JP2007031189A - Method for peeling layered double hydroxide, double hydroxide nanosheet, composite thin film material thereof, method for producing the same, and method for producing layered double hydroxide thin film material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily peeling an LDH having inorganic anions as an intermediate layer, and to provide a double hydroxide nanosheet obtained thereby. <P>SOLUTION: The method for peeling a layered double hydroxide comprises a process where a layered double hydroxide is mixed with an aprotic polar organic solvent. The layered double hydroxide is represented by any of [M<SP>2+</SP><SB>1-x</SB>M<SP>3+</SP><SB>x</SB>(OH)<SB>2</SB>]<SP>x+</SP>[A<SP>n-</SP><SB>x/n</SB>-mH<SB>2</SB>O]<SP>x-</SP>(1), [Li<SP>+</SP><SB>1-x</SB>M<SP>3+</SP><SB>x</SB>(OH)<SB>2</SB>]<SP>(2x-1)+</SP>[A<SP>n-</SP><SB>(2x-1)/n</SB>-mH<SB>2</SB>O]<SP>(2x-1)-</SP>(2), and [M<SP>2+</SP><SB>1-x</SB>Ti<SP>4+</SP><SB>x</SB>(OH)<SB>2</SB>]<SP>2x+</SP>[A<SP>n-</SP><SB>2x/n</SB>-mH<SB>2</SB>O]<SP>2x-</SP>(3), wherein, M<SP>2+</SP>is a bivalent metal ion; M<SP>3+</SP>is a tervalent metal ion; A<SP>n-</SP>is an inorganic anion selected from the group consisting of NO<SB>3</SB><SP>-</SP>,Cl<SP>-</SP>, ClO<SB>3</SB><SP>-</SP>, ClO<SB>4</SB><SP>-</SP>, F<SP>-</SP>, Br<SP>-</SP>, I<SP>-</SP>, CO<SB>3</SB><SP>2-</SP>, SO<SB>4</SB><SP>2-</SP>and their mixture; n is the bivalent of the inorganic anion; m is a real number larger than 0; and x satisfies 0<x<0.5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for peeling a layered double hydroxide (hereinafter referred to simply as LDH), a double hydroxide nanosheet obtained thereby, a composite thin film material using the same, a method for producing the same, And it is related with the manufacturing method of a layered double hydroxide thin film. Specifically, the present invention relates to a method for easily peeling LDH composed of inorganic anions.

  With the progress of manufacturing technology, high-quality single crystal layers (or nanosheets) can be obtained and are attracting attention as new nanomaterials. Construction of a novel nanodevice using such a nanosheet is also expected.

Many of the nanosheets obtained at present are anionic nanosheets having a negative charge, as represented by Ti _1- δO ₂ nanosheets and MnO ₂ nanosheets, for example.

  On the other hand, there are few reports on the production of cationic nanosheets having a positive charge. If a good quality cationic nanosheet is obtained, the applicability and flexibility in material synthesis can be expanded, and the selection range of nanomaterials can be expanded.

  As a candidate material for the cationic nanosheet, layered double hydroxide (LDH) has attracted attention. LDH is sometimes referred to as hydrotalcite or a hydrotalcite-like substance, taking the name from hydrotalcite, which is a representative of this structure of minerals.

There is a technique for synthesizing cationic nanosheets from LDH (see, for example, Non-Patent Document 1 and Patent Document 1).
Non-Patent Document 1 and Patent Document 1 disclose obtaining double hydroxide nanosheets by dispersing LDH containing an amino acid between layers in formamide. In Non-Patent Document 1 and Patent Document 1, LDH is represented by the general formula (1).
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] [A ⁿ⁻ _{x / n} · mH ₂ O] (1)
Here, M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-interlayer anion, m is a rational number, n represents a rational number integer, x is not exceeding 1.

In the above formula (1), [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] represents an LDH basic layer (host layer).
And can later become a double hydroxide nanosheet. On the other hand, in (1) above, [A ⁿ⁻ _{x / n} · mH ₂ O] is called an intermediate layer (guest layer). The LDH is formed by alternately laminating basic layers and intermediate layers.

In LDH described in Non-Patent Document 1 and Patent Document 1, A ^n-include alanine, leucine, serine, lysine, amino acid histidine and the like. Since these amino acids in LDH have good dispersibility with respect to formamide, double water represented by [M 2 ⁺ _1-x M ³⁺ _x (OH) ₂ ] in the above formula (1). An oxide nanosheet can be obtained.

There is another technique for synthesizing cationic nanosheets from LDH (see, for example, Non-Patent Document 2 and Non-Patent Document 3).
In the techniques described in Non-Patent Documents 2 and 3, LDH having an anionic organic surfactant such as dodecyl sulfate ion (DDS) as an intermediate layer is refluxed in butanol or heated in 2-hydroxyethyl methacrylate. Thus, it is disclosed that a cationic nanosheet is obtained.

Hibino, Chem. Mater. , 2004, 16, 5482-5488 Adachi-Pagano et al., Chem. Commun. , 2000, 91 S. O'Leary et al., Chem. Commun. , 2002, 1506 JP 2005-89269 A

  However, these technologies described in Non-Patent Documents 1 to 3 and Patent Document 1 are commonly used in the production of various LDHs by causing alkali (for example, NaOH) to act and precipitate, and for inclusion of amino acids or DDS. The settling method is adopted. The crystallinity of LDH containing amino acids or organic anions such as DDS obtained by the coprecipitation method is generally low, and the crystallite size is as small as several tens of nanometers or less.

  Since such LDH is used as a starting material, there is a problem that a high-quality double hydroxide nanosheet cannot be obtained in a large area.

  In particular, during the production of LDH containing amino acids, there is a problem that pH adjustment is necessary and the process is complicated.

  Thus, the manufacturing method of LDH which contains an organic anion as an intermediate | middle layer is complicated and limited, and the quality of obtained LDH is also low. Therefore, it can be advantageous if LDH obtained by an arbitrary method, in particular, LDH containing a high crystallinity and high quality inorganic anion as an intermediate layer, represented by a hydrothermal synthesis method, can be used as a starting material. .

  Accordingly, an object of the present invention is to provide a method for easily peeling LDH having an inorganic anion as an intermediate layer, and a double hydroxide nanosheet obtained thereby.

  A further object of the present invention is to provide a layered double hydroxide (LDH) thin film material (also simply referred to as a thin film material) using the obtained double hydroxide nanosheet, a composite thin film material using the double hydroxide nanosheet, and It is to provide a manufacturing method thereof.

