JP4671102B2 - Method for producing colloidal crystals - Google Patents

Description

The present invention is to remove core particles from a core / shell type colloidal particle in which one or more shells composed of a nanosheet layer or the like are laminated around the template particle, or such a core / shell type colloidal particle. the hollow colloidal particles obtained by, relates manufacturing method of the colloidal crystal obtained by regularly arranged.

  It is known that so-called monodispersed colloidal particles having small particle size variations are regularly arranged to form an ordered structure (colloidal crystal) by evaporating the solvent in which the colloidal particles are dispersed. . Moreover, colloidal particles can be regularly arranged by the interaction between particles even in a solvent in which the colloidal particles are dispersed to form a colloidal crystal.

  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, wavelengths in the range from ultraviolet light or visible light to infrared light can be reflected. Furthermore, when visible light is reflected, it is known to show iridescence (iris color). Utilizing these characteristics, colloidal crystals are optical filters that do not transmit light of a specific wavelength, mirrors that reflect specific light, new optical functional materials called photonic crystals, optical switches, or optical sensors. The application to etc. is considered.

Such colloidal crystals have been disclosed in several publications. As a production method thereof, for example, a method is known in which colloidal particles of silica or polystyrene are deionized in an aqueous dispersion to remove impurities (see Patent Documents 1 and 2).
Further, as a method for controlling the structure of the colloidal crystal, a method of heating or cooling a dispersion of colloidal particles (see Patent Document 3), a method of applying shear flow (see Patent Documents 4 and 5), and a method of applying vibration. (See Patent Document 6) and the like are known.
Examples of colloidal crystal applications include an optical filter with a structure in which a colloidal crystal composed of polystyrene particles is sandwiched between two transparent flat plates (see Patent Document 7), and a colloidal crystal composed of polystyrene particles is gelled with a polymer. Colloidal crystal gels produced by this method (see Patent Documents 8 to 10) are known.

In order to form a colloidal crystal as described above, so-called monodispersed colloidal particles with a small variation in particle diameter are indispensable.
However, such colloidal particles have hitherto been only, for example, polystyrene particles synthesized by emulsion polymerization or silica particles by the Stover method. Since such polystyrene particles and silica particles have a small refractive index, they are not suitable for applications such as photonic crystals, which hinders the application development of colloidal crystals.

  Also, in order to use as a physical property control material such as a photonic crystal, it is important to control the structure of the colloidal crystal such as the lattice constant and the crystal type. However, in a colloidal crystal composed of polystyrene particles, silica particles, etc., the structure control is very difficult, and there is no choice but to rely on physical methods such as heating, cooling, shear flow, or vibration.

In order to solve this problem, various proposals have heretofore been made. For example, Non-Patent Document 1 discloses colloidal particles in which a SiO ₂ shell is formed on the surface of a ZnS core, colloidal particles in which a ZnS shell is formed on the surface of a SiO ₂ core, and core particles from these colloidal particles. SiO ₂ shells and ZnS shells obtained by removing the are disclosed. This document describes that the optical characteristics can be controlled by changing the thickness of the shell relative to the core.

  Further, in Non-Patent Document 2, the surface of a negatively charged polystyrene sphere is alternately coated with a positively charged polymer electrolyte and a negatively charged polymer electrolyte, and this surface is positively charged 4- Colloidal particles obtained by adsorbing (dimethylamino) pyridine (DMAP) stabilized Au nanoparticles and further coating the surface with a polymer electrolyte are disclosed. In this document, when a dispersion containing such core / shell type colloidal particles is held on a quartz plate, the colloidal particles undergo gravity sedimentation and water evaporation, and the colloidal particles can be regularly arranged. Are listed.

Japanese Patent Laid-Open No. 5-85716 Japanese Patent Application Laid-Open No. 6-1000043 JP 11-319539 A JP 2002-28471 A JP 2003-212700 A JP 2002-128600 A European Patent No. 0482394 US Pat. No. 4,632,517 US Pat. No. 4,627,689 U.S. Pat. No. 4,451,412 Krassimer P. Velikov et al., Langmuir 2001, 17, 4779-4786 Zhijian Liang, et al., Chem. Mater. 2003, 15, 3176-3183

  Non-Patent Document 2 describes an example in which polystyrene spheres with Au nanoparticles attached to their surfaces are regularly arranged. However, in general, there are many reports on core / shell type colloidal particles, but there are very few examples of producing colloidal crystals using such core / shell type colloidal particles. In particular, there has never been an example of successful ordered arrangement of core / shell colloidal particles using nanosheets capable of precisely controlling the thickness of the shell.

An object of the present invention is to provide, in the conventional polystyrene particles or silica particles or the like made from the novel colloidal particles having different refractive indexes, to provide a manufacturing method of the colloidal crystals can respond to a wide range of applications.
Another problem to be solved by the present invention is to remove a template from core / shell colloidal particles (particularly core / shell colloidal particles using nanosheets) or core / shell colloidal particles. to provide a hollow mold manufacturing method of the colloidal crystals obtained by regularly arranged colloid particles obtained by.

In order to solve the above problems, a method for producing a colloidal crystal according to the present invention includes:
A template particle having a particle diameter of 0.01 μm to 10 μm is dispersed in a first dispersion medium, and the first and second positive and negative charges in the first dispersion medium are different from the template particle on the surface of the template particle. A first intermediate layer forming step of forming an intermediate layer;
In the first dispersion medium, the surface of the first intermediate layer formed on the surface of the template particle is made of a substance different from the template particle, and the charge in the first dispersion medium is A coating step of stacking a shell whose positive and negative are different from those of the first intermediate layer to produce core / shell type colloidal particles;
The colloidal particles are dispersed in a second dispersion medium whose pH is adjusted so that the absolute value of the surface charge of the colloidal particles is 15 mV or more in terms of zeta potential and within the range of pH 4 to 10, and the colloidal particles And a crystallization step of regularly arranging the colloidal particles by an electric repulsive force acting in between.
In this case, before the crystallization step, a template removal step is performed in which the template particles are extracted and removed from the core / shell type colloid particles using a solvent that dissolves the template particles to produce hollow type colloid particles. Further, it may be provided.
In addition, the shell, around the template particles, silicate, titanate, phosphate, niobate, vanadate, tungstate, molybdate, graphite, transition metal dichalcogenide, or What consists of a nanosheet layer obtained by laminating | stacking the nanosheet obtained by acid-treating the layered compound which consists of a bivalent metal phosphochalcogenide, and making it peel into a thin film form is preferable.
Further, the crystallization step, wherein the colloidal particles prior to dispersing into the second dispersion medium, the colloidal particles by firing, the shell arbitrariness preferred that further comprises a firing step to crystallize.

