WO2024010212A1 - Method for manufacturing copper microplates, method for manufacturing hybrid microplates containing copper microplates, and hybrid microplates manufactured thereby - Google Patents

Abstract

The present invention relates to a method for manufacturing copper microplates, a method for manufacturing hybrid microplates containing the copper microplates, and hybrid microplates manufactured thereby, wherein the method for manufacturing copper microplates comprises the steps of: (a) preparing a mixture solution containing a copper precursor, acetonitrile, a capping agent, a reducing agent, and a solvent, and (b) heating the mixture solution to produce copper microplates.

Description

Method for producing copper plate-shaped microparticles, method for producing hybrid plate-shaped microparticles containing copper plate-shaped microparticles, and hybrid plate-shaped microparticles produced thereby

The present invention relates to a method for manufacturing copper plate-shaped microparticles and hybrid plate-shaped microparticles containing the same, and to hybrid plate-shaped microparticles manufactured by the above production method that can be used as a catalyst material.

Gold (Au) and silver (Ag) nanoparticles have strong localized surface plasmon resonance properties and have been used as catalyst materials, but their high price makes them difficult to use in actual industrial and environmental fields. It's not easy.

Copper (Cu) is about 22,000 times more abundant than gold (Au) and 1,000 times more abundant than silver (Ag), and is a material that possesses localized surface plasmon resonance characteristics, but is damaged by oxygen and moisture in the air. Because it is easily oxidized, it was not easy to use it as a catalyst material.

In particular, two-dimensional metal nanostructures containing nanoplates have great potential as high-performance catalyst materials due to their high specific surface area and high ratio of atoms exposed to the surface, but copper (Cu ) Two-dimensional metal nanostructures have not yet been widely used as catalyst materials due to the difficulty of synthesizing two-dimensional metal nanostructures as well as the vulnerability to oxidation of the materials themselves.

The technical problem to be solved by the present invention is to develop a novel manufacturing method that can synthesize copper plate-shaped microparticles (Cu microplate), which are promising as a catalyst material, in high yield, and to protect the surface vulnerable to oxidation of the copper plate-shaped microparticles. The present invention provides a method for manufacturing hybrid plate-shaped microparticles by combining plate-shaped microparticles with heterogeneous materials, and hybrid plate-shaped microparticles produced thereby.

In order to achieve the above technical problem, the present invention includes the steps of (a) preparing a mixed solution containing a copper precursor, acetonitrile, a capping agent, a reducing agent, and a solvent, and (b) preparing the mixed solution. We propose a method for manufacturing copper plate-shaped microparticles, which includes the step of producing copper plate-shaped microparticles by heating.

At this time, the mixed solution prepared in step (a) includes copper (II) chloride (CuCl ₂ ), acetonitrile, hexadecylamine (HDA), potassium iodide (KI), and l-ascorbic acid. It is characterized as an aqueous solution containing (l-ascorbic acid, AA).

In another aspect of the invention, the present invention is a method for producing hybrid plate-shaped microparticles that are a composite of copper plate-shaped microparticles manufactured according to the above method and a heterogeneous material, including (A) manufacturing copper plate-shaped microparticles according to the above-described method. We propose a method for manufacturing hybrid plate-shaped microparticles containing copper plate-shaped microparticles, including the step of (B) introducing a heterogeneous material to the surface of the copper plate-shaped microparticles.

At this time, in step (B), a core containing copper plate-shaped micro particles and copper sulfide (Cu ₂ S) are formed through a sulfidation reaction between the copper plate-shaped micro particles and sodium sulfide (Na ₂ S). Hybrid plate-shaped microparticles with a core-shell structure composed of a shell containing

In addition, in step (B), copper (Cu) atoms on the surface of the copper plate-shaped micro-particles are replaced with gold (Au) atoms through a galvanic replacement reaction, thereby forming Cu-Au bimetal hybrid plate-shaped particles. Micro particles can be manufactured.

