KR101400005B1 - Noble Metal Nanoparticles with High Surface Area and Synthetic Method thereof - Google Patents

Abstract

The present invention relates to a method for rapidly synthesizing raspberry-like gold nanoparticles (Au RLNPs) having a large number of corners and a large surface area in solution in a single step in a high yield. The noble metal nanoparticles were synthesized through the reduction of HAuCl ₄ , which is simply mediated with non-ionic Brij surfactants in base conditions without the addition of other reducing or organic materials. The synthesized nanoparticles were large in surface area and stable under basic or neutral conditions. Such nanoparticles can be usefully applied in various fields. The surface plasmon resonance of the unique, very red-shifting noble metal nanoparticles is rough and originates from the surface of Au RLNPs such as raspberry. The size of noble metal nanoparticles could be controlled by varying the amount of NaOH and HAuCl ₄ .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noble metal nanoparticles having a large surface area,

The present invention relates to a method for rapidly synthesizing raspberry-like gold nanoparticles (Au RLNPs) having a large number of corners and a large surface area in solution in a single step in a high yield.

Interest in the synthesis of noble metal nanoparticles with controlled sizes and shapes continues to grow because these nanoparticles are highly specific and highly dependent on their structural properties and are therefore highly applicable (MA El-Sayed, Acc. Chem. Res. CJ Murphy et al., J. Phys. Chem. B 109,13857 (2005), Y. Xia et al (2005), R. Ferrando et al., Chem. Rev. 108, 845 , Angew Chem. Int. Ed., 48, 60 (2009)). The size control of the spherical noble metal nanoparticles can be carried out by biological detection (NL Rosi and CA Mirkin, Chem. Rev. 105, 1547 (2005), D. Gerion et al., J. Am. Chem. Soc. 124, And catalysts (NR Jana et al., J. Phys. Chem. B 103, 115 (1999), NR Jana and T. Pal, Langmuir 15, 3458 (1999)). The preparation of useful noble metal nanoparticles with anisotropic morphology depends on the development of reliable manufacturing methods for unique structures and on a reliable assessment of the effect of geometry on physical and chemical behavior (Y. Xiong and Y. Xia, Adv. Mater. 19, 3385 (2007), SE Habas et al., Nat.Mater . 6, 692 (2007)).

Gold nanoparticles have complex optical properties ranging from visible to near-infrared spectra. This is generally less toxic and the surface can easily functionalize (S. Eustis and MA El-Sayed, Chem. Soc. Rev. 35, 209 (2006)). Because of this feature, gold nanoparticles are suitable for both basic research and technical applications (MA El-Sayed, Acc. Chem. Res. 34, 257 (2001), R. Ferrando et al., Chem. Y. Xia et al., Angew. Chem. Int. Ed., 48, 60 (2009), PK Jain et al., J. Phys. Chem. Res. 41, 1578 (2008), M. Hu et al., Chem. Soc. Rev. 35, 1084 (2006)). Bar (BD Busbee et al., Adv . Mater. 15, 414 (2003), B. Nikoobakht and MA El-Sayed, Chem. Mater. 15, 1957 (2003)), fiber-like (H. Yoo et al. , Chem. Comm., 46, 6813 (2010)), a hollow structure (SE Skrabalak et al., Acc. Chem. Res. 41, 1587 (2008), H. Yoo et al., Adv. (2011)), disc types (JE Millstone et al., Small 5, 646 (2009)) and multilayer plates (MH Jang et al., J. Mater. And size of gold nanoparticles have been synthesized in solution through physical and chemical approaches. Recently, multi-branch gold nanoparticles with many corners and vertices have attracted much attention because of their unique optical properties and large surface area (GH Jeong et al., J. Coll. Int. Sci. 329, 97 . Lu et al., Langmuir 24 , 1058 (2008), BK Jena and CR Raj, Langmuir 23, 4064 (2007), OM Bakr et al., Chem. Mater. 18, 3297 (2006), X. Zou et al (2006), Nanotechnology 17, 4758 (2006), C.-H. Kuo and MH Huang, Langmuir 21, 2012 (2005), CL Nehl, H. Liao, and JH Hafner, Nano Lett. . Hao et al., Nano Lett . 4, 327 (2004), PS Kumar et al., Nanotechnology 19, 015606 (2008), H.-Y. Wu, M. Liu, and MH Huang, J. Phys. Chem . B 110, 19291 (2006) , S. Chen et al., J. Am. Chem. Soc. 125, 16186 (2003), Y. Xiao et al., Langmuir 21, 5659 (2005), S. Guo et al., Cryst. Growth Des. 8, 3581 (2008), Z. Li, V. Ravaine et al., Adv. Funct. Mat. 17, 618 (2007), L. Wang and Y. Yamauchi, J. Am Chem. Soc. 131, 9152 (2009), J. Xie et al., Chem. Mater. 19, 2823 (2007)).

