Au nanoparticles loaded with bimetals for photocatalysis and their preparation method

Abstract

This invention discloses Au nanoparticles loaded with bimetallic compounds for photocatalysis and their preparation method, belonging to the field of photocatalytic materials technology. Preparation steps: S1: Tetrachloroauric acid, quaternary ammonium salt, and citric acid are added to a sodium borohydride solution and stirred at 25-120℃ for 1-3 hours to obtain solution A; solution B is prepared containing quaternary ammonium salt, tetrachloroauric acid, ascorbic acid, silver nitrate, and hydrochloric acid; solutions A and B are mixed and stirred at 25-50℃ for 1-15 hours to obtain Au nanoparticles; S2: Solution C is prepared containing quaternary ammonium salt, a first metal source, and ascorbic acid; solution D is prepared containing quaternary ammonium salt, a second metal source, NaOH, and ascorbic acid; Au nanoparticles are mixed with solution C and reacted at 40-80℃ for 1-5 hours; then the supernatant is removed by centrifugation, and solution D is added again, reacting for 1-5 hours to obtain Au nanoparticles loaded with bimetallic compounds. This invention enables controllable nanoparticle structure and allows for metal loading at different sites by adjusting synthesis parameters.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, and in particular to Au nanoparticles loaded with bimetallic materials for photocatalysis and their preparation method. Background Technology

[0002] Solar energy, as a clean, renewable, and safe energy source, is considered an ideal alternative to traditional fossil fuels and a driver of green industrial transformation. Photocatalysis is a typical pathway for utilizing solar energy, effectively converting solar energy into chemical energy, which is of great significance for promoting industrial chemical transformation. Among numerous photocatalytic nanomaterials, noble metal nanoparticles have attracted much attention due to their unique localized surface plasmon resonance (LSPR) properties. Benefiting from controllable LSPR properties, noble metal nanoparticles can convert photon energy from ultraviolet, visible, and near-infrared light regions, showing great potential in the field of efficient solar energy utilization.

[0003] When LSPR is excited, nanoparticles can capture photon energy, forming a localized enhanced electromagnetic field and inducing the generation of hot carriers. These hot carriers are ultimately dissipated as heat through coupling with the phonon modes of the metal nanoparticles. The enhanced electromagnetic field, hot carriers, and photothermal effects described above can all be used to drive chemical transformations on metal surfaces, demonstrating broad application prospects.

[0004] Au nanoparticles have been extensively studied due to their chemical stability, biocompatibility, and unique plasmonic properties. However, as a precious metal, the large-scale application of Au nanoparticles is limited by their high cost and resource scarcity. Furthermore, Au nanoparticles face key drawbacks in photocatalytic applications, including relatively low LSPR efficiency (needing improvement), complex and uncontrollable structural size, potential promotion of side reactions, and masking of surface active sites. Summary of the Invention To address the problems of uncontrollable structural size, relatively insufficient LSPR efficiency, and masking of surface active sites in the photocatalytic application of Au nanoparticles, this invention provides Au nanoparticles loaded with bimetals for photocatalysis. The present invention provides a method for preparing Au nanoparticles supported on bimetals for photocatalysis, comprising the following steps: S1. Add tetrachloroauric acid, quaternary ammonium salt and citric acid to sodium borohydride solution and stir at 25-120℃ for 1-3h to obtain solution A; prepare solution B containing quaternary ammonium salt, tetrachloroauric acid, ascorbic acid, silver nitrate and hydrochloric acid; mix solution A and solution B and stir at 25-50℃ for 1-15h, then centrifuge to obtain Au nanoparticles, disperse the Au nanoparticles in water to obtain Au nanoparticle dispersion.

[0005] In step S1, Au nanoparticles of different shapes are prepared by adjusting the amounts of citric acid, silver nitrate and hydrochloric acid; when the amounts of citric acid, silver nitrate and hydrochloric acid are all 0, spherical Au nanoparticles are prepared; when the amounts of citric acid, silver nitrate and hydrochloric acid are not equal to 0, bipyramidal Au nanoparticles are prepared.

[0006] The quaternary ammonium salt is a long-chain alkyl cationic quaternary ammonium salt, preferably hexadecyltrimethylammonium chloride or hexadecyltrimethylammonium bromide.

