Flexible fluorescence sensor and preparation method and application thereof

Abstract

The invention provides a flexible fluorescence sensor as well as a preparation method and application thereof. The flexible fluorescence sensor comprises TCTG particles and dual-network hydrogel, the TCTG particles are distributed in network pores of the dual-network hydrogel to form functional gel, the TCTG particles are formed by Ti3C2TxMXene nanosheets and graphene quantum dots, the dual-network hydrogel is formed by acrylamide and sodium carboxymethyl cellulose, and the TCTG particles are distributed in the network pores of the dual-network hydrogel to form functional gel. The functional gel is soaked in a hydrochloric acid glycol solution for treatment. The flexible fluorescence sensor provided by the invention can integrate the structural advantages of all the components, so that a synergistic coupling effect is possibly generated, a fluorescence detection function with excellent mechanical strength, frost resistance and high sensitivity is integrated into a multifunctional system, the food spoilage condition can be reliably monitored in real time under a harsh environmental condition, and the application prospect is wide. And health and economic risks caused by occupational exposure and environmental emission in an aquatic product supply chain are solved.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and in particular to a flexible fluorescent sensor and a preparation method and application thereof. Background Art

[0002] Hydrogen sulfide (H2S) is a potent neurotoxin that inhibits cytochrome c oxidase, an enzyme in the mitochondrial electron transport chain, leading to cellular hypoxia and metabolic dysfunction. Workers in seafood processing, storage, and distribution face elevated risk of H2S exposure due to gas accumulation in poorly ventilated areas. Furthermore, the decomposition of fish waste in landfills and wastewater treatment facilities leads to localized H2S emissions, exacerbating environmental and public health concerns. Therefore, accurate detection and quantification of H2S throughout the seafood supply chain is crucial to ensuring food safety, mitigating health risks, and minimizing economic losses due to spoilage.

[0003] Compared to traditional detection methods such as electrochemical and chromatographic techniques, fluorescent sensors offer ultrasensitive and selective H2S detection in environmental monitoring, food safety, and chemical analysis. However, most mainstream research on fluorescent sensors still utilizes solution systems, which are prone to issues such as photobleaching, limited analyte storage, and signal instability. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the prior art to at least a certain extent. To this end, one object of the present invention is to provide a flexible fluorescent sensor and a preparation method and application thereof.

[0005] In the first aspect of the present invention, a flexible fluorescent sensor is proposed, which comprises TCTG particles and a double network hydrogel, wherein the TCTG particles are distributed in the network pores of the double network hydrogel to form a functional gel, and the TCTG particles are composed of Ti3C2T x MXene nanosheets and graphene quantum dots are formed, the double network hydrogel is formed by acrylamide and sodium carboxymethyl cellulose, and the functional gel is immersed in a hydrochloric acid ethylene glycol solution.

[0006] According to the above-mentioned flexible fluorescent sensor provided by the present invention, it includes TCTG particles and a double network hydrogel, wherein the TCTG particles are distributed in the network pores of the double network hydrogel to form a functional gel, and the double network hydrogel is formed by acrylamide and sodium carboxymethyl cellulose. Compared with the single network hydrogel, the double network hydrogel can provide a better controlled environment and adjustable selectivity, thereby improving the stability, sensitivity and moisture resistance of the flexible fluorescent sensor, making it an excellent solid phase matrix. In addition, the integration of TCTG particles with the double network hydrogel matrix can promote physical or chemical crosslinking to form a strong polymer-nanoparticle network, thereby enhancing the overall mechanical properties. Specifically, Ti3C2T x MXene nanosheets have abundant surface polar functional groups, which can form strong hydrogen bonds and electrostatic interactions with polymer chains in hydrogels, forming a soft hydrogel matrix and a rigid Ti3C2T x Load transfer between MXene nanosheets is facilitated, while surface charge, reactivity, and compatibility with various polymer systems are enhanced. Consequently, the overall mechanical strength is enhanced, and the hydrogel's limited responsiveness to external stimuli is mitigated. Graphene quantum dots (GQDs), with their photostability, excellent electron acceptor / donor properties, and low toxicity, can be used as a material for detecting volatile organic compounds. Finally, the resulting functionalized gel is treated in a hydrochloric acid-ethylene glycol solution. The HCl-induced protonation of the –COO⁻ and amide groups enhances hydrogen bonding and ionic interactions, thereby increasing the crosslink density. Ethylene glycol (EG) replaces water in the network, reducing hydrophilicity and increasing hydrogen bonding density, resulting in a denser and more mechanically robust hydrogel structure. This significantly improves the stability and reliability of the flexible fluorescent sensor.

