Prussian blue analogues and preparation method and application of composite sensing film thereof

Abstract

The application provides a preparation method and application of a Prussian blue analogue and a composite sensing film thereof, and belongs to the technical field of Prussian blue analogues, wherein a Prussian blue analogue with high catalytic activity and in a uniform spherical shape can be prepared by hydrothermal reaction of a glucose-assisted soluble transition metal hexacyanide salt and a soluble transition metal salt. After the Prussian blue analogue is combined with a flexible substrate, a composite sensing film with flexibility, air permeability and tailorability can be prepared by electrospinning. The composite sensing film can also be applied to diapers. The application is beneficial to solving the technical problems of Prussian blue analogue morphology control difficulty, particle agglomeration and inability to be flexibly integrated into a wearable body.

Description

Technical Field

[0001] This invention relates to the field of Prussian blue analogues, specifically to the preparation methods and applications of Prussian blue analogues and their composite sensing membrane materials. Background Technology

[0002] As a biological fluid, urine carries a wealth of physiological and pathological information in its chemical composition. For diabetic patients, insufficient insulin secretion or insulin resistance can lead to elevated blood glucose levels. Urine glucose concentration directly reflects the degree of glucose metabolism disorder in the body and is a key indicator for auxiliary screening and diabetes management in diabetic patients.

[0003] Natural horseradish peroxidase (HRP) is the core catalyst in urine glucose colorimetric detection systems, possessing advantages such as high substrate specificity, high catalytic efficiency, and good biocompatibility. However, most natural HRPs are proteases, which have disadvantages such as high cost, poor stability, easy inactivation, and difficulty in recycling, limiting the large-scale promotion and practical application of point-of-care testing (POCT) technology. Currently, the development direction of alternatives to natural enzymes has attracted widespread attention.

[0004] Prussian blue analogues (PBAs) are a class of three-dimensional coordination polymers with a face-centered cubic open framework structure, as shown in the schematic diagram below. Figure 1 As shown, the general formula can be expressed as In this model, A represents potassium, lithium, or sodium, while M1 and M2 represent transition metal ions (such as Fe, Co, Ni, and Cu). Although PBA materials exhibit catalytic performance similar to HRP, their regulatory mechanisms are unclear, making it difficult to obtain PBA materials with good catalytic performance, high detection sensitivity, and high stability for the detection of urinary glucose. Furthermore, most existing PBA materials are used in the form of nano-dispersions, and the particles in these dispersions are prone to aggregation, thus limiting their applications. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a method for preparing Prussian blue analogues and their composite sensing films and their applications, aiming to solve the technical problems of difficult morphology control, easy particle agglomeration, and inability to flexibly integrate PBA materials into wearable bodies.

[0006] In a first aspect, embodiments of this application provide a method for preparing a Prussian blue analogue, comprising the following steps: S1, Dissolve a soluble transition metal hexacyano salt and glucose in water to obtain the first mixture; S2, dissolve a soluble transition metal salt in water to obtain a second mixture; S3, the first mixture is added to the second mixture, and after thorough stirring, a hydrothermal reaction is carried out to obtain a Prussian blue analogue.

[0007] Furthermore, the molar ratio of the soluble transition metal hexacyano salt, the soluble transition metal salt, and glucose is 1~1.5:1~1.5:3.3~5.

[0008] Furthermore, in step S1, the soluble transition metal hexacyano salt includes any one or a combination of two of sodium ferrocyanide and potassium ferrocyanide.

[0009] Furthermore, in step S2, the soluble transition metal salt includes any one or a combination of two or more of the transition metal chloride, transition metal sulfate, and transition metal nitrate.

[0010] Furthermore, in step S2, the transition metal in the soluble transition metal salt includes any one or a combination of two or more of Fe, Co, Ni, and Cu.

[0011] Furthermore, in step S3, the hydrothermal reaction temperature is 110~140℃ and the time is 12~20h.

[0012] Secondly, embodiments of this application provide a Prussian blue analogue, prepared by the preparation method described in the first aspect.

[0013] Furthermore, the Prussian blue analogue has a spherical morphology with a particle size of 100-160 nm and a pure cubic crystal structure, containing Fe. 2+ / Fe 3+ The ratio is 2.2~2.3, the Michaelis constant for H2O2 is 0.18~0.2mM, and the detection limit for glucose is as low as 1.1~1.15 μM.

[0014] Thirdly, embodiments of this application provide a composite sensing membrane, including a flexible substrate and a sensing material loaded in the flexible substrate; the sensing material includes a Prussian blue analog prepared by the preparation method described in the first aspect or a Prussian blue analog as described in the second aspect.

[0015] Fourthly, embodiments of this application provide a method for preparing a composite sensing membrane, comprising: mixing a flexible polymer and a Prussian blue analogue and dispersing them in a solvent to obtain a spinning solution; electrospinning the spinning solution to obtain a composite sensing membrane; wherein the Prussian blue analogue includes the Prussian blue analogue prepared by the preparation method described in the first aspect or the Prussian blue analogue described in the second aspect.

[0016] Furthermore, the flexible polymer includes any one or a combination of two or more of polycaprolactone, polyurethane, polyethylene terephthalate, chitosan, sodium alginate, gelatin, and silk fibroin.

[0017] Furthermore, the mass ratio of the flexible polymer to the Prussian blue analogue is 1.2:(0.05~0.25).

[0018] Furthermore, the electrospinning process parameters include: positive pressure 8~15kV, negative pressure 6~10kV, and feed rate 2~3mL / h.

[0019] Fifthly, embodiments of this application provide the application of the composite sensing membrane described in the third aspect or the composite sensing membrane prepared by the preparation method described in the fourth aspect in diapers.

[0020] The beneficial effects of this application are as follows: The method for preparing Prussian blue analogues provided in this application involves dissolving a soluble transition metal hexacyano salt and glucose in water to obtain a first mixture, then dissolving the soluble transition metal salt in water to obtain a second mixture. The first mixture is then added to the second mixture and stirred thoroughly before a hydrothermal reaction is carried out. This method can directionally prepare uniform, spherical, highly active PBA materials. The synthesis process is simple, low-cost, and easy to scale up. Its Michaelis constants for H2O2 and TMB are 0.19 mM and 0.17 mM, respectively, which are lower than the Michaelis constant of 3.7 mM for natural horseradish peroxidase, indicating that it has a higher affinity for both substrates.

[0021] The method for preparing the composite sensing membrane provided in this application combines physical blending with electrospinning processes to uniformly disperse PBA in a flexible substrate. The resulting composite sensing membrane possesses both good flexibility and catalytic activity. Furthermore, when the composite sensing membrane is placed between the skin-friendly surface layer and the absorbent layer of a diaper, it can effectively distinguish between healthy and pathological states through visually perceptible color changes within a glucose concentration range of 0.5-1.5 mM. It exhibits good anti-interference capabilities in simulated urine systems, making it suitable for daily home urine glucose monitoring for special groups such as infants, disabled elderly, and patients with urinary incontinence.

