KR101889045B1 - Fully crystallized colloidal crystal, photonic pigments including the same, and process for forming fully crystallized colloidal crystal - Google Patents

Abstract

In a spherical colloidal crystal according to the present invention, a plurality of nanoparticles are fully crystallized and arranged from the center and a surface and an average diameter thereof is 5 to 90 um. If necessary, a broadband light absorbing layer is further included on the surface of the colloidal crystal. Accordingly, the present invention can implement a clearer reflective color.

Description

TECHNICAL FIELD [0001] The present invention relates to a colloidal crystal, a method of manufacturing the colloidal crystal, a method of manufacturing the colloidal crystal, a method of manufacturing the colloidal crystal,

The present disclosure relates to fully crystallized colloidal crystals, optical pigments comprising them, and a process for the preparation of fully crystallized colloidal crystals.

Particles floating in the liquid can spontaneously crystallize and form colloidal crystals. However, colloidal crystals formed in accordance with a number of colloidal crystal methods known to date are mostly crystal of the surface arrangement. That is, the particles are regularly arranged on only a few layers of the surface of the colloidal crystal and the inside shows an irregular arrangement of the particles.

Colloidal crystals show a variety of interesting optical functionality coming from regular gratings. However, in order for the photo-functionality of the colloidal crystal to be sufficiently exhibited, the colloidal crystal must be completely crystallized. There is also a growing need for a process for producing fully crystallized colloidal crystals.

The present invention seeks to provide fully crystallized colloidal crystals.

The present invention seeks to provide an optical pigment comprising a fully crystallized colloidal crystal.

The present invention seeks to provide a process for producing fully crystallized colloidal crystals.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not to be construed as limiting the invention as defined by the appended art, except as may be apparent to one of ordinary skill in the art, It will be possible.

The colloidal crystals according to the embodiments are spherical colloidal crystals having a mean diameter of 5 to 90 탆 and arranged in a completely crystallized state from the center to the surface of the plurality of nanoparticles.

The nanoparticles may be hydrophilic nanoparticles.

And a broadband light absorbing layer on the surface of the colloidal crystal.

The thickness of the broadband light absorbing layer may be 5 to 20 nm.

The reflectance at a wavelength other than the reflection wavelength by the colloidal crystal structure may be 7% or less.

The reflectance at the reflection wavelength by the colloidal crystal structure may be 20% or more.

The average size of the nanoparticles may range from 160 to 300 nm.

The reflectance at the reflection wavelength by the above-mentioned colloidal crystal structure may be 30% or more.

The light pigments according to embodiments include the colloidal crystals.

The method of producing colloidal crystals according to embodiments provides a water in oil type emulsion in which water droplets in which hydrophilic nanoparticles are dispersed are dispersed in an oil continuous phase and the aqueous solvent of the droplets is vaporized, Heating the solution to a temperature below the boiling point of the water-soluble solvent so that the plurality of hydrophilic nanoparticles are completely crystallized from the center to the surface to obtain a fully crystallized spherical colloidal crystal having an average diameter of 5 to 90 탆.

Heating to a temperature below the boiling point may be continued for at least 24 hours.

And forming a broadband light absorbing layer on the surface of the spherical colloidal crystal.

The broadband light absorbing layer may be formed by dropping a carbon precursor solution on the colloidal crystal, and drying the resultant in a vacuum condition.

The broadband light absorbing layer may be formed to a thickness of 5 to 20 nm.

The broadband light absorbing layer may be formed such that the reflectance at a wavelength other than the reflection wavelength by the colloidal crystal structure is 7% or less.

The broadband light absorbing layer may be formed such that the reflectance at the reflection wavelength by the colloidal crystal structure is 20% or more.

The average size of the hydrophilic nanoparticles may range from 160 to 300 nm.

The spherical colloidal crystals according to the embodiments of the present invention are colloidal crystals in which a plurality of nanoparticles are completely crystallized from the center to the surface. Therefore, since there are many layers arranged without an amorphous layer therein, the reflection color according to the colloidal crystal structure becomes clear. Therefore, when the colloidal crystals are formed in a size similar to that of the conventional colloidal crystals arranged on the surface, a clearer reflection color can be realized, and a similar reflection color can be realized even when a colloidal crystal is formed to a size much smaller than the conventional one.

In addition, the spherical colloidal crystals according to the embodiments of the present invention can further improve the sharpness of the reflection color by introducing the broad band light absorbing layer.

