WO2020180011A1 - Humidity-responsive photonic crystal composite, method for preparing same, and sensor using same - Google Patents

Abstract

The present invention relates to a humidity-responsive photonic crystal composite, a method for preparing same, and a sensor using same and, more specifically, to: a photonic crystal composite having humidity responsiveness and an IPN structure, in which, by including a photonic crystal structure, which is prepared by UV curing a reactive CLC mixture and then removing a non-reactive chiral dopant, and hydrogel and a salt that permeate into the internal space of the photonic crystal structure, various colors are reflected according to the degree of swelling due to moisture; a method for preparing same; and a sensor using same. The photonic crystal composite of the present invention can be effectively used as a humidity sensor and a biosensor since, by controlling the degree of swelling due to moisture, various colors are reflected according to humidity and ions. The method for preparing the photonic crystal composite according to the present invention maximizes swelling according to the absorption of moisture by breaking hydrogen bonds between carboxyl groups of a polymer. The sensor using the photonic crystal composite according to the present invention allows easy detection, with the naked eye, of various colors reflected according to humidity or calcium ions, and can be reused through recovery through acid treatment.

Description

Humidity-responsive photonic crystal composite, manufacturing method thereof, and sensor using same

The present invention relates to a humidity-reactive photonic crystal composite, a method of manufacturing the same, and a sensor using the same, and more particularly, to a photonic crystal structure prepared by removing a non-reactive chiral dopant after UV curing a reactive CLC mixture, and to the inner space of the photonic crystal structure. The present invention relates to a photonic crystal composite having an IPN structure having a humidity reactivity in which various colors reflected according to the degree of swelling by moisture, including the infiltrated hydrogel and salt, and a method of manufacturing the same, and a sensor using the same.

The biosensor can be applied to various fields such as medical use, environmental use, food use, military use, industrial use. However, the biosensor technology applied to date requires a large amount of samples to recognize the biomaterial to be detected. In addition, in order to analyze a sample, there is a hassle of having to go through a very complex process such as an analyte input step, a signal generation step, a signal amplification step, a complex analysis result interpretation step, etc., and it is very expensive to apply to real life.

Among the biosensors, a sensor that detects humidity uses an electrolyte polymer obtained by polymerization of vinyl monomers containing salts to detect humidity. However, since most of the electrolyte polymers have high water solubility, they dissolve in condensation or high humidity for a long period of time, resulting in a change over time. To this end, an electrolyte was introduced by copolymerization with various hydrophobic monomers or by graft copolymerization on a hydrophobic polymer. Alternatively, as in Japanese Patent Laid-Open No. 2007-100096, the water resistance of the polymer copolymer is improved by using the IPN structure of the humidity-reactive polymer copolymer, but there is a problem that it is difficult to detect immediately visually.

From this point of view, there is a need to manufacture an optical sensor capable of visually detecting a change in color (or intensity) without a battery using a photonic crystal that is easy to detect a biological material or a chemical material and reflects light at a specific wavelength.

The hydrogel polymer can be used as a polymer having an IPN structure because a volume change can be easily generated by the application of an external stimulus through absorption (or desorption) of water. Photonic crystals represent a spirally twisted molecular orientation in which a cholesteric liquid crystal (CLC) gives a specific optical property, and it can be used as a sensor by using a pitch that changes due to external stimuli because it is easy to manufacture a one-dimensional photonic structure. have. That is, as the polymer penetrated into the IPN structure expands/contracts in response to an external stimulus, a color change may be induced in the corresponding CLC.

However, there is a need to improve the functional aspect of the sensor by controlling the degree of swelling so that various levels of humidity can be sensed and reused.

The present invention was devised to solve the above problems, and an object of the present invention is to provide a photonic crystal composite having an IPN structure having humidity reactivity.

Another object of the present invention is to provide a method of manufacturing the photonic crystal composite.

In addition, an object of the present invention is to provide a method of measuring humidity using the photonic crystal composite.

In addition, an object of the present invention is to provide a sensor including the photonic crystal composite.

In order to achieve the above object, the present invention,

A photonic crystal structure prepared by UV curing a reactive CLC (Cholesteric Liquid Crystals) mixture and then removing a non-reactive chiral dopant;

A hydrogel penetrating into the inner space of the photonic crystal structure; And

It includes a salt, and provides a photonic crystal complex having an IPN (Interpenetrating Polymeric Network) structure having humidity reactivity.

In order to achieve the above other object, the present invention,

A first step of UV-curing the reactive CLC mixture and then removing the non-reactive chiral dopant to prepare a photonic crystal structure;

A second step of forming a complex having an IPN structure by penetrating the hydrogel into the inner space of the photonic crystal structure; And

It provides a method for producing a photonic crystal composite having humidity reactivity comprising a third step of reacting the IPN-structured composite with a salt to form a photonic crystal composite having humidity reactivity.

The hydrogel may include acrylic acid, diacrylate (TPGDA), and a photoinitiator.

The salt may be a sodium salt or potassium salt that reacts with the carboxyl group of the hydrogel.

In order to achieve the above another object, the present invention,

It provides a method of measuring humidity using a photonic crystal composite having humidity reactivity.

In order to achieve the above another object, the present invention,

It provides a sensor comprising a photonic crystal composite having humidity reactivity.

The sensor may be a humidity sensor or a biosensor for detecting calcium ions.

The calcium ions form a cross-link with the carboxyl group of the hydrogel, and the contracted and expanded hydrogel induces contraction and expansion of the photonic crystal structure, thereby changing the wavelength range of the optical band gap, thereby detecting calcium ions.

The calcium ions may include calcium ions in human plasma or saliva.

The change in the wavelength range may be performed at pH 2 to 12.

By means of solving the above problems, the photonic crystal composite of the present invention can be used as a humidity sensor and a biosensor by controlling the degree of swelling in moisture and reflecting colors according to humidity and ions in various ways.

In addition, the method of manufacturing a photonic crystal composite according to the present invention maximizes swelling due to absorption of moisture by destroying hydrogen bonds between carboxyl groups of a polymer, and has an effect that the manufacturing method is simple and the manufacturing cost is low.

In addition, the sensor using the photonic crystal composite of the present invention exhibits various colors reflected according to humidity or calcium ions, so that it can be easily detected by the naked eye, and can be reused through recovery through acid treatment.

