JP5809210B2 - Metal oxide composite having hollow core and porous shell layer and method for producing the same - Google Patents

Description

  The present invention is recoverable and reusable and can be used as a catalyst or antibacterial agent or drug carrier, the interior being wholly or partly hollow (hollow core or partially hollow core) core)), and a metal oxide composite having a core / shell structure including a metal oxide shell layer having pores as a whole and a method for producing the same.

  Metal oxide nanoparticles have been tried for various applications due to their unique industrially useful properties. For example, titanium dioxide nanoparticles have unique chemical properties such as the generation of radicals upon absorption of light in the ultraviolet region and the decomposition of organic substances and antibacterial effects. It is used. On the other hand, titanium dioxide products such as Degussa P25 are composed of nanograins having a size of about 30 nm and may exhibit an agglomeration phenomenon, but exhibit a photocatalytic effect when sufficiently dispersed in water.

  However, fine metal oxide nanoparticles such as P25 and titanium dioxide nanoparticles of 100 nm or less have unique effects such as being dispersed in water and exhibiting excellent performance as a catalyst or antibacterial agent. It was the biggest problem that was difficult. Nanoparticles that are discharged into nature without being collected are seriously harmful to the human body and the environment, and therefore, recovery of nanoparticles after use is a more important issue than the development of nanoparticles.

  In recent years, research results (Non-patent Document 1) on the collection and use of magnetism by putting a cluster of magnetic nanoparticles in the center of submicron-sized titanium dioxide beads have been published. However, in this case, the dark brown magnetic nanoparticles at the center of the titanium dioxide beads not only absorb a considerable amount of light, but also the amount of titanium dioxide exposed on the bead surface involved in the catalytic reaction is relatively small. Because of its low photocatalytic performance, it is used for biosensors after surface modification rather than for photocatalyst.

  In addition, in a method for producing a submicron sized titanium dioxide composite with improved surface area (Patent Document 1), an amorphous titanium dioxide shell is formed on an organic polymer bead by a sol-gel reaction, The organic polymer is burned and removed by heat treatment in an electric furnace at ℃ or higher, and titanium dioxide is crystallized into the anatase phase. Since this method uses a high-temperature electric furnace, it consumes a large amount of energy, and titanium dioxide nanocrystals agglomerate in the process of high-temperature treatment to reduce pores. Therefore, the surface area showing catalytic properties is not so large.

  The performance of metal oxide nanoparticles such as titanium dioxide nanoparticles has been confirmed in various fields, and the amount of their use is increasing, so at present, the surface area is large so that the properties can be maximized. There is a need for a recoverable metal oxide composite and a method for producing the same.

Chinese Patent Application No. 101210120 Korean Published Patent No. 10-2011-0133405

Analytical Chemistry, Liyun Ji et al., 2012, 84, 2284-2291 Angewandte Chemie International Edition 2009, 48, 5875-5879

  It is an object of the present invention to have a hollow core structure inside, wherein the hollow core is completely hollow or contains internal particles having a diameter smaller than the diameter of the hollow core, and metal oxide nanoparticles on the surface It is an object of the present invention to provide a metal oxide composite in which agglomerates have a porous shell layer. In the metal oxide composite, when the hollow core is only partially hollow and includes internal particles, the internal particles are located inside the shell layer like a rattle of a toy. May be.

  The metal oxide composite can be applied to a catalytic reaction, an antibacterial reaction, and the like because the surface of the metal oxide nanoparticles is often exposed and the performance of the nanoparticles is effectively exhibited. At the same time, the metal oxide composite can be recovered and reused using centrifugation or magnetism using the weight of the metal oxide composite. In addition, the metal oxide composite can be applied to a case where a drug is placed inside and delivered to a desired position by using a hollow structure and a porous property, and is gradually released to maintain a medicinal effect. it can.

  That is, the object of the present invention is to maximize the performance of the metal oxide nanoparticles because the material has a large surface area, and can be recovered and reused, and used as a catalyst, an antibacterial agent or a drug carrier. An object of the present invention is to provide a metal oxide composite which can be entirely or partially hollow inside and a method for producing the same.

  The team has been working hard to maintain the performance of metal oxide nanoparticles, such as titanium dioxide, and to facilitate recovery and reuse. Found the fact that it dissolves. On the other hand, amorphous metal oxide nanoparticles crystallize when a hydrothermal reaction occurs. Therefore, a cluster-like layer (shell layer before treatment) is formed on the amorphous silica beads so that amorphous metal oxide nanoparticles (nanogel) constitute a shell layer before treatment. When hydrothermal reaction treatment is carried out, the silica dissolves and the inside becomes partly or partly hollow, and the amorphous metal oxide constituting the shell layer before the treatment has its own phase (in the case of titanium dioxide) depending on the substance. Focusing on crystallization in the anatase phase, it was discovered that a metal oxide composite having the structure described later can be produced while maintaining the properties of the metal oxide nanoparticles, and the present invention has been completed.

  A metal oxide composite according to an embodiment of the present invention includes two or more layers of metal oxide nanoparticles connected to each other, a shell layer having pores existing between the metal oxide nanoparticles, and an inside of the shell layer. And a hollow core that is a space.

  The metal oxide nanoparticles may have a size of 20 nm or less.

  The metal oxide composite may further include internal particles present in the hollow core in a size different from that of the hollow core.

  The inner particles may have a diameter smaller than that of the hollow core.

  The internal particles may be any one selected from the group consisting of silica particles, magnetic nanoparticles, clusters including magnetic nanoparticles, silica particles including magnetic nanoparticles, and combinations thereof.

