Responsive aerogel and use thereof

Abstract

The present invention relates to the technical field of gas detection, and particularly relates to a responsive aerogel and the use thereof. The responsive aerogel is prepared according to the following steps: mixing and dissolving a metal organic framework material and lead acetate, so as to obtain an adsorption-response integrated probe; and mixing a silk fibroin, polyethylene glycol diacrylate and the adsorption-response integrated probe, and subjecting the mixture to a photocuring reaction under the action of a photo-crosslinking agent, so as to obtain the responsive aerogel. A double-grid aerogel substrate generated by the reaction of the silk fibroin and the polyethylene glycol diacrylate can adsorb water molecules in environments with different humidities to wet the substrate, such that a saturated microscopic water environment is provided for a colorimetric reaction on the surface of a pore wall, thereby effectively relieving the interference of environmental humidity on the response. A quantitative method established by using the responsive aerogel can be used for high-sensitivity quantitative detection of hydrogen sulfide in livestock and poultry farms.

Description

A responsive aerogel and its applications Technical Field

[0001] This invention relates to the field of gas detection technology, and more particularly to a responsive aerogel and its applications. Background Technology

[0002] With the large-scale and intensive development of my country's livestock and poultry farming industry, harmful gases generated from livestock and poultry farming endanger animal and human health and pollute the ecological environment, becoming a key factor restricting the industry's development. Current gas detection technologies, such as gas chromatography-mass spectrometry, spectrophotometry, and laser absorption spectroscopy, while accurate, are complex to operate, costly, and have long analysis cycles, making them difficult to use in production lines. Metal semiconductor-based gas sensors, although small and portable, suffer from high operating temperatures, high energy consumption, and low selectivity and stability, limiting their large-scale long-term application. Colorimetric sensors based on various chemically responsive dyes have become a research hotspot in the field of harmful gas detection due to their simple design, low cost, and good selectivity. However, most of these chemical dyes are acid-base indicators and redox dyes, making it difficult to achieve specific gas detection. Furthermore, dye accumulation limits gas transmission efficiency, making it difficult to achieve high-sensitivity detection. In addition, the livestock and poultry farming environment is characterized by significant interference, high and fluctuating humidity, posing challenges to the research and application of colorimetric sensors. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a responsive aerogel. The hydrogen sulfide colorimetric sensing method established based on this responsive aerogel can be directly used for the high-sensitivity enrichment detection of hydrogen sulfide gas and can overcome the influence of different humidity levels in the detection environment.

[0004] The technical solution adopted in this invention is as follows:

[0005] In a first aspect, the present invention provides a responsive aerogel, which is prepared according to the following steps:

[0006] Metal-organic framework materials were mixed and dissolved with lead acetate to obtain an adsorption-responsive integrated probe;

[0007] Silk fibroin, polyethylene glycol diacrylate, and the adsorption-responsive integrated probe are mixed and photocured under the action of a photocrosslinking agent to obtain the responsive aerogel.

[0008] Silk fibroin, as a framework, has a three-dimensional porous structure. The double-network aerogel substrate formed by interweaving with polyethylene glycol can adsorb water molecules in the environment, providing a saturated micro-water environment for the colorimetric reaction on the pore wall surface, thereby effectively mitigating the interference of environmental humidity on the response.

[0009] In a preferred embodiment of the present invention, the concentration of silk fibroin in the mixed solution is 10-40 mg / mL, the volume fraction of polyethylene glycol diacrylate is 1 / 64-1 / 8, the concentration of lead acetate is 25-200 mg / mL, and the concentration of metal-organic framework material is 3.25-15 mg / mL.

[0010] More preferably, the concentration of silk fibroin in the mixed solution is 20 mg / mL, the volume fraction of polyethylene glycol diacrylate is 1 / 32, the concentration of lead acetate is 50 mg / mL, and the concentration of metal-organic framework material is 7.5 mg / mL.

[0011] In a preferred embodiment of the present invention, the photocuring reaction is carried out by simultaneous irradiation at 365nm and 405nm for at least 3 minutes.

