JP2002104825A - Manufacturing method of crystalline titanium oxide single molecular film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a TiO2 single molecular film. Namely, to turn TiO2, which is useful as such photo-functional materials as photocatalyst, into a single-molecular film with controlled surface pressure and area, by utilizing bi-lyophilic molecule of organic ammonium at a boundary between vapor and liquid. SOLUTION: In manufacturing a single-molecular film of crystalline TiO2 with thickness of around 1 nm at a boundary between vapor and liquid, a) an orthorhombic layered cesium titanate (CsxTi2-x/4O4, x=0.60-0.75) is reacted with an acid solution to synthesize a laminar titanate HxTi2-x/4O4.H2O in powder. The powder is dispersed and agitated in an amine solution to spall the laminar crystal into thin pieces of anisotropy shaped micro-crystal with thickness of 1 nm or less and width of about 1 μm. A hydrosol suspending thin pieces of TiO2 micro-crystal is then formed. b) An organic ammonium molecule is extended above the surface of the hydrosol for complex formation with thin pieces of TiO2 micro-crystal to form the TiO2 single-molecular film c) The surface pressure of the TiO2 single-molecular film is kept at 0.1 mN-1m-70 mNm-1, and its surface area is controlled to 1 cm2-800 cm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a TiO ₂ monomolecular film. More specifically, by utilizing an organic ammonium amphiphilic molecule at the air-water interface, Ti is useful as a photofunctional material such as a photocatalyst.
The present invention relates to a method for producing O ₂ as a monomolecular film whose surface pressure and area are controlled.

[0002]

As a method of manufacturing the Related Art TiO ₂ as a monomolecular film or a ultrathin film close to it, is the minimum unit, the sol - gel method was applied to air-water interface to "two-dimensional sol - gel method" only Known [Moriguchi
Et al. Am. Chem. Soc. , 1995, 11
7, 1139-1140). For example, when a trace amount of a chloroform solution of titanium butoxide is spread on a water surface, a hydrolysis / polycondensation reaction occurs at the air-water interface, and an island-shaped floating polycondensate in which butoxy groups are partially left is obtained. When this is compressed, it becomes a uniform and dense interfacial polycondensation thin film having a film thickness at the molecular level. However, the monomolecular film produced by this method is crystallographically amorphous (amorphous), and as such is poor in applicability as a material.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and aims to overcome the limitations of the conventional monomolecular film derived from the sol-gel method. An object of the present invention is to provide a novel TiO ₂ monomolecular film manufacturing method that can maintain a crystalline order in a film unlike the conventional one, and can be handled similarly to a conventional sol-gel amorphous film. Is to provide.

[0004]

The present invention SUMMARY OF] is as to solve the foregoing problems, crystalline ultrathin film of TiO ₂ is formed on the air-water interface, that is, the thickness, characterized in that a longitudinal 1nm Provided is a monolayer of TiO ₂ crystals.

Further, the present invention relates to an orthorhombic layered cesium titanate (Cs _x Ti _{2-x / 4} O ₄ , x = 0.60 to 0.75)
Is reacted with an aqueous acid solution to form a layered titanate H _x Ti _{2-x / 4} O ₄
· H ₂ O powder was synthesized and then dispersed stirring the powder in the amine aqueous solution, than the thickness 1nm a layered crystal, about the width 1μ
Also provided is a method for producing the above monomolecular film using a TiO ₂ hydrosol obtained by exfoliating a flake microcrystal having an anisotropic shape of m.

More specifically, a monomolecular film is produced by developing organic ammonium molecules on the water surface of the hydrosol and forming a complex with TiO ₂ flake microcrystals. Specifically, the surface pressure of the TiO ₂ monomolecular film is 0.1 mN ^-1 m to 70 mNm ^-1 , and the area is 1 cm ² to 8.
The manufacturing method is controlled to be 00 cm ² .

That is, the present invention relates to: a) orthorhombic layered cesium titanate (Cs _x Ti _{2-x / 4}
O ₄ , x = 0.60-0.75) is reacted with an aqueous acid solution to synthesize layered titanate H _x Ti _{2-x / 4} O ₄ .H ₂ O powder,
This powder is dispersed and stirred in an aqueous amine solution to form a hydrosol in which TiO ₂ flake microcrystals are suspended by exfoliating the layered crystals to anisotropic flake microcrystals having a thickness of 1 nm or less and a width of about 1 μm, b) developing an organic ammonium molecule on the water surface of the hydrosol and forming a complex with TiO ₂ flake microcrystals to form a TiO ₂ monomolecular film; c) reducing the surface pressure of the TiO ₂ monomolecular film to 0.1 mN ^-1 m
７０70 mNm ⁻¹ and the area is 1 cm ² ８００800
By controlling the cm ^2, and a method of thickness at air-water interface to produce a crystalline TiO ₂ monomolecular ultra thin film of about 1 nm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as described above, a hydrosol in which TiO ₂ flake microcrystals are suspended is synthesized from a layered titanic acid, and an organic ammonium molecule is developed on the water surface to form an air-water interface. In crystalline T
An iO ₂ monolayer is derived.