Furthermore, in another aspect of the invention, the present invention provides hybrid plate-shaped microparticles with a core (Cu)-shell (Cu ₂ S) structure that are manufactured according to the method for manufacturing the hybrid plate-shaped microparticles and can be used as a photocatalyst or catalyst material, and Cu- We propose Au bimetal hybrid plate-shaped microparticles.

The method for manufacturing copper plate-shaped microparticles according to the present invention is to produce copper (Cu) plate-shaped microparticles with a size of about 6 μm and an aspect ratio of 65 by 95% by introducing acetonitrile as a ligand. It can be synthesized in high yield.

In addition, according to the method for manufacturing hybrid plate-shaped micro particles according to the present invention, the copper plate-shaped micro particles are used as a seed material to produce Cu@Cu with a core (Cu)-shell (Cu ₂ S) structure based on an aqueous solution. It is possible to synthesize hybrid plate-shaped materials based on copper plate-shaped micro particles, such as _2S metal-semiconductor hybrid materials and Cu-Au bimetal hybrid materials, and the hybrid plate-shaped materials can be used as photocatalysts and catalyst materials with high catalytic activity. You can.

Figure 1 is a conceptual diagram showing the entire hybridization path from the synthesis of copper plate-shaped microparticles (Cu microplate) to the formation of Cu@Cu ₂ S or Cu-Au hybrid plate-shaped microparticles performed in the examples of the present application.

Figure 2(a) is an SEM image of Cu nanocrystals synthesized in the absence of KI, Figure 2(b) is an SEM image of Cu nanocrystals synthesized in the presence of 1.6 μM KI, and Figure 2(c) is the SEM image of the Cu nanocrystals synthesized in the absence of KI. Figure 2(b) is the XRD pattern of the Cu microplate, and Figure 2(d) is the UV-Vis-NIR spectrum of the Cu microplate shown in Figure 2(b) (the inset shows the Cu microplate. Photo of aqueous colloidal dispersion).

Figures 3(a) to 3(d) are SEM images, TEM images, XRD patterns, and UV-Vis-NIR spectra, respectively, of Cu microplates grown in the presence of acetonitrile, and the inset of Figure 3(d) shows This is a photograph of an aqueous colloidal dispersion of Cu microplates grown in the presence of .

Figures 4(a) to 4(d) show the SEM image _, TEM image, _XRD pattern, and (d) UV-Vis- NIR spectrum, Figure 4(e) is a STEM-EDS elemental mapping image of the Cu@Cu ₂ S hybrid microplate, and the inset of Figure 4(d) is a photograph of the aqueous colloidal dispersion of the Cu@Cu ₂ S hybrid microplate. am.

Figure 5(a) is a UV-Vis-NIR absorption spectrum showing the photodecomposition behavior of methylene blue (MB) in the presence of a Cu@Cu ₂ S hybrid microplate irradiated with sunlight for 120 minutes, and Figure 5(b) ) and Figure 5(c) are results showing the decomposition behavior of MB over time in the presence of Cu@Cu ₂ S hybrid microplate or Cu microplate, and Figure 5(d) shows Cu@Cu ₂ S hybrid microplate as a photocatalyst. This is the result of verifying the recyclability of .

Figures 6(a) and 6(b) are SEM images of the Cu-Au hybrid microplate obtained after the galvanic substitution reaction between HAuCl ₄ and Cu microplate, and Figures 6(c) and 6(d) are respectively the above This is a UV-Vis-NIR spectrum and a STEM-EDS elemental mapping image of the Cu-Au hybrid microplate, and the inset in Figure 6(c) is a photograph of the aqueous colloidal dispersion of the Cu-Au hybrid microplate.

