DESC:FIELD OF INVENTION:
The present disclosure generally relates to the field of material synthesis. More specifically, the present disclosure relates to a method for preparing graphene oxide nanosheets. The method for preparation of the said graphene oxide nanosheets is cost effective, simple, efficient and requires lesser time as compared to methods known in the art.

BACKGROUND OF INVENTION:
Graphene oxide nanosheets are synthesized by the oxidation of graphite into graphite oxide followed by the exfoliation of the graphite oxide into graphene oxide nanosheets. The properties of the Graphene oxide nanosheets are strongly dependent on the synthesizing method, which influences the various properties, number and type of oxygen-containing groups in the formed graphene oxide nanosheets.

Graphene oxide nanosheets offer an encouraging opportunity to assemble an ultrathin, high-flux and energy-efficient sieving membranes because of their unique two-dimensional and mono-atom thick structure, outstanding mechanical strength and good flexibility as well as their facile and large-scale industrial application in nanoelectronics, hydrogen production and storage, drug delivery, gas sensing, catalysis, photovoltaics as well as biofunctionalization and fluorescence biosensors.

Graphene oxide (GO) nanosheets also offer an extraordinary potential for making functional nanocomposite materials with high chemical stability, strong hydrophilicity, and excellent antifouling properties. Because the numerous uses of graphene oxide nanosheets often rely on expensive materials, costly facilities, and highly complex synthesis.

At present, numerous methods have been employed to synthesize graphene oxide nanosheets, for example Abedalkader Alkhouzaam et al. in the article titled “Synthesis of graphene oxides particle of high oxidation degree using a modified Hummers method." Ceramics International 46.15 (2020): 23997-24007, discloses a modified Hummers’ method for the synthesis of graphene oxide nanosheets, wherein the method is divided into two groups. In group 1, the reaction was started with 1 gram of graphite in 190 grams of H2SO4 and H3PO4 mixture (9:1 wt.%), making graphite to H2SO4 ratio of 1:170.2 wt.% and graphite to H3PO4 ratio of about 1:19.4 wt.%. This mixture was stirred in an ice bath for several minutes, then after that, it was stirred for 30 minutes at 85°C, followed by the addition of 50 ml DI water. This reaction mixture was stirred at 85°C with three different samples with time intervals of 30, 60, and 90 minutes, followed by the addition of 150 ml DI water and 40 ml H2O2. These mixtures were washed with dilute HCl and proceeded for centrifugation. A similar process was followed for group 2, with changes in the composition. Initially, 1 gram of graphite was added to the 55 grams of H2SO4 and H3PO4 mixture (9:1) while placed in an ice bath. Then, 3 grams of KMnO4 was added to this mixture and stirred in an ice bath for some time. After that, this mixture was heated to 95°C, stirred for 30 minutes, and added 50 ml of DI water. With constant stirring, this mixture was divided into three samples with time intervals of 30, 60, and 90 minutes, followed by the addition of 150 ml DI water and 20 ml H2O2. These mixtures were washed with dilute HCl and proceeded for centrifugation. The resulting samples from both groups were dried in an oven at 80°C for approximately 48 hours (Table 1). The reference emphasized the utility of Raman spectroscopy in characterization of graphene oxides and revealed that the D and G bands provide insights into crystallite size and defect density. The study utilized spectral deconvolution to analyze first-order bands, with results indicating that crystallite sizes ranged from 9 to 24 nm across different samples. The authors noted that the ID/IG ratio is inversely related to crystallite size, supporting the conclusion that variations in this ratio reflect differences in structural quality among the graphene oxide nanosheets analyzed. Moreover, disclosed graphene Oxide nanosheet synthesis method is time consuming, involves a use of high amount of acids and other reactants, requires an equipment set for achieving temperature variation at various stages (for achieving a lower temperature or higher temperature during the reactions) and obtained graphene oxide nanosheets samples are not defect free.

Guillermo Santamaría-Juárez et al. in the article titled "Safer modified Hummers’ method for the synthesis of graphene oxide with high quality and high yield." Materials Research Express 6.12 (2020): 125631, also used Hummers’ method but with slightly different reactant compositions, wherein the synthesis of graphene oxide nanosheets begins with 3 grams of graphite mixed with 18 grams of KMnO4 in a solution of 360 mL of sulfuric acid and 40 mL of phosphoric acid, maintaining a 9:1 volume ratio. The H2SO4 and H3PO4 solution increases the acidity, and with the addition of KMnO4, this becomes a powerful oxidizing agent. To prevent explosions, both mixtures are cooled before being combined. This resulted in a mildly exothermic reaction at 35–40 °C, and the reaction solution turns dark green. The mixture was then heated to 50 °C and stirred continuously for 12 hours. During this process, the solution turns dark brown, which indicates the oxidation of graphite powder into graphite oxide. The reaction mixture was allowed to cool down to an ambient temperature, followed by an addition of 400 mL of ice-cold deionized water to lower the viscosity and control the temperature of the reaction mixture for preventing overheating. To eliminate the excess metal ions, 9 ml of 30% H2O2/DI water was added, which turned the solution bright yellow. Obtained bright yellow solution was centrifuged at 1500 rpm for 1 hour, followed by rinsing with DI water, HCl (30%), and ethanol to remove byproducts. After multiple stages of rinsing and centrifugation, the solution was filtered and vacuum-dried overnight at room temperature.

