A photonic crystal lactate sensor, a preparation method and application thereof

Abstract

The present application relates to photonic crystal materials and lactic acid analysis detection technical field, particularly to a kind of preparation method and application of photonic crystal lactic acid sensor, including lactic acid responsive hydrogel matrix film and embedding therein uniform orientation's multiple one-dimensional magnetic nanochain, the one-dimensional magnetic nanochain is by monodisperse magnetic nanoparticle with non-tightly packed one-dimensional chain arrangement.The maximum value that the sensitivity of photonic crystal lactic acid sensor of the present application can reach in visible spectral range is >=11.5nm / mM, and the response range of the photonic crystal lactic acid sensor is the interval that lactic acid concentration is from 0 to 50mM.The photonic crystal lactic acid sensor of the present application can distinguish the minimum lactic acid concentration change of 0.87mM in the liquid to be measured in specific environment only by relying on human eye to identify sensor color change, and the degree of visualization is high, and can be used repeatedly.

Description

Technical Field

[0001] This invention relates to the fields of photonic crystal materials and lactic acid analysis and detection technology, and in particular to a method for preparing and applying a photonic crystal lactic acid sensor. Background Technology

[0002] Lactic acid is one of the important anaerobic metabolic products in the human body and an important biomarker in clinical diagnosis and sports medicine. In the field of medical diseases, the accumulation of lactate in the tissue microenvironment is a characteristic of inflammatory diseases and cancer. Lactic acid serves as a key indicator for early warning of tissue hypoxia, prognosis of critical illnesses, metabolic disorders, and sepsis. In the field of sports health, as an anaerobic metabolic product, monitoring lactate during exercise helps assess exercise intensity, determine lactate thresholds, and assist athletes in developing training plans to avoid muscle damage caused by excessive anaerobic exercise. Studies have shown a positive correlation between blood lactate levels and sweat lactate levels, and sweat lactate concentration is closely related to exercise intensity and the degree of tissue hypoxia. Excessive lactate in muscles during strenuous activity can lead to soreness, pain, and fatigue. Therefore, monitoring lactate levels in sweat is crucial for health protection, especially for high-intensity anaerobic exercise.

[0003] Current conventional lactate detection technologies, such as fluorescence spectroscopy and liquid chromatography, while offering good accuracy, suffer from drawbacks including time-consuming detection processes, the need for sophisticated equipment, and high costs. Electrochemical sensors can achieve rapid detection to some extent, but electrochemical sweat sensors still face several challenges. Electrochemical lactate detection often requires enzymes or precious metals as recognition units, but these units suffer from stringent operating conditions, poor long-term stability, and difficulty in recycling. Furthermore, the high cost of enzymes and precious metals limits their application. Enzyme-based sensors generally suffer from high operating costs, and their main components are unstable during production, handling, transportation, and storage; enzymes are prone to inactivation; and detection procedures are complex. These issues severely limit the widespread application of these sensors, making them unsuitable for the daily monitoring needs of wearable devices.

[0004] Responsive photonic crystal hydrogels can undergo volume phase transitions through expansion or contraction under the influence of external responsive substances, resulting in changes in structural color. These changes can be visually identified by the naked eye as variations in the concentration of the responsive substance. Responsive photonic crystal hydrogel sensors offer advantages such as high color saturation, non-destructive nature, recyclability, good color stability, and applicability to dynamic detection, attracting increasing attention.

[0005] Currently reported photonic crystal lactate sensors are opal and inverse opal structures, both of which are close-packed. However, their sensitivity is not high within the physiological concentration range of lactate in human sweat, with a sensitivity (spectral shift range per mM lactate, Δλ / mM) of only 2.3 nm. Considering that the spectral resolution of the human eye is around 10 nm, their visual resolution is only around 4.3 mM lactate, making it impossible to achieve naked-eye visual monitoring of sweat lactate. Because the photonic crystal structures in these sensors are all closely packed, the responsive gel accounts for only 26%. WU X, JIN D, LI M, et al. Wearable analytical platform for colorimetric detection of sweat lactate using spherical colloidal photonic crystal hydrogel[J / OL]. Microchemical Journal, 2024, 200: 110327. disclosed a photonic crystal lactate sensor using an inverse opal structure. After removing the template, a large number of voids are left. In order to maintain structural stability, they require high mechanical strength. Therefore, the gel expansion should not be too large, so a high degree of cross-linking is required. It can be cyclically detected 5 times. LI Q, LIU S, MBOLA NM, et al. Responsive hydrogel-based three-dimensional photonic crystal sensor for lactic acid detection[J / OL]. Analytical and Bioanalytical Chemistry, 2022,414(26): 7695-7704. This paper discloses a photonic crystal lactic acid sensor with an opal structure that is brittle and cannot meet the flexibility requirements of wearable devices. The solubility of the responsive material in the solvent used is limited, which restricts the proportion of the responsive material. It can be cyclically detected 20 times.

[0006] Therefore, it remains a challenge to fabricate a photonic crystal lactic acid sensor with high sensitivity and naked-eye visibility. Summary of the Invention

[0007] To address the problems existing in the prior art, one of the objectives of this invention is to provide a photonic crystal lactic acid sensor that can achieve high-sensitivity detection relying solely on human visual recognition.

[0008] The second objective of this invention is to provide a method for preparing a photonic crystal lactic acid sensor, which has a simple process and operation, a short preparation cycle, low cost, and is easy to control.

[0009] The third objective of this invention is to provide an application of a photonic crystal lactic acid sensor.

