Fluorescent colorimetric card based on fluorescent nanofibers and method for rapidly detecting hydrogen sulfide gas by using fluorescent colorimetric card

Abstract

The invention belongs to the technical field of rapid detection of food and agricultural products, and particularly relates to a fluorescent colorimetric card based on fluorescent nanofibers and a method for rapidly detecting hydrogen sulfide gas by using the fluorescent colorimetric card. The method comprises the following steps: firstly, synthesizing gold nanoclusters; then modifying a vinyl alcohol-ethylene copolymer nanofiber membrane based on the synthesized gold nanoclusters, and finally preparing the fluorescent colorimetric card based on the vinyl alcohol-ethylene copolymer nanofiber membrane modified by the synthesized gold nanoclusters. The fluorescent colorimetric card prepared by the invention can realize visual reading of hydrogen sulfide gas response signals, so as to realize qualitative identification of salmonella typhimurium in food. Moreover, the prepared fluorescent colorimetric card has the advantages of low cost, portability, visual detection and the like, is suitable for non-destructive detection of salmonella typhimurium in multiple scenes, and has important significance for guaranteeing the safety of food and agricultural products.

Description

Technical Field

[0001] The present invention belongs to the technical field of rapid detection of food and agricultural products, and particularly relates to a fluorescence colorimetric card based on fluorescent nanofibers and a method for rapidly detecting hydrogen sulfide gas produced by Salmonella typhimurium. Background Art

[0002] Food pathogenic bacteria are pathogenic bacteria that can cause food poisoning or use food as a transmission medium. In China, the number of reported cases of foodborne diseases caused by pathogenic bacteria in food each year accounts for about 40% to 50% of all reported cases. Food is prone to cross-contamination by foodborne pathogenic bacteria during breeding, processing, transportation, and cooking. Once food is contaminated by pathogenic bacteria, it will not only cause huge economic losses, but also pose great harm to human health once the contaminated food enters the food chain, triggering a series of food safety and life health problems, inducing symptoms such as nausea, vomiting, fever, abdominal pain, and diarrhea. Salmonella typhimurium is a Gram-negative bacterium and one of the most common foodborne pathogenic bacteria in the world, usually present in animal-derived foods such as poultry, meat, milk, and eggs. Therefore, it is of great significance to develop a detection method for Salmonella typhimurium.

[0003] Currently, the gold standard for detecting Salmonella typhimurium is the traditional plate counting method, but this method has a long detection cycle and is very time-consuming. In recent years, detection methods such as polymerase chain reaction, immunoassay, high-performance liquid chromatography, and mass spectrometry have also been used in the field of rapid identification of foodborne pathogens. However, these methods usually require complex pretreatment procedures, time-consuming preparations, and expensive advanced instruments. Salmonella typhimurium can decompose sulfur-containing amino acids (such as cystine, cysteine, and methionine) in food under the action of amino acid enzymes to produce hydrogen sulfide gas with a putrid egg-like odor, which is one of its important biochemical characteristics. Other foodborne pathogenic bacteria usually do not produce hydrogen sulfide gas. Therefore, the production of hydrogen sulfide can be used to distinguish Salmonella typhimurium from other genera.

[0004] Therefore, developing a gas sensor that can detect hydrogen sulfide to achieve portable on-site detection of Salmonella typhimurium is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] In order to overcome the deficiencies of existing methods, the present invention provides a method for rapidly detecting hydrogen sulfide gas produced by Salmonella typhimurium using fluorescent nanofibers. The prepared fluorescence colorimetric card can realize visual reading of the hydrogen sulfide gas response signal, and further realize qualitative identification of Salmonella typhimurium in food. The fluorescence colorimetric card prepared by the present invention has the advantages of low cost, portability, visual detection, etc., and is suitable for non-destructive detection of Salmonella typhimurium in multiple scenarios.

