Hydrophilic and hydrophobic modification method of laser-induced graphene

Abstract

The invention discloses a hydrophilic and hydrophobic modification method of laser-induced graphene, and relates to the technical field of graphene modification.The method comprises the steps that laser-induced graphene is subjected to heat treatment, and hydrophilic or hydrophobic laser-induced graphene is obtained; according to the method, tearing and separation in graphene sheet layers are caused by heat treatment energy, and the size and morphology of the graphene sheet layers are changed; carbon atoms in the graphene can obtain relatively high energy due to thermal vibration, so that the carbon atoms are shifted from original positions, different defects are formed, the wettability of the surface of the laser-induced graphene is influenced, and the hydrophilic or hydrophobic laser-induced graphene is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene modification, and particularly relates to a method for hydrophilic and hydrophobic modification of laser-induced graphene. Background Art

[0002] Common hydrophobic materials such as silica, polytetrafluoroethylene, silica gel, rubber, etc. are difficult to simultaneously meet biocompatibility, ice inhibition, and high-efficiency heat conduction. Research has found that the structure and surface properties of graphene can affect the ice crystal growth mode, and graphene simultaneously has excellent properties of heat conduction and electricity conduction, which can meet the requirements of an external heating field, and its tested biocompatibility also makes it have good application prospects in the biomedical field.

[0003] For adjustable wettability, graphene also shows great potential. Research shows that the controllable wettability of graphene comes from the change of the microstructure. For a single layer of carbon atoms arranged in a two-dimensional honeycomb structure, it is essentially hydrophobic. Under the stimulation of external conditions, graphene can be adjusted from hydrophobic to hydrophilic, and can also be changed from hydrophilic to hydrophobic, which is attributed to the changeable surface morphology and controllable functional groups. Therefore, the ice crystal control effect and good photothermal recovery performance of graphene itself, combined with the hydrophilic and hydrophobic modification of its surface to achieve an ice control effect, make it an excellent material that can inhibit icing.

[0004] However, the simple sheet structure of two-dimensional graphene cannot meet the needs of most actual industries, and its defective edge structure will instead affect the surface wettability. Common three-dimensional graphene preparation methods include self-assembly method, CVD method, catalytic template method, 3D printing method, etc. These traditional preparation methods face problems such as high cost, low yield, complex process, and difficulty in preparing three-dimensional continuous covalent graphene. At present, research has found that three-dimensional covalent graphene obtained by the laser-induced graphene (LIG) method has unique advantages. The three-dimensional graphene prepared by this method has controllable morphology, stable structure, high quality, and is easy to operate and mass-produce.

[0005] Graphene modification is to introduce or remove functional groups or active substances on the surface of graphene, thereby providing different surface properties, and element doping and morphology change will also affect the wettability of graphene. There are various methods for surface hydrophilic and hydrophobic regulation of LIG. For example, adjusting the laser focus, laser scanning spacing, non-polar solvent compound preparation, etc. can all achieve the regulation of hydrophilic and hydrophobic, but these methods all have problems such as high cost, complex process, and difficulty in switching the hydrophilic and hydrophobic states. Therefore, there is an urgent need to propose a new method with low cost and simple process to quickly change the hydrophilic and hydrophobic properties of three-dimensional LIG. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for hydrophilic and hydrophobic modification of LIG, which utilizes the energy of heat treatment to cause tearing and detachment in the graphene sheets, changing their size and morphology; and the carbon atoms in the graphene will obtain higher energy due to thermal vibration, resulting in the displacement of carbon atoms from their original positions, forming different defects, affecting the wettability of the LIG surface, and obtaining hydrophilic or hydrophobic LIG.

[0007] The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0008] One of the objects of the present invention is to provide a method for hydrophilic and hydrophobic modification of LIG, which heat-treats the LIG to obtain hydrophilic or hydrophobic LIG.

[0009] Further, the temperature of the heat treatment is 50 - 1000 °C, the heating rate is 0.1 - 10 °C / min, and the holding time is 0.1 - 8 h.

[0010] Further, the LIG is monolayer LIG or multilayer LIG. By using the laser-induced technology to obtain LIG with controllable thickness, rapid, high-quality, low-cost, and large-scale preparation of LIG can be realized.

[0011] Further, the monolayer LIG is prepared by laser irradiation of a carbon-containing precursor laid flat on a substrate.

[0012] Further, the multilayer LIG is prepared by repeating the operations of laying flat and laser irradiating the carbon-containing precursor on the monolayer LIG.

