A photonic crystal hydrogel sensor and its preparation method and application

Abstract

The present invention belongs to the field of component detection technology and discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps: dissolving a functional monomer, a cross-linking agent, and a photoinitiator in an organic solvent to obtain a mixed solution; adding vinyl ferrocene to the mixed solution and dispersing it to obtain a prepolymer solution; infiltrating the prepolymer solution into a photonic crystal template and irradiating it under ultraviolet light to obtain a composite A; the photonic crystal template is composed of polystyrene composite particles coated with silica; etching composite A in hydrofluoric acid, transferring the polymer photonic crystal to a plexiglass sheet to obtain composite B; etching composite B in hydrofluoric acid, and then placing it in deionized water to obtain a photonic crystal hydrogel sensor. After the hydrofluoric acid etching, the SiO2 shell layer is removed, and the PS core layer is retained, forming a special opal and inverse opal composite structure polymer photonic crystal, which has a higher comprehensive refractive index, a more sensitive response, and a better detection effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of component detection, and specifically relates to a photonic crystal hydrogel sensor and a preparation method and application thereof. Background Art

[0002] Sodium nitrite is used as a food additive in meat production because it enhances the freshness of meat and effectively inhibits microorganisms, thereby preserving the structure and nutritional value of the meat. Sodium nitrite is also a strong oxidant. Generally speaking, excessive sodium nitrite entering the bloodstream can convert normal hemoglobin into methemoglobin, depriving the blood of its oxygen-carrying function. This leads to hypoxia and loss of vitality in tissues and tissues, potentially causing poisoning. Sodium nitrite is widely present in our daily lives, primarily in trace amounts in our diets. Therefore, monitoring sodium nitrite levels during use is extremely important. Exceeding the recommended daily intake limit can cause sodium nitrite poisoning and even death.

[0003] Currently, the determination of sodium nitrite in various foods is mainly based on instrumental analysis, including spectral detection, chromatography, electrochemical analysis, capillary electrophoresis, etc. Spectroscopic detection is a commonly used analytical method that is non-destructive, rapid, and highly accurate. However, it suffers from a high detection limit and is unable to detect trace amounts of sodium nitrite.

[0004] Chromatographic detection is one of the most commonly used methods, with the characteristics of high separation efficiency and high sensitivity. However, the required instruments and equipment are relatively complex, the operation is complicated, and the detection process takes a lot of time.

[0005] Electrochemical analysis is a highly accurate and sensitive analytical method with a short detection time, but it has high requirements on the environmental conditions of sample preparation and analysis process;

[0006] In addition, capillary electrophoresis is also a commonly used method with the advantages of high separation efficiency and the ability to separate various ionic components. However, its separation process has high requirements for sample preparation and processing, and requires more professional technicians to operate.

[0007] Visual detection methods have many advantages. First, they do not require complex sample pre-treatment steps, simplify the analysis process, and save time and labor costs. Secondly, these methods usually respond quickly and can accurately detect the content of sodium nitrite in a short time. In addition, the visual detection method is simple to operate and does not require professional instruments and equipment and complex analytical techniques, which makes it have broad potential in practical applications. For example, the patent document with publication number CN108680572B discloses a method for rapid detection of nitrite by color / fluorescence dual signal visualization, which mainly constructs a carbon dot neutral red composite system combined with ordinary filter paper to obtain a test paper, and then uses software to extract the RGB value of each test paper, establish a matrix and a multiple linear regression model, and then detect the content of nitrite in the food to be tested. The above detection method has the advantages of intuitive and accurate detection results, but the preparation process of the detection system is cumbersome and the detection limit is relatively high. Summary of the Invention

[0008] The purpose of the present invention is to provide a photonic crystal hydrogel sensor and its preparation method and application, which solves the problems of cumbersome and limited detection methods in existing detection methods.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for preparing a photonic crystal hydrogel sensor comprises the following steps:

[0011] S1, dissolving a functional monomer, a cross-linking agent, and a photoinitiator in an organic solvent to obtain a mixed solution;

