KR101138220B1 - Method for preparing nanoparticles - Google Patents

Abstract

The present invention relates to a method for preparing nanoparticles, and more particularly, by preparing a composite of metal nanoparticles and inorganic oxide nanoparticles according to a sol-gel process by using a branched polymer as a reducing agent, the complex is a separate reducing agent. Or do not need a stabilizer, can be prepared at room temperature, atmospheric pressure, can control the size and shape of the nanoparticles as desired, to provide a composite having excellent characteristics such as long-term dispersion stability, small size, narrow size distribution, etc. Can be.

Ultrabranched polymers, gold nanoparticles, self-assembly, template synthesis, inorganic oxides

Description

Method for preparing nanoparticles {Method for preparing nanoparticles}

The present invention relates to a method for preparing nanoparticles, and more particularly, by preparing a composite of metal nanoparticles and inorganic oxide nanoparticles according to a sol-gel process by using a branched polymer as a reducing agent, the complex is a separate reducing agent. Or do not need a stabilizer, can be prepared at room temperature, atmospheric pressure, can control the size and shape of the nanoparticles as desired, the production of nanoparticles having excellent characteristics such as long-term dispersion stability, small size, narrow size distribution It is about a method.

Titanium dioxide (titania) in a controlled form has been of great interest in recent decades because of its wide application in photoelectric conversion engineering and photocatalysts to photo-electrochromic and sensors. The operating mechanism of these functional materials depends on the interfacial process. Thus, some degree of fine tuning of the particle morphology is expected to significantly extend the scientific and technological potential of titania. Many efforts have been made to obtain titania nanostructures of various shapes. Currently developed methods mainly include sol, hydrothermal, solvent heat, oxidation, chemical vapor deposition and sol-gel molding methods. Except for the last method, other methods are usually carried out at high temperatures. Relatively low reaction temperatures require long reaction times or additional surfactants. In contrast, the sol-gel template route is easy and versatile, where, along with sol-gel chemistry, small surfactant molecules or micelles generated from a set of amphiphilic block copolymers are used as template formulations. However, since these micelles are kinetically stable, they are closely related to various conditions such as solvent, temperature, pH, or concentration in order to control the micelle shape.

Hyperbranched polyglycidol (HBP) macromolecules, on the other hand, consist of many hydroxy groups and polyester segments as shown in FIG. 1 to provide a spherical shape and a fully branched structure. Oxygen atoms derived from adjacent hydroxy groups and ether segments can serve as capping agents for inorganic oxides through coordination bonds, which can be a template for preparing inorganic oxide nanoparticles by sol-gel processes. It is considered to be.

However, no studies on inorganic oxide nanostructures mediated by supramolecular polymers have been reported.

An object of the present invention can be prepared at room temperature, atmospheric pressure using the ultra-branched polymer as a template for the production of nanoparticles, and effective and easy particle size or structure by controlling the mixing method of the metal or its oxide precursor and the ultra-branched polymer It is to provide a method for producing a controlled nanoparticle.

It is another object of the present invention to provide a composite of nanoparticles and a method for preparing the same, wherein inorganic oxide nanoparticles or metal nanoparticles are prepared through in situ self-assembly using supramolecular polymer as a template for preparing nanoparticles. It is.

In order to achieve the above object, the present invention provides a method for producing a metal or oxide nanoparticles thereof comprising the step of reacting at least one metal precursor in a hyperbranched polymer solution.

The invention is also prepared according to the process for producing the metal or oxide nanoparticles of the invention and has a tube structure of amorphous, solid sphere, hollow sphere, solid rod, or open ends, with or without voids. Provided are metals or oxide nanoparticles thereof.

The present invention also provides a method for producing a nanoparticle composite comprising reacting an inorganic oxide nanoparticle and a metal precursor in a hyperbranched polymer solution.

The present invention also provides a method for producing a nanoparticle composite comprising reacting a metal nanoparticle and an inorganic oxide precursor in a hyperbranched polymer solution.

The present invention also provides a nanoparticle composite prepared by the method for producing a nanoparticle of the present invention.

The present invention also provides a catalyst comprising the nanoparticle composite of the present invention.

The present invention can be used to prepare the inorganic oxide / metal nanoparticles composites by sol-gel process at room temperature, atmospheric pressure without the addition of a separate reducing agent and stabilizer by using the ultrabranched polymer, the metal nanoparticles are long-term dispersion stability, small size And it has excellent features such as narrow size distribution, heterogeneous metal nanoparticles can be automatically prepared according to the addition of other metal precursors, or according to the reducing ability of the other metal precursors, mixing with the supramolecular polymer when preparing inorganic oxide nanoparticles By controlling the method, it is possible to effectively control the size or structure of the nanoparticles.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated concretely.

The present invention relates to a method for producing a metal or oxide nanoparticles thereof comprising reacting at least one metal precursor in a hyperbranched polymer solution.

In the method of preparing the metal or oxide nanoparticles of the present invention, in preparing the nanoparticles through a sol-gel process, a superbranched polymer is used instead of a surfactant, and a metal or an oxide precursor is added to the hyperbranched polymer solution. It is characterized by controlling the size or structure of the nanoparticles by controlling.

Method for producing a metal or oxide nanoparticles of the present invention can produce a single or heterogeneous metal nanoparticles. More specifically,

In the case of a single metal nanoparticle, it can be prepared by adding one metal precursor in the supramolecular polymer solution.

In the case of dissimilar metal nanoparticles, heterogeneous nanoparticles are prepared by reacting a heterogeneous metal precursor mixed solution with a supramolecular polymer solution, or metal nanoparticles are prepared by reacting a kind of metal precursor with a supramolecular polymer solution, and the other metal is sequentially The precursor can be added to produce dissimilar metal nanoparticles depending on the reducing ability of other metal precursors.

