AU2021106312A4 - Preparation method and application of graphene quantum dots with uniform size - Google Patents
Preparation method and application of graphene quantum dots with uniform size Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 51
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 43
- 238000000034 method Methods 0.000 claims abstract description 21
- 239000002096 quantum dot Substances 0.000 claims abstract description 15
- 238000009826 distribution Methods 0.000 claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 10
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 10
- 239000007772 electrode material Substances 0.000 claims abstract description 7
- 239000002994 raw material Substances 0.000 claims abstract description 6
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 7
- 238000009210 therapy by ultrasound Methods 0.000 claims description 6
- 239000006185 dispersion Substances 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- -1 polytetrafluoroethylene Polymers 0.000 claims description 4
- 239000012286 potassium permanganate Substances 0.000 claims description 4
- 239000004317 sodium nitrate Substances 0.000 claims description 4
- 235000010344 sodium nitrate Nutrition 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
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- 239000010935 stainless steel Substances 0.000 claims description 3
- 239000012300 argon atmosphere Substances 0.000 claims description 2
- 238000003837 high-temperature calcination Methods 0.000 claims 1
- 238000010335 hydrothermal treatment Methods 0.000 claims 1
- 238000007789 sealing Methods 0.000 claims 1
- 238000004146 energy storage Methods 0.000 abstract description 8
- 230000003647 oxidation Effects 0.000 abstract description 6
- 238000007254 oxidation reaction Methods 0.000 abstract description 6
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- 230000000694 effects Effects 0.000 description 8
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- 239000000243 solution Substances 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 4
- 230000007847 structural defect Effects 0.000 description 4
- 238000004630 atomic force microscopy Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000002484 cyclic voltammetry Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
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- 238000012360 testing method Methods 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
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- 239000003513 alkali Substances 0.000 description 1
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- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical group Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
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- 229910001416 lithium ion Inorganic materials 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
Abstract
The invention provides a preparation method of graphene quantum dots with uniform size
and application thereof. The method adopts a top-down strategy, takes graphene oxide as a raw
material, utilizes an ultrasonic-assisted hydrothermal method, cuts carbon-carbon bonds with
ultrasonic mechanical stress assisted by strong oxidation of nitric acid, and then carries out
high-temperature heat treatment to prepare graphene quantum dot materials with uniform and
pure size distribution. The method has simple process and mild conditions, and the prepared
graphene quantum dots have good purity, small particle size and uniform size distribution. As
the electrode material of energy storage devices, the graphene quantum dot material has
excellent conductivity, high specific capacity, excellent rate performance, fast ion adsorption
and transmission rate and long cycle life, and has good application potential in the field of
energy storage devices.
Description
Preparation method and application of graphene quantum dots with uniform size
TECHNICAL FIELD The invention relates to the technical field of nano materials, in particular to a preparation
method of graphene quantum dots with uniform size.
BACKGROUND In recent years, carbonaceous materials have been widely used in various fields because of their high conductivity, low cost, green and non-toxic, high chemical stability and wide temperature range. Graphene (G), as a new type of carbon material, is a planar two-dimensional atomic crystal composed of a single layer of carbon atoms bonded by Sp2 hybrid carbon atoms with regular hexagonal lattice structure. Since it was discovered in 2004, it has been widely studied in the field of nanotechnology because of its unique physical and chemical properties. Especially, graphene materials have been widely used in the field of electrode materials for lithium-ion batteries or supercapacitors due to their high conductivity and fast ion adsorption ability. However, the interlayer stacking of graphene will lead to the decrease of electrical and thermal conductivity. In the preparation process, structural defects will also greatly reduce its electrical and thermal conductivity. Therefore, the purity of graphene in the preparation process cannot be guaranteed, and its agglomeration problem cannot be well solved, which limits its application in the field of energy storage. These ultrafine graphene nanosheets, which are formed by limiting the size of highly crystalline graphene with a single atom or a few atoms thickness below 100 nm, are called graphene quantum dots (GQDs). As a new type of zero-dimensional carbon nanoparticles, due to the strong quantum confinement effect and edge effect of quantum dots, energy band gaps can be generated in the lattice. However, if the size of graphene quantum can be controlled below Onm, its quantum confinement effect and edge effect will be significantly enhanced, which will endow graphene quantum dots with new physical properties, such as photoluminescence, high conductivity, chemical inertness, excellent stability and environmental friendliness. In addition, due to the nanoscale structure of graphene quantum dots, a large number of structural defects and edge states are introduced into the pure graphene plane, which limits the energy band gap and localized charge carriers, and makes it have high surface area and excellent electron transport capacity. However, the conjugated electronic structure and specific properties of GQDs depend on the edge electronic state and the quantum constraint which depends on the size, which makes them face the challenge of accurately controlling the size in the preparation process. Generally speaking, the synthetic route of GQDs can be divided into top-down and bottom-up methods. However, the bottom-up method requires strict and complex reaction conditions and specific organic materials, and the preparation work must use complex process steps. Compared with the bottom-up strategy, the top-down method can control the production conditions more effectively. This top-down method mainly includes strong acid and strong alkali oxidation, high temperature hydrothermal solution, ultraviolet etching method, microwave method, electron beam etching and so on. However, the existing process steps are complicated, the process is complex, the cost is high, the yield is low, the size can not be controlled, and it is not suitable for mass production and application.