1 is a schematic view for explaining a method for producing a fully crystallized colloidal crystal according to an embodiment,
2 is a schematic view of a colloidal crystal in which a crystallized arrangement exists only on a conventional surface,
3 is an electron microscope image of a colloidal crystal prepared according to Example 1,
4 (a) is a confocal microscope image of a spherical colloidal crystal,
4 (b) is an electron microscope image of spherical colloidal crystals cut in half,
5 (a) is an SEM photograph and a cross-sectional simulated image of a spherical colloidal crystal formed according to Example 1,
5 (b) is an SEM photograph and a cross-sectional simulated image of the colloidal crystal produced by the comparative example, FIG. 6 is a graph showing the result of measuring the color of the colloidal crystal produced according to Example 1,
7 is an EDX (Energy Dispersive X-ray) image of a colloidal crystal including a broadband light absorbing layer (carbon coating layer) prepared according to Example 3,
8 (a) is a graph showing the results of measurement of the reflection color before and after the formation of the broadband light absorbing layer (carbon coating layer)
8 (b) is a digital image of the colloidal crystals before and after the formation of the broadband light absorbing layer (carbon coating layer).
FIG. 9 is a graph showing the results of measuring the color of the colloidal crystals formed using silica nanoparticles of different sizes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view for explaining a method for producing a colloidal crystal; FIG.

Referring to FIG. 1, the colloidal crystal 100 may be formed by removing a solvent from a droplet containing hydrophilic nanoparticles to self-assemble the nanoparticles. First, a water-in-oil type emulsion 50 in which water droplets 30 dispersed in the water phase 20 are dispersed in the oil phase continuous phase 40 is prepared (S1).

The hydrophilic nanoparticles 10 may be nanoparticles having an average size of about 160 nm to 300 nm. Depending on the average size of the hydrophilic nanoparticles 10, the color of the colloidal crystals of the final product may be different. According to the Bragg reflection law, the reflection color can be controlled according to the size of the nanoparticles 10. For example, when the nanoparticle 10 has a size of 260 to 300 nm, the color of the colloidal crystal 100 may be red. When the diameter of the nanoparticles 10 is 210 to 250 nm, the color of the colloidal crystal 100 may be green. When the diameter of the nanoparticles 10 is 160 to 200 nm, the color of the colloidal crystal 100 may be blue. The relationship between the diameter and the reflection color described above is exemplary and it can be seen that various colors can be displayed as a reflection color by controlling the diameter of the nanoparticle 10. [

The nanoparticles 10 are preferably hydrophilic because they must be dispersed in the water phase 20 and the nanoparticles 10 must be filled from the inside of the colloidal crystals. Examples of the hydrophilic nanoparticles 10 include particles of silica (SiO ₂ ), titanium dioxide (TiO ₂ ), zinc oxide (ZnO ₂ ) and the like, but any hydrophilic material that can be prepared as nano-sized particles can be used without limitation. Most of the metal oxides or non-metal oxides are hydrophilic and therefore applicable as nanoparticles 10. The size of the colloidal crystal 100 can be determined according to the size of the droplet 30 and the concentration of the nanoparticles 10 in the droplet 30. As the size of the droplet 30 is larger and the concentration of the nanoparticles 10 in the droplet 30 is larger, the size of the colloidal crystal 100 can be increased.

The continuous phase oil phase 40 may include an aliphatic hydrocarbon-based organic solvent or an aromatic hydrocarbon-based organic solvent that is not immersed in water. In an exemplary embodiment, the aliphatic hydrocarbon-based organic solvent or aromatic hydrocarbon-based organic solvent may be selected and used by those skilled in the art without particular limitation, among those having 6 to 20 carbon atoms. For example, the aliphatic hydrocarbon-based organic solvent may include, but is not limited to, a linear or branched aliphatic hydrocarbon having 6 to 20 carbon atoms or 10 to 20 carbon atoms. For example, the aromatic hydrocarbon-based organic solvent may include toluene, and the aliphatic hydrocarbon may include hexadecane, but is not limited thereto.

On the other hand, a surfactant can be used to stabilize the water-in-oil type emulsion 50. For example, Pluronic F108, SPAN 80 (Sorbitan monooleate) may be used as the surfactant, but the present invention is not limited thereto.

Subsequently, the water-in-oil type droplet 30 is dried to self-assemble the nanoparticles 10 (S2).

At this time, the drying is allowed to take place as slowly as possible, that is, the drying is delayed so that self-assembly does not occur from the surface of the droplet 30 but self-assembly occurs from the center.

For example, the drying time is preferably 10 hours or more, preferably 12 hours or more, and more preferably 24 hours or more.

