JP2004099385A - Metallic thin wire-including thin film and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic thin wire-including thin film with a metallic thin wire uniformly arranged and having sufficient aspect ratio. <P>SOLUTION: The metallic thin wire-including thin film is composed of a mesoporous silica thin film having ≤1 μm film thickness and 1-50 nm central fine pore diameter and the metallic thin wires formed in the fine pores of the mesoporous silica thin film and having 1-50 nm average diameter and the average aspect ratio of ≥5. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１９】
得られた実施例５〜８の金属細線包接薄膜のＴＥＭ写真を図７〜１０に示した。図７は、実施例５で得られた金で構成された棒状の金属細線を有する金属細線包接薄膜のＴＥＭ写真である。この金属細線は、平均直径が６．８ｎｍであり、アスペクト比が５以上であり、長さ２００ｎｍを超えるものもあることが確認された。
【０１２０】
図８は、実施例６で得られた銀で構成された棒状の金属細線を有する金属細線包接薄膜のＴＥＭ写真である。この金属細線は、平均直径が６．９ｎｍであり、平均アスペクト比が約１０であり、長さ１５０ｎｍ以上のものもあることが確認された。
【０１２１】
図９は、実施例７で得られたニッケルで構成された棒状の金属細線を有する金属細線包接薄膜のＴＥＭ写真である。この金属細線は、平均直径が７．０ｎｍであり、平均アスペクト比が約１０であり、長さ１５０ｎｍ以上のものであることが確認された。
【０１２２】
図１０は、実施例８で得られた銅で構成された棒状の金属細線を有する金属細線包接薄膜のＴＥＭ写真である。この金属細線は、平均直径が６．５ｎｍであり、アスペクト比が５以上であり、長さ１００ｎｍ以上のものであることが確認された。
【０１２３】
【発明の効果】
以上説明したように、本発明によれば十分なアスペクト比を有し、配列が均一な金属細線を備える金属細線包接薄膜を得られる。この結果、金属細線の両端に電極をつけることで使用する量子素子又は触媒等への応用が可能となる。
【図面の簡単な説明】
【図１】メソポーラスシリカ薄膜の細孔内に形成された金属細線のそれぞれの形状を示す模式図である。
【図２】実施例１で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率２０万倍）を示す図である。
【図３】比較例１で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率１０万倍）を示す図である。
【図４】実施例２で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率２５万倍）を示す図である。
【図５】実施例３で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率１０万倍）を示す図である。
【図６】実施例４で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率１０万倍）を示す図である。
【図７】実施例５で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率１０万倍）を示す図である。
【図８】実施例６で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率１５万倍）を示す図である。
【図９】実施例７で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率７万３千倍）を示す図である。
【図１０】実施例８で得られた金属細線包接薄膜の走査型電子顕微鏡写真（倍率７万３千倍）を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin metal wire inclusion film and a method of manufacturing the same, and more particularly, to a thin metal wire inclusion film suitable for a quantum device, a catalyst, and the like, and a method of manufacturing the same.
[0002]
[Prior art]
Research on template synthesis of metal fine wires and metal particles in powder carriers having mesopores such as FSM-16, MCM-41, and HMM-1 has been actively conducted in recent years (for example, see Non-Patent Document 1). . In such a metal thin wire, there is a social demand for obtaining a thinner and longer metal thin wire. Such fine metal wires and metal particles are considered to exhibit unique behavior in physical properties and chemical reactivity, and are synthesized into magnetic materials such as nanodevices and storage media by synthesizing regularly arranged fine metal wires and metal particles. The application of is expected. In addition, since the metal is finely divided, the specificity of the surface is expressed as macro physical properties with an increase in the proportion of atoms present on the surface of the particle, and it shows characteristics different from those of bulk metal, so it can be used as a catalyst. The application of is also expected.
[0003]
On the other hand, with respect to such a fine metal wire, for example, in Japanese Patent Application Laid-Open No. 2002-102698 (Patent Document 1), the pores of a powdery porous body having pores having a center pore diameter of 1 to 50 nm are disclosed. Discloses that a fine metal wire having an average diameter of 1 to 50 nm and an average aspect ratio of 3 or more is formed.
[0004]
However, even if a fine metal wire is produced using a powdery porous body as described in the above-mentioned publication, processing for application to a device is difficult with a powder, and it has a sufficient aspect ratio and an arrangement of It has been difficult to produce uniform fine metal wires.
[0005]
[Patent Document 1]
JP 2002-102698 A
[Non-patent document 1]
A. Fukuoka, Y. Sakamoto, M. {Ichikawa} et al. , @J. {Am. {Chem. $ Soc, $ 14, $ 3373 (2001)
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems of the related art, and has an object to provide a thin metal wire cladding thin film having a sufficient aspect ratio and having a uniform array of thin metal wires, and a method of manufacturing the same. And
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, it has been surprising that a mesoporous silica thin film is used as a carrier for supporting metal ions, and a metal is supported in the thin film by a specific method. In particular, they have found that a thin metal wire inclusion thin film having a sufficient aspect ratio and having a uniform array of thin metal wires can be obtained, thereby completing the present invention.
[0008]
That is, the metal thin wire inclusion thin film of the present invention has a thickness of 1 μm or less, and a mesoporous silica thin film having a center pore diameter of 1 to 50 nm,
A fine metal wire having an average diameter of 1 to 50 nm formed in the pores of the mesoporous silica thin film and an average aspect ratio of 5 or more;
It is characterized by having.
[0009]
In the metal thin wire inclusion thin film of the present invention, the mesoporous silica thin film preferably has a pore having a 2d-hexagonal structure, a 3d-hexagonal structure, or a cubic structure.
[0010]
Further, in the thin metal wire cladding thin film of the present invention, the shape of the thin metal wire in the pore is a rod shape, a bead shape in which the spherical portions are connected in the longitudinal direction, or a predetermined distance in the longitudinal direction of the rod shape portion. A necklace shape having a spherical portion formed by the above, or a rod-shaped, rosary-shaped or necklace-shaped metal wire is two-dimensionally or three-dimensionally combined with a net-like shape. preferable.
[0011]
Further, in the thin metal wire cladding thin film of the present invention, the metal constituting the thin metal wire is selected from the group consisting of a group 8 metal, a group 9 metal, a group 10 metal, a group 11 metal, chromium and manganese. Preferably, the material is at least one selected metal.
[0012]
In addition, the first method for producing a thin metal wire clathrate thin film of the present invention comprises a solution containing a mesoporous silica thin film having a thickness of 1 μm or less and having a central pore diameter of 1 to 50 nm and ions of a predetermined metal. And a metal ion supporting step of supporting the metal ions inside and outside the pores of the mesoporous silica thin film,
The metal ions supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step were brought into contact with the vapor of the reducing agent in a state where the metal ions were left without being removed, and the metal ions were introduced into the pores of the mesoporous silica thin film. A reducing agent introducing step of introducing the reducing agent vapor,
A photoreduction step of irradiating the mesoporous silica thin film obtained from the reducing agent introduction step with light to reduce the metal ions, and forming a thin metal wire made of the metal in pores of the mesoporous silica thin film,
Is included.
[0013]
In the first method for producing a thin metal wire clathrate thin film according to the present invention, (i) a vacuum evacuation step of evacuating water in pores of the mesoporous silica thin film before the reducing agent introduction step, (ii) A) a water vapor introduction step of introducing water vapor into the pores of the mesoporous silica thin film before the reducing agent introduction step; and (iii) a water vapor introduction step on the surface of the mesoporous silica thin film before the metal ion supporting step. It is preferable that the method further includes at least one of a hole forming step of providing a new through-hole connecting the outside and the outside.
[0014]
In addition, the second method for producing a thin metal wire clathrate thin film of the present invention comprises a solution containing a mesoporous silica thin film having a thickness of 1 μm or less and having a central pore diameter of 1 to 50 nm and ions of a predetermined metal. And a metal ion supporting step of supporting the metal ions inside and outside the pores of the mesoporous silica thin film,
The metal ions supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step were brought into contact with the vapor of the reducing agent in a state where the metal ions were left without being removed, and the metal ions were introduced into the pores of the mesoporous silica thin film. A reducing agent introducing step of introducing the reducing agent vapor,
A heat reduction step of applying heat to the mesoporous silica thin film obtained from the reducing agent introduction step to reduce the metal ions, and forming a thin metal wire made of the metal in pores of the mesoporous silica thin film,
Is included.