  The outer diameter of the metal oxide composite may be 100 nm to 10 μm.

  The thickness of the shell layer may be smaller than half the outer diameter of the metal oxide composite and have a value of 20 to 100 nm.

The metal oxide may be any one selected from the group consisting of ZrO ₂ , SnO ₂ , CeO ₂ , Al ₂ O ₃ , V ₂ O ₃ , Fe ₂ O ₃ , Y ₂ O ₃ , and combinations thereof. It may be.

The magnetic nanoparticles include FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O ₄ , MnFe ₂ O ₄ , Fe, Co, Ni, FeCo, FePt, and combinations thereof. Any one selected from may be included.

The metal oxide composite may have a specific surface area measured by a BET method of 100 to 300 m ² / g.

  The metal oxide constituting the metal oxide nanoparticles may have crystallinity.

  The metal oxide nanoparticles contained in the shell layer may be made of titanium dioxide, and the titanium dioxide may be of anatase phase.

  According to another embodiment of the present invention, there is provided a method for producing a metal oxide composite comprising pre-treatment particles in which a pre-treatment shell layer containing amorphous metal oxide nanoparticles is formed on a surface of a core containing silica. A hollow core provided by removing all or part of the core is formed by a first step of manufacturing and a hydrothermal treatment of the particles before the treatment, and the shell layer before the treatment is shelled by the hydrothermal treatment. Forming a layer and producing a metal oxide composite comprising the shell layer and a hollow core therein.

  The shell layer may include metal oxide nanoparticles having a size of 20 nm or less connected to each other and include pores formed between the metal oxide nanoparticles.

  The core containing silica in the first step may include magnetic nanoparticles or clusters containing magnetic nanoparticles. The magnetic nanoparticles or clusters containing the magnetic nanoparticles may be included in internal particles present in the hollow core.

The amorphous metal oxide nanoparticles in the first stage are amorphous nanoparticles made of ZrO ₂ , SnO ₂ , CeO ₂ , Al ₂ O ₃ , V ₂ O ₃ , Fe ₂ O ₃ , or Y ₂ O _3. It may be a particle.

  The amorphous metal oxide nanoparticles in the first stage may be made of a metal oxide that crystallizes by the hydrothermal reaction.

  The first step may include a step of mixing and stirring silica dispersed in a solvent and an organometallic precursor corresponding to the metal oxide nanoparticles.

  The hydrothermal treatment in the second stage includes a preparation stage for preparing a pre-treatment solution in which the pre-treatment particles and water are mixed, and the pre-treatment solution is placed in a hydrothermal reactor at a temperature of 120 ° C. or higher. And a treatment step of producing a treated solution containing a metal oxide complex by hydrothermal reaction for more than an hour.

The organometallic precursor of the metal oxide nanoparticles may include a trialkoxy metal or a tetraalkoxy metal represented by the following chemical formula 1.
M (OR) _z (Formula 1)
In the above chemical formula 1, M is a metal, R is any one selected from the group consisting of linear or branched alkyl groups having 1 to 10 carbon atoms, and z is 3 or 4. .

  The metal oxide nanoparticles may have a size of 20 nm or less.

  The outer diameter of the metal oxide composite may be 100 nm to 10 μm.

  The thickness of the shell layer may be smaller than half the outer diameter of the metal oxide composite and have a value of 20 to 100 nm.

  A drug carrier according to still another embodiment of the present invention includes the metal oxide complex. The drug carrier is capable of carrying a drug in the space inside the shell layer, which is the whole or a part of the hollow core, and the inflow of the drug into the pores of the shell layer or from the pores of the shell layer Drug release is possible.

  A catalyst according to another embodiment of the present invention includes the metal oxide composite. The metal oxide composite has the catalytic activity of the metal oxide nanoparticles and can be easily recovered.

  An antibacterial agent according to another embodiment of the present invention includes the metal oxide complex.

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

  A metal oxide composite according to an embodiment of the present invention includes a shell layer having pores and a hollow core that is a space inside the shell layer.

  The shell layer may be one in which metal oxide nanoparticles form a cluster in the form of a shell. The shell layer may have a structure in which two or more layers of the metal oxide nanoparticles are included and the nanoparticles are connected to each other and have pores between the nanoparticles.

  The metal oxide nanoparticles may have a size of 20 nm or less, and by forming a composite so as to include such fine metal oxide nanoparticles, it is possible to combine nanoparticles that are difficult to recover. It has the advantage that it can be recovered in the form of a body.

  The hollow core is a space where the whole or a part of the inside of the shell layer is hollow, and when part of the hollow core is hollow, the hollow core may contain internal particles of a size smaller than the hollow core. Good.

  The internal particles may include functional particles, and the functional particles are any one selected from the group consisting of silica particles, magnetic nanoparticles, or silica particles including magnetic clusters, and combinations thereof. It may be. The silica particles containing the magnetic cluster may be magnetic silica beads in which the silica is surrounded by a cluster of magnetic nanoparticles.

That is, the internal particles may be simple silica or may have a core / shell structure including a cluster core of magnetic nanoparticles and a shell surrounding the cluster core of magnetic nanoparticles. The nanoparticles constituting the magnetic cluster include FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O ₄ , MnFe ₂ O ₄ , Fe, Co, Ni, FeCo, FePt, and Any one selected from the group consisting of these combinations may be used, and the cluster core of the magnetic nanoparticles may have superparamagnetism.

  The inner particles may be located in a hollow core inside the shell layer, or may have a structure that moves inside like a rattle of a toy.