[0010] One of the solutions adopted to achieve the objective of this invention is: a photonic crystal lactic acid sensor, comprising a lactic acid responsive hydrogel matrix membrane and multiple uniformly oriented one-dimensional magnetic nanochains embedded therein, wherein the one-dimensional magnetic nanochains are formed by monodisperse magnetic nanoparticles arranged in a non-closely packed one-dimensional chain-like manner.

[0011] The photonic crystal lactic acid sensor of the present invention can achieve high-sensitivity detection by relying solely on human eye recognition within the lactic acid concentration range of 0-50mM. In particular, it achieves full-spectrum visible light visualization detection within the physiological concentration range of human sweat lactic acid (3-20mM), solving the problems of low sensitivity and visualization of current photonic crystal lactic acid sensors.

[0012] Preferably, the raw materials for preparing the lactic acid responsive hydrogel matrix membrane include non-lactic acid responsive hydrophilic polymeric monomers and lactic acid responsive monomers, wherein the molar ratio of the non-lactic acid responsive hydrophilic polymeric monomers to the lactic acid responsive monomers is 1-20:1.

[0013] Preferably, the molar ratio of the non-lactic acid responsive hydrophilic monomer to the lactic acid responsive monomer is 8-20:1.

[0014] Preferably, the molar ratio of the non-lactic acid responsive hydrophilic monomer to the lactic acid responsive monomer is 1-8:1.

[0015] Preferably, the molar ratio of the non-lactic acid responsive hydrophilic monomer to the lactic acid responsive monomer is 2-5:1.

[0016] Preferably, the molar ratio of the non-lactic acid responsive hydrophilic monomer to the lactic acid responsive monomer is 3:1.

[0017] Preferably, the lactic acid responsive monomer is a monomer containing a phenylboronic acid group.

[0018] Preferably, the lactic acid-responsive monomer containing the phenylboronic acid group includes at least one of 3-acrylamidophenylboronic acid, 3-methylacrylamidophenylboronic acid, 4-((2-acrylamidoethyl)carbamoyl)-3-fluorophenyl)boronic acid, and 4-vinylphenylboronic acid.

[0019] Preferably, the non-lactic acid responsive hydrophilic polymerizable monomer includes at least one of acrylamide, N-(2-hydroxypropyl)methacrylamide, N-(2-hydroxyethyl)acrylamide, N-hydroxymethylacrylamide, and N-tris(hydroxymethylacrylamide).

[0020] Preferably, the magnetic nanoparticles include oxides or sulfides containing at least one of iron, cobalt, and nickel, and the magnetic nanoparticles have a particle size of 60-300 nm.

[0021] Preferably, the magnetic nanoparticles include Fe3O4, Fe3S4, NiS, CoNiFe2O4, NiFe2O4, etc.

[0022] Preferably, the thickness of the lactic acid responsive hydrogel matrix membrane is 10-400 μm.

[0023] Preferably, the lactic acid-responsive hydrogel matrix membrane in the photonic crystal lactic acid sensor comprises 50% or more by mass. For example, the mass percentage of the lactic acid-responsive hydrogel matrix membrane in the photonic crystal lactic acid sensor can be any percentage such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97.5%, etc., and is not limited to the listed values.

[0024] The photonic crystal lactic acid sensor of the present invention can further improve the mass percentage of lactic acid responsive hydrogel matrix film and achieve high sensitivity under the premise of low magnetic nanoparticle (based photonic crystal) mass percentage.

[0025] Preferably, the photonic crystal lactic acid sensor further includes a substrate, and the lactic acid responsive hydrogel matrix film and multiple uniformly oriented one-dimensional magnetic nanochains embedded therein are bound to the surface of the substrate.

[0026] Preferably, the substrate comprises a glass substrate or a flexible substrate. The flexible substrate includes a PET substrate, etc.

[0027] The photonic crystal lactic acid sensor of the present invention can exist freely in the detection environment without being bound (without a substrate or without chemical bonding with the substrate), or it can be bound to a glass substrate or other flexible substrate by chemical means (attached to the substrate, with chemical bonding between it and the substrate). The substrate includes a glass substrate or a polyethylene terephthalate (PET) flexible substrate. The substrate surface is modified by introducing hydrophilic groups or carbon-carbon double bond groups. The modified substrate forms hydrogen bonds with the gel monomer through carboxyl groups or double bond groups, thereby binding the gel matrix to the substrate surface.

[0028] The solution adopted to achieve the second objective of this invention is: a method for preparing the aforementioned photonic crystal lactic acid sensor, comprising the following steps;

[0029] Step 1: Mix monodisperse magnetic nanoparticles with non-lactic acid responsive hydrophilic monomers, lactic acid responsive monomers, crosslinking agents, initiators and dispersion medium solvents to obtain a homogeneous prepolymer solution.

[0030] Step 2: Place the prepolymer liquid obtained in Step 1 under an external uniform magnetic field to initiate polymerization. After the reaction is complete, the photonic crystal lactic acid sensor is obtained.

[0031] Preferably, in step 1, the concentration of magnetic nanoparticles in the prepolymer solution is 0.5-50 mg / mL, the concentration of non-lactic acid responsive hydrophilic polymerizable monomer is 0.5-10 mmol / mL, and the concentration of lactic acid responsive monomer is 0.5-5 mmol / mL.

[0032] The initiator is 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, potassium persulfate, ammonium persulfate, or azobisisobutyronitrile. The amount of initiator is 0.2%-10% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive polymerizable monomers. The crosslinking agent is at least one of methylenebisacrylamide, ethylene glycol dimethacrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. The amount of crosslinking agent is 0.25%-5% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive hydrophilic polymerizable monomers. The dispersion medium solvent is at least one of dimethyl sulfoxide, a mixture of water and dimethyl sulfoxide, and dimethylformamide.

