WO2020089946A1

WO2020089946A1 - A system and method for scaled-up synthesis of doped and functionalized graphene derivatives through mechanical exfoliation process

Info

Publication number: WO2020089946A1
Application number: PCT/IN2019/050814
Authority: WO
Inventors: Akshay VIVEK SINGHAL; Anshul KUMAR SHARMA; Ayushi KAUSHIK
Original assignee: Log 9 Materials Scientific Private Limited
Priority date: 2018-11-03
Filing date: 2019-11-04
Publication date: 2020-05-07

Abstract

The various embodiments of the present invention provide a mechanical exfoliation method for the bulk synthesis of doped and functionalized graphene nano-platelets. The particulate ceramic material is subjected to washing and annealing for surface activation and removal of contaminants. The graphene ceramic composites are obtained by coating, carbonization and dopant incorporation followed by graphitization. The doped graphene ceramic composite are subjected to exfoliation with or without simultaneous ultra-sonication for obtaining doped graphene sheet. The exfoliated graphene sheets obtained from doped graphene ceramic composite are subjected to ultra-sonication and centrifugation. The ceramic residue obtained after exfoliation is reused. The present invention provides a cost-effective and eco-friendly approach for the synthesis of graphene derivatives with tunable dopant type, functional moiety and concentration. The mechanical shearing and ultra-sonication of the doped and functionalized graphene composite provides a route for the synthesis of graphene derivatives nano-platelets.

Description

A SYSTEM AND METHOD FOR SCALED-UP SYNTHESIS OF DOPED AND

FUNCTIONALIZED GRAPHENE DERIVATIVES THROUGH MECHANICAL

EXFOLIATION PROCESS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of Indian Provisional Patent Application with serial number No. 201811016704, filed on May 03, 2018 and subsequently postdated by 6 Months to November 03, 2018 with the tile,“MECHANICAL EXFOLIATION ROUTE FOR SCALED-UP-SYNTHESIS OF DOPED AND FUNCTIONALIZED GRAPHENE DERIVATIVES”, and the content of which is incorporated herein by reference in its entirety.

BACKGROUND

Technical field

[0002] The present invention is generally related to a field of nanotechnology and synthesis of doped and functionalized graphene nano-platelets for a plurality of technological applications. The present invention is particularly related to a synthesis of p- and n- doped graphene nano-platelets and functionalized graphene nano-platelets from graphene ceramic composite using a mechanical exfoliation route. The present invention is more particularly related to a system and method a synthesis of p- and n- doped graphene nano-platelets and functionalized graphene nano-platelets from graphene ceramic composite through an eco- friendly, cost-effective and scaled-up synthesis route.

Description of the Related Art

[0003] Graphene is a two-dimensional material comprising a single atomic layer sp2 hybridized carbon atoms. Graphene in its pristine form is a semi-metal having extremely high conductivityand chemically inert surface which makes it difficult to use in some applications. [0004] The most commonly used method for manipulating the properties of graphene is by the incorporation of atoms in the structure of the material or by the addition of some functional groups on the graphene surface. The doped and functionalized graphene derivatives are obtained by a plurality of chemical routes such as chemical vapor deposition, solid state synthesis, solvothermal synthesis and the like.

[0005] The chemical method of synthesis illustrate a plurality of disadvantages such as introduction of chemical impurities, low yield of the product, expensive precursors, long processing timeand the like. These methods of synthesis comprise a plurality of steps for the synthesis and purification of the final material.

[0006] Hence there is a need for manipulation in the graphene structure for increasing the technological applications of the graphene material.Also there is a need for a synthesis route with scaled-up yield, cost-effective technique as well as an eco-friendly approach for the synthesis of doped and functionalized graphene derivatives.

[0007] The above-mentioned shortcomings, disadvantages and problems are addressed herein, which will be understood by studying the following specifications.

OBJECTIVES OF THE EMBODIMENTS

[0008] The primary objective of the present invention is to provide a technique to synthesize doped and functionalized graphene nano-platelets via exfoliation.

[0009] Another objective of the present invention is to synthesize doped graphene ceramic composite.

[0010] Yet another objective of the present invention is to synthesize functionalized graphene ceramic composite. [0011] Yet another objective of the present invention is to provide a method of mechanical shearing of doped and functionalized graphene sheets from graphene ceramic composite and ultra-sonication of the sheared sheets to form graphene nano-platelet derivatives.

