Three-dimensional chiral nanostructure and manufacturing method therefor

Abstract

A method for manufacturing a three-dimensional chiral nanostructure, according to one embodiment of the present invention, comprises the steps of: synthesizing chiral nanoparticles; forming a shell structure coating the chiral nanoparticles and having a porous structure; removing at least a portion of the chiral nanoparticles by using the porous structure to supply an etchant into the shell structure; and forming a dissimilar metal layer in the region from which the chiral nanoparticles have been removed.

Description

3D chiral nanostructure and method for manufacturing the same

[0001] The present invention relates to a three-dimensional chiral nanostructure and a method for manufacturing the same.

[0002]

[0003] A chiral structure refers to a structure having an asymmetric structure that possesses no mirror image symmetry. Within a chiral structure, the electric dipoles and magnetic dipoles generated by incident electromagnetic waves interact in the same direction, thereby breaking the degeneracy of right-sided and left-sided polarization. Consequently, chiral structures have different refractive indices for left-sided and right-sided light, and thus, when linearly polarized light is incident on a chiral material, a photoactive characteristic in which the polarization state rotates is exhibited.

[0004]

[0005] One of the technical problems that the technical concept of the present invention aims to solve is to provide a three-dimensional chiral nanostructure that can be utilized in various fields and a method for manufacturing the same.

[0006]

[0007] A three-dimensional chiral nanostructure according to one embodiment of the present invention comprises a seed layer containing gold (Au) and a heterogeneous metal layer surrounding the seed layer and containing gold (Au) and a different metal, and the structure comprising the seed layer and the heterogeneous metal layer can form a crystallographically 432 symmetry structure.

[0008] A method for manufacturing a three-dimensional chiral nanostructure according to one embodiment of the present invention may include the steps of synthesizing chiral nanoparticles, forming a shell structure having a porous structure by coating the chiral nanoparticles, removing at least a portion of the chiral nanoparticles by supplying an etching agent into the shell structure using the porous structure, and forming a heterogeneous metal layer in the region where the chiral nanoparticles have been removed.

[0009]

[0010] By including a heterogeneous metal layer, a three-dimensional chiral nanostructure that can be utilized in various fields can be provided.

[0011] By using a shell structure having a porous structure, a method for manufacturing a three-dimensional chiral nanostructure comprising a heterogeneous metal layer having a three-dimensional shape of chiral nanoparticles transferred thereto can be provided.

[0012] The various and beneficial advantages and effects of the present invention are not limited to those described above and may be more easily understood in the process of explaining specific embodiments of the present invention.

[0013]

[0014] FIG. 1 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0015] FIG. 2 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0016] FIG. 3 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0017] FIG. 4 is a flowchart illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0018] FIGS. 5a to 5f are drawings illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0019] FIGS. 6a and 6b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0020] FIGS. 6c and 6d are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0021] FIG. 7 is an electron microscope image illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0022] FIGS. 8a and 8b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0023] FIGS. 9a and 9b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0024] FIGS. 10a to 10e are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0025] FIGS. 11a to 11e are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0026] FIGS. 12a to 12e are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0027] FIGS. 13a to 13c are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0028] FIGS. 14a to 14d are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0029]

[0030] Hereinafter, preferred embodiments of the present invention will be described as follows with reference to the attached drawings.

[0031] Embodiments of the present invention may be modified in various different forms or combined in various ways, and the scope of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation, and elements indicated by the same reference numerals in the drawings are the same elements.

[0032]

[0033] 3D chiral nanostructures

[0034] FIG. 1 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0035] Referring to FIG. 1, a three-dimensional chiral nanostructure (100) according to one embodiment of the present invention may include a seed layer (10) and a heterogeneous metal layer (20) surrounding the seed layer (10).

[0036] The seed layer (10) may be located in a central region that includes the center of the three-dimensional chiral nanostructure (100). The seed layer (10) may include a first metal, for example, gold (Au). For example, the seed layer (10) may be made of gold (Au). The seed layer (10) itself may have a chiral shape or a non-chiral shape. For example, if the seed layer (10) has a relatively small size, it may have a non-chiral shape, and if it has a relatively large size, it may have a chiral shape. For example, the seed layer (10) may have a shape that is symmetric with respect to a central axis. The seed layer (10) may have a spherical shape, a rectangular shape with rounded corners, a rectangular shape, or a shape similar thereto. The size of the seed layer (10) may be, for example, in the range of about 10 nm to about 200 nm. The above 'size' may refer to the diameter or the width in one direction.

[0037] A heterogeneous metal layer (20) surrounds the seed layer (10) and can define the surface of the three-dimensional chiral nanostructure (100). The heterogeneous metal layer (20) may include a second metal different from the first metal. The heterogeneous metal layer (20) may not include the first metal. For example, the heterogeneous metal layer (20) may be made of a metal other than gold (Au). The heterogeneous metal layer (20) may include at least one of silver (Ag), palladium (Pd), platinum (Pt), copper (Cu), and nickel (Ni).