Figure 7(a) is the UV-Vis-NIR absorption spectrum of 4-nitrophenol (4-NP) aqueous solution and 4-NP aqueous solution mixed with NaBH ₄ , and Figure 7(b) is the UV-Vis-NIR absorption spectrum of the Cu-Au hybrid microplate with 4- UV-Vis spectra recorded at 50-second intervals after addition to an aqueous solution containing NP and NaBH ₄ , and Figure 7(c) shows the catalytic hydrogenation of 4-NP and NaBH ₄ in the presence of a Cu-Au hybrid microplate. A plot of ln(A _t /A ₀ ) and reaction time t (where A _t and A ₀ are the absorbance at time t and time 0, respectively), and Figure 7(d) is a plot of Cu-Au for catalytic hydrogenation reaction. This is the result of verifying the recyclability of the hybrid microplate.

In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Since embodiments according to the concept of the present invention can make various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

The terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “include” or “have” are intended to indicate the existence of a described feature, number, step, operation, component, part, or combination thereof, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not preclude the existence or addition of steps, operations, components, parts, or combinations thereof.

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

Embodiments according to the present specification may be modified into various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments described in detail below. The embodiments of this specification are provided to more completely explain the present specification to those with average knowledge in the art.

<Example>

Synthesis of copper (Cu) microplates

To synthesize Cu microplates (MPs), 42 mg of CuCl ₂ ·2H ₂ O was added to deionized water (15 mL) under magnetic stirring. Then, 0.179 g hexadecylamine (HDA), 25 μL KI (1 M) and 1 mL of acetonitrile were introduced into the solution. Next, the solution was vortexed for approximately 10 seconds to remove any agglomerated clumps. After stirring the solution at 9000 rpm overnight, 0.132 g of l-ascorbic acid (AA) was added to the solution and stirred until the resulting mixture completely changed from blue to white. The solution was transferred to an oil bath and heated at 85° C. for 7 hours with stirring. The obtained product was centrifuged at 5000 rpm for 30 minutes and washed repeatedly with AA aqueous solution. Cu MP was dispersed in aqueous AA solution at a final concentration of 0.8 mg/mL.

Cu@Cu ₂ Synthesis of S hybrid microplates

500 μL of the synthesized Cu microplate (23.5mM) was added to a glass vial along with 5mL PVP aqueous solution (M _{w ≈} 55 kDa) with a concentration of 0.1 g/mL. Next, Na ₂ S·9H ₂ O solution (1 mL, 20 mM) was added, and the solution quickly turned dark brown. After reaction for 5 minutes, the product was centrifuged at 12,500 rpm for 8 minutes and washed three times with deionized water to obtain Cu@Cu ₂ S hybrid microplates.

Synthesis of Cu-Au hybrid microplates

A 20 mL scintillation vial was filled with 2 mL of Cu microplate (94.0 mM). AA (5.5 mL, 1 M) and 2 mL PVP ( M _{w ≈} 10 kDa, 5 wt% in deionized water) were added to the vial, and the reaction mixture was stirred rapidly for 3 min at room temperature. To create Cu-Au microplates, HAuCl ₄ aqueous solution (0.5 mL, 0.025 M) was added to the vial at a rate of 10 mL/h using a syringe pump. The solution was aged for an additional 3 minutes at room temperature until its color stabilized. The solution was then centrifuged at 12,500 rpm for 8 min and washed three times with deionized water.

<Experimental example>

Cu microplates were synthesized with PVP and AA acting as a colloidal stabilizer and reducing agent, respectively, and I ^- , which acts as a capping agent during synthesis, played an important role in the formation of the plate-like structure. As shown in Figure 2(a), when I ^- ions were not present, Cu nanocrystals of various shapes such as cubes, double pyramids, and nanowires were obtained. However, under the same experimental conditions, when I ^- ions were added at a concentration of 1.6 μM, Cu microplates were obtained, while quasi-spherical particles were also obtained (Figure 2(b)). As the concentration of I ^- ions increased up to 1.6 μM, the yield of plate-shaped particles increased, but at higher concentrations, the yield of plate-shaped particles decreased. The average size of the prepared Cu microplate was calculated to be 4.3 ± 0.6 μm, and the thickness of the microplate was measured to be ~133 nm.