In addition, the supramolecular polymer may include one or more selected from the structures of Formulas 1 to 3 below:

[Formula 1]

[Formula 2]

(3)

More specifically, as an example of the supramolecular polymer, hyperbranched polyglycidol (HBP) is composed of many hydroxy groups and polyether segments, as shown in FIG. 1, showing a spherical shape and a fully branched structure. As polymers, oxygen atoms of adjacent hydroxy groups and ether segments can act as protective agents of inorganic oxides through coordination bonds. In addition, hydroxy groups can serve as condensation moieties for sol-gel processes.

The supramolecular polymer may have a number average molecular weight of 90 to 150,000, but is not particularly limited thereto.

Further, the metal precursor is a metal nitrate-based compound, a metal sulfate-based compound, a metal acetoacetate-based compound, a metal halide-based compound of a metal selected from the group consisting of Group 3 to Group 15 metals, lanthanides and actinium metals , A compound of a metal perchloroate series, a metal sulfamate series compound, a metal styrate series compound, a metal alkoxide series compound and the like can be used.

Iron (II) nitrate, iron (III) nitrate, manganese nitrate, cobalt nitrate, zinc nitrate, nickel nitrate or the like can be used as the metal nitrate-based compound.

Iron sulfate (II), iron sulfate (III), manganese sulfate, cobalt sulfate, nickel sulfate, copper sulfate, or zinc sulfate may be used as the metal sulfate-based compound.

Examples of the metal acetoacetate-based compound include iron trifluoroacetoacetate, cobalt hexafluoroacetoacetate, manganese hexafluoroacetoacetate, nickel hexafluoroacetoacetate, copper hexafluoroacetoacetate, and zinc hexafluoroacetate (iron acetylacetate). Fe (acac) ₃ ), cobalt acetylacetonate (Co (acac) ₃ ), barium acetylacetonate (Ba (acac) ₂ ) and strontium acetylacetonate (Sr (acac) ₂ ), platinum acetylacetonate (Pt ( acac) ₂ ), or palladium acetylacetonate (Pd (acac) ₂ ) and the like.

Examples of the metal halide-based compound include iron (II) chloride, iron (III) chloride, cobalt chloride, nickel chloride, copper chloride, zinc chloride, gadolinium chloride, iron (II) bromide, iron (III) bromide, and cobalt bromide , Nickel bromide, copper bromide, zinc bromide, iron (II) iodide, iron (III) iodide, manganese iodide, nickel iodide, copper iodide, zinc iodide, cobalt iodide , Titanium tetrachloride, zirconium tetrachloride, tantalum pentachloride, tin tetrachloride, tungsten chloride, molybdenum tetrachloride, manganese chloride, titanium tetrabromide, zirconium tetrabromide, tantalum pentabromide, tin tetrabromide, or manganese bromide Use etc Can.

Iron (III) perchlororate, cobalt perchlororate, manganese perchlororate, nickel perchlororate, copper perchlororate, or zinc perchlororate may be used as the metal perchloroate-based compound.

As the metal sulfamate-based compound, iron sulfamate, manganese sulfamate, nickel sulfamate, cobalt sulfamate, copper sulfamate, or zinc sulfamate may be used.

Iron styrate, manganese styrate, nickel styrene, copper styrene, cobalt styrene, or zinc styrate may be used as the metal styrate-based compound.

Titanium tetraisopropoxide (Ti (OiC ₃ H ₇ ) ₄ ), zirconium tetrabutoxide (Zr (OC ₄ H ₉ ) _4, etc.) may be used as the metal alkoxide-based compound.

In addition, the method of manufacturing the metal or oxide nanoparticles of the present invention can control the size or structure of the nanoparticles by controlling the addition rate of the metal precursor to the supramolecular polymer solution, more specifically, the metal precursor When added in one-pot, solid spherical nanoparticles can be prepared. The solid spherical nanoparticles may have an average diameter of 10 nm to 2000 nm in size. In addition, the surface of the nanoparticles may have a smooth shape.

The solid spherical nanoparticles can be controlled in a concentration dependent manner with respect to the content of the metal precursor. That is, as the concentration of the metal precursor increases, the size of the nanoparticles may increase.

In addition, when the addition rate of the metal precursor is added in 10μl to 100mL per minute, it is possible to prepare hollow spherical nanoparticles. In the case of the hollow spherical (or capsule) nanoparticles, the inner diameter may have a size of 1 nm to 100 nm, the outer diameter of 10 to 500 nm.

The hollow spherical nanoparticles can also be controlled in concentration depending on the content of the metal precursor. That is, as the concentration of the metal precursor increases, the sizes of the inner and outer diameters of the nanoparticles may increase.

In addition, the hyperbranched polymer solution may be prepared by dissolving the hyperbranched polymer in a solvent such as alcohol, water, or an organic solvent having a dielectric constant of 3 or more.

Preferably, the solvent is a mixed solution of alcohol and water.

This is because the metal precursor is sensitive to moisture, and thus the hydrolysis rate of the metal precursor may be improved when water is included in the sol-gel process.

When it contains 90.0 to 99.99 parts by weight of water based on 100 parts by weight of the first branch polymer solution, the nanoparticles may exhibit a tube structure in which both ends are open. If it is out of the above range, it may be difficult to control the reaction of the metal oxide precursor.

The length, diameter, and inner diameter of the nanoparticles of the tube structure of the open shape at both ends may be 10 to 5000 nm, 10 to 500 nm, 1 to 100 nm, respectively.

The self-assembly process of at least one metal precursor in the supramolecular polymer solution may be performed at 10 to 50 ° C. under 0.5 to 2 atmospheres, but is not particularly limited thereto.

