KR101734426B1 - Hollow nano rattle particle for preparing less-noble metal nanoparticle and less-noble metal nanoparticle prepared thereby - Google Patents

Abstract

The present invention relates to hollow nanorottle particles suitable for the production of nanoparticles based on noble metals or alloys thereof and to a method for producing nanoparticles by seed-engineering therewith.
The nano-ruttle particles comprising the porous silica nanocomposite of the present invention and the gold nanocrystals trapped in the pores of the present invention can be easily and easily prepared using hybrid nanocrystals, and can be produced not only from nickel but also from alloys of nickel and other metals And can be used as a nanoreactor for the production of nanoparticles containing various metal cores and porous silica shells of a predetermined size, and the produced nanoparticles can also be post-modified. In addition, the nanoparticles containing the noble metal core and the porous silica shell of the present invention can form stable colloids in an aqueous medium, are stable under harsh conditions, and reacted molecules can easily approach the active metal core, . ≪ / RTI >

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to hollow nanorottle particles for manufacturing noble metal nanoparticles and a method for manufacturing nanoparticles using the same,

The present invention relates to a hollow nanoreactor suitable for the production of nanoparticles based on noble metals or alloys thereof and to a method for producing nanoparticles by seed-engineering therewith.

The yolk @ shell nanoparticles have a functional core inside the porous and porous nanoshell, and only spatially confined molecules selectively enter the void space. It has been receiving much attention because it can act as an emerging nanoreactor. Most recent research has focused on the development of highly durable and highly reusable nanocatalyst systems that act as catalysts for efficient and selective deformation of organic molecules. Recently. A new angle approach using a hollow nanoreactor to synthesize and refine nanoparticles within the constraints of the internal space protected by some researchers is presented. For example, the present inventors had invented a nano-reactor, Au @ h -SiO ₂ may help in using a blank in silica Au nanoparticles in the seed (seed) grow a noble metal of Au, Pt, Ag nanoparticles. The approach of synthesizing nanoparticles using a hollow nanoreactor can control the morphology under high precursor conditions and synthesize nanoparticles without organic ligands. In the case of noble metals, when a mild reductant is used, Au nanoparticles act as seeds and start to grow from Au nanoparticles. However, in the case of non-precious metals that are difficult to reduce, a strong reducing agent is required. In this case, crystal nuclei are generated not only inside the nanoreactor but also throughout the solution.

Accordingly, the present inventors have tried to solve these problems and to expand the usefulness of hollow nanoparticles. Of these, non-noble metal nanoparticles which are not noble metals and which are difficult to control and reduce, We have focused on the development of nanoreactors for the synthesis of nickel nanoparticles. As a result, it has been found that, in order to grow nickel nanoparticles using hollow nanoparticles, a nickel-grown catalyst comprising an assembly of catalytically active Au / Pd-heterojunction- nanocrystals within a hollow silica nanoshell As a result of the seed engineering using the nanor reactor, it was found that the nickel nanoparticles grown in the nanoreactor have catalytic activity for the dehydrogenation reaction of the ammonia borane compound, which is known as the hydrogen storage material, and the reduction reaction of the chemoselective nitroarenene compound In addition, it showed selectivity and conversion rate even when reused several times, and it was confirmed to be very useful as a catalyst. Furthermore, it has been confirmed that when the nanoreactor is used, not only nickel but also alloy nanoparticles of nickel and various metals can be synthesized and post-deformed. Thus, the present invention has been completed.

It is therefore an object of the present invention to provide hollow nanotube rattle particles suitable as nanoreactors for the production of nanoparticles based on noble metals or alloys thereof and nanoparticles thereof by seed- And a method for producing the same. However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

In accordance with one aspect of the present invention, the present invention provides a hollow porous silica nanocomposite and an entrapped gold and palladium heterodimer nanocrystal (Au / Pd < _{RTI ID} = 0.0 > (SiO2). ≪ / RTI >

The nanotubes according to the present invention induce the nucleation and growth of metal species such as alloys with metals, especially nickel or nickel and other metals, as catalysts and the like, It can be usefully used as a spatially confined nanoreactor for synthesis of nanoparticles.

Hereinafter, the present invention will be described in more detail.

The heterodimer nanocrystals of gold and palladium in the nanotubes of the present invention preferably have spherical gold and palladium nanoparticles of 2 to 10 nm and 2 to 10 nm in diameter, respectively, of a dumbbell shape with a very narrow interface Au / Pd heterodimer nanoparticles. Further, the size of the pupil is preferably 10 to 50 nm, and the size (diameter) of the nanotubes is preferably 20 to 100 nm.

In another aspect, the present invention relates to a method of producing the nanotarticle particles. More specifically, the manufacturing method includes the following steps.

a) a solution containing an iron oxide nanocrystal, a gold ion complex and a palladium ion is encapsulated in the presence of a polyethylene glycol surfactant to encapsulate the nanotubes with a silica nanocomposite so that the gold nanocrystals are hybrid nanocrystals attached to the iron oxide nanocrystals And silica nanospheres containing palladium ions;

b) treating the silica nanospheres with sodium borohydride to reductively dissolve the iron oxide nanocrystals and etching the silica nanospheres.

The iron oxide nanocrystals in step a) can be synthesized by a known method (for example, J. Park, K. An, Y. Hwang, J.-G. Park, H.-J. Noh, J .-Y. Kim, J.-H. Park , N.-M. Hwang and T. Hyeon, Nat. Mater., 2004, 3, 891-895.), the film-forming reaction is known reverse micelle (reverse micelle (See, for example, KM Yeo, J. Shin and IS Lee, Chem . Commun ., 2010, 46, 64-66). Specifically, iron oxide nanoparticles dispersed in cyclohexane are mixed with cyclohexane in which the surfactant is dispersed, and then a gold ion complex is added thereto. Thereafter, a solution containing palladium ions is added to form a droplet containing a gold ion complex And an outer cyclohexane phase containing iron oxide nanocrystals is formed on the surface of the iron oxide nanocrystals, and then an aqueous ammonia solution and tetraethylorthosilicate (TEOS) are continuously added to deposit gold nanocrystals on the iron oxide nanocrystals, A silica shell containing palladium ions can be formed around the iron oxide nanocrystals.

