CN106670495A - Preparation method of network-state Ag-Au-Pd trimetal porous material - Google Patents

Abstract

The invention proposes a method for preparing a networked Ag-Au-Pd trimetallic porous material. Under appropriate conditions, the spongy silver nanostructure surface suspended in the mixed solution of chloroauric acid and potassium chloropalladate undergoes rapid and partial replacement, and the generated gold and palladium nanoparticles are uniformly distributed and form a rough surface. By changing the concentration of the mixed solution, the surface roughness and metal atomic ratio can be effectively regulated. When the total content of noble metals Au and Pd is very low (the sum of the atomic percentages is less than 10%), the Ag-Au-Pd trimetallic porous material exhibits ultra-high SERS detection sensitivity for rhodamine B molecules adsorbed on its surface, It has very high catalytic activity to the reaction system of reducing 4-nitrophenol with sodium borohydride. The preparation method proposed by the invention is fast, low in cost and easy to scale up, and provides an effective way for the preparation of multi-metal porous nanomaterials.

Description

A kind of preparation method of network Ag-Au-Pd trimetallic porous material

technical field

The present invention relates to a method for preparing a networked Ag-Au-Pd trimetallic porous material with ultra-high SERS sensitivity and ultra-high catalytic activity. In particular, the method is based on a low-cost, easy-to-scale replacement reaction, and the reaction conditions Gentle, repeatable, and easy to control.

Background technique

Noble metal (gold, silver, platinum, palladium) nanomaterials have attracted great attention due to their broad application prospects in catalysis, biosensing, optical devices, and molecular detection (such as surface-enhanced Raman scattering (SERS)). Its performance mainly depends on the shape and size (such as pore size) of the material. Metal nanoparticles exhibit extremely high chemical reactivity due to the size effect, but they are prone to aggregation and difficult to reuse. Materials with submicron-scale apparent scale and three-dimensional network nanopore structure can not only avoid these shortcomings of nanoparticles, but also have more reactive areas. In particular, its three-dimensional pore structure can provide more SERS "hot spots" and catalytically active sites in the third dimension.

Multimetallic nanomaterials combine the intermetallic synergistic effect and the interfacial effect of electron transfer between metals, especially, the properties can be tuned by the ratio of metals. A large number of studies on bimetallic nanostructure materials at home and abroad have shown that the specific surface area and metal interface play a decisive role in the improvement of catalytic activity. However, there are still few reports on the network-like Ag-Au-Pd trimetallic porous nanomaterials.

The invention proposes a method for preparing a networked Ag-Au-Pd trimetallic porous material. Under appropriate conditions, the spongy silver nanostructure surface suspended in the mixed solution of chloroauric acid and potassium chloropalladate undergoes rapid and partial replacement, and the generated gold and palladium nanoparticles are uniformly distributed and form a rough surface. In the case of very low total content of noble metals Au and Pd (less than 10% atomic percent), the Ag-Au-Pd trimetallic porous material exhibited ultra-high SERS detection sensitivity for rhodamine B molecules adsorbed on its surface, and the The reaction system of reducing 4-nitrophenol with sodium borohydride has very high catalytic activity.

Contents of the invention

The purpose of the present invention: to propose a preparation method of a networked Ag-Au-Pd trimetallic porous material, and introduce its application in the field of SERS molecular detection and catalysis. The preparation method is low in cost and mild in reaction (it only needs to be heated in a water bath). By simultaneously controlling the concentration of chloroauric acid and potassium chloropalladate, the surface roughness and bimetallic interface of the product can be regulated, thereby achieving ultra-high SERS sensitivity and high catalytic activity. The preparation method will have good application prospects in the field of preparation of multifunctional porous materials.

The technical scheme of the present invention is: prepare sodium borohydride and silver nitrate solution of certain concentration, take 25mL sodium borohydride aqueous solution, add 5mL glycerol; Under vigorous stirring at room temperature, add 5mL silver nitrate solution rapidly, wait to react after 5 minutes , the suspension was filtered and washed with deionized water, and freeze-dried for 6-10 hours to obtain a spongy silver nanostructure; then, 3-10 mg of the dried spongy silver nanostructure was added to the In the mixed solution composed of potassium, the solvent is a mixed solution of deionized water and ethylene glycol. After reacting for 10 minutes at a constant temperature of 50-70°C under vigorous stirring, the suspended matter is taken out, soaked in saturated saline, and then After repeated washing with deionized water, the product was dried in an oven.