In addition, since the method of manufacturing the metal or the oxide nanoparticles of the present invention uses the ultrabranched polymer as a reducing agent, self-assembly of one or more metal precursors may occur in a state in which a separate oxidizing agent or reducing agent is not added.

The mechanism of controlling the size or structure of the metal oxide nanoparticles using the supramolecular polymer is described below with reference to FIG. 12.

In a typical sol-gel process, HBP serves as a nucleation center. In the presence of a small amount of water, the in-situ hydrolysis of the metal oxide monomer is completed, followed by a co-condensation process to form a Ti-O-Ti network, resulting in a large number of titania / HBP complexes. Form a nuclei. These nuclei rapidly aggregate through crosslinking and polymerization processes to form spherical aggregates in subsequent co-condensation. When a suitable amount of metal oxide precursor is added all at once, the high concentration of metal oxide precursor leads to the rapid formation of large amounts of metal oxide aggregates. High concentrations of these aggregates tend to rapidly agglomerate and self-assemble to form solid spheres and can continue to mature until a critical size is reached. Reducing the amount of metal oxide precursor used produces relatively low amounts of metal oxide aggregates. The content is spontaneously solid sphere Enough to aggregate but smaller sized particles are formed (FIG. 12A).

When the metal oxide precursor is added in a controlled manner, the aggregates initially formed in the reaction system can self-assemble into a hollow structure in a controlled manner in a significantly lower concentration state (FIG. 12B).

When the water content is increased, it promotes the hydrolysis rate of the metal oxide precursor, thereby satisfying the conditions for the anisotropic growth of the aggregates, as a result can form metal oxide nanotubes (Fig. 12c).

The present invention is also prepared according to the method of producing the metal or oxide nanoparticles of the present invention, and has a tube structure of amorphous, solid spherical shape, hollow spherical shape, solid bar shape or open ends, with or without voids Or it relates to the oxide nanoparticles.

The nanoparticles of the present invention may have various sizes and structures depending on the amount of metal or its oxide precursor added, the method of addition, and the presence or absence of water in the solvent. It is possible to prepare a nanostructure of at a time.

Nanoparticles prepared according to the method for producing a metal or oxide nanoparticles of the present invention may have a tube structure of an amorphous, solid sphere, hollow sphere, solid rod, or both ends open. In addition, the nanoparticles may have a structure with or without voids.

The present invention also relates to a method for producing a nanoparticle composite comprising reacting an inorganic oxide nanoparticle and a metal precursor in a hyperbranched polymer solution.

The method for preparing a nanoparticle composite of the present invention may include preparing an inorganic oxide nanoparticle and growing a metal nanoparticle in situ on the nanoparticle to prepare a composite.

In addition, the method for producing a nanoparticle composite of the present invention is characterized in that the ultra-branched polymer can be prepared under an aqueous solution at room temperature and atmospheric pressure without using a separate reducing agent or oxidizing agent to prepare metal nanoparticles by reducing the metal precursor. .

Referring to the method of manufacturing the nanoparticle composite of the present invention in detail as follows.

The first step is to prepare inorganic oxide nanoparticles in the first branch polymer solution.

Inorganic oxide nanoparticles can be prepared in the form of a solid sphere by adding an inorganic oxide precursor to the supramolecular polymer solution at one-pot.

The inorganic oxide may be a compound represented by the following formula (4):

[Formula 4]

M _x O _y

Where

M is a metal of Groups 1 to 14,

x is an integer from 1 to 5,

y represents the integer of 1-10.

More specifically, the compound of Formula 4 may be SiO ₂ , TiO ₂ , GeO ₂ , or the like.

Tetraethyl orthosilicate, tetramethyl orthosilicate, methyl triethoxysilane, phenyl triethoxysilane, dimethyl dimethoxy silane, ethyl triethoxysilane, titania tetraisopropoxide, tetraethyl germanium, or These mixtures may be used alone or in combination of two or more, but is not particularly limited thereto.

In the method for producing a nanoparticle composite of the present invention, the second step is to add a metal precursor to the inorganic oxide nanoparticles to self-assemble the metal nanoparticles to prepare a composite in which the metal nanoparticles are deposited on the inorganic oxide nanoparticles Step.

The metal nanoparticles may be grown according to a polyol process using a branched polymer as a template at room temperature and atmospheric pressure.

The type of the metal precursor is as described above.

The present invention also relates to a method for producing a nanoparticle composite comprising reacting a metal nanoparticle and an inorganic oxide precursor in a hyperbranched polymer solution.

In the method for preparing a nanoparticle composite of the present invention, a single or dissimilar metal nanoparticle is prepared by using a branched polymer as a template, and the nanoparticle and the inorganic oxide precursor are reacted to disperse the metal nanoparticles onto the inorganic oxide nanoparticle matrix. It may comprise the step of preparing a nanoparticle composite in the form.

Referring to the method of manufacturing the nanoparticle composite of the present invention in detail as follows.

The first step is to prepare single or dissimilar metal nanoparticles by reacting one or more metal precursors in the hyperbranched polymer solution.

The metal nanoparticles may be prepared according to a polyol process using a branched polymer as a template at room temperature and atmospheric pressure.

In the case of a single metal nanoparticle, it can be prepared by adding one metal precursor in the supramolecular polymer solution.

In the case of dissimilar metal nanoparticles, dissimilar metal nanoparticles may be prepared by reacting a mixed solution of dissimilar metal precursors with a supramolecular polymer solution, or metal nanoparticles may be prepared by reacting a kind of metal precursor with a hyperbranched polymer solution, and sequentially Other metal precursors can be added to produce dissimilar metal nanoparticles depending on the reducing ability of the other metal precursor.

The metal may be a metal of Groups 3 to 15, a lanthanide group, or an actinium group metal. More specifically, it may be a transition metal such as Au, Ag, Pt, Pd, Co, or an alloy thereof.

