A preparation method of a dual-signal sensor and its use in nitrite detection

Abstract

The present invention belongs to the technical field of food safety detection, and specifically relates to a preparation method of a dual-signal sensing detection system and its use in nitrite detection. The steps are as follows: Step 1, prepare an oleic acid-coated up-conversion nanomaterial; Step 2, prepare an amination up-conversion nanomaterial; Step 3, introduce 3-aminophenol into the sensor to prepare a dual-signal sensor for nitrite detection; By determining the standard nitrite content and constructing a standard curve, the detection of nitrite content in food is realized; The present invention realizes rapid, economical and accurate detection of nitrite in food through the preparation of an up-conversion fluorescence sensor, with a wide concentration detection range and a low detection limit; The designed dual-signal sensor detects nitrite, improves the accuracy of detection and the ability of on-site detection, and has good practical prospects.

Description

Technical Field

[0001] The invention belongs to the field of food safety detection, and in particular relates to a preparation method of a dual-signal sensor and application of the dual-signal sensor in nitrite detection. Background Art

[0002] In the production and processing of foods such as smoked meat and bacon, nitrite is often added in the form of potassium or sodium salt. Nitrite has the functions of coloring, sterilization and antibacterial, improving flavor and taste, and anti-oxidation, and has been used as a food additive for a long time. However, in recent years, some unscrupulous companies have illegally added nitrite in order to maintain the color, aroma and shelf life of meat products. Excessive nitrite can cause human poisoning, and in severe cases, it can lead to death. In addition, nitrite reacts with a variety of amino compounds to generate carcinogenic nitroso compounds, which pose a great threat to human health and safety. Therefore, the detection of nitrite in meat products is of great significance to ensure public safety.

[0003] At present, the commonly used detection methods for nitrite are mainly high performance liquid chromatography, ion chromatography, etc. However, these methods have some disadvantages, such as expensive instruments and equipment, high detection cost, unsuitability for on-site detection, and the need to use some toxic reagents. Therefore, it is very necessary to develop a method for rapid, highly sensitive, and easy on-site detection of nitrite. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-signal detection method for nitrite in food, so as to solve the problems of the above-mentioned prior art, such as high detection cost, complicated detection steps and unsuitability for on-site detection.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] Step 1, dissolving yttrium chloride hexahydrate, ytterbium chloride hexahydrate, and thulium chloride hexahydrate in methanol A, then adding oleic acid and 1-octadecene, heating and stirring for the first time under argon protection to obtain a transparent solution, cooling to room temperature, and obtaining a coolant; mixing ammonium fluoride, sodium hydroxide, and methanol B, and then adding them to the coolant, heating and reacting twice to completely volatilize the methanol; under argon protection, heating and stirring for the second time, cooling to room temperature, and obtaining a reaction product; washing the reaction product with a mixture of ultrapure water and ethanol, and vacuum drying to obtain oleic acid-coated upconversion nanoparticles;

[0007] Step 2, modifying the surface of the oleic acid-coated upconversion nanomaterial with amino groups: first, adding the oleic acid-coated upconversion nanomaterial prepared in step 1 to hydrochloric acid and performing ultrasound for a period of time; then adding deionized water and ammonia water to carry out a first stirring reaction, adding tetraethyl orthosilicate after the reaction to perform a second stirring reaction, and then adding 3-aminopropyltriethoxysilane after the reaction to perform a third stirring reaction; after the reaction, the product obtained is dispersed in ultrapure water after centrifugation and washing to obtain an amino upconversion nanomaterial;

[0008] Step 3: Preparation of dual signal sensor

[0009] (1) weighing a certain amount of 3-aminophenol and dissolving it in a mixed solution of ethanol and water, and performing ultrasonic treatment under stirring to obtain a 3-aminophenol solution;

[0010] (2) Adding the amino upconversion nanomaterial prepared in step 2 to the hydrochloric acid solution, adding the 3-aminophenol solution under continuous stirring; after stirring for a period of time, adding a mixture of ethanol and water, and after incubation, obtaining a dual-signal sensor for detecting nitrite.