[0015]
In the second method for producing a thin metal wire clathrate thin film of the present invention, (i) a vacuum evacuation step of evacuating water in pores of the mesoporous silica thin film before the reducing agent introduction step, (ii) A) a water vapor introduction step of introducing water vapor into the pores of the mesoporous silica thin film before the reducing agent introduction step; and (iii) a water vapor introduction step on the surface of the mesoporous silica thin film before the metal ion supporting step. It is preferable that the method further includes at least one of a hole forming step of providing a new through-hole connecting the outside and the outside.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
[0017]
(Mesoporous silica thin film)
The mesoporous silica thin film according to the present invention has a thickness of 1 μm or less and a center pore diameter of 1 to 50 nm. The mesoporous silica thin film is a porous silica body having mesopores, and in the case of a thin film, the thickness is 1 μm or less, more preferably 0.1 to 0.5 μm, and the thickness with respect to the surface area. Is a state that can be neglected, and is used in a sense different from a bulky state of a substance such as crystals or solids on a lump. When the thickness of such a mesoporous silica thin film exceeds 1 μm, the uniformity of the pore arrangement of the mesoporous silica thin film is deteriorated, and cracks tend to occur due to distortion of the film shrinkage during firing. However, a mesoporous silica thin film having a thickness of 1 μm or less is produced, and a mesoporous silica thin film having a uniform pore arrangement is laminated again by forming a mesoporous silica thin film thereon, and such lamination is repeated. Thereby, a laminated thin film having a thickness of 1 μm or more can be manufactured.
[0018]
The central pore diameter is a curve (pore diameter distribution curve) obtained by plotting a value (dV / dD) obtained by differentiating the pore volume (V) by the pore diameter (D) against the pore diameter (D). The pore diameter at the maximum peak. The pore size distribution curve can be determined by the method described below. That is, the mesoporous silica thin film is cooled to liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, the adsorption amount is determined by a constant volume method or a weight method, and then the pressure of the introduced nitrogen gas is gradually increased. The adsorption amount of nitrogen gas is plotted against each equilibrium pressure to obtain an adsorption isotherm. Using this adsorption isotherm, a pore size distribution curve can be obtained by a calculation method such as the Cranston-Inklay method, the Pollimore-Heal method, or the BJH method. In the mesoporous silica thin film according to the present invention, if the central pore diameter is less than 1 nm, the metal ion-containing solution is less likely to be introduced into the pores, making it difficult to carry metal ions. If it exceeds, the porosity of the thin film becomes excessively large, and the strength of the thin film becomes insufficient.
[0019]
Such a mesoporous silica thin film is prepared by using a surfactant as a template and using a silicon alkoxide or the like as a silica source. As such a silica source, any compound capable of forming a -Si-O- bond can be used. Not limited. Such a thin film is made of, for example, silicon oxide, and has a highly crosslinked network structure based on a skeleton -Si-O- in which silicon atoms are bonded via oxygen atoms. In such a silicon oxide, at least a part of the silicon atoms may form a carbon-silicon bond at two or more positions of the organic group. Examples of such an organic group include, but are not limited to, divalent or higher valent organic groups generated by removing two or more hydrogens from hydrocarbons such as alkanes, alkenes, alkynes, benzenes, and cycloalkanes. Instead, the organic group may have an amide group, amino group, imino group, mercapto group, sulfone group, carboxyl group, ether group, acyl group, vinyl group, or the like. In such a mesoporous silica thin film, aluminum, titanium, magnesium, zirconium, tantalum, niobium, molybdenum, cobalt, nickel, gallium, beryllium, yttrium, lanthanum, hafnium, tin, lead, vanadium, It may contain an inorganic component such as boron.
[0020]
Further, the mesoporous silica thin film according to the present invention preferably has one or more peaks at a diffraction angle corresponding to a d value of 1 nm or more in X-ray diffraction measurement. Such a peak of X-ray diffraction means that a periodic structure having a d value corresponding to the peak angle is present in the sample. Therefore, the presence of one or more peaks at the diffraction angle corresponding to the d value of 1 nm or more means that the pores are regularly arranged at intervals of 1 nm or more.
[0021]
Further, the pores of the mesoporous silica thin film according to the present invention are formed not only on the surface of the thin film but also inside the thin film. The arrangement state of the pores (pore arrangement structure or structure) in such a thin film is not particularly limited, but is preferably a 2d-hexagonal structure, a 3d-hexagonal structure or a cubic structure. Further, such a pore arrangement structure may have a disordered pore arrangement structure.
[0022]
Here, that the thin film has a hexagonal pore arrangement structure means that the arrangement of the pores in the thin film is a hexagonal structure (S. Inagaki, et al., J. Chem. Soc., Chem. Commun. , 680, 1993; S. Inagaki, et. Al., Bull. Chem. Soc. Jpn., 69, 1449; 1996, Q. Huo et al., Science, 268, 1324, 1995)). Further, that the thin film has a cubic pore arrangement structure means that the arrangement of the pores in the thin film is a cubic structure (J. C. Vartuli et al., Chem. Mater., 6, 6, 2317, 1994; {Q. {Huo et al., Nature, {368, 317, {1994}). Further, that the thin film has a disordered pore arrangement structure means that the arrangement of the pores is irregular (P.T.Tanev.et.al.,. Science, .267, .865, .1995; S.A. {Bagshaw et al., Science, 269, 1242, 1995; R. Ryo et al., J. Phys. Chem., 100, 17718, 1996). Further, it is preferable that the cubic structure has Pm-3n, Im-3m or Fm-3m symmetry. The symmetry is determined based on the notation of a space group.
[0023]
When the thin film has a regular pore arrangement structure such as hexagonal or cubic, not all of the pores need to have these regular pore arrangement structures. That is, the thin film may have both a regular pore arrangement structure such as hexagonal and cubic and a disordered irregular pore arrangement structure. However, it is preferable that 80% or more of all the pores have a regular pore arrangement structure such as hexagonal or cubic.
[0024]
Further, as the mesoporous silica thin film according to the present invention, a thin film having a peak showing the (100) plane in X-ray diffraction measurement of 50,000 cps or more and a half-value width of the peak of 0.21 ° or less is used. Is preferred. Further, the intensity of the peak is more preferably 56000 cps or more, and the half width of the peak is more preferably 0.20 ° or less. Such a mesoporous silica thin film is particularly excellent in the crystallinity, the smoothness of the surface of the pores, and the orientation of the pores, and is suitable for producing a thin metal wire inclusion thin film. In such X-ray diffraction measurement, the intensity and half width of the peak (present at a Bragg angle of 0.17 ° to 3.54 °) indicating the (100) plane of the mesoporous silica thin film are measured by using an RAD-B (manufactured by Rigaku Corporation). ) Can be performed under the conditions of a radiation source CuKα, an X-ray tube voltage of 30 kV, and an X-ray tube current of 20 mA. In performing such a measurement, it is preferable that the entrance slit and the light receiving slit have DS: 0.5, SS: 0.5, and RS: 0.3.
[0025]
Further, the mesoporous silica thin film according to the present invention has an initial intensity (I) of a peak showing the (100) plane in X-ray diffraction measurement.₁) And a mesoporous silica thin film are coated with an acidic solution (15 wt% chloroplatinic acid (H₂PtCl₆) An acidic solution having a pH of 0.6 obtained by mixing an aqueous solution, water, and ethanol at a volume ratio of 1: 2: 2) for 24 hours, and after the acid resistance test, the peak intensity (I₂) Is the following relational expression (1):
(1- (I₂/ I₁)) × 100 ≦ 90 ° (1)
It is preferable to use one that satisfies the following. Such a mesoporous silica thin film has sufficient acid resistance, and is excellent in the smoothness of the surface of the pores and the orientation of the pores, and is suitable for producing a thin metal wire inclusion thin film. Here, (1- (I₂/ I₁)) × 100 (%) indicates a reduction rate (%) after the acid resistance test. I before and after such acid resistance test₁And I₂By comparing the relationship with the above, the acid resistance of the mesoporous silica thin film can be evaluated. Such a reduction rate is more preferably 70% or less, and further preferably 40% or less.
[0026]
The acid resistance test is a test in which a mesoporous silica thin film is sufficiently dried and then impregnated with the acidic solution for 24 hours. The X-ray diffraction measurement of the mesoporous silica thin film before and after such an acid resistance test was performed by using RINT-2000 (manufactured by Rigaku Corporation) as an X-ray diffractometer with an X-ray tube voltage of 40 kV and an X-ray tube current of 30 mA. Except for this, the measurement can be performed under the same conditions as in the X-ray diffraction measurement.
[0027]
(Method for producing mesoporous silica thin film)
The mesoporous silica thin film according to the present invention comprises a partial polymerization step of reacting a silica source such as the silicon alkoxide described above in an acidic solvent to obtain a liquid containing a silicon alkoxide partial polymer, and a solution of the silicon alkoxide partial polymer and a surfactant. To form a complex comprising the silicon alkoxide partial polymer and the surfactant, and a thin film for forming a mesoporous silica thin film by thinning and drying a liquid containing the complex. And a forming step. Hereinafter, a method for producing a mesoporous silica thin film will be described in detail using silicon alkoxide as an example of a silica source.
[0028]
In the partial polymerization step, a liquid containing a silicon alkoxide partial polymer is obtained by reacting a silicon alkoxide in an acidic solvent. Here, the silicon alkoxide is represented by the following general formula (2).