[0012] S2. adding vinylferrocene to the mixed solution and dispersing the resulting system to obtain a prepolymer solution;

[0013] The molar ratio of the functional monomer, the crosslinking agent, the organic solvent, the photoinitiator and the vinyl ferrocene is 5:(0.1-1):(5-10):0.1:(0.5-2.0);

[0014] S3, first infiltrating the prepolymer solution into the photonic crystal template, and when the photonic crystal template becomes transparent, covering the photonic crystal template with a plexiglass sheet, and then irradiating it under ultraviolet light to obtain a composite A;

[0015] The photonic crystal template consists of polystyrene composite particles coated with silica, with the structure of PS@SiO2;

[0016] S4, etching the composite A in hydrofluoric acid, and transferring the polymer photonic crystal to a plexiglass sheet to obtain composite B;

[0017] S5. The complex B is placed in hydrofluoric acid for etching and then placed in deionized water to remove excess hydrofluoric acid, thereby obtaining a photonic crystal hydrogel sensor.

[0018] Further, in S1, the functional monomer is methacrylic acid, acrylic acid, hydroxyethyl methacrylate or methyl methacrylate;

[0019] The crosslinking agent is ethylene glycol dimethacrylate or N,N-methylenebisacrylamide;

[0020] The photoinitiator is 2-hydroxy-2-methylpropiophenone.

[0021] Furthermore, in S1, the organic solvent is ethanol or methanol.

[0022] Furthermore, in S3, the irradiation time under the ultraviolet lamp is 2-6 hours.

[0023] Furthermore, the mass fraction of the hydrofluoric acid is 1%-4%, and the complex A is etched in the hydrofluoric acid for 12-18 hours.

[0024] Furthermore, in S5, the complex B is placed in hydrofluoric acid for etching for 4-8 hours, and then placed in water to remove excess hydrofluoric acid.

[0025] The invention also discloses a photonic crystal hydrogel sensor prepared by the preparation method.

[0026] The present invention also discloses the application of the photonic crystal hydrogel sensor in visual detection of sodium nitrite, wherein a substance containing sodium nitrite is mixed with an active catalase solution, and then a hydrogen peroxide solution is added to obtain a detection solution;

[0027] The photonic crystal hydrogel sensor is placed in the detection solution. After the response is balanced, the sodium nitrite content is determined by judging the color change and the shift of the reflection peak position of the photonic crystal hydrogel sensor.

[0028] Furthermore, the activity of the catalase is 300-600 U·mL -1 ;

[0029] The concentration of the hydrogen peroxide solution is 5%-25%; the pH of the hydrogen peroxide solution is 2-12;

[0030] The sodium nitrite solution and the catalase solution are mixed for 2 to 30 minutes.

[0031] Furthermore, the photonic crystal hydrogel sensor can detect sodium nitrite content of 0.05-500 mg·L -1 .

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] The present invention discloses a method for preparing a photonic crystal hydrogel sensor. The method comprises preparing a prepolymer solution containing functional monomers such as vinylferrocene, a crosslinking agent, and an initiator. The prepolymer solution is then infiltrated into a photonic crystal template composed of composite particles. The template is then covered with a plexiglass sheet and irradiated under ultraviolet light to initiate a polymerization reaction. After polymerization is complete, the template is etched with hydrofluoric acid to obtain a responsive polymer photonic crystal, which is then transferred to the plexiglass sheet to form a photonic crystal hydrogel sensor. Because the photonic crystal template is composed of PS@SiO2 composite particles, the SiO2 shell is removed after hydrofluoric acid etching, while the PS core layer is retained, thereby forming a special opal and inverse opal composite structure polymer photonic crystal. Compared to traditional single inverse opal structure photonic crystals, this type of structure has a higher comprehensive refractive index, a more sensitive response, and better detection effects.