This monomolecular film has a surface pressure of 0.1 mNm ^-1 to
70 mNm ^-1 (preferably 15 mNm ^{-1 to} 40 mN
m ^-1 ) and an area of 1 cm ^{2 to} 800 cm ² (preferably 100
very stably controlled in cm ² ~400cm ^2),
Holding the pressure for a long time does not change the area of the membrane. Therefore, it can be handled similarly to a conventional sol-gel amorphous membrane.

[0010] For example, this monolayer has a hydrosol concentration of 0.002 per liter of solution based on titanic acid.
g ~ 4g, preferably 0.04g ~ 0.2g) and pH
(9.5 to 13, preferably around 11.5) or by selecting appropriate organic molecules, they can be accumulated on the solid substrate. According to the present invention, the application range is expected to expand to the synthesis of hybrid materials with ceramics and organic substances whose thickness is controlled at the molecular level.

On the other hand, the present invention provides a method for producing a crystalline TiO ₂ monomolecular film different from an amorphous monomolecular film derived from a two-dimensional sol-gel method. Conventional two-dimensional sol
The monomolecular film obtained by the gel method is crystallographically amorphous, whereas the monomolecular film obtained by the present invention has a thickness of 1 n.
m is a monomolecular film in which flake microcrystals of anisotropic shape having a width of about 1 μm are arranged. In addition, because of the unique shape of flakes, it is convenient for synthesizing ceramic thin films with a high specific surface area, and is most expected to be applied to photocatalytic materials where the ability to collect contaminants on the surface is important. .

Hereinafter, a method for producing a TiO ₂ monomolecular film of the present invention will be described in more detail with reference to examples.

[0013]

EXAMPLES (Example 1) Sasaki et al. Am. C
hem. Soc. , 1996, 118, 8329-83.
With reference to the method described in 35, a hydrosol in which flaky TiO ₂ microcrystals were suspended was synthesized.

That is, titanium dioxide (TiO ₂ ) and cesium carbonate (Cs ₂ CO ₃ ) are mixed at a molar ratio of 5.3: 1, and the mixture is heated at 800 ° C. for one hour in a platinum crucible with a lid to form a carbonate. Was disassembled. This calcined product is crushed in a mortar,
By repeating firing at 0 ° C. for 20 hours twice, a layered cesium titanate of orthorhombic structure (Cs _x Ti _{2-x / 4} O ₄ , x
= 0.70).

Next, with respect to 200 ml of 1N hydrochloric acid,
And dispersed and stirred at a rate of 1 g of the cesium titanate powder.
And react at room temperature for a total of 96 hours while exchanging hydrochloric acid.
Was. This allows the cesium ions between the layers to become hydrogen ions
To form a layered titanate H_xTi_{2-x / 4}O_Four・ H_TwoO powder
was gotten. Finally, 0.4 g of this layered titanate powder
Concentration 0.0825moldm^-3Of tetrabutyla hydroxide
Nmonium ((C_FourH₉) _FourNOH) 100 milliliter aqueous solution
Added to the turtle and stirred vigorously. By reaction for more than 2 weeks
The resulting hydrosol is a layered H_xTi_{2-x / 4}O_Four・
H_TwoFlake-like TiO in which O is peeled into individual layers_TwoMicrocrystal
(Thickness 0.75nm, width 1μm)
And exhibited a translucent to milky color tone.

The hydrosol thus obtained was diluted about 20 times to 0.2 g per liter of solution based on titanic acid. Since the absorption spectrum of the diluted sol showed a sharp absorption peak at 268 nm as before the dilution,
It was found that the exfoliated flake microcrystals did not aggregate and stack even after dilution, and that the thickness was maintained.

This diluted sol (pH = 11 to 12) is filled in a Langmuir trough (a water tank for forming a monomolecular film of organic molecules on the water surface, ie, a Langmuir film), and dioctadecyldimethylammonium bromide ((C
A chloroform solution of ₁₈ H ₃₇ ) ₂ (CH ₃ ) ₂ NBr) (concentration: 1.6 × 10 ⁻³ moldm ⁻³ ) was developed by 0.03 ml. After the chloroform was evaporated, the area of the trough was reduced at a rate of 15 cm ² min ⁻¹ while maintaining the temperature at 20 ° C., and the change in surface pressure at that time was measured. The area-surface pressure curve thus obtained is shown in FIG.