[0033] Preferably, in step 2, the intensity of the uniform magnetic field is 100-1000 Gs. Prepolymerization of the prepolymer is initiated under the applied uniform magnetic field, with the magnetic field direction perpendicular to the surface of the prepolymer.

[0034] Preferably, step 2 further includes the following steps: the prepolymer liquid from step 1 is coated onto the surface of the surface-modified substrate and then placed under an external uniform magnetic field to initiate polymerization. After the reaction is completed, the substrate-bound photonic crystal lactic acid sensor is obtained.

[0035] The photonic crystal lactic acid sensor of this invention can exist freely in the detection environment without constraint (without a substrate or without chemical bonds between it and the substrate), or it can be chemically bound to a glass substrate or other flexible substrate (attached to the substrate, with chemical bonds between it and the substrate). The substrate includes a glass substrate or a polyethylene terephthalate (PET) flexible substrate. The substrate surface is modified by introducing hydrophilic groups or carbon-carbon double bond groups. The modified substrate forms hydrogen bonds with the gel monomers through carboxyl groups or double bond groups, binding the gel matrix to the substrate surface. Specifically, the surface modification method for the PET flexible substrate involves curing a layer of polyacrylic acid on the surface of the polyethylene terephthalate flexible substrate using ultraviolet light, thereby attaching carboxyl groups to the surface of the glass substrate or PET flexible substrate. Carbon-carbon double bond modification is then performed on the surface of the glass substrate.

[0036] In this invention, the sensitivity of the photonic crystal lactic acid sensor refers to the shift in wavelength (λ) corresponding to the maximum value of the photonic crystal diffraction peak when the lactic acid concentration (mM) changes by a unit amount; that is, the rate of change of λ with lactic acid concentration. The high sensitivity of this invention means that, in a specific detection environment, the maximum sensitivity achievable by the photonic crystal lactic acid sensor in the visible spectrum is ≥11.5 nm / mM with a substrate and ≥4.3 nm / mM without a substrate, both achieving naked-eye visibility. The response range of the photonic crystal lactic acid sensor is from 0 to 50 mM lactic acid concentration. With a substrate, the photonic crystal lactic acid sensor of this invention can distinguish a 0.87 mM change in lactic acid concentration in the environment simply by the human eye recognizing the sensor's color change. This photonic crystal lactic acid sensor achieves full-spectrum visible light monitoring within the physiological concentration range of human sweat lactic acid (3-20 μm), with high visibility. The highest sensitivity of the photonic crystal lactic acid sensor of this invention can reach 11.5 nm / mM.

[0037] This invention can regulate the sensitivity of a photonic crystal sensor by adjusting the concentration of lactic acid-responsive monomers or the amount of crosslinking agent, enabling high-sensitivity sensors to be visible to the naked eye within the range of 0-20mM, and low-sensitivity sensors to be visible to the naked eye within the range of 0-50mM.

[0038] Preferably, when the amount of crosslinking agent accounts for 0.25%-1% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive hydrophilic polymeric monomers, and / or the molar ratio of non-lactic acid responsive hydrophilic polymeric monomers to lactic acid responsive monomers is 1-8:1, the prepared photonic crystal sensor has high sensitivity, with a maximum value ≥11.5 nm / mM, and can make the sensor visible to the naked eye in the range of 0-20 mM.

[0039] Preferably, when the amount of crosslinking agent accounts for more than 1% and less than 5% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive hydrophilic polymeric monomers, and / or the molar ratio of non-lactic acid responsive hydrophilic polymeric monomers to lactic acid responsive monomers is greater than 8, the prepared photonic crystal sensor has low sensitivity and can make the sensor visible to the naked eye in the range of 0-50mM.

[0040] The solution adopted to achieve the third objective of this invention is: an application of the aforementioned photonic crystal lactic acid sensor, applying the photonic crystal lactic acid sensor to the fields of wearable motion monitoring and medical health.

[0041] Preferably, the photonic crystal lactic acid sensor is used to detect the concentration of lactic acid in human sweat.

[0042] The specific application method involves placing the photonic crystal lactic acid sensor in the test solution or on the skin surface, observing the color change of the photonic crystal hydrogel, measuring the wavelength of the Bragg diffraction peak of the corresponding color using a fiber optic spectrometer, and reading the hue value (Hue°) of the corresponding color using mobile phone color analysis software. The correspondence between the Bragg diffraction peak wavelength and hue value and the lactic acid concentration is analyzed, and finally the concentration of the corresponding lactic acid in the test solution is determined based on the color observed by the naked eye.

[0043] The present invention has the following advantages and beneficial effects:

[0044] The photonic crystal lactic acid sensor of the present invention has a maximum sensitivity of ≥11.5 nm / mM in the visible spectrum range, and the response range of the photonic crystal lactic acid sensor is the range of lactic acid concentration from 0 to 50 mM.

[0045] The photonic crystal lactic acid sensor of the present invention can distinguish the lactic acid concentration change in the test liquid as low as 0.87mM by relying solely on the human eye to recognize the sensor color change in a specific environment. The photonic crystal lactic acid sensor of the present invention achieves full-spectrum detection of visible light within the physiological concentration range of human sweat lactic acid, with high visualization and can be used repeatedly.

[0046] The photonic crystal lactic acid sensor of this invention has a high proportion of lactic acid-responsive gel, resulting in a higher density of lactic acid-responsive material and thus higher sensitivity and cycling stability. The required mass percentage of magnetic nanoparticles (photonic crystals) is relatively small, enabling high-sensitivity detection even with low photonic crystal content.

[0047] The photonic crystal lactic acid sensor of the present invention also has the advantages of being simple to operate, easy to prepare, low in cost, and not requiring complex precision instruments.

