Photonic crystal ionogels, methods of making and uses thereof

Abstract

The application discloses a photonic crystal ionic gel, a preparation method and application thereof. The method comprises the following steps: synthesizing magnetic nano-particles by using a solvothermal method; adding the magnetic nano-particles into a solution containing monomers, a crosslinking agent, an initiator, a salt and water; under the induction of a magnetic field, the magnetic nano-particles develop color in a hydrogel precursor solution; meanwhile, a heat source is applied to solidify the magnetic nano-particles into a gel state, thereby obtaining the photonic crystal ionic gel. The preparation method is simple, the photonic crystal ionic gel prepared by the method maintains the structure and characteristics of the photonic crystal and has good mechanical properties and flexibility; meanwhile, the addition of sodium chloride enhances the conductivity and sensitivity of the gel, and the photonic crystal ionic gel can be used as a stress flexible sensor. During the deformation process of the photonic crystal ionic gel, the color and conductivity of the gel can be observed to realize double-mode real-time monitoring.

Description

Technical Field

[0001] This invention relates to a photonic crystal ion gel, its preparation method, and its application, belonging to the field of hydrogel flexible sensors. Background Technology

[0002] Photonic crystals are special optical materials that construct a lattice structure that matches the wavelength of light through periodic variations in the dielectric constant in space. This structure forms a "photonic bandgap," preventing light of specific frequencies from penetrating and giving photonic crystals the ability to control light propagation. When the frequency of a light wave matches the frequency of the photonic bandgap, the light wave is completely reflected, producing a stable iridescent structure. By adjusting the lattice parameters or refractive index, this color can be flexibly controlled, leading to its widespread application in optics, electronics, and optoelectronics.

[0003] Hydrogels are flexible polymer materials formed by the entanglement of polymer chains containing hydrophilic groups, possessing tunable physical and chemical properties. Hydrogels exhibit excellent flexibility, elasticity, and water absorption and retention capabilities. In recent years, due to their advantages such as low cytotoxicity, biocompatibility, degradability, and responsiveness, hydrogels have attracted widespread attention from researchers in various fields.

[0004] Currently, there are reports on the application of combining photonic crystals with gels of different systems. For example, combining gels with photonic crystals can be used for chiral amino acid recognition (X. Qiu, Y. Li, Y. Hua, et al., A molecularly imprinted gel photonic crystal sensor for recognition of chiral amino acids, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 283(2022)121719.), combining photonic crystals with photothermal sensitive gels can realize photothermal sensing (L. Cai, Y. Wang, L. Sun, et al., Bio-Inspired Multi-Responsive Structural Color Hydrogel with Constant Volume and Wide Viewing Angles, Advanced Optical Materials, 9(2021)2100831.), and making photonic crystal gels into photonic inks can realize 3D printing of photonic crystals (J. Liao, C. Ye, J. Guo, et al., 3D-printable colloidal photonic crystal). crystals, Materials Today, 56 (2022) 29-41.) etc. Summary of the Invention

[0005] The purpose of this invention is to provide a photonic crystal ion gel, its preparation method, and its application. This method utilizes a mechanically superior dual-network hydrogel. Under magnetic field induction, photonic crystals are arranged in a one-dimensional chain pattern, and a heat source is applied to fix them within the gel, thus producing a photonic crystal ion gel. During deformation, the visible color change is combined with the resistance change in signal reading, achieving a fusion of macroscopically visualized color and precise data.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] The preparation method of photonic crystal ion gel involves first synthesizing magnetic nanoparticles using a solvothermal method, then adding the magnetic nanoparticles to a solution containing monomers, crosslinking agents, initiators, salts, and water. Under the induction of a magnetic field, the magnetic nanoparticles are colored in a hydrogel precursor solution, while a heat source is applied to solidify and gel them. The specific steps are as follows:

[0008] (1) Ferrocene and 30% hydrogen peroxide solution were added to acetone and a solvothermal reaction was carried out at 220±10℃ to obtain magnetic nanoparticles.