  In this specification, the term “thin film material” means a thin film material composed of a layered double hydroxide obtained by re-lamination of double hydroxide nanosheets, and a thin film material derived therefrom. Note that "composite thin film material" intends a thin film material derived from layer-by-layer stacking of double hydroxide nanosheets and anionic polymer layers.

The method for exfoliating a layered double hydroxide according to the present invention includes a step of mixing the layered double hydroxide with an aprotic polar organic solvent, and the layered double hydroxide is represented by the following formulas (1) to (1): (3)
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2) [M 2 ⁺ _1−x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ⁿ⁻ _{2x / n} · mH ₂ O] ^2x− (3)
Here, in the formulas (1) to (3), M ²⁺ is a divalent metal ion, and M ³⁺ is 3
The valence metal ion, A _{^{n-is, NO 3 -, Cl -,}} ClO 3 -, ClO 4 -, F -, Br -, I -, CO 3 2-, SO 4 2-, and mixtures thereof Wherein n is a valence of the inorganic anion, m is a real number greater than 0, and x is 0 <x <0.5, whereby Achieve the goal.

The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.

  The aprotic polar organic solvent may be selected from the group consisting of formamide, dimethyl sulfoxide, methylformamide, and dimethylformamide.

  The mixing step may be purged with an inert gas and shaken at room temperature for 1-24 hours.

The double hydroxide nanosheet according to the present invention is
A double hydroxide nanosheet represented by any one of formulas (4) to (6),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4),
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5),
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6),
In the formula (4) to the formula (6), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, and x is 0 <x <0.5,
The size of the double hydroxide nanosheet in the longitudinal direction is 5 nm or more and 50 μm or less, and the thickness of the double hydroxide nanosheet is 0.3 nm or more and 2 nm or less, thereby achieving the above object.

The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.
The double hydroxide nanosheet obtained by the method for exfoliating a layered double hydroxide according to the present invention includes a step of mixing the layered double hydroxide with an aprotic polar organic solvent, and the layered double hydroxide nanosheet. The hydroxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1),
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2), [M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3),
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Where m is a real number greater than 0 and x is 0 <x <0.5, thereby achieving the above object.

The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.

  The aprotic polar organic solvent may be selected from the group consisting of formamide, dimethyl sulfoxide, methylformamide, and dimethylformamide.

A method for producing a layered double hydroxide thin film according to the present invention includes a step of mixing the layered double hydroxide with an aprotic polar organic solvent, and a mixed solution obtained by the mixing step by spin coating or dipping. And applying to the substrate by coating, the layered double hydroxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1),
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2), [M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3),
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Where m is a real number greater than 0 and x is 0 <x <0.5, thereby achieving the above object.

A step of ion exchange of the imparted product obtained in the imparting step may be further included.
The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.

  The aprotic polar organic solvent may be selected from the group consisting of formamide, dimethyl sulfoxide, methylformamide, and dimethylformamide.

A method for producing a composite thin film material comprising a double hydroxide nanosheet and an anionic polymer layer according to the present invention is a step of mixing a layered double hydroxide with an aprotic polar organic solvent, the layered double water The oxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1),
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2),
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3),
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Where m is a real number greater than 0 and x is 0 <x <0.5, and the substrate is sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1 Anionic high selected from the group consisting of-(4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamido) -1,2-ethanedinyl) sodium, polyanilinepropane sulfonic acid, and polyaniline sulfonic acid With molecule A step of, the mixed solution obtained in said step of mixing on the anionic polymer includes a step of imparting, thereby achieving the above object.

The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.

  The aprotic polar organic solvent may be selected from the group consisting of formamide, dimethyl sulfoxide, methylformamide, and dimethylformamide.

  The mixing step may be purged with an inert gas and shaken at room temperature for 1-24 hours.

  The method may further include a step of alternately applying the step of applying the anionic polymer and the step of applying the mixed solution.

The composite thin film material comprising at least one pair of double hydroxide nanosheets and an anionic polymer layer according to the present invention, the double hydroxide nanosheet is represented by any one of formulas (4) to (6):
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4),
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5),
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6),
Here, in the formulas (4) to (6), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, and x is 0 <x <0.5. The size of the double hydroxide nanosheet in the longitudinal direction is from 5 nm to 50 μm, the thickness of the double hydroxide nanosheet is from 0.3 nm to 2 nm, and the anionic polymer layer is Sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1- (4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamido) -1,2-ethanedinyl) sodium, polyanilinepropanesulfonic acid And the group consisting of polyaniline sulfonic acid, thereby achieving the above object.

The M ²⁺ may be selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca.

The M ³⁺ may be selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.

  The at least one set of double hydroxide nanosheets and the anionic polymer layer may be alternately stacked.

The method according to the invention comprises the step of mixing the layered double hydroxide with an aprotic polar organic solvent. The layered double hydroxide (LDH) is represented by any one of the formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, in the formulas (1) to (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl -, ClO _{3 ^{-, ClO 4 -, F -}} , Br -, I -, CO 3 2-
, SO ₄ ²⁻ , and a mixture thereof, an inorganic anion, n
Is the valence of the inorganic anion, m is a real number greater than 0, and x is 0 <x <0.5.

The LDH has a basic layer [M 2 ⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , [Li ⁺ _1-x M ^{3 +} _x (OH) ₂ ] ^{(2x-1) +} , and [M ^{2 +} _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} is a water molecule and an inorganic anion intermediate layer [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− , [A ⁿ⁻ _{(2x−1), respectively. / n} · mH ₂ O] ^{(2x-1) -and} [A ^n- _{2x / n} · mH ₂ O] ^2x- .

  Usually, water molecules are hydrogen-bonded to the hydroxyl group of the basic layer, and maintain a state in harmony with the anion intermediate layer. However, by mixing the LDH and a very polar aprotic polar solvent, the carbonyl group or triphenyl group in the solvent molecule has a strong interaction with the basic layer and can be replaced with a water molecule. .

  On the other hand, the other end in the solvent molecule, the amine group or the methyl group, has a weak binding force with the above-mentioned inorganic anion intermediate layer. Therefore, when the above-described substitution occurs, the hydrogen bond in LDH is reduced and peeling easily occurs. obtain.

  In addition, since LDH used for peeling uses an inorganic anion as an anion for the intermediate layer, it is produced by an arbitrary method such as LDH obtained by a coprecipitation method and LDH obtained by a hydrothermal synthesis method. LDH can be applied.

  In particular, LDH produced by a hydrothermal synthesis method is a plate crystal having high crystallinity, high crystallinity, and large lateral size (that is, a large aspect ratio). Therefore, such LDH is used as a starting material. If used, a high-quality LDH nanosheet having a large size (for example, micron order) and high crystallinity can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a flowchart showing a method for peeling LDH of the present invention.