[0012] Yet another objective of the present invention is to provide doped graphene derivatives with desired dopant type and concentration.

[0013] Yet another objective of the present invention is to provide a technique to dope the graphene derivatives with p- and n-type dopants.

[0014] Yet another objective of the present invention is to provide a process of doping which comprises dopants selected fromgroup 13 elements and group 15 elements.

[0015] Yet another objective of this invention is to provide functionalized graphene derivatives with desired functional groups and concentration.

[0016] Yet another objective of the present invention is to provide a process of functionalizing graphene nano-platelets with sulphur, Ti02, EDTA, Fe304, Mn02, ethylene oxide and a plurality of organic functional groups selected from hydroxyl, amine, amide, carboxylic, imine, ester and the like.

[0017] Yet another objective of thepresent invention is to provide a method comprising the use of oxides of aluminium, silicon, zinc, magnesium, calcium, zirconium and the like.

[0018] Yet another objective of the present invention is to provide a process which comprises of use of carbon sources like sucrose, fructose, lactose, coal tar, asphalt, recycled plastics and the like. [0019] Yet another objective of the present invention is to provide a plurality of solvents/stabilizing agents such as water, acetone, ethanol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), dimethyl formamide (DMF) and the like for mechanically exfoliating the doped and functionalized composites.

[0020] Yet another objective of the present invention is to provide a shearing process for the exfoliation of the doped and functionalized graphene derivatives from graphene ceramic composite at a rotation speed of 500-4000 rpm with or without simultaneous sonication.

[0021] Yet another objective of the present invention is to provide a method for the synthesis of graphene derivatives with controllable dimension and crystallinity.

[0022] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

[0023] The various embodiments herein provide a method for the scaled-up synthesis of doped and functionalized graphene nano-platelets using a mechanical exfoliation technique. The embodiments of the present invention provide a method for synthesizing doped and functionalized graphene nano-platelets which is both simple and cost-effective.

[0024] According to one embodiment herein, a graphene ceramic based composite material is provided, which is further exfoliated mechanically to produce doped and functionalized graphene derivatives. [0025] According to one embodiment herein, doped graphene ceramic based composite is used for mechanical exfoliation of graphene derivatives from the composite material. The mechanically sheared graphene derivatives are further ultra-sonicated to form doped graphene nano-platelets.

[0026] According to one embodiment herein, functionalized graphene based ceramic composite is mechanically exfoliated to form functionalized graphene derivatives. The mechanically sheared functional graphene derivatives are ultra- sonicated to form functional graphene nano-platelets.

[0027] According to one embodiment herein, a process for the mechanical shearing of graphene derivatives in a sonicator bath is provided for the synthesis of doped and functionalized graphene nano-platelets.

[0028] According to one embodiment herein, a method for the synthesis of doped graphene composite and doped graphene nano-platelets with control over the final dopant type and concentration is provided. The type of dopant to be incorporated as well as the concentration of the dopant is tunable or adjusted according to the need of the application.

[0029] According to one embodiment herein, a process for the synthesis of graphene ceramic composite and graphene nano-platelets doped with p- and n-type materials is provided. The p-type doping is obtained by doping with group 13 elements while n-type doping of the graphene ceramic composite is obtained by group 15 elements of the periodic table.

[0030] According to one embodiment herein, a process for the synthesis of functionalized graphene ceramic based composite and functionalized graphene nano-platelets is provided. The type of functional moieties and concentration on the graphene nano-platelets’ surface are tunable according to the need of the application. [0031] According to one embodiment herein, a process for the synthesis of functionalized graphene ceramic based composite and functionalized graphene nano-platelets is provided. The process utilizes oxides of aluminium, silicon, zinc, magnesium, calcium, zirconium and the like as the ceramic source. The process further utilizessucrose, fructose, lactose, coal tar, asphalt, recycled plastics and the like as the source of carbon for the synthesis of graphene ceramic composite.

[0032] According to one embodiment herein, a plurality of solvents/stabilizers are provided for the synthesis of doped graphene derivatives such as water, acetone, ethanol, NMP, DMSO, IPA, DMF and the like.

[0033] According to one embodiment herein, a method of synthesizing doped graphene ceramic composite is provided which controls the size of the graphene nano-platelets and thecrystallinity of the graphene nano-platelets by use of appropriate solvents/stabilizing agents, ceramic and carbon sources.