[0048] In the preparation method of this invention, the magnetic nanoparticles used can be directly mixed with non-lactic acid responsive hydrophilic monomers and lactic acid responsive monomers to obtain a prepolymer solution. Subsequently, the magnetic nanoparticles are assembled using a magnetic field, and then subjected to a polymerization reaction in one step to obtain a photonic crystal lactic acid sensor. The preparation method is simple, easy to control, and convenient for industrial production.

[0049] The preparation method of the present invention provides a photonic crystal lactic acid sensor with adjustable sensitivity. Attached Figure Description

[0050] Figure 1 This is a digital photograph of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention;

[0051] Figure 2The images shown are field emission scanning electron microscope (SEM) images of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention, wherein (A) is a field emission scanning electron microscope image of the photonic crystal lactic acid sensor, (B) is an enlarged view of the selected portion of (A), and (C) is an enlarged view of the selected portion of (B).

[0052] Figure 3 The image shows an optical microscope image of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention, wherein (A) is an optical microscope image of the photonic crystal lactic acid sensor and (B) is a magnified view of the selected portion of (A).

[0053] Figure 4 The thermogravimetric analysis diagram, infrared analysis diagram, and component analysis diagram of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention are shown, wherein (A) is the thermogravimetric analysis diagram, (B) is the infrared analysis diagram, and (C) is the component analysis diagram.

[0054] Figure 5 The images show the reflection spectrum, digital photograph of the structural color, and lactic acid response curve of the photonic crystal lactic acid sensor in buffer solutions with different lactic acid concentrations in Example 1 of the present invention, where (A) is the reflection spectrum, (B) is the digital photograph of the structural color, and (C) is the lactic acid response curve.

[0055] Figure 6 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention;

[0056] Figure 7 The image shows an optical microscope image of the photonic crystal lactic acid sensor in Embodiment 1 of the present invention, wherein (A) is a cross-sectional view of the photonic crystal lactic acid sensor in a buffer solution with a lactic acid concentration of 0 mM, and (B) is a cross-sectional view of the photonic crystal lactic acid sensor in a buffer solution with a lactic acid concentration of 20 mM.

[0057] Figure 8 The diagrams shown in Example 1 of this invention are the cycle stability analysis diagram and the response time analysis diagram in buffer solutions with different lactic acid concentrations for the photonic crystal lactic acid sensor. (A) is the cycle stability analysis diagram and (B) is the response time analysis diagram.

[0058] Figure 9 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 2 of the present invention;

[0059] Figure 10 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 3 of the present invention;

[0060] Figure 11 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 4 of the present invention;

[0061] Figure 12This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 5 of the present invention;

[0062] Figure 13 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 6 of the present invention;

[0063] Figure 14 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 7 of the present invention;

[0064] Figure 15 The images show lactic acid response curves of different photonic crystal lactic acid sensors prepared in Example 8 of the present invention, wherein (A) is a lactic acid response curve of a photonic crystal lactic acid sensor attached to a treated polyethylene terephthalate flexible substrate, and (B) is a lactic acid response curve of a photonic crystal lactic acid sensor not attached to a substrate.

[0065] Figure 16 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 9 of the present invention;

[0066] Figure 17 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 10 of the present invention;

[0067] Figure 18 The images show lactic acid response curves of different photonic crystal lactic acid sensors prepared in Example 11 of the present invention, wherein (A) is a lactic acid response curve of a photonic crystal lactic acid sensor attached to a treated polyethylene terephthalate flexible substrate, and (B) is a lactic acid response curve of a photonic crystal lactic acid sensor not attached to a substrate.

[0068] Figure 19 The images shown are digital photographs of the structural colors exhibited by the photonic crystal lactic acid sensor in buffer solutions of different lactic acid concentrations in Example 12 of the present invention, and lactic acid response curves. (A) is a digital photograph of the exhibited structural colors, and (B) is a lactic acid response curve.

[0069] Figure 20 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Embodiment 13 of the present invention;

[0070] Figure 21 This is a lactic acid response curve of the photonic crystal lactic acid sensor in Comparative Example 1 of the present invention;

[0071] Figure 22 This is a digital photograph of the photonic crystal lactic acid sensor in Comparative Example 2 of the present invention;

[0072] Figure 23 The image shows the lactic acid response curve of the photonic crystal lactic acid sensor in Comparative Example 3 of the present invention. Detailed Implementation

[0073] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0074] In this embodiment of the invention, the surface modification method for the PET substrate is as follows: 0.5 g of acrylic acid and 0.2 g of 2-hydroxy-2-methylphenylacetone are dissolved in 1.0 g of dimethyl sulfoxide and dispersed evenly in an ultrasonic cleaner to obtain a modified solution. The modified solution is coated onto a flexible polyethylene terephthalate substrate, cured with ultraviolet light, and then washed with deionized water and dried to obtain the modified PET flexible substrate.

[0075] The surface modification method of the glass substrate is as follows: 3-(isobutenamide)propyltrimethoxysilane is uniformly coated on the glass substrate, placed at room temperature for 2 hours, and then cleaned and dried with anhydrous ethanol to obtain a glass substrate with double bonds attached to the surface.

[0076] The above modification methods can also be replaced by other methods disclosed in the prior art. The modification methods are only applied in this invention and are not considered as inventive points.

