Ion-responsive structural color hydrogel, preparation method thereof and application thereof in ion detection

Abstract

The present invention relates to an ion-responsive structural color hydrogel, a preparation method thereof and an application thereof in ion detection, belonging to the technical field of polymer materials. The method comprises the following steps: by means of soap-free emulsion polymerization, methacrylic acid is added to make the surface of polystyrene microspheres carry negative charges, and reaction conditions are adjusted to prepare monodisperse polystyrene microspheres with different particle sizes, and a photonic crystal template is made thereof by using the vertical deposition method; a photonic hydrogel film is prepared by using the "sandwich" template method, precursor solutions 1 and 2 are respectively prepared, the precursor solution 1 is filled into the photonic crystal template, and photopolymerization is induced by light to obtain an ion-responsive structural color film with a three-dimensional periodic arrangement structure, and then the film is immersed in the precursor solution 2 and cured by ultraviolet light to obtain a double-network photonic hydrogel film. The obtained film material can be used for rapid ion detection, has strong applicability and reusability, and is simple to prepare and low in cost, and is expected to be widely applied.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a stretchable and reusable portable rapid ion detection test strip. Background Art

[0002] Photonic crystals are periodic dielectric structures with photonic bandgap properties. When the photonic crystal bandgap falls within the visible light range, a visible color will be exhibited, which is called structural color. Usually, by constructing hydrogels and photonic crystals, the position of the photonic bandgap can be greatly adjusted under different external stimuli to control the propagation of light. Such responsive photonic crystals have prospective applications in many fields, such as photonic papers, chemical and biological sensors, optical active components, and anti-counterfeiting.

[0003] The responsive photonic crystal hydrogels have significant advantages of non-fading, high stability, and bright colors, making them ideal colorimetric detection devices. For example, Zhang et al. developed an ion-responsive photonic hydrogel sensor, which is composed of poly(N-isopropylacrylamide-co-benzo-18-crown-6 acrylamide) hydrogel and Fe3O4 colloidal nanocrystal clusters (CNC) chains. It can achieve highly selective colorimetric detection of Pb 2+ 2+ with the naked eye, and at the same time, it can remove Pb 2+ 2+ in water, which is very important for human health and environmental protection. Some people copolymerized two kinds of carbon dots (CDs), ethanol-sensitive CD and Cu(II)-ion-responsive CD, into the matrix of the copolymer of acrylic acid and 2-hydroxyethyl methacrylate to achieve dual-mode sensing of solvents and metal ions. It can show good linear detection for the corresponding ions. Lu Li developed a simple, inexpensive, and rapid method for effective on-site detection of mercury ions, realizing visual semi-quantitative detection of mercury ions with the naked eye.

[0004] However, at present, many researchers prepare detection sensors for metal ions, which requires selecting corresponding hydrogels for modification, and most of the photonic crystal colorimetric sensors are inverse opal structures, which are more complex in the manufacturing process compared to opal structures. Breaking through the limitation of metal ions and turning the attention to common anions in daily life, whether it is possible to prepare a photonic crystal hydrogel sensor with simple operation, portability, non-toxicity, and high reuse rate is a huge challenge. Summary of the Invention

[0005] In order to overcome the disadvantages and deficiencies existing in the prior art, the primary object of the present invention is to provide a preparation method for a reusable ion-responsive structural color hydrogel.

[0006] Another object of the present invention is to provide an ion-responsive structural color hydrogel prepared by the above preparation method.

[0007] Another object of the present invention is to provide the application of the above ion-responsive structural color hydrogel in ion detection.

[0008] Another object of the present invention is to provide a stretchable and reusable portable rapid ion detection test strip. By studying the appearance and disappearance of structural colors of the composite film in different ion solutions through the structural color changes caused by the ion responsiveness of the thin film material, the results show that the prepared structural color film has strong applicability and is easy to prepare. It is a low-cost stretchable and reusable portable rapid ion detection test strip, which is expected to be widely used in life.

