KR20070018972A - Composite nanofiber, composite nanofiber mass, composite structure, and processes for producing these - Google Patents

Abstract

Silica nanofibers are induced by a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton capable of forming water-insoluble crystals at room temperature by the presence of water molecules, and the crystalline polymer filaments in the silica are metal ions. By concentrating, the composite nanofiber which contains a metal or metal ion in silica inside can be implement | achieved. Moreover, the composite nanofiber of this invention can be manufactured easily by fixing the polymer structure used as a scaffold of a metal ion in silica, concentrating a metal ion to the scaffold, or reducing the metal ion. Moreover, a metal containing silica nanofiber can be obtained easily by removing a polymer component from the assembly | assembly of a composite nanofiber, a composite nanofiber, and a structure. These nanofibers can be aggregated and integrated, and aggregated and integrated assemblies and structures can express various shapes.

Composite nanofiber, composite nanofiber assembly, composite structure

Description

Composite Nanofibers, Composite Nanofiber Aggregates, Composite Structures and Methods for Manufacturing the Same {COMPOSITE NANOFIBER, COMPOSITE NANOFIBER MASS, COMPOSITE STRUCTURE, AND PROCESSES FOR PRODUCING THESE}

The present invention relates to nanofibers containing metals or metal ions in silica nanofibers, assemblies and structures in which the nanofibers are collected, and methods for producing these nanofibers and nanofiber assemblies.

This application claims priority to Japanese Patent Office pursuant to Japanese Patent Application No. 2004-161234 filed on May 31, 2004 and Japanese Patent Application No. 2004-243580 filed on August 24, 2004, the contents of which are incorporated herein by reference. .

It is known that a material having a nano-sized structure exhibits characteristics different from that of a bulk state. Among them, nanofibers having a nanometer thickness and a length of several tens of times or more are unique in fiber shape due to their high aspect ratio. Because of expressing the size effect of, it is attracting attention as one of the advanced materials. Silica nanofibers have a high aspect ratio and a large surface area unique to nanofibers, and have various physical properties such as semiconductor properties, conductivity, surface properties, and mechanical strength inherent in inorganic materials. Its application is promising in various high-tech materials fields. In addition, one strand of nanofibers (one-dimensional) is aggregated into a cloth (two-dimensional) or a block (three-dimensional) while maintaining the characteristics of the nanofibers, thereby making a structure, the use of silica nanofibers dramatically It is expected to expand.

In particular, the combination of silica nanofibers with functional materials such as other inorganic materials and organic materials has a wide range of application possibilities. For example, by combining with inorganic materials such as metals, electronic materials, optical materials, catalysts, colorants, sensors, etc. Applications in many areas are expected.

As a material combining silica and metal or metal ions, a composite material in which a metal complex is immobilized on mesoporous silica is used for a chemical reaction catalyst, an electrochemical sensor, a solid polymer electrolyte and the like. In the case of application of a complex in which a metal complex is introduced into mesoporous silica, the high surface area of the silica surface, the uniform distribution of the complex active point in the nanocavity, the rapid diffusion of the substrate compound, and the catalyst carrier Since many advantages, such as heat resistance and acid resistance, are expected, a metal complex immobilization technique having mesoporous silica as a support attracts much attention (see Non-Patent Document 1).

However, the silica used for the composite material of these conventional metal complexes and silica was limited to the bulk powder or particle | grain state of silica. Therefore, since the composite fine particles have a particle shape having an aspect ratio of almost 1: 1, the composite fine particles cannot be aggregated and integrated only with the composite fine particles, and it is difficult to form a structure in which the characteristics unique to the nanostructured material are maintained.

In addition, the manufacturing method requires a step of introducing an amino group, an imino group, or the like for coordinating metal ions into the silica skeleton by chemical bonding, and the process is complicated.

As a fine composite material of silica and a metal, for example, mesoporous silica / metal nanowire composite by reducing a metal ion solution in a channel of MCM-41 series mesoporous silica (see Non-Patent Document 2 and Non-Patent Document 3). Many studies have been made on silica fine particles / metal nanoparticle composites (see Non-Patent Document 4) by bonding metal ions to silica fine particles.

However, in these conventional composites of metal nanoparticles and nanowires and other materials, it is difficult to form metal nanoparticles or nanowires unless a fixed space of a material having a fixed shape is used. Thus, the degree of freedom of silica is low, thus forming wires. It was limited to the bulk silica and the particle shape which have a hole to make, and it was difficult to control the shape of a composite body. For this reason, it was difficult to highly integrate a composite and the metal nanowire inside.

Non-Patent Document 1: B. Lee et al., Langmuir, (2003), 19, p4246-4252

<Non-Patent Document 2>: G. Hornyak et al., Chem. Eur. J. 1997, 3, No. 12, p1951-1956

Non-Patent Document 3: Yong-Jin Han, Chem. Mater., 2000, 12, p 2068-2069

Non-Patent Document 4: V. G. Pol et al., Chem. Mater., 2003, 15, p1111-1118

[Initiation of invention]

[Problem to Solve Invention]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is a metal-containing silica nanofiber in which metal ions or atoms are immobilized in a structure and highly collectable, a composite nanofiber in which a functional polymer is further complexed with the metal-containing silica nanofiber, and these highly aggregated It is to provide an assembly or structure, and a simple method for producing them.

[Means for solving the problem]

In the present invention, silica nanofibers are induced by the crystalline polymer filaments of a polymer having a linear polyethyleneimine skeleton which can form water-insoluble crystals at room temperature by the presence of water molecules, and the crystalline polymer filaments in the silica. By concentrating valent metal ions, a composite nanofiber containing metal or metal ions in silica can be realized. This composite nanofiber can be aggregated and integrated, and aggregated and integrated assemblies and structures can express various shapes. Moreover, the composite nanofiber of this invention can be manufactured easily by fixing the polymer structure used as a scaffold of a metal ion in silica, concentrating a metal ion to the scaffold, or reducing the metal ion. Moreover, a metal containing silica nanofiber can be obtained easily by removing a polymer component from the assembly | assembly of a composite nanofiber, a composite nanofiber, and a structure.

That is, the present invention relates to a composite nanofiber containing a polymer having a linear polyethyleneimine skeleton in which at least one metal or metal ion is arranged in silica nanofibers, an assembly in which the composite nanofibers are associated with each other, and the aggregates thereof. It is to provide a composite structure formed by further association.

In addition, the present invention provides a composite nanofiber, a composite nanofiber assembly, and a metal-containing silica nanofiber, a metal-containing silica nanofiber assembly, and a metal-containing silica nanofiber structure from which a polymer component is removed from the composite structure.

The present invention also provides a step of (1) dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton, and (2) Contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber; (3) the polymer-containing silica nanofiber and a metal ion A method for producing a composite nanofiber comprising a step of bringing a solution into contact and coordinating metal ions to a linear polyethyleneimine skeleton in the polymer, and (4) a transition metal coordinated to the linear polyethyleneimine skeleton in the polymer after the step. Manufacturing method of composite nanofibers having a process of reducing ions To provide.

Moreover, this invention provides the manufacturing method of the metal containing silica nanofiber which has a process of removing the polymer component in the composite nanofiber after obtaining a composite nanofiber by the said process.

[Effects of the Invention]

The composite nanofiber and the metal-containing silica nanofiber of the present invention can be associated with each other to be highly aggregated and integrated to form an assembly having a two-dimensional or three-dimensional spatial shape of micro to millimeter order. The association shape can be adjusted to various shapes, such as a lettuce shape, a fiber shape, a sponge shape, an aster shape, a cactus shape, and a dandelion shape, for example. In addition, by combining the composite nanofiber assemblies or the assemblies through other composite nanofibers, it is possible to form a structure having a macroscopic shape of a size of millimeter order or more. The outer shape of the structure can be formed into any shape, and can be formed into disc, columnar, plate, filter, film, spherical, rod, etc. according to the requirements of a specific application. It can be processed in various states such as cylinder and cylinder. Inside the structure, there is an aggregate shape of the aggregate, and the aggregate is based on the composite nanofiber or metal-containing silica nanofiber of the present invention. Thus, the structure has a three-dimensional network structure in which these nanofibers are complex.

In addition, the composite nanofiber and the metal-containing silica nanofiber of the present invention contain metal ions and metals therein. Since metal ions contain ions such as alkali metals, alkaline earth metals and transition metals, these nanofibers can be expected to be applied to solid electrolytes, solid catalysts, nanoadditives, and nano thin film materials.

In addition, metal ions are spontaneously reduced or reduced by heat treatment or a reducing agent so that the metal ions become a particulate or wire metal via the metal cluster. Thereby, the film-like structure which consists of nanofibers containing a metal nanowire, the sponge-like structure which consists of nanofibers containing a metal nanowire, and the mesh structure which consists of nanofibers containing a metal nanowire can be provided. In addition, the metal nanoparticles may be distributed in these shaped composite structures.

Among them, silica nanofibers containing crystals of transition metals, especially precious metals, have high usefulness, and are widely used in nanotechnology domains such as nanometal catalysts, nanometal conductive materials, nanometal colorants, nanometal sensors, photoimaging materials, Wide application can be expected as an optoelectronic material and a medical material.

According to the production method of the present invention, a composite nanofiber is formed by a sol-gel reaction of a silica source which proceeds only on the surface of a nanometer-thick crystalline polymer filament, and after silica of a certain thickness covers the crystalline polymer filament, By fixing an ion and reducing metal ion as needed, it can manufacture easily in a short time.

In addition, since the polymer component in the composite nanofiber of the present invention can be easily removed by sintering or the like, it is also easy to manufacture metal-containing silica nanofibers containing metal nanoparticles and metal nanowires therein.

1 is a transmission electron micrograph of a composite nanofiber structure in Example 1 of the present invention.

2 is a high resolution transmission electron micrograph of gold nanowires in a composite nanofiber structure in Example 1 of the present invention.

3 is a transmission electron micrograph of a composite nanofiber structure in Example 2 of the present invention.

4 is a high resolution transmission electron micrograph of platinum nanowires in a composite nanofiber structure in Example 2 of the present invention.

5 is a scanning electron micrograph of a composite nanofiber structure in Example 4 of the present invention.

Best Mode for Carrying Out the Invention

The composite nanofiber of the present invention is a composite material in which a metal or metal ion and a polymer having a linear polyethyleneimine skeleton are contained in silica nanofibers.

(Polymer having a linear polyethyleneimine skeleton)

The linear polyethyleneimine backbone as used in the present invention refers to a linear polymer backbone having ethyleneimine units of secondary amines as main structural units. Although structural units other than ethyleneimine unit may exist in the frame | skeleton, in order to form a crystalline polymer filament, it is preferable that the fixed chain length of a polymer chain consists of continuous ethyleneimine units. The length of the linear polyethyleneimine skeleton is not particularly limited as long as the polymer having the skeleton can form a crystalline polymer filament, but in order to suitably form the crystalline polymer filament, It is preferable that it is 10 or more, and it is especially preferable that it is the range of 20-10000.

The polymer used in the present invention may be one having the linear polyethyleneimine skeleton in its structure, and may be a crystalline polymer filament in the presence of water even if the shape is linear, star-shaped, or comb-shaped. .

In addition, even if these linear, star-shaped, or comb-shaped polymers consist only of a linear polyethyleneimine skeleton, what consists of block copolymers of a block consisting of a linear polyethyleneimine skeleton (hereinafter abbreviated as polyethyleneimine block) and other polymer blocks You can do it. As another polymer block, For example, water-soluble polymer blocks, such as polyethyleneglycol, polypropionylethyleneimine, polyacrylamide, or polystyrene, polyphenyloxazoline of polyoxazoline, polyoctyloxazoline, polydodecyloxazoline, Hydrophobic polymer blocks, such as polymethyl methacrylate and polybutyl methacrylate of polyacrylates, can be used. By setting it as a block copolymer with these other polymer blocks, the shape and characteristic of a crystalline polymer filament can be adjusted.

Although the ratio of the linear polyethyleneimine skeleton in the polymer when the polymer having the linear polyethyleneimine skeleton has another polymer block or the like is not particularly limited as long as it is a range in which a crystalline polymer filament can be formed, it is appropriately crystalline. In order to form a polymer filament, it is preferable that the ratio of the linear polyethyleneimine skeleton in a polymer is 25 mol% or more, It is more preferable that it is 40 mol% or more, It is further more preferable that it is 50 mol% or more.