[0009] (2) Using a one-pot method, polyvinyl alcohol, acrylamide, methylenebisacrylamide and water are stirred evenly at 90±5℃ to form a mixed solution. Then ammonium persulfate, magnetic nanoparticles and sodium chloride are added and ultrasonically mixed evenly to obtain a photonic crystal ion gel precursor solution.

[0010] (3) Transfer the photonic crystal ion gel precursor liquid into a polytetrafluoroethylene mold, place it on a magnet, apply a heat source to solidify it, and obtain the photonic crystal ion gel.

[0011] In step (1), the particle size of the magnetic nanoparticles can be controlled by adjusting the amount of oxidant added.

[0012] Preferably, in step (1), the mass ratio of acetone to ferrocene is 78:1, the mass ratio of 30% hydrogen peroxide solution to ferrocene is 2.6:1, and the solvothermal reaction time is 72 hours.

[0013] Preferably, in step (2), the mass ratio of polyvinyl alcohol, acrylamide, methylenebisacrylamide and water is 2:21:0.16:70.

[0014] Preferably, in step (2), the mass ratio of polyvinyl alcohol to sodium chloride is 1:0 to 1:4.5, and the sodium chloride content is not 0, more preferably 1:3.5 to 1:4.5.

[0015] Preferably, in step (2), the mass of ammonium persulfate is 0.1% to 3% of the mass of acrylamide.

[0016] Preferably, in step (3), the magnetic field strength of the magnet is 5000 to 8000 Gs.

[0017] Preferably, in step (3), the temperature of the heat source is 50 to 70°C.

[0018] The present invention provides a photonic crystal ion gel prepared by the above preparation method.

[0019] Furthermore, the present invention provides the application of the above-mentioned photonic crystal ion gel in the fabrication of flexible sensors.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) This invention combines a dual-network gel with a magnetic nanoparticle photonic crystal and introduces conductive sodium chloride. By controlling the amount of sodium chloride added, the resulting photonic crystal ion gel maintains the structure and characteristics of the photonic crystal and has good mechanical properties and flexibility, while enhancing the conductivity and sensitivity of the gel.

[0022] (2) The preparation method of the present invention is simple and low cost. By applying different degrees of force to the photonic crystal ion gel, the synchronous changes in the color and conductivity of the gel can be observed during the deformation process of the photonic crystal ion gel, thereby realizing dual-mode real-time monitoring of sensor performance. Attached Figure Description

[0023] Figure 1 This is a photograph of the photonic crystal ion gel prepared in Example 1.

[0024] Figure 2 This is a photograph of the photonic crystal ion gel prepared in Example 2.

[0025] Figure 3 This is a photograph of the photonic crystal ion gel prepared in Example 3.

[0026] Figure 4 This is a physical image of the hydrogel system prepared in Comparative Example 1.

[0027] Figure 5 This is a physical image of the photonic crystal ion gel prepared for Comparative Example 2.

[0028] Figure 6 Conductivity diagrams of photonic crystal ion gels prepared with different mass ratios of polyvinyl alcohol to sodium chloride.

[0029] Figure 7 The diagram shows the tensile strain-resistance effect test of the photonic crystal ion gel prepared in Example 2 (a), the curve of relative resistance versus tensile strain (b), the calculated strain coefficient curve (dashed line in b), and the relative resistance values ​​(c) for different levels of tensile strain (50-500%).

[0030] Figure 8 The digital graph (ah) shows the color change of the photonic crystal ion gel prepared in Example 2 and the brightness change of the LED lamp during the stretching and recovery process in the circuit, as well as the corresponding reflection spectrum (i) and relative resistance change (j) when the color changes. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0032] Example 1

[0033] 1. Weigh acetone and ferrocene in a mass ratio of 78:1, sonicate for 30 minutes, then add 30% hydrogen peroxide in a mass ratio of 2.6:1 to ferrocene, and magnetically stir for 2 hours to disperse evenly. Transfer the mixture to a reaction vessel and solvate at 220℃ for 72 hours to obtain a magnetic nanoparticle solution.