Prior to peeling, a process for producing LDH used in the present invention will be described.
The LDH used in the present invention is produced, for example, by a hydrothermal synthesis method described in “Chem. Lett. 2004, 33, 1122” by Iyi et al.

  Note that the LDH production method applicable to the present invention may be a coprecipitation method and is not limited to the hydrothermal synthesis method. The LDH applicable to the present invention is an LDH containing an inorganic anion produced by any method.

  Step S101: A first metal salt containing a monovalent metal or a divalent metal, a second metal salt containing a trivalent metal or a tetravalent metal, and a hydrolysis reagent are mixed.

The monovalent metal is, for example, Li. The divalent metal is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The anion constituting the first metal salt is selected from the group consisting of NO ³⁻ , Cl ⁻ , and CO ₃ ²⁻ . The first metal salt may be any combination of the monovalent metal or divalent metal and the anion.

The trivalent metal is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La. The tetravalent metal is, for example, Ti. The anion constituting the second metal salt is selected from the group consisting of NO ³⁻ , Cl ⁻ , and CO ₃ ²⁻ . The second metal salt can be any combination of the trivalent or tetravalent metal and the anion.

  When a monovalent metal is selected as the first metal salt, the second metal salt is preferably a trivalent metal. When a tetravalent metal is selected as the second metal salt, a divalent metal is preferred as the first metal salt.

  The hydrolysis reagent is hexamethylenetetraamine or urea.

  Step S102: Hydrothermal treatment of the mixture obtained in Step S102. The mixture is heated under high pressure in the temperature range of 100 ° C. to 200 ° C. for 10 hours to 30 hours.

Step S103: The reaction product obtained in step S102, then immersed in a solution of a salt containing the desired anion (inorganic anion represented by the later-described A ^n-) ion exchange.

  In that case, it is known that the reaction proceeds effectively by coexisting an appropriate amount of acid in addition to the anion-containing salt. For example, it can be achieved without impairing crystallinity by treatment with an acid-salt mixed solution as described in Iyi et al., “Chem. Mater. 2004, 16, 2926”. By the ion exchange, carbonate ions located in the intermediate layer are removed and replaced with the target inorganic anions.

  It is known that LDH with high crystallinity of the order of microns can be obtained by using the hydrothermal synthesis method. Such a hydrothermal synthesis method is not suitable for the production of LDH using an organic anion such as amino acid as an intermediate layer as shown in the prior art.

  In addition, in the said process S101-process S103, although the case where the hydrothermal synthesis method was employ | adopted was explained in full detail, you may employ | adopt a coprecipitation method.

  In this case, the hydrolysis reagent in step S101 can be alkali hydroxide or ammonia. Instead of step 102, the mixture may be hydrolyzed and aged in the temperature range from room temperature to 100 ° C.

  In the present invention, in addition to the usual LDH obtained by the conventional coprecipitation method, LDH crystals produced by the hydrothermal synthesis method and having a large lateral size and high crystallinity can be used directly as a starting material. .

LDH obtained in steps S101 to S103 is represented by any one of formulas (1) to (3).
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, in the formulas (1) to (3), M ²⁺ is a divalent metal ion described above, M ³⁺ is above trivalent metal ion, A ^n-is, NO ₃ ^-, Cl _{^{-, ClO 3 -, ClO 4}} -, F -, Br -,
An inorganic anion selected from the group consisting of I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, n is the valence of the inorganic anion, and m is a real number greater than 0. X is 0 <x <0.5.

The inorganic anion is preferably Cl ⁻ , F ⁻ , Br ⁻ or I ⁻ , and more preferably NO ₃ ⁻ or ClO ₄ ⁻ . This is because the tendency of exfoliation in an aprotic polar organic solvent described later varies depending on the type of anion contained in LDH, and NO ₃ ⁻ and ClO ₄ ⁻ have high exfoliation ability.

  In addition, when a some inorganic anion (namely, mixture) is included, each of a some inorganic anion is mixed in arbitrary ratios according to a valence, for example in the said process S103. Such ratios are easily understood by those skilled in the art.

[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] in the above formula (1), [Li ⁺ _1-x in the above formula (2)
M ³⁺ _x (OH) ₂ ] and [M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] in the above formula (3) are LD
It is called a basic layer (host layer) of H, and can later become a double hydroxide nanosheet.

On the other hand, [A ⁿ⁻ _{X / n} · mH ₂ O] in the above (1), [A ⁿ⁻ _{(2x-1) / n} · mH ₂ O] in the above formula ( ₂ ), and the above formula (3) [A ⁿ⁻ _{2x / n} · mH ₂ O] is called an intermediate layer (guest layer). The obtained LDH is formed by alternately laminating basic layers and intermediate layers.

  The LDH represented by any of the above formulas (1) to (3) obtained in step S101 to step S103 is mixed with an aprotic polar organic solvent (step S110 in FIG. 1).

  The aprotic polar organic solvent is selected from the group consisting of formamide, dimethyl sulfoxide, methylformamide and dimethylformamide. These aprotic polar organic solvents are easy to solvate to cations, while vice versa for anions, and thus can promote LDH stripping. The aprotic polar organic solvent may preferably be dimethyl sulfoxide, dimethylformamide, methylformamide, more preferably formamide. This is because the peeling ability may vary depending on the type of aprotic polar organic solvent and tends to increase in the order of the above solvents.

By the step S110, the LDH is easily peeled off, and [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ], [Li ⁺ _1-x M ³⁺ _x (OH) ₂ ], or [M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] is obtained. The double hydroxide nanosheet thus obtained has a size in the longitudinal direction of 5 nm or more and 50 μm or less, and a thickness of 0.3 nm or more and 2 nm or less.

  The inventors of the present invention have found by ingenuity that LDH containing an inorganic anion is peeled off by an aprotic polar organic solvent having a high dielectric constant, such as formamide, to obtain a double hydroxide nanosheet.

The peeling mechanism is as follows.
The LDH used in the present invention comprises a base layer [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , [Li ⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{(2x-1) +} , and , [M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} are respectively a water molecule and an inorganic anion intermediate layer [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− , [A ⁿ⁻ _{( 2x-1) / n} · mH ₂ O] ^{(2x-1) -and} [A ^n- _{2x / n} · mH ₂ O] ^2x- . Usually, water molecules are hydrogen bonded to the hydroxyl group of the basic layer, and maintain a state in harmony with the inorganic anion intermediate layer. However, by mixing LDH and a very polar aprotic polar solvent, the carbonyl group or triphenyl group in the solvent molecule has a strong interaction with the basic layer and can be replaced with a water molecule. On the other hand, the other end in the solvent, the amino group or the methyl group, has a weak binding force with the inorganic anion intermediate layer. Therefore, when the above substitution occurs, the hydrogen bond in the LDH decreases, and the solvent molecules Can be further connected by hydrogen bonds, and solvent molecules can further invade between the layers to swell, and peeling can easily occur.