[0038] The three-dimensional chiral nanostructure (100) may have a chiral shape, for example, an asymmetric structure that does not have any mirror image symmetry. The three-dimensional chiral nanostructure (100) may have a helicoid structure and may have a crystallographically 432 symmetry structure. The '432 symmetry structure' is one of the crystal groups according to Hermann-Mauguin notation and belongs to the cubic crystal system. In some embodiments, when the seed layer (10) has a chiral shape, the seed layer (10) may have the same shape as the three-dimensional chiral nanostructure (100) but a smaller size. For example, the seed layer (10) may also have a 432 symmetry structure.

[0039] The three-dimensional chiral nanostructure (100) has a direction perpendicular to each face <100> It corresponds to the direction, and the direction from the center to the vertex is <111> It corresponds to the direction, and the direction from the center to the center of the corner <110> It may correspond to a direction. Additionally, the three-dimensional chiral nanostructure (100) may have a crystal plane of high Miller index. A crystal plane of high Miller index refers to a crystal plane that satisfies the conditions h > 0, k > 0, and l > 0 in the Miller index expressed as {hkl}, which represents the characteristics of the crystal plane, and in particular, may refer to a crystal plane that is a combination of a crystal plane of low Miller index such as {100}, {110}, {111}, etc. Nanoparticles composed of crystal planes of high Miller index generally have more than 20 faces exposed in a single particle, and the curvature at the edges or vertices where the crystal planes join together may be greater than that of crystal planes of low Miller index. However, the shape of such a three-dimensional chiral nanostructure (100) is exemplary, and the shape of the three-dimensional chiral nanostructure (100) can be varied.

[0040] The length (L1) of one edge in the cube shape of the three-dimensional chiral nanostructure (100) may be, for example, in the range of about 50 nm to about 500 nm, for example, in the range of about 100 nm to about 200 nm.

[0041] In the following embodiments, for configurations using the same reference numerals, descriptions that overlap with the description with reference to FIG. 1 are omitted.

[0042]

[0043] FIG. 2 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0044] Referring to FIG. 2, a three-dimensional chiral nanostructure (100a) according to one embodiment of the present invention may further include a shell structure (30) in addition to a seed layer (10) and a heterogeneous metal layer (20). The description above with reference to FIG. 1 may be applied equally to the seed layer (10), the heterogeneous metal layer (20), and the structure.

[0045] The shell structure (30) can surround the heterogeneous metal layer (20) and may have a spherical surface. The shell structure (30) may have a porous structure and may contain a plurality of pores inside. The shell structure (30) may be made of a non-metallic material, for example, a dielectric material. For example, the shell structure (30) may include porous silica (SiO2), porous titanium dioxide (TiO2), etc.

[0046] The three-dimensional chiral nanostructure (100a) may have a spherical shape as a whole due to the shell structure (30). However, in the three-dimensional chiral nanostructure (100a), light and material can be transmitted into the shell structure (30), and since the metal region including the seed layer (10) and the heterogeneous metal layer (20) has a chiral shape, the three-dimensional chiral nanostructure (100a) may have chiral properties.

[0047]

[0048] FIG. 3 is a schematic perspective view illustrating a three-dimensional chiral nanostructure according to one embodiment of the present invention.

[0049] Referring to FIG. 3, a three-dimensional chiral nanostructure (100b) according to one embodiment of the present invention may consist only of a heterogeneous metal layer (20) without including a seed layer (10) (see FIG. 1). The heterogeneous metal layer (20) may fill the central region of the three-dimensional chiral nanostructure (100b). In some embodiments, the three-dimensional chiral nanostructure (100b) may further include a shell structure (30), as in the embodiment of FIG. 2.

[0050]

[0051] Method for manufacturing three-dimensional chiral nanostructures

[0052] FIG. 4 is a flowchart illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0053] FIGS. 5a to 5f are drawings illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0054] Referring to FIG. 4, a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention may include the steps of synthesizing chiral nanoparticles (KP) (S110), forming a shell structure (30) having a porous structure (S120), removing at least a portion of the chiral nanoparticles (KP) (S130), forming a heterogeneous metal layer (20) in the area where the chiral nanoparticles (KP) have been removed (S140), and removing the shell structure (30) (S150). The step of forming a shell structure (30) having a porous structure (S120) may include the step of forming a preliminary shell structure (30P) coated with chiral nanoparticles (KP) (S122) and the step of partially dissolving the preliminary shell structure (30P) with high-temperature water to form a porous structure (S124).

[0055]

[0056] Referring to Fig. 5a, a step (S110) of synthesizing chiral nanoparticles (KP) can be performed.

