working cycles in the model reaction of catalytic reduction of 4-nitrophenol.

[0015] The second objective of this invention is to provide a method for preparing the above-mentioned recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0016] According to the present invention, a preferred method for preparing a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material includes the following steps:

[0017] Ag9 solution was mixed with sodium borohydride (NaBH4) solution and vortexed. Barium nitrate (Ba(NO3)2) solution was added and vortexed again to obtain a mixture. The mixture was allowed to stand to obtain a dark brown gel. After washing, a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material was obtained.

[0018] According to the present invention, preferably, the Ag9 solution is prepared by the following method: silver nitrate (AgNO3) and 4-mercaptobenzoic acid (H2mba) are dispersed in ultrapure water, ultrasonically treated, and ammonia (NH3·H2O) is added to the system to obtain a yellow transparent solution, which is the Ag9 solution.

[0019] Further preferably, the molar ratio of AgNO3 to water is 1:6 (mmol / mL), the molar ratio of H2mba to water is 1:6 (mmol / mL), the ultrasonic treatment time is 20 min, and after adding ammonia, the mass fraction of ammonia in the system is 25 wt%.

[0020] According to the present invention, preferably, the molar concentration of Ag9 in the mixture is 1-15 mM.

[0021] Most preferably, the molar concentration of Ag9 in the mixture is 5 mM.

[0022] According to the present invention, preferably, the molar concentration of NaBH4 in the mixture is 2-50 mM.

[0023] Most preferably, the molar concentration of NaBH4 in the mixture is 10 mM.

[0024] According to the present invention, preferably, the molar concentration of Ba(NO3)2 in the mixture is 20-100 mM.

[0025] Most preferably, the molar concentration of Ba(NO3)2 in the mixture is 40 mM.

[0026] According to the present invention, preferably, the vortex treatment time is 20-60 seconds and the settling time is 2-10 hours.

[0027] The optimal vortex treatment time is 30 seconds, followed by a settling time of 3 hours.

[0028] According to the present invention, preferably, the detergent used for washing is ultrapure water.

[0029] A third objective of this invention is to provide applications of the aforementioned recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0030] Applications of recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0031] According to the present invention, a preferred application method is as follows: a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material is added to a 4-nitrophenol (4-NP) solution, and then a NaBH4 solution is added to it under continuous stirring to initiate a catalytic reduction reaction.

[0032] According to the present invention, preferably, the volume ratio of the hydrogel composite catalyst material to the 4-nitrophenol (4-NP) solution is (10-50):(0.5-5), in mg / mL.

[0033] Most preferably, the volume ratio of the hydrogel composite catalyst to the 4-nitrophenol (4-NP) solution is 25:1, in mg / mL.

[0034] According to the present invention, preferably, the molar concentration of the 4-NP solution is 20-100 μM.

[0035] Most preferably, the molar concentration of the 4-NP solution is 60 μM.

[0036] According to the present invention, preferably, the molar concentration of the NaBH4 solution is 250-350 mM.

[0037] According to the present invention, preferably, the volume ratio of 4-nitrophenol (4-NP) solution to NaBH4 solution is 1:1.

[0038] The principle of this invention:

[0039] The silver nanoclusters Ag9 in this invention are low molecular weight gelling agents. Ba is added to their aqueous solution. 2+ Afterwards, a portion of Ag9 and Ba 2+ A supramolecular hydrogel composed of nanofibers was constructed through self-assembly via coordination interactions, inter-cluster π···π interactions, and CH···π interactions. During this self-assembly process, the presence of the reducing agent NaBH4 facilitated the reduction of another portion of Ag9, generating silver nanoparticles (Ag NPs) which were then immobilized within the framework of the supramolecular hydrogel. The porous structure within the hydrogel provides a large specific surface area, allowing for the in-situ generation of silver nanoparticles on the hydrogel nanofibers, which in turn immobilize and disperse the Ag NPs. The in-situ formed Ag NPs provide abundant catalytic active sites, and the immobilization effect of the hydrogel matrix effectively prevents their aggregation, thus maintaining high catalytic performance. In the model reaction of 4-NP reduction to 4-AP, this silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material maintained 80% catalytic efficiency after 8 working cycles.