[0007] S2. Prepare solution C containing quaternary ammonium salt, first metal source, and ascorbic acid; prepare solution D containing quaternary ammonium salt, second metal source, NaOH, and ascorbic acid; centrifuge the Au nanoparticle dispersion to remove the supernatant, add solution C, mix well, and react in a water bath at 40-80 ℃ for 1-5 h; after the reaction is complete, centrifuge to remove the supernatant, add solution D again, mix well, and react at room temperature for 1-5 h, finally centrifuge to obtain Au nanoparticles loaded with bimetallic compounds.

[0008] The first metal source and the second metal source are salts of different metals.

[0009] In step S2, by adjusting the amount of the first metal source, the loading position of the bimetal on the surface of Au nanoparticles can be controlled, thereby achieving bimetal loading at different positions on the surface of Au nanoparticles.

[0010] Preferably, the first metal source is silver nitrate.

[0011] Preferably, the second metal source is chloropalladium acid.

[0012] In the above preparation method, spherical or bipyramidal Au nanoparticles can be prepared in step S1. Furthermore, by controlling the amount of silver nitrate in step S2, bimetallic compounds can be loaded onto one end of the spherical Au nanoparticles, or onto the edges or tips of the bipyramidal Au nanoparticles. That is, the structure of the nanoparticle catalyst can be controlled by controlling the preparation parameters. The obtained bimetallic Au nanoparticles include an Au nanoparticle template and two other metal nanoparticles loaded at different locations on the template.

[0013] Compared with the prior art, the advantages of the present invention are: (1) The method of the present invention can achieve controllable structure of Au nanoparticles, and can also load bimetals on different parts of the surface of Au nanoparticles by controlling the preparation parameters.

[0014] (2) The Au nanoparticles loaded with bimetals prepared in this invention exhibit excellent catalytic effects in the photocatalytic degradation of organic pollutants, and the catalytic reaction rate is significantly better than that of pure Au nanoparticles or Au nanoparticles loaded with a single metal.

[0015] (3) The preparation method of the present invention is simple and highly reproducible, the nanoparticles are highly stable, and the application range is wide. It can be extended to the synthesis of more bimetallic nanoparticles at the nanoscale and has strong stability.

[0016] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the Au nanospheres prepared in Example 1. Figure 2 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of the Au nanospheres loaded with Ag / Pd bimetals prepared in Example 1. (a) is the TEM image, and (b) is the EDX elemental distribution map.

[0018] Figure 3 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of Au nanobipyramidal particles loaded with Ag / Pd bimetals obtained in Example 2. (a) is the TEM image, and (b) is the EDX elemental distribution map.

[0019] Figure 4 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of Au nanobipyramidal particles loaded with single metal Ag. (a) is the TEM image, and (b) is the EDX elemental distribution map.

[0020] Figure 5 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of the Au nanobipyramidal particles loaded with Ag / Pd bimetal prepared in Example 3. (a) is the TEM image, and (b) is the EDX elemental distribution map. Detailed Implementation

[0021] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] Example 1 A method for preparing bimetallic Au nanoparticles for photocatalysis is as follows: (1) 0.25 mL of 10 mM tetrachloroauric acid solution and 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution were added to 0.60 mL of 10 mM sodium borohydride solution and stirred at 30 °C for 3 h to obtain solution A. 0.20 mL of solution A was added to solution B, which was prepared by mixing 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, 4 mL of 10 mM tetrachloroauric acid solution and 15 mL of 0.1 M ascorbic acid solution. The mixture was stirred at 30 °C for 12 h. After centrifugation, spherical Au nanospheres were obtained and dispersed in 10 mL of deionized water to obtain Au nanosphere dispersion.

[0023] (2) After centrifuging 1 mL of the above Au nanosphere dispersion twice to remove the supernatant, add it to solution C, which is prepared by mixing 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 1 μL of 0.01 M silver nitrate solution, and 10 μL of 0.1 M ascorbic acid solution. After mixing evenly, stir and react in a 60 ℃ water bath for 4 h. Then centrifuge twice to remove the supernatant. Then add solution D, which is prepared by mixing 40 μL of 0.01 M hexadecyltrimethylammonium bromide solution, 5 μL of 0.01 M sodium hydroxide solution, 30 μL of 0.01 M ascorbic acid solution, and 10 μL of 0.01 M chloropalladic acid solution. After mixing evenly, stir and react at room temperature for 2 h. Finally, centrifuge the resulting solution at 5000 rpm for 10 min to obtain Au nanospheres loaded with Ag / Pd bimetallic particles. Disperse them in 1 mL of deionized water to form a dispersion of Au nanospheres loaded with Ag / Pd bimetallic particles.