[0011] Preferably, in step 1, the dosage ratio of yttrium chloride hexahydrate, ytterbium chloride hexahydrate, gadolinium chloride hexahydrate, and methanol A is 120.6 mg: 38.8 mg: 0.7 mg: 10 mL; the first heating and stirring reaction is at a temperature of 160° C. for 30 min; the second heating and stirring reaction is at a temperature of 300° C. for 1 h; the volume ratio of methanol A, oleic acid, and 1-octadecene is 3:4.5:10.5;

[0012] The dosage ratio of methanol A, ammonium fluoride, sodium hydroxide and methanol B is 10mL:74.1mg:50mg:10mL; the volume ratio of ultrapure water and ethanol in the ultrapure water and ethanol mixed solution is 1:3; the heating reaction is carried out twice, the first time is 70°C for 30min, and the second time is 100°C water bath reaction for 10-15min.

[0013] Preferably, in step 2, the usage ratio of the oleic acid-coated upconversion nanomaterial, hydrochloric acid, deionized water, ammonia water, tetraethyl orthosilicate and 3-aminopropyltriethoxysilane is 50 mg: 1.5 mL: 10 ml: 2.5 mL: 50 μL: 400 μL.

[0014] Preferably, in step 2, the ultrasonic time period is 5-10 min; the first stirring reaction time is 10-15 min; the second stirring reaction time is 7-10 h, and the third stirring reaction time is 3-4 h.

[0015] Preferably, in step three (1), the usage ratio of 3-aminophenol, water and ethanol is 0.436 g: 2 mL: 2 mL; the ultrasonic treatment time is 5-10 min, and the stirring speed is 500 rpm.

[0016] Preferably, in step 3 (2), the concentration of hydrochloric acid is 0.1 mol / L, the concentration of the amination upconversion nanomaterial is 2 mg / mL, and the concentration of the 3-aminophenol solution is 2 mmol / L;

[0017] The usage ratio of the hydrochloric acid solution, the amino up-conversion nanomaterial, the 3-aminophenol solution, the ethanol and the water is 500 μL: 300 μL: 400 μL: 1000 μL: 1000 μL;

[0018] The stirring time is 20-30 minutes, the rotation speed is 200 rpm; the incubation time is 10-20 minutes, and the incubation temperature is 25°C.

[0019] The dual-signal sensor prepared according to the present invention is used to detect the nitrite content in meat products, and the specific detection steps are as follows:

[0020] (1) Establishment of a standard curve of nitrite content: adding hydrochloric acid solution and 3-aminophenol solution to a dual-signal sensor to obtain a mixed solution, and then adding nitrite standard solutions with different concentration gradients; each nitrite standard solution with a concentration gradient corresponds to a mixed solution, and the two are in a one-to-one correspondence; after incubation, a detection solution is obtained; the fluorescence intensity signal characteristic value and the absorbance signal characteristic value of the detection solution are measured, and a standard curve of nitrite concentration and the fluorescence intensity signal characteristic value and the absorbance signal characteristic value is constructed;

[0021] (2) Detection of nitrite content in food samples: extract the supernatant solution after pretreatment of the meat product, and then follow the operation of step (1), except that the nitrite standard solution is replaced by the extracted supernatant solution, and then measure the characteristic value of the fluorescence intensity signal and the characteristic value of the absorbance signal, and substitute them into the standard curve of step (1) to calculate the nitrite content in the meat product.

[0022] Preferably, the concentration of the nitrite standard solution in step (1) is 0.1-200 μg / mL; the dosage relationship of the hydrochloric acid solution, 3-aminophenol and the nitrite standard solution is 500 μL: 300 μL: 200 μL; the concentration of the hydrochloric acid solution is 0.1 mol / L, and the pH value is 1; the concentration of the 3-aminophenol is 2 mmol / L.

[0023] Preferably, the incubation time in step (1) is 15 minutes and the incubation temperature is 25°C; the steps for determining the fluorescence intensity signal characteristic value and absorbance signal characteristic value of nitrite are as follows: the fluorescence value at 450nm under 980nm excitation light is used as the fluorescence intensity signal characteristic value, and the absorbance value at 450nm is determined by using an ultraviolet spectrophotometer as the absorbance signal characteristic value.