[0007] The flexible fluorescent sensor provided by the present invention is composed of an enhanced double network structure consisting of a heterojunction fluorescent material of MXene-loaded GQDs and a hydrogel. It can integrate the structural advantages of each component, thereby potentially producing a synergistic coupling effect, integrating excellent mechanical strength, antifreeze performance and highly sensitive fluorescence detection functions into a multifunctional system. In particular, it can reliably monitor food spoilage in real time under harsh environmental conditions, and address the health and economic risks brought about by occupational exposure and environmental emissions in the aquatic product supply chain.

[0008] In some embodiments of the present invention, the concentration of HCl in the ethylene glycol hydrochloride solution is 0.1 mol / L-2 mol / L, preferably 0.2 mol / L-1 mol / L. For example, the concentration of HCl is 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.7 mol / L, 2.0 mol / L, or a range between any two of the above values. Controlling the concentration of HCl within the above range not only improves the gel strength and elongation, but also significantly improves the gel network structure, thereby facilitating the fluorescence stability of the flexible fluorescent sensor.

[0009] In some embodiments of the present invention, the functional gel is immersed in the ethylene glycol hydrochloride solution for a period of 20-40 minutes. For example, the immersion time is 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, or any range between any two of the aforementioned values. Controlling the immersion time within the aforementioned range can improve gel strength, elongation, and toughness, thereby enhancing the stability and responsiveness of the flexible fluorescent sensor.

[0010] In some embodiments of the present invention, the mass ratio of acrylamide to sodium carboxymethyl cellulose is 2:(0.01-0.1), preferably 2:(0.03-0.07). For example, the mass ratio of acrylamide to sodium carboxymethyl cellulose is 2:0.01, 2:0.02, 2:0.04, 2:0.06, 2:0.08, 2:0.1, or any range between any two of the aforementioned values. Controlling the mass ratio of acrylamide to sodium carboxymethyl cellulose within the aforementioned range can improve the strength and ductility of the double-network hydrogel, ensuring gel flexibility, thereby enhancing the stability and fluorescence responsiveness of the flexible fluorescent sensor.

[0011] In some embodiments of the present invention, the Ti3C2T x The mass ratio of MXene nanosheets and graphene quantum dots is (1-4): (4-1). For example, the mass ratio is 1:4, 1:2, 1:1, 2:1, 4:1, etc., or the range between any two of the above values. x The mass ratio of MXene nanosheets and graphene quantum dots is within the above range, which can enhance the fluorescence intensity of TCTG.

[0012] In some embodiments of the present invention, the mass ratio of the TCTG particles to the acrylamide is 1:(15000-3000), preferably 1:(10000-4000). The mass ratio of TCTG particles to acrylamide within the above range can improve the mechanical properties of the hydrogel.

[0013] In some embodiments of the present invention, the particle size of the TCTG particles is no greater than 100 nm. For example, the particle size of the TCTG particles is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., or a range between any two of the above values.

[0014] In a second aspect of the present invention, the present invention provides a method for preparing the flexible fluorescent sensor, which comprises: (1) Ti3C2T x A mixed suspension of MXene nanosheets and graphene quantum dots in aqueous solution undergoes hydrothermal reaction to obtain TCTG particles; (2) dispersing the TCTG particles in a suspension aqueous solution of sodium carboxymethyl cellulose, and then mixing with acrylamide to undergo polymerization and cross-linking under the action of a cross-linking agent and an initiator to obtain a functional gel; (3) Immersing the functional gel in a hydrochloric acid ethylene glycol solution for treatment.

[0015] This method can be used to prepare a flexible fluorescent sensor with stable performance and strong fluorescence response.