[0012] In a preferred embodiment of the present invention, the photocrosslinking agent is potassium persulfate, photoinitiator 1173, and Ru(bpy)3]Cl2.

[0013] As a preferred embodiment of the present invention, the metal-organic framework material is prepared according to the following steps: using aluminum salt and 2,5-thiophene dicarboxylic acid as raw materials, and adding N,N-dimethylformamide to react, thus obtaining the material.

[0014] In a second aspect, the present invention provides an application of the responsive aerogel in the detection of hydrogen sulfide gas.

[0015] A third aspect of the present invention provides a method for detecting hydrogen sulfide using a responsive aerogel, comprising the following steps:

[0016] The responsive aerogel was used to filter the hydrogen sulfide gas to be tested. The Euclidean distance of the color change of the responsive aerogel under the action of hydrogen sulfide was measured, and the hydrogen sulfide concentration was calculated by combining the pre-calibration curve.

[0017] As a preferred embodiment of the present invention, the specific process for measuring the color change value of the responsive aerogel is as follows:

[0018] Obtain color images of responsive aerogels in a closed environment with constant illumination;

[0019] Extract the mean values ​​of the three color channels of the responsive aerogel region in the image;

[0020] Calculate the Euclidean distance between the mean values ​​of the three color channels of the responsive aerogel before and after the reaction.

[0021] As a preferred embodiment of the present invention, the formula for calculating the Euclidean distance is as follows:

[0022] Wherein, R, G, and B are the mean values ​​of the three color channels of the responsive aerogel region after the reaction, and R0, G0, and B0 are the mean values ​​of the three color channels of the responsive aerogel region before the reaction.

[0023] In a preferred embodiment of the present invention, the pre-calibration curve is obtained by performing the same experiment multiple times with different hydrogen sulfide concentrations to obtain the corresponding color change values, and then establishing a relationship curve between the color change values ​​and their respective corresponding hydrogen sulfide concentrations through fitting.

[0024] In a fourth aspect, the present invention provides a sensor for detecting hydrogen sulfide gas, comprising the aforementioned responsive aerogel.

[0025] The responsive aerogel prepared by this invention has the following advantages:

[0026] This invention first uses silk fibroin and polyethylene glycol diacrylate as raw materials, adding a photocrosslinking agent to prepare a dual-network aerogel substrate. The silk fibroin reacts with potassium persulfate under light, solidifies, and dries to form a three-dimensional porous aerogel. The polyethylene glycol diacrylate reacts with photoinitiator 1173 under light, solidifies, and forms a polyethylene glycol gel. The silk fibroin and polyethylene glycol gel interweave and solidify, forming a dual-network gel. The silk fibroin network serves as the supporting framework of the aerogel, and the addition of the polyethylene glycol network significantly enhances its hydrophilicity, providing a microscopic water environment for colorimetric reactions by adsorbing water molecules from the environment, thereby eliminating the influence of varying humidity levels.

[0027] In this invention, the metal-organic framework can adsorb hydrogen sulfide gas and lead ions. Lead acetate, as a colorimetric probe, can react with hydrogen sulfide gas under humid conditions to generate lead sulfide, thus changing the color from white to black. The combination of the metal-organic framework and lead acetate realizes the co-adsorption function of the colorimetric probe and the target gas, constructing an integrated adsorption-response probe, which greatly improves the binding efficiency of gas molecules and the colorimetric probe, thereby achieving highly sensitive enrichment detection of hydrogen sulfide gas.

[0028] The silk fibroin-polyethylene glycol aerogel prepared by this invention has a primary microporous structure as the dual-network aerogel substrate and a secondary nanoporous structure as the adsorption-responsive integrated probe. The responsive aerogel prepared by mixing the two not only maintains the three-dimensional porous structure of the silk fibroin-polyethylene glycol aerogel, but also distributes the responsive integrated probe on its pore wall surface, so that the responsive aerogel has a hierarchical porous structure, which effectively improves the mass transfer of gas molecules inside while increasing the colorimetric probe loading.