The type of the metal precursor is as described above.

In the method of preparing a nanoparticle composite of the present invention, the second step is a composite in which metal nanoparticles are dispersed on an inorganic oxide nanoparticle matrix by adding an inorganic oxide precursor to a metal nanoparticle solution at one time. To prepare a step.

The inorganic oxide may use the compound of Formula 4, and more specifically, SiO ₂ , TiO ₂ , or GeO ₂ may be used alone or two or more, but is not particularly limited thereto.

The type of the inorganic oxide precursor is as described above.

The present invention also relates to a nanoparticle composite produced by the method for producing a nanoparticle composite of the present invention.

The nanoparticle composite is prepared according to the method for preparing a nanoparticle composite of the present invention, and has a structure in which metal nanoparticles are deposited on inorganic oxide nanoparticles, or metal nanoparticles are dispersed on an inorganic oxide nanoparticle matrix. It has a structure of the form, the nanoparticles are characterized in that produced in situ ( in situ ) as a template for the hyperbranched polymer.

The nanoparticle composite may have excellent characteristics such as long-term dispersion stability, small size, narrow size distribution.

The invention also relates to a catalyst comprising the nanoparticle composite of the invention.

Nanoparticle complexes of the present invention, such as titania / gold nanoparticle complexes, can be used as catalysts because they exhibit excellent catalytic reactivity to the reduction of 4-nitrophenol.

Hereinafter, the present invention will be described in more detail through examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the examples given below.

Preparation Example 1 Synthesis of Hyperbranched Polyglycidol

HBP was synthesized through anionic ring-opening multibranched polymerization. The polymerization was carried out in a reactor equipped with a mechanical stirrer and a dosing pump under a nitrogen atmosphere. 50 mL of glycidol (Aldrich) aliquots in a reactor containing trimetholpropane, partially deprotonated (10%) by sodium methylate solution (3.7 M in methanol, Aldrich) for at least 12 hours at 95 ° C. Was added slowly. After the reaction was complete (without excess epoxide), the reaction was dissolved in methanol and neutralized by filtration in cation exchange resin. The polymer was precipitated three times with acetone from methanol solution, and then vacuum dried at 80 ℃ for 20 hours.

^{As a result of 13} C-NMR spectral analysis, the final HBP had a number average molecular weight of 3400 g / mol.

Example 1 Preparation of Solid Spherical Titania Nanoparticles

All reactions were carried out in pure ethanol solution (200 proof) at room temperature. To prepare titania solid particles with size control, TTIP was injected all at once by content (0.25, 0.20 and 0.15 mL) into a 10 mL conduit containing 5 mL of HBP solution (0.05 g / mL) under magnetic stirring. Stirring was stopped when the solution became turbid. After standing for 10 minutes, the titania spheres were washed by centrifugation three times and redispersed with ethanol.

Example 2 Preparation of Hollow Spherical Titania Nanoparticles

By using a syringe pump (Harvard Apparatus Model 11) TTIP was added slowly (0.15 / min) to the conduit by content (0.25, 0.30 and 0.35 mL) to obtain hollow titania particles with size control.

Example 3 Preparation of Tubular Titania Nanoparticles

Water is premixed by content (2.5, 5.0 and 10.0 μl) with HBP solution (0.05 g / mL) and 0.25 mL of TTIP is added slowly to the reactor (0.1 mL / min), from hollow structure to tube Final titania particles having various shapes were prepared.

Example 4 Preparation of Single Metal Nanoparticles

In order to prepare single metal nanoparticles, nanoparticles were prepared through a sol-gel process by adding them to the first branch polymer solution at a time (one-pot reaction).

The single metal nanoparticles were prepared at room temperature and atmospheric pressure. Specifically, 0.1 mL of metal precursors (HAuCl ₄ , AgNO ₃ , K ₂ PtCl ₄ , Na ₂ PdCl ₄ , RuCl ₂ ) were injected into 1 mL of HBP aqueous solution (5 mg / mL) with magnetic stirring. After stirring, the final metal nanoparticles were purified via dialysis treatment.

Example 5 Preparation of Dissimilar Metal Nanoparticles

To prepare dissimilar metal nanoparticles, 0.01 mL of a metal precursor mixed aqueous solution (HAuCl ₄ : K ₂ PtCl ₄ = 1: 1; HAuCl ₄ : Na ₂ PdCl ₄ = 1: 1, HAuCl ₄ : RuCl ₂ = 1: 1 ) Was injected into 1 mL of HBP aqueous solution (5 mg / mL) with vigorous stirring to prepare nanoparticles.

Example 6 Preparation of Dissimilar Metal Nanoparticles

To prepare dissimilar metal nanoparticles, 0.05 mL of AgNO ₃ , K ₂ PtCl ₄ and Na ₂ PdCl ₄ solutions (0.01 M) were injected into 1 mL of HBP aqueous solution (5 mg / mL) with vigorous stirring, respectively, to Ag, Pt and Pd nanoparticles were prepared. Next, 0.05 mL of HAuCl ₄ solution was injected into the final mixture containing the metal nanoparticles, respectively. After vigorous stirring for 30 minutes, heterogeneous nanoparticles in which Au was deposited on the surface were obtained.

Example 7 Preparation of Titania / Gold Nanoparticle Composite

Titania solid spheres prepared according to Example 1 were collected by centrifugation and finally resuspended in 3 mL of deionized water. After the final colloidal solution was transferred to a vial, 1 mL of an aqueous solution of HAuCl ₄ (0.01 M) was added and stirred vigorously at room temperature. After stirring for an additional 5 hours, it was centrifuged three times for the final colloid and redispersed with ethanol. The titania / gold nanoparticle composite was finally collected and vacuum dried at 40 ° C. for 6 hours.