[0024] Preferably, in step (2), the meat product is pretreated and then a nitrite solution is extracted, and the steps are as follows: after homogenization, n-octane is added to remove foam, and a mixed solution of potassium ferrocyanide and zinc acetate is added to generate a precipitate; after centrifugation, grease is removed using a separatory funnel; the amount ratio of the meat product, n-octane, potassium ferrocyanide and zinc acetate is 5g:100μL:12.5mL:5mL; the solution obtained after separation is added to the step (1) to replace the nitrite standard solution; then the characteristic value of the fluorescence intensity signal and the characteristic value of the absorbance signal are determined, and the nitrite content in the meat product is calculated by bringing them into the standard curve of step (1).

[0025] The measured nitrite fluorescence intensity signal characteristic value and absorbance signal characteristic value, the detection range of the standard solution of nitrite is 0.1-200 μg / mL and 0-100 μg / mL, and the minimum detection limit of nitrite is 0.032 μg / mL and 0.1 μg / mL.

[0026] The present invention provides the use of a dual-signal sensor based on upconversion nanomaterials for detecting nitrite in food; preferably, the food includes bacon, ham and sausage.

[0027] The present invention discloses the following technical effects:

[0028] 1. The present invention discloses a dual-signal detection method for nitrite in food, which uses upconversion nanomaterials as fluorescent energy donors and 3-aminophenol as energy acceptor carriers. After nitrite is added, it forms a complex with 3-aminophenol, and a fluorescence internal rate effect occurs with the fluorescent donor, resulting in a decrease in the fluorescence intensity of the upconversion nanomaterial. At the same time, the formation of the complex is accompanied by a change in the color of the solution, and the absorbance value of the solution is measured by an ultraviolet spectrophotometer. The content of nitrite is proportional to the change in fluorescence intensity and inversely proportional to the absorbance value. Therefore, the combination of the two methods successfully constructs an efficient nitrite detection system.

[0029] 2. The specific detection system constructed by the present invention uses upconversion nanomaterials as fluorescence donors. Such nanomaterials have low autofluorescence and avoid interference from background fluorescence in the food substrate. The prepared dual-signal sensor detects nitrite by both fluorescence and ultraviolet methods, which improves the detection accuracy. The 3-aminophenol diazo agent used has specificity for nitrite detection, overcomes the shortcomings of traditional methods, and can achieve high-sensitivity detection of nitrite, which is crucial to ensuring food and environmental safety.

[0030] 3. The dual-signal detection method for nitrite established by the present invention has a linear concentration range of 0.1-200 μg / mL for the characteristic value of the fluorescence intensity signal, has a wide linear detection range, and a detection limit LOD of 0.032 μg / mL. The detection range of the characteristic value of the absorbance signal is 0-100 μg / mL, and the detection limit LOD is 0.1 μg / mL. The results obtained by fluorescence and ultraviolet detection are far lower than the detection limit specified by the state. Therefore, the designed sensing method can meet the high-sensitivity detection of nitrite content in food, has good versatility, and has higher detection accuracy and sensitivity than traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of nitrite detection using a dual-signal sensor based on upconversion materials.

[0032] Figure 2 This is a transmission electron microscopy image of the upconversion nanoparticles prepared in Example 1.

[0033] Figure 3 The fluorescence standard curve established for detecting different concentrations of nitrite in Example 1; wherein A is a fluorescence signal diagram of the sensor for detecting different concentrations of nitrite; and B is a standard curve established based on the nitrite concentration and the characteristic value of the fluorescence intensity signal of the sensor at 450 nm.

[0034] Figure 4 The absorbance value standard curve established for detecting different concentrations of nitrite in Example 1; wherein A is a diagram of the sensor absorbance signal for detecting different concentrations of nitrite, and the inset is a real shot of the dual-signal system with different concentrations of nitrite added; B is a standard curve established based on the nitrite concentration value and the absorbance signal characteristic value of the sensor.

[0035] Figure 5 Specificity analysis of dual signal sensors. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0040] The words “including,” “having,” “containing,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0041] The sodium nitrite and 3-aminophenol used in the present invention were purchased from Jiangsu Aikang Biopharmaceutical Research and Development Co., Ltd.

[0042] Figure 1 The figure is a schematic diagram of the dual-signal detection principle of nitrite in food. The specific steps are detailed in the embodiment.