[0009] To achieve the above object, the specific solution adopted by the present invention is as follows:

[0010] A preparation method of an ion-responsive structural color hydrogel, comprising the following steps:

[0011] (1) Using soap-free emulsion polymerization, adding methacrylic acid to make the surface of polystyrene microspheres carry negative charges, adjusting the reaction conditions to prepare monodisperse polystyrene microspheres with different particle sizes, and using the vertical deposition method to prepare them into a photonic crystal template;

[0012] (2) Using the "sandwich" template method to prepare a photonic hydrogel film; mixing the polymer monomer A, initiator and crosslinking agent evenly to obtain the precursor solution 1, and mixing the polymer monomer B, initiator and crosslinking agent evenly to obtain the precursor solution 2, wherein the polymer monomer A is an acrylamide compound; the polymer monomer B is a compound containing a quaternary amine group; filling the precursor solution 1 into the photonic crystal template obtained in step (1), and inducing polymerization by light to obtain an ion-responsive structural color film with a three-dimensional periodic arrangement structure; then immersing the film in the precursor solution 2 for 24 hours, and curing by ultraviolet light to obtain a double-network photonic hydrogel film.

[0013] The adjustment of the reaction conditions in step (1) is to control the amount of methacrylic acid used to be 100 - 1500 μL, the amount of styrene used to be 1 - 20 mL, the reaction temperature to be 75 - 80 °C, the reaction time to be 6 - 12 h, and the rotation speed to be 500 - 1500 rpm. The diameter of the prepared monodisperse polystyrene microspheres is 170 - 350 nm.

[0014] The photonic crystal template in step (1) is prepared by controlling the self-assembly behavior of monodisperse polystyrene microspheres to prepare a three-dimensional structure photonic crystal template, specifically according to the following steps: dispersing monodisperse polystyrene microspheres with different particle sizes in ultrapure water to prepare a suspension with a mass fraction of 1%; vertically inserting the plasma-treated glass slide into the suspension, the reaction conditions are 50 °C, the reaction humidity is 65% RH, and after the solvent evaporates, a photonic crystal template is deposited.

[0015] The polymer monomer A described in step (2) is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid; the polymer monomer B is acryloyloxyethyltrimethylammonium chloride or methacryloyloxyethyltrimethylammonium chloride.

[0016] The initiator described in step (2) is 2-hydroxy-2-methyl-1-phenylpropan-1-one (1173) or azobisisobutyronitrile; the crosslinking agent is N,N'-methylenebisacrylamide (BIS), glycerol dimethacrylate or ethylene glycol dimethacrylate.

[0017] In the precursor solution 1 described in step (2), the dosage of the crosslinking agent is 1-4 wt% of the mass of the polymer monomer A, and the dosage of the initiator is 1-4 wt% of the mass of the polymer monomer A; in the precursor solution 2, the dosage of the crosslinking agent is 1-4 wt% of the mass of the polymer monomer B, and the dosage of the initiator is 1-4 wt% of the mass of the polymer monomer B.

[0018] The mixing in step (2) is ultrasonicated in a water bath for 5-10 min; the photoinduced polymerization is irradiated under an 18-36 W ultraviolet lamp for 60-180 min.

[0019] An ion-responsive structural color hydrogel prepared by the above preparation method.

[0020] The application of the above ion-responsive structural color hydrogel in ion detection. Further, the ion is an anion.

[0021] A stretchable and reusable portable rapid ion detection test strip prepared by using the above ion-responsive structural color hydrogel.

[0022] By adjusting the structural color of the photonic crystal template or the ions exchanged in the film, the structural color of the film is controlled.

[0023] The structural color thin film material prepared by the present invention is applied to ion detection and has the function of being reused at the same time. The prepared stretchable and reusable portable rapid ion detection test strip exhibits different structural colors in different ion solutions and can also show different structural colors at different chloride ion concentrations.

[0024] The present invention has the following advantages and beneficial effects compared with the prior art:

[0025] (1) In the preparation process of a stretchable and reusable portable rapid ion detection test strip of the present invention, a double network structure is formed after the photonic crystal template is mixed with the polymer, enhancing the mechanical properties and practicality of the material.

[0026] (2) The preparation method of the present invention is reliable, with mild and controllable conditions, and can produce a photon hydrogel film with ion response. The Bragg diffraction effect caused by the face-centered cubic structure of the photonic crystal enables the material to maintain good structural color properties.

[0027] (3) The stretchable and reusable portable rapid ion detection test strip prepared by the present invention can achieve instant colorimetric detection, identify different ions according to the corresponding structural color, and can also detect chloride ions within a certain concentration range, thus realizing its application in daily life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a preparation flow chart of a stretchable and reusable portable rapid ion detection test strip.

[0029] Figure 2 FIG. is a physical picture of a polystyrene photonic crystal template.

[0030] Figure 3 FIG. is a reflection spectrum diagram of a polystyrene photonic crystal template.

