CN111359549B

CN111359549B - Preparation method of composite hydrogel and aerogel

Info

Publication number: CN111359549B
Application number: CN202010170726.5A
Authority: CN
Inventors: 顾佳俊; 袁洋; 李镕臣; 张荻
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2020-03-12
Filing date: 2020-03-12
Publication date: 2022-08-09
Anticipated expiration: 2040-03-12
Also published as: CN111359549A

Abstract

The invention provides a preparation method of composite hydrogel and aerogel, relates to the field of composite materials, and particularly relates to a preparation method of chitin hydrogel and aerogel embedded with metal nanoparticles. The preparation method of the composite hydrogel mainly comprises two steps, namely: sequentially removing proteins and minerals in fungi by alkali cooking and acid washing to obtain chitin hydrogel; and step two, soaking the obtained chitin hydrogel into a metal ion aqueous solution, and reducing the chitin hydrogel by using a reducing agent to obtain the chitin composite hydrogel embedded with the metal nanoparticles. The preparation method of the composite aerogel is characterized in that the composite aerogel is subjected to supercritical drying or freeze drying to obtain the composite aerogel. The method is made of natural organisms, has good biocompatibility and can be naturally degraded; organic reagents are not needed in the preparation process, and the preparation method is green, safe and environment-friendly; the prepared composite hydrogel and the metal nanoparticles in the aerogel are densely and uniformly dispersed in the chitin and are not easy to fall off.

Description

Preparation method of composite hydrogel and aerogel

Technical Field

The invention relates to the field of composite materials, in particular to a preparation method of composite hydrogel and aerogel.

Background

The hydrogel and the aerogel are both gel, the dispersed phases of the gel are respectively water and air, and the solid phases are all chain solid materials which are mutually crosslinked to form a porous network framework. The hydrogel is widely applied to the fields of tissue engineering, drug carriers, biosensors, intelligent response and the like. Aerogels contain a large number of pore structures, and the pores are filled with air, so that they have very low density and low thermal conductivity and are often used as thermal insulation materials. In addition, the aerogel has a high specific surface area and is widely applied to the aspects of filtration, catalysis, electrode materials and the like.

The porous network backbone of hydrogels is typically a polymeric material such as polyvinyl alcohol, polyacrylamide, and block copolymers. Besides synthetic polymers, in recent years, biopolymers have begun to be applied as components of hydrogels in the fields of antibiosis, wound healing, drug loading, and the like because of their advantages of good biocompatibility, nontoxicity, and easy degradation.

The commonly used biological macromolecules are cellulose, silk fibroin, sodium alginate, chitin and their derivatives. These biopolymers and their derivatives are usually prepared by a series of fine chemical purification methods and require complexing with synthetic polymers to prepare structurally stable hydrogels. Currently, the aerogel mainly includes silica aerogel, carbon aerogel (such as graphene aerogel), metal oxide aerogel and organic polymer aerogel.

Chinese patent publication No. CN105061782B discloses a high-performance graphene/cellulose self-assembled composite hydrogel and aerogel and a preparation method thereof, which comprises (1) soaking a cellulose raw material, and then performing fiber dissociation to prepare a paper pulp dispersion; (2) adding graphite oxide into the prepared paper pulp dispersion liquid, and performing ultrasonic dispersion to obtain a graphene oxide/cellulose mixed solution; (3) adding a reducing agent into the graphene oxide/cellulose mixed solution, reducing for 3-24h at 40-100 ℃, or washing the obtained product by adopting a hydrothermal reduction method to obtain the graphene/cellulose self-assembled composite hydrogel. The preparation methods of these aerogels and their raw materials involve complicated chemical reactions, generate more pollutants, and are difficult to produce on a large scale.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for preparing a composite hydrogel and aerogel.

The purpose of the invention is realized by the following technical scheme: a preparation method of composite hydrogel comprises the following steps:

A. sequentially removing proteins and minerals in the fungi by alkaline cooking and acid washing, and leaving cell walls of the fungi to obtain chitin hydrogel;

B. and soaking the obtained chitin hydrogel in a metal ion aqueous solution, and reducing by using a reducing agent to obtain the chitin composite hydrogel embedded with the metal nanoparticles.

Preferably, the fungus comprises one of mushroom, agaric and tremella, the mushroom comprises pleurotus eryngii, and the main component of the cell wall of the fungus is chitin.