[0040] Technical features and key advantages of this invention:

[0041] 1. This invention introduces Ba into an aqueous solution of Ag9. 2+ And NaBH4, through supramolecular self-assembly, partially Ag9 and Ba 2+ A supramolecular hydrogel composed of nanofibers was constructed through coordination interactions, inter-cluster π···π and CH···π interactions. During the hydrogel construction process, the introduction of the reducing agent NaBH4 enabled another part of Ag9 to participate in the reduction, thereby generating silver nanoparticles (Ag NPs) and fixing them on the nanofibers of the hydrogel.

[0042] 2. This invention employs a one-pot method to simultaneously construct supramolecular hydrogels, reduce Ag9 to generate silver nanoparticles (Ag NPs), and load the silver nanoparticles in situ onto hydrogel nanofibers. The method is simple and efficient, and the generated silver nanoparticles exhibit high stability and good dispersibility.

[0043] 3. The silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material of the present invention has a large specific surface area, which is conducive to sufficient solid-liquid contact, thereby facilitating the catalytic reaction.

[0044] 4. The silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material of the present invention is a heterogeneous catalyst with high catalytic efficiency and can be effectively recycled.

[0045] 5. The silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material of the present invention can still maintain 80% catalytic efficiency after 8 working cycles in the typical reaction of catalytic reduction of 4-NP, and has a high reusability.

[0046] 6. In this invention, Ag9 is a metal nanocluster with a size of less than 5 nm. It is a novel inorganic material with a special structure and outstanding properties. Attached image description:

[0047] Figure 1 This is an SEM image of the core sample of the composite catalytic material prepared in Example 2 of the present invention.

[0048] Figure 2 This is a TEM image of the core sample of the composite catalytic material prepared in Example 2 of the present invention.

[0049] Figure 3 The image shows the X-ray diffraction pattern of the core sample of the composite catalytic material prepared in Example 2 of this invention.

[0050] Figure 4 This is a small-angle X-ray scattering spectrum of the core sample of the composite catalytic material prepared in Example 2 of the present invention.

[0051] Figure 5 The X-ray photoelectron spectrum is shown for the core sample of the composite catalytic material prepared in Example 2 of this invention.

[0052] Figure 6 This is a SEM image of the Ag9 / Ba(NO3)2 hydrogel sample prepared in Comparative Example 1 of this invention.

[0053] Figure 7 This is a TEM image of the Ag9 / Ba(NO3)2 hydrogel sample prepared in Comparative Example 1 of this invention.

[0054] Figure 8 The UV-Vis absorption spectrum of the core sample of the composite catalytic material in Example 5 of this invention for catalytic reduction of 4-NP is shown.

[0055] Figure 9 The curves of the core sample of the composite catalytic material in Example 5 of this invention during 8 working cycles when used for the catalytic reduction of 4-NP. Detailed implementation method:

[0056] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto.

[0057] All raw materials used in the examples are conventional raw materials and commercially available products.

[0058] 1. Transmission electron microscopy (TEM): TEM can be used to observe the microstructure of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0059] 2. Scanning electron microscope (SEM): SEM can be used to observe the surface morphology of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0060] 3. X-ray diffraction (XRD): XRD can be used to determine the internal structure of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0061] 4. Small-angle X-ray scattering (SAXS): SAXS can be used to determine the internal structure of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0062] 5. X-ray photoelectron spectroscopy (XPS): XPS can be used to analyze the elemental composition and chemical state of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials.

[0063] 6. Ultraviolet-visible absorption spectroscopy (UV-vis): UV-vis can be used to analyze changes in the concentration of substrate 4-NP in catalytic reactions.

[0064] Example 1

[0065] The preparation method of Ag9 solution is as follows:

[0066] Accurately weigh AgNO3 (1 mmol, 170 mg) and H2mba (1 mmol, 155 mg) and disperse them in 6 mL of ultrapure water; then sonicate at 40 kHz for 20 minutes at room temperature; simultaneously, add NH3 to the above mixed solution during sonication. . H2O (25% by mass, 0.5 mL) yielded a yellow, transparent Ag9 solution with a molar concentration of 15.87 mmol. . L -1 .