[0034] According to one embodiment herein, a method to exfoliate doped graphene sheets from doped graphene ceramic composite is provided. The doping in graphene ceramic composites is performed by incorporation of the precursor comprising dopant materials in the reaction mixture comprising of carbon sources such as sucrose, fructose, lactose, coal tar, asphalt, recycled plastics and the like.The ceramic material such as oxides of aluminium, silicon, zinc, magnesium, calcium, zirconium and the like. The carbonization of the coated material on the ceramic surface is carried out in a temperature range of 200 to 400° C. The graphitization of the carbonized composite is carried out under inert atmospheric temperature conditions maintained in a range of 600-950°. The step results in the formation of doped graphitic carbon on ceramic particles. [0035] According to one embodiment herein, a method to exfoliate functionalized graphene sheets from functionalized graphene based ceramic composite is provided. The functionalization of the graphene ceramic composite is obtained by the post-treatment of the graphitized ceramic based composite. The post-treatment comprises the direct addition of the functional moiety in an aqueous solution to the graphene ceramic composite. The time period of functionalization of the reaction varies between the range of 8-15 hoursand is carried out in predetermined temperature and pressure conditions.

[0036] According to one embodiment herein, the doped and functionalized composites are mechanically exfoliated in solvents like water, ethanol, acetone, NMP, IPA, DMSO, DMF and the like to obtain doped and functionalized graphene sheets respectively. The doped and functionalized graphene derivative obtained are further ultra-sonicated and centrifuged resulting in the formation of doped and functionalized graphene nano-platelets, respectively. The residual ceramic material post exfoliation is reused for carbonization and further exfoliation.

[0037] According to one embodiment herein, a method of synthesizing exfoliated doped graphene nano-platelets from doped graphene ceramic composite comprises the following steps. The particulate ceramic material is washed and annealed for surface activation and removal of contaminants. Annealing of the particulate ceramic material is performed at a temperature of 200°C. The annealed particulate ceramic material is coated and carbonized with carbon source/precursors. The carbon source is selected from a group consisting of sucrose, fructose, lactose, coal tar, asphalt and recycled plastic. The annealed particulate ceramic material is functionalized in presence of graphene to obtain graphene ceramic composite. The graphene ceramic composite are subjected to graphitization. The functionalization comprises incorporating dopant in the graphene ceramic composite. Carbonization of coated ceramic material is performed at a temperature range of 200-400°C. The graphitization is performed at a temperature range of 600-950°C under atmospheric temperature. The graphene ceramic composite is doped with dopant precursor. The doped graphene ceramic composite is exfoliated by ultra-sonication and centrifugation to obtain graphene nano-platelets. The particulate ceramic material is used again for the synthesis of graphene nano-platelets.

[0038] According to one embodiment herein, the graphene ceramic composite is synthesized by coating carbon precursor on the ceramic material. The carbon precursor and the ceramic material is subjected to carbonization and graphitization.

[0039] According to one embodiment herein, the step of doping the graphene ceramic composite with dopant precursor composition comprises the following steps. The graphene ceramic composite is treated with a dopant precursor solution with the concentration of the dopant precursor solution in a range of 3% w/w- 10% w/w with respect to graphene ceramic composite. The dopant precursor selected from a group consisting of boron, nitrogen and phosphorus. The dopant precursor solution is synthesized in solvents selected from a group consisting of hexamethyene-tetra amine and boric acid.

[0040] According to one embodiment herein, the step of functionalizing graphene ceramic composite comprises the following steps. The graphene ceramic composite is treated with acids. The acids are selected from a group consisting of H2S04, HN03, NaOH and KOH. The acids create a plurality of active site on the graphene ceramic composite surface. The graphene ceramic composite comprising a plurality of active sites is treated with precursors/inorganic groups. The precursors are selected from a group consisting of EDTA, thiourea, Fe304, Mn02. The concentration of precursor is in a range of 0.5%w/w-5%w/w with respect to graphene ceramic composite. The functionalized graphene ceramic composite is exfoliated to obtain functionalized graphene nanoplatelets.