1 is an IPN according to the present invention It shows the manufacturing process of the array film.

2 is an FT-IR spectrum of an array film according to an embodiment or a comparative example of the present invention.

3 is a scanning electron microscope (SEM) image of a layer structure of an array film according to an embodiment or a comparative example of the present invention.

4 is a photograph of a dry or wet state of an array film according to an embodiment or a comparative example of the present invention.

5A and 5B are UV-Vis spectra and λ _PBG according to pH of an array film according to a comparative example of the present invention, respectively.

6 is a photograph of a dry state and a wet state of an acetone-treated array film according to an embodiment of the present invention.

7A and 7B are UV-Vis spectra of dots in a dry or wet state of an array film according to an embodiment and a comparative example of the present invention, respectively.

8 is a photograph of an array film according to an embodiment of the present invention at different relative humidity (RH).

9 shows the change in the spiral pitch of CLC by KOH and CaCl ₂ aqueous solution.

10 is a photograph of an array film according to an embodiment of the present invention treated with 1mM, 3mM, and 8mM CaCl ₂ aqueous solution and then exposed to human breath.

11 is a photograph showing a color change of an image included in an array film according to an embodiment of the present invention.

12 is a photograph of a film treated with HNO ₃ on an array film according to an embodiment of the present invention reacted with CaCl ₂ .

13 is a photograph after treatment of CaCl ₂ , HNO ₃ and KOH four times in a row on the array film according to an embodiment of the present invention.

14 is a photograph of an array film according to an embodiment of the present invention at different pH values.

15A and 15B are UV-Vis spectrum and λ _PBG according to pH of an array film according to an embodiment of the present invention, respectively.

16 is a UV-Vis spectrum over time after CaCl ₂ is treated on an array film according to an embodiment of the present invention.

17 is a photograph showing a change in color reflected after dropping water on an array film according to an embodiment of the present invention.

18A and 18B are UV-Vis spectra measured after treating an array film according to an embodiment of the present invention with CaCl ₂ of various volumes and concentrations, respectively.

19A and 19B are UV-Vis spectra and photographs of an array film according to an embodiment of the present invention treated with plasma and saliva of hypocalcemia-i, hypocalcemia-ii, and normal and hypercalcemia, respectively.

20A and 20B are respectively FeCl ₂ ·4H ₂ O, Zn(NO ₃ ) ₂ ·6H ₂ O, Cu(NO ₃ ) ₂ ·3H ₂ O, Mg(NO ₃ ) ₂ ·6H ₂ O, NaNO ₃ and A photograph of an array film according to an embodiment of the present invention treated with an aqueous solution of CaCl ₂ , a change in wavelength, and a UV-Vis spectrum.

21 is a photograph showing a reaction result of an array film according to an embodiment of the present invention and each set having different C _Ca and C _Mg values.

22 is a UV-Vis spectrum showing a reaction result between an array film according to an embodiment of the present invention and each set having different C _Ca and C _Mg values.

Hereinafter, the present invention will be described in more detail.

According to an aspect of the present invention, a photonic crystal structure prepared by removing a non-reactive chiral dopant after UV curing a reactive CLC (Cholesteric Liquid Crystals) mixture; A hydrogel penetrating into the inner space of the photonic crystal structure; And a salt; It provides a photonic crystal complex having a humidity reactivity of the IPN (Interpenetrating Polymeric Network) structure.

First, a photonic crystal structure made of a reactive CLC mixture will be described.

CLC are cholesteric liquid crystals. Among photonic crystals, cholesteric liquid crystals exhibit a spirally twisted molecular orientation that imparts specific optical properties, and have the advantage of being easy to fabricate a one-dimensional photon structure.

The reflection wavelength of the cholesteric liquid crystal can be expressed as λ=n×P×cosθ.

When the cholesteric liquid crystal is irradiated with unpolarized light, circular polarization of a given handiness due to the interaction between the incident light of the selected wavelength and the spiral structure (winding in the left-hand direction or winding in the right-hand direction depending on the handiness of the spiral) ), 50% of its intensity is reflected, and the remaining 50% is transmitted as annular polarization of opposite handiness.

In addition, when the average refractive index (n) of the cholesteric liquid crystal material is constant, the reflection wavelength (λ) of the cholesteric liquid crystal material is dependent on the pitch P of the spiral. That is, since the cholesteric optical material exhibits a unique reflection pattern as it exhibits selective light reflection by the pitch of the helix, the CLC can be used as a sensor using a pitch that is changed by an external stimulus.

The photonic crystal structure may be prepared by mixing and curing a non-reactive chiral dopant and a reactive nematic mesogen, and then removing the chiral dopant.

Non-reactive chiral dopants are C15, CB15, CM21, R/S-811, CM44, CM45, CM47, R/S-2011, R/S-3011, R/S-4011, R/S-5011 and R/S It is characterized in that any one dopant selected from the group consisting of -1011, and preferably CB15 ((S)-4-cyano-4'-(2-methylbutyl)biphenyl) may be used.

The reactive nematic mesogen is characterized in that it is any one mesogen selected from the group consisting of RM 82, RM 257, RM308, and RMM727, and preferably RMM727 may be used.

RMM727 is a mixture containing acryloyloxy group, 1,6-hexamethylenediol diacrylate, (2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one), and the acrylic Reactive acryloyloxy mesogen APBMP, AHBCP, AHBMP, and AHBPCHP may be used as a material containing a loyloxy group.

Although the chiral dopant has been removed from the photonic crystal structure, the helical structure can be maintained as it is and can exhibit light reflection characteristics like cholesteric liquid crystals. Accordingly, the pitch is changed by the external stimulus, so that the reflected color can be displayed so that it can be easily checked with the naked eye.

Next, the hydrogel penetrating into the inner space of the photonic crystal structure will be described.

The hydrogel may include acrylic acid, diacrylate (TPGDA), and a photoinitiator.

TPDGDA can be used as a crosslinking agent to induce maximum expansion of PAA hydrogel droplets.

Photoinitiators include molecules that absorb UV or UV-Vis to generate free radicals. A single photoinitiator may be used or mixtures of photoinitiators may be used. The photoinitiator may be selected such that the absorption wavelength of the photoinitiator overlaps the emission wavelength of the light source used for initiation.