[0077] Example 1

[0078] Monodisperse superparamagnetic iron oxide nanoparticles with a particle size of 120 nm were mixed uniformly with N-(2-hydroxyethyl)acrylamide (HEAAm), 3-acrylamidophenylboronic acid (AAPBA), crosslinking agent methylenebisacrylamide (BIS), photoinitiator 2-hydroxy-2-methyl-1-phenylpropanone (HMPP), and solvent dimethyl sulfoxide (DMSO) to form a prepolymer solution. In the prepolymer solution, the concentration of superparamagnetic nanoparticles was 10 mg / mL, the concentration of HEAAm monomer was 2.5 mmol / mL, the concentration of AAPBA monomer was 0.83 mmol / mL, and the concentrations of BIS and HMPP were 0.5% and 0.5% of the total molar amounts of HEAAm and AAPBA monomers, respectively. DMSO was used as the solvent.

[0079] The prepolymer solution was coated onto a surface-modified polyethylene terephthalate flexible substrate and placed under a uniform magnetic field of 400 Gs, with the magnetic field direction perpendicular to the surface of the prepolymer solution. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction in the uniform magnetic field. After standing for 1 min, it was cured with a UV lamp for 5 min to obtain a photonic crystal lactic acid sensor. After the reaction was complete, it was washed with water for 4 minutes. Five times, the photonic crystal lactic acid sensor was finally immersed in a phosphate buffer solution with a pH of 6.0 and a buffer concentration of 0.1M.

[0080] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0081] Figure 1 This is a top view of a digital photograph of the product of this embodiment. As can be seen from the figure, the photonic crystal lactic acid sensor is composed of a flexible polyethylene terephthalate substrate at the bottom and a lactic acid-responsive photonic crystal gel film bound thereon. In this embodiment, the photonic crystal lactic acid sensor is a circle with a diameter of 2 cm. In other embodiments, photonic crystal lactic acid sensors of other shapes and diameters can be made as needed. The function of the photonic crystal lactic acid sensor of this invention is not limited by shape and diameter.

[0082] Figure 2 This is a field emission scanning electron microscope image of the product of this embodiment. The image shows that the gel membrane contains an ordered chain structure with equal particle spacing.

[0083] Figure 3 The images shown are optical microscope images of the product of this embodiment. (A) is an optical microscope image of the photonic crystal lactic acid sensor, and (B) is a magnified view of the selected part of (A). It can be seen from the image that the gel membrane contains an ordered chain structure with equal particle spacing inside.

[0084] Figure 4 (A) is the thermogravimetric analysis spectrum of the product obtained in this embodiment. The organic phase component of the product is 93%, indicating that the gel content in the photonic crystal lactic acid sensor of the present invention is relatively high. Figure 4 Image (B) shows the infrared spectrum of the product obtained in this embodiment, located at 3269 cm⁻¹. -1 1630cm -1 The absorption peaks at 1427 cm⁻¹ are attributed to the stretching vibrations of the N–H group and C=O group of the HEAAm acrylamide group (–CONH–), respectively. -1 1334cm -1 The peak at that point is the stretching vibration peak of the benzene ring skeleton and the BO bond of AAPBA, proving that the gel was obtained by copolymerization of HEAAm and AAPBA. Figure 4 (C) is the component analysis diagram of the product of this embodiment. The composition of the lactic acid responsive gel is: Fe3O4 2.91 wt%; PVP 1.14 wt%; HEAAm 6 5.91 wt%; AAPBA 3 0.04 wt%.

[0085] Tests showed that the lactic acid-responsive photonic crystal gel film of the photonic crystal lactic acid sensor in this embodiment fractured when the tensile stress reached 40 kPa.

[0086] Figure 5 (A) shows the reflectance spectra of the product of this embodiment in buffer solutions with different lactic acid concentrations (0, 5, 10, 15, 20 mM), reflecting the monotonic shift of the Bragg diffraction peak of the sensor towards longer wavelengths as the lactic acid concentration increases. (B) is a digital photograph of the structural color exhibited by the product of this embodiment in buffer solutions with different lactic acid concentrations (0, 5, 10, 15, 20 mM). It can be seen that as the lactic acid concentration increases, the sensor exhibits a clear structural color change visible to the naked eye, with the color starting from purple and then monotonically shifting to red, eventually becoming red. The colors at different lactic acid concentrations in this figure correspond one-to-one with the diffraction peak positions in (A). (C) is a curve of the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 11.5 nm / mm.

[0087] Figure 6 The graph shows the hue values ​​of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 9.8 ° / mM.

[0088] Figure 7 Image (A) is an optical microscope image showing the cross-sectional thickness of the product of this embodiment in a buffer solution with a lactic acid concentration of 0, with a thickness of 24.15 micrometers; Figure 7 Image (B) is an optical microscope image showing the cross-sectional thickness of the product of this embodiment in a buffer solution with a lactic acid concentration of 20 mM, with a thickness of 35.78 micrometers.

[0089] Figure 8 Figure (A) shows the cyclic stability analysis of the photonic crystal lactic acid sensor in this embodiment in a buffer solution with lactic acid concentration of 0-20 mM. The test results show that the response sensitivity of the photonic crystal lactic acid sensor in this embodiment remains stable after 50 cycles. Figure 8 Figure (B) shows the response time analysis of the photonic crystal lactic acid sensor in this embodiment in buffer solutions with lactic acid concentrations of (0, 5, 10, 15, 20 mM). All of them complete 90% of the lactic acid response within 1-2 minutes and reach stability within 5 minutes.

[0090] Example 2

[0091] The difference between this embodiment and Embodiment 1 is that the prepared prepolymer liquid is coated on the surface of an unmodified glass substrate for subsequent operations (without contact with the substrate).

[0092] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0093] Figure 9 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 4.7 nm / mM.