[0034] The present invention discloses a method for visually detecting sodium nitrite using a photonic crystal hydrogel sensor. The method mainly utilizes the inhibition of catalase activity by sodium nitrite, thereby affecting the redox process of the system, hindering the contraction of the ferrocenyl photonic crystal, and reducing the blue shift of the reflection peak of the photonic crystal. The present invention detects the sodium nitrite content through the color change and reflection peak position shift of the sensor. The higher the sodium nitrite content, the stronger the inhibitory effect, the less the sensor reflection peak shifts, and the less obvious the color change. The photonic crystal hydrogel sensor prepared by the present invention has good acid-base stability and the minimum detection limit for sodium nitrite content is 0.05 mg·L -1 Compared with traditional spectral detection, chromatography, electrochemical analysis and capillary electrophoresis, the present invention does not require specific specialists, is simple to operate, has high sensitivity, fast response speed, is cheap and portable, and can perform on-site real-time detection without relying on other analytical instruments.

[0035] Furthermore, the pH of the added hydrogen peroxide solution is 2-12. Regardless of whether it is an acidic environment or an alkaline environment, the photonic crystal hydrogel sensor prepared by the present invention can detect the content of sodium nitrite, indicating that the photonic crystal hydrogel sensor prepared by the present invention has good acid-base stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Graphs showing the reflection spectra of the composite redox photonic crystal sensor prepared in Example 1 of the present invention before and after equilibrium when no sodium nitrite is present.

[0037] Figure 2 Graphs showing the reflectance spectra of the single-structure redox photonic crystal sensor prepared in Example 2 of the present invention before and after equilibrium in the absence of sodium nitrite.

[0038] Figure 3The composite redox photonic crystal sensor prepared in Example 4 of the present invention has a detection content of 500 mg·L -1 Sodium nitrite, its reflectance spectrum before and after equilibrium.

[0039] Figure 4 The composite redox photonic crystal sensor prepared in Example 5 of the present invention has a detection content of 5 mg·L -1 Sodium nitrite, its reflectance spectrum before and after equilibrium.

[0040] Figure 5 The composite redox photonic crystal sensor prepared in Example 6 of the present invention has a detection content of 0.05 mg·L -1 Sodium nitrite, its reflectance spectrum before and after equilibrium.

[0041] Figure 6 The composite redox photonic crystal sensor prepared in Example 7 of the present invention can detect a concentration of 50 mg·L at pH = 4. -1 Sodium nitrite, its reflectance spectrum before and after equilibrium.

[0042] Figure 7 The composite redox photonic crystal sensor prepared in Example 8 of the present invention can detect a content of 50 mg·L at pH=8. -1 Sodium nitrite, its reflectance spectrum before and after equilibrium.

[0043] Figure 8 The composite redox photonic crystal sensor prepared in Example 8 of the present invention detected a content of 50 mg·L at pH = 12. -1 Sodium nitrite, its reflectance spectrum before and after equilibrium. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0045] The components described and illustrated in the drawings and embodiments of the present invention may be arranged and designed in a variety of different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. All other embodiments derived by those skilled in the art based on the drawings and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or apparatus.

[0047] Photonic crystals, also known as photonic bandgap materials, are dielectric structures with photonic bandgap characteristics formed by the periodic arrangement of at least two dielectric materials. This specific structure selectively blocks the propagation of light of specific wavelengths. Therefore, the unique bandgap structure of photonic crystals gives photonic crystals excellent optical properties. Photonic crystals prepared by self-assembly of nanoparticles of different sizes can exhibit different structural colors under visible light. The application of photonic crystals in molecular recognition utilizes the stimulus responsiveness of molecular recognition agents. Molecular recognition agents can bind to target analytes to cause functional polymers to produce stimulus responses and undergo volume phase changes, resulting in changes in the bandgap position of the photonic crystal and a macroscopic change in color.

[0048] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0049] S1. preparing a mixed solution containing a functional monomer, a cross-linking agent, an organic solvent and a photoinitiator in a certain proportion;

[0050] S2. Vinylferrocene is added to the mixed solution, and finally dispersed by ultrasonic treatment to obtain a prepolymer solution for standby use.