[0029] This invention utilizes responsive aerogels to establish a colorimetric quantitative method based on digital image color difference values, solving the problem that colorimetric sensing cannot accurately quantify.

[0030] In summary, this invention addresses the problems of low sensitivity and humidity interference in existing colorimetric detection technologies by developing a hydrophilic responsive aerogel with a hierarchical porous structure for stable and highly sensitive detection of hydrogen sulfide. Attached Figure Description

[0031] Figure 1 is a schematic diagram illustrating the preparation principle of the responsive aerogel in this invention.

[0032] Figure 2 shows the morphological characterization of silk fibroin and polyethylene glycol aerogels. SEM images of silk fibroin aerogels prepared from solutions of different concentrations: (A) 0.5% (w / w); (B) 1% (w / w); (C) 2% (w / w); (D) 4% (w / w). (E) Scanning electron microscopy image of silk fibroin prepared with 0.01 μmol / L [Ru(bpy)3]Cl2. (F) SEM image of polyethylene glycol aerogel.

[0033] Figure 3 shows the morphology, hydrophilicity, mechanical properties, and interaction between silk fibroin and polyethylene glycol diacrylate (PEG) in the silk fibroin-polyethylene glycol (PEG) dual-network aerogel. (A) Physical images of silk fibroin-PEG aerogels with different concentrations of silk fibroin and PEG diacrylate. (B) SEM images of silk fibroin-PEG aerogels with a mass fraction of 2% silk fibroin and different concentrations of PEG diacrylate. (C) FTIR of silk fibroin, PEG diacrylate, and silk fibroin-PEG aerogel. (D) Water absorption of silk fibroin-PEG aerogels with different PEG diacrylate contents. (E) Physical image of the silk fibroin-PEG aerogel elastomer. Wherein, I, II, III, and IV refer to the volume fractions of PEG diacrylate in the mixture during preparation: 0, 1 / 64, 1 / 32, and 1 / 16, respectively.

[0034] Figure 4. Morphological and structural characterization of the responsive aerogels. (A) Metal-organic framework material MIL-53. (B) Lead-loaded MIL-53. (C) SEM image of the responsive aerogel. (D) SEM image of lead-loaded MIL-53 and EDS spectra of aluminum (Al), lead (Pb), and sulfur (S). (E) FTIR of the responsive aerogel. (F) XRD of the responsive aerogel. (G) Nitrogen adsorption-desorption isotherms of MIL-53 and lead-loaded MIL-53.

[0035] Figure 5. Colorimetric response of responsive aerogels to hydrogen sulfide. (A) Schematic diagram of hydrogen sulfide gas transport principle. (B) Adsorption of hydrogen sulfide by MIL-53. (C) Schematic diagram of water adsorption by the polyethylene glycol layer. (D) Response differences of different internal structures. (E) Response of responsive aerogels with different MIL-53 contents to hydrogen sulfide. (F) Effect of polyethylene glycol diacrylate content on the response. (G) Optimization of response time. (H) Gradient response of responsive aerogels. (I) Selectivity of responsive aerogels. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the method provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0037] This invention provides a responsive aerogel (SF-PEGDA-MIL-53@Pb), which uses a silk fibroin-polyethylene glycol (SF-PEGDA) bi-mesh aerogel as a three-dimensional porous substrate and loads MIL-53 (a metal-organic framework material), a highly efficient adsorbent for hydrogen sulfide (H2S), to construct a hierarchical porous structure, facilitating the transport and adsorption enrichment of H2S molecules. The SF-PEGDA-MIL-53@Pb aerogel achieves color change output based on the classical reaction between lead acetate (Pb(Ac)2) and H2S. Since MIL-53 also exhibits good adsorption performance for Pb(Ac)2, a highly sensitive detection strategy integrating adsorption, enrichment, and response is realized. The SF-PEGDA bi-mesh aerogel designed and prepared in this invention can adsorb water molecules from different humidity environments to wet the substrate, providing a saturated micro-aqueous environment for the colorimetric reaction on the pore wall surface, thereby effectively mitigating the interference of environmental humidity on the response. Furthermore, to address the issue of inaccurate quantification by colorimetric sensors, this invention establishes a colorimetric quantification method based on digital image color difference values ​​using SF-PEGDA-MIL-53@Pb aerogel. This method can be used for highly sensitive quantitative detection of hydrogen sulfide in livestock and poultry farms, providing a solution and technical support for highly sensitive, low-cost on-site detection of gases in livestock and poultry farming environments.