Xiaodong Chen et al. used Hummers’ method to make graphene oxide nanosheets. The preparation method of graphene oxide starts by dissolving 1 g of sodium nitrate in 70 mL of concentrated H2SO4 under a continuous stirring. Next step was followed in an ice bath at 0–4°C, wherein 2 g of flake graphite was added to the solution and stirred for 30 minutes. After that, 8 grams of potassium permanganate was gradually introduced while maintaining stirring for another 30 minutes. The temperature was raised to 35–45°C, and the mixture was stirred for 300 minutes to complete the oxidation process. Then, 240 mL of deionized water was gradually added, and the mixture was stirred at 65–75°C for another 120 minutes. After 5 minutes of additional heating to 95°C, 25 mL of 30% hydrogen peroxide was added, which caused the solution to turn yellow. It was then stirred for an additional 30 minutes. To remove impurities, 40 mL of 5% hydrochloric acid was mixed and stirred for 30 minutes. The hot mixture was then filtered under a vacuum and extracted. Using the DI water filter, the obtained hot mixture cake was washed and centrifuged multiple times in order to achieve a pH in the range of 5 to 6. At last, to get the graphene oxide powder, the solution was dried using vacuum drying (Table 1). Spectroscopy analysis viz. Raman parameters from Raman spectra such as peak position and Full Width at Half Maximum (FWHM) to assess microstructure of the obtained graphene oxide indicates a D band at 1350 cm-1 which correlates with defects in the graphitic structure, while the G band at 1580 cm-1 relates to sp2 carbon vibrations. The authors also noted significant shifts in D and G bands for graphene oxide, suggesting alterations in lattice symmetry due to oxidation processes. Moreover, the disclosed graphene oxide synthesis method is a time consuming, involves a use of high amount acid and other reactants, requires an equipment set for achieving temperature variation at various stages (for achieving a lower temperature or higher temperature) and obtained graphene oxide lacks purity and have alterations in the lattice symmetry during synthesis.

Marcano et al. in the article titled “Improved synthesis of graphene oxide,” ACS Nano, vol. 4, no. 8, pp. 4806–4814, Aug. 2010, doi: 10.1021/nn1006368 discloses a method for synthesizing graphene oxide nanosheets with interlayer spacings of 9.5 Å, 9.0 Å, and 8.0 Å for IGO, HGO+, and HGO, respectively, with an additional peak at 3.7 Å in the XRD HGO spectrum. Presence of the additional peak at 3.7 Å in the graphene oxide nanosheets (HGO) suggests presence of residual graphite, moreover the obtained nanosheets require further purification process to achieve desirable properties in the graphene oxide nanosheets.

Surekha et al. in the conference proceeding titled “FTIR, Raman and XRD analysis of graphene oxide films prepared by modified Hummers method." Journal of Physics: Conference Series. Vol. 1495. No. 1. IOP Publishing, 2020, disclosed a modified Hummers method for preparing graphene oxide nanosheets and observed a peak at 10.64° (d = 0.817 nm) and a broad peak at 26.3° (d = 0.34 nm) in the XRD diffraction pattern of the graphene oxide. Observed broader peak indicates the presence of unreacted graphite alongside the graphene oxide. In addition, the Raman spectra of graphene oxide (GO) nanosheets, highlights prominent peaks at approximately 1344 cm-1 (D band) and 1597 cm-1 (G band), wherein observed variations in the peak positions correlate with changes in graphene oxide thickness, and wherein a blue shift in the D peak indicates reduction in thickness. Accordingly, the obtained nanosheets contain unreacted graphite.

Moreover, available methods for graphene oxide, and graphene oxide nanosheet synthesis are time consuming, involve the use of a high amount of the acids and other reactants, require an exclusive thermal set up for achieving a temperature variation at various stages (for achieving a lower temperature or higher temperature during the process) of the synthesis, even then the obtained nanosheets lacks purity because of traces of the unreacted graphite and other side reaction products.

Accordingly, there is an urgent need in the art to develop an environment friendly, a safe and an economic, method for synthesis of graphene oxide (GO), and graphene oxide (GO) nanosheets by using low-cost raw materials and facile yet scalable with improved properties to provide commercial advantages.

Accordingly, the present invention discloses a an economic, a safe, a less time taking, an environmentally friendly, a commercially scalable and an energy efficient method for synthesizing graphene oxide and graphene oxide nanosheets at an ambient temperature without using any exclusive thermal energy set up to provide an efficient graphene oxide nanosheet with a high lateral surface area.
OBJECTIVES OF THE PRESENT INVENTION
The primary object of the present invention is to provide an economic, a safe, a less time taking, an environmentally friendly and an energy efficient method for synthesizing graphene oxide at room temperature without using any thermal energy set up.
Another objective of the present invention is to provide an economic, a safe, a less time taking, an environmentally friendly and an energy efficient method for synthesizing graphene oxide without employing any temperature reduction setup, with the least amount of reactant, solvents and other chemical.
Another objective of the present invention is to provide an easy, an economic, and an energy efficient method for synthesizing graphene oxide nanosheets at room temperature without employing any temperature reduction setup, with the least amount of reactant, solvents and other chemicals.
Yet another objective of the present invention is to provide an efficient graphene oxide nanosheet of thickness less than 2 nm and a high lateral surface area.
These and other objects of the present invention will be apparent from the drawings and descriptions herein. Every object of the invention is attained by at least one embodiment of the present invention.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates the X-ray diffraction (XRD) pattern of the graphene oxide nanosheets synthesized with the method for synthesizing graphene oxide nanosheets of the present invention.
Figure 2 illustrates the Raman Spectra of graphene oxide nanosheet as synthesized with the method for synthesis of graphene oxide nanosheets of the present invention.

Figure 3. illustrates (i) the HRTEM (High-resolution transmission electron microscopy), (ii) Selected area electron diffraction (SAED) (iii) Transmission electron microscopy, and (iv) magnified image of GO layers image of graphene oxide nanosheet as synthesized with the method for synthesizing graphene oxide nanosheets of the present invention.

Figure 4 illustrates the FTIR (Fourier transformation Infra-red) spectrum of graphene oxide nanosheet as synthesized with the method for synthesizing graphene oxide the present invention.