[0013] Preferably, the carbon-containing precursor is one or more of polymers, lignin, cellulose, activated carbon, charcoal, biomass carbon, graphite, coke, phenolic resin, pyrolytic carbon, etc.

[0014] Preferably, the form of the carbon-containing precursor is one or several of thin films, powders, fibers, gels, and blocks.

[0015] Preferably, the substrate is made of one or more of polymers, metals, carbon, and carbon fibers.

[0016] Preferably, the form of the substrate is one or several of thin films, powders, fibers, papers, cloths, and foams.

[0017] Further, the surface of the LIG has a micro-structure designed by modeling software and formed by laser irradiation. The patterned design of the LIG can enable controllable transformation of its pattern and can be applied to microfluidic chips, sensors, detection devices, etc.

[0018] Preferably, the microstructure is one or more of a straight line, a circle, a square, a rectangle, a triangle, a trapezoid, a parallelogram, an arrow shape, a rhombus, an ellipse, a pentagram, a hexagon, and an octagon.

[0019] Preferably, the laser is one or several of a solid laser, a liquid laser, a gas laser, a semiconductor laser, an optical fiber laser, a pulsed laser, and a continuous wave laser.

[0020] Preferably, the laser wavelength of the laser irradiation is 1 to 1000 μm, the laser power is 0.1 to 100 W, the scanning rate is 1 to 2000 mm / s, the spot size is 10 -9 ~10 2 m, the scanning pitch is 0.01 to 5 mm, the pulse frequency is 1 to 100 kHz, the focal length is 1 to 200 cm, and the voltage is 0.01 to 1000 kV.

[0021] The second object of the present invention is to provide a hydrophilic or hydrophobic LIG prepared by the hydrophilic-hydrophobic modification method of the LIG.

[0022] Furthermore, the hydrophilic LIG is a superhydrophilic LIG, and the water contact angle is less than 5°.

[0023] Furthermore, the hydrophobic LIG is a superhydrophobic LIG, and the water contact angle is greater than 150°.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention modifies the LIG by heat treatment, changes its pore size and morphology, and quickly realizes the hydrophilic-hydrophobic state transition of the LIG.

[0026] 2. The hydrophilic-hydrophobic modification method of the LIG provided by the present invention has the characteristics of low cost, simple operation, and easy promotion, and can be applied on a large scale in multiple fields. Description of the Drawings

[0027] Figure 1 Scanning electron microscope image of the single-layer LIG prepared in Example 1;

[0028] Figure 2 Transmission electron microscope image of the single-layer LIG prepared in Example 1;

[0029] Figure 3 Cross-sectional scanning electron microscope image of the multi-layer LIG prepared in Example 1;

[0030] Figure 4 Water contact angle image of the LIG-300 prepared in Example 1;

[0031] Figure 5Water contact angle diagram of the patterned LIG prepared in Example 1;

[0032] Figure 6 Water contact angle diagram of the LIG-500 prepared in Example 2;

[0033] Figure 7 Scanning electron microscope images of the patterned LIG, LIG-300, and LIG-500 prepared in Example 1 and Example 2;

[0034] Figure 8 Cross-sectional scanning electron microscope image of the LIG prepared in Example 10. Detailed implementation mode

[0035] In order to make the technical means, creative features, achieved purposes, and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments and illustrations.

[0036] Example 1

[0037] (1) Lay a polyethersulfone film (thickness 120 μm, pore size 0.22 μm) flat on a polyimide paper (thickness 150 μm), and irradiate the polyethersulfone film with a carbon dioxide laser. The laser wavelength is 10.6 μm, the laser power is 10 W, the scanning rate is 200 mm / s, the scanning spacing is 0.1 mm, the pulse frequency is 20 kHz, the focal length is 20 cm, and the voltage is 0.1 kV to obtain a single-layer LIG.

[0038] (2) Repeat the operations of laying and laser irradiating the polyethersulfone film in step (1) 7 times, and finally obtain a multi-layer LIG on the polyimide paper.

[0039] (3) Use a fiber laser to etch a Y-shaped microstructure designed with AutoCAD software on the surface of the multi-layer LIG. The laser wavelength is 1064 nm, the laser power is 2 W, the scanning rate is 500 mm / s, the scanning spacing is 0.1 mm, the pulse frequency is 20 kHz, the focal length is 20 cm, and the voltage is 0.1 kV to obtain a patterned LIG.

[0040] (4) Heat the patterned LIG in a muffle furnace at a heating rate of 5 °C / min to 300 °C and hold for 1 h to obtain LIG-300.

