KR20130042363A - Novel fabrication of polyethyleneimine-capped au-ag alloy nanoparticles - Google Patents

Abstract

PURPOSE: A method for preparing gold-silver alloy nanoparticles is provided to synthesize a large amount of gold-silver alloy nanoparticle through one-step using polyethyleneimine. CONSTITUTION: A method for preparing gold-silver alloy nanoparticles comprises: a step of reacting polyethyleneimine in an aqueous mixture containing chlorauric acid(HAuCl4) and silver nitrate(AgNO3); a step of dissolving the silver chloride generated through reaction of the chlorauric acid(HAuCl4) and silver nitrate(AgNO3) in the aqueous mixture; and a step of heating the mixture and stirring. The particle size of the gold-silver alloy nanoparticle is 1-10 nm. The gold-silver alloy nanoparticle is used as a catalyst in reduction of 4-nitrophenol.

Description

Manufacturing method of high concentration gold-silver alloy nanoparticles using polyethyleneimine {NOVEL FABRICATION OF POLYETHYLENEIMINE-CAPPED Au-Ag ALLOY NANOPARTICLES}

The present invention relates to a method for producing gold-silver alloy nanoparticles by a chemical method, more specifically, it is possible to control the content of gold and silver, and to synthesize a large amount of gold-silver alloy nanoparticles in one step. The present invention relates to a method for preparing gold-silver alloy nanoparticles, and thus gold-silver alloy nanoparticles.

One important phenomenon that takes place on the surface of the alloy is surface segregation, in which the chemical composition of the surface is completely deformed, resulting in different particle interior and surface properties. This occurs because of differences in bonding strength between members, differences in atomic sizes, differences in heat of sublimation, and differences in surface energy.

Moreover, in the case of the metal alloy nanoparticles, the surface separation occurs not only because of the above-mentioned reasons but also by reaction conditions, the degree of miscibility of the elements, and the rate at which the elements are reduced.

However, alloys of gold and silver can form homogeneous alloys without surface separation, since gold and silver have very similar lattice constants and are perfectly mixed regardless of the content ratio of gold and silver.

For this reason, gold-silver alloy nanoparticles have become a very interesting research topic, and it is known that conventional nanoparticles can produce homogeneous nanoparticles, have very high chemical stability, and thus can be used in any environment.

Gold-silver alloy nanoparticles can be synthesized by a variety of physical and chemical methods, a representative example of the physical method is the evaporation and condensation of gold-silver alloy in a 2-butanol solution (GC Papavassiliou, J. Phys. F: Metal phys. 6 (1976) L103-L105). The disadvantage of this method is that the nanoparticle size increases as the silver content of the alloy nanoparticles increases. Another method is to perform pulsed laser irradiation of bulk gold-silver alloys in water (Lee et al, Chem Commun. (2001) 1782-1783). This method also has the disadvantage that mass production is impossible.

In the case of the chemical method, the gold precursor and the silver precursor are prepared together with a reducing agent. Generally, gold chloride is used as gold chloride (HAuCl ₄ ), silver precursor is silver nitrate (AgNO ₃ ), reducing agent sodium borohydride (NaBH ₄ ), citrate (Citrate), hydrazine (hydricazine), etc. are used. . The production by chemical method has the advantage of the possibility of mass production, but when the mixture of geum chloride (HAuCl ₄ ) and silver nitrate (AgNO ₃ ) is mixed, silver chloride (AgCl) is precipitated and it is not possible to manufacture a large amount at one time. have.

Accordingly, the technical problem to be achieved by the present invention is to provide a method for synthesizing a large amount of gold-silver alloy nanoparticles in one-step.

The present invention is characterized by synthesizing a large amount of gold-silver alloy nanoparticles in one-step. Administering polyethylenimine to an aqueous mixture containing gold chloride (HAuCl ₄ ) and silver nitrate (AgNO ₃ ) to dissolve the silver chloride generated from the gold chloride and the silver nitrate; And it relates to a gold-silver alloy nanoparticles manufacturing method comprising the step of heating and stirring the aqueous mixture to obtain gold-silver alloy nanoparticles.

The gold-silver alloy nanoparticles prepared by the above production method have an average particle diameter in the range of 1 to 10 nm, and have a spherical shape. Due to the rich amine functionality of the polyethyleneimine (PEI), (i) not only acts as a dissolving agent of silver chloride (AgCl) as a by-product, but also (ii) reducing agent of gold chloride and silver nitrate, (iii) gold-silver alloy nanoparticles It acts as a stabilizer.