It is most preferable to use Fe ₃ O ₄ as the iron oxide in the step a), and Au ³⁺ complex is preferably used as the gold ion complex, and it is most preferable to use HAuCl ₄ . As the polyethylene glycol surfactant, polyoxyethylene nonylphenyl ether (for example, Igepal CO-520) is preferably used.

It is thought that the formation of the hybrid nanocrystals in the step a) is due to the reduction of the gold ion by the polyethylene glycol surfactant and the preferential crystal nucleation of the gold on the surface of the iron oxide. In the step a), when the nano spheres are treated with sodium borohydride, only the iron oxide crystals from the iron oxide / gold hybrid nanocrystals are quickly removed through the reduction decomposition step. This is promoted by the gold crystals attached, and in the absence of gold crystals attached, the iron oxide crystals are not decomposed. In step b), the iron oxide is selectively decomposed with sodium borohydride and the silica is etched, so that the gold / palladium heterojunction nanocrystals remain in the cavity of the porous silica nanocarp, and the nanotubes of the present invention are produced .

According to the manufacturing method of the present invention, the pupil size of the nanotubes produced can be easily controlled by changing the size of the iron oxide nanocrystals used.

When the nanotubes produced by the method of the present invention are used as a template, nanoparticles containing a porous silica shell and a noble metal such as nickel, which is difficult to produce by conventional methods due to difficulty in reduction and control, But also an alloy of nickel and other metals can be used to produce nanoparticles as described above, and the nanoparticles are advantageous in that post-transformation is possible.

On the other hand, the present invention relates to a method for producing nanoparticles comprising a noble metal or an alloy core thereof and a porous silica shell using the nanotubes as a template.

The preparation method can be carried out by reacting a metal salt with a reducing agent in an aqueous suspension containing the nanotubes. As the metal in the above manufacturing method, a non-noble metal is preferable, and nickel, cobalt or an alloy thereof may be used, but the present invention is not limited thereto. Examples of the metal salt include nitrate, sulfate, oxalate, phosphate, chloride, bromide, and acetate of the above metal, but are not limited thereto. As the reducing agent, hydrazine, hydrogen peroxide, ascorbic acid, hydroxylamine, citric acid, phosphorus, and the like may be used, but the present invention is not limited thereto. According to the above manufacturing method, the core-shell structure in which the non-noble metal nanocrystals grow selectively by the Au / Pd nanoparticles in the hollow silica, selectively grows only in the pores of the pores, and the noble metal core is coated with the porous silica shell Of nanoparticles are produced. In the case of using nano-ruttle particles having only gold nanocrystals without palladium crystals, gold nano-crystals act as seeds with respect to noble metals under a gentle reducing agent, and noble metals can grow. In the case of noble metals such as nickel, If the ions are not reduced and strong reducing agents are used, they grow relatively unwantedly outside the silica shell, not inside the silica shell.

In another aspect, the present invention relates to nanoparticles comprising a non-noble metal core and a porous silica shell prepared by the above process. The size of the nanoparticles is preferably 20 to 100 nm, and the size of the noble metal core is preferably 5 to 50 nm. Since the thermally stable silica shell protects the nanoparticles, the nanoparticles can change their morphology and crystallinity under a certain condition, for example, in a reducing atmosphere of Ni / Co @ SiO ₂ through an annealing process at 700 ° C. As a result, the nanoparticles synthesized by the nanoreactor can undergo a post-treatment process.

The nanoparticles are readily dispersed in an aqueous suspension to produce stable colloids. In addition, the silica nanotubes stabilize the active metal core under harsh conditions and provide a passage through which the reactive molecules can be diffused by the porous structure. Therefore, the nanoparticles can be usefully used as a catalyst and a biosensor.

The nano-ruttle particles comprising the porous silica nanocomposite of the present invention and the gold nanocrystals trapped in the pores of the present invention can be easily and easily prepared using hybrid nanocrystals, and can be produced not only from nickel but also from alloys of nickel and other metals And can be used as a nanoreactor for the production of nanoparticles containing various metal cores and porous silica shells of a predetermined size, and the produced nanoparticles can also be post-modified. In addition, the nanoparticles containing the noble metal core and the porous silica shell of the present invention can form stable colloids in an aqueous medium, are stable under harsh conditions, and reacted molecules can easily approach the active metal core, . ≪ / RTI >

