A nanocomposite membrane based on silk protein and zeolite imidazole framework material, and its preparation method and application

Abstract

The present invention discloses a nanocomposite membrane based on silk protein and zeolite imidazole framework material, its preparation method, and application. The preparation method comprises the following steps: uniformly dispersing zeolite imidazole framework ZIF-67 powder into a silk protein (SF) solution to prepare a mixed solution, spreading the mixed solution, and drying it to obtain an SF / ZIF-67 nanomaterial composite membrane. The SF / ZIF-67 nanomaterial composite membrane is used to prepare the positive electrode of a triboelectric nanogenerator, which can improve the output performance of the triboelectric nanogenerator and can directly collect low-frequency mechanical energy in the environment and convert it into electrical energy, making it a green and environmentally friendly energy device.

Description

Technical Field

[0001] The present invention belongs to the field of triboelectric generators, and in particular relates to a nanocomposite film for triboelectric nanogenerators and a preparation method thereof. Background Art

[0002] In recent years, triboelectric nanogenerators (TENGs) have rapidly developed in fields such as healthcare, environmental protection, and energy. Researchers have been pursuing higher output power, a fundamental requirement for all energy harvesters. A growing number of new materials and methods have been introduced to enhance output performance. Composite films, due to their customizable composition, good wear resistance, and inherently rough surface, have proven to be ideal candidates for triboelectric layers.

[0003] Metal-organic frameworks (MOFs) are a class of porous crystalline materials composed of metal ions or metal clusters self-assembled with organic ligands through coordination bonds. Due to their high designability, MOFs have been applied in many fields, including gas adsorption and separation, chemical sensing, catalysis, and drug delivery, including TENGs. While some progress has been made, the application of MOFs in triboelectric nanogenerators is still in its early stages.

[0004] Zeolitic imidazolate frameworks (ZIFs) are a class of MOFs with a zeolite skeleton. They are composed of transition metal ions Zn or Co coordinated with imidazole-based organic compounds. They combine the advantages of both zeolites and MOFs: large surface area, high crystallinity, and excellent thermal and chemical stability. ZIFs are rapidly becoming a research hotspot at the intersection of energy, materials, and life sciences. However, their application in TENGs has not been reported.

[0005] In recent years, friction generators made of biomaterials such as starch, chitosan, fiber, gelatin, etc. have been widely studied, involving fields such as implantable devices, healthcare and environmental monitoring, but the cumbersome processing steps make it difficult to apply them in practice. Summary of the Invention

[0006] The present invention aims to provide a high-performance, easily industrializable nanofilm based on ZIFs and a preparation method thereof, as well as an application thereof in a triboelectric nanogenerator.

[0007] ZIF-67 is a zeolitic imidazole framework material (ZIFs), the coordination metal is Co and the organic ligand is 2-methylimidazole. The structural formula is shown below: The source of ZIF-67 can be a commercial product, or it can be prepared by a synthetic method, such as a room temperature synthesis method, a solvent thermal method, a microwave-assisted method, and the like.

[0008] Silk fibroin (SF) is prepared from silkworm cocoons, has a wide source, and has excellent biocompatibility.

[0009] The present invention is achieved through the following technical solutions:

[0010] The invention provides a nanocomposite membrane based on silk protein and zeolite imidazole framework material, which is composed of silk protein and zeolite imidazole framework material ZIF-67 powder, wherein the ZIF-67 powder accounts for 1-20% of the weight of the nanocomposite membrane, and the particle size distribution of the ZIF-67 powder is 100-1000 nanometers.

[0011] In a preferred embodiment, the ZIF-67 powder accounts for 3-11% by weight of the nanocomposite film, and more preferably 6-10.5% by weight.

[0012] In a preferred embodiment, the thickness of the nanocomposite film is 10 to 50 μm.

[0013] In a preferred embodiment, the particle size distribution of ZIF-67 powder is 400-600 nanometers.

