KR20140115877A - Process for Preparing Hollow Multimetallic Oxide Nanoparticle - Google Patents

Abstract

The present invention relates to a method for manufacturing a multi-metallic oxide nanoparticle having a hollow structure. More specifically, the present invention relates to a method for manufacturing a multi-metallic oxide nanoparticle which includes the step of heating a mixture of a first transition metal oxide nanoparticle, a second transition metal salt, water, and a surfactant under an acidic composition, and having the standard reduction potential of the first transition metal oxide nanoparticle to be higher than the standard reduction potential of the second transition metal ion.

Description

Technical Field [0001] The present invention relates to a process for preparing a hollow multimetal oxide nanoparticle,

The present invention relates to a method for producing a hollow-structure multimetal oxide nanoparticle. More particularly, the present invention relates to a method for preparing a transition metal oxide nanoparticle comprising heating a mixture of a first transition metal oxide nanoparticle, a second transition metal salt, water and a surfactant under acidic conditions, Wherein the dislocation is greater than the standard reduction potential of the second transition metal ion.

Chemical transformation of inorganic nanoparticles is a powerful tool for the production of nanostructures with high structural and structural complexity and thus extends the range of nanostructured materials that can be produced.

Of the various chemical transformation methods, galvanic replacement reactions are most versatile to produce hollow metal nanostructures with controllable pore structures and compositions.

The galvanic substitution reaction involves a corrosion process driven by an electrochemical potential difference between two metal species. Due to the oxidative dissolution of metal nanoparticles used as a reactive template, a hollow interior is created.

Recent developments have enabled the production of highly complex hollow metal and alloy nanostructures. However, it is difficult to achieve the chemical transformation of the ion system through the galvanic substitution reaction.

Hollow oxide nanoparticles are attracting much attention because of their potential for energy, catalyst and medical applications. Although considerable advances have been made in the synthesis of hollow metal oxide nanoparticles (Z. Wang, L. Zhou, XW Lou, Adv . Mater . 24 , 1903 (2012); K. An, T. Hyeon, Nano Today 4 , 359 (2009); Y. Piao et al . , Nat . Mater . 7 , 242 (2008); S. Peng, S. Sun, Angew . Chem . Int . Ed . 46 , 4155 (2007)), the synthesis of hollow multimetallic oxide nanoparticles remains a great challenge.

The inventors of the present invention have completed the present invention by confirming that a hollow multimetal oxide nanostructure can be prepared through a galvanic substitution reaction also for transition metal oxide nanoparticles.

It is an object of the present invention to provide a method for producing a metal oxide nanoparticle comprising heating a mixture of a first transition metal oxide nanoparticle, a second transition metal salt, water and a surfactant under acidic conditions, Metal oxide nanoparticles of the second transition metal ion is greater than the standard reduction potential of the second transition metal ion.

The above-mentioned object of the present invention is achieved by a method for producing a metal oxide nanoparticle comprising heating a mixture of a first transition metal oxide nanoparticle, a second transition metal salt, water and a surfactant under acidic conditions, Is greater than the standard reduction potential of the second transition metal ion.

The first transition metal oxide may be Mn ₃ O ₄ , MnO ₂ , Co ₃ O ₄ , Fe ₃ O ₄ , PbO ₂ or CeO ₂ . The second transition metal salt may also be selected from the group consisting of iron (II) perchlorate, tin (II) perchlorate, vanadium (III) chloride, titanium (III) chloride, chromium (II) chloride, II) < / RTI > chloride.

The surfactant may be selected from the group consisting of C ₁ -C ₁₈ carboxylic acids such as oleic acid, octanoic acid, stearic acid and decanoic acid; C ₃ -C ₁₈ alkyl amines such as oleylamine, octylamine, hexadecylamine, octadecylamine or tri-n-octylamine, and the like. RNH ₂ ), C ₁ -C ₁₈ alcohols such as oleyl alcohol, octanol or butanol, or mixtures thereof.

The pH of the mixture is preferably 0.0 to 6.0. Acids such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid or perchloric acid may be added to adjust the pH of the mixture. In addition, the heating temperature of the mixture may be 30 ° C to 100 ° C.