[0038] Example 1

[0039] A responsive aerogel is prepared according to the following steps:

[0040] (1) Synthesis of an adsorption-responsive integrated probe

[0041] Step 1: Weigh 1800 mg of aluminum nitrate (nonahydrate) and 620 mg of 2,5-thiophene dicarboxylic acid, mix them, and dissolve them in a mixed solvent of 18 mL of N,N-dimethylformamide and 25 mL of ultrapure water. Sonicate for 10 min to ensure complete dissolution. Place the mixture in a reaction vessel and heat to 100 °C for 5 h. After the reaction is complete, wash three times with N,N-dimethylformamide, soak in acetone overnight, and then dry in a 60 °C oven for 24 h. The metal-organic framework MIL-53 is synthesized as an adsorbent.

[0042] Step 2: Prepare a mixed solution containing 100 mg / mL lead acetate and 15 mg / mL MIL-53, place it on a magnetic stirrer, heat to 90°C, and stir for 1 hour. Then place it in a 25°C water bath to recrystallize the lead acetate, obtaining MIL-53-adsorbed lead acetate.

[0043] (2) Weigh 40 mg of silk fibroin and add it to 400 μL of ultrapure water. Let it stand for 10 min until completely dissolved. Add 31.25 μL of polyethylene glycol diacrylate solution, 500 μL of the mixed solution after MIL-53 adsorption of lead acetate, 2.33 μL of 6 mg / mL [Ru(bpy)3]Cl2 solution, 50 μL of 60 mg / mL KPS solution, and 1 μL of 1173 solution. Add ultrapure water to a final volume of 1 mL and shake to mix. Ru ions redox-excite KPS under light irradiation, and the excited-state KPS initiates cross-linking of silk fibroin. Irradiate simultaneously with 365 nm ultraviolet light and 405 nm blue light for 3 min. Then freeze in a -80℃ ultra-low temperature freezer for 3 h and then vacuum dry in a freeze dryer for 24 h to obtain the final product.

[0044] Example 2

[0045] A responsive aerogel is prepared according to the following steps:

[0046] (1) Synthesis of an adsorption-responsive integrated probe

[0047] Step 1: Weigh 1800 mg of aluminum nitrate (nonahydrate) and 620 mg of 2,5-thiophene dicarboxylic acid, mix them, and dissolve them in a mixed solvent of 18 mL of N,N-dimethylformamide and 25 mL of ultrapure water. Sonicate for 10 min to ensure complete dissolution. Place the mixture in a reaction vessel and heat to 100 °C for 5 h. After the reaction is complete, wash three times with N,N-dimethylformamide, soak in acetone overnight, and then dry in a 60 °C oven for 24 h. The metal-organic framework MIL-53 is synthesized as an adsorbent.

[0048] Step 2: Prepare a mixed solution containing 50 mg / mL lead acetate and 6.5 mg / mL MIL-53, place it on a magnetic stirrer, heat to 90°C, and stir for 1 hour. Then place it in a 25°C water bath to recrystallize the lead acetate, obtaining MIL-53-adsorbed lead acetate.

[0049] (2) Weigh 20 mg of silk fibroin and add it to 400 μL of ultrapure water. Let it stand for 10 min until completely dissolved. Add 15.6 μL of polyethylene glycol diacrylate solution, 500 μL of the mixed solution after MIL-53 adsorption of lead acetate, 2.33 μL of 6 mg / mL [Ru(bpy)3]Cl2 solution, 50 μL of 60 mg / mL KPS solution, and 1 μL of 1173 solution. Add ultrapure water to a final volume of 1 mL and shake to mix. Irradiate simultaneously with 365 nm ultraviolet light and 405 nm blue light for 3 min. Then freeze in a -80℃ ultra-low temperature freezer for 3 h and vacuum dry in a freeze dryer for 24 h to obtain the final product.