Example 8 Preparation of Inorganic Oxide / Different Metal Nanoparticle Composite

SiO ₂ / Au / Pt, TiO ₂ / Au / Pt and GeO ₂ / Au / Pt composites were prepared, respectively. Specifically, to prepare a SiO ₂ / Au / Pt composite, 0.5 mL of Au / Pt heterogeneous gold nanoparticle solution was added to a vial containing 1 mL of pure ethanol. Next, 0.1 mL of ammonia water (28 wt%) and 20 μl of tetraethyl oxysilane (TEOS) were injected sequentially with vigorous stirring. After stirring for 2 hours, the final SiO ₂ / Au / Pt complex was collected, washed by centrifugation three times and redispersed with ethanol.

To prepare the GeO ₂ / Au / Pt complex, 20 μl of tetraethyl germanium (TEOG) was added to a vial containing 0.5 mL of Au / Pt heterogeneous nanoparticle solution and 0.5 mL of pure ethanol. Stirring was continued until the solutions became slightly cloudy. After standing for 10 minutes, the germanium spheres were washed by centrifugation three times and redispersed with pure ethanol.

To prepare the TiO ₂ / Au / Pt complex, 0.5 mL of Au / Pt heterogeneous nanoparticle solution was dried under vacuum and redispersed in 1 mL of pure ethanol. 20 μl of titania tetraisopropoxide (TTIP) was injected directly into the solution with vigorous stirring. Stirring was continued until the solution became slightly cloudy. After standing for 10 minutes, the TiO ₂ / Au / Pt complex was washed by centrifugation three times and redispersed with pure ethanol.

(Characteristic identification)

Samples for transmission electron microscopy (TEM) were placed on a carbon coated copper electron microscope grid and dried in air. TEM analysis was performed using JEOL 1200 EX at 120 keV.

Samples for scanning electron microscopy (SEM) were placed on a silicon plate and dried in air, and then subjected to SEM analysis using a JSM-6700F microscope by accelerating a 10 kV voltage.

Fourier Transform Infrared (FTIR) spectra were obtained at ¹ cm ⁻¹ resolution using a Bruker FT-IR spectrophotometer between 4000 and 400 cm ⁻¹ . IR measurement of the powder sample was carried out in the form of KBr pellets.

Energy dispersive X-ray spectroscopy (EDS) analysis was performed using the OXFORD ISIS system attached to the SEM.

Thermogravimetric analysis (TGA) data was recorded using a TA instrument Q500. Samples were tested in the range of 20-600 ° C. using a 10 ° C. heating rate. The furnace was cleaned with ultrapure nitrogen at a flow rate of 50 mL / min. The structure of the final product was tested by X-ray diffraction (XRD) with an automated Philips powder diffractometer using nickel-filtered CuKa radiation. The diffraction pattern was collected in a 2θ range of 15-90 ° in 0.02 ° steps and counted at 2 s / step intervals.

Accurate concentrations of gold nanoparticles in titania / gold nanoparticle composites were analyzed using an atomic emission spectrophotometer equipped with a Jarrell Ash 955 inductively coupled plasma system.

All UV-vis absorption spectra of the samples were recorded at room temperature on a UV-1650PC device (SHIMADZU).

As shown in FIG. 2, as a result of preparing single metal nanoparticles using Au, Ag, Pt, Pd, and Ru precursors in the hyperbranched polymer solution, it was confirmed that spherical single nanoparticles were formed (TEM). Pictures).

The formation of single nanoparticles is also demonstrated through the UV-vis spectrum (FIG. 3).

Next, dissimilar metal nanoparticles were prepared by adding a mixed solution of different metal precursors (Au / Pt, Au / Pd, Au / Ru) in the hyperbranched polymer solution, as shown in FIG. It was confirmed that nanoparticles were formed, which is demonstrated by the UV-vis spectrum of FIG. 5.

In addition, the metal nanoparticles were prepared by reacting the respective metal precursors in the hyperbranched polymer solution, and Au / Pt, Au / Pd, and Au / Ru dissimilar metal nanoparticles were prepared by adding gold precursors. As shown in Figure 3, it was confirmed that spherical nanoparticles were formed, which is demonstrated by the UV-vis spectrum of FIG.

Next, nanoparticles are prepared by reacting an inorganic oxide precursor in a hyperbranched polymer solution, or a composite is prepared by reacting single or dissimilar metal nanoparticles with an inorganic oxide precursor, as shown in FIG. 8. In addition to the formation of inorganic oxide nanoparticles, it was confirmed that a complex in a form in which metal nanoparticles are dispersed on the inorganic oxide nanoparticle matrix was formed.

<Experiment 1> Investigation of the size or structure of the nanoparticles according to the method of injecting the inorganic oxide at a time or by controlling the speed

When 0.25 mL of TTIP was injected all at once into 5 mL of pure ethanol solution containing HBP (0.05 g / mL), titania solid spheres were obtained after the sol-gel process and verified by TEM analysis.

As shown in FIG. 9A, finally, titania particles of a certain form were separated and exhibited almost spherical shapes having an average diameter of 420 nm. In a representative SEM image, the titania spheres had a fairly smooth surface morphology (FIG. 9B).

In addition, as shown in the TEM photographs shown in FIGS. 9C and 9D, when the addition amount of TTIP decreased to 0.20 and 0.15 mL, the average diameter of the titania spheres decreased to 220 and 55 nm, respectively. The final particles were well dispersed in pure ethanol solution. This means that all the titania particles from the TTIP injection method are solid spheres. In addition, it can be seen from the above results that the size of titania particles decreases when the amount of TTIP added is reduced.