The class of photoinitiators includes α-hydroxy ketones. A commercial example of a photoinitiator of this class is Irgacure.

The hydrogel penetrates the photonic crystal structure and forms an IPN structure.

The IPN structure is an Interpenetrating Polymer Network (IPN). IPNs are polymers comprising two or more networks that are at least partially interlaced on a molecular scale but cannot be separated unless covalently bonded to each other and chemical bonds are broken. It can be produced by infiltrating a monomer into a previously formed crosslinked structure, and forming a second crosslinked structure between the impregnated monomers.

Finally, salt is explained.

Salts can react with the carboxyl groups of the hydrogel. This reaction is a reaction between a carboxyl group and an acid group of a salt, and a salt can be selected in consideration of the pKa (about 4.3) of the carboxyl group of the hydrogel. Preferably it may be a sodium salt or a potassium salt, more preferably NaOH or KOH.

Hydrogel carboxyl groups form hydrogen bonds to limit swelling due to moisture. If the hydrogel is treated with a salt, hydrogen bonds between carboxyl groups can be broken and a complex can be formed. Hydrogels with broken hydrogen bonds may have different degrees of swelling depending on humidity.

According to another aspect of the present invention, a first step of preparing a photonic crystal structure by removing a non-reactive chiral dopant after UV curing a reactive CLC mixture; A second step of forming a complex having an IPN structure by penetrating the hydrogel into the inner space of the photonic crystal structure; And a third step of forming a photonic crystal composite having humidity reactivity by reacting the IPN-structured composite with a salt. It provides a method for producing a photonic crystal composite having humidity reactivity.

First, a first step of manufacturing a photonic crystal structure will be described.

A photonic crystal structure can be obtained by injecting and curing a mixture of a non-reactive chiral dopant and a reactive nematic mesogen between two substrates stacked in parallel, and then removing the upper substrate and removing the chiral dopant.

Non-reactive chiral dopants are C15, CB15, CM21, R/S-811, CM44, CM45, CM47, R/S-2011, R/S-3011, R/S-4011, R/S-5011 and R/S It is characterized in that any one dopant selected from the group consisting of -1011, and preferably CB15 ((S)-4-cyano-4'-(2-methylbutyl)biphenyl) may be used.

The reactive nematic mesogen is characterized in that it is any one mesogen selected from the group consisting of RM 82, RM 257, RM308, and RMM727, and preferably RMM727 may be used.

RMM727 is a mixture containing RMM727 acryloyloxy group (acryloyloxy), 1,6-hexamethylenediol diacrylate, (2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one), As the material containing the acryloyloxy group, reactive acryloyloxy mesogen APBMP, AHBCP, AHBMP and AHBPCHP may be used.

Next, a second step of forming an IPN-structured composite will be described.

The hydrogel may include AA (Acrlyic acid), diacrylate (TPGDA) and a photoinitiator.

TPDGDA can be used as a crosslinking agent to induce maximum expansion of PAA hydrogel droplets.

Photoinitiators include molecules that absorb UV or UV-Vis to generate free radicals. A single photoinitiator may be used or mixtures of photoinitiators may be used. The photoinitiator may be selected such that the absorption wavelength of the photoinitiator overlaps the emission wavelength of the light source used for initiation.

The hydrogel penetrates the photonic crystal structure and forms an IPN structure.

The IPN structure is an Interpenetrating Polymer Network (IPN). IPNs are polymers comprising two or more networks that are at least partially interlaced on a molecular scale but cannot be separated unless covalently bonded to each other and chemical bonds are broken. It can be produced by infiltrating a monomer into a previously formed crosslinked structure, and forming a second crosslinked structure between the impregnated monomers.

Finally, a third step of reacting with a salt to form a photonic crystal complex having humidity reactivity will be described.

Salts can react with the carboxyl groups of the hydrogel. This reaction is a reaction between a carboxyl group and an acid group of a salt, and a salt can be selected in consideration of the pKa (about 4.3) of the carboxyl group of the hydrogel. Preferably it may be a sodium salt or a potassium salt, more preferably NaOH or KOH.

Hydrogel carboxyl groups form hydrogen bonds to limit swelling due to moisture. If the hydrogel is treated with a salt, hydrogen bonds between carboxyl groups can be broken and a complex can be formed. Hydrogels with broken hydrogen bonds may have different degrees of swelling depending on humidity.

Furthermore, a treatment with acetone may be further included in order to expand the range of swelling.

In addition, an acid treatment process may be further included. The carboxy group of the hydrogel may be recovered through acid treatment, and salt treatment and ion treatment may be performed again.

According to another aspect of the present invention, a method of measuring humidity using a photonic crystal composite having humidity reactivity is provided.

In the IPN structured photonic crystal complex, hydrogen bonds between carboxyl groups are destroyed by salt treatment. Hydrogen bonds between carboxyl groups that limit the expansion of the hydrogel can be broken through salt treatment. The photonic crystal composite thus manufactured may have a different degree of swelling depending on the degree of humidity, and may exhibit various reflective colors. Humidity can be measured by detecting the reflected color with the naked eye.

According to another aspect of the present invention, a sensor is provided, characterized in that it is manufactured using a photonic crystal composite. The sensor according to the present invention may be a humidity sensor or a biosensor for detecting calcium ions.

The humidity sensor can detect humidity by using various reflected colors that appear when the photonic crystal complex in which the hydrogen bond of the carboxyl group is disconnected expands or contracts according to humidity.

The biosensor can detect the ions by using ion exchange to occur when the photonic crystal complex in which the hydrogen bond of the carboxyl group is disconnected through salt treatment detects calcium ions.

Calcium ions form a cross-link with the carboxy group of the hydrogel, and the contracted and expanded hydrogel induces contraction and expansion of the photonic crystal structure, thereby changing the wavelength range of the optical band gap, thereby detecting calcium ions.

As monovalent ions are exchanged for divalent ions, the degree of expansion or contraction of the photonic crystal complex changes, and various reflected colors can be detected with the naked eye according to the change.