According to the production method of the present invention, a large amount of gold-silver alloy nanoparticles can be manufactured by one-step, and the content of gold and silver can be freely adjusted according to the purpose of use.

변화 그래프이다.
도 7의 (a)는 은 나노입자, Au_0.25Ag_0.75, Au_0.5Ag_0.5 , Au_0.75Ag_0.25, 금 나노입자를 촉매로 사용하여 4-나이트로페놀을 수소화붕소나트륨에 의하여 환원시키는 반응에서, 반응시간(t)에 따른

변화 그래프이다.
도 7의 (b)는 금-은 합금 나노입자 촉매의 금 함량에 따른 4-나이트로페놀 환원반응의 반응속도상수 변화 그래프이다.Figure 1 (a) is a graph showing the UV-vis absorption spectrum change of Au _0.5 Ag _0.5 with the reaction time.
Figure 1 (b) is a UV-vis absorption line graph according to the gold content of the gold-silver alloy nanoparticles.
Figure 1 (c) is a graph of the maximum SPR band position change according to the gold content of the gold-silver alloy nanoparticles.
Figure 1 (d) is a graph of light absorption spectral absorption line comparison of a simple mixture of gold-silver alloy nanoparticles and gold and silver nanoparticles.
2 is an EF-TEM image according to the gold content of the gold-silver alloy nanoparticles produced by the present invention. Figure 2 (a) is silver nanoparticles, Figure 2 (b) is Au _0.25 Ag _0.75 , Figure 2 (c) is Au _0.5 Ag _0.5 , Figure 2 (d) is Au _0.75 Ag _0.25 , Figure 2 (e) is an EF-TEM image of gold nanoparticles.
Figure 3 is a graph of the EDX analysis of the gold-silver alloy nanoparticles produced by the present invention. Figure 3 (a) is Au _0.25 Ag _0.75 , Figure 3 (b) is Au _0.5 Ag _0.5 , Figure 3 (c) is a graph of EDX analysis results of Au _0.75 Ag _0.25 .
Figure 4 (a) is an XRD pattern of Au _0.5 Ag _0.5 produced by the present invention.
(B) of FIG. 4 is XPS spectrum of silver in the state reduced by polyethyleneimine.
(C) of FIG. 4 is XPS spectrum of gold in the state reduced by polyethylenimine.
5 is a graph of UV-vis spectral change of 4-nitrophenol in the reaction of reducing 4-nitrophenol by sodium borohydride.
FIG. 6 (a) is a graph of UV-vis spectrum change when gold-silver alloy nanoparticles (Au _0.5 Ag _0.5 ) are used as a catalyst in a reaction of reducing 4-nitrophenol by sodium borohydride.
Figure 6 (b) is a reaction of reducing 4-nitrophenol by sodium borohydride, in the case of using gold-silver alloy nanoparticles (Au _0.5 Ag _0.5 ) as a catalyst, according to the reaction time (t)

It is a change graph.
7 (a) shows the reaction of reducing 4-nitrophenol by sodium borohydride using silver nanoparticles, Au _0.25 Ag _0.75 , Au _0.5 Ag _0.5 , Au _0.75 Ag _0.25 , and gold nanoparticles as catalysts. According to reaction time (t)

It is a change graph.
Figure 7 (b) is a graph of the reaction rate constant change of the 4-nitrophenol reduction reaction according to the gold content of the gold-silver alloy nanoparticle catalyst.

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

The present invention is characterized by synthesizing a large amount of gold-silver alloy nanoparticles in one-step. Administering polyethylenimine to an aqueous mixture containing gold chloride (HAuCl ₄ ) and silver nitrate (AgNO ₃ ) to dissolve the silver chloride generated from the gold chloride and the silver nitrate; And it relates to a gold-silver alloy nanoparticles manufacturing method comprising the step of heating and stirring the aqueous mixture to obtain gold-silver alloy nanoparticles.

The gold-silver alloy nanoparticles prepared by the above production method have an average particle diameter in the range of 1 to 10 nm, and have a spherical shape. Due to the rich amine functionality of the polyethyleneimine (PEI), (i) not only acts as a dissolving agent of silver chloride (AgCl) as a by-product, but also (ii) reducing agent of gold chloride and silver nitrate, (iii) gold-silver alloy nanoparticles It acts as a stabilizer.

