A fluorescence sensing unit, array and method of preparation thereof for fish freshness monitoring

Abstract

The present application relates to a kind of fluorescent sensing unit, array and its preparation method, wherein the preparation method of unit includes dissolving terbium chloride hexahydrate, 2-amino terephthalic acid and 1,10-phenanthroline and adding sodium hydroxide solution to obtain metal organic framework fluorescent powder by heating;Dissolve citric acid, urea into N,N-dimethylformamide and heat, mix with potassium hydroxide solution, dry to obtain fluorescent carbon quantum dots;Metal organic framework fluorescent powder is mixed with fluorescent carbon quantum dots in ethanol solution, to obtain fluorescent sensing mixed solution, then obtain fluorescent sensing film forming liquid, after being made into film, trimming obtains fluorescent sensing unit.The fluorescent sensing array can respond color change according to the TVB-N released by fish meat spoilage that fluorescent sensing unit can produce, so the current TVB-N concentration of fish meat can be judged according to the color change of fluorescent sensing unit.

Description

Technical Field

[0001] This invention belongs to the field of food testing technology, specifically relating to a fluorescence sensing unit, array, and preparation method for monitoring the freshness of fish. Background Technology

[0002] Fish is rich in nutrients, has a unique taste, and has positive effects on human health, making it very popular among consumers.

[0003] However, fish is highly perishable during processing, transportation, and storage. Under the combined effects of microbial metabolism and biochemical reactions, the high protein and low fat content of fish makes it prone to spoilage. This not only causes changes in texture, color, and odor but also results in the loss of nutrients and the production of substances harmful to human health. Freshness is a fundamental quality attribute for assessing the edibility of fish; spoiled fish exhibits a significant change in freshness. TVB-N (volatile basic nitrogen) is produced during fish spoilage; therefore, detecting the concentration or content of TVB-N in fish can determine its freshness.

[0004] Traditional methods for detecting fish freshness include liquid chromatography, gas chromatography, electronic nose, and electronic tongue. While these methods are relatively accurate, they have limitations such as being complex, time-consuming, potentially destructive, or requiring specialized personnel. Therefore, there is a need to develop a rapid, non-destructive, and easy-to-operate sensor for monitoring fish freshness. Summary of the Invention

[0005] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a fluorescence sensing unit, array, and preparation method thereof for monitoring the freshness of fish meat that meets the aforementioned requirements.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for fabricating a fluorescence sensing array, comprising:

[0008] S1. Dissolve terbium chloride hexahydrate, 2-aminoterephthalic acid and 1,10-phenanthroline and add sodium hydroxide solution, then heat to obtain a metal-organic framework fluorescent solution;

[0009] S2. Dry the metal-organic framework fluorescent solution to obtain metal-organic framework fluorescent powder;

[0010] S3. Dissolve citric acid and urea in N,N-dimethyldiformamide and heat to obtain a fluorescent carbon quantum dot solution;

[0011] S4. Mix the fluorescent carbon quantum dot solution with potassium hydroxide solution and dry to obtain fluorescent carbon quantum dots;

[0012] S5. Mix metal-organic framework fluorescent powder and fluorescent carbon quantum dots in an ethanol solution to obtain a fluorescent sensing mixture;

[0013] S6. Disperse methylcellulose and polyethylene glycol in an aqueous solution and add a fluorescence sensing mixture to obtain a fluorescence sensing film-forming solution.

[0014] S7. After the fluorescent sensing film-forming solution is made into a thin film, it is trimmed to obtain the fluorescent sensing unit.

[0015] In a preferred embodiment, the ratio of terbium chloride hexahydrate, 2-aminoterephthalic acid, 1,10-phenanthroline, sodium hydroxide and water in S1 is 0.5-1g: 0.2-0.8g: 0.2-0.7g: 3-8mL: 40-70mL; and the heating temperature is 120℃-200℃.

[0016] In a preferred embodiment, before drying, the metal-organic framework fluorescent solution is centrifuged and washed. The centrifugation speed is 8000-12000 rpm and the time is 3-5 min.