The biosensor according to the present invention can also detect calcium ions in human plasma or saliva. Variation of the wavelength range of the optical band gap may be performed at pH 2 to 12.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. On the other hand, the illustrations and detailed descriptions of configurations, actions and effects thereof that can be easily recognized by those of ordinary skill in the art will be simplified or omitted, and will be described in detail centering on parts related to the present invention.

<Example>

material

RMM727 (reactive LC mixture, Merck, UK), CB15 (Shinton, Germany), AA (Junsei, Japan), tri(propylene glycol) diacrylate (TPGDA, Sigma-Aldrich, USA), trichloro-(1H,1H, 2H,2H,2H,2H hyperfluorotoxyl) silan (PFOTS, 97%, Sigma-Aldrich, USA), Irgacure 500 (photoinitiator, Ciba Inc., Switzerland), 3-(trimethhosilyl) propyl methacrylate (TMSPMA, 98%, Sigma-Aldrich, USA), acetone, Norland optical adhesive 65 (NOA65, Norland Products, USA), micro-pearls, potassium hydroxide (KOH, DC Chemical, Korea), Calcium chromaticity measurement (MAK022, USA Sigma-Aldrich, copper(II) nitrate 3-hydrate (Cu(NO3)2·3H2O, Japan Junsei), zinc nitrate 6-hydrate (Zn(NO3)2·6H2O, Sigma- Aldrich, USA), magnesium nitrate 6-hydrate (Mg(NO3)2·6H2O, Sigma-Aldrich, USA), sodium nitrate (NaNO3, Duksan, South Korea), iron(II) chloride 4-hydrate (FeCl2·4H2O, Samchun, South Korea), human serum (Sigma-Aldrich, USA), and pH buffer solution (Samchun, South Korea) were used as they were Bare glass slides (Marienfeld, Germany) were sequentially ethanol and deionized (DI). Washed in water DI water was purified using an inverse symptom system (μPure RO, Romax, South Korea).

Example 1-Acetone/KOH-treated photonic crystal IPN array film

1 shows the manufacturing process of the IPN _acetone/KOH array film.

Referring to FIG. 1, a uniform film of a reactive CLC mixture was prepared between two glass slides. The upper and lower slides were treated with PFOTS and TMSPMA, respectively. The glass slide was put into a sealed chamber and the PFOTS-treated top glass was coated in such a way that the PFOTS in a small container evaporated at 70° C. for 30 minutes. Using a spin coater (SPIN-1200D, Midas, South Korea), the bottom slide was coated with TMSPMA by operating at 3000 rpm for 45 seconds and drying in an oven at 110° C. for 60 minutes. This coating on the bottom slide will react with the reactive CLC mixture. The glass coated with PFOTS and TMSPMA was fixed at an interval of 6 μm using a micropulse bonded with NOA65.

A reactive CLC mixture was prepared by mixing RMM727 and CB15 at 60° C. for 12 hours by magnetic stirring. The CB15 content of the mixture of RMM727 and CB15 is expressed as pi (Φ). The clear homogeneous mixture turned milky as the temperature dropped to 25°C. The gap between the two slides was filled with a reactive CLC mixture by capillary action.

UV curing was performed at 365nm for 10 minutes using a UV curing machine (Innocure 100N, Lichtzen, South Korea). After UV curing, the slide coated with PFOTS was removed so that the CLC _solid film remained on the lower slide coated with TMSPMA. The slide was washed with acetone to extract unreacted chiral dopant. The light band spacing of the film attached to the glass was measured using a UV-Vis spectrometer.

A mixture of acrylic acid, TPGDA, and Irgacure 500 (98.5/0.5/1 wt%) was dropped on the surface of the film, and penetration proceeded after 30 minutes. The penetrating film was exposed to UV light with a photomask for 10 minutes at a distance of 6 cm from the sample, followed by UV curing. On the opaque photomask, there were transparent dots, each 2mm in diameter, and the centers were 4mm apart from each other.

The photonic crystal IPN array film was washed 5 times with water to remove uncured acrylic acid monomers in regions other than dots. The photonic crystal IPN array film was put in acetone and immersed in 1M KOH solution for 5 minutes to form a carboxylate to prepare an IPN _acetone/KOH array film. Hereinafter, it is referred to as IPN _acetone/KOH array film.

Example 2-KOH-treated photonic crystal IPN array film

It was the same as in Example 1, but was prepared without the treatment of acetone that proceeds after removing the acrylic acid monomer to obtain a photonic crystal IPN array film. Hereinafter, it is referred to as IPN _KOH array film.

Example 3-IPN array sensor

An array sensor was fabricated using the film prepared in Example 1 or Example 2.

Comparative Example 1-Untreated IPN Array Film

It was the same as in Example 1, but was prepared without the treatment of KOH and acetone that proceed after removing the acrylic acid monomer to obtain a photonic crystal IPN array film. Hereinafter, it is referred to as an untreated IPN array film.

<Evaluation and results>

General information

The actual Ca ²⁺ ion concentration in human plasma and saliva was detected using a calcium chromaticity measurement kit (MAK022, Sigma-Aldrich, USA). To measure the concentration of free Ca ²⁺ ions (C _Ca ) in human plasma and saliva, 90 μL of each chromogenic reagent was added to a cuvette containing 50 μL of a calcium standard and sample (human serum, saliva). Mix gently. Into the mixed solution prepared in the cuvette, 60 μL of calcium analysis buffer was additionally added, mixed gently, and reacted at room temperature for 5 to 10 minutes while protecting from light.

To prepare a standard curve, 0 μL, 2 μL, 4 μL, 6 μL, 8 μL, and 10 μL of 5 mM standard solutions were added for each cuvette, and the total amount was adjusted to 50 μL with DI water to prepare a calcium standard solution with different C _Ca values.

A cross-sectional image of the photon IPN film was photographed using a field emission scanning electron microscope (FE-SEM, SU8220, Hitachi, Japan) operated with an acceleration voltage of 15 kV.

The FE-SEM sample was prepared by coating the cracked cross section of the photonic crystal IPN film with platinum.

It attenuated total reflection FT-IR spectrum (FT / IR-4100, Japan jaseuko) is to collect the average of 64 scans were obtained with respect to meeting the range of from ^-1 600-1800cm of 4cm ^-1 resolution.