[0041] According to one embodiment herein, the step of exfoliating the doped graphene ceramic composite by ultra-sonication and centrifugation to obtain graphene nano-platelets comprises the following steps. The functionalized graphene ceramic composite is dispersed in solvent/stabilizing agent in a metal beaker. The graphene ceramic composite is stirred in solvent/stabilizing agent in the beaker by a mechanical stirrer at 4000-5000 rpm. The mechanical stirrer shears the graphene ceramic composite particles. The solvent/stabilizing agent is collected in a beaker. The collected solvent/stabilizing agent is ultrasonicated for 3-4 hours. The the ultrasonicated solvent/stabilizing agent is centrifuged to collect a plurality of layers of graphene nanoplatelets and separated ceramic composite. The layer of ceramic composite of separated from graphene nanoplatelets. Mechanical shearing exfoliates graphene sheets from ceramic composite.

[0042] According to one embodiment herein, the solvent/stabilizing agent is selected from a group consisting of water, acetone, ethanol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), dimethyl formamide (DMF).

[0043] According to one embodiment herein, the ceramic material is selected from a group consisting of oxides of aluminum, oxides of silicon, oxides of zinc, oxides of magnesium, oxides of calcium and oxides of zirconium.

[0044] According to one embodiment herein, the ceramic material is a substrate on which graphene is grown. [0045] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0047] FIG. l is a flow chart illustrating a method for the exfoliation of doped graphene nano-platelets from doped graphene ceramic composite, according to one embodiment herein.

[0048] FIG.2 is a flow chart illustrating a process for the exfoliation of functionalized graphene nano-platelets from functionalized graphene ceramic composite, according to one embodiment herein.

[0049] FIG.3 is isometric line diagram illustrating exfoliation setup used for the synthesis of doped graphene derivatives, according to one embodiment herein.

[0050] The features of the present invention are described in drawings and of which a few are not shown in all. These features can be combined with any or all other features that exist in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS HEREIN

[0051] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0052] The various embodiments of the present invention provide a method for the scaled-up synthesis of doped and functionalized graphene nano-platelets using a mechanical exfoliation technique. The embodiments of the present invention provide a method for synthesizing doped and functionalized graphene nano-platelets which is both simple and cost- effective.

[0053] According to one embodiment herein, a method of synthesizing exfoliated doped graphene nano-platelets from doped graphene ceramic composite comprises the following steps. The particulate ceramic material is washed and annealed for surface activation and removal of contaminants. Annealing of the particulate ceramic material is performed at a temperature of 200°C. The annealed particulate ceramic material is coated and carbonized with carbon source/precursors. The carbon source is selected from a group consisting of sucrose, fructose, lactose, coal tar, asphalt and recycled plastic. The annealed particulate ceramic material is functionalized in presence of graphene to obtain graphene ceramic composite. The graphene ceramic composite are subjected to graphitization. The functionalization comprises incorporating dopant in the graphene ceramic composite. Carbonization of coated ceramic material is performed at a temperature range of 200-400°C. The graphitization is performed at a temperature range of 600-950°C under atmospheric temperature. The graphene ceramic composite is doped with dopant precursor. The doped graphene ceramic composite is exfoliated by ultra-sonication and centrifugation to obtain graphene nano-platelets. The particulate ceramic material is used again for the synthesis of graphene nano-platelets.

[0054] According to one embodiment herein, the graphene ceramic composite is synthesized by coating carbon precursor on the ceramic material. The carbon precursor and the ceramic material is subjected to carbonaization and graphitization.

[0055] According to one embodiment herein, the step of doping the graphene ceramic composite with dopant precursor composition comprises the following steps. The graphene ceramic composite is treated with a dopant precursor solution with the concentration of the dopant precursor solution in a range of 3% w/w- 10% w/w with respect to graphene ceramic composite. The dopant precursor selected from a group consisting of boron, nitrogen and phosphorus. The dopant precursor solution is synthesized in solvents selected from a group consisting of hexamethyene-tetra amine and boric acid.