The shape of the multi-metal oxide nanoparticles may be a nanobox or a nanocage. As used herein, the term "nanobox" refers to a nanoparticle consisting of a hollow interior and solid walls. Also, in the present specification, the term "nanocage" refers to a nanoparticle composed of a hollow interior and porous walls.

The size of the first transition metal oxide nanoparticles may be 5 nm to 100 nm, and the size of the multimetal oxide nanoparticles may be 5 nm to 100 nm.

In a nanoscale galvanic substitution reaction, a redox-couple reaction takes place between the multivalent metal ions. The metal ions in the nanoparticles are displaced by other metal ions in the solution.

In one embodiment of the present invention, iron (II) perchlorate and Mn ₂ O ₃ nanoparticles are reacted (galvanic substitution reaction) to form Mn ₃ O ₄ / γ-Fe ₂ O ₃ nanobox or γ-Fe ₂ O ₃ A nanocage can be manufactured. The above-mentioned chabbinite substitution reaction can be explained on the basis of the standard reduction potential difference of Fe ^{3 +} / Fe ^{2 +} pair and Mn ₃ O ₄ / Mn ^{2 +} pair. Since the Fe ^{3 +} / Fe ^{2 +} A pair of standard reduction potential (0.77 V) that the Mn ₃ O ₄ / Mn ^{2 +} A pair of smaller than the standard reduction potential (1.82 V), oxidized Fe ^{2 +} is a Fe ^{3 +} At the same time, Mn ₃ O ₄ is reduced to Mn ^{2 +} .

In another embodiment of the present invention, when FeCl ₂ or FeCl ₃ is reacted instead of iron (II) perchlorate, nanoparticles are converted to nanocages only in the case of FeCl ₂ . This fact confirms that Fe ^{2 +} ion acts as a selective reducing agent for Mn ^{3 +} ions in Mn ₃ O ₄ nanoparticles.

Electrons are released due to the oxidation of Fe ^{2 +} , and then Mn ^{3 +} is reduced to Mn ^{2 +} , thereby generating positive charge deficiencies at the octahedral sites of the Mn ₃ O ₄ nanoparticles. The defects are supplemented by being the Mn ^{+ 2} ions substituted with Fe ^{3 +} ions.

When the galvanic substitution reaction is initiated, the reduced Mn < ^{2 + &} gt ^; ions dissolve leaving an empty octahedral site near the surface of the nanoparticles. At the same time, some of the oxidized Fe < ^{3 +} > ions present in the solution diffuse to the surface of the nanoparticles and fill immediately accessible vacancies.

The reduced Mn ^{2 +} ion emission flow of and thus oxidation of the solution Fe ^{3 +} ions to the Mn ₃ O ₄ of the Mn ₃ O ₄ nanoparticles and a phase precipitate (topotactic precipitation) on the nanoparticle surface outermost shell To convert Mn ₃ O ₄ to γ-Fe ₂ O ₃ . This disturbs the outward diffusion of Mn ^{2 +} species inside. This conversion occurs mainly around the edges of the shell.

As the number of vacant octahedral sites increases due to the remarkable dissolution of the reduced Mn ^{2 +} ions, the residual lattice of tetrahedral Mn ^{2 +} ions and oxygen anions may completely collapse. By this process, pinholes are produced during the initial stage of the reaction in the region not covered by the? -Fe ₂ O ₃ layer, i.e. in the middle of the basal plane.

As the galvanic substitution proceeds, the Fe ^& lt ^{; 2 + &} gt ^; ions move inward and reduce the octahedral Mn < ^{3 + &} gt ^; ions inside the Mn ₃ O ₄ nanoparticles. By its role as a passage for continuously moving the reduction of Mn ^{2 +} ions from the nano-box pin holes are, thus formed formed during the early stages of the galvanic displacement reaction, the rest of the core species, i.e. tetrahedra Mn ^{2 +} ions and the oxygen anion Promote dissolution.

The above-mentioned galvanic substitution reaction proceeds until the side walls of the core become hollow, thereby forming a heterostructured Mn ₃ O ₄ / Fe ₂ O ₃ nanocage. At this stage, due to the open structure of the nascent γ-Fe ₂ O ₃ nanocage, the precipitation of γ-Fe ₂ O ₃ occurs inside the hollow of the γ-Fe ₂ O ₃ nanocage, do.