The polymer having a linear polyethyleneimine skeleton can be easily obtained by hydrolyzing a polymer having a linear skeleton (hereinafter abbreviated as precursor polymer) composed of polyoxazolines serving as a precursor under acidic conditions or alkaline conditions. have. Therefore, the shape, such as linear, star shape, or comb shape, of a polymer having a linear polyethyleneimine skeleton can be easily designed by controlling the shape of the precursor polymer. The degree of polymerization and terminal structure can also be easily adjusted by controlling the degree of polymerization or terminal functional groups of the precursor polymer. In addition, when forming the block copolymer which has a linear polyethyleneimine skeleton, it can obtain by making a precursor polymer into a block copolymer, and selectively hydrolyzing the linear skeleton which consists of polyoxazolines in the precursor.

Precursor polymer can be synthesize | combined by the synthesis method, such as a cationic polymerization method or a macromonomer method, using the oxazoline-type monomer, and by selecting a synthesis | combination method and an initiator suitably, linear shape, a shape, a comb shape, etc. Precursor polymers of various shapes can be synthesized.

As a monomer which forms the linear skeleton which consists of polyoxazolines, oxazoline monomers, such as methyl oxazoline, ethyl oxazoline, methylvinyl oxazoline, and phenyl oxazoline, can be used.

As a polymerization initiator, the compound which has functional groups, such as an alkyl chloride group, a brominated alkyl group, an alkyl iodide group, a toluenesulfonyloxy group, or a trifluoromethylsulfonyloxy group, can be used in a molecule | numerator. These polymerization initiators are obtained by converting the hydroxyl groups of many alcohol compounds. Among them, brominated, iodide, toluenesulfonated, and trifluoromethylsulfonated by functional group conversion are preferable because of high polymerization initiation efficiency, and alkyl bromide and alkyl toluenesulfonate are particularly preferable.

Moreover, what converted the terminal hydroxyl group of poly (ethylene glycol) into bromine or iodine, or the toluenesulfonyl group can also be used as a polymerization initiator. In that case, it is preferable that the polymerization degree of poly (ethylene glycol) is the range of 5-100, and it is especially preferable if it is the range of 10-50.

Moreover, the pigment | dye which has a functional group which has a cation ring-opening living polymerization initiation capability, and which has a porphyrin skeleton, a phthalocyanine skeleton, or a pyrene skeleton which has the light emission function, energy transfer function, and electron transfer function by light is a polymer obtained Special functions can be given to

The linear precursor polymer is obtained by polymerizing the oxazoline monomer with a polymerization initiator having a monovalent or divalent functional group. As such a polymerization initiator, for example, methyl chloride benzene, methyl benzene bromide, methyl iodide, toluene sulfonate methylbenzene, trifluoromethyl sulfonate methylbenzene, methane bromide, methane iodide, toluene sulfonate or toluene sulfonic anhydride, trifluoro Monovalent ones such as romethylsulfonic anhydride, 5- (4-bromomethylphenyl) -10,15,20-tri (phenyl) porphyrin, or bromomethylpyrene, dibromomethylbenzene, methyliode iodide, di And divalent ones such as bromomethylbiphenylene or dibromomethyl azobenzene. Moreover, linear polyoxazoline used industrially, such as poly (methyl oxazoline), poly (ethyl oxazoline), or poly (methyl vinyl oxazoline), can also be used as a precursor polymer as it is.

The precursor polymer in the form is obtained by polymerizing the oxazoline monomer as described above with a polymerization initiator having a trivalent or higher functional group. Examples of the trivalent or higher polymerization initiator include trivalent ones such as tribromomethylbenzene, tetravalent ones such as tetrabromomethylbenzene, tetra (4-chloromethylphenyl) porphyrin, tetrabromoethoxyphthalocyanine, and hexabromo. And pentavalent or higher ones such as methylbenzene and tetra (3,5-ditosylethyloxyphenyl) porphyrin.

In order to obtain a comb-shaped precursor polymer, a linear polymer having a polyvalent polymerization initiator can be used to polymerize the oxazoline monomer from the polymerization initiator, but for example, a side chain such as an ordinary epoxy resin or polyvinyl alcohol It can also be obtained by halogenating the hydroxyl group of the polymer having a hydroxyl group with bromine, iodine or the like, or converting the toluenesulfonyl group, and using the converted portion as a polymerization initiator.

Moreover, a polyamine type polymerization terminator can also be used as a method of obtaining comb shaped precursor polymer. For example, comb-shaped polyoxazolin is formed by polymerizing oxazoline using a monovalent polymerization initiator and binding the terminal of the polyoxazoline to amino groups of polyamines such as polyethyleneimine, polyvinylamine, and polypropylamine. You can get it.

The hydrolysis of the linear skeleton which consists of polyoxazolines of the precursor polymer obtained by the above may be under all conditions under acidic conditions or alkali conditions.

In hydrolysis under acidic conditions, hydrochloride of polyethyleneimine can be obtained by, for example, stirring polyoxazoline under heating in an aqueous hydrochloric acid solution. By treating the obtained hydrochloride with excess ammonia water, a crystal powder of basic polyethyleneimine can be obtained. Although the hydrochloric acid aqueous solution to be used may be concentrated hydrochloric acid or an aqueous solution of about 1 mol / L, it is preferable to use 5 mol / L hydrochloric acid aqueous solution in order to perform hydrolysis efficiently. In addition, the reaction temperature is preferably around 80 ° C.

Hydrolysis under alkaline conditions can convert polyoxazoline into polyethyleneimine, for example by using aqueous sodium hydroxide solution. After reacting under alkaline conditions, excess sodium hydroxide can be removed by washing the reaction solution with a dialysis membrane, thereby obtaining a crystal powder of polyethyleneimine. The concentration of sodium hydroxide to be used should just be in the range of 1-10 mol / L, and in order to perform more efficient reaction, it is preferable that it is the range of 3-5 mol / L. In addition, the reaction temperature is preferably around 80 ° C.

The amount of acid or alkali used in hydrolysis under acidic conditions or alkaline conditions may be 1 to 10 equivalents relative to the oxazoline units in the polymer, and about 3 equivalents is preferred for improving the reaction efficiency and simplifying the post-treatment. .

By the said hydrolysis, the linear skeleton which consists of polyoxazolines in a precursor polymer turns into a linear polyethyleneimine skeleton, and the polymer which has this polyethyleneimine skeleton is obtained.

In addition, when forming a block copolymer of a linear polyethyleneimine block and another polymer block, the precursor polymer is a block copolymer made of a linear polymer block made of polyoxazolines and another polymer block, and the precursor polymer. It can obtain by selectively hydrolyzing the linear block which consists of polyoxazolines in it.

When the other polymer block is a water-soluble polymer block such as poly (N-propionylethyleneimine), poly (N-propionylethyleneimine) is converted to poly (N-formylethyleneimine) or poly (N-acetylethyleneimine). In comparison, block copolymers can be formed using those having high solubility in organic solvents. That is, after cationic ring-opening living polymerization of 2-oxazoline or 2-methyl-2-oxazoline in the presence of the above-mentioned polymerization initiating compound, the obtained living polymer is further polymerized with 2-ethyl-2-oxazoline to obtain poly (N A precursor polymer comprising a -formylethyleneimine) block or a poly (N-acetylethyleneimine) block and a poly (N-propionylethyleneimine) block is obtained. The precursor polymer is dissolved in water, and an emulsion is formed by mixing and stirring an incompatible organic solvent with water in which a poly (N-propionylethyleneimine) block is dissolved in the aqueous solution. By adding an acid or an alkali to the aqueous phase of the emulsion, the poly (N-formylethyleneimine) block or the poly (N-acetylethyleneimine) block is preferentially hydrolyzed to form a linear polyethyleneimine block and a poly Block copolymers having (N-propionylethyleneimine) blocks can be formed.

When the valence of the polymerization start compound used here is 1 and 2, it will become a linear block copolymer, and if it is more than a valence, a molded block copolymer will be obtained. Moreover, the polymer obtained by making a precursor polymer into a multistage block copolymer can also be set as a multistage block structure.

(Metals, metal ions)

The metal ion in the present invention coordinates with the polyethyleneimine unit in the skeleton to form a metal complex by the strong coordination ability of the polyethyleneimine skeleton in the polymer having the linear polyethyleneimine skeleton. The metal complex is obtained by coordinating metal ions to a polyethyleneimine unit. Unlike the processes of ionic bonding and the like, a complex may be formed by coordinating polyethyleneimine whether the metal is a cation or an anion. Therefore, the metal species of the metal ions are not limited as long as they can coordinate with the polyethyleneimine units in the polymer having a linear polyethyleneimine skeleton, and are not limited to alkali metals, alkaline earth metals, transition metals, semimetals, lanthanide metals, and polyoxometalates. Kinds of metal compounds and the like, and metal ions having these metal species can be preferably used.

As said alkali metal ion, ion, such as Li, Na, K, Cs, is mentioned. As counter anions of alkali metal ions, Cl, Br, I, NO ₃ , SO ₄ , PO ₄ , ClO ₄ , PF ₆ , BF ₄ , F ₃ CSO ₃ and the like can be suitably used.

Examples of alkaline earth metal ions include ions such as Mg, Ba, and Ca.

The transition metal-based ion may be a transition metal cation (M ^{n +} ), an acid radical anion (MOx ^{n −} ) formed by a bond with oxygen, or an anion (MLx ^{n −} ) formed by a halogen bond. It can use suitably. In addition, in this specification, a transition metal refers to Sc, Y of group 3 of periodic table, and the transition metal element in 4th-6th cycle of group 4-12.

As the transition metal cation, the following transition metal cations (M ^{n +} ), for example, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ru, Rh, Pd, Ag Monovalent, divalent, trivalent, or tetravalent cations of Cd, W, Os, Ir, Pt, Au, and Hg. The counter anion of these metal cations may be any of Cl, NO ₃ , SO ₄ , or polyoxometallate anion, or an organic anion of carboxylic acids. However, it is preferable to produce a complex by suppressing a reduction reaction, such as pH which is easy to reduce with polyethyleneimine frame | skeleton, such as Ag, Au, and Pt, to acidic conditions.

In the transition metal anion to as the transition metal anion (MOx ^{n -),} for example, _{MnO 4, MoO 4, ReO 4} , WO 3, RuO 4, CoO 4, anions of _{CrO 4, VO 3, NiO 4} , UO 2 Can be mentioned.

The metal ion of the present invention may be in the form of a metal compound of polyoxometallates in which the transition metal anion is fixed in silica via a metal cation assigned to an ethyleneimine unit in a polymer having a linear polyethyleneimine skeleton. Specific examples of the polyoxometallates include molybdates, tungstates and vanadates in combination with transition metal cations.

In addition, anion (MLx ^{n −} ) containing the following metals, for example, AuCl ₄ , PtCl ₆ , RhCl ₄ , ReF ₆ , NiF ₆ , CuF ₆ , RuCl ₆ , In ₂ Cl ₆ , the metal may be Coordinated anions can also be suitably used for complex formation.

Examples of the semimetal ions include Al, Ga, In, Tl, Ge, Sn, Pb, Sb, and Bi. Among them, Al, Ga, In, Sn, Pb, and Tl are preferable.

Examples of the lanthanum-based metal ions include trivalent cations such as La, Eu, Gd, Yb, and Eu.

The metal in this invention should just be a thing obtained by reducing metal ion, and the said metal ion is mentioned as an example of the metal ion species. Among them, transition metals such as Au, Ag, Cu, Pt, Pd, Mn, Ni, Rh, Co, Ru, Re, and Mo may be preferably used. Among these transition metals, Au, Ag, Pt, and Pd are Since the metal ion is coordinated with polyethyleneimine, it can be preferably used since it is spontaneously reduced at room temperature or in a heated state.

In addition, the metal or metal ion in a composite nanofiber may be 1 type, or 2 or more types may be sufficient as it.