[0056] According to one embodiment herein, the step of functionalizing graphene ceramic composite comprises the following steps. The graphene ceramic composite is treated with acids. The acids are selected from a group consisting of H2S04, HN03, NaOH and KOH. The acids create a plurality of active site on the graphene ceramic composite surface. The graphene ceramic composite comprising a plurality of active sites is treated with precursors/inorganic groups. The precursors are selected from a group consisting of EDTA, thiourea, Fe304, Mn02. The concentration of precursor is in a range of 0.5%w/w-5%w/w with respect to graphene ceramic composite. The functionalized graphene ceramic composite is exfoliated to obtain functionalized graphene nanoplatelets. [0057] According to one embodiment herein, the step of exfoliating the doped graphene ceramic composite by ultra-sonication and centrifugation to obtain graphene nano-platelets comprises the following steps. The functionalized graphene ceramic composite is dispersed in solvent/stabilizing agent in a metal beaker. The graphene ceramic composite is stirred in solvent/stabilizing agent in the beaker by a mechanical stirrer at 4000-5000 rpm. The mechanical stirrer shears the graphene ceramic composite particles. The solvent/stabilizing agent is collected in a beaker. The collected solvent/stabilizing agent is ultrasonicated for 3-4 hours. The the ultrasonicated solvent/stabilizing agent is centrifuged to collect a plurality of layers of graphene nanoplatelets and separated ceramic composite. The layer of ceramic composite of separated from graphene nanoplatelets. Mechanical shearing exfoliates graphene sheets from ceramic composite.

[0058] According to one embodiment herein, the solvent/stabilizing agent is selected from a group consisting of water, acetone, ethanol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), dimethyl formamide (DMF).

[0059] According to one embodiment herein, the ceramic material is selected from a group consisting of oxides of aluminum, oxides of silicon, oxides of zinc, oxides of magnesium, oxides of calcium and oxides of zirconium.

[0060] According to one embodiment herein, the ceramic material is a substrate on which graphene is grown.

[0061] According to one embodiment herein, a mechanical shearing method is provided for obtaining doped graphene sheets from graphene ceramic composite. The exfoliated graphene sheets are ultra-sonicated to obtain doped graphene nano-platelets. [0062] According to one embodiment herein, the mechanical shearing setup is coupled with simultaneous ultra-sonication to obtain doped graphene nano-platelets.

[0063] According to one embodiment herein, a method is provided for the synthesis of doped graphene derivatives. The doping of the graphene ceramic composite is a regulated process, where the type and concentration of the dopant used is manipulated or tweaked according to the need.

[0064] According to one embodiment herein, p-type and n-type doping in graphene ceramic composite is provided. The p-type and n-type doping in the graphene ceramic composite is obtained by employing elements from the group 13 element andgroup 15 element of the periodic table respectively.

[0065] According to one embodiment herein, a mechanical exfoliation route is provided for obtaining functionalized graphene sheets from graphene ceramic composite. The functionalized graphene sheets exfoliated are further ultra-sonicated to obtain functionalized graphene nano-platelets.

[0066] According to one embodiment herein, the graphene ceramic based composite is functionalized by various organic groups like hydroxyl, amine, amide, carboxylic, imine and ester. The graphene ceramic based composite is functionalized by a plurality of inorganic groups such as sulphur, Ti02, EDTA, Fe304, Mn02, ethylene oxide and the like.

[0067] According to one embodiment herein, a mechanical shearing process of the functionalized graphene based composite is provided with simultaneous sonication of the exfoliation setup. [0068] According to one embodiment herein, a process involving the synthesis of doped graphene derivatives utilizes oxides of aluminium, silicon, zinc, magnesium, calcium, zirconium and the like as the ceramic source.The process involving the synthesis of doped graphene derivatives utilizes sucrose, fructose, lactose, coal tar, asphalt, recycled plastics and the like as the source of carbon.

[0069] According to one embodiment herein, a method of exfoliating graphene derivatives sheets from ceramic composite is provided. The exfoliation process is carried out in solvents like water, acetone, ethanol, NMP, IPA, DMSO, DMF and the like. These solvents also function as stabilizers for the synthesized doped and functionalized graphene nano-platelets.

[0070] According to one embodiment herein, a route is provided for the synthesis of doped and functionalized graphene nano-platelets to attain control over the size and crystallinity of the final graphene derivatives.