The XRD pattern of the Cu microplate is shown in Figure 2(c). The characteristic peaks at ~43.3°, ~50.5°, and ~74.1° are attributed to the {111}, {200}, and {220} crystal planes of face-centered cubic (fcc) Cu, respectively, which suggests that the synthesized Cu nanocrystals are free from impurities such as oxides. This shows that it is of high purity without any traces. In the XRD pattern, the peak of {111} crystal plane is prominent, while the relative intensity of other peaks is low. The intensity ratio between the {111} and {200} diffraction peaks in the did. This indicates that the Cu microplate is dominated by the {111} plane and the {111} plane tends to be preferentially oriented parallel to the surface of the support substrate. The UV-Vis-NIR spectrum of the aqueous colloidal dispersion of Cu microplates is shown in Figure 2(d). The localized surface plasmon resonance (LSPR) characteristic band at 597 nm is strong and narrow, confirming the high purity of Cu nanocrystals. The inset of Figure 2(d) shows the synthesized Cu microplate aqueous solution, which has a dark brown color typical of Cu nanocrystals.

In this example, a small amount of acetonitrile was added to the reaction medium (water) to increase the yield of microplates in the final product. Acetonitrile is known to act as a ligand that forms a complex with metal ions. This coordination effect can significantly lower the reduction rate of Cu ²⁺ ions and consequently reduce the equilibrium concentration of Cu atoms. As a result, the sequential formation of nucleation sites is suppressed and the number of seeds in the nucleation step is reduced. In this way, larger Cu microplates can be formed with high yield by reducing the number of seeds while maintaining a constant Cu precursor concentration.

When synthesizing Cu nanocrystals, the progress of the reaction can be monitored by observing unique color changes. After the injection of AA into the reaction mixture containing Cu precursor (CuCl ₂ ·2H ₂ O), HDA, and KI, the blue aqueous solution turns white, indicating the reduction of Cu ²⁺ ions. When the reaction mixture was heated at 85°C for 1 hour, it changed from white to light yellow, orange, and reddish brown. The solution then turned brown and dark brown over 7 hours. However, when acetonitrile was added, the color change of the reaction was relatively slow and a reddish brown color appeared after 2 hours. These results indicate that the reaction was slower when acetonitrile was present.

Figures 3(a) and 3(b) show SEM and TEM images of the products obtained under the same conditions in the presence of acetonitrile, respectively. When acetonitrile was introduced, the plate yield (percentage of plate-like structure in the product) increased from 65.4% to 95.1% and the lateral dimensions of the obtained nanoplates also increased to 5.8 ± 1.3 μm. The average thickness was measured to be ~92 nm, indicating that the aspect ratio of the microplate was substantially increased. These results indicate that the growth path of Cu microplates was dramatically affected by acetonitrile and lateral growth was promoted, which is consistent with expectations. Meanwhile, in this example, the optimal ratio of acetonitrile to water was found to be ~0.07. According to the experimental results, as the ratio of acetonitrile to water increased to 0.07, the yield of plate-shaped particles among the total particles obtained increased. However, if the ratio is increased greater than 0.07, the microplate collapses and the particle size of the resulting microplate becomes smaller.

The XRD pattern of the Cu microplate grown in the presence of acetonitrile is shown in Figure 3(c), and the pattern is not significantly different from the pattern shown in Figure 2(c). However, the intensity ratio between the {111} and {200} diffraction peaks increased to ∼4.41, confirming that both the yield of plate-shaped particles and the lateral dimensions of the synthesized microplates increased in the presence of acetonitrile. According to the selected area electron diffraction (SAED) pattern of the Cu microplate, six diffraction points with six-fold rotational symmetry indicate that the microplate has a single crystal structure with the {111} crystal plane as the main plane, which is consistent with the XRD analysis results. Confirms. Figure 3(d) shows the UV-Vis-NIR spectrum of the aqueous colloidal dispersion of Cu microplates synthesized after adding acetonitrile. Although the position of the LSPR band barely changed, the intensity of the peak increased, indicating that the shape uniformity of the reaction product was improved by increasing the yield of plate-shaped particles.