Seed-based synthesis, seedless syntheses, and reducing agents or shape indicators have been used to direct solution-phase synthesis of such unique gold nanoparticles. Although such gold nanoparticles are being synthesized, controlling the size of the multibranched gold nanoparticle synthesis method and controlling it with a simple method remains a challenge. In particular, the main reason for the difficulty in synthesizing such a structure is that the metal is generally homogeneously crystallized and symmetrically crystallized during nucleation and growth (Y. Xia et al., Angew. Chem. Int. XW Lou et al., Chem. Mater. 18, 3921 (2006), M. Yamamoto et al., Chem.Mater . 17, 5391 (2005), XW Teng and H. Yang, Nano Lett. 2005). An amphipathic polymer or a surfactant may be used as a form-indicating agent to prepare multi-branched metal nanoparticles. For example, Wang et al. Synthesized gold spheres similar to raspberry by reacting with sodium acetate in aniline and Triton X-100 emulsion for 24 hours at 4 ° C (S. Guo et al., Cryst. Growth Des. 8, 3581 (2008)). Yamaguchi et al. Have reported that platinic F127 block copolymers have been used to synthesize platinum nanoparticles with many corners and corner atoms (L. Wang and Y. Yamauchi, J. Am. Chem. Soc. 131, 9152 (2009)). However, there have been few reports of easy synthesis of size-controlled multi-branch gold nanoparticles that are simply mediated by surfactants without other reducing agents or organic molecules (J. Xie et al., Chem. Mater. 19, 2823 (2007) ).

An object of the present invention is to provide a process for producing noble metal nanoparticles whose surface area is wide and whose size is controlled by a simple process.

The present inventors synthesized raspberry-like gold nanoparticles (Au RLNPs) in solution in a fast, simple, one-step, high-yield, high-edge and very surface area. For the synthesis of raspberry-like gold nanoparticles, Au ^{n +} precursors and the commercially available amphoteric nonionic surfactant Brij 35 were reacted in a strong basic aqueous solution. The pH dependent form and optical properties of the raspberry-like gold nanoparticles were also tested. The size of raspberry-like gold nanoparticles could be easily controlled by varying the amounts of NaOH and HAuCl ₄ .

The present invention provides a method for preparing raspberry-like noble metal nanoparticles having a large number of corners and having rough surfaces by adding and mixing a nonionic surfactant and a noble metal ion solution in a basic aqueous solution.

The present invention also provides a method for producing raspberry-like noble metal nanoparticles, wherein said nonionic surfactant is at least one selected from polyethylene glycol dodecyl ether, Triton X-100 and nonylphenyl pentaethylene glycol .

The present invention also provides a method for producing raspberry-like noble metal nanoparticles, wherein the noble metal ion is a gold ion, a platinum ion or a silver ion.

The present invention also provides a method for preparing raspberry-like noble metal nanoparticles, characterized in that the particle size is controlled by changing the amount of the base and noble metal ions to be reacted.

The present invention also provides a method for preparing raspberry-like noble metal nanoparticles, wherein the basic aqueous solution has a pH of> 10 or a strong base. At pH> 10, raspberry-like noble metal nanoparticles can be formed in a shorter time.