Interestingly, slow addition of 0.25 mL TTIP to the reaction conduit using a syringe pump (0.1 mL / min) produced hollow titania nanoparticles, as demonstrated by TEM and SEM micrographs (FIGS. 10A and 10B). The final particles showed a constant, hollow sphere. As measured by TEM observation, the mean outer and inner diameters of the particles were 115 nm and 38 nm, respectively. In particular, when the amounts of TTIP added increased to 0.30 mL and 0.35 mL, the final titania particles also showed a hollow structure (FIGS. 10C and 10D). When the TTIP addition amount was increased to 0.30 mL and 0.35 mL through the TEM observation, the average outer diameter of titania particles increased to 128 nm and 140 nm, respectively. In addition, the average inner diameter of the hollow spheres also increased to 55 nm and 80 nm. These results mean that both the mean inner and outer diameters of the hollow titania sphere can be adjusted by simply controlling the concentration of TTIP used in the reaction system.

To test the growth process of the hollow titania spheres, TEM analysis was performed on the samples obtained during the reaction.

As shown in FIGS. 10E and 10F, the samples consist of free nanoparticles, isolated hollow spheres and hollow hollow spheres / nanoparticle aggregates, wherein the hollow spheres are surrounded by a few unformed nanoparticles. . The hollow sphere in the hollow sphere / nanoparticle aggregates is less than 70 nm, smaller than that of the final sample obtained after completion of the reaction (average outer diameter is 140 nm, FIG. 10D). The results indicate that the growth of hollow spheres occurs as small nanoparticles forming continue to deposit on the surface of the hollow sphere being formed.

Experimental Example 2 Investigation of Size or Structure of Titania Nanoparticles According to Water Addition

Since TTIP is sensitive to moisture (white precipitates form immediately upon exposure to air), the inclusion of water in the sol-gel process tends to dramatically improve the hydrolysis rate of TTIP. To investigate the effect of water content on the morphology of titania particles, water was added to the reaction mixture containing pure ethanol and HBP (0.05 g / mL) by content, and TTIP was added slowly (0.1 mL / min).

As shown in FIG. 11A, when 2.5 μl of water was used, the final titania particles exhibited a well defined hollow structure with 125 nm and 42 nm mean outer and inner diameters. When 5 μl of water was added, most of the final titania particles (average outer and inner diameters of 130 nm and 45 nm) showed a similar morphology as using 2.5 μl of water. Only slightly tube-like particles were produced (FIG. 11B). However, when the water content increased to 10 μl, the final titania nanoparticles showed a tube form (FIG. 11C). As shown in FIGS. 11D and 11E, the average length and diameter of the titania were 250 nm and 48 nm, respectively. The average inner diameter was about 10 nm. The final tubes were also found to be open at both ends as indicated by the arrows, as shown in FIG. 11E. This interesting phenomenon means that the evolution of the titania nanoparticles from hollow spheres to tubes can be obtained by controlling the water content under the HBP template.

In most conventional sol-gel preparations, precipitation of amphiphilic titania is generally caused by uncontrolled branching of the Ti-O-Ti network because hydrolysis and condensation proceed very quickly and immediately. In order to control the evolution of the titania structure and form under conditions similar to the solution, it is necessary to separate the hydrolysis and condensation steps. Potential alternative solutions may include protecting agents that are resistant to hydrolysis in the sol-gel process. HBP molecules can be made up of many hydroxy and ether groups to provide a template. These adjacent hydroxy groups and ether groups can protect the TTIP monomer through coordination bonds. In addition, hydroxy groups provide condensation moieties for the sol-gel process. Based on the experimental results, the formation and growth mechanisms of the titania solid particles, hollow spheres and nanotubes can be inferred and are shown in FIG. 12.

In a typical sol-gel process, HBP serves as a key generation center for protecting in situ hydrolysing TTIP monomers and provides co-condensation to form subsequent Ti-O-Ti networks. Titania / HBP complex nuclei can be formed. These nuclei can then quickly gather through crossover and polymerization to form sphere aggregates in the co-condensation process. When all of the appropriate amounts of TTIP are added at once, high concentrations of TTIP lead to rapid formation of large amounts of titania aggregates. High concentrations of these aggregates tend to rapidly agglomerate and self-assemble to form solid spheres, and can continue to mature until a critical size is reached (FIG. 12A). Although reducing TTIP usage produces titania aggregates with relatively low concentrations, the concentrations are high enough to spontaneously aggregate into solid spheres but form smaller size particles. Therefore, size control means that it depends on the amount of TTIP added.

When TTIP is added in a controlled manner, aggregates initially formed in the reaction system can be self-assembled into a hollow structure in a controlled manner at a fairly low concentration (FIG. 12B).

When TTIP is added continuously, newly formed aggregates are continuously deposited on the surface of the hollow spheres being manufactured to induce growth of the hollow spheres. This fact was directly demonstrated by TEM observations of particles growing in the samples obtained in the ongoing reaction system (FIGS. 10E and 10F). The increase in the internal diameter of the titania hollow sphere from 38 nm to 80 nm with increasing TTIP can be explained by the Ostwald ripening process. During this process, the titania nucleus on the inner shell of the hollow sphere with higher surface energy will dissolve and transfer outwards to widen the hollow sphere interior space.

Obtaining titania tube nanostructures requires anisotropic growth of smaller aggregates. The inclusion of a small amount of water in the sol-gel process can lead to fast hydrolysis of TTIP and can make unidirectional growth of titania nanoparticles. If the reaction system contains a small amount of water (2.5 μl), the hydrolysis rate of TTIP is not sufficient to reach critical values with unidirectional growth of titania nanoparticles. Thus, titania still aggregates into well-defined hollow spheres. If more water content is used (5 μl), the hydrolysis rate is relatively faster and a few irregular tube-like structures are produced. Further increasing the water content to 10 μl, the accelerated hydrolysis satisfies the conditions for the anisotropic growth of the aggregates, resulting in titania nanotubes (FIG. 12C). In conclusion, morphological evolution from hollow spheres to tubes, depending on the amount of water used, can be achieved by promoting the rate of hydrolysis of TTIP.

