Method for enhancing hydrophobicity and mechanical property of aerogel intelligent colorimetric label

Abstract

The invention discloses a method for enhancing hydrophobicity and mechanical performance of an aerogel intelligent colorimetric label, and belongs to the technical field of aerogel. Comprising the following steps: adding a beewax hydrophobic modified halloysite nanotube as a nanofiller into an aerogel matrix, and freeze-drying to obtain the aerogel intelligent colorimetric label, wherein the aerogel matrix is a gelatin / carrageenan-black rice anthocyanin solution. By utilizing the method disclosed by the invention, the hydrophobicity and the mechanical property of the aerogel intelligent colorimetric label can be enhanced, and the pore size of aerogel is reduced, so that the color sensitivity of the aerogel intelligent colorimetric label is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogels, and in particular relates to a method for enhancing the hydrophobicity and mechanical properties of aerogel-based intelligent colorimetric labels. Background Art

[0002] During the entire supply chain, aquatic products and other meat products are susceptible to micro-corruption due to physical, chemical and biological factors, which affects product quality. However, traditional petroleum-based packaging cannot monitor the changes in food freshness in real time, resulting in serious food waste. Therefore, visual monitoring and detection of food freshness changes has become an urgent problem to be solved in the field of food intelligent packaging.

[0003] Smart colorimetric labels are an innovative food quality testing tool that can provide a visual solution for food freshness in a simple, efficient and low-cost manner. They can usually be summarized into two parts: base material and indicator. The working principle is: when food begins to deteriorate during storage, it will produce substances that change the pH of the surrounding environment. At this time, the indicator loaded in the smart colorimetric label will change color. At present, smart colorimetric labels are usually in the form of films or hydrogels. Because the structure of this type of form is too dense and the material itself is hydrophilic, the indication sensitivity is low, and the label is easy to gelatinize and migrate to the food, affecting the food quality.

[0004] Therefore, in the prior art solutions, the smart colorimetric labels used in the field of smart food packaging, Patent 202111172153.0 discloses a migration-resistant hydrogel-based freshness colorimetric indicator label and a preparation method thereof, wherein the sponge structure provided by the polyvinylidene fluoride porous film is utilized to improve the sensitivity and hydrophobicity of the colorimetric label. Patent 202111172154.5 discloses a colorimetric food freshness smart indicator label and a preparation method thereof, which utilizes an alkyl ketene dimer to construct a layer of hydrophobic structure in a cellulose-anthocyanin porous film, retaining its water vapor permeability and color rendering while being hydrophobic. However, the preparation method of the prior art solution is too complicated and difficult to operate, and polyvinylidene fluoride, alkyl ketene dimer, etc. need to be used as base materials. These materials not only have high production costs, but also easily cause environmental pollution after post-processing, and the comprehensive effect is not high. Biomass materials such as gelatin and carrageenan are sustainable, biocompatible and environmentally friendly, but they are hydrophilic in nature, which can easily lead to indicator migration, affecting indicator sensitivity and food quality. Therefore, how to use these biomass materials to prepare smart colorimetric labels with good sensitivity and high hydrophobicity becomes the key. Summary of the invention

[0005] Existing film and hydrogel smart colorimetric labels have low color sensitivity and poor hydrophobicity. In practical applications, they cannot accurately indicate the freshness of food and affect food quality. Therefore, the present invention proposes a method for enhancing the hydrophobicity and mechanical properties of aerogel smart colorimetric labels.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Technical Solution 1: A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps: adding beeswax hydrophobically modified halloysite nanotubes as nanofillers into an aerogel matrix and freeze-drying the aerogel smart colorimetric labels; wherein the aerogel matrix is ​​a gelatin / carrageenan-black rice anthocyanin solution.

[0008] The present invention uses gelatin / carrageenan-black rice anthocyanin solution as a matrix material, and uses beeswax hydrophobically modified halloysite nanotubes as nanofillers for addition, so that the matrix is ​​more tightly bound, and the aerogel pore size distribution is smaller. At the same time, a hydrophobic nanostructure appears on the porous pore wall of the aerogel, so that it has hydrophobic properties and its color sensitivity is guaranteed.

