JP2010087489A - Colloidal crystal, and light-emitting amplifier using the same - Google Patents

Abstract

A colloidal crystal having high light emission enhancement effect, less deterioration, fading and outflow of a luminescent material, a large degree of freedom of material selection, hardly causing concentration quenching, and high thermal stability, and light emission using the same Providing an amplifier.
A monodispersed spherical mesoporous silica arranged regularly and a luminescent substance introduced into mesopores of the monodispersed spherical mesoporous silica, the luminescent substance comprising a luminescent organic dye, an organometallic compound, and the like. Colloidal crystals comprising at least one selected from coordinate compounds, polymer light-emitting materials, and semiconductor nanoparticles, and a light-emitting amplifier using the same.
[Selection] Figure 10

Description

  The present invention relates to a colloidal crystal and a light-emitting amplifier using the same, and more particularly to a colloidal crystal capable of enhancing fluorescence emitted from a light-emitting substance and a light-emitting amplifier using the colloidal crystal.

It is known that colloidal particles with a small variation in particle size (so-called monodisperse) are dispersed in a solvent and the solvent is evaporated, and the colloidal particles are regularly arranged to form a regular structure (colloidal crystal). Yes. Such a colloidal crystal can reflect an electromagnetic wave having a wavelength corresponding to the lattice constant by Bragg diffraction.
For example, when the colloidal crystal is made of colloidal particles having a particle size on the order of submicron, it is possible to Bragg-reflect wavelengths in the range from ultraviolet light and visible light to infrared light. When visible light is Bragg-reflected, the colloidal crystal exhibits a structural color. Utilizing these characteristics, colloidal crystals are color materials that use structural colors, optical filters that do not transmit light of a specific wavelength, mirrors that reflect specific light, and novel optical functional materials called photonic crystals. Applications to optical switches, optical sensors, etc. are considered.

  The Bragg reflection of the colloidal crystal means that the colloidal crystal has a stop band and there exists light having a wavelength that cannot be transmitted. When the luminescent material is present in the colloidal crystal and the stop band matches the emission wavelength of the luminescent material, the emitted light is confined in the colloidal crystal and resonates by repetitive reflection on the colloidal crystal surface. Leads to laser light oscillation.

Various proposals have been made for light enhancement using colloidal crystals.
For example, Patent Document 1 discloses that
(1) The polystyrene particles are regularly arranged to form a colloidal crystal, the surface of the colloidal crystal is covered with a precursor polymer of polydimethylsilicon gel, and the precursor polymer is gelled to form a colloidal crystal film.
(2) Between the two colloidal crystal films, poly (ethylene glycol) diacrylate in which rhodamine and a photopolymerization initiator are dissolved is injected, and the light emitting layer is fixed by irradiation with ultraviolet light.
A laser oscillation device obtained by this is disclosed.
In the same document,
(A) In order to obtain a laser beam, the reflection band of the colloidal crystal thin film must completely overlap with the emission spectrum of the light emitting layer,
(B) When the excitation light energy is 150 nJ / pulse, laser oscillation light can be obtained, and the spectral line width (= half-value width) is 1 nm or less,
(C) When rhodamine is not fixed with a polymer, the laser oscillation light cannot be observed if the device is left overnight. However, when rhodamine is fixed with a polymer, the device is stable even after the device is left for more than a week. The point that laser oscillation light can be excited on, and
(D) The obtained laser oscillation device oscillates at a lower threshold than a normal laser oscillator,
Is described.

Non-Patent Document 1 discloses a photonic produced by a vertical deposition method using a mixed solution of a dispersion of monodisperse poly (styrene-methyl methacrylate-acrylic acid) spherical particles and an aqueous solution in which rhodamine B is dissolved. Crystals are disclosed.
In the same document,
(1) By increasing the excitation energy, the emission intensity increases and at the same time the spectrum width becomes narrower, and (2) when the excitation intensity approaches the maximum, the half width of the emission peak becomes 15 nm,
Is described.

JP 2006-287024 A

Mingzhr Li et al., "Coherent control of spontaneous emission by photonic crystals", Chemical Physics Letters 444 (2007)

The laser oscillation device disclosed in Patent Document 1 can oscillate a single wavelength laser with low energy and does not require an external resonator, so that the device can be miniaturized.
However, in order to express the characteristics of the colloidal crystal, it is necessary to prepare two colloidal crystal films having the same thickness and structure, and to fix the colloidal crystal film by gelation. is there.
In addition, organic dyes used in the light emitting layer are easily deteriorated and faded and have poor stability. When such an organic dye is solidified with a polymer material such as polyethylene glycol, the deterioration of the dye can be suppressed to some extent. However, for this purpose, it is necessary to use a polymer material having a high solubility of the organic dye, and the degree of freedom in material selection is low. Further, it is difficult to uniformly disperse the pigment in the polymer material, and it is difficult to obtain a stable and uniform light emitting layer.
Furthermore, since it is necessary to separate the light emitting layer and the colloidal crystal layer into a three-layer structure, there is a limit to miniaturization of the device. In addition, since the structure including the colloidal particles is basically composed of an organic substance, it is flexible but has poor thermal stability.

On the other hand, the photonic crystal disclosed in Non-Patent Document 1 has a structure in which a dye as a light emitting layer exists between colloidal particles, and the colloid layer and the light emitting layer are integrated.
However, in order to introduce an organic dye between colloidal particles, it is necessary to use a water-soluble organic dye. Since many luminescent organic dyes have low solubility in water, usable dyes are limited. In addition, the organic dye introduced between the colloidal crystals is likely to aggregate and easily cause a phenomenon (concentration quenching) in which the amount of luminescence is reduced, so that the control of the dye concentration is complicated. Furthermore, since the organic dye is not specially solidified, it tends to flow out of the crystal.
Furthermore, since the photonic crystal has a structure made of an organic material, it has poor thermal stability. Further, although a certain degree of light emission enhancement is recognized by increasing the excitation light intensity, a large enhancement effect is not obtained, and the half-value width of the light emission peak remains at about 15 nm.

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a colloidal crystal that has little deterioration, fading and outflow of a luminescent material, has a high degree of freedom in material selection, and hardly causes concentration quenching, and a light emitting amplifier using the colloidal crystal. .
Another object of the present invention is to provide a colloidal crystal capable of obtaining a large light emission enhancement effect and a fluorescence amplifier using the colloidal crystal.
Furthermore, another problem to be solved by the present invention is to provide a colloidal crystal having high thermal stability and a light emitting amplifier using the same.

In order to solve the above problems, the colloidal crystal according to the present invention is:
Monodispersed spherical mesoporous silica regularly arranged;
A luminescent material introduced into the mesopores of the monodispersed spherical mesoporous silica,
The gist of the light-emitting substance is any one or more selected from light-emitting organic dyes, organometallic coordination compounds, polymer light-emitting materials, and semiconductor nanoparticles.
The luminescent material preferably has an emission spectrum that overlaps with the reflection spectrum of the colloidal crystal.
The gist of the light-emitting amplifier according to the present invention is that the colloidal crystal according to the present invention is used.

When a luminescent substance is introduced into the mesopores of monodispersed spherical mesoporous silica and colloidally crystallized, the deterioration, fading and outflow of the luminescent substance can be suppressed. In addition, a high-concentration luminescent substance can be introduced uniformly, and there is little risk of causing concentration quenching. Furthermore, there are few restrictions on the luminescent substance that can be introduced into the mesopores, and the degree of freedom in material selection is great. Moreover, since it is based on silica, it has high thermal, mechanical and chemical stability.
Further, when the emission spectrum of the luminescent substance and the reflection spectrum of the colloidal crystal overlap, the light generated by exciting the luminescent substance is resonated and enhanced within the stop band. Therefore, the light emission enhancement effect equivalent to or higher than that of the conventional light emitting amplifier can be obtained. In addition, since it is not necessary to have a three-layer structure, the manufacturing process is simple and the apparatus can be further miniaturized.