[0057] The chiral nanoparticles (KP) are removed in at least a portion during a subsequent process and can function as a template for forming a heterogeneous metal layer (20) in the removed area. The chiral nanoparticles (KP) can be prepared by reacting seed particles with a growth solution and an organic material.

[0058] The seed particles may have various shapes, such as, for example, a cube, a sphere, a prism, a rod, a plate, a hexahedron, an octahedron, a dodecahedron, etc. The seed particles may contain gold (Au), but are not limited thereto. The seed particles may have a size of, for example, 10 nm to 50 nm.

[0059] The growth solution may include a metal precursor, a capping agent, and a reducing agent. Chiral nanoparticles (KP) may be formed by the reduction of metal ions of the metal precursor to the surface of the seed particles within the growth solution. The metal precursor may include, for example, chloroauric acid (HAuCl4), and the capping agent may include cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), or polyvinylpyrrolidone (PVP). The reducing agent may include ascorbic acid or a substance having an oxidation potential at the same level as ascorbic acid, for example, hydroxylamine, hydroquinone, succinic acid, etc. The capping agent may inhibit the self-nucleation of metal ions, and the reducing agent may act to promote the reduction of metal ions.

[0060] The above organic material is a material having a thiol group and may include, for example, at least one of cysteamine, 2-naphthalenethiol (2-NT), 4-aminothiophenol (4-ATP), 2-aminothiophenol (2-ATP), lipoic acid, and 3,3'-diethylthiadicarbocyanine iodide (DTDC I). Alternatively, the above organic material may be an amino acid containing cysteine ​​(Cys) or a peptide containing cysteine-phenylalanine, and may include, for example, at least one of cysteine ​​(Cys) and glutathione. The above peptide may include both D- and L-forms, which are enantiomers.

[0061] The seed particles may grow asymmetrically due to the organic material to form chiral nanoparticles (KP). Accordingly, the shape of the chiral nanoparticles (KP) may change depending on the type of organic material. The organic material may be mainly adsorbed on a portion of the surface of the seed particles, thereby hindering the attachment of the metal ions. Therefore, the surface of the seed particles may grow at different rates depending on the region, forming chiral nanoparticles (KP) having a chiral structure. The chiral properties of the chiral nanoparticles (KP) may be transferred depending on the chirality of the organic material, and the structure of the particles may be determined in various ways. For example, when using L-form organic thiols such as L-cysteine ​​(L-cys) and L-glutathione (L-GSH), chiral nanoparticles (KP) having L-form chirality can be prepared, and when using D-form organic thiols such as D-cysteine ​​(D-cys) and D-glutathione (D-GSH), chiral nanoparticles (KP) having D-form chirality can be prepared.

[0062] The chiral nanoparticle (KP) may have the same shape as the three-dimensional chiral nanostructure (100) of FIG. 1 and may have a crystallographically 432 symmetry structure. The chiral nanoparticle (KP) may be referred to, for example, as chiral gold 432 helicoid III, and the g-factor, which represents a value quantifying the degree of asymmetry of circularly polarized light, may be, for example, about 0.3.

[0063]

[0064] In one embodiment, the growth solution is prepared by adding CTAB (100 mM, 80 mL) as the capping agent, gold chloride acid (10 mM, 10 mL) as the metal precursor, ascorbic acid (0.1 M, 47.5 mL) as the reducing agent, and an organic thiol (5 mM, 500 μL) to distilled water (395 mL). The seed particles may have a size of about 40 nm. After about two hours, chiral nanoparticles (KP), which are chiral plasmonic gold nanoparticles having a shape modified by the organic thiol, are synthesized. Next, the obtained chiral nanoparticles (KP) are prepared by washing through centrifugation (5000 rpm, 30 sec).

[0065]

[0066] Referring to FIG. 5b, a step (S122) of forming a preliminary shell structure (30P) coated with chiral nanoparticles (KP) to form a shell structure (30) may be performed.

[0067] This step may include a step of capping chiral nanoparticles (KP) and a step of coating a preliminary shell structure (30P). For example, the preliminary shell structure (30P) may include silica in an amorphous state.

[0068] In one embodiment, the surface of chiral nanoparticles (KP) is substituted with PEG (Polyethylene glycol). To this end, mPEG-SH (Poly(ethylene glycol) methyl ether thiol) (0.25 mM, 1.5 mL) and chiral nanoparticles (KP) (25 mL) are stirred at 30 °C for 30 minutes with CTAB (1 mM, 25 mL) ligand to maintain dispersion. The chiral nanoparticles (KP) with surfaces substituted with PEG are centrifuged at 2000 G for 3 minutes, and then washed twice with ethanol to remove residual reactants. Silica coating can be performed using the Stöber method. By this step, the dispersion of chiral nanoparticles (KP) in ethanol, which is the solvent on which the Stφber method is performed, is secured, and by allowing the ether group of PEG to act as a hydrogen bonding site for silanol, high-resolution silica coating on the surface of chiral nanoparticles (KP), which is a metal surface, can be promoted.