  Such a discovery overturns the common knowledge that, unless LDH contains an amino acid or an anionic surfactant, it is not exfoliated by formamide, and it is possible to use LDH containing inorganic ions. It is. As a result, large LDH crystals with good crystallinity produced by a hydrothermal synthesis method, which has been impossible in the past, can be used directly as starting materials, so that the complexities seen in the production of LDH containing amino acids can be used. No process is required, contributing to labor savings. As a matter of course, it is not necessary to replace the intermediate layer of the obtained LDH with an organic anion such as an amino acid. Moreover, since a double hydroxide nanosheet having a large area and high crystallinity can be easily obtained, it can be an extremely simple method.

In step S110 of FIG. 1, the mixed solution may be purged with an inert gas and shaken at room temperature for 1 to 24 hours. As a result, the LDH can be reliably peeled off.

  Next, an LDH thin film material using the double hydroxide nanosheet obtained in Embodiment 1 and a manufacturing method thereof will be described.

(Embodiment 2)
FIG. 2 is a schematic view of an LDH thin film material (a) and an organic-LDH thin film material (b) using the double hydroxide nanosheet according to the present invention.

  The LDH thin film material 200 shown in FIG. 2A includes a plurality of double hydroxide nanosheets 220 and an anionic intermediate layer 230 sandwiched between the plurality of double hydroxide nanosheets 220.

The plurality of double hydroxide nanosheets 220 can be manufactured, for example, by the method described in Embodiment 1, and is represented by any one of formulas (4) to (6).
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4)
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6)
Here, in Formula (4)-Formula (6), M ^<2+> is a bivalent metal ion and M ^<3+> is a trivalent metal ion. x is a rational number in the range of 0 <x <0.5. Specifically, M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn and Ca. M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni and La.

The intermediate layer 230 is an inorganic anion, and is Cl ⁻ , F ⁻ , Br ⁻ or I ⁻ , and more preferably NO ₃ ⁻ or ClO ₄ ⁻ .

  The LDH thin film material 200 is located on the substrate 210. The substrate 210 can be any substrate such as a glass substrate or a Si substrate depending on the application.

  The LDH thin film material 200 can be an alignment film, unlike the LDH of the starting material used in the first embodiment. For this reason, the LDH thin film material 200 is a thin film material that is dense and smooth and extremely transparent compared to an LDH thin film material obtained by directly applying an LDH powder as a starting material. The LDH thin film material 200 has applicability as a novel optical element.

  The LDH thin film material 200 can also be used for modified electrodes, surface plasmon resonance (SPR), crystal oscillator microbalance (QCM), molecular recognition devices, and the like using the sensor ability. More specifically, by forming the LDH thin film material 200 on a substrate such as an electrode, the intermediate layer 230 of the LDH thin film material 200 is easily ion-exchanged with a specific anion and exhibits a sensor capability. By detecting electrical changes and weight changes caused by such ion exchange, it is possible to identify anions and quantitatively measure ion-exchanged anions.

  In particular, according to the present invention, the LDH thin film material 200, which is an alignment film with good crystallinity, can be used for the above-described devices and the like, so that the anisotropy of electron conduction can be utilized, which can be advantageous.

  Next, referring to FIG. 1 again, a method of manufacturing the LDH thin film material 200 having excellent crystallinity will be described. This is performed following step S110 in FIG.

Step S120: The mixed solution obtained in Step S110 is applied to the substrate. The application to the substrate is preferably spin coating or dip coating. Thereby, since the mixed solution can be applied to the substrate with a uniform thickness, the formation of the alignment film can be promoted. As described above in Embodiment 1, the LDH as the starting material is completely separated into a single layer in the mixed solution. By simply applying such a mixed solution to the substrate, the double hydroxide nanosheet can be densely rearranged. As a result, an unprecedented LDH alignment film can be easily obtained. Note that the substrate to which the mixed solution is applied does not necessarily have a plate shape, and any object can be adopted as the substrate as long as the above-described spin coating or dip coating can be applied.

Step S120 preferably includes a step of drying the mixed solution applied to the substrate. This can evaporate unwanted formamide. For drying, any heating means such as an oven may be used, or drying may be performed while being held in the air. You may repeat the said process after drying until it becomes the LDH thin film material of desired thickness.
As described above, since a high-quality LDH alignment film can be obtained simply by applying the mixed solution to the substrate, the yield in device manufacturing can be improved. Since a conventional application method such as spin coating or dip coating can be employed, the degree of freedom in material design can be increased.

  Next, another example using the double hydroxide nanosheet obtained in the first embodiment is shown. Reference is again made to FIG.

  The organic-LDH thin film material 240 shown in FIG. 2B includes a plurality of double hydroxide nanosheets 220 and an anionic intermediate layer 250 sandwiched between the plurality of double hydroxide nanosheets 220. The plurality of double hydroxide nanosheets 220 are the double hydroxide nanosheets obtained in the first embodiment. The intermediate layer 250 is an organic anion different from the intermediate layer 230 in FIG. The organic-LDH thin film material 240 is located on the substrate 210. The substrate 210 can be any substrate such as a glass substrate or a Si substrate depending on the application.

  Such an organic-LDH thin film material 240 is an alignment film. In particular, since the organic anion of the intermediate layer 250 is oriented in a predetermined direction, the function of the organic anion can be exhibited more. For example, when an organic anion containing a laser dye is used as the intermediate layer 250, the organic-LDH thin film material 240 can function as an optical element such as a phosphor or a light emitting element.

  Although FIG. 2B illustrates the case where an organic anion is included as the intermediate layer 250, any anion having a desired function can be applied to the intermediate layer 250 depending on the device design.

  Next, referring to FIG. 1 again, a method for manufacturing the organic-LDH thin film material 240 shown in FIG. 2B will be described.

  The organic-LDH thin film material 240 is manufactured following step S120.

  Step S130: The LDH thin film material obtained in Step S120 is ion-exchanged. In ion exchange, anions are exchanged. The anion can be, for example, an organic anion such as p-toluenesulfonate ion, but is not limited thereto as long as it is an ion-exchangeable anion. Since the ion exchange is appropriately performed without losing the orientation of the LDH thin film material obtained in step S120, the LDH thin film material after the ion exchange can also be an orientation film, so that the function of the organic anion is not impaired. Can be maintained.

