A method for preparing a colorimetric chip for detecting food spoilage marker gases

Abstract

The present application relates to the technical field of gas detection, and provides a preparation method of a colorimetric chip for detecting food spoilage marker gas, which comprises the following steps: self-assembling polystyrene nanospheres, taking uniform size polystyrene nanospheres, obtaining a three-dimensional ordered polystyrene nanosphere monolithic template through a centrifugal self-assembling mode; filling a precursor lead acetate, in-situ growing Pb-MOFs, preparing OM-Pb-MOFs, removing unreacted precursors, and preparing a colorimetric detection chip; the colorimetric chip has good stability; in addition, the hierarchical porous structure of the detection chip is beneficial to gas mass transfer, so that the detection limit is relatively low. In the use process, the detection chip does not need to be directly contacted with food in a sealed bag, but reacts with hydrogen sulfide generated by food spoilage to generate a signal, so that the detection chip has the advantages of non-contact and non-destructive, and the generated color signal is easy to identify.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas detection, and particularly relates to a preparation method of a colorimetric chip for detecting food spoilage marker gas. BACKGROUND

[0002] Food safety is closely related to human health. Food is prone to be corroded by microorganisms, enzymes, temperature and other factors during transportation, storage and sales, thereby reducing its freshness and even producing substances harmful to human body. Therefore, the detection of food freshness has great significance. At present, the spoilage degree or freshness of food is mainly evaluated by sensory evaluation method, physical and chemical determination method. The sensory evaluation method has the advantages of directness, simplicity and rapidness, but is easily affected by subjective factors. The physical and chemical determination method is more reliable, but needs special experimental equipment and instruments, is complicated to operate, is high in cost and needs special operators. Therefore, it is necessary to provide a simple, portable and real-time method for food quality and safety monitoring, which has great significance for regulating food market order, maintaining food safety and protecting human health.

[0003] Hydrogen sulfide is a volatile gas produced by the decomposition of sulfur-containing amino acids (methionine and cysteine) by bacteria during food spoilage. Therefore, hydrogen sulfide can be used as a food spoilage marker gas. Although gas chromatography analysis, gas chromatography-mass spectrometry analysis and selected ion flow tube mass spectrometry can accurately determine the gas composition, they are difficult to be applied and detected conveniently due to high operation cost and slow processing rate. In addition, semiconductor-based chemical resistors have been partially applied, but they are difficult to be applied in food spoilage detection field due to poor selectivity and high working temperature. Colorimetric sensors have attracted widespread attention due to their easy preparation, convenient use and naked-eye observation. However, the reported lead acetate-based colorimetric sensors have high detection limit and low sensitivity, which are difficult to meet the food spoilage detection. SUMMARY

[0004] In order to solve the problem that the lead acetate-based colorimetric sensor in the prior art has high detection limit but low sensitivity, which is difficult to meet the food spoilage detection, the present application provides a preparation method of a colorimetric chip for detecting food spoilage marker gas.

[0005] In one aspect, the present application provides a preparation method of a colorimetric chip for detecting food spoilage marker gas, comprising the following steps,

[0006] S1, self-assembling polystyrene nanospheres, taking uniform size polystyrene nanospheres, obtaining a three-dimensional ordered polystyrene nanosphere monolithic template by centrifugal self-assembly method;

[0007] S2, filling precursor lead acetate, the polystyrene nanosphere monolithic template after drying is immersed in lead acetate aqueous solution, keep enough time to make lead acetate molecule suffuse in the ordered hole of polystyrene nanosphere monolithic template;

[0008] S3, in-situ growth of Pb-MOFs, the template filled with lead acetate molecules prepared in step S2 is taken out, immersed in 1,3,5-benzenetricarboxylic acid ethanol solution, and Pb-MOFs are grown in-situ in the gap of the template to obtain micropores and mesopores;