[0069] In one embodiment, PEG-capped chiral nanoparticles (KP) (10 mL) were mixed with anhydrous ethanol (19 mL), distilled water (8.33 mL), NH4OH (13.3 M, 7 mL) acting as a catalyst for silica condensation, and a TEOS (tetraethyl orthosilicate) solution (10 vol% in isopropanol, 738 μL) corresponding to a silica precursor, and vigorously stirred at 30 °C for 2 hours. To remove residual reactants, the product was centrifuged at 1500 G for 3 minutes and washed three times with 25 mL of ethanol.

[0070]

[0071] FIGS. 6a and 6b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0072] Referring to FIG. 6a, it can be confirmed through transmission electron microscopy (TEM) images that a silica coating forming a preliminary shell structure (30P) on the aforementioned chiral nanoparticle (KP) has been successfully formed. In FIG. 6a, the image on the left is before the formation of the preliminary shell structure (30P), and the image on the right is after the formation of the preliminary shell structure (30P).

[0073] Referring to FIG. 6b, it can be seen that after the formation of the pre-shell structure (30P), the peak of the g-element shifts to a long wavelength. This is because the refractive index (1.43) of amorphous silica is higher than the refractive index (1.33) of water surrounding the chiral nanoparticle (KP) before the formation of the pre-shell structure (30P), and from this, it can be seen that the pre-shell structure (30P) is coated on the chiral nanoparticle (KP).

[0074]

[0075] Referring to FIG. 5c, a step (S124) of partially dissolving a preliminary shell structure (30P) with hot water to form a porous structure can be performed. By doing so, a shell structure (30) having a porous structure can be formed.

[0076] This step can be performed by utilizing the solubility of the material forming the pre-shell structure (30P), such as amorphous silica, in high-temperature water. In one embodiment, chiral nanoparticles (KP) coated with a silica pre-shell structure (30P) are centrifuged at 1500 G for 3 minutes and then dispersed in distilled water. Afterward, the solution is stirred in an oil bath at 95°C for 30 minutes. Afterward, the solution is centrifuged at 1500 G for 3 minutes and washed twice with ethanol.

[0077]

[0078] FIGS. 6c and 6d are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0079] Referring to FIG. 6c, TEM images according to the dissolution time in the porous structure formation process are shown. When the dissolution time is 30 minutes, it can be seen that a porous structure has been formed. As the dissolution time increases to 60 minutes, the size of the pores within the shell structure (30) increases, and the shape of the internal chiral nanoparticles (KP) is more clearly recognized, and when the dissolution time is 120 minutes, almost no pre-shell structure (30P) remains. Accordingly, the dissolution time can be selected to be approximately 30 minutes.

[0080] Referring to FIG. 6d, it can be seen that the peak of the g-element shifts to a shorter wavelength as the porous structure is formed. This is because the refractive index decreases as water fills the pores of the porous structure, and it can be seen that the porous shell structure (30) is formed.

[0081]

[0082] However, in some embodiments, the step (S122) of forming a preliminary shell structure (30P) coated with chiral nanoparticles (KP) as described above with reference to FIG. 5b and 5c, and the step (S124) of partially dissolving the preliminary shell structure (30P) in hot water to form a porous structure, may be implemented as a single step. The steps may be integrated into a single process, for example, through a chemical process of forming a shell using a surfactant micelle as a template for the porous structure.

[0083] In one embodiment, an anhydrous ethanol (15 mL), NH4OH (13.3 M, 20 μL), TEOS (40 μL), and chiral nanoparticles (KP) (12.5 mL) were added to CTAB (6 mM, 34 mL), a high concentration surfactant micelle to provide a porous structure template, and a solution of CTAB (100 mM, 1 mL) concentrated 12.5 times was added and stirred at 47.5 °C for 2 hours and 30 minutes. After stirring, to remove residual reaction products, the product was centrifuged at 1500 G for 3 minutes and washed three times with 12.5 mL of ethanol.

[0084] FIG. 7 is an electron microscope image illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0085] Referring to FIG. 7, it can be seen through TEM images that a porous silica coating forming a porous shell structure (30) on chiral nanoparticles (KP) is formed through a single process as described above. In FIG. 7, the left image is before the formation of the porous shell structure (30), and the right image is after the formation of the porous shell structure (30).

[0086]

[0087] Referring to FIG. 5d, a step (S130) of removing at least some of the chiral nanoparticles (KP) can be performed.

[0088] Chiral nanoparticles (KP) surrounded by a shell structure (30) can be selectively etched against the shell structure (30). In this step, the chiral nanoparticles (KP) can be removed by supplying an etchant through the porous structure of the shell structure (30). The etching process may use, for example, 5-fold diluted aqua regia. Depending on the embodiments, the chiral nanoparticles (KP) may be partially or completely removed. The remaining chiral nanoparticles (KP) may be referred to as a seed layer (10).

