CN112047332A - Preparation method and application of Janus graphene oxide - Google Patents

Preparation method and application of Janus graphene oxide Download PDF

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CN112047332A
CN112047332A CN202010678368.9A CN202010678368A CN112047332A CN 112047332 A CN112047332 A CN 112047332A CN 202010678368 A CN202010678368 A CN 202010678368A CN 112047332 A CN112047332 A CN 112047332A
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graphene oxide
janus
constant temperature
janus graphene
water
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刘培松
惠飞
李小红
张治军
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Suzhou University
Henan University
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Henan University
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Abstract

The invention provides a preparation method and application of Janus graphene oxide, which comprises the following steps: uniformly mixing concentrated sulfuric acid and concentrated phosphoric acid in an ice water bath, respectively adding potassium permanganate and graphite into the mixed acid solution, and reacting at constant temperature; cooling, separating, washing and drying to obtain graphene oxide powder; dispersing in a dispersion medium, stirring at constant temperature, and adjusting pH; adding an organic silicon modifier, stirring at constant temperature, and separating and drying after the reaction is finished; and (3) placing the surface modified graphene oxide in alkaline water, reacting at constant temperature under the action of mechanical force, separating and washing to obtain the purified Janus graphene oxide. The graphene oxide is prepared by taking graphite as a raw material and adopting an improved Hummers method, so that large-scale preparation can be realized. Janus graphene oxide obtained by adopting a liquid-phase mechanical stripping method has amphiphilicity, can be stably dispersed in deionized water for more than 30 days, has a Zeta potential as high as-36.9 mV, and shows excellent dispersion stability.

Description

Preparation method and application of Janus graphene oxide
Technical Field
The invention relates to the technical field of nano materials, in particular to a preparation method and application of Janus graphene oxide.
Background
The Janus material has asymmetric physical or chemical properties (such as hydrophile/hydrophobicity, polarity/nonpolar, positive charge/negative charge and the like), has surface and interface characteristics which are not possessed by conventional materials, and shows excellent performance and attractive application prospects in the fields of Pickering emulsion preparation, interface assembly, optical probes, catalysis and the like. At present, the preparation method of Janus materials mainly comprises an interface protection method, a phase separation method, a micro-processing method, a self-assembly method, a template removal method and the like. Graphene and derivatives thereof have excellent properties such as strong mechanical properties, excellent thermal and chemical stability, flexibility and transparency, and the like, and are widely researched in the fields of electronic devices, polymers, microemulsions, and the like. The preparation of Janus graphene and graphene oxide with anisotropy attracts extensive attention of technologists by adjusting the material structure as an important means to obtain the required electronic and mechanical properties.
In the practical application process, the macro preparation of the Janus structure material in an economic, convenient and environment-friendly manner still remains the main technical challenge facing at present. Most researches still focus on the improvement of the prior art such as an interface protection method and a template removal method, for example, Jeon et al (i. Jeon, et al. adv. mater. 2019, 31, 1900438) dynamically modifies graphene oxide at a liquid-liquid interface, and different chemical functional groups are grafted on two sides of the graphene oxide, so that Janus graphene oxide is obtained, and the method provides possibility for continuously preparing Janus graphene oxide. However, according to the method, high-quality single-layer or few-layer graphene oxide is still required to be used as a raw material, and the Janus graphene can be obtained only through a liquid-liquid interface reaction, so that the problems of low efficiency and high cost still exist. Therefore, the development of a low-cost, high-efficiency and environment-friendly Janus graphene oxide macroscopic preparation method is still a very challenging research work, and is also the key point for obtaining and applying the Janus graphene oxide.