[0050] Example 3

[0051] A responsive aerogel is prepared according to the following steps:

[0052] (1) Synthesis of an adsorption-responsive integrated probe

[0053] Step 1: Weigh 1800 mg of aluminum nitrate (nonahydrate) and 620 mg of 2,5-thiophene dicarboxylic acid, mix them, and dissolve them in a mixed solvent of 18 mL of N,N-dimethylformamide and 25 mL of ultrapure water. Sonicate for 10 min to ensure complete dissolution. Place the mixture in a reaction vessel and heat to 100 °C for 5 h. After the reaction is complete, wash three times with N,N-dimethylformamide, soak in acetone overnight, and then dry in a 60 °C oven for 24 h. The metal-organic framework MIL-53 is synthesized as an adsorbent.

[0054] Step 2: Prepare a mixed solution containing 400 mg / mL lead acetate and 30 mg / mL MIL-53, place it on a magnetic stirrer, heat to 90°C, and stir for 1 hour. Then place it in a 25°C water bath to recrystallize the lead acetate, obtaining MIL-53-adsorbed lead acetate.

[0055] (2) Weigh 80 mg of silk fibroin and add it to 400 μL of ultrapure water. Let it stand for 10 min until completely dissolved. Add 125 μL of polyethylene glycol diacrylate solution, 500 μL of the mixed solution after MIL-53 adsorption of lead acetate, 2.33 μL of 6 mg / mL [Ru(bpy)3]Cl2 solution, 50 μL of 60 mg / mL KPS solution, and 1 μL of 1173 solution. Add ultrapure water to a final volume of 1 mL and shake to mix. Irradiate simultaneously with 365 nm ultraviolet light and 405 nm blue light for 3 min. Then freeze in a -80℃ ultra-low temperature freezer for 3 h and vacuum dry in a freeze dryer for 24 h to obtain the final product.

[0056] In the preparation process of the responsive aerogels provided in Examples 1-3, silk fibroin and polyethylene glycol diacrylate undergo photocuring under the action of a photocrosslinking agent to obtain a dual-network aerogel substrate. The dual-network aerogel substrate and the solution after MIL-53 adsorbs lead acetate undergo photocuring under the action of a photocrosslinking agent to obtain the final responsive aerogel. This dual-network aerogel substrate has a porous structure, which improves gas transport. Simultaneously, the dual-network aerogel substrate also has water absorption properties, thus enabling the final prepared responsive aerogel to resist humidity interference.

[0057] Since the responsive aerogels provided in Examples 1 to 3 have essentially the same performance, the following description will only use Example 1 as an example to illustrate its performance and effects.

[0058] 1. Synthesis and characterization of double-grid aerogel substrates

[0059] To test the performance of the dual-network aerogel substrate, the separately prepared dual-network aerogel substrate is described below. The specific process is as follows:

[0060] (1) Synthesis of double-grid aerogel substrate

[0061] Weigh 40 mg of silk fibroin of different masses and add it to 400 μL of ultrapure water. Let it stand for 10 min to dissolve completely. Add 31.25 μL of polyethylene glycol diacrylate solution, 2.33 μL of 6 mg / mL [Ru(bpy)3]Cl2 solution, 50 μL of 60 mg / mL KPS solution, and 1 μL of 1173 solution. Add ultrapure water to a final volume of 1 mL and shake to mix. Then, irradiate with 365 nm UV light and 405 nm blue light simultaneously for 3 min to cure. Then, freeze in an ultra-low temperature freezer at -80 °C for 3 h and then vacuum dry in a freeze dryer for 24 h.