(Silica nanofiber)

The silica nanofibers constituting the composite nanofiber of the present invention have a fiber shape having a thickness of several to several hundred nm, preferably of a thickness of 15 to 100 nm. The length of the fibrous shape of the silica nanofibers is not particularly limited, but is preferably in the range of 0.1 μm to 3 mm. Since the silica nanofibers are formed by coating silica with a crystalline polymer filament formed by a polymer having a linear polyethyleneimine skeleton, the silica nanofibers have a hollow shape.

As silica of this silica nanofiber, the silica obtained by the sol-gel reaction of a well-known conventional silica source can be used.

(Composite nanofiber, metal-containing silica nanofiber)

In the composite nanofiber of the present invention, a polymer having a linear polyethyleneimine skeleton in which at least one metal or metal ion is disposed is contained in the silica nanofiber, and the composite nanofiber is capable of constructing various shapes. to be.

The shape of the composite nanofiber of the present invention is the same as that of the silica nanofibers constituting the composite nanofiber, and has a structure based on a fiber shape having a thickness of about several to several hundred nm, preferably of a thickness of 15 to 100 nm. The composite nanofiber of the present invention can express various shapes by the association of the primary structures as well as the shape of the primary structure. Although the length of the fibrous shape which is the primary structure is not specifically limited, The thing of the range of 0.1 micrometer-3 mm is preferable.

Metal or metal ion in a composite nanofiber exists by coordinating with the polymer which has a linear polyethyleneimine skeleton. Since metal ions coordinate with a polymer having a linear polyethyleneimine skeleton to form a complex, it is considered that the metal complex exists in the hollow silica nanofibers.

In addition, it is thought that metal exists in a silica nanofiber in the state of the crystal which the metal ion which formed the metal complex reduced. The metal can form a wire shape or particle shape via a cluster by reduction. The particle | grains may be in the state which the plurality contacted, and the wire-shaped thing and the particle-shaped thing may be mixed in a silica nanofiber. The thickness of the wire shape or the particle size of the particle shape is of nanometer order smaller than the thickness of the primary structure, and if the wire shape is about 2 to 20 nm, the particle size is about 2 to 20 nm. It is preferable.

The composite nanofiber of the present invention is an assembly having a two-dimensional or three-dimensional spatial shape of a micro-millimeter order by association of the nanofiber shapes (in this specification, the assembly is referred to as a composite nanofiber assembly). Can be formed). The association shape can be adjusted to various shapes, such as a lettuce shape, a fiber shape, a sponge shape, an aster shape, a cactus shape, and a dandelion shape, for example. These association shapes can be controlled by the geometrical shape of the polymer structure having a linear polyethyleneimine skeleton, the molecular weight, the non-ethyleneimine moiety to be introduced into the polymer, and the conditions for forming the crystals formed by the polymer, and the like. The molecular structure, degree of polymerization, composition, and method for producing the polymer crystal of the polymer to be used are particularly affected.

In addition, the composite nanofiber aggregates or the composite nanofiber aggregates are bonded to each other through the composite nanofibers, so that a structure having a macroscopic shape having a size of millimeter order or more (in the present specification, the structure is called a composite structure). ) Can be formed. The outer shape of the structure can be formed into any shape, and can be formed into disc, columnar, plate, filter, film, spherical, rod, etc. according to the requirements of a specific application. It can be processed in various states such as cylinders. Inside the structure, there is an assembly shape of the composite nanofiber assembly, and the assembly is based on the composite nanofiber of the present invention. Therefore, the structure has a three-dimensional network structure in which the composite nanofibers are complex.

The content of silica in the composite nanofiber of the present invention is not particularly limited as long as the above various structures can be formed, but the above various structures can be stably formed in the range of 30 to 80 mass%. In addition, content of a metal or metal ion can be suitably adjusted according to various uses.

In addition, the polymer in the composite nanofiber of the present invention having a reduced metal therein can be easily removed by firing or the like, whereby the nanofiber containing nanoparticles or nanowire-shaped metal in the silica nanofiber (this specification) In particular, the nanofibers may be referred to as metal-containing silica nanofibers). Since the metal-containing silica nanofibers can maintain the aggregate shape and the structure shape when the polymer is removed, the aggregates and structures of the metal-containing silica nanofibers can also be formed.

As described above, the composite nanofibers and the metal-containing silica nanofibers of the present invention have metals or metal ions therein and can form various shapes, and thus, the first half region of nanotechnology, for example, nanometal catalysts and nanoparticles. Wide application can be expected as a metal conductive material, nano metal colorant, nano metal sensor, and medical material. In particular, since the composite nanofiber also includes a polymer having a linear polyethyleneimine skeleton, the composite nanofiber has application potential in fields such as biotechnology and environmentally compatible products.

(Method of producing a composite nanofiber)

In order to manufacture the composite nanofiber of the present invention, it is considered that the shape control of silica and the presence of coordinating molecules capable of concentrating metal ions in the silica are essential. In the production method of the present invention, by using a polymer having a linear polyethyleneimine skeleton as its coordinating molecule, (i) polymers having a linear polyethyleneimine skeleton are associated to form various shapes, and the sol gel is formed on the surface of the assembly of the polymer. By advancing the reaction, silica is fixed, (ii) metal ions are highly concentrated by a polymer having a linear polyethyleneimine skeleton present in the silica, and metal ions are reduced therein as necessary, thereby reducing the metal ions therein. It is possible to realize a composite nanofiber that is contained in and can form various shapes.

In the above (i), since the linear polyethyleneimine skeleton in the polymer having a linear polyethyleneimine skeleton is soluble in water, but exists as an insoluble association at room temperature, the linear polyethyleneimine skeleton portions of the polymers form crystals so as to form a crystal. It can form nanometer-thick crystalline polymer filaments having the properties of. This crystalline polymer filament functions as a template. In addition, many chains of free polyethyleneimine irrelevant to a crystal exist on the surface of the crystalline polymer filament, and these free chains are in a state of hanging on the surface of the crystalline polymer filament. These chains are scaffolds for fixing the silica polymerized in the vicinity thereof and at the same time serve as a catalyst for polymerizing the silica source.

Here, the sol-gel reaction is performed on the surface of the crystalline polymer filament having the linear polyethyleneimine skeleton, thereby producing a polymer-containing silica nanofiber in which the surface of the crystalline polymer filament is coated with silica. At this time, the shape formed by the crystalline polymer filament is copied to the silica, so that the polymer-containing silica nanofiber can construct various shapes that the crystalline polymer filament can induce.

In addition, since the crystalline polymer filament having a linear polyethyleneimine skeleton provides a hydrogel which can be easily controlled in the presence of water, the hydrogel is formed into an arbitrary shape and then crystallized in the hydrogel. The polymer filaments are crosslinked by chemical bonding by a compound having two or more functional groups, and then subjected to a sol-gel reaction, whereby a structure made of polymer-containing silica nanofibers containing individual polymer aggregates in a large silica gel mass is obtained. . Since the external shape of the hydrogel can be formed into various shapes, the structure can be macroscopically shaped.

By contacting the polymer-containing silica nanofibers capable of constructing these various shapes with a metal ion aqueous solution, many metal ions enter the polymer-containing silica nanofibers by the function of (ii), and the metal ions are linear polyethyleneimines in silica. In order to form a coordination bond with the polymer having a backbone, the association of the polymer in the silica nanofibers is disintegrated, and instead, a polymer / metal ion complex is formed, so that the polymer and the metal ion having the linear polyethyleneimine skeleton are separated from the silica nanoparticles. The composite nanofiber contained in a fiber is obtained.

The polymer / metal ion complex is spontaneously reduced there, or reduced by the addition of another reducing agent, converting to metal crystals via metal clusters. When the metal is reduced, the shape of the structure formed by the silica nanofibers or the silica nanofibers does not change, and since the polymer inside the silica nanofibers cannot be discharged from the silica nanofibers, the polymer having a linear polyethyleneimine skeleton is used. The composite nanofiber which contains the polymer and metal which have a linear polyethyleneimine frame | skeleton shape-controlled by a silica nanofiber is obtained.

As a specific method of manufacturing the composite nanofiber of the present invention, the following steps (1) to (3),

(1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton;

(2) contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber;

(3) A step of bringing the polymer-containing silica nanofibers into contact with a solution in which metal ions are dissolved to coordinate metal ions to a linear polyethyleneimine skeleton in the polymer.

Method for producing a composite nanofiber consisting of,

Or the process of following (1)-(4),

(1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton;

(2) contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber;

(3) contacting the polymer-containing silica nanofibers with a solution in which metal ions are dissolved to coordinate metal ions to the linear polyethyleneimine skeleton in the polymer;

(4) reducing the transition metal ions coordinated to the linear polyethyleneimine skeleton in the polymer;

The manufacturing method of the composite nanofiber which consists of these is mentioned.

(Step of Obtaining Crystalline Polymer Filament)

In the production method of the present invention, (1) a polymer having a linear polyethyleneimine skeleton is first dissolved in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of the polymer having a linear polyethyleneimine skeleton. A crystalline polymer filament having a linear polyethyleneimine skeleton which is a template of the composite nanofiber shape of the present invention is formed. Here, the polymer which has a linear polyethyleneimine skeleton which can be used is the same as that mentioned above.

In the polymer having the linear polyethyleneimine skeleton, the linear polyethyleneimine skeleton expresses crystallinity in an aqueous medium to crystallize, and the crystals associate with each other to form a crystalline polymer filament. The crystalline polymer filaments may be in a hydrogel state having a three-dimensional network structure by physical bonding of the crystalline polymer filaments in the presence of water, and chemical crosslinking is achieved by crosslinking the crystalline polymer filaments with a crosslinking agent. It can also be set as the crosslinked hydrogel which has. By using these hydrogels, adjustment of the shape of the composite nanofiber assembly obtained by adjusting the preparation conditions of the hydrogel can be facilitated, and when forming the composite nanofiber structure, control of the external shape becomes easy. It is preferable because of that.

The crystalline polymer filament is obtained by crystallization of a plurality of linear polyethyleneimine skeletons in the primary structure of a polymer having a linear polyethyleneimine skeleton in the presence of water molecules, whereby the polymers are associated with each other and grow in a fibrous form. It is to have.

The crystalline polymer filament has a thickness in the range of about 1 to 100 nm, preferably in the range of 2 to 30 nm, more preferably in the range of 2 to 10 nm, and at least 10 times the length of the fiber, preferably at least 100 times the fibrous shape (hereinafter, The fibrous shape of the crystalline polymer filament may be referred to as a primary shape).

Polyethyleneimines which have been widely used in the past are branched polymers obtained by ring-opening polymerization of cyclic ethyleneimine, and primary amines, secondary amines and tertiary amines exist in the primary structure. Therefore, the branched polyethyleneimine is water-soluble but has no crystallinity. Therefore, in order to make a hydrogel using the branched polyethyleneimine, a network structure must be formed by covalent bonding with a crosslinking agent. However, the linear polyethyleneimine which the polymer used for this invention has as a frame | skeleton is comprised only by secondary amine, The linear amine imine of this secondary amine type can be crystallized while being water-soluble.

It is known that the crystal structure of the linear polyethyleneimine varies greatly depending on the number of crystals contained in the ethyleneimine unit of the polymer (Y. Chatani et al., Macromolecules, 1981, Vol. 14, p. 315-321). Anhydrous polyethyleneimine is superior in crystal structure characterized by a double helix structure, but it is known that when a monomer unit contains two molecules of water, the polymer grows into a crystal characterized by a zigzag structure. In fact, the crystal of linear polyethyleneimine obtained in water is a crystal containing two molecules of water in one monomer unit, and the crystal is insoluble in water at room temperature.

In the present invention, the crystalline polymer filament of the polymer having a linear polyethyleneimine skeleton is formed by crystal expression of a linear polyethyleneimine skeleton as in the case described above, and the polymer is in the form of a linear, star, or comb shape. Even if it is a polymer which has a linear polyethyleneimine skeleton in a primary structure, a crystalline polymer filament is obtained.

The presence of the crystalline polymer filament can be confirmed by X-ray scattering, and the crystalline hydrogel in the vicinity of 20 °, 27 °, and 28 ° is 2θ angle value in a wide-angle X-ray diffractometer (WAXS). This is confirmed by the peak value derived from the chain polyethyleneimine skeleton.