[0006] To achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows;

[0007] S1. Synthesize gold nanoclusters:

[0008] First, mix the chloroauric acid solution with the reduced glutathione solution to obtain a mixture; then add ultrapure water to the mixture and carry out a heating reaction under stirring conditions. After the reaction ends, a gold nanocluster solution is obtained;

[0009] Preferably, in step S1, the dosage relationship of the chloroauric acid solution, the reduced glutathione solution, and the ultrapure water is 0.2 - 10 mL: 0.5 - 15 mL: 2 - 30 mL, where the concentration of the chloroauric acid solution is 5 - 50 mM and the concentration of the reduced glutathione solution is 5 - 50 mM; the temperature of the heating reaction is 50 - 120 °C, and the reaction time is 6 - 48 hours; the prepared gold nanocluster solution is a yellow solution under natural light and emits orange fluorescence under ultraviolet light, and the emission peak is located at 570 - 680 nm.

[0010] S2. Preparation of gold nanocluster-modified PVA-co-PE nanofiber membrane:

[0011] (1) Preparation of PVA-co-PE nanofiber membrane: Dissolve vinyl alcohol ethylene copolymer (hereinafter referred to as PVA-co-PE) in a mixed solution of isopropanol and ultrapure water, and stir under water bath conditions to obtain a PVA-co-PE solution; ultrasonically treat the obtained PVA-co-PE solution to remove the bubbles in the solution, and then use the solution as a spinning solution, set the spinning conditions, and carry out spinning. After spinning, a nanofiber membrane is obtained, which is the PVA-co-PE nanofiber membrane after drying;

[0012] (2) Activation of PVA-co-PE nanofiber membrane with sodium hydroxide: Cut the PVA-co-PE nanofiber membrane prepared in step (1) as needed and soak it in a sodium hydroxide solution for incubation. After the incubation ends, take out the PVA-co-PE nanofiber membrane and wash it with ultrapure water to obtain a sodium hydroxide-activated nanofiber membrane;

[0013] (3) Functionalization of PVA-co-PE nanofiber membrane with cyanuric chloride: Immerse the sodium hydroxide-activated nanofiber membrane in step (2) into a 1,4-dioxane solution containing cyanuric chloride for incubation. After incubation, take out the nanofiber membrane and wash it successively with 1,4-dioxane, water, and acetone (to remove the unreacted cyanuric chloride on the membrane surface). After washing, a cyanuric chloride-functionalized nanofiber membrane is obtained;

[0014] (4) Amino-modified PVA-co-PE nanofiber membrane: Immerse the cyanuric chloride-functionalized nanofiber membrane obtained in step (3) in an anhydrous ethanol solution of 1,3-propanediamine. After immersion, take out the nanofiber membrane and wash it with ethanol. After washing, dry it to obtain the amino-modified nanofiber membrane;

[0015] (5) Gold nanocluster-modified PVA-co-PE nanofiber membrane: Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the gold nanocluster solution prepared in step S1, incubate to activate the surface carboxyl groups to obtain the activated gold nanocluster solution; Immerse the amino-modified nanofiber membrane obtained in step (4) in the activated gold nanocluster solution. After immersion, take out the nanofiber membrane and wash it with ultrapure water. After washing, dry it to obtain the gold nanocluster-modified nanofiber membrane.

[0016] Preferably, in (1) of step S2, the dosage relationship of PVA-co-PE, isopropanol, and ultrapure water is 0.2 - 2 g: 2 - 8 mL:

[0017] 2 - 8 mL; the temperature of the water bath is 40 - 90 °C, and the water bath time is 2 - 24 hours;

[0018] The electrospinning conditions are: the electrospinning voltage is 2 - 80 kV, the feeding rate is 1 - 10 mL / h, the electrospinning temperature is 15 - 45 °C, and the distance from the spinneret to the surface of the collector is 10 - 30 cm; the drying temperature is 40 - 80 °C, and the drying time is 2 - 48 hours.

[0019] Preferably, in (2) of step S2, the length of the cut nanofiber membrane is 0.5 - 20 cm, and the width is 0.5 - 20 cm; the concentration of the sodium hydroxide solution is 0.2 - 10 M; the incubation temperature is 10 - 60 °C, and the incubation time is 0.5 - 12 hours.