[0016] In some embodiments of the present invention, Ti3C2T x The MXene nanosheets and GQDs mixture was mixed in deionized water and stirred at room temperature for 30-60 minutes to form a uniform suspension. The mixed solution was then treated at 90-110°C for 4-6 hours. The reaction product was freeze-dried at -60°C for 24-36 hours to obtain TCTG particles. x The specific preparation methods of MXene nanosheets and TCTG can be found in the patent (CN119662235A).

[0017] In some embodiments of the present invention, the cross-linking agent includes one or more of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and ethylene glycol diacrylate.

[0018] In some embodiments of the present invention, the initiator comprises a photoinitiator, and the photoinitiator comprises Irgacure-2959 photoinitiator.

[0019] In a third aspect of the present invention, the present invention proposes the application of the above-mentioned flexible fluorescent sensor in detecting H2S.

[0020] The present invention has at least the following beneficial effects: (1) The present invention uses Ti3C2T xA heterojunction of MXene nanosheets loaded with GQDs (TCTG) was used as a fluorescent sensing unit and introduced into a dual-mode cross-linked double-network hydrogel prepared based on acrylamide and sodium carboxymethyl cellulose to prepare an intelligent fluorescent indicator label (flexible fluorescent sensor). This intelligent fluorescent indicator label can produce a fluorescent response to changes in the content of H2S volatilization during the storage and spoilage of fish, and determine the quality of the fish based on the changes in the fluorescent signal of the label.

[0021] (2) The intelligent fluorescent indicator label provided by the present invention integrates excellent mechanical strength, antifreeze performance and high-sensitivity fluorescence detection function into a multifunctional system, which can reliably monitor food spoilage in real time under harsh environmental conditions. At the same time, it solves the key needs of health and economic risks brought by occupational exposure and environmental emissions in the aquatic product supply chain. The intelligent fluorescent indicator label can operate reliably in complex and harsh cold chain logistics environments.

[0022] (3) The flexible fluorescent sensor provided by the present invention can accurately simulate the quality of fish meat during cold chain transportation and trading, and can effectively improve the quality monitoring capability of fish meat during cold chain transportation and trading, and provide convenience for quality inspectors to conduct rapid and real-time detection, which can effectively avoid damage to fish meat products and achieve non-destructive testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 1 is a stress-strain curve diagram of the PCT′ double network hydrogel provided in Examples 1-4 of the present invention and Comparative Example 1; Figure 2 Graphs showing the corresponding elastic modulus (E) and toughness (T) of the PCT′ double network hydrogels provided in Examples 1-4 of the present invention and Comparative Example 1; Figure 3 1 is a scanning electron micrograph and EDS elemental spectrum of TCTG dispersed in the hydrogel network of Example 1 of the present invention; Figure 4 1. The scanning electron microscope images and three-dimensional images of surface roughness of the PCT′ double network hydrogels of Example 1 and Comparative Example 1 of the present invention; Figure 5 1 is a stress-strain curve of the PCT double network hydrogels of Examples 1, 5-7 and Comparative Example 2 of the present invention; Figure 61 is a graph showing the fracture strain and stress trends of the PCT double network hydrogels of Examples 1, 5-7 and Comparative Example 2 of the present invention; Figure 7 are the corresponding elastic modulus (E) and toughness (T) of the PCT double network hydrogels of Examples 1, 5-7 and Comparative Example 2 of the present invention; Figure 8 1 is a graph showing the stress-strain behavior and cyclic tensile test results of the PCT double network hydrogel under different loading conditions according to Example 1 of the present invention; Figure 9 1 is a stress-strain curve diagram of the hydrogels of Examples 8-11 of the present invention and Comparative Example 3; Figure 10 1 is a graph showing the fracture strain and stress trends of the hydrogels of Examples 8-11 of the present invention and Comparative Example 3; Figure 11 Graphs showing the corresponding elastic modulus (E) and toughness (T) of the hydrogels of Examples 8-11 of the present invention and Comparative Example 3; Figure 12 3. This is a graph showing the fluorescence stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescence sensor PCT′ of Example 1 of the present invention under different humidity conditions; Figure 13 3. This is a graph showing the mechanical stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ of Example 1 of the present invention under different humidity conditions; Figure 14 3. This is a graph showing the fluorescence stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescence sensor PCT′ at different temperatures according to Example 1 of the present invention; Figure 15 3. This is a graph showing the mechanical stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ at different temperatures according to Example 1 of the present invention; Figure 16 Graph showing the water weight loss results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ of Example 1 of the present invention under sealed and unsealed storage environments; Figure 17 This is a graph showing the long-term stability test results of the PCT′ double-network hydrogel of Example 1 of the present invention as a smart fluorescent indicator label within 30 days; Figure 18 1 is a graph showing the sensitivity test results of PCT′ to H2S according to Example 1 of the present invention; Figure 19 1 is a graph showing the specificity and anti-interference test results of PCT′ to H2S according to Example 1 of the present invention; Figure 2090° shear adhesion test results of the PCT′ double-network hydrogel of Example 1 of the present invention as a smart fluorescent indicator label; Figure 21 This is a diagram showing the actual application results of the PCT′ double-network hydrogel of Example 1 of the present invention as an intelligent fluorescent indicator label during the storage of fish. DETAILED DESCRIPTION