When the core / shell type or hollow type colloidal particles are dispersed in the second dispersion medium having a pH of 4 to 10 so that the absolute value of the surface charge is 15 mV or more in terms of zeta potential, there is a relative relationship between the colloidal particles. Large electrical repulsion acts. As a result, colloidal particles are regularly arranged in the solvent, or colloidal particles are regularly arranged as the solvent is removed to form a colloidal crystal.
For example, the core / shell type colloidal particles (or hollow type colloidal particles obtained by removing the template from the core) having a nanosheet layer in the shell have a surface charge absolute value of less than 15 mV at zeta potential near pH 7. And colloidal crystals may not be obtained. In contrast, when such a core / shell type colloidal particle is subjected to a certain treatment (for example, a firing treatment), the absolute value of the surface charge becomes 15 mV or more in zeta potential, and this potential is stabilized. Colloidal crystals can be produced with good reproducibility.

  Hereinafter, an embodiment of the present invention will be described in detail. The method for producing a colloidal crystal according to the first embodiment of the present invention is a method for producing a colloidal crystal composed of core / shell type colloidal particles, and includes a coating step and a crystallization step. The colloidal crystal according to the first embodiment of the present invention is obtained by such a method.

  First, the coating process will be described. In the coating step, template particles having a particle diameter of 0.01 μm to 10 μm are dispersed in a first dispersion medium, and a shell made of a material different from the template particles is laminated around the template particles in the first dispersion medium. In this step, core / shell type colloidal particles are produced.

The first dispersion medium is not particularly limited, but it is preferable to use water, an aqueous solution prepared by adding an acid, an alkali, or the like to water to adjust the pH.
As the template particles, for example, those having a negative charge or a positive charge in a first dispersion medium such as water can be used. Specifically, there are those composed of polymer particles such as polystyrene (PS) and polymethyl methacrylate (PMMA), silica, and the like as negatively or positively charged template particles.

  Template particles made of silica can be easily reduced in particle size variation (so-called “monodisperse”). Therefore, when monodispersed silica particles are used as template particles, monodispersed colloidal particles can be easily produced. As a result, colloidal particles can be easily arranged regularly, and a colloidal crystal in which colloidal particles are arranged very regularly can be obtained. Further, since silica is relatively easy to remove as will be described later, even hollow colloidal particles can be easily produced.

  In addition, template particles made of polystyrene or polymethyl methacrylate can easily produce “monodispersed” colloidal particles as in the case of template particles made of silica. Therefore, a colloidal crystal in which colloidal particles are arranged very regularly can be obtained. Further, since polystyrene or polymethyl methacrylate is relatively easy to remove as described later, even hollow colloidal particles can be easily produced.

  The particle diameter of the template particles is 0.01 μm to 10 μm. If the particle diameter is less than 0.01 μm, the shell may not be uniformly coated because the template particles are small. On the other hand, when the thickness exceeds 10 μm, the template particles are large, so that the shell may not be uniformly coated.

Moreover, it is preferable that the dispersion | variation in the particle diameter of a template particle is 10% or less. When the variation of the template particles exceeds 10%, the variation in the particle diameter of the colloid particles tends to increase accordingly, and it may be difficult to regularly arrange the colloid particles. On the other hand, when the variation in particle diameter is 10% or less, the arrangement of colloidal particles in the colloidal crystal can be made more uniform.
In the present invention, “variation of particle diameter” means a value obtained by subtracting the minimum value of the particle diameter from the maximum value of the particle diameter and dividing the value by the average value of the particle diameters, expressed as 100 fractions. Say. Such a variation in particle diameter can be measured by measuring a particle size distribution, for example.

  The shell is made of a material different from the template particles. The shell may be one in which fine particles (nanoparticles) are adsorbed on the surface of template particles, or a nanosheet layer in which nanosheets are laminated on the surface of template particles. In particular, when the shell includes a nanosheet layer, there is an advantage that the thickness of the shell can be precisely controlled.

  Nanoparticles, for example, reduce the solution of metal salts and metal oxides, hydrolyze metal alkoxides, hydrothermal, coprecipitation, and other liquid phase methods, and oxidize metal halides. It can be obtained by a vapor phase method such as thermal decomposition or evaporation / condensation of metal by plasma or induction electricity.

In addition, the nanosheet can be obtained, for example, by peeling a layered compound to a monomolecular layer or several molecular layers.
Examples of such layered compounds include silicates such as clay mineral montmorillonite, and iso- and polyhetero such as titanate, phosphate, niobate, vanadate, tungstate, and molybdate. Examples thereof include ion-exchange layered compounds of acid salts and molecular layered compounds such as graphite, transition metal dichalcogenides, and divalent metal phosphochalcogenides.
These layered compounds can be separated into single-layer or several-layer thin-sheet nanosheets by applying acid treatment with hydrochloric acid or nitric acid in a dispersion medium such as water, and dispersed in a colloidal form in the dispersion medium. it can. The thickness of the nanosheet is approximately 0.5 nm to 1.5 nm. The nanosheet has a flaky shape, for example.

The nanosheet layer is preferably configured by combining nanosheets having a width of 5 nm to 500 nm. “Combined configuration” means that the nanosheet layer may be formed using only nanosheets having the same composition, or the nanosheet layer may be formed using a plurality of types of nanosheets having different compositions. .
When nanosheets having a predetermined width are used, when producing colloidal particles, there are almost no gaps between the nanosheets, and a nanosheet layer having a uniform thickness can be formed. Get smaller. Therefore, in this case, the arrangement of colloidal particles in the colloidal crystal can be made more uniform.

When the width of the nanosheet is less than 5 nm, for example, the nanosheet is dispersed in a first dispersion medium such as water, and template particles are added thereto to produce colloidal particles. There is a possibility that the viscosity of the medium becomes high, and it becomes difficult to uniformly mix with the template particles.
On the other hand, when the width of the nanosheet exceeds 500 nm, when the nanosheet is formed around the template particles to form the nanosheet layer, the nanosheets are likely to overlap each other, and the thickness of the nanosheet layer may be uneven. . In addition, a gap is likely to be generated in the nanosheet layer. As a result, there may be a large variation in the particle size of the colloidal particles.
Here, the “width of the nanosheet” can be expressed by, for example, an average of the maximum width and the minimum width of the nanosheet.

  The template particle and the nanosheet or nanoparticle constituting the shell (hereinafter simply referred to as “nanosheet or the like”) may have different positive and negative charges in the first dispersion medium. In this case, since the template particles and the nanosheets are attracted to each other by electrical interaction in the first dispersion medium such as water, the nanosheets gather around the template particles and easily form a shell. Can be made.

  Further, the template particles and the nanosheets or the like may have the same positive / negative charge in the first dispersion medium. In this case, it is preferable to form a first intermediate layer having positive and negative charges different from the template particles and the shell before the coating step (first intermediate layer forming step). When the first intermediate layer is provided between the template particle and the shell, the shell can be formed around the template particle via the intermediate layer, so that the template particle and the shell are positively charged or negatively charged. Even so, core / shell colloidal particles can be easily produced.