[0024] Figure 1 This is a scanning electron microscope image of the Au nanospheres obtained in step (1). It can be concluded that the Au nanospheres are spherical Au nanospheres with an average diameter of 59.6 nm.

[0025] Figure 2 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of the Ag / Pd bimetallic Au nanospheres prepared in step (2). (a) is the TEM image, and (b) is the EDX elemental distribution map. It can be seen that the Ag / Pd bimetallic Au nanospheres exhibit a distinct Janus structure, with the bimetallic loading located at one end of the spherical structure. The EDX elemental distribution results show that the nanospheres contain three metal elements, confirming the successful bimetallic loading.

[0026] Example 2 A method for preparing bimetallic Au nanoparticles for photocatalysis is as follows: (1) 0.25 mL of 10 mM tetrachloroauric acid solution, 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, and 2 mL of 0.1 M citric acid solution were added to 0.60 mL of 10 mM sodium borohydride solution and stirred at 30 °C for 3 h to obtain solution A. 0.20 mL of solution A was added to solution B, which was prepared by mixing 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, 4 mL of 10 mM tetrachloroauric acid solution, 0.4 mL of 5 mM silver nitrate solution, 0.8 mL of 2 M hydrochloric acid solution, and 15 mL of 0.1 M ascorbic acid solution. The mixture was stirred at 30 °C for 12 h, and after centrifugation, bipyramidal Au nanoparticles were obtained and dispersed in 10 mL of deionized water to obtain Au nanoparticle bipyramidal dispersion.

[0027] (2) Take 1 mL of the above Au nano biconical dispersion, centrifuge twice to remove the supernatant, and add it to solution C, which is prepared by mixing 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 1 μL of 0.02 M silver nitrate solution and 10 μL of 0.06 M ascorbic acid solution. After mixing evenly, stir and react for 4 h in a 60 ℃ water bath, and then centrifuge twice to remove the supernatant. After removing the supernatant, a solution D was added, which consisted of 40 μL of a 50 mM cetyltrimethylammonium bromide solution, 5 μL of a 0.01 M sodium hydroxide solution, 30 μL of a 0.05 M ascorbic acid solution, and 1 μL of a 0.01 M chloropalladic acid solution. The mixture was stirred at room temperature for 2 h. Finally, the resulting solution was centrifuged at 5000 rpm for 10 min to obtain Au nanobipyramidal particles loaded with Ag / Pd bimetallic compounds. These particles were then dispersed in 1 mL of deionized water to form a dispersion of Au nanobipyramidal particles loaded with Ag / Pd bimetallic compounds.

[0028] Figure 3 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of Au nanoparticles loaded with Ag / Pd bimetallic compounds. (a) is the TEM image, and (b) is the EDX elemental distribution map. It can be seen that step (1) prepares bipyramidal Au nanoparticles, with the bimetallic Ag / Pd distributed as nanoparticles on the edges of the Au nanoparticles. The EDX elemental distribution map further confirms the presence of the three metal elements in the nanoparticles. Comparing step (1) of Example 1 and Example 2, it can be seen that in step (1), spherical Au nanoparticles are prepared without the addition of citric acid, silver nitrate, and hydrochloric acid; while bipyramidal Au nanoparticles are prepared when citric acid, silver nitrate, and hydrochloric acid are added simultaneously.

[0029] Following the same preparation method as in Example 2, without adding solution D in step (2), Au nanobipyramidal particles loaded with a single metal Ag were obtained. Figure 4 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of Au nanoparticles loaded with single-metal Ag. (a) is the TEM image, and (b) is the EDX elemental distribution map. It can be concluded that single-metal Ag is uniformly distributed on the surface of the Au nanoparticles.

[0030] Example 3 A method for preparing bimetallic Au nanoparticles for photocatalysis is as follows: (1) Follow step (1) of Example 2.

[0031] (2) After centrifuging 1 mL of Au nanobipyramidal dispersion twice to remove the supernatant, add solution C, which is a mixture of 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 5 μL of 0.02 M AgNO3 solution, and 10 μL of 0.06 M ascorbic acid solution. Stir the mixture at 60 °C for 4 h, and then centrifuge twice to remove the supernatant. After removing the supernatant, add solution D, which is a mixture of 40 μL of 50 mM hexadecyltrimethylammonium chloride solution, 5 μL of 0.01 M NaOH solution, 1 μL of 0.01 M chloropalladic acid solution, and 30 μL of 0.05 M ascorbic acid solution. Stir the mixture at room temperature for 2 h. Finally, centrifuge the resulting solution at 5000 rpm for 10 min to obtain Au nanobipyramidal particles loaded with Ag / Pd bimetallic compounds. Disperse these particles in 1 mL of deionized water to form a dispersion of Au nanobipyramidal particles loaded with Ag / Pd bimetallic compounds.

