KR101946145B1 - A Method for preparing metal oxide nanoparticle and metal hydroxide nanoparticle in aqueous solution - Google Patents

Abstract

The present invention relates to a process for preparing metal oxide or metal hydroxide nanoparticles comprising the step of reacting a metal salt with a polyethyleneimine and an alkylamine in an aqueous solution. According to the present invention, metal oxide or metal hydroxide nanoparticles can be produced with simple, safe, environmentally friendly and high production efficiency by using water as a solvent even at a relatively low temperature as compared with the conventional method.

Description

[0001] The present invention relates to a metal oxide nanoparticle and a metal hydroxide nanoparticle in aqueous solution,

The present invention relates to a method for producing metal oxide and metal hydroxide nanoparticles, and more particularly, to a method for producing metal oxide and metal hydroxide nanoparticles, which comprises reacting a metal salt with polyethyleneamine and alkylamine in an aqueous solution.

Studies on metal oxides and metal hydroxide nanoparticles have been attracting attention due to their diverse application possibilities, and they are actively undergoing. In particular, iron oxide nanoparticles are highly biocompatible and can be used for medical purposes such as MRI contrast agents. Manganese oxide nanoparticles can also be used as sensors and catalysts. In addition, metal hydroxide nanoparticles are also being applied to capacitors and batteries capable of energy storage.

To date, metal hydroxides and metal hydroxide nanoparticles have been prepared by a number of methods including hydrothermal synthesis, chemical vapor deposition, and sol-gel method. However, in order to use these methods, a temperature of 100 ° C or higher is required, or a high pressure of several tens of atmospheres is required. Or a reaction time longer than 3 hours is required or the reaction proceeds in a harmful organic solvent, and the synthesis process is complicated, and mass production is not suitable.

For example, Korean Patent Publication No. 2012-0013519 discloses a method for producing iron oxide nanoparticles based on thermal decomposition of an oleic acid iron complex, but the method uses an organic solvent at an inert atmosphere at a temperature of about 300 ° C There is a problem in that the manufacturing cost is increased.

Korean Patent Registration No. 1423563 discloses a method for producing nanoparticles using polyethyleneimine as a reducing agent and a stabilizer, but it has a disadvantage in that crystal structure of iron oxide nanoparticles can not be completely controlled when only polyethylene is used.

Accordingly, the present inventors have made intensive investigations to solve the problems of the prior art as described above. As a result, the present inventors have found that the use of a polyethyleneimine and an alkylamine, and a solvent that is easy to handle, such as water, It is possible to remarkably simplify the manufacturing process and to improve the working environment since the metal nanoparticles can be produced, and the present invention has been completed.

KR 2012-0013519 A KR 1423563 B

It is an object of the present invention to provide a simple and safe method for producing metal oxide and metal hydroxide nanoparticles having high production efficiency.

The present invention provides a process for preparing metal oxide or metal hydroxide nanoparticles comprising the step of reacting a metal salt with a polyethyleneimine and an alkylamine in an aqueous solution.

The method for producing nanoparticles of the present invention can be carried out in an aqueous solution. That is, water can be used as the main solvent. In the conventional manufacturing method, a solvent which is harmful to a human body such as an organic solvent or accompanies an environmental pollution problem is used in most cases, but the present invention can drastically improve such a problem. In addition, there is also the advantage that there is no need for separate wastewater treatment facilities and atmospheric purification facilities. This is not only a great advantage in industry, but also very beneficial to the environment.

The metal salt may include, but is not limited to, an iron salt, a manganese salt, a nickel salt, a cobalt salt, or a mixture thereof, including a transition metal.

The iron salt may be at least one selected from the group consisting of iron acetate, iron halide, iron nitrate, iron sulfate, iron hydroxide, iron chlorate, iron perchlorate, hydrates thereof and mixtures thereof. Preferably, iron perchlorate monohydrate (Fe (ClO ₄ ) ₂ .4H ₂ O) can be used.

The manganese salt may be selected from the group consisting of manganese sulfate (MnSO4), manganese nitrate (Mn (NO3) 3), manganese nitrate (MnCO2CH3) 2, manganese chloride (MnCl2), manganese bromide (MnBr2) and manganese perchlorate ), Hydrates thereof, and mixtures thereof. Preferably, manganese chloride tetrahydrate (MnCl ₂ .4H ₂ O) can be used.