  The metal oxide composite has a hollow core structure that is entirely or partially hollow inside, includes a porous metal oxide shell layer, and has an outer diameter of several hundred nm to several μm and several tens of nm. Having a thickness of Therefore, the metal oxide composite has good water dispersibility because the weight of the composite itself is moderately heavy, and can be easily recovered by low-speed centrifugation without adding a precipitant.

  Furthermore, since a commercially available filter having pores smaller than the outer diameter of the metal oxide composite can be easily separated, the recovery and reuse efficiency is improved. When the metal oxide composite includes internal particles having magnetism, it can be easily recovered even in a magnetic field.

  The size of the metal oxide nanoparticles is 20 nm or less, and may be 1 to 20 nm. Further, the thickness of the shell layer may be 20 to 100 nm.

  It is known that metal oxide nanoparticles having a size of 20 nm or less are particularly difficult to recover. However, when the metal oxide nanoparticles are aggregated and connected to each other to have a structure of two or more layers as included in the shell layer of the metal oxide composite, the structure of the metal oxide composite In addition to having strength suitable for maintenance, pores in the shell layer are sufficiently secured, and the surface of the metal oxide nanoparticles contained in the shell layer is sufficiently exposed.

  This form is the result of this research team that has continued to make efforts to maintain the performance of conventional metal oxide nanoparticles with a size of 100 nm or less as well as to facilitate recovery and reuse. Provided is a composite capable of easily recovering metal oxide nanoparticles without going through a high-temperature sintering step that easily loses the performance of oxide nanoparticles.

  However, the metal oxide composite may have a form in which part of the shell layer is destroyed in the crystallization and water washing steps of the shell layer of the metal oxide composite.

The metal oxide constituting the metal oxide nanoparticles can be applied to a metal oxide that can be crystallized by a hydrothermal reaction via a sol-gel reaction. As the metal oxide nanoparticles contained in the shell layer, for example, ZrO ₂ , SnO ₂ , CeO ₂ , Al ₂ O ₃ , V ₂ O ₃ , Fe ₂ O ₃ , Y ₂ O ₃ , and combinations thereof are used. be able to.

  FIG. 1 is a conceptual diagram illustrating a cross section of a metal oxide composite according to an embodiment of the present invention.

  Referring to FIG. 1, the diagram on the right side includes a silica sphere surrounding a cluster composed of superparamagnetic nanoparticles as an example of an inner particle inside a hollow core of a metal oxide composite, and a part of the hollow core It is sectional drawing of the metal oxide composite of the form which is hollow.

  The figure on the left side of FIG. 1 shows a form in which the hollow core of the metal oxide composite is hollow, and a functional substance such as a medicine can be placed in the internal space. The shell layer is formed by connecting metal oxide nanoparticles to each other, and is connected to each other in a manner similar to a cluster to form a layer having a relatively constant thickness.

  The center diagram of FIG. 1 is a conceptual diagram showing a cross section of an example in which inner particles having a diameter smaller than the inner diameter of the metal oxide composite are included in the hollow core of the metal oxide composite. The beads are shown by way of example.

  FIG. 1 illustrates some exemplary forms of metal oxide composites according to one embodiment of the present invention, but is not limited thereto. Any metal oxide composite having a shell layer containing metal oxide nanoparticles and having a hollow core in which all or part of the inside is hollow is included in the embodiment of the present invention.

  Specifically, as an exemplary form of the metal oxide composite according to an embodiment of the present invention, a composite composed only of a shell layer 10 containing metal oxide nanoparticles and a hollow core 00 that is an internal space thereof. Body (left side); composite (center) including shell layer 10 including metal oxide nanoparticles, hollow core 00 which is an internal space thereof, and silica beads 20 located in hollow core 00; metal oxide nano A composite (including a shell layer 10 containing particles, a hollow core 00 that is an internal space thereof, and silica beads (internal particles) 20 that are located in the hollow core 00 and surround a cluster 30 made of magnetic nanoparticles ( On the right).

  The metal oxide composite has a large space (hollow core 00) inside the composite due to its structure, and the nanosize exists between the metal oxide nanoparticles in the shell layer including the metal oxide nanoparticles. It has many pores. Therefore, the ratio of the metal oxide nanoparticles exposed on the surface that can participate in the chemical reaction is high.

  That is, the unique advantage of the metal oxide composite according to an embodiment of the present invention is that despite the fact that the metal oxide composite including the metal oxide nanoparticles is formed to facilitate recovery and reuse. The ratio of the surface metal oxide nanoparticles involved in a chemical reaction or the like is kept relatively high so that the activity as a catalyst or an antibacterial agent is not sacrificed. In the present invention, instead of using the conventional method of forming cavities by high-temperature baking or etching, a shell layer containing crystalline metal oxide nanoparticles is formed by hydrothermal treatment, which is economical and environmentally friendly. Metal oxide nanoparticles can be provided in a gentle and safe manner.

  Although there is no restriction | limiting in particular in the whole magnitude | size and shape of the said metal oxide composite, It is preferable to have an outer diameter of 100 nm-10 micrometers. When the outer diameter of the metal oxide composite is less than 100 nm, an aggregation phenomenon that is a characteristic of the nanoparticles themselves may occur between the metal oxide composites, and an aggregation phenomenon between the composites may occur. On the other hand, when the outer diameter of the metal oxide composite exceeds 10 μm, the weight of the metal oxide composite becomes heavy and dispersion in a solvent becomes difficult.

  The metal oxide nanoparticles contained in the shell layer may have a size of 20 nm or less. The thickness of the shell layer is not particularly limited, but is preferably 20 nm or more considering that the structure and strength cannot be maintained unless at least two layers of nanoparticles are accumulated. In addition, if the shell layer is too thick, the movement of reactants through the pores of the shell layer is limited. Therefore, in order to minimize such problems, the thickness of the shell layer is 100 nm or less. Preferably there is.

