FIELD OF INVENTION:
. The present invention relates to the field of synthesis of graphene oxide (GO)
nanosheets. The present invention in particular relates to green synthesis of
graphene oxide (GO) nanosheets using Chlorella pyrenoidosa (Algae).
DESCRIPTION OF THE RELATED ART:
Graphene oxide (GO) is one of the most important form of carbon that has
attracted a lot of interest due to the presence of abundant oxygen containing
surface groups like carboxyl, hydroxyl, carbonyl and epoxide. The presence of
these groups and layered structure offers potential applications of GO and its
composites.
The article entitled "Envelopment-internalization synergistic effects and
metabolic mechanisms of graphene oxide on single-cell Chlorella vulgaris are
dependent on the nanomaterial particle size" talks about the nanomaterials tested
here were larger graphene oxide nanosheets (GONS) and small graphene oxide
quantum dots (GOQD). GONS intensively entrapped single-celled Chlorella
vulgaris, and envelopment by GONS reduced the cell permeability [Ouyang S, Hu
X, Zhou Q; ACS Appl Mater Interfaces, 7(32):18104-12. 2015 Aug 19].
The article entitled "Application of various immobilization techniques for algal
bioprocesses" talks about the C. vulgaris cells immobilized on electrospun
chitosan nano- fiber mats yielded an efficient nitrate removal rate (87 %) as a
result of the dual action of nitrate removal by the microalgal cells and electrostatic
binding of the nitrate ions on chitosan nanofibers (Eroglu et al. 2012). In other
studies from the authors5 laboratories, the resulting microalgal composites with
multilayer graphene (Wahid et al. 2013b) or graphene oxide sheets (Wahid et al.
2013a) also achieved significant nitrate uptake rates, without being toxic for the
microalgal cells [Ela Eroglu, Steven M. Smith and Colin L. Raston; Springer
International Publishing Switzerland; 2015].
The article entitled "The effects of graphene oxide, on green algae Raphidocelis
subcapitata" talks about the environment, graphene can interact with biological
systems and is expected to exhibit toxicological effects.
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The ecotoxicity of graphene and its derivatives, viz.: graphene oxide (GO)
depends on their physicochemical properties, including purity, diameter, length,
surface charge, functionalization and aggregation state. In this study the effects of
graphene oxide (GO) on green algae Raphidocelis subcapitata have been
evaluated. The shading effect caused by GO agglomeration in culture medium
may also contribute to reduce algal density. The results reported here provide
knowledge regarding the GO toxicity on green algae, contributing to a better
understanding of its environmental behavior and impacts [Nogueira PF,
Nakabayashi D, Zucolotto V; Journal Article Research Support, Non-U.S. Gov't;
09-02-2016].
The article entitled "Competitive binding of natural amphiphiles with graphene
derivatives" talks about the graphene derivatives by natural amphiphiles is
essential for elucidating the biological and environmental implications of this
emerging class of engineered nanomaterials [Slaven Radic, Nicholas K.
Geitner, Ramakrishna Podila, Aleksandr Kakinen, Pengyu Chen, Pu Chun
Ke & Feng Ding; Scientific Reports 3, Article number: 2273; 2013].
The article entitled "A green approach to the synthesis of graphene nanosheets"
talks about the graphene can be viewed as an individual atomic plane extracted
from graphite, as unrolled single-walled carbon nanotube or as an extended flat
fullerene molecule. In this paper, a facile approach to the synthesis of high quality
graphene nanosheets in. large scale through electrochemical reduction, of
exfoliated graphite oxide precursor at cathodic potentials (completely reduced
potential: -1.5 V) is reported [Hui-Lin Guo, Xian-Fei Wang, Qing-Yun
Qian, Feng-Bin Wang and Xing-Hua Xia; ACS Nano, 3 (9), pp 2653-2659;
2009].
The article entitled "Effect of metals, metalloids and metallic nanoparticles on
microalgae growth and industrial product biosynthesis: a review" talks that
Microalgae are a source of numerous compounds that can be used in many
branches of industry. Synthesis of such compounds in microalgal cells can be
amplified under stress conditions. Exposure to various metals can be one of
methods applied to induce cell stress and synthesis of target products in
i 8 - 0 f - - * - 2 G f i r 16- MO-
4 - •
microalgae cultures. The presence of graphene oxide (GO) increased toxicity of
Cd towards Microcystis aeruginosa, while Cd toxicity towards Chlamydomonas
reinhardtii was reduced in the presence of titanium dioxide engineered
nanoparticles (ENPs). Finally, the presence of engineered nanoparticles was
reported to decrease intracellular content of Cu and Pb in Chlorella kesslerii and
wall-possessing Chlamydomonas reinhardtii, as metal binding to nanoparticles
reduces availability of Cu and Pb to these microalgal strains [Krystian Miazek,
Waldemar Iwanek, Claire Remade, Aurore Richel and Dorothee Goffin; Int. J.