In addition, the present invention provides raspberry-like noble metal nanoparticles produced by the above-described method and having high number of corners, a rough surface, a wide surface area, and stable in basic and neutral conditions.

The present invention also provides raspberry-like noble metal nanoparticles characterized in that the nanoparticles have a particle size of 10 to 1,000 nm.

The noble metal nanoparticle production method of the present invention can produce noble metal nanoparticles having a large surface area simply by a single process.

In addition, the noble metal nanoparticles prepared by the method of the present invention are stable in basic and neutral conditions and can be applied to various fields.

In addition, the method of the present invention can control the size of nanoparticles by controlling the amount of base and noble metal ions.

1 is 1㎖ Brij35 aqueous solution (19.3 wt%), it is a raspberry similar gold nanoparticle prepared by mixing at room temperature 10 mM HAuCl ₄ aqueous solution of 100 mM NaOH aqueous solution of 100 ㎕, and 50 ㎕. (a) is a micrograph of a SEM type Raspberry-like gold nanoparticle of the present invention and (b) is a TEM photograph, and (c) is a particle size distribution of the particles, and the average particle size is 67 ± 12 nm. (d) is a UV-visible light spectrum of raspberry-like gold nanoparticles 20 minutes (solid line) and 8 hours (dotted line) after mixing the reactants.
Figure 2 shows the change in raspberry-like gold nanoparticles when the pH is lowered. (a) is a UV-visible light spectrum recorded immediately after adding HCl to a gold nanoparticle aqueous solution containing Brij 35 surfactant. The solution pH is (b) pH = 10.62, (c) pH = 6.59, (d) pH = 4.05, and (e) pH = 3.22. The maximum surface plasmon resonance band gradually shifted toward blue as the pH was lowered. SEM photographs of gold nanoparticles at each pH are shown below.
3 is 20 ㎕ (a) and 100 mM NaOH aqueous solution of 200 ㎕ (b) (1 ㎖ Brij35 aqueous solution (200 mM), and 50 ㎕ of 10 mM HAuCl ₄ aqueous solution; Brij35 aqueous solution of 1 mM (200 mM) and 50 (C) and 200 μl (d) of a 10 mM HAuCl ₄ aqueous solution containing 100 mM NaOH at room temperature under the same conditions as in Example 1. All reactions were stopped after 30 minutes after mixing the reactants (A) 120 nm, (b) 45 nm, (c) 142 nm, and (d) 314 nm.
Fig. 4 shows the change in the synthesis process of raspberry-like gold nanoparticles. (a) shows the change in color of the reaction mixture, showing a slight yellow color immediately after mixing all the reactants (left), but blue after about 5 minutes (right). (b) is the change of UV-visible spectrum according to the reaction time. It is a mixture of 19.3 wt% Brij35 solution and HAuCl ₄ aqueous solution before adding NaOH, and all the reagents including NaOH and red Minute (black line) and the spectrum observed after 5 minutes (blue line).
Figure 5 shows the color change of the solution from blue to purple after adding HCl to the raspberry-like gold nanoparticle solution.

Hereinafter, the configuration of the present invention will be described in more detail with reference to specific embodiments. However, it is apparent to those skilled in the art that the scope of the present invention is not limited to the description of the embodiments below.

reagent

Polyglycol dodecyl ether ((C ₂ H ₄ O) ₂₃ C ₂ H ₂₅ OH, Brij 35, Acros Organics), HAuCl ₄ .3H ₂ O (99.9%, Sigma-Aldrich), NaOH %, Sigma-Aldrich) were used as received. All stock solutions were prepared before each reaction. All glass containers were rinsed thoroughly with deionized water before use and then rinsed thoroughly.

Example 1: Synthesis of raspberry-like gold nanoparticles

An aqueous solution of Brij35 (1 ml; 19.3 wt%) was mixed by shaking for 30 seconds with aqueous NaOH solution (100 쨉 l; 100 mM). Aqueous HAuCl ₄ (50 μl; 10 mM) was added and the reaction mixture was shaken vigorously for 1 min. The pale yellow reaction mixture turned blue in 5 min at room temperature. The reaction mixture was sufficiently reacted for 20 minutes or more and then purified by centrifugation at 13,500 rpm for 5 minutes. The reaction mixture was re-dispersed three times in ultrapure water and photographed. The pH of the reaction medium was adjusted by adding HCl (0.1 M) slightly.

