KR101415729B1 - Synthesis of layered double hydroxide or mixed oxide embedding nanoparticles - Google Patents

Abstract

The present invention relates to a layered double hydroxide and a process for producing the layered double hydroxide, and more particularly to a layered double hydroxide and a mixed metal oxide capturing nanoparticles and a method for producing the same.
The nanoparticle-layered double hydroxide complex of the present invention can be produced under mild conditions, and mass production and production cost can be reduced. In addition, composites are made using synthetic nanoparticles whose physical properties such as size are controlled, so that the properties of the composite can be controlled. The nanoparticle-layered double hydroxide of the present invention can be used as a layered double hydroxide in various applications such as an anion exchanger, a catalyst support, an electronic material, an optical coating material, an ultraviolet absorber, a photocatalyst, The characteristics depending on the interaction of the matrix can be additionally given. Since the composite material forms a layered double hydroxide structure surrounding the nanoparticles, the penetration of foreign substances such as gas and moisture can be reduced, and the nanoparticles can be protected from the external environment. On the other hand, the spatial binding force of the nanoparticles in the composite is increased, thereby preventing phase separation or aggregation of the nanoparticles when heat is applied. In the quantum dot nanoparticle-layered double hydroxide or mixed metal oxide composite, a metal oxide or a layered double hydroxide acts as a surface protective layer of a quantum dot, thereby improving the luminescence property.

Description

TECHNICAL FIELD [0001] The present invention relates to a layered double hydroxide or mixed metal hydroxide capturing nanoparticles and a method for producing the same. BACKGROUND ART [0002]

The present invention relates to a layered double hydroxide and a process for producing the layered double hydroxide, and more particularly to a layered double hydroxide and a mixed metal oxide capturing nanoparticles and a method for producing the same.

The two-dimensional metal hydroxide is composed of octahedral units of divalent or trivalent metal ions and hydroxide ions. As the divalent metal ion, zinc, magnesium, cobalt, nickel, iron ion and the like can be used, and as the trivalent metal ion, aluminum, chromium, gallium ion and the like can be used. Two-dimensional metal hydroxides are totally positively charged by the presence of arbitrarily distributed trivalent metal ions. Generally, it is synthesized in an aqueous solution, which is composed of alternating positive and negative ions as shown in FIG. 1 due to anions (for example, carbonate ions (CO ₃ ^{2 -} )) in the aqueous solution and electrostatic attraction.

Mixed metal oxides produced through the heat treatment of such layered double hydroxides are highly stable and can have various optical, electrical, and magnetic properties depending on various combinations of divalent and trivalent metal ions.

On the other hand, attempts have been made to modify the layered double hydroxides to give new properties, for example, PCT / EP2006 / 069206 discloses layered double hydroxides capable of bonding with rubber particles. Layered double hydroxide and an organic anion capable of bonding to the rubber. Modified layered double hydroxides are used as nanocomposites in combination with rubber.

However, there is a continuing need for new ways of using the layered double hydroxides to provide more diverse properties.

A problem to be solved by the present invention is to develop a method for producing a layered double hydroxide having new properties by modifying a layered double hydroxide.

Another problem to be solved in the present invention is to develop a layered double hydroxide having new properties by modifying layered double hydroxides.

Another problem to be solved in the present invention is to develop mixed metal oxides using modified layered double hydroxides.

In order to solve the above problems, the present invention provides a method for producing nanoparticle-LDH complexes, wherein an aqueous solution of divalent and trivalent metal cations is reacted with hydroxide ions and anionic nanoparticles.

In the practice of the present invention, the reaction of the divalent and trivalent metal cation aqueous solutions with the hydroxide ions and the anionic nanoparticles is characterized in that the hydroxide ions and the anionic nanoparticles are added to an aqueous solution of a divalent metal and a trivalent metal ion to coprecipitate . The hydroxide ion may be used in the form of an aqueous NaOH solution.

In the present invention, the nanoparticles are understood to be particles of several hundred nanometers to several nanometers, which can be inserted between layers of a layered double hydroxide. As raw materials for the nanoparticles, metals, semiconductors, and inorganic materials can be used. The metal nanoparticles may be metal particles or particles coated with a metal such as silica, and the metal may be a single metal or an alloy. The semiconductor nanoparticles are particles such as quantum dots made of a semiconductor compound. For example, compounds such as Cd, Se, Zn, and S may be quantum dots having a core / shell shape.

In the present invention, the anionic nanoparticles are nanoparticles having an anionic group capable of reacting with LDH. Examples of anionic groups that can react with LDH include carboxylates, sulfates, sulfonates, nitrates, phosphates, and phosphonates.