When preparing the sponge-like silver nanostructure, the optimum concentration ranges of sodium borohydride and silver nitrate aqueous solution are 0.05-0.2M and 0.02-0.04M respectively.

Take 25mL of sodium borohydride solution, add 5mL of glycerin, and quickly add 5mL of silver nitrate solution under vigorous stirring at room temperature. After reacting for 5 minutes, filter the suspension and wash it with deionized water, freeze-dry for 6-10 hours to obtain a sponge silver nanostructures.

The solution and the sponge-like silver nanostructure can be configured at room temperature or slightly higher than room temperature.

In the process of preparing network-like Ag-Au-Pd tri-metallic porous material by displacement reaction, 3-10 mg of the dry sponge-like silver nanostructure is added to a mixed solution consisting of 1-4 mL of chloroauric acid and potassium chloropalladate, and the solvent It is a mixture of deionized water and ethylene glycol, and the volume ratio of the two is 1:10 to 1:5.

In the mixed solution, the concentration of chloroauric acid ranges from 11.58×10 ^-7 M to 20.58×10 ^-7 M, and the concentration of potassium chloropalladate ranges from 2.57×10 ^-7 M to 11.58×10 ^-7 M.

Under vigorous stirring, react at a constant temperature of 50-70°C for 10 minutes.

The reacted product needs to be soaked in saturated saline to remove the AgCl by-product generated on the surface.

Compared with other methods, the sponge-like silver nanostructure synthesized by the wet chemical method in the first step of the present invention does not require any additives or templates; the second step of displacement reaction only needs to be carried out at a lower temperature (50-70° C.) for continuous After 10 minutes, a network-like Ag-Au-Pd trimetallic porous material can be obtained. The preparation method proposed by the invention is fast, low in cost and easy to be scaled up.

Beneficial effects of the present invention:

(1) A method for preparing a network-like Ag-Au-Pd trimetallic porous material with ultra-high SERS sensitivity and high catalytic activity was proposed, which was successfully obtained by a displacement reaction under heating in a water bath at 60°C.

(2) Compared with other methods, this preparation method also has the following unique advantages:

①The preparation process does not require any additives and templates, and the operation is simple, fast and low in cost;

② Good controllability, the product size and metal atomic ratio can be controlled by adjusting the concentration of chloroauric acid and potassium chloropalladate;

③Low cost and good prospects for industrial application;

④ It has strong applicability and can be extended to other multifunctional nanoporous materials.

Description of drawings

Figure 1 is the XRD diffraction pattern of (a) sponge-like nano-silver and Ag-Au-Pd; (b) the FESEM image of sponge-like nano-silver and (c) trimetallic nanostructure, the inset is before and after the replacement reaction of a single silver connecting line picture of.

Fig. 2 is the EDX and surface scanning diagram (inset) of the Ag-Au-Pd tri-metallic porous material with different components network as shown in Fig. 1 . (a) Ag _91.8 Au _4.5 Pd _3.7 ; (b) Ag _91.3 Au _5.5 Pd _3.2 ; (c) Ag ₉₀ Au _7.8 Pd _2.2 ; (d) Ag _89.1 Au _9.1 Pd _1.8 ; (e) Ag _88.9 Au _9.4 Pd _1.7 .

Figure 3 is (a) sponge-like silver nanostructure; (b) Ag _91.8 Au _4.5 Pd _3.7 ; (c) Ag ₉₀ Au _7.8 Pd _2.2 ; (d) Ag _89.1 Au _9.1 Pd _1.8 ; (e) Ag _88.9 Au _9.4 Pd _1.7 SERS spectrum of 10 ^-6 M rhodamine B molecule adsorbed on the surface.

Figure 4 is the color change of (a) 4-NP solution before and after the catalytic reaction; under the catalysis of 0.5 mg (b) network-like Ag ₉₀ Au _7.8 Pd _2.2 nanostructure and (c) sponge-like silver nanostructure, sodium borohydride reduction UV-Vis absorption spectrum of 4-NP solution, inset shows the reaction rate.