[0014] In the present invention, the “nanocomposite membrane based on silk protein and zeolite imidazole framework material” is referred to as “SF / ZIF-67 nanocomposite membrane” for short.

[0015] The present invention also provides a method for preparing the nanocomposite membrane based on silk protein and zeolite imidazole framework material, comprising the following steps: uniformly dispersing ZIF-67 powder into silk protein solution to prepare a mixed solution, then spreading and drying the mixed solution to obtain the nanocomposite membrane.

[0016] In a preferred embodiment, the solid content of the silk protein solution is 4-6 wt%.

[0017] In a preferred embodiment, the dispersion method is stirring and ultrasonication, and the dispersion time is 3-7 minutes.

[0018] In a preferred embodiment, the mixed liquid is poured into a rectangular parallelepiped mold and spread evenly.

[0019] In a preferred embodiment, the drying temperature is 35-45° C. and the drying time is 20-30 hours.

[0020] The present invention further provides the use of the nanocomposite film based on silk protein and zeolite imidazole framework material or the nanocomposite film based on silk protein and zeolite imidazole framework material obtained according to the preparation method of the present invention in a friction nanogenerator.

[0021] The present invention further provides a method for preparing the triboelectric nanogenerator in the above application, comprising the following steps:

[0022] (a) A piece of aluminum foil is attached to one side of the nanocomposite membrane based on silk protein and zeolite imidazole framework material and current is drawn out to serve as the positive electrode of the triboelectric nanogenerator;

[0023] (b) Another piece of aluminum foil is attached to one side of a polydimethylsiloxane (PDMS) membrane of the same size and current is drawn to serve as the negative electrode of the triboelectric nanogenerator;

[0024] (c) Under the action of external force, the positive electrode of the friction nanogenerator and the negative electrode of the friction nanogenerator generate an AC signal of the same frequency through contact-separation motion, forming a friction nanogenerator.

[0025] In a preferred embodiment, the nanocomposite membrane based on silk protein and zeolite imidazole framework material is cut into small sizes, with a size of (2-5) × (2-5) cm 2 .

[0026] In a preferred embodiment, the positive and negative electrodes of the friction nanogenerator use copper conductive glue to draw out current.

[0027] In a preferred embodiment, the friction nanogenerator is of a vertical contact-separation type.

[0028] In a preferred embodiment, the positive and negative electrodes of the vertical contact-separation friction nanogenerator are initially in a separated state. When the positive and negative electrodes perform contact-separation motions of a certain frequency under the action of an external force, an alternating current signal of the same frequency is obtained.

[0029] In the present invention, unless otherwise specified, operations are carried out at room temperature, which refers to 10 to 30°C.

[0030] The present invention further provides a triboelectric nanogenerator prepared according to the preparation method of the triboelectric nanogenerator.

[0031] The present invention further provides applications of the above-mentioned triboelectric nanogenerator in the fields of liquid crystal display and capacitors.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention has developed a SF / ZIF-67 nanocomposite film for the preparation of the positive electrode of the friction nanogenerator. ZIF-67 is introduced into SF as a dual-functional filler. In addition to having the advantages of MOF, it also has excellent chemical and thermal stability. The addition of ZIF-67 filler, in addition to serving as a charge capture site with similar effects to traditional fillers, also increases the amount of triboelectric charge generated by friction between the positive and negative electrodes by changing the surface roughness and hydrophobicity of the membrane, while also changing the dielectric properties of the composite membrane to improve the ability of the film to store charge and reduce charge loss. These effects have been verified by detailed electrical tests, theoretical analysis and finite element simulation. Compared with the friction nanogenerator (S-TENG) based on pure SF film, the output voltage of the friction nanogenerator (ZS-TENG) of the present invention can reach 2 times. The maximum instantaneous output power density of ZS-TENG is 144μW cm -2 It is 5 times that of S-TENG.