The increase in yield and particle size of plate-shaped particles due to the addition of acetonitrile can be explained as follows. For shape-controlled synthesis of metal nanocrystals, it is important to precisely control the reduction kinetics of Cu(II) ions. The total free energy of plate-like particles is high due to the relatively large surface area and lattice strain energy due to defects. As a result, the formation of plate-shaped particles is thermodynamically unfavorable and can only be formed by inducing the reaction under fully kinetically controlled conditions. When acetonitrile is introduced, Cu(II) ions can react with acetonitrile to form intermediate species, which can act as a reservoir to suppress supersaturation of Cu(II) ions in solution. . Therefore, the reduction reaction is substantially slowed down and the formation of nanocrystals is critically influenced by reaction kinetics rather than reaction thermodynamics, allowing efficient formation of plate-shaped particles. Additionally, the slow reduction rate of Cu(II) ions inhibits successive nucleation formation, reducing the number of nuclei formed. Based on the Gibbs-Thomson equation, a slow reduction rate favors the growth of newly formed Cu atoms on existing seeds, while a fast reaction rate favors self-nucleation. Therefore, when acetonitrile is introduced into the reaction system, large microplates can be formed because more Cu atoms are added to the already formed plate-shaped particles.

Cu@Cu ₂ S hybrid nanostructures can be effectively synthesized by exposing pre-obtained Cu nanocrystals to sulfur compounds of various oxidation states and transforming them into sulfides. Meanwhile, even if the sulfidation reaction proceeds through an aqueous solution process, it relies on chemicals such as hydrogen sulfide and ammonium sulfide, which are toxic and highly volatile, making it difficult to precisely control the reaction. Therefore, in this example, a strategy was adopted to synthesize Cu@Cu ₂ S hybrid nanostructures in an aqueous solution at room temperature using sodium sulfide (Na ₂ S), which is highly soluble in water and relatively less harmful than hydrogen sulfide or ammonium sulfide. Since the sulfurization reaction mainly occurs on the surface of the Cu crystal, after the reaction, Cu ₂ S completely coats the surface of the Cu nanocrystal to obtain a core (Cu)/shell (Cu ₂ S) structure.

Figures 4(a) and 4(b) are SEM and TEM images of Cu@Cu ₂ S hybrid microplates obtained by adding a specific concentration of Na ₂ S aqueous solution and aging at room temperature for 5 minutes, showing originally uniform and smooth microplates. It shows that the top and bottom surfaces of the plate have become very rough. Additionally, from the AFM image and height profile of the hybrid microplate, the surface was very rough and the thickness was measured to be ~131 nm, indicating that the thickness increased due to the sulfidation reaction. According to Figure 4(c) showing the XRD analysis results of the hybrid microplate, it was confirmed that a new peak corresponding to Cu ₂ S (JCPDS file no. 84-1770) was generated by sulfidation reaction with Na ₂ S. These results show that the Cu microplate was successfully converted into a Cu@Cu ₂ S hybrid microplate.

The UV-Vis-NIR spectrum of the Cu@Cu ₂ S hybrid microplate shown in Figure 4(d) shows broadband absorption in the 300-800 nm wavelength region, and in the inset of Figure 4(d), the Cu@Cu ₂ The S hybrid microplate aqueous colloidal dispersion appeared dark gray. From the energy-dispersive X-ray spectroscopy (STEM-EDS) mapping image in Figure 4(e), it was confirmed that Cu and S were uniformly distributed within the hybrid microplate. Summarizing the above results, it was confirmed that a Cu@Cu ₂ S hybrid microplate could be obtained in a short time by chemically converting the surface of the Cu microplate to Cu ₂ S using Na ₂ S in an aqueous solution at room temperature. The optimal concentration of Na ₂ S in the aqueous solution used in the sulfurization process in this example was about 0.3 mM. When the Na ₂ S concentration was less than 0.3 mM, little change in the shape of the microplate was observed, and when the Na 2 S concentration was greater than 0.3 mM, the microplate was damaged.