[0009] S4, OM-Pb-MOFs preparation, the ethanol solution of 1,3,5-benzenetricarboxylic acid with template immersed in step S3 is centrifuged, the speed and time of centrifugation are centrifuged, after removing the supernatant, tetrahydrofuran is added, and the step S4 is repeated three times to completely remove the polystyrene monolithic template, and the ordered macroporous structure is obtained, and the OM-Pb-MOFs are obtained;

[0010] S5, removing unreacted precursors, the OM-Pb-MOFs obtained in step S4 are washed with ethanol and pure water respectively for three times in turn to remove unreacted precursors;

[0011] S6, preparation of colorimetric detection chip, the washed OM-Pb-MOFs are dispersed in water, and the water with dispersed OM-Pb-MOFs is dropped on filter paper, which can be used as a colorimetric chip for hydrogen sulfide gas molecule detection.

[0012] Further, the size of the polystyrene nanosphere in step S1 is 200 nm, 400 nm, 600 nm or 1000 nm.

[0013] Further, the speed of centrifugal self-assembly in step S1 is 3000 r / min, and the centrifugation time is 8 h.

[0014] Further, the drying method in step S2 is room temperature drying.

[0015] Further, the concentration of lead acetate aqueous solution in step S2 is 0.09 M, and the soaking time is 24 h.

[0016] Further, the concentration of 1,3,5-benzenetricarboxylic acid ethanol solution in step S3 is 0.01 M, and the soaking time is 8 h.

[0017] Further, the speed of centrifugation in step S4 is 8000 r / min, and the time is 5 min.

[0018] The other aspect provides a colorimetric chip for detecting food spoilage marker gas, comprising a carrier and OM-Pb-MOFs, the OM-Pb-MOFs are attached to the carrier, and the carrier is an adsorbing material with porosity.

[0019] Further, the OM-Pb-MOFs have a hierarchical porous structure, which includes micropores, mesopores and macropores.

[0020] Further, the micropore quantity > mesopore quantity > macropore quantity.

[0021] The present application has the following advantages:

[0022] The colorimetric chip has good stability, and the hierarchical porous structure of the detection chip is beneficial to gas mass transfer, so that the detection limit is low. In the use process, the detection chip does not need to be in direct contact with the food in the sealed bag, but reacts with hydrogen sulfide generated by food spoilage to generate a signal, so it has the advantages of non-contact and non-destructive, and the generated color signal is easy to identify. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A colorimetric chip for detecting food spoilage marker gas is prepared according to the preparation process shown in the figure.

[0024] Figure 2 The OM-Pb-MOFs nitrogen adsorption-desorption-BET pore size distribution graph of the present application. DETAILED DESCRIPTION

[0025] The specific embodiments of the present application will be described below in conjunction with the embodiments of the present application. If not specifically indicated, the technical means used in the following examples and experimental examples are conventional means familiar to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial channels.

[0026] Pb-MOFs is a lead-based metal organic framework material.

[0027] A colorimetric chip for detecting food spoilage marker gas is prepared according to the preparation process shown in the figure.

[0028] S1, self-assembled polystyrene nanospheres, uniform size polystyrene nanospheres are taken, and a three-dimensional ordered polystyrene nanosphere monolithic template is obtained by centrifugal self-assembly; the diameter of the polystyrene nanospheres is 200 nm, 400 nm, 600 nm or 1000 nm, the centrifugal self-assembly speed is 3000 r / min, and the centrifugal time is 8 h.

[0029] S2, filling precursor lead acetate, immersing the polystyrene nanosphere monolithic template dried at room temperature in a lead acetate aqueous solution, keeping enough time to make lead acetate molecules fill in the ordered pores of the polystyrene nanosphere monolithic template; the concentration of the lead acetate aqueous solution is 0.09M, and the immersion time is 24h.