It is a schematic block diagram of the colloidal crystal which concerns on this invention. It is a figure explaining the principle of light emission enhancement. 3 (a) and 3 (b) are SEM images of monodispersed spherical mesoporous silica obtained in Comparative Example 1 and Example 1, respectively. The left diagram in FIG. 4 is an SEM image of monodispersed spherical mesoporous silica obtained in Example 2, and the right diagram in FIG. 4 is an SEM image of colloidal crystals obtained in Example 2. It is a schematic block diagram of the experimental apparatus for measuring the amplification of the light by a colloid crystal. It is an emission spectrum of rhodamine 610. It is an angle-resolved reflection spectrum of a colloidal crystal (Comparative Example 1) produced from Rh610-MMSS1. It is an angle-resolved reflection spectrum of the colloidal crystal (Example 1) produced from Rh610-MMSS2. It is an angle-resolved reflection spectrum of the colloidal crystal (Example 2) produced from Rh610-MMSS3. It is an emission spectrum of the colloidal crystal (Example 1) produced from Rh610-MMSS2. It is a figure which shows the relationship between the excitation intensity | strength of the emission spectrum of the colloidal crystal obtained in Example 1 and Comparative Example 1, and luminescence intensity. It is a figure which shows the relationship between the excitation intensity | strength of the colloidal crystal (Example 2) produced from Rh610-MMSS3, light emission intensity, and a half value width. It is a figure which shows the light absorbency change (1-7 hours) when the particle | grains (Rh610-MMSS2) obtained in Example 1 are disperse | distributed to ion-exchange water. It is a figure which shows the light absorbency change (1-7 hours) when the particle | grains (Rh610-MMSS2) obtained in Example 1 are disperse | distributed to chloroform. It is a figure which shows the light absorbency change of the chloroform dispersion liquid of the two types chloroform solution 1 and 2 from which rhodamine density | concentration differs, and the particle | grains (Rh610-MMSS3) obtained in Example 2. FIG. The left figure and the right figure in FIG. 16 are external appearance photographs of the colloidal crystals obtained in Comparative Example 3 and Example 3, respectively. 17A is an excitation / fluorescence spectrum of rhodamine 610, and FIG. 17B is a reflection spectrum of the vertical reflection of the colloidal crystal obtained in Example 3. FIG. FIG. 18A is an emission spectrum of the colloidal crystal obtained in Example 3, and FIG. 18B is an enlarged view thereof. It is a figure which shows the excitation light intensity dependence of the peak intensity of the colloidal crystal obtained in Example 3. It is a figure which shows the angle dependence (directivity) of the peak position of the spectrum of the colloidal crystal obtained in Example 3. FIG.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Colloidal crystal]
The colloidal crystal according to the present invention is
Monodispersed spherical mesoporous silica regularly arranged;
A luminescent material introduced into the mesopores of the monodisperse spherical mesoporous silica;
It has.

[1.1 Monodispersed spherical mesoporous silica]
[1.1.1 Composition]
Monodispersed mesoporous silica spheres may be those of silica alone, or silica as the main component, may include an oxide of a metal element M ₁ other than silica. The metal element M ₁ is not particularly limited, those capable of producing a divalent or more metal alkoxides are preferred. When the metal element M ₁ is capable of producing a bivalent or higher valent metal alkoxide, spherical particles containing an oxide of the metal element M ₁ can be easily produced. Examples of the metal element _{M 1,} specifically, is Al, Ti, Mg, Zr and the like.
The content of silica in the monodispersed spherical mesoporous silica is preferably 50 wt% or more, and more preferably 80 wt% or more.

[1.1.2 Shape]
Monodispersed spherical mesoporous silica is composed of monodispersed and spherical particles. The monodispersed spherical mesoporous silica may be solid particles or hollow particles.
In the present invention, “monodisperse” means that the degree of monodispersion (CV value) represented by the formula (1) is 15% or less.
Monodispersity = (standard deviation of particle diameter) × 100 / (average value of particle diameter) (1)
In order to produce a colloidal crystal in which monodispersed spherical mesoporous silicas are in contact with each other, the monodispersity is preferably 10% or less.
On the other hand, in order to produce a colloidal crystal in which monodispersed spherical mesoporous silicas are not in contact with each other, the monodispersity is preferably 15% or less.
When a method described later is used, monodispersed spherical mesoporous silica having a monodispersity of 10% or less or 5% or less is obtained.

“Spherical” means that the average sphericity of each particle is 13% or less when a plurality of (preferably 20 or more) particles manufactured under the same conditions are observed with a microscope. Say. The “sphericity” is an index representing the degree of deviation of the outer shape of each particle from the perfect circle, and the circumscribed circle and the particle with respect to the radius (r ₀ ) of the smallest circumscribed circle in contact with the particle surface. This is a value represented by the ratio (= Δr _max × 100 / r ₀ (%)) of the maximum value (Δr _max ) of the distance in the radial direction from each point on the surface. When a method described later is used, monodispersed spherical mesoporous silica having a sphericity of 7% or less or 3% or less is obtained.

[1.1.3 Mesopores]
Monodispersed spherical mesoporous silica has mesopores. In the case of producing monodispersed spherical mesoporous silica using the method described later, the mesopores can be regularly arranged by optimizing the type and amount of addition of the surfactant.
The size of the mesopores can be controlled (from 1 to 50 nm) by optimizing the molecular length of the surfactant.
Since monodispersed spherical mesoporous silica has mesopores, the specific surface area is extremely large. When a method described later is used, monodispersed spherical mesoporous silica having a BET specific surface area of 800 m ² / g or more or 1000 m ² / g or more can be obtained.
The luminescent material described later is introduced into the mesopores of monodispersed spherical mesoporous silica. When the monodispersed spherical mesoporous silica is a hollow particle, the luminescent substance may be introduced into at least the mesopores, and may be introduced into both the mesopores and the cavities.

[1.1.4 Average particle diameter and shell thickness]
The average particle diameter of the monodispersed spherical mesoporous silica is not particularly limited, and an optimal one can be selected according to the purpose. When the method described later is used, monodispersed spherical mesoporous silica having an average particle diameter of 0.1 to 1.5 μm is obtained.
In order to obtain a light emission enhancement effect, it is preferable to select an average particle size of monodispersed spherical mesoporous silica so that the emission spectrum of the luminescent material and the reflection spectrum of the colloidal crystal overlap. In order to obtain a large light emission enhancement effect, the larger the overlap between the emission spectrum of the luminescent material and the reflection spectrum of the colloidal crystal, the better.
Furthermore, when the monodispersed spherical mesoporous silica is a hollow particle, the thickness of the shell is not particularly limited, and an optimum thickness can be selected according to the purpose.

[1.2 Regular array]
The colloidal crystal according to the present invention is formed by regularly arranging monodispersed spherical mesoporous silica in which a luminescent substance is introduced into mesopores. The regular array is not limited as long as the monodispersed spherical mesoporous silica is regularly arrayed, and the array does not necessarily need to be closely packed.

[1.2.1 Types of regular array]
As a regular array, specifically,
(1) A colloidal crystal obtained by dispersing monodispersed spherical mesoporous silica in a dispersion medium and volatilizing the dispersion medium (hereinafter referred to as “close-packed colloidal crystal”),
(2) A colloidal crystal obtained by regularly arranging particles while dispersing monodispersed spherical mesoporous silica in a dispersion medium (hereinafter referred to as “solution type colloidal crystal”),
(3) A colloidal crystal obtained by adding a gelling agent to a dispersion medium of a solution-type colloidal crystal and gelling the gelling agent in a state where the particles are regularly arranged (hereinafter referred to as “gel-fixed colloid”). Crystal)),
and so on.
In general, in a close-packed colloidal crystal, monodispersed spherical mesoporous silica particles are in contact with each other. On the other hand, in the solution-type colloidal crystal and the gel-immobilized colloidal crystal, the monodispersed spherical mesoporous silica particles are not in contact with each other and are regularly arranged in the dispersion medium or in the gel with a certain interval.

The solution-type colloidal crystal (water-dispersed colloidal crystal) is a colloidal crystal in which monodispersed spherical mesoporous silica is regularly arranged by osmotic pressure. Water is usually used as the dispersion medium, but is not limited thereto.
Colloidal particles are often charged in water by dissociation of surface functional groups. In the case of silica colloid, the particles are negatively charged due to dissociation of silanol groups and dissociate hydrogen ions as counter ions. Counter ions and cations in the solution become an ion cloud surrounding the particles, forming an electric double layer. When two particles approach, osmotic pressure acts between the ion clouds and a repulsive force is generated between the particles. It is known that this repulsive force (osmotic pressure) generally becomes stronger as the ion concentration in the solution is lower.

  The solution type colloidal crystal is a colloidal particle regularly arranged by osmotic pressure between particles, and is generated only when the ion concentration of the colloidal dispersion is extremely low. When colloidal particles having a particle diameter of several hundred nm are used, the lattice constant of the solution-type colloidal crystal is about the wavelength of visible light, and a photonic crystal in the visible light region can be produced. Solution type colloidal crystals have the advantage that they are less affected by monodispersity (CV value) of particle size compared to close-packed colloidal crystals in which particles are in contact with each other, because the particles are separated from each other. . A solution-type colloidal crystal can be produced even when CV = 15%.

  On the other hand, the solution-type colloidal crystal has a drawback that its bonding force is weak and the crystal structure collapses due to flow. For this reason, when actually used, it is desirable to fix it with a gel or the like.

Gel-immobilized colloidal crystals are obtained by immobilizing solution-type colloidal crystals with gels, and are characterized by high mechanical strength and resistance to contamination by impurities. In order not to dry the gel-immobilized colloidal crystal, the gel-immobilized colloidal crystal is held between two substrates (for example, a quartz glass plate) via a spacer, and is stored in a state where the dispersion medium is filled between the substrates. The dispersion medium is not particularly limited, and water, ethylene glycol, glycerin, DMSO, or a mixed liquid containing two or more of these can be used. As will be described later, the Bragg reflection wavelength can be controlled by adjusting the refractive index of the dispersion medium.
Various materials can be used for the gel for fixing the particles. Specific examples of the gel include polymer gels such as polyacrylamide, poly N, N-methylenebisacrylamide, gelatin, agar, and polyethylene glycol.