[0031] Figure 4 FIG. is an electron microscope characterization diagram of a stretchable and reusable portable rapid ion detection test strip: (a) is the photonic crystal template; (b) and (c) are the photonic crystal hydrogel composite films; (d) is the cross-section of the photonic crystal hydrogel composite film; where the scale of (a), (b), and (c) is 500 nm, and the scale of (d) is 2 μm.

[0032] Figure 5 FIG. is a mechanical property characterization diagram of a stretchable and reusable portable rapid ion detection test strip.

[0033] Figure 6 FIG. is a physical picture of a stretchable and reusable portable rapid ion detection test strip.

[0034] Figure 7 FIG. is a reflection spectrum diagram of a stretchable and reusable portable rapid ion detection test strip in different ion solutions.

[0035] Figure 8 FIG. is an application schematic diagram of a stretchable and reusable portable rapid ion detection test strip.

[0036] Figure 9 FIG. is a detection time schematic diagram of a stretchable and reusable portable rapid ion detection test strip. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings, but the implementation manners of the present invention are not limited thereto. Unless otherwise specified, the test methods used in the following embodiments are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0038] In an embodiment of the present invention, the polymer monomer includes one or more of the following compounds:

[0039]

[0040] Among them, R1, R2, R3, and R4 each represent hydrogen, C1-C 10 linear or branched alkyl, C1-C 10 alkoxy, hydroxyl, carboxyl, C1-C 10 cycloalkyl, and their derivatives or combinations thereof.

[0041] According to the present invention, the cross-linking agent is N,N-methylenebisacrylamide (BIS), glycerol dimethacrylate or ethylene glycol dimethacrylate; the initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) or azobisisobutyronitrile.

[0042] The preparation process of the stretchable and reusable portable rapid ion detection test strip in the following embodiments is as Figure 1 shown, and the specific operation steps are as follows:

[0043] Step 1: Using soap-free emulsion polymerization, add methacrylic acid to make the surface of polystyrene microspheres carry negative charges, and adjust different reaction conditions to prepare monodisperse polystyrene microspheres with different particle sizes. Adjusting different reaction conditions means controlling the amount of methacrylic acid used to be 100-1000 μL, the amount of polystyrene used to be 1-20 mL, the reaction temperature to be 75-80 °C, the reaction time to be 6-12 h, and the rotation speed to be 500-1500 rpm. The diameter of the prepared monodisperse polystyrene microspheres is 170-350 nm.

[0044] Step 2: Interface-induced self-assembly of polystyrene colloidal crystal microspheres is carried out by the vertical deposition method to form a face-centered cubic (FCC)-packed photonic crystal template. Immediately afterwards, precursor solution 1 (composed of polymer monomer A, initiator, and cross-linking agent) is filled into the photonic crystal template, and polymerization curing is carried out using an ultraviolet lamp with a power of 18 - 36 W for a curing time of 60 - 180 min to obtain an ion-responsive structural color film with a three-dimensional periodic arrangement structure. Then, the film is immersed in precursor solution 2 (composed of polymer monomer B, a compound containing a quaternary amine group, initiator, and cross-linking agent) for 24 hours, and polymerization curing is carried out using an ultraviolet lamp with a power of 18 - 36 W for a curing time of 60 - 180 min to prepare a photonic crystal-gel composite system, obtaining a stretchable and reusable portable rapid ion detection test strip.

[0045] The above-prepared reusable ion-responsive photonic hydrogel film is characterized in that: by adjusting the structural color of the photonic crystal template or adjusting the counter-ion, the structural color of the film is controlled.

[0046] The above portable rapid ion detection test strip obtains an ion detection film by exchanging counter-ions with a small hydration radius.

[0047] The stretchable and reusable portable rapid ion detection test strip prepared by the present invention can be applied to an ion detection sensor. It can achieve instant colorimetric detection, identify different ions according to the corresponding structural color, and can also detect chloride ions within a certain concentration range, thus realizing applications in daily life and further enhancing its practicality.

[0048] Example 1

[0049] This example provides a synthesis method of polystyrene colloidal crystal microspheres. Polystyrene colloidal crystal microspheres with different particle sizes are prepared by adjusting different reaction conditions and are prepared into a photonic crystal template by the vertical deposition method. The specific operations are as follows:

[0050] Step 1: 70 - 95 mL of pure water, 100 - 1500 μL of methacrylic acid, and 1 - 20 mL of styrene are respectively added into a round-bottom flask, and magnetic stirring is carried out at 75 - 80 °C and 500 - 1500 rpm for 6 - 12 h to prepare polystyrene colloidal crystal microspheres with different particle sizes; among them, the particle size of the polystyrene microspheres is related to the contents of methacrylic acid and styrene. Decreasing the content of styrene or increasing the content of methacrylic acid results in polystyrene microspheres with a smaller particle size. The controllable range of the particle size of the polystyrene microspheres is 200 nm to 350 nm.