To delay the drying of the droplets 30, that is, to delay the drying, the aqueous solution or water is saturated in the oil phase 40, and the drying is continued for a long time by lowering the heating temperature as much as possible.

The water-soluble solvent 20 of the water-in-oil type droplet 30 has a low solubility in the oil phase 40 and slowly moves toward the oil phase 40. At this time, when the aqueous solution or the water is saturated with the oil phase 40 and then dried, the solubility of the water phase 20 in the oil phase 40 is further reduced, and the drying can be delayed. The method of saturating the water in the oil phase (40) is saturated by leaving a few drops of water in the oil phase (40) and leaving it in the over night.

On the other hand, when the temperature is increased, the solubility of the aqueous solvent (20) in the droplet (30) to the oil phase (40) increases and the removal of the aqueous solvent (20) is accelerated. Thus, the drying proceeds from room temperature to below the breaking point of the water-based solvent 20. [ Preferably from room temperature to 80 ° C, more preferably from room temperature to 60 ° C. When proceeding at room temperature, drying may be too slow, so it may be preferable to conduct drying at about 60 캜.

Then, after the solvent of the droplet 30 is completely vaporized, the remaining oily phase 40 solution is removed to obtain a fully crystallized colloidal crystal 100 (S3). The removal of the oil phase (40) solution can be carried out by a washing and drying process.

Washing can be carried out using hexane or the like capable of extracting the oily phase (40) solution. The spherical colloidal crystal 100 manufactured in accordance with the embodiment of the present invention can be completely crystallized without any amorphous state from the center C to the surface S as illustrated in a schematic view of a section cut along the equatorial plane of Fig. .

On the other hand, the colloidal crystals prepared by the conventional methods known to date (J. Am. Chem. Soc., 2006, 128, 10897 or Sci. Rep., 2013, 3, 2371) polystyrene) so that a crystallized arrangement exists only on the surface 1a as shown in FIG. 2, and the interior 1b has an irregular arrangement of particles to exhibit an amorphous state.

The colloidal crystal 100 obtained through the vaporization delay has an average diameter of 5 to 90 탆, preferably 50 탆 or less, more preferably 20 탆 or less, still more preferably 10 탆 or less, The hydrophilic nanoparticles of the hydrophilic nanoparticles of the respective layers Ln, Ln-1, Ln-2, ..., L1 are overlapped with each other so that the reflection color becomes clearer.

In the above description, the colloidal crystal 100 is formed by forming a water-in-oil type emulsion and then delaying the aqueous solution of the liquid droplet. However, after forming the water type emulsion, the droplet oil solvent is dried, It is of course possible to form a fully crystallized spherical colloidal crystal by allowing a plurality of lipophilic nanoparticles to be completely crystallized from the center to the surface by a delayed drying method in which the drying is performed for a long time by lowering the heating temperature as much as possible.

A thin broadband light absorber 200 is then formed on the surface of the colloid crystal 100 to treat the remaining color of the color other than the color represented by the colloidal crystal 100 structure with noise. The broadband light absorbing layer 200 may be a visible light wavelength light absorbing layer. For example, the broadband light absorbing layer 200 may be composed of nanoparticles of carbon, gold, silver or the like or various quantum dots capable of absorbing visible light having a wavelength of 380 nm to 800 nm.

Accordingly, the broadband light absorbing layer 200 absorbs all the light in the wavelength range of the visible light, and the reflection color due to the structure of the colloidal crystal 100 becomes clearer.

The thickness of the broadband light absorbing layer 200 is 5 to 20 nm, and the remaining reflection color other than the reflection color represented by the structure of the colloidal crystal 100 is treated with noise to minimize the reduction of reflectance of the reflection color by the structure of the colloidal crystal 100 can do.

The broad band light absorbing layer 200 can be introduced by various coating layer forming methods. For example, a carbon precursor solution may be dropped on the colloidal crystal 100 and then dried in a vacuum condition. Alternatively, the carbon nanoparticle dispersion may be dispersed in the colloidal crystal 100 It can be formed in such a manner that it is dropped and infiltrated. The concept of the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

Example  One

Silica nanoparticles were prepared by the STOVER method using the reaction of tetraethylorthosilicate (TEOS) solution with ammonia solution. The size of the silica nanoparticles was controlled by controlling the ratio of each solution used.

In order to prepare spherical ordered colloidal crystals, a 10% by mass colloidal solution containing silica nanoparticles having a size of 280 nm was prepared and dissolved in a hexadecane solution containing 1% or more of a surfactant in a mass ratio of 1:10 And then mixed with vortex for 10 minutes to form a water-in-oil type emulsion.