[1.2.2 Bragg condition]
In general, a structure in which colloidal particles having a uniform particle size are periodically arranged is defined as a colloidal crystal because of its similarity to a normal crystal, and selectively reflects light of a specific wavelength based on Bragg reflection. The Bragg reflection wavelength λ of the close-packed colloidal crystal is expressed by equation (2).
λ = 2d / m (n _eff ² −sin ² θ) ^1/2 (2)
Here, λ is a specific reflection wavelength, d is a reflection surface interval, m is the order of Bragg reflection, n _eff is an effective refractive index, and θ is an incident angle.

As shown in the equation (2), theoretically, the Bragg reflection wavelength is defined as light having one specific wavelength. However, since there are strains and defects in the actual colloidal crystal, the reflection spectrum is not a single line but has a predetermined width.
In addition, among the luminescent substances, those having a complex and fine excitation level structure (for example, organic dyes) often have an emission spectrum having a width of about several tens of nanometers.
Of this emission spectrum, the light in the portion overlapping the reflection spectrum of the colloidal crystal is confined in the colloidal crystal and amplified by resonance. Therefore, if the reflection surface interval d (that is, the average particle diameter of monodispersed spherical mesoporous silica) is optimized so that the overlap between the emission spectrum and the reflection spectrum becomes large, a strong emission enhancement effect can be obtained.

On the other hand, the Bragg reflection wavelength of the solution-type colloid crystal and the gel-immobilized colloid crystal depends on the volume fraction φ of the dispersion. When the particle diameter is D and the effective refractive index is n _eff , the Bragg reflection wavelength λ of the vertical reflection of the solution-type colloidal crystal and the gel-immobilized colloidal crystal is expressed by the equation (2 ′).
λ≈1.436Dn _eff / φ ^1/3 (2 ′)
From the equation (2 ′), it can be seen that the Bragg reflection wavelength λ can be controlled by changing the volume fraction φ and the effective refractive index n _eff of the dispersion even if the particle diameter D is the same.

  In the case where the overlap between the emission spectrum and the reflection spectrum is optimized, when the excitation energy is increased, the emission peak from the luminescent substance increases and the half width of the emission peak decreases. In the case where the overlap between the emission spectrum and the reflection spectrum is optimized, when the excitation energy is increased to a certain value or more, the half-value width of the emission peak becomes 5 nm or less.

[1.3 Luminescent substances]
[1.3.1 Types of luminescent substances]
The luminescent material is introduced into the mesopores of at least monodisperse spherical mesoporous silica. The luminescent material may be any material as long as it has high luminous efficiency, can be introduced into the mesopores, and the monodispersed spherical mesoporous silica can form a colloidal crystal when introduced into the mesopores.
In the present invention, the luminescent substance is composed of any one or more selected from luminescent organic dyes, organometallic coordination compounds, polymer light-emitting materials, and semiconductor nanoparticles.

A light-emitting organic dye is one that has a low probability of occurrence of a non-radiative process such as relaxation via vibration and a high quantum yield. As long as it emits strongly, it may be either fluorescent or phosphorescent. Any light emission intensity that can be used as a fluorescent indicator, a dye laser, or an organic electroluminescence (EL) element is sufficient.
Specific examples of the luminescent organic dye include rhodamine (see formula (a)), coumarin, fluorescein, pyrene, dansylic acid, cyanine dye, merocyanine dye, styryl dye, benzstyryl dye, pyromethane, oxazine, kitten red, DCM, as well as derivatives thereof.

As the organometallic coordination compound, those having at least one ligand that suppresses the rotation of molecules such as a phenylpyridine skeleton and a phenanthroline skeleton, and reducing the deactivation at the time of light emission can be used. The metal contained in the organometallic coordination compound is not particularly limited as long as it emits light when it becomes a coordination compound. Examples of the metal include iridium, platinum, gold, silver, copper, palladium, rhenium, aluminum, zinc, praseodymium, and ruthenium.
Specifically, as an organometallic coordination compound,
Tris (2-phenylpyridine) iridium (III),
Tris (8-hydroxyquinolinato) gallium (III),
Tris (dibenzoylmethane) -mono (4,7-diphenylphenanthroline) europium (III),
Tris (8-hydroxyquinolinol) aluminum (see formula (c)),
Tris (2,2-bipyridyl) ruthenium (see formula (d)),
Bis (8-hydroxyquinolinato) zinc,
As well as derivatives thereof.

As the polymer light emitting material, a known polymer material capable of emitting fluorescence or phosphorescence is used. Specific examples of the polymer light-emitting material include (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), and polyvinylcarbazole (PVK). ), Polythiophene derivatives, and polysilanes such as polymethylphenylsilane (PMPS) are preferably used. Further, these polymer materials can be used by doping with a low molecular material such as a perylene dye. Any material that can form a polymer in the pores can be used without being limited to these materials.
Specifically, as the light-emitting polymer material,
Tetrakis (4-carboxyphenyl) porphine (see formula (b)),
Poly (1,4-phenylene vinylene),
As well as derivatives thereof.

A semiconductor nanoparticle refers to a fluorescent substance in which excitons are spatially confined in a nano-order particle, and a so-called quantum confinement effect provides a light emission intensity higher than the bulk. The substance which comprises a semiconductor nanoparticle is not specifically limited.
Specifically, as semiconductor nanoparticles,
(1) Group I-VII compound semiconductor such as CuCl,
(2) II-VI group compound semiconductors such as ZnS, CdS, CdSe, CdTe, ZnSe,
(3) III-V compound semiconductors such as GaAs and InAs,
(4) Group IV semiconductors such as Si and Ge,
and so on.
The semiconductor nanoparticles may have a core-shell structure and can be appropriately selected according to the target wavelength.

  Any one of these light-emitting substances may be used, or two or more kinds thereof may be used in combination. Among these, rhodamine and derivatives thereof are suitable as luminescent substances to be introduced into mesopores because of their high emission intensity.

[1.3.2 Amount of luminescent substance]
The content of the luminescent material is not particularly limited, and an optimum one is selected according to the purpose. In general, the higher the content of the luminescent substance, the more colloidal crystals with higher luminescence intensity can be obtained. On the other hand, when the content of the luminescent substance is excessive, the emission intensity is lowered due to concentration quenching. However, in the present invention, since the luminescent substance is introduced into the mesopores, concentration quenching is small even when a relatively large amount of the luminescent substance is introduced.

[2. Colloidal crystal production method (1)]
The method for producing a colloidal crystal according to the first embodiment of the present invention includes a monodispersed spherical mesoporous silica production step, a luminescent substance adsorption step, and an alignment step.

[2.1 Monodispersed spherical mesoporous silica production process]
The monodispersed spherical mesoporous silica production step is a step of producing monodispersed spherical mesoporous silica.
Monodispersed spherical mesoporous silica
(1) A raw material containing a silica raw material and a surfactant is mixed in a solvent to produce precursor particles made of silica containing a surfactant,
(2) removing the surfactant from the precursor particles;
Can be obtained.
Hollow monodispersed spherical mesoporous silica is obtained by adding cavitation particles to a solution when preparing precursor particles.

[2.1.1 Silica raw material]
Silica raw materials include
(1) Tetraalkoxysilanes (silane compounds) such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane,
(2) Trimethoxysilanol, triethoxysilanol, trimethoxymethylsilane, trimethoxyvinylsilane, triethoxyvinylsilane, triethoxy-3-glycidoxypropylsilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ- (methacryloxypropyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, etc. Trialkoxysilane (silane compound),
(3) dialkoxysilanes (silane compounds) such as dimethoxydimethylsilane, diethoxydimethylsilane, diethoxy-3-glycidoxypropylmethylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane,
(4) Sodium metasilicate (Na ₂ SiO ₃ ), sodium orthosilicate (Na ₄ SiO ₄ ), sodium disilicate (Na ₂ Si ₂ O ₅ ), sodium tetrasilicate (Na ₂ Si ₄ O ₉ ), water Sodium silicate such as glass (Na ₂ O · nSiO ₂ , n = 2 to 4),
(5) Kanemite (NaHSi ₂ O ₅ .3H ₂ O), sodium disilicate crystals (α, β, γ, δ-Na ₂ Si ₂ O ₅ ), macatite (Na ₂ Si ₄ O ₉ ), eyelite ( _{Na 2 Si 8 O 17 · xH} 2 O), magadiite _{(Na 2 Si 14 O 17 ·} xH 2 O), kenyaite _{(Na 2 Si 20 O 41 ·} xH 2 O) layered silicates, such as,
(6) Precipitating silica such as Ultrasil (Ultrasil), Cab-O-Sil (Cabot), HiSil (Pittsburgh Plate Glass), colloidal silica, fumed silica such as Aerosil (Degussa-Huls),
Etc. can be used.

Further, hydroxyalkoxysilane can also be used as the silica raw material. The term “hydroxyalkoxysilane” refers to a hydroxy group (—OH) attached to the carbon atom of the alkoxy group of alkoxysilane. As the hydroxyalkoxysilane, tetrakis (hydroxyalkoxy) silane having four hydroxyalkoxy groups and tris (hydroxyalkoxy) silane having three hydroxyalkoxy groups can be used.
The type of hydroxyalkoxy group and the number of hydroxy groups are not particularly limited, but in the hydroxyalkoxy group such as 2-hydroxyethoxy group, 3-hydroxypropoxy group, 2-hydroxypropoxy group, 2,3-dihydroxyproxy group, etc. Those having a relatively small number of carbon atoms (having about 1 to 3 carbon atoms) are advantageous from the viewpoint of reactivity.