[0043] Embodiment 1:

[0044] The oleic acid-coated upconversion nanomaterials were prepared by high-temperature pyrolysis: 120.6 mg of yttrium chloride hexahydrate, 38.8 mg of ytterbium chloride hexahydrate, and 0.7 mg of thulium chloride hexahydrate were accurately weighed and ultrasonically dispersed in 10 mL of methanol solvent, 4 mL of oleic acid and 9 mL of 1-octadecene were added, and the mixture was stirred magnetically at 160 ° C for 30 min under an argon environment to obtain a transparent solution; after cooling to room temperature, a mixed solution containing 50 mg of sodium hydroxide and 74.1 mg of ammonium fluoride dissolved in 10 mL of methanol was added dropwise; the flask was sealed and heated at 70 ° C for 40 min to volatilize the methanol, and then heated to 100 ° C under an argon flow, and the excess methanol and air in the device were removed after staying for 10 min; then the mixture was stirred magnetically at 300 ° C for 1 h, cooled to room temperature, and centrifuged to obtain the upconversion nanoparticle precipitate, and washed three times with a mixed solution of ultrapure water and ethanol with a volume ratio of 1:3, and dried to obtain pure oleic acid-coated upconversion nanoparticles; Figure 2 is a transmission electron microscopy image of the prepared amino upconversion nanoparticles;

[0045] In order to obtain an upconversion nanomaterial with good water solubility, an amino upconversion nanomaterial was prepared: 50 mg of oleic acid-coated upconversion nanoparticles were weighed and dispersed in 1.5 mL of 0.1 mol / L hydrochloric acid solution and subjected to ultrasonic treatment to remove the surface oleic acid groups; after the treatment, the upconversion nanoparticles were dispersed in 30 mL of ethanol and ultrasonically dispersed, and then 10 mL of deionized water and 2.5 mL of ammonia water were added and stirred at 65° C. for 10-15 min; 50 μL of tetraethyl orthosilicate was added and reacted for 7 h, and then 400 μL of 3-aminopropyltriethoxysilane was added and reacted for 3 h; after the reaction was completed, the mixture was centrifuged and separated to collect the amino upconversion nanomaterial;

[0046] Then, a dual-signal sensor for nitrite detection was prepared: first, a 3-aminophenol solution was prepared: 0.436 g of 3-aminophenol was weighed and dissolved in a mixture of 2 mL of ethanol and 2 mL of water, and after continuous stirring and ultrasonic treatment, a 2 mmol / L 3-aminophenol solution was obtained; then, the amino upconversion nanomaterial prepared in step 2 was added to a hydrochloric acid solution with a pH of 1, and the 3-aminophenol solution was added under continuous stirring; after stirring for a period of time, a mixture of ethanol and water was added, and after incubation for 10 minutes, a dual-signal sensor for nitrite detection was obtained.

[0047] Detection of nitrite content in bacon, ham and sausage using the dual-signal sensor prepared in Example 1:

[0048] (1) Establishment of standard curve for nitrite fluorescence detection: The prepared dual-signal sensor was added to 0.5 mL of hydrochloric acid solution (pH = 1), and then 0.3 mL of diazo agent 3-aminophenol (2 mmol / L) was added; then different concentrations of nitrite standard solutions were added to obtain different concentrations of detection solutions. After incubation, the fluorescence intensity signal characteristic value of the detection solution was measured ( Figure 3 A); linear fitting was performed based on the characteristic values ​​of nitrite concentration and fluorescence intensity signal to establish a standard curve for nitrite content detection ( Figure 3 B); Specifically: prepare nitrite solutions of different concentrations such as 0.1, 0.5, 2, 10, 50, 100, and 200 μg / mL, take 200 μL of each and add them to the specific detection system, and collect the characteristic value of the fluorescence signal after incubation at 25°C for 15 minutes;

[0049] The step of determining the characteristic value of the fluorescence intensity signal of the detection solution is as follows: the fluorescence intensity value at 450nm under the excitation of 980nm excitation light is the characteristic value of the fluorescence intensity signal of the detection solution.