[0041] Figure 1 Scanning electron microscope image of the single-layer LIG prepared in Example 1. From Figure 1It can be seen that LIG has a honeycomb-like porous three-dimensional structure with a hierarchical pore distribution, containing macropores with a pore diameter of 1-5 μm connected by graphite sheets; this three-dimensional porous graphene can effectively overcome the problems of stacking and aggregation of graphene sheets, which is beneficial to the full play of the excellent physical and chemical properties of graphene itself when applied in optoelectronic thermal, electrochemical energy storage, advanced electronic devices, etc.

[0042] Figure 2 It is the transmission electron microscope image of the single-layer LIG prepared in Example 1. From Figure 2 It can be seen that LIG has a very thin network structure, which is the stacking of a few graphene sheets and has good crystal quality.

[0043] Figure 3 It is the cross-sectional scanning electron microscope image of the multi-layer LIG prepared in Example 1. From Figure 3 It can be seen that the thickness of the multi-layer LIG is about 496 μm, and the thickness of the substrate is about 150 μm.

[0044] Figure 4 It is the water contact angle image of LIG-300 prepared in Example 1. From Figure 4 It can be seen that LIG-300 reaches the superhydrophobic state (contact angle is 158.4°).

[0045] Figure 5 It is the water contact angle image of the patterned LIG prepared in Example 1. From Figure 5 It can be seen that the contact angle of the untreated LIG is only 98.6°.

[0046] Example 2

[0047] The preparation steps of Example 2 are the same as those of Example 1. The difference from Example 1 is that the heat treatment temperature is adjusted to 500 °C to obtain LIG-500.

[0048] Figure 6 It is the water contact angle image of LIG-500 prepared in Example 2. From Figure 6 It can be seen that LIG-500 reaches the superhydrophilic state (contact angle is 1.6°).

[0049] Figure 7 It is the scanning electron microscope image of the patterned LIG, LIG-300 and LIG-500 prepared in Example 1 and Example 2. From Figure 7It can be seen that the tearing and detachment in the graphene sheets generated by high-temperature treatment change its pore size and morphology. The edge protrusions of LIG-300 reduce the contact area and adhesion force between the surface and the liquid, and the microscopically uneven rough surface morphology may also reduce the solid-liquid surface interaction; the internal pits are in the Cassie-Baxter state, where there is trapped air between the liquid droplet and the rough grooves, resulting in a decrease in the liquid-solid contact area at the bottom of the droplet and an increase in the liquid-gas contact area, so it has excellent hydrophobicity. For LIG-500, the pore size expands and the roughness is further improved. The carbon atoms in graphene obtain higher energy due to thermal vibration, causing the carbon atoms to shift from their original positions, forming different defects, partial collapse of its structure, and partial fragmentation of the surface, instead presenting an overall hydrophilic morphology.

[0050] Example 3

[0051] The preparation steps of Example 3 are the same as those of Example 1. The difference from Example 1 is that the heat treatment temperature is adjusted to 400 °C to obtain LIG-400 (the water contact angle is 116.7°).

[0052] Example 4

[0053] The preparation steps of Example 4 are the same as those of Example 1. The difference from Example 1 is that the heat treatment temperature is adjusted to 50 °C to obtain LIG-50 (the water contact angle is 104.3°).

[0054] Example 5

[0055] The preparation steps of Example 5 are the same as those of Example 1. The difference from Example 1 is that the heat treatment temperature is adjusted to 1000 °C to obtain LIG-1000 (the water contact angle is 0°).

[0056] Example 6

[0057] The preparation steps of Example 6 are the same as those of Example 1. The difference from Example 1 is that the heating rate of the heat treatment is adjusted to 0.1 °C / min. The water contact angle of the untreated LIG is 99.3°, the water contact angle of LIG-300 is 159.3°, and the water contact angle of LIG-500 is 1.6°.

[0058] Example 7

[0059] The preparation steps of Example 7 are the same as those of Example 1. The difference from Example 1 is that the heating rate of the heat treatment is adjusted to 10 °C / min. The water contact angle of the untreated LIG is 97.4°, the water contact angle of LIG-300 is 157.3°, and the water contact angle of LIG-500 is 1.1°.

[0060] Example 8

[0061] The preparation steps of Example 8 are the same as those of Example 1. The difference from Example 1 is that the heat treatment holding time is adjusted to 0.1 h. The water contact angle of untreated LIG is 98.9°, the water contact angle of LIG-300 is 158.6°, and the water contact angle of LIG-500 is 1.3°.