[0030] S3, in-situ growth of Pb-MOFs, the template filled with lead acetate molecules prepared in step S2 is taken out and immersed in 1,3,5-benzenetricarboxylic acid ethanol solution, so that the microporous and mesoporous structure of Pb-MOFs is in-situ grown in the gap; the concentration of 1,3,5-benzenetricarboxylic acid ethanol solution is 0.01M, and the soaking time is 8h.

[0031] S4, preparation of OM-Pb-MOFs, the 1,3,5-benzenetricarboxylic acid ethanol solution with the template immersed in step S3 is centrifuged, the speed and time of centrifugation are carried out, and after removing the supernatant, tetrahydrofuran is added, and the step S4 is repeated three times to completely remove the polystyrene monolithic template to obtain an ordered macroporous structure, and obtain OM-Pb-MOFs; the speed of centrifugation is 8000r / min, and the time is 5min.

[0032] S5, removing unreacted precursors, the OM-Pb-MOFs obtained in step S4 are washed with pure water and ethanol three times respectively to remove unreacted precursors;

[0033] S6, preparation of colorimetric detection chip, the washed OM-Pb-MOFs are dispersed in water, and the water with dispersed OM-Pb-MOFs is dropped on filter paper, which can be used as a colorimetric chip for hydrogen sulfide gas molecule detection.

[0034] The OM-Pb-MOFs are ordered multi-level hole lead-based metal organic framework materials.

[0035] Example 1

[0036] Combined Figure 1 It is explained that the colorimetric chip for detecting food spoilage marker gas includes a carrier and OM-Pb-MOFs, and the OM-Pb-MOFs are attached to the carrier, and the carrier is a porous adsorbent material, and the filter paper is specifically selected.

[0037] The OM-Pb-MOFs are hierarchical porous structures, and the hierarchical porous structure includes microporous, mesoporous and macroporous structures, and the number of micropores > the number of mesopores > the number of macropores.

[0038] 76.4mg of 1,3,5-benzenetricarboxylic acid and 138mg of lead acetate are accurately weighed, 4ml of ethanol is added to the benzenetricarboxylic acid, and 4ml of pure water is added to the lead acetate, and ultrasonic treatment is carried out for 10min to completely dissolve them.

[0039] Take 5% concentration of 200 nm diameter polystyrene microspheres 1 ml, centrifugation at 3000 r / min for 8 h, pour off the supernatant, dry at room temperature to get assembled polystyrene microsphere template, soak the template in lead acetate aqueous solution for 24 h, so that the lead acetate molecules can fill into the gap between the polystyrene microsphere template, then add 1,3,5-benzenetricarboxylic acid ethanol solution, in-situ growth of Pb-MOFs, then add 8 ml of tetrahydrofuran to etch the polystyrene microspheres, centrifugation at 8000 r / min for 5 min to obtain the precipitate, finally wash with pure water, ethanol three times to remove unreacted precursors and other impurities, disperse the obtained OM-Pb-MOFs in pure water, take 10 μl and drop on filter paper to be used as a colorimetric hydrogen sulfide sensor.

[0040] Example 2

[0041] In combination Figure 1 It is explained that the colorimetric chip for detecting food spoilage marker gas includes a carrier and OM-Pb-MOFs, the OM-Pb-MOFs are attached to the carrier, and the carrier is an adsorbent material with porosity, specifically a filter paper.

[0042] The OM-Pb-MOFs have a hierarchical porous structure, which includes microporous, mesoporous and macroporous structures, and the number of micropores > the number of mesopores > the number of macropores.

[0043] Accurately weigh 76.4 mg of 1,3,5-benzenetricarboxylic acid and 138 mg of lead acetate, add 4 ml of ethanol to the benzenetricarboxylic acid and 4 ml of pure water to the lead acetate, respectively, and ultrasonic treatment for 10 min to make them completely dissolved.