The nickel salt may be at least one selected from the group consisting of nickel sulfate, nickel chloride, nickel acetate, nickel carbonate, nickel hydroxide, hydrates thereof and mixtures thereof. Preferably, nickel acetate dihydrate can be used.

The cobalt salt may be at least one selected from the group consisting of cobalt sulfate, cobalt chloride, cobalt acetate, cobalt carbonate, cobalt hydroxide, hydrates thereof, and mixtures thereof. Preferably, cobalt acetate saponate can be used.

In the present invention, the polyethyleneimine can make the nanoparticles formed as a stabilizer or a capping agent maintain the nano-size.

Polyethyleneimine (PEI) is a polymer composed of an amine group and an alkyl group, and has a chelating effect, a reducing power, and a capping power for a metal ion. For this reason, even at high concentration of metal ions, the metal is caught in the ionic state, which simultaneously causes reduction and capping. Polyethyleneimine is divided into branched and linear in molecular structure. The branched polyethylenimine (B-PEI) may be represented by the following general formula (1) and the linear polyethylenimine (L-PEI) may be represented by the following general formula (2). In the present invention, both B-PEI and L-PEI can produce nanoparticles of uniform size without agglomeration.

[Chemical Formula 1] B-PEI

[Chemical Formula 2] L-PEI

The molecular weight (degree of polymerization) of PEI is not considered to be a major factor in the method of the present invention for producing nanoparticles. As a result of experiments on PEI having molecular weights of 25,000, 70,000 and 750,000, which are commercially available, there was little difference in the characteristics of the prepared nanoparticles even when the molecular weights were different. Accordingly, it is considered that all PEI can be used regardless of the molecular weight, but it is preferable to use PEI having a molecular weight of 20,000 to 1,000,000 as a non-limiting example.

In the present invention, the alkylamine may increase the pH value of the reaction solution to induce a sol-gel reaction to form metal oxide or metal hydroxide nanoparticles.

As shown in FIG. 7, it was observed that the pH value of the reaction decreased during the synthesis. In addition, when NaOH instead of hexylamine was used to increase the pH of the reaction solution, the XRD pattern of the product was confirmed by α-Fe ₂ O ₃ (JCPDS file no. 80-2377) and iron hydroxide (JCPDS file no. 81-2022) (Fig. 8). It was confirmed that the Fe ₃ O ₄ crystal structure having a part of the Fe ₃ O ₄ crystal structure was formed. That is, alkylamine can also act to increase the pH of the reaction solution like NaOH.

In particular, the alkylamine in the present invention plays an important role in the formation of Fe ₃ O ₄ (magnetite) crystal structure as a reactant in the preparation of iron oxide nanoparticles.

The alkylamine may have 6 to 20 carbon atoms, and hexylamine, heptylamine, octylamine and the like may be preferably used, but the present invention is not limited thereto. When an alkylamine having more than 20 carbon atoms is used, phase separation may occur and the amine may not mix well with water.

In the method for producing nanoparticles of the present invention, the size, shape, and degree of aggregation of the nanoparticles may vary depending on the reaction temperature and the concentration of the metal salt.

That is, the self-assembly of nanoparticles can increase at high reaction temperatures.

When the reaction temperature is low, the size of the generated nanoparticles is not uniform and the production efficiency may be decreased. As the temperature increases, the size becomes uniform and the reaction speed becomes faster. In consideration of this point, the reaction temperature is preferably 20 to 95 ° C, but not necessarily limited to 100 ° C or less.

The size of the metal oxide and metal hydroxide nanoparticles produced in the present invention can be controlled by changing the content (concentration) of the metal salt while maintaining other conditions.

In the present invention, the molar concentration ratio based on C ₂ H ₅ N, which is the unit of the polyethyleneimine with respect to the molar concentration of the metal salt in the reaction liquid, is preferably 0.2 to 1.0, more preferably 0.55 to 0.65. If it is less than 0.2, a small number of nuclei are formed due to a lack of reducing power, the particle growth can not be controlled due to the lack of the capping force, so that intergranular bonding may occur and problems such as agglomeration may occur. The particles may not be uniform in size due to obstruction of the growth of the particles, and problems such as aggregation may occur.