FIG. 1 is a photograph showing the results of transmission electron microscopic analysis of nanoparticles obtained after attempting to synthesize Au @ h -SiO ₂ -containing Ni nanoparticles using various reducing agents. (A) ascorbic acid (b) hydrogen peroxide (c) hydrazine Monohydrate (d) It shows the result of using sodium borohydride, which is a strong reducing agent.
Figure 2 is a photograph showing a transmission electron microscope, and a high-resolution transmission electron microscope (sapdo) analysis, respectively _{(a) (Fe 3 O 4} / Au) @ (SiO 2 / Ni 2 +), (b) (Fe 3 O ₄ / AuPt ^{2 +} ) @SiO ₂ and (c) (Fe ₃ O ₄ / Au) @ (SiO ₂ / Pd ²⁺ ) core-shell nanoparticles and core-shell nanoparticles were treated with sodium borohydride, (D) Au @ h-SiO ₂ (e) (Fe ₃ O ₄ / AuPt) @ h -SiO ₂ (illustration: energy dispersive X-ray atom map, Au (red ), Pt (green)) (f) (Au / Pd) @ h-SiO ₂ .
The iron oxide nanoparticles of time Figure 3 using the microemulsion method to the control experiment no silane and titanium tetrachloride gold acid tetra _{(a) Ni (NO 3)} 2, (b) Na 2 PtCl 4, (c) Na ₂ PdCl ₄ , and a high-resolution transmission electron microscope (not shown) and an energy spectroscopy analysis result of the nanoparticles obtained by treating the nanoparticles with PdCl ₄ .
FIG. 4 shows a transmission electron microscope, a high-resolution transmission electron microscope (not shown), and an energy spectroscopy analysis of nanoparticles obtained by treating Na ₂ PtCl ₄ with iron oxide nanoparticles in the absence of tetraethoxysilane using a microemulsion method as a control experiment Fig.
5 is Ni (NO ₃₎ a variety of synthesis by the concentration of _{2 (Fe - O 4 / Au} ) @SiO 2 / Ni 2 + Au @ h the transmission of -SiO ₂ nanoparticles obtained by treatment with hydrogen, sodium boron (A) 16 mg / mL, and (b) 32 mg / mL, respectively, of the Ni (NO ₃ ) ₂ added in the initial synthesis, , (c) 48 mg / mL, and the histogram shows the size distribution of gold nanoparticles.
FIG. 6 is a graph showing a transmission electron microscopic analysis result of nanoparticles obtained by treating (Fe _- O ₄ ) @SiO ₂ / M ^{2 +} (M: Ni, Pt, Pd) with sodium borohydride. Ni, (b) Pt, and (c) Pd.
FIG. 7 is a graph showing the results of analysis of the reaction of (Fe _- O _{4 /} Au) @ SiO ₂ / Pd ^{2 +} with sodium borohydride by a transmission electron microscope and a high-resolution transmission electron microscope. (A) 10, (b) 20, (c) 30, and (d) 60 minutes, respectively, of reaction time (illustration: energy dispersive X-ray atom map, Au (red), Pd (yellow)).
FIG. 8 is a diagram showing a transmission electron microscope and an energy spectroscopy histogram showing the reaction of (Fe ₃ O _{4 /} Au) @ SiO ₂ / Pd ^{2 +} with sodium borohydride according to the reaction time. (A) 0, (b) 10, (c) 20, (d) 30, (e) 40, Pd < / RTI > heterodimer.
9 is a (Fe _- O _{4 /} Au) composite by varying the concentration of the Na ₂ PdCl ₄ obtained by treatment with boron sodium hydrogen ^{_{@SiO 2 / Pd 2 + (Au}} / Pd) @ h -SiO 2 nanoparticles (B) 8 mg / mL, (c) 32 mg / mL, and (c) the concentration of Na ₂ PdCl _{4 in} the initial synthesis, (d) 64 mg / mL, and the histogram shows the size distribution of the Au / Pd heterodimer in the hollow silica.
FIG. 10 is a transmission electron microscope image of Ni @ SiO _2. FIG. 10 (a) shows a high resolution transmission electron microscope image (b) (STEM and HAADF images), and XRD analysis (a red graph shows a face-centered cubic structure Ni). JCPDS Card No. 01-1260).
11 is a magnetization curve according to the intensity of a magnetic field of Ni @ SiO ₂ , which is a result of (a) 300 K, (b) 5 K. FIG.
12 shows the result of transmission electron microscopic analysis of Ni growth using (Au / Pd) @ h -SiO ₂ with respect to the reaction time. As shown in FIG. 12, 20, (d) 30, (e) 60, and (f) 90 minutes.
FIG. 13 is a graph showing the hydrogen volume generated according to the reaction time of the dehydrogenation reaction of ammonia borane, wherein (a) various concentrations of Ni @ SiO ₂ (b) Ni @ SiO ₂ Of the present invention.
FIG. 14 is a photograph of a Ni @ SiO ₂ solution, (a) before the atmosphere is exposed to the atmosphere, and (b) after 5 minutes after the magnet is applied.
FIG. 15 is a view showing a high-resolution transmission electron microscope image of Ni / Co @ SiO ₂ , wherein (a) before annealing (b) annealing in a hydrogen atmosphere at 700 占 폚 (illustration: energy dispersive X- , Co (yellow)).

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrative purpose only and that the scope of the present invention is not limited to these embodiments.

Reference example  1. Experimental Method

1-1. Au @ h -SiO ₂ Using Ni  Nanoparticle synthesis

The Au @ h -SiO ₂ nanoparticles were synthesized by a conventional method, specifically, a method in which iron oxide nanoparticles were surrounded by silica using a micelle method to synthesize core-shell nanostructures. During this process, / Iron oxide hybrid nanoparticles were synthesized. The synthesized core-shell nanoparticles were treated with sodium borohydride to synthesize Au @ h -SiO ₂ . The synthesized Au @ h -SiO ₂ has a structure in which Au nanoparticles of 3.3 nm are formed in hollow silica. To grow Ni, ₂ mg of Au @ h -SiO ₂ and 10 mg of nickel chloride (2) were dissolved in 1 mL of distilled water. After that the ascorbic acid (L-ascorbic acid) a reducing agent, hydrogen peroxide, hydrazine monohydrate, boron hydrogen and dropped in distilled water was dissolved 2.2 mmol of sodium into the solution contained a 1mL Au @ h -SiO ₂ 1 hr 30 min at 45 ℃ Lt; / RTI > After one hour and 30 minutes, the solution was centrifuged and washed three times with water to separate the nanoparticles, but Ni did not grow.

