Claims:WE CLAIM:
1. A novel process of preparing anthraquinone modified grapheneflakes with maximum coverage, high purity and higher yield in a solvent free method by surface functionalization of anthraquinone at graphene flakes, for use in various electrochemical sensors and energy storage applications, the claimed process comprises of following steps:

a. Solvent assisted exfoliation of graphite to form high surface, less defective and higher length graphene flakes and
b. Surface functionalization of the said graphene flakes with anthraquinone by high energy ball milling method to form anthraquinone modified grapheneflakes.

2. A novel process of preparing anthraquinone modified grapheneflakes with maximum coverage, high purity and higher yield by surface functionalization of anthraquinone at graphene flakes, for use in various electrochemical sensors and energy storage applications, the claimed process comprises of following steps:

a. Solvent assisted exfoliation of graphite comprising of dispersing 100 mg of graphite powder in 30 ml NMP followed by sonication for 12 hrs to form high surface, less defective and higher length graphene flakes and
b. Surface functionalization of the said graphene flakes with anthraquinone by high energy ball milling method comprising of incorporating equal amounts of diazonium salt of anthraquinone and the said graphene flakes by high energy ball milling method to form anthraquinone modified grapheneflakes wherein the formed anthraquinone modified grapheneflakes was isolated and washed many times with cold water and ethanol to remove unwanted products.

3. An anthraquinone modified grapheneflakes prepared by the process as claimed in claim 1 and 2.

4. An electrode prepared from anthraquinone modified graphene flakes of claim 3 for electrochemical detection of dopamine in biological samples at lower detection limits and greater sensitivity wherein oxidation peak of dopamine shall not overlap with oxidisablebiological molecules thereby eliminating interference effects faced in detection of dopamine in anodic electrochemical oxidation process.

Dated this 18th day of March 2020

For UNIVERSITY OF MADRAS
By its Patent Agent

Dr.B.Deepa
, Description:Form 2

THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“SURFACE FUNCTIONALISATION OF ANTHRAQUINONE AT GRAPHENE FLAKES BY BALL MILLING TO DEVELOP AN ELECTROCHEMICAL SENSOR FOR DOPAMINE”

in the name of UNIVERSITY OF MADRAS an Indian National having address at Dept of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai-600 025, Tamil Nadu, India.

The following specification particularly describes the invention and the manner in which it is to be performed
FIELD OF THE INVENTION:
The present invention relates to the field of electrochemistry. More particularly the present invention relates to a novel process of preparing anthraquinone modified graphene flakes and products thereof for use in various electrochemical sensors and energy storage applications.

BACKGROUND OF THE INVENTION:
Functionalization of graphite is important for using in electrochemical application. There are various methods available for the functionalization of graphite. Directelectrochemical method is adapted to synthesis anthraquinone functionalised graphene for energy storage applications. Ferrocene modified graphene is also synthesised by electrochemical method. Both chemical and electrochemical method can be applied for the functionalization of graphene. However the availablemethod poses various drawbacks as it demands utilization of solvents and low yield thereby making the method expensive and inefficient. Thus there exists a need in the state of art to develop a novel method for Functionalization of graphite which is devoid of above said drawbacks.

OBJECTIVE OF THE INVENTION:
The main objective of the present invention is to develop a novel process of preparing anthraquinone modified graphene flakes for use in various electrochemical sensors and energy storage applications.
Another objective of the present invention is to functionalise graphene flakes by a surfactant assisted exfoliation method being to obtain high coverage of anthraquinone at GNF by ball milling based C-C bond forming reaction.
Yet another objective of the present invention is to characterize the anthraquinone functionalise graphene flakes by various instrumental methods like FT-IR, Raman, TGA, SEM and XPS studies
Further objective of the present invention is to exploit the anthraquinone functionalised graphene flakes for the electrochemical detection of dopamine with greater sensitivity.