[0022] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0024] Figure 1It has a face-centered cubic structure similar to Prussian blue; Figure 2 Morphological characterization images of the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3; Figure 3 EDS elemental distribution maps of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3; Figure 4 Morphology and EDS elemental distribution diagrams of the composite sensing films prepared in Examples 6 and 8; Figure 5 Crystal structure characterization diagrams of the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3; Figure 6 The surface chemical state analysis diagrams are shown for the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3. Figure 7 The surface-enhanced Raman spectra of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 8 Nitrogen adsorption-desorption isotherms and corresponding pore size distribution diagrams of Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3. Figure 9 The glucose colorimetric sensing performance test charts of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 are shown. Figure 10 The glucose colorimetric sensing performance test results of the composite sensing membranes prepared in Examples 6 and 8 are shown. Figure 11 A color comparison chart of diaper integration and simulated urine detection. Detailed Implementation

[0025] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0027] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0031] In the preparation of Prussian blue analogues, on the one hand, there is a lack of systematic morphology control methods, making it impossible to directionally prepare highly active, uniform spherical PBA materials; on the other hand, PBA sensing materials are mostly used in the form of dispersions, leading to easy particle aggregation and making flexible integration into wearable devices impossible. Currently, composite sensing membranes generally suffer from severe embedding of active sites, low mass transfer efficiency, and weak colorimetric response. Furthermore, the high absorbency of diaper substrates leads to rapid urine diffusion and loss, resulting in insufficient reaction time for the sensing membrane and preventing stable visual detection.

[0032] To address the technical challenges of controlling the morphology of Prussian blue analogues, their tendency to agglomerate, and their inability to be flexibly integrated into wearable devices, this application provides a method for preparing Prussian blue analogues and their composite sensing membranes, as well as their applications. Specifically, a glucose-assisted hydrothermal reaction between a soluble transition metal hexacyano salt and a soluble transition metal salt allows for the directional preparation of uniform, spherical, highly active Prussian blue analogues. This Prussian blue analogue, after being composited with a flexible substrate and then electrospun, can produce a composite sensing membrane that is flexible, breathable, and customizable. This composite sensing membrane can also be applied to diapers for home-based, visual detection of urinary glucose.

[0033] In a first aspect, embodiments of this application provide a method for preparing a Prussian blue analogue, comprising the following steps: S1, Dissolve a soluble transition metal hexacyano salt and glucose in water to obtain the first mixture; S2, dissolve a soluble transition metal salt in water to obtain a second mixture; S3, the first mixture is added to the second mixture, and after thorough stirring, a hydrothermal reaction is carried out to obtain a Prussian blue analogue.

[0034] In this process, glucose acts as a crystal growth regulator. It contains multiple ortho-hydroxyl groups, which can coordinate with metal ions in soluble transition metal salts, reducing the concentration of the free metal ions in the system and thus slowing down the coordination precipitation reaction rate of the metal ions with the hexacyanate metal ions in soluble transition metal hexacyano salts. At the same time, glucose also acts as a small molecule soft template. During the growth of PBA crystals, it selectively adsorbs onto the high-energy crystal faces of PBA grains, occupies the active sites on the high-energy crystal faces, raises the originally low growth energy barrier of the high-energy crystal faces, thereby reducing the difference in growth energy barriers between crystal faces and inhibiting anisotropic crystal growth. In addition, glucose and its degradation products partially remain on the surface of PBA particles, forming steric hindrance and inhibiting the aggregation of PBA nanoparticles, ultimately forming spherical PBA particles with regular morphology and uniform particle size.

[0035] More specifically, in the embodiments of this application, when introducing glucose, the method adopted is to prepare a first solution by mixing a soluble transition metal hexacyano salt with glucose. Compared with mixing glucose with a soluble transition metal salt, the free Fe of glucose can be released simultaneously. 3+ The system utilizes a dual mechanism of slow-release regulation and a soft template for crystal growth, relying on the ortho-hydroxyl groups of glucose molecules and trace amounts of free Fe subsequently entering the system. 3+ The formation of weak coordination bonds continuously reduces the instantaneous free Fe in the system. 3+ Concentration, gradual Fe 3+ With [Fe(CN)6] 4- The coordination precipitation rate is improved; simultaneously, glucose can selectively adsorb high-energy crystal planes of PBA grains, inhibiting anisotropic crystal growth, ultimately obtaining homogeneous spherical PBA products with a pure cubic phase of 100~160 nm, and also removing Fe from the surface. 2+ / Fe 3+ The ratio was stably controlled within the optimal catalytic range of 2.2 to 2.3, ensuring the efficiency of the peroxidase-like ping-pong catalytic cycle, improving the affinity for H2O2 and TMB substrates, and optimizing the glucose detection limit.

[0036] It can be noted that, in some embodiments, replacing the premixing agent with premixing glucose with a soluble transition metal salt will produce two types of irreversible negative reactions: first, glucose, as a weak reducing aldose, will react with oxidizing Fe... 3+ Premature occurrence of sustained redox side reactions directly alters the intrinsic iron ion valence ratio in the system, resulting in Fe... 2+ / Fe 3+ The ratio deviates significantly from the optimal range, disrupting the ping-pong catalytic cycle of peroxidase-like enzymes, significantly reducing substrate affinity and degrading glucose detection performance; secondly, glucose prematurely chelates a large amount of Fe.3+ [Fe(CN)6] was subsequently added dropwise. 4- When in solution, the local cyanide concentration is instantaneously supersaturated, triggering explosive disordered nucleation and generating agglomerates that are a mixture of ultrafine fragments and large grains. The grain size distribution is extremely wide, and at the same time, it is easy to induce the formation of rhombohedral phase impurities, making it impossible to obtain a regular spherical pure cubic phase PBA.

[0037] Furthermore, in some embodiments, when adding the first mixture to the second mixture, a peristaltic pump is preferably used to add the first mixture dropwise at a uniform rate to the second mixture. This operation results in a mixture rich in [Fe(CN)6]. 4- The first mixture continuously and uniformly enters with excess Fe 3+ The second mixed liquid system with the base is maintained at an extremely low instantaneous free cyanide concentration, which ensures that the coordination precipitation reaction rate is uniform and controllable, the nucleation and grain growth processes proceed synchronously and stably, and the synthesis kinetics of uniform nanoparticles are matched, ultimately resulting in spherical PBA particles with narrow particle size distribution and excellent dispersibility.