Experimental Example 3 Component Analysis of Titania Nanostructures

As described above, Tinatia particles may be due to the high content of HBP / titania aggregates. To confirm this fact, the chemical composition and structure of a typical sample containing a large amount of titania solid spheres with an average diameter of 460 nm was specifically examined (FIGS. 9A and 9B).

FIG. 13A shows the energy-dispersive X-ray spectrum (EDS) of the titania sample, showing the presence of C, O and Ti elements on the surface of the particle. The C, O and Ti signals are from HBP and titania, while the strong silver signal is from the silver coating before SEM observation. The atomic percentages of C, O and Ti were 41.5, 47.7 and 10.8%, respectively (table inside FIG. 13A). This means that the surface of titania particles is composed of HBP (C: O = 3: 2) and titania (Ti: O = 1: 2).

The weight percentage of titania on the surface of the titania particles is 48.5%, which is lower than the titania particles measured by thermogravimetric analysis (55.8%, FIG. 13B). This suggests that the final titania microspheres have a relatively large amount of HBP deposited on the surface, which may be an advantage for protecting the final particles from aggregation.

In addition, as shown in FIG. 13B, weight loss from 200 to 250 ° C. and above 250 ° C. will be due to the gradual deposition of HBP in the surface bound HBP and titania matrix.

Another evidence of the composition and structure of titania spheres was obtained by FTIR. As shown in FIG. 13C, certain characteristic bands such as CH scratch vibrations at 2925 and 2868 cm ⁻¹ and scratch vibrations of ether groups (COC) at 1620 cm ⁻¹ indicate the presence of HBP molecules. At 1127 cm ⁻¹ , the bands may correspond to CO-Ti, which is a characteristic of titania connected to HBP. The 800 cm ^-1 lower broadband is evidence of the existence of the Ti-O-Ti band. These evidences lead to the conclusion that the final titania particles consist of large amounts of HBP / titania aggregates and are crosslinked with each other through co-condensation and polymerization processes to form HBP / titania networks.

Additional structural information of the titania sphere was obtained by X-ray diffraction analysis. The titania particles under preparation did not exhibit characteristic diffraction peaks. This suggests an amphipathic structure and can occur by non-ordered packing of HBP / titania aggregates. The titania sample is annealed at 600 ° C. for 3 hours to remove the HBP component and the remaining titania can be converted to crystalline form.

Experimental Example 4 Component Analysis of the Inorganic Oxide / Gold Nanoparticle Composite

The synthetic strategy shown in the present invention is characterized in that the reaction is carried out at room temperature, and no separate surfactant is used. There is no example of making titania nanostructures of various shapes in an easy manner. In addition, the inventors have paid attention to the reducing ability of HBP molecules contained in the final titania nanostructures, which can provide an effective alternative for in situ preparation of functional titania-based complexes with reducing and optoelectronic functions. HBP molecules have large amounts of hydroxy groups in them and can act as self-reducing and self-stabilizing agents for various host metal nanoparticles by so-called similar polyol processes. As in a typical example, gold nanoparticles are successfully mediated by HBP molecules adsorbed within titania microspheres (average diameter of 55 nm) at the time of manufacture, resulting in in situ, resulting in titania / gold nanoparticle complexes. .

As shown in FIG. 14A, gold nanoparticles having an average diameter of 5 nm or less formed in situ are deposited on titania nanoparticles (indicated by arrows).

Further evidence for the formation of gold nanoparticles was obtained through UV-vis (FIG. 14B) and EDS (FIG. 14C) analysis, showing characteristic gold nanoparticles and strong gold atomic signals, respectively, at 550 nm. As measured by ICP analysis, the content of gold nanoparticles was 2.5% by weight.

Experimental Example 5 Investigation of Reduction Capacity of Nanoparticles

One important application of metal nanoparticles is to activate and catalyze certain reactions that are difficult to carry out. For this reason, the catalytic function of the final titania / gold nanoparticle complex in the reduction of water-soluble 4-nitrophenol, a dangerous and toxic source of contamination, was investigated.

Catalytic reduction of 4-nitrophenol was carried out in a standard quartz cell (length: 1 cm, volume is about 3 mL). In a typical reaction, 1 mL of an aqueous NaBH ₄ solution (0.15M) is added to a quartz cell containing 1.7 mL of 4-nitrophenol solution (0.20 mM), which immediately turns the light yellow to yellowish green. The titania / gold nanoparticle composite colloid (4.8 mg dissolved in 0.3 mL distilled water) was added quickly, and then UV-vis spectra were recorded at room temperature at 3 minute intervals.

The absorption peak of 4-nitrophenol immediately shifts to red from 317 nm to 400 nm with the addition of NaBH ₄ . This means that 4-nitrophenolate ions were formed. Correspondingly, the color of the solution changed significantly from bright yellow to yellow green (inside FIG. 15). In the absence of a catalyst, 4-nitrophenolate ions are not reduced even under the strong reducing agent NaBH ₄ . Even more surprisingly, the addition of titania / gold nanoparticles to the reaction system gradually faded the yellow-green color of 4-nitrophenol to become dramatically colorless (inside FIG. 15). This indicates that a reduction reaction occurred. The bleaching can be quantitatively monitored using a UV-vis microscope, and over time a continuous decrease in peak intensity was observed at 400 nm (FIG. 15). On the other hand, a new incident peak appeared at 300 nm, due to the formation of 4-aminophenol. Other metal nanoparticles (Ag, Pd, Pt, etc.) can also be deposited on titania nanostructures already formed by similar processes. From this it is possible to produce various functional complexes for the purpose of comprehensive application.

