KR101436857B1 - Gold nanotoroids and synthetic method thereof - Google Patents

Abstract

An Au nanotoroid having a ring-shaped structure and having an empty center part is successfully synthesized by a seed-mediated method using Brij35 surfactant acting as a reducing agent, a surface stabilizer, and a shape indicator. The relative amount of Au seed nanoparticles has an important effect on yield and form of an obtained Au nanostructure. An available synthesis mechanism is predicted by analyzing time-resolved images and UV-visible ray spectrum.

Description

TECHNICAL FIELD The present invention relates to gold nanocrystals and synthetic methods thereof,

The present invention relates to a gold nanocyclomer and a method for synthesizing the same. More particularly, the present invention relates to a gold nanocyclomer and a method for synthesizing the gold nanocyclomer using a seed-mediated method using a nonionic surfactant functioning as a reducing agent, a surface stabilizer and a shape- Were synthesized successfully.

Gold colloidal nanoparticles and microparticles have attracted a great deal of attention because of their complex spectral characteristics over the visible and near infrared wavelength ranges, generally considered to be low toxicity, and easy functionalization of surface functionalities [Jain PK et al ., 2008 Acc. Chem. Res. 41 1578, Eustis S and El-Sayed MA 2006 Chem. Soc. Rev. 35 209, Hu M. et al., 2006 Chem. Soc. Rev. 35 1084]. In addition to their potential applicability, their properties are also dependent on the actual geometry, thus increasing interest in the controlled form of anisotropic nanoparticles and microparticle synthesis [El-Sayed MA 2001 Acc. Chem. Res. 34 25, Xia Y. et al., 2009 Angew. Chem. Int. Ed. 48 60, Murphy CJ et al., 2005 J. Phys. Chem. B 109 13857, Treguer-Delapierre M. et al., 2008 Gold Bull. 41 195, Jones MR et al., 2011 Chem. Rev. 111 3736]. The development of a unique nanostructure synthesis process is at the forefront of nanoparticle science.

Nonionic polymeric surfactants include porous films [Attard GS et al., 1997 Science . 278 838, Luo K. et al., 2007 Adv. Mater. 19 1506], powder-like nanomaterials [Attard GS et al., 1997 Angew. Chem. Int. Ed. Engl. 36 1315], anisotropic nanoparticles [Wang D. et al., 2004 Angew. Chem. Int. Ed. 43 6169, Yu SH et al., 2004 J. Nanosci. Nanotec. 4 291] and nanotubes [Kijima T. et al., 2004 Angew. Chem. Int. Ed. 43 228], which is useful for the synthesis of novel metallic nanostructures. In general, these nanostructures have been prepared in liquid crystalline (LLC) phases using high concentrations of nonionic polymeric surfactants, primarily as a soft template or structure directing agent. Recently, a unique Au microcrystal synthesis has been reported by our research team using a nonionic Brij surfactant used as a reducing agent, a capping agent and a structure directing agent [Jang MH, Kim JK and Yoo H 2012 J. Nanosci. Nanotech. 12 4088, Yoo H. et al., 2011 Adv. Mater. 23 4431, Jang MH, Kim JK, Tak H and Yoo H 2011 J. Mater. Chem. 21 17606]. Au microns of triangular or hexagonal crystals were synthesized using, for example, an aqueous solution containing an Au precursor and a nonionic Brij 35 ((C ₂ H ₄ O) ₂₃ C ₁₂ H ₂₅ OH) surfactant [Yoo H. et al. , 2011 Adv. Mater. 23 4431]. Hexagonal multilayer Au spirangles were also synthesized in a high yield in a fashion that can be controlled through a simple process in an aqueous solution of Brij 700 ((C ₂ H ₄ O) ₁₀₀ C ₁₈ H ₃₇ OH) [Jang MH, Kim JK, Tak H and Yoo H 2011 J. Mater. Chem. 21 17606]. Importantly, the growth of these nanocrystals was achieved at a relatively low Brij surfactant concentration than is required for liquid crystals.