In the present invention, the anionic nanoparticles may be prepared by reacting nanoparticles with an amphoteric compound having an anionic functional group capable of reacting with LDH and a surface bonding group capable of binding to nanoparticles.

In the present invention, the amphoteric compound includes an anionic group capable of reacting with LDH, for example, a carboxylate, a sulfate, a sulfonate, a nitrate, a phosphate and a phosphonate, preferably a carboxylate to be.

It is also possible to use surface bonding groups capable of chemically bonding to the surface of the nanoparticles such as acrylate, methacrylate, hydroxyl, chloride, bromide, amine, epoxy, thiol, vinyl, disulfide, polysulfide, carbamate There may be mentioned ammonium, sulfonic, sulfinic, sulfonium, phosphonium, phosphinic acid, isocyanate, hydride, imide, nitrosobenzyl, dinitrosobenzyl, phenol, acetoxy, And preferably a cyano group or a dithiano group which can be easily bonded to gold nanoparticles or the like.

The amphoteric compound comprises at least two carbon atoms, preferably at least six carbon atoms, more preferably at least eight carbon atoms, most preferably at least ten carbon atoms, Atoms, preferably not more than 500 carbon atoms, and most preferably not more than 100 carbon atoms.

A suitable amphoteric compound according to the invention is lipoic acid.

In the present invention, it is preferable that the anionic nanoparticles are added at the time when the cationic two-dimensional metal hydroxide starts to form in the aqueous solution.

In one aspect, the present invention provides a nanoparticle-LDH complex having an anionic nanoparticle interposed between LDH layers represented by the following chemical formula (1).

(1)

(One)

Wherein, M ^{2 +} is a divalent metal ion, such as ^{Zn 2 +, Mn 2 +,} Ni 2 +, Co 2 +, Fe 2 +, Cu 2 +, Sn 2 +, Ba 2+, Ca 2 + and Mg ^{2 +} a, M ^{3 +} is a trivalent metal ion, such as ^{3 +} Al, Cr ^{+ 3,} Fe ^{+ 3,} Co ^{+ 3,} Mn ^{+ 3,} Ni ^3+, and Ce ^{3 +} and Ga ^{+ 3,} m and n are m has a value of 1 to 10, b has a value of 0 to 10, X may be a suitable anion known to a person skilled in the art, and at least a part of the anion nanoparticle Lt; / RTI > Examples of anions known to those of ordinary skill in the art include, but are not limited to, hydroxides, carbonates, bicarbonates, nitrates, chlorides, bromides, sulfonates, sulfates, bisulfates, vanadates, tungstates, Borate, phosphate, and the like, and Keggin-ions.

In the practice of the present invention, the size of the nanoparticles is suitably 10 nm or less on the structure of the composite to be formed. The weight ratio of the nanoparticles to the double metal hydroxide is preferably 1/50 or less of the composite structure.

According to another aspect of the present invention, there is provided a method for producing a mixed metal oxide characterized in that a layered double hydroxide having nanoparticles inserted therein is heated to be oxidized. In the practice of the present invention, an anionic nanoparticle is added to an aqueous solution of a divalent metal and a trivalent metal ion to coprecipitate it to prepare a composite of nanoparticles-LDH, and heat-treated to prepare a mixed metal oxide.

In one aspect, the present invention provides a composite consisting of metal nanoparticles or quantum dots and mixed metal oxides derived from LDH.

The nanoparticle-layered double hydroxide complex of the present invention can be produced under mild conditions, and mass production and production cost can be reduced. In addition, composites are made using synthetic nanoparticles whose physical properties such as size are controlled, so that the properties of the composite can be controlled.

The nanoparticle-layered double hydroxide of the present invention can be used as a layered double hydroxide in various applications such as an anion exchanger, a catalyst support, an electronic material, an optical coating material, an ultraviolet absorber, a photocatalyst, The characteristics depending on the interaction of the matrix can be additionally given. Since the composite material forms a layered double hydroxide structure surrounding the nanoparticles, the penetration of foreign substances such as gas and moisture can be reduced, and the nanoparticles can be protected from the external environment. On the other hand, the spatial binding force of the nanoparticles in the composite is increased, thereby preventing phase separation or aggregation of the nanoparticles when heat is applied.

In the quantum dot nanoparticle-layered double hydroxide or mixed metal oxide composite, a metal oxide or a layered double hydroxide acts as a surface protective layer of a quantum dot, thereby achieving a phenomenon such as improvement in luminescence property.