[0089] In one embodiment, 5 times diluted aqua regia (20 mL) is added to chiral nanoparticles (KP) (10 mL) surrounded by a shell structure (30). After 30 minutes, the etching process is stopped with an excess amount of ethanol, and the nanoparticle structure is centrifuged at 2000 G and washed three times with 10 mL of ethanol.

[0090]

[0091] FIGS. 8a and 8b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0092] Referring to FIG. 8a, TEM images according to etching time are shown. As the etching time increases, it can be observed that the size of the chiral nanoparticles (KP) within the shell structure (30) decreases. The size of the remaining chiral nanoparticles (KP), i.e., the size of the seed layer (10), can be selected in various ways depending on the application of the three-dimensional chiral nanostructure formed finally. For example, if the three-dimensional chiral nanostructure is to be applied in the catalytic field, the seed layer (10) is controlled to have a relatively large size to apply a relatively high strain to the heterogeneous metal layer (20) formed in the subsequent process, and if the three-dimensional chiral nanostructure is to be applied in the optical field, the seed layer (10) is controlled to have a relatively small size to utilize the unique optical properties of the metal elements constituting the heterogeneous metal layer (20). The seed layer (10) can change from a chiral shape to a non-chiral shape as the etching time increases. In some embodiments, the seed layer (10) can be completely removed after 60 minutes of etching time.

[0093] Referring to FIG. 8b, as the size of the chiral nanoparticle (KP) and the resulting chirality decrease as the etching time increases, it can be seen that the g-element decreases and the peak shifts to a shorter wavelength. At the point where 30 minutes of etching time using aqua regia has passed, there is almost no signal of the g-element, and correspondingly, in the transmission electron microscope image of FIG. 8a, the seed layer (10) in a non-chiral structure state remains within the shell structure (30). The shell structure (30) in this step may also be referred to as a 'chiral silica mold'. Inside the chiral silica mold, a space with a chiral shape can be maintained after the chiral nanoparticle (KP) mold is etched.

[0094]

[0095] Referring to FIG. 5e, a step (S140) of forming a heterogeneous metal layer (20) in the area where chiral nanoparticles (KP) have been removed may be performed.

[0096] A heterogeneous metal layer (20) can be grown using a seed layer (10) as a seed. In such seed-mediated growth, the reduction potential and reaction rate of metal ions can be controlled through a coordination complex to induce selective growth on the surface of the seed layer (10) without self-nucleation outside the chiral silica mold. That is, heterogeneous growth is caused by lowering the reduction potential, and a coordination complex can be used for this purpose.

[0097] In one embodiment, a growth solution is prepared by mixing distilled water (1.2 mL), acetonitrile (1 mL), ascorbic acid (100 mM, 0.1 mL) as a reducing agent, and a chiral silica mold (0.3 mL). The growth solution is stirred at 25 °C, and 5 μL of a solution in which AgNO3, a metal precursor, is dissolved in acetonitrile solvent at 2 mM is injected every 3 minutes. The product is centrifuged at 1500 G for 3 minutes and then dispersed in 1 mL of a 10 wt% PVP (Polyvinylpyrrolidone) (Mw 3500) solution.

[0098] Acetonitrile was used due to its property of forming coordination complexes with transition metals, which can lower the reduction potential. The reaction rate was further controlled by adding small amounts of Ag-nitrile complexes to the growth solution.

[0099]

[0100] FIGS. 9a and 9b are electron microscope images and graphs illustrating a method for manufacturing a three-dimensional chiral nanostructure according to an embodiment of the present invention.

[0101] Referring to FIG. 9a, TEM images according to the injection amount of the Ag-nitrile composite are shown. As the injection amount increases, the silver (Ag) forming the heterogeneous metal layer (20) grows and can be seen filling the inside of the chiral silica mold.

[0102] Referring to FIG. 9b, as the injection amount increases, it can be seen that the g-component increases and the peak shifts to a longer wavelength. This is because a heterogeneous metal layer (20) is growing chirally inside.

[0103]

[0104] Referring to FIG. 5f, a step (S150) of removing the shell structure (30) can be performed.

[0105] The shell structure (30) can be selectively removed from the heterogeneous metal layer (20). In this step, a surface stabilizer for the heterogeneous metal layer (20) and an etchant for the shell structure (30) may be supplied. However, in some embodiments, this step may be omitted, in which case the three-dimensional chiral nanostructure (100a) described above with reference to FIG. 2 may be manufactured.

[0106] In one embodiment, the shell structure (30) is etched by a sodium hydroxide (NaOH) treatment that hydrolyzes amorphous silica together with polyvinyl pyrrolidone (PVP), which is a surface stabilizer for nanoparticles. A three-dimensional chiral nanostructure coated with the shell structure (30) is dispersed in 0.8 mL of distilled water, and PVP (Mw 3500, 10 wt%, 0.1 mL) and NaOH (1 M, 0.1 mL) are added. The mixture is reacted at 25 °C for 120 minutes. Afterward, the final solution is centrifuged at 1500 G for 3 minutes and redispersed in 1 mL of distilled water for characterization.