Disclosure of Invention
The technical problem to be solved is as follows: the invention aims to provide a preparation method and application of Janus graphene oxide, wherein multilayer graphene oxide is prepared by an improved Hummes method, and then the multilayer graphene oxide is functionalized to obtain surface modified graphene oxide. And opening Van der Waals force between the surface modified graphene oxide layers by using alkali liquor and mechanical stress to expose a fresh surface, and endowing the graphene oxide with a hydrophobic surface containing a large number of organic functional groups on one surface and a hydrophilic surface containing hydroxyl groups and other groups on the other surface, so that the Janus graphene oxide is obtained.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:
a preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing concentrated sulfuric acid and concentrated phosphoric acid in a volume ratio of 8: 1-9: 1 in an ice water bath, slowly adding potassium permanganate and graphite in a mass ratio of 1: 0.2-0.5 into the mixed acid solution, and reacting at a constant temperature of 35-60 ℃ for 6-12 hours;
(2) cooling, separating, washing to pH =7, and drying at 120 ℃ for 2h to obtain graphene oxide powder;
(3) dispersing the obtained graphene oxide powder in 100 mL of dispersion medium at a concentration of 0.05-0.5%, stirring at a constant temperature for 0.5-3 h, and adjusting the pH to 9-10 by using a pH regulator;
(4) adding an organic silicon modifier, stirring at constant temperature for 0.5-3 h, separating after the reaction is finished, and drying at 120 ℃ for 2 h;
(5) and (3) placing the surface modified graphene oxide in alkaline water, then reacting for 3-8 h at constant temperature under the action of mechanical force, separating and washing to obtain the purified Janus graphene oxide.
Preferably, the hydrolysis medium in the step (3) is water and C1~C2One or more than two of the alcohols in (1).
Preferably, the pH regulator in the step (3) is ammonia water.
Preferably, the organosilicon modifier in the step (4) is one or more organosilicon compounds, and the organosilicon compound is R'nSi（OR”）4-nOr organosilicon compounds capable of reacting with hydroxyl, wherein R 'is one or more of methyl, ethyl, vinyl and other alkyl containing active functional group, R' includes but is not limited to C1-C16The carbon chain compound of (1); the organosilicon compound capable of reacting with hydroxyl is chlorosilane or/and silazane.
Preferably, the mass ratio of the graphene oxide to the organic silicon modifier is 1: 3-20.
Preferably, the mechanical force in the step (5) is one or more of ultrasound, mechanical stirring and emulsification shearing.
Preferably, the chemical agent used in the alkaline water in the step (5) is NaOH or NaHCO3Or one or more of KOH.
Janus graphene oxide prepared by the method is adopted.
Furthermore, one surface of Janus graphene oxide is modified with an organic silicon modifier, the other surface of Janus graphene oxide is provided with a naked hydroxyl and an unsaturated residual bond, the Janus graphene oxide has hydrophilic and hydrophobic surfaces, the Janus graphene oxide can be stably dispersed in water for more than 10 days, and the Zeta potential of the dispersion liquid is-36.9 mV.
In the application of the Janus graphene oxide, the Janus graphene oxide can form a stable interface film on an oil-water interface, and is used for emulsifying oil-water microemulsion and efficiently washing oil; meanwhile, the method can be transferred to a silicon chip for constructing a memristor dielectric layer.
Has the advantages that:
1. according to the invention, graphite is directly used as a raw material, the improved Hummers method is adopted to prepare the graphene oxide, the preparation of the graphene oxide can be realized on a large scale, the acid liquor can be recycled, and the Janus graphene oxide is obtained by adopting a liquid-phase mechanical stripping method.
2. The preparation process does not need any traditional means such as template, interface protection and the like, and the reaction medium is C1~C2Alcohol and water, use of organic reagent solvents without harmfulness, flammability and explosion, process ringAnd (5) protecting. Meanwhile, the preparation process adopts a liquid phase method, is suitable for large-scale preparation and has low cost.
3. The Janus graphene oxide provided by the invention has amphipathy, can be stably dispersed in deionized water for more than 30 days, has a Zeta potential as high as-36.9 mV, and shows excellent dispersion stability.