Fig. 5 is (a) the relationship between the logarithm of the absorbance at 400 nm and the reaction time of different components of Ag-Au-Pd porous materials in the 4-NP catalytic reaction; (b) the relationship between the gold/palladium atomic ratio and the reaction rate.

detailed description

The present invention adopts the replacement reaction to successfully prepare the network-like Ag-Au-Pd tri-metallic porous material, and the specific implementation method is as follows:

Example 1

Preparation of network-like Ag-Au-Pd tri-metallic porous material: first prepare sponge-like silver nanostructure: configure a mixed solution of NaBH ₄ water/glycerol with a concentration of 0.1M (5mL glycerol is mixed with 25mL deionized water) , under vigorous stirring at room temperature, 5 mL of AgNO ₃ aqueous solution with a concentration of 0.025 M was quickly added, and the stirring was continued until the solution became clear. The black suspension was washed with deionized water and freeze-dried for 6 hours. Then, 5 mg of dry spongy silver nanostructures were added to a mixed solution consisting of 2 mL of chloroauric acid and potassium chloropalladate, and the solvent was a mixed solution of deionized water and ethylene glycol (the volume ratio of the two was 1:8 ), the concentration of chloroauric acid was 11.58×10 ^-7 M, and the concentration of potassium chloropalladate was 11.58×10 ^-7 M. After vigorously stirring and reacting at a constant temperature of 60°C for 10 minutes, the suspended matter was taken out, soaked in saturated saline, washed repeatedly with deionized water, and finally dried in an oven at 50°C.

Fig. 1(a) is a comparison chart of the XRD peaks of the sponge-like silver nanostructure obtained in Example 1 before and after the displacement reaction occurs. It can be found that the peak widths of the four crystal planes are significantly broadened after the catalytic reaction occurs, and the peak ratio of the (200) crystal plane to the (111) crystal plane peak decreases. Figure 1(b) and (c) are the SEM images before and after the displacement reaction, respectively, and it can be seen that the porous nanostructure has not changed significantly. However, as can be seen from the TEM image in the inset, particles with a diameter of about 5 nm appeared on the surface of the silver nanowires constituting the network structure. Figure 2(a) is the EDS spectrum of the product obtained in Example 1. The element surface scan in the inset shows that gold and palladium elements are evenly coated on the surface of the porous silver. It can be concluded that the metal atomic ratio is Ag:Au:Pd=91.8:4.5:3.7. Therefore, this sample was named Ag _91.8 Au _4.5 Pd _3.7 .

Example 2

The concentration of chloroauric acid was changed to 13.89×10 ^-7 M, the concentration of potassium chloropalladate to 9.26×10 ^-7 M, and other conditions were the same as in Example 1.

Figure 2(b) is the EDS spectrum of the product obtained in Example 2. It can be concluded that the metal atoms are Ag:Au:Pd=91.3:5.5:3.2. Therefore, this sample was named Ag _91.3 Au _5.5 Pd _3.2 .

Example 3

Change the concentration of chloroauric acid to 18.52×10 ^-7 M, the concentration of potassium chloropalladate to 4.63×10 ^-7 M, and other conditions are the same as in Example 1.

Figure 2(c) is the EDS spectrum of the product obtained in Example 3. It can be concluded that the metal atomic ratio is Ag:Au:Pd=91.3:7.8:2.2. Therefore, this sample was named Ag ₉₀ Au _7.8 Pd _2.2 .

Example 4

Change the concentration of chloroauric acid to 19.84×10 ^-7 M, the concentration of potassium chloropalladate to 3.31×10 ^-7 M, and other conditions are the same as in Example 1.

Figure 2(d) is the EDS spectrum of the product obtained in Example 4. It can be concluded that the metal atomic ratio is Ag:Au:Pd=89.1:9.1:1.8. Therefore, this sample was named Ag _89.1 Au _9.1 Pd _1.8 .

Example 5

Change the concentration of chloroauric acid to 20.58×10-7M, the concentration of potassium chloropalladate to 2.57×10-7M, and other conditions are the same as in Example 1.

Figure 2(e) is the EDS spectrum of the product obtained in Example 5. It can be concluded that the metal atomic ratio is Ag:Au:Pd=89.1:9.4:1.7. Therefore, the sample was named Ag _88.9 Au _9.4 Pd _1.7 .

Example 6

When preparing samples for SERS molecular detection, take 2.0 mg of dry nanomaterials and place them on a glass slide, then add 50 microliters of 10 ⁻⁶ M rhodamine B solution dropwise, and dry them in the air. Fig. 3 is a SERS detection spectrum of 10 ^-6 M rhodamine B molecules adsorbed on the surface of the sponge-like silver nanostructure and Ag-Au-Pd trimetallic porous material with different components network. It can be seen that all the Ag-Au-Pd trimetallic porous materials exhibit ultra-high SERS detection sensitivity for rhodamine B molecules adsorbed on their surfaces, and the performance is better than that of the sponge-like silver nanostructure (curve a). In particular, the sample Ag _89.1 Au _9.1 Pd _1.8 has the best SERS detection sensitivity (curve d).