A_(4-a)-Si- (OR)_a(2)
[In the formula (2), R represents a hydrocarbon group, A represents a hydrogen atom, a halogen atom, a hydroxyl group or a hydrocarbon group, and a represents an integer of 1 to 4. ]
[0029]
In the general formula (2), examples of the hydrocarbon group represented by R include a chain, cyclic, and alicyclic hydrocarbon group. Such a hydrocarbon group is preferably a chain alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group or an ethyl group. When A is a hydrocarbon group, examples of the hydrocarbon group include an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a phenyl group, and a substituted phenyl group. it can. The silicon alkoxide represented by the general formula (2) may be used alone or in combination of two or more.
[0030]
As the silicon alkoxide represented by the general formula (2), a mesoporous silica thin film having good crystallinity can be obtained.₃)₄And Si (OC) represented by the formula:₂H₅)₄It is preferable to use tetraethoxysilane (TEOS) represented by
[0031]
The alkoxyl group (-OR) of the silicon alkoxide undergoes hydrolysis under acidic conditions to become a hydroxyl group (-OH), and the hydroxyl group portion is condensed to have a high molecular weight. When the silicon alkoxide has a hydroxyl group or a halogen atom in addition to the alkoxyl group, these functional groups may contribute to the hydrolysis reaction. Therefore, the silicon alkoxide partial polymer is a polymer obtained by a hydrolysis reaction and a condensation reaction, and a part of the alkoxyl group (—OR) and / or the hydroxyl group (—OH) remains unreacted. Polymer.
[0032]
The silicon alkoxide partial polymer can be obtained by stirring silicon alkoxide in an acidic solvent (an aqueous solution of hydrochloric acid, nitric acid or the like, or an alcohol solution or the like). Examples of the acid contained in the acidic solvent include boric acid, bromic acid, fluoric acid, sulfuric acid, and phosphoric acid in addition to the above-mentioned acids, and two or more of these acids may be used as a mixture. . Since the hydrolysis reaction of the alkoxyl group of the silicon alkoxide tends to occur in a low pH region, it is possible to promote partial polymerization by lowering the pH of the system. The reaction temperature in the partial polymerization step can be, for example, 15 to 25 ° C., and the reaction time can be 30 to 90 minutes.
[0033]
Next, in the complex forming step, the silicon alkoxide partial polymer obtained in the partial polymerization step is brought into contact with a surfactant to form a complex comprising the silicon alkoxide partial polymer and the surfactant. Let me know.
[0034]
Such surfactants may be cationic, anionic, or nonionic, and specifically include alkyltrimethylammonium, alkylammonium, dialkyldimethylammonium, and benzylammonium. Chloride, bromide, iodide or hydroxide; fatty acid salts, alkyl sulfonates, alkyl phosphates, polyethylene oxide nonionic surfactants, primary alkylamines and the like.
[0035]
Among the above surfactants, examples of the polyethylene oxide-based non-ionic surfactant include a polyethylene oxide-based non-ionic surfactant having a hydrocarbon group as a hydrophobic component and polyethylene oxide as a hydrophilic portion. . As such a surfactant, for example, a compound represented by the general formula C_nH_{2n + 1}(OCH₂CH₂)_mThose represented by OH, wherein n is 10 to 30 and m is 1 to 30, can be suitably used.
[0036]
In addition, as such a surfactant, an ester of sorbitan with a fatty acid such as oleic acid, lauric acid, stearic acid, or palmitic acid, or a compound in which polyethylene oxide is added to these esters can also be used.
[0037]
Furthermore, a triblock copolymer type polyalkylene oxide can also be used as such a surfactant. Such a surfactant comprises polyethylene oxide (EO) and polypropylene oxide (PO), and has a general formula (EO)_x(PO)_y(EO)_xAre represented. x and y each represent the number of repetitions of EO and PO, but x is preferably 5 to 110, y is preferably 15 to 70, x is 13 to 106, and y is more preferably 29 to 70.
[0038]
As the above triblock copolymer, (EO)₁₉(PO)₂₉(EO)₁₉, (EO)_Thirteen(PO)₇₀(EO)_Thirteen, (EO)₅(PO)₇₀(EO)₅, (EO)_Thirteen(PO)₃₀(EO)_Thirteen, (EO)₂₀(PO)₃₀(EO)₂₀, (EO)₂₆(PO)₃₉(EO)₂₆, (EO)₁₇(PO)₅₆(EO)₁₇, (EO)₁₇(PO)₅₈(EO)₁₇, (EO)₂₀(PO)₇₀(EO)₂₀, (EO)₈₀(PO)₃₀(EO)₈₀, (EO)₁₀₆(PO)₇₀(EO)₁₀₆, (EO)₁₀₀(PO)₃₉(EO)₁₀₀, (EO)₁₉(PO)₃₃(EO)₁₉, (EO)₂₆(PO)₃₆(EO)₂₆Is mentioned. These triblock copolymers are available from BASF, Aldrich, and the like, and can provide a triblock copolymer having desired x and y values at a small-scale production level. The above triblock copolymers can be used alone or in combination of two or more.
[0039]
Further, a star diblock copolymer in which two polyethylene oxide (EO) chains-polypropylene oxide (PO) chains are bonded to two nitrogen atoms of ethylenediamine, respectively, can also be used. Such a star diblock copolymer has a general formula ((EO)_x(PO)_y)₂NCH₂CH₂N ((PO)_y(EO)_x)₂Are represented. Here, x and y represent the number of repetitions of EO and PO, respectively, x is preferably 5 to 110, y is preferably 15 to 70, x is 13 to 106, and y is 29 to 70. preferable.
[0040]
Among such surfactants, a mesoporous silica thin film having high crystallinity can be obtained._pH_{2p + 1}N (CH₃)₃] (Preferably a halide salt). In this case, the alkyl group in the alkyltrimethylammonium preferably has 8 to 18 carbon atoms. Such materials include octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, decyltrimethylammonium bromide, and octyltrimethylammonium bromide.
[0041]
When the silicon alkoxide partial polymer is brought into contact with the surfactant, a surfactant may be directly added to the liquid containing the silicon alkoxide partial polymer, and water, an organic solvent, water and an organic solvent may be added. It may be added after being dissolved in a mixture with a solvent to form a surfactant solution. Further, an acid may be added to the surfactant solution to form a preferable acidic atmosphere. As such an acid, it is possible to use the same acid as that used for the above-mentioned acidic solvent.
[0042]
When the surfactant or the surfactant solution is added to the liquid obtained by the partial polymerization step, the surfactant forms micelles in the solution. The micelle serves as a supramolecular template, and a complex of the silicon alkoxide partial polymer and the surfactant micelle is formed. Since the silicon alkoxide partial polymer does not enter the inside of such a surfactant micelle, the inside of the micelle becomes a pore portion in a mesoporous silica thin film which is a final product. Therefore, the pore diameter of the mesoporous silica thin film can be controlled by changing the molecular chain length of the surfactant.
[0043]
The molar ratio between the silicon alkoxide partial polymer and the surfactant is such that the surfactant is 0.005 to 0.02 mol with respect to 0.1 mol of the silicon alkoxide since a highly crystalline mesoporous silica thin film is obtained. Is preferred. The complex formation step can be performed, for example, by stirring at 10 to 30 ° C. for 30 to 90 minutes. In addition, the amount of the solvent at this time is preferably mixed at a ratio of 0.2 to 10 mol with respect to 0.1 mol of silicon alkoxide, and more preferably at least 0.2 mol of water in the solvent. If the amount of such a solvent is less than the lower limit, silicon alkoxide tends to be difficult to condense in a chain form, and if it exceeds the upper limit, the concentration of silicon alkoxide in the liquid containing the complex and The viscosity of the solution decreases, and when the liquid containing the composite is allowed to adhere to the substrate, cissing is observed and a uniform thin film tends to be hardly formed.
[0044]
The liquid containing the complex in the complex forming step has an acid concentration of 0.00057 to 0.0086 eq / l, and the acid content of the liquid containing the complex is 0.1 mol based on 0.1 mol of silicon alkoxide. 2.3 × 10^-4~ 3.8 × 10^-4It is preferably mol. Hereinafter, unless otherwise specified, the acid concentration is the concentration of the acid in the liquid containing the complex, and the acid content is the amount of the substance of the acid with respect to 0.1 mol of the silicon alkoxide in the liquid containing the complex. And The concentration of the acid is more preferably 0.00059 to 0.0080 eq / l, and the content of the acid is 2.4 × 10^-4~ 3.5 × 10^-4More preferably, it is mol. The mesoporous silica thin film prepared under such conditions is particularly excellent in crystallinity, smoothness of the surface of the pores, acid resistance and orientation of the pores, and is suitable for producing a thin metal wire inclusion thin film. is there. When the content of such an acid is less than the lower limit, the rate of hydrolysis and the rate of polycondensation become slow, and it tends to be difficult to prepare a mesoporous silica thin film. The resulting mesoporous silica thin film tends to have insufficient crystallinity, smoothness of pore surface, acid resistance and pore orientation.
[0045]
Further, the crystal structure of the obtained mesoporous silica thin film can be controlled by the composition of the composite. For example, when tetramethoxysilane is used as the silicon alkoxide and alkyltrimethylammonium chloride is used as the surfactant, when the amount of tetramethoxysilane is 1 mol, the amount of alkyltrimethylammonium chloride is 0.04. By setting it to 0.15 mol, the crystal structure can be hexagonal. On the other hand, when the amount of tetramethoxysilane is 1 mol and the amount of alkyltrimethylammonium chloride is 0.15 to 0.19 mol, the crystal structure can be made cubic.