[0107]

[0108] Characterization of 3D chiral nanostructures

[0109] FIGS. 10a to 10e are electron microscope images and graphs for explaining the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention. FIGS. 10a to 10e illustrate the results of a characteristic analysis of a three-dimensional chiral nanostructure of the structure of FIG. 1, in which a heterogeneous metal layer (20) includes silver (Ag).

[0110] Referring to FIG. 10a, it can be confirmed by energy-dispersive X-ray spectroscopy (EDS) that a heterogeneous metal layer (20) of silver (Ag) has been grown on a seed layer (10) of gold (Au).

[0111] Referring to FIG. 10b, scanning electron microscope (SEM) analysis can confirm that the shape of the chiral nanoparticle (KP) corresponding to the mold has been successfully transferred to the heterogeneous metal layer (20).

[0112] Referring to FIG. 10c, it can be seen that the chiral nanostructure containing a heterometal layer (20) of silver (Ag) has a shorter plasmonic resonance wavelength than the chiral nanoparticle (KP) containing gold (Au), and therefore has a peak of the g-component at a shorter wavelength than the chiral nanoparticle (KP).

[0113] FIG. 10d is a TEM image of a three-dimensional chiral nanostructure, and with reference to FIG. 10e, the crystallographic properties of silver (Au) are confirmed by the analysis results according to Selected Area Electron Diffraction (SAED), and it is confirmed that the heterogeneous metal layer (20) is a silver (Au) single crystal.

[0114]

[0115] FIGS. 11a to 11e are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention. FIGS. 11a to 11e illustrate the results of a characteristic analysis of a three-dimensional chiral nanostructure of the structure of FIG. 1, in which a heterogeneous metal layer (20) includes palladium (Pd).

[0116] In the case of this embodiment, when forming the heterogeneous metal layer (20) described above with reference to FIG. 5e, in order to grow palladium (Pd) on the seed layer (10) inside the chiral silica mold, distilled water (0.56 mL), acetonitrile (1.2 mL), PVP (Mw 55000, 5 wt%, 0.2 mL), Na2PdCl4 (4 mM, 0.32 mL) which is a palladium (Pd) precursor, ascorbic acid (50 mM, 0.2 mL) which is a reducing agent, and a chiral silica mold (0.3 mL) are mixed and then stirred at 30 °C for 120 minutes. The formed three-dimensional chiral nanostructure is centrifuged at 1500 G for 3 minutes and then dispersed in 1 mL of distilled water. Afterwards, the shell structure (30) is removed as described above with reference to FIG. 5f.

[0117] Referring to FIG. 11a, it can be seen that a heterogeneous metal layer (20) of palladium (Pd) has been grown on a seed layer (10) of gold (Au) by EDS.

[0118] Referring to FIG. 11b, SEM analysis can confirm that the shape of the chiral nanoparticle (KP) corresponding to the mold has been successfully transferred to the heterogeneous metal layer (20).

[0119] Referring to FIG. 11c, it can be seen that the chiral nanostructure containing a heterogeneous metal layer (20) of palladium (Pd) shifts to a short wavelength when the shell structure (30) is removed.

[0120] FIG. 11d is a TEM image of a three-dimensional chiral nanostructure, and with reference to FIG. 11e, analysis results according to SAED confirmed that the heterogeneous metal layer (20) is a palladium (Pd) single crystal.

[0121]

[0122] FIGS. 12a to 12e are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention. FIGS. 12a to 12e illustrate the results of a characteristic analysis of a three-dimensional chiral nanostructure of the structure of FIG. 1, in which a heterogeneous metal layer (20) includes platinum (Pt).

[0123] In the case of this embodiment, when forming the heterogeneous metal layer (20) described above with reference to FIG. 5e, in order to grow platinum (Pt) on the seed layer (10) inside the chiral silica mold, distilled water (0.9 mL), PVP (Mw 55000, 5 wt%, 0.2 mL), platinum (Pt) precursor K2PtCl4 (20 mM, 0.25 mL), reducing agent ascorbic acid (50 mM, 0.1 mL), and chiral silica mold (0.3 mL) are mixed and then stirred at 30 °C for 60 minutes. The formed three-dimensional chiral nanostructure is centrifuged at 1500 G for 3 minutes and then dispersed in 1 mL of distilled water. Afterward, the shell structure (30) is removed as described above with reference to FIG. 5f.

[0124] Referring to FIG. 12a, it can be seen that a heterogeneous metal layer (20) of platinum (Pt) has been grown on a seed layer (10) of gold (Au) by EDS.

[0125] Referring to FIG. 12b, SEM analysis can confirm that the shape of the chiral nanoparticle (KP) corresponding to the mold has been successfully transferred to the heterogeneous metal layer (20).