[0051] The functional monomer is methacrylic acid, acrylic acid, hydroxyethyl methacrylate or methyl methacrylate, the crosslinking agent is ethylene glycol dimethacrylate or N,N-methylenebisacrylamide, the solvent is ethanol, methanol or water, the photoinitiator is 2-hydroxy-2-methylpropiophenone, and the molar ratio of the functional monomer, the crosslinking agent, the organic solvent, the photoinitiator and the vinyl ferrocene is 5:(0.1-1):(5-10):0.1:(0.5-2.0).

[0052] S3. The photonic crystal template is tilted, generally at an angle of about 15° to the horizontal plane. The ordered units on the photonic crystal template are PS@SiO2 composite particles. The obtained prepolymer solution is then infiltrated from the edge of the photonic crystal template. After the prepolymer solution is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is placed on the photonic crystal template. The template is then exposed to ultraviolet light for 2-6 hours. Vinyl ferrocene undergoes a polymerization reaction under the action of the functional monomer, and a vinyl ferrocene polymer is introduced into the photonic crystal to obtain a complex A.

[0053] S4. Finally, the composite A is taken out and etched with hydrofluoric acid having a mass fraction of 1% to 4% for 12 to 18 hours to obtain a composite B;

[0054] S5. Putting the complex B into water to remove excess hydrofluoric acid, thereby obtaining a composite redox photonic crystal hydrogel sensor.

[0055] When the composite redox photonic crystal hydrogel sensor is used to detect sodium nitrite, the specific process is as follows:

[0056] A hydrogen peroxide solution with a pH of 2-12 and a volume concentration of 5%-25% is prepared, a substance containing sodium nitrite is mixed with a certain activity of catalase for a period of time, and then the hydrogen peroxide solution is added to obtain a detection solution; then the prepared photonic crystal sensor is placed in the detection solution, and sodium nitrite is detected by observing the shift in the reflection peak position and color change of the sensor.

[0057] The ferrocene system has the advantages of mild redox conditions, high biocompatibility, and more flexible participation in gel structure construction. By utilizing the hydrophilic and hydrophobic changes of the ferrocene group before and after redox reactions, the ferrocene system can be combined with a photonic crystal to produce a photonic crystal polymer film that exhibits swelling in response to redox reactions, thereby causing the photonic crystal sensor to exhibit color changes. Hydrogen peroxide and catalase can undergo a violent redox reaction at certain concentrations, and sodium nitrite can inhibit the activity of catalase. The novel opal and inverse opal composite polymer photonic crystal sensor prepared by the present invention achieves rapid visual detection of sodium nitrite based on the catalytic inhibition of catalase.

[0058] Sodium nitrite inactivates the enzyme, preventing it from decomposing hydrogen peroxide. Consequently, the sensor will not respond if hydrogen peroxide is not decomposed (decomposition of hydrogen peroxide can oxidize the ferrocene groups on the sensor). This is an indirect detection method. The higher the sodium nitrite concentration, the greater the degree of enzyme inactivation and the lower the degree of oxidation of hydrogen peroxide and ferrocene groups.

[0059] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0060] Example 1

[0061] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0062] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0063] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain a composite structure polymer photonic crystal of opal and inverse opal structure. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor.

[0064] The ordered units on the photonic crystal template are PS@SiO2 composite particles. The special feature is that the particles used in traditional templates are pure silica, and the result after polymerization etching is an inverse opal structure polymer. This one is composed of PS@SiO2 composite particles. Polymerization etching can only remove silica, and the polystyrene particles are retained. The result is a polymer photonic crystal with both opal and inverse opal structures. This structure is more sensitive to response.

[0065] The method for visual detection of sodium nitrite is as follows:

[0066] Prepare a H2O2 aqueous solution with a pH of 7 and a volume concentration of 15%, and mix the substance containing sodium nitrite with 400 U·mL -1 After mixing for a period of time, hydrogen peroxide solution is added to obtain a detection solution;

[0067] The prepared photonic crystal sensor was placed in the above detection solution, the color change of the sensor was observed, and the reflection spectrum before and after equilibrium was recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor was not placed in the mixed solution system to be detected.