The UV-Vis spectrum of the CLC film was obtained in the range of 300 to 900 nm by placing the film perpendicular to the beam of a UV-Vis spectrometer (UV-2401PC, Shimadzu Japan). The spot and background UV-Vis spectra of the photonic crystal IPN array were obtained using a screen with a 1 mm hole through which the UV-Vis beam passes.

Photonic Crystal IPN Array Film

(1) structure

In order to confirm the structure of the IPN array film manufactured according to the present invention, the structure of the photonic crystal IPN array film was confirmed before and after KOH treatment by analyzing a Fourier transform infrared (FT-IR) spectrum and a scanning electron microscope (SEM) image.

2 is an FT-IR spectrum of an IPN array film according to an embodiment or a comparative example of the present invention. Figure 2 (a) is an untreated IPN array film according to Comparative Example 1, (b) is a KOH-treated IPN array film according to Example 2, (c) is acetone / KOH-treated IPN array film according to Example 1 Is the FT-IR spectrum.

Referring to Figure 2 (a), the FT-IR spectrum of the untreated photonic crystal IPN array film shows a peak at 890cm ^-1 , 1253cm ^-1 representing hydrogen-bonded hydroxyl groups, and CO, C=C (aromatic) and C = O, respectively in correspondence to the (carbonyl) appears at 1510cm ^-1 and 1728cm ^-1. These are all manifested by mesogenic mixtures.

Referring to (b) of FIG. 2, in the IPN _KOH array film, the hydrogen-bonded hydroxyl group band almost disappears at 890cm ^-1 after KOH treatment, while the opposite side symmetry and symmetrical stretching causes new in 1565cm ^-1 and 1400cm ^-1 . The band appears. According to this result, it was confirmed that the KOH treatment prevented hydrogen bonding by ionizing the carboxyl group.

Referring to (b) and (c) of FIG. 2, there is only a slight difference between the FT-IR spectra of the IPN _KOH and IPN _acetone/KOH array films. This means that the acetone treatment does not affect the functional groups.

3 is a scanning electron microscope (SEM) image of a layer structure of an IPN array film according to an embodiment or a comparative example of the present invention. 3A is an extracted photonic crystal CLC film, (b) is an untreated IPN array film according to Comparative Example 1, (c) is an IPN _KOH array film according to Example 2, (d) is according to Example 1. This is an SEM image of the IPN _acetone/KOH array film.

Referring to FIG. 3, it can be seen that the structure of the photonic crystal layer appears in all samples by showing the reflected color in all samples. That is, it was confirmed that extraction of dopant, penetration of AA, UV curing, and treatment of KOH or acetone/KOH did not significantly affect the structure of the regular photonic crystal layer.

In measuring the layer spacing of each sample, each layer represents P/2 and P is the helical pitch. The measured P values were 260 nm, 282 nm, 290 nm and 306 nm for the dopant extraction film and untreated IPN, IPN _KOH and IPN _acetone/KOH array films, respectively. The degree of swelling increased in the order of dopant extraction film, untreated IPN, IPN _KOH, and IPN _acetone/KOH array film. This is a result of reflecting the P value measured from the SEM image.

(2) range of colors

In order to confirm the range of the reflected color of the IPN array film prepared according to the present invention, the color and UV-Vis spectrum of the array film according to the dry/wet state, different pH, and different amounts of Ca ²⁺ were analyzed.

4 is a photograph of a dry or wet state of an IPN array film according to an embodiment or a comparative example of the present invention. 4(i) is an IPN array film according to Comparative Example 1 in a dry state, (ii) is an IPN array film according to Example 2 in a dry state, and (iii) is an IPN array film according to Example 1 in a dry state. , (iv) is an IPN array film according to Comparative Example 1 in a wet state, (v) is an IPN array film according to Example 2 in a wet state, (vi) is a photograph of an IPN array film according to Example 1 in a wet state And UV-vis spectrum.

Referring to Figures 4(i) and (iv), in the case of the wet IPN array film according to Comparative Example 1, the background and the reflected color of the dots are not significantly changed because hydrogen bonding of the dots prevents the absorption of water to the IPN. Does not. The difference in color between the background and dots (λ _PBG ) may appear due to the infiltrated PAA network increasing the helix pitch of the CLC structure.

5A and 5B are UV-Vis spectra and λ _PBG according to pH of the IPN array film according to Comparative Example 1 of the present invention, respectively. Referring to FIG. 5A, as the pH increases, the reflected color changes from blue to green and continuously to red. The change to red is due to the increase in helical pitch as the entangled PAA expands. Referring to FIG. 5B, it can be seen that the degree of dehydrogenation of the carboxyl group varies with pH, and thus λ _PBG increases with pH. The color reflected at the largest pH 12 was green with λ _PBG = 570 nm. This means that the PAA network needs to be further expanded to get reddish red as the reflected color.

Therefore, in order to maximize the swelling of the film by water, the photonic crystal IPN film was immersed in 1M KOH aqueous solution (IPN array film according to Example 2). The penetration of K ⁺ ions into the IPN film breaks the hydrogen bonds between carboxyl groups in the PAA network by forming the corresponding salt (COO-K ⁺ ) and the film can absorb more water.

Referring to (ii) and (v) of FIG. 4, when the IPN _KOH array film according to Example 2 is immersed in water, the color of the background did not change much from blue, but the color of the dots changed to green. The appearance of green may mean that the IPN structure has expanded due to the absorption of water by the infiltrated PAA network.

Furthermore, in order to maximize the effect of the KOH treatment, the photon IPN array film was swollen in acetone, a good solvent of CLC _solid , before immersion in 1M KOH aqueous solution (IPN array film according to Example 1). When the degree of CLC expansion in acetone increases, K ⁺ ions can easily penetrate the film.

Referring to (iii) and (vi) of FIG. 4, the IPN _acetone/KOH array film after acetone/KOH treatment showed red dots on a blue background in a wet state, and when the film was dried, the original blue dots were restored. That is, it was confirmed that all reflected colors including red can be obtained as a result of the application of the acetone/KOH treatment.

6 is a photograph of a dry state and a wet state of an acetone-treated IPN array film according to an embodiment of the present invention. (i) is a film in a dry state and (ii) is a film in a wet state. It was confirmed that when the photonic crystal IPN array film was immersed in acetone, the CLC structure expanded, the color of the IPN dots changed to dark green and the background color changed to green.