Preferably, the alkaline cooking operation in step a specifically comprises: soaking the cell wall of the fungus in the concentration of 0.2-

Heating in 10mol/L alkali solution at 80-100 deg.c for 1-24 hr; the alkali solution comprises one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution.

More preferably, the concentration of the alkali solution is preferably 0.5-4mol/L, the effect is optimal when the concentration is 1mol/L, and other components such as protein in the mushroom are not completely removed when the concentration is lower than 0.2 mol/L; above 10mol/L, chitin, which is the main component of mushrooms, is decomposed, and the network structure of chitin is destroyed.

More preferably, the heating temperature is preferably 100 ℃, and when the temperature is lower than 80 ℃, the dissociation and dissolution speed of other impurities such as protein is too slow. The heating time is preferably 4 to 15 hours, and most preferably 6 hours.

Preferably, the pickling operation in the step a specifically includes: soaking the fungal cell wall subjected to alkaline cooking in an acid solution with the concentration of 0.1-1mol/L for 0.5-4 hours; the acid solution comprises an inorganic acid, and the inorganic acid comprises one of hydrochloric acid, acetic acid and nitric acid.

Preferably, the chitin hydrogel in the step B is soaked in a metal ion aqueous solution for 1-6 hours, and the metal ion solution is a complex solution of metal ions and comprises chloroauric acid solution, gold ammonia solution, Au (OH) ₄ ^- Solutions, palladium ammonia solutions, platinum ammonia solutions, silver ammonia solutions, copper ammonia solutions, Cu (OH) ₄ ^2- One of a solution, a copper ethylenediamine solution and a nickel ammonia solution; and the reducing agent in the step B comprises one of sodium borohydride solution, hydrazine hydrate, dimethylamino borane solution and stannous chloride solution.

The preparation method of the composite aerogel is characterized by comprising the following steps: and carrying out supercritical drying or freeze drying on the composite hydrogel to obtain the composite aerogel.

Preferably, the supercritical drying specifically comprises the following steps:

a. sequentially soaking the composite hydrogel into ethanol aqueous solutions with different proportions for 2 hours respectively to obtain ethanol gel;

b. and (3) drying the ethanol gel in a supercritical drying instrument to obtain the composite aerogel.

Preferably, the proportion of the ethanol aqueous solution is 5:5, 7:3, 9:1 and 10:0 in sequence.

Preferably, the freeze-drying specifically comprises the following steps:

a1, freezing the composite hydrogel at low temperature;

b1, placing the composite hydrogel frozen at low temperature into a freeze dryer to be dried for 24 hours or more, and obtaining the composite aerogel.

Preferably, the low-temperature freezing is refrigerator freezing or liquid nitrogen freezing or refrigerator freezing and then liquid nitrogen freezing.

In summary, compared with the prior art, the invention has the following beneficial effects:

(1) according to the preparation method of the composite hydrogel and the aerogel, provided by the invention, the raw materials are from fungal cell walls in nature, the structure types are rich, the raw materials are rich, the environment is protected, and the composite hydrogel and the aerogel can be naturally degraded;

(2) the alkali, the acid solution, the metal ion salt solution and the reducing agent used in the preparation method of the composite hydrogel and the aerogel are all chemical reagents commonly used in industry, do not need organic reagents and can be repeatedly used;

(3) the metal nanoparticles in the composite hydrogel and aerogel prepared by the preparation method provided by the invention are embedded in chitin, are not easy to fall off and agglomerate, and are dense and uniformly dispersed.

Drawings

FIG. 1 is a digital photograph of chitin hydrogel and gold nanoparticle chitin composite hydrogel of example 1;

FIG. 2 is a digital photograph of chitin aerogel and gold nanoparticle chitin composite aerogel of example 2;

figure 3 is an XRD pattern of chitin aerogel and gold nanoparticle chitin composite aerogel in example 2;

FIG. 4 is SEM images of chitin aerogel surface of example 2 at different magnifications;

FIG. 5 is SEM images of the chitin aerogel of example 2 at different magnifications;

fig. 6 is an SEM image of the interior of gold nanoparticle chitin composite aerogel in example 2;

FIG. 7 is a TEM image of a cross section of gold nanoparticle chitin composite aerogel in example 2;

FIG. 8 is a photograph of a composite hydrogel of chitin with nickel nanoparticles as in example 4;

FIG. 9 is a digital photograph of a nickel nanoparticle chitin composite aerogel according to example 5;

FIG. 10 is a digital photograph of the copper nanoparticle chitin composite hydrogel of example 6;

FIG. 11 is a digital photograph of the silver nanoparticle chitin composite hydrogel of example 7;

fig. 12 is an SEM image of the surface of the gold nanoparticle chitin composite aerogel after natural drying in air in comparative example 1;

FIG. 13 is a flow chart of the preparation of composite hydrogels and aerogels of examples 1-10.