Examples of tetrakis (hydroxyalkoxy) silane include tetrakis (2-hydroxyethoxy) silane, tetrakis (3-hydroxypropoxy) silane, tetrakis (2-hydroxyproxy) silane, tetrakis (2,3-dihydroxypropoxy) silane, and the like. .
As tris (hydroxyalkoxy) silane, methyltris (2-hydroxyethoxy) silane, ethyltris (2-hydroxyethoxy) silane, phenyltris (2-hydroxyethoxy) silane, 3-mercaptopropyltris (2-hydroxyethoxy) silane, Examples include 3-aminopropyltris (2-hydroxyethoxy) silane and 3-chloropropyltris (2-hydroxyethoxy) silane.
These hydroxyalkoxysilanes can be synthesized by reacting an alkoxysilane with a polyhydric alcohol such as ethylene glycol or glycerin (see, for example, Doris Brandhuber et al., Chem. Mater. 2005, 17, 4262). .

Among these, tetraalkoxysilane and tetrakis (hydroxyalkoxy) silane are suitable as silica raw materials because the number of silanol bonds generated by hydrolysis increases and a strong skeleton can be formed.
In addition, these silica raw materials may be used alone or in combination of two or more. However, when two or more kinds of silica raw materials are used, the reaction conditions during the production of the precursor particles may be complicated. In such a case, the silica raw material is preferably used alone.

When the precursor particles contain an oxide of a metal element M ₁ other than silica, a raw material containing a metal element M ₁ in addition to the silica raw material is used.
The raw material containing a metal element M ₁ is,
(1) Al-containing alkoxide such as aluminum butoxide (Al (OC ₄ H ₉ ) ₃ ), aluminum ethoxide (Al (OC ₂ H ₅ ) ₃ ), aluminum isopropoxide (Al (OC ₃ H ₇ ) ₃ ) And salts such as sodium aluminate and aluminum chloride,
(2) Ti such as titanium isopropoxide (Ti (Oi-C ₃ H ₇ ) ₄ ), titanium butoxide (Ti (OC ₄ H ₉ ) ₄ ), titanium ethoxide (Ti (OC ₂ H ₅ ) ₄ ), etc. Containing alkoxide,
(3) Mg-containing alkoxide such as magnesium methoxide (Mg (OCH ₃ ) ₂ ), magnesium ethoxide (Mg (OC ₂ H ₅ ) ₂ ),
(4) Zr such as zirconium isopropoxide (Zr (Oi-C ₃ H ₇ ) ₄ ), zirconium butoxide (Zr (OC ₄ H ₉ ) ₄ ), zirconium ethoxide (Zr (OC ₂ H ₅ ) ₄ ), etc. Containing alkoxide,
Etc. can be used.

[2.1.2 Surfactant]
The surfactant serves as a template for forming mesopores in the particles. The type of the surfactant is not particularly limited, and various surfactants can be used. The pore structure in the particles can be controlled according to the type of surfactant used, the amount added, and the like.

The surfactant is particularly preferably an alkyl quaternary ammonium salt. The alkyl quaternary ammonium salt refers to one represented by the following formula (a).
_{CH 3 - (CH 2) n} -N + (R 1) (R 2) (R 3) X - ··· (a)
(A) In the _{formula, R 1, R 2, R} 3 each represent an alkyl group having 1 to 3 carbon atoms. R ₁ , R ₂ and R ₃ may be the same as or different from each other. In order to facilitate aggregation (formation of micelles) between alkyl quaternary ammonium salts, it is preferable that R ₁ , R ₂ , and R ₃ are all the same. Further, at least one of R ₁ , R ₂ , and R ₃ is preferably a methyl group, and all are preferably methyl groups.
(A) In formula, X represents a halogen atom. Although the kind of halogen atom is not particularly limited, X is preferably Cl or Br in view of availability.
(A) In formula, n represents the integer of 7-21. Generally, the smaller n is, the smaller the mesopore central pore diameter is obtained. On the other hand, as n increases, the central pore diameter increases, but if n increases too much, the hydrophobic interaction of the alkyl quaternary ammonium salt becomes excessive. As a result, a layered compound is generated and a spherical porous body cannot be obtained. n is preferably 9 to 17, and more preferably 13 to 17.

Among those represented by the formula (a), alkyltrimethylammonium halide is preferable. Examples of the alkyltrimethylammonium halide include hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, nonyltrimethylammonium halide, decyltrimethylammonium halide, undecyltrimethylammonium halide, dodecyltrimethylammonium halide, and the like.
Among these, alkyltrimethylammonium bromide or alkyltrimethylammonium chloride is particularly preferable.

  When synthesizing silica particles, one type of alkyl quaternary ammonium salt may be used, or two or more types may be used. However, since the alkyl quaternary ammonium salt serves as a template for forming mesopores in the silica particles, the type greatly affects the shape of the mesopores. In order to synthesize silica particles having more uniform mesopores, it is preferable to use one kind of alkyl quaternary ammonium salt.

[2.1.3 Cavity-forming particles]
The cavitation particles serve as a template for forming cavities, and are added as necessary. The cavity-forming particles may be any particles that can form a shell mainly composed of silica around them and can be easily removed after the shell is formed. In order to obtain monodispersed spherical hollow particles, the cavity-forming particles must also be monodispersed spherical.
As the cavity forming particles, for example,
(1) Polymer colloidal particles such as polystyrene, polymethyl methacrylate, polypropylene, melamine formaldehyde, which can be decomposed by firing or removed by an organic solvent,
(2) Basic compound particles such as calcium carbonate and magnesium carbonate that can be removed by acid such as hydrochloric acid,
and so on.
When polymer colloidal particles are used as the cavities forming particles, those having a basic functional group (for example, amino group) having a function of promoting polycondensation of the silica raw material on the particle surface are used. When there is no such functional group on the particle surface, silica alone undergoes polycondensation in a region other than the particle surface to obtain a by-product. On the other hand, when polymer colloidal particles whose surface is modified with such functional groups are used, polycondensation of the silica raw material proceeds preferentially on the particle surface to form a shell, thereby suppressing the formation of by-products. Can do.

[2.1.4 Solvent]
As the solvent, an organic solvent such as water or alcohol, a mixed solvent of water and an organic solvent, or the like is used. The alcohol may be any of monovalent alcohols such as methanol, ethanol, and propanol, divalent alcohols such as ethylene glycol, and trivalent alcohols such as glycerin.
When a mixed solvent of water and an organic solvent is used, the content of the organic solvent in the mixed solvent can be arbitrarily selected according to the purpose. In general, when an appropriate amount of an organic solvent is added to the solvent, control of the particle size and particle size distribution is facilitated.

[2.1.5 Mixing ratio]
In general, when the concentration of a raw material containing a silica raw material and a metal element M ₁ added as necessary (hereinafter simply referred to as “silica source”) is too low, silica particles cannot be obtained in a high yield. Moreover, it becomes difficult to control the particle size and particle size distribution, and the uniformity of the particle size decreases. Therefore, the concentration of the silica source is preferably 0.005 mol / L or more. The concentration of the silica source is more preferably 0.008 mol / L or more.
On the other hand, if the concentration of the silica source is too high, the surfactant functioning as a template for forming mesopores is relatively insufficient, and regularly arranged mesopores cannot be obtained. Accordingly, the concentration of the silica source is preferably 0.03 mol / L or less. The concentration of the silica source is more preferably 0.015 mol / L or less.

Generally, when the concentration of the surfactant is too low, a template for forming mesopores is insufficient, and regularly arranged mesopores cannot be obtained. Therefore, the concentration of the surfactant is preferably 0.003 mol / L or more. The concentration of the surfactant is more preferably 0.01 mol / L or more.
On the other hand, if the surfactant concentration is too high, silica particles cannot be obtained in high yield. Therefore, the concentration of the surfactant is preferably 0.03 mol / L or less. The concentration of the surfactant is more preferably 0.02 mol / L or less.

[2.1.6 Reaction conditions]
When a silane compound such as alkoxysilane or hydroxyalkoxysilane is used as the silica material, this is used as it is as a starting material.
On the other hand, when a compound other than a silane compound is used as the silica raw material, a basic material such as sodium hydroxide is added in advance to the silica raw material in water (or an alcohol aqueous solution to which an alcohol is added if necessary). Add. The addition amount of the basic substance is preferably about equimolar to the silicon atom in the silica raw material. When a basic substance is added to a solution containing a silica raw material other than the silane compound, a part of the Si— (O—Si) ₄ bond already formed in the silica raw material is cut, and a uniform solution is obtained. The amount of basic substance contained in the solution affects the yield and porosity of the hollow particles, so after a homogeneous solution is obtained, a dilute acid solution is added to the solution, and excess base present in the solution is added. Neutralize sex substances. The addition amount of the dilute acid solution is preferably an amount corresponding to 1/2 to 3/4 times mol of silicon atoms in the silica raw material.