[0034] (2) The preparation method of the nanocomposite membrane of the present invention is simple and easy to realize industrial production. ZIF-67 is prepared by a room temperature aqueous phase method, which reduces the cost.

[0035] (3) In terms of energy collection and conversion, the present invention can directly collect low-frequency mechanical energy in the environment and convert it into electrical energy, thereby achieving self-power supply, which can be used to directly light up LED lights or charge capacitors to store electrical energy. It is a new type of green and environmentally friendly energy device with good practicality and has a huge application market as a supplementary energy source. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the SEM image of the ground SF / ZIF-67 powder in Example 1, with a scale bar of 500 nm.

[0037] Figure 2 Schematic diagram of the vertical contact-separation friction nanogenerator in Example 3, wherein: 1—aluminum foil, 2—SF / ZIF-67 nanocomposite film, 3—PDMS film, 4—aluminum foil, 5—copper conductive adhesive.

[0038] Figure 3 This is a comparison of the output performance of the triboelectric nanogenerators in Comparative Example 1 and Examples 3-8, with the horizontal axis representing time (seconds) and the vertical axis representing voltage (V). DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Any variation or replacement that is not conceivable through creative work should be encompassed within the scope of protection of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims of this application.

[0040] Example 1

[0041] ZIF-67 powder was prepared using the following room-temperature aqueous method: 1 g of cobalt(II) acetate tetrahydrate was dissolved in 15 mL of deionized water, and 2.64 g of 2-methylimidazole was dissolved in 10 mL of deionized water. These were then mixed and stirred at room temperature for 24 hours. The dispersion was then centrifuged at 10,000 rpm for 6 minutes to obtain a dark purple precipitate. This precipitate was then washed with deionized water and centrifuged again three times. The precipitate was then washed with anhydrous ethanol and centrifuged again, again three times, until the supernatant solution became clear and transparent. The product was then dried at 80°C for 24 hours. The product was dark purple crystalline ZIF-67.

[0042] The microstructure of ZIF-67 powder after grinding is as follows: Figure 1 As shown, the particle size distribution is 400-600 nm.

[0043] The ZIF-67 powder ground in Example 1 was used in Examples 3-8.

[0044] Example 2

[0045] The silk protein SF solution was prepared using the following method: First, silk fibers were extracted by boiling silk cocoons in a 0.02M sodium carbonate solution for 45 minutes to remove sericin. Then, the extracted silk fibers were rinsed in deionized water five times and then dried in an oven at 40°C for 24 hours to obtain degummed silk. Secondly, the prepared degummed silk was immersed in a 9.3M lithium bromide solution and heated at 60°C for 4 hours to completely dissolve it. Thirdly, the mixed solution was dialyzed for 48 hours using a 3500MWCO dialysis membrane to remove lithium bromide ions and initially obtain a silk protein solution, which was then centrifuged twice at 9000rpm for 20 minutes. Finally, the silk protein solution was further purified by filtration twice through a 5μm filter membrane. The solid content of the SF solution was 5.4wt%.

[0046] In Examples 3-8 and Comparative Example 1, the SF solution of Example 2 was used.

[0047] Example 3

[0048] 0.0410 g of ground ZIF-67 powder was dispersed into 10.2090 g of silk fibroin solution. The mixture was stirred and sonicated for a total of 5 minutes to ensure uniform dispersion of the ZIF-67 in the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 0.4 wt.%) before being poured into a rectangular mold. After drying at 40°C for 24 hours, a SF / ZIF-67 nanocomposite film (thickness: ~40 μm) was obtained.