Figure 5 illustrates the process flow diagram of the method for synthesizing of graphene oxide nanosheets of the present invention.

Figure 6 illustrates the SEM (Scanning electron microscope) image of graphene oxide nanosheet as synthesized with the method for synthesizing graphene oxide of the present invention.

Figure 7 illustrates the Energy-dispersive X-ray Spectroscopy (EDS) image of graphene oxide nanosheet as synthesized with the method for synthesizing graphene oxide of nanosheet the present invention.

SUMMARY OF THE PRESENT INVENTION
This summary is provided to introduce a selection of concepts in a simplified manner that is described elaborately in detailed description. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended to determine the scope of the invention.
In an aspect of the present invention, there is provided an economic, a safe, a less time taking, an environment friendly and an energy efficient method for synthesizing graphene oxide.
In another aspect of the present invention, there is provided an economic, a safe, a less time taking, an environment friendly and an energy efficient method for synthesizing graphene oxide nanosheets.
In yet another aspect of the present invention, there is provided an efficient graphene oxide nanosheet with a high lateral area.
In one of the preferred aspects, the present invention provides a method for synthesizing graphene oxide, the method comprising: a). adding a graphite source to sulfuric acid (H2SO4) at room temperature ranging from 20 °C to 35 °C followed by a continuous stirring for 1 to 5 hours to obtain a reaction mixture; b). oxidizing the reaction mixture by adding an oxidizing agent to the reaction mixture with the continuous stirring up to completion of an oxidation reaction to obtain a solution mixture; c). quenching the oxidation reaction by adding a deionized water into the solution mixture followed by adding H2O2 to obtain a graphene oxide slurry and a supernatant; and d). collecting the graphene oxide slurry by separating the supernatant.
In another the preferred aspect of the present invention, a method for synthesizing graphene oxide nanosheets, the method comprising: a.) adding a graphite source to sulfuric acid (H2SO4) in a ratio ranging from 1:20 (w/v) to 1:30 (w/v) at a temperature of 20 °C to 35 °C followed by a continuous stirring at a rate of 200-500 rpm for 1 to 5 hours to obtain a reaction mixture; b.) adding an oxidizing agent to the reaction mixture at a rate of 10 grams to50 grams / minutes with the continuous stirring and incubating for 1 to 2 hours to obtain a solution mixture, wherein the oxidizing agent is added to the reaction mixture in a ratio ranging from 1 2 (w/v) to 1:8 (w/v) of the oxidizing agent to sulphuric acid; c.) adding deionized water to the solution mixture in a ratio ranging from 1:40 (w/v) to 1:50 (w/v) of the graphite source to the deionized water, followed by adding H2O2 in a ratio ranging from 1:2 (w/v) to 1:5 (w/v) of the graphite source to H2O2, to obtain a graphene oxide slurry and a supernatant; d.) removing the supernatant and recovering the graphene oxide slurry; e.) washing the graphene oxide slurry with the deionized water followed by washing with an aqueous acidic solution having the deionized water and dilute HCl in a ratio of 1:10, followed by washing with deionized water to obtain a neutral graphene oxide slurry of pH 7, wherein the deionized water is used in a ratio ranging from 1:70 (w/v) to 1:80 w/v) of the graphite source to the deionized water; and f.) exfoliating the neutral graphene oxide slurry by adding the deionized water up to achieving a concentration ranging from 4 mg/ml to 20 mg/ml of the neutral graphene oxide slurry and sonicating said of the neutral graphene oxide slurry at a frequency ranging from 15 to 25KHz, preferably 20KHz followed by mixing at shear rate of 3000 rpm to 8000 rpm to obtain the graphene oxide nanosheets with an interlayer spacing in a range from 0.5 nm to 1.2 nm.
In yet another preferred aspect of the present invention, a graphene oxide nanosheet comprises a single layered graphene oxide nanosheet, wherein the graphene oxide nanosheet is characterized to have a thickness of < 2 nm and a lateral size ranging from 2-15 microns.
DESCRIPTION OF THE INVENTION:
The present disclosure addresses the drawbacks of the art and provides for a method for preparing of graphene oxide nanosheets. Further, the method for preparation of said graphene oxide nanosheets is cost effective, simple, efficient and requires less time as compared to other existing methods.

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, the singular forms "a", "and", and "the" include plural referents unless the context dictates otherwise. Thus, for example, reference to "a compound" includes a plurality of such compounds, and reference to "the step" includes reference to one or more steps and equivalents thereof known to those skilled in the art, and so forth.

The term “some” as used herein is defined as “none, or one, or more than one, or all.” Accordingly, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would all fall under the definition of “some.” The term “some embodiments” may refer to no embodiments or to one embodiment or to several embodiments or to all embodiments. Accordingly, the term “some embodiments” is defined as meaning “no embodiment, or one embodiment, or more than one embodiment, or all embodiments.”

The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the spirit and scope of the claims or their equivalents.

More specifically, any terms used herein such as but not limited to “includes”, “comprises”, “has”, “consists” and grammatical variants thereof is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. The specification will be understood to also include embodiments which have the transitional phrase “consisting of” or “consisting essentially of” in place of the transitional phrase “comprising.” The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim, except for impurities associated therewith. The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed disclosure.

Whether or not a certain feature or element was limited to being used only once, either way it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do NOT preclude there being none of that feature or element, unless otherwise specified by limiting language such as “there NEEDS to be one or more. ” or “one or more element is REQUIRED.”

As used herein, the term “about” is used to indicate a degree of variation or tolerance in a numerical or quantitative value. It indicates that the disclosed value is not intended to be strictly limiting, and may vary by plus or minus 5%, without departing from the scope of the invention.
Unless otherwise defined, all terms, and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having an ordinary skill in the art.

Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements presented in the attached claims. Some embodiments have been described for the purpose of illuminating one or more of the potential ways in which the specific features and/or elements of the attached claims fulfil the requirements of uniqueness, utility and non-obviousness.

Use of the phrases and/or terms such as but not limited to “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or variants thereof do NOT necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or alternatively in the context of more than one embodiment, or further alternatively in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

As used herein the terms “method” and “process” have been used interchangeably. The present application describes a method of preparing graphene oxide nanosheets from artificial graphite using less quantity of chemicals such as H2SO4, KMnO4, H2O2 and deionized H2O. Scalability of the process is also feasible, which is quite safer and less expensive as compared to prior techniques. Graphene oxide nanosheets obtained from this oxidation-reduction/ chemical process is mostly single layer with high solubility in aqueous as well as organic polar solvents along with the comparatively larger lateral size. The method of preparing of the said graphene oxide nanosheets is cost effective, safe, requires less time and environmentally friendly as compared to the prior methods.

In an aspect of the present invention, there is provided an economic, a safe, a less time taking, an environmentally friendly and an energy efficient method for synthesizing graphene oxide.
In another aspect of the present invention, there is provided an economic, a safe, a less time taking, an environmentally friendly and an energy efficient method for synthesizing graphene oxide nanosheets.
In yet another aspect of the present invention, there is provided an efficient graphene oxide nanosheet with high lateral area.
In one of the preferred aspects, the present invention provides a method for synthesizing graphene oxide, the method comprising: a). adding a graphite source to sulfuric acid (H2SO4) at room temperature ranging from 20 °C to 35 °C followed by a continuous stirring for 1 to 5 hours to obtain a reaction mixture; b). oxidizing the reaction mixture by adding an oxidizing agent to the reaction mixture with the continuous stirring up to completion of an oxidation reaction to obtain a solution mixture; c). quenching the oxidation reaction by adding a deionized water into the solution mixture followed by adding H2O2 to obtain a graphene oxide slurry and a supernatant; and d). collecting the graphene oxide slurry by separating the supernatant.
In an aspect of the present invention, the quenching is an exothermic process and raises temperature up to 70 to120 °C of the solution mixture.
In yet another aspect of the present invention, the graphene oxide slurry is washed with a washing agent to obtain a neutral graphene oxide slurry of pH 7, wherein the washing agent is selected from the deionized water, an aqueous acidic solution having the deionized water and an acid in a ratio of 1:10, and a mixture thereof, wherein the deionized water in the washing agent is employed in a ratio ranging from 1:70 (w/v) to 1:80 w/v) of the graphite source to the deionized water.
In still another aspect of the present invention, the graphite source and sulfuric acid (H2SO4) are present in a ratio ranging from 1:20 (w/v) to 1:30 (w/v) in the reaction mixture, wherein the oxidizing agent is added to the reaction mixture a ratio ranging from 1: 2 (w/v) to 1:8 (w/v) of the oxidizing agent to sulphuric acid, wherein the deionized water is added in a ratio ranging from 1:40 (w/v) to 1:50 (w/v) of the graphite source to the deionized water, and wherein the H2O2 is added in a ratio ranging from 1:2 (w/v) to 1:5 (w/v) of the graphite source to H2O2.
In another aspect of the present invention, the oxidizing agent is selected from KMnO4, KMnO4, K2S2O8, K2Cr2O7 and a mixture thereof.
In yet another aspect of the present invention, the acid in the washing agent is HCl.
In still another aspect of the present invention, the oxidation reaction is completed in 1 to 2 hours, and wherein the collected graphene oxide slurry is dried at room temperature under vacuum.
In one of the preferred aspects of the present invention, In another the preferred aspect of the present invention, a method for synthesizing graphene oxide nanosheets, the method comprising: a.) adding a graphite source to sulfuric acid (H2SO4) in a ratio ranging from 1:20 (w/v) to 1:30 (w/v) at a temperature of 20 °C to 35 °C followed by a continuous stirring at a rate of 200-500 rpm for 1 to 5 hours to obtain a reaction mixture; b.) adding an oxidizing agent to the reaction mixture at a rate of 10 grams to 50 grams / minutes with the continuous stirring and incubating for 1 to 2 hours to obtain a solution mixture, wherein the oxidizing agent is added to the reaction mixture in a ratio ranging from 1: 2 (w/v) to 1:8 (w/v) of the oxidizing agent to sulphuric acid; c.) adding deionized water to the solution mixture in a ratio ranging from 1:40 (w/v) to 1:50 (w/v) of the graphite source to the deionized water, followed by adding H2O2 in a ratio ranging from 1:2 (w/v) to 1:5 (w/v) of the graphite source to H2O2, to obtain a graphene oxide slurry and a supernatant; d.) removing the supernatant and recovering the graphene oxide slurry; e.) washing the graphene oxide slurry with the deionized water followed by washing with an aqueous acidic solution having the deionized water and dilute HCl in a ratio of 1:10, followed by washing with deionized water to obtain a neutral graphene oxide slurry of pH 7, wherein the deionized water is used in a ratio ranging from 1:70 (w/v) to 1:80 w/v) of the graphite source to the deionized water; and f.) exfoliating the neutral graphene oxide slurry by adding the deionized water up to achieving a concentration ranging from 4 mg/ml to 20mg/ml of the neutral graphene oxide slurry and sonicating said neutral graphene oxide slurry at a frequency ranging from 15KHz to 25KHz followed by mixing at a shear rate of 3000 rpm to 8000 rpm to obtain the graphene oxide nanosheets.
In an aspect of the present invention, the graphite source is selected from a natural graphite source, an artificial graphite source or a laboratory synthesized graphite source, or a mixture thereof, preferably an artificial graphite source.
In still another aspect of present invention, the exfoliation reduces the neutral graphene oxide slurry, wherein the obtained graphene oxide nanosheets are reduced graphene oxide (rGO) nanosheets with an interlayer space ranging from 0.5 nm to 1.2 nm and have energy storage capacity.
In yet another aspect of present invention, the exfoliation reduces the neutral graphene oxide slurry, wherein the obtained graphene oxide nanosheets are reduced graphene oxide (rGO) nanosheets, and wherein the reduced graphene oxide (rGO) nanosheets have energy storage capacity and are employed for making energy devices, composites and electronic devices.

