Method for reducing gold and platinum noble metal nanoparticles through silver nanowires

Abstract

The invention discloses a method for reducing gold and platinum noble metal nanoparticles through silver nanowires, which is characterized in that gold and platinum noble metal nanoparticles are replaced on the silver nanowires through simple replacement reaction, and the original micromorphology of the silver nanowires is maintained. By controlling the amount, the adding mode and the adding condition of the added noble metal acid, selective replacement of the silver nanowires can be achieved, and the growth size and distribution of the nanoparticles can be controlled. The prepared AgNWs-Au and AgNWs-Pt with the root nodule-like structures are uniform in form and controllable in growth, the preparation process is simple and rapid, the reproducibility is high, and the obtained sample is stable in property. The development requirement of a material subject on a multifunctional composite material is met to a certain extent, and the composite material has a wide application prospect in the fields of electro-catalysis and sensing.

Description

Technical Field

[0001] The invention relates to the field of nano material preparation, and in particular to a method for reducing gold and platinum noble metal nanoparticles through silver nanowires. Background Art

[0002] Silver nanowires have been widely used in many fields due to their one-dimensional structure and metallic conductivity, and a number of technologies for silver nanowires have also emerged. In the traditional preparation process of silver nanowires, the polyol method can be used to achieve large-scale production because of its lower equipment cost and simpler process compared to the template method, electrochemical deposition method, etc. The polyol method of reducing silver nitrate with ethylene glycol was used to obtain silver nanowires with a good aspect ratio. PVP was used as a morphology control agent to achieve one-dimensional growth of silver nanowires. At the same time, Fe was introduced into it. 3+ , Cu 2+ 、Na + Metal ions also affect the morphology of silver nanowires. At the same time, with the application of silver nanowires in conductive, optical, antimicrobial, biomedical and catalytic industries, pure silver nanowires can no longer meet the material performance requirements of various industries, and new materials and modified materials with better performance are urgently needed.

[0003] Because silver nanowires are not like other organic materials, they usually have rich functional groups such as hydroxyl, amine and ester groups on their surfaces for chemical grafting modification, which makes the composite materials for silver nanowires usually prepared by electrochemical reduction and other methods. The method of using the reduction of noble metal acid replacement proposed in the present invention can effectively simplify the preparation method, and only use the stronger reducibility of elemental silver than noble metals such as gold and platinum to prepare, and then control the growth size and distribution of noble metal particles on silver nanowires by adjusting the concentration of noble metal acid and reaction conditions, so as to achieve controllable synthesis of AgNWs@Au and AgNWs@Pt. Summary of the invention

[0004] In view of this, the present invention provides a method for reducing gold and platinum noble metal nanoparticles by silver nanowires.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for reducing gold and platinum noble metal nanoparticles by silver nanowires comprises the following steps:

[0007] S1: heating PVP, stirring and dissolving it in ethylene glycol to prepare a PVP-ethylene glycol solution;

[0008] S2: dissolving silver nitrate in ethylene glycol under light-proof conditions to prepare a silver nitrate-ethylene glycol solution;

[0009] S3: adding sodium chloride into ethylene glycol and stirring to dissolve to prepare a sodium chloride-ethylene glycol solution;

[0010] S4: Pour the PVP-ethylene glycol solution into a reactor, add the sodium chloride-ethylene glycol solution, heat, inject the silver nitrate-ethylene glycol solution into the reactor, and react in an oil bath and stirring environment;

[0011] S5: After the reaction is completed, the mixture is thoroughly stirred and then centrifuged to purify to obtain pure silver nanowires;

[0012] S6: Add the prepared chloroauric acid solution and chloroplatinic acid solution of fixed concentration into a fixed volume of silver nanowire aqueous dispersion, stir thoroughly and then freeze-dry the sample.

[0013] Preferably, in S1, PVP is polyvinyl pyrrolidone with a molecular weight of 1,600,000, the mass of PVP is 2 g, the concentration of PVP-ethylene glycol solution is 12.5 g / L, and the temperature is heated to 170°C.