The melting point of the differential scanning calorimeter (DSC) of the crystalline polymer filament also depends on the primary structure of the polymer of the polyethyleneimine skeleton, and the melting point is approximately 45 to 90 ° C.

The crystalline polymer filaments may form a hydrogel having a three-dimensional network structure by physical bonding of the crystalline polymer filaments in the presence of water, and also have a chemical crosslinking by crosslinking the crystalline polymer filaments with a crosslinking agent. Crosslinked hydrogels may also be formed.

In the hydrogel of the crystalline polymer filament, the crystalline polymer filaments associated with each other in the presence of water form a three-dimensional shape of micro to millimeter size (hereinafter, the fine three-dimensional shape may be referred to as a secondary shape). have. Between these secondary shaped associations, the crystalline polymer filaments in the association are further physically associated to form a crosslinked structure, thereby forming a three-dimensional network structure composed of crystalline polymer filaments as a whole. Since they occur in the presence of water, hydrogels containing water are formed in the three-dimensional network structure. When a crosslinking agent is used, the crystalline polymer filaments are chemically crosslinked, and the three-dimensional network structure is a crosslinked hydrogel immobilized by chemical crosslinking.

The three-dimensional network structure referred to here is a network structure formed by physical crosslinking by hydrogen bonding of free ethylene imine chains in which crystalline polymer filaments are present on the surface, unlike ordinary polymer hydrogels. Therefore, at a temperature above the melting point of the crystal, the crystal dissolves in water, and the three-dimensional network structure is also dismantled. However, when it returns to room temperature, the crystalline polymer filament grows, and physical crosslinking is formed between the crystals by hydrogen bonding, so that the three-dimensional network structure appears again.

The secondary shape formed by the crystalline polymer filament in the hydrogel is formed by adjusting the geometrical shape of the polymer structure, the molecular weight, the non-ethyleneimine moiety which can be introduced into the primary structure, and the conditions for forming the crystalline polymer filament. For example, it can control to various shapes, such as a fiber shape, a brush shape, and a property. In addition, the hydrogel can generally maintain its external shape (hereinafter, the external shape of the hydrogel may be referred to as a tertiary shape), but since the hydrogel can be arbitrarily deformed by external force, the shape can be easily controlled. It is.

The crystalline polymer filament is obtained by dissolving a polymer having a linear polyethyleneimine skeleton in a solvent using a property in which a polymer having a linear polyethyleneimine skeleton is insoluble in water at room temperature, and then depositing it in the presence of water.

As a specific method, a polymer having a linear polyethyleneimine skeleton is dissolved in water or a mixed solvent of water and a hydrophilic organic solvent (these are referred to as an aqueous medium in the present specification), and the solution is heated and then cooled, or a linear polyethylene The method etc. which melt | dissolve the polymer which has an imine frame | skeleton in a hydrophilic organic solvent, and add water to the solution are mentioned as an example.

The solvent which melt | dissolves the polymer which has a linear polyethyleneimine skeleton can use an aqueous medium or a hydrophilic organic solvent suitably. As this hydrophilic organic solvent, hydrophilic organic solvents, such as methanol, ethanol, tetrahydrofuran, acetone, dimethylacetamide, dimethyl sulfone oxide, dioxirane, pyrrolidone, are mentioned, for example.

In order to precipitate crystalline polymer filaments from a solution of a polymer having a linear polyethyleneimine skeleton, precipitation occurs in an aqueous medium because the presence of water is indispensable.

In addition, a hydrogel made of crystalline polymer filaments can be obtained by adjusting the amount of the polymer having a linear polyethyleneimine skeleton in the above method. For example, the hydrogel firstly disperses a polymer having a linear polyethyleneimine skeleton in a fixed amount of water and heats the dispersion to obtain a transparent aqueous solution of a polymer having a polyethyleneimine skeleton. Then, it is obtained by cooling a polymer aqueous solution in a heated state to room temperature. The hydrogel is deformed by external forces such as shearing force, but generally has a state such as ice cream that can maintain a shape, and can be deformed into various shapes.

In the said method, 100 degreeC or less is preferable and, as for heating temperature, it is more preferable that it is the range of 90-95 degreeC. The polymer content in the polymer dispersion is not particularly limited as long as it is a range from which a hydrogel is obtained, but is preferably in the range of 0.01 to 20% by mass, and more preferably in the range of 0.1 to 10% by mass in order to obtain a stable hydrogel. . As described above, when the polymer having a linear polyethyleneimine skeleton is used, hydrogel can be formed even at a very small polymer concentration.

By the process of reducing the temperature of the said aqueous polymer solution to room temperature, the secondary shape of the crystalline polymer filament in the hydrogel obtained can be adjusted. If the method of lowering temperature is illustrated, after maintaining an aqueous polymer solution at 80 degreeC for 1 hour, it will be 60 degreeC over 1 hour, and is maintained at that temperature for 1 hour. After that, the temperature was lowered to 40 ° C. over 1 hour, and then naturally cooled to room temperature. The polymer aqueous solution was cooled with ice water at freezing point or methanol / dry ice below freezing point or with acetone / dry ice refrigerant solution. The method of maintaining a state thing in a water bath of room temperature, or the method of lowering temperature to room temperature in said aqueous polymer solution in a room temperature water bath or room temperature air environment, etc. are mentioned.

Since the process of lowering the temperature of the aqueous polymer solution strongly influences the association of the crystalline polymer filaments in the hydrogel obtained, the secondary shapes formed by the crystalline polymer filaments in the hydrogel obtained by the other method are the same. Not.

When the temperature of the aqueous polymer solution is kept constant and the concentration is lowered in multiple steps, the secondary shape formed by the crystalline polymer filament in the hydrogel can be made into a fiber shape. When this is quenched and returned to room temperature, it can be made into the shape of a petal. Moreover, when this is quenched again with acetone in a dry ice state and returned to room temperature, it can be set as a wave form. Thus, the form of the secondary shape which the crystalline polymer filament in the hydrogel of this invention forms can be set to various shapes.

The hydrogel obtained by the above is an opaque gel, in which a crystalline polymer filament made of a polymer having a polyethyleneimine skeleton is formed, and the crystalline polymer filaments are physically crosslinked by hydrogen bonding, and the three-dimensional physical It forms the netting structure. The crystalline polymer filaments in the formed hydrogel remain insoluble at room temperature, but when heated, the crystalline polymer filaments dissociate and the hydrogel is changed into a sol state. Therefore, the physical hydrogel of the present invention can be reversibly changed from sol to gel and from gel to sol by heat treatment.

The hydrogel referred to in the present invention contains at least water in the three-dimensional network structure, but a hydrogel containing an organic solvent is obtained by adding a hydrophilic organic solvent in the preparation of the hydrogel. As this hydrophilic organic solvent, hydrophilic organic solvents, such as methanol, ethanol, tetrahydrofuran, acetone, dimethylacetamide, dimethyl sulfone oxide, dioxirane, pyrrolidone, are mentioned, for example.

It is preferable that it is the range of 0.1-5 times with respect to the volume of water, and, as for content of the organic solvent, it is more preferable if it is the range which is 1-3 times.

By containing the said hydrophilic organic solvent, the form of a crystalline polymer filament can be changed, and the crystal of a different form from a simple aqueous system can be obtained. For example, even in a branched secondary shape having fibrous spread in water, when a certain amount of ethanol is included in the production thereof, a spherical secondary shape such as a fiber shrinkage can be obtained.

In producing the hydrogel according to the present invention, a hydrogel containing a water-soluble polymer is obtained by adding another water-soluble polymer. As the water-soluble polymer, for example, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, poly (N-isopropylacrylamide), polyhydroxyethyl acrylate, polymethyloxazoline, polyethyloxa Sleepy etc. are mentioned.

It is preferable that it is the range of 0.1-5 times with respect to the mass of the polymer which has a linear polyethyleneimine skeleton, and, as for content of a water-soluble polymer, it is more preferable if it is a range which is 0.5-2 times.

By containing the above water-soluble polymer, the form of the crystalline polymer filament can be changed, and a secondary shape of a form different from a simple aqueous system can be obtained. It is also effective in increasing the viscosity of the hydrogel and improving the stability of the hydrogel.

Furthermore, the crosslinked hydrogel in which the crystalline polymer filament surfaces in the hydrogel are linked by chemical bonding can be obtained by treating the hydrogel obtained by the above method with a compound containing at least a bifunctional group reacting with the amino group of polyethyleneimine.

An aldehyde crosslinking agent, an epoxy crosslinking agent, an acid chloride, an acid anhydride, an ester crosslinking agent can be used as a compound containing the bifunctional group which can react with the said amino group at room temperature. As aldehyde crosslinking agent, malonyl aldehyde, succinyl aldehyde, glutaryl aldehyde, phthaloyl aldehyde, isophthaloyl aldehyde, terephthaloyl aldehyde, etc. are mentioned, for example. Moreover, as an epoxy crosslinking agent, polyethyleneglycol diglycidyl ether, bisphenol A diglycidyl ether, glycidyl chloride, glycidyl bromide, etc. are mentioned, for example. Examples of the acid chlorides include malonic acid chloride, succinylic acid chloride, glutaric acid chloride, adipic acid chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, and the like. . In addition, examples of the acid anhydride include phthalic anhydride, succinylic anhydride, glutaric anhydride, and the like. Moreover, as an ester crosslinking agent, a malonyl acid methyl ester, succinylic acid methyl ester, glutaryl acid methyl ester, a phthaloyl acid methyl ester, polyethyleneglycol carboxylic acid methyl ester, etc. are mentioned.

The crosslinking reaction can be performed either by dipping the obtained hydrogel into a solution of the crosslinking agent or by adding a crosslinking agent solution into the hydrogel. At this time, the crosslinking agent penetrates into the hydrogel with the change in the penetration pressure in the system, where the crystalline polymer filaments are connected by hydrogen bonding to cause a chemical reaction of ethyleneimine with the nitrogen atom.

The crosslinking reaction proceeds by reaction with free ethyleneimine on the surface of the crystalline polymer filament, but if the reaction does not occur inside the crystalline polymer filament, the reaction is carried out at a temperature below the melting point of the crystalline polymer filament forming the hydrogel. It is preferable to carry out, and more preferably, the crosslinking reaction is performed at room temperature.

When the crosslinking reaction proceeds at room temperature, the crosslinked hydrogel can be obtained by leaving the hydrogel mixed with the crosslinking agent solution. The time for the crosslinking reaction may be several minutes to several days, and the crosslinking proceeds suitably by leaving it overnight.

The amount of crosslinking agent may be 0.05 to 20% with respect to the number of moles of ethyleneimine units in the polymer having a polyethyleneimine skeleton used for forming the hydrogel, and more preferably 1 to 10%.

The hydrogel can express gel structures of various morphologies because the gelling agent is a crystalline polymer filament. In addition, even a small amount of crystalline polymer filament has a high water retention because it forms a three-dimensional network structure suitably in water. Moreover, the polymer which has a linear polyethyleneimine skeleton to be used is easy for structural design and synthesis | combination, and the manufacture of a hydrogel is simple. In addition, the shape of the hydrogel can be fixed by crosslinking between the crystalline polymer filaments in the hydrogel with a crosslinking agent.

(Step of Obtaining Polymer-Containing Silica Nanofiber)

In the manufacturing method of this invention, following the process of said (1), (2) the nanofiber which coat | covered the said crystalline polymer filament with silica by making the said crystalline polymer filament contact alkoxysilane in presence of water (in this specification, The nanofiber is called a polymer-containing silica nanofiber). In addition, a structure made of polymer-containing silica nanofibers is brought into contact by contacting a silica source in a state where the crystalline polymer filaments are crosslinked with a crosslinking agent, the crystalline polymer filaments form a hydrogel, or the hydrogel is crosslinked with the crosslinking agent. You can get it.

As a method of contacting the crystalline polymer filament and the alkoxysilane, a solution in which a silica source is dissolved is added to a solvent which can be used in a conventional sol-gel reaction in a dispersion of an crystalline polymer filament in water or a hydrogel or a crosslinked hydrogel of a crystalline polymer filament. And sol-gel reaction at room temperature. By this method, a polymer-containing silica nanofiber and a structure of the polymer-containing silica nanofiber can be easily obtained.