[0038] It can be noted that, in some embodiments, when the order of addition is reversed, the second mixture containing iron salts is added dropwise to the mixture rich in [Fe(CN)6]. 4- The first mixture has an extremely high cyanide concentration at the base and a small amount of Fe. 3+ Upon entry, the local ion supersaturation increases sharply, and a large number of amorphous ultrafine crystal nuclei erupt instantly. The small crystal grains that precipitate earlier continue to serve as secondary heterogeneous nucleation sites, constantly inducing new crystals to deposit on the surface, ultimately causing severe particle agglomeration and uneven grain size.

[0039] Furthermore, in some embodiments, the molar ratio of the soluble transition metal hexacyano salt, the soluble transition metal salt, and glucose is 1~1.5:1~1.5:3.3~5; and / or, Soluble transition metal hexacyano salts include any one or a combination of two of sodium ferrocyanide and potassium ferrocyanide; and / or, Soluble transition metal salts include any one or more combinations of transition metal chlorides, transition metal sulfates, and transition metal nitrates; and / or, The transition metals in soluble transition metal salts include any one or a combination of two or more of Fe, Co, Ni, and Cu.

[0040] In the technical solution of this application embodiment, the cyano group in the soluble transition metal hexacyano salt and the metal ion in the soluble transition metal salt form a three-dimensional network structure through bridging. By adjusting the added precursor, the particle structure can be changed, crystal defects can be improved, and the rate of coordination precipitation reaction can be optimized, thereby directionally controlling the structure and performance of PBA material.

[0041] Furthermore, in some embodiments, the hydrothermal reaction temperature is 110~140°C and the time is 12~20h.

[0042] In the technical solution of this application embodiment, under suitable hydrothermal reaction temperature and time, PBA crystals can be formed slowly and uniformly, taking into account both moderate crystallinity and good dispersibility; at the same time, under hydrothermal conditions, glucose can act as a weak reducing agent to reduce the metal ions in the system to the metal ions in the lower valence state, thereby regulating the nucleation and growth of PBA crystals in the system.

[0043] Secondly, embodiments of this application provide a method for preparing a Prussian blue analogue, which is prepared by the method of the first aspect.

[0044] Among them, the three-dimensional coordination polymer with an open framework formed by the hydrothermal reaction of glucose-assisted soluble transition metal hexacyano salt and soluble transition metal salt has a uniform particle morphology and moderate crystallinity, which solves the technical problems of traditional Prussian blue analogues such as difficulty in morphology control, easy particle aggregation, and inability to be flexibly integrated into wearable bodies.

[0045] Furthermore, in some embodiments, the Prussian blue analogue has a spherical morphology with a particle size of 100-160 nm and a pure cubic crystal structure, containing Fe. 2+ / Fe 3+ The ratio is 2.2~2.3, the Michaelis constant for H2O2 is 0.18~0.2mM, and the detection limit for glucose is as low as 1.1~1.15 μM.

[0046] In the technical solution of this application embodiment, PBA consists of uniform spherical particles with a particle size of 100-160 nm. This size ensures sufficient specific surface area and exposure of active sites while avoiding the problems of easy agglomeration and sedimentation of ultra-small particles. The pure cubic phase structure of PBA crystals has moderate lattice defects, and thus possesses both catalytic activity and chemical stability. In this reaction system, Fe... 2+ / Fe 3+ The ratio is 2.2~2.3, and the Fe content in the system is... 2+ Catalytic decomposition of H2O2 and its oxidation to Fe 3+ The generated Fe 3+ Re-catalytic oxidation of TMB and reduction back to Fe 2+ This meets the electron transfer requirements of the ping-pong mechanism catalyzed by peroxidase-like enzymes; the Michaelis constants (Km) of this PBA material for H2O2 and TMB are much lower than those for natural horseradish peroxidase, indicating that PBA has a higher affinity for both substrates; its linear correlation coefficient R in the glucose concentration range of 0.1–50 μM is [missing value]. 2With a sensitivity of 0.9888 and a detection limit as low as 1.11μM, it combines high sensitivity with high stability, making it suitable for practical testing scenarios.

[0047] Thirdly, embodiments of this application provide a composite sensing membrane, including a flexible substrate and a sensing material loaded in the flexible substrate; the sensing material includes a Prussian blue analog prepared by the preparation method of the first aspect or a Prussian blue analog prepared by the second aspect.

[0048] The flexible substrate provides a uniform loading carrier and good mechanical flexibility. The Prussian blue analogue loaded inside the substrate has high catalytic stability and can respond quickly to the detection substrate. Through the synergistic effect of the flexible substrate and the Prussian blue analogue, the composite sensing membrane has both flexibility and high sensitivity.

[0049] Fourthly, embodiments of this application provide a method for preparing a composite sensing membrane, comprising: mixing a flexible polymer and a Prussian blue analogue and dispersing them in a solvent to obtain a spinning solution; electrospinning the spinning solution to obtain a composite sensing membrane; the Prussian blue analogue includes the Prussian blue analogue prepared by the method of the first aspect or the Prussian blue analogue of the second aspect.

[0050] In this method, flexible polymers and Prussian blue analogues are co-dispersed in a solvent to form a uniform and stable spinning solution. Electrospinning is then used to achieve uniform composite of PBA in a flexible substrate, which solves the problem of difficult recovery and integration of PBA dispersion.

[0051] Furthermore, in some embodiments, the flexible polymer includes any one or a combination of two or more of polycaprolactone, polyurethane, polyethylene terephthalate, chitosan, sodium alginate, gelatin, and silk fibroin.

[0052] In the technical solution of this application embodiment, the flexible polymer has good biocompatibility and can stably encapsulate and disperse Prussian blue analogues. The resulting composite sensing membrane is stretchable, bendable, and cuttable, and has good flexibility and stability.

[0053] Furthermore, in some embodiments, the mass ratio of the flexible polymer to the Prussian blue analogue is 1.2:(0.05~0.25).

[0054] In the technical solution of this application embodiment, the mass ratio of flexible polymer to Prussian blue analogue is controlled within a suitable range of 1.2:(0.05~0.25). The sufficient PBA content in this range can provide sufficient redox active sites, ensuring that the composite sensing membrane has high sensitivity. At the same time, the sufficient proportion of flexible polymer can uniformly encapsulate and disperse PBA particles, effectively inhibiting particle agglomeration caused by excessive PBA. This mass ratio range has both spinning stability and high sensitivity sensing performance.

[0055] Furthermore, in some embodiments, the process parameters for electrospinning include: positive pressure 8~15kV, negative pressure 6~10kV, and feed rate 2~3mL / h.