The content of gold and silver in the gold-silver alloy nanoparticles is about the same as the ratio of the initial gold chloride and silver nitrate, and the alloy nanoparticles of perfectly homogeneous zero-valent Au and zero-valent Ag Is generated. _{^{Au 3+ (AuCl 4 - / Au}} + 1.002V vs SHE) and in light of the reduction potential of the ^{Ag + (Ag + / Ag,} + 0.7996V vs SHE), the gold-silver alloy nanoparticles are formed of gold atoms are first It can be seen that the crystal nuclei are formed, and then the remaining gold atoms and silver atoms proceed in the order of covering the surface of the gold crystal nuclei.

In the present specification, the expressions Au _0.25 Ag _0.75 , Au _0.5 Ag _0.5 , Au _0.75 Ag _0.25 refer to gold chloride and silver nitrate, respectively, in 25:75. Gold-silver alloy nanoparticles prepared by mixing in a ratio of 50:50 and 75:25.

Hereinafter, the present invention will be described in more detail with reference to examples which are preferred embodiments of the present invention. However, the following examples are intended to assist the understanding of the present invention, and the scope of the present invention is not limited to the following examples.

<Examples>

One embodiment of the gold-silver alloy nanoparticles production is as follows. Aqueous solution containing a certain amount of HAuCl ₄ and AgNO ₃ (total concentration is maintained at 5.1mM) mixed with 6.0ml 2% (w / w) PEI 6.0ml, and stirred at 100 ℃ 180 minutes gold-silver alloy nano Particles were synthesized. The mixing ratio of HAuCl ₄ and AgNO ₃ used in the present invention is equivalent to the gold and silver content of the gold-silver alloy nanoparticles to be prepared. Therefore, the amount of HAuCl ₄ and AgNO ₃ introduced into the present invention may vary depending on the gold-silver alloy nanoparticles of the desired gold content. In addition, the stirring time is preferably 60 minutes to 180 minutes.

<Test Example 1>

Confirmation of Gold-Silver Alloy Nanoparticles.

In order to confirm that gold-silver alloy nanoparticles were formed by the present invention, an optical absorption spectra was used. By simply mixing gold and silver nanoparticles, two Surface Plasmon Resonance (SPR) bands appear at 400 nm and 520 nm, respectively. On the other hand, only one SPR band of gold-silver alloy nanoparticles appears between 400 nm and 520 nm.

Figure 1 (a) is a graph showing the UV-vis absorption spectrum change with the reaction time of Au _0.5 Ag _0.5 . In FIG. 1A, line (i) is the spectrum before reaction, line (ii) is the spectrum after 15 minutes, line (iii) is the spectrum after 30 minutes, and line (iv) is after 1 hour. The spectrum, line v, refers to the spectrum after 2 hours, and the line vi relates to the spectrum after 3 hours.

The upper right insertion diagram included in (a) of FIG. 1 shows a change in the maximum absorption wavelength according to the reaction time of Au _0.5 Ag _0.5 . As a result, it can be seen that the production rate of the gold-silver alloy nanoparticles increases as the reaction time increases according to (a) of FIG. 1.

Figure 1 (b) discloses the UV-vis absorption line according to the gold-silver content of the gold-silver alloy nanoparticles prepared by the present invention. Line (i) is silver nanoparticle, line (ii) is Au _0.25 Ag _0.75 nanoparticle, red (iii) is Au _0.5 Ag _0.5 nanoparticle, line (iv) is Au _0.75 Ag _0.25 nanoparticle, line (v) is The UV-vis absorption line of gold nanoparticles is shown. Figure 1 (c) is the change in the maximum SPR band position according to the change in the gold content. As a result, it can be seen that the production of gold-silver alloy nanoparticles controlled by the present invention.

Figure 1 (d) is an absorption line graph of a mixture of physically mixed gold nanoparticles and silver nanoparticles and gold-silver alloy nanoparticles produced by the present invention (by mixing the hydrochloric acid and silver nitrate in a ratio of 1: 1 Optical absorption spectra absorption line graph comparing the absorption line of the prepared Au _0.5 Ag _0.5 ).

<Test Example 2>

Investigate the shape and size of nanoparticles.

The shape and size of silver nanoparticles, gold-silver alloy nanoparticles, and gold nanoparticles produced by the present invention can be confirmed by transmission electron microscope (EF-TEM).