As an alkoxysilane used as a silica source, trivalent or more alkoxysilanes (alkoxysilane which has three or more substituents), such as tetraalkoxysilanes and alkyltrialkoxysilanes, are mentioned.

Examples of the tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra-t-butoxysilane and the like.

Examples of the alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane and iso-propyltri. Methoxysilane, iso-propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimeth Methoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropylmethoxysilane, 3-mercaptotriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxy Silane, Phenyltrimethoxysilane, Phenyltriethoxysilane, p-chloromethylphenyl Rime silane, p- chloro and the like on the phenyl triethoxysilane, dimethyl dimethoxysilane, dimethyl diethoxysilane, diethyl dimethoxysilane, diethyl diethoxysilane.

The sol-gel reaction to obtain a polymer-containing silica nanofiber proceeds in the presence of crystalline polymer filaments in an aqueous medium, but the reaction does not occur on an aqueous medium but proceeds on the surface of the crystalline polymer filaments. Therefore, in the complex reaction conditions, the reaction conditions are arbitrary unless the crystalline polymer filaments are dissolved.

In order to make the crystalline polymer filament insoluble, the presence of water in the aqueous liquid containing a hydrophilic organic solvent during the sol-gel reaction is preferably 20% or more, more preferably 40% or more.

In the sol-gel reaction, when the amount of the alkoxysilane which is a silica source is excessive with respect to ethyleneimine which is a monomer unit of polyethyleneimine, a polymer containing silica nanofiber can be suitably formed. As excess degree, it is preferable that it is the range of 2 to 1000 times equivalent amount with respect to ethylene imine.

In addition, it is preferable to make the polymer concentration in the aqueous medium at the time of forming a crystalline polymer filament into 0.1-30% based on the quantity of the polyethyleneimine contained in the polymer. In addition, the amount of polyethyleneimine in the aqueous medium can be set to a concentration exceeding 30% by concentrating in a state where the crystalline form of the crystalline polymer filament is maintained. As a concentration method at this time, the method of performing normal pressure filtration or pressure reduction filtration of the dispersion liquid of the said crystalline polymer filament, the hydrogel of the crystalline polymer filament at normal temperature, etc. can be used.

Although the sol-gel reaction time varies from 1 minute to several days, in the case of methoxysilanes having high reaction activity of the alkoxysilane, the reaction time may be 1 minute to 24 hours, and the reaction efficiency is increased, so that the reaction time is 30 minutes. It is more suitable if it sets to -5 hours. In the case of ethoxysilanes and butoxysilanes having low reaction activity, the sol-gel reaction time is preferably 24 hours or more, and the time is preferably about one week.

The polymer-containing silica nanofiber obtained in this step is composed of the above-mentioned crystalline polymer filament and silica covering the crystalline polymer filament, and its thickness is 10 to 1000 nm, preferably 15 to 100 nm, and the length is thick. It is 10 times or more, preferably 100 times or more.

The silica content of the polymer-containing silica nanofibers varies with a constant width depending on the reaction conditions, but can be in the range of 30 to 90 mass% of the entire polymer-containing silica nanofibers. The content of silica increases with increasing polymer amount used in the sol-gel reaction. Moreover, it increases by lengthening a sol-gel reaction time.

Polymer-containing silica nanofibers are composites having a crystalline polymer filament of a polymer having a straight polyethyleneimine skeleton as a core and the crystalline polymer filaments coated with silica. Therefore, the polymer-containing silica nanofiber can adsorb highly concentrated metal ions by the ethyleneimine unit present in the crystalline polymer filament.

In addition, the polymer-containing silica nanofibers may be associated with each other to form structures having various shapes. The structure consists of polymer-containing silica nanofibers by contacting a silica source in a state in which the crystalline polymer filaments are crosslinked with a crosslinking agent, in which the crystalline polymer filaments form a hydrogel, or in a state in which the hydrogel is crosslinked with the crosslinking agent. Can be obtained. Therefore, the structure has the shape derived from the shape which the hydrogel, crosslinked hydrogel, etc. of said crystalline polymer filament form.

The structure of the polymer-containing silica nanofibers is optionally formed by forming a tertiary shape of a hydrogel or a crosslinked hydrogel formed by the crystalline polymer filament, and then coating the crystalline polymer filament in the hydrogel with silica to form an arbitrary shape. It is a molded structure. In addition, in the structure of the polymer-containing silica nanofibers, since the secondary shape of the aggregate formed in the hydrogel is also copied, the aggregate of the polymer-containing silica nanofibers derived from the secondary shape formed by the crystalline polymer filament. There is an association shape which is formed.

As described above, the structure of the polymer-containing silica nanofibers can be arbitrarily molded because the tertiary shape formed from the crystalline polymer filament can be fixed. In addition, the aggregate shape of the structure of the polymer-containing silica nanofibers has a geometrical shape of the polymer structure of the polymer to be used, a molecular weight, a non-ethyleneimine moiety which can be introduced into the primary structure, and a silica source. Depending on the amount of use, it may have various shapes such as fiber shape, brush shape, appearance, lettuce shape, sponge shape, aster shape, cactus shape, and dandelion shape. The size of these association | aggregate shape can be made into the magnitude | size of about 3 micrometers-about 1 mm. This size shape is a three-dimensional shape formed from the association and spatial arrangement of the polymer-containing silica nanofibers that are the basic unit. The polymer-containing silica nanofibers serving as the basic unit include a core of a crystalline polymer filament. That is, in the structure of the polymer-containing silica nanofibers, crystalline polymer filaments are connected to each other by physical bonding by hydrogen bonding in water, and are arranged in a space to form a three-dimensional template of various shapes, and silica is immobilized along the template. By doing so, it is considered that the polymer-containing silica nanofibers are associated with each other to form a form arranged in the space.

In the structure of the polymer-containing silica nanofibers, the associations of the crystalline polymer filaments are further bonded to each other to fix the physically cross-linked hydrogel with silica, but the polymer structure, the polymer concentration, the amount of the silica source, etc. used are adjusted. Thus, when fixing with silica, the physical crosslinking between the aggregates is cleaved, and the aggregate of the crystalline polymer filament or the plurality of aggregates of the aggregate is immobilized with silica to take out the aggregate of the polymer-containing silica nanofibers. It is also possible.

The association shape of the polymer-containing silica nanofibers is the geometrical shape of the polymer structure when producing the polymer-containing silica nanofibers, the molecular weight, the non-ethyleneimine moiety that can be introduced in the primary structure, and the polymer-containing silica nanofibers. By adjusting the formation conditions and the like of the structure, the aggregate shape in the structure of the polymer-containing silica nanofibers can be adjusted. The association shape largely depends on the molecular structure of the polymer to be used, the degree of polymerization, the composition, and the method of temperature reduction in producing the structure of the polymer-containing silica nanofiber.

For example, a polymer having a linear polyethyleneimine skeleton and having a degree of polymerization of 300 or more linear polyethylenimine is naturally reduced from a temperature of 80 ° C. or higher to room temperature to obtain a hydrogel, and then subjected to a sol-gel reaction using the hydrogel. A composite structure of polymer-containing silica nanofibers having an associative aggregate shape can be obtained. In the lettuce-like association, the thickness of the leaf forming portion becomes thick as the polymer concentration in the polymer solution decreases when crystallizing the polymer, but when the concentration is 2% or more, the thickness of the leaf portion is around 100 nm. At 1% or less, the leaf thickness is around 500 nm.

In addition, when using a polyethylenimine in star form, the secondary shape obtained can also be controlled by changing the structure of the central residue used as the nucleus. For example, when the central moiety has a large pie plane such as porphyrin, the aggregate shape in the structure of the resulting polymer-containing silica nanofibers is an aster shape, and the crystal size of one aster shape is about 2 to 6 µm. . At concentrations above 1%, the number of arms of the aster is small, each arm tends to bind, at lower concentrations the number of arms is high, and each arm tends to fall. In the case of a small structure such that the central moiety is a benzene ring, the associative shape in the structure of the resulting polymer-containing silica nanofibers is a fiber in which many yarns are bound, the fibers are entangled with each other, and the sponge-containing polymer-containing silica nanoparticles as a whole. Form the structure of the fiber. The thickness of one fiber shape is around 150 nm.

Moreover, the structure of the polymer-containing silica nanofibers of various external shapes can also be obtained by using a crosslinked hydrogel crosslinked by chemical bonding between the crystalline polymer filaments. Its shape and size can be the same as the size and shape of the container used at the time of producing the crosslinked hydrogel, and can be produced in any shape, for example, disk, columnar, plate or spherical. Moreover, it can also shape | mold in a desired shape by cutting | disconnecting or shaving a crosslinked hydrogel. By immersing the crosslinked hydrogel thus formed in a solution of a silica source, a structure of a polymer-containing silica nanofiber of any shape can be obtained simply. The time to be immersed in the solution of the silica source varies from 1 hour to 1 week depending on the type of the silica source to be used. Therefore, it is necessary to prepare it appropriately, but in the solution of methoxysilanes, it may be about 1 to 48 hours. In the solution of oxy silanes, about 1 to 7 days are suitable.

As such, the polymer-containing silica nanofibers dissolve a polymer having a linear polyethyleneimine skeleton, precipitate in the presence of water to obtain a crystalline polymer filament, and then easily contact the crystalline polymer filament with an alkoxysilane in the presence of water. It can manufacture. In the production method, it is possible to perform the step of obtaining the polymer-containing silica nanofibers and the sol-gel reaction step of silica in a short time. Moreover, the dispersion liquid of a crystalline polymer filament and the hydrogel of a crystalline polymer filament can be manufactured easily, and the structure of a polymer containing silica nanofiber can be manufactured easily by making the dispersion liquid or a hydrogel contact an alkoxysilane.

(Step of obtaining composite nanofiber)

In the manufacturing method of this invention, following the process of said (2), (3) the said polymer containing silica nanofiber and the solution which the metal ion melt | dissolved are contacted, and a metal ion is coordinated to the linear polyethyleneimine skeleton in the said polymer. By the step, a composite nanofiber containing a polymer having a metal ion and a linear polyethyleneimine skeleton in the silica nanofiber can be obtained.

Here, as the metal ion which can be used, said metal ion can be used. A solution in which metal ions are dissolved can be produced by dissolving a salt containing the metal ions in water.

The method of contacting the polymer-containing silica nanofibers with the solution in which the metal ions are dissolved in the step (3) is not particularly limited. For example, the polymer-containing silica nanofibers obtained by the step (2) may be metal. The method of immersing in the aqueous solution of an ion is mentioned. By this method, metal ions can be simply concentrated in silica nanofibers. Since the metal concentrated in the polymer-containing silica nanofibers forms coordination bonds with the crystalline polymer filaments inside the silica nanofibers, the crystalline polymer filaments in the silica are disintegrated, and instead the polymer and metal ions having a linear polyethyleneimine skeleton This coordinated metal complex is formed. Thereby, the composite nanofiber which contains the polymer which has the metal ion and linear polyethyleneimine skeleton of this invention in a silica nanofiber can be obtained easily.

When the metal ions are concentrated in the silica nanofibers, the more polymers in the polymer-containing silica nanofibers, and the higher the mixing ratio of metal ions to the polymers, the greater the amount of metal ions concentrated in the silica. In the composite nanofiber containing the metal ion of this invention, 0.1-0.5 times of metal ion can form a complex with respect to the number-of-moles of the nitrogen atom of the polyethyleneimine skeleton contained in a polymer containing silica nanofiber.

When obtaining the composite nanofiber containing a metal ion, when immersing a polymer containing silica nanofiber in the aqueous solution of a metal ion, it is especially suitable that the quantity of the metal ion is about 0.1-10 times with respect to an ethyleneimine unit.

After the metal ions enter, the product is taken out and washed with normal temperature or cold water to obtain a composite nanofiber containing the metal ion of the present invention and a polymer having a linear polyethyleneimine skeleton in a silica nanofiber.

Further, following the step (3), the polymer having the linear polyethyleneimine skeleton with the metal is subjected to the step of (4) reducing the transition metal ion coordinated to the linear polyethyleneimine skeleton in the polymer. The composite nanofiber contained in can be obtained.