  Next, a composite thin film material using the double hydroxide nanosheet obtained in Embodiment 1 and a production method thereof will be described.

(Embodiment 3)
FIG. 3 is a schematic view of a composite thin film material using a double hydroxide nanosheet according to the present invention.

  The composite thin film material 300 includes at least one set of an anionic polymer layer 310 and a double hydroxide nanosheet 320.

  The anionic polymer layer 310 is composed of sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1- (4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamide) -1,2- Ethanedinyl) sodium, polyaniline propane sulfonic acid, and polyaniline sulfonic acid.

The double hydroxide nanosheet 320 can be manufactured, for example, by the method described in Embodiment 1, and is represented by any one of formulas (4) to (6).
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4)
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6)
Here, in Formula (4)-Formula (6), M ^<2+> is a bivalent metal ion and M ^<3+> is a trivalent metal ion. x is a rational number in the range of 0 <x <0.5. Specifically, M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn and Ca. M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni and La.

  The composite thin film material 300 may include a plurality of sets of the anionic polymer layer 310 and the double hydroxide nanosheet 320. In this case, the anionic polymer layer 310 and the double hydroxide nanosheet 320 may be alternately layer-by-layer stacked.

  Further, the composite thin film material 300 may be formed on the substrate 210. The substrate 210 can be selected according to the application, such as a Si substrate or a quartz glass substrate. In addition, since nanosheets have flexible mechanical properties, it is possible to coat not only on a flat substrate but also on the surface of a substrate having a curvature. When the composite thin film material 300 is formed on the substrate 230, an adhesive layer 330 for bonding the anionic polymer layer 310 of the composite thin film material 300 and the substrate 330 may be applied. The adhesive layer 330 can be, for example, cationic polyethyleneimine.

  Thus, since the double hydroxide nanosheet according to the present invention is cationic and has a large area, it can function as a linker for laminating an anionic polymer layer, which has been impossible in the past. Since such a composite thin film material 300 can incorporate various functional molecules, metal complexes, clusters, and the like at the nano level, it can be used in a wide range of applications such as catalysts, sensors, and antistatic coatings.

  With reference to FIG. 1 again, a method for manufacturing the composite thin film material 300 will be described. The composite thin film material 300 is manufactured following step S110. Since step S110 is similar to step S110 described in the first embodiment, a description thereof will be omitted.

  Step S140: sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1- (4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamido) -1,2-ethanedinyl) sodium, polyaniline An anionic polymer selected from the group consisting of propane sulfonic acid and polyaniline sulfonic acid is applied to the substrate. The substrate can be, for example, a Si substrate or a quartz glass substrate. It is desirable to previously apply polyethyleneimine to the substrate. Cationic polyethyleneimine can improve the adhesion between the substrate and the anionic polymer. In this case, the application method may be performed by immersing the substrate in an aqueous solution containing an anionic polymer for a predetermined time. Preferably, after the anionic polymer is applied, the substrate is washed with water.

  Step S150: Applying the mixed solution of Step S110 onto the anionic polymer. The mixed solution in step S110 is in a colloidal state. Similar to step S140, the substrate to which polyethyleneimine has been applied may be immersed in the mixed solution for a predetermined time. Preferably, after the mixed solution is applied, the substrate is washed with water.

  Step S140 and step S150 may be repeated as many times as necessary, and laminated to a desired thickness.

  As described above, according to the present invention, a high-crystalline cationic double hydroxide nanosheet and an anionic polymer are layered against a bulky and large anion such as an anionic polymer that cannot be ion-exchanged. By laminating by bilayer, it is possible to easily form a laminated structure. Further, the thickness can be controlled in units of 1 nm by the number of repetitions of step S140 and step S150. Also, the surface so controlled can be very smooth.

  Next, examples will be described, but it should be noted that the present invention is not limited to the examples.

LDH, a starting material for stripping, was prepared. Mg (NO ₃ ) ₂ · 6H ₂ O (0.02 mol) as the first metal salt, Al (NO ₃ ) ₃ · 9H ₂ O (0.01 mol) as the second metal salt, and the hydrolysis reagent Hexamethylenetetraamine (0.026 mol) was mixed and dissolved in an 80 cm ³ aqueous solution. The mixture is placed in an autoclave at 140 ° C., 24
Heated for hours (hydrothermal treatment). The obtained reaction product was filtered, washed with water, and then dried in the air to obtain a solid.

  After the solid matter was dissolved in a hydrochloric acid solution for elemental analysis, the contained metal ions were quantified using an inductively coupled plasma emission spectrometer ICP-AES SPS1700HVR (SEIKO, Japan). Carbonate ions were quantified by acid / base titration.

As a result, the composition of the solid was [Mg _0.65 Al _0.33 (OH) ₂ ] [(CO ₃ ) _0.17 · 0.5H ₂ O] (that is, M ²⁺ in the above formula (1) was Mg, M ³⁺ but Al, a ^n-was found to be CO ^3- and is). The weight fraction of each element is Mg 20.4 wt% (calculated value 20.3 wt%), Al 11.6 wt% (calculated value 11.4 wt%), C2.6 wt% (calculated value 2.6 wt%), respectively. Showed good agreement with the calculated values. That is, the product was confirmed to be typical carbonated Mg—Al LDH.

Next, 0.5 g of the dried solid was treated with 500 cm ³ of an aqueous solution containing NaNO ₃ (0.75 mol) and HNO ₃ (0.0025 mol). Specifically, the aqueous solution containing solids was purged with nitrogen gas together with the container, sealed, and then shaken at room temperature for 1 day to remove carbonate ions by ion exchange and converted to nitric acid type LDH. Again, the solid was collected, washed with water and dried in vacuo. The collected solids were analyzed as follows.

  X-ray diffraction data of a solid material (hereinafter referred to as nitrate-type Mg—Al LDH) was measured.

FIG. 4 is a diagram showing an X-ray diffraction pattern of nitrate-type Mg—Al LDH.
The X-ray diffraction pattern of Mg-Al LDH was measured with an X-ray powder diffractometer Rint 2000S (Rigaku, Japan). The measurement conditions were 40 kV / 30 mA using a CuKα ray (λ = 0.15405 nm), and a scanning speed of 1.5 ° 2θ / min.