[0017] In a preferred embodiment, the ratio of citric acid, urea and N,N-dimethyldimethylamide in S3 is 2-5g: 3-8g: 20-50mL.

[0018] In a preferred embodiment, the heating temperature in S3 is 120℃~200℃, and the heating time is 4~8h.

[0019] In a preferred embodiment, before drying, S4 further centrifuges and washes the mixture of fluorescent carbon quantum dot solution and potassium hydroxide solution at a speed of 13,000 to 18,000 rpm for 8 to 15 minutes.

[0020] On the other hand, the present invention also provides a method for preparing a fluorescent sensing array, which uses the method for preparing a fluorescent sensing unit as described above, and changes the mixing ratio of metal-organic framework fluorescent powder and fluorescent carbon quantum dots to obtain a fluorescent sensing unit that changes color at different TVB-N concentrations.

[0021] Multiple fluorescent sensing units that change color at different TVB-N concentrations are combined into a fluorescent sensing array.

[0022] In a preferred embodiment, the ratio of methylcellulose, polyethylene glycol and water in S6 is 1-3g: 0.2-0.8g: 30-70mL.

[0023] Thirdly, the present invention also provides a fluorescence sensing unit, which is prepared using the fluorescence sensing unit preparation method of any of the above claims.

[0024] Fourthly, the present invention also provides a fluorescence sensing array, which is prepared using the fluorescence sensing array preparation method as described in any of the above claims.

[0025] Compared with the prior art, the beneficial effects of this invention are:

[0026] The fluorescence sensing unit prepared by the method of the present invention can respond to the release of TVB-N from spoiled fish by changing color, thereby determining the current TVB-N concentration in the fish based on the color change of the fluorescence sensing unit. Furthermore, the TVB-N concentration required for the fluorescence sensing unit to generate a response can be changed by adjusting the proportion of materials added in steps S1 and S3.

[0027] The metal-organic framework fluorescent solution used in the above-mentioned method for preparing fluorescent sensing units has abundant pores, a large specific surface area, and good photostability, which can improve the monitoring performance of the fluorescent sensing unit and give it excellent sensitivity.

[0028] The fluorescence sensor array prepared by the method of the present invention uses different concentrations of fluorescence sensing solution in the preparation of each fluorescence sensing unit, resulting in different response concentrations of TVB-N released by fish spoilage. Therefore, the freshness of fish can be judged based on the color change of the fluorescence sensor array, thus visualizing the freshness of fish and obtaining the detection result directly by colorimetry. It has advantages such as high sensitivity, high throughput analysis, high accuracy and simple operation when monitoring the freshness of fish. Attached Figure Description

[0029] Figure 1 The diagram shown is a schematic representation of a method for using a fluorescence sensing array according to an embodiment of the present invention.

[0030] Figure 2 The diagram shows the color change process of the fluorescence sensing array as the TVB-N concentration increases, according to an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the figures in the embodiments of this application.

[0032] The following description provides several embodiments of this application. Different embodiments can be substituted or combined. Therefore, this application can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0033] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of this application. Various processes or components may be appropriately omitted, substituted, or added to the examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0034] This application provides a method for fabricating a fluorescence sensing unit, comprising:

[0035] S1. Dissolve terbium chloride hexahydrate, 2-aminoterephthalic acid and 1,10-phenanthroline and add sodium hydroxide solution, then heat to obtain a metal-organic framework fluorescent solution;

[0036] S2. Dry the metal-organic framework fluorescent solution to obtain metal-organic framework fluorescent powder;

[0037] In the above-mentioned S1 of this application, the ratio of terbium chloride hexahydrate, 2-aminoterephthalic acid, 1,10-phenanthroline, sodium hydroxide, and water is: 0.5-1 g : 0.2-0.8 g : 0.2-0.7 g : 3-8 mL : 40-70 mL; the heating temperature is 120℃-200℃. After dissolving terbium chloride hexahydrate, 2-aminoterephthalic acid, and 1,10-phenanthroline in water, sodium hydroxide solution is added and stirred until homogeneous. Then, the mixture is transferred to a polytetrafluoroethylene reactor and heated to obtain a metal-organic framework fluorescent solution.