[0050] Figure 3 A standard curve was established for fluorescence detection of different concentrations of nitrite; Figure 3 It can be seen that with the increase of nitrite concentration, the fluorescence signal at 450nm continues to decrease; the standard curve of nitrite content detection is obtained by linear fitting, y=-5.85x-1048.15; where y is the characteristic value of the fluorescence intensity signal, x is the nitrite concentration ( Figure 3 B), correlation coefficient R 2 =0.9878, the detection limit LOD was 0.032 μg / mL, and the linear range was 0.1-200 μg / mL.

[0051] (2) Establishment of the UV detection standard curve for nitrite: The prepared dual-signal sensor was added to 0.5 mL of hydrochloric acid solution (pH = 1), and then 0.3 mL of diazo agent 3-aminophenol (2 mmol / L) was added; then different concentrations of nitrite standard solutions were added to obtain different concentrations of detection solutions. After incubation, the absorbance signal characteristic value of the detection solution was measured ( Figure 4 A); linear fitting was performed based on the nitrite concentration and absorbance signal characteristic value to establish a standard curve for nitrite content detection ( Figure 4 B); Specifically: prepare nitrite solutions of different concentrations such as 0, 5, 25, 55, 80, 90, 100 μg / mL, take 200 μL of each and add them to the specific detection system, and collect the characteristic value of the absorbance signal after incubation at 25°C for 15 minutes;

[0052] The step of determining the characteristic value of the absorbance signal of the detection solution is as follows: using an ultraviolet spectrophotometer to collect the absorbance value of the dual signal sensor at 450nm, which is the characteristic value of the absorbance intensity signal of the detection solution.

[0053] Figure 4 A standard curve was established to detect the absorbance values ​​of different concentrations of nitrite at 450 nm; Figure 4 It can be seen that with the increase of nitrite concentration, the absorbance value at 450nm continues to rise; the standard curve of nitrite content detection is obtained by linear fitting y=0.0016x+0.2418; where y is the absorbance value, x is the nitrite concentration (Figure B), and the correlation coefficient R 2 =0.9888, the detection limit LOD was 0.1 μg / mL, and the linear range was 0-100 μg / mL.

[0054] (3) Detection of nitrite content in smoked meat: Weigh 5g smoked meat sample, homogenize and add 5mL saturated borax solution, 12.5mL potassium ferrocyanide solution and 5mL zinc acetate solution. Precipitation can be seen. Stir and shake for 10min to produce more precipitation. Add a small amount of distilled water and stir evenly. Drain into a 500mL volumetric flask with a glass rod. Wash the beaker with distilled water 3-4 times, drain into the volumetric flask, and then transfer to a large beaker and let stand for 30min. After the protein is completely precipitated, take the upper clear liquid and filter it. Pour 30mL of the filtrate into the waste liquid bucket, and store the rest of the filtrate for later use. Take 500μL of the filtrate into the sensor for detection. After incubation for 15min, measure the characteristic value of the fluorescence signal and the characteristic value of the absorbance signal, and bring them into the standard curve obtained in steps (1) and (2). Calculate the content of nitrite in smoked meat as 3.15μg / mL.

[0055] (4) Detection of nitrite content in ham: Weigh 5g of ham sample, homogenize and add 5mL of saturated borax solution, 12.5mL of potassium ferrocyanide solution and 5mL of zinc acetate solution. Precipitation can be seen. Stir and shake for 10min to produce more precipitation. Add a small amount of distilled water and stir evenly. Drain into a 500mL volumetric flask with a glass rod. Wash the beaker with distilled water 3-4 times, drain into the volumetric flask, and then transfer to a large beaker and let stand for 30min. After the protein is completely precipitated, take the upper clear liquid and filter it. Pour 30mL of the filtrate into the waste liquid bucket, and store the rest of the filtrate for later use. Take 500μL of the filtrate into the sensor for detection. After incubation for 15min, measure the characteristic value of the fluorescence signal and the characteristic value of the absorbance signal, and bring them into the standard curve obtained in steps (1) and (2). The nitrite content in the ham is calculated to be 7.45μg / L.