[0068] Depend on Figure 1 The reflection spectra before and after equilibrium show that without sodium nitrite inhibition, the reflection peak position of the composite structure photonic crystal sensor moves from the initial 672nm to 584nm, and from red to orange, a total shift of 88nm.

[0069] Example 2

[0070] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0071] Step 1: First, a mixture was prepared with hydroxyethyl methacrylate as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, ethanol as the organic solvent, and 2-hydroxy-2-methylpropiophenone as the photoinitiator in a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. 0.3 g of vinyl ferrocene was then added to the mixture, and the resulting prepolymer was ultrasonically treated for later use.

[0072] First, the photonic crystal template is tilted 15°, and the ordered units of the photonic crystal on the photonic crystal template are silica particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an inverse opal structure polymer photonic crystal. The excess hydrofluoric acid is removed in water to obtain a photonic crystal hydrogel sensor.

[0073] The method for visual detection of sodium nitrite is as follows:

[0074] Prepare a H2O2 aqueous solution with a pH of 7 and a volume concentration of 15%, and mix the substance containing sodium nitrite with 400 U·mL -1 After mixing for a period of time, hydrogen peroxide solution is added to obtain a detection solution;

[0075] The prepared photonic crystal sensor was placed in the above detection solution, the color change of the sensor was observed, and the reflection spectrum before and after equilibrium was recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor was not placed in the mixed solution system to be detected.

[0076] Depend on Figure 2 The reflectance spectra before and after equilibration show that, without sodium nitrite inhibition, the reflection peak position of the single-structure photonic crystal sensor shifted from the initial 672nm to 649nm, a total shift of 23nm. The color remained red, showing a minimal change. Compared with Example 1, this shift decreased by 65nm, indicating that the composite-structure photonic crystal sensor has higher detection sensitivity.

[0077] Example 3

[0078] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0079] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0080] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an opal and inverse opal structure composite polymer photonic crystal. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor for use.

[0081] The method for visual detection of sodium nitrite is as follows:

[0082] Prepare a H2O2 aqueous solution with a pH of 7 and a volume concentration of 15%; add 500mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0083] Then, the prepared photonic crystal sensor was placed in the detection solution of the above three elements, the color change of the sensor was observed, and the reflection spectrum before and after equilibrium was recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor was not placed in the mixed solution system to be detected.

[0084] Depend on Figure 3 The reflection spectrum before and after equilibrium shows that the reflection peak position of the photonic crystal sensor has moved from the initial 655nm to 638nm, a total shift of 17nm. The color at equilibrium changes from orange to orange-yellow, thus achieving the goal of 500mg·L -1 Visual response detection of sodium nitrite.

[0085] Example 4

[0086] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0087] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0088] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an opal and inverse opal structure composite polymer photonic crystal. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor for use.

[0089] The method for visual detection of sodium nitrite is as follows:

[0090] Prepare an aqueous H2O2 solution with a pH of 7 and a volume concentration of 15%;

[0091] 5mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0092] Then, the photonic crystal sensor prepared in step 1 is placed in the detection solution of the above three, the color change of the sensor is observed, and the reflection spectrum before and after equilibrium is recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor is not placed in the mixed solution system to be detected.

[0093] Depend on Figure 4 The reflection spectra before and after equilibrium show that the reflection peak position of the photonic crystal sensor has moved from the initial 655nm to 575nm, a total shift of 80nm. The color at equilibrium changes from orange to yellow-green, thus achieving the target concentration of 5mg·L -1 Visual response detection of sodium nitrite.

[0094] Example 5

[0095] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0096] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0097] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an opal and inverse opal structure composite polymer photonic crystal. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor for use.

[0098] The method for visual detection of sodium nitrite is as follows:

[0099] Prepare an aqueous H2O2 solution with a pH of 7 and a volume concentration of 15%;

[0100] 0.05mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0101] Then, the photonic crystal sensor prepared in step 1 is placed in the detection solution of the above three, the color change of the sensor is observed, and the reflection spectrum before and after equilibrium is recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor is not placed in the mixed solution system to be detected.