1-2. ( Fe ₃ O ₄ / Au ) @ ( SiO ₂ / M ^{2 +} ) (M = Pd , Ni ) And ( Fe ₃ O ₄ / AuPt ^{2 +} ) @ SiO ₂ Nanoparticle synthesis

The iron oxide (Fe ₃ O ₄ ) nanoparticles having a particle size of about 10 nm were prepared by the method reported previously (J. Park, K. An, Y. Hwang, J.-G. Park, H.-J. Noh, J.-Y. Kim, J.-H. Park, N.-M. Hwang and T. Hyeon, Nat . Mater ., 2004, 3, 891-895). _{Since, (Fe 3 O 4 / Au} ) @ (SiO 2 / M 2+) (M = Pd, Ni) and ^{_{(Fe 3 O 4 / AuPt 2}} +) @SiO 2 Reverse micelle method was used to synthesize nanoparticles. 10 ml of cyclohexane was added to a round bottom flask, 0.6 ml of Igepal CO-520 was added, and the mixture was dispersed by ultrasonication. 3 mg of iron oxide (Fe ₃ O ₄ ) nanoparticles dispersed in cyclohexane were then added. Then, the solution was dissolved in distilled water to prepare a solution having a concentration of 16 mg / mL, and then 0.05 mL of the solution was slowly added dropwise to the reaction solution. A solution of sodium tetrapalladate (Na ₂ PdCl ₄ ), nickel nitrate (Ni (NO ₃ ) ₂ ) or sodium tetrapretinate (Na ₂ PtCl ₄ ) dissolved in distilled water to a concentration of 16 mg / Slowly drop one drop into each reaction. Thereafter, an aqueous ammonia solution (28-30 wt%) 0.16 mL was added. Finally, 0.2 mL of tetraethoxysilane was added and the reaction was allowed to proceed for 21 hours. All the procedures were carried out with stirring to make the reaction solution clear. Thereafter, the nanoparticles were agglutinated by centrifugation and then dispersed again in water or ethanol to remove impurities to finally obtain nanoparticles.

1-3. In the process of surrounding silica Tetraethoxy Silane  In addition, Hydrochloric acid tetrachloride and Tetraethoxy Silane  Experimental method when excluded

10 ml of cyclohexane was added to a round bottom flask, 0.6 ml of Igepal CO-520 was added, and the mixture was dispersed by ultrasonication. 3 mg of iron oxide (Fe ₃ O ₄ ) nanoparticles dispersed in cyclohexane were then added. Then, a solution of 16 mg / mL was prepared by dissolving HAuCl ₄ in distilled water, and 0.05 mL of the solution was slowly dropped into the reaction solution (this procedure was excluded from the experiment except for hydrochloric acid tetrachloride) . Then, a solution prepared by dissolving sodium tetrapalladate (Na ₂ PdCl ₄ ), nickel nitrate (Ni (NO ₃ ) ₂ ) or sodium tetrapretinate (Na ₂ PtCl ₄ ) in distilled water to a concentration of 16 mg / Slowly drop one drop into each reaction. Thereafter, an aqueous ammonia solution (28-30 wt%) 0.16 mL was added. In all the experimental procedures, the reaction solution was stirred and stirred for transparency. The nanoparticles were agglutinated by centrifugation, and then dispersed again in water or ethanol to remove impurities to finally obtain nanoparticles.

1-4. Hydrochloric acid tetrachloride  Except that Fe ₃ O ₄ @SiO ₂ / M ^{2 +} (M: Ni , Pd , Pt ) Synthesis of nanoparticles

10 ml of cyclohexane was added to a round bottom flask, 0.6 ml of Igepal CO-520 was added, and the mixture was dispersed by ultrasonication. 3 mg of iron oxide (Fe ₃ O ₄ ) nanoparticles dispersed in cyclohexane were then added. Then, a solution prepared by dissolving sodium tetrapalladate (Na ₂ PdCl ₄ ), nickel nitrate (Ni (NO ₃ ) ₂ ) or sodium tetrapretinate (Na ₂ PtCl ₄ ) in distilled water to a concentration of 8 mg / mL, and slowly dropped one drop into each reaction. Then 0.16 mL of aqueous ammonia solution (28-30 wt%) was added. Finally, 0.2 mL of tetraethoxysilane is added and the reaction is allowed to proceed for 21 hours. All experimental procedures were carried out by stirring to make the reaction solution clear. The resulting nanoparticles were agglutinated by centrifugation, and then dispersed again in water or ethanol to remove impurities to finally obtain nanoparticles.

1-5. Fe ₃ O ₄ @SiO ₂ / M ^{2 +}  (M = Pd , Ni , Pt )of Sodium borohydride  process

The reaction was initiated by adding 1 mL of 0.2 M sodium borohydride solution to a solution of 3 mg of Fe ₃ O ₄ @SiO ₂ / M ^{2 +} (M = Pd, Ni, Pt) dispersed in 2 mL of distilled water. The reaction is carried out with stirring at 40 DEG C for 1 hour. The color of the brown solution at the beginning of the reaction gradually turns black and hydrogen gas is generated. The resulting nanoparticles were agglomerated using centrifugation and then dispersed again in water to remove impurities to finally obtain nanoparticles.