[0051] Step 2: Disperse the polystyrene colloidal crystal microspheres with different particle sizes prepared in Step 1 in water to prepare a suspension with a mass fraction of 1%; vertically insert the plasma-treated glass slide into the solution, with the reaction conditions being 50 °C and the reaction humidity being 65% RH. After the solvent evaporates, a polystyrene photonic crystal template is deposited.

[0052] Experimental results: The above reaction synthesized six kinds of polystyrene colloidal crystal microspheres with different particle sizes of 200 nm, 230 nm, 250 nm, 265 nm, 280 nm, and 300 nm, and assembled them into photonic crystal templates S1, S2, S3, S4, S5, and S6 by the vertical deposition method; the photonic crystal templates were in FCC close packing, as shown in (a) of Figure 4 ; their structural colors were S1 (red), S2 (orange), S3 (yellowish green), S4 (green), S5 (blue-green), and S6 (blue), as shown in Figure 2 . Perform reflection spectrum characterization on the photonic crystal template, as shown in Figure 3 : The reflection wavelength of S1 was 638 nm, the reflection wavelength of S2 was 582 nm, the reflection wavelength of S3 was 549 nm, the reflection wavelength of S4 was 520 nm, the reflection wavelength of S5 was 477 nm, and the reflection wavelength of S6 was 452 nm. The structural colors of the six photonic crystal templates corresponded to their reflection wavelengths.

[0053] Example 2

[0054] This example provides a preparation method for a stretchable and reusable portable rapid ion detection test strip, including the following steps:

[0055] Step 1: Polymer monomer A is an acrylamide compound; polymer monomer B is a compound containing a quaternary amine group; the initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) or azobisisobutyronitrile; the crosslinking agent is N,N'-methylenebisacrylamide (BIS), glycerol dimethacrylate, or ethylene glycol dimethacrylate. Mix and ultrasonically treat in a water bath for 15 - 30 min to obtain precursor solutions 1 and 2 respectively;

[0056] Step 2: Fill the precursor solution 1 prepared in the above step into the photonic crystal template S1 in Example 1. After irradiating with a 36 W ultraviolet lamp for 1 h, then immerse the film in the precursor solution 2 for 24 hours, and use an 18 - 36 W ultraviolet lamp for polymerization curing, with the curing time being 60 - 180 min, to obtain a reusable ion-responsive photonic hydrogel film. The electron micrographs are as shown in (b) and (c) of Figure 4 .

[0057] Result discussion: The synthesized structural color composite film exhibited strong mechanical properties and high hydrophilicity. As shown in Figure 5The formation of the double network shown improves the mechanical properties of the film. As the content of monomer A gradually increases, the mechanical properties continue to improve. When the mass of monomer A is twice that of monomer B, the elongation at break can reach 1600%. The composite film gradually changes from iridescent to milky white after swelling in water, which is due to the excessive red shift of the maximum reflectivity (due to the increased spacing caused by swelling) towards the near-infrared. When the film is immersed in different anion solutions, such as Br - 、I - 、BF4 - 、PF6 - and Tf2N - (bis(trifluoromethanesulfonyl)imide), these less hydrated anions will replace the Cl - in the film, and the reflection peak will gradually blue-shift. The composite film prepared with polystyrene microspheres with a particle size of 200 nm can achieve full-color reflection of visible light. As shown in Figure 6 ; its corresponding reflection spectrum is as shown in Figure 7 . The principle of its responsiveness is that strong polymer electrolytes can quickly exchange ions in the solution, and different counterions have different hydration radii, charge densities, and interaction abilities with polymer groups, thus dominating the swelling and shrinking of the photonic crystal hydrogel, causing changes in the photonic crystal period, and achieving optical response to ions in aqueous solution.

[0058] Example 3

[0059] This example provides a stretchable and reusable portable rapid ion detection test strip prepared by the above method, including the following steps:

[0060] Step 1: Immerse the composite film prepared in Example 2 in a Tf2N - ion solution and store it;

[0061] Step 2: Use the film exchanged with Tf2N - in Step 1 to detect different concentrations of chloride ions.