[0025] Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the scope of protection of the present invention. The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0026] Example 1 This embodiment provides a flexible fluorescence sensor, and the specific preparation process is as follows: (1) Different masses of citric acid and urea were weighed in a molar ratio of 6:10 and dissolved in 10 mL of deionized water. The precursor solution was then transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 12 h in a high-temperature vacuum oven. The reaction solution was transferred to a dialysis bag and dialyzed for 12 h. The solution in the bag was then vacuum-freezed to obtain GQDs powder. At a reaction temperature of 35 °C, Ti3AlC2 (3 g) was added to a mixed solution consisting of 9 M HCl (50 mL) and LiF (3 g). Single-layer or few-layer Ti3C2T was then prepared by ultrasonic centrifugation. x Nanosheets, the supernatant was collected and freeze-dried to obtain gray powder, i.e. single-layer or few-layer Ti3C2Tx nanosheet powder. x A mixture of 1:1 GQDs and 1:1 MgCl2O3 (MgCl2O3) was added to 20 ml of deionized water and stirred at room temperature for 40 minutes to form a homogeneous suspension. The mixed solution was then transferred to an autoclave containing a polytetrafluoroethylene container and treated at 100°C for 5 hours. The reaction product was freeze-dried at -60°C for 30 hours to obtain TCTG powder with a particle size of 50 nm.

[0027] (2) Disperse 1.0 mg of TCTG powder in 10 mL of CMC suspension aqueous solution, where the mass concentration of CMC in the CMC suspension aqueous solution is 2%. Then add 6 g of acrylamide and mix. Stir at room temperature (500 rpm) for 30 minutes, during which 10 mg of N,N'-methylenebisacrylamide is added. After stirring, add 100 mg of Irgacure-2959 photoinitiator to the solution. Finally, pour the pregel solution into a polytetrafluoroethylene mold and perform free radical polymerization under ultraviolet-visible light with a wavelength of 405 nm and a power of 100 W for 5 minutes to obtain a heterojunction functionalized double network hydrogel (PCT).

[0028] (3) The PCT was immersed in a 0.5 M hydrochloric acid / ethylene glycol (HCl / EG) solution for 30 min to obtain a flexible fluorescent sensor (PCT′).

[0029] Example 2 This embodiment provides a flexible fluorescent sensor. The specific preparation process differs from that of embodiment 1 only in the following aspects: (3) The PCT was immersed in a 1.0 M hydrochloric acid / ethylene glycol (HCl / EG) solution for 30 min to obtain a flexible fluorescent sensor (PCT′).

[0030] Example 3 This embodiment provides a flexible fluorescence sensor. The specific preparation process differs from that of Example 1 only in the following aspects: (3) The PCT was immersed in a 1.5 M hydrochloric acid / ethylene glycol (HCl / EG) solution for 30 min to obtain a flexible fluorescent sensor (PCT′).

[0031] Example 4 This embodiment provides a flexible fluorescence sensor. The specific preparation process differs from that of Example 1 only in the following aspects: (3) The PCT was immersed in a 2.0 M hydrochloric acid / ethylene glycol (HCl / EG) solution for 30 min to obtain a flexible fluorescent sensor (PCT′).

