A method for size separation of single-layer graphene oxide
By combining an oil/water two-phase system with anionic surfactants, and utilizing interfacial adsorption and electrostatic repulsion, the problems of low size separation efficiency and structural changes in single-layer graphene oxide in existing technologies are solved. This achieves high-precision, low-energy-consumption size separation of graphene oxide, which is applicable to aerogels, composite fibers, biosensors and other fields.
Patent Information
- Application Number
- CN202310673478.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-08
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2043-06-08
AI Technical Summary
Existing technologies are difficult to efficiently and with low energy consumption separate monolayer graphene oxide into smaller sizes, and existing methods may lead to structural changes or low precision, which cannot meet the application requirements of high-performance graphene oxide materials.
By combining an oil/water two-phase system with anionic surfactants, monolayer graphene oxide is separated into large and small parts through interfacial adsorption and electrostatic repulsion, and the separation is carried out using settling and centrifugation techniques.
It achieves high-precision single-layer graphene oxide size separation with low energy consumption and no structural changes, applicable to graphene oxide materials in different fields, and improves separation efficiency and repeatability.
Abstract
Description
Technical Field
[0001] This invention relates to the field of two-dimensional graphene oxide nanomaterials technology, and in particular to a method for separating the size of a single layer of graphene oxide. Background Technology
[0002] Graphene oxide is a two-dimensional nanomaterial, and monolayer graphene oxide refers to a single atomic layer of graphene oxide with a thickness of approximately 1 nm. Due to its unique properties, graphene oxide has been widely used in aerogels, composite fibers, biosensors, and conductive electrodes.
[0003] The size of graphene oxide has a significant impact on the performance of graphene oxide materials, with different sizes having different applications. For example, large-sized graphene oxide (>20 μm) is suitable for preparing filter materials and electrode materials, medium-sized graphene oxide (2–20 μm) is suitable for composite materials, and small-sized graphene oxide (<2 μm) can be used as drug carriers, biosensors, and solar cell units in pharmaceuticals, biomaterials, and optoelectronic materials. Furthermore, the narrower the size distribution of graphene oxide, the better the performance of the resulting devices. Therefore, how to separate the crude graphene oxide with a wide size distribution to obtain graphene oxide with a narrow size distribution has become a key issue restricting the application of high-performance graphene oxide materials.
[0004] Currently, reported methods for separating graphene oxide by size mainly include precipitation, liquid crystal filtration, centrifugation, ultrasonication, pH adjustment, membrane filtration, and electrophoresis. However, precipitation and liquid crystal filtration require long periods (1-2 weeks) of static separation, resulting in low efficiency; pH adjustment can achieve low dimensional accuracy; ultrasonication and centrifugation require multiple ultrasonic and centrifugation operations, consuming a lot of energy and altering the structure and original size of monolayer graphene oxide, leading to poor repeatability; membrane filtration requires specially customized membranes, which are prone to clogging during use; electrophoresis only has a good separation effect on multilayer graphene oxide or graphene oxide particles, and is prone to redox reactions that cause changes in the structure of graphene oxide.
[0005] Therefore, developing a method for separating the size of monolayer graphene oxide that is simple to operate, low in energy consumption, highly efficient, precise, and reproducible is promising. Summary of the Invention
[0006] The purpose of this invention is to provide a method for separating the size of single-layer graphene oxide, addressing the shortcomings of existing technologies.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0008] This invention provides a method for separating the size of monolayer graphene oxide, comprising the following steps:
[0009] 1) After mixing water and organic solvent, let it stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase;
[0010] 2) Add the surfactant and aqueous solution of monolayer graphene oxide to the oil phase and aqueous phase respectively, let stand, repeatedly collect the oil-water interface layer solution, wash and centrifuge the interface layer solution in sequence to obtain large-sized monolayer graphene oxide; centrifuge the remaining aqueous phase solution to obtain small-sized monolayer graphene oxide.