Although synthetic routes using non-ionic surfactants are quite convenient, a more effective strategy for growing Au microcrystals is required to design and optimize the morphology of Au particle materials for future applications. In particular, Au structures using the previously synthesized Brij surfactants are relatively large (edge lengths, ca. ~ 2 μm) and may limit their potential availability [Yoo H. et al., 2011 Adv. Mater. 23 4431, Jang MH, Kim JK, Tak H and Yoo H 2011 J. Mater. Chem. 21 17606]. In order to synthesize anisotropic nano Au particles using a nonionic surfactant, the inventors employed a gradual seeding method, which is a preferred synthesis technique for preparing anisotropic nanocrystals from new metals [Murphy CJ et al., 2005 J Phys. Chem. B 109 13857, Golee and Murphy CJ 2004 Chem. Mater. 16 3633, Liu M and Guyot-Sionnest P 2005 J. Phys. Chem. B 109 22192, Millstone JE et al., 2005 J. Am. Chem. Soc. 127 5312].

It is an object of the present invention to provide a method for simply synthesizing a gold nano-annular body having a shape similar to a ring in which the center of the gold nanoparticles having various shapes is empty.

The present inventors have invented a new and simple solution-based seed-mediated method using a non-ionic Brij 35 surfactant to synthesize Au nanocoronoids having a ring-like structure at the center.

The present invention

a) preparing a mixed solution a by adding Au seed nanoparticles having an average particle diameter of less than 5 nm to a growth solution A containing a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst;

b) the prepared mixed solution a immediately contains a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst, wherein the concentration of the nonionic surfactant, the cationic gold precursor-containing aqueous solution and the alkali catalyst is in the composition To the growth solution B equal to or higher than the concentration of the component;

c) mixing the prepared mixed solution b immediately with a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst, wherein a concentration of a nonionic surfactant higher than that of the growth solution A and the growth solution B, an aqueous solution containing a cationic gold precursor And an alkaline catalyst to produce a mixed solution c; And

d) allowing the prepared mixed solution c to stand at room temperature for 12 hours or more.

If the reaction time is less than 12 hours, the reaction does not occur sufficiently and the cyclic compound is not formed. When the reaction time exceeds 100 hours, the efficiency of synthesis of cyclic compounds with time is low and the economical efficiency is low.

The present invention also relates to a method for producing a gold-containing surfactant characterized in that the nonionic surfactant is at least one selected from the group consisting of polyoxyethylene glycol dodecyl ether, glycerin fatty acid ester, sucrose fatty acid ester and sorbitan fatty acid ester. And a method for synthesizing a nano-cyclic compound.

In the present invention, there is no particular limitation on the kind of the alkali catalyst, and various alkali catalysts such as ammonia and NaOH can be used.

Further, no particular limitation is not, chloroauric acid and potassium (KAuCl _4), chloroauric acid sodium (NaAuCl _4), chloroauric acid (HAuCl _4), brominated Keumsan sodium (NaAuBr _4), yeomhwageum (AuCl) on the type of cationic gold precursor, Gold (III) chloride (AuCl ₃ ), gold bromide (AuBr ₃ ), and the like.

Further, the present invention relates to a gold nano-annular body produced by the above-mentioned synthesis method and having a particle diameter of 900 nm or less and a through hole formed at the center. If the particle size exceeds 900 nm, there is little advantage as a nanoparticle. In the specific examples of the present invention, gold nanocrystals having an average particle size of about 300 to 600 nm were obtained, but the particle size may be smaller or larger within a nanometer range depending on reaction time, temperature, and reactant concentration.

According to the present invention, it is possible to synthesize a gold nano-annular body having a hole at the center and having a structure similar to a ring by a simple method, and the synthesized gold nanocyclers can be used for various applications such as biosensors, bio- . ≪ / RTI >