[0067] Example 2

[0068] The preparation method of recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material includes the following steps:

[0069] (1) Preparation of NaBH4 aqueous solution

[0070] Accurately weigh NaBH4 powder, add ultrapure water, and vortex to prepare a 50 mM NaBH4 aqueous solution.

[0071] (2) Preparation of Ba(NO3)2 aqueous solution

[0072] Accurately weigh Ba(NO3)2 powder, add ultrapure water, and vortex to prepare a 100mM Ba(NO3)2 aqueous solution.

[0073] (3) Preparation of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials

[0074] Transfer 0.158 mL of Ag9 solution to a centrifuge tube, then add 0.1 mL of NaBH4 solution and 0.042 mL of ultrapure water, and vortex for 30 s to mix completely. Next, add 0.2 mL of Ba(NO3)2 solution, vortex for 30 s, and let stand for 3 h. Wash the resulting dark brown gel three times with ultrapure water to obtain a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0075] The morphology of the core sample of the prepared silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material was tested, and the obtained SEM and TEM images are shown below. Figure 1 , Figure 2 As shown, the composite catalytic material is composed of nanofibers, with silver nanoparticles loaded on the nanofibers of the hydrogel.

[0076] Experimental Example 1

[0077] The X-ray diffraction pattern of the silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material prepared in Example 2 is shown below. Figure 3 As shown, the composite material exhibits characteristic diffraction peaks at 38.1°, 44.3°, 64.4°, and 77.5°, corresponding to the (111), (200), (220), and (311) crystal planes of the face-centered cubic silver nanoparticles, respectively, confirming the formation of silver nanoparticles; the small-angle X-ray scattering spectrum is shown below. Figure 4 As shown, compared with Ag9 / Ba(NO3)2 hydrogel without NaBH4 (Comparative Example 1), the interfacial spacing decreased due to the loading of silver nanoparticles in the hydrogel fibers; X-ray photoelectron spectroscopy is as follows. Figure 5 As shown, the peak of the carboxyl carbon (Oc=O) in the silver nanoparticles shifts towards a direction with higher binding energy, indicating that the carboxyl group is the nucleation site for the formation of Ag NPs on Ag9 / Ba(NO3)2 hydrogel fibers.

[0078] In summary, this invention successfully prepared a silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material with high stability, and the hydrogel carrier plays a good role in dispersing and fixing the silver nanoparticles.

[0079] Example 3

[0080] The preparation method of recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material includes the following steps:

[0081] (1) Preparation of NaBH4 aqueous solution

[0082] Performed according to Example 2.

[0083] (2) Preparation of Ba(NO3)2 aqueous solution

[0084] Performed according to Example 2.

[0085] (3) Preparation of recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials

[0086] Transfer 0.158 mL of Ag9 solution to a centrifuge tube, then add 0.04 mL of NaBH4 solution and 0.102 mL of ultrapure water, and vortex for 30 s to ensure complete mixing. Next, add 0.2 mL of Ba(NO3)2 solution, vortex for 30 s, and let stand for 3 h. Wash the resulting dark brown gel three times with ultrapure water to obtain a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0087] Example 4

[0088] The preparation method of recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material includes the following steps:

[0089] (1) Preparation of NaBH4 aqueous solution

[0090] Accurately weigh NaBH4 powder, add ultrapure water, and vortex to prepare a NaBH4 aqueous solution with a concentration of 250 mM.

[0091] (2) Preparation of Ba(NO3)2 aqueous solution

[0092] Performed according to Example 2.

[0093] (3) Preparation of silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic materials

[0094] Transfer 0.158 mL of Ag9 solution to a centrifuge tube, then add 0.1 mL of NaBH4 solution and 0.042 mL of ultrapure water, and vortex for 30 s to ensure complete mixing. Next, add 0.2 mL of Ba(NO3)2 solution, vortex for 30 s, and let stand for 3 h. Wash the resulting precipitate three times with ultrapure water to obtain the silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material.

[0095] Comparative Example 1

[0096] The preparation method of Ag9 / Ba(NO3)2 hydrogel is as follows:

[0097] (1) Preparation of Ba(NO3)2 aqueous solution

[0098] Performed according to Example 2.