The perchlorate moiety of the aqueous solution of iron (II) perchlorate seems to have no effect on the formation of the hollow structure, since no morphological change was observed when the Mn ₃ O ₄ nanoparticles were reacted with perchloric acid . Further, when the same reaction is carried out by using Mn ₃ O ₄ nanoparticles of different shapes as a starting material, a structure similar to a cage having different shapes can be produced.

According to the method of the present invention, hollow multimetal oxide nanoparticles having a controllable pore structure and composition can be simply produced by a galvanic substitution reaction. In addition, the method of the present invention is suitable for mass production of hollow multimetal oxide nanoparticles.

1A is a TEM (transmission electron microscope) photograph of Mn ₃ O ₄ nanoparticles synthesized in Example 1 of the present invention, FIG. 1A 1 is a low magnification photograph of the Mn ₃ O ₄ nanoparticle, and FIG. Is a HRTEM (high resolution transmission electron microscope) photograph of a single crystal recorded along the [111] axis, FIG. 1A2 is a HRTEM (high resolution transmission electron microscope) photograph of Mn ₃ O ₄ single crystal nanoparticles recorded along the [011] axis, ≪ / RTI > shows the corresponding FT (Fourier Transform) pattern. 1B is a low magnification TEM photograph (B1) and HRTEM photograph (B2) of the γ-Fe ₂ O ₃ nanocage synthesized in Example 3 of the present invention, and the inset of FIG. 1B2 shows a corresponding FT pattern. 1C is a TEM photograph of the Co ₃ O ₄ nanoparticles synthesized in Example 2 of the present invention (left) and a TEM photograph of the SnO ₂ nanocage synthesized in Example 7 of the present invention (right). 1D is a TEM photograph of Mn ₃ O ₄ / SnO ₂ nanoparticles (left) and SnO ₂ nanoparticles (right) synthesized in Examples 4 and 5 of the present invention, respectively. FIG. 1E shows the relationship between the molar fraction of Fe in the reaction product and the iron (II) content in the synthesis process using Mn ₃ O ₄ nanoparticles (solid circle) and its bulk counterpart (open circle) Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) data presented as a function of the amount of perchlorate added. The dotted line in FIG. 1E shows the case where Mn is completely substituted with Fe. 1F shows a powder X-ray diffraction (XRD) pattern for Mn ₃ O ₄ nanoparticles, Mn ₃ O ₄ / γ-Fe ₂ O ₃ nanocages and γ-Fe ₂ O ₃ nanocages. For comparison, an XRD pattern known for Mn ₃ O ₄ (bottom) and γ-Fe ₂ O ₃ (top) is shown in FIG. 1F. FIG. 1G is a saturation magnetization curve obtained by measurement of a superconducting quantum interference device (SQUID).
Figure 2A shows a schematic diagram and, Mn ₃ O ₄ localized dissolution, and in the form of changes in the Mn ₃ O ₄ nanoparticles through surface precipitation of the γ-Fe ₂ O ₃ for the conversion of Mn ₃ O ₄ nanoparticles . Figures 2B-2E illustrate the reaction of an aqueous iron (II) perchlorate solution of 1 mL of 0.4 M (B), 0.6 M (C), 1.0 M (D) and 1.6 M (E) with Mn ₃ O ₄ nanoparticles HRTEM photographs of synthesized hollow nanostructures. Each insertion is a corresponding FT pattern. FIG. 2F is a photograph of a high-angle annular dark-field scanning TEM (HAADF-STEM) for the nano box of FIG. 2B. As shown in FIGS. 2B and 2F, pinholes are formed on the surface of the nanobox, which means that pores are developed inside the nanoparticles by a mechanism similar to pinhole corrosion. The pinholes served as a transport path during the dissolution of the nanoparticle core. FIG. 2G is a TEM photograph and the corresponding EFTEM (energy-filtered TEM) photograph of the nanobox of FIG. 2C, in which Fe species were deposited at the corners. Fig. 2H is a HAADF-STEM photograph of the nanocage of Fig. 2D, in which an open hollow structure is shown. FIG. 2I is a TEM photograph and corresponding EFTEM photograph of the nanocage of FIG. 2E.
Figure 3 is a graphical representation of the results of an experiment on the formation of a hollow (a) 0.4 M, (b) 0.8 M, (c) 1.6 M and (e) 2.0 M hollow (II) perchlorate aqueous solution and Mn ₃ O ₄ nanoparticles, X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements on nanostructures. FIG. 3A shows XAS at the Mn L _2,3 -edges of the original Mn ₃ O ₄ nanoparticles and the hollow nanostructure, and FIGS. 3B and 3C compare the bulk materials γ-Fe ₂ O ₃ and Fe ₃ O ₄ XAS (FIG. 3B) at one, Fe L _{2 , 3} -edge and XMCD spectra for the used nanostructures (FIG. 3C).
FIG. 4 is a TEM photograph (FIG. 4A, inset (scale bar = 10 nm) high magnification TEM photograph) and HRTEM photograph (FIG. 4B, FIG. 4B) of Co ₃ O ₄ / SnO ₂ nanocage synthesized in Example 6 of the present invention. Insertion is EFTEM photo).
FIG. 5A is a TEM photograph of CeO ₂ nanoparticles used in Example 8 of the present invention, and FIGS. 5B and 5C are TEM images of CeO ₂ / γ-Fe ₂ O ₃ nanocages synthesized in Example 8 of the present invention And FIG. 5D is an EFTEM photograph of the CeO ₂ / γ-Fe ₂ O ₃ nanocage.