[0102] Depend on Figure 5 The reflection spectra before and after equilibrium show that the reflection peak position of the photonic crystal sensor has moved from the initial 655nm to 558nm, a total shift of 97nm. The color at equilibrium changes from orange to green, thus achieving the target concentration of 0.05mg·L -1 Visual response detection of sodium nitrite.

[0103] The results obtained in Examples 3-5 show that the minimum detection limit of the photonic crystal hydrogel sensor prepared in the present invention for sodium nitrite content is 0.05 mg·L -1 The results can be determined by the visible changes in the structural color of the photonic crystal hydrogel sensor and the wavelength changes obtained by the fiber optic spectrometer.

[0104] Example 6

[0105] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0106] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0107] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an opal and inverse opal structure composite polymer photonic crystal. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor for use.

[0108] The method for visual detection of sodium nitrite is as follows:

[0109] Prepare an H2O2 aqueous solution with a pH of 4 and a volume concentration of 15%;

[0110] 50mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0111] Then, the prepared photonic crystal sensor was placed in the detection solution of the above three elements, the color change of the sensor was observed, and the reflection spectrum before and after equilibrium was recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor was not placed in the mixed solution system to be detected.

[0112] Depend on Figure 6 The reflectance spectra before and after equilibrium show that when the pH of hydrogen peroxide is adjusted to 4, the reflection peak position of the photonic crystal sensor moves from the initial 650nm to 605nm, a total shift of 45nm, and the color at equilibrium changes from orange to yellow.

[0113] Example 7

[0114] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0115] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0116] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain an opal and inverse opal structure composite polymer photonic crystal. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor for use.

[0117] The method for visual detection of sodium nitrite is as follows:

[0118] Prepare an aqueous H2O2 solution with a pH of 8 and a volume concentration of 15%;

[0119] 50mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0120] Then, the photonic crystal sensor prepared in step 1 is placed in the detection solution of the above three, the color change of the sensor is observed, and the reflection spectrum before and after equilibrium is recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor is not placed in the mixed solution system to be detected.

[0121] Depend on Figure 7 The reflectance spectra before and after equilibrium show that when the pH of hydrogen peroxide is adjusted to 8, the reflection peak position of the photonic crystal sensor moves from the initial 650nm to 608nm, a total shift of 42nm, and the color at equilibrium changes from orange to yellow.

[0122] Example 8

[0123] The present invention discloses a method for preparing a photonic crystal hydrogel sensor, comprising the following steps:

[0124] First, hydroxyethyl methacrylate was used as a functional monomer, ethylene glycol dimethacrylate was used as a cross-linking agent, ethanol was used as an organic solvent, and 2-hydroxy-2-methylpropiophenone was used as a photoinitiator. A mixed solution was prepared at a molar ratio of 5:0.1:5:0.1, wherein the volume of hydroxyethyl methacrylate was 650 μL. Then, 0.3 g of vinyl ferrocene was added to the mixed solution. Finally, the obtained prepolymer solution was ultrasonically treated and set aside.

[0125] First, the photonic crystal template is tilted 15°, and the ordered units on the photonic crystal template are PS@SiO2 composite particles. Then, the prepolymer liquid obtained in step 1 is infiltrated from the edge of the photonic crystal template. When it is completely infiltrated until the photonic crystal template becomes transparent, a plexiglass sheet is covered on the photonic crystal template, and then it is placed under ultraviolet light for 4 hours. Finally, it is taken out and etched with hydrofluoric acid with a mass fraction of 3% for 16 hours to obtain a composite structure polymer photonic crystal of opal and inverse opal structure. The prepolymer liquid is placed in water to remove excess hydrofluoric acid to obtain a photonic crystal hydrogel sensor.

[0126] The method for visual detection of sodium nitrite is as follows:

[0127] Prepare an aqueous H2O2 solution with a pH of 12 and a volume concentration of 15%;

[0128] 50mg·L -1 of sodium nitrite and 400 U·mL -1 After mixing with catalase for 30 minutes, it was mixed with H2O2 aqueous solution to obtain a detection solution;

[0129] Then, the photonic crystal sensor prepared in step 1 is placed in the detection solution of the above three, the color change of the sensor is observed, and the reflection spectrum before and after equilibrium is recorded by a fiber optic spectrometer. Before equilibrium, the photonic crystal sensor is not placed in the mixed solution system to be detected.