[0062] (2) Characterization of the double-grid aerogel substrate

[0063] As shown in Figure 2 (A-D), low-concentration (0.5% wt) fibrin precursor solutions exhibited fibrous structures of varying sizes after crosslinking. Increasing the concentration (1% wt) resulted in the formation of more protein fibers, which began to connect into sheets. At concentrations of 2 wt% and 4 wt%, crosslinking resulted in a uniform and well-defined porous structure. Furthermore, it was determined that a crosslinking agent Ru(II) concentration of 0.02 μM resulted in an interconnected porous structure. As shown in Figure 2 (E), when the Ru concentration was too low, the protein molecules could only crosslink into interwoven strips, lacking a fixed macroscopic shape. Because the polymerized polyethylene glycol diacrylate chains were too flexible, they could not support the original porous structure after water loss; therefore, as shown in Figure 2 (F), the dried polyethylene glycol gel was dense internally.

[0064] A bi-network aerogel was prepared by mixing silk fibroin with a polyethylene glycol diacrylate precursor solution. Compared to pure silk fibroin aerogel, as shown in the SEM image in Figure 3B, the pore size of the silk fibroin-polyethylene glycol aerogel is significantly reduced, and the pore walls are thicker and smoother. The FTIR image in Figure 3C shows a pore size of 1640 cm⁻¹ in the silk fibroin-polyethylene glycol aerogel. -1 1527cm -1 1236cm -1 Characteristic peaks correspond to amide I, amide II, and amide III, respectively, with amide II and amide III being characteristic of silk fibroin coil cross-linking. 1097 cm⁻¹ -1 1731cm -1 The characteristic peaks are attributed to the stretching vibrations of COC and C=O after the polymerization of polyethylene glycol diacrylate. Compared with the spectra of silk fibroin and polyethylene glycol diacrylate, no new characteristic peaks appeared in the silk fibroin-polyethylene glycol spectrum, indicating that the cross-linking of silk fibroin and polyethylene glycol diacrylate is mainly through hydrogen bonding.

[0065] As shown in Figure 3D, the pure silk fibroin aerogel has extremely low water absorption in this environment, resulting in no significant change in mass. Conversely, the silk fibroin-polyethylene glycol aerogel exhibits a significant increase in mass, with the water absorption rate and mass change increasing with increasing polyethylene glycol diacrylate content. This change in hydrophilicity can also be verified by measuring the water contact angle. With increasing polyethylene glycol diacrylate content, the water contact angle decreases from 47.5° to 29.5°.

[0066] Figure 3 shows the actual aerogel of E. Although the silk fibroin network has good rigidity to maintain its three-dimensional porous framework, it is easily broken and fragmented under external forces. After adding a soft and elastic polyethylene glycol diacrylate network, the silk fibroin-polyethylene glycol aerogel can recover after being twisted 540° and bent 180°.

[0067] 2. Characterization of the MIL-53 adsorption of lead acetate during the preparation process, i.e., the adsorption-response integrated probe.

[0068] Figure 4A shows MIL-53 particles with irregular shapes exhibiting an aggregated state. Figure 4B shows that after adsorbing lead acetate, the surface of MIL-53 has a more pronounced particle texture and a higher degree of aggregation. Figure 4C shows that in the EDS image of MIL-53@Pb, lead and aluminum elements are intertwined and distributed, further indicating the formation of a mutually adsorbed composite material. MIL-53 and lead acetate have good crystallinity, and their characteristic diffraction peaks in the XRD spectrum are consistent with the reported results. The XRD of the MIL-53@Pb composite probe differs from that of MIL-53 and lead acetate, showing new characteristic peaks at 9.79°, 19.52°, 20.12°, 22.42°, 25.25°, and 28.34°, indicating that the MIL-53@Pb composite exhibits a new crystal structure. The pore structure of the MIL-53@Pb composite was investigated by testing N2 adsorption-desorption curves. The specific surface area of ​​MIL-53 is 360.6464 m². 3 / g, with an average pore size of 10.6408 nm. The specific surface area of ​​MIL-53@Pb is 11.6112 m² / g. 2 The average pore size of the lead acetate in MIL-53 was not significantly different from that in MIL-53, remaining at approximately 10.5826 nm. This indicates that the adsorption of lead acetate by MIL-53 occurs only on the surface, without pore blockage, which is beneficial for the transport of hydrogen sulfide.