[0044] Take 5% concentration of 200 nm diameter polystyrene microspheres 1 ml, centrifugation at 3000 r / min for 8 h, pour off the supernatant, dry at room temperature to get assembled polystyrene microsphere template, soak the template in lead acetate aqueous solution for 24 h, so that the lead acetate molecules can fill into the gap between the polystyrene microsphere template, then add 1,3,5-benzenetricarboxylic acid ethanol solution, in-situ growth of Pb-MOFs, then add 8 ml of tetrahydrofuran to etch the polystyrene microspheres, centrifugation at 8000 r / min for 5 min to obtain the precipitate, finally wash with pure water, ethanol three times to remove unreacted precursors and other impurities, disperse the obtained OM-Pb-MOFs in pure water, take 10 μl and drop on filter paper to be used as a colorimetric hydrogen sulfide sensor.

[0045] Example 3

[0046] In combination Figure 1To illustrate, the colorimetric chip for detecting food spoilage marker gas comprises a carrier and OM-Pb-MOFs attached to the carrier, and the carrier is an adsorbent material with porosity, specifically filter paper.

[0047] The OM-Pb-MOFs have hierarchical porous structure, and the hierarchical porous structure comprises microporous, mesoporous and macroporous structures, and the number of micropores > the number of mesopores > the number of macropores.

[0048] Accurately weigh 76.4 mg of 1,3,5-benzenetricarboxylic acid and 138 mg of lead acetate, respectively add 4 ml of ethanol to the 1,3,5-benzenetricarboxylic acid and 4 ml of pure water to the lead acetate, and ultrasonically treat for 10 min to completely dissolve them.

[0049] Take 1 ml of 5% concentration polystyrene microspheres with a diameter of 600 nm, centrifuge at a speed of 3000 r / min for 8 h, discard the supernatant, and dry at room temperature to obtain an assembled polystyrene microsphere template. Soak the template in a lead acetate aqueous solution for 24 h to allow the lead acetate molecules to fill into the gaps between the polystyrene microsphere templates. Then add an ethanol solution of 1,3,5-benzenetricarboxylic acid, and in-situ growth of Pb-MOFs can be realized. Then add 8 ml of tetrahydrofuran to etch the polystyrene microspheres, centrifuge at a speed of 8000 r / min for 5 min to obtain a precipitate, and finally wash with pure water and ethanol three times to remove unreacted precursors and other impurities. Disperse the obtained OM-Pb-MOFs in pure water, take 10 μl and drop it on the filter paper to serve as a colorimetric hydrogen sulfide sensor.

[0050] Example 4

[0051] In combination Figure 1 To illustrate, the colorimetric chip for detecting food spoilage marker gas comprises a carrier and OM-Pb-MOFs attached to the carrier, and the carrier is an adsorbent material with porosity, specifically filter paper.

[0052] The OM-Pb-MOFs have hierarchical porous structure, and the hierarchical porous structure comprises microporous, mesoporous and macroporous structures, and the number of micropores > the number of mesopores > the number of macropores.

[0053] Accurately weigh 76.4 mg of 1,3,5-benzenetricarboxylic acid and 138 mg of lead acetate, respectively add 4 ml of ethanol to the 1,3,5-benzenetricarboxylic acid and 4 ml of pure water to the lead acetate, and ultrasonically treat for 10 min to completely dissolve them.

[0054] Take 5% concentration diameter 1000nm polystyrene microspheres 1ml, centrifugation at 3000r / min speed for 8h, pour off supernatant, dry at room temperature to obtain assembled polystyrene microsphere template, immerse the template in lead acetate aqueous solution for 24h, so that the lead acetate molecules can fill into the gap between the polystyrene microsphere template, then add 1,3,5-benzene tricarboxylic acid ethanol solution, in-situ growth of Pb-MOFs, then add 8ml tetrahydrofuran to etch the polystyrene microspheres, centrifugation at 8000r / min for 5min to obtain the precipitate, finally wash with pure water, ethanol three times to remove unreacted precursors and other impurities, disperse the obtained OM-Pb-MOFs in pure water, take 10ul and drop on filter paper to obtain a colorimetric hydrogen sulfide sensor.