[0020] Preferably, in (3) of step S2, the 1,4-dioxane solution of cyanuric chloride is obtained by mixing cyanuric chloride and 1,4-dioxane; the concentration of the 1,4-dioxane solution of cyanuric chloride is 2 - 50% (wt%); the incubation temperature is 10 - 60 °C, and the incubation time is 5 - 240 minutes.

[0021] Preferably, in (4) of step S2, the anhydrous ethanol solution of 1,3-propanediamine is obtained by mixing 1,3-propanediamine and anhydrous ethanol; the concentration of the anhydrous ethanol solution of 1,3-propanediamine is 0.2 - 10 M; the incubation temperature is 10 - 60 °C, and the incubation time is 0.5 - 12 hours; the drying temperature is 10 - 80 °C, and the drying time is 2 - 48 hours.

[0022] Preferably, in step S2(5), the dosage relationship of the gold nanocluster solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and N-hydroxysuccinimide concentrations is 2-50 mL: 0.2-5 mL: 0.2-5 mL; where the concentration of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is 1 μM-1 mM; the concentration of N-hydroxysuccinimide is 0.5-500 μM;

[0023] The incubation temperature is 10-60 °C, and the incubation time is 0.5-24 hours; the soaking temperature is 10-60 °C, and the soaking time is 0.5-24 hours; the number of times of washing with ultrapure water is 2-5 times.

[0024] S3. Preparation of a fluorescence colorimetric card;

[0025] (1) Preparation of a sodium sulfide standard solution:

[0026] Prepare n sodium sulfide standard solutions with different concentration gradients, and the concentrations are C1, C2, C3,..., C n , where n is a positive integer;

[0027] (2) Preparation of a standard fluorescence colorimetric card

[0028] Immerse the nanofiber membrane modified with gold nanoclusters in sodium sulfide standard solutions with different concentrations C1, C2, C3,..., C n . After oscillating incubation, take out the nanofiber membrane modified with gold nanoclusters, dry it, arrange it in ascending order of sodium sulfide concentration, and place it under an ultraviolet lamp to obtain fluorescence optical photos of the nanofiber membrane, which are respectively recorded as P1, P2, P3,..., P n ; Arrange them in order to obtain a fluorescence colorimetric card.

[0029] Preferably, in step S3(1), the concentration range of the sodium sulfide standard solution is 1×10 -10 -10 M;

[0030] Preferably, in step S3(2), the temperature of the oscillating incubation is 10-60 °C, and the time of the oscillating incubation is 1-30 minutes; the drying temperature is 10-80 °C, and the drying time is 2-48 hours.

[0031] S4. Detection of hydrogen sulfide gas produced by Salmonella typhimurium in an actual sample

[0032] Place the sample to be tested in a sealed sample box. At the same time, place the nanofibers modified with gold nanoclusters in the sample box without direct contact with the sample. Seal the sample box with a sealing film. After storing the sample for a period of time, take out the nanofiber membrane and obtain its fluorescence optical photo under ultraviolet light, and compare it with the fluorescence colorimetric card to obtain the content of hydrogen sulfide produced by Salmonella typhimurium in the analyte, realizing the visual detection of hydrogen sulfide gas.

[0033] Preferably, in step S4, the storage temperature is 0 - 60 °C, the distance between the nanofibers modified with gold nanoclusters and the sample is 1 - 50 cm, and the storage time is 2 - 144 hours.

[0034] Advantages of the present invention:

[0035] (1) The present invention first proposes a sensing detection method for the gas produced by Salmonella typhimurium. Compared with the existing detection methods, the present invention is simple to operate, does not require sample treatment, has low cost, does not require large-scale instrument equipment and professional operators, and can meet the detection needs of large-scale food and agricultural products, providing a new method for the portable detection of hydrogen sulfide gas produced by Salmonella typhimurium.