Hereinafter, the present invention will be described in more detail with reference to the following examples or drawings. It is to be understood, however, that the following description of the embodiments or drawings is intended to illustrate specific embodiments of the invention and is not intended to be exhaustive or to limit the scope of the invention to the precise forms disclosed.

Example  One. Mn ₃ O ₄  Manufacture of nanoparticles

To a solution of 0.17 g of manganese (II) acetate (Adrich), 0.67 g of oleylamine (Acros) and 0.14 g of triethylamine in 15 mL of xylene in a 50 mL three-necked flask equipped with a reflux condenser and a magnetic stir bar Oleic acid (Aldrich) was dissolved. Thereafter, the flask was slowly heated to 90 DEG C in the air with stirring. 1 mL of deionized water was rapidly injected into the flask. The reaction mixture was heated in air at 90 < 0 > C for 1.5 h.

The TEM image (FIG. 1A) of the synthesized Mn ₃ O ₄ nanoparticles shows that the Mn ₃ O ₄ nanoparticles have a tetragonal shape with a width and a length of about 20 nm and a height of about 5 nm . Figure 1A1 is a low magnification photograph of the Mn ₃ O ₄ nanoparticles, recorded also inserted diagram of 1A1 is a HRTEM (high resolution transmission electron microscope) photograph of the single crystal recorded along the [111], Fig. 1A2 is along the [011] HRTEM (high resolution transmission electron microscope) photograph of Mn ₃ O ₄ single crystal nanoparticles, and the inset of FIG. 1A 2 shows a corresponding FT (Fourier transform) pattern. The high-resolution TEM photographs of the Mn ₃ O ₄ nanoparticles and the corresponding Fourier transform patterns show that the top and side surfaces of the Mn ₃ O ₄ nanoparticles are surrounded by {001} facets and {100} Stacked, its vertices and corners are slightly truncated.

Example  2. Co ₃ O ₄  Manufacture of nanoparticles

1 mmol of cobalt (II) perchlorate (Aldrich) was dissolved in 15 mL of octanol in a 100 mL flask equipped with a reflux condenser and ultrasonicated for 10 minutes. 10 mmol of oleylamine and 1 mL of water were then added to the flask in succession with stirring at 60 DEG C in air. The reaction mixture was heated to 160 < 0 > C for 6 hours in air. FIG. 1C (left), which is a TEM photograph of Co ₃ O ₄ synthesized in this embodiment.

Example  3. Galvanic  Substitution reaction Mn ₃ O ₄ / γ- Fe ₂ O ₃  And? Fe ₂ O ₃ Manufacturing

Iron (II) perchlorate (Aldrich) of various concentrations (0.1 to 3.0 M) was added to 16 mL of the Mn ₃ O ₄ suspension prepared in Example 1 and then heated to 90 ° C for 2 hours in air to obtain Mn ₃ O ₄ /? -Fe ₂ O ₃ and? -Fe ₂ O ₃ . The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol.