[0009] Furthermore, the preparation method of the beeswax hydrophobically modified halloysite nanotubes comprises the following steps: mixing beeswax and halloysite nanotubes, adding a solvent, heating to dissolve, and drying to obtain the beeswax hydrophobically modified halloysite nanotubes.

[0010] Furthermore, the mass ratio of the beeswax to the halloysite nanotubes is 5:1.

[0011] Furthermore, the solvent is anhydrous ethanol.

[0012] Furthermore, the preparation method of the gelatin / carrageenan-black rice anthocyanin solution comprises the following steps: dissolving gelatin (Gelatin, Gel), carrageenan (Carrageenan, Car) and black rice anthocyanin in deionized water respectively to obtain a gelatin solution, a carrageenan solution and a black rice anthocyanin solution; mixing the gelatin solution and the carrageenan solution, adjusting the pH to 4.0, and then adding the black rice anthocyanin solution to obtain a gelatin / carrageenan-black rice anthocyanin solution.

[0013] Furthermore, the ratio of gelatin to deionized water is 5 g:100 mL; and / or;

[0014] The ratio of carrageenan to deionized water is 1 g: 100 mL; and / or;

[0015] The dosage ratio of the black rice anthocyanin to deionized water is 1 mg: 1 mL.

[0016] Furthermore, the usage ratio of the beeswax hydrophobically modified halloysite nanotubes to the gelatin / carrageenan-black rice anthocyanin solution is 1.2 g: 40 mL.

[0017] Furthermore, the freeze-drying refers to freezing at -80°C for 48 hours.

[0018] Technical Solution 2: An aerogel-based intelligent colorimetric label prepared using the above method.

[0019] Technical solution three: Application of an aerogel-based intelligent colorimetric label in food testing.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] The method of the present invention can enhance the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, reduce the pore size of aerogels, and thus improve their color sensitivity. The hardness of the prepared aerogel-based smart colorimetric labels was tested by a texture analyzer at a strain of 1 mm, and it can reach 1560.52±102.67g, which is much greater than the hardness of the blank group 641.02±15.79g. In the 2500ppm ammonia response test, the color response was 60s, and the color difference value was 3.09±0.16, which was much greater than the 1.15±0.75 of the blank group, and the colors of the front and back surfaces could be clearly distinguished by the naked eye.

[0022] The method of the invention has the advantages of simple and rapid preparation and good repeatability, uses natural substances such as gelatin, carrageenan, beeswax and halloysite nanotubes, and has the advantages of sustainable development, good biocompatibility and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 is a scanning electron microscope image of the halloysite nanotube and the beeswax hydrophobically modified halloysite nanotube in Example 1;

[0025] Figure 2 TEM images of the halloysite nanotubes and the beeswax hydrophobically modified halloysite nanotubes in Example 1;

[0026] Figure 3 This is a scanning electron microscope image of the aerogel-based smart colorimetric label in Comparative Example 1;

[0027] Figure 4 This is a scanning electron microscope image of the aerogel-based smart colorimetric label in Comparative Example 2;

[0028] Figure 5This is a scanning electron microscope image of the aerogel-based smart colorimetric label in Comparative Example 3;

[0029] Figure 6 This is a scanning electron microscope image of the aerogel-based smart colorimetric label in Comparative Example 4;

[0030] Figure 7 This is a scanning electron microscope image of the aerogel-based smart colorimetric label in Example 1;

[0031] Figure 8 The water contact angle test results of different aerogel-based smart colorimetric labels are shown in FIG. 1 , FIG. 2 , FIG. 3 , FIG. 4 , and Example 1, respectively;

[0032] Fig. 9 This is a test result diagram of the advancing angle of the aerogel-based smart colorimetric label prepared in Example 1;

[0033] Fig.10 This is a test result diagram of the receding angle of the aerogel-based smart colorimetric label prepared in Example 1. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] A hydrophobic and structurally enhanced aerogel-based intelligent colorimetric label, comprising: beeswax hydrophobically modified halloysite nanotubes as a filler and gelatin / carrageenan-black rice anthocyanin solution as a matrix. The preparation method comprises the following steps:

[0040] S1, preparing beeswax hydrophobically modified halloysite nanotubes and gelatin / carrageenan-black rice anthocyanin solutions respectively;

[0041] S2. Add the beeswax hydrophobically modified halloysite nanotubes into the gelatin / carrageenan-black rice anthocyanin solution, stir thoroughly, pour into a mold and freeze-dry to obtain an aerogel smart colorimetric label.

