Eco-Friendly In Situ Fabrication of Reduced Graphene Oxide Gold Nanocomposites for Catalysis and Dye Degradation

Article abstract of DOI:10.1134/S003602441813023X

Abstract: The invention represents a development of robust eco-friendly method use for water waste management and polluted water. The inadvertent role of peanut peels extract helps to simultaneously convert and form reduced graphene oxide gold nanocomposite (rGO@AuNCs) in single step. Fabricated nanocomposite was evaluated for its catalytic performance using reduction of 4-nitrophenol to 4-aminophenol as well as elimination of methylene blue (MB) and malachite green (MG) dyes from water. Graphene oxide (GO) and rGO@AuNCs, were synthesized using simplified approaches and preliminary characterization was done using UV–Vis spectrophotometer and Fourier transform infrared spectroscopy. Least concentration of rGO@AuNCs is required to eliminate MB and MG around 77 and 93%, respectively. Furthermore, surface morphology and elemental analysis of rGO@AuNCs confirm successful fabrication methods as well as X?ray diffraction pattern confirms the crystalline behavior of nanocomposite. The study illustrates an environment-friendly and cost effective in situ fabrication rGO@AuNCs from industrial agro waste for an environmental remediation.

Full text of DOI:10.1134/S003602441813023X

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2018, Vol. 92, No. 13, pp. 2750–2756. © Pleiades Publishing, Ltd., 2018.
PHYSICAL CHEMISTRY OF NANOCLUSTERS
AND NANOMATERIALS
Eco-Friendly In Situ Fabrication of Reduced Graphene Oxide Gold
Nanocomposites for Catalysis and Dye Degradation1
Pravin O. Patila,*, Sanchita S. Mahalea, Mahesh P. Morea, Pravin V. Bhandaria,
Prashant K. Deshmukha, and Sanjay B. Baria
aDepartment of Quality Assurance, H. R. Patel Institute of Pharmaceutical Education and Research,
Shirpur, Dist. Dhule, Maharashtra
* е-mail: rxpatilpravin@yahoo.co.in
Received October 24, 2017
Abstract—The invention represents a development of robust eco-friendly method use for water waste man-
agement and polluted water. The inadvertent role of peanut peels extract helps to simultaneously convert and
form reduced graphene oxide gold nanocomposite (rGO@AuNCs) in single step. Fabricated nanocomposite
was evaluated for its catalytic performance using reduction of 4-nitrophenol to 4-aminophenol as well as
elimination of methylene blue (MB) and malachite green (MG) dyes from water. Graphene oxide (GO) and
rGO@AuNCs, were synthesized using simplified approaches and preliminary characterization was done
using UV–Vis spectrophotometer and Fourier transform infrared spectroscopy. Least concentration of
rGO@AuNCs is required to eliminate MB and MG around 77 and 93%, respectively. Furthermore, surface
morphology and elemental analysis of rGO@AuNCs confirm successful fabrication methods as well as X-ray
diffraction pattern confirms the crystalline behavior of nanocomposite. The study illustrates an environment-
friendly and cost effective in situ fabrication rGO@AuNCs from industrial agro waste for an environmental
remediation.
Keywords: graphene oxide, industrial-agro waste, methylene blue, malachite green, 4-nitrophenol, environ-
mental remediation
DOI: 10.1134/S003602441813023X
INTRODUCTION
made towards fabrication of graphene based nano-
composites [4].
Single-layer of graphene oxide (GO) is usually pro-
duced by the chemical oxidation of graphite, which is
a harsh chemical reaction in presence of H2SO4 and
KMnO4. Exfoliated graphite forms a stable dispersion
in water and different organic solvents such as ethanol,
Metal nanoparticles–graphene nanohybrid sys-
tems become highly important in catalysis and dye
removal because of their large surface area, high elec-
tronic transport capacity and extraordinary chemical
stability [5]. The interest in the use of graphene-based
dimethyl sullfoxide, etc. [1]. A synthesized material at materials in the field of catalysis is due to the activity
and stability of graphene-based catalysts through tai-
loring its structures/morphologies, catalytic perfor-
mance, and design for synthesis, catalytic mechanisms
[6]. Textile industries are using dyes in larger amount
and their wastage is also been increasing, synthetic
dyes are less costly but produces toxicity to aquatic
animals and humans. The rate of degradation of dyes
is much slower due to complex chemical structure and
difficult in decomposition. Several methods have been
reported previously for the treatment of dye bearing
effluents, but they are generally inefficient for the
complete removal of dyes. Adsorption and removal of
dyes using metal nanoparticles–graphene nanohybrid
is the method of choice for the treatment of waste
water [7].
nanoscale shows enormous structural and functional
properties. These advancements in nanotechnology
deals with the exploration and exploitation of nano-
materials with their synthesis, characterization, evalu-
ation, etc. [2]. Conventional composite materials
unable to show such efficient properties thought the
nanocomposite owing to their unique desirability and
surface, structural properties shows significant prog-
ress in 21st century. The significant aspect for explor-
ing the research of the graphene-based nano compos-
ites is the yearning to combine the promising proper-
ties of graphene with other fundamental
nanomaterials [3]. Applications and recent needs of
energy and environmental remediation approaches as
well as to check the possibilities attension has been
Peanut (Arachis hypogaea) is an important food
crop grown in over 100 countries with a total produc-
1
The article is published in the original.
2750