[0069] 3. Characterization of responsive aerogels

[0070] Figure 4D shows that the responsive aerogel maintains the three-dimensional porous structure of the double-mesh aerogel substrate, with the MIL-53@Pb probe uniformly distributed on the pore walls. Figure 4F shows that the XRD pattern of the responsive aerogel retains the characteristic peaks (30.44°, 21.42°) of the silk fibroin-polyethylene glycol aerogel substrate, while also exhibiting characteristic peaks of lead acetate (9.10°, 15.47°, 22.26°, 35.34°) and MIL-53@Pb (19.52°, 28.34°), indicating that the MIL-53@Pb probe was successfully loaded onto the silk fibroin-polyethylene glycol substrate. The FTIR of Figure 4E shows the presence of a 1406 cm⁻¹ line in the responsive aerogel spectrum. -1 658cm -1 Two new characteristic peaks were observed. This is attributed to the bending vibration of the -OH groups in lead acetate. The N2 adsorption-desorption curves of the responsive aerogel in Figure 4G exhibited a type II isotherm similar to that of MIL-53@Pb, while the initial silk fibroin-polyethylene glycol aerogel showed approximately zero N2 adsorption. This clearly demonstrates that the silk fibroin-polyethylene glycol aerogel serves as the primary microporous structure, while the uniformly distributed MIL-53@Pb provides the secondary nanoporous structure, successfully constructing a hierarchical porous structure.

[0071] 4. Detection of hydrogen sulfide using responsive aerogels

[0072] Figure 5D shows that the densely structured aerogel did not react even in high concentrations (4 ppm) of hydrogen sulfide, while the porous aerogel exhibited a good gradient response to different concentrations of hydrogen sulfide. This is because the porous aerogel, after freeze-drying, can effectively improve gas transport and ensure sufficient contact between the gas and the response probe. Besides its inherent structural advantages, adding materials with nanopores to the surface of a porous substrate to construct a hierarchical porous structure is an effective strategy to improve the capture rate of the target gas, accelerate the reaction with the probe, and thus improve detection sensitivity. Figure 5E shows that the aerogel with added MIL-53 showed a significant improvement in response throughout the entire reaction time compared to the aerogel without MOF, with the highest response observed at a MIL-53 concentration of 7.5 mg / mL. Therefore, a MIL-53 concentration of 7.5 mg / mL was determined to be the optimal condition.

[0073] Besides high sensitivity, the responsive aerogels exhibit good response stability under different humidity levels. Figure 5F shows the response values ​​of responsive aerogels with different polyethylene glycol diacrylate (PEG) contents to 1 ppm hydrogen sulfide at different humidity levels (20%, 40%, 60%, 80%, 90% RH). Without PEG, the response ED value gradually decreased from 98.96 to 54.23 with increasing humidity. This is because although increased humidity increases the degree of molecular ionization, the adsorption of water molecules on the substrate causes self-expansion, leading to increased transparency and thus a decrease in the ED value. When the volume fraction of PEG is greater than 1 / 64, the standard deviation of the response ED values ​​under different humidity levels drops below 5, confirming that this method can reduce response differences and mitigate the influence of humidity. Furthermore, the responsive aerogels with 1 / 64 PEG added showed higher responses to different concentrations of hydrogen sulfide than those without PEG. Specifically, at a hydrogen sulfide concentration of 1 ppm, the response value increased by 3.39 times. This is because the substrate absorbs water, providing an excellent aquatic environment for the colorimetric reaction and promoting the ionization of lead acetate and hydrogen sulfide molecules.