[0034] 2. The obtained magnetic nanoparticle solution was precipitated under a magnet, the supernatant was discarded, and anhydrous ethanol was added for ultrasonic cleaning. This washing process was repeated three times. The supernatant was then discarded. Pure magnetic nanoparticles were obtained.

[0035] 3. Add polyvinyl alcohol, acrylamide, methylenebisacrylamide and water to a round-bottom flask in a mass ratio of 2:21:0.16:70, and stir at 90°C to fully dissolve and mix them evenly.

[0036] 4. Cool the mixture obtained above to room temperature, add pure magnetic nanoparticles and ammonium persulfate initiator, and sonicate to mix them evenly.

[0037] 5. Pour the solution obtained in step 4 into a polytetrafluoroethylene mold, place it on a 5000GS magnet, and apply a heat source at 60°C to solidify the solution into a gel state, thus obtaining a photonic crystal ion gel.

[0038] Figure 1 The image shows a physical picture of the photonic crystal ion gel prepared in Example 1. It can be seen that when sodium chloride is not added to the photonic crystal ion gel precursor solution, the prepared photonic crystal ion gel has a bright color, indicating that the photonic crystals are regularly arranged and fixed in the gel system.

[0039] Example 2

[0040] 1. Weigh acetone and ferrocene in a mass ratio of 78:1, sonicate for 30 minutes, then add 30% hydrogen peroxide in a mass ratio of 2.6:1 to ferrocene, and magnetically stir for 2 hours to disperse evenly. Transfer the mixture to a reaction vessel and solvate at 220℃ for 72 hours to obtain a magnetic nanoparticle solution.

[0041] 2. The obtained magnetic nanoparticle solution was precipitated under a magnet, the supernatant was discarded, and anhydrous ethanol was added for ultrasonic cleaning. This washing process was repeated three times. The supernatant was then discarded. Pure magnetic nanoparticles were obtained.

[0042] 3. Add polyvinyl alcohol, acrylamide, methylenebisacrylamide and water to a round-bottom flask in a mass ratio of 2:21:0.16:70, and stir at 90°C to fully dissolve and mix them evenly.

[0043] 4. Cool the mixture obtained above to room temperature, add sodium chloride at a mass ratio of 1:3.5 to polyvinyl alcohol, and sonicate to mix it evenly.

[0044] 5. Add pure magnetic nanoparticles and ammonium persulfate initiator to the mixture obtained in step 4, and sonicate to mix them evenly.

[0045] 6. Pour the solution obtained in step 5 into a polytetrafluoroethylene mold, place it on a 5000Gs magnet, and apply a heat source at 60°C to solidify the solution into a gel state, thus obtaining a photonic crystal ion gel.

[0046] Figure 2 The image shows a physical picture of the photonic crystal ion gel prepared in Example 2. It can be seen that the photonic crystal ion gel prepared when the mass ratio of polyvinyl alcohol to sodium chloride is 1:3.5 is brightly colored, indicating that the photonic crystals are regularly arranged and fixed in the gel system.

[0047] Example 3

[0048] 1. Weigh acetone and ferrocene in a mass ratio of 78:1, sonicate for 30 minutes, then add 30% hydrogen peroxide in a mass ratio of 2.6:1 to ferrocene, and magnetically stir for 2 hours to disperse evenly. Transfer the mixture to a reaction vessel and solvate at 220℃ for 72 hours to obtain a magnetic nanoparticle solution.

[0049] 2. The obtained magnetic nanoparticle solution was precipitated under a magnet, the supernatant was discarded, and anhydrous ethanol was added for ultrasonic cleaning. This washing process was repeated three times. The supernatant was then discarded. Pure magnetic nanoparticles were obtained.

[0050] 3. Add polyvinyl alcohol, acrylamide, methylenebisacrylamide and water to a round-bottom flask in a mass ratio of 2:21:0.16:70, and stir at 90°C to fully dissolve and mix them evenly.

[0051] 4. Cool the mixture obtained above to room temperature, add sodium chloride at a mass ratio of 1:4.5 to polyvinyl alcohol, and sonicate to mix it evenly.

[0052] 5. Add pure magnetic nanoparticles and ammonium persulfate initiator to the mixture obtained in step 4, and sonicate to mix them evenly.

