JP2013188674A - Particle structure and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new particle structure applicable to various purposes by forming a regular two-dimensional array structure of small particles on a surface of a large particle accumulation body, and to provide a manufacturing method thereof.SOLUTION: A manufacturing method of a particle structure includes a process for forming an accumulation body of coated particles from the coated particles, and a process for applying a suspension on the accumulation body of coated particles, the suspension containing coating particles, that have a particle size smaller than that of the coated particles, and a solvent. When coming into contact with the solvent of the suspension, the coated particle is charged with an opposite sign from the sign of the coating particle.

Description

  The present invention relates to a particle structure and a manufacturing method thereof.

  In general, spherical fine particles having a uniform size can be easily collected to form a densely packed structure (hcp or fcc structure), and the regular structure can be applied to various applications. is there. For example, a two-dimensional particle aggregate having a closely packed structure can be applied to a reflection film, an antireflection film, or an etching mask using an optical interference effect. It can be applied to devices, pulse laser devices, and the like. Here, two-dimensional means that one side of the aggregate is sufficiently smaller than the other two sides, and three-dimensional means that the characteristic lengths of the three sides of the aggregate are comparable. . Particles for forming colloid photonic crystals that are currently attracting attention are required to have high shape uniformity of several to 10% or less in terms of the CV value of the particle diameter. In 1947, it can be said that it started after the synthesis of monodisperse latex particles. Today, crystals are produced under microgravity in order to obtain large crystals on the cm scale.

  The colloidal crystal is a solvent drying process from a suspension of spherical silica particles, polystyrene particles, polymethyl methacrylate resin particles, and particles having a chemical substance adsorbed on the surfaces (Patent Documents 1 and 2), or a narrow space. It can be easily manufactured by confinement of the concentrated suspension in (Patent Document 3). These colloidal crystals are fragile soft matter in which particles are aggregated, and in actual use, it is necessary to fix the particles and the substrate or between the particles, or to fill the particle gaps with a solid. For example, it is known to form an element by filling a gap with a gel and fixing a crystal (Patent Document 4). In addition, an inversion ordered structure made of a polymer or oxide can be made using the particle arrangement as a template. In particular, the inversion regular structure mainly composed of isopropylacrylamide can change the interference wavelength not only by the volume change due to deformation but also by the volume change due to temperature and pH change, and can be applied to a physicochemical sensor ( Patent Document 5).

Japanese Patent No. 2783487 Japanese Patent No. 2828386 Japanese Patent No. 3760227 Japanese Patent No. 3533442 Japanese Patent No. 4284642 JP-A-2005-300767

  Since the regular structure of conventional crystals is mostly a simple structure using particles of the same particle size, it is necessary to try to create a particle structure from particles of different particle sizes in order to obtain more complex response characteristics. There is. However, colloidal crystals having the same particle size and isotropic interaction between spherical particles cannot essentially coexist with particles having different particle sizes as described above.

  Although the particles constituting the crystal can form a mixed system with particles (also referred to as small particles) having a particle size smaller than the particle size, the small particles are composed of particles constituting the crystal (also referred to as large particles). It was supposed to fill the gaps between the crystals irregularly. For example, when the ratio of the diameters of the large particles and the small particles constituting the crystal is (2√3-3) /3=0.1547 or less, and the small particles do not affect the attractive force between the large particles. The small particles were supposed to fill the gaps between the large particles. However, if the ratio exceeds 0.1547, exceptions are observed for nanoparticles with anisotropic interactions, but small particles are excluded from large particle aggregates, or the regularity of the aggregates is reduced. In particular, two or more kinds of particles having a close particle diameter could not be regularly arranged in a three-dimensional crystal.

  On the other hand, a technique for forming a fine particle line by creating a two-dimensional particle structure from a mixed suspension of large particles and small particles using a coating method is known (Patent Document 6). In this case, it is reported that these particles have a regular structure at the meniscus portion. However, since such a structure is realized by advection accumulation (Patent Documents 1 and 2) and the Meniscus Stick-Slip motion, the small particles are not surely arranged with respect to the regular structure of the large particles.

  In view of the above problems, the present invention provides a new particle assembly applicable to various uses by forming a regular two-dimensional array structure of small particles on the surface of the large particle assembly, and a method for manufacturing the same. The purpose is to do.

  In order to achieve the above object, a method for producing a particle structure according to the present invention includes a step of forming an aggregate of coated particles from coated particles, and coated particles and a solvent having a particle size smaller than the particle size of the coated particles. And applying a suspension containing the particles on the aggregate of particles to be coated, and when the particles to be coated come into contact with the solvent of the suspension, they are charged to a sign opposite to the sign of the particles to be coated. It is characterized by being particles.