[0055] Example 5 Sensitivity comparison experiment

[0056] The colorimetric chip prepared by the application for efficiently detecting the food spoilage marker hydrogen sulfide gas changes from white to yellow brown when reacting with hydrogen sulfide; the detection principle is that hydrogen sulfide ionizes into sulfhydryl ion (HS-) and sulfur ion (S2-) after contacting with water; when contacting with lead ion (Pb2+), lead sulfide (PbS) is generated.

[0057] The control experiment group is a commercialized lead acetate test strip as a colorimetric chip, and the blank experiment group is 10ul pure water dropped on filter paper as a colorimetric chip; the experimental group is divided into four groups, and the colorimetric chips prepared by examples 1-4 are selected respectively, and three repeats are set in each group.

[0058] Place the colorimetric chip of each group in a sealed space, provide different concentrations of H2S, and react with the colorimetric chip in the sealed space. Because the concentrations of H2S are different, the colorimetric chip changes in color, the colorimetric chip after detection is collected by using a scanner to collect the colorimetric chip image, then the RGB value of the image is read by using Matlab, and the Euclidean distance DE is introduced to establish the relationship between DE and the concentration of hydrogen sulfide.

[0059]

[0060] The subscripts 0 and i respectively represent the RGB values of the colorimetric detection chip without detecting hydrogen sulfide and detecting hydrogen sulfide.

[0061] The experimental results are shown in Table 1.

[0062] Table 1 Color change of colorimetric chip after reaction with different concentrations of hydrogen sulfide

[0063]

[0064]

[0065] From Table 1, it can be seen that the experimental group can detect H2S at a concentration of 50 ppb, and the detection limit is significantly lower than that of the control group. The sensitivity of the four experimental groups is better than that of the control group. By comparing the four experimental groups, it is found that the effect of experimental group 2 is the best (the greater the Euclidean distance, the greater the color change). Therefore, the colorimetric chip prepared in Example 2 is used for subsequent experiments.

[0066] The detection limit is calculated by using the detection limit calculation formula LOD = 3δ / S, where δ represents noise and S represents sensitivity.

[0067] Example 6 Food spoilage detection experiment

[0068] The colorimetric chip prepared in Example 2 is placed in a sealed bag, and an equal amount of food, such as pork or flower shell, is placed in the sealed bag. The colorimetric chip reacts with hydrogen sulfide produced during the spoilage of the food, resulting in a visible color change, which can be used to judge the freshness of the food.

[0069] Take 25g of pork in a disposable sealed bag, and place the colorimetric chip in the sealed bag but not in contact with the pork. Seal the sealed bag and store it in a refrigerator at 4°C.

[0070] Take about 20g of flower shell in a disposable sealed bag, and place the detection chip in the sealed bag but not in contact with the flower shell. Seal the sealed bag and store it in a refrigerator at 4°C.

[0071] The color of the colorimetric chip gradually changes from white to black brown, so the freshness of the food can be judged by observing the color change of the sensor chip with the naked eye.

[0072] Example 7 Colorimetric chip indicating effect of food spoilage at different environmental temperatures

[0073] Take about 20g of flower shell in a disposable sealed bag, and place the colorimetric chip prepared in Example 2 in the sealed bag but not in contact with the flower shell. Set up 5 experimental groups for the 1st temperature group to the 5th temperature group, and seal the sealed bags of the 5 experimental groups in 4°C, 20°C, 30°C, 38°C and 60°C environments, respectively.

[0074] Within the same time range, as the environmental temperature increases, the color change of the colorimetric chip becomes more obvious, indicating that the spoilage rate of the food increases with the increase of the temperature. The colorimetric chip prepared by the present application has good stability at 4°C-60°C, and the detection effect is not affected by the increase of the environmental temperature.

