A preparation method of amphiphilic Janus graphene oxide

Abstract

The present invention belongs to the technical field of graphene oxide modification, and discloses a method for preparing amphiphilic Janus graphene oxide. First, an organic solvent is added to an aqueous graphene oxide solution and then allowed to stand for a treatment. After the treatment is completed, a cationic surfactant is added to the organic solvent layer to obtain an oil-water two-phase system in which the graphene oxide is located at the oil-water interface; a modifier is injected into the oil phase and the water phase of the oil-water two-phase system, respectively, and the modifier reacts with both sides of the graphene oxide to obtain an interface layer. The interface layer is post-treated to obtain amphiphilic Janus graphene oxide. The present invention can avoid the disadvantage of poor emulsification performance of graphene oxide in the emulsion template method, and at the same time, different chemical modifications can be performed on both sides of the graphene oxide through the oil phase and the water phase, respectively, thereby improving efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene oxide modification, and in particular to a method for preparing amphiphilic Janus graphene oxide. Background Art

[0002] Graphene oxide (GO) is a common two-dimensional material with a thickness of 1 to 2 nm and a width of up to tens of microns. Janus graphene oxide refers to a single layer of graphene oxide with different chemical structures attached to its two sides. When the chemical structures on both sides are hydrophilic and hydrophobic, respectively, it is called amphiphilic Janus graphene oxide. Amphiphilic Janus graphene oxide is often used as a Pickering emulsifier and nano-displacement material. Due to its large aspect ratio and specific surface area, Janus graphene oxide can enhance its adsorption strength at the oil-water interface and form a membrane structure with a certain strength. Therefore, compared with other nanoparticles, Janus graphene oxide performs better in Pickering emulsifiers and nano-displacement materials.

[0003] Currently, the main methods for preparing Janus graphene oxide are emulsion templates and solid nanoparticle templates. In the emulsion template method, graphene oxide is first used as a Pickering emulsifier to produce a water-in-oil or oil-in-water emulsion. Chemical modifiers in the aqueous and oil phases then react with the inner and outer interfaces of the graphene oxide to produce Janus graphene oxide. In the solid nanoparticle template method, nanoparticles are first dispersed in a solvent, graphene oxide is adsorbed onto the surface of the nanoparticles, and then reacted with the chemical modifier. Finally, the solid nanoparticles are removed to produce Janus graphene oxide. Both methods have certain drawbacks. In the emulsion template method, the amphiphilicity of graphene oxide before modification is not obvious, resulting in poor emulsification. Therefore, it is difficult to obtain a stable Pickering emulsion, resulting in a high concentration of non-Janus modified graphene oxide impurities in the prepared Janus graphene oxide. The nanoparticle template method has multiple steps and cannot simultaneously modify both sides of the graphene oxide.

[0004] Therefore, it is of great significance to study and obtain a preparation method of amphiphilic Janus graphene oxide, which can avoid the large amount of impurities in Janus graphene oxide while improving the emulsification effect and preparation efficiency. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing amphiphilic Janus graphene oxide, the purpose of which is to improve the preparation efficiency while solving the problem of poor emulsification performance of graphene oxide.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing amphiphilic Janus graphene oxide, comprising the following steps:

[0008] (1) adding an organic solvent to the graphene oxide aqueous solution and allowing the solution to stand for a treatment, and adding a cationic surfactant to the organic solvent layer after the treatment is completed to obtain an oil-water two-phase system in which the graphene oxide is located at the oil-water interface;

[0009] (2) A modifier is injected into the oil phase and the water phase of the oil-water two-phase system respectively, and the modifier reacts with the two sides of the graphene oxide to obtain an interface layer, which is post-treated to obtain amphiphilic Janus graphene oxide.

[0010] Preferably, the volume ratio of the organic solution to the graphene oxide aqueous solution in step (1) is 1 to 4:1.

[0011] Preferably, the cationic surfactant in step (1) is one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide, and the molar volume ratio of the cationic surfactant to the organic solution is 0.001 to 0.01 mol:1L.

[0012] Preferably, the organic solution in step (1) is ethyl acetate, toluene, petroleum ether, cyclohexane, n-hexane, dichloroethane, carbon tetrachloride or chloroform.

[0013] Preferably, in the graphene oxide aqueous solution in step (1), the mass fraction of graphene oxide is 0.08 to 0.12%.

[0014] Preferably, the standing treatment time in step (1) is 2 to 5 hours.

[0015] Preferably, the modifier injected into the oil phase in step (2) is octylamine, dodecylamine, octadecylamine, 3-(2-aminoethylamino)propyltriethoxysilane, 3-aminopropyltriethoxysilane or amino-terminated polystyrene.