SUMMARY The purpose of the invention is to solve the shortcomings of the prior art and provide a method for preparing graphene quantum dots with uniform size with simple process and controllable size. The graphene quantum dots prepared by the invention have a good development prospect in the field of electrode materials used as energy storage devices. In order to achieve the above purpose, the invention adopts the following technical scheme to realize: In order to achieve the above purpose, the invention adopts the following technical scheme to realize: The invention relates to a preparation method of graphene quantum dots with uniform size, which comprises the following steps: taking graphene oxide as a raw material, and carrying out ultrasonic treatment in nitric acid environment to further oxidize the graphene oxide and attach more epoxy functional groups on the graphene oxide. Then, with the help of hydrothermal conditions, graphene oxide is cut into quantum dot materials with the same size (1-5 nm). And finally, eliminating oxygen-containing functional groups at the edge of the quantum dots through high-temperature heat treatment, and evaporating nitric acid left in the oxidation process to obtain graphene quantum dot materials with the size less than 5 nm. Preferably, the preparation steps are as follows: (1) Preparation of graphene oxide: graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid are used as raw materials, and graphene oxide powder is prepared by hummers method. (2) Ultrasonic pretreatment: dispersing 25-100mg graphene oxide in 50ml concentrated nitric acid solution for ultrasonic treatment for a period of time to obtain orange-yellow dispersion liquid. (3) Hydrothermal reaction: the dispersion liquid is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, sealed and reacted at 80-180°C for 8-24h; After cooling to room temperature, the solution was centrifuged at 8000r/min for 10 minutes to remove the upper liquid, and the obtained light yellow slurry was placed in a Petri dish and naturally dried in a ventilated place; (4) High-temperature treatment: the sample is placed in a tube furnace and calcined at high temperature under argon atmosphere, and bright black products are collected to obtain graphene quantum dots with uniform size distribution. In the step (1), the graphite powder is 800 mesh flake graphite, and the mass fraction of concentrated sulfuric acid is 98wt%.
In step (1), the mass ratio of graphite powder, sodium nitrate and potassium permanganate is preferably 2: 1: 6. In the step (2), concentrated nitric acid with a mass fraction of 68% is used as a dispersant in the ultrasonic environment. The mass of graphene oxide is preferably 50mg. In the step (2), the ultrasonic time is 2-6h, preferably 4h. In the step (3), the hydrothermal reaction temperature is preferably 100 C., and the reaction time is preferably 12h. In the step (4), the graphene quantum dots are purified by high-temperature heat treatment, and the reaction temperature is 500-800°C and the reaction time is 2-4h. In the step (4), the sample is placed in a tube furnace for heat treatment under argon flowing atmosphere, and the roasting temperature is preferably 700°C, the heating rate is 5C/min, and the holding time is preferably 240min, and then cooled to room temperature under argon protection. The layers of the prepared graphene quantum dots (GQDs) are 1-3 layers, the average size is 1-5nm, and most of them (85-90%) are below 3nm. The graphene quantum dots prepared by the preparation method of the graphene quantum dots are applied as electrode materials of energy storage devices. According to the preparation method of graphene quantum dots, based on a top-down strategy, an ultrasonic-assisted hydrothermal method is adopted, and ultrasonic mechanical stress is used to assist strong oxidation of strong acid to cut graphene oxide materials to obtain graphene quantum dots; and the prepared graphene quantum dots are pure and have uniform size distribution. According to the preparation method of the graphene quantum dots, the raw materials are cheap and easily obtained graphene oxide materials, and because the surface has a large number of oxygen-containing groups, the graphene quantum dots are easily dispersed in an aqueous solution. According to the preparation method of the graphene quantum dot, an ultrasonic pretreatment method is adopted, so that graphene oxide exists in the form of a single sheet layer, the further oxidation of graphene oxide in nitric acid solution is