[0038] In addition, before drying, S2 centrifuged and washed the metal-organic framework fluorescent solution at 8000–12000 rpm for 3–5 min. After centrifugation and washing, the metal-organic framework fluorescent solution was dried at 50℃–80℃ for 4–8 h.

[0039] The metal-organic framework fluorescent powder obtained through the above steps is used as the framework material for the fluorescent sensing unit.

[0040] S3. Dissolve citric acid and urea in N,N-dimethyldiformamide and heat to obtain a fluorescent carbon quantum dot solution;

[0041] S4. Mix the fluorescent carbon quantum dot solution with potassium hydroxide solution and dry to obtain fluorescent carbon quantum dots;

[0042] The ratio of citric acid, urea and N,N-dimethyldicarboxamide in S3 above is 2-5g: 3-8g: 20-50mL;

[0043] The concentration of potassium hydroxide solution in S4 is 30–60 mg / mL;

[0044] The ratio of fluorescent carbon quantum dot solution to potassium hydroxide solution is 20-40 mL: 40-80 mL.

[0045] When heating is performed via S3, the heating temperature is 120℃~200℃ and the time is 4~8h.

[0046] Before drying, S4 was centrifuged and washed with a mixture of fluorescent carbon quantum dot solution and potassium hydroxide solution. The centrifugation speed was 13,000 to 18,000 rpm and the time was 8 to 15 min.

[0047] After centrifugation and washing, the mixture of fluorescent carbon quantum dot solution and potassium hydroxide solution was dried at a temperature of 50℃ to 80℃ for 4 to 8 hours.

[0048] Specifically, the steps involve adding citric acid and urea to N,N-dimethyldimethylamide, sonicating until dissolved, transferring the dissolved mixture to a polytetrafluoroethylene reactor for heating, and obtaining a fluorescent carbon quantum dot solution.

[0049] The fluorescent carbon quantum dot solution obtained in steps S3 and S4 can fill the gaps in the framework formed by the metal-organic framework fluorescent powder with fluorescent carbon quantum dots, and emit light according to the concentration of TVB-N to perform fluorescence sensing.

[0050] S5. Mix metal-organic framework fluorescent powder and fluorescent carbon quantum dots in an ethanol solution to obtain a fluorescent sensing mixture;

[0051] S6. Disperse methylcellulose and polyethylene glycol in an aqueous solution and add a fluorescence sensing mixture to obtain a fluorescence sensing film-forming solution.

[0052] In a preferred embodiment, the ratio of methylcellulose, polyethylene glycol and water in S6 is 1-3g: 0.2-0.8g: 30-70mL.

[0053] S7. After the fluorescent sensing film-forming solution is made into a thin film, it is trimmed to obtain the fluorescent sensing unit.

[0054] The fluorescence sensing unit prepared by the above method can respond to the release of TVB-N from spoiled fish by changing color. Therefore, the current TVB-N concentration in the fish can be determined based on the color change of the fluorescence sensing unit. Furthermore, the TVB-N concentration required for the fluorescence sensing unit to generate a response can be changed by adjusting the proportions of the materials added in steps S1 and S3.

[0055] The metal-organic framework fluorescent solution used in the above-mentioned method for preparing fluorescent sensing units has abundant pores, a large specific surface area, and good photostability, which can improve the monitoring performance of the fluorescent sensing unit and give it excellent sensitivity.

[0056] In addition, by first preparing fluorescent sensing units that respond to different TVB-N concentrations during the fabrication process, and then combining them, a fluorescent sensing array can be fabricated to indicate the TVB-N concentration.

[0057] Specifically, the fabrication method of the fluorescent sensing array begins with step S5 of the fluorescent sensing unit fabrication method, which involves mixing metal-organic framework fluorescent powders of varying masses with fluorescent carbon quantum dots to obtain a variety of fluorescent sensing units. The fabrication steps are as follows:

[0058] S5. Mix metal-organic framework fluorescent powders of different masses with fluorescent carbon quantum dots in an ethanol solution to obtain fluorescent sensing mixtures of different concentrations.