[0016] Preferably, the modifier injected into the aqueous phase in step (2) is amine-terminated polyoxyethylene, amine-terminated polyacrylic acid or chitosan.

[0017] Preferably, the thickness of the interface layer in step (2) is 2 to 5 mm.

[0018] Preferably, the post-treatment in step (2) includes washing, centrifugation and drying, and the washing reagents are NaOH solution and the organic solvent in step (1) in sequence, and the mass fraction of NaOH solution is 0.08-0.12 wt%.

[0019] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) Compared with the emulsion template method, the present invention can stably adsorb graphene oxide to the oil-water interface through electrostatic adsorption, avoiding the emulsification step and the disadvantage of poor emulsification performance of graphene oxide; and all graphene oxide grafting reactions in the present invention occur at the oil-water interface, and the aqueous phase system hardly contains graphene oxide, thereby significantly reducing non-Janus structure modified graphene oxide impurities.

[0021] (2) Compared with nano solid particles, the present invention has fewer steps and can simultaneously connect different chemical structures on both sides of graphene oxide to obtain amphiphilic Janus graphene oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0023] Figure 1 This is a scanning electron microscope photograph of the amphiphilic Janus graphene oxide prepared in Example 1;

[0024] Figure 2 This is an optical microscope photograph of the amphiphilic Janus graphene oxide prepared in Example 1 used as a Pickering emulsifier to form an oil-in-water emulsion with toluene and water. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing amphiphilic Janus graphene oxide, comprising the following steps:

[0026] (1) adding an organic solution to a graphene oxide aqueous solution and allowing the solution to stand for a treatment, and adding a cationic surfactant to the organic solvent layer after the treatment is completed to obtain an oil-water two-phase system in which the graphene oxide is located at the oil-water interface;

[0027] (2) A modifier is injected into the oil phase and the water phase of the oil-water two-phase system respectively, and the modifier reacts with the two sides of the graphene oxide to obtain an interface layer, which is post-treated to obtain amphiphilic Janus graphene oxide.

[0028] The present invention adds a positively charged ionic emulsifier to the oil phase in an oil-water two-phase system. The positively charged ionic emulsifier is easily enriched at the oil-water interface, thereby giving the oil-water interface a certain positive charge. Since graphene oxide is a negatively charged colloidal particle, under the action of electrostatic force, the graphene oxide in the water phase will be adsorbed and spread on the oil-water interface. Then, hydrophilic and lipophilic chemical modifiers are added to the water phase and the oil phase respectively. Through the ring-opening addition reaction between the amino group and the epoxy group, different chemical structures can be grafted on both sides of the graphene oxide to obtain amphiphilic Janus graphene oxide.

[0029] In the present invention, the volume ratio of the organic solution to the graphene oxide aqueous solution in step (1) is preferably 1 to 4:1, more preferably 1.5 to 3.5:1, and more preferably 2 to 3:1.

[0030] In the present invention, the cationic surfactant in step (1) is preferably one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide, and the molar volume ratio of the cationic surfactant to the organic solution is 0.001 to 0.01 mol:1L, more preferably 0.003 to 0.009 mol:1L, and more preferably 0.005 to 0.006 mol:1L.

[0031] In the present invention, the organic solution in step (1) is preferably ethyl acetate, toluene, petroleum ether, cyclohexane, n-hexane, dichloroethane, carbon tetrachloride or chloroform.

[0032] In the present invention, in the graphene oxide aqueous solution of step (1), the mass fraction of graphene oxide is preferably 0.08 to 0.12%, more preferably 0.09 to 0.11%, and more preferably 0.1 to 0.105%.

[0033] In the present invention, the standing treatment time in step (1) is preferably 2 to 5 hours, more preferably 2.5 to 4.5 hours, and even more preferably 3 to 4 hours.

[0034] In the present invention, the purpose of the static treatment is to allow the graphene oxide in the water phase to be adsorbed to the oil-water interface to form a layer.

[0035] In the present invention, after the cationic surfactant is added in step (1), it is subjected to water phase replacement. The reagent for the water phase replacement is deionized water. The purpose of the water phase replacement is to remove excess graphene oxide that is not adsorbed by the oil-water interface.

[0036] In the present invention, a hydrophobic and lipophilic modifier is injected into the oil phase in step (2), and the modifier is preferably octylamine, dodecylamine, octadecylamine, 3-(2-aminoethylamino)propyltriethoxysilane, 3-aminopropyltriethoxysilane or amino-terminated polystyrene.