  That is, for example, when both the template particles and the nanosheets are positively charged or both are negatively charged, the nanosheets and the like are less likely to collect around the template particles. By forming a first intermediate layer that is opposite to the positive and negative charges between the template particle and the nanosheet, the first intermediate layer can mediate the bond between the template particle and the nanosheet. . The first intermediate layer is different from the template particles, nanosheets, and the like in terms of positive and negative charges in the dispersion medium. The first intermediate layer can be formed, for example, by coating the template particles in advance before reacting the template particles with the nanosheet or the like.

As the first intermediate layer having a positive charge in the first dispersion medium, for example, a cationic polymer electrolyte can be used. Specific examples include amine polymers such as polyethyleneimine (PEI) and polyallylamine.
An anionic polymer electrolyte or the like can be used as the first intermediate layer that is negatively charged in the dispersion medium. Specific examples include polymers containing carboxyl groups and sulfonic acid groups such as polyacrylic acid and polystyrene sulfonic acid.

Only one layer of the shell may be laminated around the template particle, or two or more layers may be laminated. When a plurality of shells are laminated around the template particles, a second intermediate in which the positive and negative charges in the first dispersion medium are different from the shells on the surface of the template particles on which the first shell is laminated. It is preferable to laminate | stack a layer and a shell alternately (continuous lamination process). When the second intermediate layer is provided between the shells, core / shell type colloidal particles in which a plurality of shells are laminated can be easily produced.
Therefore, the particle diameter, refractive index, etc. of the colloidal particles can be controlled. Further, even colloidal particles having almost the same particle variation as the template particles can be produced. Furthermore, the interference effect of the colloidal crystal can be controlled according to the number of laminated shells. Thereby, the optical characteristics of the colloidal crystal in which colloidal particles are regularly arranged can be easily controlled.
Note that, for the second intermediate layer, various materials similar to those of the first intermediate layer described above can be used depending on whether the charge of the shell is positive or negative.

FIG. 1A shows a schematic cross-sectional view of a core / shell type colloidal particle. In FIG. 1A, colloidal particles 1 are obtained by laminating a plurality of nanosheet layers 15 around template particles 11. The template particle 11 has a particle diameter of 0.01 μm to 10 μm. The nanosheet layer 15 is composed of a nanosheet 151 having a monomolecular layer or several molecular layers. In this example, the nanosheet layer 15 is made of titanium dioxide (titania).
Further, in the colloidal particle 1 of this example, a first intermediate layer 13 a is formed between the nanosheet layer 15 and the template particle 11. The first intermediate layer 13a is a resin layer made of polyethyleneimine (PEI). Further, as shown in FIG. 3, the template particle 11 is made of silica (SiO ₂ ) having a negative charge on the surface.

The nanosheet layer 15 is formed by agglomerating nanosheets 151 having a flaky shape and a width of about 5 to 500 nm around the template particles 11. As shown in the partially enlarged view of FIG. 2, the nanosheets 151 are arranged around the template particle 11 so as to hardly overlap each other and with almost no gap to form the nanosheet layer 15.
In addition, a plurality of nanosheet layers 15 are laminated around the template particles 11, and a resin layer made of PEI is formed between the nanosheet layers 15 as the second intermediate layer 13b. In FIG. 1, the number of stacked nanosheet layers 15 is omitted for the sake of drawing creation.

Next, the crystallization process will be described. In the crystallization step, the colloidal particles are dispersed in a second dispersion medium whose pH is adjusted so that the absolute value of the surface charge of the colloidal particles is 15 mV or more in terms of zeta potential and is in the range of pH 4-10 . by electrical repulsion acting between colloidal particles is a step for arranging colloid particles regularly.

  The second dispersion medium used when regularly arranging the colloidal particles is not particularly limited, but it is preferable to use water, an aqueous solution prepared by adding acid or alkali to water, and the like. In this case, the pH of the second dispersion medium is preferably 4-10. When the pH is less than 4 and when the pH exceeds 10, the influence of the narrow ions increases and a good colloidal crystal cannot be obtained.

When the absolute value of the surface charge of the colloidal particles is 15 mV or more by simply dispersing the colloidal particles in the second dispersion medium, a colloidal crystal may be produced using a known method as it is. .
On the other hand, when the absolute value of the surface charge of the colloidal particles is less than 15 mV in zeta potential by simply dispersing the colloidal particles in the second dispersion medium, the absolute value of the surface charge in the second dispersion medium is Processing is performed so that the zeta potential is 15 mV or more. Specific examples of such processing include the following.

The first method for setting the absolute value of the surface charge to 15 mV or higher in terms of zeta potential is to adjust the pH of the second dispersion medium. Colloidal crystals are generally produced by dispersing colloidal particles in water having a pH of around 7. This is because when the ions are contained in water, the charges of the ions and the colloidal particles interfere with each other, and the colloidal particles may not be aligned.
However, in the case of core / shell type colloidal particles, the zeta potential may be less than 15 mV near pH 7 depending on the material of the shell. Therefore, even if such core / shell type colloidal particles are dispersed in water having a pH of around 7, a good colloidal crystal cannot be obtained because the electric repulsion is small.
Therefore, in such a case, it is preferable to adjust the pH of the second dispersion medium within the range of pH 4 to 10 so that the absolute value of the surface charge of the colloidal particles is 15 mV or more in terms of zeta potential.

For example, when the shell is made of a nanosheet layer and the nanosheet layer is made of a titania nanosheet, the absolute value of the surface charge of the titania nanosheet near pH 7 is less than 15 mV in terms of zeta potential. Therefore, in such a case, it is preferable to shift the pH of the second dispersion medium to the acidic side or the alkaline side within the range of pH 4 to 10 so that the zeta potential is 15 mV or more.
When shifting the pH of the second dispersion medium to the acidic side, the pH is specifically preferably 4-6. In addition, when the pH of the second dispersion medium is shifted to the alkali side, the pH is specifically preferably 8 to 10.
In this case, the second dispersion medium is preferably an acidic aqueous solution such as an aqueous hydrochloric acid solution or an aqueous acetic acid solution, or an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous ammonia solution.

The second method to the absolute value of the surface charge 15mV or more zeta potential, prior to dispersing the colloidal particles in the second dispersion medium, forms a colloidal particle baked, this and (firing step to crystallize the shell ). When the shell is made of an inorganic material, when the shell is baked, the crystal structure of the shell is changed, and a larger zeta potential may be exhibited in the second dispersion medium having a predetermined pH.

  For example, in the vicinity of pH 7, the absolute value of the surface charge of the titania nanosheet is relatively small. However, when such a titania nanosheet is fired under predetermined conditions, the crystal structure changes, and the absolute value of the surface charge exceeds 15 mV in zeta potential near pH 7. Therefore, when colloidal particles whose shell is composed of a titania nanosheet layer are fired before crystallization, a relatively large electric repulsion is generated even in the vicinity of pH 7 where the influence of the narrow ions is small, and a good colloidal crystal is obtained. It is done.