  It was confirmed that all the peaks coincided with the rhombohedral unit cell showing the LDH structure. These peaks are obtained by interference of X-rays in the base layers arranged in parallel and periodically. From this data, the lattice constant of LDH was determined. The unit cell had an a-axis length of 0.3050 nm and a c-axis length of 2.675 nm. The interlayer distance of the basic layer was 0.89 nm. This distance is in good agreement with literature values for nitrate-type Mg—Al LDH. This indicates that nitrate-type Mg—Al LDH excellent in crystallinity was obtained.

  Next, using a scanning electron microscope JEOL JSM-6700F (JEOL, Japan), surface observation of nitrate-type Mg—Al LDH was performed. Observation was an acceleration voltage of 10 kV.

FIG. 5 is a view showing an SEM image of nitrate-type Mg—Al LDH.
From the figure, it was found that the nitrate type Mg—Al LDH was a hexagonal plate-like crystal having a size of about 10 μm in a planar shape. In LDH using an amino acid as an intermediate layer, it can be difficult to produce such a large crystal. By using inorganic anions as the intermediate layer, hydrothermal treatment is possible, and LDH crystals well developed in the two-dimensional direction can be easily obtained.

  Next, using a high-resolution transmission electron microscope JEM-3000F (JEOL, Japan), nitrate-type Mg—Al LDH was observed in more detail. Observation was performed at an acceleration voltage of 300 kV.

FIG. 6 is a diagram showing a TEM image (a) and an electron diffraction pattern (b) of nitrate-type Mg—Al LDH.
FIG. 6 (a) TEM image also showed that LDH had a hexagonal plate shape as in FIG. Moreover, the electron diffraction pattern of FIG. 6B showed a clear spot indicating that the nitrate-type Mg—Al LDH is hexagonal.

  As described above with reference to FIG. 4 to FIG. 6, as described, LDH crystals containing inorganic ions as an intermediate layer and having a micron order size have been successfully manufactured.

Next, peeling was performed using the prepared nitrate-type Mg—Al LDH. Nitric acid type Mg—Al LDH 0.05 g was mixed with 100 cm ³ of formamide in a flask. The flask was purged with nitrogen gas and then sealed. The mixture was stirred (shaken) at room temperature for 12 hours at a rotation speed of 170 rpm. It was visually confirmed that the obtained solution was a transparent solution having no precipitate. This suggests that the nitrate-type Mg—Al LDH was peeled off by formamide.

  The clear solution was then centrifuged for 20 minutes at a rotational speed of 30000 rpm, and the following analysis was performed on the settled colloidal sediment.

  The X-ray diffraction pattern of the obtained colloidal sediment was measured with an X-ray powder diffractometer Rint 2000S (Rigaku, Japan).

The results are shown in FIG.
FIG. 7 is a diagram showing an X-ray diffraction pattern (a) of Mg—Al LDH, an X-ray diffraction pattern (b) of formamide and colloidal sediment, and a square of structure factor F (c).

FIG. 7 (a) shows only a part of the X-ray diffraction pattern of the starting nitrate-type Mg—Al LDH shown in FIG.
As shown in FIG. 7B, a remarkable halo was observed in the X-ray diffraction pattern 2θ = 20 ° to 30 ° of the colloidal sediment. This was confirmed to be due to formamide remaining in the colloidal sediment (blank data). Further, the X-ray diffraction pattern (indicated by an arrow in the figure) on the low-angle side of the colloidal sediment showed a broad diffraction pattern, and a clear peak as seen in FIG. This is because the basic layer of nitrate-type Mg-Al LDH (parallel and regularly arranged) is randomly arranged in the colloidal sediment, so that no interference of X-rays occurs. Conceivable. That is, it strongly suggests that the nitrate-type Mg—Al LDH has been peeled off.

  Next, the structure factor F was used to examine the peeling of nitrate-type Mg—Al LDH in more detail.

From previous reports, H _0.7 Ti _1.825 □ _0.175 O ₄ · H ₂ O (□ indicates vacancies), H _0.13 Mn
The X-ray diffraction pattern of the colloidal precipitate composed of the peeled layered basic layer (host layer) such as O ₂ · 0.7H ₂ O and HCa ₂ Nb ₃ O ₁₀ · 1.5H ₂ O It is known to show a broad diffraction pattern different from the distinct peak seen in FIG. More importantly, it has been found that this broad diffraction pattern exhibits a profile that roughly matches the square of the base layer structure factor.
Based on these findings, Mg—Al LDH (here, the basic layer is Mg in which M ²⁺ is Mg, M ³⁺ is Al, and x = 1/3 in the above formula (1)). _2/3 Al _1/3 (OH) ₂ ) was calculated using equation (7).
F = f _{Mg / Al} + 2f _OH cos 2π · 2z · sin θ / λ (7)
Here, f _{Mg / Al} and f _OH are virtual atomic species (2 / 3Mg + 1 / 3Al) and (O + H
) Is the X-ray diffraction angle, and λ is the X-ray wavelength (λ = 0.15405 nm). In the above equation (7), since the LDH basic layer is centrally symmetric in the xy plane, only the cos term is considered. Based on previous reports, z, which is the position of OH, was set to 0.10 nm.

  The result obtained from the equation (7) is shown in FIG. The profile in FIG. 7 (c) was found to be similar to the low angle X-ray diffraction pattern of the colloidal sediment in FIG. 7 (b). From this, it was confirmed that the entire sample of Mg-Al LDH was completely peeled off by formamide.

  Conventionally, it has been reported that LDH containing organic anions such as amino acids as an intermediate layer is colloidalized by formamide, and it has been claimed that this is due to exfoliation. It was found that the contained LDH can be easily peeled off by an aprotic polar solvent such as formamide. It should be understood that such a discovery is first discovered through ingenuity.

Next, the production of LDH nanosheets was confirmed using the above colloidal sediment (hereinafter referred to as LDH nanosheets or double hydroxide nanosheets).
The LDH nanosheets were observed using a high resolution transmission electron microscope JEM-3000F (JEOL, Japan) equipped with a Gatan-666 electron energy loss spectrometer and an energy dispersive X-ray analyzer. The acceleration voltage was 300 kV.

FIG. 8 is a diagram showing a TEM image and an electron diffraction pattern of an LDH nanosheet.
The TEM image in FIG. 8 shows that the LDH nanosheet has a spread of about 2 μm in the two-dimensional direction. It also shows that the LDH nanosheet maintains the hexagonal structure of LDH used as the starting material. As a result of EDX analysis, Mg, Al, O, C, and Cu were detected. Among the detected elements, C and Cu correspond to the constituent elements of the TEM grid. Further, the ratio of Mg to Al was 1.6. This value almost coincides with the ratio of Mg to Al in the starting nitrate-type Mg—Al LDH of 1.91.