4. The Janus graphene oxide nanosheet is used as a solid particle emulsifier, can form a stable interface film on an oil-water interface, is used for preparing oil-water microemulsion, and can also be used as an efficient oil displacement material in tertiary oil recovery. Meanwhile, a Janus interface film formed on an oil-water interface can be transferred to a silicon chip to construct a memristor dielectric layer.
Drawings
Fig. 1 is a schematic flow chart of preparation of Janus graphene oxide in examples 1 to 6.
Fig. 2 is an X-ray diffraction (XRD) pattern of the raw material graphite (a) used in example 2 and the prepared graphene oxide, modified graphene oxide, and Janus graphene oxide.
Fig. 3 is a scanning electron micrograph and a transmission electron micrograph of the Janus graphene oxide powder prepared in example 3.
Fig. 4 is a water contact angle between the graphene oxide (a) and the modified graphene oxide (b) prepared in example 4 and the hydrophilic surface (c) and the hydrophobic surface (d) of Janus graphene oxide, and a water contact angle between the hydrophilic surface (e) and the hydrophobic surface (f) of Janus graphene oxide prepared in example 5.
Fig. 5 shows the dispersion-transfer characteristics of Janus graphene oxide prepared in example 4 between water and chloroform.
Fig. 6 is a photograph of a pincering emulsion stabilized by Janus graphene oxide as an emulsifier prepared in example 6 and an optical microscope photograph.
Fig. 7 shows the stripping effect of Janus graphene oxide on crude oil adsorbed on the surface of a core slice (a) and a comparative experiment of deionized water (b) in example 6.
Fig. 8 is a schematic diagram of the transfer of the Janus graphite oxide prepared in example 7 onto the surface of a p-type doped silicon wafer, and the resistance change behavior exhibited by the Janus graphite oxide as a dielectric layer of a memristor.
Detailed Description
Example 1
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 180 mL of concentrated sulfuric acid and 20 mL of concentrated phosphoric acid in an ice water bath, slowly adding 40 g of potassium permanganate into the mixed acid solution for multiple times, then adding 5 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 50 ℃, and stirring at constant temperature for 12 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 100 mL of water at a concentration of 0.2% by sonication, and then stirred at 60 ℃ for 30min, 0.1 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) adding 1.0 g of organic modifier hexamethyldisilazane into the dispersion liquid under the carrying of ethanol, stirring at a constant temperature of 60 ℃ for 30min, then reacting at a constant temperature of 80 ℃ for 2h, centrifuging the surface-modified graphene oxide at 10000 rpm for 30min after the reaction is finished, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into alkaline water with the concentration of 1 mol/L of sodium hydroxide, then carrying out ultrasonic treatment for 2h at 80 ℃ for 5 h, carrying out ultrasonic treatment for 30min, carrying out centrifugal washing separation for 30min at 12000 rpm, repeating the washing separation for 5 times, and drying for 2h at 120 ℃ to obtain the purified Janus graphene oxide.
The preparation flow of Janus graphene oxide is shown in FIG. 1.
Example 2
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 340 mL of concentrated sulfuric acid and 60 mL of concentrated phosphoric acid in an ice water bath, slowly adding 50 g of potassium permanganate into the mixed acid solution for multiple times, then adding 10 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 50 ℃, and stirring at constant temperature for 12 h;
(2) cooling and filtering, recycling the filtrate, adding the filter cake into 2L of ice water, and adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate. Filtering and washing the obtained graphene oxide dispersion liquid to pH =7, and drying a filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 50 g of water at a concentration of 0.1% by sonication, and then stirred at 60 ℃ for 30min, 0.2 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) adding 1.0 g of organic modifier hexadecyl trimethoxy silane into the dispersion liquid under the carrying of ethanol, stirring at constant temperature of 40 ℃ for 1 h, then reacting at constant temperature of 80 ℃ for 3h, centrifuging the surface modified graphene oxide at 10000 rpm for 30min after the reaction is finished, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium hydroxide of 1.0 mol/L and the concentration of sodium bicarbonate of 0.2 mol/L, then carrying out ultrasonic shearing and emulsification for 2h at constant temperature of 80 ℃, carrying out ultrasonic treatment for 30min, carrying out washing and separation by centrifuging for 30min at 12000 rpm, repeating for 5 times, and drying for 2h at 120 ℃ to obtain the purified Janus graphene oxide.