In the present invention, the ratio of the molar concentration of the alkylamine to the molar concentration of the metal salt in the reaction liquid is preferably 1.0 to 3.0, more preferably 1.5 to 2.5. If it is less than 1.0, the size and shape may not be constant due to lack of reducing power due to lack of reducing power. If it is more than 3.0, the particle growth is not applied uniformly due to excessive reducing power, .

The reaction of the present invention can proceed for a shorter time than in the prior art. Preferably 2 to 12 hours.

The reaction of the present invention can proceed at atmospheric pressure, and manufacturing cost can be reduced.

The present invention can control the size of the metal oxide nanoparticles produced by using polyethyleneimine to 10 to 50 nm, preferably 20 to 30 nm.

The present invention can control the size of nickel hydroxide nanoparticles produced by using polyethyleneimine to preferably 80 to 100 nm.

The present invention can control the size of the cobalt hydroxide nanoparticles produced by using polyethyleneimine to preferably 250 to 450 nm.

The metal oxide nanoparticles prepared according to the present invention have a particle shape, and the metal hydroxide nanoparticles may have a plate shape.

Preferably, the metal oxide nanoparticles may be iron oxide (Fe ₃ O ₄ ) nanoparticles, manganese oxide (Mn ₃ O ₄ ) nanoparticles, and the like. The iron oxide (Fe ₃ O ₄ ) may be magnetite (magnetite).

Preferably, the metal hydroxide nanoparticles may be nickel hydroxide (Ni (OH) ₂ ) nanoparticles, cobalt hydroxide (Co (OH) ₂ ) nanoparticles, and the like.

According to the present invention, metal oxide or metal hydroxide nanoparticles can be produced with simple, safe, environmentally friendly and high production efficiency by using water as a solvent even at a relatively low temperature as compared with the conventional method.

1 is a perchlorate, iron monohydrate according to the first embodiment of the invention _{(Fe (ClO 4) 2 ·} xH 2 O) and a Fe composite by an aqueous solution containing hexylamine heated at 95 ℃ for 3 hours ₃ O ₄ (A) TEM image of nanoparticles, (b) HR-TEM image and (c) XRD pattern.
Figure 2 is a manganese chloride hexahydrate (MnCl _{2 ·} 4H ₂ O), and hexyl and the aqueous solution containing the amine synthesized by heating at 90 ℃ for 3 hours, Mn ₃ O ₄ nanoparticles according to the second embodiment of the present invention ( a) TEM image, and (b) XRD pattern.
3 (a) is a TEM image of Fe ₃ O ₄ nanoparticles prepared according to Example 3 of the present invention, and FIG. 3 (b) is a TEM image of Fe ₃ O ₄ nanoparticles prepared according to Example 4 of the present invention (C) is a TEM image of Fe ₃ O ₄ nanoparticles prepared according to Example 5 of the present invention, and (d) is a TEM image of Fe ₃ O ₄ nanoparticles prepared according to Example 6 of the present invention Image.
4 is a TEM image of Fe ₃ O ₄ nanoparticles prepared according to Example 7 of the present invention. (b) an SEM image and (c) an XRD pattern.
5 is an SEM image (a), (b) and (c) TEM image, (d) ED pattern and (e) XRD pattern of Fe ₃ O ₄ nanoparticles prepared according to Example 8 of the present invention.
6 is a TEM image, (d) and (e) EDS mapping of the Fe ₃ O ₄ nanoparticles prepared according to Example 9 of the present invention, and (f) EDS element ratio.
FIG. 7 shows changes in pH of the Fe ₃ O ₄ nanoparticles according to the present invention at different reaction times.
8 shows the XRD analysis results of the Fe ₃ O ₄ nanoparticles according to the present invention.
FIG. 9 shows X-ray photoelectron spectroscopy (XPS) analysis results for Fe ₃ O ₄ prepared according to Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples and experimental examples. However, the following Examples and Experimental Examples are for illustrating the present invention, and the scope of the present invention is not limited by the following Examples and Experimental Examples.