  Here, it is preferable to include a step of further heating at a temperature equal to or higher than the melting point of the coated particles and lower than the melting point of the coated particles. Alternatively, it is preferable to include a step of further heating at a temperature lower than the melting point of the coated particles and higher than the melting point of the coated particles.

  The particle structure of the present invention includes an aggregate of coated particles and a layer of coated particles having a particle size smaller than the particle size of the coated particles and formed on the coated particle aggregate. The coated particles and the coated particles are characterized in that they are particles that are charged to opposite signs when in contact with a predetermined solvent.

  Here, it is preferable that one kind or two or more kinds of coated particles regularly fit in the gaps on the surface of the aggregate of coated particles. Alternatively, it is preferable that one kind or two or more kinds of coated particles are uniformly adsorbed on the surface of the aggregate of coated particles. Further, the melting point of the coated particles is preferably lower than the melting point of the particles to be coated. Alternatively, the melting point of the coated particles is preferably higher than the melting point of the particles to be coated. In addition, the coated particles are dissolved and fused in the gaps between the coated particles constituting the surface of the aggregate of coated particles to form a fused particle of the coated particles, and the fused particles of the coated particles are formed between the coated particles. It is preferable that they are arranged at intervals of. Alternatively, it is preferable that the surface of the aggregate of coated particles is coated with a continuous film of coated particles formed by dissolution and fusion of coated particles. Further, it is preferable that the coated particles are arranged at a predetermined interval on the surface of the coated particle fusion body formed by dissolution and fusion of the aggregate of coated particles. Alternatively, it is preferable that the coated particles are uniformly adsorbed on the surface of the fused particles formed by dissolution and fusion of the collected particles.

  According to the present invention, particles in which a two-dimensional array structure of coated particles having a particle size smaller than the particle size of the coated particles is regularly formed on the surface of the aggregate of coated particles without breaking the array structure. A structure can be manufactured. In addition, according to the present invention, it is possible to manufacture a particle structure in which a two-dimensional array structure of coated particles having a particle diameter ratio of 0.1574 or more is regularly formed on the surface of an aggregate of coated particles. .

Effect 1 (Production of alloy grain arrangement structure)
In particular, a structure reflecting the period of the surface in which coated particles (also referred to as small particles) are metal particles and a plurality of small particles are accumulated in the concave portions of the aggregate of coated particles (also referred to as large particles) can be manufactured. When the melting point of the small particles is lower than the melting point of the large particles, the manufactured particle structure is heated to the melting point of the small particles or more and less than the melting point of the large particles, so that the small particles dissolve and become small at each concave point created by the large particles. A structure with an array of particle melts is obtained. At this time, for example, as shown in FIG. 2, when the small particles are made of metal small particles 14 a and 14 b of different materials, the small particles 14 a and 14 b are formed in the concave portions 12 a of the particle aggregate 12 of the large particles 10. The particle structure 30 in which the alloys 14c are arranged can be manufactured. In addition, if the small particles of different materials are a combination of iron particles, cobalt particles, nickel particles, platinum particles or palladium particles, an ordered magnetic alloy (for example, FePt, CoPt, FePd, CoPd, etc.) is formed in each concave portion. Can be arranged. If the small particles are a combination of three kinds of small particles, an ordered magnetic alloy (for example, FeNiPt, CoNiPt, etc.) with controlled saturation magnetization can be arranged. These can be a granular layer of a magnetic recording medium.

Effect 2 (Manufacture of metal thin films)
In particular, when the applied small particles are metal particles, and the small particles are uniformly adsorbed on the surface of the large particle aggregate (or the small particles cover the surface of the large particle aggregate), When the melting point of the small particles is lower than the melting point of the large particles, the manufactured structure is heated above the melting point of the small particles to below the melting point of the large particles, so that the metal particles, which are small particles, dissolve and the large particles accumulate. The body surface can be uniformly covered with a metal film. At this time, for example, as shown in FIG. 3, when the adsorbed small particles are a mixture of small metal particles 14d and 14e of different materials, the particle aggregate 12 of the large particles 10 is covered with an alloy metal film 14f. The particle structure 40 can be manufactured. At this time, if the stop band of the large particle aggregate coincides with the plasmon absorption band of the metal film, a quenching state can be realized, and it is possible to detect a slight band movement and a change in width with high sensitivity. Applicable to sensors.