  The electron diffraction pattern of FIG. 8 showed a clear spot indicating that the LDH nanosheet was hexagonal. The a-axis length of the unit cell obtained from the electron diffraction pattern was 0.31 nm, which almost coincided with the a-axis length (0.3050 nm) of the unit cell of nitric acid Mg-Al LDH as a starting material.

  From the above, it was found that the LDH nanosheet was peeled well in a state where the crystal structure of the nitrate-type Mg—Al LDH used as the starting material was maintained without being impaired.

  Next, the surface topography of the LDH nanosheet was examined using a Seiko SPS-100 atomic force microscope (AFM). Samples for surface topography were prepared by adsorbing LDH nanosheets on a Si substrate. The measurement was performed with a cantilever equipped with a silicon chip in a tapping mode of 14 N / m.

FIG. 9 is a diagram showing an AFM image of the LDH nanosheet.
FIG. 9 shows a state in which the LDH nanosheets are adsorbed on the substrate as a single sheet except for some overlap. The size of each sheet was about 2 μm as described above with reference to FIG. The thickness of the LDH nanosheet obtained from the step between the LDH nanosheets was 0.81 ± 0.05 nm, confirming that it was a single layer sheet.

Next, a novel composite thin film material was manufactured using the LDH nanosheet obtained in Example 1. The Si substrate and the quartz substrate were washed for 20 minutes each in methanol / hydrochloric acid (mixed at a volume ratio of 1: 1) and concentrated sulfuric acid. Next, after the substrate was washed with water, the substrate was immersed in polyethyleneimine (PEI, 1.25 g / dm ³ , pH = 9) for 20 minutes. As a result, positively charged PEI was applied (coated) to the substrate. Next, a substrate (PEI / Sub) to which PEI was applied (where Sub represents a substrate) was immersed in an aqueous solution of sodium 4-styrenesulfonate (PSS) (1 g / dm ³ ) for 20 minutes, and then water Washed with. Then PS
Add S / PEI / Sub to a colloidal solution (0.5 g / dm ³ ) containing LDH nanosheets.
It was immersed for 0 minutes and washed again with water. In this way, (LDH nanosheet / PSS) _{n = 1} / PEI / Sub was obtained. Thereafter, the step of applying PSS and LDH nanosheet was repeated n times (n; cumulative number, 1 ≦ n ≦ 10) to obtain a composite thin film material (LDH nanosheet / PSS) _n .

  The surface topography of the composite thin film material when n = 1 was examined using a Seiko SPS-100 atomic force microscope (AFM). The measurement was performed with a cantilever equipped with a silicon chip in a tapping mode of 14 N / m.

FIG. 10 is a diagram showing an AFM image of LDH nanosheet / PSS / PEI / Sub. Here, a Si substrate was used as the substrate.
The presence of PSS and PEI was not confirmed on the surface. This indicates that the whole is coated with LDH nanosheets. It can be seen that the LDH nanosheet covering the surface has a large size in the range of several hundred nanometers to several micrometers and covers the substrate surface almost efficiently. Since the LDH nanosheet was positioned on the negatively charged PSS, it was confirmed that the LDH nanosheet was positively charged (cationic).

Next, Hitachi U-4000 of composite thin film material (LDH nanosheet / PSS) _n
Using a spectrophotometer (Hitachi, Japan), an ultraviolet / visible absorption spectrum was measured in a transmission mode. The measurement was performed immediately after the accumulation of LDH nanosheets.

FIG. 11 is a diagram showing an ultraviolet / visible absorption spectrum of a composite thin film material (LDH nanosheet / PSS) _n . Here, quartz glass was used as the substrate.
In the figure, the ultraviolet and visible absorption spectra for the cumulative number n = 1 to 10 are shown, and the inset shows the relationship between the absorbance at the wavelength of 193 nm and the cumulative number. Absorption in the vicinity of about 200 nm, which is seen in any spectrum, is due to PSS. The absorbance of this PSS increased as the cumulative number increased.

  More specifically, as shown in the inset, the absorbance of PSS increased linearly as the cumulative number n increased, and an absorbance of 0.34 was obtained at the cumulative number n = 10. Such a linear increase in the absorbance of PSS depending on the cumulative number indicates that a composite thin film material composed of a multilayer film in which LDH nanosheets and PSS are alternately laminated is formed. The absorbance 0.34 is comparable to the absorbance obtained with a multilayer film in which PSS is laminated using polydiallyldimethylammonium chloride (PDDA). Therefore, the LDH nanosheet according to the present invention can be effective as a novel cationic linker in producing a multilayer film composed of an anionic polymer.

Next, the X-ray diffraction pattern of the composite thin film material (LDH nanosheet / PSS) _{n is the same as} the X-ray diffraction pattern of the nitrate-type Mg—Al LDH crystal and LDH nanosheet which are the starting materials described above. Determined by Rint 2000S (Rigaku, Japan). The measurement conditions are the same.

FIG. 12 is a diagram showing an X-ray diffraction pattern of a composite thin film material (LDH nanosheet / PSS) _n . Here, a Si substrate was used as the substrate. In order to avoid complication of the figure, only X-ray diffraction patterns with cumulative number n = 3, 5 and 10 are shown in the figure.
All diffraction patterns showed a diffraction peak at 2θ = 4.4 °. From this, it was found that the interlayer distance of PSS was about 2.2 nm. The diffraction peaks at 2θ = 4.4 ° were all broad, but the peak intensity increased as the cumulative number n increased. Further, in the composite thin film material having the cumulative number n = 10, a second-order diffraction peak was confirmed at 2θ = 8.6 °.

  Thus, according to the present invention, a multilayer film made of an anionic polymer can be produced by using a cationic double hydroxide nanosheet (LDH nanosheet) as a linker. In particular, since the double hydroxide nanosheet according to the present invention has a larger area than the conventional double hydroxide nanosheet, a high-quality multilayer film can be obtained, which can be advantageous in material design.

  As described above, according to the present invention, a double hydroxide nanosheet can be easily produced from LDH having an inorganic anion as an intermediate layer. Double hydroxide nanosheets can be useful as novel cationic nanomaterials. Further, by using this double hydroxide nanosheet, an oriented LDH thin film material, and further a novel composite thin film material can be provided. Such LDH thin film materials and composite thin film materials using double hydroxide nanosheets can be used for catalysts, sensors, antistatic coatings and the like.