1B shows a low magnification TEM (FIG. 1B1), HRTEM (FIG. 1B2) and corresponding FT patterns (inset of FIG. 1B2) for γ-Fe ₂ O ₃ synthesized using 2.0 M iron (II) perchlorate, . Referring to FIG. 1B, it can be seen that the original Mn ₃ O ₄ nanoparticles were completely converted into a nanocage with an empty interior and a hole in the shell. The outer shape of the nanocage is almost the same as that of the original Mn ₃ O ₄ nanoparticles. Also, as can be seen in the HRTEM of FIG. 1B2, it can be seen that the shell of the nanocage is a single-crystal steady structure with highly ordered continuous lattice fringes.

FIG. 1E shows the relationship between the molar fraction of Fe in the reaction product and the iron (II) content in the synthesis process using Mn ₃ O ₄ nanoparticles (solid circle) and its bulk counterpart (open circle) Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) data presented as a function of the amount of perchlorate added. As shown in FIG. 1E, the molar ratio of iron to manganese in the nanocage is 91: 9, which indicates that the manganese ions in the original nanoparticles were almost completely replaced by the iron ions. When bulk Mn ₃ O ₄ powder was used, the molar ratio of Fe in the product was significantly low (less than 25%). The dotted line in FIG. 1E shows the case where Mn is completely substituted with Fe. 1F shows a powder X-ray diffraction (XRD) pattern for Mn ₃ O ₄ nanoparticles, Mn ₃ O ₄ / γ-Fe ₂ O ₃ nanocages and γ-Fe ₂ O ₃ nanocages. For comparison, an XRD pattern known for Mn ₃ O ₄ (bottom) and γ-Fe ₂ O ₃ (top) is shown in FIG. 1F. 1F, it can be seen that as the concentration of iron (II) perchlorate increases, the tetragonally distorted Mn ₃ O ₄ spinel is converted to the cubic γ-Fe ₂ O ₃ spinel. This fact is also confirmed by FIG. 1G. FIG. 1G is a saturation magnetization curve obtained by measurement of a superconducting quantum interference device (SQUID). As shown in FIG. 1G, the magnetization of the produced nanoparticles increased steadily as the Fe content increased.

Figures 2B-2E illustrate the reaction of an aqueous iron (II) perchlorate solution of 1 mL of 0.4 M (B), 0.6 M (C), 1.0 M (D) and 1.6 M (E) with Mn ₃ O ₄ nanoparticles HRTEM photographs of the synthesized hollow nanostructures, with each insertion being a corresponding FT pattern. When the concentration of the aqueous iron (II) perchlorate solution was low, the core of the Mn ₃ O ₄ nanoparticles was partially dissolved to produce a nanobox having a relatively thick wall. As the concentration of iron (II) perchlorate increased, the pore size increased and the nanobox was converted into nanocage (FIGS. 2D and 2H). During the intermediate step of the substitution reaction, both the nanobox and the nanocage showed a continuous fringe pattern, which means that the lattice orientation of the original Mn ₃ O ₄ nanoparticles is retained. Figures 2B through 2E and their insertions show a slight increase in the interplanar distance between the (100) plane of the Mn ₃ O ₄ nanoparticles and the (110) plane of the γ-Fe ₂ O ₃ nanoparticles . However, such changes did not change the alignment of the lattice along the square bottom of the nanoparticles. Preservation of this lattice alignment implies topotactic transformation. FIG. 2F is a photograph of a high-angle annular dark-field scanning TEM (HAADF-STEM) for a nano box of FIG. 2B, in which a pinhole is formed on a (011) plane. FIG. 2G is a TEM photograph and a corresponding EFTEM photograph of the nanobox of FIG. 2C showing the accumulation of Fe species in the shell region of the nanocage. Fig. 2H is a HAADF-STEM photograph of the nanocage of Fig. 2D, in which an open hollow structure is shown. FIG. 2I is a TEM photograph and the corresponding EFTEM photograph of the nanocage of FIG. 2E showing that the Fe species were uniformly deposited over the entire surface of the nanocage.