[0056] In the technical solution of this application embodiment, the voltage range can avoid the problems of insufficient low-voltage stretching causing droplets and high-voltage electric field disorder causing uneven fiber thickness, resulting in a more regular fiber structure; the feed rate of 2~3mL / h can supply liquid at a uniform speed, preventing the accumulation of spinning solution or fiber breakage.

[0057] This application provides the application of composite sensing membranes prepared by the third aspect or the fourth aspect in diapers.

[0058] The composite sensing membrane's excellent flexibility and biocompatibility allow it to adhere to the skin surface. Furthermore, the electrospun fiber membrane possesses a porous structure, providing excellent mass transfer channels for reactants and facilitating rapid urine penetration and contact with active substances within the membrane. Simultaneously, this composite sensing membrane can catalyze the production of H2O2 from glucose via glucose oxidase (GOx), and PBA catalyzes the oxidation of the substrate TMB by H2O2, resulting in a blue color. Without complex instruments, urine glucose levels can be monitored simply by observing the color change with the naked eye. This diaper with integrated sensing function offers multiple advantages, including non-invasive wear, automatic sampling, and immediate detection, making it suitable for daily diabetes screening and long-term metabolic monitoring in special groups such as infants, disabled elderly, and patients with urinary incontinence.

[0059] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0060] I. Preparation Method Example 1 This embodiment provides a method for preparing a Prussian blue analogue, including the following steps: S1, 1.4522 g sodium ferrocyanide decahydrate (0.003 mol) and 1.9817 g glucose monohydrate (0.01 mol) were dissolved in 10 mL of distilled water to obtain the first mixture; S2, Dissolve 0.8109 g of ferric chloride hexahydrate (0.003 mol) in 10 mL of distilled water to obtain the second mixture; S3, the first mixture was added dropwise to the second mixture at a constant rate using a peristaltic pump, and the mixture was magnetically stirred at 25°C and 500 r / min for 10 min, then sealed and placed in an oven at 120°C for hydrothermal reaction for 16 h. After the reaction was completed, the mixture was centrifuged, washed three times each with distilled water and anhydrous ethanol, and dried under vacuum at 100°C for 24 h to obtain the Prussian blue analogue (PBA-2).

[0061] Example 2 This embodiment provides a method for preparing a Prussian blue analogue. Compared with Example 1, the only difference is that in step S1, 2.9725 g (0.015 mol) of glucose monohydrate is added so that the molar ratio of soluble transition metal hexacyano salt, soluble transition metal salt, and glucose is 1:1:5. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0062] Example 3 This embodiment provides a method for preparing a Prussian blue analogue. Compared with Example 1, the only difference is that in step S1, sodium ferrocyanide decahydrate is replaced with 0.9878 g (0.003 mol) of anhydrous potassium ferrocyanide. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0063] Example 4 This embodiment provides a method for preparing a Prussian blue analogue. Compared with Example 1, the only difference is that in step S3, the hydrothermal reaction temperature is 130°C. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0064] Example 5 This embodiment provides a method for preparing a Prussian blue analogue. Compared with Example 1, the only difference is that in step S3, the hydrothermal reaction time is 18 hours. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0065] Example 6 This embodiment provides a method for preparing a composite sensing membrane, comprising: mixing 1.2g of polycaprolactone and 0.05g of the Prussian blue analog prepared in Example 1, dispersing the mixture in 12mL of chloroform / methanol solvent (5:1 v / v), magnetically stirring at 60℃ and 500r / min for 15h to obtain a spinning solution, electrospinning the spinning solution using a positive pressure of 10kV, a negative pressure of 8kV, and a feed rate of 2mL / h, and drying at 25℃ for 6h to obtain the composite sensing membrane.

[0066] Example 7 This embodiment provides a method for preparing a composite sensing membrane. Compared with Example 6, the only difference is that the flexible polymer is polyethylene terephthalate. Other experimental parameters and conditions are basically the same as those in Example 6, and will not be repeated here.

[0067] Example 8 This embodiment provides a method for preparing a composite sensing membrane. Compared with Example 6, the only difference is that the amount of Prussian blue analogue prepared in Example 1 is changed to 0.25g. Other experimental parameters and conditions are basically the same as in Example 6, and will not be repeated here.

[0068] Example 9 This embodiment provides a method for preparing a composite sensing membrane. Compared with Example 6, the only difference is that the electrospinning parameters are: positive voltage 12kV, negative voltage 10kV, and feed rate 3mL / h. Other experimental parameters and conditions are basically the same as those in Example 6, and will not be repeated here.

[0069] Example 10 This embodiment provides a method for preparing a composite sensing membrane. Compared with Example 6, the only difference is that the electrospinning parameters are: positive voltage 8kV, negative voltage 6kV, and feed rate 2.5mL / h. Other experimental parameters and conditions are basically the same as those in Example 6, and will not be repeated here.

[0070] Comparative Example 1 This comparative example provides a method for preparing a Prussian blue analogue, comprising the following steps: S1, dissolve 1.4522g of sodium ferrocyanide decahydrate in 10mL of distilled water to obtain the first mixture; S2, Dissolve 0.8109g of ferric chloride hexahydrate in 10mL of distilled water to obtain the second mixture; S3, the first mixture was added dropwise to the second mixture at a constant rate using a peristaltic pump, and the mixture was magnetically stirred at 25°C and 500 r / min for 10 min, then sealed and placed in an oven at 120°C for hydrothermal reaction for 12 h. After the reaction was completed, the mixture was centrifuged, washed three times each with distilled water and anhydrous ethanol, and dried under vacuum at 100°C for 24 h to obtain the Prussian blue analogue (PBA-1).

[0071] Comparative Example 2 This comparative example provides a method for preparing a Prussian blue analogue, comprising the following steps: S1, dissolve 0.9681g sodium ferrocyanide decahydrate and 1.9817g glucose monohydrate in 10mL of distilled water to obtain the first mixture; S2, dissolve 0.4899g of ferric citrate in 10mL of distilled water to obtain the second mixture; S3, the first mixture was added dropwise to the second mixture at a constant rate using a peristaltic pump, and the mixture was magnetically stirred at 25°C and 500 r / min for 10 min, then sealed and placed in an oven at 120°C for hydrothermal reaction for 16 h. After the reaction was completed, the mixture was centrifuged, washed three times each with distilled water and anhydrous ethanol, and dried under vacuum at 100°C for 24 h to obtain the Prussian blue analogue (PBA-3).