[0014] Preferably, in S2, the mass of silver nitrate is 2 g, the volume of ethylene glycol is 40 mL, and the concentration of the silver nitrate-ethylene glycol solution is 50 g / L.

[0015] Preferably, in S3, the mass of sodium chloride is 67.2 mg, the volume of ethylene glycol is 160 ml, and the concentration of the sodium chloride-ethylene glycol solution is 0.42 g / L.

[0016] Preferably, in S4, the volume of the PVP-ethylene glycol solution is 160 ml; the volume of the sodium chloride-ethylene glycol solution is 16 ml; the volume of the silver nitrate-ethylene glycol solution is 40 ml, and the mass ratio of PVP to silver nitrate is 1:1.

[0017] Preferably, in S4, the temperature is heated to 110°C.

[0018] Preferably, in S4, the injection rate of the silver nitrate-ethylene glycol solution is 2 mL / min.

[0019] Preferably, in S4, the reaction is carried out in an oil bath at 110° C. with stirring for 12 h.

[0020] Preferably, the centrifugal purification method described in S5 is performed using a centrifuge at a rotation speed of 4000 r / min for 20 min.

[0021] Preferably, in S6, the concentration of the chloroauric acid solution is 0.4 mg / ml, the concentration of the chloroplatinic acid solution is 2 mg / ml, the stirring speed is 200 r / min, and the stirring time is 2 min.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] (1) The present invention simplifies the experimental steps and can prepare silver nanowires with high purity and good aspect ratio under simpler conditions. The prepared silver nanowires can effectively maintain the reaction activity and can be applied to various production fields;

[0024] (2) The present invention uses a simple replacement reaction to attach precious metal particles such as gold and platinum to the surface of silver nanowires, and prepares AgNWs@Au and AgNWs@Pt nodule-like structures with a certain high specific surface area, which can allow precious metals to replace the original silver, so that the material can grow and reduce in a microscopic manner to achieve controllable morphology, and the reduced nano precious metal particles are attached to the surface of the nanowires. To a certain extent, it meets the development needs of materials science for multifunctional composite materials. It has broad application prospects in the fields of electrocatalysis and sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a result diagram of centrifugal purification and separation of silver nanowires once in a method of reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0026] Figure 2 This is a result diagram of centrifugal purification and separation of silver nanowires twice in a method of reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0027] Figure 3 This is a graph showing the results of three centrifugal purification and separation of silver nanowires in a method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to the present invention;

[0028] Figure 4 This is a graph showing the results of centrifugal purification and separation of silver nanowires four times in a method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to the present invention;

[0029] Figure 5 The AgNWs-Au diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0030] Figure 6 An AgNWs-Au-Pt diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0031] Figure 7 An AgNWs-Pt diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires according to the present invention;

[0032] Figure 8 The AgNWs-Au energy spectrum diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0033] Fig. 9 The AgNWs-Au-Pt energy spectrum diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0034] Fig.10 The AgNWs-Pt spectrum diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0035] Fig.11 The AgNWs@Au diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0036] Fig.12 The AgNWs@Au1 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0037] Fig.13 The AgNWs@Au2 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0038] Fig.14 The AgNWs@Au3 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0039] Fig.15 The AgNWs@Au4 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0040] Fig.16 The AgNWs@Pt diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0041] Fig.17 The AgNWs@Pt1 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0042] Fig.18 The AgNWs@Pt2 diagram of the present invention is a method for reducing gold and platinum noble metal nanoparticles by silver nanowires;

[0043] Fig.19 The AgNWs@Pt3 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0044] Fig. 20 The AgNWs@Pt4 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0045] Fig.21The AgNWs-Au1 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0046] Fig. 22 The AgNWs-Au2 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0047] Fig.23 The AgNWs-Au3 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0048] Fig.24 The AgNWs-Au4 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0049] Fig.25 The AgNWs-Pt1 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0050] Fig.26 The AgNWs-Pt2 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0051] Fig. 27 The AgNWs-Pt3 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0052] Fig.28 The AgNWs-Pt4 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0053] Fig.29 The AgNWs-Pt3 (×10000) diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0054] Fig.30 The AgNWs-Pt4 (×10000) diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0055] Fig.31 The AgNWs@Au-0.5 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0056] Fig.32 The AgNWs@Au-1 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0057] Fig.33 The AgNWs@Au-2 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0058] Fig.34 The AgNWs@Au-3 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0059] Fig.35 The AgNWs@Au-5 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0060] Fig.36 The AgNWs@Au-6 diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0061] Fig.37 This is a AgNWs@Au-3 (×10000) diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0062] Fig.38 This is a AgNWs@Au-6 (×10000) diagram of a method for reducing gold and platinum noble metal nanoparticles by silver nanowires of the present invention;