A water-in-oil emulsion containing a silica colloidal solution was slowly evaporated at a temperature of 60 캜 for a period of time of 24 hours or more in water contained in the emulsion. After the water was completely evaporated, the hexadecane was washed with hexane solution to evaporate the hexane solution to obtain colloidal crystals. After removing the unnecessary solvent remaining on the surface by annealing at 500 DEG C for 30 minutes, spherical colloidal crystals were obtained.

3 is an electron microscope image of the colloidal crystals produced. FIG. 3 (a) is a low-magnification image of a colloidal crystal having various sizes, and FIG. 3 (b) is a high-magnification image showing a surface crystal structure of a colloidal crystal. From the results of FIG. 3, it can be seen that the spherical colloidal crystals were formed very uniformly.

To confirm that the prepared colloidal crystals have an internal arrangement, a solution having the same refractive index as that of the silica nanoparticles was prepared using a mixed solution of glycerol and water at the same ratio. The fluorescent dyes (rhodamine) were applied to the outside of the particle to confirm the internal arrangement of the spherical colloid crystals by confocal microscope and electron microscope.

Fig. 4 (a) is a confocal microscope image of a spherical colloidal crystal, and Fig. 4 (b) is an electron microscope image of spherical colloidal crystals cut in half.

It can be seen that the spherical colloidal crystals produced from the image of FIG. 4 have a fully crystallized form from the center to the surface, rather than having only an array on the surface.

Example  2

A spherical colloidal crystal (Example) prepared in Example 1 and having a mean diameter of 10 mu m and having a completely crystallized phase was prepared by the method described in the 2006 paper and evaporated at 100 DEG C within 1 hour to have the same diameter, In order to compare the reflection colors of colloidal crystals having only an array (comparative example), reflected light for the same light source was confirmed using a spectrometer.

5 (a) is an SEM photograph and a cross-sectional simulated image of a spherical colloidal crystal prepared according to Example 1, and FIG. 5 (b) is a SEM photograph and a cross-sectional image of a colloidal crystal prepared by a comparative example Image.

The reflection color is influenced by the angle of the incident light and the size of the particle which is arranged in accordance with Bragg's diffraction law. The result of measuring the reflection color is illustrated in Fig. It can be seen that the peak of the reflection color in the 610 nm region which is the reflection color wavelength by the completely crystallized colloidal crystal structure according to the embodiment is significantly larger than the reflection color peak of the colloidal crystal having only the surface arrangement according to the comparative example.

This is because, in the case of colloidal crystals completely crystallized from the center to the surface, the beams reflected by Bragg's diffraction law interfere with each other and the peaks become larger.

Example  3

A phenol / formaldehyde precursor was prepared as a carbon precursor. To 20wt% NaOH solution, 20wt% phenol solution in which 6.5mmol of phenol was dissolved in NaOH and 36wt% formaldehyde solution in which 13mmol of formaldehyde was dissolved were reacted at 70 ° C for 1 hour. Neutralized with a 0.6M HCl solution and then dried in an oven to obtain a phenol / formaldehyde precursor. Subsequently, a phenol / formaldehyde precursor was diluted in ethanol to obtain an 80% (v / v) solution. The phenol / formaldehyde precursor solution diluted in ethanol was dropped on the spherical colloidal crystals and wetted, followed by drying under vacuum conditions.

The thickness of the carbon absorbent layer to be coated can be controlled by the concentration of the precursor used and the amount of precursor injected or by washing the precursor after drying. The precursor was reacted for one day at 100 ℃ for crosslinking, and the colloidal crystals coated with the precursor were sintered at high temperature (700 ℃) under an inert gas condition to prepare spherical colloidal crystals having a carbon layer on the surface. This carbon coating method is an advantageous method that does not affect the structure of the colloidal crystals that are completely arranged while introducing a uniform carbon layer into the colloidal crystals.

7 is an EDX (Energy Dispersive X-ray) image of a carbon-coated colloidal crystal. As a result of EDX mapping, the component was identified as Si and most of the outer surface layer was identified as C component.

Example  4

In order to confirm the change in the optical characteristics of the carbon-coated colloidal crystal, the colloidal crystals before the carbon coating layer formed in Example 1 and the colloidal crystals after the carbon coating layer formed in Example 3 were irradiated with the reflected light from the same light source using a spectrometer Respectively.