A small particle suspension is applied to the large particle mass (a) and the suspension wets the mass (b). Since the large particles and the small particles have opposite charges, the small particles approach the surface of the aggregate and adsorb as the solvent evaporates (c). When the solvent is completely evaporated, a particle structure can be produced in which small particles are left on the surface of the aggregate (d). Small particles (in this case, a mixture of different kinds of metal particles) accumulate in the concave portions of the large particle aggregate (a). When this particle structure is heated above the melting point of the small particles and below the melting point of the large particles, the particles in the recesses are dissolved to form an alloy (b). The alloy has an array that reflects the array of large particle aggregates (c). Small particles (in this case, a mixture of different metal particles) are uniformly adsorbed on the surface of the large particle aggregate (a). When this particle structure is heated above the melting point of the small particles and below the melting point of the large particles, a metal thin film covering the entire surface of the large particle aggregate is formed (b). It is an AFM image showing a close packed structure of silica particles having a diameter of 1 μm modified with amino groups (Photo 1). FIG. 2 is an AFM image showing a regular structure of polystyrene particles having a diameter of 0.209 μm modified with a carboxyl group and accumulated in a concave portion of a finely packed structure of 1 μm diameter silica particles modified with an amino group (Photo 2). FIG. 6 is an enlarged view of FIG. 5 (Photo 2), which is an AFM image showing a regular structure with a large aggregate composed of small particles and a small aggregate (Photo 3). FIG. 7 is a conceptual diagram of FIG. 6 (Photo 3). FIG. 4 is an AFM image showing the state of a carboxyl group-modified 0.1 μm diameter polystyrene particle adsorbed on the entire surface of a finely packed structure of amino group-modified 1 μm diameter silica particles (Photo 4). FIG. 9 is an enlarged view of FIG. 8 (Photo 4), and shows an AFM image in which polystyrene particles are adsorbed on the entire surface of silica particles (Photo 5). FIG. 6 is an AFM image showing a finely packed structure of 1 μm diameter polystyrene particles modified with a carboxyl group (Photo 6). FIG. 7 is an AFM image showing the structure when a carboxyl group-modified 0.209 μm polystyrene particle suspension is applied to the surface of a finely packed structure of 1 μm diameter polystyrene particles modified with a carboxyl group (Photo 7).

  Hereinafter, a preferred embodiment for carrying out the present invention will be described with reference to FIG. As shown in FIG. 1, for example, a particle assembly 12 having a regular structure with large particles 10 is prepared by a known technique, and a suspension 16 of small particles 14 is applied to the surface thereof. At this time, it is assumed that the large particle 10 has a surface that is oppositely charged from the small particle 14 when it contacts the solvent 18 of the suspension 16. For this reason, the small particles 14 are adsorbed on the surface of the large particles 10 by electric force. Furthermore, since the concave portion 12a of the particle aggregate 12 of the large particles 10 has a large electric force, the small particles 14 are likely to accumulate there. Thus, by dividing the structure formation by the large particles 10 and the small particles 14 having opposite charges into two stages, a more complicated particle structure 20 is reliably realized.

  In the present invention, large particles that are charged when suspended in a solvent are regularly arranged to form a large particle aggregate, and the large particle aggregate is formed on the surface of the large particle aggregate from which the solvent has been removed in advance. A more complicated structure is produced by post-coating a suspension containing small particles and a solvent which are smaller than the size of the large particles constituting the particles and which are oppositely charged. The present invention makes use of the surface of the large particle aggregate to create a two-dimensional array structure of small particles that interact isotropically and coexist with the original large particle aggregate to form a more complicated regular structure. Is realized.

  The present inventor noticed that different size particles can coexist on the surface because the anisotropic force acts on the surface unlike the inside of the colloidal crystal. When small particles having the following charge are adsorbed by approaching the surface of the large particle aggregate using a combination of the evaporation process of the solvent and electric force, the small particles are put on the large particle aggregate. Has been found to be regularly arranged. The present inventor has paid attention to the fact that the solvent has an action of charging the large particles and the small particles oppositely to each other and an action of regularly arranging the small particles close to the surface of the aggregate of the large particles. It was found that small particles can be regularly arranged on an aggregate of large particles by evaporating.