[0032] Example 5 This embodiment provides a heterojunction functionalized double network hydrogel (PCT), the specific preparation process of which differs from that of Example 1 as follows: In step (2), the amount of TCTG powder added was 0.5 mg.

[0033] Example 6 This embodiment provides a heterojunction functionalized double network hydrogel (PCT), the specific preparation process of which differs from that of Example 1 as follows: In step (2), the amount of TCTG powder added was 1.5 mg.

[0034] Example 7 This embodiment provides a heterojunction functionalized double network hydrogel (PCT), the specific preparation process of which differs from that of Example 1 as follows: In step (2), the amount of TCTG powder added was 2 mg.

[0035] Example 8 This embodiment provides a double network hydrogel (PC), the specific preparation process of which is as follows: A 6g CMC suspension (0.5wt%) was prepared and mixed with 6g acrylamide. The mixture was stirred at room temperature (500 rpm) for 30 minutes, during which time 10mg of N,N'-methylenebisacrylamide was added. After stirring, 100mg of Irgacure-2959 photoinitiator was added. Finally, the pregel solution was poured into a polytetrafluoroethylene mold and subjected to free radical polymerization under 405nm UV-visible light at 100W for 5 minutes to obtain a dual-mode cross-linked PC dual-network hydrogel.

[0036] Example 9 This embodiment provides a double network hydrogel (PC), and the specific preparation process thereof differs from that of Example 8 only in the following aspects: The concentration of CMC is 1 wt%.

[0037] Example 10 This embodiment provides a double network hydrogel (PC), and the specific preparation process thereof differs from that of Example 8 only in the following aspects: The concentration of CMC is 2 wt%.

[0038] Example 11 This embodiment provides a double network hydrogel (PC), and the specific preparation process thereof differs from that of Example 8 only in the following aspects: The concentration of CMC is 3 wt%.

[0039] Comparative Example 1 This comparative example provides a flexible fluorescent sensor, and the specific preparation process is different from that of Example 1 as follows: (3) Immerse PCT in ethylene glycol solution for 30 minutes to obtain a flexible fluorescent sensor (PCT′) Comparative Example 2 This comparative example provides a heterojunction functionalized double network hydrogel (PCT), the specific preparation process of which differs from that of Example 1 as follows: In step (2), the amount of TCTG powder added was 0 mg.

[0040] Comparative Example 3 This comparative example provides an acrylamide single network hydrogel, the specific preparation process of which is as follows: 6 g of water (CMC concentration: 0 wt%) was mixed with 6 g of acrylamide. The mixture was stirred at room temperature (500 rpm) for 30 minutes, during which time 10 mg of N,N'-methylenebisacrylamide was added. After stirring, 100 mg of Irgacure-2959 photoinitiator was added to the solution. Finally, the pregel solution was poured into a polytetrafluoroethylene mold and free radical polymerization was performed under 405 nm UV-visible light at 100 W for 5 minutes to obtain a dual-mode cross-linked PC dual-network hydrogel.

[0041] Test 1

[0042] The stress-strain curves of the PCT' double network hydrogels provided in Examples 1-4 and Comparative Example 1 are shown in FIG. Figure 1 As shown, the corresponding elastic modulus (E) and toughness (T) of the PCT' double network hydrogels provided in Examples 1-4 and Comparative Example 1 are as follows Figure 2 As shown. Figure 1-2 It can be seen that higher HCl concentration (≥1.0 M) increased the stiffness of the hydrogel but reduced its flexibility, and 0.5 MHCl / EG treatment achieved the best balance of strength, elongation and toughness.

[0043] Figure 3 The TCTG SEM images and EDS elemental spectra of the TCTG dispersed in the hydrogel network of Example 1 are shown in FIG. Figure 3 Scanning electron microscopy results show that TCTG is randomly distributed within the hydrogel network. The uniform distribution of Cl elements indicates the successful preparation of PCT′ double network hydrogel after acid induction and solvent exchange.