Example 2: Characterization

The obtained nanoparticles were photographed with a Hitachi S-4800 SEM microscope and a JEOL JEM-2010 Luminography (Fuji FDL-5000) Ultramicrotome (CRX) TEM microscope. Samples for TEM analysis were prepared by centrifuging the nanoparticle mixture at 13,500 rpm twice for five minutes. The particles were then resuspended in 100 μl of ultrapure water and 10 μl of solution was fixed on a Cu lattice coated with Formvar. Absorption spectra were recorded with a UV spectra spectrophotometer (UVICON XS). The pH of the solution was measured with an Orion 420 A ⁺ pH meter.

result

The present inventors have found that by reducing Au ³⁺ ions (HAuCl ₄ ) using water-soluble polyoxyethylene glycol dodecyl ether ((C ₂ H ₄ O) ₂₃ C ₁ H ₂₅ OH, Brij 35) and NaOH, Raspberry-like gold nanoparticles (Au RLNPs) were synthesized. The repeating unit (-CH ₂ -CH ₂ -O-) of the oxyethylene group and in particular the hydroxyl groups in the Brij surfactant can be effective reducing agents for reducing metal ions (H. Yoo et al., Adv. Mater. 23, 4431 (2011), MH Jang et al., J. Mater. Chem. 21, 17606 (2011), H. Liang et al., J. Phys. Chem. C 114, 7427, W. Li, Y. Guo, and P. Zhang, J. Phys. Chem. C 114, 6413 (2010)). During the growth of Au RLNPs, the color of the reaction solution changed from light yellow to blue. The size and shape of the synthesized gold nanoparticles were determined by SEM (FIG. 1 (a)) and TEM (FIG. 1 (b)). Most of the gold nanoparticles have rough surfaces and many corners It was similar to raspberry. Other nanostructures such as spheres with facets, for example, have not been observed, indicating high yields of raspberry-like gold nanoparticles. The gold nanoparticles of the present invention had a narrow size distribution and an average particle size of 67 +/- 12 nm (150 Au RLNPs were randomly selected and measured) (Figure 1 (c)). Au RLNPs were generated and analyzed by UV-visible spectroscopy. Initially, the reaction mixture exhibited a band around 310 nm, mainly due to the presence of the Au ^{n +} complex in the aqueous Brij surfactant solution. Within 5 minutes this peak disappeared and a new band was created (Figure 4). The solid line in Fig. 1 (d) shows the surface plasmon resonance (SPR) of Au RLNPs recorded after 20 minutes of mixing all the reactants. The maximum peak was 650 nm, which was very red - shifted compared to the previously reported spherical gold nanoparticles. Spherical gold nanoparticles with a particle size of less than 50 nm usually exhibit the maximum surface plasmon resonance band at 510-535 nm and larger spherical gold nanoparticles (eg, particle size 99 nm) exhibit a maximum surface plasmon resonance band at 575 nm (S. Link and MA El-Sayed , J. Phys. Chem. B 103, 8410 (1999)). Surface plasmon resonance of anisotropic gold nanoparticles (e.g., nanorods) is strongly dependent on the morphology of the nanoparticles (S. Link et al., J. Phys. Chem. B 103, 3073 (1999)). It has been reported that the SPR of multi-branch gold nanoparticles is red-shifted compared to the SPR of spherical gold nanoparticles, which appears to be mainly the effect of many corners and vertices on gold nanoparticles (GH Jeong et al., J BK Jena and CR Raj, Langmuir 23, 4064 (2007), OM Bakr et al., &Quot; Chem . Int. Sci. 329, 97 (2009), L. Lu et al., Langmuir 24,1058 . Mater. 18, 3297 (2006 ), X. Zou et al., Nanotechnology 17, 4758 (2006), C.-H. Kuo and MH Huang, Langmuir 21, 2012 (2005), CL Nehl, H. Liao, and JH Hafner, Nano Lett. 6 , 683 (2006), E. Hao et al., Nano Lett. 4, 327 (2004), PS Kumar et al., Nanotechnology 19, 015606 (2008)). The SPR of strongly red-shifted Au RLNPs confirms that the nanoparticles have a non-spherical shape and a rough surface.