BRIEF DESCRIPTION OF DRAWINGS:
Figure 1 depicts the schematic representation of surface modification of graphene flakes.
Figure 2 depicts A) FE-SEM images of GNF-AQ, B) EDAX image of GNF-AQ, C) XRD spectra of a) GNF, and b) GNF-AQ, D) Raman Spectra of a) GNF, and b) GNF-AQ
Figure 3A) depicts the Nyquist plots of a) bare GCE, b GNF/GCE, and c) GNF-AQ in the presence of 10 mM [Fe(CN)6]3-/4- containing 0.1 M KCl as the supporting electrolyte. AC Amplitude: 5 mV; Frequency range: 0.01 Hz to 100 kHz. Inset: Randles equivalent circuit. B)CV behaviour of a) bare GCE, b) GNF-AQ in the presence of 10 mM [Fe(CN)6]3-/4- containing 0.1 M KClsolution recordedat a scan rate of 50 mV•s-1. C) Cyclic voltammogramsbehaviour of a) bare/GCE, b)GNF/GCE3, c) 3.3 × 10-4 M of DA on GCE, and d)GNF-AQin the presence of 3.3 × 10-4 M of DA with 0.1 M phosphate buffer solution (pH 7.0) at a scan rate of 50 mV·s-1. D) Cyclic voltammograms of 3.3 × 10-4 M of DA on the GNF-AQin 0.1 KCl containing PB (pH 7.0) at the different scan rates of 10 - 330 mV.s-1/2.
Figure 4A)depcits thedifferentail pulse voltammograms of DA with different concentrations on the GNF-AQin 0.1 KCl containing PB (pH 7.0) and the concentrations ranges from 0.3 × 10-6 M to 5.3 × 10-5 M. Inset Calibration plot of the Ip vs. Conc. of DA. B) Amperometric response of GNF-AQupon successive addition of 10 µM of DA, and other interfering chemicals to 0.1 M KCl containing PB (pH 7.0). The applied potential for DA is 0.1 V, respectively. C) Amperometric response of GNF-AQat an applied potential 0.1 V to subsequent addition of different concentrations ranges from of 0.6 x 10-6 to 13 x 10-6M of DA in the presence of 0.1 M KCl containing PB (pH 7.0). D) Plot of Ipc vs. Conc. of DA.

SUMMARY OF THE INVENTION:
The present invention disclose a novel process of preparing anthraquinone modified graphene flakes with maximum coverage, high purity and higher yield in a solvent free method by surface functionalization of anthraquinone at graphene flakes, for use in various electrochemical sensors and energy storage applications. The process of the present invention comprises (i) Solvent assisted exfoliation of graphite to form high surface, less defective and higher length graphene flakes and (ii) Surface functionalization of the graphene flakes with anthraquinone by high energy ball milling method to form anthraquinone modified graphene flakes.

DETAILED DESCRIPTION OF THE INVENTION:
The present invention relates to a novel process of preparing anthraquinone modified graphene flakes and products thereof for use in various electrochemical sensors and energy storage applications.
In the present work, we have demonstrated the surfactant mediated exfoliation of graphite to produce a high surface less defective higher length graphene flakes and it can be used for various electrochemical sensor applications. In the present work we are interested to incorporate redox active molecules like 2-aminoanthraquione through diazonium salt method based on ball milling. By this approach we obtained a high coverage of redox active molecules in a solvent free method. The anthraquinone functionalised graphene flakes modified electrodes can be used for the electrochemical detection of dopamine in biological samples at lower detection limits
The present invention discloses a two-step method to prepare high yield anthraquinone functionalised graphene flakes. In the first step, exfoliation of high surface area graphene flakes by surfactant assisted exfoliation of graphite and the surface functionalisation with anthraquinone can be achieved by high energy ball milling method in which both diazonium salt of anthraquinone and graphene flakes were placed in a ball. Under optimised experimental condition, we are getting maximum coverage of anthraquinone modified graphene sheet in a large scale production. The coverage and surface modification of anthraquinone at graphene sheet was confirmed by various spectroscopic and microscopic methods. The electrochemical behaviour of the redox active molecules modified graphene was measured by electrochemical impedance and cyclic voltammetry methods.
The anthraquinone functionalised graphene sheet can be utilised as surface modification of GCE and showing excellent 2e and 2H transfer reaction. The functionalised electrode can be used for the electrochemical detection of dopamine. Dopamine is considered as one of neurotransmitter and the deficiency of dopamine in biological system is associated with various diseases like alzheimer’s and Parkinson. Also the quality meat can be assured by measuring the concentration level of dopamine in tissues. Hence it is important issue to develop a sensor for the quantitative detection of dopamine in biological samples. Among various analytical techniques, electrochemical method is considered to be simple and high accuracy for the quantitation detection of dopamine. Various electrochemical methods have been proposed for the quantitative detection of dopamine in biological samples.
Usually electrochemical detection of dopamine is failed due to overlapping of the oxidation peak of dopamine with ascorbic acid and uric acid. It is difficulty to resolve the oxidation peak of all these molecules. In the present method solve this issue and discriminate the oxidation peak position of dopamine with other two molecules. Hence the proposed method has some advantage for the quantitative detection of dopamine in biological samples.
Synthesis of graphenenanoflakes: 100 mg of graphite powder was dispersed in 30 ml NMP and then sonicated for 12hr.Then subsequently the diazonium salt of 2-anthraquinone was prepared by conventional method. The reductive addition of anthraquinone onto graphene flakes was carriedout by ball milling approach.
The resulting anthraquinone functionalized graphene flakes was isolated and washed many times with cold water and ethanol to remove the unwanted products. Finally the product was characterized with various instrumental techniques including FT-IR, XRD, Zeta potential studies, SEM and TEM studies.
Detailed studies have been made to understand the surface coverage of anthraquinone on graphene flakes and electrochemical chemical characteristics. Further the anthraquinone modified graphene flakes can be utilized for the electrochemical oxidation of dopamine as marker for various diseases. The schematic representation of surface modification of graphene flakes is shown in Fig.1.
Graphenenanoflakes with a few layered are formed by NMP exfoliation method. Also reveals the morphology of GNF can be found from FE-SEM studies (Fig.2A). From Fig. 2B the elemental composition of GNF can be calculated and inferred that 10% of oxygen counted. X-ray diffraction (Fig. 2B) results reveal that subsequent modification of AQ and the intense peak at 2? value of 26.40 corresponds to the plane of (002).From Fig. 2D depicted the Raman pattern of GNF before and after modification with AQ, additionally the intensity of G band is higher than D band corresponds to low-defect content.
The basic electrochemical behaviour of anthraquinone modified graphene flakes was confirmed by cyclic voltammetry and electrochemical impedance studies to study the interfacial electron transfer behaviour in phosphate buffer medium (Fig. 3A). FromFig. 3B the redox probe can be explain about facile and enhanced electron transfer process. The electrochemical oxidation of dopamine was investigated in both bare graphene flakes and anthraquinone modified graphene by cyclic voltammetry method in phosphate buffer medium (Fig. 3C). Figure.3D inferred the effect of scan rate on the redox reaction of GNF modified AQ and increasing potential scan rate reveals that the surface adsorption process.
Differential pulse voltammetry method was exploited for the sensitive detection of dopamine (Fig.4A). Amperometry method was employed to selective detection of dopamine in presence other oxidisable biological molecules like ascorbic acid and uric acid which are the major interfering moleculesin anodic electrochemical oxidation process overlapping with the oxidation potential of dopamine(Fig.4B). Hence it is not possible to resolve the oxidation peak potential of individual molecules in usual electrochemical methods nevertheless the present method is adopted to eliminate the interference of other two oxidisable molecules and it can be possible to measure the exact concentration of dopamine in biological samples.

