The present disclosure relates generally to graphene oxide quantum dots. More specifically, the disclosure provides a process for synthesis of graphene oxide quantum dots from potato paste using an alkaline medium. The disclosure also provides the graphene oxide quantum dots prepared by the process.
BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art. [0003] It is well known that, carbon and its allotropes have a vast range of applications, such as biomedical, reinforcement of composites, electronics circuit, and energy storage applications. It has also been observed that carbon and its derivatives are highly effective in the quantum dot range, because the surface to volume ratio dramatically increases and the band structure can be tuned in presence of heteroatoms. Among the carbon allotropes, sp2-hybridized graphene or carbon nanotube (CNT) is an attractive material for its unique properties, such as ultrahigh surface to volume ratio, high electrical conductivity, high thermal conductivity, excellent chemical stability and easy ability to functionalize based on the application. However, the foldable nature of graphene dramatically reduces the surface area, increases the resistivity and reduces the processability during formation of a composite. Therefore, graphene quantum dots which are alternatives to CNTs that overcome their drawbacks have come to the forefront of research. However, the n-n interaction among the pure graphene quantum dots reduces its surface area and dispersivity in polar and non-polar solvent. To overcome the same, graphene oxide based quantum dots were discovered and their synthesis has become of major interest. Several methods to prepare graphene oxide quantum dots with different carbon sources and under different chemical environments have been reported in scientific journals. Some of these processes use highly toxic acidic medium, such as concentrated nitric and sulfuric acid, that

can be harmful for the environment and removal of which is a major challenge that results in lower yields and increase in cost. Some processes require high temperatures for synthesis in the range of about 400°C to 1000°C, while in other methods graphite is used as carbon source. Although abundant graphite is a non-renewable resource.
[0004] Therefore, there is a need in the art to develop a new method of synthesizing graphene oxide quantum dots that is safe, economical and employs a renewable carbon source.
OBJECTS OF THE INVENTION
[0005] An object of the present disclosure is to provide a process for
synthesizing graphene oxide quantum dots in an alkaline medium.
[0006] Another object of the present disclosure is to provide a process for
synthesizing graphene oxide quantum dots from renewable resource of potato
starch in an alkaline medium.
[0007] Yet another object of the present disclosure is to provide a process that
is economical, safe to use, provides high yield and does not require high
temperature requirements.
SUMMARY OF THE INVENTION
[0008] This summary is provided to introduce a selection of concepts in a
simplified form that are further described below in Detailed Description section.
This summary is not intended to identify key features or essential features of the
claimed subject matter, nor is it intended to be used as an aid in determining the
scope of the claimed subject matter.
[0009] Aspects of the present disclosure provide a process for synthesizing
graphene oxide quantum dots (GOQDs) from potato starch as carbon source
and using an alkaline medium.
[0010] In an aspect, the present disclosure provides a process of synthesizing
graphene oxide quantum dots comprising the steps of: (a) grinding a potato to
form a potato paste; (b) dispersing this paste in deionized water and adding

ammonium hydroxide solution; (c) placing the mixture of step (b) in a
hydrothermal reactor in a temperature range of about 140°C to about 200° C
for about 10 to about 15 hours; and (d) cooling to room temperature followed
by filtering and drying to give the graphene oxide quantum dots.
[0011] In an embodiment, the potato paste dispersed in deionized water may
have a weight percentage range of about 10wt% to about 40wt%.
[0012] In an embodiment, the ammonium hydroxide solution may be a
solution of ammonium hydroxide in water. In an embodiment, the
concentration of the ammonium hydroxide solution may be in a range of about
lmol to about 5mol.
[0013] In an embodiment, the filtration of step (d) may be performed by a
cellulose acetate membrane.
[0014] In an aspect, the present disclosure provides graphene oxide quantum
dots obtained by a process comprising the steps of: (a) grinding a potato to
form a potato paste; (b) dispersing this paste in deionized water and adding
ammonium hydroxide solution; (c) placing the mixture of step (b) in a
hydrothermal reactor in a temperature range of about 140°C to about 200° C
for about 10 to about 15 hours; and (d) cooling to room temperature followed
by filtering and drying to give the graphene oxide quantum dots.
[0015] Other aspects of the invention will be set forth in the description which
follows, and in part will be apparent from the description, or may be learnt by the
practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0017] Figure 1 provides a pictorial image of graphene oxide quantum dots prepared by a process as per an embodiment of the present disclosure.

[0018] Figure 2 provides a UV spectrum of graphene oxide quantum dots prepared by a process as per an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0020] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. [0021] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0022] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be

construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. [0023] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0024] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise. [0025] Unless the context requires otherwise, throughout the specification which follow, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense that is as "including, but not limited to."
[0026] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. [0027] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0028] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0029] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0030] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention. [0031] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. [0032] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0033] The term 'Graphene oxide quantum dot' or 'GOQD' as used herein refers to zero-dimensional nanoparticles comprising one or more layers of graphene oxide and having strong quantum property.