A series of recent studies have shown that metal-semiconductor hybrid nanocrystals can be used as high-performance and efficient photocatalysts. Cu@Cu ₂ S hybrid nanocrystals have broadband absorption characteristics and excellent chemical stability, making them a more effective photocatalyst than Cu nanocrystals. To investigate the photocatalytic activity of the hybrid microplate, a photooxidative decomposition experiment of the organic dye methylene blue (MB) was conducted under solar irradiation in the presence of Cu microplate or Cu@Cu ₂ S hybrid microplate. Figure 5(a) is a UV-Vis-NIR absorption spectrum showing the decomposition behavior of MB over time in the presence of Cu@Cu ₂ S hybrid microplates upon solar irradiation. Almost 85% of MB was decomposed after 120 minutes of reaction. showed significantly improved results compared to pure Cu microplates. Figure 5(b) shows the time-dependent decomposition results of MB when irradiated with sunlight in the presence of Cu microplates or Cu@Cu ₂ S hybrid microplates. At this time, C ₀ represents the initial MB concentration and C _t represents the MB concentration at reaction time t. After combining Cu and Cu ₂ S through sulfidation reaction, photocatalytic performance was significantly improved under the same reaction conditions. For quantitative comparison, when ln(C ₀ /C _t ) was expressed as a function of t, it showed a linear relationship as shown in Figure 5(c). These results show that the photocatalytic decomposition of MB follows the pseudo-first-order kinetic equation ln(C ₀ /C _t ) = K _app t (where K _app is the apparent rate constant). K _app for the Cu@Cu ₂ S hybrid microplate was determined to be 0.0162 min ^-1 , which is much larger than that of the pure Cu microplate (0.0006 min ^-1 ).

When evaluating the practical utility of a catalyst, recovery and reuse of the catalyst are one of the most important considerations. Because the Cu@Cu ₂ S hybrid microplate was several micrometers in size, it was easily separated from the reaction solution by centrifugation after the photocatalytic reaction. The hybrid microplate was used in multiple reaction cycles to investigate its reusability as a photocatalyst. The results in Figure 5(d) confirm that the catalytic activity of the hybrid microplate is still high even after three additional cycles. Even after three additional MB photolysis cycles, the structure of the Cu@Cu ₂ S hybrid microplate remained intact, demonstrating the excellent photocatalytic stability of the Cu@Cu ₂ S hybrid nanoplate.

Galvanic replacement reactions provide a simple and versatile route to produce bimetallic nanocrystals with porous structures. When a metal ion with a higher reduction potential comes into contact with another metal with a lower reduction potential in an electrolyte, an electrochemical reaction occurs spontaneously and the metal tends to corrode the lower its reduction potential. Specifically, when a noble metal salt solution is introduced into an aqueous suspension of metal nanocrystals with a low reduction potential, the noble metal ions are reduced and deposited on the surface of the nanocrystals while the metal nanocrystals are spontaneously oxidized. Cu nanostructures serve as sacrificial templates for the fabrication of Cu-Au bimetallic nanostructures. Since the standard reduction potential of the AuCl ₄ ^- /Au pair (1.00 V vs. standard hydrogen electrode, SHE) is much higher than that of the Cu ²⁺ /Cu pair (0.34 V vs. SHE), the substitution reaction (3Cu ⁰ + 2AuCl ₄ ^- → 3Cu ²⁺ + 2Au ⁰ + 8Cl ^- ) occurred spontaneously. Since the reaction involves stoichiometric substitution of three Cu atoms with two Au atoms, cavities are formed on the surface of the Cu nanocrystal after the reaction, resulting in the formation of a Cu-Au bimetallic nanostructure with a porous structure.