[0046]
Next, a thin film forming step will be described. In the thin film forming step, the liquid containing the composite is thinned and dried to form a mesoporous silica thin film. The method of thinning is not particularly limited. For example, a film having a uniform thickness can be formed by attaching or applying a liquid containing the composite on a substrate. As such a substrate, the shape and the material are not particularly limited as long as the liquid containing the composite can be attached or applied, and examples thereof include a plate-like molded product and a film made of metal, resin, and the like. Can be Grooves or projections may be formed on the surface of the substrate with a certain periodicity, or may be flat.
[0047]
When applying the liquid containing the composite to the substrate, the method is not particularly limited, and various coating methods can be adopted. For example, it can be applied using a bar coater, a roll coater, a gravure coater, or the like. In addition, dip coating, spin coating, spray coating and the like are also possible.
[0048]
In the thin film forming step, the relative humidity when the liquid containing the composite is thinned is not particularly limited, but is preferably 50% or more because the crystallinity is further improved.
[0049]
When the liquid containing the composite is applied to a substrate or the like, the applied thickness can be appropriately selected depending on the concentration. In order to prevent cracking due to distortion during heat shrinkage and to efficiently perform heating and drying after coating, it is preferable that the coating thickness is thin, for example, 10 μm in an undried state (a liquid state including a composite). The following is preferred.
[0050]
Preferably, the method further includes a solvent addition step of adding a solvent to the liquid containing the complex before the thin film formation step. By adding the solvent, the viscosity and the solid content of the liquid containing the composite are reduced, so that the thickness obtained when the liquid is thinned can be reduced. In addition, the change in viscosity of the liquid during thinning can be reduced, and the uniformity of the pore arrangement of the obtained mesoporous silica thin film can be improved. The solvent to be added to the liquid containing the complex in the solvent addition step is not particularly limited, and includes, for example, water and alcohol. As the alcohol, methanol, ethanol, isopropanol and the like can be used. The amount of the solvent added to the liquid containing the complex in the solvent addition step is not particularly limited, but is preferably an amount such that the viscosity of the liquid after the addition becomes 10 Pa · s or less, and is preferably 5 Pa · s or less. It is more preferable that the amount is small.
[0051]
After thinning by a method such as coating on a substrate, the resulting thin film is air-dried and / or dried by heating to react the composite, thereby forming a mesoporous silica thin film containing a surfactant. At the time of heating and drying, for example, heating is performed at 70 to 150 ° C., more preferably 100 to 120 ° C., and the condensation reaction of the silicon alkoxide partial polymer is advanced to form a three-dimensional crosslinked structure. As a result, a mesoporous silica thin film containing a surfactant is obtained. The time for heating and drying can be set to, for example, 20 to 80 minutes in consideration of the time for improving the crystallinity of the mesoporous silica thin film containing a surfactant and economical problems.
[0052]
The thickness of the surfactant-containing mesoporous silica thin film obtained in the thin film forming step is preferably 1 μm or less, more preferably 0.1 to 0.5 μm. If the film thickness exceeds 1 μm, the uniformity of the pore arrangement of the mesoporous silica thin film tends to deteriorate. However, after a mesoporous silica thin film having a thickness of 1 μm or less was prepared, a liquid containing the composite was applied again and dried by heating to form a mesoporous silica thin film having a highly uniform pore arrangement. Can be set to 1 μm or more.
[0053]
The center pore diameter of the mesoporous silica thin film containing a surfactant is 1 to 50 nm, more preferably 1 to 30 nm, since a thin film having high crystallinity and an appropriate specific surface area can be obtained. More preferably, it is 1 to 10 nm.
[0054]
Further, it is preferable that the method further includes a surfactant removing step of removing the surfactant from the surfactant-containing mesoporous silica thin film to obtain a mesoporous silica thin film after the thin film forming step. The method of removing the surfactant is not particularly limited, and for example, a method of baking or a method of treating with a solvent such as water or alcohol can be used. In the firing method, a mesoporous silica thin film containing a surfactant is fired at 300 to 1000C, preferably 300 to 600C. The heating time may be about 30 minutes, but it is preferable to heat for 1 hour or more to completely remove the surfactant component. The calcination can be performed in the air, and may be performed by introducing an inert gas such as nitrogen. In addition, it is preferable that the baking is performed in an oxygen-containing atmosphere having an oxygen concentration of 0.1% to 25% and at a temperature of 300 ° C to 600 ° C.
[0055]
When removing the surfactant from the surfactant-containing mesoporous silica thin film using a solvent, for example, the surfactant-containing mesoporous silica thin film is immersed in a solvent having high surfactant solubility. Water, ethanol, methanol, acetone and the like can be used as the solvent.
[0056]
When a cationic surfactant is used, a method in which a mesoporous silica thin film containing a surfactant is immersed in ethanol or water to which a small amount of hydrochloric acid is added and heated at 50 to 70 ° C can be used. By this method, a cationic surfactant can be extracted. When an anionic surfactant is used, the surfactant can be extracted in a solvent to which an anion has been added. When a nonionic surfactant is used, it is possible to extract only with a solvent. In addition, it is also possible to apply an ultrasonic wave at the time of extraction.
[0057]
As described above, the mesoporous silica thin film from which the surfactant has been removed is suitable as a template (host material) for forming a thin metal wire in a thin metal wire inclusion film described later.
[0058]
(Metal thin wire inclusion thin film)
The metal thin wire inclusion thin film of the present invention, the mesoporous silica thin film, and a fine metal wire having an average diameter formed in the pores of the mesoporous silica thin film is 1 to 50 nm, and the average aspect ratio is 5 or more. , Is provided. The average diameter is more preferably 1 to 30 nm, further preferably 1 to 15 nm. Further, the average aspect ratio is more preferably 10 or more, and further preferably 30 to 10,000. Further, the length of such a thin metal wire is preferably 100 nm or more, and more preferably 300 nm or more. Furthermore, it is more preferable that such a thin metal wire is continuously formed in the pores of the thin film in a densely packed state throughout the pores.
[0059]
When the average diameter of such a thin metal wire is less than 1 nm, durability and heat resistance become insufficient when used as a quantum element (quantum thin wire) and a catalyst. On the other hand, when the average diameter of the fine metal wire exceeds 50 nm, the ratio of surface atoms in the fine metal wire is reduced, and the specificity of the fine metal wire surface is hardly expressed as macro physical properties. When the average aspect ratio of the thin metal wire is less than 5, the effect of improving the catalytic activity becomes insufficient because a selective crystal plane hardly appears, and the length is not sufficient for application to quantum devices and the like. Will be enough. Furthermore, when the length of the thin metal wire is less than the lower limit, the length tends to be insufficient for application to quantum devices and the like.
[0060]
The average diameter and average aspect ratio of the fine metal wires according to the present invention are the average values of the diameter and the aspect ratio (length / diameter) of 20 fine metal wires randomly extracted in a transmission electron micrograph, respectively. Say.
[0061]
Further, the shape of the fine metal wires in the pores may be a rod shape (a) as shown in FIG. 1, a bead shape in which spherical portions are connected in the longitudinal direction (b), or spaced apart at a predetermined interval in the longitudinal direction of the rod portions. (C), or a net (d) (e) in which the rod-shaped, rosary-shaped or necklace-shaped thin metal wires are two-dimensionally or three-dimensionally connected. Is preferred. It is more preferable that such rod-shaped (a), rosary-shaped (b), and necklace-shaped (c) thin metal wires are arranged in parallel without contacting the thin metal wires in adjacent pores.
[0062]
When the shape of the thin metal wire is a rod shape (a), a rosary shape (b), and a necklace shape (c), and the thin metal wires are arranged in parallel, there is a mesoporous space between the thin metal wires. The present inventors presume that the presence of the pore wall of the silica thin film results in electrical insulation. Also, when such parallel metal thin wires are used as a magnetic material, each thin wire becomes a single magnetic domain, and magnetic domain reversal due to interference between adjacent magnetic domains is suppressed. There is a possibility that the magnetic recording material will have a high recording density.
[0063]
In addition, a net-like metal wire (d) or (e) formed by two-dimensionally or three-dimensionally connecting rod-shaped, rosary-shaped or necklace-shaped metal fine wires is a quantum device exhibiting unprecedented physical properties and chemical behavior. The present inventors speculate that, when used as a catalyst, the catalyst has characteristic catalytic activity such as having reaction selectivity and sufficiently high heat resistance.
[0064]
The atoms constituting the thin metal wires are not particularly limited as long as they are metal atoms, but may be selected from metals belonging to Group 8, metals belonging to Group 9, metals belonging to Group 10, metals belonging to Group 11, chromium (Cr) and manganese (Mn). More preferably, it is at least one metal selected from the group consisting of noble metal atoms.