[0034] In an embodiment, the present disclosure provides a process of
synthesizing graphene oxide quantum dots comprising the steps of: (a)
grinding a potato to form a potato paste; (b) dispersing this paste in deionized
water and adding ammonium hydroxide solution; (c) placing the mixture of
step (b) in a hydrothermal reactor in a temperature range of about 140° C to
about 200°C for about 10 to about 15 hours; and (d) cooling to room
temperature followed by filtering and drying to give the graphene oxide
quantum dots.
[0035] In an embodiment, the potato may be washed before grinding. The
grinding may be done manually or via a grinding machine.
[0036] In an embodiment, the potato paste dispersed in deionized water may
have a weight percentage range of about 10wt% to about 40wt%.
[0037] In an embodiment, the ammonium hydroxide solution may be a
solution of ammonium hydroxide in water. In an embodiment, concentration
of the ammonium hydroxide solution may be in a range of about lmol to
about 5mol.
[0038] In an embodiment, about 10 gms of potato paste may require about
40mL of 25wt% ammonium hydroxide solution.
[0039] In a preferred embodiment, the hydrothermal reaction may be
performed for about 12 hours.
[0040] In an embodiment, the filtration of step (d) may be performed by a
cellulose acetate membrane. In an embodiment, the filtration may be
performed multiple times, iteratively, wherein each iteration may be
performed by a membrane of different porosity.
[0041] In an embodiment, the drying may be performed by vacuum drying or
air drying.
[0042] In an embodiment, pH during the reaction conditions in the
hydrothermal reactor may be maintained at about 8 to about 9.
[0043] Conventionally, graphene oxide quantum dots have been prepared by
reactions involving highly acidic medium wherein it is difficult to remove the
acid after the reaction. Apart from acidic medium, graphene oxide quantum

dots have also been synthesized using light alkaline environment with use of urea; however the yields obtained from this process are as low as 5%. The present disclosure overcomes these drawbacks of conventional processes. [0044] In an embodiment, the process of the present disclosure provides high yields of graphene oxide quantum dots. The process is efficacious, easy to operate and may be employed for mass production of GOQDs. [0045] The process of the present disclosure is cost effective as the source for carbon is potato. The process is also less toxic compared to those employing strong sulfuric acid and nitric acid.
[0046] In an embodiment, the present disclosure provides graphene oxide quantum dots obtained by the process comprising the steps of: (a) grinding a potato to form a potato paste; (b) dispersing this paste in deionized water and adding ammonium hydroxide solution; (c) placing the mixture of step (b) in a hydrothermal reactor in a temperature range of about 140°C to about 200°C for about 10 to about 15 hours; and (d) cooling to room temperature followed by filtering and drying to give the graphene oxide quantum dots. [0047] In an embodiment, the graphene oxide quantum dots have a diameter in the range of 5nm to 1 OOnm.
[0048] The quantum dots obtained by the above process may be employed in a variety of applications, including but not limited to, biological applications such as drug delivery, imaging; electrochemical or luminescence sensors; composite synthesis; optoelectronic devices; among others. [0049] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES
[0050] The present invention is further explained in the form of following
examples. However, it is to be understood that the following examples are merely
illustrative and are not to be taken as limitations upon the scope of the invention.
[0051] Materials and Methods:
[0052] Potato was obtained from a local vendor in Rajpura market, Punjab,
India.
[0053] EXAMPLE 1: Preparation of Graphene Oxide Quantum Dots
[0054] Plain potato was cleaned using clean water and then cleaned with
deionized water. The cleaned potato was ground to paste using deionized
water to give lOgms of the potato paste. 20mL of IN Ammonium hydroxide
solution was added to the potato paste. The mixture was kept in a
hydrothermal reactor for about 12 hours at a temperature of 180°C. After
heating in the reactor, the mixture was naturally cooled to room temperature.
The coarse particles from the mixture where then removed via filtration with a
cellulose filter paper, Whatmann® qualitative filter paper, Grade 1. The
filtrate obtained was then air dried to give the graphene oxide quantum dots
particles. The yield for the particles obtained was 25%.
[0055] The ultraviolet spectrum of the graphene oxide quantum dots obtained
from the above process was studied and the UV spectrum is provided in
Figure 1.
[0056] The foregoing examples are merely illustrative and are not to be taken as
limitations upon the scope of the invention. Various changes and modifications to
the disclosed embodiments will be apparent to those skilled in the art. Such
changes and modifications may be made without departing from the scope of the
invention.
ADVANTAGES OF THE PRESENT INVENTION
[0057] The present disclosure provides a process of preparing graphene oxide quantum dots that is easy and sourced from cheap materials.

[0058] The present disclosure provides a process of preparing graphene oxide quantum dots in high yields.
[0059] The present disclosure provides a process of preparing graphene oxide quantum dots that is environmentally safe and industrially scalable.

We Claim:

1. A process of synthesizing graphene oxide quantum dots comprising the steps of: (a) grinding a potato to form a potato paste; (b) dispersing this paste in deionized water and adding ammonium hydroxide solution; (c) placing the mixture of step (b) in a hydrothermal reactor in a temperature range of 140°C to 200°C for 10 to 15 hours; and (d) cooling to room temperature followed by filtering and drying to give the graphene oxide quantum dots.
2. The process as claimed in claim 1, wherein the potato paste dispersed in deionized water has a weight percentage range of 10wt% to 40wt%.
3. The process as claimed in claim 1, wherein the concentration of ammonium hydroxide solution is in a range of lmol to 5mol.
4. The process as claimed in claim 1, wherein pH for step (c) is in the range of 8 to 9.