Mol. Sci., 16, 23929-23969; 2015].
The article entitled "Synthesis and electrochemical analysis of algae cellulosepolypyrrole-
graphene nanocomposite for supercapacitor electrode" talks about the
nanocomposite has been developed using extracted cellulose from marine algae
coated with conductive polypyrrole and graphene nanoplateletes. The
nanocomposite fabricated via in situ polymerization was used as an electrode for a
supercapacitor device. The nanocomposite material has been electrochemically
characterized using cyclic voltammetry to test its potential to super-capacitive
behavior [Aphale A, Chattopadhyay A, Mahakalakar K, Patra P.; J Nanosci
Nanotechnol.; 15 (8):6225-9. 2015 Aug].
Publication No. WO2013188521 (Al) relates to a system and device for filtering
fluids using graphene oxide (GO). GO- based filters may be used for the efficient
removal of microorganisms from organic and aqueous liquids and may be used to
prevent fuel biodeterioration. GO can be applied as a sole column or filter matrix,
in combination with a support media, or in combination with existing fuel and
lubricant filters for the removal of microorganisms from these fluids. The purpose
of the GO media will be the removal of biological contaminants, including
bacteria, fungi, yeast, algae, and other cells.
Publication No. 20140199777 relates to the GO filter media made of a plurality of
GO particles, a structural core coated with GO, a non-porous structural membrane
coated with GO, or a filtering membrane coated with GO. A method for sampling
impurities found in an environmental sample is also provided.
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Thus in view of the above prior arts, it is clear that synthesis of Graphene oxides
nanosheets using Chlorella pyrenoidosa have not been reported till date.
Thus, present invention aims to provide Green synthesis of graphene oxide (GO)
nanosheets using Chlorella pyrenoidosa (Algae).
OBJECTS OF THE INVENTION:
The principal object of the present invention is to provide green synthesis of
graphene oxide (GO) nanosheets using Chlorella pyrenoidosa (Algae).
Another object of the present invention is to provide a novel, cost effective and
environment friendly method for the biosynthesis of GO nanosheets.
Yet another object of the present invention is to provide a green alternative to the
tradition chemical precursor.
SUMMARY OF THE INVENTION:
The present invention provides Green synthesis of graphene oxide (GO)
nanosheets using Chlorella pyrenoidosa (Algae). The invention demonstrates a
novel, cost effective and environment friendly method for the biosynthesis of GO
nanosheets using easily available algae extract of Chlorella pyrenoidosa. The
Scanning Electron Microscopy (SEM) and FTIR results confirm the formation of
GO nanosheets. Green synthesis of Graphene oxide (GO) using biological
precursor offers a green alternative to the tradition chemical precursor.
BREIF DESCRIPTION OF THE DRAWING:
It is to be noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be considered for
limiting of its scope, for the invention may admit to other equally effective
embodiments.
Fig 1: SEM image of synthesized graphene oxide
Fig 2: FTIR spectrum of synthesized graphene oxide
1 1 & - Q - 4 - 2Q-17. 26 : lO
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DETAILED DESCRIPTION OF THE DRAWING:
The present invention provides Green synthesis of graphene oxide (GO)
nanosheets using Chlorella pyrenoidosa (Algae). The invention demonstrates a
novel, cost effective and environment friendly method for the biosynthesis of GO
nanosheets using easily available algae extract of Chlorella pyrenoidosa. The
Scanning Electron Microscopy (SEM) and FTIR results confirm the formation of
GO nanosheets. Green synthesis of Graphene oxide (GO) using biological
precursor offers a green alternative to the tradition chemical precursor.
In the present invention, Chlorella pyrenoidosa (Algae) precursor is used as a
reducing agent for green synthesis of Graphene Oxide. Before reduction, Graphite
powder has been refluxed in HNO3 for 24 hr. to avoid the use of toxic chemicals .
The mild oxidation method has been used throughout the synthesis process for
further reduction. Thus, the method is an ecofriendly and nontoxic method as
well.
The method for the green synthesis of Graphene Oxide (GSGO) using Chlorella
pyrenoidosciis as follows:
1. Graphite was functionalized with Oxygen groups by refluxing graphite
powder in cone. HNO3 for 24 hours.