[0071] FIG. 1 is a flow chart illustrating a method for the exfoliation of doped graphene nano-platelets from doped graphene ceramic composite, according to one embodiment herein. The particulate ceramic material is subjected to washing and annealing for surface activation and removal of contaminants (101). The graphene ceramic composites are obtained by coating, carbonization and dopant incorporation followed by graphitization (102). The doped graphene ceramic composite are subjected to exfoliation with or without simultaneous ultra- sonication for obtaining doped graphene sheets (103). The exfoliated graphene sheets obtained from doped graphene ceramic composite are subjected to ultra-sonication and centrifugation (104). The ceramic residue obtained after exfoliation is reused in Step 2 (105). [0072] FIG.2 is a flow chart illustrating a process for the exfoliation of functionalized graphene nano-platelets from functionalized graphene ceramic composite, according to one embodiment herein. Washing and annealing the ceramic material for the surface activation and removal of contaminants (201). Coating and carbonizing the carbon precursor, followed by graphitization (202). Surface functionalization of the graphene ceramic composite by direct addition (203). Exfoliating the composite to obtain functionalized graphene sheets with or without simultaneous ultra- sonication (204). Centrifuging the exfoliatedfunctionalizing graphene sheets to obtain a plurality of layered functionalized graphene nano-sheets (205). The residual graphene ceramic composite is obtained after exfoliation and utilized in step 202 (206).

[0073] FIG. 3is isometric line diagram illustrating exfoliation setup used for the synthesis of doped graphene derivatives, according to one embodiment herein. This setup comprises of a metal beaker 301, solvent/stabilizing agent with doped graphene ceramic composite 302, metallic stirrer blades 303, metal shaft 304. The solvent/stabilizing agent with dispersed doped graphene ceramic composite 302 are stirred in the metal beaker 301 mechanically by means of metal blades 303 rotating on a shaft 304 operated by an external power supply. The mechanical shearing setup is immersed in an ultra-sonicator bath 305.

[0074] According to one embodiment herein, following are the steps involved in the synthesis of doped graphene nano-platelets from doped ceramic composite are provided. The doped graphene ceramic composite is obtained by performing carbonization and graphitization of the reaction mixture comprising of dopant precursors, carbon sources and metal oxides. The dopant precursors are selected fromgroup 13 elements and group 15 elements of the periodic table. The carbon sources are selected from a group consisting of sucrose, fructose, lactose, coal tar, asphalt, recycled plastics and the like. The metal oxides are selected from a group consisting of aluminium, silicon, zinc, magnesium, calcium, zirconium and the like as the ceramic material. The removal of contaminant and surface activation of the particulate ceramic material is performed by annealing at 200° C (Step 1). The annealed ceramic particulates undergo carbonization and graphitization in the presence of the aforementioned dopant and carbon precursor to obtain doped graphene ceramic composite (Step 2). Mechanical shearing of the doped graphene layers from the dispersion containing doped graphene ceramic composite in organic solvents like acetone, ethanol, water, IPA, DMSO, NMP, DMFand the like. (Step 3). The exfoliated doped graphene sheets are ultra-sonicated and centrifuged to obtain doped graphene nano-platelets. The residual ceramic particulates are reused for carbonization and graphitization mentioned above in step 2.

[0075] According to one embodiment herein, route followed for the synthesis of functionalized graphene ceramic composite and functionalized graphene nano-platelets is provided. The graphene ceramic composite is synthesized by the coating of the carbon precursor on the ceramic material followed by its carbonization and graphitization. The functionalization of the synthesized graphene ceramic composite is obtained by the direct reaction of the precursors with the graphene composite in solution phase.

[0076] According to one embodiment herein, an exfoliation system for the synthesis of graphene derivatives is provided. Themethod utilizesa system comprising metal blades which provide the required energy for shearing of doped or functionalized graphene sheets from graphene ceramic composite, at a rotation speed of 500-4000 rpm. The mechanical shearing of the composite is done both in the presence or absence of simultaneous ultra-sonication. The mechanically sheared graphene derivatives’ sheets are ultra-sonicated for duration of 2-4 hoursand centrifuged to obtain doped or functionalized graphene nano-platelets. The ceramic residue after mechanical exfoliation is reused in further carbonization and graphitization steps.

[0077] According to one embodiment herein, the current methods for the synthesis of graphene and its derivatives are highly costly and chemical intensive. Further the scaling up the graphene nanoplatelet production using available methods is cumbersome.

[0078] According to one embodiment herein, graphene nanoplatelet production is easily scaled up based on the requirement. The method can be utilized for the synthesisi of graphene nanoplatelets, doped graphene nanoplatelets and functionalized graphene nanoplatelets. The method disclosed in the present invention, can be utilized for achieving graphene nanoplatelts with controllable dimension and crystallinity. The advantage of the method disclosed in the present invention is that the ceramic substrate is reusable. After shearing the ceramic particles are again carbonized and graphitized for the production of graphene nanoplatelets. Thus making the method cost effective.