[0063] Fig.39 This is a picture of AgNWs (×2000) obtained by filtering through a metal filter in a method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to the present invention;

[0064] Fig.40 This is a picture of AgNWs (×5000) obtained by metal filter filtration in a method of reducing gold and platinum precious metal nanoparticles by silver nanowires in the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] Example 1

[0067] This example is a simple method for preparing purified silver nanowires. Figure 1-4As shown, 2g PVP (molecular weight of 1600000) was heated to 170°C and stirred and dissolved in 160ml ethylene glycol to prepare a 12.5g / L PVP-ethylene glycol solution, 2g silver nitrate was dissolved in 40ml ethylene glycol under light-proof conditions to prepare a 50g / L silver nitrate-ethylene glycol solution, 67.2mg sodium chloride was placed in 160ml ethylene glycol and stirred and dissolved to prepare a 0.42g / L sodium chloride-ethylene glycol solution, 160ml PVP-ethylene glycol solution was poured into a reactor, 16ml sodium chloride-ethylene glycol solution was added, heating was turned on and heated to 110°C, 40ml silver nitrate-ethylene glycol solution was injected into the reactor at a rate of 2mL / min, the mass ratio of PVP to silver nitrate was 1:1, and the reaction was carried out in an oil bath at 110°C and stirred for 12h. After the reaction was completed, a portion of the silver nanowires was taken out and filtered using a 1600-mesh metal filter to obtain silver nanowires. At the same time, the other part was added with ethanol and mixed, and then centrifuged to obtain purified silver nanowires.

[0068] Example 2

[0069] This example is a substitution reaction of excess chloroauric acid and chloroplatinic acid on silver nanowires. Figure 5-10 As shown, after the last centrifugation, water / ethanol was added to the purified silver nanowires to obtain two different dispersion systems of silver nanowires, both with a concentration of 10 mg / ml. Excess chloroauric acid and chloroplatinic acid aqueous solutions were added to the water-dispersed silver nanowires, with a concentration of 0.4 mg / ml of chloroauric acid and 2 mg / ml of chloroplatinic acid. In addition, chloroplatinic acid and chloroauric acid were added in sequence. Three different aqueous dispersions were prepared at the same time, namely AgNWs-Au, AgNWs-Pt and AgNWs-Au-Pt. The samples were freeze-dried and the sample morphology was observed by scanning electron microscopy.

[0070] Example 3

[0071] This embodiment is a substitution reaction of silver nanowires with a controlled amount of noble metal acid. Figure 11-20 As shown, take 10ml of silver nanowire aqueous dispersion in a small beaker and keep the reaction condition at room temperature and stirring. Add 3.5ml of chloroauric acid solution each time, and the concentration is the same as the previously configured solution concentration. The amount of chloroauric acid added is 3.5ml, 7ml, 10.5ml and 14ml respectively, and four reaction samples of AgNWs@Au1, AgNWs@Au2, AgNWs@Au3 and AgNWs@Au4 are obtained respectively. After each addition of chloroauric acid solution, stir thoroughly to complete the reaction.

[0072] Following the same method, chloroplatinic acid was added to obtain AgNWs@Pt1, AgNWs@Pt2, AgNWs@Pt3 and AgNWs@Pt4, respectively. After each addition of chloroplatinic acid solution, the reaction should be fully stirred to complete. After freeze-drying the sample, the sample morphology was observed by scanning electron microscopy.