1 is a scanning electron micrograph (a) and a transmission electron micrograph (b) (size bar: 200 nm) of synthesized Au nanocyclers; (c) is a high-resolution TEM image (size bar: 100 nm) of the Au nanoclay in the box portion of the insert; (d) is an electron diffraction pattern of a selected portion of the nano-Au annulus ((c) inset within the box part, the bar: 5 nm ^-1).
FIG. 2 shows the UV-visible spectrum (a) and the SEM image (bd) of the Au nanostructures produced by varying the reaction time. 100 占 퐇 of a solution of Au seed nanoparticles was added to the growth solution A. Au nanostructures were obtained after 4 hours (b), 6 hours (c) and 24 hours (d). Size bar: 200 nm.
Fig. 3 shows changes in the UV-visible light spectrum (a) and the change in the SEM image (bd) of Au nanostructures produced at different reaction times. 1000 占 퐇 of Au seed nanoparticle solution was added to the growth solution A. Au nanostructures were obtained after 3 hours (b), 5 hours (c) and 24 hours (d). Size bar: (b) 100 nm, (c) and (d) 200 nm.
Fig. 4 shows changes in the UV-visible spectrum (a) and the change in the SEM image (bd) of Au nanostructures produced at different reaction times. Au seed nanoparticle solution was not used. Au nanostructures were obtained after 7 hours (b) and 24 hours (d). Size bar: 500 nm.
5 is a diagram illustrating a possible mechanism of synthesis of seed-mediated Au nanostructures using non-ionic Brij.
The left side of FIG. 6 is a TEM photograph of Au nanocyclers (size rod; 50 nm); The center is a picture taken with a high-resolution TEM within the box of the left TEM photograph (size bar: 5 nm); The right side is the electron diffraction pattern of the selected portion of the Au nanocyclamate (whole part of each TEM photograph, bar: 5 nm ^-1 ).
7 is a TEM photograph of Au nanostructures prepared in the preparation of nanocyclers prepared by adding 100 μl of Au seed nanoparticle solution to the growth solution A. FIG. Au nanostructures were obtained after 6 h of reaction time (size rod: 50 nm); The center is a high-resolution TEM image of the in-box portion of the left TEM photograph (size bar: 5 nm); The right side is the electron diffraction pattern of the selected portion of the Au nanocylic body (total of each TEM, rod: 5 nm ^-1 ). The diffracted points represent hexagonal symmetry, and each Au nanoclinic shows a highly crystalline fcc structure of gold. The points diffracted in the [111] zoneaxis are {220} (square points), 1/3 {422} (points within triangles) and {200} (points in circles).

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 scope of the embodiments.

reagent

(C ₂ H ₄ O) ₂₃ C ₁₂ H ₂₅ OH, Brij 35, Acros Organics}, 2 nm gold nanoparticle solution (Ted Pella Inc.), HAuCl ₄ .3H ₂ O ( hydrogen tetrachloro aurate trihydrate, 99.9%, Sigma Aldrich), NaOH (98.0%, Sigma Aldrich), HCl, HNO ₃ , acetone and ethanol were used as purchased. All stock solutions were prepared immediately prior to each reaction. All glass containers were used after washing with aqua regia _{(v: HNO 3 v = 3} :: 1, HCl) and rinse thoroughly with ultrapure water.

Example 1: Synthesis of Au nanocyclers

Au nanocyclers were synthesized by reducing Au ³⁺ ions (from HAuCl ₄ ) to 2 nm Au seed nanoparticles using Brij 35 and NaOH aqueous solutions. Three kinds of growth solutions were prepared. To prepare solutions A and B, 2 ml of Brij35 aqueous solution (50 mM) was thoroughly mixed by shaking for 30 seconds in 50 μl of HAuCl ₄ aqueous solution (10 mM) and 50 μl of aqueous NaOH solution (10 mM). Similarly, Growth Solution C was prepared by mixing 20 ml of Brij35 aqueous solution (50 mM) with 500 μl of HAuCl ₄ aqueous solution (10 mM) and 500 μl NaOH aqueous solution (10 mM) for 30 seconds and thoroughly mixing. Au nano cyclic synthesis was initiated by adding 100 μl of 2 nm Au seed nanoparticles to Growth Solution A. 100 占 퐇 of the growth solution A was quickly added to the growth solution B and then added to the growth solution C. The reaction mixture was vigorously shaken for at least one minute and then left as such for 72 hours. The mixture was then purified by centrifugation (5 min; 13,500 rpm), redispersed three times in ultrapure water and then characterized. To change the amount of Au seed nanoparticles, a solution of 2 nm Au seed nanoparticles added to the growth solution A was varied from 0 to 1000 μl. The reaction was carried out at room temperature and was not heated.