[0126] Referring to FIG. 12c, it can be seen that the chiral nanostructure containing a heterogeneous metal layer (20) of platinum (Pt) shifts to a short wavelength when the shell structure (30) is removed.

[0127] FIG. 12d is a transmission electron microscope image of a three-dimensional chiral nanostructure, and with reference to FIG. 12e, analysis results according to SAED confirmed that the heterogeneous metal layer (20) is a platinum (Pt) polycrystalline layer. From this, it can be seen that the method of forming the heterogeneous metal layer (20) using the chiral silica mold according to the embodiments of the present invention can be applied to materials that grow as polycrystalline layers, in addition to materials such as silver (Au) and palladium (Pd) which are known to grow as single crystals on a gold (Au) seed layer (10).

[0128]

[0129] FIGS. 13a to 13c are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention. FIGS. 13a to 13c illustrate the results of a characteristic analysis of a three-dimensional chiral nanostructure of the structure of FIG. 2, in which a heterogeneous metal layer (20) includes copper (Cu).

[0130] In the case of this embodiment, when forming the heterogeneous metal layer (20) described above with reference to FIG. 5e, in order to grow copper (Cu) on the seed layer (10) inside the chiral silica mold, distilled water (1 mL), poly(acrylic acid) (18 mg / mL, 0.1 mL) that forms a coordination bond with copper (Cu) ions, PVP (Mw 55000, 100 mg / mL, 0.025 mL), CuCl2 (800 mM, 0.01 mL) which is a copper (Cu) precursor, N2H4 (55 wt%, 0.018 mL) which is a reducing agent, and a chiral silica mold (0.15 mL) are mixed and then stirred at 30 °C for 30 minutes. The formed three-dimensional chiral nanostructure is centrifuged at 1500 G for 3 minutes, and then [into] 1 mL of dimethylformamide Disperse.

[0131] Referring to Fig. 13a, TEM analysis confirms that copper (Cu) has grown inside the chiral silica mold and completely filled the inside of the chiral silica mold.

[0132] Referring to Fig. 13b, the analysis of the circular dichroism (CD) signal according to growth time shows that as the growth time of copper (Cu) increases, the difference in circular dichroism absorption increases, thereby confirming that copper (Cu) has grown chirally.

[0133] Referring to FIG. 13c, it was confirmed that the g-element of the chiral nanostructure containing a heterogeneous metal layer (20) of copper (Cu) is about -0.09.

[0134]

[0135] FIGS. 14a to 14d are electron microscope images and graphs illustrating the characteristics of a three-dimensional chiral nanostructure according to an embodiment of the present invention. FIGS. 14a to 14d illustrate the results of a characteristic analysis of a three-dimensional chiral nanostructure of the structure of FIG. 2, in which a heterogeneous metal layer (20) includes nickel (Ni).

[0136] In the case of the present embodiment, when forming the heterogeneous metal layer (20) described above with reference to FIG. 5e, in order to grow nickel (Ni) on the seed layer (10) inside the chiral silica mold, a chiral silica mold (1 mL), a nickel (Ni) precursor NiCl2 (100 mM, 35 μL), and a reducing agent N2H4 (55 wt%, 30 μL) are mixed and then stirred at 55 °C for 90 minutes. The formed three-dimensional chiral nanostructure is centrifuged at 1500 G for 3 minutes and then dispersed in 1 mL of distilled water.

[0137] Referring to Fig. 14a, TEM analysis confirms that nickel (Ni) has grown inside the chiral silica mold and completely filled the inside of the chiral silica mold.

[0138] Referring to FIG. 14b, it was confirmed that the g-element of the chiral nanostructure containing a heterogeneous metal layer (20) of nickel (Ni) is about -0.02.

[0139] Referring to Fig. 14c, the SAED analysis results show that distinct diffraction spots (left) and faint ring-shaped patterns (right) coexist. These diffraction features indicate the coexistence of polycrystalline and partial crystal orientation, which may be attributed to anisotropic growth characteristics or structural orientation during the crystal growth process of the material.

[0140] Referring to FIG. 14d, the analysis of the sample’s magnetic hysteresis curve (MH curve) revealed a hysteresis loop, which indicates the ferromagnetic properties of the chiral nanostructure containing the nickel (Ni) heterometal layer (20). The presence of remnant magnetization and coercivity implies that the magnetic moment is maintained even after the external magnetic field is removed, which is consistent with the characteristics of ferromagnetic nanoparticles.

[0141]

[0142] The structure of three-dimensional chiral nanostructures has been limited to mainly gold (Au). This is because the interactions of materials used in the manufacturing process of chiral nanoparticles (KP), the stability of the high Miller index plane, and appropriate growth kinetics at temperatures near room temperature do not function in the same way in other metallic materials. However, according to the embodiments of the present invention, by using chiral nanoparticles (KP) made of gold (Au) as a template to transfer the shape of chiral nanoparticles (KP) to various metallic materials, three-dimensional chiral nanostructures including a heterogeneous metal layer (20) other than gold (Au) can be effectively formed.