[0062] Result discussion: As shown in Figure 8 , the film shows different colors in solutions with different ratios of Cl - and Tf2N - . As the concentration of Tf2N - ions increases, the composite film gradually blue-shifts. When it is placed in ten concentrations of Cl- ion solutions from 0.01 M to 0.10 M, its reflection peak also gradually red-shifts. According to the maximum value of its reflection peak, three marked interval points can be found, which are 0.02 M, 0.05 M, and 0.10 M respectively. At the same time, different concentrations are divided into three intervals, corresponding to the three colors of red, orange, and yellow respectively. Its reaction time is as shown in Figure 9As shown. Therefore, we can quickly observe its color with the naked eye to judge the concentration of chloride ions in the solution.

[0063] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of an ion-responsive structural color hydrogel, characterized in that: It includes the following steps: (1) By means of soap-free emulsion polymerization, methacrylic acid is added to make the surface of polystyrene microspheres carry negative charges. The reaction conditions are adjusted to prepare monodisperse polystyrene microspheres with different particle sizes, and a photonic crystal template is prepared therefrom by the vertical deposition method; (2) A photonic hydrogel film is prepared by the "sandwich" template method; the polymer monomer A, initiator and crosslinking agent are mixed evenly to obtain precursor solution 1, and the polymer monomer B, initiator and crosslinking agent are mixed evenly to obtain precursor solution 2. Wherein, the polymer monomer A is acrylamide or 2-acrylamido-2-methylpropanesulfonic acid; the polymer monomer B is acryloyloxyethyltrimethylammonium chloride or methacryloyloxyethyltrimethylammonium chloride; the precursor solution 1 is filled into the photonic crystal template obtained in step (1), and photopolymerization is induced by light to obtain an ion-responsive structural color film with a three-dimensional periodic arrangement structure; then the film is immersed in the precursor solution 2 for 24 hours, and ultraviolet curing is carried out to obtain a double-network photonic hydrogel film, that is, the ion-responsive structural color hydrogel.

2. The preparation method according to claim 1, characterized in that: The adjustment of the reaction conditions in step (1) is to control the dosage of methacrylic acid to be 100 - 1500 μL, the dosage of styrene to be 1 - 20 mL, the reaction temperature to be 75 - 80 °C, the reaction time to be 6 - 12 h, and the rotation speed to be 500 - 1500 rpm. The diameter of the prepared monodisperse polystyrene microspheres is 170 - 350 nm.

3. The preparation method according to claim 1, characterized in that: The photonic crystal template in step (1) is prepared by controlling the self-assembly behavior of monodisperse polystyrene microspheres to prepare a three-dimensional photonic crystal template. Specifically, it is carried out according to the following steps: monodisperse polystyrene microspheres with different particle sizes are dispersed in ultrapure water to prepare a suspension with a mass fraction of 1%; the plasma-treated glass slide is vertically inserted into the suspension, and the reaction conditions are 50 °C and the reaction humidity is 65% RH. After the solvent evaporates, a photonic crystal template is deposited.

4. The preparation method according to claim 1, wherein: The initiator in step (2) is 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) or azobisisobutyronitrile; the crosslinking agent is N,N'-methylenebisacrylamide (BIS), glycerol dimethacrylate or ethylene glycol dimethacrylate.

5. The preparation method according to claim 4, characterized in that: In the precursor solution 1 in step (2), the dosage of the crosslinking agent is 1 - 4 wt% of the mass of the polymer monomer A, and the dosage of the initiator is 1 - 4 wt% of the mass of the polymer monomer A; in the precursor solution 2, the dosage of the crosslinking agent is 1 - 4 wt% of the mass of the polymer monomer B, and the dosage of the initiator is 1 - 4 wt% of the mass of the polymer monomer B.

6. The preparation method according to claim 1, characterized in that: The mixing in step (2) is carried out by ultrasonic treatment in a water bath for 5 - 10 min; the photopolymerization induced by light is carried out under an 18 - 36 W ultraviolet lamp for 60 - 180 min.

7. An ion-responsive structural color hydrogel prepared by the preparation method according to any one of claims 1 - 6.

8. Application of the ion-responsive structural color hydrogel according to claim 7 in ion detection.

9. The application according to claim 8, wherein: The ion is an anion.

10. A stretchable and reusable portable rapid ion detection test strip, which is prepared by using the ion-responsive structural color hydrogel described in claim 7.

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