In conclusion, the present invention can be carried out at room temperature and atmospheric pressure without the need for a separate oxidizing agent or reducing agent by preparing a nanoparticle by reacting a metal precursor or an inorganic oxide precursor in the supramolecular polymer solution.

In addition, the nanoparticles can be freely controlled in the form or structure of the nanoparticles by simply controlling the method of adding a metal precursor or an inorganic oxide precursor to the supramolecular polymer solution, the amount of addition, the presence of water in the solvent.

In addition, the present invention can be prepared simply by adding a metal precursor sequentially, or by adding another metal precursor to the metal nanoparticles in the production of dissimilar metal nanoparticles.

In addition, the present invention is to prepare a composite of metal nanoparticles / inorganic oxide nanoparticles in the form of the metal nanoparticles dispersed on the inorganic oxide nanoparticle matrix by reacting the metal nanoparticles and the inorganic oxide precursor in the first branch polymer solution The spherical composite may be prepared by self-assembly of nanoparticles in-situ through a method of reacting inorganic oxide nanoparticles with a metal precursor to prepare spherical composites in which metal nanoparticles are deposited on inorganic oxide nanoparticles. Characterized in that it can.

In addition, the composites of metal nanoparticles / inorganic oxide nanoparticles of the present invention, such as titania / gold nanoparticle composites, are characterized by excellent catalytic function for the reduction of 4-nitrophenol.

FIG. 1 shows a schematic structure of hyperbranched polyglycidol (a) and its optimized geometric model (b) according to the Polak-Ribiere conjugate gradient algorithm obtained using HyperChem ^™ (release 8.0.3 for Windows) It is.

2 is a TEM photograph of single metal nanoparticles prepared in the supramolecular polymer solution of the present invention.

Figure 3 shows the UV-vis spectrum results of the single metal nanoparticles prepared in the supramolecular polymer solution of the present invention.

4 is a TEM photograph of dissimilar metal nanoparticles prepared in the supramolecular polymer solution of the present invention.

Figure 5 shows the UV-vis spectrum (a) and XRD pattern (b) of the dissimilar metal nanoparticles prepared in the first branch polymer solution of the present invention.

6 is a TEM photograph of dissimilar metal nanoparticles prepared in the supramolecular polymer solution of the present invention.

Figure 7 shows the UV-vis spectrum results of the dissimilar metal nanoparticles prepared in the first branch polymer solution of the present invention.

8 is a TEM photograph of a composite of inorganic oxide nanoparticles and inorganic oxide nanoparticles / metal nanoparticles in the supramolecular polymer solution of the present invention.

FIG. 9 shows TEM (a) and SEM (b) photographs of titania particles obtained by adding 0.25 mL of TTIP at a time in the first branch polymer solution of the present invention, and TEM photographs of titania spheres show TTIP 0.20 mL (c). And 0.15 mL (d).

FIG. 10 is a TEM (a) and SEM (b) photograph of a titania hollow sphere prepared by slowly adding 0.25 mL of TTIP (0.1 mL / min) in the first branch polymer solution of the present invention, and TTIP 0.30 mL (c) and TEM photographs of the hollow titania spheres obtained from the addition of 0.35 mL (d) are also shown, and TEM photographs (e and f) of the growing titania hollow spheres obtained during the reaction.

11 shows titania particles prepared by adding 2.5 mL of water (a), 5.0 (b), and 10.0 μl (c) in the first branch polymer solution of the present invention, and then slowly adding 0.25 mL of TTIP (0.1 mL / min). TEM photographs of the (d) and (e) shows the enlarged TEM photographs of (c).

12 is a schematic diagram of the formation mechanism of titania particles having various shapes in a sol-gel process, a) is a solid sphere obtained by injecting TTIP at a time, and b) is a hollow sphere obtained by slowly adding TTIP. , c) represents nanotubes obtained by slowly adding TTIP by adding water.

FIG. 13 shows EDS (a) and TGA spectra (b) of titania samples of solid spheres having an average diameter of 460 nm of the present invention and before (bottom, solid) and after (top, dashed) firing at 600 ° C. for 3 hours. The FTIR spectrum (c) and XRD pattern (d) of the titania sample are shown.

FIG. 14 shows a TEM photograph (a), UV-vis spectrum (b) and EDS spectrum (c) of a TiO ₂ / gold composite formed in situ in a titiatia sphere (average diameter of 55 nm) of the present invention. .

FIG. 15 shows continuous UV-vis spectral results of reduction of 4-nitrophenol (0.2 mM) in the presence of NaBH ₄ (0.15M) using TiO ₂ / gold complex (48 mg) as catalyst.

delete

Claims (20)

delete delete delete delete delete delete delete delete delete delete delete delete delete A method for producing a nanoparticle composite comprising reacting an inorganic oxide nanoparticle and a metal precursor in a hyperbranched polymer solution. The method of claim 14, Inorganic oxide is a method for producing a nanoparticle composite which is a compound represented by the formula (4): [Formula 4] M _x O _y Where M is a metal of Groups 1 to 14, x is an integer from 1 to 5, y represents the integer of 1-10. The method of claim 14, Inorganic oxide nanoparticles is a method for producing a nanoparticle composite prepared by reacting an inorganic oxide precursor in a hyperbranched polymer solution. A method for producing a nanoparticle composite comprising reacting a metal nanoparticle and an inorganic oxide precursor in a hyperbranched polymer solution. The method of claim 17, Metal is at least one selected from the group consisting of transition metals and alloys thereof. 19. A nanoparticle composite prepared by the method of any one of claims 17 or 18. delete

Images