[0073] Example 4

[0074] This example is a replacement reaction of a fixed silver nanowire coating with a noble metal acid. Figure 21-30 As shown, 3 ml of silver nanowire-ethanol dispersion was added dropwise to a glass slide, and excess ethanol was volatilized under natural ventilation to obtain a silver nanowire film. The obtained glass slide carrying silver nanowires was placed in a diluted chloroauric acid solution, which was obtained by diluting the original concentration of chloroauric acid solution ten times. The glass slide should be completely immersed in the chloroauric acid solution, and the reaction time was 30 seconds. After the reaction, the glass slide was cleaned with deionized water and dried under natural air drying conditions. The progress of the reaction was controlled by controlling the concentration of the immersed chloroauric acid. Taking 3 ml of chloroauric acid solution as an example, it was 30 ml after dilution. Four gradients of 3 ml, 4 ml, 5 ml, and 6 ml were set to characterize the replacement effect of silver nanowires on gold, and samples AgNWs-Au1, AgNWs-Au2, AgNWs-Au3, and AgNWs-Au4 were obtained.

[0075] According to the same method, the glass slide was immersed in the diluted chloroplatinic acid solution to ensure that the glass slide was completely immersed in the chloroplatinic acid solution. The reaction time was 2 minutes. After the reaction, the glass slide was cleaned with deionized water and dried under natural air drying conditions. Four gradients of 3ml, 4ml, 5ml, and 6ml were set to characterize the replacement effect of silver nanowires on platinum, and samples AgNWs-Pt1, AgNWs-Pt2, AgNWs-Pt3, and AgNWs-Pt4 were obtained. After the samples were freeze-dried, the sample morphology was observed by scanning electron microscopy.

[0076] Example 5

[0077] This embodiment is a replacement reaction of silver nanowires with noble metal acid under controlled conditions. Figure 31-38As shown, 100 mg PVP was fully dissolved in water, 10 ml of silver nanowire aqueous dispersion was added to the aqueous solution of PVP, the reaction conditions were kept stirring, and the reaction temperature was 70-80 ° C. Different amounts of chloroauric acid were added, and the concentration was the same as the previously configured solution concentration. The amount of chloroauric acid added was 0.5 ml, 1 ml, 2 ml, 3 ml, 5 ml and 6 ml, respectively, and six reaction samples of AgNWs@Au-0.5, AgNWs@Au-1, AgNWs@Au2, AgNWs@Au3, AgNWs@Au5, and AgNWs@Au6 were obtained respectively. After each addition of chloroauric acid solution, the reaction should be fully stirred to complete the reaction. After the sample was freeze-dried, the sample morphology was observed by scanning electron microscopy.

[0078] Among them, the silver nanowires after being filtered through the metal filter are shown in the figure below. Figure 39-40 shown.

[0079] In Experimental Example 1, as the number of centrifugal purifications increases, the shorter silver nanowires and silver nanoparticles in the sample are gradually removed, but at the same time, some longer silver nanowires will agglomerate and entangle together, thus being unable to disperse and causing losses. Therefore, the speed of centrifugal purification can be adjusted to below 4000r / min, while the centrifugal time is controlled to be less than 20min, and the number of centrifugal purifications is controlled to be less than 4 times, so as to avoid the long silver nanowires from agglomerating into agglomerates during the purification process.

[0080] In Experimental Example 2, under the displacement of excess chloroauric acid and chloroplatinic acid, the original silver was oxidized, and the gold and platinum in the chloroauric acid and chloroplatinic acid were reduced to form single gold nanoparticles and single platinum nanoparticles. The reaction products are no longer distributed in the form of nanowires.

[0081] In Experimental Example 3, as the amount of chloroauric acid added increases, the generation of gold nanoparticles gradually increases. At the beginning, the gold nanoparticles mainly grow at the intertwined contact points of the silver nanowires and grow along the structure of the silver nanowires. As the amount of chloroauric acid added increases, the gold nanoparticles begin to increase and further replace and consume the nearby silver. This eventually leads to the breakage and thinning of the silver nanowires. This is more obvious in the reaction with chloroplatinic acid. The increase in the amount of chloroplatinic acid added causes the original silver nanowires to be consumed rapidly, but the platinum generated at the same time gathers near the silver nanowires as a carrier, thereby generating platinum nanoparticles distributed in a linear shape. At the same time, as the amount added increases, the average size of the noble metal particles obtained by replacement gradually increases, showing a trend of growth toward both ends, but at the same time, due to the influence of factors such as the lack of morphological control, they cannot grow linearly.