accelerated, and the graphene oxide sheet layer is broken into particles with hundreds ofnm by mechanical stress. According to the preparation method of the graphene quantum dot, the cutting process is carried out through hydrothermal reaction, the reaction temperature is 80-180'C, the conditions are mild, and the test conditions are easy to control. The hydrothermal reaction time is 8-24h, the preparation process is simple, and the prepared graphene quantum dots are uniform in size. According to the preparation method of graphene quantum dots, various oxygen-containing groups and excess nitric acid can be well removed by high-temperature heat treatment, and the purity of products is guaranteed. According to the preparation method of the graphene quantum dot, due to the confinement effect and edge effect of the quantum dot, a large number of structural defects and edge states exist, so that the active area is increased, the electron transmission rate is accelerated, and the capacitance of the graphene quantum dot material is further improved. To sum up, compared with the prior art, the gain effect of the invention is as follows:
According to the preparation method of graphene quantum dots provided by the invention, graphene oxide with low cost is used as a raw material, and an innovative ultrasonic-assisted hydrothermal synthesis method is adopted, so that the synthesis process is mild and the process is simple, and the prepared graphene quantum dots have better purity, higher yield, small particle size and uniform size distribution. The graphene quantum dot material prepared by the invention shows excellent conductivity, high charge storage capacity and fast ion adsorption and transmission rate. As an electrode material for energy storage devices, this electrode material shows high specific capacity, excellent rate performance and long cycle life in terms of electrochemical performance, which will be beneficial to the application of graphene quantum dot materials in the field of energy storage.
BRIEF DESCRIPTION OF THE FIGURES The invention will be further explained with reference to the attached drawings and examples, in which: Fig. 1 shows (a) atomic force microscopy and height distribution of graphene oxide, (b) atomic force microscopy and height distribution of graphene oxide particles after ultrasonic treatment, (c) atomic force microscopy, (d) height distribution and (e) size distribution histogram of graphene quantum dots in embodiment 1. Fig. 2 is (a) a high-resolution transmission electron micrograph and (b) a size distribution histogram of graphene quantum dots in embodiment 1 Fig. 3 is a cyclic voltammetry curve of graphene quantum dots in example 1 at a scanning rate of 1OOmV s-1. Fig. 4 is a constant flow discharge curve of graphene quantum dots in embodiment 1 at a current density of 1A g-1 .
DESCRIPTION OF THE INVENTION The following describes the technical scheme of the present invention in further detail with reference to the drawings and specific embodiments. Eembodiment 1 (1) Preparation of graphene oxide: Add 26mL concentrated sulfuric acid into a beaker in ice-water bath at 0°C, then add Ig graphite powder, 0.5g sodium nitrate and 3g potassium permanganate, stir for 2 hours, and then take it out of the ice-water bath. Add 46mL of water into the beaker, control the system temperature at 35C, and stir for 30min. Then at 95C, keep stirring for 15min, and then add 140mL of warm water. 3.3% H202 solution was added dropwise until no bubbles were generated in the system. Centrifuge, and then centrifugally wash with 5% hydrochloric acid solution, absolute ethyl alcohol and deionized water respectively. The precipitate obtained by centrifugation was put into a vacuum freeze dryer and dried at -45C for
24h to obtain graphite oxide powder. As shown in fig. 1 (a), the obtained graphene oxide is a monolithic layer with smooth surface and a thickness of about 1 nm due to the existence of oxygen-containing groups. (2) Ultrasonic pretreatment: 50mg of graphene oxide was dispersed in 50ml of concentrated nitric acid solution and ultrasonic treatment was carried out for 4 hours to obtain orange-yellow dispersion. The obtained graphene oxide fragments are shown in Figure 1 (b). After ultrasonic treatment, the average thickness of graphene oxide fragments is about 1.5nm, which is caused by structural defects caused by the increase and further oxidation of oxygen-containing functional groups. In addition, the size of single-layer graphene fragments ranges from tens to hundreds of nm.