<Material>

Perchlorate iron monohydrate _{(Fe (ClO 4) 2 ·} H 2 O), manganese chloride tetrahydrate _{(MnCl 2 · 4H 2 O)} , hexylamine, octylamine, dodecylamine, and BPEI (MW = 25,000 and 750, 000 , 50 wt% water solution) was purchased from Aldrich and used without further purification. Linear PEI (LPEI, MW = 25,000) was purchased from Polysciences. The water was purified by ion exchange (deionized water).

&Lt; Example 1 >

0.5 g of BPEI (MW = 750, 000, 50 wt% water solution) and 0.202 g of hexylamine were dissolved in 100 mL of deionized water, and the mixture was heated to 95 ° C with magnetic stirring. In _{1 mL 10 mM Fe (ClO 4} ) 2 · H ₂ O was added the solution was heated for 3 hours at the same temperature. During the heating process, the color of the solution changed from cyan to black. The final product was collected by repeated centrifugation and washed with a mixture of deionized water and acetone to remove residual reagent. The resulting Fe ₃ O ₄ nanoparticles were redispersed in water for subsequent characterization.

&Lt; Example 2 >

_{Fe (ClO 4) 2 · 10} mM in H ₂ O instead of MnCl _{2 ·} 1 mL were prepared and the Mn ₃ O ₄ nanoparticles in the same manner as in Example 1 except that the addition of the 4H ₂ O in the reaction solution.

&Lt; Example 3 >

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1, except that octylamine was used instead of hexylamine.

<Example 4>

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1, except that dodecylamine was used instead of hexylamine.

&Lt; Example 5 >

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1 except that BPEI (MW = 25, 000, 50 wt% solution in water) was used.

&Lt; Example 6 >

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1 except that LPEI was used.

&Lt; Example 7 >

0.30 g of PEI (MW = 750, 000, 50 wt% solution in water) and 0.101 g of hexylamine (10 mM) were dissolved in 100 mL of deionized water and heated to 95 ° C with magnetic stirring. 0.294 g (10 mM) of Nickel (II) acetate tetrahydrate was added to 3 mL of deionized water and heated at the same temperature for 3 hours. The final product was collected by repeated centrifugation and washed with deionized water to remove residual reagents to produce Ni (OH) ₂ nanoparticles.

&Lt; Example 8 >

0.30 g of PEI (MW = 750, 000, 50 wt% solution in water) and 0.101 g of hexylamine (10 mM) were dissolved in 100 mL of deionized water and heated to 95 ° C with magnetic stirring. 0.177 g (10 mM) of Cobalt (Ⅱ) acetate was added to 5 mL of deionized water and heated at the same temperature for 3 hours. The final product was collected by repeated centrifugation and washed with deionized water to remove residual reagents to produce Co (OH) ₂ nanoparticles.

&Lt; Example 9 >

0.50 g of PEG (MN = 20,000) and 0.129 g of octylamine (10 mM) were dissolved in 100 mL of deionized water, and the mixture was heated to 90 DEG C with magnetic stirring. 0.294 g (10 mM) of nickel (Ⅱ) acetate tetrahydrate and 0.99 g (5 mM) of Manganese (Ⅱ) chloride tetrahydrate were added to 5 mL of deionized water and heated at the same temperature for 10 hours. The final product was collected by repeated centrifugation and washed with deionized water to remove residual reagent.

&Lt; Comparative Example 1 &

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1 except that BPEI was not used. As a result, Fe ₃ O ₄ particles having a large size of about 150 nm were produced (see FIGS. 3A and 3B).

&Lt; Comparative Example 2 &

Fe ₃ O ₄ nanoparticles were prepared in the same manner as in Example 1, except that hexylamine was not used. As a result, nanoparticles of 12 to 40 nm in size were produced. The XRD pattern of the product shows the presence of a mixture of crystal structures containing Fe ₃ O ₄ and α-Fe ₂ O ₃ (FIGS. 3c and d).

It can be seen from the above Examples and Comparative Examples that the polyethyleneimine serves as a main capping agent for the formation of nano-sized particles and hexylamine plays an important role in the formation of the Fe ₃ O ₄ crystal structure.