In one of the preferred aspects of the present invention, the graphene oxide nanosheet is characterized to have a thickness of < 2 nm and a lateral size ranging from 2-15 microns.
In an aspect of the present invention, the graphene oxide nanosheet is dispersible in an aqueous as well as an organic solution, wherein the aqueous solvent is selected from water, deionized water, distilled water and mineral water, and wherein the organic solvent is selected from acetone, ethyl acetate, hexane, heptane, dichloromethane, methanol, ethanol, tetrahydrofuran (THF), acetonitrile (AcN), dimethylformamide (DMF), toluene, and dimethylsulfoxide (DMSO).
In an aspect of the present invention, the graphene oxide nanosheets are cost effective, safer, and environmentally friendly as the graphene oxide nanosheets are dispersible in the aqueous as well as the organic medium.
In an aspect of the present invention, the graphene oxide nanosheet is a reduced graphene oxide (rGO) nanosheet and has an energy storage capacity and are employed for making energy devices, composites and electronic devices.

EXAMPLES:
The present disclosure is further illustrated by reference to the following examples which is for illustrative purpose only and does not limit the scope of the disclosure in any way. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representative features, methods, compositions, and results. These examples are not intended to exclude equivalents and variations of the present disclosure, which are apparent to one skilled in the art.

Example 1: Preparing of graphene oxide nanosheets
10 grams of an artificial graphite was added in 230 ml of H2SO4 at normal room temperature (25 to 35 °C) in a glass vessel and the reaction mixture was stirred continuously, wherein the step skips any requirement of reaction being carried out at a reduced temperature of 0 – 10 Degrees Celsius for which an additional and an expensive temperature set-up is required. During stirring of the reaction mixture (Graphite + H2SO4), 40 grams of KMnO4 was introduced into the mixture at very low rate i.e. 10 grams to 50 grams per minutes to obtain a solution mixture. Once addition of KMnO4 is completed, the solution mixture was turned green from black. The mixture was further stirred for approximately 90-120 minutes, until the colour of the mixture turns into dirty pink from green. In the next step, reaction was quenched using 450 ml of deionized water followed by the addition of 30 ml of H2O2, and in the subsequent step the reaction mixture was incubated up to achieving a golden-yellowish colour in the reaction mixture. The quenching step raised temperature of reaction mixture up to 70 to 120 °C. After, a while supernatant was discarded, and a graphene oxide slurry was obtained. The graphene oxide slurry was washed using 750 ml of deionized water and 1:10 aqueous HCl solution. Further washing of graphene oxide slurry is carried out until pH value of 7 was achieved. Graphene oxide slurry obtained with neutral pH 7 was further exfoliated by adding deionized water into the slurry and sonication at a frequency ranging from 15KHz to 25KHz, followed by a high shear mixing at rate of 3000 rpm to 8000 rpm to get graphene oxide nanosheets.

Table 1. Comparison of GO Nanosheet Synthesis Methods (Chemicals used per gram of graphite)

SN Oxidant Acid Additional
Oxidant H2O2 Reaction Time (in hours) Reference
1 9.4 grams KMnO4 170 grams H2SO4 + 19.4 H3PO3 -- 20 ml 2 h + 48 h drying-1st step [01]
2 3 grams KMnO4 43.64 grams H2SO4 + 11.17 grams H3PO4 -- 20 ml 2 h + 48 h drying-2nd step [01]
3 6 grams KMnO4 120 ml H2SO4 + 13.3 ml H3PO4 -- 3 ml > 12 hours + overnight drying [02]
4 4 g KMnO4 35 ml H2SO4 0.5 g NaNO3 12.5 ml > 9 hours [03]
5 6 g KMnO4 120 ml H2SO4 + 13.3 ml H3PO4 10 ml 12 hours +overnight drying [04]
6 3 g KMnO4 12.5 ml HF (graphite purification) + 22.5 ml H2SO4 0.5 g NaNO3 1.5 ml >3 hours + 24 hours drying [05]
7 4 g KMnO4 40 ml H2SO4 6 g H3BO3 3 ml 18 hours-1st step [06]
8 4 g KMnO4 40 ml H2SO4 3 g H3BO3 + 2 g NaNO3 3 ml 1 hour-2nd step [06]
9 3.6 g KMnO4 66.7 ml H2SO4 1 ml >12 hours [07]
10 4 g KMnO4 23 ml H2SO4 -- 3 ml >2 hours Present Invention

Method comparison under Table 1, clearly reveals that the methods of synthesis of the graphene oxide and graphene oxide nanosheet of the present invention is an economic, a safe, a less time taking, an environmentally friendly and an energy efficient.
Example 2: Characterization of graphene oxide nanosheets
The synthesized graphene oxide nanosheets are characterized by X-ray diffraction (P-XRD), Raman Spectroscopy, Transmission electron microscopy (TEM) and Fourier – transform infrared spectroscopy (FTIR).