[0065]
In the present invention, the raw material compound used for forming the fine metal wire is not particularly limited. For example, when forming the fine metal wire of the above metal, a salt or a complex salt of the above metal can be used. More specifically, as a raw material compound for a platinum fine metal wire, H₂PtCl₆, Pt (NO₂)₂(NH₃)₂, [Pt (NH₃)₆] Cl₄, H₂Pt (OH)₆, PtCl₂(NH₃)₂, Pt (NH₃)₄Cl₂, Pt (NH₃)₄(OH)₂, Pt (NH₃)₄(OH)₄, K₂PtCl₄, PtCl₄, PtCl₂And the like.
[0066]
As described above, the thin metal wire clathration thin film of the present invention has a sufficient aspect ratio and can obtain a thin metal wire having a uniform arrangement, and is suitable for a quantum device, a catalyst, and the like. Such a thin metal wire clathration thin film can be produced by the production method described below.
[0067]
(Production method of metal thin wire inclusion thin film)
The first method for producing a thin metal wire clathrate thin film of the present invention comprises a mesoporous silica thin film having a thickness of 1 μm or less and having a central pore diameter of 1 to 50 nm and a solution containing ions of a predetermined metal. Contacting and supporting the metal ions inside and outside the pores of the mesoporous silica thin film; and the metal supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step. A reducing agent introducing step of bringing the reducing agent vapor into the pores of the mesoporous silica thin film by contacting with a reducing agent vapor in a state where the ions are left without being removed, and obtained from the reducing agent introducing step. The metal ions are reduced by irradiating light to the mesoporous silica thin film to form a thin metal wire made of the metal in pores of the mesoporous silica thin film. A light reduction step that is a method which comprises a.
[0068]
First, the metal ion supporting step will be described. Using a mesoporous silica thin film as a carrier, as a method of supporting metal ions inside and outside the pores of such a thin film, the raw material compound of the fine metal wire is methanol, alcohol such as ethanol, water, benzene or the like. By dissolving in these mixtures and impregnating the solution (hereinafter, referred to as a supporting solution or a solution containing metal ions) with the mesoporous silica thin film, and bringing the solution into contact with the thin film, the pores of the mesoporous silica thin film and Predetermined metal ions can be supported outside the pores.
[0069]
The metal ion-containing solution preferably has a concentration of the raw material compound in the solution of 0.1 to 50% by weight, more preferably 1 to 20% by weight. If the concentration of such a metal ion-containing solution is less than the lower limit, the amount of metal ions carried in the metal ion carrying step described below tends to be insufficient, while if the concentration exceeds the upper limit, metal When the ion-containing solution becomes more acidic and the —Si—O— skeleton of the mesoporous silica thin film collapses, it tends to be difficult to form a fine metal wire. The impregnation time of the mesoporous silica thin film into such a metal ion-containing solution is preferably 6 hours or more, and more preferably 15 to 48 hours. If the impregnation time is less than the lower limit, the metal ions are insufficiently supported, and it tends to be difficult to form thin metal wires.
[0070]
Here, the metal ion means a metal salt or complex salt or the like as a raw material compound dissociated in a solution, and usually refers to a charged atom or a group of atoms. When the complex salt dissociates, a complex ion is generated. Further, usually, in an aqueous solution, a metal ion exists as an aqua complex. Also, when the carrier liquid adheres to the inside and outside of the pores of the thin film due to contact with the thin film and the solvent evaporates or volatilizes, the metal ions are present in a stable state such as a metal salt or a complex salt as a raw material compound. Inferred. However, in the production method of the present invention, it is difficult to clearly determine the state of their presence in each production step, and thus the metal ions, complex ions, salts, and complex salts are collectively referred to as metal ions. It is assumed that.
[0071]
In the metal ion supporting step, it is also possible to apply ultrasonic waves to the solution impregnating the thin film in order to promote the supporting of the metal ions in the pores. Also, in addition to such a method, a method in which a raw material compound of a solid thin metal wire and a mesoporous silica thin film are mixed in a solid phase, heated in a closed vessel, and then an excess raw material compound is removed by washing or the like, It is also possible to use a material that generates a vapor such as a metal alkoxide or a material that easily sublimates as a raw material and contact the vapor with a mesoporous silica thin film to introduce the raw material compound into the pores of the mesoporous silica thin film. is there.
[0072]
In addition, before the metal ion supporting step, the method may further include a hole forming step of providing a new through hole connecting the inside of the pore and the outside on the surface of the mesoporous silica thin film. Here, the through hole may be a hole or a cut connecting the inside of the pore and the outside, and the shape is not particularly limited. There is no particular limitation on the method of providing a new through-hole (opening). For example, a method of making a cut of about 1 mm or 0.5 mm on the surface of the mesoporous silica thin film with a razor or the like is possible. Conventionally, mesoporous silica (porous silica) supporting metal ions is in the form of a powder, and the surface of the particles has a large area in contact with the external space, and the pores of the porous silica also have an area in contact with the external space. It was wide. However, a part of the mesoporous silica thin film used in the method for producing a thin metal wire inclusion thin film of the present invention is in contact with the substrate. Therefore, the area where the pore contacts the space outside the pore is small. Therefore, when metal ions are supported, since the metal ions are unlikely to enter the pores, it is possible to support a large amount of metal ions in the pores by providing such new through holes. Become.
[0073]
Further, it is preferable to provide an evacuation step as at least a step before the metal ion supporting step. The mesoporous silica thin film easily adsorbs water when left in the air. In particular, the hexagonal structure of the mesoporous silica thin film has extremely long and thin pores. Therefore, once the water is physically adsorbed, the water at the back of the pores cannot easily go out. Therefore, when water is adsorbed in the pores of the thin film, it becomes difficult for the metal ion-containing solution to enter the pores, and the metal ions tend to be hardly carried in the pores.
[0074]
Next, the reducing agent introduction step will be described. In the reducing agent introducing step, the metal ions supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step are brought into contact with a reducing agent vapor in a state where they remain without being removed, and the mesoporous The reducing agent vapor is introduced into the pores of the silica thin film. In the case of producing a thin metal wire inclusion thin film as described above, if reduction is performed with the carrier liquid remaining outside the pores (the thin film surface) of the mesoporous silica thin film, a metal is deposited on the thin film surface and used for a quantum device or the like. It is presumed to be undesirable. Therefore, after impregnating the thin film with the carrier liquid, the metal ion-containing solution attached to the thin film surface is wiped off with absorbent cotton or the like, and then the reducing agent vapor is introduced into the pores of the thin film to reduce the metal ions. The present inventors speculated.
[0075]
However, from the above assumptions, when the present inventors reduce the metal ions by irradiating the metal ion-containing solution with light in a state where the metal ion-containing solution does not remain on the thin film surface, only the metal ions carried in the pores are reduced. Was reduced, and it was difficult to deposit metal densely in the pores. Thus, the present inventors performed a photoreduction step in a state where the metal ions carried outside the pores were not removed and remained, whereby metal was deposited on the surface of the thin film. In addition to finding a thin metal wire inclusion film of the present invention in which a thin metal wire is formed, a method for producing the thin metal wire inclusion film of the present invention was found. The metal deposited on the surface of the thin film can be easily removed by, for example, gently wiping with a cotton soaked with alcohol.
[0076]
In the method for producing a thin metal wire inclusion thin film according to the present invention, the metal is densely packed in the pores by performing the photoreduction step in a state where the metal ions carried outside the pores are left without being removed. The reason why a thin metal wire was obtained is not clear, but as the solvent of the metal ion-containing solution supported outside the pores evaporates, the concentration of metal ions increases, And since the outside of the pores is filled (connected) with this solution, the concentration of metal ions in the pores also increases. That is, the metal carried outside the pore moves into the pore. The present inventors speculate that, by this, a fine metal wire in which metal was densely packed in the pores could be obtained.
[0077]
Such a state in which the metal ions are left without being removed specifically means that the metal ion-containing solution is 1 cm on the thin film surface.²Preferably, 0.1 to 700 μl is attached, more preferably 1 to 500 μl. When the amount of such a metal ion-containing solution is less than the lower limit, the metal ion-containing solution does not uniformly adhere to the surface of the thin film, and the metal ions enter the pores of the thin film when reducing the metal ions. The supply amount becomes discontinuous, and it tends to be difficult to form a thin metal wire. On the other hand, if the upper limit is exceeded, the metal ion-containing solution tends not to stay on the surface of the thin film and spill from the surface of the thin film. The amount of the metal ion-containing solution attached can be measured with a micropipette.
[0078]
The amount (μg) of metal ions carried inside and outside the pores of the thin film (entire thin film) is 1 cm in the entire thin film.²It is preferably carried at 0.001 μg or more, more preferably at 0.01 μg or more. If the amount of metal ions carried in such an entire thin film is less than the lower limit, the amount of metal ions carried outside the pores into the pores is insufficient, and the metal is densely packed in the pores. A fine metal wire that is clogged cannot be produced, and tends to be metal particles.
[0079]
The amount of the reducing agent introduced is preferably 1/20 to 1/3, more preferably 1/15 to 1/5, and more preferably 1/12 to 1/8 of the saturated vapor pressure of the reducing agent. More preferably, Examples of such a reducing agent include alcohols such as methanol, ethanol, and isopropyl alcohol. Among them, methanol is preferable because of its strong reducing power.