  A silica source is added to a solvent containing a predetermined amount of a surfactant to perform hydrolysis and polycondensation. Thereby, surfactant functions as a template and the precursor particle | grains containing a silica and surfactant are obtained. In addition, when cavitation particles are contained in the solvent, precursor particles in which shells containing silica and a surfactant are formed on the surface of the cavitation particles are obtained.

  As the reaction conditions, optimum conditions are selected according to the type of silica raw material, the particle size of the precursor particles, and the like. In general, the reaction temperature is preferably -20 to 100 ° C. The reaction temperature is more preferably 0 to 80 ° C, more preferably 10 to 40 ° C.

[2.1.7 Removal of surfactant]
When the surfactant is removed from the precursor particles after drying, monodispersed spherical mesoporous silica is obtained. As a method for removing the surfactant,
(1) A firing method in which the precursor particles are fired at 300 to 1000 ° C. (preferably 300 to 600 ° C.) for 30 minutes or longer (preferably 1 hour or longer) in the air or under an inert atmosphere.
(2) The precursor particles are immersed in a good solvent for a surfactant (for example, methanol containing a small amount of hydrochloric acid), stirred while heating at a predetermined temperature (for example, 50 to 70 ° C.), and the interface in the thin film An ion exchange method to extract the active agent,
and so on.
In the case where the precursor particles include cavitation particles, when the cavitation particles are composed of polymer colloid particles, the cavitation particles can also be removed by the same method as that for the surfactant. Alternatively, it can be removed by immersion in an organic solvent (toluene, chloroform, benzene, etc.). On the other hand, when the cavitation particles are made of a basic compound, the cavitation particles can be removed with an acid such as hydrochloric acid.
Depending on the type of the luminescent substance, the adsorption of the luminescent substance may be easier when the surfactant remains in the mesopores. In such a case, the removal of the surfactant may be omitted.

[2.2 Luminescent substance adsorption process]
The luminescent substance adsorption process is a process in which the luminescent substance is adsorbed in the mesopores of monodispersed spherical mesoporous silica.
There are various methods for introducing the luminescent substance into the mesopores, and an optimum method can be selected according to the type of the luminescent substance.

Usually, when a luminescent substance is introduced into mesopores, it is often adsorbed by dissolving the luminescent substance in a solvent and adding monodispersed spherical mesoporous silica to the solution. At this time, the substance can be efficiently introduced into the mesopores by methods such as (1) selection of an optimal solvent, (2) modification of the luminescent substance, and (3) modification of the mesopores.
For example, water is usually used as the solvent for dissolving the luminescent material, but ethanol, acetone, ethylene glycol, glycerin, chloroform, and the like can be used as the solvent in the case of a luminescent material that is difficult to dissolve in water.

  Further, the Alq3 complex (tris (8-hydroxyquinolinol) aluminum) used as the organic EL element light emitting layer is dissolved in alcohol such as ethanol or chloroform. When an adsorption experiment is performed with Alq3 dissolved in ethanol and chloroform at the same concentration, a larger amount of Alq3 can be introduced into the mesopores when dissolved in chloroform. This is because Alq3 in ethanol is more stable than in the mesopores of mesoporous silica, whereas it is more unstable in chloroform than in the mesopores. For this reason, when chloroform is used, it is often introduced into mesopores that can exist more stably. Thus, by selecting an optimum solvent, a large amount of a luminescent substance can be easily introduced into mesoporous silica.

  In addition, Ru (bby) 3 complex (tris (2,2-bipyridyl) ruthenium) is highly hydrophilic and easily dissolved in ethanol and methanol, but in that state, only a very small amount is in the mesopores. Cannot be introduced. On the other hand, when a long-chain alkyl group is introduced at the end of the bipyridyl group, it becomes soluble in a hydrophobic solvent such as benzene. The alkyl-modified Ru (bby) 3 complex dissolved in benzene can be adsorbed at a high concentration in the mesopores (30 mg / 100 mg).

  TCPP (tetrakis (4-carboxyphenyl) porphine) is a kind of porphyrin derivative having four carboxyl groups in the molecule. Therefore, when an amino group is introduced into the mesopores of mesoporous silica, adsorption of TCPP dissolved in THF proceeds very efficiently. Introduction of an organic functional group such as an amino group into mesoporous silica can be performed with reference to existing literature (for example, Journal of Catalysis 251 (2007) 249-257, Chemistry Letters Vol. 35, No. 9). (2006) 1014-1015 etc.).

Furthermore, ZnS nanoparticles which are a kind of semiconductor nanoparticles include, for example,
(1) Organically modifying the pore walls of monodispersed spherical mesoporous silica with tris (methoxy) (mercaptopropylsilane)
(2) synthesizing ZnS nanoparticles in a reverse micelle solution of sodium bis (2-ethylhexyl) sulfosuccinate;
(3) Add organically modified monodispersed spherical mesoporous silica to the reverse micelle solution of ZnS and stir for several hours.
Can be introduced into mesopores (see, for example, J. Phys. Chem. B 2004, 108, 11509-11513).
In addition, ZnO nanoparticles are, for example,
_{(1) (C 2 H 5} O) 3 Si (CH 2) 3 NH (CH 2) and refluxed with the addition of monodisperse mesoporous silica spheres to ₂ anhydrous toluene solution of NH _2, the pore inner walls of ethylene diamino group Qualify,
(2) Synthesize ZnO crystals in the pores by chelating Zn ions,
Can be introduced into the mesopores (see, for example, Optical Materials 25 (2004) 79-84).
In addition, CdS nanoparticles are prepared by adding monodispersed spherical mesoporous silica before firing to a methanol solution of Cd (OAc) ₂ .2H ₂ O (cadmium acetate) and stirring at 60 ° C. for 3 hours to perform H ₂ S treatment. By doing so, it can be introduced into the mesopores. When Zn (OAc) ₂ .2H ₂ O (zinc acetate) is used as a precursor instead of cadmium acetate, ZnS can be introduced into the mesopores by the same synthesis procedure.

[2.3 Arrangement process]
The arranging step is a step of regularly arranging monodispersed spherical mesoporous silica. The method for regularly arranging monodispersed spherical mesoporous silica is not particularly limited, and various methods can be used.

As a method for regularly arranging monodispersed spherical mesoporous silica, specifically,
(1) A method of immersing electrodes in a dispersion in which monodispersed spherical mesoporous silica is dispersed, and applying direct current electrolysis between the electrodes (arrangement method using electrophoresis),
(2) A method of injecting a dispersion liquid in which monodispersed spherical mesoporous silica is dispersed between substrates having a constant interval and self-assembling the monodispersed spherical mesoporous silica in a regularly arranged state,
(3) A method in which a dispersion in which monodispersed spherical mesoporous silica is dispersed is applied to the substrate surface using dip coating, spin coating,
(4) A polymer monomer (for example, acrylamide), a crosslinking agent (for example, methylenebisacrylamide), and a photopolymerization initiator (for example, camphorquinone) are added in advance to the monodispersed spherical mesoporous silica dispersion. , A method in which monodispersed spherical mesoporous silica is regularly arranged in a liquid and then gelled by light irradiation,
(5) A method of dispersing monodispersed spherical mesoporous silica in a dispersion medium in which the ion concentration is adjusted, and allowing the particles to be regularly arranged in the dispersion medium by leaving it as it is.
and so on.

In order to regularly arrange the particles in the dispersion medium, it is necessary to make the ion concentration in the colloidal dispersion extremely low. Furthermore, in order to adjust the stop band of the colloidal crystal and the emission spectrum wavelength of the luminescent material, it is necessary to control the particle concentration to adjust the particle spacing of the colloidal crystal.
Therefore, when preparing a solution-type colloidal crystal, an ion exchange resin or the like is added to the aqueous dispersion of monodispersed spherical mesoporous silica to sufficiently reduce the ion concentration in the dispersion, and further, the dispersion is made into desired particles. It is necessary to concentrate so that it may become a space | interval.
In addition, when preparing gel-immobilized colloidal crystals, it is necessary to add a gelling agent to the dispersion in which the ion concentration is reduced and concentrated, and apply this onto a substrate such as a glass substrate to cure the gel. There is. When a dispersion containing a gelling agent is injected into the gap between the substrates, the spacing of which is appropriately adjusted, and gelled, a gel-immobilized colloidal crystal having a uniform film thickness can be obtained. The gelation method is not particularly limited, but when an ultraviolet curable gel is used, it can be easily gelled by irradiating ultraviolet rays with an ultraviolet lamp or the like.

[3. Colloidal crystal production method (2)]
The method for producing a colloidal crystal according to the second embodiment of the present invention includes a monodispersed spherical mesoporous silica production step, an alignment step, and a luminescent substance adsorption step.

[3.1 Monodispersed spherical mesoporous silica production process]
The monodispersed spherical mesoporous silica production step is a step of producing monodispersed spherical mesoporous silica. The details of the monodispersed spherical mesoporous silica production process are the same as those in the first embodiment, and thus the description thereof is omitted.