[0079] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

[0080] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope. [0081] Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications.

[0082] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the claims submitted below. The scope of the invention will be ascertained by the following claims.

Claims

CLAIMS: What is claimed is:

1. A method of synthesizing exfoliated doped graphene nano-platelets from doped graphene ceramic composite, the method comprises steps of:

washing and annealing particulate ceramic material for surface activation and removal of contaminants, and wherein annealing of the particulate ceramic material is performed at a temperature of 200°C;

coating and carbonizing annealed particulate ceramic material with carbon source/precursors, and wherein the carbon source is selected from a group consisting of sucrose, fructose, lactose, coal tar, asphalt and recycled plastic;

functionalizing annealed particulate ceramic material in presence of graphene to obtain graphene ceramic composite, and wherein the graphene ceramic composite are subjected to graphitization, and wherein the functionalization comprisesincorporating dopant in thegraphene ceramic composite, and wherein carbonization of coated ceramic material is performed at a temperature range of 200-400°C, and wherein the graphitization is performed at a temperature range of 600-950°C under atmospheric temperature;

doping the graphene ceramic composite with dopant precursor;

exfoliating the doped graphene ceramic composite by ultra-sonication and centrifugation to obtain graphene nano-platelets; and

reusing the particulate ceramic material again for the synthesis of graphene nano platelets.

2. The method according to claim 1 , wherein the graphene ceramic composite is synthesized by coating carbon precursor on the ceramic material, and wherein the carbon precursor and the ceramic material is subjected to carbonatization and graphitization.

3. The method according to claim 1, wherein the step of doping the graphene ceramic composite with dopant precursorcomposition comprises the steps of:

treating graphene ceramic composite with a dopant precursor solution with the concentration of the dopant precursor solution in a range of 3% w/w- 10% w/w with respect to graphene ceramic composite, and wherein the dopant precursor selected from a group consisting of boron, nitrogen and phosphorus, and wherein the dopant precursor solution is synthesized in solvents selected from a group consisting of hexamethyene- tetra amine and boric acid.

4. The method according to claim 1, wherein the step of functionalizing graphene ceramic compositecomprises the steps of:

treating the graphene ceramic composite with acids, and wherein the acids are selected from a group consisting of H2SO4, HNO3, NaOH and KOH, and wherein the acids create a plurality of active site on the graphene ceramic composite surface; and treating the graphene ceramic composite comprising a plurality of active sites with precursors/inorganic groups, and wherein the precursors are selected from a group consisting of EDTA, thiourea, FeTfr, Mn0₂, and wherein the concentration of precursor is in a range of 0.5%w/w-5%w/w with respect to graphene ceramic composite, and wherein the functionalized graphene ceramic composite is exfoliated to obtain functionalized graphene nanoplatelets.

5. The method according to claim 1, wherein the step of exfoliating the doped graphene ceramic composite by ultra-sonication and centrifugation to obtain graphene nano- plateletscomprises the steps of:

dispersing functionalized graphene ceramic composite in solvent/stabilizing agent in a metal beaker;

stirring the graphene ceramic composite in solvent/stabilizing agent in the beaker by a mechanical stirrer at 4000-5000 rpm, and wherein the mechanical stirrer shears the graphene ceramic composite particles;

collecting the solvent/stabilizing agent in a beaker;

ultrasonicating the collected solvent/stabilizing agent for 3-4 hours; and centrifuging the ultrasonicated solvent/stabilizing agent to collect a plurality of layers of graphene nanoplatelets and separated ceramic composite, and wherein the layer of ceramic composite of separated from graphene nanoplatelets, and wherein mechanical shearing exfoliates graphene sheets from ceramic composite.

6. The method according to claim 5, wherein the solvent/stabilizing agent is selected from a group consisting of water, acetone, ethanol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), dimethyl formamide (DMF).

7. The method according to claim 1, wherein the ceramic material is selected from a group consisting of oxides of aluminum, oxides of silicon, oxides of zinc, oxides of magnesium, oxides of calcium and oxides of zirconium.

8. The method according to claim 1, wherein the ceramic material is a substrate on which graphene is grown.