[0032] Figure 5 These are transmission electron microscope (TEM) images and EDX elemental distribution maps of the Au nanoparticles loaded with Ag / Pd bimetallicity prepared in Example 3. (a) is the TEM image, and (b) is the EDX elemental distribution map. It can be seen that the bimetallicity is concentrated at the tips of the Au nanoparticles. The EDX elemental distribution results show the presence of three metallic elements in the nanoparticles, further confirming the successful loading of the bimetallicity.

[0033] A comparison of Examples 2 and 3 shows that, with other preparation parameters remaining the same, adjusting the amount of AgNO3 in step (2) allows for the preparation of Au nanoparticles with different loading positions of bimetallic particles. The study found that in step (2), substitution and co-reduction deposition reactions occur between Ag and Pd ions on the surface of the Au nanoparticles. With a fixed Pd ion concentration, a higher amount of AgNO3 results in more Ag ions on the surface of the Au nanoparticles. During the substitution and co-reduction process, the Ag ions promote the deposition of Pd towards both ends of the Au nanoparticle surface, ultimately accumulating at the tips of the Au nanoparticle bipyramidal particles.

[0034] Application examples The pure Au nanospheres obtained in step (1) of Example 1, the Au nanosphere particles loaded with bimetals obtained in step (2), the Au nanobipyramidal particles loaded with bimetals prepared in Example 2, the Au nanobipyramidal particles loaded with single metal Ag, and the Au nanobipyramidal particles loaded with bimetals in Example 3 were used as research objects and were used as photocatalysts for photocatalytic degradation of 4-nitrophenol.

[0035] Experimental Method: Two μL of the photocatalyst-containing dispersion prepared in each example was dispersed in the test solution. The test solution was formed by mixing 60 μL of a 5 mM 4-nitrophenol solution with 3 mL of a 50 mM sodium borohydride aqueous solution. The solution was then irradiated with a 300 W xenon lamp for 50 min, with the lamp 15 cm away from the sample. The UV-Vis absorption spectrum of the solution was measured every 10 min. After five tests, the photocatalytic degradation rate of 4-nitrophenol was calculated. The experiment was conducted three times to obtain the average photocatalytic degradation rate of 4-nitrophenol, as shown in Table 1.

[0036] Table 1. Performance test of photocatalytic conversion of 4-nitrophenol by nanoparticles

[0037] The results in the table show that, under the same catalyst dosage, the bimetallic Au nanoparticles prepared in Examples 1, 2, and 3 of this invention all exhibit excellent 4-nitrophenol degradation performance. The photocatalytic degradation rates of pure Au nanospheres and Au nanopyramidal particles loaded with a single metal are both lower than those of the bimetallic Au nanoparticles. This indicates that the bimetallic-loaded Au nanoparticles of this invention have significant advantages in photocatalytic conversion applications. Furthermore, comparing the bimetallic-loaded Au nanoparticles of Examples 1-3, it can be seen that the photocatalytic degradation rate of the bimetallic-loaded Au nanospheres obtained in Example 1 is superior to the other two types of bimetallic-loaded Au nanopyramidal particles. This demonstrates that the selection of the Au nanoparticle template shape is particularly crucial to the photocatalytic conversion rate. Simultaneously, the preparation method of the bimetallic-loaded Au nanoparticles of this invention is simple and universal, applicable to the synthesis of different bimetallic-loaded Au nanoparticles to obtain nano-photocatalysts with high photocatalytic activity.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. The application of Au nanoparticles loaded with bimetals in the photocatalytic degradation of organic pollutants, characterized in that, The preparation method of the Au nanoparticles loaded with bimetal is as follows: S1. Add 0.25 mL of 10 mM tetrachloroauric acid solution and 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution to 0.60 mL of 10 mM sodium borohydride solution and stir for 3 h to obtain solution A; take 0.20 mL of solution A and add it to solution B, which is prepared by mixing 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, 4 mL of 10 mM tetrachloroauric acid solution and 15 mL of 0.1 M ascorbic acid solution, stir and react for 12 h, centrifuge to obtain spherical Au nanospheres, and then disperse them in 10 mL of deionized water to obtain Au nanosphere dispersion; S2. After centrifuging 1 mL of the above Au nanosphere dispersion twice to remove the supernatant, add it to solution C, which is prepared by mixing 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 1 μL of 0.01 M silver nitrate solution, and 10 μL of 0.1 M ascorbic acid solution. After mixing evenly, stir and react in a 60 ℃ water bath for 4 h, then centrifuge to remove the supernatant. Then add solution D, which is prepared by mixing 40 μL of 0.01 M hexadecyltrimethylammonium bromide solution, 5 μL of 0.01 M sodium hydroxide solution, 30 μL of 0.01 M ascorbic acid solution, and 10 μL of 0.01 M chloropalladic acid solution. After mixing evenly, stir and react at room temperature for 2 h. Finally, centrifuge to obtain Au nanospheres loaded with Ag / Pd bimetallic compounds. Au nanospheres loaded with Ag / Pd bimetals exhibit a Janus structure.