As shown in fig. 2, the structures of graphite, graphene oxide, modified graphene oxide, and Janus graphene oxide were measured in the range of 5 ° to 60 ° using an X-ray diffractometer. As can be seen from fig. 2a, graphite has a very high crystallinity with a very strong (002) absorption peak at 2 ϴ =26.4 ° and an interlayer spacing of 0.34 nm. The graphene oxide XRD spectrum shows a sharp diffraction peak at a position 2 ϴ -10.8 ℃, the interlayer distance is 0.82nm, and the increase of the interlayer distance is caused by introducing various functional groups in the stripping and oxidation processes. XRD patterns of the modified graphene oxide and Janus graphene oxide show a broad peak with lower intensity at 23 ℃, which is attributed to the surface organic modifier. An obvious strong absorption peak does not exist in an XRD (X-ray diffraction) spectrum of Janus graphene oxide, which means that the interlayer structure of the modified graphene oxide is stripped, and the Janus graphene oxide is successfully prepared.
Example 3
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 180 mL of concentrated sulfuric acid and 20 mL of concentrated phosphoric acid in an ice water bath, slowly adding 40 g of potassium permanganate into the mixed acid solution for multiple times, then adding 15 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 60 ℃, and stirring at constant temperature for 6 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 20 g of water at a concentration of 0.5% by sonication, and then stirred at 60 ℃ for 30min, 0.5 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) 1 g of organic modifier gamma-methacryloxypropyltrimethoxysilane is added into the dispersion liquid under the carrying of ethanol, stirred for 30min at the constant temperature of 60 ℃, and then reacted for 2h at the constant temperature of 80 ℃. After the reaction is finished, centrifuging the surface modified graphene oxide at 10000 rpm for 30min, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium bicarbonate being 1.5 mol/L, then carrying out ultrasonic shearing for 30min at a constant temperature of 60 ℃ for 2h, carrying out ultrasonic treatment for 30min, carrying out centrifugal washing for 5 times at 12000 rpm, and drying for 2h at 120 ℃ to obtain the purified Janus graphene oxide.
As shown in fig. 3, a scanning electron microscopy image of Janus graphene oxide shows that the drying process causes the nanoplatelets to stack on top of each other, forming aggregates. Then, the powder is dispersed in water by ultrasonic waves, and the appearance of the powder is observed by using a high-resolution transmission electron microscope after the powder is dripped on a copper mesh, so that the number of the prepared Janus graphene oxide layers is small, and the surface of the Janus graphene oxide layer is wrinkled.
Example 4
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 170 mL of concentrated sulfuric acid and 30 mL of concentrated phosphoric acid in an ice water bath, slowly adding 40 g of potassium permanganate into the mixed acid solution for multiple times, then adding 5 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 1 h, heating to 50 ℃, and stirring at constant temperature for 12 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 100 g of water at a concentration of 0.05% by sonication, and then stirred at 60 ℃ for 30min, 0.5 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) adding 2 g of organic modifier dimethyl diethyl silane into the dispersion liquid under the carrying of ethanol, stirring at a constant temperature of 60 ℃ for 30min, then reacting at a constant temperature of 80 ℃ for 2h, centrifuging the surface modified graphene oxide at 10000 rpm for 30min after the reaction is finished, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium hydroxide of 1.2 mol/L, then carrying out ultrasonic treatment for 1 h and stirring at a constant temperature of 80 ℃ for 2h and shearing for 1 h for 30min, carrying out centrifugal washing at 12000 rpm for 5 times, and drying at 120 ℃ for 2h to obtain the purified Janus graphene oxide.