7A and 7B are UV-Vis spectra of dots in a dry or wet state of an array film according to an embodiment and a comparative example of the present invention, respectively. 7A is a spectrum of a dot in an air-drying state and FIG. 7B is a spectrum of a dot in a wet state. Each (i) is an array film according to Comparative Example 1, (ii) is an array film according to Example 2, and (iii) is a result of an array film according to Example 1. _Referring to FIG. 7, it can be seen that when the film is dried, the λ _PBG value is restored to the λ _PBG value of the untreated IPN array film. In addition, in the case of the IPN _acetone/KOH array film, it was confirmed that the difference between λ _{PBG in the} wet and dry states was 150 nm or more.

8 is a photograph of a film at different relative humidity (RH) of an IPN array according to an embodiment of the present invention. Referring to FIG. 8, as the relative humidity increased, the color was continuously changed from sky blue to red. That is, it was confirmed that the humidity can be detected by a change in color that can be recognized by the naked eye using the film of the present invention having various spectrums according to humidity.

The reflected color is highly dependent on the expansion of the photonic crystal structure. The expansion of the photonic crystal structure is controlled by the amount of divalent ions complexed to the IPN array film. The carboxy group of the IPN film can be converted into a metal salt, and when a divalent ion is used, a bridge can be formed between the carboxy groups.

9 shows the change in the spiral pitch of CLC by KOH and CaCl ₂ aqueous solution. Referring to FIG. 9, since Ca ²⁺ , which is a divalent ion, breaks hydrogen bonds to form a crosslinked structure, the spiral pitch is expanded and contracted. The degree of expansion can be controlled through the number of crosslinked structures, and the color of the IPN _{acetone/KOH-CaCl2} array film can be determined. Accordingly, the film of the present invention can be used for hidden images that generate various colors.

10 is a photograph of an array film according to Example 1 of the present invention treated with 1mM, 3mM, and 8mM CaCl ₂ aqueous solution and then exposed to human breath (high humidity). The letters K, N, and U exposed to a moist environment produced yellow K, green N and blue U, respectively. The letter "U" treated with 8mM CaCl ₂ showed no color change before and after exposure to high humidity. This can be seen as a result of all carboxylate groups being combined with Ca ²⁺ ions. The formation of cross-links with all carboxylates inhibited the absorption of water and expansion of IPN. In other words, it was confirmed that the number of crosslinked structures was controlled according to the amount of calcium ions, and various images could be generated using the colors displayed through them.

(3) Use as a security label

Since it is possible to create various images, it is possible to include an image that is hidden in a dry state and appears in a humid condition according to the user's breath. Since this film can have various images and colors, it can also be used as an anti-counterfeiting film.

11 is a photograph showing a color change of an image included in the array film according to Example 1 of the present invention. Referring to FIG. 11, it was confirmed that the letter "KNU" changed from blue (i) to red (ii) after exposure to moisture due to human breathing. That is, the image can be hidden on the label made of the IPN _acetone/KOH film of the present invention, and a genuine product can be used as a security label to easily distinguish a genuine product from a counterfeit product by using human breath.

Photonic crystal IPN sensor

(1) recovery

In order to determine the reusability of the IPN array film prepared according to the present invention, it was confirmed whether the function was recovered by repeated treatment of KOH and CaCl ₂ after acid treatment.

12 is a photograph of a film treated with HNO ₃ (0.1 M) on an array film according to an embodiment of the present invention reacted with CaCl ₂ . (i) is a photograph of the array film reacted with CaCl _2, and the number under the dot is the C _Ca of CaCl ₂ treated on each dot. (ii) is a photograph of a film treated with HNO ₃ and (iii) is a photograph of a film treated with KOH again. Referring to (i) and (ii), it was confirmed that when the array film reacted with CaCl ₂ was treated with HNO ₃ , the cross-linking of calcium ions was broken and the carboxy group was recovered, and blue dots appeared. Referring to (iii), it was confirmed that when the HNO ₃ treated film was treated with KOH again, hydrogen bonds were destroyed and the initial red color of the IPN _acetone/KOH array film was restored.

That is, the crosslinked structure of the IPN array film prepared according to the present invention could be removed by HNO ₃ treatment as shown in Formula 1 below.

13 is a photograph after treatment of CaCl ₂ , HNO ₃ and KOH four times in a row on the array film according to an embodiment of the present invention. (a) to (d) show the results according to 1 to 4 cycles, (i) after treatment with 2mM CaCl ₂ , (ii) after drying, and (iii) after treatment with HNO ₃ (0.1M) ( iv) is a photograph of a film after acetone treatment, and (v) is a KOH treatment.

Referring to FIG. 13, it was confirmed that the color of each step did not change significantly even if the cycle was repeated. These recovery results can be seen to mean successful complexation by CaCl ₂ and complete recovery by HNO ₃ treatment. That is, it was confirmed that the array film according to the present invention can be reused through recovery through acid treatment even over multiple cycles.

(2) pH dependence

Since hydrogen bonds can be broken at high pH, the IPN _acetone/KOH array film needs to be checked for pH dependence. In order to confirm the pH dependence of the array film according to the present invention, it was confirmed whether hydrogen bonds were maintained at different pH values and the change in reflected color accordingly. The results were analyzed based on the color of the dots of the array film, the UV-Vis spectrum, and λ _PBG .

14 is a photograph of an array film according to an embodiment of the present invention at different pH values. The number above the dot is the respective pH. It was confirmed that the dots turned blue at pH 2 and pH 4, turned green at pH 6, and turned red at pH 8, pH 10, and pH 12. This indicates that the swelling of the IPN _acetone/KOH array film is pH dependent. When the pH is lower than pKa, the COO-K ⁺ salt is converted to COOH groups, causing the dots to shrink. On the other hand, when the pH was higher than pKa, the electrostatic repulsion between the COO- groups increased and the dots expanded. The carboxyl group of the array film according to the present invention has a pKa of about 4.3.

15A and 15B are UV-Vis spectrum and λ _PBG according to pH of an IPN array film according to an embodiment of the present invention, respectively. Referring to FIG. 15 in comparison with FIG. 5, the λ _PBG according to the pH of the IPN _KOH array film was similar to that of the untreated photonic crystal IPN array film, except that the λ _PBG value shifted red at the same pH value. In other words, it was confirmed that even if acetone/KOH was treated according to the present invention, there was no particular change in the dependence of pH, so that it could be used for sensors and other applications.