[3.2 Arrangement process]
The arranging step is a step of regularly arranging monodispersed spherical mesoporous silica. In the present embodiment, regular arrangement of particles is performed before adsorbing the luminescent substance in the mesopores. This is different from the first embodiment.
In this embodiment, since the adsorption of the luminescent substance is performed after the regular arrangement of the particles, the regular arrangement body needs to be a close-packed colloidal crystal or a gel-immobilized colloidal crystal. Since the other points of the arrangement process are the same as those in the first embodiment, description thereof will be omitted.

[3.3 Luminescent substance adsorption process]
The luminescent substance adsorption step is a step of adsorbing the luminescent substance in the mesopores of monodispersed spherical mesoporous silica constituting the ordered array. That is, in this embodiment, after the monodispersed spherical mesoporous silica is regularly arranged, the luminescent material is adsorbed.
For example, when the luminescent substance is ionic (for example, when the luminescent substance is an organic dye or an organometallic coordination compound), the luminescent substance is adsorbed in the mesopores of the monodispersed spherical mesoporous silica particles and then dispersed. When particles are dispersed in a medium, ions of the luminescent material may flow out into the dispersion medium. In the case of a close-packed colloidal crystal, even if a small amount of ions flow out into the dispersion medium, there is little possibility of hindering regular arrangement.
However, in the case of a gel-immobilized colloidal crystal, if ions flow out into the dispersion medium before the particles are regularly arranged, precise control of the particle spacing may be difficult even if the amount of outflow is small. Therefore, when producing a gel-immobilized colloidal crystal, when the luminescent substance is ionic, it is preferable to introduce the luminescent substance after the particles are fixed in advance with a gel.
Adsorption of the luminescent substance is performed by adding a solution containing the luminescent substance to the colloidal crystal. When it is necessary to modify the inner walls of the mesopores when adsorbing the luminescent substance, the modification is performed at any appropriate time after the synthesis of the monodispersed spherical mesoporous silica or after the ordered arrangement. Since the other points of the luminescent substance adsorption step are the same as those of the first embodiment, description thereof is omitted.

[4. Light emitting amplifier]
The light-emitting amplifier according to the present invention is characterized by using the colloidal crystal according to the present invention.
High-quality and high-efficiency optical amplification elements in the visible light region are expected to be applied in the fields of measurement, processing, in-vehicle communication, and the like. As a method for amplifying light, there is a method in which light is once converted into an electric signal, processed, and then converted into light again. However, this method is complicated and wasteful in terms of energy, and the light coherence is lost.
On the other hand, the method of amplifying light with light has already been used for optical fiber communication. However, current optical amplifiers are doped with erbium (Er) ions in an optical fiber, and can only amplify at the optical wavelength for communication (about 1.5 microns), and the miniaturization is not progressing.
On the other hand, according to the present invention, it is possible to provide a small optical amplifier in the visible light region. As an application, it can be used suitably in the field of amplifying light, such as a display element, a display, a backlight, an illumination light source, an exposure light source, a reading light source, a sign, a signboard, and an interior.

[5. Action of colloidal crystal and light-emitting amplifier]
FIG. 1 shows a schematic view of a colloidal crystal according to the present invention. As shown in FIG. 1, when a monodispersed spherical mesoporous silica into which a luminescent material is introduced is arranged in a mesopore and is irradiated with excitation light from a pump source (not shown), the luminescent material in the mesopore emits light. .
On the other hand, the colloidal crystal in which the Bragg equation is established has a region where light cannot exist due to the effect of the stop band. When a colloidal crystal and a light-emitting layer such as a dye coexist, and there is an overlap between the emission spectrum of the stopband and the light-emitting layer (especially when the stopband and the emission spectrum match), when the colloidal crystal is irradiated with excitation light, As shown in FIG. 2, the light emitted when the light emitting layer is excited resonates and is enhanced within the stop band. This is because the excited light is repeatedly reflected in the direction satisfying the Bragg condition in the colloidal crystal where the emission spectrum and the stop band overlap. When the excitation light intensity is above a certain threshold, the amplified light emission is emitted at once, so the spontaneous emission of the light emitting layer is significantly amplified and can be used as a device that emits strong light such as a laser. .

Conventional light-emitting amplifiers using colloidal crystals are mainly in the form of an independent colloid layer and light-emitting layer, and can be made smaller than when an external resonator such as a mirror is used.
However, conventional light-emitting amplifiers
(1) The manufacturing process is complicated and there is a limit to downsizing.
(2) When a light-emitting substance with poor stability (for example, an organic substance such as a dye) is used, deterioration and fading easily occur due to light or oxygen.
(3) Depending on the structure of the luminescence amplifier, the luminescent material tends to flow out, and the luminescent material that can be introduced is limited.
(4) Concentration of luminescent material and easy concentration quenching,
(5) Since organic materials are used for colloidal particles, thermal, mechanical and chemical stability is poor.
There are problems such as.

In contrast, in the present invention, since a luminescent substance is introduced into the mesopores of monodispersed spherical mesoporous silica and colloidally crystallized, it is possible to emit light even when irradiated with strong light. Deterioration and fading of the substance can be suppressed, and there is little possibility that the luminescent substance flows out.
Monodispersed spherical mesoporous silica has a high specific surface area and a large pore volume, and the state in the mesopores can be freely adjusted by modification. Therefore, various light-emitting substances can be included in a highly dispersed and high concentration, and the degree of freedom in material selection is great.
In addition, since the luminescent substance is encapsulated in the mesopores, molecules are easily isolated even at high concentrations, and concentration quenching is unlikely to occur. Since the introduction of the luminescent material into the mesopores proceeds homogeneously by capillary condensation, a colloidal crystal with a uniform distribution of the luminescent material can be produced. Moreover, since the colloidal crystal according to the present invention and the light-emitting amplifier using the same are based on silica, they have high thermal, mechanical and chemical stability.

Further, when the emission spectrum of the luminescent substance and the reflection spectrum of the colloidal crystal overlap, the light generated by exciting the luminescent substance is resonated and enhanced within the stop band. Therefore, the light emission enhancement effect equivalent to or higher than that of the conventional light emitting amplifier can be obtained. In addition, since it is not necessary to have a three-layer structure, the manufacturing process is simple and the apparatus can be further miniaturized.
In addition, since the solution-type colloid crystal and the gel-immobilized colloid crystal can easily control the particle interval, it is easy to match the emission spectrum of the luminescent material with the reflection spectrum of the colloid crystal. Therefore, a colloidal crystal with high emission enhancement efficiency can be easily manufactured.

(Examples 1-2, Comparative Examples 1-2)
[1. Preparation of sample]
[1.1 Colloidal crystal whose emission wavelength and stop band coincide (Example 1)]
[1.1.1 Particle synthesis]
C ₁₆ TMACl (cetyltrimethylammonium chloride): 7.04 g was dissolved in a mixed solution of water: 873.2 g, methanol: 640 g, and ethylene glycol: 80 g at room temperature. 1N sodium hydroxide: 6.84 g was added and stirring was continued. Premixed TMOS (tetramethylorthosilicate): 5.02 g and 3-aminopropylmethoxysilane: 0.31 g were added, and the solution turned white within a few minutes to produce particles. On the next day, filtration and washing were repeated, and after drying, the particles were baked at 550 ° C. for 6 hours to obtain spherical particles (MMSS2).
When the obtained particles were observed with an SEM, they were found to be spherical particles having a very high monodispersity with a particle diameter of 320 nm (FIG. 3B).
[1.1.2 Dye adsorption]
A rhodamine derivative (Rh610) was used as the fluorescent dye. Rh610 was dissolved in ethanol at a concentration of 1 mM, MMSS2 was added at a ratio of 200 mg to 4 mL of the solution, and the mixture was stirred overnight to adsorb the dye into the silica pores. On the next day, the supernatant was separated by centrifugation to obtain rhodamine-introduced mesoporous silica particles (Rh610-MMSS2).
When the amount of the introduced dye was measured from the absorbance of the supernatant, it was 0.20 mg with respect to 100 mg of MMSS2.
[1.1.3 Colloidal crystal production]
The obtained Rh610-MMSS2 was dispersed in water and sufficiently subjected to ultrasonic treatment to prepare a Rh610-MMSS2 dispersion having high dispersibility. The dispersion was introduced between two quartz glasses whose gaps were adjusted to 30 μm. With the evaporation of the solvent, a colloidal crystal (sample 2) exhibiting a uniform pink structural color was obtained.

[1.2 Colloidal crystal whose emission wavelength and stopband do not match (Comparative Example 1)]
[1.2.1 Particle synthesis]
C ₁₆ TMACl: 7.04 g was dissolved in a mixed solution of water: 739.2 g and methanol: 800 g at room temperature. 1N sodium hydroxide: 6.84 g was added and stirring was continued. When TMOS: 5.28 g was added thereto, the solution turned white within a few minutes and particles were produced. On the next day, filtration and washing were repeated, and after drying, baking was performed at 550 ° C. for 6 hours to obtain spherical particles (MMSS1).
When the obtained particles were observed with an SEM, they were found to be spherical particles with a very high monodispersity having a particle diameter of 560 nm (FIG. 3A).
[1.2.2 Dye adsorption]
Rhodamine-introduced mesoporous silica particles (Rh610-MMSS1) were obtained according to the same procedure as in Example 1 except that MMSS1 was used as the spherical particles.
When the amount of the introduced dye was measured from the absorbance of the supernatant, it was 0.19 mg with respect to 100 mg of MMSS1.
[1.2.3 Colloidal crystal production]
The obtained Rh610-MMSS1 was dispersed in water and sufficiently sonicated to prepare a highly dispersible Rh610-MMSS1 dispersion. The dispersion was introduced between two quartz glasses whose gaps were adjusted to 30 μm. With the evaporation of the solvent, a colloidal crystal (sample 1) exhibiting a uniform pink structural color was obtained.