Detailed Description

The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, which ranges of values are to be considered as specifically disclosed herein, the invention is described in detail below with reference to specific examples:

the application extracts chitin hydrogel from fungi (mushrooms) for the first time by a simple and green method, and embeds metal nanoparticles based on the complexation of metal complex ions and chitin through chemical reduction; the nanoparticles are densely and uniformly embedded in the chitin matrix.

Example 1

A preparation method of composite hydrogel, as shown in the preparation flow of fig. 13, specifically comprising the following steps:

A. cleaning Pleurotus eryngii with distilled water for three times, and cutting into round pieces with diameter of 3cm and thickness of 0.3 cm. The cut disc is put into 1mol/L sodium hydroxide solution, boiled at 100 ℃ for 6 hours to remove protein and fat, and then washed with distilled water for three times. Then the chitosan hydrogel is put into 1mol/L hydrochloric acid solution to be soaked for 2 hours, minerals are removed, and then the chitosan hydrogel is repeatedly washed to be neutral by distilled water to obtain the chitin hydrogel.

B. The chitin hydrogel was soaked in 0.2 wt.% chloroauric acid solution for 4 hours and then washed three times with distilled water. Then the obtained product is put into 0.1mol/L sodium borohydride solution for reduction for 10 minutes, and then the obtained product is washed with distilled water for three times to obtain the gold nanoparticle embedded chitin composite hydrogel.

The composite hydrogel shown in fig. 1 is finally obtained as chitin composite hydrogel embedded with gold nanoparticles. From the left side of fig. 1, it can be seen that the chitin hydrogel is light yellow, a typical chitin color, and that the hydrogel is filled with moisture, indicating that proteins and fats have been removed cleanly, leaving only chitin. The right side of fig. 1 shows that the surface of the gold nanoparticle chitin composite hydrogel is black, and the transmitted light is dark red, which is the color of a typical gold nanoparticle sol, and indicates that dense gold nanoparticles are embedded in the composite hydrogel, and the nanoparticles are uniformly dispersed without agglomeration.

Example 2

A preparation method of a composite aerogel, as shown in a preparation flow of FIG. 13, is different from that of example 1 in that steps A to B are the same as that of example 1; the step B also comprises the following steps:

a. sequentially soaking the gold nanoparticle chitin composite hydrogel into ethanol aqueous solutions with different proportions for 2 hours respectively, wherein the proportions of the ethanol aqueous solutions are 5:5, 7:3, 9:1 and 10:0 in sequence to obtain ethanol gel.

b. Adding ethanol gel into CO ₂ And drying in a supercritical drying instrument to finally obtain the composite aerogel.

Finally, the obtained composite aerogel shown in fig. 2 is chitin composite aerogel with gold nanoparticles embedded therein. The left side of the figure 2 shows chitin aerogel, which is white; the right side is the gold nanoparticle chitin composite aerogel, which is pink, again indicating that the gold nanoparticles are uniformly dispersed in the chitin and do not agglomerate. The XRD pattern of the composite aerogel showed nanoscale gold particles contained therein (fig. 3). The surface micro-topography of the chitin aerogel is shown in fig. 4, the internal micro-topography is shown in fig. 5, and the surface and the inside are both porous network skeletons formed by chitin. The microscopic morphology of the gold nanoparticle chitin composite aerogel is almost the same as that of chitin aerogel, but in the magnified scanning electron microscope fig. 6, it can be seen that very small nanoparticles are uniformly dispersed on the chitin skeleton of the composite aerogel. From the transmission electron micrograph of fig. 7, it can be seen that the gold nanoparticles are very uniformly dispersed in the chitin polymer without severe agglomeration.

Example 3

A preparation method of a composite aerogel, as shown in a preparation flow of FIG. 13, is different from that of example 1 in that steps A to B are the same as that of example 1; the following steps are also included after the step B:

a1, freezing the composite hydrogel in a refrigerator for 2 hours, and then freezing the hydrogel in liquid nitrogen for 5 minutes.

b1, and then drying in a freeze drying instrument for 2 days to obtain the gold nanoparticle embedded chitin composite aerogel.