[0037] In the present invention, the mass volume ratio of the hydrophobic and oleophilic modifier to the graphene oxide aqueous solution is preferably 0.3-0.8 g:500 mL, more preferably 0.4-0.7 g:500 mL, and more preferably 0.5-0.6 g:500 mL.

[0038] In the present invention, in step (2), an oleophobic and hydrophilic modifier is injected into the aqueous phase, and the modifier is preferably amino-terminated polyoxyethylene, amino-terminated polyacrylic acid or chitosan.

[0039] In the present invention, the mass volume ratio of the oleophobic and hydrophilic modifier to the graphene oxide aqueous solution is preferably 0.3-0.8 g:500 mL, more preferably 0.4-0.7 g:500 mL, and more preferably 0.5-0.6 g:500 mL.

[0040] In the present invention, the reaction time of the modifier in step (2) reacting with the two sides of graphene oxide is preferably 3 to 6 hours, more preferably 4 to 5 hours.

[0041] In the present invention, after the reaction is completed, the oil phase and the water phase in the oil-water two-phase system are pumped out, leaving the interface layer.

[0042] In the present invention, the thickness of the interface layer in step (2) is preferably 2 to 5 mm, more preferably 2.5 to 4.5 mm, and even more preferably 3 to 4 mm.

[0043] In the present invention, the post-treatment in step (2) preferably includes washing, centrifugation and drying, and the washing reagents are preferably NaOH solution and the organic solvent in step (1) in sequence, and the mass fraction of NaOH solution is preferably 0.08-0.12 wt%, more preferably 0.09-0.11 wt%, and more preferably 0.1-0.105 wt%.

[0044] In the present invention, the centrifugal speed is preferably 5000-7000 rpm, more preferably 5500-6500 rpm, more preferably 5800-6200 rpm; the centrifugal time is preferably 5-10 min, more preferably 6-9 min, more preferably 7-8 min.

[0045] In the present invention, the drying is preferably vacuum drying, the temperature of the vacuum drying is preferably 60 to 100° C., more preferably 70 to 90° C., more preferably 75 to 80° C., and the vacuum degree of the vacuum drying is preferably 0.1 MPa.

[0046] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] (1) 500 mL of toluene was slowly poured into 500 mL of graphene oxide aqueous solution (the mass fraction of graphene oxide was 0.1%) along the wall of the beaker, and the mixture was allowed to stand for 3 h to allow the graphene oxide in the aqueous phase to be adsorbed to the oil-water interface. 0.0005 mol of hexadecyltrimethylammonium bromide was added to the toluene layer, and the aqueous phase in the system was replaced with deionized water to remove excess graphene oxide that was not adsorbed by the interface, thereby obtaining an oil-water two-phase system in which graphene oxide was located at the oil-water interface.

[0049] (2) 0.5 g of octadecylamine and 0.5 g of amino-terminated polyoxyethylene (n=800) were added to the oil phase and the water phase of the oil-water two-phase system, respectively. Octadecylamine and amino-terminated polyoxyethylene were allowed to react with graphene oxide at room temperature for 6 h. The oil phase and water phase in the two-phase system were respectively extracted to obtain an interface layer with a thickness of 5 mm. The interface layer was washed with 0.1 wt% NaOH solution and toluene in turn. The washed interface layer was centrifuged at a speed of 5600 rpm for 8 min and vacuum dried at 85°C (vacuum degree of 0.1 MPa) to obtain amphiphilic Janus graphene oxide.

[0050] Example 2

[0051] (1) 2 L of ethyl acetate was slowly poured along the wall of a beaker into a 500 mL graphene oxide aqueous solution (the mass fraction of graphene oxide was 0.09%). The mixture was allowed to stand for 5 h to allow the graphene oxide in the aqueous phase to be adsorbed to the oil-water interface. 0.004 mol of dodecyltrimethylammonium bromide was added to the ethyl acetate layer, and the aqueous phase in the system was replaced with deionized water to remove excess graphene oxide that was not adsorbed on the interface, thereby obtaining an oil-water two-phase system in which graphene oxide was located at the oil-water interface.

[0052] (2) 0.4 g of dodecylamine and 0.4 g of amino-terminated polyacrylic acid (n=450) were added to the oil phase and the water phase of the oil-water two-phase system, respectively. Dodecylamine and amino-terminated polyacrylic acid were allowed to react with graphene oxide at room temperature for 6 h. The oil phase and water phase in the two-phase system were respectively extracted to obtain an interface layer with a thickness of 4 mm. The interface layer was washed with 0.09 wt% NaOH solution and ethyl acetate in turn. The washed interface layer was centrifuged at 6000 rpm for 6 min and vacuum dried at 90°C (vacuum degree of 0.1 MPa) to obtain amphiphilic Janus graphene oxide.