[0059] S6. Disperse methylcellulose and polyethylene glycol in an aqueous solution, and add various fluorescent sensing mixtures of different concentrations to obtain fluorescent sensing film-forming solutions of different concentrations.

[0060] S7. After preparing thin films from various fluorescent sensing film-forming solutions of different concentrations, various fluorescent sensing units are obtained by trimming.

[0061] The above-mentioned S5-S7 methods, which involve mixing metal-organic framework fluorescent powder with fluorescent carbon quantum dots of varying masses, produce multiple fluorescent sensing film-forming solutions of different concentrations. After these solutions are fabricated into thin films, the resulting fluorescent sensing units exhibit different sensitivities to TVB-N concentrations. Specifically, the fluorescent sensing units formed from different concentrations of fluorescent sensing film-forming solutions change from green to red at different TVB-N concentrations.

[0062] This embodiment provides preferred combinations of the above-mentioned metal-organic framework fluorescent powder, fluorescent carbon quantum dots, and ethanol in different weights: 20-30 mg: 20-30 mg: 2-4 mL, 30-40 mg: 30-40 mg: 2-4 mL, 40-50 mg: 40-50 mg: 2-4 mL, 50-60 mg: 50-60 mg: 2-4 mL, 60-70 mg: 60-70 mg: 2-4 mL, and 70-80 mg: 70-80 mg: 2-4 mL.

[0063] This preferred combination enables the final fluorescent sensor array to have a superior color gradient.

[0064] S8. Combining multiple fluorescence sensing units into a fluorescence sensing array.

[0065] Because a fluorescence sensor array contains multiple fluorescence sensing units, these units change from green to red at different TVB-N concentrations. Initially, all the fluorescence sensing units in the array are green. As the TVB-N concentration from fish spoilage gradually increases, each fluorescence sensing unit will turn red at different times due to reaching its corresponding TVB-N response concentration. The current TVB-N content in the fish can be determined by the number of fluorescence sensing units that turn red.

[0066] The method of using the fluorescence sensing array prepared by the above method is as follows: Figure 1 As shown, specifically:

[0067] First, the relationship between fish freshness and the fluorescence sensor array was established. The skull of a marine fish was removed, and blood was rinsed off with an aqueous solution. 100g of fish meat was taken as a sample and placed in a sealed, transparent container along with the fluorescence sensor array. The container was placed at different temperatures (-18℃, 4℃, and 25℃) for 0–3 days. Every 2 hours, images of the fluorescence sensor array were taken under 365nm ultraviolet light. The obtained fluorescence sensor array images were correlated with the TVB-N values ​​of the fish meat at different freshness levels. The number of color changes in the fluorescence sensor units within the array was then determined based on the TVB-N values.

[0068] After establishing the control relationship, the fish meat sample was tested using a fluorescence sensing unit. The head and bones of the sea fish were removed, and the bloodstains were rinsed off with an aqueous solution. 100g of fish meat was taken as a sample. The fish meat and the fluorescence sensing array were placed together in a sealed transparent container and placed at 25℃ for 0 to 3 days. During this period, the fluorescence sensing array was photographed, and the number of red units in the photographed fluorescence sensing array was observed to obtain the freshness of the fish meat.

[0069] When the fish is first stored, all six array points on the display are green. As the TVB-N content increases, the fluorescent sensing units gradually change from green to red, and the number of red fluorescent sensing units gradually increases. The longer the fish is stored, the higher the TVB-N content becomes. National standards stipulate that when the TVB-N content is below 15 mg / 100g, the fish is classified as Grade 1 freshness. When the TVB-N content is between 15 and 30 mg / 100g, the fish is classified as Grade 2 freshness. When the TVB-N content exceeds 30 mg / 100g, the fish sample has spoiled.

[0070] The determination method for TVB-N mainly refers to the automatic Kjeldahl nitrogen determination instrument method specified in the national standard GB / T-5009.228 2016 "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food".