2. The application of Au nanoparticles loaded with bimetals in the photocatalytic degradation of organic pollutants, characterized in that, The preparation method of the Au nanoparticles loaded with bimetal is as follows: S1. Add 0.25 mL of 10 mM tetrachloroauric acid solution, 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, and 2 mL of 0.1 M citric acid solution to 0.60 mL of 10 mM sodium borohydride solution and stir for 3 h to obtain solution A. Take 0.20 mL of solution A and add it to solution B, which is prepared by mixing 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, 4 mL of 10 mM tetrachloroauric acid solution, 0.4 mL of 5 mM silver nitrate solution, 0.8 mL of 2 M hydrochloric acid solution, and 15 mL of 0.1 M ascorbic acid solution. Stir and react for 12 h. After centrifugation, the bipyramidal Au nanoparticles are obtained and dispersed in 10 mL of deionized water to obtain Au nanoparticle bipyramidal dispersion. S2. After centrifuging 1 mL of the above Au nano biconical dispersion to remove the supernatant, add it to solution C, which is prepared by mixing 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 1 μL of 0.02 M silver nitrate solution, and 10 μL of 0.06 M ascorbic acid solution. After mixing evenly, stir and react in a 60 ℃ water bath for 4 h, and then centrifuge to remove the supernatant. After removing the supernatant, solution D was added, which consisted of 40 μL of 50 mM hexadecyltrimethylammonium bromide solution, 5 μL of 0.01 M sodium hydroxide solution, 30 μL of 0.05 M ascorbic acid solution, and 1 μL of 0.01 M chloropalladic acid solution. After mixing thoroughly, the mixture was stirred and reacted for 2 h. Finally, the Au nanoparticles loaded with Ag / Pd bimetal were obtained by centrifugation. The Ag / Pd bimetal was loaded on the edges of the Au nanoparticles.

3. The application of Au nanoparticles loaded with bimetals in the photocatalytic degradation of organic pollutants, characterized in that, The preparation method of the Au nanoparticles loaded with bimetal is as follows: S1. Add 0.25 mL of 10 mM tetrachloroauric acid solution, 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, and 2 mL of 0.1 M citric acid solution to 0.60 mL of 10 mM sodium borohydride solution and stir for 3 h to obtain solution A. Take 0.20 mL of solution A and add it to solution B, which is prepared by mixing 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide solution, 4 mL of 10 mM tetrachloroauric acid solution, 0.4 mL of 5 mM silver nitrate solution, 0.8 mL of 2 M hydrochloric acid solution, and 15 mL of 0.1 M ascorbic acid solution. Stir and react for 12 h. After centrifugation, the bipyramidal Au nanoparticles are obtained and dispersed in 10 mL of deionized water to obtain Au nanoparticle bipyramidal dispersion. S2. After centrifuging 1 mL of Au nano biconical dispersion to remove the supernatant, add it to solution C, which is prepared by mixing 1 mL of 80 mM hexadecyltrimethylammonium bromide solution, 5 μL of 0.02 M AgNO3 solution and 10 μL of 0.06 M ascorbic acid solution. Stir the reaction at 60 °C for 4 h, and then centrifuge to remove the supernatant. After removing the supernatant, solution D was added, which consisted of 40 μL of 50 mM hexadecyltrimethylammonium chloride solution, 5 μL of 0.01 M NaOH solution, 1 μL of 0.01 M chloropalladic acid solution, and 30 μL of 0.05 M ascorbic acid solution. The mixture was stirred for 2 h, and finally centrifuged to obtain Au nanoparticles loaded with Ag / Pd bimetallic compounds. The Ag / Pd bimetallic compounds were loaded at the tips of the Au nanoparticles.

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