[0011] Preferably, the organic solvent in step 1) is ethyl acetate, petroleum ether, n-hexane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, or chlorobenzene; the volume ratio of water to organic solvent is 3 to 6:1.
[0012] Preferably, the surfactant in step 2) is an anionic surfactant.
[0013] Preferably, the anionic surfactant is sodium dodecylbenzenesulfonate, sodium octadecylsulfonate, ammonium dodecyl sulfate, sodium α-alkenylsulfonate, or sodium dodecyl diphenyl ether disulfonate.
[0014] Preferably, the concentration of the surfactant in the oil phase in step 2) is 0.0001–0.1 mol / L.
[0015] Preferably, the mass fraction of the monolayer graphene oxide aqueous solution in step 2) is 0.4-0.6%; the volume ratio of the monolayer graphene oxide aqueous solution to the water in step 1) is 1:5-50.
[0016] Preferably, the settling time in step 2) is 0.5 to 5 hours; the oil-water interface layer solution is collected repeatedly until it is colorless and clear; the reagent used to wash the oil-water interface layer solution is hydrochloric acid, and the mass fraction of hydrochloric acid is 0.005 to 0.015%.
[0017] Preferably, in step 2), the centrifugation time for the interface layer solution and the remaining aqueous phase solution is 8–12 min, and the centrifugation rate is 6000–8000 rpm.
[0018] Preferably, in step 2), the thickness of the oil-water interface layer solution collected each time is 0.5 to 1 mm.
[0019] The beneficial effects of this invention include the following:
[0020] 1) Compared with ultrasonication, centrifugation and membrane filtration, the reaction conditions of the present invention are mild, energy consumption is low, and there is no need for multiple ultrasonication and centrifugation, which will not cause changes in the structure and original size of monolayer graphene oxide during the separation process.
[0021] 2) Compared with precipitation and liquid crystal methods, the reaction time of this invention is shorter due to the synergistic effect of electrostatic repulsion and interfacial adsorption.
[0022] 3) Compared with electrophoresis, the present invention does not involve electro-oxidation-reduction reaction and does not change the structure of graphene oxide, and can be used to separate monolayer graphene oxide.
[0023] 4) The method for separating the size of single-layer graphene oxide in this invention has good separation accuracy. Detailed Implementation
[0024] This invention provides a method for separating the size of monolayer graphene oxide, comprising the following steps:
[0025] 1) After mixing water and organic solvent, let it stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase;
[0026] 2) Add the surfactant and aqueous solution of monolayer graphene oxide to the oil phase and aqueous phase respectively, let stand, repeatedly collect the oil-water interface layer solution, wash and centrifuge the interface layer solution in sequence to obtain large-sized monolayer graphene oxide; centrifuge the remaining aqueous phase solution to obtain small-sized monolayer graphene oxide.
[0027] In this invention, the organic solvent in step 1) is preferably ethyl acetate, petroleum ether, n-hexane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, or chlorobenzene; the volume ratio of water to organic solvent is preferably 3 to 6:1, more preferably 4 to 5:1, and even more preferably 4.5:1.
[0028] In this invention, the surfactant in step 2) is preferably an anionic surfactant.
[0029] In this invention, the anionic surfactant is preferably sodium dodecylbenzenesulfonate, sodium octadecylsulfonate, ammonium dodecyl sulfate, sodium α-alkenylsulfonate, or sodium dodecyl diphenyl ether disulfonate.
[0030] In this invention, the concentration of the surfactant in the oil phase in step 2) is preferably 0.0001 to 0.1 mol / L, more preferably 0.005 to 0.08 mol / L, and even more preferably 0.03 to 0.05 mol / L.
[0031] In this invention, the mass fraction of the monolayer graphene oxide aqueous solution in step 2) is preferably 0.4-0.6%, more preferably 0.45-0.55%, and even more preferably 0.5%; the volume ratio of the monolayer graphene oxide aqueous solution to the water in step 1) is preferably 1:5-50, more preferably 1:10-40, and even more preferably 1:20-30.