[Example 1]
Silica particles having a diameter of 1 μm were synthesized by the Stoeber method. When the zeta potential was measured after washing with pure water, the silica particles showed a potential of about +30 mV in water. Therefore, the silica particles are surface-modified with amino groups. A suspension of amino-modified silica particles having an appropriately adjusted concentration was dropped onto a glass substrate and dried to obtain a large particle aggregate (FIG. 4: Photo 1). As small particles, commercially available carboxyl group-modified polystyrene (PS) particles having a diameter of 0.209 μm were used. A commercially available suspension was washed with pure water to obtain a suspension. The PS particle had a ζ potential of about −40 mV. The diameter ratio of large particles to small particles is 0.209, exceeding 0.1574. This PS particle suspension was dropped onto the surface of the large particle aggregate, and the solvent was removed by drying to obtain a structure (FIG. 5: Photo 2). Small particles are accumulated in the depressions of the large particles, and the portions with a small number and a large number are regularly arranged (FIG. 6: Photo 3). As conceptually shown in FIG. 7, the particle structure 50 is composed of a particle aggregate 12 having a finely packed structure of large particles 10 and small particles arranged in concave portions (dents) 12a on the surface thereof. It has a triple structure with various types of hexagonal lattices 14g and 14h.

[Example 2]
Large particle aggregates were obtained from silica particles modified with amino groups similarly synthesized. As a small particle, a commercially available suspension of PS particles modified with a carboxyl group having a diameter of 0.1 μm was used as a coating suspension. The ζ potential was about the same as the 0.209 μm product. The diameter ratio is 0.1, which is below 0.1547. This PS particle suspension was similarly applied to a large particle aggregate to obtain a structure (FIG. 8: Photo 4). PS particles were adsorbed almost uniformly on the surface of the large particles (FIG. 9: Photo 5).

[Comparative Example 1]
A large particle aggregate was obtained in the same manner by using a commercially available suspension of PS particles modified with carboxyl groups having a diameter of 1 μm as a large particle (FIG. 10: Photo 6), and small 0.209 μm PS particles modified with a carboxyl group. When a structure was made in the same manner as particles, the regular structure of small particles was not obtained, and the structure of large particles was destroyed (FIG. 11: Photo 7). This is because both particles were negatively charged when the small particle suspension was applied.

10 Large particles 12 Particle aggregate 12a Recessed portion 14 Small particles 14a, 14b, 14d, 14e Small metal particles 14c of different materials Alloy 14f Metal films 14g, 14h Two types of hexagonal lattice 16 composed of small particles 16 Suspension 18 Solvent 20, 30, 40, 50 Particle structure

Claims (12)

Forming an aggregate of coated particles from coated particles;
A step of applying a suspension containing coating particles having a particle size smaller than the particle size of the particles to be coated and a solvent onto the aggregate of particles to be coated;
A method for producing a particle structure, comprising:
A production method, wherein the particles to be coated are particles that are charged to a sign opposite to the sign of the coated particles when they come into contact with the solvent of the suspension.   The production method according to claim 1, further comprising a step of heating at a temperature equal to or higher than the melting point of the coated particles and lower than the melting point of the coated particles.   The manufacturing method according to claim 1, further comprising a step of heating at a temperature lower than the melting point of the coated particles and higher than the melting point of the coated particles. An aggregate of coated particles;
A layer of coated particles having a particle size smaller than the particle size of the coated particles and formed on the aggregate of coated particles;
A particle structure comprising:
A particle structure, wherein the particles to be coated and the particles to be coated are particles that are charged to opposite signs when contacted with a predetermined solvent.   The particle structure according to claim 4, wherein one kind or two or more kinds of coated particles are regularly fitted in gaps on the surface of the aggregate of coated particles.   The particle structure according to claim 4 or 5, wherein one or two or more kinds of coated particles are uniformly adsorbed on the surface of the aggregate of coated particles.   The particle structure according to any one of claims 4 to 6, wherein the melting point of the coated particles is lower than the melting point of the particles to be coated.   The particle structure according to any one of claims 4 to 6, wherein the melting point of the coated particles is higher than the melting point of the coated particles.   The coated particles dissolve and fuse in the gaps between the coated particles constituting the surface of the aggregate of coated particles to form a fused particle fusion, and the fused particles of the coated particles are the gaps between the coated particles. The particle structure according to any one of claims 4, 5, and 7, wherein   The particle structure according to any one of claims 4, 6, and 7, wherein a surface of the aggregate of coated particles is coated with a continuous film of coated particles formed by dissolution and fusion of coated particles.   9. The coating particle according to claim 4, wherein the coating particles are arranged at a predetermined interval on a surface of the fusion particle of the coating particles formed by dissolution and fusion of the aggregate of the coating particles. Particle structure.   The particles according to any one of claims 4, 6, and 8, wherein the coated particles are uniformly adsorbed on the surface of the fused particles formed by dissolution and fusion of the aggregate of coated particles. Structure.