As the firing conditions, optimum conditions are selected according to the materials of the core and the shell. For example, when the template particles are silica and the nanosheet layer is made of titania, the firing temperature is preferably 300 ° C. or higher and 1100 ° C. or lower. When the firing temperature is less than 300 ° C., the crystallization of the shell is insufficient and a high surface charge cannot be obtained. On the other hand, if the firing temperature exceeds 1100 ° C., the silica particles of the template are melted, which is not preferable. The firing temperature is more preferably 400 ° C. or higher and 1000 ° C. or lower.
The firing time is preferably set to an optimum time according to the firing temperature so that the crystallization of the shell proceeds sufficiently.

  FIG. 1B is a schematic cross-sectional view of colloidal particles 1 ′ obtained by firing the core / shell type colloidal particles shown in FIG. When the core / shell type colloidal particles 1 having a shell composed of the nanosheet layer 15 are fired under predetermined conditions, the first intermediate layer 13a and the second intermediate layer 13b are removed by thermal decomposition, and at the same time, the nanosheet layer 15 Sintering proceeds. As a result, the core / shell type colloidal particle 1 ′ is obtained which shows a stable surface charge having a relatively large absolute value in the second dispersion medium at the same time as the nanosheet layer 15 becomes strong.

A third method for setting the absolute value of the surface charge to 15 mV or more in terms of zeta potential is to form a surface layer made of a substance having a large zeta potential on the surface of the colloid particles before crystallization of the colloid particles.
For example, in the titania nanosheet, as described above, the absolute value of the surface charge in the vicinity of pH 7 is less than 15 mV at the zeta potential, but on the alkali side, the absolute value of the zeta potential is relatively large and negative. Has a value. Therefore, when colloidal particles whose shell is composed of a titania nanosheet layer are dispersed in an alkaline aqueous solution, and a certain kind of cationic polymer is further dispersed therein, the surface of the colloidal particles is coated with the cationic polymer. Cationic polymers are characterized by maintaining a positive charge even when the pH varies. Therefore, if a surface layer made of a cationic polymer showing a relatively large zeta potential is formed on the surface of the shell made of a titania nanosheet layer, a relatively large electric repulsive force can be obtained even in the vicinity of pH 7 where there is little influence of narrow ions. To generate a good colloidal crystal.

After the colloidal particles and / or the second dispersion medium are subjected to a predetermined treatment as necessary so that the absolute value of the surface charge is 15 mV or more in zeta potential, the colloidal particles are regularly arranged. A colloidal crystal according to the invention is obtained.
As a method for regularly arranging colloidal particles, for example, a method of arranging particles by evaporating a second dispersion medium in which colloidal particles are dispersed, or a method of arranging particles by sedimentation in a second dispersion liquid is used. And a method of arranging the particles by pulling up the substrate from the second dispersion and integrating them. In this case, the colloidal particles can be arranged in a close packed structure, for example.
Further, there is a method in which colloidal particles are dispersed in a liquid and the colloidal particles are regularly arranged by electrostatic interaction or hydrophobic interaction that works between the particles of the colloidal particles in the liquid. In particular, when colloidal crystals are produced by electrostatic interaction, by removing low-molecular ions that coexist in the liquid, the electric double layer of ions near the surface of the colloidal particles becomes thicker, and the interaction between the colloidal particles Becomes stronger.

  The colloidal crystal can be immobilized, for example, by the following method. Specifically, for example, a method of polymerizing by adding a hydrophilic monomer such as acrylamide, methylenebisacrylamide, polyethylene glycol (meth) acrylate, polyethylene glycol di (meth) acrylate, or gelation of polyacrylic acid or polysaccharides There is a method of adding a hydrophilic polymer. Immobilized colloidal crystals are suitable for various materials such as optical filters that do not transmit light of specific wavelengths, mirrors that reflect specific light, optical functional materials such as photonic crystals, optical switches, and optical sensors. Can be used.

Next, a method for producing a colloidal crystal according to the second embodiment of the present invention will be described. The method for producing a colloidal crystal according to the present embodiment is a method for producing a colloidal crystal using hollow colloidal particles, and includes a coating step, a template removing step, and a crystallization step. The colloidal crystal according to the second embodiment of the present invention is obtained by such a method.
Among these, the coating process and the crystallization process are the same as those in the first embodiment described above, and thus the description thereof is omitted.

The template removal step is a step of removing the template particles from the core / shell type colloidal particles produced in the coating step to produce hollow type colloidal particles.
There are various methods for removing the template, and an optimum method is selected according to the material of the template particles and the shell.

For example, when the template particles are made of a polymer such as polystyrene or polymethyl methacrylate, there are a method of extracting and removing with a solvent that dissolves such a polymer, a method of baking the polymer, a method of treating with oxygen plasma, etc. is there. Preferably, in order to keep the particle shape spherical, a method of extracting and removing the polymer in a solvent obtained by diluting a polar solvent such as tetrahydrofuran with water is preferable.
For example, when the template particles are made of silica or the like, there are a method of heating in a sodium hydroxide aqueous solution, a method of etching with a hydrofluoric acid aqueous solution, and the like.

  FIG. 10A shows a schematic cross-sectional view of hollow colloidal particles. In FIG. 10A, the colloidal particle 2 is formed by laminating a plurality of nanosheet layers 25 around the hollow portion 21. The hollow portion 21 has a diameter of approximately 0.01 μm to 10 μm. The nanosheet layer 25 is composed of a nanosheet having a monomolecular layer or several molecular layers similar to the core / shell colloidal particles shown in FIG.

In the colloidal particle 2, a first intermediate layer 23 a is formed between the nanosheet layer 25 and the hollow portion 21. The first intermediate layer 23a is a resin layer made of polyethyleneimine (PEI) as in the case of the core / shell type colloidal particles 1 shown in FIG.
A plurality of nanosheet layers 25 are laminated around the hollow portion 21, and a resin layer made of PEI is formed as a second intermediate layer 23b between the nanosheet layers 25.

  For example, as shown in FIG. 11, the hollow colloidal particle 2 has a first intermediate layer 33a and a second intermediate layer made of polyethyleneimine on the surface of a template particle 31 made of polymethyl methacrylate or the like. The layer 33b and the nanosheet layer 35 are alternately laminated to obtain the core / shell type colloidal particles 3, and the template particles 31 are extracted and removed using tetrahydrofuran or the like. In FIGS. 10 and 11, the number of stacked nanosheet layers 25 (35) is omitted for the convenience of drawing.

  When the template particles are removed using a method other than firing, the obtained hollow colloidal particles may be further fired (firing step). As described above, when the shell is made of a certain kind of inorganic material, when the shell is fired, the crystal structure of the shell is changed, and a larger zeta potential is exhibited in the second dispersion medium having a predetermined pH. There is.