[0032] In this invention, the settling time in step 2) is preferably 0.5-5 hours, more preferably 1-4 hours, and even more preferably 2-3 hours; repeated collection is preferably until the oil-water interface layer solution is colorless and clear; the reagent used to wash the oil-water interface layer solution is preferably hydrochloric acid, and the mass fraction of hydrochloric acid is preferably 0.005-0.015%, more preferably 0.008-0.012%, and even more preferably 0.01%.
[0033] In this invention, the number of repeated collections is related to the concentration of the monolayer graphene oxide aqueous solution. When the oil-water interface layer solution is observed to be colorless and clear, the collection of the oil-water interface layer solution can be stopped.
[0034] In this invention, the preferred centrifugation time for the interface layer solution and the remaining aqueous phase solution in step 2) is 8 to 12 minutes, more preferably 9 to 11 minutes, and even more preferably 10 minutes; the preferred centrifugation rate is 6000 to 8000 rpm, more preferably 6500 to 7500 rpm, and even more preferably 7000 rpm.
[0035] In this invention, the thickness of the oil-water interface layer solution collected each time in step 2) is preferably 0.5-1 mm, more preferably 0.6-0.8 mm, and even more preferably 0.7 mm.
[0036] In this invention, after each collection of the oil-water interface layer solution in step 2), it is preferable to let the remaining solution stand for 0.5 to 3 hours, more preferably 1 to 2.5 hours, and even more preferably 1.5 to 2 hours.
[0037] In this invention, the principle of size separation of monolayer graphene oxide is as follows: Because monolayer graphene oxide has more carboxyl groups at the edges and fewer in the middle, it is a negatively charged colloidal particle in water and exhibits amphiphilicity. Both its charge and amphiphilicity are influenced by the size of the monolayer graphene oxide. Larger sizes result in a greater charge and stronger oleophilicity. Although the charge increases with size, the charge density decreases. Monolayer graphene oxide can be simultaneously subjected to hydrophobic and electrostatic forces in water. Therefore, a two-phase oil / water system is first obtained by mixing water and an organic solvent to form an oil phase and an aqueous phase. Then, an anionic surfactant is added to the oil phase. The surfactant is adsorbed onto the oil-water interface, making the interface layer negatively charged. At this point, the oil-water interface layer is both negatively charged and hydrophobic. The monolayer graphene oxide in the water is subjected to both electrostatic repulsion from the like charges at the interface and attraction from the hydrophobic forces. When the hydrophobic attraction outweighs the electrostatic repulsion, the monolayer graphene oxide is adsorbed onto the interface layer; otherwise, it is repelled. Because small-sized monolayer graphene oxide has a high charge density and poor oleophilicity, the hydrophobic attraction is less than the electrostatic repulsion. Large-sized monolayer graphene oxide has a low charge density and good oleophilicity, so the hydrophobic attraction outweighs the electrostatic repulsion. Therefore, large-sized monolayer graphene oxide is adsorbed onto the oil-water interface layer, while small-sized monolayer graphene oxide is repelled. This allows for the separation of monolayer graphene oxide of different sizes.
[0038] The technical solutions provided by the present invention will be 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.
[0039] Example 1
[0040] 100 mL of deionized water and 20 mL of ethyl acetate were mixed and allowed to stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase. Then, 0.06 g of sodium dodecylbenzenesulfonate and 20 mL of 0.5% (w / w) monolayer graphene oxide aqueous solution were added to the oil phase and the aqueous phase, respectively, and allowed to stand for 1 h. The oil-water interface layer solution was repeatedly collected with a pipette until it became colorless and clear (the number of collections was repeated 6 times, the thickness of the oil-water interface layer solution collected each time was 0.5 mm, and the remaining solution was allowed to stand for 1 h after each collection). The oil-water interface layer solutions collected 6 times were combined, washed with 0.01% (w / w) hydrochloric acid, and then centrifuged at 6000 rpm for 10 min to obtain large-sized monolayer graphene oxide.