Fig. 1 is a schematic view of an inorganic clay composed of two-dimensional layers having positive electric charge.
2 is a structural schematic diagram of a nanoparticle having a functional group on its surface.
FIG. 3 is a schematic view illustrating formation of a nanoparticle-layered double hydroxide complex through an aqueous solution reaction including a metal ion precursor, a hydroxide ion, and a nanoparticle.
FIG. 4 is a schematic diagram of liposane surface substitution of CdSe / CdS / ZnS nanoparticles synthesized in an organic solvent.
5 is a fluorescence spectrum of CdSe / CdS / ZnS nanoparticles.
6, CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex.
7 is an X-ray diffraction analysis graph of a CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex.
8 is a scanning electron microscope image of a CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex.
9 is a fluorescence change of CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex and CdSe / CdS / ZnS nanoparticles through heat treatment.
10 shows an absorption spectrum of the synthesized gold nanoparticle aqueous solution and an image of a 3 μM gold nanoparticle aqueous solution.
11 is a composite image of a layered double hydroxide and a gold nanoparticle-layered double hydroxide dispersed in an aqueous solution after synthesis.
12 is an absorption spectrum of a layered double hydroxide and a gold nanoparticle-layered double hydroxide complex.
13 is a scanning electron microscope image of a gold nanoparticle-layered double hydroxide complex and an EDS spectrum for qualitative analysis of an image area.
14 is an absorption spectrum of a gold nanoparticle-mixed metal oxide complex produced by heat treatment of a layered double hydroxide, a gold nanoparticle-layered double hydroxide complex, and a gold nanoparticle-layered double hydroxide complex in air at 400 DEG C for 2 hours.

At the beginning of the process of formation of a positively charged two-dimensional metal hydroxide in an aqueous solution, nanoparticles having functional groups on the surface are added to induce bonding by electrostatic attraction or coordination bonding between the two materials, Hydroxide complex. Further, the produced composite is heat-treated to form a nanoparticle-mixed metal oxide composite.

As shown in FIG. 2, nanoparticles having a functional group on the surface and a method for producing the nanoparticles having the functional groups on the surface are introduced into the nanoparticles with an anionic functional group capable of bonding to the LDH and a surface bonding group capable of bonding to the nanoparticle do.

The surface coupler is bonded to the surface of the nanoparticles, and the anionic functional region is located at the outermost side of the nanoparticles, thereby imparting the negative charge property and the coordination bonding property with the metal to the nanoparticles.

The principle of nanoparticle-layered double hydroxide or mixed metal oxide complex formation will be described with reference to Fig. Add surface-coated nanoparticles with negatively charged functional molecular sieves under reaction conditions while stirring a solution of a divalent metal ion precursor, a trivalent metal ion precursor, and a material that imparts a basic environment to the solution. When the aqueous solution is maintained at a specific temperature while being stirred, a basic environment as shown in Fig. 3 (A) is formed, and hydroxide ions (OH ^- ) are abundant in the aqueous solution. As shown in Fig. 3 (B) Or a two-dimensional metal hydroxide based on an octahedral unit formed by bonding between trivalent metal ions and negatively charged hydroxide ions.

Since the two-dimensional metal hydroxide contains a trivalent metal ion, it is positively charged as a whole, and at the beginning of the reaction for introducing a metal ion precursor and a basic environment into the aqueous solution, the surface of the metal hydroxide is negatively charged The nanoparticles are added to the aqueous solution.

As shown in FIGS. 3 (B) and 3 (C), when nanoparticles having a functional group having a negative charge are added at the initial stage of the reaction, an intermediate such as a positively charged precursor or a two-dimensional metal hydroxide and a functional group The nanoparticles are bound by the electrostatic attractive force or the coordination bond between the functional group and the metal ion. As the reaction progresses, a layered double hydroxide complex including nanoparticles is formed as shown in FIG. 4 (d).

These layered double hydroxides have relatively weak structural retention because the interlayer is bonded by electrostatic attraction. Therefore, when thermal energy is applied or oxidized, interlayer diatomic hydrocarbons are converted to mixed metal oxides as their structure changes.

In the following concrete examples, divalent ions of layered double hydroxide were used as zinc ions and trivalent ions were used as aluminum ions. Among the various nanoparticles, quantum dots (CdSe / CdS / ZnS, nucleus / shell / Particles were introduced.

Example 1: Quantum dot nanoparticle-layered double hydroxide complex.