[0094] Example 3

[0095] The difference between this embodiment and Example 1 is that N-(2-hydroxyethyl)acrylamide (HEAAm) is replaced with acrylamide (AM), the substrate is replaced with a surface-modified glass substrate, and the concentrations of BIS and HMPP are 0.5% and 2.0% of the total molar amount of AM and AAPBA monomers, respectively.

[0096] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0097] Figure 10 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 6.1 nm / mM.

[0098] Example 4

[0099] The difference between this embodiment and Example 1 is that N-(2-hydroxyethyl)acrylamide (HEAAm) is replaced with N-isopropylacrylamide (NIPAM), the concentration of superparamagnetic nanoparticles is 30 mg / mL, the concentrations of BIS and HMPP are 3% and 0.25% of the total molar amount of NIPAM and AAPBA monomers, respectively, and the substrate is replaced with a surface-modified glass substrate.

[0100] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 10, 20, 30, 40, 50 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0101] Figure 11The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 10, 20, 30, 40, 50 mM), with a sensitivity of 5.2 nm / mM.

[0102] Example 5

[0103] The prepolymer solution described in Example 1 was prepared and coated onto a surface-modified polyethylene terephthalate flexible substrate. The substrate was then placed under a uniform magnetic field of 100 Gs, with the magnetic field direction perpendicular to the prepolymer solution surface. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction. After standing for 1 minute, the substrate was cured with a UV lamp for 5 minutes to obtain a photonic crystal lactic acid sensor. After the reaction was complete, the substrate was washed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 7.4 and a buffer concentration of 0.08M.

[0104] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0105] Figure 12 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 11.4 nm / mM.

[0106] Example 6

[0107] The difference between this embodiment and Example 1 is that the superparamagnetic iron oxide nanoparticles are replaced with superparamagnetic NiFe2O4 nanoparticles, the concentration of superparamagnetic nanoparticles in the prepolymer solution is 20 mg / mL, and the concentrations of BIS and HMPP are 0.25% and 0.5% of the total molar amounts of HEAAm and AAPBA monomers, respectively.

[0108] After the reaction is complete, wash with water 4 times. Five times, and finally soaked in phosphate buffer solution with a pH of 5.0 and a buffer concentration of 0.2M.

[0109] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20, 25, 30 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0110] Figure 13The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20, 30 mM). It can be seen that the sensitivity of the photonic crystal lactic acid sensor is 11.3 nm / mM in the lactic acid concentration range of 0-20 mM, and the sensitivity is 2 nm / mM in the lactic acid concentration range of 20-30 mM.

[0111] Example 7

[0112] Monodisperse superparamagnetic CoNiFe2O4 nanoparticles with a particle size of 300 nm were dispersed in a prepolymer solution composed of N-hydroxymethylacrylamide (NMA), 3-methylacrylamidophenylboronic acid, a crosslinking agent (methylenebisacrylamide) (BIS), a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone) (HMPP), and dimethylformamide (DMF) as the solvent. The concentration of the superparamagnetic nanoparticles in the prepolymer solution was 0.5 mg / mL, the concentration of NMA monomer was 3 mmol / mL, the concentration of 3-methylacrylamidophenylboronic acid was 1.0 mmol / mL, and the concentrations of BIS and HMPP were 0.5% and 10% of the total molar amounts of NMA and 3-methylacrylamidophenylboronic acid monomers, respectively. DMF was used as the solvent.

[0113] The prepolymer solution was coated onto a surface-modified polyethylene terephthalate flexible substrate and placed under a uniform magnetic field of 700 Gs, with the magnetic field direction perpendicular to the surface of the prepolymer solution. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction in the uniform magnetic field. After standing for 1 min, it was cured with a UV lamp for 5 min to obtain a photonic crystal lactic acid sensor. After the reaction was complete, it was washed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 7.0 and a buffer concentration of 0.1M.

[0114] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0115] Figure 14 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 11 nm / mM.

[0116] Example 8

[0117] Monodisperse superparamagnetic Fe3S4 nanoparticles with a particle size of 90 nm, N-(2-hydroxyethyl)acrylamide (HEAAm), 3-acrylamidophenylboronic acid (AAPBA), ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent, 2-hydroxy-2-methyl-1-phenylpropanone (HMPP) as a photoinitiator, and dimethyl sulfoxide (DMSO) as a solvent were mixed uniformly to form a prepolymer solution. In the prepolymer solution, the concentration of superparamagnetic nanoparticles was 50 mg / mL, the concentration of HEAAm monomer was 7.0 mmol / mL, the concentration of 4-vinylphenylboronic acid monomer was 1.5 mmol / mL, and the concentrations of EGDMA and HMPP were 0.5% and 7% of the total molar amounts of HEAAm and AAPBA monomers, respectively. DMSO was used as the solvent.

[0118] The prepolymer solution was coated onto the surface of an untreated glass substrate and a surface-modified polyethylene terephthalate flexible substrate, respectively. The substrates were then placed under a uniform magnetic field of 200 Gs, with the magnetic field direction perpendicular to the prepolymer solution surface. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction. After standing for 1 minute, the substrates were cured with a UV lamp for 5 minutes to obtain a photonic crystal lactic acid sensor. After the reaction was complete, the photonic crystal lactic acid sensor polymerized on the glass substrate was removed with tweezers and rinsed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 6.0 and a buffer concentration of 0.1M.

[0119] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0120] Figure 15 In Figure (A), the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment, attached to the surface-modified polyethylene terephthalate flexible substrate, are plotted at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 11.3 nm / mM. Figure 15 (B) is a graph showing the Bragg diffraction peak wavelength of the photonic crystal lactic acid sensor without substrate obtained in this embodiment under different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 4.5 nm / mM.