[0062] Example 9

[0063] The preparation steps of Example 9 are the same as those of Example 1. The difference from Example 1 is that the heat treatment holding time is adjusted to 8 h. The water contact angle of untreated LIG is 100.8°, the water contact angle of LIG-300 is 160.5°, and the water contact angle of LIG-500 is 1.9°.

[0064] Example 10

[0065] The preparation steps of Example 10 are the same as those of Example 1. The difference from Example 1 is that the substrate is replaced with nickel foam and the number of polyethersulfone film layers is adjusted to 6 layers. The water contact angle of untreated LIG is 96.3°, the water contact angle of LIG-300 is 157.3°, and the water contact angle of LIG-500 is 1.0°.

[0066] Figure 8 Figure for the cross-sectional scanning electron microscope of the LIG prepared in Example 10. From Figure 8 it can be seen that LIG still binds tightly to the nickel foam, which is beneficial for subsequent high-temperature heat treatment and application in large-scale industrialization.

[0067] Example 11

[0068] The preparation steps of Example 11 are the same as those of Example 1. The difference from Example 1 is that the polyethersulfone film is replaced with a polyphenylene sulfide film (thickness 100 μm, pore size 0.2 μm). The water contact angle of untreated LIG is 97.3°, the water contact angle of LIG-300 is 155.3°, and the water contact angle of LIG-500 is 2.2°.

[0069] Example 12

[0070] The preparation steps of Example 12 are the same as those of Example 1. The difference from Example 1 is that the polyethersulfone film is replaced with a polyethersulfone block. The water contact angle of untreated LIG is 102.2°, the water contact angle of LIG-300 is 161.3°, and the water contact angle of LIG-500 is 1.4°.

[0071] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for hydrophilic and hydrophobic modification of LIG, characterized in that: The LIG is heat-treated to obtain hydrophilic or hydrophobic LIG.

2. The hydrophilic-hydrophobic modification method of LIG according to claim 1, wherein: The temperature of the heat treatment is 50 to 1000 °C, the heating rate is 0.1 to 10 °C / min, and the holding time is 0.1 to 8 h.

3. The hydrophilic-hydrophobic modification method of LIG according to claim 1, wherein: The LIG is monolayer LIG or multilayer LIG.

4. The hydrophilic and hydrophobic modification method of LIG according to claim 3, wherein: The monolayer LIG is prepared by laser irradiation of a carbon-containing precursor tiled on a substrate; Preferably, the multilayer LIG is prepared by repeating the operations of tiling and laser irradiating the carbon-containing precursor on the monolayer LIG.

5. The hydrophilic and hydrophobic modification method of LIG according to claim 4, characterized in that: The carbon-containing precursor is one or more of polymers, lignin, cellulose, activated carbon, charcoal, biomass carbon, graphite, coke, phenolic resin, pyrolytic carbon, etc.; Preferably, the form of the carbon-containing precursor is one or several of thin films, powders, fibers, gels, and blocks; Preferably, the substrate is made of one or more of polymers, metals, carbon, and carbon fibers; Preferably, the form of the substrate is one or several of thin films, powders, fibers, papers, cloths, and foams.

6. The hydrophilic and hydrophobic modification method of LIG according to claim 1, wherein: The surface of the LIG has a micro-structure designed by modeling software and formed by laser irradiation; Preferably, the micro-structure is one or more of straight lines, circles, squares, rectangles, triangles, trapezoids, parallelograms, arrow shapes, rhombuses, ellipses, pentagrams, hexagons, and octagons.

7. The hydrophilic and hydrophobic modification method of LIG according to claim 4 or 6, characterized in that: The laser is one or several of solid lasers, liquid lasers, gas lasers, semiconductor lasers, fiber lasers, pulsed lasers, and continuous wave lasers; Preferably, the laser wavelength of the laser irradiation is 1 to 1000 μm, the laser power is 0.1 to 100 W, the scanning speed is 1 to 2000 mm / s, the spot size is 10 -9 to 10 2 m, the scanning pitch is 0.01 to 5 mm, the pulse frequency is 1 to 100 kHz, the focal length is 1 to 200 cm, and the voltage is 0.01 to 1000 kV.

8. Hydrophilic or hydrophobic LIG prepared by the hydrophilic-hydrophobic modification method of the LIG according to any one of claims 1 to 7.

9. The hydrophilic or hydrophobic LIG according to claim 8, characterized in that: The hydrophilic LIG is super-hydrophilic LIG, and the water contact angle is less than 5°.

10. The hydrophilic or hydrophobic LIG according to claim 8, characterized in that: The hydrophobic LIG is super-hydrophobic LIG, and the water contact angle is greater than 150°.

Images