[0072] Comparative Example 3 This comparative example provides a method for preparing a Prussian blue analogue, comprising the following steps: S1, Dissolve 0.9681g of sodium ferrocyanide decahydrate in 10mL of distilled water to obtain the first mixture; S2, dissolve 0.4899g of ferric citrate in 10mL of distilled water to obtain the second mixture; S3, the first mixture was added dropwise to the second mixture at a constant rate using a peristaltic pump, and the mixture was magnetically stirred at 25°C and 500 r / min for 10 min, then sealed and placed in an oven at 120°C for hydrothermal reaction for 12 h. After the reaction was completed, the mixture was centrifuged, washed three times each with distilled water and anhydrous ethanol, and dried under vacuum at 100°C for 24 h to obtain the Prussian blue analogue (PBA-4).

[0073] II. Testing Methods 1. Scanning Electron Microscopy (SEM) Testing The pure PBA / PCL films prepared in Examples 1 and 1-3, as well as the PBA / PCL composite films prepared in Examples 6 and 8, were characterized by SEM to observe the surface morphology and microstructure of the samples. A Hitachi SU5000 field emission scanning electron microscope was used. Before testing, a small amount of sample was placed on the electron microscope stage, fixed with conductive adhesive, and then sputter-coated with gold in a vacuum environment to enhance its conductivity. Images were acquired at different magnifications under an accelerating voltage of 5.0 kV.

[0074] 2. Energy Dispersive Spectrometer (EDS) Test EDS was used in conjunction with SEM to analyze the types and contents of surface elements in PBA prepared in Example 1, Comparative Examples 1-3, and PBA / PCL composite membranes prepared in Example 6 and Example 8.

[0075] 3. Transmission electron microscopy (TEM) testing The PBA powder samples prepared in Example 1 and Comparative Examples 1-3 were characterized by TEM to observe their particle morphology and microcrystalline structure. A JEM-2100P transmission electron microscope was used. Before testing, a small amount of PBA powder sample was taken and dispersed in anhydrous ethanol, and ultrasonically dispersed for 5-10 minutes to prepare a uniform suspension. A small amount of suspension was pipetted onto the copper grid of the carbon support film, and after the solvent evaporated naturally, it was placed in the sample stage. Images were acquired at different magnifications under an accelerating voltage of 120 kV. Similarly, the PBA / PCL composite films prepared in Examples 6 and 8 were characterized by TEM.

[0076] 4. X-ray diffraction system (XRD) testing The structures of the PBA materials prepared in Example 1 and Comparative Examples 1-3, and the PBA / PCL composite films prepared in Examples 6 and 8 were characterized using a PANalytical Empyrean X-ray diffraction system. A Cu Kα radiation source (λ = 1.5406 Å) was used, with a scanning range (2θ) of 10° to 80° and a scanning step size of 0.02°. The scanning time was 30 min. The obtained spectra were compared with the JCPDS standard card library to determine the phase composition.

[0077] 5. X-ray photoelectron spectroscopy (XPS) testing The elemental composition and chemical states of the sample surface were analyzed using a Shimadzu AXIS SUPRA X-ray photoelectron spectrometer. A monochromatic Al Kα X-ray source (1486.6 eV) was used, and the binding energy was calibrated at C1s = 284.8 eV. Peak fitting of the high-resolution spectrum was performed using Avantage software.

[0078] 6. Confocal Raman Microscope Testing The measurements were performed using a HORIBA LabRAM Odyssey confocal microRaman spectrometer. A 532 nm laser was used as the excitation source, with an objective magnification of 50×, a grating of 600 gr / mm, and a spectral acquisition range of 2000 to 2200 cm⁻¹. -1 The laser power was 1%, maintained at 1.87 mW, and the total exposure time was 15 s (5 s × 3). The imaging mode was point-by-point scanning, the selected area was 6 μm × 6 μm, the acquisition time was 1 s, and the number of acquisitions was 1.

[0079] 7. Specific Surface Area and Pore Size Analyzer (BET) The specific surface area and pore size were analyzed using a JW-BK series fully automated analyzer. Before testing, approximately 50-100 mg of sample was placed in a sample tube and pretreated under vacuum at 80°C for 12 hours. Subsequently, nitrogen adsorption-desorption isotherms were measured at liquid nitrogen temperature (77 K). High-purity nitrogen was used as the adsorbate gas, and the relative pressure (P / P0) range was set to 0.05-0.99.

[0080] 8. Performance test of PBA glucose colorimetric sensor Prepare a 1 mg / mL GOx solution with pH 4.5 by dissolving GOx in HAc-NaAc buffer. Prepare a 0.5 mM TMB working solution and a 0.2 mg / mL LPA dispersion. Take 1 mL of LPA dispersion, 0.5 mL of GOx solution, and 2.5 mL of TMB working solution, and add 1 mL of glucose standard solution with concentrations of 0.1, 0.5, 1, 5, 10, 20, and 50 μM, respectively. Add 1 mL of HAc-NaAc buffer to the blank group. Adjust the volume to 10 mL. Incubate at 30°C in a light-protected water bath for 15 min, and then let stand at room temperature in the dark for 3 h. Measure the absorbance at 652 nm using a TU-1950 UV-Vis spectrophotometer and plot a standard curve.

[0081] 9. Testing the glucose colorimetric sensing performance of the composite sensing membrane Prepare a 1 mg / mL GOx solution with pH 4.5 by dissolving GOx in HAc-NaAc buffer, and prepare a 0.5 mM TMB working solution. Take one composite sensing membrane prepared in Example 6 (with the same PBA content as in Test 8) or Example 8 (with the same area as one composite membrane prepared in Example 6), 0.5 mL of GOx solution, 2.5 mL of TMB working solution, and add 1 mL of glucose standard solution with concentrations of 0.1, 0.5, 1, 5, 10, 20, and 50 μM, respectively. Add 1 mL of HAc-NaAc buffer to the blank group. Adjust the volume to 10 mL. Incubate at 30°C in a constant temperature water bath in the dark for 15 min, and let stand at room temperature in the dark for 3 h. Use a TU-1950 UV-Vis spectrophotometer to measure the absorbance at a wavelength of 652 nm and plot a standard curve.

[0082] 10. Diaper Integration and Simulated Urine Detection Using 165 mg urea, 35 mg sodium chloride, and 3 mg uric acid as the urine background, 0.5 mL of GOx solution, 2.5 mL of TMB working solution, and 1 mL of glucose standard solutions with concentrations of 0.5, 1.0, and 1.5 mM, respectively, were added to the urine background. The mixture was then brought to a final volume of 10 mL using HAc-NaAc buffer. A blank control group (without glucose) was used to obtain simulated urine with glucose concentrations of 0, 0.5, 1.0, and 1.5 mM. Commercially available diapers were cut into 2 cm × 2 cm pieces. The skin-friendly outer layer and absorbent layer were peeled off. A 0.25 g loaded PBA / PCL composite membrane prepared in Example 8 was sandwiched between the two layers, restoring the original layered structure. The mixture was placed in a 30°C constant temperature water bath in the dark for 3 hours. After the reaction, the absorbance was measured at a wavelength of 652 nm, and the color change of the solution was recorded.