[0121] Example 9

[0122] Monodisperse superparamagnetic iron oxide nanoparticles with a particle size of 60 nm, N-trismethylolacrylamide (NAT), 3-acrylamidophenylboronic acid (AAPBA), crosslinking agent methylenebisacrylamide (BIS), photoinitiator 2-hydroxy-2-methyl-1-phenylpropanone (HMPP), and dimethyl sulfoxide (DMSO) were mixed uniformly to form a prepolymer solution. In the prepolymer solution, the concentration of superparamagnetic nanoparticles was 40 mg / mL, the concentration of NAT monomer was 0.5 mmol / mL, the concentration of AAPBA monomer was 0.5 mmol / mL, and the concentrations of BIS and HMPP were 1.0% and 5.0% of the total molar amounts of NAT and AAPBA monomers, respectively. DMSO was used as the solvent.

[0123] The prepolymer solution was coated onto a surface-modified polyethylene terephthalate flexible substrate and placed under a uniform magnetic field of 1000 Gs, with the magnetic field direction perpendicular to the surface of the prepolymer solution. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction in the uniform magnetic field. After standing for 1 min, it was cured with a UV lamp for 5 min to obtain a photonic crystal lactic acid sensor. After the reaction was complete, it was washed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 6.0 and a buffer concentration of 0.1M.

[0124] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0125] Figure 16 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 7.3 nm / mM.

[0126] Example 10

[0127] Monodisperse superparamagnetic iron oxide nanoparticles with a particle size of 120 nm, N-(2-hydroxyethyl)acrylamide (HEAAm), 3-acrylamidophenylboronic acid (AAPBA), hydroxypropyl methacrylate (HPMA) as a crosslinking agent, 1-hydroxycyclohexylphenyl ketone as a photoinitiator, and a 1:1 volume ratio of water and dimethyl sulfoxide as a solvent were mixed uniformly to form a prepolymer solution. In the prepolymer solution, the concentration of superparamagnetic nanoparticles was 10 mg / mL, the concentration of HEAAm monomer was 10 mmol / mL, the concentration of AAPBA monomer was 5 mmol / mL, and the concentrations of BIS and 1-hydroxycyclohexylphenyl ketone were 2.0% and 0.5% of the total molar amounts of HEAAm and AAPBA monomers, respectively. The 1:1 volume ratio of water and dimethyl sulfoxide was used as the solvent.

[0128] The prepolymer solution was coated onto a surface-modified polyethylene terephthalate flexible substrate and placed under a uniform magnetic field of 200 Gs, with the magnetic field direction perpendicular to the surface of the prepolymer solution. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction in the uniform magnetic field. After standing for 1 min, it was cured with a UV lamp for 5 min to obtain a photonic crystal lactic acid sensor. After the reaction was complete, it was washed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 6.0 and a buffer concentration of 0.1M.

[0129] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0130] Figure 17 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 8.8 nm / mM.

[0131] Example 11

[0132] Monodisperse superparamagnetic NiS nanoparticles with a particle size of 120 nm, N-(2-hydroxyethyl)acrylamide (HEAAm), 4-((2-acrylamidoethyl)carbamoyl)-3-fluorophenyl)boronic acid (AFPBA), hydroxyethyl methacrylate (HEMA) as a crosslinking agent, 2-hydroxy-2-methyl-1-phenylpropanone (HMPP) as a photoinitiator, and dimethyl sulfoxide (DMSO) as the solvent were mixed uniformly to form a prepolymer solution. In the prepolymer solution, the concentration of superparamagnetic nanoparticles was 15 mg / mL, the concentration of HEAAm monomer was 3.0 mmol / mL, the concentration of AAPBA monomer was 0.83 mmol / mL, and the concentrations of HEMA and HMPP were 0.5% and 0.5% of the total molar amounts of HEAAm and AAPBA monomers, respectively. DMSO was used as the solvent.

[0133] The prepolymer solution was coated onto an untreated glass substrate and a surface-modified polyethylene terephthalate flexible substrate, respectively. The substrates were then placed under a uniform magnetic field of 400 Gs, with the magnetic field direction perpendicular to the prepolymer solution surface. Monodisperse superparamagnetic nanoparticles were evenly spaced along the magnetic field direction. After standing for 1 min, the substrates were cured with a UV lamp for 5 min to obtain a photonic crystal lactic acid sensor. After the reaction was complete, the polymerized photonic crystal lactic acid sensor was removed from the glass substrate with tweezers and rinsed with water for 4 minutes. Five times, and finally soaked in phosphate buffer solution with a pH of 6.0 and a buffer concentration of 0.1M.

[0134] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0135] Figure 18 In Figure (A), the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment and attached to the surface-modified polyethylene terephthalate flexible substrate are plotted at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 11.4 nm / mM. Figure 18 (B) is a graph showing the Bragg diffraction peak wavelength of the photonic crystal lactic acid sensor without substrate obtained in this embodiment under different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 4.1 nm / mM.

[0136] Example 12

[0137] The difference between this embodiment and Example 1 is that the concentration of the crosslinking agent BIS is 5.0% of the total molar amount of HEAAm and AAPBA monomers.

[0138] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 10, 20, 30, 40, 50 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0139] Figure 19 (A) is a digital photograph of the structural color of the product of this embodiment in buffer solutions with different lactic acid concentrations (0, 10, 20, 30, 40, 50 mM). It can be seen that as the lactic acid concentration increases, the sensor exhibits a clear structural color change visible to the naked eye, with the color starting from purple and gradually shifting to red, eventually becoming red. The colors at different lactic acid concentrations in this figure correspond one-to-one with the diffraction peaks in (B). (B) is a curve of the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 10, 20, 30, 40, 50 mM), with a sensitivity of 4.2 nm / mM.