The UV-visible light spectrum of the Au RLNPs of the present invention recorded on the eighth day after the start of the reaction shows almost no change in maximum wavelength and light absorption (dotted line in Fig. 1 (d)). This result means that there is no critical structural change in the reaction mixture over time. Microscopic observations also confirmed that the synthesized Raspberry-like gold nanoparticles stably retained their original structure for more than a month under basic conditions (the pH of the reaction mixture was maintained at 11 or higher). After removing the Brij surfactant from the reaction mixture, the particles remained stable in either base or neutral conditions. The high stability of Au RLNPs under given reaction conditions means that these particles can be applied in various applications. However, the structure of Au RLNPs changed rapidly under acidic conditions. Instability in acidic conditions was readily apparent when the solution color changed from blue to purple in a few seconds after adding HCl (Fig. 5). The SPR and structure of the particles varied with decreasing pH (Figure 2). The most red-shifted peak (~ 650 nm) was observed at pH> 11 (Au RLNPs) and gradually blue-shifted at lower pH, eventually reaching ~ 530 nm typical for spherical gold nanoparticles (a)). SEM photographs of the particles show roughness and raspberry-like morphology collapsed into a pseudo spherical nanostructure as the pH decreases (Fig. 2 (b) - (e)). These structural changes were observed under acidic conditions regardless of the presence of Brij surfactant.

The morphological changes of nanoparticles in a pseudo spherical form, such as raspberry, were mainly due to the unstable surface properties due to the high surface / volume ratio. Au RLNPs appear to be a kinematically controlled product that is readily formed in aqueous solutions of strong basic Brij surfactants. This is supported by the fact that Au RLNPs can not be synthesized under acidic conditions even in aqueous Brij surfactant solutions. Changes in the reaction conditions are thermodynamically favored, but thermodynamically unstable Au RLNPs allow thermodynamically more stable similar-spherical structures to be selected (H.-Y. Wu, M. Liu, and MH Huang, J. Phys. Chem. B 110, 19291 (2006)). This structural transition is irreversible. Similar spherical nanoparticles were not regenerated with Au RLNPs even at higher pH.

The size of Au RLNPs can be controlled by varying the amount of NaOH and HAuCl ₄ in the reaction mixture. Au RLNPs smaller than 45 nm in diameter were produced in a reaction mixture containing 200 μL NaOH (pH 12.15) rather than 20 μL (pH 10.68), and the Au RLNPs were purified after 30 min of reaction (FIG. And (b)). These results suggest that the amount of NaOH has a significant effect on the size of Au RLNPs. Size control is also affected by the amount of HAuCl ₄ used. 10 mM HAuCl ₄ solution of 100 ㎕ or 200 ㎕ in which there is no change in the other reaction conditions, the state is baehae a one (1) synthesized in a 10 mM HAuCl ₄ aqueous solution of 50 ㎕ was possible to produce a much larger Au RLNPs (each Average particle diameter 142 nm and 314 nm, Fig. 3 (c) and (d)).