[0053] Example 3

[0054] (1) 1 L of chloroform was slowly poured along the wall of a beaker into a 500 mL aqueous solution of graphene oxide (the mass fraction of graphene oxide was 0.1%). The mixture was allowed to stand for 3 h to allow the graphene oxide in the aqueous phase to be adsorbed to the oil-water interface. 0.005 mol of hexadecyltrimethylammonium chloride was added to the chloroform layer, and the aqueous phase in the system was replaced with deionized water to remove excess graphene oxide that was not adsorbed on the interface, thereby obtaining an oil-water two-phase system in which graphene oxide was located at the oil-water interface.

[0055] (2) 0.8 g of amino-terminated polystyrene (n=4000) and 0.8 g of chitosan (n=8000) were added to the oil phase and water phase of the oil-water two-phase system, respectively. The amino-terminated polystyrene and chitosan were allowed to react with graphene oxide at room temperature for 3 h. The oil phase and water phase in the two-phase system were respectively extracted to obtain an interface layer with a thickness of 3 mm. The interface layer was washed with 0.1 wt% NaOH solution and chloroform in turn. The washed interface layer was centrifuged at 5500 rpm for 10 min and vacuum dried at 60°C (vacuum degree of 0.1 MPa) to obtain amphiphilic Janus graphene oxide.

[0056] Figure 1 This is a scanning electron microscope photo of the amphiphilic Janus graphene oxide prepared in Example 1. Figure 1 It can be seen that the amphiphilic Janus graphene oxide prepared in Example 1 has a single-layer structure.

[0057] Figure 2 This is an optical microscope photograph of the amphiphilic Janus graphene oxide prepared in Example 1 used as a Pickering emulsifier to form an oil-in-water emulsion with toluene and water. Figure 2 It can be seen that the amphiphilic Janus graphene oxide prepared in Example 1 has a good emulsifying effect and is an effective Pickering emulsifier.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing amphiphilic Janus graphene oxide, characterized in that, The following steps are involved: (1) adding an organic solvent to the graphene oxide aqueous solution and allowing the solution to stand for a treatment, and adding a cationic surfactant to the organic solvent layer after the treatment is completed to obtain an oil-water two-phase system in which the graphene oxide is located at the oil-water interface; (2) injecting a modifier into the oil phase and the water phase of the oil-water two-phase system respectively, the modifier reacts with the two sides of the graphene oxide to obtain an interface layer, and the interface layer is post-treated to obtain amphiphilic Janus graphene oxide; The organic solvent in step (1) is ethyl acetate, toluene, petroleum ether, cyclohexane, n-hexane, dichloroethane, carbon tetrachloride or chloroform; The modifier injected into the oil phase in step (2) is octylamine, dodecylamine, octadecylamine, 3-(2-aminoethylamino)propyltriethoxysilane, 3-aminopropyltriethoxysilane or amino-terminated polystyrene; The modifier injected into the aqueous phase in step (2) is amino-terminated polyoxyethylene, amino-terminated polyacrylic acid or chitosan.

2. A method for preparing amphiphilic Janus graphene oxide according to claim 1, characterized in that, The volume ratio of the organic solvent to the graphene oxide aqueous solution in step (1) is 1 to 4:

1.

3. A method for preparing amphiphilic Janus graphene oxide according to claim 1, characterized in that, The cationic surfactant in step (1) is one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide, and the molar volume ratio of the cationic surfactant to the organic solvent is 0.001 to 0.01 mol:1L.

4. A method for preparing amphiphilic Janus graphene oxide according to claim 1, characterized in that, In the graphene oxide aqueous solution of step (1), the mass fraction of graphene oxide is 0.08-0.12%.

5. The method for preparing amphiphilic Janus graphene oxide according to any one of claims 2 to 4, characterized in that: The standing treatment time in step (1) is 2 to 5 hours.

6. A method for preparing amphiphilic Janus graphene oxide according to claim 1, characterized in that, The thickness of the interface layer in step (2) is 2 to 5 mm.

7. A method for preparing amphiphilic Janus graphene oxide according to claim 6, characterized in that, The post-treatment in step (2) includes washing, centrifugation and drying, and the washing reagents are NaOH solution and the organic solvent in step (1) in sequence, and the mass fraction of NaOH solution is 0.08-0.12wt%.

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