Fig. 4 is a water contact angle between graphene oxide (a) and modified graphene oxide (b) prepared in example 4 and a hydrophilic surface (c) and a hydrophobic surface (d) of Janus graphene oxide, where the graphene oxide surface contains a large number of hydrophilic hydroxyl groups, shows strong hydrophilicity, and has a water contact angle of 58 °. A large number of saturated carbon chains are bonded on the surface of the modified graphene oxide, the surface is hydrophobic, and the water contact angle reaches 157 degrees. After the prepared Janus graphene oxide is transferred to the surface of a glass sheet through a hydrophilic surface and a hydrophobic surface respectively, two Janus graphene oxide films with the hydrophilic surface exposed outside and the hydrophobic surface exposed outside can be obtained, and water contact angles of the Janus graphene oxide films are 78 degrees and 152 degrees respectively.
Fig. 5 shows the dispersion-transfer characteristics of the prepared Janus graphene oxide between water and chloroform, and the Zeta potential of the Janus graphene oxide in deionized water is-36.9 mV, so that the Janus graphene oxide can be stably dispersed for more than 30 days without precipitation, and the excellent dispersion stability is shown.
Example 5
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 360 mL of concentrated sulfuric acid and 40 mL of concentrated phosphoric acid in an ice water bath, slowly adding 50 g of potassium permanganate into the mixed acid solution for multiple times, then adding 10 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 50 ℃, and stirring at constant temperature for 12 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 20 g of water at a concentration of 0.2% by sonication, and then stirred at 60 ℃ for 30 min. 0.5 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) adding 1.0 g of organic modifier dichlorosilane into the dispersion liquid under the carrying of ethanol, stirring at a constant temperature of 60 ℃ for 30min, then reacting at a constant temperature of 80 ℃ for 2h, centrifuging the surface-modified graphene oxide at 10000 rpm for 30min after the reaction is finished, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium hydroxide of 1 mol/L, then carrying out ultrasonic stirring for 1 h at a constant temperature of 80 ℃ for 2h, carrying out ultrasonic treatment for 2h, carrying out centrifugal washing for 5 times at 12000 rpm, and drying for 2h at 120 ℃ to obtain the purified Janus graphene oxide.
Fig. 4e and 4f are water contact angles of prepared Janus graphene oxide hydrophilic surface (e) and hydrophobic surface (f), which are 88 ° and 145 °, respectively.
Example 6
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 180 mL of concentrated sulfuric acid and 20 mL of concentrated phosphoric acid in an ice water bath, slowly adding 40 g of potassium permanganate into the mixed acid solution for multiple times, then adding 4 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 50 ℃, and stirring at constant temperature for 12 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 20 g of water at a concentration of 0.2% by sonication, and then stirred at 60 ℃ for 30min, 0.5 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid, and the pH value of the dispersion liquid is adjusted to 9-10;
(4) 0.4 g of organic modifier hexadecyl trimethoxy silane is added into the dispersion liquid under the carrying of ethanol, the mixture is stirred at the constant temperature of 60 ℃ for 30min, then the mixture reacts at the constant temperature of 80 ℃ for 2h, after the reaction is finished, the surface modified graphene oxide is centrifuged at 10000 rpm for 30min, and then the mixture is dried at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium hydroxide of 1 mol/L, then carrying out ultrasonic treatment for 30min, stirring for 2h at a constant temperature of 80 ℃, carrying out ultrasonic treatment for 30min, carrying out centrifugal washing for 5 times at 12000 rpm, and drying for 2h at 120 ℃ to obtain the purified Janus graphene oxide.
The preparation flow of Janus graphene oxide is shown in FIG. 1. Mixing 20 g of liquid paraffin with 1 g of Janus-GO dispersion (concentration about 0.2%) allowed the formation of a stable microemulsion by sonication for 2 h. The obtained water droplet size of the water-in-paraffin microemulsion is less than 20 mu m and can be stabilized for more than 24 h.