When HAuCl ₄ aqueous solution was added to the aqueous dispersion of Cu microplates synthesized in the presence of acetonitrile, a galvanic substitution reaction immediately occurred and the aqueous dispersion changed from brown to blue-gray. Figures 6(a) and 6(b) show SEM images of the Cu-Au hybrid nanostructure prepared after adding HAuCl ₄ aqueous solution. The Cu-Au hybrid nanostructure maintained its plate shape and size distribution even after the galvanic substitution reaction. However, multiple nanocavities were created on the surface of individual microplates. Additionally, numerous small nanocrystals were observed on the surface of the Cu microplate after the galvanic substitution reaction, and these nanocrystals are expected to be Au nanocrystals.

After AuCl ₄ ^- ions are reduced to metallic Au on the surface of Cu microplates, there is a large lattice mismatch (12.7%) between Cu (0.3615 nm) and Au (0.4079 nm) and poor miscibility of the Cu-Au binary system at low temperatures. Due to this miscibility, the formation of a uniform alloy nanostructure was not achieved, and as a result, unlike the galvanic substitution reaction between HAuCl ₄ and Ag nanocrystals, Au nanocrystals grew epitaxially on the surface of the Cu microplate. According to EDX measurement results, the hybrid microplate showed a composition of 59% Cu and 30% Au. Figure 6(c) shows that these microparticles exhibit an LSPR extinction peak at 554 nm, indicating that the peak is slightly shifted to blue after the galvanic substitution reaction. Considering that the surface plasmon resonance for small Au nanoparticles appears at a wavelength near 500 nm, the above-described LSPR property change occurred because the alloy structure of Cu microplates and Au nanocrystals was formed through a galvanic substitution reaction. . The elemental mapping image of the Cu-Au hybrid microplate is shown in Figure 6(d), where green and blue dots represent Cu and Au, respectively. These results show that the hybrid microplate is mainly composed of Cu and Au nanocrystals decorating the microplate surface, which is consistent with the SEM and LSPR analysis results.

The Cu-Au hybrid microplate has multiple cavities on the surface, and numerous small Au nanocrystals exist on the surface and edges of the microplate. Because of this unique porous structure and surface roughness, microplates can provide numerous active sites and sites suitable for catalytic reactions. Therefore, microplates can be widely applied in catalysis. In this example, the reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH ₄ was selected as a probe reaction to demonstrate the catalytic performance of the Cu-Au hybrid microplate. 4-NP, widely used in pesticides and dyes, is one of the most toxic and hazardous pollutants, so hydrogenation of 4-NP to 4-AP using NaBH ₄ removes 4-NP within the aqueous phase. It has potential importance as an environmentally friendly and effective way to Meanwhile, the hydrogenation reaction from 4-NP to 4-AP by NaBH ₄ takes several days, so a stable and efficient catalyst is needed to dramatically reduce the reaction time. Accordingly, the present inventor used the prepared Cu-Au hybrid microplate as a catalyst in the hydrogenation reaction from 4-NP to 4-AP by NaBH ₄ . First, when NaBH ₄ is added to the 4-NP aqueous solution, the absorption peak at 318 nm moves to 400 nm because 4-NP is converted to 4-nitrophenolate ion (Figure 7(a)). . The UV-Vis spectrum recorded at 50 second intervals after adding the Cu-Au hybrid microplate to an aqueous solution containing 4-NP and NaBH ₄ is shown in Figure 7(b). The intensity of the absorption peak at 400 nm gradually decreased over time, reaching almost zero after 300 s. At the same time, an absorption peak appeared at 301 nm and its intensity increased over time, showing that the hydrogenation reaction was successful. In this experiment, the reaction rate constant ( k ) can be calculated based on the pseudo-first-order reaction rate equation because NaBH ₄ is added in excess and the reaction rate does not depend on the concentration of NaBH ₄ . Figure 7(c) is a plot of ln(A _t /A ₀ ) and reaction time t (where A _t and A ₀ are the absorbance at time t and time 0, respectively) for the Cu-Au used in this example. The k value of the hybrid microplate was calculated to be 11.6 × 10 ^-1 s ^-1 . On the other hand, the absorption spectrum of the hydrogenation reaction performed using pure Cu microplates as catalyst changed only slightly over 60 min. Therefore, the hydrogenation reaction proceeded very slowly, and pure Cu microplates were found to have poor catalytic activity.