CdSe / CdS / ZnS  Negative charge surface modification of nanoparticles

CdSe / CdS / ZnS was prepared by the following method. Octadecene and oleylamine are placed in a round bottom flask and heated at 100 ° C to alternate between vacuum and nitrogen injection, eventually turning the environment into an environment full of nitrogen gas. Then, raise the temperature of the round bottom flask to 300 ° C and add Octadecene solution, in which cadmium (Cd) and selenium (Se) are separately dissolved, into a high temperature flask at a ratio of Cd: Se = 1: 5. At this time, the ratio of Cd to Se can be adjusted according to the size of the desired nanoparticles. Thereafter, the flask as a reaction vessel is slowly cooled to obtain CdSe nanoparticles dispersed in an organic solvent. The obtained CdSe nanoparticles were dispersed in a round bottom flask containing octadecene and oleylamine solvent at 120 ° C. and then octadecene solution containing both cadmium (Cd) and sulfur (S) was added at a ratio of Cd: S = 1: 1 . Further, the above-mentioned nanoparticle solution is heated at 140 ° C. to simultaneously add the octadecene solution in which zinc (Zn) and sulfur (S) are dissolved together at a ratio of Zn: S = 1: 1. Thereafter, the flask as a reaction vessel is slowly cooled to room temperature to obtain CdSe / CdS / ZnS nanoparticles having a diameter of about 8 nm dispersed in an organic solvent.

CdSe / CdS / ZnS nanoparticles synthesized in organic solvents were dispersed in chloroform. An aqueous solution in which lipoic acid is dissolved in excess and chloroform with purified nanoparticles are stirred at room temperature. The dithiol of lipoic acid has a strong surface binding force with CdSe / CdS / ZnS nanoparticles as compared with an organic molecular ligand acting as a carboxylic acid or primary amine surface binding group, The organic molecular ligands on the surface of CdSe / CdS / ZnS nanoparticles were dispersed into the aqueous solution layer by ligand substitution with lipoic acid. The chloroform layer was removed after layer separation and only the aqueous solution layer was dialyzed to remove excess ligands present in the aqueous solution to obtain CdSe / CdS / ZnS nanoparticles with liposan surface substitution as shown in FIG. As shown in FIG. 5, the CdSe / CdS / ZnS nanoparticles have a fluorescence peak at a wavelength of 615 nm, and the absorbance zeta potential is used for analyzing the kind and size of charge on the surface of the colloid particles. The zeta potential of the liposan surface-substituted nanoparticles was -41.2 mV.

CdSe / CdS / ZnS  The nanoparticle- Layered double hydroxide  Composite synthesis

0.01 M ammonia and the above prepared 0.5 μM CdSe / CdS / ZnS nanoparticles were added while stirring 0.01 M zinc nitrate and 0.003 M aluminum nitrate aqueous solution at room temperature, and the temperature was maintained at room temperature while stirring for 24 hours.

After the reaction was completed, the nanoparticle-layered double hydroxide complex was submerged using a centrifuge, the supernatant was removed, and then redispersed in distilled water. The fluorescence of the nanoparticle-layered double hydroxide complex was analyzed, and the presence of quantum dots was confirmed through the presence of fluorescence at a wavelength of 615 nm as shown in FIG. For the CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex, X-ray diffraction analysis was performed. As shown in Fig. 7, since the amount of CdSe / CdS / ZnS nanoparticles was relatively small, no peak appeared and only a peak of the layered double hydroxide was identified. The CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex was analyzed by a scanning electron microscope (SEM), and it was confirmed that it had a plate shape as shown in FIG.

CdSe / CdS / ZnS  Nanoparticle-mixed metal oxide composite synthesis

CdSe / CdS / ZnS nanoparticle-mixed metal oxide complex was formed by drying an aqueous solution in which a CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex was dispersed on a glass substrate and drying it at 60 ° C for 12 hours .

delete

9 is a fluorescence graph after heat treatment of CdSe / CdS / ZnS nanoparticle-layered double hydroxides at 200 占 폚 in a nitrogen atmosphere. In the case of CdSe / CdS / ZnS nanoparticles, the fluorescence property disappears in the heat treatment under the same conditions. In the case of the CdSe / CdS / ZnS nanoparticle-layered double hydroxide complex, fluorescence decreases little with annealing time. Thus, it can be seen that the complex maintains fluorescence even after the formation of the CdSe / CdS / ZnS nanoparticle-mixed metal oxide complex by heat treatment under specific conditions.

Example 2: Metal nanoparticle-layered double hydroxide complex.

Manufacture of negatively charged gold nanoparticles

10 mL of an aqueous solution containing 20 μmol, 1 μmol and 40 μmol of HAuCl ₄ , lipoic acid and NaBH ₄ was reacted for 3 hours while stirring at room temperature. After addition of 4 μmol of reduced lipoic acid, an additional 3 hours The mixture is stirred at room temperature. This is purified to obtain an aqueous solution in which gold nanoparticles bonded to the surface of lipoic acid are dispersed.