In the step (3) above, a metal complex in which a polymer having a linear polyethyleneimine skeleton and a metal ion are coordinated in the silica nanofiber is formed by contact between the polymer-containing silica nanofiber and a solution in which metal ions are dissolved. By spontaneously reducing the metal ions or reducing with a reducing agent, a composite nanofiber containing a polymer having a linear polyethyleneimine skeleton with a metal of the present invention in a silica nanofiber is obtained.

In the composite nanofiber containing the reduced metal of this invention, 1-20 times metal atom can be fixed with respect to the number-of-moles of the nitrogen atom of the polyethyleneimine skeleton contained in a polymer containing silica nanofiber.

When obtaining a composite nanofiber containing a metal, when the polymer-containing silica nanofiber is immersed in a metal ion solution, the amount of the metal ion is preferably as excessive as possible with respect to the ethyleneimine unit, and is about 30 times. Suitable.

Among the above metal ions, in particular, metal ions of Au, Ag, Pt, and Pd are coordinated with polyethyleneimine, and then spontaneously reduced at room temperature or in a heated state, so that they are converted into nonionic metal nanoparticles or metal nanowires. It is preferable when obtaining the composite nanofiber of this invention containing a metal. Heating temperature should just be 100 degrees C or less, and it is especially preferable that it is 60-80 degreeC. Therefore, in order to reduce these metal ions, it can be performed only by mixing a polymer containing silica nanofiber with a metal ion solution. That is, the composite nanofiber of this invention containing a metal can be obtained, without going through the process of concentrating a metal ion in silica, and mixing this silica with a reducing agent solution. When maintaining these as metal ions, complex may be produced by suppressing a reduction reaction, such as making pH pH acidic condition.

Further, when the metal is reduced, the composite nanoparticles containing other metal species are mixed by mixing the polymer-containing silica nanofibers with one or more metal ions, concentrating other metal ions simultaneously in the composite, and then reducing their other ions. You can get fiber.

When using a metal that does not spontaneously reduce, such as these metal ions, or a metal whose spontaneous reduction is insufficient, metal crystals can be formed by a step of reducing a metal ion coordinated to a linear polyethyleneimine skeleton by a reducing agent. . Moreover, also when using the said spontaneously reducing metal ion, you may reduce it by using another reducing agent together by the process of said (4) as needed.

Examples of the reducing agent that can be used in the step include hydrogen, sodium borohydride, ammonium borohydride, aldehyde, hydrazine and the like. When the metal ions are reduced using a reducing agent, the reaction can be carried out in an aqueous medium. At this time, the metal ions are concentrated in the polymer-containing silica nanofiber, the silica is washed with water, and then mixed with a reducing agent solution. It is preferable. That is, the composite nanofiber of the present invention can be obtained by reducing only metal ions contained in silica.

When the metal ions coordinated to the linear polyethyleneimine skeleton are reduced, the shape of the polymer-containing silica nanofibers and the association and structure of the polymer-containing silica nanofibers do not change, and the polymer inside the silica nanofibers does not change. Since it cannot flow out from, finally, the composite nanofiber which contains the polymer which has a linear polyethyleneimine skeleton, and at least 1 type of metal in a silica nanofiber is obtained.

The reduced metal turns into metal particles or metal wires via metal clusters inside the silica nanofibers. The metal wire is formed by metal reduction of the concentrated metal ions along the crystalline polymer filament in the polymer containing silica nanofibers.

The reduction reaction time depends on the type of metal ion, but usually 24 hours is sufficient. In room temperature conditions, reaction time is made as long as possible, and heating conditions are basically 1 hour enough, but it is also suitable to set it as several hours according to the kind of metal ion.

In addition, by appropriately adjusting the temperature of the reduction reaction, the size of the metal in the composite nanofiber of the present invention can be adjusted. If the transition metal is in the form of a wire, the thickness is in the range of about 2 to 20 nm and the particle size is 2 to 2 in the form of a particle. The thing of the range of about 20 nm can be formed easily. When controlling the thickness of a wire shape or the particle size of a particle shape below 10 nm, it is preferable to make temperature of a reduction reaction into the temperature of 100 degrees C or less.

As described above, since the production method of the present invention requires little complicated process or dense condition setting, a composite nanofiber containing metal ions or metal in silica can be easily obtained. In addition, since the aggregate shape and structure of the polymer-containing silica nanofibers are maintained as they are, the composite nanofiber aggregates and composite nanofibers composed of composite nanofibers having the same shape as that of the aggregates and structures are used. The composite structure formed can be obtained easily, and the space shape can be controlled easily.

(Method for producing metal-containing silica nanofibers)

Furthermore, after obtaining the composite nanofiber containing the metal and the polymer which has a linear polyethyleneimine frame | skeleton in a silica nanofiber, (5) removing a polymer component in the said composite nanofiber, a composite nanofiber is made into a metal It can be set as containing silica nanofiber.

As a method of removing a polymer component from the composite nanofiber, it can be realized by a method of firing treatment or solvent washing. Since the polymer component can be completely removed, a firing treatment method in a firing furnace is preferable.

As the firing treatment, high temperature firing in the presence of air and oxygen and high temperature firing in the presence of an inert gas such as nitrogen and helium may be used, but firing in air is usually preferred.

As the temperature to be fired, the polymer having a linear polyethyleneimine skeleton which is a polymer component can be thermally decomposed at around 300 ° C, so if the temperature is 300 ° C or higher, it can be suitably removed, and the range of 300 to 900 ° C is particularly suitable.

As a specific baking method, it can carry out according to the well-known method at the time of baking mesoporous silica (Diaz et al. J. Mater. Chem. 2004, Vol. 14, p. 48). In the temperature increase, after leaving a composite sample for 10 to 30 minutes at about 100 degreeC, it heated up to 300 degreeC at the temperature increase rate of 10 degreeC / min, it was left to stand at that temperature for 1 hour, and also heated up to 500 degreeC at the same temperature increase rate. And baking for 1 to 6 hours at the temperature can be exemplified. In addition, in order to raise temperature, you may heat up to 700-800 degreeC at the same temperature increase rate, and may bake for 1 to 6 hours at the temperature. After baking, the temperature of the kiln may be naturally lowered to room temperature, or the temperature may be lowered to room temperature by allowing air to flow in the kiln.

Similarly, by removing the polymer component from the composite nanofiber assembly or composite structure, the assembly of the metal-containing silica nanofibers and the structure of the metal-containing silica nanofibers can be obtained.

As described above, the composite nanofibers and metal-containing silica nanofibers of the present invention have a large surface area possessed by silica nanofibers, excellent molecular selectivity and chemical stability derived from coated silica, and a metal or metal ion therein. Has In addition, since the aspect ratio is very high, it is also possible to form a nonwoven fabric or the like by collecting or stratifying fibers, so that a solid electrolyte, a solid catalyst, a nano additive, a nano thin film material, a nano metal catalyst, and a nano metal Wide application can be expected as a conductive material, a nanometal colorant, a nanometal sensor, a photoimaging material, an optoelectronic material, and a medical material.

In addition, a composite nanofiber containing a polymer having a linear polyethyleneimine skeleton in addition to a metal or a metal ion can easily cationize the ethyleneimine unit in the polymer, and thus, a variety of ionic materials such as anionic biomaterials. Adsorption and immobilization are also possible. In addition, the polymer having the linear polyethyleneimine skeleton can be easily blocked or grafted with other polymers, and the structure of the polymer side chain and the terminal structure can be easily controlled. Since various functions can be imparted to nanofibers, they are also useful materials in the fields of biotechnology and environmental products.

In the composite structure or the structure of the metal-containing silica nanofiber of the present invention, the secondary shape formed by the crystalline polymer filament in the presence of water is further associated to form a crosslinked structure, and thus silica is immobilized along a template connected by a physical bond. , Nano-size composite nanofibers and metal-containing silica nanofibers are associated with each other. Therefore, these structures form a highly aggregated three-dimensional network structure of these nanofibers while maintaining the properties of the composite nanofibers and the metal-containing silica nanofibers, and their shape can be arbitrarily formed to a size of millimeter or more. will be. Since these structures have a three-dimensional network structure therein, they can be usefully used in high performance filters such as biofilters and air filters, or catalysts having a high specific surface area. Moreover, since these structures are easy to control the external structure, and the structure can implement | achieve various fine aggregate shapes, it is a promising material not only for the said use but also as an advanced functional material of various fields.

Therefore, the composite nanofibers, composite structures, and the like are novel composites which completely eliminate the difficulty of shape control in the production of conventional silica materials, and are easy to manufacture. . Moreover, since the composite nanofiber, composite structure, etc. of this invention contain a metal or metal ion inside, it is a useful material not only in the general application area of a silica material but also in the area where a nano-shaped metal or a metal complex is applied.

Hereinafter, although an Example and a reference example demonstrate this invention further more concretely, this invention is not limited to these. Unless otherwise stated, "%" represents "mass%."

[Analysis by X-ray Diffraction Method]

The isolated and dried sample was placed in the holder for the measurement sample, and it was set in a wide-angle X-ray diffractometer "Rint-Ultma" manufactured by Rig Corporation, Cu / K α-ray, 40 kV / 30 mA, scanning speed 1.0 ° / min, The measurement was performed on the conditions of 10-40 degrees of scanning ranges.

[Analysis by Differential Thermal Scanning Calorimetry]

The isolated and dried sample was weighed by a measurement patch, and it was set in the thermal analyzer "DSC-7" made by Perkin Elmer, the temperature rising rate was 10 degreeC / min, and it measured in the temperature range of 20 degreeC-90 degreeC.

[Shape analysis by scanning electron microscope]

The isolated dry sample was placed on a glass slide, and it was observed with a surface observation device VE-7800 manufactured by Gence Corporation.

[Observation by transmission electron microscope]

The isolated and dried sample was placed on a carbon vapor deposited copper grid, and was then placed in a topcon, yellow instrument EM-002B, VOYAGER M3055 high resolution transmission electron microscope, or Nippon Denshi Corporation transmission electron microscope `` JEM-200CX ''. Observed.

[UV-Vis Absorption Spectrum]

The silica powder containing the metal complex was put on the quartz glass plate, and it was measured by U-3500 UV-Vis by Hitachi Co., Ltd. with an integrating sphere.

Synthesis Example 1

[Synthesis of linear polyethyleneimine-containing silica nanofibers (SLP-1)]

<Synthesis of linear polyethyleneimine (L-PEI)>

3 g of commercially available polyethyloxazoline (number average molecular weight 50000, average polymerization degree 5000, manufactured by Aldrich) was dissolved in 15 mL of 5M aqueous hydrochloric acid solution. The solution was heated to 90 ° C. in an oil bath and stirred at that temperature for 10 hours. 50 mL of acetone was added to the reaction solution, the polymer was completely precipitated, filtered, and washed three times with methanol to obtain a white polyethyleneimine powder. When the obtained powder was identified by ¹ H-NMR (heavy water), it was confirmed that the peaks of 1.2 ppm (CH ₃ ) and 2.3 ppm (CH ₂ ) derived from the side chain ethyl group of the polyethyloxazoline were completely lost. . That is, it was shown that the polyethyloxazoline was completely hydrolyzed and converted into polyethyleneimine.

The powder was dissolved in 5 mL of distilled water and 50 mL of 15% aqueous ammonia was added dropwise to the solution while stirring. After the mixture was left overnight, the precipitated polymer aggregate powder was filtered, and the polymer aggregate powder was washed three times with cold water. The crystal powder after washing | cleaning was dried at room temperature in the desiccator, and linear polyethyleneimine (L-PEI) was obtained. The yield was 2.2 g (containing crystal water). Polyethyleneimine obtained by the hydrolysis of polyoxazoline reacts only the side chain and there is no change in the main chain. Therefore, the degree of polymerization of L-PEI is the same as 5000 before hydrolysis.

<Linear polyethyleneimine-containing silica nanofibers>

The L-PEI powder obtained above was weighed in a fixed amount and dispersed in distilled water to prepare an L-PEI dispersion. The dispersion was heated to 90 ° C. in an oil bath to give a completely clear aqueous solution of 1% concentration. The aqueous solution was left to stand at room temperature, and naturally cooled to room temperature, thereby obtaining a hydrogel of an opaque L-PEI aggregate.