FIG. 10B shows a schematic cross-sectional view of the colloidal particles 2 ′ obtained by firing the hollow colloidal particles shown in FIG.
For example, when hollow type colloidal particles whose shell is composed of the nanosheet layer 25 and template particles are extracted and removed are fired under predetermined conditions, the first intermediate layer 23a and the second intermediate layer 23b are removed by thermal decomposition. At the same time, sintering of the nanosheet layer 25 proceeds. As a result, the nanosheet layer 25 is strengthened, and at the same time, a hollow colloidal particle 2 ′ that stably exhibits a surface charge having a relatively large absolute value in the second dispersion medium is obtained.

  When the hollow colloidal particles thus obtained are regularly arranged using the various methods described above, the colloidal crystal according to the present embodiment is obtained.

Next, the operation of the colloidal crystal and the production method thereof according to the present invention will be described.
Colloidal crystals are generally produced by dispersing colloidal particles in a solvent near pH 7 or removing the solvent from such a solution. The reason why the pH of the solution is in the vicinity of 7 is to reduce the influence of narrow ions. However, in the case of core / shell type colloidal particles or hollow type colloidal particles obtained by removing a template therefrom, good colloidal crystals are often not obtained. This is because, depending on the shell material, a large electrical repulsion cannot be obtained in the vicinity of pH 7.
On the other hand, when various treatments are performed on the colloidal particles and / or the second dispersion medium so that the absolute value of the surface charge is 15 mV or more in zeta potential in the range of pH 4 to 10, it becomes narrow. A relatively large electric repulsive force can be generated without being greatly affected by ions, and a good colloidal crystal can be obtained.

Further, core / shell type colloidal particles whose shell is composed of a nanosheet layer can be obtained by assembling nanosheets of one molecular layer or several molecular layers around the template particles by electrical interaction. In addition, core / shell colloidal particles each having a shell having a plurality of nanosheet layers are formed by alternately forming a first intermediate layer, a second intermediate layer, and a nanosheet layer using a layer-by-layer method. Can be obtained.
Therefore, nanosheets can be formed with a uniform thickness and almost no variation in thickness, with the nanosheets hardly overlapping around the template particles. In addition, since the thickness of the shell can be precisely controlled, monodisperse core / shell colloidal particles can be easily obtained, and the regular arrangement of the colloidal particles is facilitated.

Further, since the material and thickness of the shell can be controlled, a colloidal crystal having a refractive index different from that of conventional colloidal crystals made of silica particles or polystyrene particles can be obtained. Furthermore, in addition to the refractive index, the lattice constant of the colloidal crystal can be controlled.
As a result, it is possible to control the wavelength of the reflection peak by Bragg diffraction of the colloidal crystal, the photonic band gap, and the like. In addition, the colloidal crystal according to the present invention can be suitably used for photonic crystals, optical filters, optical functional materials such as mirrors, etc., which have been difficult in the past, and easily control the characteristics thereof. it can.

In addition, in a colloidal crystal using core / shell type colloidal particles, the characteristics of the shell can be imparted to the colloidal crystal. For example, when the shell includes a nanosheet layer that absorbs a specific wavelength, a colloidal crystal that can absorb the specific wavelength is obtained.
Further, when the template is removed from the core / shell colloidal particles, hollow colloidal particles are obtained. Since the hollow colloidal particles have a small weight, it is possible to eliminate the influence of gravity or to reduce the weight of the colloidal crystals when producing the colloidal crystals.

  As described above, core / shell colloidal particles or hollow colloidal particles are composed of novel colloidal particles having a refractive index different from that of polystyrene particles, silica particles, etc. Can be provided.

Example 1
[1. Preparation of nanosheet sol]
Cesium carbonate (Cs ₂ CO ₃ ) and titanium dioxide (TiO ₂ , hereinafter referred to as “titania”) are mixed at a molar ratio of Cs: Ti = 0.7: 1.825, and the atmosphere is at a temperature of 800 ° C. for 20 hours. Baked. Then, to synthesize a powder of _Cs 0.7 _{Ti 1.825} O ₄ was quenched to room temperature. An acid treatment was performed by adding 1000 ml of 0.1N aqueous hydrochloric acid to 1 g of this powder. In this acid treatment, the operation of replacing a new hydrochloric acid aqueous solution every day was repeated three times.
Thereafter, the solid phase was filtered, washed with water, and then air-dried to obtain a powder composed of titanic acid (H _0.7 Ti _1.825 O _{4 .H 2} O) as a layered compound. 0.5 g of this powder was added to 100 ml of an aqueous tetrabutylammonium hydroxide solution, and stirred at room temperature at a rotation speed of 150 rpm for about 1 week to obtain a titania sol (Ti _1-δ O _24δ- ). In the sol, nanosheets made of Ti _1-δ O _24δ- and having a width of about 10 nm to 200 nm are dispersed.
Next, this sol was diluted 50 times with water and the pH was adjusted to 9 to obtain a nanosheet sol.

[2. Preparation of core / shell type colloidal particles]
A polyethyleneimine (PEI) aqueous solution (pH 9) having a concentration of 2 wt% was prepared.
Next, template particles were prepared. As shown in FIG. 3, the template particle 11 is a template particle made of SiO ₂ (Seahoster KEW30 manufactured by Nippon Shokubai Co., Ltd.), has a particle diameter of 280 nm, and is dispersed in water and has a negative charge.
Next, 1 g of this template particle was mixed with 150 ml of the PEI aqueous solution prepared above, dispersed in an ultrasonic bath for 10 minutes, and further stirred for 15 minutes. Then, centrifugation for 10 minutes was performed 3 times at 4000 rpm, and the template particle | grains which formed the 1st intermediate | middle layer (resin layer) which consists of PEI on the surface were collect | recovered.
Next, the template particles forming the first intermediate layer were mixed with 150 ml of distilled water, dispersed in an ultrasonic bath for 10 minutes, and further stirred for 15 minutes. Thereafter, 5 ml of the nanosheet sol prepared above was added and stirred again for 15 minutes. Subsequently, centrifugation for 10 minutes at 4000 rpm was performed three times to collect colloidal particles in which one nanosheet layer was laminated on the template particles. In this colloidal particle, a first intermediate layer is formed between the nanosheet layer and the template particle.

  Next, the colloidal particles on which the single nanosheet layer prepared above is laminated are mixed with the PEI aqueous solution in the same manner as described above, dispersed in an ultrasonic bath, stirred, centrifuged, and the nanosheet layer A second intermediate layer was further formed on the surface. Thereafter, the mixture was mixed with distilled water in the same manner as described above, dispersed in an ultrasonic bath for 10 minutes and stirred for 15 minutes, and then 5 ml of nanosheet sol was added and stirred again for 15 minutes. Centrifugation for 10 minutes at 4000 rpm was performed three times to collect colloidal particles in which two nanosheet layers were laminated on template particles. Furthermore, the second intermediate layer and the nanosheet layer were alternately laminated to produce colloidal particles 1 in which three nanosheet layers 15 were laminated as shown in FIG. A first intermediate layer 13 a and a second intermediate layer 13 b made of PEI are formed between the template particle 11 and the nanosheet layer 15 and between each nanosheet layer 15.