The measurement results are illustrated in Fig. As shown in FIG. 8 (a), in the case where there is no carbon coating layer as the broadband light absorbing layer, the reflectance decreases in the entire wavelength region when the carbon coating layer as the contrast broadband light absorbing layer is present. This is due to the effect of the carbon coating layer absorbing light in the full-wave-range wavelength region. Therefore, when the carbon coating layer is introduced, the reflection color due to the structure of the colloidal crystal can be emphasized since the reflection at the unnecessary region of the carbon coating layer is minimized.

Figure 8 (b) is a digital image of a spherical colloidal crystal deposited on a carbon tape. As shown in FIG. 8 (b), it can be seen that before the carbon coating layer is introduced (on), white light generally appears due to the reflectance of about 15% in the entire wavelength range. On the other hand, The reflectance at the wavelength other than the reflection (red) wavelength by the structure is reduced to 7% level, but the reflectance by the structure (red) is more than 20% It can be confirmed that it shows a brighter red color. Therefore, a colloidal crystal having a high reflectance can be produced by introducing a carbon coating layer, which is a broadband light absorbing layer, in addition to the colloidal crystals that are completely arranged. Therefore, the possibility of application of the colloidal crystal to the photonic pigment can be enhanced.

Example  5

The silica nanoparticles used were changed to 280 nm, 230 nm, and 180 nm, respectively, and the remaining processes were carried out in the same manner as in Example 1 to obtain spherical colloidal crystals. The obtained colloidal crystals were confirmed by reflection spectroscopy using a spectrometer. The results are illustrated in FIG.

Colloidal crystals made of nanoparticles of 280 nm in size showed red color, colloidal crystals made of nanoparticles of 230 nm size showed green, and colloidal crystals made of 180 nm nanoparticles showed blue peak. You can check the color. From this, it can be seen that the colloidal crystals can be implemented differently in the reflection color by varying the size of the nanoparticles.

Although specific embodiments of the invention have been illustrated and described, it is to be understood that the invention is not to be limited to the disclosed embodiments, but that various modifications and variations can be made therein without departing from the spirit and scope of the invention, . Accordingly, it should be understood that such modifications or alterations should not be understood individually from the technical spirit and viewpoint of the present invention, and that modified embodiments fall within the scope of the claims of the present invention.

Claims (16)

Spherical, fully crystallized colloidal crystals in which many nanoparticles are completely crystallized from the center to the surface and are arranged in an average diameter of 5 to 90 μm,
A colloidal crystal containing a broadband light absorbing layer on the surface of the fully crystallized colloidal crystal The method according to claim 1,
The nanoparticles are spherical colloidal crystals which are hydrophilic nanoparticles. delete The method according to claim 1,
Wherein the broad band light absorbing layer has a thickness of 5 to 20 nm. The method according to claim 1,
Wherein the colloidal crystal structure has a reflectance of 7% or less at a wavelength other than the reflection wavelength. The method according to claim 1,
Wherein the colloidal crystal structure has a reflectance of 20% or more at a reflection wavelength. The method according to claim 1,
Wherein the nanoparticles have an average size of 160 to 300 nm. An optical pigment comprising a colloidal crystal according to any one of claims 1, 2, 4, 5, and 7. There is provided a water in oil type emulsion in which water droplets in which hydrophilic nanoparticles are dispersed are dispersed in an oil continuous phase,
The aqueous solution or water is saturated with the continuous oil phase, and then heated at a temperature not higher than the boiling point of the aqueous solvent for 24 hours or more to completely crystallize the hydrophilic nanoparticles from the center to the surface Thereby obtaining a fully crystallized spherical colloidal crystal having an average diameter of 5 to 90 占 퐉. delete 10. The method of claim 9,
And forming a broad band light absorbing layer on the surface of the spherical colloidal crystal. 12. The method of claim 11,
The broadband light absorbing layer is formed by dropping a carbon precursor solution on the colloidal crystal and drying it under a vacuum condition,
A method for producing a spherical colloidal crystal by forming a dispersion of carbon nanoparticles on a colloidal crystal by impregnation. 12. The method of claim 11,
Wherein the broadband light absorbing layer is formed to a thickness of 5 to 20 nm. 12. The method of claim 11,
Wherein the broadband light absorbing layer is formed such that the reflectance at a wavelength other than the reflection wavelength by the colloidal crystal structure is 7% or less. 12. The method of claim 11,
Wherein the broadband light absorbing layer is formed such that the reflectance at a reflection wavelength by the colloidal crystal structure is 20% or more. 10. The method of claim 9,
Wherein the hydrophilic nanoparticles have an average size of 160 to 300 nm.

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