Figure 3 is a graphical representation of the results of a reaction of an aqueous iron (II) perchlorate solution of 1 mL of (a) 0.4 M, (b) 0.8 M, (c) 1.6 M and (e) 2.0 M with Mn ₃ O ₄ nanoparticles X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements on nanostructures. FIG. 3A is an X-ray absorption spectrum at Mn L _{2 , 3} -edge with increasing molar ratio of iron to manganese. The XAS at the Mn L _{2 , 3} -edge of the nanobox shown in FIG. 3A is almost the same as the XAS of the original Mn ₃ O ₄ nanoparticles, and Mn ^{3 +} and Mn ^{2 +} ions are all within the spinel structure Occupies the octahedral and the tetrahedral, respectively. As can be seen from the X-ray absorption spectra (b) - (d) in FIG. 3A, the peak corresponding to the Mn ^{3 +} ion gradually disappeared and only the peaks of the Mn ^{2 +} ions remained after the completion of the substitution reaction. However, the reduction of the molar concentration of Mn ^{2 +} ions to less than 9% means that most of the Mn ^{2 +} ions have been removed from the tetrahedral sites. Both XAS and XMCD in the Fe L _{2 , 3} -corners of the nanocage were similar to XAS and XMCD of γ-Fe ₂ O ₃ (maghemite) containing only Fe ^{3 +} ions, but Fe ^{3 +} and Fe ² (Fig. 3B and 3C) of XAS and XMCD of Fe ₃ O ₄ containing all of the ⁺ ions. This result implies that Fe ^{3 +} ions were introduced into the octahedral site of the spinel structure previously occupied by Mn ^{3 +} ions.

Example  4. Galvanic  Substitution reaction Mn ₃ O ₄ / SnO ₂ Nanocage  Produce

To 16 mL of the Mn ₃ O ₄ suspension prepared in Example 1 was added 0.5 mL of an aqueous solution containing 0.34 g of oleylamine, 2.0 M tin (II) chloride aqueous solution and 0.4 mL of HCl solution (37%) , And then heated in air at 90 캜 for 2 hours to prepare Mn ₃ O ₄ / SnO ₂ nanocage. The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol. A TEM photograph of the Mn ₃ O ₄ / SnO ₂ nanocage synthesized in this example is shown in FIG. 1D (left).

Example  5. Galvanic  Substitution reaction SnO ₂ Nanocage  Produce

To 16 mL of the Mn ₃ O ₄ suspension prepared in Example 1 was added 0.5 mL of an aqueous solution containing 0.67 g of oleylamine, 0.14 g of oleic acid, 0.2 mL of HCl solution (37%) and 2.0 M of tin (II) chloride And then heated at 90 캜 for 2 hours in air to prepare SnO ₂ nanocage. The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol. A TME photograph of the SnO ₂ nanocage synthesized in this example is shown in FIG. 1D (right).

Example  6. Galvanic  Substitution reaction Co ₃ O ₄ / SnO ₂ Nanocage  Produce

2.0 M tin (II) chloride and 0.6 mL of HCl were added to a suspension of 1 mmol of Co ₃ O ₄ nanoparticles prepared in Example 2, 2 g of oleylamine, 0.14 g of oleic acid and 15 mL of xylene 1 mL of an aqueous solution containing a solution (37%) was added, and the mixture was heated at 90 ° C. for 2 hours in air to prepare a Co ₃ O ₄ / SnO ₂ nanocage. The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol.

A TEM photograph of the Co ₃ O ₄ / SnO ₂ nanocage synthesized in this example is shown in FIG. 4A (high magnification TEM image of the inset (scale bar = 10 nm)) and the Co ₃ O ₄ / SnO ₂ nanocage The HRTEM picture of the cage is also shown in Figure 4B (the inset picture is the EFTEM picture).

Example 7 Synthesis of SnO ₂ by Galvanic Substitution Article nano cage

2.0 M tin (II) chloride and 0.4 mL of HCl were added to a suspension of 1 mmol of Co ₃ O ₄ nanoparticles prepared in Example 2, 0.67 g of oleylamine, 0.14 g of oleic acid and 15 mL of xylene 1 mL of an aqueous solution containing a solution (37%) was added, and the mixture was heated at 90 ° C for 2 hours in air to prepare a SnO ₂ nanocage. The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol. A TEM photograph of the SnO ₂ nanocage synthesized in this example is shown in FIG. 1C (right).