[0080]
It is preferable that the method further includes, before the reducing agent introducing step, a water vapor introducing step of introducing water vapor into pores of the mesoporous silica thin film. By providing such a steam introduction step, the present inventors have found that more metal is precipitated in the pores by introducing metal ions existing outside the pores into the pores together with the steam. Guess. The introduction amount of such steam is not preferable because it is considered that when the steam is introduced to the saturated vapor pressure, the steam introduced into the pores becomes liquid and the metal ions are pushed out of the pores. Preferably, it is more preferably about half.
[0081]
Further, it is preferable to provide an evacuation step as at least a step before the reducing agent introduction step. The mesoporous silica thin film easily adsorbs water when left in the air. In particular, the hexagonal structure of the mesoporous silica thin film has extremely long and thin pores. Therefore, once the water is physically adsorbed, the water at the back of the pores cannot easily go out. When water is adsorbed in the pores and the pores become wet as described above, the amount of the reducing agent introduced decreases, and the reduction tends to be insufficient in the photoreduction step described below. Then, by putting the mesoporous silica thin film in a vacuum device and evacuating it, it is possible to surely reduce the metal ions.
[0082]
As a method for introducing the vapor of the reducing agent and the water into the pores of the mesoporous silica thin film, first, the mesoporous silica thin film is put in a vacuum device to be in a vacuum state. The vapor of the reducing agent and water having the above vapor pressure can be introduced into the liquid while controlling the pressure with a needle valve of the container. As such a vacuum device, a device capable of controlling the temperature is more preferable.
[0083]
Next, the photoreduction step will be described. The photoreduction step is a step of irradiating the mesoporous silica thin film obtained from the reducing agent introducing step with light to reduce metal ions, and forming a thin metal wire made of the metal in pores of the mesoporous silica thin film. . The light used for light irradiation is not particularly limited, but is preferably ultraviolet light. For such light irradiation, a high-pressure mercury lamp or the like can be used, and the irradiation time is not particularly limited as long as the metal ions are reduced.
[0084]
Hereinafter, the mechanism of forming the thin metal wire will be described. For example, when chloroplatinic acid is used as a raw material compound, the chemical formula of chloroplatinic acid is H₂PtCl₆And H in aqueous solution⁺And (PtCl₆)^2-Divided into ions. This solution is impregnated with a mesoporous silica thin film to support metal ions in the pores. Thereafter, when an alcohol such as methanol or isopropyl alcohol is introduced into the pores of the thin film, a metal carbonyl [Pt₃(CO)₆]_n ^2-Further, the carbonyl group is removed by light irradiation, and the platinum metal Pt⁰Is reduced to Then, crystal nuclei are generated first, and then discrete granular fine metal wires are formed, and the crystals are aggregated over time to form a fine metal wire. By controlling the speed of such reduction and the speed of assembling, it is also possible to control the shape of the thin metal wire or metal particle.
[0085]
When producing the thin metal wire cladding film in this way, the metal thin wire envelope obtained by the first production method of the present invention, in which the metal ions outside the pores of the mesoporous silica thin film are reduced in a state where they remain without being removed, are reduced. The contact thin film has a sufficient aspect ratio and is provided with fine metal wires having a uniform arrangement.
[0086]
In the second method for producing a thin metal wire clathrate thin film of the present invention, a mesoporous silica thin film having a thickness of 1 μm or less and having a center pore diameter of 1 to 50 nm and a solution containing ions of a predetermined metal are used. Contacting and supporting the metal ions inside and outside the pores of the mesoporous silica thin film; and the metal supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step. A reducing agent introducing step of bringing the reducing agent vapor into the pores of the mesoporous silica thin film by contacting with a reducing agent vapor in a state where the ions are left without being removed, and obtained from the reducing agent introducing step. The metal ions are reduced by applying heat to the mesoporous silica thin film to form a thin metal wire of the metal in the pores of the mesoporous silica thin film. A method which comprises a thermal reduction step.
[0087]
The metal ion supporting step and the reducing agent introducing step in the second method for producing a thin metal wire clathrate thin film of the present invention may use the same method as the metal ion supporting step and the reducing agent introducing step in the first producing method. it can.
[0088]
Incidentally, as the reducing agent in the reducing agent introduction step of the second production method of the present invention, alcohols such as methanol, ethanol and isopropyl alcohol; aldehydes such as formaldehyde and acetaldehyde; hydrazine, hydroxylamine; alkali metals such as sodium and potassium; Alkali metals such as magnesium and calcium or citrates such as ammonium, hypophosphite, formate, acetate, oxalate and sulfanilate; alkali metal borohydrides such as sodium borohydride and potassium borohydride And at least one compound selected from the group consisting of: Among such reducing agents, alcohols such as methanol, ethanol, and isopropyl alcohol are preferable, and methanol is more preferable.
[0089]
Such a reducing agent that is solid can be used as a solution by using an alcohol such as methanol and ethanol, water, an organic solvent such as benzene or a mixture thereof as a solvent, and is a liquid. The reducing agent can be used as it is, or can be used as a mixture with the above-mentioned solvent, and the vapor of such a reducing agent solution is used as the reducing agent vapor.
[0090]
Further, it is preferable to further provide a vacuum exhaust step of exhausting moisture in pores of the mesoporous silica thin film as at least a step before the reducing agent introducing step. The purpose of providing such an evacuation step is the same as the evacuation step in the first manufacturing method.
[0091]
Preferably, before the reducing agent introduction step, a water vapor introduction step of introducing water vapor into pores of the mesoporous silica thin film is further provided. Such an introduced amount of steam may be a saturated vapor pressure of steam, and is preferably the same as the introduced amount in the first production method. The method for introducing the vapor of the reducing agent and the water into the pores of the mesoporous silica thin film can be performed in a vacuum device, as in the first manufacturing method.
[0092]
Further, before the step of introducing the reducing agent, the mesoporous silica thin film obtained from the step of supporting metal ions can be fired at 300 to 700 ° C. in the air. By performing firing in the air in this manner, fine wires of a metal oxide are formed in the pores of the thin film. Thereafter, a reducing agent is introduced into the pores of the thin film, and a thermal reduction step described later can be performed to reduce the metal to a zero-valent metal. When such a metal oxide fine wire is formed, a reducing gas (for example, hydrogen, carbon monoxide or the like) or a reducing gas and N 2₂It is also possible to reduce the metal oxide to a zero-valent metal by applying heat at 300 to 700 ° C. under the condition of contacting or flowing a mixed gas of an inert gas such as the above.
[0093]
Next, the heat reduction step will be described. The temperature at which heat is applied to the mesoporous silica thin film is preferably from 150 to 800 ° C, and more preferably from 200 to 600 ° C. When such a temperature is lower than the lower limit, the reduction tends to be insufficient. On the other hand, when the temperature exceeds the upper limit, the pores collapse or the metal once formed in the pores becomes thin. It tends to come out of the hole. Further, such a temperature can be achieved by heating the vacuum device used in the reducing agent introduction step with a heater or the like. Furthermore, in this thermal reduction step, it is also possible to carry out while introducing the reducing agent. In such a case, it is preferable to control the pressure by the vacuum pump, since the saturated vapor pressure increases with the temperature.
[0094]
When producing the thin metal wire cladding thin film as described above, the metal fine wire envelope obtained by the second production method of the present invention, in which the metal ions outside the pores of the mesoporous silica thin film are reduced without being removed, and are reduced. The contact thin film has a sufficient aspect ratio and is provided with fine metal wires having a uniform arrangement.
[0095]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
[0096]
Example 1
(Preparation of mesoporous silica thin film)
Tetramethoxysilane (Si (OCH₃)₄4.1 ml of an aqueous HCl solution (a) was gently added to 15.22 g (0.10 mol) of the mixture, and the mixture was stirred for 1 hour using a magnetic stirrer (rotational speed: 200 rpm / min). A solution containing the TMOS partial polymer was obtained. Next, the surfactant triblock copolymer (EO)₂₀(PO)₇₀(EO)₂₀(Manufactured by Aldrich, product name P123) 7.2 g, H₂10 ml of O and 10 ml of EtOH were mixed and heated to 50 ° C. while stirring with a magnetic stirrer to dissolve the surfactant. Thereafter, the mixture was naturally cooled to room temperature, further added with 100 μl of an aqueous HCl solution (b), and mixed to obtain a surfactant solution.
[0097]
A surfactant solution was added to the solution containing the TMOS partial polymer and stirred for 20 minutes. Then H₂A mixed solvent of O / EtOH = 20 ml / 20 ml was added, the rotational speed of the magnetic stirrer was increased to 300 rpm / min, and the mixture was stirred for 20 minutes to obtain a solution containing a complex composed of tetramethoxysilane and a surfactant ( (Hereinafter referred to as “TMOS complex solution”). The aqueous HCl solution (a) is H₂It was prepared by adding 100 μl of a 2N aqueous HCl solution to 30 ml of O, and a 2N aqueous HCl solution was used as the aqueous HCl solution (b).