[0071] One embodiment of this application provides a specific implementation of the above-mentioned method for preparing a fluorescent sensing array: 0.8 g of terbium chloride hexahydrate and 0.4 g of 1,10-phenanthroline are dispersed in 60 mL of water, 6 mL of sodium hydroxide solution with a concentration of 0.5 mg / mL is added, the mixture is transferred to a polytetrafluoroethylene reactor, and the reaction is carried out at 180 °C for 75 h. After cooling to room temperature, a brown metal-organic framework fluorescent solution is obtained.

[0072] The metal-organic framework fluorescent solution was centrifuged at 11,000 rpm for 4 min to obtain a precipitate. The precipitate was washed three times with water and ethanol. The final product was dried at 60 °C for 5 h to obtain metal-organic framework fluorescent powder.

[0073] Add 3g of citric acid and 4g of urea to 40mL of N,N-dimethyldimethylamide, sonicate until dissolved, transfer the mixture to a polytetrafluoroethylene reactor, react at 180℃ for 7h, and then cool to room temperature to obtain a fluorescent carbon quantum dot solution.

[0074] Fluorescent carbon quantum dot solution was mixed with 80 mL of sodium hydroxide solution with a concentration of 40 mg / mL. After mixing, the mixture was centrifuged at 15000 rpm for 12 min to obtain a precipitate. The precipitate was washed repeatedly with water and ethanol 5 times. The final product was dried at 60℃ for 5 h to obtain fluorescent carbon quantum dot powder.

[0075] Table 1 shows the amounts of metal-organic framework fluorescent powder, fluorescent carbon quantum dot powder, and ethanol solution used in different concentration solutions of these materials. In Table 1, numbers ① to ⑥ refer to the amounts of metal-organic framework fluorescent powder, fluorescent carbon quantum dot powder, and ethanol solution used in each unit of the fluorescence sensing array. 1.5 g of methylcellulose and 0.5 g of polyethylene glycol were dispersed in 50 mL of aqueous solution. Different concentration solutions of metal-organic framework fluorescent powder, fluorescent carbon quantum dot powder, and ethanol solution were then added. The mixture was stirred at 500 r / min for 30 min to obtain fluorescence sensing film-forming solutions of different concentrations.

[0076] The film-forming solution was poured into a container and dried at 55°C for 6 hours to obtain 6 fluorescent sensing films with different concentrations. These fluorescent sensing films were then made into circles with a diameter of 7 mm and arranged according to the serial numbers in Table 1 to obtain a fluorescent sensing array.

[0077]

[0078] Table 1

[0079] Figure 2 The color change process of the fluorescence sensing array in this embodiment as the TVB-N concentration increases is shown. When the number of red cells in the fluorescence sensing unit is ≤3, the fish meat is detected as fresh; when the number of red cells is 4≤5, it is considered slightly fresh; and when the number of red cells is 6, it is considered spoiled.

[0080] Another embodiment of this application provides another combination of amounts of metal-organic framework fluorescent powder, fluorescent carbon quantum dot powder and ethanol solution for each unit of the fluorescent sensing array. The amounts of different concentrations of metal-organic framework fluorescent powder and fluorescent carbon quantum dot powder and ethanol solution are shown in Table 2.

[0081]

[0082] Table 2

[0083] In this embodiment of the fluorescence sensor array, when the number of red cells in the fluorescence sensor unit is ≤2, the fish meat is detected as fresh; when the number of red cells is 3≤4, it is considered slightly fresh; and when the number of red cells is ≥5, it is considered rotten.

[0084] Another embodiment of this application provides another combination of amounts of metal-organic framework fluorescent powder, fluorescent carbon quantum dot powder and ethanol solution for each unit of the fluorescent sensing array. The amounts of different concentration solutions of metal-organic framework fluorescent powder and fluorescent carbon quantum dot powder and ethanol solution are shown in Table 3.

[0085]

[0086] Table 3

[0087] In this embodiment of the fluorescence sensor array, when the number of red cells in the fluorescence sensor unit is ≤1, the fish meat is detected as fresh; when the number of red cells is 2≤3, it is considered less fresh; and when the number of red cells is ≥4, it is considered rotten.