1-6. Pd ^{2 +} Wow Ni ^{2 +} The amount of Fe ₃ O ₄ / Au ) @ ( SiO ₂ / M ^{2 +} ) (M = Pd , Ni ) synthesis

(4, 8, 32 and 64 mg / mL) were respectively prepared using sodium tetrapalladate (Na ₂ PdCl ₄ ) and nickel nitrate (Ni (NO ₃ ) ₂ ) 10 ml of cyclohexane was added to a round bottom flask, 0.6 ml of Igepal CO-520 was added, and the mixture was ultrasonicated and dispersed. 3 mg of iron oxide (Fe ₃ O ₄ ) nanoparticles dispersed in cyclohexane were then added. Then, a solution of 16 mg / mL was prepared by dissolving hydrofluoric acid (HAuCl ₄ ) in distilled water, and 0.05 mL was slowly added dropwise to the reaction solution. Then 0.05 mL of sodium tetrapalladate (Na ₂ PdCl ₄ ), nickel nitrate (Ni (NO ₃ ) ₂ ) solution was slowly added dropwise to each reaction. Then 0.16 mL of aqueous ammonia solution (28-30 wt%) was added. Finally, 0.2 mL of tetraethoxysilane is added and the reaction is allowed to proceed for 21 hours. All experimental procedures were carried out with stirring to make the reaction solution clear. The final nanoparticles were agglutinated by centrifugation and then re-dispersed in water or ethanol to remove impurities.

1-7. ( Fe ₃ O ₄ / Au ) @ ( SiO ₂ / M ^{2 +} ) (M = Pd , Ni ) And ( Fe ₃ O ₄ / AuPt ^{2 +} ) @ SiO ₂ Reductive dissolution of iron oxide of nanoparticles

A solution in which 3 mg of (Fe ₃ O ₄ / Au) @ (SiO ₂ / M ^{2 +} ) (M = Pd, Ni) or (Fe ₃ O ₄ / AuPt ^{2 +} ) @ SiO ₂ was dispersed in ₂ mL of distilled water To which 1 mL of 0.2 M sodium borohydride solution is added. The reaction was carried out with stirring at 40 ° C for 1 hour. At the beginning of the reaction, the color of the brown solution gradually became black and hydrogen gas was generated. The nanoparticles finally obtained were agglomerated using centrifugation and then dispersed again in water to remove impurities.

1-8. ( Au / Pd ) @ h- SiO ₂  Pupil Ni  Nanoparticle growth

To synthesize the nickel-hydrazine compound, 50 mg (0.2 mmol) of nickel chloride (2) was dissolved in 0.5 mL of distilled water, and then 0.109 mL (2.2 mmol) of hydrazine monohydrate was added. As soon as hydrazine was added, a purple precipitate was formed. The precipitate was coagulated with a centrifuge to disperse the precipitate and distilled water was dispersed in distilled water twice. In a sealed container, add 15 mg of the nickel-hydrazine compound synthesized in distilled water and 0.054 mL (1.1 mmol) of hydrazine monohydrate to make 1.5 mL of the solution. The resulting solution was purged with nitrogen for 30 minutes. (Au / Pd) @ h -SiO ₂ solution in which 2 mg was dispersed in 0.5 mL of distilled water from which gas had been removed was introduced into a solution containing a nickel-hydrazine compound purged with nitrogen using a syringe to initiate the reaction, Was stirred at 45 ° C for 1 hour and 30 minutes. The reaction solution was initially purple, light brown at 20 minutes after the start of the reaction, and then rapidly changed to black to generate hydrogen gas. The synthesized Ni @ SiO ₂ was separated from the reaction vessel using a small magnet and the clear solution was removed by using a syringe. After that, it was dispersed again using degassed distilled water, and then separated again using a magnet, and the transparent solution was again removed with a syringe. After that, degassed distilled water was put back and stored in a nitrogen atmosphere.

1-9. ( Au / Pd ) @ h - SiO ₂  Pupil Ni / Co  Alloy nanoparticle growth

In a sealed container, 10 mg of the nickel-hydrazine compound synthesized in distilled water and 0.054 mL (1.1 mmol) of hydrazine monohydrate were added to make 1.5 mL of the solution, which was purged with nitrogen for 30 minutes. The reaction was initiated by adding (Au / Pd) @ h -SiO ₂ solution, in which 2 mg was dispersed, to 0.5 mL of distilled water from which gas had been removed, into a solution containing nickel-hydrazine compound purged with nitrogen using a syringe. The reaction was carried out with stirring at 45 ° C. At the start of the reaction, 0.075 mL of a 0.42 M solution of cobalt chloride (CoCl ₂ ) was added to the reaction solution using a syringe, and then the reaction was further continued for 40 minutes. The reaction solution was initially purple, light brown at 20 minutes after the start of the reaction, and then rapidly changed to black to generate hydrogen gas. The synthesized Ni / Co @ SiO ₂ was centrifuged to aggregate the nanoparticles and then dispersed again in water to remove impurities.

1-10. Ni @ SiO ₂ Catalyst activity evaluation experiment

One) NH ₃ BH ₃ Dehydrogenation reaction of

To measure the amount of hydrogen gas generated, the burette was filled with water, and a 1-shrinking flask was connected to the upper part of the burette. The lower part of the burette was connected to a fractionation funnel filled with water to adjust the pressure. When hydrogen was generated during the reaction, the fractionation funnel was moved to match the water height of the burette. 1 In a shrink-flask, 1.5 mL of Ni @ SiO ₂ (0.064, 0.053, 0.043, and 0.032 mM, calculated as the number of moles of Ni) was dispersed in distilled water and 1 mmol of NH ₃ BH ₃ (30.8 mg) . The reaction begins with the addition of ammonia borane. The reaction proceeds at room temperature with stirring. In the re-use experiment, 1 mmol of ammonia borane compound was dissolved in 0.5 mL of distilled water, and the reaction was terminated.

2) Nitroaren  Hydrogenation of compounds

0.1 mmol of Nitroarene and 4 mmol (0.2 mL) of hydrazine monohydrate were added to the reactor and 0.8 mL of distilled water was added to the reactor, and 15 mol% of Ni @ SiO ₂ was added to the reaction solution through the syringe. The reaction was continued at room temperature until the nitroarenes were completely consumed. After completion of the reaction, 3 mL of ethyl acetate was added to the reaction mixture, and the product was extracted with a filter. The reaction was terminated by using TLC (0.25 mm E. Merck silica gel plates (60F-254) In order to confirm the reusability of the catalyst, the catalyst was separated by using a magnet to separate the solution, and 1 mL of distilled water and 1 mL of acetone were added to the impurities After that, the same amount of reactants were added and the reuse experiment was carried out.