With the decrease in the trough area, the surface pressure starts to increase gradually from a certain point, and thereafter, the surface pressure 25
Plateau region around mNm ^-1 (region flat on graph)
, The surface pressure rapidly increased from around 30 mNm ^-1 . T
By comparing the iO ₂ when no suspended microcrystalline results (FIG. 1 (b)), such a change in the surface pressure, the ammonium cations are charged TiO ₂ crystallites and complexing negatively It became clear that it was caused by. That is, the point at which the surface pressure starts to rise is interpreted as the point at which the TiO ₂ microcrystals initially isolated on the sol water surface approach and begin to repel. On the other hand, when held at a surface pressure exceeding 30 mNm ⁻¹ , the flaky TiO ₂ microcrystals are arranged without gaps with the plane parallel to the water surface, and a dense monomolecular film is formed.

FIG. 1 also revealed that this monomolecular film collapsed when the surface pressure reached about 70 mNm ^-1 . That is, the surface pressures shown in FIG. 1 are (a) a hybrid monomolecular film formed by complex formation of ammonium monomolecules and TiO ₂ monomolecules, and (b) a monomolecular film formed only of ammonium monomolecules. Each represents the pressure at which the membrane collapsed.

(Embodiment 2) Fabricated by the same method as in Embodiment 1.
TiO_TwoMonolayer film with surface pressure of 40mNm^-1Compress with
After holding for 1 hour or more in that state, the area of the film
Is 105cm^TwoThere was no change. From this, the present invention
TiO formed at the air-water interface by the method _TwoMonolayer
Was extremely stable.

[0021]

As described above in detail, according to the present invention, unlike a conventional amorphous monomolecular film derived from a two-dimensional sol-gel method, a new T formed from flake microcrystals having anisotropy is obtained.
An iO ₂ monolayer is induced. Since this monomolecular film can exist extremely stably at the air-water interface, it can be accumulated on the solid substrate by controlling the concentration or pH of the hydrosol or selecting an appropriate organic molecule. By producing such a cumulative film, that is, a Langmuir-Blodgett film, it is expected that the range of application is expanded to the synthesis of ceramics whose thickness is controlled at the molecular level and a hybrid material with an organic substance.

Further, since the TiO ₂ monomolecular film is made of flake-like microcrystals as a raw material, it is suitable for synthesizing a ceramic thin film having a high specific surface area. Therefore, application to a photocatalyst material in which the ability to collect contaminants on the surface is important is expected most.

[Brief description of the drawings]

FIG. 1 (a) shows a dioctadecyldimethylammonium bromide solution (chloroform solvent; concentration: 1.6 × 10 4) on a water surface of a hydrosol in which TiO ₂ flake microcrystals are suspended.
^-3 moldm ^-3 ) was developed to 0.03 ml, and the area of the trough was 15 cm ² min while maintaining the temperature at 20 ° C.
FIG. 8 is a diagram showing a change in surface pressure when the surface pressure is decreased at a speed of ^-1 . The horizontal axis is the scale of the trough area. On the other hand, (b) shows the result of developing the same solution without depleting the TiO ₂ microcrystals for comparison.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Keisuke Asai 7-3-1 Hongo, Bunkyo-ku, Tokyo F-term in Tokyo University Graduate School 4G047 CA02 CB05 CC03 CD02 4G069 AA08 AA09 AA11 BA04A BA04B BA48A BB04C BC06C BC50C CA05 CA06 CA11 EA08 FB06 FC02

Claims (4)

[Claims] 1. A method for producing a crystalline titanium oxide (TiO ₂ ) monomolecular film having a thickness of about 1 nm at an air-water interface. 2. An orthorhombic layered cesium titanate (Cs _x
Ti _{2-x / 4} O ₄ , x = 0.60-0.75) is reacted with an aqueous acid solution to synthesize layered titanate H _x Ti _{2-x / 4} O ₄ .H ₂ O powder, and then This powder is dispersed and stirred in an aqueous amine solution,
_2. The method according to claim 1, wherein a TiO2 hydrosol obtained by exfoliating the layered crystal to a flake having a thickness of 1 nm or less and a width of about 1 [mu] m is used. 3. The method according to claim 1, wherein the organic ammonium molecules are spread on the water surface of the hydrosol and are complexed with TiO ₂ flake microcrystals. 4. The TiO ₂ monolayer has a surface pressure of 0.1 mN.
m ^-1 ~70mNm ^-1, area method according to claim 1 for controlling the 1cm ² ~800cm ^2.