[0036] (2) The present invention uses the fluorescent nanomaterial gold nanoclusters to prepare a fluorescent nanofiber membrane, which has good response performance to hydrogen sulfide gas. In addition, the nanofiber membrane prepared by electrospinning has the advantages of small diameter and large specific surface area, making it an ideal material for gas sensing.

[0037] (3) The standard fluorescence colorimetric card of the fluorescent nanofiber membrane proposed by the present invention can be used for on-site detection of hydrogen sulfide gas produced by Salmonella typhimurium outside the laboratory environment and can be used in different detection scenarios, with a wider scope of application.

[0038] (4) The gas sensor proposed by the present invention can realize the real-time dynamic monitoring of the concentration of hydrogen sulfide gas produced by Salmonella typhimurium, which is of great significance for ensuring the safety of food and agricultural products. Description of the Drawings

[0039] Figure 1 It is a scanning electron microscope image of the nanofiber membrane modified with gold nanoclusters prepared in Example 1.

[0040] Figure 2 It is the fluorescence standard colorimetric card made in Example 1.

[0041] Figure 3 It is the detection of hydrogen sulfide gas produced by Salmonella typhimurium in the actual sample in Example 1. Specific Embodiment

[0042] The present invention will be described in detail by the following embodiments; however, these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The reagents used in the present invention can be obtained through conventional commercial sources without special instructions.

[0043] Example 1:

[0044] S1. Synthesis of gold nanoclusters:

[0045] First, freshly prepared chloroauric acid solution (1 mL, 20 mM) was mixed with reduced glutathione solution (1.5 mL, 20 mM), and then 7.5 mL of ultrapure water was added to the mixture. The mixture was gently stirred and heated at 70 °C for 24 hours. After the reaction, a gold nanocluster solution was obtained and stored at 4 °C. The prepared gold nanocluster solution was a yellow solution under natural light and emitted orange fluorescence under ultraviolet light, with an emission peak at 624 nm.

[0046] S2. Preparation and modification of PVA-co-PE nanofiber membrane:

[0047] (1) Preparation of PVA-co-PE nanofiber membrane: 0.8 g of copolymer PVA-co-PE was dissolved in a solvent mixture of 10 mL of isopropanol and ultrapure water (7 / 3, v / v), and the mixture was vigorously stirred in a water bath at 75 °C for 8 hours to obtain a PVA-co-PE solution; the obtained solution was ultrasonicated for 30 minutes to remove the bubbles in the solution. Then the obtained solution was used as the spinning solution and transferred to a 10 mL plastic syringe with a tubular metal needle. The syringe was installed on a DXES-1 spinning device, and the parameters were set as follows: the applied voltage was 30 kV, the controllable propulsion speed was 4 mL / h, the temperature was 24 °C, and the distance from the spinneret to the collector surface was 23 cm. After spinning, a nanofiber membrane was obtained and dried in a vacuum oven at 40 °C for 12 hours to obtain a PVA-co-PE nanofiber membrane;

[0048] (2) Activation of PVA-co-PE nanofiber membrane with sodium hydroxide: The prepared nanofiber membrane was cut into small squares of 1×2 cm, immersed in sodium hydroxide solution (50 mL, 3 M), incubated at 37 °C for 2 hours, and then washed with ultrapure water.

[0049] (3) Functionalization of PVA-co-PE nanofiber membrane with cyanuric chloride: The sodium hydroxide-activated nanofiber membrane was immersed in a 1,4-dioxane solution containing cyanuric chloride (50 mL, wt% = 10%), and incubated at 37 °C for 30 minutes. Subsequently, the membrane was taken out and washed with 1,4-dioxane, water, and acetone to remove the unreacted cyanuric chloride on the membrane surface, and a cyanuric chloride-functionalized nanofiber membrane was obtained.

[0050] (4) Amino-modified PVA-co-PE nanofiber membrane: The cyanuric chloride-functionalized nanofiber membrane was immersed in an anhydrous ethanol solution (50 mL, 3 M) of 1,3-propanediamine at 37 °C for 2 hours. Subsequently, it was washed three times with ethanol and dried to obtain the amino-modified nanofiber membrane.