The finally obtained composite aerogel is chitin composite aerogel embedded with gold nanoparticles, and the difference from the composite aerogel obtained in embodiment 2 is that the mechanical strength of the composite aerogel obtained by freeze drying is lower than that of the composite aerogel obtained by supercritical drying, and the composite aerogel obtained by freeze drying is fragile and not easy to bend.

Example 4:

a method for preparing a composite hydrogel, as shown in the preparation flow of fig. 13, which is different from the method of example 1 in that:

and B, soaking the chitin hydrogel in 0.1mol/L nickel tetraammine solution for 6 hours, and then washing the chitosan hydrogel with distilled water for three times.

Then the chitosan hydrogel is put into 0.1mol/L sodium borohydride solution for reduction for 20 minutes, and then distilled water is used for washing for three times to obtain the chitin composite hydrogel embedded with the nickel nano particles.

Finally, the nickel nanoparticle chitin composite hydrogel shown in fig. 8 is obtained. The nickel nanoparticle chitin composite hydrogel is black, because when the size of the metal nickel is smaller than 40 nanometers, the optical reflection and scattering are reduced to be almost 0, and only the optical absorption exists; meanwhile, the porous structure in the hydrogel causes multiple scattering of light, and the optical path is increased, so that the absorption is enhanced; the interband transition of nickel can occur with very small photon energy, and can absorb near infrared light, so that sunlight can be absorbed in the full spectrum.

Example 5:

a preparation method of a composite aerogel is shown in a preparation flow of FIG. 13, and is different from the preparation method of the embodiment 4 in that the steps A to B are the same as the step 4; the step B also comprises the following steps:

a. the nickel nanoparticle chitin composite hydrogel is sequentially soaked in ethanol aqueous solutions with different ratios for 2 hours respectively, wherein the ratio of the ethanol aqueous solution is 5:5, 7:3, 9:1 and 10:0 in sequence.

b. Adding the obtained ethanol gel into CO ₂ And drying in a supercritical drying instrument to finally obtain the composite aerogel embedded with the nickel nano particles.

Finally, the nickel nanoparticle chitin composite aerogel shown on the left side of fig. 9 was obtained. The nickel nanoparticle chitin composite aerogel is black, and the light absorption principle of the nickel nanoparticle chitin composite aerogel is the same as that of the nickel nanoparticle chitin composite hydrogel.

Example 6:

and step B, soaking the chitin hydrogel into a copper tetraammine solution with the concentration of 0.1mol/L for 2 hours, and then washing the chitin hydrogel with distilled water for three times.

Then the chitosan hydrogel is put into 0.1mol/L sodium borohydride solution for reduction for 20 minutes, and then the chitosan hydrogel embedded with copper nanoparticles is obtained by washing the chitosan hydrogel with distilled water for three times.

The final copper nanoparticle embedded chitin hydrogel was obtained as shown in figure 10. The copper nanoparticle chitin hydrogel is black, and the copper nanoparticle has a local plasma resonance effect and interband transition at the same time, so that the optical absorption is enhanced.

Example 7:

and step B, soaking the chitin hydrogel into a silver diammine solution with the concentration of 0.1mol/L for 8 hours, and then washing the chitin hydrogel with distilled water for three times.

Then the solution is put into 0.1mol/L sodium borohydride solution for reduction for 20 minutes, and then the solution is washed three times by distilled water to obtain the chitin composite hydrogel embedded with the silver nanoparticles.

Finally, the chitin hydrogel with embedded silver nanoparticles shown in fig. 11 was obtained. The silver nanoparticle chitin hydrogel was dark yellow, similar in color to the silver nanoparticle colloid.

Example 8:

a method for preparing a composite hydrogel, as shown in the preparation flow of fig. 13, which is different from that of example 1 in that step a specifically includes: the Auricularia auricula is washed with distilled water for three times, and cut into round pieces with diameter of 3cm and thickness of 0.1 cm. The cut disc is put into 0.2mol/L potassium hydroxide solution, boiled at 80 ℃ for 24 hours to remove protein and fat, and then washed with distilled water for three times. Then soaking in 0.1mol/L acetic acid solution for 4 hours, removing minerals, and repeatedly washing with distilled water to neutrality to obtain the chitin hydrogel.

The step B specifically comprises the following steps: the chitin hydrogel was soaked in 0.2 wt.% chloroauric acid solution for 1 hour, and then washed three times with distilled water. Then the obtained product is put into 0.1mol/L sodium borohydride solution for reduction for 10 minutes, and then the obtained product is washed with distilled water for three times to obtain the gold nanoparticle embedded chitin composite hydrogel.