Example 2: Characterization

The synthesized nanoparticles were photographed using a Hitachi S-4800 scanning electron microscope and a LEO-912AB OMEGA (Carl Zeiss, Germany) transmission electron microscope. High-resolution transmission electron microscopy, energy dispersive X-ray (EDX) and selected-area electron diffraction (SAED) patterns were measured using a JEOL JEM-2100F microscope. UV-visible spectra were recorded on a UV-1800 Shimadzu spectrophotometer. The pH of the solution was measured using an Orion 420 A ⁺ pH meter. Samples for TEM analysis were prepared by centrifuging the nanoparticle mixture twice at 13,500 rpm for 5 minutes. The particles were then resuspended in 100 μl of ultrapure water and fixed in a 10 μl aliquot on a Formvar coated Cu lattice.

result

In the examples, Au nanocyclers were synthesized by reducing Au ³⁺ ions to 2 nm Au seed nanoparticles using Brij 35 and NaOH aqueous solution. To prepare the growth solution was mixed with an aqueous solution Brij35, HAuCl ₄ aqueous solution and NaOH aqueous solution. The Au nano-annular formation was initiated by adding the Au seed nanoparticle solution to the growth solution A, and this mixture was added to the growth solution B, and this mixture was added to the growth solution C and left for 72 hours at room temperature. 1 is an SEM and TEM image of Au nanostructures obtained from 100 μl of Au seed nanoparticle solution. It was observed that the sample consisted mostly of a ring-shaped nanostructure. Au nanocyclers showed the same shape as a ring with an empty center. Some of them did not form a complete ring and showed U or V shape. The distance between the lattice stripes was 0.146 nm as measured directly from the high-resolution TEM images of the single Au nanocyclers. This can be attributed to the spacing between (220) lattice planes within the crystal's face-centered cubic (fcc) structure (Fig. 1c) [Suh I, Ohta H and Waseda Y 1988 J. Mater. Sci. 23 757]. 1D and S1 are electron diffraction patterns of selected portions of the Au nanocyclers obtained for the electron beam perpendicular to the circular plane. The diffracted points represent hexagonal symmetry, and each Au nanoclinic shows a highly crystalline fcc structure of gold. The points diffracted in [111] zoneaxis exhibited {220} (points in a square), 1/3 {422} (points within a triangle) Bragg reflections, which correspond to the lattice spacing of 0.146 nm and 0.255 nm, respectively (Fig. 1D). These diffraction points indicate that the surface of the Au nanocrystals is atomically planar [Suh I, Ohta H and Waseda Y 1988 J. Mater. Sci. 23 757, Millstone JE et al., 2009 Small 5 646, Wang ZL 2000 J. Phys. Chem. B 104 1153, Cherns D 1974 Philos. Mag. 30 , 549, Kirkland AI et al., 1990 Inst. Phys. Conf. Ser. 98 , 375].

It is noteworthy that the size of the Au nanocycles is much smaller than the size of the Au ring synthesized using the Brij35 surfactant [Yoo H. et al., 2011 Adv. Mater. 23 4431]. The average width of Au rings reported was ~ 2 ㎛. Due to the irregular shape, the size of the Au nanocyclers can not be totally averaged, but the diameter of the nanocyclers is within the range of 300-600 nm, obviously nanometer. In order to study how Au nanocrystals were made, the present inventors used a UV-visible light beam as a function of reaction time during the growth process of Au nanocyclers (100 μl of 2 nm Au seed nanoparticles in Growth Solution A) The spectroscopic data were analyzed. Figure 2a shows the variation of the UV-visible light spectrum of the Au nanocycles produced. The disappearance of the ~ 260 nm absorbance band within 4 hours of the reaction clearly shows that the Au ³⁺ cation precursor (HAuCl ₄ ) was completely consumed. At the same time, the disappearance of the ~580 nm band was observed, which corresponds to an increase in the spherical Au nanoparticles [Link S, El-Sayed MA 1999 J. Phys. Chem. B 103 , 8410]. Although a broad absorption band at the near-infrared region increased with reaction time, no further significant change in the UV-visible region was observed. Au nanocyclers are probably still too large to exhibit surface plasmon resonance in the UV-visible region.