As a result of performing X-ray diffraction measurement on the obtained assembly, it was confirmed that peaks of scattering intensity appear at 20.7 °, 27.6 °, and 28.4 °. Moreover, the endothermic peak was confirmed at 64.7 degreeC by the measurement result of the endothermic state change by a calorimetry analyzer. From these measurement results, the presence of L-PEI crystals in the hydrogel was confirmed.

To 5 mL of the hydrogel of the L-PEI aggregate obtained above, 5 mL of a mixed solution of tetramethoxysilane (TMSO) and 1/1 (volume ratio) of ethanol was added thereto, and the mixture was gently stirred for 1 minute, and left for 40 minutes as it was. Thereafter, the resultant was washed with excess acetone and washed three times with a centrifugal separator. The solid was recovered and dried at room temperature to obtain a silica nanofiber structure (SLP-1) containing L-PEI. Scattering intensity peaks appeared at 20.5 °, 27.2 ° and 28.2 ° from the X-ray diffraction measurement of the L-PEI-containing silica nanofiber structure (SLP-1).

The obtained L-PEI-containing silica nanofiber structure (SLP-1) was observed with a scanning microscope, and the L-PEI-containing silica nanofiber structure (SLP-1) was in the form of a leaf-shaped association.

Synthesis Example 2

[Synthesis of Properties Polyethylenimine-containing Silica Nanofibers (SLP-2)]

<Synthesis of Porphyrin-Centered Polyethylenimine (P-PEI)>

Jin et al., J. Porphyrin & Phthalocyanine, 3, 60-64 (1999); Jin, Macromol. Chem. By the method described in Phys., 204, 403-409 (2003), the synthesis of porphyrin-centered polymethyloxazoline as a precursor polymer was carried out as follows.

After replacing a 50 ml two-necked flask with three-way coke with argon gas, 0.0352 g of tetra (p-iodinemethylphenyl) porphyrin (TIMPP) and 8.0 ml of N, N-dimethylacetamide were added and stirred at room temperature, TIMPP was completely dissolved. To this solution, 3.4 ml (3.27 g) of 2-methyl-2-oxazoline corresponding to 1280-fold molar number was added to the porphyrin, and the reaction solution was stirred at a temperature of 100 ° C for 24 hours. After the reaction liquid temperature was lowered to room temperature, 10 ml of methanol was added, and the mixed liquid was concentrated under reduced pressure. The residue was dissolved in 15 ml of methanol and the solution was poured into 100 ml of tetrahydrofuran to precipitate the polymer. By re-precipitation of the polymer in the same manner, after suction filtration, putting the resulting polymer in a desiccator containing P ₂ O _5, the suction and dried for 1 hour astro buffer concentrator. Furthermore, it decompressed with the vacuum pump and dried under vacuum for 24 hours, and obtained precursor polymer (TPMO-P). The yield was 3.05 g and the yield was 92.3%.

The number average molecular weight by GPC of the obtained precursor polymer (TPMO-P) was 28000, and molecular weight distribution was 1.56. Moreover, when ^1- H-NMR calculated the integral ratio of the ethylene proton in a polymer arm and the pyrrole ring proton of porphyrin in a polymer center, the average degree of polymerization of each arm was 290. Therefore, the number average molecular weight by ¹ H-NMR was estimated to be 99900. ^{The fact} that the number average molecular weight value by ¹ H-NMR greatly exceeds the number average molecular weight value in GPC is consistent with that which is a general characteristic of a star polymer.

Using this precursor polymer, polymethyloxazoline was hydrolyzed by the same method as in Synthesis Example 1 to obtain star polyethylenimine (P-PEI) in which four polyethyleneimines were bonded to the porphyrin center. ^{As a result of the 1} H-NMR (TMS external standard, in heavy water) measurement, the 1.98 ppm peak derived from the side chain methyl of the precursor polymer before hydrolysis was completely lost.

<Plastic Polyethylenimine-containing Silica Nanofiber Composite>

Instead of using L-PEI powder in Synthesis Example 1, using P-PEI synthesized above, P-PEI aggregates in a hydrogel state of 1% concentration were obtained by the same method as in Synthesis Example 1.

As a result of performing X-ray diffraction measurement on the hydrogel of the obtained P-PEI aggregate, it was confirmed that peaks of scattering intensity appear at 20.4 °, 27.3 °, and 28.1 °. Moreover, the endothermic peak was confirmed at 64.1 degreeC by the measurement result of the endothermic state change by a calorimetry apparatus. From these measurement results, the presence of P-PEI crystals in the hydrogel was confirmed.

1 mL of a mixed solution of tetramethoxysilane (TMSO) and 1/1 (volume ratio) of ethanol was added to 1 mL of the hydrogel of the P-PEI aggregate thus obtained, and the mixture was lightly stirred for 1 minute, and left for 40 minutes as it was. Thereafter, the resultant was washed with excess acetone and washed three times with a centrifugal separator. The solid was recovered and dried at room temperature to obtain a P-PEI-containing silica nanofiber structure (SLP-2). As a result of X-ray diffraction measurement of the P-PEI-containing silica nanofiber structure (SLP-2), scattering peaks appeared at 20.5 °, 27.4 °, and 28.1 ° as before the silica coating.

When the obtained P-PEI containing silica nanofiber structure (SLP-2) was observed with the scanning microscope, the P-PEI containing silica nanofiber structure (SLP-2) was an aster-shaped association body shape.

Synthesis Example 3

[Synthesis of Properties Polyethylenimine-containing Silica Nanofibers (SLP-3)]

<Synthesis of star-shaped polyethyleneimine (B-PEI) centered on benzene ring>

Jin, J. Mater. According to the method described in Chem., 13, 672-675 (2003), a star polymethyloxazoline in which the arms of six polymethyloxazolines are bonded to the center of the benzene ring as a precursor polymer was synthesized as follows.

In a three-neck test tube in which a magnetic stirrer was set, 0.021 g (0.033 mmol) of hexakis (bromomethyl) benzene was added as a polymerization initiator, and a three-way coke was installed at the inlet of the test tube, and then vacuumed. Nitrogen substitution was performed. Under a stream of nitrogen, 2.0 ml (24 mmol) of 2-methyl-2-oxazoline and 4.0 ml of N, N-dimethylacetamide were added sequentially using a syringe from the inlet of the three-way coke. When the test tube was heated to 60 degreeC on the oil bath, and hold | maintained for 30 minutes, the liquid mixture became transparent. The transparent liquid mixture was further heated to 100 degreeC, and it stirred at that temperature for 20 hours, and obtained precursor polymer. The conversion rate of the monomer was 98% from the ¹ H-NMR measurement of this mixed solution. The average degree of polymerization of the polymer was calculated using this conversion rate, and the average degree of polymerization of each arm was 115. In the molecular weight measurement by GPC, the mass average molecular weight of the polymer was 22700 and the molecular weight distribution was 1.6.

Using this precursor polymer, polymethyloxazoline was hydrolyzed by the same method as in Synthesis Example 1 to obtain a star-like polyethyleneimine B-PEI having six polyethyleneimines bonded to a benzene ring core. ^{As a result of the 1} H-NMR (TMS external standard, in heavy water) measurement, the 1.98 ppm peak derived from the side chain methyl of the precursor polymer before hydrolysis was completely lost.

The obtained polymethyloxazoline was hydrolyzed in the same manner as in Synthesis Example 1 to obtain a polyethylenimine (B-PEI) in which six polyethyleneimines were bonded to the benzene ring core.

<Plastic Polyethylenimine-Containing Silica Nanofiber (SLP-3)>

Instead of using the L-PEI powder in Synthesis Example 1, using the B-PEI synthesized above, by the same method as in Synthesis Example 1, a hydrogel of B-PEI aggregate at a concentration of 1% was obtained. As a result of performing X-ray diffraction measurement on the hydrogel of the obtained B-PEI aggregate, it was confirmed that peaks of scattering intensity appear at 20.3 °, 27.3 °, and 28.2 °. Moreover, the endothermic peak was confirmed at 55.3 degrees by the measurement result of the endothermic state change by a calorimetry analyzer. From these measurement results, the presence of B-PEI crystals in the hydrogel was confirmed.

1 mL of a mixed solution of tetramethoxysilane (TMSO) and 1/1 (volume ratio) of ethanol was added to 1 mL of the hydrogel of the B-PEI assembly thus obtained, and the ice cream was lightly stirred for 1 minute, and left for 40 minutes as it was. did. Thereafter, the resultant was washed with excess acetone and washed three times with a centrifugal separator. The solid was recovered and dried at room temperature to obtain a B-PEI-containing silica nanofiber structure (SLP-3). X-ray diffraction measurements of the B-PEI-containing silica nanofiber structure (SLP-3) showed scattering intensity peaks at 20.5 °, 27.5 °, and 28.3 °.

The obtained B-PEI-containing silica nanofiber structure (SLP-3) was observed with a scanning microscope, and the B-PEI-containing silica nanofiber structure (SLP-3) was a sponge structure in which fiber-like aggregates were collected.

Synthesis Example 4

[Synthesis of linear polyethyleneimine-containing silica nanofibers (SLP-4)]

<Synthesis of Polyethyleneimine (L-PEI2) on Line>

5 g of commercially available polyethyloxazoline (number average molecular weight 500000, average polymerization degree 5000, manufactured by Aldrich) was dissolved in 20 mL of 5 M hydrochloric acid aqueous solution. The solution was heated to 90 ° C. in an oil bath and stirred at that temperature for 10 hours. 50 mL of acetone was added to the reaction solution, the polymer was completely precipitated, filtered, and washed three times with methanol to obtain a white polyethyleneimine powder. When the obtained powder was identified by ¹ H-NMR (heavy water), it was confirmed that the peaks of 1.2 ppm (CH ₃ ) and 2.3 ppm (CH ₂ ) derived from the side chain ethyl group of the polyethyloxazoline were completely lost. That is, it was shown that the polyethyloxazoline was completely hydrolyzed and converted into polyethyleneimine.

The powder was dissolved in 5 mL of distilled water and 50 mL of 15% aqueous ammonia was added dropwise to the solution while stirring. After the mixture was left overnight, the precipitated polymer crystal powder was filtered, and the crystal powder was washed three times with cold water. The crystal powder after washing | cleaning was dried at room temperature in the desiccator, and linear polyethyleneimine (L-PEI2) was obtained. The yield was 4.2 g (containing crystal water). The polyethyleneimine obtained by hydrolysis of polyoxazoline reacts only a side chain, and there is no change in a main chain. Therefore, the degree of polymerization of L-PEI2 is the same as 5000 before hydrolysis.

<Linear polyethyleneimine-containing silica nanofibers>

The L-PEI2 powder obtained above was weighed in a fixed amount and dispersed in distilled water to prepare an L-PEI2 dispersion. The dispersion was heated to 90 ° C. in an oil bath to give a 3% completely clear aqueous solution. The aqueous solution was left to stand at room temperature, and naturally cooled to room temperature to obtain a hydrogel of an opaque L-PEI2 aggregate.

As a result of performing X-ray diffraction measurement on the obtained assembly, it was confirmed that peaks of scattering intensity appear at 20.7 °, 27.6 ° and 28.4 °. Moreover, the endothermic peak was confirmed at 64.7 degreeC by the measurement result of the endothermic state change by a calorimetry analyzer. From these measurement results, the presence of L-PEI2 crystals in the hydrogel was confirmed.

1 mL of the hydrogel of the L-PEI2 aggregate obtained above was prepared in plate form, and it was added to 10 mL of aqueous solution of glutaryl aldehyde (5%), and left to stand at room temperature for 24 hours to obtain a crosslinked hydrogel. The hydrogel before the crosslinking was in an ice cream state, and the mold was arbitrarily changed by the shearing force. However, the crosslinked hydrogel obtained by the chemical crosslinking treatment became a single mass, and the change of the mold due to the shearing force did not occur. The obtained cross-linked hydrogel plate was immersed in 2 mL of a mixed solution of TMSO / EtOH (1/1) for 24 hours, then repeatedly immersed in acetone to be washed, and plate-shaped structure of L-PEI2-containing silica nanofibers (SLP-4 )

(Example 1)

<L-PEI / Gold / Silica Composite Nanofiber>

0.01 g (containing about 3.4 mg of L-PEI) of L-PEI-containing silica nanofiber structure (SLP-1) obtained in Synthesis Example 1 was immersed in an aqueous solution of 1 mL of gold ions (containing 0.02 g of NaAuCl ₄ ), After 30 minutes at room temperature and 30 minutes at 80 ° C., the mixture was washed with distilled water in a centrifuge to obtain L-PEI / gold / silica composite nanofiber. The L-PEI-containing silica nanofiber structure (SLP-1) was white, but the obtained L-PEI / gold / silica composite nanofiber structure was yellow.