2. The resultant graphite was then centrifuged, washed with DI water and dried.
3. 1 g of this graphite and 3 g of potassium permanganate were ground together
into a powder until homogeneous.
4. In a 250 mL beaker immersed in ice-bath, 30 mL 98% cone, sulphuric acid
was taken and stirred for 15 min.
5. The powder was added to the beaker pinch by pinch with continuous stirring
over 30 minutes.
6. After complete addition, the beaker was removed from the ice bath and
stirring was continued at room temperature for 30 minutes.
7. The beaker was placed back into an ice bath, followed by addition of 120 mL
DI water with rapid stirring, continued for lh.
8. A homogenous black suspension was formed which was centrifuged to
discard the acidic supernatant.
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9. The residue was washed several times (until pH was neutral) with water-
• methanol (1:1) mixture to remove the
soluble impurities.
10. To further exfoliate the GO sheets, the obtained residue was again suspended
in water and ultrasonicated for 2h.
11. The GO was then dried overnight at 40°C.
12. To further reduce the GO through green method, a 0.1 g/L suspension of GO
(20 mL) was prepared in DI water through ultrasonicated for 2 hr.
13. To the suspension, .005 g/L of Chlorella pyrenoidosa (Algae) was added
while stirring.
14. The resultant solution was kept in a shaker at 120 rpm for 24 hr at room
temperature.
15. The final obtained product (green synthesized GO) was washed and.dried.
The surface morphology of the synthesized graphene oxide was confirmed by
Scanning electron microscopy (SEM) as represented in Fig 1 .The image confirms
that the graphene oxide sheets were of 300 - 400 nm in size and wrinkled in
shape. The presence of functional groups in the graphene oxide sample was
investigated by Fourier transform infrared spectroscopy (FTIR) (Fig 2). The
presence of significant peaks at 3410 cm"1 (O-H stretching vibrations), 1740 cm"1
(C=0 stretching vibrations), 1610 cm*1 (unoxidized graphitic skeletal vibrations),
1175 cm'1 (epoxy C-0 vibrations) and 1028 cm'1 (alkoxy C-0 stretching
vibration) confirms that the graphene oxide. (GO) nanosheets have been
synthesized.
Numerous modifications and adaptations of the system of the present
invention will be apparent to those skilled in the art, and thus it is intended
by the appended claims to cover all such modifications and adaptations
which fall within the true spirit and scope of this invention.

WE CLAIM:
1. The method for the green synthesis of Graphene Oxide (GSGO) using
Chlorellapyrenoidosais includes following steps:
a) Functionalize Graphite with Oxygen groups by refluxing graphite powder
in cone. HNO3 for 24 hours.
b) Centrifuge the resultant graphite, washing with DI water and drying.
c) Ground 1 g of this graphite and 3 g of potassium permanganate together
into a powder until homogeneous.
d) In a 250 mL beaker immersed in. ice-bath, 30 mL 98% cone, sulphuric
acid was taken and stirred for 15 min.
e) Add the powder to the beaker pinch by pinch with continuous stirring over
30 minutes.
f) After complete addition, the beaker was removed from the ice bath and
stirring was continued at room temperature for 30 minutes.
g) Place the beaker back into an ice bath, followed by addition of 120 mL DI
water with rapid stirring, continued for lh.
h) A homogenous black suspension was formed which was centrifuged to
discard the acidic supernatant,
i) The residue was washed several times (until pH was neutral) with watermethanol
(1:1) mixture to remove the soluble impurities,
j) To further exfoliate the GO sheets, the obtained residue was again
suspended in water and ultrasonicated for 2h.
k) The GO was then dried overnight at 40°C.
1) To further reduce the GO through green method, a 0.1 g/L suspension of
GO (20 mL) was prepared in DI water through ultrasonicated for 2 hr.
m) To the suspension, .005 g/L of Chlorella pyrenoidosa (Algae) was added
while stirring,
n) The resultant solution was kept in a shaker at 120 rpm for 24 hr at room
temperature,
o) The final obtained product (green synthesized GO) was washed and dried.
2. The method for the green synthesis of Graphene Oxide (GSGO) using
Chlorella pyrenoidosais, as claimed in claim 1, wherein the said graphene
s/ 9 )35S^s e t s a r e °f 300 - 400 nm in size and wrinkled in shape.
3. The method for the green synthesis of Graphene Oxide (GSGO) using
Chlorella pyrenoidosais, as claimed in claim-1, wherein the said method is
cost effective and environment friendly