[0042] In step S1 of the following preferred embodiment of the present invention, the method for preparing beeswax hydrophobically modified halloysite nanotubes comprises the following steps: mixing beeswax and halloysite nanotubes, adding a solvent, heating to dissolve, and drying to obtain beeswax hydrophobically modified halloysite nanotubes.

[0043] The amount ratio of the beeswax, halloysite nanotubes and solvent must meet 5g: 1g: 100mL. The beeswax hydrophobically modified halloysite nanotubes prepared at a mass ratio of beeswax to halloysite nanotubes of 5: 1 have the characteristics of uniform coating and good distribution effect. Too much beeswax will cause beeswax to aggregate on the surface and inside of the halloysite nanotubes, thereby affecting the difficulty of dispersing the halloysite nanotubes when added to the gelatin / carrageenan solution, and there is a problem of phase separation. Too little beeswax will result in the inability of beeswax to completely coat the halloysite nanotubes, and the effect of hydrophobic modification will not be achieved. When added to the gelatin / carrageenan solution, the result of forming a hydrophobic aerogel will not be achieved.

[0044] The solvent used was anhydrous ethanol.

[0045] The purpose of heating in this method is to melt the raw beeswax into a liquid state, and then break the bonds between the beeswax molecules under heating to become free molecules, so that they are easier to dissolve in the ethanol solvent, and then make them fully contact with the halloysite nanotubes. The present invention does not specifically limit the heating temperature, and it can be above 80°C, subject to the purpose of dissolution. Exemplarily, the heating temperature in the following embodiments of the present invention is set to 90°C, and the heating time is until the beeswax is dissolved.

[0046] The purpose of drying is to remove the solvent, and the present invention has no specific limitation on the drying temperature and time. For example, in the following embodiments of the present invention, the drying temperature is set to 50° C., and the drying time is based on the complete removal of the solvent.

[0047] In step S1 of the following preferred embodiment of the present invention, the method for preparing the gelatin / carrageenan-black rice anthocyanin solution comprises the following steps:

[0048] (1) dissolving gelatin in deionized water to obtain a gelatin solution; wherein the ratio of gelatin to deionized water is 5 g:100 mL, and the concentration of the gelatin solution is 50 mg / mL. At this concentration, the gelatin solution has good gelation properties and can be entangled and cross-linked with carrageenan molecular chains to achieve a gelation effect; the dissolution process is carried out by water bath heating, and the water bath temperature is 60° C.;

[0049] Dissolve carrageenan in deionized water to obtain a carrageenan solution; wherein the ratio of carrageenan to deionized water is 1 g: 100 mL, and the concentration of the carrageenan solution is 10 mg / mL. At this concentration, the carrageenan solution is easy to be compounded with the gelatin solution. Too high a concentration will cause the carrageenan molecular chains to be self-entangled, and the carrageenan solution will directly form a gel during the dissolution process, which will affect the compounding with the gelatin solution. Too low a concentration will not improve the performance of the compounding gel. The dissolution process is heated in a water bath, and the water bath temperature is 80°C.

[0050] The black rice anthocyanidin is dissolved in deionized water to obtain a black rice anthocyanidin solution; the dosage ratio of the black rice anthocyanidin to the deionized water is 1 mg: 1 mL, and the concentration of the black rice anthocyanidin solution is 5 mg / mL. At this concentration, the black rice anthocyanidin solution is added to the mixed solution to make the solution color obvious, providing an excellent colorimetric effect for the subsequent preparation of aerogels. Too low or too high a concentration will result in poor aerogel colorimetric effect and no indication function; the dissolution process is obtained by ultrasonication at room temperature for 5 minutes;

[0051] (2) mixing the gelatin solution and the carrageenan solution, adjusting the pH to 4.0, and then adding the black rice anthocyanin solution to obtain a gelatin / carrageenan-black rice anthocyanin solution.

[0052] The volume ratio of gelatin solution to carrageenan solution is 1:1, and the mass ratio of gelatin, carrageenan and black rice anthocyanin is 5:1:0.01. The gelatin / carrageenan-black rice anthocyanin solution prepared under this ratio has good molecular chain entanglement and intermolecular hydrogen bonding, achieving the effect of cross-linked gel, and the black rice anthocyanin solution has the best color development effect only when the addition amount is met.