Fig. 6 is a photograph of a Pickering emulsion stabilized by prepared Janus graphene oxide as an emulsifier and an optical microscope picture. By mixing 20 g of liquid paraffin with 0.5 g of Janus-GO dispersion (concentration about 0.1%), a stable microemulsion can be formed by sonication for 2 h. The obtained water droplet size of the water-in-paraffin microemulsion is less than 20 mu m, and the water-in-paraffin microemulsion can be stable for more than 20 days at room temperature.
Fig. 7 shows the stripping effect of prepared Janus graphene oxide on crude oil adsorbed on the surface of a core slice (a) and a comparative experiment of deionized water (b). The two core slices saturated with crude oil are respectively placed in Janus graphene oxide dispersion liquid (mass fraction is about 0.01%) and deionized water, after 1 h, a large amount of crude oil in the core slices in the Janus graphene oxide dispersion liquid is displaced, and the deionized water cannot effectively displace the crude oil.
Example 7
A preparation method of Janus graphene oxide comprises the following steps:
(1) uniformly mixing 270 mL of concentrated sulfuric acid and 30 mL of concentrated phosphoric acid in an ice water bath, slowly adding 40 g of potassium permanganate into the mixed acid solution for multiple times, then adding 8 g of graphite into the mixed system, heating to 35 ℃, stirring at constant temperature for 30min, heating to 60 ℃, and stirring at constant temperature for 10 h;
(2) cooling, filtering, recycling filtrate, adding a filter cake into 2L of ice water, adding 5 mL of hydrogen peroxide to consume excessive potassium permanganate, filtering and washing the obtained graphene oxide dispersion liquid until the pH value is =7, and drying the filter cake at 120 ℃ for 2h to obtain graphene oxide powder;
(3) the obtained graphene oxide powder was dispersed in 50 g of water at a concentration of 0.2% by sonication, and then stirred at 60 ℃ for 30min, 0.5 mL of NH3·H2O is dripped into the graphene oxide dispersion liquid to beAdjusting the pH value of the dispersion liquid to 9-10;
(4) adding 0.5 g of organic modifier hexadecyl trimethoxy silane and 0.5 g of hexamethyldisilazane into the dispersion liquid under the carrying of ethanol, stirring at the constant temperature of 60 ℃ for 30min, then reacting at the constant temperature of 80 ℃ for 2h, after the reaction is finished, centrifuging the surface modified graphene oxide at 10000 rpm for 30min, and then drying at 120 ℃ for 2 h;
(5) adding the obtained surface modified graphene oxide into a mixed solution of water and ethanol (V: V =4: 1) with the concentration of sodium hydroxide of 1 mol/L and the concentration of potassium hydroxide of 0.2 mol/L, then carrying out ultrasonic treatment for 2h and stirring at a constant temperature of 80 ℃ for 2h and ultrasonic treatment for 30min, carrying out centrifugal washing for 5 times at 12000 rpm, and drying at 120 ℃ for 2h to obtain the purified Janus graphene oxide.
Fig. 8 is a schematic diagram of the transfer of the Janus graphite oxide prepared in example 7 onto the surface of a p-type doped silicon wafer, and the resistance change behavior exhibited by the Janus graphite oxide as a dielectric layer of a memristor. Firstly, diluting Janus graphene to 0.01%, then adding trichloromethane, fully vibrating to form a Janus graphene oxide interface film, then removing an upper water phase, transferring the Janus graphene oxide to the surface of a clear p-type doped silicon wafer according to the graph shown in figure 8a, and drying at 105 ℃ for two hours. The current-voltage curves of 8 different positions are tested by using a conductive atomic microscope, and as a result, the resistance change property is shown at the position 8 and the switching voltage is relatively consistent as shown in fig. 8 b. The dielectric layer of the memristor prepared by the method can effectively avoid the problems of polymer pollution and the like caused by a conventional transfer method.