[0049] Subsequently, the obtained nanocomposite film was cut into pieces of 2 × 2.5 cm 2 A small-sized film is made, and then one side of the film is pasted with aluminum foil with double-sided tape as an electrode and the current is drawn out with copper conductive glue to obtain the positive electrode of the friction nanogenerator. A PDMS film of the same size is taken and aluminum foil is pasted on one side as an electrode and the current is drawn out with copper conductive glue as the negative electrode of the friction nanogenerator. The positive and negative electrodes together form a vertical contact-separation friction nanogenerator, as shown in the schematic diagram. Figure 2 As shown. Figure 3 The middle figure shows 0.4%, and its output voltage is 118 V, which is twice the output voltage of comparative example 1. This experimental result confirms that the addition of ZIF-67 material is beneficial to improving the output performance of TENG.

[0050] Example 4

[0051] 0.0206 g of ground ZIF-67 powder was dispersed into 10.2794 g of silk fibroin solution. The mixture was stirred and sonicated for a total of 5 minutes to ensure uniform dispersion of the ZIF-67 in the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 0.2 wt.%) before being poured into a rectangular mold. After drying at 40°C for 24 hours, a SF / ZIF-67 nanocomposite film (thickness: ~40 μm) was obtained.

[0052] Subsequently, the obtained nanocomposite film was cut into pieces of 2 × 2.5 cm 2 The small-sized film was prepared by the same method as in Example 3 to obtain a triboelectric nanogenerator. Figure 3 The middle graph shows a 0.2% filler ratio, with an output voltage of 103 V. This result is due to a decrease in the filler mass ratio, which reduces the dielectric constant of the composite film and, consequently, the transferred charge density, resulting in a decrease in output performance.

[0053] Example 5

[0054] 0.0102 g of ground ZIF-67 powder was dispersed into 10.1898 g of silk fibroin solution. The mixture was stirred and sonicated for a total of 5 minutes to ensure uniform dispersion of the ZIF-67 in the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 0.1 wt.%) before being poured into a rectangular mold. After drying at 40°C for 24 hours, a SF / ZIF-67 nanocomposite film (thickness: ~40 μm) was obtained.

[0055] Subsequently, the obtained nanocomposite film was cut into pieces of 2 × 2.5 cm 2 The small-sized film was prepared by the same method as in Example 3 to obtain a triboelectric nanogenerator. Figure 3 The middle figure shows 0.1%, and its output voltage is 101 V. This result once again proves that the decrease in filling mass ratio leads to a decrease in the dielectric constant of the composite film and a decrease in the transfer charge density, which in turn leads to a decrease in output performance.

[0056] Example 6

[0057] 0.0636 g of ground ZIF-67 powder was dispersed into 10.5364 g of silk fibroin solution. The mixture was stirred and sonicated for a total of 5 minutes to ensure uniform dispersion of ZIF-67 within the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 0.6 wt.%) before being poured into a rectangular mold. After drying at 40°C for 24 hours, a SF / ZIF-67 nanocomposite film (thickness: ~40 μm) was obtained.

[0058] Subsequently, the obtained nanocomposite film was cut into pieces of 2 × 2.5 cm 2 The small-sized film was prepared by the same method as in Example 3 to obtain a triboelectric nanogenerator. Figure 3 The middle figure shows an output voltage of 110V at 0.6%. This phenomenon occurs because the contact angle of the composite film decreases as the ZIF-67 loading mass ratio increases. Compared to the pure SF film in Comparative Example 1, the composite film has a more hydrophilic surface, leading to increased surface discharge caused by water in the surrounding environment. Therefore, the addition of ZIF-67 is disadvantageous in this regard. These two factors together determine that the output of the TENG first increases and then decreases with increasing mass ratio.

[0059] Example 7

[0060] 0.0856 g of ground ZIF-67 powder was dispersed into 10.6144 g of silk fibroin solution. The mixture was stirred and sonicated for a total of 5 minutes to ensure uniform dispersion of the ZIF-67 in the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 0.8 wt.%) before being poured into a rectangular mold. After drying at 40°C for 24 hours, a SF / ZIF-67 nanocomposite film (thickness: ~40 μm) was obtained.