[3. Preparation of colloidal crystals]
Colloidal particles obtained by laminating three nanosheet layers prepared as described above were dispersed in an aqueous hydrochloric acid solution having a pH of 5. Thereafter, the solution was dropped on a glass plate and dried, whereby colloidal particles were regularly arranged to form a film-like colloidal crystal. This is designated as Sample E1.
In addition, for comparison, template particles made of silica with no nanosheet layer laminated are dispersed in water, dropped onto a glass plate in the same manner as described above, and dried to form a film-like array of regularly arranged template particles. Colloidal particles were prepared. This is designated as Sample C1.

  In this example, the colloidal particles used for sample E1 were further laminated with the second intermediate layer and the nanosheet layer alternately to produce colloidal particles having a total of six nanosheet layers. In the same manner as described above, the colloidal particles were dispersed in water and then dried on a glass plate to prepare a film-like colloidal crystal. This is designated as Sample E2.

  As described above, a colloidal crystal (sample E1) composed of colloidal particles in which three nanosheet layers are laminated, a colloidal crystal (sample E2) composed of colloidal particles in which six nanosheet layers are laminated, and a colloidal crystal composed only of template particles. Three types of colloidal crystals (sample C1) were prepared.

[4. Evaluation]
A transmission electron microscope (TEM) photograph of the colloidal particles obtained in this example was taken. The result is shown in FIG. For comparison, a TEM photograph was also taken for template particles made of silica with no nanosheet layer laminated, and the results are shown in FIG. In the TEM photographs shown in FIGS. 4 and 5, the white line at the bottom of the photograph indicates a length of 100 nm.
As is known from FIGS. 4 and 5, the colloidal particles coated with the nanosheet layer are found to be monodispersed in the same manner as the template particles.

  Next, scanning electron microscope (SEM) photographs of three types of colloidal crystals were taken. FIG. 6 shows an SEM photograph of sample E1, FIG. 7 shows an SEM photograph of sample E2, and FIG. 8 shows an SEM photograph of sample C1. In each SEM photograph, the white line at the bottom center is for showing a length of 1 μm. As is known from FIGS. 6 to 8, it can be seen that in any colloidal crystal (sample E1, sample E2, and sample C1), the particles are regularly arranged and crystallized.

Next, the reflection spectra of the colloidal crystals of the samples E1, E2, and C1 were measured using a spectrometer. The result is shown in FIG.
As can be seen from FIG. 9, in the samples E1 and E2, the peak of the reflection spectrum is shifted to the short wavelength side as compared with the sample C1. Further, the sample E2 coated with six nanosheet layers was shifted to the shorter wavelength side than the sample E1 coated with three layers. That is, it turns out that the one where the thickness of a nanosheet layer is larger shifts to the short wavelength side.
Thus, it can be seen that the optical properties of the colloidal crystal can be controlled by coating the nanosheet layer on the template particles.

(Comparative Example 1)
In this example, template particles made of silica and a nanosheet sol similar to that in Example 1 were directly reacted, and then crystallization of the particles after the reaction was attempted.
First, the same nanosheet sol as in Example 1 was added to an aqueous dispersion of template particles similar to that in Example 1 (Seahoster KEW30 manufactured by Nippon Shokubai Co., Ltd.) and stirred. Subsequently, the particles were collected by performing centrifugation three times in the same manner as in Example 1. However, the nanosheet was not sufficiently adsorbed on these particles.

  Furthermore, similarly to Example 1, the particles obtained in this example were dispersed in water, dropped onto a glass plate, and then dried. Thereafter, the reflection spectrum was measured with a spectrometer. However, no reflection peak was shown, and the particles of this example could not form a colloidal crystal.

(Comparative Example 2)
In this example, template particles made of silica are coated with titania particles, and crystallization of the coated particles is attempted.
First, titania particles (manufactured by Catalyst Kasei Kogyo Co., Ltd.) were added to an aqueous dispersion of template particles similar to Example 1 (Seahoster KEW30 manufactured by Nippon Shokubai Co., Ltd.) and stirred for 15 minutes. Thereby, template particles in which titania particles were partially adsorbed were obtained.

  Further, the template particles adsorbed with the titania particles were dispersed in water, dropped onto a glass plate in the same manner as in Example 1, and then dried. Thereafter, the reflection spectrum was measured with a spectrometer. However, no reflection peak was shown, and the particles of this example could not form a colloidal crystal.

(Example 2)
[1. Production of hollow colloidal particles]
First, the same nanosheet sol and PEI aqueous solution as Example 1 were prepared.
Moreover, template particles (MX300 manufactured by Soken Chemical Co., Ltd.) made of polymethyl methacrylate (PMMA) having a particle diameter of 300 nm were prepared.
Next, this template particle was mixed with the PEI aqueous solution prepared above, and then the template particle having the first intermediate layer (resin layer) made of PEI formed on the surface was recovered in the same manner as in Example 1.

  Next, the template particles forming the first intermediate layer were mixed with distilled water in the same manner as in Example 1, dispersed in an ultrasonic bath, stirred for another 15 minutes, and then the nanosheet sol prepared above was prepared. The mixture was stirred again for 15 minutes. Further, as in Example 1, centrifugation was performed to collect colloidal particles in which one nanosheet layer was laminated on the template particles.

  In the same manner as in Example 1, the second intermediate layer and the nanosheet layer were alternately laminated on this colloidal particle, thereby producing a colloidal particle 3 in which three nanosheet layers 35 were laminated as shown in FIG. . In this colloidal particle 3, the template particle 31 is made of PMMA, the first intermediate layer 33 a and the second intermediate layer made of PEI between the template particle 31 and the nanosheet layer 35, and between each nanosheet layer 35. 33b is formed.

Next, the template particles made of PMMA are extracted and removed from the colloidal particles obtained above.
That is, the colloidal particles obtained as described above were dispersed in a 0.1 wt% tetrahydrofuran aqueous solution and stirred at 50 rpm for 24 hours. Thereby, the template particles were extracted and removed, and as shown in FIG. 10, colloidal particles 2 in which the nanosheet layer 25 was laminated around the hollow portion 21 were obtained.

[2. Preparation of colloidal crystals]
Next, hollow colloidal particles obtained by laminating three nanosheet layers prepared as described above were dispersed in a pH 5 hydrochloric acid aqueous solution. Thereafter, the solution was dropped on a glass plate and dried, whereby colloidal particles were regularly arranged to form a film-like colloidal crystal. This is designated as Sample E3.
Further, for comparison, template particles made of PMMA not laminated with nanosheet layers are dispersed in water, dropped onto a glass plate in the same manner as described above, and dried to form a film-like array in which the template particles are regularly arranged. Colloidal particles were prepared. This is designated as Sample C2.

  In this example, colloidal particles in which six nanosheet layers were laminated on template particles made of PMMA were prepared, and colloidal particles were prepared by extracting and removing template particles from the colloidal particles in the same manner as described above. In the same manner as described above, the colloidal particles were dispersed in water and then dried on a glass plate to prepare a film-like colloidal crystal. This is designated as Sample E4.