[1.3 Colloidal crystal whose emission wavelength and stop band coincide (Example 2)]
[1.3.1 Particle synthesis]
C ₁₆ TMACl: 35.2 g was dissolved in a mixed solution of water: 4366 g, methanol: 3090 g, and ethylene glycol: 480 g at room temperature. 1N sodium hydroxide: 34.2 g was added and stirring was continued. When premixed TMOS: 25.08 g and 3-aminopropylmethoxysilane: 1.55 g were added, the solution whitened within a few minutes to produce particles. On the next day, filtration and washing were repeated, and after drying, baking was performed at 550 ° C. for 6 hours to obtain spherical particles (MMSS3).
When the obtained particles were observed with an SEM, they were found to be spherical particles with a very high monodispersity having a particle diameter of 370 nm (the left figure in FIG. 4).
[1.3.2 Dye adsorption]
Rhodamine-introduced mesoporous silica particles (Rh610-MMSS3) were obtained according to the same procedure as in Example 1 except that MMSS3 was used as the spherical particles.
The amount of the introduced dye was measured from the absorbance of the supernatant and found to be 0.19 mg with respect to 100 mg of MMSS3.
[1.3.3 Colloidal crystal production]
The obtained Rh610-MMSS3 was dispersed in water and sufficiently sonicated to prepare a highly dispersible Rh610-MMSS3 dispersion. The dispersion was introduced between two quartz glasses whose gaps were adjusted to 30 μm. Along with the evaporation of the solvent, a colloidal crystal (sample 3) exhibiting a uniform pink structural color was obtained (right figure in FIG. 4).

[1.4 Colloidal crystal in which pigment is introduced into gaps between spherical silica particles without pores (Comparative Example 2)]
A colloidal crystal was produced between two quartz glasses according to the same procedure as in Example 1 except that an aqueous dispersion of 300 nm spherical silica colloidal particles was used. The obtained colloidal crystals were dried with a vacuum dryer, and after sufficiently removing water in the interstices, an aqueous Rh610 solution was immersed between the glasses to try to introduce a dye into the interstices between the colloidal particles (Sample 4). .

[2. Test method]
[2.1 Measurement of rhodamine emission spectrum]
The emission spectrum of rhodamine was measured using a spectrofluorometer (FP-6500ST) manufactured by JASCO Corporation. A tungsten lamp was used as the excitation light source.
[2.2 Measurement of angle-resolved reflection spectrum]
The angle-resolved reflection spectrum was measured using a reflection / transmission spectrum measuring apparatus manufactured by Soma Optics. A halogen lamp (spot diameter: 5 mm) was used as the light source.
[2.3 Measurement of emission spectrum of colloidal crystal]
FIG. 5 shows a schematic configuration diagram of the experimental apparatus. The colloidal crystal was irradiated with excitation light (wavelength = 532 nm) by an Nd: YAG laser, and the light emitting layer in the colloidal crystal was excited to emit light. The emitted light was confined in a colloidal crystal and resonated, and the amplified light was guided to a spectroscope for spectral analysis.

[3. result]
[3.1 Emission spectrum of rhodamine]
FIG. 6 shows an emission spectrum of the luminescent organic dye (rhodamine derivative (Rh610)) used in the present invention. Rhodamine is a red-colored pigment and showed strong emission at 580 nm.

[3.2 Angle-resolved spectrum of colloidal crystals]
FIG. 7 shows an angle-resolved reflection spectrum of a colloidal crystal (sample 1, comparative example 1) produced from Rh610-MMSS1. The dotted line in the figure indicates the emission wavelength of rhodamine. The reflection band in the normal direction (incident angle 0 °) of sample 1 appeared around 1050 nm due to Bragg reflection of the colloidal crystal. When the incident angle (= detection angle) of light with respect to the sample normal direction is increased, the reflection band shifts in the low wavelength direction. However, even when the detection angle was around 90 °, the reflection band did not overlap with the emission peak of rhodamine.

  FIG. 8 shows an angle-resolved reflection spectrum of a colloidal crystal (Sample 2, Example 1) produced from Rh610-MMSS2. The dotted line in the figure indicates the emission wavelength of rhodamine. The reflection band in the normal direction (incident angle 0 °) of sample 2 appeared near 610 nm due to Bragg reflection of the colloidal crystal. As the incident angle of light (= detection angle) with respect to the sample normal direction increased, the overlap between the reflection band and the emission peak increased, and the overlap became maximum when the detection angle was around 20 °.

  FIG. 9 shows an angle-resolved reflection spectrum of a colloidal crystal (Sample 3, Example 2) produced from Rh610-MMSS3. The dotted line in the figure indicates the emission wavelength of rhodamine. The reflection band in the normal direction (incident angle 0 °) of sample 3 appeared around 715 nm due to Bragg reflection of the colloidal crystal. As the incident angle (= detection angle) of light with respect to the sample normal direction increased, the overlap between the reflection band and the emission peak increased, and the overlap became maximum when the detection angle was around 44 °.

[3.3 Enhancement and narrowing of emission peak]
FIG. 10 shows an emission spectrum of Sample 2 (Rh610-MMSS2) measured by the experimental apparatus shown in FIG. The detection angle θ was 20 °.
When the excitation light energy was 0.02 mJ / pulse or less, a broad peak having a half width of about 30 nm based on the spontaneous emission of rhodamine 610 was obtained. However, at an energy of 0.21 mJ / pulse or higher, the emission peak increased and the half-width of the peak became narrow. When the excitation energy was 2.1 mJ / pulse, the light emission amount was 140000 and the half-value width was 3.5 nm, and the emission peak was found to be significantly enhanced and narrowed.
A similar excitation experiment was performed on Sample 1 (Rh610-MMSS1), but no such enhancement or narrowing was observed.

FIG. 11 shows the relationship between the excitation intensity and emission intensity of Sample 1 (Rh610-MMSS1) and Sample 2 (Rh610-MMSS2) measured with the experimental apparatus of FIG. In sample 2 in which the reflection band largely overlaps with the emission wavelength of rhodamine, the emission peak was remarkably enhanced as the excitation energy increased.
On the other hand, no enhancement was observed in Sample 1 having no overlap between the emission peak of the dye and the reflection band. Since the amount of rhodamine adsorbed in the mesopores was almost the same, it became clear that the light emission of the dye adsorbed in the mesopores was efficiently enhanced by the reflection band of the colloidal crystal.
Furthermore, when the value obtained this time is compared with Non-Patent Document 1, emission is enhanced up to 24000 at an excitation energy of 10 (MW / cm ² ), and the peak half-value width is 15 nm. In sample 2, the excitation energy 10 (MW / cm ² ) corresponds to 0.8 mJ. In this case, the peak intensity was 75000 and the half-value width was 3.7 nm, and it was found that emission enhancement and narrowing of the line were significantly improved as compared with Non-Patent Document 1.

FIG. 12 shows the relationship between the excitation intensity of sample 3 (Rh610-MMSS3) measured with the experimental apparatus shown in FIG. The detection angle θ was 44 °.
When the excitation light energy was 0.02 mJ / pulse or less, a broad peak having a half width of about 20 nm was obtained based on spontaneous emission of rhodamine 610. However, at an energy of 0.04 mJ / pulse or higher, the emission peak increased, and the line width of the peak suddenly narrowed. It was found that when the excitation energy was 0.4 mJ / pulse, the emission amount was 16000 and the half-value width was 1.5 nm, and the emission peak was significantly enhanced and narrowed. Furthermore, when the excitation light energy was increased to 2.1 mJ / pulse, the emission peak was enhanced to 90000. As for the colloidal crystal of Example 2, it was found that a remarkable enhancement of emission and narrowing of the spectrum were observed when the reflection band and the emission peak overlapped.

[3.4 Uniformity of luminescent material]
In the colloidal crystals obtained in Example 1 and Example 2, the entire crystal surface exhibited a uniform pink color. On the other hand, the colloidal crystal obtained in Comparative Example 2 was heterogeneous and the color unevenness was remarkably observed.
Furthermore, when the ultraviolet rays were irradiated, the colloidal crystals obtained in Examples 1 and 2 exhibited an orange color based on the emission of rhodamine. On the other hand, in the colloidal crystal obtained in Comparative Example 2, light and shade were observed.
The method of the present invention for producing a colloidal crystal from spherical silica in which a dye is adsorbed in mesopores has been found to be very useful because it can easily produce a homogeneous and large-area crystal.