[0083] III. Analysis of Test Results for Each Embodiment and Comparative Example Morphological characterization images of the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 2 As shown, ah are scanning electron microscope images of Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively; il are transmission electron microscope images of Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0084] Depend on Figure 2 It can be seen that the Prussian blue analogue (PBA-2) prepared in Example 1 is a uniform nanosphere with a particle size of 100-160 nm; the Prussian blue analogue (PBA-1) prepared in Comparative Example 1 is an irregular nanosphere with a particle size of less than 100 nm; the Prussian blue analogue (PBA-3) prepared in Comparative Example 2 is a micron-sized cubic shape with a particle size of 2.2-3.9 μm; and the Prussian blue analogue prepared in Comparative Example 3 (PBA-4) is a micron-sized cubic shape with a particle size of 5-9 μm. This indicates that when ferric citrate is used as an iron source, its inherent citrate chelating groups bind Fe. 3+ Slow release eventually forms large micron-sized cubes; when ferric chloride is used as the iron source, its free Fe... 3+ The reaction rate is fast, enabling rapid and explosive nucleation. Glucose, as an additive, can regulate the morphology of PBA particles and inhibit their aggregation, ultimately forming nanospheres with uniform morphology. Furthermore, the Michaelis constant Km of the PBA material prepared in Example 1 is 0.19 mM with H2O2 as the substrate and 0.17 mM with TMB as the substrate. In contrast, the Km values ​​of horseradish peroxidase for H2O2 and TMB are 3.7 mM and 0.434 mM, respectively. Therefore, the PBA nanozyme synthesized in Example 1 has a higher affinity for H2O2 and TMB.

[0085] EDS elemental distribution maps of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 3 As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0086] Depend on Figure 3 It can be seen that the prepared Prussian blue particles all contain four elements: Fe, C, N, and O, without any impurities. Moreover, each element is uniformly distributed within the particles, which highly corresponds to the morphology, confirming that the sample composition is uniform and of good purity.

[0087] The morphology and EDS elemental distribution diagrams of the composite sensing films prepared in Examples 6 and 8 are shown below. Figure 4 As shown, a is a pure PCL membrane; b is a 0.05g PBA / PCL composite membrane; c is a 0.25g PBA / PCL composite membrane; di are SEM images of the pure PCL membrane, 0.05g PBA / PCL composite membrane, and 0.25g PBA / PCL composite membrane, respectively; jk are TEM images of the two PBA / PCL composite membranes, respectively; lm are EDS surface scan images of the two PBA / PCL composite membranes, respectively.

[0088] Depend on Figure 4 It can be seen that the pure PCL electrospun film has a uniform fiber distribution and a smooth, continuous surface. After PBA modification, the PBA / PCL composite film still maintains a complete fiber network morphology, and the fiber continuity is not disrupted. At the same time, the surface roughness of the fibers increases significantly, exhibiting obvious wrinkles and uneven structures. When the PBA content is low (0.05g), no obvious PBA phase separation or independent morphology is observed in the TEM image. The material exhibits highly uniform and dense homogeneous characteristics, indicating that PBA is likely uniformly dispersed in the PCL matrix in the form of molecular-level or extremely small aggregates. When the PBA content increases to 0.25g, significant microphase separation and self-assembly behavior occur in the system, forming a highly cross-linked dendritic nanofiber network. This interpenetrating network structure complements the surface roughness observed by SEM, jointly constructing a multi-level porous structure from both internal and surface dimensions. This indicates that Prussian blue nanoparticles have been successfully loaded onto the PCL fiber surface and uniformly dispersed, and this modification process has not adversely affected the electrospinning formability of the PCL matrix. EDS elemental surface scan analysis results show that the matrix skeleton elements (C, N, O) are uniformly distributed in the fiber network; at the same time, the characteristic Fe element can be clearly detected and is diffusely distributed, and the distribution profile of each element is highly consistent with the fiber morphology.

[0089] The crystal structure characterization diagrams of the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 5As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0090] Depend on Figure 5 It can be seen that the Prussian blue analog samples prepared in Example 1 and Comparative Examples 1-3 all exhibited typical characteristic diffraction peaks at 17.4°, 24.7°, 35.2°, 39.7°, and 43.5°, which belong to the (200), (220), (400), (420), and (422) crystal planes of cubic Prussian blue analogs, respectively. These peaks are highly consistent with the standard card (JCPDS No. 52-1907), and no impurity diffraction signals were observed, proving that the obtained products are all face-centered cubic PBA materials. Among them, Comparative Example 2 (PBA-3) and Comparative Example 3 (PBA-4), both with micron-sized cubic morphologies, showed significant differences in their XRD patterns. PBA-4 exhibited a high-intensity single diffraction peak of the standard cubic phase, while PBA-3 showed a pair of adjacent peaks at approximately 17° and 35°. This splitting characteristic is highly consistent with the XRD pattern characteristics of rhombohedral Prussian blue analogs. Therefore, PBA-3 should be indexed as a rhombohedral phase structure. Conversely, PBA-4 exhibits only a single, high-intensity diffraction peak at the same crystal plane position, indicating that it maintains a cubic phase structure. Furthermore, its peak intensity is significantly higher than the other three PBA types, suggesting a high degree of crystallinity and large grain size. In addition, PBA-1 shows the most significant diffraction peak broadening among all samples. According to the Scherrer equation, when the grain size decreases to the nanometer scale (in this application, the PBA-1 grain size is less than 100 nm), the diffraction lines will broaden significantly.

[0091] Surface chemical state analysis diagrams of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 6 As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0092] Fe of the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 2+ / Fe 3+ The proportions were tested, and the results are shown in Table 1.

[0093] Table 1. Fe content of Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 2+ / Fe 3+ Proportion Depend on Figure 6 As shown in Table 1, the Fe content in the four Prussian blue analogue (PBA) samples (PBA-1 to PBA-4) was...2+ Both with Fe 3+ The coexisting peaks at approximately 708.0 eV and 721.5 eV are attributed to Fe, respectively. 2+ 2p 3 / 2 and Fe 2+ 2p 1 / 2 The peaks at approximately 713.0 eV and 725.0 eV correspond to Fe. 3+ 2p 3 / 2 and Fe 3+ 2p 1 / 2 This indicates that all samples retain the Prussian blue structure and exhibit a mixed valence state of iron. The surface Fe content of each sample was calculated based on the fitted peak area. 2+ / Fe 3+ The relative proportions were 2.00 (PBA-1), 2.26 (PBA-2), 2.78 (PBA-3), and 6.03 (PBA-4), respectively, indicating that the content of ferric iron decreased from PBA-1 to PBA-4.