  As described above, a colloidal crystal (sample E3) composed of hollow colloidal particles in which three nanosheet layers are laminated, a colloidal crystal (sample E4) composed of hollow colloidal particles in which six nanosheet layers are laminated, and a template. Three types of colloidal crystals (sample C2) consisting only of particles were prepared.

[3. Evaluation]
A scanning electron microscope (SEM) photograph of the hollow colloidal particles from which the template particles were removed was taken. The result is shown in FIG. For comparison, SEM photographs were also taken of template particles made of PMMA without forming a nanosheet layer, and the results are shown in FIG. In the SEM photographs shown in FIG. 12 and FIG. 13, the white line shown on the right part indicates a length of 1 μm.
As is known from FIGS. 12 and 13, it can be seen that the colloidal particles coated with the nanosheet layer are monodispersed like the template particles.

Next, the reflection spectra of the colloidal crystals of the samples E3, E4, and C2 were measured using a spectrometer. The result is shown in FIG.
As can be seen from FIG. 14, in the samples E3 and E4, the peak of the reflection spectrum was shifted to the lower wavelength side as compared with the sample C2. Further, the sample E4 coated with 6 nanosheet layers was shifted to the lower wavelength side than the sample E3 coated with 3 layers.
Thus, the optical properties of the colloidal crystals could be controlled by coating the nanosheet layer on the template particles.

(Comparative Example 3)
In this example, template particles made of PMMA and a nanosheet sol similar to that in Example 1 were directly reacted, and then the production of hollow colloidal particles similar to that in Example 2 was attempted.
First, the same nanosheet sol as in Example 1 was added to an aqueous dispersion of template particles similar to Example 2 (MX300 manufactured by Soken Chemical Co., Ltd.) and stirred for 15 minutes. Subsequently, the particles were collected by performing centrifugation three times in the same manner as in Example 1. However, the nanosheet was not sufficiently adsorbed on these particles.

  Next, as in Example 2, the particles obtained in this example were dispersed in a 0.1 wt% aqueous tetrahydrofuran solution and stirred at 50 rpm for 24 hours. The particles disappeared and hollow particles were not obtained. .

(Comparative Example 4)
In this example, template particles made of PMMA are coated with titania particles, and then an attempt is made to produce hollow colloidal particles similar to those in Example 2. .
First, titania particles (manufactured by Catalyst Kasei Kogyo Co., Ltd.) were added to an aqueous dispersion of template particles similar to Example 2 (MX300 manufactured by Soken Chemical Co., Ltd.) and stirred for 15 minutes. Thereby, template particles in which titania particles were partially adsorbed were obtained.

  Further, when the template particles adsorbed with the titania particles were dispersed in a 0.1 wt% tetrahydrofuran aqueous solution and stirred at 50 rpm for 24 hours, the particles disappeared and no hollow particles were obtained.

(Example 3, Comparative Examples 5-8)
Various colloidal particles were dispersed in aqueous solutions having different pH values, and the zeta potential was measured. Further, [3. of Example 1] except that water having a pH of 7 was used as the second dispersion medium. The colloidal crystal which consists of various colloidal particles was tried according to the same procedure. The colloidal particles used are as follows.
(1) Silica particles used in Example 1 (Comparative Example 5).
(2) Polystyrene particles (W030 manufactured by Duke Scientific) (Comparative Example 6).
(3) The colloidal particles obtained in Example 1 (silica particles in which three titania nanosheet layers were laminated) were further fired at 450 ° C. for 1 hour in the atmosphere (Example 3).
(4) In place of PMMA, polystyrene particles (W030 manufactured by Duke Scientific) were used, and polystyrene extraction and removal were not performed [1. ] Core / shell type colloidal particles (polystyrene particles in which three titania nanosheet layers are laminated) produced by the same procedure as in (Comparative Example 7).
(5) Colloidal particles obtained in Example 1 (silica particles in which three titania nanosheet layers are laminated) (Comparative Example 8)

  15 and 16 show measured values of zeta potential and SEM photographs of colloidal particles on a glass plate. FIGS. 15A, 15B, and 15C are obtained by using the above-described colloidal particles (1), (2), and (3), respectively. FIGS. 16 (a) and 16 (b) use the colloidal particles (4) and (5) described above, respectively.

In the case of Comparative Example 7 (FIG. 16 (a)) and Comparative Example 8 (FIG. 16 (b)), the zeta potential was almost zero near pH 7. Therefore, none of the colloidal particles were regularly arranged, and no colloidal crystal was obtained.
In contrast, in Comparative Example 5 (FIG. 15A), Comparative Example 6 (FIG. 15B), and Example 3 (FIG. 15C), the zeta potential is negative near pH 7. And the absolute value was 15 mV or more. Therefore, all the colloidal particles were regularly arranged, and colloidal crystals were obtained. From FIG. 15, it can be seen that in the case where the shell is a core / shell type colloidal particle composed of a titania nanosheet layer, firing of the colloidal particle is effective for obtaining a good colloidal crystal in the vicinity of pH 7.

(Example 4, Comparative Examples 9, 10)
In order to investigate the influence of the pH of the second dispersion medium on the regular arrangement state of the colloidal particles, the colloidal particles were dispersed in the second dispersion medium having a different pH, and an attempt was made to produce colloidal crystals.
For colloidal particles, [2. ] Was used (silica particles in which three titania nanosheet layers were laminated). In addition, the second dispersion medium includes three types of hydrochloric acid aqueous solution having pH = 3 (Comparative Example 9), hydrochloric acid aqueous solution having pH = 5 (Example 4), and water having pH = 7 (Comparative Example 10). . Furthermore, the production of colloidal crystals was performed as described in [3] of Example 1 except that the type of the second dispersion medium was changed. The same procedure was performed.
FIG. 17 shows an SEM photograph of colloidal particles arranged on the glass plate. From FIG. 17, it can be seen that colloidal particles are not regularly arranged when pH = 3 and pH = 7, whereas colloidal particles are regularly arranged when pH = 5. The reason why regular arrangement was not performed at pH = 3 is that the influence of the narrow ions is great. Further, the reason why the regular arrangement was not performed at pH = 7 is that the absolute value of the zeta potential was small and sufficient electric repulsion did not act between the particles.

(Example 5)
[1. ] And [2. ], Colloidal particles in which three, five or ten titania nanosheet layers were laminated were prepared. Next, the obtained colloidal particles were baked at 450 ° C. for 1 hour in the air. Furthermore, [3 .. in Example 1 except that water having a pH of 7 was used as the second dispersion medium. The colloidal crystal which consists of the baked colloidal particle was produced in accordance with the same procedure as the above.

FIG. 18 shows an SEM photograph of the colloidal crystal. FIG. 18 also shows an SEM photograph of a colloidal crystal composed of template particles (SiO ₂ ). FIG. 18 shows that good colloidal crystals are obtained in both cases.