[3.5 Stability of luminescent materials]
The particles (Rh610-MMSS2) obtained in Example 1 were dispersed in ion-exchanged water and chloroform. The supernatant was taken every hour while the dispersion was stirred, and the change in absorbance was measured (up to 7 hours). FIG. 13 shows changes in absorbance when dispersed in ion-exchanged water. FIG. 14 shows changes in absorbance when dispersed in chloroform. 13 and 14 are obtained by superimposing data for 7 hours.
The absorption peak of rhodamine is around 550 nm. In the water and the chloroform dispersion of spherical particles adsorbed with rhodamine, almost no rhodamine-derived peak was observed even when stirring was continued for 7 hours. Although rhodamine is very easily dissolved in water and chloroform, rhodamine adsorbed in the mesopores of the spherical particles did not elute into the solvent even after stirring for 7 hours. From this result, it was shown that rhodamine adsorbed in the mesopores is stable.

Furthermore, organic dyes are particularly easily deteriorated in the surrounding environment (water or light). For example, when chloroform is added to rhodamine, rhodamine dissolves easily and shows a light pink color. However, when left in that state at room temperature, the pink color of the dispersion immediately disappeared and the solution turned transparent.
On the other hand, when the particles of Example 2 on which rhodamine was adsorbed were dispersed in a chloroform solution and allowed to stand at room temperature in the same manner, the solution was transparent but the particles retained the pink color peculiar to rhodamine.
In order to grasp such changes quantitatively, changes in the absorbance of the chloroform solution of rhodamine and the chloroform dispersion of the particles of Example 2 were measured. The rhodamine solution was subjected to two-level measurement at different concentrations. FIG. 15 shows the result.
At the measured concentration, the absorbance of rhodamine in the chloroform solutions 1 and 2 decreased sharply at any concentration and became almost zero within one hour.
On the other hand, the absorbance of the chloroform dispersion of the particles of Example 2 hardly changed and remained the same after 5 hours. That is, it was found that rhodamine adsorbed in the mesopores is not affected by the environment and exists stably.

(Example 3, Comparative Example 3)
[1. Preparation of sample]
[1.1 Preparation of particles]
Tetraethoxysilane and ethylene glycol were mixed at a molar ratio of 1: 4 and heated to 140 ° C. in a dry nitrogen stream. At this time, ethanol produced by the transesterification reaction was removed by distillation to obtain tetrakis (2-hydroxyethoxy) silane.
To a mixed solvent of 478.9 g of water and 320 g of methanol, 3.52 g of hexadecyltrimethylammonium chloride (surfactant) and 1.14 mL of 1N aqueous sodium hydroxide solution were added. To this, 2 mL of tetrakis (2-hydroxyethoxy) silane (silica raw material) was added at room temperature. After stirring for 8 hours and allowing to stand overnight, filtration and washing with deionized water were repeated three times to obtain a white powder. This white powder was fired at 550 ° C. for 6 hours to obtain monodispersed spherical mesoporous silica having a particle size of 197 nm (CV value: 13.8%) (Example 3).
Further, commercially available spherical silica (Stover particles) (manufactured by Nippon Shokubai Co., Ltd.) having a particle size of 317 nm (CV value: 4.2%) was used as it was (Comparative Example 3).
The obtained particles were each dispersed in water and deionized using an ion exchange resin to obtain a colloidal dispersion.

[1.2 Preparation of gel-immobilized colloidal crystals]
An acrylamide monomer, a crosslinking agent (N, N-methylenebisacrylamide), an initiator (2,2′-azobis [2-methyl-NN [2-hydroxyethyl] -propinoamide) are dissolved in water to form a gelling agent did. This was mixed with the colloidal dispersion obtained in [1.1]. The volume fraction of particles was 10 vol%, and the ratio of the crosslinking agent in the monomer was 10%.

Two glass plates were washed with ethanol and then thoroughly washed with distilled water, a spacer having a thickness of 150 μm was attached to one glass plate, and the other glass plate was overlaid and used as a mold. The spacer used was a state in which a release film on one side of a double-sided polypropylene tape was still attached. The laminated glass plate was put into a plastic bag with a chuck, and a dispersion liquid in which a gelling agent was mixed was poured between the two glass plates using a pipette. Air was expelled from the bag, the chuck was closed, drying and dust contamination were prevented, and the sample was allowed to stand for 5 to 10 minutes until the crystals grew sufficiently.
Polymerization was performed by irradiating the dispersion with ultraviolet rays using a UV lamp (365 nm, output 743 μW / cm ² ) manufactured by ASONE. The sample after gel immobilization was stored in water to prevent shrinkage due to drying. The size of the colloidal crystal is 1 cm × 2 cm × 150 μm.

[1.3 Adsorption of dye]
The gel-immobilized sample was immersed in the fluorescent substance solution for 1 hour, and the dye was adsorbed in the pores or between the particles. A rhodamine 610 aqueous solution (10 μM) was used as the fluorescent substance solution.

[2. result]
[2.1 Appearance]
The left and right views of FIG. 16 show photographs of the appearance of the colloidal crystals obtained in Comparative Example 3 and Example 3, respectively. In the case of Comparative Example 3, when immersed in an aqueous rhodamine solution for 1 hour, the entire colloidal crystal became light pink, but color unevenness was also observed. After washing for 1 hour in an aqueous rhodamine solution and washing with water, the colloidal crystals returned to the color before being immersed in the aqueous rhodamine solution.
On the other hand, in the case of Example 3, when immersed in an aqueous rhodamine solution for 1 hour, the colloidal crystals exhibited a uniform deep pink color. Even if it was immersed in an aqueous rhodamine solution for 1 hour and then washed with water, the colloidal crystals retained a color specific to rhodamine. Further, even after washing for 8 days, the color became light but exhibited a pink color peculiar to rhodamine. FIG. 16 shows that rhodamine adsorbed in the mesopores is extremely stable.

[2.2 Reflection spectrum of vertical reflection]
FIG. 17A shows an excitation / fluorescence spectrum of rhodamine 610. FIG. 17B shows the reflection spectrum of the vertical reflection of the colloidal crystal obtained in Example 3. From FIG. 17, it can be seen that the peak of the reflection spectrum of the vertical reflection of the colloidal crystal substantially coincides with the maximum value of the fluorescence spectrum of rhodamine 610. This is because when the colloidal particles are gelled, the particle concentration is controlled and the lattice spacing of the colloidal crystals is adjusted.

[2.3 Emission spectrum of colloidal crystal]
The emission spectrum of the colloidal crystal was measured using the apparatus shown in FIG. The excitation light intensity was 3.4 mJ / pulse, and the excitation light intensity was changed from 11.2 to 100% using an ND filter. The measurement angle of the spectrum was 5 ° with respect to the normal line of the sample. FIG. 18A shows an emission spectrum of the colloidal crystal obtained in Example 3. Moreover, the enlarged view is shown in FIG.18 (b).
From FIG. 18, several very sharp peaks due to laser oscillation were observed in addition to a broad spectrum due to spontaneous emission of the dye. The half width of the laser oscillation peak (strongest peak) was 0.5 nm, and the wavelength interval between the peaks was about 1 nm. The full width at half maximum of the strongest peak is narrower than the normal emission spectrum of rhodamine 610 and the spectrum at the time of enhancement of emission, and is 1 nm or less, indicating that laser oscillation occurs. The peak wavelength intervals are equal intervals, which indicates that the longitudinal oscillation mode is multi-oscillation.

FIG. 19 shows the excitation light intensity dependence of the peak intensity of the colloidal crystal obtained in Example 3. FIG. 19 shows that the peak intensity of the strongest peak increases as the excitation light intensity increases.
FIG. 20 shows the angle dependency (directivity) of the peak position of the spectrum of the colloidal crystal obtained in Example 3. The measurement angle was 5 ° to 30 °. From FIG. 20, it can be seen that as the angle is increased, the peak intensity rapidly decreases, and light having strong directivity is generated. This result also supports that laser oscillation is occurring.

Example 4
Other than using rhodamine 610, other organic dyes (LDS750, rhodamine 640, Nile blue 690, cresyl violet 670, LDS698, oxazine 720, LDS722, LD700, LD800) or organometallic coordination compounds (Alq3) Followed the same procedure as in Example 3 to prepare a gel-immobilized colloidal crystal.
Any luminescent material could be introduced into the mesopores. In addition, an emission enhancement effect was observed with any luminescent material.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  The colloidal crystal and light-emitting amplifier according to the present invention can be used for laser oscillation devices, micro light sources, display devices, displays, backlights, illumination light sources, exposure light sources, reading light sources, signs, signs, interiors, and the like.

Claims (5)

Monodispersed spherical mesoporous silica regularly arranged;
A luminescent material introduced into the mesopores of the monodispersed spherical mesoporous silica,
The luminescent substance is a colloidal crystal composed of any one or more selected from luminescent organic dyes, organometallic coordination compounds, polymer light-emitting materials, and semiconductor nanoparticles.   The colloidal crystal according to claim 1, wherein an emission spectrum of the luminescent material overlaps with a reflection spectrum of the colloidal crystal.   The light-emitting amplifier according to claim 2, wherein an emission peak from the light-emitting substance is increased by increasing excitation energy, and a half-value width of the emission peak is 5 nm or less.   The colloidal crystal according to any one of claims 1 to 3, wherein the luminescent substance is rhodamine or a derivative thereof.   A light-emitting amplifier using the colloidal crystal according to any one of claims 2 to 4.

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