[0053] The purpose of adjusting pH is to promote the electrostatic interaction between gelatin and carrageenan molecules, which can enhance the binding between the matrix and achieve a more compact structure of the complex. The principle is that the isoelectric point of the gelatin used is around pH 4.0. Under this pH condition, the NH3 + Group and OSO3 of carrageenan molecule - The groups will generate electrostatic interactions and undergo complex coagulation reactions. The solution used to adjust the pH can be any acidic solution. For example, a hydrochloric acid solution with a concentration of 0.05 wt% is selected in the following examples of the present invention.

[0054] In step S2 of the following preferred embodiment of the present invention, the ratio of the beeswax hydrophobically modified halloysite nanotubes to the gelatin / carrageenan-black rice anthocyanin solution is 1.2 g: 40 mL. Exemplarily, the following embodiments of the present invention limit the ratio to 1.2 g: 40 mL.

[0055] The freeze drying refers to freezing at -80°C for 48 hours.

[0056] The mold is a polytetrafluoroethylene round hole mold.

[0057] Aerogel-based intelligent colorimetric labels can be prepared using the above method.

[0058] The aerogel-based intelligent colorimetric label can be used in food quality testing.

[0059] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0060] The raw materials used in the present invention are all purchased from the market.

[0061] The technical solution of the present invention is further illustrated by the following embodiments.

[0062] Example 1

[0063] A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps:

[0064] S1. Preparation of beeswax hydrophobically modified halloysite nanotubes: 5 g of beeswax and 1 g of halloysite nanotubes (HNTs) were mixed, 100 mL of anhydrous ethanol was added, and the mixture was heated in a water bath at 90° C. to dissolve to obtain a mixed solution; the mixed solution was dried in an oven at 50° C. to remove the ethanol, thereby obtaining beeswax hydrophobically modified halloysite nanotubes (BW-HNTs);

[0065] S2. Preparation of gelatin / carrageenan-black rice anthocyanin solution:

[0066] Dissolve 10 mg of black rice anthocyanin in 10 mL of deionized water and sonicate at room temperature for 5 min to obtain a 1 mg / mL black rice anthocyanin solution;

[0067] Dissolve 5 g of gelatin in 100 mL of deionized water and stir magnetically in a 60 °C water bath for 1 h to obtain a 50 mg / mL gelatin solution;

[0068] Dissolve 1 g of carrageenan in 100 mL of deionized water and stir magnetically in a water bath at 80 °C for 1 h to obtain a 10 mg / mL carrageenan solution;

[0069] 20 mL of 50 mg / mL gelatin solution and 20 mL of 10 mg / mL carrageenan solution were mixed, stirred in a 60° C. water bath to obtain a mixed solution, the pH of the mixed solution was adjusted to 4.0 with a 0.05% mass concentration hydrochloric acid solution, and then 5 mL of 1 mg / mL black rice anthocyanin solution was added to obtain a gelatin / carrageenan-black rice anthocyanin solution (GC);

[0070] S3, adding 1.2 g of beeswax hydrophobically modified halloysite nanotubes into 40 mL of gelatin / carrageenan-black rice anthocyanin solution, stirring in a 60° C. water bath for 1 h, to obtain a 3% (mass concentration) beeswax hydrophobically modified halloysite nanotube aerogel precursor solution;

[0071] S4. Pour the precursor solution into a polytetrafluoroethylene mold and freeze-dry it at -80°C for 48 h to obtain the GC@BW-HNTs3 aerogel smart colorimetric label.

[0072] Comparative Example 1

[0073] A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps:

[0074] S1. Preparation of gelatin / carrageenan-black rice anthocyanin solution:

[0075] Dissolve 10 mg of black rice anthocyanin in 10 mL of deionized water and sonicate at room temperature for 5 min to obtain a 1 mg / mL black rice anthocyanin solution;

[0076] Dissolve 5 g of gelatin in 100 mL of deionized water and stir magnetically in a 60 °C water bath for 1 h to obtain a 50 mg / mL gelatin solution;

[0077] Dissolve 1 g of carrageenan in 100 mL of deionized water and stir magnetically in a water bath at 80 °C for 1 h to obtain a 10 mg / mL carrageenan solution;