[0044] Figure 4 The scanning electron microscope image and the three-dimensional image of the surface roughness of the PCT′ double network hydrogel of Example 1 and the scanning electron microscope image and the three-dimensional image of the surface roughness of the PCT′ double network hydrogel of Comparative Example 1 are shown. Figure 4 It can be seen that the microscopic surface of PCT′ double network hydrogel becomes denser and smoother after acid induction and solvent exchange.

[0045] Figure 5 1 is a stress-strain curve of the PCT double network hydrogel of Examples 1, 5-7 and Comparative Example 2; Figure 6 1 is a graph showing the fracture strain and stress trends of the PCT double network hydrogels of Examples 1, 5-7 and Comparative Example 2; Figure 7 are the corresponding elastic modulus (E) and toughness (T) of the PCT double network hydrogels of Examples 1, 5-7 and Comparative Example 2. Figure 5-7It can be seen that when the TCTG addition amount is 0.5mg-1.5mg, the elastic modulus and toughness of the PCT double network hydrogel are in the optimal balance state.

[0046] The stress-strain behavior and cyclic tensile test results of the PCT heterojunction functional double network hydrogel under different loading conditions are shown in Figure 1. Figure 8 As shown, from Figure 8 It can be seen that PCT double network hydrogel has excellent tensile fatigue resistance.

[0047] The stress-strain curves of the hydrogels of Examples 8-11 and Comparative Example 3 are as follows: Figure 9 As shown, the fracture strain and stress trends of the hydrogels of Examples 8-11 and Comparative Example 3 are as follows Figure 10 As shown in Figure 2, the corresponding elastic modulus (E) and toughness (T) (right) of the hydrogels of Examples 8-11 and Comparative Example 3 are shown in Figure 2. Figure 11 As shown. Figure 9-11 It can be seen that a moderate CMC concentration (2.0-3.0 wt%) enhances strength and ductility through hydrogen bonding, electrostatic interaction and interconducting network formation, while excessive CMC or Na⁺ reduces flexibility due to network densification and limited polymer chain mobility.

[0048] Test 2 The mechanical stability, fluorescence stability and H2S response characteristics of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ of Example 1 were measured under different environmental conditions.

[0049] The PCT and PCT′ double-network hydrogels were placed in a constant temperature and humidity incubator at 25°C and relative humidity levels of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% for 48 hours to assess their humidity stability. After incubation, samples were removed and analyzed for fluorescence intensity and mechanical properties. The PCT and PCT′ double-network hydrogels were stored at -60°C, -20°C, 0°C, 4°C, 25°C, and 35°C for 48 hours. After storage, fluorescence intensity and mechanical properties were measured.

[0050] To investigate the specificity of fluorescence response, a PCT′ flexible fluorescence sensor (radius = 15 mm) was fixed to the headspace of a sealed chamber (5 L). A four-channel gas distribution system, GC400 (Tunkon), was used to dynamically dilute various concentrations of volatile organic compounds (VOCs). Several VOCs commonly associated with fish spoilage, including H₂S, SO₂, CO, NO, methylmercaptan, and trimethylamine, were added to the sealed container containing the PCT′ flexible fluorescence sensor at a concentration of 10 ppm. Ethanol, valeraldehyde, 2-heptanone, butyric acid, ethyl acetate, and pentane were simultaneously prepared to specific concentrations (10 mg / L), and the indicator was immersed in the corresponding solutions for 60 seconds. Fluorescence intensity was measured to evaluate the selectivity of the indicator. A standard solution was prepared according to the conversion formula for pollutant concentrations in water environments: 1 ppm = 1 mg / L. In an anti-interference test, the indicator, after undergoing the above steps, was reintroduced into the sealed container and exposed to H₂S gas (10 ppm). The change in fluorescence intensity was then measured.

[0051] The fluorescence stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescence sensor PCT′ in different humidity conditions are shown in FIG. Figure 12 .from Figure 12 The fluorescence intensity of the PCT′ double-network hydrogel remains relatively stable over a wide range of relative humidity (RH), outperforming the PCT hydrogel due to its denser network and improved resistance to humidity-induced quenching. At high humidity, the PCT double-network hydrogel exhibits a fluorescence decrease caused by water absorption, swelling, and non-radiative recombination, whereas the HCl / EG treatment and MXene-GQD scaffold in the PCT′ double-network hydrogel mitigate these effects.