The present inventors also photographed the synthesized Au nanomaterial as a function of reaction time. SEM photographs taken after 24 hours of reaction (FIG. 2d) show that the Au nanocycles were effectively made. When the HAuCl ₄ extinction band disappeared (after 4 hours) the reaction medium was observed and the Au nanostructure produced was a mixture of nanoparticles and similar spherical nanoparticles similar to the 2D plate (Fig. 2b). In particular, nanoparticles similar to plates had wrinkled edges [Shankar S. et al., 2004 Nat. Mater. 2 , 482]. The nanostructures obtained after 2 hours of reaction showed almost no reduced Au particles but showed similar structure to the plate similar to Fig. 2B. However, after 6 hours of reaction, a larger Au nanoplate was observed in the reaction mixture (Fig. 2C). Most of these nanoplates are angular and interestingly there is a hole in the center or side. The high-resolution TEM photographs and electron diffraction patterns of these Au nanoparticles showed almost the same results as those of the Au nanocyclers shown in FIG. 1, indicating that these plate-like nanoparticles are highly crystallized fcc structures of gold 7). Au nanoparticles were converted to Au nano-cyclic forms when the reaction time was prolonged (more than 24 hours, Fig. 2d).

In order to synthesize Au nanocrystals with high yield, stepwise growth solution transfer is crucial. When the Au seed nanoparticle solution was directly added to the final growth solution C, the yield of the Au nanocyclomer was greatly lowered, and Au nanoprec and similar spherical Au nanoparticles were produced in most cases. In anisotropic Au nanostructure synthesis, the shape of a synthesized nanostructure can be significantly changed even if the amount of the surfactant is slightly changed. The step-wise transition of the growth solution assists the control of growth dynamics by assuring a fine concentration change of the surfactant [Murphy CJ et al., 2005 J. Phys. Chem. B 109, 13857].

Another key factor is the seed-mediated synthesis process. The results of the present invention show that the relative amount of Au seed nanoparticles has an important effect on the shape of the Au nanostructure to be synthesized. The optimum amount (50-200 μl) of Au seed nanoparticle solution yields an Au nanocycler in high yield, whereas the addition of a larger amount of Au seed nanoparticle solution (> 400 μl) during the growth stage results in less Au nanocycles Synthesized or not synthesized. 3A shows a UV-visible light spectrum of an Au nanostructure synthesized by adding 1000 μl of Au seed nanoparticle solution to growth solution A, and then sequentially transferring the growth solution as a function of reaction time. Based on the disappearance of the 260 nm absorbance band, it can be concluded that HAuCl ₄ was completely consumed within 3 to 5 hours after the initiation of growth, and the absorption band of about 580 nm corresponding to the pseudo-spherical Au nanoparticles gradually increased. In addition, a broad band representing the maximum absorbance at about 850 nm appeared within 5 hours (Fig. 3a). 3B and 3C, it was found that this wide band corresponds to the surface plasmon resonance of the Au nanoparticle. Au nanostructures fabricated within 3 hours were irregular in edge and had a length of ~ 100 nm (Fig. 3B). After 5 hours of reaction, these Au nanoparticles were converted into nanoplates of about 100-200 nm in size with smooth shapes (FIG. 3C). Interestingly, the broad SPR band shifted to a lower wavelength gradually up to 7 hours of reaction and exhibited a maximum peak at ~700 nm. After 7 hours of reaction, no further changes were observed in the SPR, and a smaller (about 50-100 nm edge length) rounded Au nanoplate was formed. SPR migration appears to be due to a reduction in the diameter or edge length of Au nanoparticles [Millstone JE et al., 2009 Small 5 646]. Based on this, it can be concluded that Au cations are reduced to form pseudo spherical Au nanoparticles and 2D Au nanostructures, and furthermore, when a larger amount of Au seed nanoparticles are used, they are transformed into round Au nanoparticles. No Au nanocyclers were observed in the reaction mixture.