[0056] (5) Detection of nitrite content in sausage: Weigh 5g sausage sample, homogenize and add 5mL saturated borax solution, 12.5mL potassium ferrocyanide solution and 5mL zinc acetate solution. Precipitation can be seen. Stir and shake for 10min to produce more precipitation. Add a small amount of distilled water and stir evenly. Drain into a 500mL volumetric flask with a glass rod. Wash the beaker with distilled water 3-4 times, drain into the volumetric flask, and then transfer to a large beaker and let stand for 30min. After the protein is completely precipitated, take the upper clear liquid and filter it. Pour 30mL of the filtrate into the waste liquid bucket, and store the rest of the filtrate for later use. Take 500μL of the filtrate into the sensor for detection. After incubation for 15min, measure the characteristic value of the fluorescence signal and the ultraviolet absorbance value, and bring it into the standard curve obtained in steps (1) and (2). Calculate the nitrite content in the sausage as 5.14μg / L.

[0057] Specificity of the detection method: In order to evaluate the specificity of the constructed dual-signal sensor for the detection of nitrite, some other ions, including acetate ions, bromide ions, fluoride ions, carbonate ions, ammonium ions, sulfate ions, magnesium ions, calcium ions, iron ions and copper ions, were selected as interfering ions to further study the fluorescence characteristics of the dual-signal sensor, taking the dual-signal sensor prepared in Example 1 as an example.

[0058] The results are as follows Figure 5 As shown, the fluorescence response efficiency of the prepared sensor to nitrite is significantly higher than that of other ions. The results show that the constructed dual-signal sensor has good specificity.

[0059] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a dual-signal sensor, characterized in that: The following steps are involved: Step 1, dissolving yttrium chloride hexahydrate, ytterbium chloride hexahydrate, and thulium chloride hexahydrate in methanol, then adding oleic acid and 1-octadecene, and heating and stirring for the first time under argon protection to obtain a transparent solution, and cooling to room temperature to obtain a coolant; After ammonium fluoride, sodium hydroxide and methanol are mixed, they are added to a coolant and heated for reaction twice to completely volatilize the methanol; under argon protection conditions, a second heating and stirring reaction is performed, and the reaction product is cooled to room temperature to obtain a reaction product; the reaction product is washed with a mixture of ultrapure water and ethanol, and vacuum dried to obtain oleic acid-coated upconversion nanoparticles; Step 2, modifying the surface of the oleic acid-coated upconversion nanomaterial with amino groups: first, adding the oleic acid-coated upconversion nanomaterial prepared in step 1 to hydrochloric acid and performing ultrasound for a period of time; then adding deionized water and ammonia water to carry out a first stirring reaction, adding tetraethyl orthosilicate after the reaction to perform a second stirring reaction, and then adding 3-aminopropyltriethoxysilane after the reaction to perform a third stirring reaction; after the reaction, the product obtained is dispersed in ultrapure water after centrifugation and washing to obtain an amino upconversion nanomaterial; Step 3, preparation of dual signal sensor; (1) weighing a certain amount of 3-aminophenol and dissolving it in a mixed solution of ethanol and water, and performing ultrasonic treatment under stirring to obtain a 3-aminophenol solution; (2) Adding the amino upconversion nanomaterial prepared in step 2 to the hydrochloric acid solution, adding 3-aminophenol solution under continuous stirring; after stirring for a period of time, adding a mixture of ethanol and water, and after incubation, obtaining a dual-signal sensor for nitrite detection.

2. The method for preparing a dual-signal sensor according to claim 1, characterized in that: In step 1, the dosage ratio of yttrium chloride hexahydrate, ytterbium chloride hexahydrate, gadolinium chloride hexahydrate, and methanol is 120.6 mg: 38.8 mg: 0.7 mg: 10 mL; the first heating and stirring reaction is at a temperature of 160° C. for 30 min; the second heating and stirring reaction is at a temperature of 300° C. for 1 h; the volume ratio of methanol, oleic acid, and 1-octadecene is 3:4.5:10.5; The amount ratio of methanol to ammonium fluoride, sodium hydroxide and methanol in the coolant is 10mL:74.1mg:50mg:10mL; the volume ratio of ultrapure water and ethanol in the ultrapure water and ethanol mixed solution is 1:3; the heating reaction is carried out twice, the first time is 70°C reaction for 30 minutes, and the second time is 100°C water bath reaction for 10-15 minutes.