  That is, the thickness of the shell layer is preferably 20 to 100 nm.

  In addition, in order to secure a space of the hollow core of the metal oxide composite, the silica beads located in the hollow core inside the shell layer of the metal oxide composite are disposed inside the shell layer of the metal oxide composite. The diameter is smaller than the diameter.

  Since the metal oxide composite has a hollow core, the inside of the composite is wholly or partly hollow, and has a porous shell layer in which metal oxide nanoparticles are connected to each other, thereby providing a space inside. In addition, the shell layer has many pores. Therefore, it is easy to move a substance necessary for a chemical reaction in and out of the shell layer of the metal oxide.

  The metal oxide composite is a composite material having advantageous properties of having characteristics similar to those of conventional metal oxide nanoparticles, being recoverable and reusable, and being economical and environmentally friendly.

  The metal oxide complex can constitute a complex while maintaining the characteristics of the metal oxide nanoparticles contained in the shell layer as it is, but as a catalyst, antibacterial or antiviral complex, drug carrier, etc. Can be used.

  In addition, when the metal oxide complex contains nanoparticles or clusters having magnetism, the metal oxide complex can be easily recovered by applying a magnetic field or performing centrifugation after the catalytic reaction or antibacterial reaction. can do.

  A method for producing a metal oxide composite according to another embodiment of the present invention includes a first stage for producing particles before treatment and a second stage for producing a metal oxide composite by a hydrothermal treatment process. The metal oxide nanoparticles may be formed into nanogel amorphous metal oxide nanoparticles, or may be crystallized by a hydrothermal treatment process in the second stage.

  In the process of producing metal oxide nanoparticles, if the process of high-temperature sintering is performed, the size of the nanoparticles themselves may change due to the high-temperature heat treatment. Depending on the size of the nanoparticles thus changed, Physical properties may change. That is, the metal oxide nanoparticles that have been subjected to high-temperature heat treatment have a problem that the characteristics due to the metal oxide being a nanomaterial may be lost.

  Therefore, the present inventors crystallized metal oxide nanoparticles by hydrothermal treatment as an exemplary embodiment for producing a metal nanoparticle composite without performing a heat treatment step at a high temperature (about 500 ° C. or higher).

  The first step is a step of producing particles before treatment in which a shell layer before treatment containing amorphous metal oxide nanoparticles is formed on the surface of a core containing silica.

  The amorphous metal oxide nanoparticles can be applied as long as they are metal oxides produced by a sol-gel reaction using an organometallic precursor and crystallized by a hydrothermal reaction. As the amorphous metal oxide nanoparticles, for example, metal oxide nanoparticles represented by the following chemical formula 2 can be applied.

aM _x O _y (Chemical Formula 2)
In the above chemical formula 2, a means amorphous, M is any one selected from the group consisting of Ti, Zr, Sn, Ce, Al, V, Fe and Y, x and y are values of x = 1 and y = 2 (when M is Ti, Zr, Sn or Ce) or x = 2 and y = 3 (when M is Al, V, Fe or Y), respectively. Have.

  The core containing silica may be a core made of silica, a core mixed with a magnetic substance in silica, a core containing magnetic nanoparticles (or clusters thereof) in silica, etc. Any material that can form a core can be used as the core.

  That is, the particles before the treatment can form a shell layer before the treatment by forming a coating layer of two or more layers of the amorphous metal oxide nanoparticles on the surface of the core containing silica. Therefore, the particles before the treatment may be those represented by the following chemical formula 3.

SiO ₂ / aM _x O _y (Chemical Formula 3)
In the above chemical formula 3, SiO ₂ means a core containing silica, and is not limited to only silica. a, x, y and M are as defined in Chemical Formula 2 above.

For example, the metal oxide nanoparticles are selected from the group consisting of ZrO ₂ , SnO ₂ , CeO ₂ , Al ₂ O ₃ , V ₂ O ₃ , Fe ₂ O ₃ , Y ₂ O ₃ , and combinations thereof. Any one may be sufficient.

  The first step may include a step of mixing and stirring silica dispersed in a solvent and an organometallic precursor corresponding to the metal oxide nanoparticles.

  The organometallic precursor is represented by the following chemical formula 1, corresponds to the metal oxide nanoparticles of the shell layer, and may be a trialkoxy metal or a tetraalkoxy metal.

M (OR) _z (Formula 1)
In the above chemical formula 1, M is a metal, and specifically may be any one selected from the group consisting of Ti, Zr, Sn, Ce, Al, V, Fe, and Y. R is any one selected from the group consisting of linear or branched alkyl groups having 1 to 10 carbon atoms. z is 3 or 4.

  In the second step, a hollow core is formed by removing all or part of the core by a hydrothermal treatment of the particles before the treatment, and the shell layer before the treatment is formed by a shell layer by the hydrothermal treatment. And forming a metal oxide composite including the shell layer and a hollow core therein. The effect of crystallizing the amorphous metal oxide nanoparticles contained in the shell layer before the treatment can be obtained by removing all or part of the silica from the metal oxide composite by the hydrothermal treatment step.

  The hydrothermal treatment in the second stage includes a preparation stage for preparing a pre-treatment solution in which the pre-treatment particles and water are mixed, and the pre-treatment solution is placed in a hydrothermal reactor at a temperature of 120 ° C. or higher. And a treatment step of producing a treated solution containing a metal oxide composite by thermal reaction.