(3) Response speed

In order to check the response speed of the IPN array film prepared according to the present invention, the time at which the color change appears after treatment with CaCl ₂ or water was measured.

16 is a UV-Vis spectrum over time after CaCl ₂ is treated on an array film according to an embodiment of the present invention. After dropping the 2mM CaCl ₂ aqueous solution on the dots, the color change of the 2 × 2 IPN _acetone/KOH array film was observed. Referring to FIG. 16, the reflective color of the red photonic crystal completely turned green within 20 minutes.

Meanwhile, the rate at which the reflected color changes after exposing the array film according to the present invention to water was measured. 17 is a photograph showing a change in color reflected after dropping water on an array film according to an embodiment of the present invention. (a) is an array film according to Example 1 treated with acetone/KOH, and (b) is an array film according to Example 2 treated with only KOH. (i) is a photograph of the film immediately after exposure to water, (ii) is 1 minute, (iii) is 10 minutes, (iv) is 30 minutes, (v) is 50 minutes, and (vi) is 60 minutes.

Referring to FIG. 17, in the array film (a) according to Example 1, the change from blue dot (i) to red dot (ii) was within 1 minute, but the array film (b) according to Example 2 was blue dot In the color change of (i), it took 10 minutes for the outer part of the dot and 50 minutes for the center, and a much longer time (60 minutes) was required to induce a complete color change of the entire dot. The color of was also green. That is, it was confirmed that the acetone treatment can accelerate the water absorption process.

(4) Effect according to volume and concentration

The array film of the present invention was tested in various volumes to confirm the difference in the effect according to the volume and concentration of the Ca ²⁺ sample. CaCl ₂ treatment of the present invention The array film is hereinafter referred to as an IPN _{acetone/KOH-CaCl2} array film.

18A is a UV-Vis spectrum measured after treating an array film with various volumes of CaCl ₂ according to an embodiment of the present invention. 3 mM CaCl ₂ aqueous solution was treated by 1.2 μL, 1.7 μL, 2.2 μL, 2.7 μL, 3.2 μL, 3.7 μL, 4.2 μL and 4.7 μL, respectively. Referring to FIG. 18A, it was confirmed that as the capacity of the CaCl ₂ aqueous solution increased, more Ca ²⁺ ions were absorbed by the dots, and thus the λ _PBG value decreased.

18B is a UV-Vis spectrum of an array film according to an embodiment of the present invention treated with samples of various C _Ca. C _Ca was 0mM, 0.4mM, 0.8mM, 2.0mM, 2.5mM, 3.0mM, 3.5mM, 4.0mM and 5.0mM, respectively. Referring to FIG. 18B, it was confirmed that λ _PBG continuously decreased with the increase of C _Ca up to 3.4 mM, the degree of expansion was inversely proportional to the amount of Ca ²⁺ and saturated at C _Ca > 3.4 mM.

On the other hand, the detection limit (LOD) and a linear range were obtained from the plot of C _Ca versus Δλ in which the λ _PBG value decreases as a result of the addition of the Ca ²⁺ aqueous solution. LOD was calculated using LOD = 3.3 × (SD/S), where SD is the standard deviation of the blank sample and S is the slope of the graph. The calculated LOD was 0.0142 mM in the linear range of 0.05 to 5 mM. The maximum detection limit of Ca ²⁺ confirmed by this experiment was also 3.4 mM. Through this, it was confirmed that images of various colors can be displayed using the array film according to the present invention within the detection limit range.

(5) Utilization for human plasma or saliva test

Analysis of UV-Vis spectra and photographs of samples of hypocalcemia (HypoCa), hypercalcemia (HyperCa), and normoemia in order to confirm whether the array film according to the present invention can detect calcium ions in human plasma and saliva I did.

Hypocalcemia-i and hypocalcemia-ii were prepared by diluting 2 times and 3 times with water, respectively, and hypercalcemia samples were prepared by mixing human plasma and saliva (0.1 mL) with CaCl ₂ aqueous solution (6 mM, 0.1 mL). Ready. Since the total calcium concentration of healthy humans was 2.2 ~ 2.6mM in plasma and 1.3 ~ 1.8mM in saliva, the plasma and saliva of normal samples were prepared at 2.45 mM and 1.53 mM, respectively.

The C _Ca values for hypocalcemia-i, hypocalcemia-ii, normal and hypercalcemia plasma were 1.22mM, 0.81mM, 2.45mM and 4.22mM, respectively, hypocalcemia-i, hypocalcemia-ii, normal and The C _Ca values for high calcium saliva were 0.76mM, 0.51mM, 1.53mM and 3.76mM, respectively.

19A and 19B are UV-Vis spectra and photographs of an array film according to an embodiment of the present invention treated with plasma and saliva of hypocalcemia-i, hypocalcemia-ii, and normal and hypercalcemia, respectively. 19A is a result for plasma, and FIG. 19B is a result for saliva.

Referring to FIG. 19A, λ _PBG of the plasma sample appears at 517 nm in the case of a normal plasma sample, and the hypocalcemia-i and hypokalemia-ii samples are shown with red shifts to 556 nm and 532 nm, respectively, and the hypercalcemia sample is blue at 493 nm. Appeared on the side.

Referring to FIG. 19B, λ _PBG of the saliva sample was shown at 524 nm in the case of a normal saliva sample, the hypocalcemia-i and hypocalcemia-ii samples were shown at 552 nm and 564 nm, respectively, and the hypercalcemia saliva sample appeared at 478 nm.

The level of normal calcium in the serum and saliva of a healthy person exists in the effective area of the array film according to the present invention, so that the reflected color can be changed according to the concentration. That is, it was confirmed that the array film of the present invention can be used as a biosensor for detecting calcium in human plasma and saliva.

(6) Ion selectivity and sensitivity

In order to evaluate the calcium ion selectivity and sensitivity of the apey film according to the present invention, the reaction with various metal ions was investigated.