Example : Experimental Results and Discussion

Example  1. Au @ h -SiO ₂ Using Ni  Attempt to grow

The inventors are the first to use the Au @ h -SiO ₂ was designed to try before seen a nickel growth. Hydrogen peroxide and hydrazine were used for the reduction of nickel (2) and mild reductants such as ascorbic acid, hydrogen peroxide, and hydrazine. As a result, it was observed that Au nanoparticles act as seeds and grow noble metals. However, in the case of nickel, it was not possible to reduce the nickel of the bivalent. Another alternative is to grow Ni on Au nanoparticles using a strong reducing agent, sodium borohydride. However, unwanted large nickel nanoparticles were formed outside Au @ h -SiO ₂ (Fig. 1). Therefore, it was recognized that a more active seed in the hollow silica nanoparticles is required to grow Ni. Therefore, the present inventor has reported that the nickel-hydrazine compound catalyzes the reductive decomposition, and attempts to introduce Pt, Pd, and Ni nanoparticles into the hollow silica as a seed. We _{(Fe 3 O 4 / Au)} @SiO 2 is Au @ h -SiO the iron going into the process ₂ (Fe ₃ O ₄₎ in the reducing melting phenomenon of the particles Pt, Pd, Ni ^{+ 2} ions in the pupil Au nano It was assumed that the particles would be deposited.

Example  2. For nickel growth seed Engineering; Genus empty silica Au / Pd  Dumbbell Heterodimer  Particle synthesis

^{Ni 2 +, Pt 2 +,} Pd 2 + ions existing (Fe ₃ O ₄ / Au) in micro-emulsion solution in the process of synthesizing a _{@SiO 2 Ni (NO 3) 2} , Na 2 PtCl 4, Na 2 PdCl 4 By introducing a solution. As a result of the TEM analysis, all the particles are in the form of a core-shell structure, and the silica shell surrounds the core made up of nanoparticles like satellites surrounding the iron oxide particles (Fig. 2a-c).

As a control experiment, a similar amount of Au and Pt was detected in the iron oxide obtained by excluding tetraethyl silicate (TEOS) and the satellite nanoparticles in the vicinity thereof. (Fig. 4), only a small amount of Pd and Ni was detected. In another control experiment, only a very small amount of Pt was observed when HAtCl ₄ and tetraethoxysilane were not added (FIG. 3). The core obtained by this observation from the nanoparticles of the shell structure, Ni ^{+ 2} and the case of Pd ^{2 +} ions, according spread throughout the silica shell _{(Fe - O 4 / Au)} @SiO 2 / Ni 2+, (Fe 3 O ₄ / Au) can be inferred to obtain the @SiO ^₂ / Pd ₂ ^+. On the other hand, in the case of Pt, the satellite nanoparticles around the iron oxide were formed together with Au and Pt (Fe ₃ O ₄ / AuPt ²⁺ ) to obtain SiO ₂ nanoparticles. When the core-shell structure nanoparticles thus obtained were treated with sodium borohydride to induce the reduction dissolution phenomenon of iron oxide (Fe ₃ O ₄ ), different reactions proceeded according to the respective metal ions. (Fe ₃ O ₄ / AuPt ²⁺ ) @ SiO ₂ did not dissolve iron oxide nanoparticles. This phenomenon is expected because the Au nanoparticles attached to the iron oxide nanoparticles are alloyed with Pt to reduce the catalytic activity. Au / Pt alloy satellite nanoparticles of 2.1 (± 0.5) nm size around 9 (± 1) nm of iron oxide (Fe ₃ O ₄ ) nanoparticles, which are special nanostructures when treated with sodium borohydride, The resulting Fe ₃ O ₄ / AuPt @ h -SiO ₂ particles in the resulting pupil of size 19 (2) were obtained (FIG. 2e). The pupil of Fe ₃ O ₄ / AuPt @ h -SiO ₂ was not suitable for Ni growth because the undissolved iron oxide (Fe ₃ O ₄ ) remained. On the other hand, in the case of (Fe _- O ₄ / Au) @ SiO ₂ / Ni ²⁺ , treatment with sodium borohydride accelerated the reduction of iron oxide (Fe ₃ O ₄ ) nanoparticles by Au nanoparticles, . Ni ^{2 +} ions, on the other hand, escaped by small pores in the silica shell during the reaction. In the initial (Fe _- O ₄ / Au) @SiO ₂ / Ni ²⁺ nanoparticles, the rat rat particles obtained without regard to the amount of Ni ions in the silica shell were Au nanoparticles in the hollow silica nanoparticles. The nanoparticles were the same as the nanoparticles obtained by treating (Fe _- O ₄ / Au) @ SiO ₂ with sodium borohydride (FIG. ₂ d and FIG. 5). As a control experiment, Fe ₃ O ₄ @SiO ₂ / M ^{2 +} (M: Ni, Pd, Pt) nanoparticles synthesized by excluding sodium hexachlorohydrochloride (HAuCl ₄ ) were treated with sodium borohydride , No reduction phenomenon of iron oxide (Fe ₃ O ₄ ) nanoparticles was observed. From these results, it can be seen that the Ni, Pt, and Pd ions hardly affect the reduction dissolution phenomenon, and the Au nanoparticles have the greatest influence on the iron oxide reducing dissolution phenomenon (FIG. 6).