The Cu-Au hybrid microplate used in this example has a large particle size of several micrometers, so it can be easily collected from the reaction mixture and reused after the catalytic reaction is completed. The reusability of the catalyst was evaluated in experiments using the same hybrid microplate repeatedly. The catalytic activity according to the conversion rate of 4-NP during five reuse cycles was confirmed to be almost the same, showing that the catalyst exhibited excellent reusability and excellent stability (Figure 7(d)). To quantitatively compare the catalytic activity of Cu-Au hybrid microplates with that of other reported catalysts, the activity parameter k (= k/m ) ( m is the total mass of catalyst added to the reaction and k is the mass of catalyst added to the hydrogenation reaction) (is the rate constant for) was calculated. The k value was calculated to be 166 s ^-1 g ^-1 for the reaction using the hybrid microplate as a _catalyst , and the corresponding value was calculated as It was confirmed to be high compared to previously reported values for heterogeneous catalysts.

The present invention is not limited to the above-mentioned embodiments, but can be manufactured in various different forms, and those skilled in the art will be able to form other specific forms without changing the technical idea or essential features of the present invention. You will be able to understand that this can be implemented. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.

Hybrid plate-shaped materials based on copper plate-shaped micro particles, such as Cu@Cu ₂ S metal-semiconductor hybrid material with core (Cu)-shell (Cu ₂ S) structure and Cu-Au bimetal hybrid material manufactured according to the present invention. can be used as a photocatalyst and catalyst material with high catalytic activity.

Claims (7)

1. (a) preparing a mixed solution containing a copper precursor, acetonitrile, a capping agent, a reducing agent, and a solvent; and

   (b) heating the mixed solution to produce copper plate-shaped micro particles; including,

   Method for manufacturing copper plate-shaped micro particles.
2. According to paragraph 1,

   In step (a),

   The mixed solution contains copper (II) chloride (CuCl ₂ ), acetonitrile, hexadecylamine (HDA), potassium iodide (KI), and l-ascorbic acid (AA). Characterized in that it is an aqueous solution that

   Method for manufacturing copper plate-shaped micro particles.
3. (A) manufacturing copper plate-shaped micro particles according to the method according to claim 1 or 2; and

   (B) introducing a heterogeneous material to the surface of the copper plate-shaped micro particles; comprising,

   Method for producing hybrid plate-shaped microparticles containing copper plate-shaped microparticles.
4. According to paragraph 3,

   In step (B),

   A hybrid of the core-shell structure consisting of a core containing copper plate-shaped micro particles and a shell containing copper sulfide (Cu ₂ S) through a sulfidation reaction between the copper plate-shaped micro particles and sodium sulfide (Na ₂ S). Characterized in producing plate-shaped micro particles,

   Method for producing hybrid plate-shaped microparticles containing copper plate-shaped microparticles.
5. According to paragraph 3,

   In step (B),

   Characterized in producing Cu-Au bimetal hybrid plate-shaped microparticles by replacing copper (Cu) atoms on the surface of the copper plate-shaped microparticles with gold (Au) atoms through a galvanic replacement reaction. ,

   Method for producing hybrid plate-shaped microparticles containing copper plate-shaped microparticles.
6. Hybrid plate-shaped micro-particles having a core-shell structure consisting of a core containing copper plate-shaped micro particles and a shell containing copper sulfide (Cu ₂ S), manufactured according to the method according to claim 4.
7. Cu-Au bimetal hybrid plate-shaped microparticles prepared according to the method described in claim 5.

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