  In such a process, the silica contained in the core is dissolved and removed from the pores of the shell layer or shell layer before treatment, and the amorphous metal oxide nanoparticles or metal oxide nanoparticles contained in the shell layer before treatment are processed. The particle precursor crystallizes.

  For example, when applying titanium dioxide as the metal oxide nanoparticles, an organometallic precursor of titanium capable of performing a sol-gel reaction is gradually added to a solvent such as a basic ethanol solution containing silica or magnetic silica. To form an amorphous titanium dioxide shell layer (shell layer before treatment) on silica, and wash the particles before treatment containing the amorphous shell layer (shell layer before treatment) and the core with water. Then, when crystallized by a hydrothermal reaction, the amorphous titanium dioxide shell layer (shell layer before treatment) changes to an anatase crystal phase, and all or part of the silica inside the shell layer is dissolved depending on the reaction concentration. As a result, the metal oxide composite can be produced.

  In the hydrothermal reaction, the lower the temperature, the shorter the time, and the higher the concentration of particles before treatment including the amorphous shell layer (shell layer before treatment) and the core, the less silica is dissolved. Therefore, a desired amount of silica can be removed by appropriately controlling the correlation between temperature, time and concentration.

  For example, 0.05 wt% / v silica was completely dissolved when hydrothermally treated at 150 ° C for 3 hours, and 0.1 wt% / v silica was completely dissolved when hydrothermally treated at 180 ° C for 3 hours. It was confirmed.

  That is, all or part of the silica contained in the core can be removed by the hydrothermal treatment. When the core is made of silica, after hydrothermal treatment, i) a part of the silica of the core is removed, and a part of the core remains without being removed to form (form) internal particles made of silica, or ii) the core All of the silica is removed to form a space free of internal particles. When the core contains silica and magnetic nanoparticles, i) a part of the silica in the core is removed and the remaining silica and magnetic nanoparticles constitute internal particles, or ii) all of the silica in the core As a result, the magnetic nanoparticles aggregate to form internal particles.

  That is, the core after hydrothermal treatment may constitute internal particles, or may be completely removed and no internal particles remain in the hollow core.

  Hereinafter, a method for producing a titanium dioxide composite to which titanium dioxide nanoparticles are applied as metal oxide nanoparticles will be described as an example. First, an iron oxide nanoparticle cluster was selected as a cluster of magnetic nanoparticles constituting the core, and was produced by the method described in Non-Patent Document 2.

The iron oxide nanoparticle cluster is formed by agglomerating small iron oxide nanoparticles having a size of 5 to 10 nm to form a cluster having an overall diameter of about 500 nm, and has a characteristic of showing a fast reaction to an external magnetic field (50 to 80 emug ⁻¹ ). By using such a magnetic material as a core, the finally produced titanium dioxide composite having a partially hollow interior has magnetism. The magnetic core is not limited to the iron oxide nanoparticle cluster described above, and may be an embodiment of the present invention as long as it has magnetic properties.

  Next, silica was selected as the shell material, and a silica layer was directly grown on the magnetic core by the Stober method, thereby manufacturing beads composed of the magnetic core and the silica shell. The beads composed of the magnetic core and the silica shell can be manufactured by the method described in Patent Document 2 filed by the present researchers, for example, using an excess amount of tetraethoxysilane (TEOS). To form a silica shell that surrounds the magnetic core, and then using a magnet to separate the silica that surrounds the magnetic body from the silica that does not surround it, and only the silica beads that surround the magnetic body are selected. can do.

  The thickness of the silica shell surrounding the magnetic body varies depending on the ratio of the magnetic core used and the TEOS. The larger the amount of TEOS, the thicker the silica shell layer. Silica beads not containing a magnetic core can be purchased or synthesized by the Stover method.

A shell layer made of amorphous titanium dioxide nanoparticles (shell layer before treatment) is obtained by gradually injecting a titanium organometallic precursor into the synthesized or purchased silica-containing basic ethanol solution and stirring well for 15 hours. A SiO ₂ / aTiO ₂ composite having a silica core formed on the silica core can be produced.

Next, the produced SiO ₂ / aTiO ₂ composite is washed with ethanol and water, sealed in an autoclave, and then hydrothermally reacted in an oven preheated to 150 to 180 ° C. for 3 hours. Thus, it is possible to produce a titanium dioxide composite SiO ₂ / cTiO ₂ (where c is an abbreviation of crystalline) in which all or part of silica is eluted and amorphous titanium dioxide is crystallized in the anatase phase. The hydrothermal reaction temperature can be expanded up and down from the above temperature, and the higher the hydrothermal reaction temperature is, the more silica is dissolved.

  In the above, the example which applied the titanium dioxide nanoparticle as a metal oxide nanoparticle was demonstrated concretely. However, the present invention is not limited to this, and can be applied as the metal oxide nanoparticles as long as the method can be applied to produce a metal oxide composite. The description of the metal oxide composite itself is omitted because it overlaps with the description of the metal oxide composite according to the embodiment of the present invention described above.

  The metal oxide composite according to the present invention can provide a composite having a porous metal oxide shell layer that is entirely or partially hollow and has a shell layer size of several hundred nm to It has a range of several μm. The metal oxide composite not only can be used as an efficient photocatalyst by utilizing the properties of the porous body and the hollow properties of which the interior is entirely or partially hollow, but it can also be used as an effective photocatalyst. It can also be used for collecting and removing bacteria, and it can also be used as a drug carrier that gradually releases a drug in a cavity. In addition, a metal oxide composite that is entirely or partially hollow inside can be easily recovered by using a normal centrifugal separation or a magnetic field depending on the weight or magnetism of the composite, and constitutes a shell layer even after recovery. Since the physicochemical properties of the surface metal oxide nanoparticles are preserved, it provides an economical and environmentally friendly material that can be reused.