20A and 20B are respectively FeCl ₂ ·4H ₂ O, Zn(NO ₃ ) ₂ ·6H ₂ O, Cu(NO ₃ ) ₂ ·3H ₂ O, Mg(NO ₃ ) ₂ ·6H ₂ O, NaNO ₃ and A photograph of an array film according to an embodiment of the present invention treated with an aqueous solution of CaCl ₂ , a change in wavelength, and a UV-Vis spectrum. Each was treated with a concentration of 4 mM (NaNO ₃ was used as equivalent to a divalent metal, and was immersed in water).

It was confirmed that the film including the crosslinked structure did not swell easily and the reflected color changed to blue when immersed in water. Since the monovalent ion Na ⁺ cannot form a crosslinked structure, the difference between the presence and absence of a metal ion was smaller than that of the divalent ion.

Referring to the graph of FIG. 20A and 20B, the IPN _acetone/KOH array film, which was initially red, was treated with divalent metal ions such as Fe ²⁺ , Zn ²⁺ , Cu ²⁺ , Mg ²⁺ and Ca ²⁺ A blue shift appeared. This means that divalent ions can form bridges between carboxyl groups. The Δλ value decreased in the order of Ca ²⁺ > Mg ²⁺ > Fe ²⁺ > Zn ²⁺ > Cu ²⁺ . It was confirmed that the largest blue shift occurred when Ca ²⁺ was added.

Referring to the photo of FIG. 20A, when treated with a mixture containing Ca ²⁺ , blue dots were observed, whereas treatment with a mixture containing Fe ²⁺ , Zn ²⁺ , Cu ²⁺ and Mg ²⁺ without Ca ²⁺ In one case, green dots were observed. This means that Ca ²⁺ has the strongest affinity with carboxylate ions for chelation among divalent ions.

The second most common ion in human saliva after Ca ²⁺ is Mg ²⁺ . Regarding the selectivity of calcium ions, the interference from Mg ²⁺ was confirmed by using 4 sets of samples. The concentrations of Ca ²⁺ and Mg ²⁺ were expressed in mM (C _Ca , C _Mg ).

21 is a photograph showing a reaction result of an array film according to an embodiment of the present invention and each set having different C _Ca and C _Mg values. Set I is _{(C Ca, C Mg) =} (1, 0), (2.2, 0), (3.5, 0), the set II is a C _Mg fixed to physiological concentration of 0.9mM (C _{Ca, Mg} C ) = (1, 0.9), (2.2, 0.9), (3.5, 0.9), in set III, C _Ca is fixed at a physiological concentration of 2.2 mM (C _Ca , C _Mg ) = (2.2, 0.5), ( 2.2, 0.9), (2.2, 1.5), set IV were (C _Ca , C _Mg ) = (0, 0.5), (0, 0.9), (0, 1.5).

22 is a UV-Vis spectrum showing a reaction result between an array film according to an embodiment of the present invention and each set having different C _Ca and C _Mg values.

Referring to FIG. 22, λ _PBG values of Set I were 575 nm, 527 nm, and 496 nm, respectively, and λ _PBG values of Set II were 535 nm, 526 nm, and 492 nm, respectively. There was no significant difference in the results of sets I and II. The λ _PBG values for Set III were 529 nm, 525 nm and 518 nm, respectively, and the λ _PBG values for Set IV were 635 nm, 627 nm and 591 nm, respectively.

^Referring to FIGS. 21 and 22, it can be seen that even in the presence of Mg ^2+, when the concentration of Ca ²⁺ ions increases, the color of the dots changes in the same manner as in the absence of Mg ²⁺ ions. Furthermore, it can be seen that the color of the red dot does not change significantly with only Mg ²⁺ ions, but the Mg ²⁺ ions mixed with Ca ²⁺ ions change the color of the dot from red to green.

Through this result, only Ca ²⁺ ions cause a color change of the dots of the film according to the present invention, and Mg ²⁺ ions having a physiological concentration affect the optical reaction of the IPN _acetone/KOH array film or the corresponding UV-vis spectrum. Therefore, it was confirmed that the array film according to the present invention has selectivity and sensitivity to calcium ions.

The foregoing has been somewhat broadly described in terms of features and technical advantages of the present invention so that the claims of the invention to be described later can be better understood. Those of ordinary skill in the art to which the present invention pertains will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims (12)

1. A photonic crystal structure prepared by UV curing a reactive CLC (Cholesteric Liquid Crystals) mixture and then removing a non-reactive chiral dopant;

   A hydrogel penetrating into the inner space of the photonic crystal structure; And

   Salt; Including, and having a humidity reactivity IPN (Interpenetrating Polymeric Network) structure photonic crystal complex.
2. The photonic crystal composite of claim 1, wherein the hydrogel comprises acrylic acid, diacrylate (TPGDA), and a photoinitiator.
3. The photonic crystal complex having humidity reactivity according to claim 1, wherein the salt is a sodium salt or potassium salt that reacts with a carboxyl group of the hydrogel.
4. A first step of UV-curing the reactive CLC mixture and then removing the non-reactive chiral dopant to prepare a photonic crystal structure;

   A second step of forming a complex having an IPN structure by penetrating the hydrogel into the inner space of the photonic crystal structure; And

   A method for producing a photonic crystal composite having humidity reactivity comprising a third step of reacting the IPN-structured composite with a salt to form a photonic crystal composite having humidity reactivity.
5. The method of claim 4, wherein the hydrogel comprises acrylic acid, diacrylate (TPGDA) and a photoinitiator.
6. The method of claim 4, wherein the salt is a sodium salt or potassium salt that reacts with the carboxyl group of the hydrogel.
7. A method of measuring humidity using the photonic crystal composite according to claim 1.
8. A humidity sensor manufactured by using the photonic crystal composite according to claim 1.
9. A biosensor for detecting calcium ions, which is manufactured using the photonic crystal complex according to claim 1.
10. The method of claim 9, wherein the calcium ions form a crosslinking bond with the carboxyl group of the hydrogel, and the contracted and expanded hydrogel induces contraction and expansion of the photonic crystal structure to change the wavelength range of the optical bandgap. Biosensor, characterized in that to detect.
11. 11. The biosensor of claim 10, wherein the calcium ions include calcium ions in human plasma or saliva.
12. The biosensor according to claim 10, wherein the change in the wavelength range is performed at a pH of 2 to 12.

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