[0061] Subsequently, the obtained nanocomposite film was cut into pieces of 2 × 2.5 cm 2 The small-sized film was prepared by the same method as in Example 3 to obtain a triboelectric nanogenerator. Figure 3 The middle graph shows 0.8%, and its output voltage is 99 V. This experimental result further proves the reason for the change in Example 6.

[0062] Example 8

[0063] 0.1050 g of ground ZIF-67 powder was dispersed into 10.3950 g of silk protein solution. The mixture was stirred and sonicated for a total of 5 min to ensure uniform dispersion of ZIF-67 in the matrix (the mass ratio of ZIF-67 powder in the SF / ZIF-67 mixture was 1 wt.%), and then poured into a rectangular parallelepiped mold. After drying at 40 ° C for 24 h, a composite film with a mass ratio of 1 wt.% was obtained (thickness: ~40 μm). Subsequently, the resulting nanocomposite film was cut into 2 × 2.5 cm 2 The small-sized film was prepared by the same method as in Example 3 to obtain a triboelectric nanogenerator. Figure 3 The middle icon shows 1%, and its output voltage is 96V.

[0064] The results of Examples 3-8 all demonstrate that adding ZIF-67 to the SF matrix generally improves the output performance of the triboelectric nanogenerator.

[0065] Comparative Example 1

[0066] A triboelectric nanogenerator based on pure SF membrane was prepared. The preparation method was the same as that in Example 3, wherein a certain amount of silk protein solution was poured into a rectangular mold, dried, and cut. The prepared triboelectric nanogenerator was named S-TENG. Its output voltage is as follows Figure 3 The middle icon indicates 0%.

Claims

1. A nanocomposite membrane based on silk protein and zeolite imidazole framework material, composed of silk protein and zeolite imidazole framework material ZIF-67 powder, wherein the ZIF-67 powder accounts for 6-10.5% of the weight of the nanocomposite membrane, and the particle size distribution of the ZIF-67 powder is 400-600 nanometers.

2. The nanocomposite membrane based on silk protein and zeolite imidazole framework material according to claim 1, characterized in that: The thickness of the composite film is 10 to 50 μm.

3. The method for preparing the nanocomposite membrane based on silk protein and zeolite imidazole framework material according to claim 1, comprising the following steps: The ZIF-67 powder is uniformly dispersed in the silk protein solution to prepare a mixed solution, and then the mixed solution is spread and dried to obtain the nanocomposite membrane.

4. The preparation method according to claim 3, characterized in that The solid content of the silk protein solution is 4-6 wt %, the dispersion method is stirring and ultrasonic, and the dispersion time is 3-7 minutes.

5. The preparation method according to claim 3, characterized in that The drying temperature is 35-45° C., and the drying time is 20-30 hours.

6. Use of the nanocomposite membrane based on silk protein and zeolite imidazole framework material according to claim 1 or 2, or the nanocomposite membrane based on silk protein and zeolite imidazole framework material obtained according to the preparation method of any one of claims 3 to 5 in a friction nanogenerator.

7. The use according to claim 6, characterized in that The method for preparing the triboelectric nanogenerator comprises the following steps: (a) A piece of aluminum foil is attached to one side of the nanocomposite membrane based on silk protein and zeolite imidazole framework material and current is drawn out to serve as the positive electrode of the triboelectric nanogenerator; (b) Another piece of aluminum foil is attached to one side of the polydimethylsiloxane film of the same size and current is drawn out to serve as the negative electrode of the triboelectric nanogenerator; (c) Under the action of external force, the positive electrode of the friction nanogenerator and the negative electrode of the friction nanogenerator generate an AC signal of the same frequency through contact-separation motion, forming a friction nanogenerator.

8. A triboelectric nanogenerator, characterized in that: The application according to claim 7 is obtained by using the preparation method of the friction nanogenerator.

9. Application of the triboelectric nanogenerator according to claim 8 in the fields of liquid crystal display and capacitors.

Images