  According to the method for producing a metal oxide composite according to the present invention, the amorphous composite having a silica core / metal oxide shell structure is subjected to a hydrothermal reaction to crystallize the metal oxide and all or part of the silica. An economical and efficient method for producing a metal oxide composite shell by dissolving a metal oxide is provided.

It is a conceptual diagram explaining the cross section of the metal oxide composite by one Embodiment of this invention. Example 1 In producing the pretreatment of the particles of the present invention is a scanning electron micrograph of (SiO _{2 /} aTiO 2 complex, core / shell structure formed of amorphous titanium dioxide shell layer on the silica beads). Scanning electron micrograph of sample 1 of a metal oxide composite produced in Example 1 of the present invention (a titanium dioxide composite having a completely or partially hollow interior and an anatase crystal phase, SiO ₂ / cTiO ₂ ) It is. It is a transmission electron micrograph of the particle | grains of FIG. It is a graph which shows the XRD pattern of the particle | grains of FIG. It is a transmission electron micrograph of the sample 2 of the metal oxide composite produced in Example 1 of the present invention (a titanium dioxide composite having a hollow interior and having an anatase crystal phase). Transmission electron of metal oxide composite (magnetic titanium dioxide composite, titanium dioxide composite having a partially hollow interior and containing magnetic silica inside and having anatase crystal phase) produced in Example 2 of the present invention It is a micrograph. It is a graph which shows the XRD pattern of the metal oxide composite of FIG. It is a graph which shows the result of having measured the photocatalytic activity of the sample 2 (titanium dioxide composite which all are hollow inside, and has an anatase crystal phase) of Example 1, and Degussa P25.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily implement the present invention. However, the present invention is not limited to the embodiments described here, and can be realized in various different forms.

Manufacture of titanium dioxide composite shell that is completely or partially hollow inside
(1) First stage: Production of core / shell structure SiO ₂ / aTiO ₂ composite having a shell layer composed of amorphous titanium dioxide nanoparticles on silica beads Silica beads can be purchased or Stover method The one synthesized by is used.
In a round bottom flask, 750 mL of absolute ethanol and 15 mL of an ethanol solution in which 5 w% / v silica beads (0.75 g, average diameter 281 nm, silica core) were dispersed were placed and mixed well. Add 3.3 mL of concentrated aqueous ammonia (28-30% aqueous solution) to this solution and mix well. Then, gradually add 9 mL of tetrabutylorthotitanate (TBOT) and stir for 15 hours. Particles before treatment (SiO ₂ / aTiO ₂ composite) in which a shell layer before treatment was formed were formed.

The SiO ₂ / aTiO ₂ complex, which is the particles before the treatment, was washed and dried several times using ethanol and water and centrifugation (average diameter 357 nm, weight 1.26 g), and water 37.5 mL Dispersed and stored.

  FIG. 2 shows a photograph of the particles before the treatment observed with a scanning electron microscope. As can be seen from the SEM image in FIG. 2, it was confirmed that the surface of the spherical particles was coated with fine particles and had an uneven surface.

(2) Second stage: crystallization of amorphous titanium dioxide constituting the shell in the SiO ₂ / aTiO ₂ complex into anatase phase 1) Solution 12 of the SiO ₂ / aTiO ₂ complex produced in the first stage .5 mL (0.42 g) was taken and mixed well with 60 mL of water to produce a pre-treatment solution that was placed in a Teflon-coated hydrothermal reactor (autoclave) and sealed (SiO _{2 to the} total solution). Concentration: 0.5 w% / v).

  The hydrothermal reactor was placed in an oven preheated to 150 ° C. and subjected to a hydrothermal reaction for 3 hours to produce a treated solution.

  The treated solution is cooled and centrifuged to obtain a titanium dioxide composite (sample 1 of the metal oxide composite of Example 1) that is wholly or partially hollow inside, and is added to 12.5 mL of water. A dispersion solution was produced by dispersion and stored.

  As a result of taking a half of the dispersion and drying it and measuring the weight, it was 0.13 g, and the total weight of the titanium dioxide composite in the produced dispersion was estimated to be 0.26 g.

It can be seen that the total amount of the produced titanium dioxide composite was reduced by 0.14 g from the total amount of the SiO ₂ / aTiO ₂ composite that was the particles before the treatment, and a considerable part of the reduction was dissolved and removed in the silica. It is presumed to be caused by water generated when the titanium dioxide gel crystallizes.

  3 to 5 show an SEM image, a TEM image, and an XRD pattern of the generated titanium dioxide composite, respectively. From the TEM image in FIG. 4, the form of the titanium dioxide composite that is entirely or partially hollow inside can be confirmed. From the XRD pattern in FIG. 5, the titanium dioxide is crystallized in the anatase phase. Can be confirmed.

2) In the hydrothermal reaction of 1) above, the concentration of the SiO ₂ / aTiO ₂ complex solution is adjusted from 0.5 w% / v to 0.1 w% / v on the basis of the SiO ₂ concentration, and the hydrothermal reaction temperature is adjusted. A titanium dioxide composite (sample 2 of the metal oxide composite of Example 1) was produced by carrying out a hydrothermal reaction at 180 ° C. under the same conditions.

  FIG. 6 shows a TEM analysis result of Sample 2. From the TEM image of FIG. 6, it can be confirmed that a metal oxide composite having a titanium dioxide shell layer that is hollow inside is produced.

The measurement results of the specific surface area using the BET method of the sample 2 is 214m ² / g, have a much better specific surface area than P25 (Degussa) having a specific surface area of 48~56m ² / g Was confirmed.