Without Au seed nanoparticles, triangular or hexagonal Au rings were created (FIG. 4C). The structural motif of the Au ring was similar to the Au nanoclinic of FIG. The edge length of the synthesized Au ring is about 600 nm, and the Au ring reported earlier (Yoo H. et al., 2011 Adv. Mater. 23 4431]. It was clearly observed that a hexagonal Au nanoplate was formed when the growth process was started (after 7 hours of reaction, Fig. 4A). After 24 hours of reaction, only a small amount of Au nanoparticles remained and the remainder was converted into triangular or hexagonal Au nanorings (FIG. 4B). Au nanoplate formation can also be confirmed by UV-visible spectral changes over time (Fig. 4A). A broad SPR band near 1000 nm gradually decreased as Au rings were generated (reaction 7-24h).

In inorganic nanocrystal synthesis, nonionic polymeric surfactants have also been used as a flexible template or structure directing agent as well as a capping agent [Rozenberg BA and Tenne R 2008 Prog. Polym. Sci. 33 40, Yu SH et al., 2004 J. Mater. Chem. 14 2124, Liu T, Burger C and Chu B 2003 Prog. Polym. Sci. 28 5]. Crystal growth can be effectively controlled by absorbing the polymeric surfactant on a specific crystalline surface [Yu SH et al., 2004 J. Nanosci. Nanotec. 4 291, Mullin J W 2001 Crystallization 4th edn (Oxford, UK: Butterworth-Heinemann), Munoz-Espir et al., 2008 Chem. Mater. 20 7301, Wang L. et al., 2005 J. Phys. Chem. B 109 3189, Sakai T and Alexandrid P 2005 Nanotechnology 16 344, Chu HC, Kuo CH and Huang MH 2006 Inorg. Chem. 45 808, Goy-Lopez S, Castro E, Taboada P and Mosquera V 2008 Langmuir 24 13186]. In the present invention, the nonionic Brij35 surfactant functioned as a reducing agent and a shape indicator in the synthesis of circular or plate-like Au nanostructures. In particular, the use of Brij35 was important for the production of round shapes. Au nanocyclers were not produced without this surfactant, and the growth of Brij 35-auxiliary nanocyclers was greatly influenced by the amount of spherical 2 nm Au seed nanoparticles added. Based on these results, 2D Au nanostructures were first produced (3-7 h) in the initiation phase of the reaction, which subsequently developed into secondary structures (ie, plates, rings and annular bodies). In the initial stage (-0-2 h), very small plate-like nanoparticles were synthesized even though the reduced Au nanoparticles were very small and the Au ³⁺ cationic precursors were not completely consumed. When 2 nm Au seed nanoparticles are present in the Brij35 aqueous solution, the Au ³⁺ ions from HAuCl ₄ can be reduced on the surface of the seed nanoparticles in an anisotropic manner and preferentially form plate-like Au nanostructures as "intermediate nanosides" I think it can be done. Au nanoprecate synthesis using a Brij surfactant as a shape-indicating agent has been previously reported [Yu SH et al., 2004 J. Nanosci. Nanotec. 4 291].

Au nanocyclers are derived from the Brij 35 secondary etching of the first plate-like intermediate nanosides. Therefore, in this process, two or more Au nanoparticles can be combined to form a larger Au nanoparticle. (Ozin GA, Arsenault AC and Cademartiri L 2009 Nanochemistry : A Chemical Approach to Nanomaterials , 2nd ed., Cambridge, UK: RSC Publishing). Furthermore, Au nanoparticles grown from small nanoparticles are defective, i.e., with a central aperture (FIG. 2c), which is believed to be due to incomplete aging of the smaller, wrinkled Au nanoparticles. Brij 35-secondary etching of Au nanoparticles begins with the defect (center hole) and goes around the nanoplate, eventually forming a softer Au nanocycler. This etching process seems to be completed within 24-72 hours of the reaction (Fig. 5 (A)). The size and shape of the plate-like intermediate nanosides varies and is highly dependent on the amount of 2 nm Au nanoparticle solution. Using significantly larger amounts of Au seed nanoparticles resulted in smaller plate-like intermediate nanosides (Figure 3c). These nanostructures had fewer defects than the particles of FIG. 2C, and thus only etching at the edges resulted in round Au nanoparticles (FIG. 5B). Based on these results, we conclude that the formation of the internal cavity on the plate-like intermediate Au nano-seed is crucial for the formation of Au nanocyclers. In Figure 5, the two growth mechanisms (A and B) may be competitive during the synthesis process. The optimum amount of Au nanoparticle seed is required to obtain Au nanocyclers at high yield.