[0082] In Experimental Example 4, the silver nanowires obtained by drying and fixing the silver nanowires on the glass slide by immersion showed obvious fractures and bends, and the immersion made it impossible for the silver nanowires to be fully mixed with the chloroauric acid solution, which resulted in more concentrated reaction sites and easier aggregation of the reaction products.

[0083] In Experimental Example 5, the reaction of chloroauric acid on the silver nanowires can be controlled by adding a morphology control agent, thereby avoiding the aggregation of over-reacted nanoparticles. Under the control of PVP, gold nanoparticles can grow along the silver nanowires and grow a nodule-like structure. The gold nanoparticles are uniformly attached to the silver nanowires as nodes. The addition of the control agent inhibits the replacement reaction to a certain extent. The problem of controlling the noble metal nanoparticles on the silver nanowires is transformed into the problem of wrapping the morphology control agent on the silver nanowires. The growth of the "nodule" is controlled by the outer "protective shell". By controlling the amount of the morphology control agent, the addition method and the addition conditions, a multi-stage controllable replacement reaction can be achieved.

[0084] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for reducing gold and platinum noble metal nanoparticles by silver nanowires, characterized in that: The following steps are involved: S1: heating PVP, stirring and dissolving it in ethylene glycol to prepare a PVP-ethylene glycol solution; S2: dissolving silver nitrate in ethylene glycol under light-proof conditions to prepare a silver nitrate-ethylene glycol solution; S3: adding sodium chloride into ethylene glycol and stirring to dissolve to prepare a sodium chloride-ethylene glycol solution; S4: Pour the PVP-ethylene glycol solution into a reactor, add the sodium chloride-ethylene glycol solution, heat, inject the silver nitrate-ethylene glycol solution into the reactor, and react in an oil bath and stirring environment; S5: After the reaction is completed, the mixture is thoroughly stirred and then centrifuged to purify to obtain pure silver nanowires; S6: Add the prepared chloroauric acid solution and chloroplatinic acid solution of fixed concentration into a fixed volume of silver nanowire aqueous dispersion, stir thoroughly and then freeze-dry the sample.

2. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In the S1, PVP is polyvinyl pyrrolidone with a molecular weight of 1,600,000, the mass of PVP is 2 g, the concentration of the PVP-ethylene glycol solution is 12.5 g / L, and the temperature is heated to 170°C.

3. The method for reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In S2, the mass of silver nitrate is 2 g, the volume of ethylene glycol is 40 mL, and the concentration of the silver nitrate-ethylene glycol solution is 50 g / L.

4. The method for reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In S3, the mass of sodium chloride is 67.2 mg, the volume of ethylene glycol is 160 ml, and the concentration of the sodium chloride-ethylene glycol solution is 0.42 g / L.

5. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In S4, the volume of the PVP-ethylene glycol solution is 160 ml; the volume of the sodium chloride-ethylene glycol solution is 16 ml; the volume of the silver nitrate-ethylene glycol solution is 40 ml, and the mass ratio of PVP to silver nitrate is 1:

1.

6. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In S4, the temperature is heated to 110°C.

7. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In the step S4, the injection rate of the silver nitrate-ethylene glycol solution is 2 mL / min.

8. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In the S4, the reaction was carried out in a 110° C. oil bath with stirring for 12 h.

9. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: The centrifugal purification method described in S5 is operated using a centrifuge at a speed of 4000 r / min for 20 min.

10. The method of reducing gold and platinum noble metal nanoparticles by silver nanowires according to claim 1, characterized in that: In S6, the fixed concentrations of the chloroauric acid solution and the chloroplatinic acid solution are 0.4 mg / ml and 2 mg / ml respectively, the stirring speed is 200 r / min, and the stirring time is 2 min.

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