[0078] 20 mL of 50 mg / mL gelatin solution and 20 mL of 10 mg / mL carrageenan solution were mixed, stirred in a 60° C. water bath to obtain a mixed solution, the pH of the mixed solution was adjusted to 4.0 with a 0.05% mass concentration hydrochloric acid solution, and then 5 mL of 1 mg / mL black rice anthocyanin solution was added to obtain a gelatin / carrageenan-black rice anthocyanin solution (GC);

[0079] S2. Pour the gelatin / carrageenan-black rice anthocyanin solution into a polytetrafluoroethylene mold and freeze-dry it at -80°C for 48 h to obtain a GC aerogel smart colorimetric label.

[0080] Comparative Example 2

[0081] A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps:

[0082] S1. Preparation of gelatin / carrageenan-black rice anthocyanin solution:

[0083] Dissolve 10 mg of black rice anthocyanin in 10 mL of deionized water and sonicate at room temperature for 5 min to obtain a 1 mg / mL black rice anthocyanin solution;

[0084] Dissolve 5 g of gelatin in 100 mL of deionized water and stir magnetically in a 60 °C water bath for 1 h to obtain a 50 mg / mL gelatin solution;

[0085] Dissolve 1 g of carrageenan in 100 mL of deionized water and stir magnetically in a water bath at 80 °C for 1 h to obtain a 10 mg / mL carrageenan solution;

[0086] 20 mL of 50 mg / mL gelatin solution and 20 mL of 10 mg / mL carrageenan solution were mixed, stirred in a 60° C. water bath to obtain a mixed solution, the pH of the mixed solution was adjusted to 4.0 with a 0.05% mass concentration hydrochloric acid solution, and then 5 mL of 1 mg / mL black rice anthocyanin solution was added to obtain a gelatin / carrageenan-black rice anthocyanin solution (GC);

[0087] S2, adding 0.40 g of halloysite nanotubes to 40 mL of gelatin / carrageenan-black rice anthocyanin solution, stirring in a 60° C. water bath for 1 h, to obtain a 1% (mass concentration) halloysite nanotube aerogel precursor solution;

[0088] S3. Pour the precursor solution into a polytetrafluoroethylene mold and freeze-dry it at -80°C for 48 h to obtain the GC@HNTs1 aerogel smart colorimetric label.

[0089] Comparative Example 3

[0090] A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps:

[0091] S1. Preparation of gelatin / carrageenan-black rice anthocyanin solution:

[0092] Dissolve 10 mg of black rice anthocyanin in 10 mL of deionized water and sonicate at room temperature for 5 min to obtain a 1 mg / mL black rice anthocyanin solution;

[0093] Dissolve 5 g of gelatin in 100 mL of deionized water and stir magnetically in a 60 °C water bath for 1 h to obtain a 50 mg / mL gelatin solution;

[0094] Dissolve 1 g of carrageenan in 100 mL of deionized water and stir magnetically in a water bath at 80 °C for 1 h to obtain a 10 mg / mL carrageenan solution;

[0095] 20 mL of 50 mg / mL gelatin solution and 20 mL of 10 mg / mL carrageenan solution were mixed, stirred in a 60° C. water bath to obtain a mixed solution, the pH of the mixed solution was adjusted to 4.0 with a 0.05% mass concentration hydrochloric acid solution, and then 5 mL of 1 mg / mL black rice anthocyanin solution was added to obtain a gelatin / carrageenan-black rice anthocyanin solution (GC);

[0096] S2, adding 0.80 g of halloysite nanotubes to 40 mL of gelatin / carrageenan-black rice anthocyanin solution, stirring in a 60° C. water bath for 1 h, to obtain a 2% halloysite nanotube aerogel precursor solution;

[0097] S3. Pour the precursor solution into a polytetrafluoroethylene mold and freeze-dry it at -80°C for 48 h to obtain the GC@HNTs2 aerogel smart colorimetric label.