[0051] (5) Gold nanocluster-modified PVA-co-PE nanofiber membrane: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (1 mL, 15 μM) and N-hydroxysuccinimide (1 mL, 7.5 μM) were added to the gold nanocluster solution (10 mL) and incubated for 1 hour to activate the surface carboxyl groups. The amino-modified nanofiber membrane was placed in the activated gold nanocluster solution and immersed at 37 °C for 8 hours. Then it was washed three times with ultrapure water and dried to obtain the gold nanocluster-modified nanofiber membrane; Figure 1 It is the scanning electron microscope image of the prepared gold nanocluster-modified nanofiber membrane.

[0052] S3. Establish a fluorescence rapid detection prediction model

[0053] (1) Preparation of sodium sulfide standard solution:

[0054] Twelve sodium sulfide standard solutions with different concentration gradients were prepared, with concentrations of C1 = 1×10 -7 M, C2 = 1×10 - 6 M, C3 = 1×10 -5 M, C4 = 1×10 -4 M, C5 = 1.5×10 -4 M, C6 = 2×10 -4 M, C7 = 3×10 -4 M, C8 = 4×10 -4 M, C9 = 6×10 -4 M, C 10 = 8×10 -4 M, C 11 = 1×10 -3 M, C 12 = 1×10 -2 M;

[0055] (2) Preparation of a standard fluorescence color comparison card

[0056] 1 mL of different concentrations C2, C3, C4, C 11 , C 12Transfer 1.5 mL of the sodium sulfide standard solution into a centrifuge tube. Place the nanofiber membrane modified with gold nanoclusters into it. After oscillating and incubating for 5 minutes, take it out. Dry it in a vacuum oven at 40 °C for 8 hours. After drying, arrange them in ascending order of sodium sulfide concentration. Place them under an ultraviolet lamp and use a camera to obtain the fluorescence optical photos of each nanofiber membrane, which are respectively denoted as P2, P3, P4, P 11 , P 12 ; Arrange them in order, and then the standard fluorescence colorimetric card can be obtained; Figure 2 Figure 1 is the fluorescence colorimetric card made in Example 1. It can be seen from the figure that the prepared nanofiber membrane emits orange fluorescence under the ultraviolet lamp. As the concentration of sodium sulfide increases, the fluorescence signal of the nanofiber membrane gradually weakens. When the sodium sulfide concentration is 10 -2 M, the fluorescence of the nanofiber membrane is completely quenched.

[0057] S4. Rapid prediction of hydrogen sulfide gas produced by Salmonella typhimurium in actual samples, using chicken as the test sample;

[0058] Weigh 100 g of the chicken sample and place it in a sealed sample box with a volume of 500 mL. Place the nanofiber modified with gold nanoclusters inside the sample box, keeping a 3-cm distance between the nanofiber modified with gold nanoclusters and the sample. Seal the sample box with a sealing film. After storing the sample at 24 °C for 0, 8, 16, and 24 hours, take out the nanofiber membrane and obtain its fluorescence optical photo under the ultraviolet lamp, and compare it with the standard fluorescence colorimetric card established in S3 respectively to achieve the visual detection of hydrogen sulfide gas produced by Salmonella typhimurium in the test substance.

[0059] Figure 3 Figure 2 is the detection of hydrogen sulfide gas produced by Salmonella typhimurium in the actual sample in Example 1. It can be seen from the figure that the nanofiber membrane modified with gold nanoclusters emits strong orange fluorescence. As the storage time increases, the fluorescence of the nanofiber membrane gradually weakens. By comparing with the fluorescence standard colorimetric card, it can be found that when the chicken sample is stored for 8 hours, the fluorescence of the nanofiber membrane is similar to P4. Therefore, it can be determined that the concentration of hydrogen sulfide gas in the sample box is about 10 -4 M at this time; when the sample is stored for 16 hours, the fluorescence intensity of the nanofiber membrane is between P 11 and P 12 , indicating that the concentration of hydrogen sulfide gas in the sample box is in the range of 10 -3 ~10 -2 M at this time; when the sample is stored for 24 hours, the fluorescence of the nanofiber membrane is completely quenched, indicating that the concentration of hydrogen sulfide gas in the sample box is greater than or equal to 10 -2 M at this time.