2 is an EF-TEM image according to the gold content of the gold-silver alloy nanoparticles produced by the present invention. Figure 2 (a) is silver nanoparticles, Figure 2 (b) is Au _0.25 Ag _0.75 , Figure 2 (c) is Au _0.5 Ag _0.5 , Figure 2 (d) is Au _0.75 Ag _0.25 , Figure 2 (e) is an EF-TEM image of gold nanoparticles.

An aqueous solution containing the synthesized gold-silver alloy nanoparticles was sonicated for 15 minutes, and a very small amount of the sonicated aqueous solution was dried on a carbon-coated copper grid. According to Figure 2, each nanoparticle is all spherical, the average particle size is 7.0 ± 2.5 nm, 4.2 ± 1.3 nm, 5.2 ± 1.5 nm, 6.0 ± 1.4 nm, 7.5 ± 1.5 nm, respectively.

<Test Example 3>

Investigation of the content of gold and silver in gold-silver alloy nanoparticles.

Figure 3 is a graph of the EDX analysis of the gold-silver alloy nanoparticles produced by the present invention. 3, it can be seen that the gold and silver contents of the gold-silver alloy nanoparticles almost coincide with the ratio of the initial gold chloride and silver nitrate. Figure 3 (a) is Au _0.25 Ag _0.75 , Figure 3 (b) is Au _0.5 Ag _0.5 , Figure 3 (c) is a graph of EDX analysis results of Au _0.75 Ag _0.25 . The ratio of gold and silver in each alloy particle is 22.7: 77.3, 48.5: 51.5, and 76.1: 23.9, which is almost identical to the ratio of initial gold chloride and silver nitrate.

<Test Example 4>

Crystal structure confirmation of gold-silver alloy nanoparticles.

X-ray diffraction (XRD) analysis was performed to confirm the crystal structure of the gold-silver alloy nanoparticles. Figure 4 (a) is an XRD pattern of Au _0.5 Ag _0.5 produced by the present invention. According to (a) of FIG. 4, 2θ = 38.2, 44.2, 64.5, 77.4 showing that the surface center cubic (fcc) gold or silver particles are reflected along the (111), (200), (220), and (311) planes. The peak at can be observed. Since gold and silver have almost similar lattice constants (4.07825 and 4.0862, respectively), the XRD pattern of the gold-silver alloy nanoparticles does not show any difference even if the ratio of gold and silver is different.

<Test Example 5>

Check the zero-valent state of gold-silver alloy nanoparticles

Photoelectron spectroscopy (XPS) was used to confirm the oxidation state of gold and silver of the gold-silver alloy nanoparticles (Au _0.5 Ag _0.5 ), and the oxidation number of gold and silver was found to be zero. (B) of FIG. 4 is an XPS spectrum of silver in the state reduced by polyethyleneimine, and FIG. 4 (c) is an XPS spectrum of the gold of the state reduced by polyethyleneimine. The peaks at 368 eV and 374 eV are 3d _5/2 and 3d _3/2 peaks of the metal silver (Ag ⁰ ), respectively. The peaks at 83.7 eV and 87.4 eV shown in (c) of FIG. Au ⁰ ) peaks of 4f _7/2 and 4f _5/2 .

<Test Example 6>

In the reaction of reducing 4-nitrophenol by sodium borohydride, the measurement of the reduction reaction rate when Au _0.5 Ag _0.5 is used as a catalyst.

The catalytic properties of gold nanoparticles, silver nanoparticles, Au _0.25 Ag _0.75 , Au _0.5 Ag _0.5 , Au _0.75 Ag _0.25 prepared by the present invention are _4- nitrophenol (4-B) by sodium borohydride (NaBH ₄ ). Nitrophenol) can be confirmed by using the gold-silver alloy nanoparticles as a catalyst for the reduction reaction. 4-aminophenol, which is a product of the reduction reaction, can be used in many fields such as photographic developer, corrosion inhibitor, and dyeing agent, and thus a catalyst capable of directly reducing 4-nitrophenol is required. have.

According to Fig. 5, in the reaction for reducing 4-nitrophenol with sodium borohydride, when no catalyst is used, reduction of 4-nitrophenol with favorable equilibrium does not occur (4-nitrophenol / 4- The standard reduction potentials of aminophenol and H ₃ PO ₃ / BH ₄ are -0.76V and -1.33V, respectively. This is because the sodium borohydride becomes basic in liquid form to form 4-nitrophenolate ions (4-Nitro phenolate). FIG. 5 graphically shows the change in UV-vis spectrum when NaBH ₄ is administered to _4- nitrophenol solution without gold-silver alloy nanoparticles. 5 shows the basic condition because sodium borohydride is in excess in the catalysis reaction condition of the present study, the nitrophenol is changed to nitrophenolate, the maximum absorbance is changed from 317 nm to 400 nm.