[0143] Depending on the metal material introduced, three-dimensional chiral nanostructures exhibit different properties, such as crystal structure and electromagnetic properties including polarization control, and each metal material has its own unique advantages. Therefore, appropriate metal materials can be selected depending on the application of the three-dimensional chiral nanostructures. For example, if the three-dimensional chiral nanostructures contain gold (Au), silver (Ag), and copper (Cu), which have relatively excellent plasmonic properties and different plasmon resonance wavelength bands, they can be applied optically, such as for polarization control, chiral sensing, and chiral photocatalysis. For example, if the three-dimensional chiral nanostructures contain platinum (Pt), palladium (Pd), copper (Cu), and nickel (Ni), which have relatively excellent catalytic properties and high activity for different chemical reactions, they can be applied to enantiomer-selective organic chemistry and electrochemical reactions. For example, if the three-dimensional chiral nanostructures include platinum (Pt) and nickel (Ni) which have excellent spin-orbit interaction or ferromagnetic properties, they can be applied to spintronic devices. As such, according to the embodiments of the present invention, three-dimensional chiral nanostructures specialized for various applications can be provided.

[0144]

[0145] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention.

[0146]

[0147] The three-dimensional chiral nanostructure and the method for manufacturing the same according to an embodiment of the present invention can be used in the sensor and catalyst industries, such as ultra-high performance polarization control, ultra-high sensitivity chiral sensing, and asymmetric catalytic reactions.

Claims

1. A seed layer containing gold (Au); and Surrounding the seed layer, it includes a heterogeneous metal layer comprising gold (Au) and other metals, and The structure comprising the seed layer and the heterogeneous metal layer is a three-dimensional chiral nanostructure that forms a crystallographically 432 symmetry structure.

2. In Paragraph 1, The above seed layer is a three-dimensional chiral nanostructure having a non-chiral shape.

3. In Paragraph 2, The above seed layer is a three-dimensional chiral nanostructure having a spherical shape.

4. In Paragraph 1, The seed layer is a three-dimensional chiral nanostructure that crystallographically forms the 432 symmetry structure.

5. In Paragraph 1, A three-dimensional chiral nanostructure comprising a shell structure having a porous structure surrounding the above heterogeneous metal layer.

6. In Paragraph 5, The above shell structure is a three-dimensional chiral nanostructure containing porous silica (SiO2).

7. In Paragraph 5, The above shell structure is a three-dimensional chiral nanostructure that forms a sphere together with the above seed layer and the above heterogeneous metal layer.

8. In Paragraph 1, The size of the seed layer is in the range of 10 nm to 70 nm, and A three-dimensional chiral nanostructure in which the size of the heterogeneous metal layer is in the range of 100 nm to 200 nm.

9. In Paragraph 1, The above heterogeneous metal layer is a three-dimensional chiral nanostructure comprising at least one of silver (Ag), palladium (Pd), platinum (Pt), copper (Cu), and nickel (Ni).

10. Step of synthesizing chiral nanoparticles; A step of forming a shell structure having a porous structure by coating the above chiral nanoparticles; A step of removing at least some of the chiral nanoparticles by supplying an etchant into the shell structure using the above porous structure; and A method for manufacturing a three-dimensional chiral nanostructure comprising the step of forming a heterogeneous metal layer in the region from which the chiral nanoparticles have been removed.

11. In Paragraph 10, A method for manufacturing a three-dimensional chiral nanostructure comprising the chiral nanoparticles and the heterogeneous metal layer, wherein the chiral nanoparticles and the heterogeneous metal layer comprise different metal materials.

12. In Paragraph 10, The above shell structure is a method for manufacturing a three-dimensional chiral nanostructure containing porous silica (SiO2).

13. In Paragraph 10, The step of forming the above shell structure is, A step of forming a preliminary shell structure for coating the above chiral nanoparticles; and A method for manufacturing a three-dimensional chiral nanostructure comprising the step of partially dissolving the above-mentioned preliminary shell structure with high-temperature water to form a porous structure.

14. In Paragraph 10, A method for manufacturing a three-dimensional chiral nanostructure, comprising the step of removing at least a portion of the chiral nanoparticles, which includes the step of etching the chiral nanoparticles using aqua regia.

15. In Paragraph 10, The above chiral nanoparticles have a crystallographic 432 symmetry structure, and A method for manufacturing a three-dimensional chiral nanostructure in which the above 432 symmetry structure is transferred to the above heterogeneous metal layer.

16. In Paragraph 10, A method for manufacturing a three-dimensional chiral nanostructure, further comprising the step of removing the shell structure after the step of forming the heterogeneous metal layer.

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