Further, the lattice constant d and the effective refractive index n _eff of each colloidal crystal were measured. The grating constant d and the effective refractive index n _eff are determined using the Bragg equation λ = the relationship between the incident angle θ and the reflection peak wavelength λ using an angle-resolved reflection spectrum device (an angle variable unit is installed in S-2650 manufactured by Soma Optics). It was obtained by substituting and fitting to 2d (n _eff ² −sin ² θ) ^1/2 . Further, the reflection spectrum of each colloidal crystal was measured using a spectrometer.
Table 1 below shows the lattice constant d and effective refractive index n _eff of each colloidal particle. FIG. 19 shows the reflection spectrum of each colloidal crystal. FIG. 19 shows that the peak of the reflection spectrum is shifted to the longer wavelength side as the number of titania nanosheet layers is increased. This is because as the number of titania nanosheet layers increases, the lattice constant d decreases and the effective refractive index n _eff increases.

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

  The colloidal crystal according to the present invention can be used for optical filters, mirrors that reflect specific light, photonic crystals, optical switches, optical sensors, and the like.

FIG. 1A is a cross-sectional explanatory view of a colloid particle in which a nanosheet layer is laminated around a template particle, and FIG. 1B is a colloid obtained by firing the colloid particle shown in FIG. It is a section explanatory view of particles. The elements on larger scale which show the structure of the nanosheet layer in the colloidal particle shown to Fig.1 (a). Explanatory drawing which shows the template particle | grains which consist of silica. 1 is a transmission electron micrograph of colloidal particles according to Example 1. FIG. The transmission electron micrograph of the template particle which consists of silica concerning Example 1. FIG. The scanning electron micrograph of the colloidal crystal (sample E1) which consists of colloidal particles which laminated | stacked three nanosheet layers concerning Example 1. FIG. The scanning electron micrograph of the colloidal crystal (sample E2) which consists of colloidal particles which laminated | stacked six nanosheet layers concerning Example 1. FIG. The scanning electron micrograph of the colloidal crystal (sample C1) which consists only of template particles concerning Example 1. FIG. The figure which shows the peak of the reflection spectrum of three types of colloidal crystals of the samples E1, E2, and C1 concerning Example 1. FIG. FIG. 10A is a cross-sectional explanatory diagram of hollow colloidal particles obtained by removing template particles from core / shell type colloidal particles, and FIG. 10B is shown in FIG. FIG. 3 is a cross-sectional explanatory view of hollow colloidal particles obtained by firing hollow colloidal particles. Cross-sectional explanatory drawing of the colloidal particle which laminated | stacked the nanosheet layer around the template particle | grains which consist of PMMA. The scanning electron micrograph of the colloidal particle which the nanosheet layer laminated | stacked around the hollow part concerning Example 2. FIG. The scanning electron micrograph of the template particle | grains which consist of PMMA which does not form the nanosheet layer concerning Example 2. FIG. The figure which shows the peak of the reflection spectrum of three types of colloidal crystals of the samples E3, E4, and C2 concerning Example 2. FIG. Various colloidal particles (FIG. 15 (a): silica, FIG. 15 (b): polystyrene, FIG. 15 (c): core / shell type colloidal particles obtained by laminating a titania nanosheet layer around silica particles and firing at 450 ° C. ) Is a diagram showing the relationship between the pH of the dispersion medium and the zeta potential of the colloidal particles, and SEM photographs of various colloidal particles arranged in pH 7 water. Various colloidal particles (FIG. 16 (a): core / shell type colloidal particles in which titania nanosheet layer is laminated around polystyrene particles, FIG. 16 (b): core / shell type in which titania nanosheet layer is laminated around silica particles 2 is a diagram showing the relationship between the pH of the dispersion medium and the zeta potential of the colloidal particles, and SEM photographs of various colloidal particles arranged in pH 7 water. It is a figure which shows the relationship between pH of a 2nd dispersion medium, and the regular arrangement | sequence state of a colloid particle. It is a SEM photograph of the colloidal crystal which consists of the silica particle (with baking) by which the silica particle and the titania nanosheet layer were laminated | stacked in multiple layers. It is a figure which shows the reflection spectrum of the colloidal crystal which consists of a silica particle (with baking) by which multiple layers of the silica particle and the titania nanosheet layer were laminated | stacked.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Colloid particle 11 Template particle 13a 1st intermediate | middle layer 13b 2nd intermediate | middle layer 15 Nanosheet layer

Claims (10)

A template particle having a particle diameter of 0.01 μm to 10 μm is dispersed in a first dispersion medium, and the first and second positive and negative charges in the first dispersion medium are different from the template particle on the surface of the template particle. A first intermediate layer forming step of forming an intermediate layer;
In the first dispersion medium, the surface of the first intermediate layer formed on the surface of the template particle is made of a substance different from the template particle, and the charge in the first dispersion medium is A coating step of stacking a shell whose positive and negative are different from those of the first intermediate layer to produce core / shell type colloidal particles;
The colloidal particles are dispersed in a second dispersion medium whose pH is adjusted so that the absolute value of the surface charge of the colloidal particles is 15 mV or more in terms of zeta potential and within the range of pH 4 to 10, and the colloidal particles And a crystallization step in which the colloidal particles are regularly arranged by an electric repulsive force acting between them.   After the coating step, on the surface of the shell formed on the surface of the template particle, the second intermediate layer in which the charge in the first dispersion medium is different from the shell, and the shell are alternately arranged. The method for producing a colloidal crystal according to claim 1, further comprising a continuous laminating step of laminating the layers.   Before the crystallization step, the method further comprises a template removal step of extracting and removing the template particles from the core / shell type colloidal particles using a solvent that dissolves the template particles to produce hollow type colloidal particles. The method for producing a colloidal crystal according to claim 1 or 2.   The shell has a silicate, titanate, phosphate, niobate, vanadate, tungstate, molybdate, graphite, transition metal dichalcogenide, or divalent around the template particle. The colloidal crystal production according to any one of claims 1 to 3, which is a nanosheet layer obtained by laminating nanosheets obtained by acid-treating a layered compound comprising a metal phosphochalcogenide and peeling it into a thin film. Method.   The colloidal crystal production method according to claim 4, wherein the nanosheet is a titania nanosheet.   6. The colloidal crystal according to claim 5, wherein the crystallization step is to disperse the colloidal particles in the second dispersion medium having a pH of 4 to 6 or a pH of 8 to 10, and to regularly arrange the colloidal particles. Manufacturing method.   The crystallization step further includes a firing step of firing the colloid particles and crystallizing the shell before dispersing the colloid particles in the second dispersion medium. A method for producing a colloidal crystal according to claim 1.   The method for producing a colloidal crystal according to any one of claims 1 to 7, wherein the template particles are silica.   The method for producing a colloidal crystal according to any one of claims 1 to 7, wherein the template particles are polystyrene or polymethyl methacrylate.   The method for producing a colloidal crystal according to any one of claims 1 to 9, wherein the colloidal particles are arranged in a close packed structure.

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