Claims (10)

1. A preparation method of Janus graphene oxide is characterized by comprising the following steps:
(1) uniformly mixing concentrated sulfuric acid and concentrated phosphoric acid in a volume ratio of 8: 1-9: 1 in an ice water bath, slowly adding potassium permanganate and graphite in a mass ratio of 1: 0.2-0.5 into the mixed acid solution, and reacting at a constant temperature of 35-60 ℃ for 6-12 hours;
(2) cooling, separating, washing to pH =7, and drying at 120 ℃ for 2h to obtain graphene oxide powder;
(3) dispersing the obtained graphene oxide powder in 100 mL of dispersion medium at a concentration of 0.05-0.5%, stirring at a constant temperature for 0.5-3 h, and adjusting the pH to 9-10 by using a pH regulator;
(4) adding an organic silicon modifier, stirring at constant temperature for 0.5-3 h, separating after the reaction is finished, and drying at 120 ℃ for 2 h;
(5) and (3) placing the surface modified graphene oxide in alkaline water, then reacting for 3-8 h at constant temperature under the action of mechanical force, separating and washing to obtain the purified Janus graphene oxide.
2. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: the hydrolysis medium in the step (3) is water and C1~C2One or more than two of the alcohols in (1).
3. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: and (4) the pH regulator in the step (3) is ammonia water.
4. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: the organic silicon modifier in the step (4) is one or more organic silicon compounds, and the organic silicon compound is R'nSi（OR”）4-nOr organosilicon compounds capable of reacting with hydroxyl, wherein R 'is one or more of methyl, ethyl, vinyl and other alkyl containing active functional group, R' includes but is not limited to C1-C16The carbon chain compound of (1); the organosilicon compound capable of reacting with hydroxyl is chlorosilane or/and silazane.
5. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: the mass ratio of the graphene oxide to the organic silicon modifier is 1: 3-20.
6. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: and (5) the mechanical force is one or more than two of ultrasonic, mechanical stirring and emulsification shearing.
7. The method for preparing Janus graphene oxide according to claim 1, wherein the method comprises the following steps: the chemical agents used in the alkaline water in the step (5) are NaOH and NaHCO3Or one or more of KOH.
8. Janus graphene oxide prepared by the preparation method of Janus graphene oxide according to any one of claims 1-7.
9. The Janus graphene oxide of claim 8, wherein: one surface of Janus graphene oxide is modified with an organic silicon modifier, the other surface of Janus graphene oxide is provided with naked hydroxyl and unsaturated residual bonds, the Janus graphene oxide has hydrophilic and hydrophobic surfaces, the Janus graphene oxide can be stably dispersed in water for more than 10 days, and the Zeta potential of a dispersion liquid is-36.9 mV.
10. The use of Janus graphene oxide according to claim 8, wherein: the Janus graphene oxide can form a stable interface film at an oil-water interface, and is used for emulsifying oil-water microemulsion and efficiently washing oil; meanwhile, the method can be transferred to a silicon chip for constructing a memristor dielectric layer.
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CN112876751A (en) * 2021-03-29 2021-06-01 青岛科技大学 Janus-like graphene/natural latex composite membrane and preparation method thereof
CN116731266A (en) * 2023-08-14 2023-09-12 内蒙古大学 Graphene oxide nanosheets and preparation method thereof

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US20170173546A1 (en) * 2012-03-21 2017-06-22 The Texas A&M University System Amphiphilic nanosheets and methods of making the same

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Publication number Priority date Publication date Assignee Title
US20170173546A1 (en) * 2012-03-21 2017-06-22 The Texas A&M University System Amphiphilic nanosheets and methods of making the same

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112876751A (en) * 2021-03-29 2021-06-01 青岛科技大学 Janus-like graphene/natural latex composite membrane and preparation method thereof
CN116731266A (en) * 2023-08-14 2023-09-12 内蒙古大学 Graphene oxide nanosheets and preparation method thereof
CN116731266B (en) * 2023-08-14 2023-11-03 内蒙古大学 Graphene oxide nanosheets and preparation method thereof

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