Manufacture of titanium dioxide composites with internal magnetic particles with a structure that is partially hollow inside
(1) Production of magnetic silica beads containing magnetic clusters 1) FeCl ₃ (1.95 g, 12.0 mmol) and trisodium citrate (0.60 g, 2.04 mmol) were dissolved in 60 mL of ethylene glycol and acetic acid Sodium (3.60 g, 26.5 mmol) was added to produce a pre-treatment solution of the magnetic cluster, which was stirred for 30 minutes. The stirred pre-treatment solution was transferred to a Teflon-coated hydrothermal reactor (autoclave), sealed, and reacted in an oven at 200 ° C. for 14 hours to produce a solution containing clusters of magnetic nanoparticles.

  The solution was cooled to room temperature, and the clusters were washed with ethanol and distilled water three times, and the magnetic nanoparticle clusters were collected with a magnet and dispersed in 30 mL of ethanol. As a result of taking 1 mL of the solution in which the clusters of magnetic nanoparticles were dispersed, separating and drying the solid and measuring the weight, it was 0.0241 g, and the average diameter of the magnetic clusters was 508 nm.

  2) In order to form a silica shell on the cluster of magnetic nanoparticles, 15 mL of a solution in which the cluster of magnetic nanoparticles was dispersed in ethanol was taken, and ethanol was added thereto to make 3 L.

  Distilled water (300 mL) and trisodium citrate (1.35 g) were added, and the mixture was stirred with a stirrer. 90 mL of concentrated ammonia water was added and stirred for 1 hour, and then 135 mL of TEOS was added and stirred at 20 ° C. for 14 hours to produce magnetic silica beads consisting of a cluster of magnetic nanoparticles and a silica shell surrounding the cluster. The solution was centrifuged, and the precipitate was washed with ethanol and water several times, further separated with a magnet and dispersed in 15 mL of ethanol.

  As a result of taking 1 mL of the solution, separating and drying the solid and measuring the weight, it was 0.0619 g (average diameter 721 nm). That is, the weight increased by the silica shell is 0.0379 g, and the thickness of the silica shell is 107 nm.

  3) Next, the silica beads of Example 1 were replaced with the magnetic silica beads, and the same reaction was performed as follows.

(2) First step: Production of a core / shell structure magnetic SiO ₂ / aTiO ₂ composite having a shell layer composed of amorphous titanium dioxide nanoparticles on magnetic silica beads 300 mL of absolute ethanol in a round bottom flask and the above 14 mL of an ethanol solution in which magnetic silica beads (average diameter 721 nm) were dispersed was added and diluted, and 1.32 mL of concentrated aqueous ammonia was added and stirred. Next, 1.8 mL of TBOT was gradually added and stirred for 15 hours, and particles before treatment having amorphous titanium dioxide having an average thickness of 55 nm on the surface of the magnetic silica beads (magnetic SiO ₂ / aTiO ₂ composite) Manufactured.

  The particles before the treatment were washed several times using ethanol, water and a magnet, and dispersed in 28 mL of water. As a result of taking 2 mL of the solution in which the particles before the treatment were dispersed, separating and drying the solid, and measuring the weight, it was 0.0822 g (average diameter 832 nm). That is, the weight increased by the amorphous titanium dioxide shell is 0.0203 g, and the thickness of the shell is 55 nm.

(3) Second stage: crystallization of amorphous titanium dioxide into anatase phase in magnetic SiO ₂ / aTiO ₂ composite 1) Magnetic SiO ₂ / aTiO ₂ composite produced in the first stage (average diameter 832 nm) Take 3 mL of the solution and mix well with 90 mL of water to produce a pre-treatment solution that is placed in a Teflon-coated hydrothermal reactor (autoclave) and sealed (about 0.1 w% / v on silica basis). ).

  The hydrothermal reactor was placed in an oven preheated to 150 ° C. for crystallization reaction for 3 hours to produce a treated solution.

  The treated solution is cooled and centrifuged to obtain a magnetic titanium dioxide composite (sample of Example 2) having a partially hollow interior, which is dispersed in 3 mL of water to produce a dispersion solution and stored. did.

As a result of taking 2 mL of the dispersion solution, separating the solid contained therein and drying it, and measuring the weight, it was 0.0438 g. This is a decrease of 0.0384 g from the sample dried from the same volume of magnetic SiO ₂ / aTiO ₂ composite solution (0.0822 g), and the decrease is contained in the core of the particles before processing. It is judged that the silica was dissolved and the water generated by the crystallization of the titanium dioxide gel constituting the shell layer before the treatment was removed.

7 and 8 show the TEM image and XRD pattern of the produced titanium dioxide composite of Example 2, respectively. From the TEM image of FIG. 7, most of the silica contained in the core of the particle before processing is dissolved, and the cluster of magnetic nanoparticles is not fixed at a specific position inside the titanium dioxide shell like the rattle of the toy. An image of the existing titanium dioxide composite can be confirmed. From the XRD pattern of FIG. 8, Fe ₃ O ₄ (magnetite) crystals and titanium dioxide crystallized in the anatase phase were formed on the metal oxide composite of Example 2. It can be confirmed that it exists.

Catalytic Activity and Recovery Experiment of Titanium Dioxide Composite Catalytic activity experiment was performed using P25 (Degussa), the titanium dioxide composite sample of sample 2 synthesized in Example 1, and a sample not containing titanium dioxide particles (see UV in FIG. 9). Each was carried out. P25 and Sample 1 of Example 1 were each used at a concentration of 0.01 mg / mL on a TiO ₂ basis and ordered with 50 mL of 10 ppm methylene blue and two 15 W UV-B lamps located 30 cm above The photocatalytic reaction was performed using the manufactured box.