In the X-ray diffraction measurement of the composite nanofiber structure, sharp scattering peaks derived from Au were found at 38.1 °, 44.4 °, 64.5 °, and 77.6 °.

The transmission electron micrograph of the obtained composite nanofiber structure was shown in FIG. 1, and the high resolution transmission electron micrograph is shown in FIG. In FIG. 2, the nanowire of the core-shaped gold and the silica layer which coat | covered it were confirmed.

(Example 2)

<L-PEI / Platinum / Silica Composite Nanofibers>

0.015 g (containing about 5.1 mg of PEI) of L-PEI-containing silica nanofiber structure (SLP-1) obtained in Synthesis Example 1 was immersed in an aqueous solution of 1.5 mL of platinum ions (containing 0.034 g of Na ₂ PtCl ₄ ). After 30 minutes at room temperature and 30 minutes at 80 ° C, the mixture was washed with distilled water in a centrifuge to obtain L-PEI / platinum / silica composite nanofibers. The L-PEI-containing silica nanofiber structure (SLP-1) was white, but the obtained composite nanofiber structure was gray.

In the X-ray diffraction measurement of the composite, sharp scattering peaks derived from Pt were found at 40.0 °, 46.4 °, and 67.7 °.

The transmission electron micrograph of the obtained composite nanofiber structure was shown in FIG. 3, and the high resolution transmission electron micrograph is shown in FIG. In FIG. 4, core-shaped platinum nanowires and silica layers covering them were identified.

(Example 3)

<L-PEI / Palladium / Silica Composite Nanofiber>

0.015 g (containing about 5.1 mg of PEI) of L-PEI-containing silica nanofiber structure (SLP-1) obtained in Synthesis Example 1 was contained in an aqueous solution of 1.5 mL of palladium ion (containing 0.025 g of Pd (NO ₃ ) ₂ ). After immersion for 1.5 hours, the silica solid was washed with water. Dispersing the silica solids after washing the hands of 2mL and added to NaBH ₄ solution (containing a reducing agent 0.02g) in 1mL in the dispersion, it was allowed to stand in room temperature for 30 minutes. The solid was washed with distilled water in a centrifuge to obtain an L-PEI / palladium / silica composite nanofiber structure. The L-PEI-containing silica nanofiber structure (SLP-1) was white, but the obtained L-PEI / palladium / silica composite nanofiber was dark gray.

In the X-ray diffraction measurement of the composite, sharp scattering peaks derived from Pd were found at 38.8 °, 45.6 °, and 66.3 °.

(Example 4)

<P-PEI / Gold / Silica Composite Nanofibers>

Using the P-PEI-containing silica nanofiber structure (SLP-2) obtained in Synthesis Example 2, the gold-ion aqueous solution was reduced by the same method as in Example 1, and the P-PEI / gold / silica composite nanofiber structure Got.

In the X-ray diffraction measurement of the obtained composite nanofiber structure, sharp scattering peaks derived from Au were confirmed at 38.0 °, 44.6 °, 64.7 °, and 77.7 °.

The transmission electron micrograph of the obtained composite nanofiber structure was shown in FIG. In FIG. 5, the three-dimensional shape of the assembly in the composite nanofiber structure was confirmed.

(Example 5)

<B-PEI / Gold / Silica Composite Nanofiber>

Using the B-PEI-containing silica nanofiber structure (SLP-3) obtained in Synthesis Example 3, by the same method as in Example 1, the aqueous gold ion solution was reduced to produce the B-PEI / gold / silica composite nanofiber structure. Got.

In the X-ray diffraction measurement of the obtained composite nanofiber assembly, sharp scattering peaks derived from Au were found at 38.3 °, 44.6 °, 64.8 °, and 77.7 °.

(Example 6)

<L-PEI2 / silver / silica composite nanofiber>

0.03 g of plate-like structure (SLP-4) of the L-PEI2 containing silica nanofiber obtained in Synthesis Example 4 was immersed in 4 mL of silver nitrate aqueous solution (1M) for 1 hour at room temperature. Subsequently, the plate was washed with distilled water to obtain a green L-PEI 2 / silver / silica composite nanofiber structure. In the absorption spectrum measurement of the obtained composite nanofiber structure plate, plasmon absorption derived from silver nanocrystals was observed at 420 nm. In addition, scattering peaks derived from silver were found at 38.2, 44.4, 64.6, and 77.5 degrees in the X-ray diffraction measurement.

(Example 7)

<L-PEI / gold, platinum / silica composite nanofiber>

0.02 g (containing about 6.8 mg of PEI) of L-PEI-containing silica nanofiber structure (SLP-1) obtained in Synthesis Example 1 was mixed with 2 mL of gold and platinum ions (0.02 g of NaAuCl ₄ , Na ₂ PtCl ₄ 0.023 g), and the mixture was allowed to proceed for 30 minutes at room temperature and 30 minutes at 80 ° C, and then washed with distilled water in a centrifuge. Changing from white to pale yellow, an L-PEI / gold / platinum / silica composite nanofiber structure was obtained. X-ray diffraction measurements of the composite nanofiber structure showed scattering peaks derived from Au and Pt at 38.1, 40.1, 44.2, 46.4, 64.6, 67.7, and 77.6 °.

(Example 8)

<L-PEI / copper ion / silica composite nanofiber>

50 mg (0.319 mmol) of L-PEI-containing silica nanofiber structures (SLP-1) obtained in Synthesis Example 1 were measured and added to 5 mL of copper nitrate aqueous solution (2 mM). The white structure in the mixture turned blue. After leaving the mixture for 3 hours, the mixture was filtered, washed three times with distilled water, and then dried to obtain a blue L-PEI / copper ion / silica composite nanofiber structure.

As a result of measuring the obtained composite nanofiber structure in an absorption spectrum, strong absorption of the complex formed by copper-nitrogen (Cu-N) coordination was found at 303 nm and 630 nm.

(Example 9)

<L-PEI / Sodium Ion / Silica Composite Nanofiber>

50 mg (0.319 mmol of nitrogen) of the L-PEI-containing silica nanofiber structure (SLP-1) obtained in Synthesis Example 1 was measured and added to 5 mL of triflate sodium NaSO ₃ CF ₃ aqueous solution (2 mM). After leaving the mixture for 3 hours, the mixture was filtered, washed three times with distilled water, and then dried to obtain an L-PEI / sodium ion / silica composite nanofiber structure.

In the WAXS measurement of the L-PEI / sodium ion / silica composite nanofiber structure after drying, the diffraction pattern derived from L-PEI in the L-PEI-containing silica nanofiber structure (SLP-1) disappears, and instead, 21 °, Diffraction patterns appeared at 32 ° and 37 °. In addition, melting point was found at 169 ℃ in DSC observation. From this, it was found that a complex of L-PEI and sodium ions was formed in the silica nanofibers.

Claims (28)

A composite nanofiber comprising at least one metal or metal ion and a polymer having a linear polyethyleneimine skeleton in a silica nanofiber. The method of claim 1, A composite nanofiber obtained by coordinating the at least one metal or metal ion with a polymer having a linear polyethyleneimine skeleton. The method of claim 1, The composite nanofiber of the polymer having a linear polyethyleneimine skeleton is a chain, star-shaped, or comb-shaped polymer. The method of claim 1, The composite nanofiber in which the polymer having a linear polyethyleneimine skeleton consists of a block copolymer of a linear polyethyleneimine block and another polymer block. The method of claim 1, The composite nanofiber in which the ratio of the polyethyleneimine skeleton in the polymer which has the said linear polyethyleneimine skeleton is 40 mol% or more. The method of claim 1, The composite nanofiber in which content of silica exists in 30 to 80 mass%. The method of claim 1, Composite nanofibers having a thickness in the range of 15 to 100 nm. The method of claim 1, And said at least one metal or metal ion is at least one metal ion selected from alkali metal ions, alkaline earth metal ions, transition metal ions, semimetal ions, lanthanum metal ions and polyoxometalates. The method of claim 1, Composite nanofiber wherein the at least one metal or metal ion is a transition metal. The method of claim 9, Said transition metal is at least one metal crystal selected from Au, Ag, Cu, Pt, Pd, Mn, Ni, Rh, Co, Ru, Re, Mo. The method of claim 9, Composite nanofiber having the transition metal has a nanowire shape or nanoparticle shape. The composite nanofiber assembly as described in any one of Claims 1-11 which mutually associates. The method of claim 12, The composite nanofiber assembly, wherein the assembly is a mesh-like assembly. A composite structure comprising the composite nanofiber aggregates according to claim 12 associated with each other. The metal containing silica nanofiber formed by removing the polymer in the composite nanofiber of any one of Claims 9-11. The metal-containing silica nanofiber assembly in which the metal-containing silica nanofibers according to claim 15 are associated with each other. The metal containing silica nanofiber structure in which the metal containing silica nanofiber assembly of Claim 16 associates with each other. (1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton; (2) contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber; (3) A method for producing a composite nanofiber comprising the step of bringing the polymer-containing silica nanofibers into contact with a solution in which metal ions are dissolved and coordinating metal ions to a linear polyethyleneimine skeleton in the polymer. (1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton; (2) contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber; (3) a step of bringing the polymer-containing silica nanofibers into contact with a solution in which metal ions are dissolved to coordinate metal ions to a linear polyethyleneimine skeleton in the polymer; (4) A method for producing a composite nanofiber comprising the step of reducing transition metal ions coordinated to a linear polyethyleneimine skeleton in the polymer. The method of claim 18 or 19, The said alkoxysilane is a trivalent or more alkoxysilane manufacturing method of the composite nanofiber. The method of claim 18 or 19, The composite nano in which the amount of the alkoxysilane to be brought into contact with the crystalline polymer filament in the step (2) is in the range of 2 to 1000 times the amount of the ethyleneimine unit of the polymer having the linear polyethyleneimine skeleton forming the crystalline polymer filament. Method of making fibers. The method of claim 18 or 19, A method for producing a composite nanofiber, wherein the alkoxysilane is one or two selected from the group consisting of tetraalkoxysilanes and trialkoxyalkylsilanes. The method of claim 18 or 19, A method for producing a composite nanofiber, wherein the polymer having a linear polyethyleneimine skeleton is a chain, star, or comb polymer. The method of claim 18 or 19, A method for producing a composite nanofiber in which the polymer having a linear polyethyleneimine skeleton consists of a block copolymer of a linear polyethyleneimine block and another polymer block. The method of claim 18 or 19, The manufacturing method of the composite nanofiber whose ratio of the polyethyleneimine skeleton in the polymer which has the said linear polyethyleneimine skeleton is 40 mol% or more. The method of claim 18 or 19, A method for producing a composite nanofiber, wherein the metal ion is a transition metal ion. The method of claim 26, And said transition metal ion is at least one transition metal ion selected from Au, Ag, Cu, Pt, Pd, Mn, Ni, Rh, Co, Ru, Re, Mo. (1) a step of dissolving a polymer having a linear polyethyleneimine skeleton in a solvent, followed by precipitation in the presence of water to obtain a crystalline polymer filament of a polymer having a linear polyethyleneimine skeleton; (2) contacting the crystalline polymer filament with an alkoxysilane in the presence of water to coat the crystalline polymer filament with silica to obtain a polymer-containing silica nanofiber; (3) a step of bringing the polymer-containing silica nanofibers into contact with a solution in which metal ions are dissolved to coordinate metal ions to a linear polyethyleneimine skeleton in the polymer; (4) reducing the transition metal ions coordinated to the linear polyethyleneimine skeleton in the polymer to obtain a composite nanofiber; (5) The manufacturing method of the metal containing silica nanofiber which consists of a process of removing the polymer component in the said composite nanofiber.

Images