X-ray diffraction:
The X-ray diffraction (XRD) pattern of graphene oxide (GO) nanosheet synthesized in the present invention is presented in Figure 1. A prominent (001) peak observed at 2? = 10.1° corresponds to an interlayer spacing (d001) of 0.868 nm, calculated using below mentioned Bragg’s equation (Equation 1).
n?=2d sin? Equation 1
where n is the order of diffraction, an integer (usually n = 1 for simplicity), ? is the wavelength of the incident X-ray beam, d is the interplanar spacing between crystal planes, and ? is the angle of incidence (or Bragg angle) at which constructive interference occurs. For the studying the XRD pattern of the graphene oxide (GO) nanosheet of the present invention, the X-ray beam having wavelength 1.5406 Å was employed. Observed expanded interlayer spacing of 0.868 nm is an indicative of successful oxidation, resulting in the incorporation of oxygen-containing functional groups and water molecules between the graphene oxide layers. The disruption of van der Waals forces due to oxidation contributes to the increased layer-to-layer distance, a characteristic feature of the synthesized graphene oxide nanosheets of the present invention. Such structural modifications are essential for improving the hydrophilicity and functionality of graphene oxide nanosheet for various applications.
The crystallite height (Lc) of GO nanosheet was determined using the Debye-Scherrer equation (Equation 2):
D=K?/ßcos? Equation 2
where the Scherrer constant (K) was set to 0.89, a standard value for layered materials like GO nanosheet, D is crystallite size for particular miller indices. The ß is full width at half maximum (FWHM) for the (001) peak (10.15°), and its value was 1.335°. The (001) peak was used to determine crystallite height (Lc) in layered materials i.e. graphene oxide nanosheets of the present invention. It was employed to estimate the crystallite size, reflecting the coherence length along the stacking direction. The calculated crystallite size was 5.9 nm. Additionally, a broad peak observed at around 2? = 20.1° is indicative of an increase in order within the structure of the neutralized graphene oxide nanosheets (H2O-washed GO sample). This peak corresponds to the presence of partially re-aggregated graphene oxide sheets after washing.
The changes in the XRD pattern from graphite, particularly the shift in the 2? angle from nearly 26.6° (002) to peak at 10.1° (001), are directly associated with the oxidation reaction. During the process, the oxidizing agent (i.e. KMnO4) acts as an intercalating agent, while concentrated H2SO4 oxidizes the graphite structure, allowing oxygen-containing functional groups and water molecules to insert between the graphite layers. This intercalation significantly increases the interlayer distance, leading to the formation of the graphite oxide. The subsequent exfoliation process further separates these layers, resulting in the formation of graphene oxide nanosheets with an expanded d-spacing of 0.868 nm. The observed structural changes confirm the extent of oxidation and intercalation achieved during the reaction.
The Graphene oxide nanosheets shows a wide peak around 2? = 20 -27° corresponds to 002 plane with d spacing of 8.68 ?. This increase in d spacing of the graphene oxide is due to the intercalation of ions between graphene oxide nanolayers.

Raman Spectroscopy:
This technique is very fast and non-destructive technique having high resolutions, which is used for characterization of carbon material for the parameters like sp3 hybridized carbon content, sp2 hybridized carbon content and defects states present within the material.
Graphene oxide nanosheet obtained from this invention exhibits G band around 1587cm-1 and D band around 1358 cm-1.
Raman spectroscopy is a versatile and non-destructive tool for studying the vibrational properties of materials, offering insights into structural characteristics, defects, and bonding. The positions of peaks in Raman spectra can shift due to external or intrinsic factors, which are commonly categorized as redshift or blueshift. A redshift refers to the movement of Raman peaks to lower wavenumbers and often occurs due to tensile strain, increased functionalization, or interaction with external molecules. Conversely, a blueshift, where peaks shift to higher wavenumbers, is typically attributed to compressive strain or reduced interlayer interactions in the material.
For carbon-based layered materials, Raman spectra exhibit characteristic bands such as D, G, 2D, and D+G bands, each corresponding to distinct vibrational phenomena. The D-band, observed between 1330–1350 cm?¹, originates from the breathing modes of sp² carbon rings and is activated by structural defects. The G-band, typically located between 1580–1600 cm?¹, arises from E2g phonon vibrations at the Brillouin zone center, indicative of sp² hybridized carbon atoms. The 2D-band, centered around 2700 cm?¹, is the second-order overtone of the D-band and provides information on the number of layers and the stacking order. The D+G band, observed at ~2900 cm?¹, results from the combination of D- and G-band vibrations and is also associated with structural disruptions.
In the Raman spectrum of the GO nanosheets of the present invention, the D-band was located at 1350 cm?¹, while the G-band was at 1591 cm?¹. The slight redshift was observed in the G-band, which is an indicative of oxidation and increased functionalization of the graphitic sheets. Obtained intensity ratio I?/I? ˜ 1.018 indicated a substantial degree of oxidation. The 2D-band, observed at 2685 cm?¹, was broader and of low intensity, which reflects a disrupted p-p stacking and reduced graphitic order. Additionally, the D+G band at 2880 cm?¹, with low intensity, further corroborated the presence of defects and oxygenated functional groups.
The subsequent analysis will summarize findings from various studies that employed Raman spectroscopy to investigate GOs.

Infrared spectroscopy (IR):
Fourier-transform infrared spectroscopy (FTIR) technique has been used to study the functional groups present by the graphene oxide and graphene oxide nanosheet of the material. Graphene oxide nanosheets contains various functional groups such as carbonyl, carboxylic, epoxy and hydroxyl group as depicted in the FTIR spectra.