(3) Hydrothermal reaction: the pretreated sample is transferred to a stainless steel autoclave lined with polytetrafluoroethylene for hydrothermal reaction at 100°C for 12 hours. After cooling
to room temperature, the obtained solution was centrifuged at 8000r/min for 10mmin, and the upper layer of liquid was removed. The obtained light yellow slurry was placed in a Petri dish and naturally dried in a ventilated place for 24h. (4) High-temperature heat treatment: the sample is placed in a tube furnace for heat treatment under argon flowing atmosphere, the roasting temperature is preferably 700°C, the
heating rate is preferably 5C/min, the holding time is preferably 240min, and then cooled to
room temperature under argon protection. Bright black graphene quantum dots are obtained, as shown in the attached figure 1 (c, d), and graphene quantum dots with diameters between 1 and nm are distributed on the whole surface. In addition, considering the theoretical thickness of a single layer of graphene (0.34nm), graphene quantum dot material is an oligopolymer sheet (1-3 layers). Meanwhile, as shown in Fig.1(e) and Fig.2, about 88.8% of graphene quantum dots are distributed between 1 and 3 nm in size, which means uniform size distribution.
Effect verification test: electrochemical test is conducted by CHI760D electrochemical workstation (Chenhua, Shanghai). Cyclic voltammetry and constant current charge and discharge adopt a typical three-electrode system, in which the auxiliary electrode is platinum electrode, the reference electrode is saturated calomel, and the industrial electrode is tabletted foam nickel coated with active material (90%), acetylene black (5%) and polytetrafluoroethylene (PTFE, 5%). As shown in Fig.3, the cyclic voltammetry curve is nearly rectangular and shows mirror symmetry without obvious peak value, which indicates the canonical double-layer capacitance behavior and high reversibility. Fig.4 shows the charging and discharging direction of graphene quantum dots at constant current. the almost symmetrical triangular curve shows linear potential time diagram, excellent reversibility and high capacitance of 296.7F g- 1. the results show that graphene quantum dots can be used in the field of energy storage. The above is only a preferred embodiment of the present invention, and it is not meant to limit the present invention in other forms. Any person familiar with this profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the technical scheme of the present invention still belong to the protection scope of the technical scheme of the present invention.
Claims (3)
- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Preparation method of graphene quantum dots with uniform size, which is characterized by comprising the following steps: (1) Preparation of graphene oxide: graphite powder, sodium nitrate, potassium permanganate and concentrated sulfuric acid are used as raw materials, and graphene oxide powder is prepared by hummers method. (2) Ultrasonic pretreatment: dispersing 25-100mg graphene oxide in 50ml concentrated nitric acid solution and performing ultrasonic treatment for 2-6h to obtain orange-yellow dispersion liquid. (3) Hydrothermal reaction: the dispersion liquid is transferred to a stainless steel autoclave lined with polytetrafluoroethylene for sealing, and reacts for 8-24h at 80-180°C, where the hydrothermal treatment is carried out in the environment of concentrated nitric acid with mass fraction of 68%. After cooling to room temperature, the solution was centrifuged at 8000r/min for 10 minutes to remove the upper liquid, and the obtained light yellow slurry was placed in a Petri dish and naturally dried in a ventilated place. (4) High-temperature heat treatment: the sample is placed in a tube furnace for high temperature calcination under argon atmosphere, and bright black products are collected to obtain graphene quantum dots with uniform size distribution; The number of graphene quantum dots prepared is 1-3, and the average size is 1-3 nm. The prepared graphene quantum dot material has electric double layer capacitance behavior.
- 2. The preparation method of graphene quantum dots with uniform size according to claim 1, characterized in that, in step (4), the graphene quantum dots are purified by high-temperature heat treatment at 500-800°C for 2-4h.
- 3. Application of the graphene quantum dots prepared by the preparation method of graphene quantum dots according to any one of claims 1-2 as electrode materials of electric double layer supercapacitors.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114836760A (en) * | 2022-05-16 | 2022-08-02 | 大连民族大学 | Preparation method of rust remover containing graphene quantum dot corrosion inhibitor |
| CN115924896A (en) * | 2022-12-26 | 2023-04-07 | 上海纳米技术及应用国家工程研究中心有限公司 | Method for preparing graphene quantum dots by using heterogeneous catalyst |
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2021
- 2021-08-21 AU AU2021106312A patent/AU2021106312A4/en not_active Ceased
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114836760A (en) * | 2022-05-16 | 2022-08-02 | 大连民族大学 | Preparation method of rust remover containing graphene quantum dot corrosion inhibitor |
| CN115924896A (en) * | 2022-12-26 | 2023-04-07 | 上海纳米技术及应用国家工程研究中心有限公司 | Method for preparing graphene quantum dots by using heterogeneous catalyst |
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