In the absence of Au seed nanoparticles, Au ³⁺ ions are reduced at relatively slow rates, forming a triangular or hexagonal intermediate Au nanoparticle with mostly corners and vertices. This Au nanoparticle gradually changes into triangular or hexagonal Au nanorings in aqueous Brij35 solution. Note that such Au nanorings were not observed in the early stages of the reaction and showed much larger edge lengths than the intermediate Au nanoparticles. This can be explained by the fact that during the formation of the larger 2D nanostructures {Figure 5 (C)}, the Au nanorings were formed through the etching of Au nanoparticles initially created. It is believed that Brij35 is strongly bound to the surface of the intermediate Au nanoplate, resulting in etching in the center of the nanoplate. In particular, re-organization of the Au material from the center to the edge of the Au nanoparticle can provide a larger Au ring. In the previous study, it was found that in synthesized Au ring by heat treatment, the synthesized ring has a larger edge length ( ca. ~ 2 μm) [Yoo H. et al., 2011 Adv. Mater. 23 4431], but similar etch mechanisms have been proposed. By using a seed-mediated synthesis strategy, the inventors have successfully synthesized Au materials (nanocyclers and nanorings) with nano-sized edge lengths. They are expected to be applicable to various fields.

In conclusion, the present inventors have successfully synthesized an Au nano-cyclic structure having a hollow center through a seed-mediated method using a Brij 35 surfactant functioning as a reducing agent, a surface stabilizer and a shape-indicating agent. The relative amounts of Au seed nanoparticles have a significant effect on the yield of Au nano cyclic synthesis and on the morphology of the synthesized Au nanostructures. Au nanocrystals can be synthesized with high yield by using an optimal range of 50-200 μL of 2 nm Au seed nanoparticle solution. Mechanically, the Au nanocyclers appear to originate from the Brij 35 secondary etching of the initially grown plate-like intermediate Au nanosides that form from the inner through holes to the edges of the Au plate.

Claims (7)

a) preparing a mixed solution a by adding Au seed nanoparticles to a growth solution A containing a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst;
b) the prepared mixed solution a immediately contains a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst, wherein the concentration of the nonionic surfactant, the cationic gold precursor-containing aqueous solution and the alkali catalyst is in the composition To the growth solution B equal to or higher than the concentration of the component;
c) mixing the prepared mixed solution b immediately with a nonionic surfactant, a cationic gold precursor-containing aqueous solution and an alkali catalyst, wherein a concentration of a nonionic surfactant higher than that of the growth solution A and the growth solution B, an aqueous solution containing a cationic gold precursor And an alkaline catalyst to produce a mixed solution c; And
d) leaving the prepared mixed solution c for not less than 12 hours but not longer than 100 hours.
The method according to claim 1,
Wherein the nonionic surfactant is at least one selected from the group consisting of polyoxyethylene glycol dodecyl ether, glycerin fatty acid ester, sucrose fatty acid ester and sorbitan fatty acid ester. .
The method according to claim 1,
Wherein the alkali catalyst is an aqueous solution of NaOH.
The method according to claim 1,
The cationic gold precursor Keumsan potassium chloride (KAuCl _4), chloroauric acid sodium (NaAuCl _4), chloroauric acid (HAuCl _4), brominated Keumsan sodium (NaAuBr _4), yeomhwageum (AuCl), yeomhwageum (Ⅲ) (AuCl ₃₎ And gold bromide (AuBr ₃ ).
The method according to claim 1,
Wherein the steps a) to d) are carried out at room temperature.
A gold nanoclinic body produced by a method according to any one of claims 1 to 4, wherein a through hole is formed at the center.
The method of claim 6,
Wherein the gold nanocrystalline has a particle diameter of 300 nm or more and 900 nm or less.

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