[0094] The surface-enhanced Raman spectra of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 7 As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0095] Depend on Figure 7 It can be seen that all Prussian blue analogue samples exhibit characteristic peaks related to C≡N vibrations. From PBA-1 to PBA-4, the characteristic peak positions shift significantly, with PBA-2 and PBA-1 mainly at 2148 cm⁻¹. -1 and 2156cm -1 The peak at 2080 cm⁻¹ shows a single main peak, attributed to the coordinated cyano vibration of a relatively high-valence metal ion. The main peak of PBA-1 shifts to the right compared to PBA-2, indicating a higher valence state of iron in PBA-1. In contrast, the peak positions of PBA-3 and PBA-4 shift significantly towards lower wavenumbers and split into multiple characteristic peaks, indicating that the valence state of iron in PBA-3 and PBA-4 is lower than that in PBA-1 and PBA-2. The peak at 2080 cm⁻¹ in PBA-4 is... -1 and 2121 cm -1 The presence of a distinct strong absorption peak indicates that the valence state of iron in PBA-3 is higher than that in PBA-4, which is highly consistent with the XPS analysis results.

[0096] The nitrogen adsorption-desorption isotherms and corresponding pore size distribution diagrams of the Prussian blue analogs prepared in Examples 1 and Comparative Examples 1-3 are shown below. Figure 8As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0097] The specific surface area of ​​the Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 was tested, and the results are shown in Table 2.

[0098] Table 2. Specific surface area of ​​Prussian blue analogues prepared in Example 1 and Comparative Examples 1-3 Depend on Figure 8 As shown in Table 2, the Prussian blue analogue samples prepared in Example 1 and Comparative Examples 1-3 all exhibit typical Type IV adsorption isotherms. Among them, PBA-1, PBA-2, and PBA-4 show obvious H3-type hysteresis loops in the relative pressure range of P / P0 = 0.4-1.0, indicating that their pores are mainly dominated by irregular slit pores formed by the disordered stacking of nanoparticles. The adsorption-desorption curves of PBA-3 almost overlap, with very little hysteresis loop, and its embedded BJH pore size distribution curve shows a weak signal in the mesoporous region. In terms of saturated adsorption capacity, the pore volume and pore development of the samples follow the order PBA-1 > PBA-3 > PBA-2 > PBA-4. The BET multi-point specific surface area calculation results also confirm this order, which are 161.22, 60.39, 32.34, and 13.22 m² / g, respectively. Furthermore, the specific surface area of ​​PBA-3 (60.39 m² / g) was significantly higher than that of PBA-2 (32.34 m² / g), which was consistent with its SEM ( Figure 2 The morphology is closely related. Although the main grain size of PBA-3 is approximately 2.2-3.9 μm, there are obvious cracks and faults on the grain surface and edges, and a large number of incompletely crystallized nano-sized particles and debris are attached to the surface of the micron-sized bulk. These microcracks and nano-sized debris together provide additional nitrogen adsorption sites, thus significantly increasing the total apparent specific surface area of ​​PBA-3. In contrast, PBA-4 has the lowest specific surface area (13.22 m² / g), which is consistent with its dense micron-sized cubic morphology.

[0099] Following the "Glucose Colorimetric Sensing Performance Test of PBA" in the above test method, the glucose colorimetric sensing performance of the Prussian blue analogs prepared in Example 1 and Comparative Examples 1-3 was tested, and the results are as follows: Figure 9As shown, PBA-1, PBA-2, PBA-3, and PBA-4 correspond to the Prussian blue analogues prepared in Comparative Example 1, Example 1, Comparative Example 2, and Comparative Example 3, respectively; ad represents the color development ability of PBA-1, PBA-2, PBA-3, and PBA-4 after reacting in the dark for three hours; eh represents the ultraviolet-visible absorption spectra of PBA with different structures; and il represents the standard curves for glucose colorimetric detection of PBA with different structures and their linear fitting equations.

[0100] Depend on Figure 9 It can be seen that under the same experimental conditions, after three hours of reaction in the dark, all four PBAs could catalyze the color development of the system, but the color intensity varied when the glucose concentration was the same. Further quantitative monitoring of the reaction process using UV-Vis absorption spectroscopy revealed that as the substrate concentration increased (from 0.1 μM to 50 μM), the intensity of the characteristic absorption peak at 650 nm for each system gradually increased, which is attributed to the formation of typical TMB oxidation products. Subsequently, a standard curve was plotted with glucose concentration on the x-axis and absorbance at 652 nm on the y-axis. The slope of the linear equation reflects the catalytic efficiency of the material in catalyzing glucose oxidation and mediating TMB color development; a larger slope indicates a stronger absorbance response per unit concentration change and higher catalytic activity. The coefficient of determination (R²)... 2 The linear correlation between absorbance and glucose concentration was characterized by R. 2 A value closer to 1 indicates a better linear relationship and higher quantitative reliability of the method. Calculations show that the limits of detection (LODs) for the four materials are 0.72, 1.11, 2.91, and 11.18 μM, respectively. PBA-1 and PBA-2, being nanoscale structures with large specific surface areas and abundant catalytic sites, exhibit lower LODs and higher sensitivity; PBA-1 has the lowest LOD and the best theoretical catalytic activity, but its data fluctuates significantly in the low-concentration region, resulting in slightly poorer linear correlation. PBA-3 and PBA-4, with micron-sized particles, show a significant decrease in specific surface area, leading to weakened catalytic efficiency and signal response, and a significantly higher LOD. PBA-4 has a detection limit as high as 11.18 μM, exhibiting extremely poor sensitivity, and R0... 2 The concentrations are significantly low, the signal is weak, the data is discrete, the linear fitting effect is poor, and it is difficult to achieve effective detection of low-concentration glucose.

[0101] Following the "Glucose Colorimetric Sensing Performance Test of Composite Sensing Membrane" in the above test method, the glucose colorimetric sensing performance of the composite sensing membranes prepared in Examples 6 and 8 was tested, and the results are as follows. Figure 10As shown, a is the XRD comparison spectrum of pure PCL membrane and PBA / PCL composite membrane with different contents; b and c are the colorimetric comparison of glucose at different concentrations after 3 hours of reaction of 0.05g PBA / PCL composite membrane and 0.25g PBA / PCL composite membrane, respectively; de are the UV-Vis absorption spectra of PBA / PCL composite membrane with different contents, respectively; f and g are the standard curves for glucose colorimetric detection of PBA / PCL composite membrane with different contents and their linear fitting equations, respectively.