According to FIG. 6, it can be seen that when the nanoparticles are used as catalysts, reduction of 4-nitrophenol into 4-aminophenol occurs. According to (a) of FIG. 6, the 400 nm peak of the UV-vis spectrum gradually decreases and the 308 nm peak of 4-aminophenol gradually increases, indicating the progress of the above reduction reaction. In addition, the color of the solution changes from light yellow to light green. Figure 6 (a) is a change in the UV-vis spectrum when using Au _0.5 Ag _0.5 . The same result occurs for other nanoparticles (Au _0.25 Ag _0.75 , Au _0.75 Ag _0.25 ). As soon as sodium borohydride is administered, the gold-silver nanoparticles begin to catalyze and receive electrons from BH4- and transfer electrons to 4-nitrophenol.

와 각각 0.1mM의 Au_0.5Ag_0.5 용액 30

를 초 정제수 2.6mL와 혼합하였다. 1.0M NaBH4 100

를 투여한 후 용액을 저어주고, 시간에 따른 반응물 변화를 측정하기 위하여 UV-vis 흡수스펙트럼을 관측하였다.
10 ℃ 4-nitrophenol at 25 ℃, PMMA (poly (methylmethacrylate) cell) 15

And Au _0.5 Ag _0.5 solution at 0.1 mM each 30

Was mixed with 2.6 mL of ultra purified water. 1.0M NaBH4 100

After administration of the solution, the solution was stirred, and the UV-vis absorption spectrum was observed to measure the change of reactant with time.

Since sodium borohydride was used at a much higher concentration than 4-nitrophenol, assuming that the concentration of sodium borohydride remains constant throughout the reaction, the overall reaction is similar to that of 4-nitrophenol. pseudo-first reaction).

를 그래프로 도시한 것이며, Au_0.5Ag_0.5의 반응속도상수는 25℃에서 1.60 X 10^-2s^-1이다.
6 (b) shows the reaction time (t) in order to calculate the reaction rate constant.

It is shown graphically, the reaction rate constant of Au _0.5 Ag _0.5 is 1.60 X 10 ^-2 s ^-1 at 25 ℃.

<Test Example 7>

Comparison of Reduction Rate by Catalyst

를 그래프로 도시한 것이며, 금 나노입자, Au_0.25Ag_0.75, Au_0.75Ag_0.25, 은 나노입자 용액의 반응속도상수는 25℃에서 각각

이다. 도 7의 (b)는 금 함량에 따른 반응속도상수의 변화를 나타내며, 기하급수적으로 증가하는 모습을 보였다.The reaction rate was measured by substituting the Au _0.5 Ag _0.5 solution of Test Example 6 with silver nanoparticles, Au _0.25 Ag _0.75 , Au _0.75 Ag _0.25 , and gold nanoparticle solutions, respectively. Figure 7 (a) is according to the reaction time (t) to calculate the reaction rate constant for each catalyst

The reaction rate constants of the gold nanoparticles, Au _0.25 Ag _0.75 , Au _0.75 Ag _0.25 , and silver nanoparticle solutions are respectively 25 ° C.

to be. Figure 7 (b) shows the change in the reaction rate constant according to the gold content, it was shown to increase exponentially.

Claims (5)

Adding and reacting polyethylenimine to an aqueous mixture including hydrochloric acid (HAuCl ₄ ) and silver nitrate (AgNO ₃ );
Dissolving silver chloride produced by the reaction of the gold chloride acid with the silver nitrate in the aqueous mixture; And
Method of producing a gold-silver alloy nanoparticles comprising the step of heating and stirring the aqueous mixture to obtain gold-silver alloy nanoparticles. The method of claim 1,
The gold or silver content of the gold-silver alloy nanoparticles is a method of producing a gold-silver alloy nanoparticles, characterized in that formed equal to the ratio of gold chloride and silver nitrate before the reaction. Gold-silver alloy nanoparticles prepared according to claim 1. The gold-silver alloy nanoparticles of claim 3, wherein the gold-silver alloy nanoparticles have an average particle diameter of 1 to 10 nm. The method of claim 3,
The gold-silver alloy nanoparticles are gold-silver alloy nanoparticles, characterized in that used as a catalyst in the reduction reaction of 4-nitrophenol.

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