[0053] 6. Pour the solution obtained in step 5 into a polytetrafluoroethylene mold, place it on a 5000Gs magnet, and apply a heat source at 60°C to solidify the solution into a gel state, thus obtaining a photonic crystal ion gel.

[0054] Figure 3The image shows a physical photograph of the photonic crystal ion gel prepared in Example 3. It can be seen that the photonic crystal ion gel prepared with a polyvinyl alcohol to sodium chloride mass ratio of 1:4.5 still possesses structural color, but the color is dull. This indicates that increasing the amount of sodium chloride alters the refractive index of the polymer system, causing the prepared photonic crystal ion gel to have color, but the color begins to darken.

[0055] Comparative Example 1

[0056] The gel system used in this comparative example differs from that in the previous examples, as detailed below:

[0057] 1. Weigh acetone and ferrocene in a mass ratio of 78:1, sonicate for 30 minutes, then add 30% hydrogen peroxide in a mass ratio of 2.6:1 to ferrocene, and magnetically stir for 2 hours to disperse evenly. Transfer the mixture to a reaction vessel and solvate at 220℃ for 72 hours to obtain a magnetic nanoparticle solution.

[0058] 2. The obtained magnetic nanoparticle solution was precipitated under a magnet, the supernatant was discarded, and anhydrous ethanol was added for ultrasonic cleaning. This washing process was repeated three times. The supernatant was then discarded. Pure magnetic nanoparticles were obtained.

[0059] 3. Weigh 2.5g of gelatin, 0.12g of acrylamide and 0.048mmol of methylenebisacrylamide, and dissolve them at 65℃ to obtain a gelatin-acrylamide mixed solution.

[0060] 4. After cooling the mixed solution to room temperature, add pure magnetic nanoparticles and potassium persulfate, and stir to dissolve.

[0061] 5. Place the solution obtained in step 4 on a magnet and observe whether the magnetic nanoparticles in this system are arranged into one-dimensional chains under the induction of the magnetic field, producing structural color.

[0062] Figure 4 The image shows the actual hydrogel system prepared in Comparative Example 1. It can be seen that when magnetic nanoparticles are added to the system and induced by a magnetic field, the mixed system does not produce structural color, and the magnetic nanoparticles are severely aggregated, indicating that the gel system is not suitable as a carrier for magnetic nanoparticles.

[0063] Comparative Example 2

[0064] 1. Weigh acetone and ferrocene in a mass ratio of 78:1, sonicate for 30 minutes, then add 30% hydrogen peroxide in a mass ratio of 2.6:1 to ferrocene, and magnetically stir for 2 hours to disperse evenly. Transfer the mixture to a reaction vessel and solvate at 220℃ for 72 hours to obtain a magnetic nanoparticle solution.

[0065] 2. The obtained magnetic nanoparticle solution was precipitated under a magnet, the supernatant was discarded, and anhydrous ethanol was added for ultrasonic cleaning. This washing process was repeated three times. The supernatant was then discarded. Pure magnetic nanoparticles were obtained.

[0066] 3. Add polyvinyl alcohol, acrylamide, methylenebisacrylamide and water to a round-bottom flask in a mass ratio of 2:21:0.16:70, and stir at 90°C to fully dissolve and mix them evenly.

[0067] 4. Cool the mixture obtained above to room temperature, add sodium chloride in a mass ratio of 1:6 with polyvinyl alcohol, and sonicate to mix it evenly.

[0068] 5. Add pure magnetic nanoparticles and ammonium persulfate initiator to the mixture obtained in step 4, and sonicate to mix them evenly.

[0069] 6. Pour the solution obtained in step 5 into a polytetrafluoroethylene mold, place it on a 5000Gs magnet, and apply a heat source at 60°C to solidify the solution into a gel state, thus obtaining a photonic crystal ion gel.