[0098]
Next, a substrate lifting device (manufactured by SIGMA; SG SP 26-100) was installed in a vinyl box, and a thin film forming process was performed by a dip coating method. The substrate was immersed in the TMOS composite solution at a rate of 20 mm / min using the above apparatus, left standing in the solution for 30 seconds, and then pulled up at a rate of 20 mm / min. Dilute hydrofluoric acid (HF: H₂O = 1: 50) and a silicon wafer (2 cm × 5 cm) subjected to a surface treatment was used. Note that the relative humidity in the thin film forming step was fixed at 30%. Next, the substrate to which the TMOS composite solution was attached was air-dried at room temperature for 24 hours and dried at 100 ° C. for 1 hour. Thereafter, the resultant was baked at 400 ° C. for 1 hour in an air flow at 1 liter / min to obtain a mesoporous silica thin film having a 2d-hexagonal structure and a thickness of 0.4 μm.
[0099]
(Preparation of thin metal wire inclusion film)
Using a safety razor on the obtained mesoporous silica thin film, a new through-hole was formed at an interval of about 0.5 mm diagonally to the orientation plane. The mesoporous silica thin film was put into a vacuum device equipped with a vacuum pump (manufactured by Vacuum Kiko; GVD-050A) capable of controlling the temperature, and evacuated for 24 hours. 1 wt% H as metal ion containing solution₂PtCl₆15 wt% H solution₂PtCl₆5 cc, 10 cc of water, and 10 cc of ethanol were prepared, and a mesoporous silica thin film evacuated was put into this solution, and ultrasonic dispersion was performed for 10 minutes in an ultrasonic cleaner (manufactured by SND; US-1). Impregnated for 24 hours. The mesoporous silica thin film was pulled up, and the thin film was put again in a vacuum device in a state where the carrier liquid adhering to the thin film surface was left without being removed, and evacuated for 24 hours. Thereafter, the temperature was set to 25 ° C., and the thin film was exposed to steam having a vapor pressure of 10 Torr for 10 minutes by introducing steam having a vapor pressure of 10 Torr into the vacuum apparatus. Similarly, methanol (reducing agent) having a vapor pressure of 10 Torr was removed. The reducing agent vapor was introduced into the pores of the mesoporous silica thin film by exposing the thin film to the vapor for 10 minutes.
[0100]
Note that the state in which the carrier liquid is left without being removed in the present embodiment means that the carrier liquid is approximately 70 μl / cm on the thin film surface.²It is in a state of being attached, and the amount of metal ions carried on the entire thin film is about 0.7 μg / cm.²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0101]
(Formation of fine metal wires by photoreduction)
Ultraviolet light (wavelength 365 nm, light intensity 13 mW / cm) was applied to the thin film in which the reducing agent had been introduced using an ultra-high pressure mercury lamp (manufactured by Ushio Inc., part number UXM-500SX).²) For 72 hours⁴⁺To Pt⁰Of metal. The light intensity at the sample position was 7 mW / cm.²Met. After that, vacuum drying was performed at room temperature for 6 hours to remove residual gas.
[0102]
As a result, as shown in a transmission electron microscope (TEM) photograph (manufactured by JEOL Ltd., JEM2000EX) of FIG. 2, platinum metal forms a rod-shaped fine metal wire in the pores of the periodic structure (8 nm) of the mesoporous silica thin film. It was confirmed that. It was confirmed that this fine metal wire had an average diameter of 6 nm, an average aspect ratio of 30, and a length of 100 to 200 nm. From FIG. 2, it was also confirmed that the fine metal wires in the pores were arranged in parallel without intersecting with the adjacent fine metal wires.
[0103]
Comparative Example 1
A mesoporous silica thin film was produced in the same manner as in Example 1. Next, in the preparation of the thin metal wire inclusion thin film in Example 1, the mesoporous silica thin film was pulled up from the supporting liquid, the supporting liquid attached to the thin film surface (outside the pores) was wiped off, and then the thin film was put again in the vacuum device for 24 hours. A thin metal wire clathrate thin film was obtained in the same manner as in Example 1 except that the vacuum evacuation was performed. The amount of metal ions carried on the entire thin film in this comparative example was 1.7 × 10^-4μg / cm²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0104]
As a result, as shown in the TEM photograph of FIG. 3, no fine metal wire was formed in the pores of the mesoporous silica thin film, and it was confirmed that metal particles were sparsely deposited in the pores of the thin film.
[0105]
Example 2
In the preparation of the mesoporous silica thin film in Example 1, 4.1 ml of an aqueous HCl solution (a) was prepared by adding 200 μl of a 2N aqueous HCl solution to 30 ml of water. Octadecyl ammonium chloride (hereinafter referred to as "C₁₈TMACl ”) using 3.41 g (0.010 mol) of H₂A surfactant solution was obtained in the same manner as in Example 1, except that the mixture was mixed with 10 ml of O and heated to 50 ° C. while stirring with a magnetic stirrer to dissolve the surfactant. A mesoporous silica thin film was obtained in the same manner as in Example 1 except that the aqueous HCl solution (a) and the surfactant solution were used. This thin film had a thickness of 0.4 μm and had a 3d-hexagonal structure.
[0106]
Further, a thin metal wire clathrate thin film was obtained in the same manner as in Example 1, except that the obtained mesoporous silica thin film having a 3d-hexagonal structure was used. Note that the state in which the carrier liquid is left without being removed in the present embodiment means that the carrier liquid is approximately 70 μl / cm on the thin film surface.²It is in a state of being attached, and the amount of metal ions carried on the entire thin film is about 0.7 μg / cm.²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0107]
As a result, as shown in the TEM photograph of FIG. 4, it was confirmed that platinum metal formed a necklace-shaped fine metal wire in the pores of the periodic structure (4 nm) of the mesoporous silica thin film. It was confirmed that this thin metal wire had an average diameter of 1.5 nm, an average aspect ratio of 100, and a length of 100 to 200 nm. Further, it was confirmed from FIG. 4 that the fine metal wires in the pores were arranged in parallel without intersecting with the adjacent fine metal wires.
[0108]
Example 3
A mesoporous silica thin film was obtained in the same manner as in Example 2. This thin film had a thickness of 0.4 μm and had a 3d-hexagonal structure. Further, a thin metal wire clathrate thin film was obtained in the same manner as in Example 1, except that the obtained mesoporous silica thin film having a 3d-hexagonal structure was used. Note that the state in which the carrier liquid is left without being removed in the present embodiment means that the carrier liquid is approximately 70 μl / cm on the thin film surface.²It is in a state of being attached, and the amount of metal ions carried on the entire thin film is about 0.7 μg / cm.²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0109]
As a result, as shown in the TEM photograph of FIG. 5, it was confirmed that platinum metal formed a fine metal wire in the pores of the periodic structure (4 nm) of the mesoporous silica thin film. It was confirmed that this fine metal wire had an average diameter of 1.5 nm.
[0110]
In the above Examples 2 and 3, despite using the same mesoporous silica thin film having the 3d-hexagonal structure, metal beads having different shapes such as beads and nets were obtained. This is because, in a normal mesoporous silica thin film having a 3d-hexagonal structure, a certain pore and a pore adjacent thereto are three-dimensionally bonded to each other, so that the network-like thin metal wire shown in Example 3 is formed. Then, the present inventors speculate. However, the mesoporous silica thin film of Example 2 was subjected to uniaxial compressive stress, the pores of the thin film were crushed, and only the specific uniaxial pores became effective. The present inventors speculate that a rosary-shaped fine metal wire was obtained.
[0111]
Example 4
In the preparation of the mesoporous silica thin film in Example 1, 4.1 ml of an aqueous HCl solution (a) was prepared by adding 200 μl of a 2N aqueous HCl solution to 30 ml of water. As a surfactant, C₁₈Using 5.67 g (0.017 mol) of TMACl,₂A surfactant solution was obtained in the same manner as in Example 1, except that the mixture was mixed with 10 ml of O and heated to 50 ° C. while stirring with a magnetic stirrer to dissolve the surfactant. A mesoporous silica thin film was obtained in the same manner as in Example 1, except that the aqueous HCl solution (a) and the surfactant solution were used and the relative humidity in the thin film forming step was set to 70%. This thin film had a thickness of 0.4 μm and was confirmed to have a cubic structure.
[0112]
Also, a thin metal wire clathrate thin film was obtained in the same manner as in Example 1 except that the obtained mesoporous silica thin film having a cubic structure was used. Note that the state in which the carrier liquid is left without being removed in the present embodiment means that the carrier liquid is approximately 70 μl / cm on the thin film surface.²It is in a state of being attached, and the amount of metal ions carried on the entire thin film is about 0.7 μg / cm.²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0113]
As a result, as shown in the TEM photograph of FIG. 6, it was confirmed that platinum metal formed a reticulated metal fine wire in the pores of the periodic structure (11 nm) of the mesoporous silica thin film. It was confirmed that this metal thin wire had an average diameter of the spherical portion of 4 nm.