[0052] The mechanical stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ in different humidity conditions are shown in FIG. Figure 13 .from Figure 13 It can be seen that the PCT′ hydrogel treated with acid induction and solvent exchange has excellent mechanical stability under different humidity environments.

[0053] The fluorescence stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescence sensor PCT′ at different temperatures of Example 1 are shown in FIG. Figure 14 .from Figure 14 It can be seen that at low temperatures, the PCT′ double network hydrogel maintains fluorescence, while the PCT double network hydrogel suffers intensity loss due to ice formation, surface frost, and light scattering, which interferes with GQD excitation and emission. These results confirm that the PCT′ double network hydrogel has excellent structural and optical stability under variable environmental conditions.

[0054] The mechanical stability test results of the heterojunction functionalized double network hydrogel PCT and the flexible fluorescent sensor PCT′ of Example 1 at different temperatures are shown in FIG. Figure 15 As shown, from Figure 15 It can be seen that the PCT′ hydrogel treated with acid induction and solvent exchange has excellent mechanical stability under different temperature environments (-60 ℃~35 ℃).

[0055] The water loss of PCT and PCT' double network hydrogels in Example 1 under sealed and unsealed storage conditions is shown in Figure 2. Figure 16 As shown, from Figure 16 It can be seen that compared with PCT hydrogel, PCT′ double network hydrogel showed significantly improved water retention under both sealed and unsealed conditions, with only ~10% water loss in the unsealed environment and only <2% water loss in the sealed environment.

[0056] The long-term stability of the PCT' double network hydrogel as a smart fluorescent indicator label in Example 1 within 30 days is shown in FIG. Figure 17 .from Figure 17 As can be seen, after the introduction of 0.1ppm H2S, the probe exhibited high long-term stability, with minimal response change (2.32% - 2.43%) over 30 days. This small error range highlights the reliability and repeatability of the probe measurement.

[0057] The sensitivity of PCT' to H2S in Example 1 is as follows Figure 18 As shown, from Figure 18 As the H2S concentration increases from 0 to 20 ppm, the fluorescence intensity of the PCT′ smart fluorescent indicator tag shows a strong linear correlation with the H2S concentration. The Pearson R value of the linear relationship is 0.9757, and the LOD calculated based on the fluorescence intensity is 62.13 ppb.

[0058] The specificity and anti-interference test results of PCT' in Example 1 for H2S are as follows: Figure 19 As shown, from Figure 19 It can be seen that the PCT′ flexible fluorescence sensor can specifically adsorb H2S and has excellent anti-interference ability.

[0059] The 90° shear adhesion test results of the PCT′ double network hydrogel of Example 1 as a smart fluorescent indicator label are as follows: Figure 20 As shown, from Figure 20 The PCT′ intelligent fluorescent indicator exhibited strong initial adhesion (~3 N) and stable shear load capacity (1.5–2.0 N) in a 90° shear test, demonstrating excellent interfacial adhesion and mechanical stability. Its excellent energy dissipation properties make it suitable for applications in bioadhesives, flexible electronics, and soft robotics.

[0060] Test 3 The practical application of the PCT′ double-network hydrogel of Example 1 as an intelligent fluorescent indicator label in the fish storage process.

[0061] 500g of salmon fillets were rinsed with distilled water and placed in a sealed food storage container. A PCT' intelligent fluorescent indicator label was affixed to the inside of the container lid. The container was then placed in a constant-temperature incubator at 0°C and 25°C. The label's fluorescence intensity was measured regularly, and images of the fillets' freshness and spoilage were captured under sunlight and 365nm UV-visible light.

[0062] The results are as follows Figure 21 As shown, the fluorescence intensity of a PCT′ smart fluorescent indicator tag changes at different time points as H2S concentration increases in the headspace of a food storage box due to fresh food spoilage. The PCT′ dual-network hydrogel was used as a smart fluorescent indicator tag to monitor the quality of salmon during refrigerated and ambient storage. The indicator tag, fixed to the inside of the fresh-keeping box lid through its adhesive properties, responds in real time to H2S released during salmon spoilage. Experiments showed that under refrigerated storage, the indicator's fluorescence intensity remained stable for the first six days, then began to weaken slightly on the ninth day and dimmed significantly from days 12 to 15, indicating gradual spoilage. In contrast, at ambient temperature, the fluorescence began to quench within 12 hours and reached its lowest point after 48 hours, indicating rapid progression of spoilage. The fluorescence intensity is highly correlated with H2S concentration, effectively reflecting the freshness and degree of spoilage of fish, and has broad application prospects in food safety monitoring.