As shown in FIG. 10, it can be seen from the absorption spectrum of this aqueous solution that a peak appears near the wavelength of 513 nm. Analysis of the size of hydrated particles through a dynamic light scattering particle size analyzer reveals that it is 5.2 nm and the zeta potential is -35.4 mV. Therefore, it can be seen that the gold nanoparticles synthesized with the negatively charged molecular sieve on the surface are synthesized.

Gold nanoparticles - Layered double hydroxide  Composite synthesis

0.01 M ammonia and 0.125 μM gold nanoparticles were added while stirring at a room temperature with 0.01 M zinc nitrate and 0.003 M aqueous solution of aluminum nitrate, and the temperature was maintained at room temperature while stirring for 24 hours.

After the reaction is completed, the gold nanoparticle-layered double hydroxide complex is decanted using a centrifuge and the supernatant is removed. As in FIG. 11, the supernatant is removed and redispersed in distilled water. As shown in FIG. 12, it was confirmed that gold nanoparticle peaks existed between the wavelengths of 500 nm and 600 nm through the light absorption characteristics.

An aqueous solution in which the gold nanoparticle-layered double hydroxide complex was dispersed was dropped on an aluminum foil and then dried. As shown in FIG. 13, it was confirmed by SEM observation that the shape of the gold nanoparticle-layered double hydroxide complex had a plate-like structure. As shown in FIG. 13 (B), the EDS qualities The presence of gold nanoparticles was confirmed by the gold peak of the analysis.

Gold nanoparticles - Mixed metal oxide composite synthesis

The gold nanoparticle-layered double hydroxide complex dispersed aqueous solution was dropped on a glass substrate, dried, and heated at 400 ° C for 2 hours to form a gold nanoparticle-mixed metal oxide complex. As shown in FIG. 14, it can be seen that the relative size of the absorption peak of the gold nanoparticle-mixed metal oxide complex formed through the heat treatment is larger than that of the gold nanoparticle-layered double hydroxide complex.

Claims (20)

Characterized in that an aqueous solution of divalent and trivalent metal cations is reacted with hydroxide ions and anionic quantum dot nanoparticles. The method of claim 1, wherein the anionic quantum dot nanoparticles are inserted between LDH layers. 3. The method of claim 1 or 2, wherein the anion QD nanoparticle is formed with an anion group capable of reacting with LDH in the QD nanoparticle. 4. The method of claim 3, wherein the anionic group is selected from the group consisting of carboxylate, sulfate, sulfonate, nitrate, phosphate and phosphonate. delete delete The method of claim 1, wherein the divalent metal is ^{Zn 2 +, Mn 2 +,} Ni 2 +, Co 2 +, Fe 2 +, Cu 2 +, Sn 2 +, Ba 2+, Ca 2 + and Mg ^{2 +} select at least one from the group consisting of: and, wherein the trivalent metal is ³⁺ Al, Cr ^{+ 3,} Fe ^{+ 3,} Co ^{+ 3,} Mn ^{+ 3,} Ni ^{+ 3,} Ce ^{+ 3} and one from the group consisting of Ga ^{3 +} Of the total volume of the nanoparticle-LDH composite. The method of claim 1, further comprising an anion that is not bound to the nanoparticles. The method for producing a nanoparticle-LDH complex according to claim 1, wherein a hydroxide ion and a quantum dot anion nanoparticle are added to the aqueous solution of the divalent and trivalent metal cations to be coprecipitated. Wherein the layered double hydroxide in which the anionic quantum dot nanoparticles are inserted between the layers is heated and heat treated. 11. The method of claim 10, wherein the layered double hydroxide in which the nanoparticles are intercalated between layers is prepared by reacting an aqueous solution of divalent and trivalent metal cations with hydroxide ions and anionic quantum dot nanoparticles. delete Wherein the nanoparticle-LDH complex is characterized in that anionic quantum dot nanoparticles are inserted between the LDH layers. delete delete 14. The nanoparticle-LDH complex according to claim 13, wherein the anion is at least one selected from the group consisting of carboxylate, sulfate, sulfonate, nitrate, phosphate and phosphonate. 14. The nanoparticle-LDH complex according to claim 13, wherein the nanoparticle-LDH complex is a plate-like complex. 14. The nanoparticle-LDH complex of claim 13, wherein the weight ratio of the nanoparticles to the LDH is 1/50 or less. 14. The nanoparticle-LDH complex according to claim 13, wherein the nanoparticles have a size of 10 nm or less. Anion QD nanoparticles, and mixed metal oxides heat-treated with LDH.

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