[0130] Depend on Figure 8 The reflectance spectra before and after equilibrium show that when the pH of hydrogen peroxide is adjusted to 12, the reflection peak position of the photonic crystal sensor moves from the initial 650nm to 605nm, a total shift of 45nm, and the color at equilibrium changes from orange to yellow.

[0131] The results obtained in Examples 6-8 show that the redox photonic crystal hydrogel sensor prepared in the present invention has good acid-base stability when detecting sodium nitrite content. The results can be determined by the visual changes in the structural color of the photonic crystal hydrogel sensor and the wavelength changes obtained by the fiber optic spectrometer.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a photonic crystal hydrogel sensor, characterized in that: The steps include: S1, dissolving a functional monomer, a cross-linking agent, and a photoinitiator in an organic solvent to obtain a mixed solution; S2. adding vinylferrocene to the mixed solution and dispersing the resulting system to obtain a prepolymer solution; The molar ratio of the functional monomer, the crosslinking agent, the organic solvent, the photoinitiator and the vinyl ferrocene is 5:(0.1-1):(5-10):0.1:(0.5-2.0); The functional monomer is methacrylic acid, acrylic acid, hydroxyethyl methacrylate or methyl methacrylate; S3, first infiltrating the prepolymer solution into the photonic crystal template, and when the photonic crystal template becomes transparent, covering the photonic crystal template with a plexiglass sheet, and then irradiating it under ultraviolet light to obtain a composite A; The photonic crystal template consists of polystyrene composite particles coated with silica, with the structure of PS@SiO2; S4, etching the composite A in hydrofluoric acid, and transferring the polymer photonic crystal to a plexiglass sheet to obtain composite B; S5. The complex B is placed in hydrofluoric acid for etching, and then placed in deionized water to remove excess hydrofluoric acid, thereby obtaining a photonic crystal hydrogel sensor.

2. The method for preparing a photonic crystal hydrogel sensor according to claim 1, characterized in that: In S1, the crosslinking agent is ethylene glycol dimethacrylate or N,N-methylenebisacrylamide; The photoinitiator is 2-hydroxy-2-methylpropiophenone.

3. The method for preparing a photonic crystal hydrogel sensor according to claim 1, wherein: In S1, the organic solvent is ethanol or methanol.

4. The method for preparing a photonic crystal hydrogel sensor according to claim 1, wherein: In S3, the irradiation time under UV light is 2-6 h.

5. The method for preparing a photonic crystal hydrogel sensor according to claim 1, wherein: The mass fraction of the hydrofluoric acid is 1%-4%, and the complex A is etched in the hydrofluoric acid for 12-18 hours.

6. The method for preparing a photonic crystal hydrogel sensor according to claim 1, wherein: In S5, the complex B is placed in hydrofluoric acid for etching for 4-8 hours, and then placed in water to remove excess hydrofluoric acid.

7. A photonic crystal hydrogel sensor prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the photonic crystal hydrogel sensor according to claim 7 in visual detection of sodium nitrite in food, characterized in that: After mixing a substance containing sodium nitrite with an active catalase solution, a hydrogen peroxide solution is added to obtain a test solution; The photonic crystal hydrogel sensor is placed in the detection solution. After the response is balanced, the sodium nitrite content is determined by judging the color change and the shift of the reflection peak position of the photonic crystal hydrogel sensor.

9. The use according to claim 8, characterized in that The activity of the catalase is 300-600 U·mL -1 ; The concentration of the hydrogen peroxide solution is 5%-25%; the pH of the hydrogen peroxide solution is 2-12; The sodium nitrite solution and the catalase solution are mixed for 2 to 30 minutes.

10. The use according to claim 8, characterized in that The photonic crystal hydrogel sensor can detect sodium nitrite content of 0.05-500 mg·L -1 .

Images