The Fourier Transform Infrared Spectroscopy (FTIR) analysis of Graphene Oxide (GO) nanosheet is presented in Figure 2. The FTIR spectrum of the prepared graphene oxide nanosheets of the present invention revealed an introduction of oxygen-containing functional groups into the graphene structure as a result of the oxidation of the graphite. Said structural transformation was further confirmed through the observation of characteristic peaks corresponding to various functional groups.
The FTIR spectrum of the graphene oxide nanosheets exhibited a broad peak between 2500 cm?¹ and 3300 cm?¹, which was attributed to the O-H stretching vibrations of carboxylic acid groups. This peak overlaps with the O-H stretching vibration of alcohol groups, which appears in the region of 3200 cm?¹ to 3600 cm?¹. The overlap indicates the presence of hydrogen-bonded hydroxyl and carboxylic groups, which are characteristic of a highly oxidized graphene oxide surface. A peak was located around 1350 cm-1, which was assigned to O-H bending vibrations. A prominent sharp peak at approximately 1720 cm?¹ was observed, which was assigned to the stretching vibrations of carbonyl (C=O) groups. Another sharp peak around 1620 cm?¹ was noted, which corresponds to the stretching vibrations of unoxidized sp²-hybridized carbon atoms. This peak signifies the presence of aromatic domains within the GO structure, representing the sp² carbon network that remains after oxidation. Additionally, a peak around 1040 cm?¹ was detected, which is characteristic of the stretching vibrations of C-O single bonded groups.
The FTIR spectrum of graphene oxide (GO) nanosheets confirms the presence of various oxygen-containing functional groups that contribute to its hydrophilic properties and reactivity. Key peaks include O-H stretching vibrations (~3200–3600 cm?¹), indicative of hydroxyl and carboxylic acid groups; C=O stretching (~1720 cm?¹), associated with carboxyl functionalities; aromatic C=C stretching (~1620 cm?¹), representing sp²-hybridized carbon domains; and C-O stretching (~1040 cm?¹), linked to epoxy and alkoxy groups. These functional groups facilitate effective dispersion in water and other polar solvents, making Graphene Oxide nanosheets highly hydrophilic. These functional groups play critical role in some of the applications where the material is needed to be mixed with water/non-aqueous solvent with stability such as concrete and paints.
Transmission electron microscopy (TEM):
TEM micrographs shown in the figure represents that the synthesized graphene oxide nanosheets are very thin (few layer) with sheet like morphology. HRTEM image also confirms the few layered structure as analysed by the corners of the sheets.
The HRTEM image of the graphene oxide nanosheet sample of the present invention (Fig. 3b(i)) shows a lattice spacing of approximately 0.7 nm, typical of oxidized graphene layers. The selected area electron diffraction (SAED) pattern (Fig. 3b(ii)) confirms the polycrystalline nature of the sample, with slightly diffuse rings indicating randomly oriented crystalline domains. Figure 3b(iii) reveals that the number of layers in the sample ranges from 4 to 5.
The occurrence of well-ordered single-crystalline diffraction is typically attributed to a more regular carbon framework within the graphene oxide nanosheet structure.
SEM Analysis:
The SEM image (Figure 6) of the synthesized graphene oxide nanosheets of the present invention showed a wrinkled structure with a visible layered arrangement, characteristic of oxidized graphene-based materials. These features result from layer expansion and exfoliation caused by oxidation. The observed morphology highlight’s introduction of functional groups during the modified improved Hummers Method, distinguishing graphene oxide from artificial graphite.
Studies have shown that oxidized graphene-based materials exhibit a wrinkled morphology with visible layered arrangements due to layer expansion during oxidation. The modified Improved Hummers Method leads to the destruction of graphite's laminated structure and graphene oxide delamination.
Highly wrinkled, exfoliated sheet-like structures and separated graphitic layers with oxygen-containing functional groups are attributed to high oxidation levels.
Energy-dispersive X-ray Spectroscopy (EDS) Analysis:
EDS is a widely used analytical technique for determining the elemental composition of materials. In the case of graphene oxide (GO) nanosheet, EDS spectra is essential for identifying the presence and proportions of key elements like carbon (C) and oxygen (O), which confirm the successful synthesis and level of oxidation of the material. By analysing the relative intensities of carbon and oxygen peaks, the degree of functionalization with oxygen-containing groups can be evaluated. Additionally, EDS helps detect trace impurities that may arise from the synthesis process or external factors.
The EDS spectrum of the synthesized graphene oxide nanosheet sample of the present invention primarily showed strong peaks for carbon and oxygen, which aligns with its expected composition. Carbon is the dominant element (56.59 wt.%), followed by oxygen (40.68 wt. %), resulting in a calculated C:O ratio of ~1.4. This ratio indicates significant oxidation and the successful introduction of oxygen-containing functional groups into the carbon lattice. A minor platinum peak (2.74 wt. %) is observed due to the sputter coating applied during sample preparation. These findings align well with previous studies, which reported similar compositions, such as 56.2 wt. % C and 42.90 wt. % O and 60 wt. % C and 37 wt. % O. The absence of detectable impurities further confirms the high purity of the synthesized GO nanosheet sample.
Advantage of the present invention over existing solutions:
a. Artificial graphite powder is used as a preferable feedstock.
b. Less acid used in the process of synthesis of the graphene oxide and the graphene oxide nanosheets.
c. The method for synthesizing the graphene oxide and the graphene oxide nanosheets involve lesser reaction time.