[0074] Responsive aerogels prepared using a precursor solution containing 20 mg / mL silk fibroin, 1 / 32 (v / v) volume fraction of polyethylene glycol diacrylate, 50 mg / mL lead acetate, and 7.5 mg / mL metal-organic framework were reacted with hydrogen sulfide in concentrations ranging from 0 to 5 ppm. In Figure 5, the ED value of the responsive aerogels shown in G and H reacting with 0.25 ppm hydrogen sulfide for 30 s was 8.17. Converted to Lab space, ΔE = 2.1, which is less than the threshold of 3 that the human eye can clearly detect. However, the ED value calculation shows that 0.25 ppm can be detected, which is the detection limit of this sensor. The ED value was calculated using the following formula:

[0075] The formula for calculating Euclidean distance is as follows:

[0076] Wherein, R, G, and B are the mean values ​​of the three color channels of the responsive aerogel region after the reaction, and R0, G0, and B0 are the mean values ​​of the three color channels of the responsive aerogel region before the reaction.

[0077] A functional model was established between the ED value and the hydrogen sulfide concentration. The results show that there is a cubic polynomial correlation between the ED value (Y) and the hydrogen sulfide concentration (x), with an R-value of 0.991. Specifically: 10000Y = -4 + 135x - 0.83595x 2 +0.0036466x 3

[0078] Figure 5, I, shows the effect of exposing the responsive aerogel to various interfering molecules, including the inorganic gas ammonia, the organic gases dimethylformamide, ethyl acetate, methylamine, and methanol, as well as other types of volatile sulfides, including thiols and thioethers. The responsive aerogel showed excellent responsiveness only to hydrogen sulfide, and no color change was observed when exposed to 5 ppm of other interfering gases. The ED values ​​were all less than 10, demonstrating excellent selectivity.

[0079] It will be apparent to those skilled in the art that the present invention is not limited to the details of the above embodiment 1, and anything within the scope of the technical solution and claims of the present invention should fall within the protection scope of the present invention.

Claims

1. A responsive aerogel, characterized in that, It is prepared according to the following steps: Metal-organic framework materials were mixed and dissolved with lead acetate to obtain an adsorption-responsive integrated probe; Silk fibroin, polyethylene glycol diacrylate, and the adsorption-responsive integrated probe are mixed and photocured under the action of a photocrosslinking agent to obtain the responsive aerogel.

2. The responsive aerogel according to claim 1, characterized in that, The concentration of silk fibroin in the mixed solution is 10–40 mg / mL, the volume fraction of polyethylene glycol diacrylate is 1 / 64–1 / 8, the concentration of lead acetate is 25–200 mg / mL, and the concentration of metal-organic framework material is 3.25–15 mg / mL.

3. The responsive aerogel according to claim 1, characterized in that, The photocuring reaction is carried out by simultaneous irradiation at 365nm and 405nm for at least 3 minutes.

4. The responsive aerogel according to claim 1, characterized in that, The photocrosslinking agent is potassium persulfate, photoinitiator 1173, and Ru(bpy)3]Cl2.

5. The responsive aerogel according to claim 1, characterized in that, The metal-organic framework material is prepared according to the following steps: using aluminum salt and 2,5-thiophene dicarboxylic acid as raw materials, and adding N,N-dimethylformamide to react, thus obtaining the material.

6. The application of the responsive aerogel according to any one of claims 1 to 5 in the detection of hydrogen sulfide gas.

7. A method for detecting hydrogen sulfide using a responsive aerogel according to any one of claims 1 to 5, characterized in that, Includes the following steps: The responsive aerogel was used to filter the hydrogen sulfide gas to be tested. The Euclidean distance of the color change of the responsive aerogel under the action of hydrogen sulfide was measured, and the hydrogen sulfide concentration was calculated by combining the pre-calibration curve.

8. The method according to claim 7, characterized in that, The specific process for measuring the color change value of responsive aerogels is as follows: Obtain color images of responsive aerogels in a closed environment with constant illumination; Extract the mean values ​​of the three color channels of the responsive aerogel region in the color image; Calculate the Euclidean distance between the mean values ​​of the three color channels of the responsive aerogel before and after the reaction.

9. A sensor for detecting hydrogen sulfide gas, characterized in that, It includes the responsive aerogel as described in any one of claims 1 to 5.

Images