[0060] Note: The above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; therefore, although the present specification has described the present invention in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a fluorescence colorimetric card based on fluorescent nanofibers, characterized in that, It includes the following steps: S1. Synthesize gold nanoclusters: First, mix the chloroauric acid solution with the reduced glutathione solution to obtain a mixture; then add ultrapure water to the mixture and carry out a heating reaction under stirring conditions. After the reaction ends, a gold nanocluster solution is obtained; S2. Preparation of gold nanocluster-modified PVA-co-PE nanofiber membrane: (1) Preparation of PVA-co-PE nanofiber membrane: Dissolve the vinyl alcohol-ethylene copolymer in a mixed solution of isopropanol and ultrapure water and stir under water bath conditions to obtain a PVA-co-PE solution; Ultrasonically treat the obtained PVA-co-PE solution to remove the bubbles in the solution, then use the solution as a spinning solution, set the spinning conditions, and carry out spinning. After spinning, a nanofiber membrane is obtained, which is dried to obtain the PVA-co-PE nanofiber membrane; (2) Activate the PVA-co-PE nanofiber membrane with sodium hydroxide: Cut the PVA-co-PE nanofiber membrane prepared in step (1) as needed and soak it in a sodium hydroxide solution for incubation. After incubation, take out the PVA-co-PE nanofiber membrane and wash it with ultrapure water to obtain a sodium hydroxide-activated nanofiber membrane; (3) Functionalize the PVA-co-PE nanofiber membrane with cyanuric chloride: Immerse the sodium hydroxide-activated nanofiber membrane in step (2) in a 1,4-dioxane solution containing cyanuric chloride for incubation. After incubation, take out the nanofiber membrane and wash it successively with 1,4-dioxane, water, and acetone to obtain a cyanuric chloride-functionalized nanofiber membrane; (4) Modify the PVA-co-PE nanofiber membrane with amino groups: Immerse the cyanuric chloride-functionalized nanofiber membrane obtained in step (3) in an anhydrous ethanol solution of 1,3-propanediamine. After soaking, take out the fiber membrane and wash it with ethanol, and then dry it to obtain an amino-modified nanofiber membrane; (5) Modify the PVA-co-PE nanofiber membrane with gold nanoclusters: Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the gold nanocluster solution prepared in step S1, incubate, and activate the surface carboxyl groups to obtain an activated gold nanocluster solution; Place the amino-modified nanofiber membrane obtained in step (4) in the activated gold nanocluster solution for soaking. After soaking, take out the fiber membrane and wash it with ultrapure water, and then dry it to obtain a gold nanocluster-modified nanofiber membrane; S3. Preparation of a standard fluorescence colorimetric card; (1) Prepare a sodium sulfide standard solution; Prepare sodium sulfide standard solutions with n different concentration gradients, with concentrations of C1, C2, C3, ……, C n , where n is a positive integer; (2) Prepare a fluorescence colorimetric card; Immerse the nanofiber membrane modified with gold nanoclusters into sodium sulfide standard solutions with different concentrations C1, C2, C3, ……, C n After oscillating and incubating, take out the nanofiber membrane modified with gold nanoclusters, dry it, arrange it in ascending order of sodium sulfide concentration, and place it under an ultraviolet lamp to obtain fluorescence optical photos of the nanofiber membrane, denoted as P1, P2, P3, ……, P n ; Arrange them in order to obtain a fluorescence colorimetric card.

2. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, wherein, In step S1, the dosage relationship of the chloroauric acid solution, the reduced glutathione solution, and the ultrapure water is 0.2 - 10 mL: 0.5 - 15 mL: 2 - 30 mL, where the concentration of the chloroauric acid solution is 5 - 50 mM, and the concentration of the reduced glutathione solution is 5 - 50 mM; the temperature of the heating reaction is 50 - 120 °C, and the reaction time is 6 - 48 hours; the prepared gold nanocluster solution is a yellow solution under natural light and emits orange fluorescence under ultraviolet light, and the emission peak is located at 570 - 680 nm.

3. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, characterized in that, In step S2(1), the dosage relationship of PVA-co-PE, isopropyl alcohol and ultrapure water is 0.2 - 2 g: 2 - 8 mL: 2 - 8 mL; the temperature of the water bath is 40 - 90 °C, and the water bath time is 2 - 24 hours; the spinning conditions are: the spinning voltage is 2 - 80 kV, the propulsion speed is 1 - 10 mL / h, the spinning temperature is 15 - 45 °C, and the distance from the spinneret to the surface of the collector is 10 - 30 cm; the drying temperature is 40 - 80 °C, and the drying time is 2 - 48 hours.

4. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, characterized in that, In step S2(2), the length of the nanofiber membrane after cutting is 0.5 - 20 cm, and the width is 0.5 - 20 cm; the concentration of the sodium hydroxide solution is 0.2 - 10 M; the incubation temperature is 10 - 60 °C, and the incubation time is 0.5 - 12 hours.

5. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, wherein, In step S2(3), the 1,4-dioxane solution of cyanuric chloride is obtained by mixing cyanuric chloride and 1,4-dioxane; the concentration of the 1,4-dioxane solution of cyanuric chloride is 2 - 50% (wt%); the incubation temperature is 10 - 60 °C, and the incubation time is 5 - 240 minutes.

6. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, characterized in that, In step S2(4), the absolute ethanol solution of 1,3-propanediamine is obtained by mixing 1,3-propanediamine and absolute ethanol; the concentration of the absolute ethanol solution of 1,3-propanediamine is 0.2 - 10 M; the incubation temperature is 10 - 60 °C, and the incubation time is 0.5 - 12 hours; the drying temperature is 10 - 80 °C, and the drying time is 2 - 48 hours.

7. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, wherein, In step S2(5), the dosage relationship of the gold nanocluster solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide concentrations is 2 - 50 mL: 0.2 - 5 mL: 0.2 - 5 mL; among them, the concentration of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is 1 μM - 1 mM; the concentration of N-hydroxysuccinimide is 0.5 - 500 μM; the incubation temperature is 10 - 60 °C, the incubation time is 0.5 - 24 hours; the soaking temperature is 10 - 60 °C, the soaking time is 0.5 - 24 hours; the number of times of washing with ultrapure water is 2 - 5 times.

8. The preparation method of the fluorescence colorimetric card based on fluorescent nanofibers according to claim 1, wherein, In (1) of step S3, the concentration range of the sodium sulfide standard solution is 1×10 -10 ~10 M; in (2) of step S3, the temperature of the oscillatory incubation is 10~60 °C, and the time of the oscillatory incubation is 1~30 minutes; the temperature of the drying is 10~80 °C, and the time of the drying is 2~48 hours.

9. Use of the fluorescence colorimetric card prepared by the method according to any one of claims 1-8 for detecting hydrogen sulfide gas produced by Salmonella typhimurium, characterized in that, The steps are as follows: Place the sample to be tested in a sealed sample box. At the same time, place the nanofiber modified with gold nanoclusters in the sample box and do not directly contact it with the sample; seal the sample box with a sealing film, store the sample for a period of time, then take out the nanofiber membrane, and obtain its fluorescence optical photo under an ultraviolet lamp, and compare it with the fluorescence colorimetric card, then the visual detection of hydrogen sulfide gas produced by Salmonella typhimurium in the sample to be tested can be realized.

10. The use according to claim 9, characterized in that, In step S4, the storage temperature is 0 - 60 °C, the distance between the gold nanocluster-modified nanofiber and the sample is 1 - 50 cm, and the storage time is 2 - 144 hours.

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