3. The method for preparing a dual-signal sensor according to claim 1, characterized in that: In step 2, the usage ratio of the oleic acid-coated upconversion nanomaterial, hydrochloric acid, deionized water, ammonia water, tetraethyl orthosilicate and 3-aminopropyltriethoxysilane is 50 mg: 1.5 mL: 10 ml: 2.5 mL: 50 μL: 400 μL.

4. The method for preparing a dual-signal sensor according to claim 1, characterized in that: In step 2, the ultrasonic treatment period is 5-10 minutes; the first stirring reaction period is 10-15 minutes; the second stirring reaction period is 7-10 hours, and the third stirring reaction period is 3-4 hours.

5. The method for preparing a dual-signal sensor according to claim 1, characterized in that: In step 3 (1), the usage ratio of 3-aminophenol, water and ethanol is 0.436 g: 2 mL: 2 mL; the ultrasonic treatment time is 5-10 min, and the stirring speed is 500 rpm.

6. The method for preparing a dual-signal sensor according to claim 1, characterized in that: In step 3 (2), the concentration of hydrochloric acid is 0.1 mol / L, the concentration of the amination upconversion nanomaterial is 2 mg / mL, and the concentration of the 3-aminophenol solution is 2 mmol / L; The usage ratio of the hydrochloric acid solution, the amino up-conversion nanomaterial, the 3-aminophenol solution, the ethanol and the water is 500 μL: 300 μL: 400 μL: 1000 μL: 1000 μL; The stirring time is 20-30 minutes, and the rotation speed is 200 rpm; the incubation time is 10-20 minutes, and the incubation temperature is 25°C.

7. Use of the dual signal sensor prepared by the method according to any one of claims 1 to 6 for detecting the nitrite content in meat products, characterized in that: The specific detection steps are as follows: (1) Establishment of a standard curve for nitrite content: Add hydrochloric acid solution and 3-aminophenol solution to a dual-signal sensor to obtain a mixed solution, and then add nitrite standard solutions with different concentration gradients; Each nitrite standard solution with a concentration gradient corresponds to a mixed solution, and the two are in a one-to-one correspondence; After incubation, a test solution is obtained; The fluorescence intensity signal characteristic value and the absorbance signal characteristic value of the detection solution are measured, and a standard curve of nitrite concentration and the fluorescence intensity signal characteristic value and the absorbance signal characteristic value is constructed; (2) Detection of nitrite content in food samples: extract the supernatant solution after pretreatment of the meat product, and then follow the operation of step (1), except that the nitrite standard solution is replaced by the extracted supernatant solution, and then measure the characteristic value of the fluorescence intensity signal and the characteristic value of the absorbance signal, and substitute them into the standard curve of step (1) to calculate the nitrite content in the meat product.

8. The use according to claim 7, characterized in that The concentration of the nitrite standard solution in step (1) is 0.1-200 μg / mL; the dosage relationship of the hydrochloric acid solution, 3-aminophenol and the nitrite standard solution is 500 μL: 300 μL: 200 μL; the concentration of the hydrochloric acid solution is 0.1 mol / L, and the pH value is 1; the concentration of the 3-aminophenol is 2 mmol / L.

9. The use according to claim 7, characterized in that: The incubation time in step (1) is 15 minutes, and the incubation temperature is 25°C; the steps for determining the fluorescence intensity signal characteristic value and absorbance signal characteristic value of nitrite are as follows: the fluorescence value at 450nm under 980nm excitation light is used as the fluorescence intensity signal characteristic value, and the absorbance value at 450nm is determined by using an ultraviolet spectrophotometer as the absorbance signal characteristic value.

10. The use according to claim 7, characterized in that In step (2), the meat product is pretreated to extract a nitrite solution, and the steps are as follows: after homogenization, n-octane is added to remove foam, and a mixed solution of potassium ferrocyanide and zinc acetate is added to generate a precipitate; after centrifugation, grease is removed using a separatory funnel; the amount ratio of the meat product, n-octane, potassium ferrocyanide and zinc acetate is 5g:100μL:12.5mL:5mL; the solution obtained after separation is added to the step (1) to replace the nitrite standard solution; then the characteristic value of the fluorescence intensity signal and the characteristic value of the absorbance signal are determined, and the nitrite content in the meat product is calculated by bringing them into the standard curve of step (1).

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