[0041] The remaining aqueous solution was centrifuged at 8000 rpm for 8 min to obtain small-sized monolayer graphene oxide.
[0042] In this embodiment, 85% of the large-sized monolayer graphene oxide obtained has a particle size ≥10μm, and 82% of the small-sized monolayer graphene oxide obtained has a particle size <10μm.
[0043] Example 2
[0044] 1 L of deionized water and 250 mL of toluene were mixed and allowed to stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase. Then, 0.5 g of sodium octadecyl sulfonate and 20 mL of 0.4% (w / w) monolayer graphene oxide aqueous solution were added to the oil phase and the aqueous phase, respectively, and allowed to stand for 3 h. The oil-water interface layer solution was repeatedly collected with a pipette until it became colorless and clear (the number of collections was repeated 3 times, the thickness of the oil-water interface layer solution collected each time was 0.8 mm, and the remaining solution was allowed to stand for 0.5 h after each collection). The oil-water interface layer solutions collected from the 3 times were combined and washed with 0.005% (w / w) hydrochloric acid. Then, the solution was centrifuged at 6500 rpm for 8 min to obtain large-sized monolayer graphene oxide.
[0045] The remaining aqueous solution was centrifuged at 7000 rpm for 10 min to obtain small-sized monolayer graphene oxide.
[0046] In this embodiment, 84% of the large-sized monolayer graphene oxide obtained has a particle size ≥10μm, and 79% of the small-sized monolayer graphene oxide obtained has a particle size <10μm.
[0047] Example 3
[0048] 500 mL of deionized water and 100 mL of chloroform were mixed and allowed to stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase. Then, 0.1 g of ammonium dodecyl sulfate and 10 mL of 0.6% (w / w) monolayer graphene oxide aqueous solution were added to the oil phase and the aqueous phase, respectively, and allowed to stand for 0.5 h. The oil-water interface layer solution was repeatedly collected with a pipette until it became colorless and clear (the number of collections was repeated twice, the thickness of the oil-water interface layer solution collected each time was 1 mm, and the remaining solution was allowed to stand for 0.5 h after each collection). The oil-water interface layer solutions collected from the two collections were combined and washed with 0.015% (w / w) hydrochloric acid. Then, the solution was centrifuged at 8000 rpm for 12 min to obtain large-sized monolayer graphene oxide.
[0049] The remaining aqueous solution was centrifuged at 6000 rpm for 12 min to obtain small-sized monolayer graphene oxide.
[0050] In this embodiment, 86% of the large-sized monolayer graphene oxide obtained has a particle size ≥10μm, and 76% of the small-sized monolayer graphene oxide obtained has a particle size <10μm.
[0051] Example 4
[0052] 600 mL of deionized water and 200 mL of n-hexane were mixed and allowed to stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase. Then, 2 g of ammonium dodecyl sulfate and 60 mL of 0.5% (w / w) monolayer graphene oxide aqueous solution were added to the oil phase and the aqueous phase, respectively, and allowed to stand for 5 h. The oil-water interface layer solution was repeatedly collected with a pipette until it became colorless and clear (the number of collections was repeated 5 times, the thickness of the oil-water interface layer solution collected each time was 1 mm, and the remaining solution was allowed to stand for 2 h after each collection). The oil-water interface layer solutions collected 5 times were combined, washed with 0.015% (w / w) hydrochloric acid, and then centrifuged at 8000 rpm for 12 min to obtain large-sized monolayer graphene oxide.
[0053] The remaining aqueous solution was centrifuged at 8000 rpm for 10 min to obtain small-sized monolayer graphene oxide.