[0070] Figure 5 The image shows a physical picture of the photonic crystal ion gel prepared in Comparative Example 2. It can be seen that the photonic crystal ion gel prepared when the mass ratio of polyvinyl alcohol to sodium chloride is 1:6 has no structural color at all, and a large amount of sodium chloride is precipitated after polymerization. It can be inferred that the large amount of sodium chloride precipitated during polymerization disrupts the regular arrangement of the photonic crystal in the polymer system.

[0071] Figure 6 Conductivity diagrams of photonic crystal ionogels prepared with different mass ratios of polyvinyl alcohol to sodium chloride. The conductivity of the prepared gels increases with increasing sodium chloride content.

[0072] Figure 7 The diagram shows (a) of the tensile strain-resistance effect test of the photonic crystal ion gel prepared in Example 2, (b) the curve of relative resistance versus tensile strain, (c) the calculated strain coefficient curve (the dashed line in b), and the relative resistance values ​​at different levels of tensile strain (50-500%). Figure 7 As can be seen, the photonic crystal ion gel sensor of this invention exhibits a relatively large change in resistance during strain, demonstrating high sensitivity to resistance changes caused by deformation. Furthermore, the sensor exhibits good cyclic tensile stability, with signal hysteresis being almost negligible.

[0073] Figure 8The digital graphs show the color change of the photonic crystal ion gel prepared in Example 2 and the brightness change of the LED lamp during the stretching and recovery process in the circuit, as well as the corresponding reflection spectrum and relative resistance change when the color changes. Figure 8 h represents the LED's off state when no power is applied and the circuit is not connected. The LED and the prepared photonic crystal ion gel are connected together in the circuit, and power is applied, as shown below. Figure 8 As shown in (a), the LED bulb lights up, proving that the prepared photonic crystal ion gel is conductive. The gel is then subjected to stretching deformation (…). Figure 8 (a)-8(d)) As can be seen from the digital images, with the increase of stretching deformation, the gel gradually changed from its original yellow to purple, and the spectrum underwent a blue shift. Figure 8 (i)). Simultaneously, the LED light's brightness gradually decreases, indicating an increase in gel resistance. When the gel reaches its maximum stretching deformation, the bulb is at its dimmest, and the relative resistance reaches its maximum value compared to the initial gel. Figure 8 (j)). Next, the gel was restored from its stretched deformation. The gel color shifted back to its initial state, and the LED brightness returned to its initial level. The gel was subjected to 5 cycles of stretching and restoration, and its relative resistance was measured. Figure 8 (i)) can be seen that it exhibits good tensile stability.

Claims

1. A method for preparing photonic crystal ion gels, characterized in that, The specific steps are as follows: (1) Ferrocene and 30% hydrogen peroxide solution were added to acetone and a solvothermal reaction was carried out at 220±10℃ to obtain magnetic nanoparticles. (2) Using a one-pot method, polyvinyl alcohol, acrylamide, methylenebisacrylamide and water are stirred evenly at 90±5℃ to form a mixed solution. Then ammonium persulfate, magnetic nanoparticles and sodium chloride are added and ultrasonically mixed evenly to obtain a photonic crystal ion gel precursor solution. The mass ratio of polyvinyl alcohol to sodium chloride is 1:0~1:4.5 and the sodium chloride is not 0. (3) Transfer the photonic crystal ion gel precursor liquid into a polytetrafluoroethylene mold, place it on a magnet, apply a heat source to solidify it, and obtain the photonic crystal ion gel.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of acetone to ferrocene is 78:1, the mass ratio of 30% hydrogen peroxide solution to ferrocene is 2.6:1, and the solvothermal reaction time is 72 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of polyvinyl alcohol, acrylamide, methylenebisacrylamide and water is 2:21:0.16:

70.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of polyvinyl alcohol to sodium chloride is 1:3.5 to 1:4.

5.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass of ammonium persulfate is 0.1% to 3% of the mass of acrylamide.

6. The preparation method according to claim 1, characterized in that, In step (3), the magnetic field strength of the magnet is 5000~8000Gs.

7. The preparation method according to claim 1, characterized in that, In step (3), the heat source temperature is 50~70℃.

8. The photonic crystal ion gel prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the photonic crystal ion gel according to claim 8 in the fabrication of flexible sensors.

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