[0140] Example 13

[0141] The difference between this embodiment and Example 1 is that the concentration of HEAAm monomer is 10 mmol / mL and the concentration of AAPBA monomer is 0.5 mmol / mL.

[0142] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 10, 20, 30, 40, 50 mM) for later use. 1 ml of each lactic acid solution of different concentrations was added to the photonic crystal lactic acid sensor, and the photonic crystal lactic acid sensor displayed different structural colors.

[0143] Figure 20 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this embodiment at different lactic acid concentrations (0, 10, 20, 30, 40, 50 mM), with a sensitivity of 4.0 nm / mM.

[0144] Comparative Example 1

[0145] The difference between this comparative example and Example 1 is that water is used as the solvent.

[0146] Figure 21 The graph shows the Bragg diffraction peak wavelengths of the photonic crystal lactic acid sensor obtained in this comparative example at different lactic acid concentrations (0, 5, 10, 15, 20 mM), with a sensitivity of 0.25 nm / mM. In Example 1, the photonic crystal lactic acid sensor had a sensitivity of 11.5 nm / mM. The lactic acid-responsive monomer AAPBA used had poor solubility in water, resulting in fewer responsive units in the obtained lactic acid-responsive gel, thus leading to low sensitivity.

[0147] Comparative Example 2

[0148] The difference between this comparative example and Example 1 is that the concentration of HEAAm monomer is 0.5 mmol / mL and the concentration of AAPBA monomer is 1.0 mmol / mL.

[0149] Figure 22 This is a digital photograph of the photonic crystal lactic acid sensor obtained in this comparative example. As can be seen from the image, it only has the intrinsic color of magnetic particles and no obvious structural color.

[0150] Comparative Example 3

[0151] Pod-shaped nanochains were prepared according to the preparation process of Example 1 in patent CN110987820 A.

[0152] Different amounts of lactic acid were dissolved in buffer solution and thoroughly mixed to prepare lactic acid solutions of different concentrations (0, 5, 10, 15, 20 mM) for later use. 1 ml of lactic acid solution of different concentrations was added to the nanochains, and a magnetic field was applied. The nanochains showed different structural colors in the solution.

[0153] Figure 23 The curves of the Bragg diffraction peak wavelengths of the nanochains obtained in this comparative example under different lactic acid concentrations (0, 5, 10, 15, 20 mM) are shown, with a sensitivity of 1.2 nm / mM.

[0154] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0155] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An application of a photonic crystal lactic acid sensor, characterized in that: The photonic crystal lactic acid sensor is used to detect the lactic acid concentration in human sweat. The photonic crystal lactic acid sensor includes a lactic acid-responsive hydrogel matrix membrane and multiple uniformly oriented one-dimensional magnetic nanochains embedded therein. The one-dimensional magnetic nanochains are formed by monodisperse magnetic nanoparticles arranged in a non-closely packed one-dimensional chain. The raw materials for preparing the lactic acid responsive hydrogel matrix membrane include non-lactic acid responsive hydrophilic polymerizable monomers and lactic acid responsive monomers, wherein the lactic acid responsive monomers are monomers containing phenylboronic acid groups; the non-lactic acid responsive hydrophilic polymerizable monomers include at least one of acrylamide, N-(2-hydroxypropyl)methacrylamide, N-(2-hydroxyethyl)acrylamide, N-hydroxymethylacrylamide, and N-trimethylolacrylamide; The fabrication method of the photonic crystal lactic acid sensor includes the following steps; Step 1: Mix monodisperse magnetic nanoparticles with non-lactic acid responsive hydrophilic monomers, lactic acid responsive monomers, crosslinking agents, initiators and dispersion medium solvents to obtain a homogeneous prepolymer solution. Step 2: Place the prepolymer liquid obtained in Step 1 under an external uniform magnetic field to initiate polymerization. After the reaction is complete, the photonic crystal lactic acid sensor is obtained. In step 1, the concentration of magnetic nanoparticles in the prepolymer solution is 0.5-50 mg / mL, the concentration of non-lactic acid responsive hydrophilic polymerizable monomers is 0.5-10 mmol / mL, and the concentration of lactic acid responsive monomers is 0.5-10 mmol / mL. The dispersion medium solvent is at least one of dimethyl sulfoxide, a mixture of water and dimethyl sulfoxide, and dimethylformamide.

2. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: The molar ratio of the non-lactic acid responsive hydrophilic monomer to the lactic acid responsive monomer is 1-20:

1.

3. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: The magnetic nanoparticles include oxides or sulfides containing at least one of iron, cobalt, and nickel, and the particle size of the magnetic nanoparticles is 60-300 nm.

4. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: The thickness of the lactic acid responsive hydrogel matrix membrane is 10-400 μm.

5. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: In step 1, the initiator is 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, potassium persulfate, ammonium persulfate, or azobisisobutyronitrile. The amount of initiator is 0.2%-10% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive polymeric monomers. The crosslinking agent is at least one of methylenebisacrylamide, ethylene glycol dimethacrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. The amount of crosslinking agent is 0.25%-5% of the total molar amount of lactic acid responsive monomers and non-lactic acid responsive hydrophilic polymeric monomers.

6. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: In step 2, the uniform magnetic field strength is 100-1000 Gs.

7. The application of the photonic crystal lactic acid sensor according to claim 1, characterized in that: Step 2 further includes the following steps: coating the prepolymer liquid from step 1 onto the surface of the surface-modified substrate and then placing it under an external uniform magnetic field to initiate polymerization. After the reaction is completed, the substrate-bound photonic crystal lactic acid sensor is obtained.

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