  FIG. 9 shows a result obtained by collecting a sample of 3 mL per hour during the photocatalytic reaction, measuring an absorption spectrum, and reacting for 50 minutes.

It was confirmed that the titanium dioxide composite shell had a performance similar to that of P25, and the whole amount was recovered by centrifugation after the reaction. It was confirmed that the photocatalytic effect was the same as or better than the conventional one, and that the entire amount could be recovered by a method such as centrifugation. Therefore, the titanium dioxide composite of Sample 2 of Example 1 is evaluated as a material superior to conventional commercially available titanium dioxide.
The preferred embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto, and various modifications and improvements of the present invention defined in the claims are also included in the present invention. Is included in the scope of rights.

00 Hollow core that is hollow in whole or in part 10 Shell layer containing metal oxide nanoparticles 20 Silica beads 30 Cluster of magnetic nanoparticles

Claims (16)

Including two or more layers of metal oxide nanoparticles connected to each other, including a shell layer having pores existing between the metal oxide nanoparticles, and a hollow core that is a space inside the shell layer;
The metal oxide nanoparticles are metal oxide composites having a size of 20 nm or less, and the hollow core is formed on the surface of a core made of amorphous silica with TiO ₂ , ZrO ₂ , SnO ₂ , shell layer including _{CeO 2, Al 2 O 3,} V 2 O 3, Fe 2 O 3, Y 2 O 3, and the amorphous metal oxide nanoparticles selected from the group consisting of is formed, This is hydrothermally treated to remove all or part of the amorphous silica in the core, and the shell layer before the treatment is crystallized by the hydrothermal treatment to form a shell layer. , Metal oxide composites. Further comprising internal particles present in the hollow core in a size different from that of the hollow core;
The metal oxide composite according to claim 1, wherein the inner particles have a diameter smaller than that of the hollow core.   The internal particles are any one selected from the group consisting of silica particles, magnetic nanoparticles, clusters containing magnetic nanoparticles, silica particles containing magnetic nanoparticles, and combinations thereof. Metal oxide composite.   The metal oxide composite according to claim 1, wherein an outer diameter of the metal oxide composite is 100 nm to 10 μm.   5. The metal oxide composite according to claim 4, wherein the thickness of the shell layer is smaller than half of the outer diameter of the metal oxide composite and has a value of 20 to 100 nm. The magnetic nanoparticles include FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O ₄ , MnFe ₂ O ₄ , Fe, Co, Ni, FeCo, FePt, and combinations thereof. The metal oxide composite according to claim 3, comprising any one selected from the group consisting of: The metal oxide composite according to claim 1, wherein the metal oxide composite has a specific surface area measured by a BET method of 100 to 300 m ² / g. The metal oxide composite according to claim 1 , wherein the metal oxide nanoparticles contained in the shell layer are made of titanium dioxide, and the titanium dioxide is of anatase phase . A group consisting of TiO ₂ , ZrO ₂ , SnO ₂ , CeO ₂ , Al ₂ O ₃ , V ₂ O ₃ , Fe ₂ O ₃ , Y ₂ O ₃ , and combinations thereof on the surface of the core made of amorphous silica A first step of producing pre-processed particles in which a pre-process shell layer comprising amorphous metal oxide nanoparticles that are any one selected from:
The step of hydrothermal treatment of particles prior to the treatment at 120 ° C. or higher, the which all or part of the core is removed, to form a hollow core provided, shell layer before the treatment was crystallized by the hydrothermal treatment Forming a shell layer and producing a metal oxide composite including the shell layer and a hollow core therein;
The method for producing a metal oxide composite, wherein the shell layer includes metal oxide nanoparticles having a size of 20 nm or less connected to each other and includes pores formed between the metal oxide nanoparticles. The core containing silica in the first stage includes magnetic nanoparticles or clusters containing magnetic nanoparticles;
The method for producing a metal oxide composite according to claim 9 , wherein the magnetic nanoparticles or the clusters containing the magnetic nanoparticles are contained in internal particles present in the hollow core. 10. The metal according to claim 9 , wherein the first stage includes a step of mixing and stirring amorphous silica dispersed in a solvent and an organometallic precursor corresponding to the amorphous metal oxide nanoparticles. A method for producing an oxide composite. The hydrothermal treatment in the second stage includes a preparation stage for preparing a pre-treatment solution in which the pre-treatment particles and water are mixed, and the pre-treatment solution is placed in a hydrothermal reactor at a temperature of 150 ° C. or higher. It comprises two or more layers of metal oxide nanoparticles that are hydrothermally reacted for more than an hour to remove part or all of the amorphous silica in the core and crystallize the amorphous metal oxide nanoparticles and are connected to each other, The manufacturing method of the metal oxide composite of Claim 9 including the process step which manufactures the processed solution containing the shell layer composite which has the pore which exists between the said metal oxide nanoparticles . The method for producing a metal oxide composite according to claim 11 , wherein the organometallic precursor of the metal oxide nanoparticles includes a trialkoxy metal or a tetraalkoxy metal represented by the following chemical formula 1.
M (OR) _z (Formula 1)
In the above chemical formula 1, M is a metal, R is any one selected from the group consisting of linear or branched alkyl groups having 1 to 10 carbon atoms, and z is 3 or 4. .   A drug carrier comprising the metal oxide complex according to claim 1. Photocatalyst metal oxide according to claim 1, comprising a conjugate is TiO _2.   An antibacterial agent comprising the metal oxide composite according to claim 1.