(Fe ₃ O ₄ / Au) @ SiO ₂ / Pd ^{2 +} was treated with sodium borohydride to have a nano rattle structure. TEM images showed nanoparticles containing spherical, rather than spherical, nanoparticles in the pupil of 21 (± 2) nm (FIG. 2f). For more detailed analysis, we used HRTEM, STEM and EDX to show that the inner elliptical nanoparticles are spherical Au of about 2.5 nm and Au / Pd heterodimer nanoparticles of dumbbell shape with Pd nanoparticles having a very narrow interface (Fig. 7D). HRTEM analysis of the reaction time showed that iron oxide (Fe ₃ O ₄ ) nanoparticles were dissolved by reducing dissolution phenomenon 10 minutes after the start of the reaction and Au nanoparticles remained in the vacant space (FIG. 7A). As the reaction time gradually increased, the pupil gradually expanded and the size of 12 (± 1) nm was extended to 21 (± 2) nm in 1 hour at reaction time of 10 minutes. And Pd migrated to Au nanoparticles gradually inward. For the first time, the crystal of Pd was observed 20 minutes after the start of the reaction, and the crystal size gradually increased to 4.9 (± 0.8) nm (FIGS. 7 and 8). These results can be interpreted as the phenomenon that Pd reduced in the silica shell migrates to Au nanoparticles in hollow silica. As a control experiment, when the concentration of Pd ions in the silica shell was increased in (Fe ₃ O ₄ / Au) @ SiO ₂ / Pd ^{2 +} , sodium dibromide was treated with dibutyrate Au / Pd It was confirmed that the size of the Au nanoparticles of the nanoparticles is constant but the size of the Pd crystal increases (FIG. 9).

Example  3. Nickel growth only inside the hollow nanoreactor

(Au / Pd) @ h -SiO ₂ is a nano-rattle structure in which the hollow silica particles contain nanoparticles with catalytic activity of Pd crystals. In the hollow nanoparticles planned in the research process, nickel hydrazine It is a nanoparticle conforming to a nanoreactor capable of synthesizing nickel nanoparticles by reducing the compound. A mixture of nickel chloride (2) and hydrazine was added to a solution containing a closed reactor (Au / Pd) @ h -SiO ₂ and stirred at 45 ° C. The color of the reaction solution turned purple to light brown in the initial 20 minutes and then bubbled into a sudden black solution. The black powder obtained after 1 hour and 30 minutes of reaction was analyzed by TEM and STEM. As a result, 23 (± 3) nm Ni nanoparticles started to grow by hollow Au / Pd nanoparticles in hollow silica, In-core-shell structure of Ni @ SiO ₂ was synthesized. The resulting Ni nanoparticles were selectively grown only in hollow silica (Fig. 10A). HRTEM and XRD analysis showed polycrystalline Ni nanoparticles having a face-centered cubic structure (Fig. 10b, c). The magnetization change according to the magnetic field was measured and it was confirmed that Ni @ SiO ₂ is a super paramagnetic material at 300 K and a ferromagnetic material at 5 K (FIG. 11). The reaction time was analyzed by TEM. As a result, only 24% of the nanoreactor was grown at 20 minutes after the reaction. As the reaction progressed, (Au / Pd) @ h -SiO ₂ changed to Ni @ SiO ₂ , upon completion of the reaction, 94% of nano-reactor of 94%, was a Ni @ SiO ₂ (FIG. 12). As a result, Ni hydrazine compound is decomposed due to the catalytic action of Pd crystal, Ni crystal nuclei are formed on the surface of Pd nanoparticles, and Ni crystal nuclei are generated by the generated Ni crystal nuclei.

Example  4. Synthesized Ni @ SiO ₂ Judging the catalytic efficiency of

To determine the efficiency of the synthesized Ni @ SiO ₂ , we examined the catalytic activity of the dehydrogenation of ammonia borane (NH ₃ BH ₃ , AB) compounds required for hydrogen storage and production. The graph of FIG. 13 is a graph showing the generation of hydrogen by decomposition of ammonia borane (2M, 2 mL) compound with Ni @ SiO ₂ as the reaction time progresses at room temperature. The experiment proceeded at various Ni / AB molar ratios (0.046 to 0.032), resulting in a stoichiometric ratio of hydrogen (67 mL, 3 mmol) produced within 15 min. The reaction rate of each graph is proportional to the molar ratio of Ni / AB, and the conversion frequency (TOF) of each graph has a constant value. The average conversion frequency calculated for Ni mole number is 8.0 mol ^-1 , which is smaller than the value of 30.7 min ^-1 for the 6.5 nM nickel nanoparticle, which has the highest reported organic ligand. However, the conversion frequency defined by the number of moles of hydrogen produced per surface area of nickel nanoparticles has a value of 4.6 × 10 ^-18 mol · min ^-1 · nm ^{-2 for} Ni @ SiO ₂ and the highest conversion frequency in the case of ^{5.02 × 10 -18 mol · min -1} · nm - had a value of ^2. As a result, it was found that the Ni nanoparticles without the organic ligands having high catalytic activity were grown in the porous hollow silica shell of Ni @ SiO ₂ . In the catalyst reuse experiment, no significant decrease in catalytic activity was observed even after 5 reuses (FIG. 13). To further investigate the catalytic activity of Ni @ SiO _2, the present inventors reduced the industrially important reduction of nitroarenes in aqueous solution at room temperature using hydrazine, a mild reducing agent (Table 1). Reduction was attempted at room temperature using para nitroresien (0.1M), hydrazine (4M) and 15 mol% Ni @ SiO ₂ . Experimental results show that p-diaminobenzene was converted to 99% or more in 30 minutes. For the 10 nm size nanoparticles Ni of the known eotneunde that the switching frequency is a report 10h ^-1, Ni @ SiO ₂ had a value of the switching frequency greater than 13 h ^-1 value. Ni @ SiO ₂ is well dispersed during the reaction and can be easily recovered using the magnet after the reaction (FIG. 14). The reusability of Ni @ SiO ₂ recovered from the magnet was confirmed and the conversion and selectivity similar to the initial catalyst activity persisted during the third reuse. At the same reaction conditions, the reduction reaction of nitroarenes substituted with various functional groups was tried. When 99% conversion was made, it took 4 hours reaction time at all functional groups. In addition, while various functional groups (halogen, carbonyl, alkenyl groups) did not have a significant effect during the reduction of the nitro group to the amine group at a high conversion frequency, the reduction of the nitro group was 83% Respectively. The reason why it is possible to maintain the high chemical selectivity of the high nitro group reduction reaction under the mild condition of Ni @ SiO ₂ is that the porous silica shell protects the Ni nanoparticles synthesized without organic ligands on the surface.