&Lt; Experimental Example 1 > TEM and SEM analysis

TEM and high-resolution TEM (HRTEM) images of the Fe ₃ O ₄ nanoparticles obtained in Example 1 were obtained using a JEM-2100F microscope operated at 200 kV.

FIG. 1A is a characteristic SEM image of the Fe ₃ O ₄ nanoparticles, and Fe ₃ O ₄ It can be seen that the nanoparticles were successfully synthesized in the water phase.

SEM images of Mn ₃ O ₄ obtained in Example 2 were obtained using a JEM-2100F microscope operated at 200 kV.

<Experimental Example 2> XRD analysis

A powder X-ray diffraction (XRD) pattern for the Fe ₃ O ₄ nanoparticles obtained in Example 1 was obtained using a Rigaku D-MAX / A diffractometer (35 kV and 35 mA).

Powder XRD results 30.1 °, 35.5 °, 43.1 ° , 57.1 °, and 62.7 ° naetneunde show a diffraction peak at a peak, which respectively face-centered cubic Fe ₃ O (220) ₄ (magnetite), 311, 400, (FIG. 1C, Fd3m , a = 8.375 A, Joint Committee on Powder Diffraction Standards [JCPDS] file No. 88-0315).

XRD analysis was also performed on the Mn ₃ O ₄ nanoparticles obtained in Example 2. The pattern obtained suggests a tetragonal Mn ₃ O ₄ (hermannite) structure (cf. FIG. 2b, a = 5.765 Å and c = 9.442 Å, JCPDS file No. 80-0382).

&Lt; Experimental Example 3 > XPS analysis

X-ray photoelectron spectroscopy (XPS) data for Fe ₃ O ₄ obtained in Example 1 was obtained using a Thermo Scientific K-Alpha spectrometer.

The Fe XPS 2p core level spectra included two sets of 2p peaks (FIG. 9). One set there is respectively configured in the 709.3 and 722.7 eV in Fe 2p _3/2 and Fe 2p _1/2 peak, which corresponds to Fe ₃ O _4. α-Fe ₂ O ₃ and γ-Fe ₂ O ₃ contain Fe peaks at the other 719.2 eV, suggesting that the product is Fe ₃ O ₄ in the absence of peaks. A typical TEM image of the product shows that octahedral nanoparticles having a size of 20 to 30 nm have been generated (FIG. 1).

Claims (9)

A process for preparing metal oxide nanoparticles comprising reacting a metal salt with a polyethyleneimine and an alkylamine in an aqueous solution, said process comprising the step of reacting a molar concentration of the metal salt with a molar concentration based on C ₂ H ₅ N, Is in the range of 0.2 to 1.0. The method according to claim 1,
Wherein the metal salt is an iron salt, a manganese salt, a nickel salt, a cobalt salt or a mixture thereof. The method according to claim 1,
Wherein the alkylamine has 6 to 20 carbon atoms. The method according to claim 1,
Wherein the step is carried out in a reaction solution having a molar concentration of alkylamine to molar concentration of metal salt of 1.0 to 3.0. Reacting a metal salt with a polyethyleneimine and an alkylamine in an aqueous solution, said method comprising the steps of: preparing a metal hydroxide nanoparticle having a molar concentration based on C ₂ H ₅ N as a unit of polyethyleneimine relative to the molar concentration of the metal salt Is in the range of 0.2 to 1.0. &Lt; / RTI &gt; 6. The method of claim 5,
Wherein the metal salt is an iron salt, a manganese salt, a nickel salt, a cobalt salt or a mixture thereof. 6. The method of claim 5,
Wherein the alkylamine has 6 to 20 carbon atoms. The method according to claim 1,
Wherein the metal oxide nanoparticles are iron oxide (Fe ₃ O ₄ ) nanoparticles or manganese oxide (Mn ₃ O ₄ ) nanoparticles. 6. The method of claim 5,
Wherein the metal hydroxide nanoparticles are nickel hydroxide (Ni (OH) ₂ ) nanoparticles or cobalt hydroxide (Co (OH) ₂ ) nanoparticles.

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