[0098] Comparative Example 4

[0099] A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, comprising the following steps:

[0100] S1. Preparation of gelatin / carrageenan-black rice anthocyanin solution:

[0101] Dissolve 10 mg of black rice anthocyanin in 10 mL of deionized water and sonicate at room temperature for 5 min to obtain a 1 mg / mL black rice anthocyanin solution;

[0102] Dissolve 5 g of gelatin in 100 mL of deionized water and stir magnetically in a 60 °C water bath for 1 h to obtain a 50 mg / mL gelatin solution;

[0103] Dissolve 1 g of carrageenan in 100 mL of deionized water and stir magnetically in a water bath at 80 °C for 1 h to obtain a 10 mg / mL carrageenan solution;

[0104] 20 mL of 50 mg / mL gelatin solution and 20 mL of 10 mg / mL carrageenan solution were mixed, stirred in a 60° C. water bath to obtain a mixed solution, the pH of the mixed solution was adjusted to 4.0 with a 0.05% mass concentration hydrochloric acid solution, and then 5 mL of 1 mg / mL black rice anthocyanin solution was added to obtain a gelatin / carrageenan-black rice anthocyanin solution (GC);

[0105] S2, adding 1.2 g of halloysite nanotubes (HNTs) into 40 mL of gelatin / carrageenan-black rice anthocyanin solution, stirring in a 60° C. water bath for 1 h, to obtain a 3% (mass concentration) halloysite nanotube aerogel precursor solution;

[0106] S3. Pour the precursor solution into a polytetrafluoroethylene mold and freeze-dry it at -80°C for 48 h to obtain the GC@HNTs3 aerogel smart colorimetric label.

[0107] Figure 1 The scanning electron microscope images of the halloysite nanotubes and the beeswax hydrophobically modified halloysite nanotubes in Example 1; as can be seen from Figures a and b, the halloysite nanotubes present a smooth tubular structure without other coatings on the surface, while as can be seen from Figures c and d, the beeswax hydrophobically modified halloysite nanotubes have obvious coatings on the surface while retaining the tubular structure, which is clearly reflected in the enlarged image, confirming that the beeswax is successfully coated on the halloysite nanotubes.

[0108] Figure 2 The transmission electron micrographs of the halloysite nanotubes and the beeswax hydrophobically modified halloysite nanotubes in Example 1 are as follows; as can be seen from Figures a and b, the halloysite nanotubes are hollow tubular nanomaterials, and their surfaces and interiors are smooth and free of coatings, while in Figures c and d, the surfaces of the beeswax hydrophobically modified halloysite nanotubes are obviously coated with beeswax, and are also nanotube-shaped, with the surface beeswax successfully coated on the surface and interior of the halloysite nanotubes.

[0109] Figure 3-7The scanning electron microscope images of different aerogel-based smart colorimetric labels are shown in the following order: Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Example 1. As can be seen from the figure, the pore distribution of Comparative Example 1 is uneven, with macropores and micropores coexisting and irregular morphology. With the addition of halloysite nanotubes, the pore structures of Comparative Examples 2, 3 and 4 change significantly, and the pore size distribution becomes smaller, especially in Comparative Example 4, which has the smallest pores and thin pore walls. This indicates that the halloysite nanotubes, as nanofillers, enhance the intermolecular interactions between the matrices and tightly combine the components. Compared with Example 1, in Comparative Example 4, only the halloysite nanotubes are not modified, which leads to an increase in the pore size of the prepared aerogel-type smart colorimetric label. This is due to the hydrophobicity of beeswax itself. However, the pore distribution of Example 1 is still very regular, and the pore wall is relatively thin, which shows that the halloysite nanotubes hydrophobically modified by beeswax still play the role of nanofillers, making the matrix tightly bound. In addition, rough micro-nano structures appear on the pore walls, which shows that the halloysite nanotubes hydrophobically modified by beeswax are well bonded to the matrix.

[0110] Figure 8 The water contact angle test results of different aerogel-type smart colorimetric labels are shown in the figure; the order from left to right is Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Example 1; it can be seen from the figure that the water contact angle of Comparative Example 2 with the addition of halloysite nanotubes is increased from 92.4±4.05° to 107.12±1.74° for Comparative Example 1 without the addition of halloysite nanotubes, and the effect is very significant. This is because the halloysite nanotubes, as nanofillers, make the matrix more tightly bound, resulting in good hydrophobicity on the aerogel surface. With the increase of the concentration of halloysite nanotubes, the water contact angles of Comparative Examples 2, 3 and 4 show an increasing trend; compared with Example 1, Comparative Example 4 is only the halloysite nanotubes that have not been modified, which leads to the water contact angle of the prepared aerogel-type smart colorimetric label being increased from 113.31±1.30° to 121.35±1.60°, which shows that the beeswax hydrophobic modified halloysite nanotubes significantly improve the hydrophobicity of the aerogel.