The flowchart which shows the method of peeling LDH of this invention Schematic diagram of LDH thin film material (a) and organic-LDH thin film material (b) using double hydroxide nanosheets according to the present invention Schematic diagram of composite thin film material using double hydroxide nanosheet according to the present invention The figure which shows the X-ray-diffraction pattern of nitric acid type Mg-Al LDH The figure which shows the SEM image of nitric acid type Mg-Al LDH The figure which shows the TEM image (a) and electron diffraction pattern (b) of nitric acid type Mg-Al LDH The figure which shows the X-ray-diffraction pattern (a) of Mg-Al LDH, the X-ray-diffraction pattern (b) of formamide and a colloidal sediment, and the square of the structure factor F (c) The figure which shows the TEM image and electron diffraction pattern of LDH nanosheet The figure which shows the AFM image of a LDH nanosheet The figure which shows the AFM image of LDH nanosheet / PSS / PEI / Sub The figure which shows the ultraviolet and visible absorption spectrum of a composite thin film material (LDH nanosheet / PSS) _n Diagram showing X-ray diffraction pattern of composite thin film material (LDH nanosheet / PSS) _n

Explanation of symbols

200 LDH thin film material 210 Substrate 220, 320 Double hydroxide nanosheet 230, 250 Intermediate layer 300 Composite thin film material 310 Anionic polymer layer 340 Adhesive layer

Claims (27)

A method for peeling off a layered double hydroxide,
Mixing the layered double hydroxide with an aprotic polar organic solvent,
The layered double hydroxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Wherein m is a real number greater than 0 and x is 0 <x <0.5. The method of claim 1, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The method of claim 1, wherein M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.   The method of claim 1, wherein the aprotic polar organic solvent is selected from the group consisting of formamide, dimethylsulfoxide, methylformamide, and dimethylformamide.   The method according to claim 1, wherein the mixing is purged with an inert gas and shaken at room temperature for 1 to 24 hours. A double hydroxide nanosheet represented by any one of formulas (4) to (6),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4)
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6)
Here, in the formulas (4) to (6), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, and x is 0 <x <0.5. The double hydroxide nanosheet has a size in the longitudinal direction of 5 nm to 50 μm, and the double hydroxide nanosheet has a thickness of 0.3 nm to 2 nm. The double hydroxide nanosheet according to claim 6, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The double hydroxide nanosheet according to claim 6, wherein said M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La. A double hydroxide nanosheet obtained by a method of exfoliating a layered double hydroxide, the method comprising:
Mixing the layered double hydroxide with an aprotic polar organic solvent,
The layered double hydroxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ² , SO ₄ ²⁻ , and mixtures thereof, A double hydroxide nanosheet wherein the valence is m is a real number greater than 0 and x is 0 <x <0.5. The double hydroxide nanosheet according to claim 9, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The double hydroxide nanosheet according to claim 9, wherein M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.   The double hydroxide nanosheet according to claim 9, wherein the aprotic polar organic solvent is selected from the group consisting of formamide, dimethylsulfoxide, methylformamide, and dimethylformamide. A method for producing a layered double hydroxide thin film material,
Mixing the layered double hydroxide with an aprotic polar organic solvent;
Applying the mixed solution obtained in the mixing step to a substrate by spin coating or dip coating,
The layered double hydroxide is represented by any one of formulas (1) to (3),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Wherein m is a real number greater than 0 and x is 0 <x <0.5.   The method according to claim 13, further comprising a step of ion exchange of the imparted product obtained in the imparting step. The method of claim 13, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The method of claim 13, wherein M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.   14. The method of claim 13, wherein the aprotic polar organic solvent is selected from the group consisting of formamide, dimethylsulfoxide, methylformamide, and dimethylformamide. A method for producing a composite thin film material comprising a double hydroxide nanosheet and an anionic polymer layer,
A step of mixing a layered double hydroxide with an aprotic polar organic solvent, wherein the layered double hydroxide is represented by any one of formulas (1) to (3);
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} [A ⁿ⁻ _{x / n} · mH ₂ O] ^x− (1)
_{^{[Li + 1-x M 3+}} x (OH) 2] (2x-1) + [A n- (2x-1) / n · mH 2 O] (2x-1) - ... (2)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} [A ^n- _{2x / n} · mH ₂ O] ^2x- (3)
Here, the formula (1) to the formula (3), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-is, NO ₃ ^-, Cl ^-, An inorganic anion selected from the group consisting of ClO ₃ ⁻ , ClO ₄ ⁻ , F ⁻ , Br ⁻ , I ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , and mixtures thereof, and n is the inorganic anion Wherein m is a real number greater than 0 and x is 0 <x <0.5;
Sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1- (4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamido) -1,2-ethanedinyl) sodium, polyanilinepropane Providing an anionic polymer selected from the group consisting of sulfonic acid and polyaniline sulfonic acid;
Applying the mixed solution obtained in the mixing step onto the anionic polymer. The method of claim 18, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The method of claim 18, wherein the M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La.   The method of claim 18, wherein the aprotic polar organic solvent is selected from the group consisting of formamide, dimethylsulfoxide, methylformamide, and dimethylformamide.   19. The method of claim 18, wherein the mixing step is purged with an inert gas and shaken at room temperature for 1 to 24 hours. The method according to claim 18, further comprising the step of alternately applying the step of applying the anionic polymer and the step of applying the mixed solution. A composite thin film material comprising at least one set of double hydroxide nanosheets and an anionic polymer layer,
The double hydroxide nanosheet is represented by any one of formulas (4) to (6),
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} (4)
[Li ⁺ _1-x M3 ⁺ _x (OH) ₂ ] ^{(2x-1) +} (5)
[M ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ] ^{2x +} (6)
Here, in the formulas (4) to (6), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, and x is 0 <x <0.5. The size in the longitudinal direction of the double hydroxide nanosheet is 5 nm or more and 50 μm or less, and the thickness of the double hydroxide nanosheet is 0.3 nm or more and 2 nm or less,
The anionic polymer layer is composed of sodium 4-styrenesulfonate, sodium polyvinylsulfonate, poly- (1- (4- (3-carboxy-4-hydroxyphenylazo) -benzenesulfonamide) -1,2- Etanedinyl) sodium, polyaniline propane sulfonic acid, and a composite thin film material selected from the group consisting of polyaniline sulfonic acid. The composite thin film material according to claim 24, wherein the M ²⁺ is selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, and Ca. The composite thin film material according to claim 24, wherein said M ³⁺ is selected from the group consisting of Al, Cr, Mn, Fe, Co, Ni, and La. The composite thin film material according to claim 24, wherein the at least one set of double hydroxide nanosheets and the anionic polymer layer are alternately laminated.

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