[0099] (2) Preparation of Ag9 / Ba(NO3)2 hydrogel

[0100] Transfer 0.158 mL of Ag9 solution to a centrifuge tube, then add 0.2 mL of Ba(NO3)2 solution and 0.142 mL of ultrapure water. Vortex for 30 seconds to mix completely, and let stand for 3 hours to obtain the Ag9 / Ba(NO3)2 hydrogel. Its SEM and TEM images are shown below. Figure 6 , Figure 7 As shown, the hydrogel is composed of helical nanofibers. Since no NaBH4 solution was added, no particulate matter was loaded on the nanofibers.

[0101] Comparative Example 2

[0102] The preparation method of silver cluster-based silver nanoparticle / metal ion composite catalytic material includes the following steps:

[0103] (1) Preparation of NaBH4 aqueous solution

[0104] Performed according to Example 2.

[0105] (2) Preparation of NaNO3 aqueous solution

[0106] Accurately weigh NaNO3 powder, add ultrapure water, and vortex to prepare a 100mM NaNO3 aqueous solution.

[0107] (3) Preparation of silver cluster-based silver nanoparticle / metal ion composite catalytic materials

[0108] 0.158 mL of Ag9 solution was transferred to a centrifuge tube, followed by the addition of 0.1 mL of NaBH4 solution and 0.042 mL of ultrapure water. The mixture was vortexed for 30 seconds to ensure complete mixing. Subsequently, 0.2 mL of NaNO3 solution was added, the mixture was vortexed for 30 seconds, and allowed to stand for 3 hours to obtain a precipitate. Comparison with the previous example shows that no hydrogel formation was observed when NaNO3 replaced Ba(NO3)2, indicating that NaNO3 cannot coordinate and self-assemble to form a hydrogel.

[0109] Comparative Example 3

[0110] The preparation method of silver cluster-based silver nanoparticle / metal ion composite catalytic material includes the following steps:

[0111] (1) Preparation of NaBH4 aqueous solution

[0112] Performed according to Example 2.

[0113] (2) Preparation of Co(NO3)2 aqueous solution

[0114] Accurately weigh Co(NO3)2 powder, add ultrapure water, and vortex to prepare a 100mM Co(NO3)2 aqueous solution.

[0115] (3) Preparation of silver cluster-based silver nanoparticle / metal ion composite catalytic materials

[0116] 0.158 mL of Ag9 solution was transferred to a centrifuge tube, followed by the addition of 0.1 mL of NaBH4 solution and 0.042 mL of ultrapure water. The mixture was vortexed for 30 seconds to ensure complete mixing. Subsequently, 0.2 mL of Co(NO3)2 solution was added, the mixture was vortexed for 30 seconds, and allowed to stand for 3 hours to obtain a precipitate. Comparison with the previous example shows that no hydrogel formation was observed when Co(NO3)2 replaced Ba(NO3)2, and Co(NO3)2 was also unable to coordinate and self-assemble to form a hydrogel.

[0117] Comparative Example 4

[0118] The preparation method of silver cluster-based silver nanoparticle / metal ion composite catalytic material includes the following steps:

[0119] (1) Preparation of NaBH4 aqueous solution

[0120] Performed according to Example 2.

[0121] (2) Preparation of Fe(NO3)3 aqueous solution

[0122] Accurately weigh Fe(NO3)3 powder, add ultrapure water, and vortex to prepare a Fe(NO3)3 aqueous solution with a concentration of 100 mM.

[0123] (3) Preparation of silver cluster-based silver nanoparticle / metal ion composite catalytic materials

[0124] 0.158 mL of Ag9 solution was transferred to a centrifuge tube, followed by the addition of 0.1 mL of NaBH4 solution and 0.042 mL of ultrapure water. The mixture was vortexed for 30 seconds to ensure complete mixing. Subsequently, 0.2 mL of Fe(NO3)3 solution was added, the mixture was vortexed for 30 seconds, and allowed to stand for 3 hours to obtain a precipitate. Comparison with the previous example shows that no hydrogel formation was observed when Fe(NO3)3 replaced Ba(NO3)2, and Fe(NO3)3 was also unable to coordinate and self-assemble to form a hydrogel.