Example 8 by galvanic replacement reaction CeO ₂ / γ- Fe ₂ O ₃ Article nano cage

To a suspension of 1 mmol of the previously prepared CeO ₂ nanoparticles, 0.67 g of oleylamine, 0.14 g of oleic acid and 15 mL of xylene, 1 mL of 1.0 M iron (II) chloride aqueous solution was added, CeO ₂ / γ-Fe ₂ O ₃ nanocage was prepared by heating in air at 90 ° C. for 2 hours. The product mixture was cooled to room temperature and centrifuged to obtain the product, which was then washed with ethanol. A TEM photograph of the CeO ₂ nanoparticles used in this example is shown in FIG. 5A, and TEM photographs of the synthesized CeO ₂ / γ-Fe ₂ O ₃ nanocage are shown in FIGS. 5B and 5C, An EFTEM picture of the cage is shown in Figure 5D.

Example  9. Structural analysis of the prepared nanoparticles

TEM images were obtained at 200 kV using a JEOL EM-2010 transmission electron microscope (TEM). High resolution TEM (HRTEM) was performed using a JEOL 2200FS transmission electron microscope at 200 kV. Energy-filtered TEM images were recorded on a Tecnai F20 transmission electron microscope. Elemental analysis was performed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) (Shimadzu). An X-ray diffraction pattern was obtained using a Rigaku D / max 2500 diffractometer equipped with a rotating anode and a Cu K? Radiation source (? = 0.15418 nm). Magnetization measurements were performed using an MPMS 5XL Quantum Design SQUID magnetometer. Fe and Mn L _{2 , 3} -edge XAS and XMCD measurements were performed at Beamline 2A of the Pohang Accelerator Laboratory. Nitrogen adsorption and desorption isotherms were measured at 77 K using a Micromeritics ASAP 2000 gas adsorption analyzer. The total surface area and pore volume were measured using a BET (Brunauer-Emmett-Teller) equation and a single-point method.

Claims (12)

Heating a mixture of first transition metal oxide nanoparticles, a second transition metal salt, water and a surfactant under acidic conditions, wherein the standard reduction potential of the first transition metal oxide nanoparticles is higher than the second transition metal ion Is greater than the standard reduction potential of the hollow multimetal oxide nanoparticles. The method of claim 1, wherein the first transition metal oxide is selected from the group consisting of Mn ₃ O ₄ , MnO ₂ , Co ₃ O ₄ , Fe ₃ O ₄ , PbO ₂ and CeO ₂ . Method of manufacturing nanoparticles. The method of claim 1, wherein said second transition metal salt is selected from the group consisting of iron (II) perchlorate, tin (II) perchlorate, vanadium (III) chloride, titanium (III) chloride, chromium (II) chloride, (II) < / RTI > chloride. ≪ RTI ID = 0.0 > 11. < / RTI > The hollow fiber of claim 1, wherein the surfactant is any one selected from the group consisting of C ₁ -C ₁₈ carboxylic acids, C ₃ -C ₁₈ alkylamines, and C ₁ -C ₁₈ alcohols, or a mixture thereof. Method of manufacturing metal oxide nanoparticles. The method according to claim 4, wherein the C ₁ -C ₁₈ carboxylic acid is selected from the group consisting of oleic acid, octanoic acid, stearic acid and decanoic acid. (Method for producing hollow multimetal oxide nanoparticles). The method of claim 4, wherein the C ₁ -C ₁₈ alkylamine is selected from the group consisting of oleylamine, octylamine, hexadecylamine, octadecylamine, and tri- octylamine. < / RTI >< RTI ID = 0.0 > 11. < / RTI > The method of claim 4, wherein the C ₁ -C ₁₈ alcohol is selected from the group consisting of oleyl alcohol, octanol, and butanol. . 2. The method of claim 1, wherein the pH of the mixture is 0.0 to 6.0. The method according to claim 1, wherein the heating temperature of the mixture is 30 ° C to 100 ° C. The method of claim 1, wherein the shape of the multi-metal oxide nanoparticles is a nano-box or a nanocage. 2. The method of claim 1, wherein the first transition metal oxide nanoparticles have a size of 5 nm to 100 nm. The method of claim 1, wherein the multimetal oxide nanoparticles have a size of 5 nm to 100 nm.

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