[0102] Depend on Figure 10It can be seen that the pure PCL film exhibits obvious characteristic diffraction peaks near 21.4° and 23.8°, which can be attributed to the (110) and (200) crystal planes of the semi-crystalline PCL orthorhombic crystal system. After introducing PBA to prepare the composite film, PBA / PCL still retains the above-mentioned characteristic diffraction peaks of PCL, indicating that the composite of PBA has not destroyed the intrinsic crystal structure of the PCL matrix. The vertical lines at the bottom of the figure correspond to the characteristic diffraction positions of the Prussian blue standard phase (PDF card number 00-052-1907). Careful observation reveals that pure PCL does not have diffraction peaks at these positions; while in the 0.25g PBA / PCL composite film (blue curve) with a higher PBA content, in addition to the original peaks of PCL, new characteristic diffraction peaks clearly appear at the corresponding standard vertical line positions. Although the 0.05g PBA / PCL composite film (red curve) also shows corresponding diffraction peaks at the same positions, the peak intensity is weaker and relatively less obvious due to the lower PBA content. Despite this, the diffraction peaks of the composite film matched well with those of the standard card, confirming that PBA was successfully incorporated into the PCL substrate, thus successfully constructing the PBA / PCL composite film material. As the glucose concentration increased from 0.1 μM to 50 μM, the composite film changed color from colorless to blue after 3 hours of reaction, indicating that the sensor exhibits a threshold response characteristic to glucose. Further quantitative analysis using UV-Vis absorption spectroscopy showed that both composite films exhibited good linearity in the 0-50 μM range. The limit of detection (LOD) was calculated according to the 3σ / S principle, with the 0.05 g PBA / PCL composite film showing a low LOD of 9.32 μM, superior to the 11.6 μM of the 0.25 g composite film. Compared to the pure PBA-2 solution system (LOD = 1.11 μM), the sensor sensitivity decreased after immobilizing PBA in the PCL matrix. This is attributed to the diffusion restriction of glucose molecules within the PCL network during the solid-liquid heterogeneous reaction, and the reduced accessibility of active sites due to the embedding of some PBA nanoparticles in the matrix. This mass transfer limitation is more pronounced at higher PBA loadings (0.25 g), where particle aggregation reduces the effective specific surface area, limiting catalytic efficiency at low concentrations (<20 μM). Therefore, the 0.05 g membrane actually exhibits a lower detection limit. However, when the glucose concentration increases to 50 μM, the absorbance of the 0.25 g PBA / PCL composite membrane is significantly higher than that of the 0.05 g membrane. This indicates that although the higher loading slightly sacrifices sensitivity at low concentrations, its higher absolute PBA content allows for a stronger and clearer colorimetric signal under high glucose stimulation.

[0103] After diaper integration and simulated urine testing according to the above testing method, the color comparison chart of simulated urine with different glucose concentrations is shown below. Figure 11As shown, a) is the visualization color development result of the PBA / PCL composite membrane based on diaper substrate in glucose solutions of different concentrations (concentrations from left to right are 0, 0.5, 1.0, and 1.5 mM); b) is the anti-interference color development test result of glucose at different concentrations in a simulated urine system (containing urea, sodium chloride, and uric acid); c) is the UV-Vis absorption spectrum corresponding to different glucose concentrations in the simulated urine system. The simulated urine with a glucose concentration of 0.5 mM belongs to the healthy range, the simulated urine with a glucose concentration of 1.0 mM belongs to the transition range, and the simulated urine with a glucose concentration of 1.5 mM belongs to the pathological range.

[0104] Depend on Figure 11 It can be seen that within the glucose concentration range of 0.5-1.5mM, the diaper exhibits a visible blue gradient change, which can clearly distinguish between the healthy range (<0.8mM) and the pathological range (>1.39mM). Furthermore, it has good anti-interference performance under simulated urine conditions, and the test results are stable.

[0105] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a Prussian blue analogue, characterized in that, Includes the following steps: S1, Dissolve a soluble transition metal hexacyano salt and glucose in water to obtain the first mixture; S2, dissolve a soluble transition metal salt in water to obtain a second mixture; S3, the first mixture is added to the second mixture, and after thorough stirring, a hydrothermal reaction is carried out to obtain a Prussian blue analogue.

2. The method for preparing the Prussian blue analogue according to claim 1, characterized in that, The molar ratio of the soluble transition metal hexacyano salt, the soluble transition metal salt, and glucose is 1~1.5:1~1.5:3.3~5; and / or, The soluble transition metal hexacyano salt includes any one or a combination of two of sodium ferrocyanide and potassium ferrocyanide; and / or, The soluble transition metal salt includes any one or a combination of two or more of transition metal chlorides, transition metal sulfates, and transition metal nitrates; and / or, The transition metal in the soluble transition metal salt includes any one or a combination of two or more of Fe, Co, Ni, and Cu.

3. The method for preparing the Prussian blue analogue according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 110~140℃ for 12~20h.

4. A Prussian blue analogue, characterized in that, It is prepared by any one of claims 1-3.

5. The Prussian blue analogue according to claim 4, characterized in that, The Prussian blue analogues are spherical in shape, with a particle size of 100-160 nm, and have a pure cubic crystal structure. (Fe...) 2+ / Fe 3+ The ratio is 2.2~2.3, the Michaelis constant for H2O2 is 0.18~0.2mM, and the detection limit for glucose is as low as 1.1~1.15 μM.

6. A composite sensing membrane, characterized in that, Includes a flexible substrate and a sensing material loaded in the flexible substrate; The sensing material includes a Prussian blue analog obtained by the preparation method of any one of claims 1-3 or a Prussian blue analog obtained by any one of claims 4-5.

7. A method for preparing a composite sensing membrane, characterized in that, include: The flexible polymer and the Prussian blue analogue were mixed and dispersed in a solvent to obtain a spinning solution. The spinning solution is electrospun to obtain a composite sensing membrane; Wherein, the Prussian blue analogue is a Prussian blue analogue prepared by the preparation method of any one of claims 1-3 or a Prussian blue analogue of any one of claims 4-5.

8. The method for preparing the composite sensing membrane according to claim 7, characterized in that, The flexible polymer includes any one or a combination of two or more of polycaprolactone, polyurethane, polyethylene terephthalate, chitosan, sodium alginate, gelatin, and silk fibroin; and / or, The mass ratio of the flexible polymer to the Prussian blue analogue is 1.2:(0.05~0.25).

9. The method for preparing the composite sensing membrane according to claim 7, characterized in that, The electrospinning process parameters include: positive pressure 8~15kV, negative pressure 6~10kV, and feed rate 2~3mL / h.

10. The application of the composite sensing membrane according to claim 6 or the composite sensing membrane prepared by the preparation method according to claims 7-9 in diapers.

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