[0125] In summary, comparing examples 2-4, it can be seen that only Ba... 2+ It can construct supramolecular hydrogels composed of nanofibers with Ag9 through coordination interactions, inter-cluster π···π and CH···π interactions.

[0126] Example 5

[0127] The silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material of Example 1 was used for the catalytic reduction of 4-NP, and the steps are as follows:

[0128] (1) Preparation of 4-NP solution

[0129] Accurately weigh 4-NP powder, add ultrapure water, and vortex to prepare a 60 μM 4-NP aqueous solution.

[0130] (2) Preparation of NaBH4 aqueous solution

[0131] Accurately weigh NaBH4 powder, add ultrapure water, and vortex to prepare a NaBH4 aqueous solution with a concentration of 300 mM.

[0132] (3) 25 mg of the recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material prepared in Example 1 was added to 1 mL of 4-NP solution. Then, 1 mL of NaBH4 solution was injected into it under continuous stirring to start the reduction reaction. The reaction was catalyzed by the well dispersed silver nanoparticles in the hydrogel composite catalytic material.

[0133] At regular intervals, a portion of the reaction mixture was transferred to a cuvette, and the UV-Vis absorption spectrum was recorded. The results are as follows: Figure 8 As shown, the catalytic reaction is monitored, and the catalytic efficiency is high.

[0134] (4) After the catalytic reaction is complete, the recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material is removed from the solution and washed three times with ultrapure water. The operation in step (3) is repeated eight times to test the recyclability characteristics of the silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material. The working curve is shown in Figure [Figure number missing]. Figure 9 As shown, it can be seen that the catalytic efficiency can still be maintained at 80% after 8 working cycles, and the reuse rate is high.

Claims

1. A recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material, wherein the hydrogel composite catalytic material is composed of Ag9 and Ba 2+ Through self-assembly, it exhibits a nanofiber-like microstructure, with silver nanoparticles loaded in situ on the nanofibers of the hydrogel. The recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material was prepared by the following method: Ag9 solution was mixed with sodium borohydride (NaBH4) solution and vortexed. Barium nitrate (Ba(NO3)2) solution was added and vortexed to obtain a mixture. The mixture was allowed to stand to obtain a dark brown gel. After washing, a recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material was obtained. In the mixture, the molar concentration of Ag9 is 1-15 mM, the molar concentration of NaBH4 is 2-50 mM, the molar concentration of Ba(NO3)2 is 20-100 mM, the vortex treatment time is 20-60 seconds, the standing time is 2-10 hours, and the detergent used for washing is ultrapure water. During the hydrogel construction process, the introduction of the reducing agent NaBH4 enables another portion of Ag9 to participate in the reduction, thereby generating silver nanoparticles (Ag NPs), which are then fixed on the nanofibers of the hydrogel.

2. The recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material according to claim 1, characterized in that, Ag9 solution is prepared as follows: silver nitrate (AgNO3) and 4-mercaptobenzoic acid (H2mba) are dispersed in ultrapure water and sonicated. At the same time, ammonia (NH3·H2O) is added to the system to obtain a yellow transparent solution, which is Ag9 solution.

3. The recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material according to claim 2, characterized in that, In the preparation of Ag9 solution, the molar ratio of AgNO3 to water was 1:6 (mmol / mL), the molar ratio of H2mba to water was 1:6 (mmol / mL), the ultrasonic treatment time was 20 min, and after adding ammonia, the mass fraction of ammonia in the system was 25 wt%.

4. The application of the recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material according to claim 1 is as follows: the recyclable silver cluster-based silver nanoparticle / metal ion hydrogel composite catalytic material is added to a 4-nitrophenol (4-NP) solution, and then NaBH4 solution is added to it under continuous stirring to start the catalytic reduction reaction.

5. The application according to claim 4, characterized in that, The volume ratio of the hydrogel composite catalyst to the 4-nitrophenol (4-NP) solution is (10-50):(0.5-5), in mg / mL. The molar concentration of the 4-NP solution is 20-100 μM, the molar concentration of the NaBH4 solution is 250-350 mM, and the volume ratio of the 4-nitrophenol (4-NP) solution to the NaBH4 solution is 1:1.

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