In order to form anisotropic metal nanostructures, symmetric crystallization must be prevented (Y. Xia et al., Angew. Chem. Int. Ed., 48, 60 (2009), XW Lou et al., Chem. 3921 (2006), M. Yamamoto et al., Chem. Mater. 17, 5391 (2005), XW Teng and H. Yang, Nano Lett. 5, 885 (2005)). This can be achieved using structure-directing agents that act differentially on specific metal surfaces and direct subsequent crystallization. Polymeric surfactants have been used to prepare various types of anisotropic nanocrystals as soft casting or structure directing agents (KL Kelly et al., J. Phys. Chem. B 107, 668 (2003), BA Rozenberg and R. Tenne, Prog. Polym. Sci., 33, 40 (2008), S.-H. Yu and H. Colfen, J. Mater. , 14, 2124 (2004), T. Liu et al., Prog. Polym. Sci. 28, 5 (2003) , JW Mullin, crystallisation, 4th edn., Butterworth-Heinemann, Oxford, UK (2001), R. Munoz-Espi et al., Chem. Mater. 20, 7301 (2008), S Yu et al., J. Nanosci., Nanotechnol., 4, 291 (2004)). It is also known that nonionic surfactants form micelles and / or liquid crystals in aqueous solution above critical concentrations, and that these structures can be used as flexible molds to produce materials such as porous materials and powders with a wide surface area (GS Attard et al., Science 278, 838 (1997), GS Attard et al., Angew. Chem. Int . In particular, the favorable adsorption of the polymer hydrophobic group on the surface of the precipitated metal seed and the unique structure of the polymer play an important role in the formation of multi-branched metal nanostructures using amphipathic block copolymers (L. Wang and Y. Yamauchi, J. Am Chem. Soc. 131, 9152 (2009)). In the present invention, a relatively high concentration (19.3 wt%) of an amphipathic anionic Brij35 surfactant appears to influence the growth of the particles, creating a raspberry-shaped structure with a rough surface and a large edge. However, it is also noteworthy that the strong base reaction conditions generated by the addition of relatively large amounts of NaOH are crucial for the formation of Au RLNPs. Au RLNPs appear to be mechanically controlled products that are easily reduced by Brij surfactants under strong base conditions. As in the case of inhomogeneously crystallized gold nanoparticles, Au RLNPs have been successfully synthesized through mechanically controlled processes at high pH (> 11). These nanoparticles are structurally stable under basic conditions, irrespective of the presence of Brij surfactants, but are expected to change to a more stable spherical form without being thermodynamically stable under acidic conditions. The synthesis method of the present invention, in which surfactant use and pH control are important factors for nanoparticle growth with multi-branch nanoparticles, without other precursors, reducing agents and form indicators, is a unique synthesis method.

conclusion

The high yield of stable raspberry-like gold nanoparticles (Au RLNPs) has been demonstrated using non-ionic Brij surfactants in strong base conditions. The surface plasmon resonance of the unique, very red moving Au RLNPs is rough and originates from the surface of Au RLNPs such as raspberry. The size of the Au RLNPs can be controlled by varying the amount of NaOH and HAuCl ₄ . This single step synthesis was fast, simple, and efficient because the commercially available Brij 35 surfactant could act as a reducing agent, a capping agent and a shape-indicating agent. The synthesized Au RLNPs are very stable and have a large surface area under basic or neutral conditions, which is likely to be practically applicable. The synthesis method of the present invention is expected to be applicable to the production of nanomaterials having large surface area and high availability (KK Tanabe and SM Cohen, Chem. Soc. Rev. 40, 498 (2011), JE Lee et al., Acc Chem. Res. 44. 893 (2011), K. Ariga et al., Bull. Chem. Soc. Jpn. 85, 1 (2012)).

Claims (7)

A method for preparing noble metal nanoparticles having a large number of corners and having rough surfaces by adding a nonionic surfactant and one kind of a noble metal ion solution of gold ion, platinum ion or silver ion in a basic aqueous solution to reduce noble metal ions.
The method according to claim 1,
Wherein the nonionic surfactant is at least one selected from the group consisting of polyethylene glycol dodecyl ether, Triton X-100, and nonylphenyl pentaethylene glycol.
delete The method according to claim 1,
Characterized in that the particle size is controlled by changing the amount of the base and noble metal ions to be reacted.
The method according to claim 1,
Wherein the basic aqueous solution is a strong bases aqueous solution having a pH > 10 or more.
6. A process for the preparation of a compound according to any one of claims 1, 2, 4 and 5,
Precious metal nanoparticles with many corners, rough surface, wide surface area and stable in basic and neutral conditions.
The method according to claim 6,
Wherein the nanoparticles have a particle diameter of 10 to 1,000 nm.

Images