Example  5. Synthesis of alloy nanoparticles using nanoreactor

In order to confirm whether it is possible to synthesize alloy nanoparticles by using a seed engineering approach to synthesize Ni nanoparticles, the present inventor has developed a cobalt-hydrazine compound prepared by mixing a cobalt chloride (CoCl ₂ ) and a hydrazine compound with a nickel Was added to the growing reaction solution. As a result, Co ^{2 +} was reduced like Ni ^{2 +} and Ni / Co alloy nanoparticles could be synthesized with core / shell structure of Ni / Co @ SiO ₂ synthesized in hollow silica. As a control experiment, when Co ^{2 +} and Fe ^{2 +} -hydrazine compounds were grown using (Au / Pd) @ h -SiO ₂ nanorods except Ni, Co and Fe were not reduced. As a result, it was found that the reduction of Co ^{2 +} occurs after the crystal nucleus of Ni was formed on the surface of Au / Pd nanoparticles. On the other hand, in the case of CuCl ₂ , it was confirmed that Cu formed crystal nuclei in addition to hollow silica to form very large Cu particles. The synthesized Ni / Co @ SiO ₂ can change its morphology and crystallinity through a 700 ℃ annealing process in a reducing atmosphere. This is because the thermally stable silica shell protects the nanoparticles. As a result, the nanoparticles synthesized by the nanoreactor can undergo a post-treatment process (FIG. 15).

Claims (11)

Comprising nanotubes comprising nanotubes, hybrid nanocrystals of gold and palladium (Au / Pd @ SiO ₂ ) entrapped in a hollow porous silica nanocarp and an internal cavity of the silica nanocarp. A nanoreactor for producing noble metal nanocrystals selected from the group consisting of nickel, cobalt and alloys thereof in the inner cavity of the silica nanocarp.
The nanoclay of claim 1, wherein the hybrid nanocrystals of the gold and palladium are each 2 to 10 nm in size, the pore size is 10 to 50 nm, and the nano-rattle particle size is 20 to 100 nm. A nanoreactor comprising rattle particles.
a) a solution containing an iron oxide nanocrystal, a gold ion complex and a palladium ion is encapsulated in the presence of a polyethylene glycol surfactant to encapsulate the nanotubes with a silica nanocomposite so that the gold nanocrystals are hybrid nanocrystals attached to the iron oxide nanocrystals And silica nanospheres containing palladium ions; And b) treating the silica nanospheres with sodium borohydride to reductively dissolve the iron oxide nanocrystals and etching the silica nanocomposite to form a hollow porous silica nano shell and entrapped ) Nano rattle particles comprising gold and palladium hybrid nanocrystals (Au / Pd @ SiO ₂ ) were prepared,
c) reacting the metal salt with a reducing agent in an aqueous suspension comprising the nanorattle particles, wherein the metal salt is a non-noble metal selected from the group consisting of nickel, cobalt and alloys thereof,
A method for producing nanoparticles comprising nanocrystals of noble metal located in the inner cavity of a silica nanocarp.
The method according to claim 3, wherein Fe ₃ O ₄ is used as iron oxide in step (a), and HAuCl ₄ is used as a gold ion complex.
The method according to claim 3, wherein the film forming reaction of step (a) is carried out by mixing an aqueous solution containing iron oxide nanocrystals and a gold ion complex in a cyclohexane solution containing a polyethylene glycol surfactant to form droplets containing gold ion complexes and iron oxide Characterized in that it is carried out by forming a reverse micelle system comprising an outer cyclohexane phase containing nanocrystals, adding a solution containing palladium, and continuously adding an aqueous ammonia solution and tetraethylorthosilicate (TEOS). Way.
The method according to claim 5, wherein Fe ₃ O ₄ is used as iron oxide, HAuCl ₄ is used as a gold ion complex, polyoxyethylene nonylphenyl ether is used as a polyethylene glycol surfactant, sodium palladium And a palladium solution is used.
The method according to claim 3, wherein the reducing agent is hydrazine, hydrogen peroxide, ascorbic acid, hydroxylamine, citric acid, or phosphorus as the reducing agent.
The nanocomposite according to claim 3, wherein the size of the nanoparticles including noble metal nanoparticles located in the inner pores of the silica nano shell is preferably 20 to 100 nm, and the size of the noble metal core is 5 to 50 nm .
4. The process according to claim 3, wherein the metal salt is a nitrate, sulfate, oxalate, phosphate, chloride, bromide or acetate of a metal selected from the group consisting of nickel, cobalt and alloys thereof.
The method according to claim 9, wherein the metal salt is nickel chloride or cobalt chloride.
A nanoparticle prepared by the method of any one of claims 3 to 10 and comprising nanocrystals of noble metal located in the inner cavity of the silica nanocarp, the nanoparticle having a size of 20 to 100 nm, The noble metal core has a size of 5 to 50 nm.

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