Example 9:

a method for preparing a composite hydrogel, as shown in the preparation flow of fig. 13, which is different from that of example 1 in that step a specifically includes: the tremella is washed three times by distilled water and cut into round pieces with the diameter of 3cm and the thickness of 0.1 cm. The cut disc is put into 10mol/L sodium hydroxide solution, boiled at 90 ℃ for 1 hour to remove protein and fat, and then washed with distilled water for three times. Then soaking in 0.5mol/L nitric acid solution for 0.5 h, removing minerals, and repeatedly washing with distilled water to neutrality to obtain chitin hydrogel.

Example 10:

a method for preparing a composite hydrogel, as shown in the preparation flow of fig. 13, which is different from that of example 1 in that step a specifically includes: the step A specifically comprises the following steps: the tremella is washed three times by distilled water and cut into round pieces with the diameter of 3cm and the thickness of 0.1 cm. The cut disc is put into 4mol/L sodium hydroxide solution, boiled for 15 hours at 100 ℃ to remove protein and fat, and then washed with distilled water for three times. Then the chitosan hydrogel is put into 1mol/L nitric acid solution to be soaked for 0.5 hour, minerals are removed, and then the chitosan hydrogel is repeatedly washed to be neutral by distilled water to obtain the chitosan hydrogel.

Comparative example 1

A method for preparing a composite aerogel, which is different from the method in example 2 in that: placing the gold nanoparticle chitin composite hydrogel in a laboratory, and naturally drying the hydrogel.

The finally obtained gold nanoparticle chitin composite aerogel is shown in fig. 12, and a large number of folds on the surface can be seen, and a porous network framework is not formed. This is because the surface tension of water is relatively large, and in a naturally dry state, the chitin skeleton is contracted by the surface tension of water during evaporation of water, and finally, the pores are blocked.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

1. The preparation method of the composite hydrogel is characterized by comprising the following steps:

A. sequentially removing proteins and minerals in the fungi by alkaline cooking and acid washing, and leaving cell walls of the fungi to obtain chitin hydrogel; the alkaline cooking operation specifically comprises: soaking fungi in 0.5-1mol/L alkali solution, and heating at 80-100 deg.C for 1-24 hr; the alkali solution comprises one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution; the pickling operation specifically comprises: soaking the cell wall of the fungus after the alkaline cooking operation in an acid solution with the concentration of 0.1-1mol/L for 0.5-4 hours; the acid solution comprises inorganic acid, and the inorganic acid comprises one of hydrochloric acid, acetic acid and nitric acid;

B. soaking the obtained chitin hydrogel in a metal ion aqueous solution, and reducing the chitin hydrogel by using a reducing agent to obtain a chitin composite hydrogel embedded with metal nanoparticles; the method specifically comprises the following steps: the chitin hydrogel is soaked in a metal ion aqueous solution for 1-6 hours, and the metal ion solution is a complex solution of metal ions and comprises chloroauric acid solution, gold ammonia solution and Au (OH) ₄ ^- Solutions, palladium ammonia solutions, platinum ammonia solutions, silver ammonia solutions, copper ammonia solutions, Cu (OH) ₄ ^2- One of a solution, a copper ethylenediamine solution and a nickel ammonia solution;

the reducing agent comprises one of sodium borohydride solution, hydrazine hydrate, dimethylamino borane solution and stannous chloride solution; the fungus comprises one of mushroom, agaric and tremella, the mushroom comprises pleurotus eryngii, and the main component of the cell wall of the fungus is chitin.

2. A method for preparing a composite aerogel from the composite hydrogel according to claim 1, comprising the following steps: and carrying out supercritical drying or freeze drying on the composite hydrogel to obtain the composite aerogel.

3. The method for preparing a composite aerogel according to claim 2, wherein the supercritical drying specifically comprises the following steps:

4. The method for preparing a composite aerogel according to claim 2, wherein the freeze-drying specifically comprises the following steps:

a1, freezing the composite hydrogel at low temperature;

5. The method for preparing composite aerogel according to claim 4, wherein the low-temperature freezing is refrigerator freezing or liquid nitrogen freezing or refrigerator freezing first and then liquid nitrogen freezing.

6. The preparation method of the composite aerogel according to claim 3, wherein the proportion of the ethanol aqueous solution is 5:5, 7:3, 9:1 and 10:0 in sequence.