[0063] Application 1: Quality inspectors monitor fish quality changes in real time from delivery to sales locations Fish quality testing process (1) Before the fish enters the cold chain delivery vehicle, 500g of fish meat is collected as a sample and placed in a fresh-keeping box equipped with a PCT' intelligent fluorescent indicator label; (2) Use 365nm ultraviolet light to illuminate the flexible fluorescent sensor during the logistics and transaction stages, and conduct random inspections at irregular intervals; (3) Real-time monitoring of fish quality changes through changes in fluorescence intensity Application 2: PCT' intelligent fluorescent indicator label operates reliably in complex and harsh cold chain logistics environments PCT' intelligent fluorescent indicator label copes with complex and harsh environment testing (1) First, the PCT′ intelligent fluorescent indicator label was attached to the inside of a fresh-keeping box containing 500g of fish. Then, various fresh food items were randomly placed in a cold chain delivery vehicle. The delivery vehicle was accelerated, braked suddenly, and turned suddenly to cause the surrounding fresh food items to squeeze and collide with the intelligent indicator label. (2) Then start different low-temperature refrigeration and different humidity control storage environments; (3) By measuring the integrity, mechanical properties and fluorescence intensity stability of the PCT′ intelligent fluorescent indicator label, it is determined whether it can cope with the complex and harsh cold chain environment and operate reliably.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A flexible fluorescence sensor, characterized in that: The invention comprises TCTG particles and a double network hydrogel, wherein the TCTG particles are distributed in the network pores of the double network hydrogel to form a functional gel, and the TCTG particles are composed of Ti3C2T x MXene nanosheets and graphene quantum dots are formed, the double network hydrogel is formed by acrylamide and sodium carboxymethyl cellulose, and the functional gel is immersed in a hydrochloric acid ethylene glycol solution.

2. The flexible fluorescent sensor according to claim 1, characterized in that: The concentration of HCl in the ethylene glycol hydrochloride solution is 0.1 mol / L-2 mol / L.

3. The flexible fluorescent sensor according to claim 1, characterized in that: The functional gel is immersed in the hydrochloric acid ethylene glycol solution for 20 minutes to 40 minutes.

4. The flexible fluorescent sensor according to any one of claims 1 to 3, characterized in that: The mass ratio of the acrylamide to the sodium carboxymethyl cellulose is 2:(0.01-0.1).

5. The flexible fluorescent sensor according to any one of claims 1 to 3, characterized in that: The Ti3C2T x The mass ratio of MXene nanosheets and graphene quantum dots is (1-4):(4-1).

6. The flexible fluorescent sensor according to any one of claims 1 to 3, characterized in that: The mass ratio of the TCTG particles to the acrylamide is 1:(15000-3000).

7. The flexible fluorescent sensor according to any one of claims 1 to 3, characterized in that: The particle size of the TCTG particles is no greater than 100 nm.

8. A method for preparing the flexible fluorescent sensor according to any one of claims 1 to 7, characterized in that: include: (1) Ti3C2T x A mixed suspension of MXene nanosheets and graphene quantum dots in aqueous solution undergoes hydrothermal reaction to obtain TCTG particles; (2) dispersing the TCTG particles in a suspension aqueous solution of sodium carboxymethyl cellulose, and then mixing with acrylamide to undergo polymerization and cross-linking under the action of a cross-linking agent and an initiator to obtain a functional gel; (3) Immersing the functional gel in a hydrochloric acid ethylene glycol solution for treatment.

9. The method according to claim 8, wherein the cross-linking agent comprises one or more of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and ethylene glycol diacrylate; And / or, the initiator is selected from photoinitiators.

10. Use of the flexible fluorescent sensor according to any one of claims 1 to 7 in detecting H2S.

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