Reference:
Alkhouzaam, Abedalkader, et al. "Synthesis of graphene oxides particle of high oxidation degree using a modified Hummers method." Ceramics International 46.15 (2020): 23997-24007.
Santamaría-Juárez, Guillermo, et al. "Safer modified Hummers’ method for the synthesis of graphene oxide with high quality and high yield." Materials Research Express 6.12 (2020): 125631.
Chen, Xiaodong, et al. "Mechanism of oxidization of graphite to graphene oxide by the hummers method." ACS omega 7.27 (2022): 23503-23510.
Marcano, Daniela C., et al. "Improved synthesis of graphene oxide." ACS nano 4.8 (2010): 4806-4814.
Surekha, G., et al. "FTIR, Raman and XRD analysis of graphene oxide films prepared by modified Hummers method." Journal of Physics: Conference Series. Vol. 1495. No. 1. IOP Publishing, 2020.
Zhang, Qiang, et al. "Synthesis of graphene oxide using boric acid in hummers method." Colloids and Surfaces A: Physicochemical and Engineering Aspects 652 (2022): 129802.
V C Jayawardena, D R Jayasundara, G Amaratunga, V Jayaweera, Method for the synthesis of graphene oxide, 2019-07-02, US20180029887A1. [Online]. Available: https://patents.google.com/patent/US20180029887A1/en#patentCitations ,CLAIMS:1. A method for synthesizing graphene oxide, the method comprising:
a. adding a graphite source to sulfuric acid (H2SO4) at a room temperature ranging from 20 °C to 35 °C, followed by a continuous stirring for 1 to 5 hours to obtain a reaction mixture;
b. oxidizing the reaction mixture by adding an oxidizing agent to the reaction mixture with the continuous stirring up to completion of an oxidation reaction to obtain a solution mixture;
c. quenching the oxidation reaction by adding a deionized water into the solution mixture followed by adding H2O2 to obtain a graphene oxide slurry and a supernatant; and
d. collecting the graphene oxide slurry by separating the supernatant.
2. The method as claimed in claim 1, wherein the graphene oxide slurry is washed with a washing agent to obtain a neutral graphene oxide slurry of pH 7, wherein the washing agent is selected from deionized water, an aqueous acidic solution having deionized water and an acid in a ratio of 1:10, and a mixture thereof, wherein the acid is HCl, and wherein the deionized water in the washing agent is employed in a ratio ranging from 1:70 (w/v) to 1:80 w/v) of the graphite source to the deionized water.
3. The method as claimed in claim 1, wherein the graphite source and sulfuric acid (H2SO4) are present in a ratio ranging from 1:20 (w/v) to 1:30 (w/v) in the reaction mixture, wherein the oxidizing agent is added to the reaction mixture a ratio ranging from 1:4 (w/v) to 1:8 (w/v) of the oxidizing agent to sulphuric acid, wherein the deionized water is added in a ratio ranging from 1:40 (w/v) to 1:50 (w/v) of the graphite source to the deionized water, and wherein the H2O2 is added in a ratio ranging from 1:2 (w/v) to 1:5 (w/v) of the graphite source to H2O2.
4. The method as claimed in claim 1, wherein the oxidizing agent is selected from KMnO4, K2S2O8, K2Cr2O7and a mixture thereof.
5. The method as claimed in claim 1, wherein the oxidation reaction is completed in 1 to 2 hours, and wherein the collected graphene oxide slurry is dried at room temperature under vacuum.
6. A method for synthesizing graphene oxide nanosheets, the method comprising:
a.) adding a graphite source to sulfuric acid (H2SO4) in a ratio ranging from 1:20 (w/v) to 1:30 (w/v) at a temperature of 20 °C to 35 °C followed by a continuous stirring at a rate of 200-500 rpm for 1 to 5 hours to obtain a reaction mixture;
b.) adding an oxidizing agent to the reaction mixture at a rate of 10 grams to 50 grams per minutes with the continuous stirring and incubating for 1 to 2 hours to obtain a solution mixture, wherein the oxidizing agent is added to the reaction mixture in a ratio ranging from 1:2 (w/v) to 1:8 (w/v) of the oxidizing agent to sulphuric acid;
c.) adding deionized water to the solution mixture in a ratio ranging from 1:40 (w/v) to 1:50 (w/v) of the graphite source to the deionized water, followed by adding H2O2 in a ratio ranging from 1:2 (w/v) to 1:5 (w/v) of the graphite source to H2O2, to obtain a graphene oxide slurry and a supernatant;
d.) removing the supernatant and recovering the graphene oxide slurry;
e.) washing the graphene oxide slurry with the deionized water followed by washing with an aqueous acidic solution having the deionized water and dilute HCl in a ratio of 1:10, followed by washing with deionized water to obtain a neutral graphene oxide slurry of pH 7, wherein the deionized water is used in a ratio ranging from 1:70 (w/v) to 1:80 w/v) of the graphite source to the deionized water; and
f.) exfoliating the neutral graphene oxide slurry by adding the deionized water up to achieving a concentration ranging from 4 mg/ml to 20 mg/ml of the neutral graphene oxide slurry, and sonicating said neutral graphene oxide slurry at a frequency ranging from 15KHz to 25KHz followed by mixing at shear rate of 3000 rpm to 8000 rpm to obtain the graphene oxide nanosheets.
7. The method as claimed in claim 6, wherein the exfoliation reduces the neutral graphene oxide slurry, wherein the obtained graphene oxide nanosheets are reduced graphene oxide (rGO) nanosheets with an interlayer space ranging from 0.5 nm to 1.2 nm and have energy storage capacity.
8. The method as claimed in claim 1 or claim 6, wherein the graphite source is selected from a natural graphite source, an artificial graphite source or a laboratory synthesized graphite source, or a mixture thereof, preferably an artificial graphite source.
9. A graphene oxide nanosheet comprises a single layered graphene oxide nanosheet, wherein the graphene oxide nanosheet characterized to have a thickness of < 2 nm and a lateral size ranging from 2-15 microns.
10. The graphene oxide nanosheet as claimed in claim 9, wherein the graphene oxide nanosheet is dispersible in an aqueous as well as an organic solvent, wherein the aqueous solvent is selected from water, deionized water, distilled water and mineral water, and wherein the organic solvent is selected from acetone, ethyl acetate, hexane, heptane, dichloromethane, methanol, ethanol, tetrahydrofuran (THF), acetonitrile (AcN), dimethylformamide (DMF), toluene, and dimethylsulfoxide (DMSO), and wherein the graphene oxide nanosheet is a reduced graphene oxide (rGO) nanosheet and has an energy storage capacity.