[0054] In this embodiment, 82% of the large-sized monolayer graphene oxide obtained has a particle size ≥10μm, and 81% of the small-sized monolayer graphene oxide obtained has a particle size <10μm.
[0055] Example 5
[0056] 60 mL of deionized water and 10 mL of xylene were mixed and allowed to stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase. Then, 0.004 g of sodium dodecyl diphenyl ether disulfonate and 10 mL of 0.6% (w / w) monolayer graphene oxide aqueous solution were added to the oil phase and the aqueous phase, respectively, and allowed to stand for 3 h. The oil-water interface layer solution was repeatedly collected with a pipette until it became colorless and clear (the number of collections was repeated 4 times, the thickness of the oil-water interface layer solution collected each time was 0.6 mm, and the remaining solution was allowed to stand for 1.5 h after each collection). The oil-water interface layer solutions collected 4 times were combined, washed with 0.01% (w / w) hydrochloric acid, and then centrifuged at 7000 rpm for 10 min to obtain large-sized monolayer graphene oxide.
[0057] The remaining aqueous solution was centrifuged at 6500 rpm for 12 min to obtain small-sized monolayer graphene oxide.
[0058] In this embodiment, 87% of the large-sized monolayer graphene oxide obtained has a particle size ≥10μm, and 78% of the small-sized monolayer graphene oxide obtained has a particle size <10μm.
[0059] The method for separating monolayer graphene oxide of this invention has good separation accuracy; and compared with ultrasonic, centrifugal and membrane filtration methods, it has mild reaction conditions, low energy consumption, and does not cause changes in the structure and original size of monolayer graphene oxide during the separation process; compared with precipitation and liquid crystal methods, the reaction time is shorter; and compared with electrophoresis, no electro-oxidation-reduction reaction occurs, and the structure of graphene oxide is not changed, so it can be used to separate monolayer graphene oxide.
[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for separating the size of a single layer of graphene oxide, characterized in that, It includes the following steps: 1) After mixing water and organic solvent, let it stand to obtain an oil / water two-phase system containing an oil phase and an aqueous phase; 2) Add the surfactant and the aqueous solution of monolayer graphene oxide to the oil phase and the aqueous phase respectively, let them stand, collect the oil-water interface layer solution repeatedly, and wash and centrifuge the interface layer solution in sequence to obtain large-size monolayer graphene oxide. The remaining aqueous solution was centrifuged to obtain small-sized monolayer graphene oxide. Step 2) The surfactant is an anionic surfactant; Step 1) The organic solvent is ethyl acetate, petroleum ether, n-hexane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, or chlorobenzene; the volume ratio of water to organic solvent is 3~6:1; The anionic surfactant is sodium dodecylbenzenesulfonate, sodium octadecylsulfonate, ammonium dodecyl sulfate, sodium α-alkenylsulfonate, or sodium dodecyl diphenyl ether disulfonate.
2. The method according to claim 1, characterized in that, Step 2) The concentration of the surfactant in the oil phase is 0.0001~0.1mol / L.
3. The method according to claim 1 or 2, characterized in that, The mass fraction of the monolayer graphene oxide aqueous solution in step 2) is 0.4~0.6%; the volume ratio of the monolayer graphene oxide aqueous solution to the water in step 1) is 1:5~50.
4. The method according to claim 3, characterized in that, Step 2) The settling time is 0.5~5h; the oil-water interface layer solution is collected repeatedly until it is colorless and clear; the reagent used to wash the oil-water interface layer solution is hydrochloric acid, and the mass fraction of hydrochloric acid is 0.005~0.015%.
5. The method according to claim 4, characterized in that, Step 2) The centrifugation time for the interface layer solution and the remaining aqueous phase solution is 8-12 min, and the centrifugation rate is 6000-8000 rpm.
6. The method according to claim 4 or 5, characterized in that, Step 2) The thickness of the oil-water interface layer solution collected each time is 0.5~1mm.