Example 7

When testing the catalytic performance of the sample, take 0.2mL of 0.1M sodium borohydride solution and add it to 2.8mL of 4×10 ^-5 M 4-nitrophenol solution, then add 0.5mg of catalyst and immediately carry out the ultraviolet absorption spectrum test. It can be observed from Figure 4(a) that after adding 0.5 mg of network-like Ag ₉₀ Au _7.8 Pd _2.2 , the 4-nitrophenol solution quickly faded within 3.5 minutes, indicating that 4-nitrophenol had been completely reduced. The maximum value of the absorption peak of 4-nitrophenol solution is at the wavelength of 400nm. From the continuous decrease of the absorption intensity at 400nm and the continuous increase of the absorption intensity at 295nm, it can be known that 4-nitrophenol has been reduced to 4-aminophenol by sodium borohydride , the inset is the catalytic rate. Figure 4(b) is the ultraviolet-visible absorption spectrum of sodium borohydride reduction 4-nitrophenol solution during the catalytic reaction. It can be concluded from the linear relationship diagram in the illustration that the catalytic rate is 1.23×10 ^-2 /s. Its catalytic rate is significantly higher than that of the sponge-like silver nanostructures under the same test conditions (as shown in Figure 4c).

Figure 5(a) is the relationship between the logarithm of the absorbance at 400nm and the reaction time of Ag-Au-Pd porous materials with different components in the catalytic reaction of 4-NP. It can be seen that the network Ag ₉₀ Au _7.8 Pd _2.2 The highest activity. This performance optimization result is consistent with the conclusion of the curve of the reaction rate constant versus Au/Pd atomic ratio in Fig. 5(b).

Claims (7)

1. a kind of preparation method of the metal polyporous materials of network-like Ag-Au-Pd tri-, is characterized in that, prepare certain density sodium borohydride and silver nitrate solution, take 25mL sodium borohydride aqueous solutions, add 5mL glycerine；In the case where room temperature is stirred vigorously, 5mL silver nitrate solutiones are rapidly joined, question response filtered suspension and deionized water cleaning after 5 minutes, and freeze-drying 6-10 hours obtain sponge silver nanostructured；Then, the sponge silver nanostructured that 3-10mg is dried is added in the mixed solution being made up of 1-4mL gold chlorides and potassium chloropalladate, solvent is the mixed liquor of deionized water and ethylene glycol, with vigorous stirring, after reacting 10 minutes under 50-70 DEG C of constant temperature, suspension is taken out, be put into saturated aqueous common salt and soak, again deionized water is cleaned repeatedly, finally product is put into baking oven and is dried.

2. preparation method according to claim 1, it is characterised in that when preparing sponge silver nanostructured, sodium borohydride is respectively 0.05-0.2M and 0.02-0.04M with the concentration of silver nitrate aqueous solution.

3. preparation method according to claim 1, it is characterized in that, take 25mL sodium borohydride solutions, add 5mL glycerine, in the case where room temperature is stirred vigorously, 5mL silver nitrate solutiones are rapidly joined, question response is after 5 minutes, suspension is filtered and deionized water cleaning, freeze-drying 6-10 hours obtain sponge silver nanostructured.

4. preparation method according to claim 1, it is characterised in that aliquot replacement reaction is carried out by sponge silver nanostructured and gold chloride, potassium chloropalladate mixed solution and prepares the metal polyporous materials of network-like Ag-Au-Pd tri-.

5. the preparation method of the metal polyporous materials of network-like Ag-Au-Pd tri- according to claim 1, it is characterized in that, the sponge silver nanostructured that 3-10mg is dried is added in the mixed solution being made up of 1-4mL gold chlorides and potassium chloropalladate, wherein, gold chloride concentration range is 11.58 × 10^-7M～20.58 × 10^-7M, potassium chloropalladate concentration range is 2.57 × 10^-7M～11.58 × 10^-7M。

6. preparation method according to claim 1, it is characterised in that for deionized water and the mixed liquor of ethylene glycol, both volume ratios are 1: 10～1: 5 to the solvent that configuration gold chloride is adopted with potassium chloropalladate mixed solution.

7. preparation method according to claim 1, it is characterised in that with vigorous stirring, after reacting 10 minutes under 50-70 DEG C of constant temperature, suspension is taken out, be put into saturated aqueous common salt and soak, again deionized water is cleaned repeatedly, finally product is put into baking oven and is dried.