[0111] Figure 9-10 The test results of the advancing angle and receding angle of the aerogel-based smart colorimetric label prepared in Example 1 ( Fig. 9 All four figures are the advancing angles of the samples, which are the changing trends of the water contact angles from 0 to 15 seconds. The water contact angle at 15 seconds is the final advancing angle; Fig.10 All four figures are receding angles, which are changes in the water contact angles of the samples within 15-35 seconds, and the water contact angle at 35 seconds is the final receding angle). It can be seen from the figures that the advancing angle of Example 1 can eventually reach 120°, and the receding angle can eventually reach 97°, both of which are greater than 90°, indicating that the material is a hydrophobic material.

[0112] Comparative Example 5

[0113] The same as Example 1, except that, in the preparation process of beeswax hydrophobically modified halloysite nanotubes, the amount of beeswax used is changed to 1 g.

[0114] The aerogel smart colorimetric label prepared by using this comparative example has poor hydrophobicity, and its water contact angle is lower than that of the aerogel smart colorimetric label prepared by using a dosage ratio of beeswax to halloysite nanotubes of 5:1.

[0115] Comparative Example 6

[0116] Same as Example 1, except that the mass of carrageenan is replaced by gum arabic.

[0117] The aerogel smart colorimetric label prepared by this comparative example has poor matrix bonding, and its hardness test is lower than that of the aerogel smart colorimetric label prepared by carrageenan and other quality.

[0118] Comparative Example 7

[0119] The same as Example 1, except that in step S2, the amount of carrageenan solution and gelatin mixed is 10 mL, and other parameters remain unchanged.

[0120] The aerogel smart colorimetric label prepared by this comparative example has poor matrix bonding and is not fully cross-linked, resulting in poor mechanical properties such as hardness of the aerogel smart colorimetric label and failure to present a good aerogel structure.

[0121] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels, characterized in that: The following steps are involved: The hydrophobically modified halloysite nanotubes of beeswax are added as nanofillers into an aerogel matrix and freeze-dried to obtain an aerogel intelligent colorimetric label; wherein the aerogel matrix is ​​a gelatin / carrageenan-black rice anthocyanin solution.

2. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 1, characterized in that: The preparation method of the beeswax hydrophobically modified halloysite nanotubes comprises the following steps: mixing beeswax and halloysite nanotubes, adding a solvent, heating to dissolve, and drying to obtain the beeswax hydrophobically modified halloysite nanotubes.

3. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 2, characterized in that: The mass ratio of the beeswax to the halloysite nanotubes is 5:

1.

4. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 3, characterized in that: The solvent is anhydrous ethanol.

5. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 1, characterized in that: The preparation method of the gelatin / carrageenan-black rice anthocyanin solution comprises the following steps: dissolving gelatin, carrageenan and black rice anthocyanin in deionized water respectively to obtain a gelatin solution, a carrageenan solution and a black rice anthocyanin solution; mixing the gelatin solution and the carrageenan solution, adjusting the pH to 4.0, and then adding the black rice anthocyanin solution to obtain a gelatin / carrageenan-black rice anthocyanin solution.

6. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 5, characterized in that: The ratio of gelatin to deionized water is 5 g:100 mL; and / or The ratio of carrageenan to deionized water is 1 g: 100 mL; and / or The ratio of the black rice anthocyanin to deionized water is 1 mg: 1 mL; and / or The volume ratio of the gelatin solution to the carrageenan solution is 1:

1.

7. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 1, characterized in that: The usage ratio of the beeswax hydrophobically modified halloysite nanotubes to the gelatin / carrageenan-black rice anthocyanin solution is 1.2 g:40 mL.

8. The method for enhancing the hydrophobicity and mechanical properties of aerogel-based smart colorimetric labels according to claim 1, characterized in that: The freeze drying refers to freezing at -80°C for 48 hours.

9. An aerogel-based smart colorimetric label prepared by the method according to any one of claims 1 to 8.

10. Use of the aerogel-based intelligent colorimetric label as claimed in claim 9 in food testing.

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