To conclude :
A uniform size graphene flakes was synthesised by surfactant assisted exfoliation method. The attachment of anthraquinone can be accomplished by subsequent ball milling method by mixing of an equal quantity of diazonium salt of anthraquinone and graphene flakes.Optimisation of experimental condition like quantity of anthraquinonediazonium salt. graphene flakes and rotation speed ball and milling time.
Anthraquinone functionalised graphene flakes was characterised by using various analytical instruments to study the coverage and electrochemical behaviour of modified graphene and nature of binding.
The basic electrochemical behaviour of anthraquinone modified graphene flakes was confirmed by cyclic voltammetry and electrochemical impedance studies to study the interfacial electron transfer behaviour in phosphate buffer medium.The electrochemical oxidation of dopamine was investigated in both bare graphene flakes and anthraquinone modified graphene by cyclic voltammetry method in phosphate buffer medium.
For high sensitive electrochemical detection of biological important molecules with well resolved peak to peak separation was noted. By this method it is possible to measure the concentration of individual molecules by using differential pulse voltammetry.
In one of the preferred embodiment the present invention shall disclose a novel process of preparing anthraquinone modified graphene flakes with maximum coverage, high purity and higher yield in a solvent free method by surface functionalization of anthraquinone at graphene flakes, for use in various electrochemical sensors and energy storage applications. The process of the present invention comprises of following steps:
a. Solvent assisted exfoliation of graphite to form high surface, less defective and higher length graphene flakes and
b. Surface functionalization of the graphene flakes with anthraquinone by high energy ball milling method to form anthraquinone modified graphene flakes.
In another preferred embodiment the present invention shall disclose a novel process of preparing anthraquinone modified graphene flakes with maximum coverage, high purity and higher yield by surface functionalization of anthraquinone at graphene flakes, for use in various electrochemical sensors and energy storage applications. The process of the present invention comprises of following steps:
a. Solvent assisted exfoliation of graphite comprising of dispersing 100 mg of graphite powder in 30 ml NMP followed by sonication for 12 hrs to form high surface, less defective and higher length graphene flakes and
b. Surface functionalization of the graphene flakes with anthraquinone by high energy ball milling method comprising of incorporating equal amounts of diazonium salt of anthraquinone and the graphene flakes by high energy ball milling method to form anthraquinone modified graphene flakes in which the formed anthraquinone modified graphene flakes was isolated and washed many times with cold water and ethanol to remove unwanted products.
In yet another preferred embodiment the present invention shall disclose an anthraquinone modified graphene flakes prepared by the above described process.
In further preferred embodiment, the present invention shall disclose an electrode prepared from anthraquinone modified graphene flakes for electrochemical detection of dopamine in biological samples at lower detection limits and greater sensitivity in which oxidation peak of dopamine shall not overlap with oxidisable biological molecules thereby eliminating interference effects faced in detection of dopamine in anodic electrochemical oxidation process.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.