[0075] Example 8 OM-Pb-MOFs nitrogen adsorption-desorption-BET pore size distribution

[0076] Combining Figure 2To illustrate, the pore size distribution of the OM-Pb-MOFs prepared in Example 2 was obtained by nitrogen isothermal adsorption-desorption experiment, and the pore size distribution graph is shown in Figure 2 , Figure 2 The horizontal axis in the graph represents the pore size, and the vertical axis represents the pore size distribution. Figure 2 It can be seen from the graph that the number of micropores > the number of mesopores > the number of macropores.

[0077] The colorimetric detection chip has good stability, and the hierarchical porous structure of the detection chip is beneficial to gas mass transfer, so that the detection limit is low. The detection chip does not need to be in direct contact with the food in the sealed bag during use, but reacts with hydrogen sulfide generated by food spoilage to generate a signal, so it has the advantages of non-contact and non-destructive, and the color signal generated is easy to identify.

[0078] For those skilled in the art, the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application; therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0079] The above is only a preferred embodiment of the present application, and is not intended to limit the present application, and any minor modification, equivalent replacement and improvement made according to the technical essence of the present application to the above embodiments should be included in the protection scope of the technical scheme of the present application.

Claims

1. A method for preparing a colorimetric chip for detecting food spoilage marker gases, characterized by, The method comprises the following steps of: S1, self-assembling polystyrene nanospheres, taking uniform size polystyrene nanospheres, and obtaining a three-dimensional ordered polystyrene nanosphere monolithic template by centrifugal self-assembly; S2, filling a lead acetate precursor, immersing the dried polystyrene nanosphere monolithic template in a lead acetate aqueous solution for a sufficient time to allow the lead acetate molecules to fill the ordered pores of the polystyrene nanosphere monolithic template; S3, in-situ growth of Pb-MOFs, taking out the template filled with lead acetate molecules prepared in step S2, immersing in an ethanol solution of 1,3,5-benzenetricarboxylic acid, and allowing the Pb-MOFs to grow in-situ in the template gap to obtain micropores and mesopores; S4, OM-Pb-MOFs preparation, centrifuging the ethanol solution of 1,3,5-benzenetricarboxylic acid with the template immersed in step S3, and centrifuging at a speed and for a time, adding tetrahydrofuran after removing the supernatant, and repeating the step S4 three times to completely remove the polystyrene monolithic template to obtain an ordered macroporous structure and obtain OM-Pb-MOFs; S5, removing unreacted precursors, sequentially washing the OM-Pb-MOFs obtained in step S4 with ethanol and pure water for three times respectively to remove unreacted precursors; S6, preparing a colorimetric detection chip, dispersing the washed OM-Pb-MOFs in water, and dropping the water with dispersed OM-Pb-MOFs on filter paper to obtain a colorimetric chip for hydrogen sulfide gas molecule detection; The colorimetric detection chip prepared by the preparation method comprises a carrier and OM-Pb-MOFs, the OM-Pb-MOFs are attached to the carrier, the carrier is an adsorbing material with porosity, the OM-Pb-MOFs are hierarchical porous structures, and the hierarchical porous structures comprise micropores, mesopores and macropores.

2. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The polystyrene nanospheres in step S1 have a diameter of 200 nm, 400 nm, 600 nm or 1000 nm.

3. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The centrifugal self-assembly in step S1 is performed at a speed of 3000 r / min for 8 h.

4. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The drying method in step S2 is room temperature drying.

5. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The concentration of the lead acetate aqueous solution in step S2 is 0.09 M, and the immersion time is 24 h.

6. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The concentration of the ethanol solution of 1,3,5-benzenetricarboxylic acid in step S3 is 0.01 M, and the immersion time is 8 h.

7. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The centrifuging in step S4 is performed at a speed of 8000 r / min for 5 min.

8. The method for preparing a colorimetric chip for detecting food spoilage marker gases according to claim 1, wherein, The number of micropores > the number of mesopores > the number of macropores.

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