[0114]
Examples 5 to 8
(Preparation of mesoporous silica thin film)
A mesoporous silica thin film was obtained in the same manner as in Example 2. This thin film had a thickness of 0.4 μm and had a 3d-hexagonal structure.
[0115]
(Preparation of metal thin wire inclusion thin film using second manufacturing method)
New through holes were formed in the obtained mesoporous silica thin film using a safety razor at an interval of about 1 mm diagonally to the orientation plane. Thereafter, the mesoporous silica thin film was placed in a vacuum device (a device similar to that in Example 1) capable of controlling the temperature, and the vacuum was evacuated for 24 hours. The supporting liquid was prepared by mixing the raw material compounds and the solvents shown in Table 1 at a weight ratio (wt%) or a volume ratio (Vol ratio), and a evacuated mesoporous silica thin film was added to this solution. Similarly, ultrasonic dispersion was performed for 10 minutes, and impregnation was performed for 24 hours. The mesoporous silica thin film was pulled up, and the thin film was put again in a vacuum device in a state where the carrier liquid adhering to the thin film surface was left without being removed, and evacuated for 24 hours. Thereafter, the temperature was set to 25 ° C., and the thin film was exposed to steam having a vapor pressure of 10 Torr for 10 minutes by introducing steam having a vapor pressure of 10 Torr into the vacuum device. The reducing agent vapor was introduced into the pores of the thin film by exposing the thin film to the vapor of the agent for 10 minutes.
[0116]
The temperature of the vacuum device containing the mesoporous silica thin film into which the reducing agent vapor has been introduced is raised in 2 hours to a temperature shown in Table 1 by controlling a heater using a PID controller, and the temperature is shown in Table 1 The metal ions were reduced by applying heat only for a period of time and the vacuum was cooled to 25 ° C over 2 hours. By such a method, the thin metal wire inclusion thin films of Examples 5 to 8 were obtained.
[0117]
Note that the state in which the carrier liquid was left without being removed in Examples 5 to 8 means that the carrier liquid was approximately 70 μl / cm on the thin film surface.²It is in a state of being attached, and the amount of metal ions carried on the entire thin film is about 0.7 μg / cm.²Was calculated. The amount of metal ions carried on the entire thin film was 1 cm of a 0.4 μm thick thin film.²It was expressed by the supported amount per unit.
[0118]
[Table 1]

[0119]
FIGS. 7 to 10 show TEM photographs of the obtained thin metal wire inclusion films of Examples 5 to 8. FIG. 7 is a TEM photograph of a thin metal wire cladding thin film having a bar-shaped thin metal wire made of gold obtained in Example 5. It was confirmed that this metal thin wire had an average diameter of 6.8 nm, an aspect ratio of 5 or more, and a length of more than 200 nm.
[0120]
FIG. 8 is a TEM photograph of a thin metal wire clathrate having a bar-shaped thin metal wire made of silver obtained in Example 6. It was confirmed that this metal thin wire had an average diameter of 6.9 nm, an average aspect ratio of about 10, and a length of 150 nm or more.
[0121]
FIG. 9 is a TEM photograph of a thin metal wire inclusion thin film having a rod-shaped thin metal wire made of nickel obtained in Example 7. It was confirmed that this thin metal wire had an average diameter of 7.0 nm, an average aspect ratio of about 10, and a length of 150 nm or more.
[0122]
FIG. 10 is a TEM photograph of a thin metal wire inclusion thin film having a rod-shaped thin metal wire made of copper obtained in Example 8. It was confirmed that this fine metal wire had an average diameter of 6.5 nm, an aspect ratio of 5 or more, and a length of 100 nm or more.
[0123]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a thin metal wire inclusion film having a sufficient aspect ratio and having a uniform array of thin metal wires. As a result, it is possible to apply the present invention to a quantum device or a catalyst used by attaching electrodes to both ends of the thin metal wire.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the shape of each of fine metal wires formed in pores of a mesoporous silica thin film.
FIG. 2 is a view showing a scanning electron micrograph (magnification: 200,000 times) of the thin metal wire clathration thin film obtained in Example 1.
FIG. 3 is a view showing a scanning electron micrograph (magnification: 100,000 times) of the thin metal wire inclusion thin film obtained in Comparative Example 1.
FIG. 4 is a view showing a scanning electron micrograph (magnification: 250,000 times) of the thin metal wire clathration thin film obtained in Example 2.
FIG. 5 is a view showing a scanning electron micrograph (magnification: 100,000 times) of the thin metal wire clathration thin film obtained in Example 3.
FIG. 6 is a view showing a scanning electron micrograph (magnification: 100,000 times) of the thin metal wire clathration thin film obtained in Example 4.
FIG. 7 is a scanning electron micrograph (magnification: 100,000 times) of the thin metal wire clathration thin film obtained in Example 5.
FIG. 8 is a view showing a scanning electron micrograph (magnification: 150,000 times) of the thin metal wire clathration thin film obtained in Example 6.
FIG. 9 is a view showing a scanning electron micrograph (magnification: 73,000 times) of the thin metal wire clathration thin film obtained in Example 7.
FIG. 10 is a scanning electron micrograph (magnification: 73,000 times) of the thin metal wire clathrate obtained in Example 8.

Claims (12)

A mesoporous silica thin film having a thickness of 1 μm or less and a central pore diameter of 1 to 50 nm;
A fine metal wire having an average diameter of 1 to 50 nm formed in the pores of the mesoporous silica thin film and an average aspect ratio of 5 or more;
A thin metal wire clathrate thin film comprising: The thin metal wire inclusion thin film according to claim 1, wherein the pores of the mesoporous silica thin film have a 2d-hexagonal structure, a 3d-hexagonal structure, or a cubic structure. The shape of the thin metal wire in the pores, the shape of a rod, a necklace having a spherical portion formed at a predetermined interval in the longitudinal direction of a rosary or rod-shaped portion in which the spherical portions are connected in the longitudinal direction, or The thin metal wire clathration thin film according to claim 1 or 2, wherein the thin metal wire has a net shape formed by two-dimensionally or three-dimensionally connecting rod-shaped, rosary-shaped or necklace-shaped thin metal wires. The metal constituting the thin metal wire is at least one metal selected from the group consisting of a group 8 metal, a group 9 metal, a group 10 metal, a group 11 metal, chromium and manganese. Item 5. The thin metal wire inclusion thin film according to any one of Items 1 to 3. Contacting a solution containing ions of a predetermined metal with a mesoporous silica thin film having a film thickness of 1 μm or less and having a central pore diameter of 1 to 50 nm, inside and outside the pores of the mesoporous silica thin film A metal ion supporting step of supporting the metal ions,
The metal ions supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step were brought into contact with the vapor of the reducing agent in a state where the metal ions were left without being removed, and were placed in the pores of the mesoporous silica thin film. A reducing agent introducing step of introducing the reducing agent vapor,
A photoreduction step of irradiating the mesoporous silica thin film obtained from the reducing agent introduction step with light to reduce the metal ions, and forming a thin metal wire made of the metal in pores of the mesoporous silica thin film,
A method for producing a thin metal wire clathrate thin film, comprising: Before the reducing agent introduction step, a vacuum evacuation step of evacuating water in pores of the mesoporous silica thin film,
The method for producing a thin metal wire inclusion thin film according to claim 5, further comprising: Before the reducing agent introduction step, a water vapor introduction step of introducing water vapor into the pores of the mesoporous silica thin film,
7. The method for producing a thin metal wire inclusion thin film according to claim 5, further comprising: Before the metal ion supporting step, a hole forming step of providing a new through hole connecting the inside of the pore and the outside on the surface of the mesoporous silica thin film,
The method for producing a thin metal wire clathrate thin film according to any one of claims 5 to 7, further comprising: Contacting a solution containing ions of a predetermined metal with a mesoporous silica thin film having a film thickness of 1 μm or less and having a central pore diameter of 1 to 50 nm, inside and outside the pores of the mesoporous silica thin film A metal ion supporting step of supporting the metal ions,
The metal ions supported outside the pores of the mesoporous silica thin film obtained from the metal ion supporting step were brought into contact with the vapor of the reducing agent in a state where the metal ions were left without being removed, and were placed in the pores of the mesoporous silica thin film. A reducing agent introducing step of introducing the reducing agent vapor,
A heat reduction step of applying heat to the mesoporous silica thin film obtained from the reducing agent introduction step to reduce the metal ions, and forming a thin metal wire made of the metal in pores of the mesoporous silica thin film,
A method for producing a thin metal wire clathrate thin film, comprising: Before the reducing agent introduction step, a vacuum evacuation step of evacuating water in pores of the mesoporous silica thin film,
The method for producing a thin metal wire inclusion film according to claim 9, further comprising: Before the reducing agent introduction step, a water vapor introduction step of introducing water vapor into the pores of the mesoporous silica thin film,
The method for producing a thin metal wire inclusion thin film according to claim 9, further comprising: Before the metal ion supporting step, a hole forming step of providing a new through hole connecting the inside of the pore and the outside on the surface of the mesoporous silica thin film,
The method for producing a thin metal wire inclusion thin film according to any one of claims 9 to 11, further comprising:

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