[0088] The present invention also provides a fluorescence sensing unit, which is prepared using the fluorescence sensing unit preparation method of any of the above embodiments.

[0089] In addition, the present invention also provides a fluorescence sensing array, which is prepared using the fluorescence sensing array preparation method of any of the above embodiments.

[0090] The fluorescence sensor array prepared by the method of the present invention uses different concentrations of fluorescence sensing solution in the preparation of each fluorescence sensing unit, resulting in different response concentrations to TVB-N released during fish spoilage. Therefore, the freshness of fish can be judged based on the color change of the fluorescence sensor array, thereby visualizing the freshness of fish and obtaining the detection result directly by colorimetry. It has advantages such as high sensitivity, high throughput analysis, high accuracy and simple operation when monitoring the freshness of fish.

[0091] In addition, the metal-organic framework fluorescent solution used in the fluorescence sensing array preparation method of the present invention has abundant pores, large specific surface area and good photostability, which can improve the monitoring performance of the fluorescence sensing array.

[0092] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Other embodiments of this disclosure will be readily apparent to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. A method for fabricating a fluorescence sensing unit, characterized in that, include: S1. Dissolve terbium chloride hexahydrate, 2-aminoterephthalic acid and 1,10-phenanthroline and add sodium hydroxide solution, then heat to obtain a metal-organic framework fluorescent solution; S2. Dry the metal-organic framework fluorescent solution to obtain metal-organic framework fluorescent powder; S3. Dissolve citric acid and urea in N,N-dimethyldiformamide and heat to obtain a fluorescent carbon quantum dot solution; S4. Mix the fluorescent carbon quantum dot solution with potassium hydroxide solution and dry to obtain fluorescent carbon quantum dots; S5. Mix the metal-organic framework fluorescent powder with the fluorescent carbon quantum dots in an ethanol solution to obtain a fluorescent sensing mixture. S6. Disperse methylcellulose and polyethylene glycol in an aqueous solution and add the fluorescence sensing mixture to obtain a fluorescence sensing film-forming solution. S7. After the fluorescence sensing film-forming liquid is made into a thin film, it is trimmed to obtain a fluorescence sensing unit. in, The ratio of terbium chloride hexahydrate, 2-aminoterephthalic acid, 1,10-phenanthroline, sodium hydroxide, and water in S1 is: 0.5–1 g : 0.2–0.8 g : 0.2–0.7 g : 3–8 mL : 40–70 mL; the heating temperature is 120°C–200°C. The ratio of citric acid, urea and N,N-dimethyldicarboxamide in S3 is 2-5g: 3-8g: 20-50mL; The heating temperature in S3 is 120℃~200℃, and the heating time is 4~8h.

2. The method for fabricating a fluorescence sensing unit as described in claim 1, characterized in that, Before drying, the S2 step involves centrifuging and washing the metal-organic framework fluorescent solution. The centrifugation speed is 8000-12000 rpm and the time is 3-5 min.

3. The method for fabricating a fluorescence sensing unit as described in claim 1, characterized in that, Before drying, step S4 involves centrifuging and washing the mixture of fluorescent carbon quantum dot solution and potassium hydroxide solution. The centrifugation speed is 13,000 to 18,000 rpm and the time is 8 to 15 minutes.

4. The method for fabricating a fluorescence sensing unit as described in claim 3, characterized in that, The ratio of methylcellulose, polyethylene glycol and water in S6 is 1-3g: 0.2-0.8g: 30-70mL.

5. A method for fabricating a fluorescence sensing array, characterized in that, By applying the preparation method of the fluorescent sensing unit as described in any one of claims 1-4, and changing the mixing ratio of the metal-organic framework fluorescent powder and the fluorescent carbon quantum dots, a fluorescent sensing unit that changes color at different TVB-N concentrations is obtained; and multiple fluorescent sensing units that change color at different TVB-N concentrations are combined into a fluorescent sensing array.

6. A fluorescence sensing unit, characterized in that, Prepared using the method described in any one of claims 1-3.

7. A fluorescence sensing array, characterized in that, Prepared using the method described in claim 5.

Images