ECO-FRIENDLY IN SITU FABRICATION OF REDUCED GRAPHENE OXIDE
tion of 38 million tons in 2010 [8]. Peanut shell is also Preparation of Peanut Peel Extracts (PPE)
2751
known as peanut hulls [9]. However, peanut pod con-
tains 35% of the shell, which is considered agricultural
waste, obtained after the removal of groundnut seed
from its pod. Peanut shell may contain lignin, cellu-
lose, luteolin, and hemicelluloses [10], which can be
used as reinforcing filler in polymer composite [11].
However, there is limited study on graphene based
metal nanocomposite and yet no study has been
reported on exploring the properties of gold nanopar-
ticles based graphene composite investigated in pres-
ent approach.
To the best of our knowledge, the use of naturally
available agricultural waste material has not been
investigated so far, using one pot synthetic approach.
Therefore, an attempt has been made for the first time
to assess the potency of peanut peel extract towards the
metal nanoparticles-graphene nanohybrid synthesis.
This novel method has several advantages including
low cost, simplicity, and potential for large-scale pro-
duction, a green and eco-friendly method without
using any toxic chemicals [12]. The literature has
revealed that the metal nanoparticles, as well as rGO,
exhibits good dye adsorption property, thus we estab-
lished a synergistic effect of both rGO and metal
nanoparticle in dye adsorption using graphene nano-
composite [13–15].
Peanut peels used in this study were obtained from
a local market in Shirpur city (Dhule, Maharashtra,
India). First, the collected peels were extensively
washed with tap water to remove dust, sprayed with
deionized water, and washed with 0.1 mol/L HCl.
Next, the peels were washed with deionized water till
the filtrate free from chloride ions. Then, the peels
were dried in an oven at 60°C till they reached a con-
stant weight. After that, the dry peels were crushed
into powder. These peanut peels (5.0 g) were heated
using distilled water (100 mL) at 80°C, followed by fil-
tration using a muslin cloth to remove insoluble mate-
rial. The prepared extract was stored in refrigerator
4°C for further studies [17].
Phytochemical Tests for Agro Waste PPE
PPE was tested for presence of potential phytocon-
stituents present into an extracted material. The test
protocols were set according to earlier reported meth-
ods [18].
Preparation of rGO@AuNCs
The GO solution (0.3 mg/mL) and HAuCl4 solu-
tion (0.047 mg/mL) were mixed together, incubated at
room temperature to promote interaction between
gold ions and graphene surfaces. After 30 min, the
mixture was transferred to heating bath of 80°C tem-
perature with subsequent addition of extracted Agro
waste (PPE) was added. After few minutes of reaction,
the resulting solution was centrifuged (6000 rpm) for
15 min and washed three times with DI water to
remove any unreacted precursor. The fabricated com-
posite was resuspended into small amount of water
and freeze dried at –40°C, dried free flowing powder
was collected after lyophilization [19].
EXPERIMENTAL
Materials
Graphite powder was kindly gifted by Asbury car-
bon, New Jersey, USA. All chemicals used were of
analytical grade and used without further purification.
Peanut peels were collected from the local market in
Shirpur city (Dhule, Maharashtra, India).
Preparation of GO
GO was prepared by the oxidation of natural
graphite powder according to an improved Hummers
method as precisely developed into our lab [16]. An
amount of accurately weighed 3.0 g of accurately
weighed graphite powder was mixed with 70 mL con-
centrated H2SO4 under constant stirring in an ice bath.
After complete homogenization, 9.0 g of KMnO4 were
added slowly keeping the temperature of the suspen-
sion lower than 10°C for 30 min. A pasty mass was
formed, and the reaction mixture was transferred to a
40°C water bath and vigorously stirred for about
15 min. Afterwards, 150 mL deionized water was
added and the solution was stirred for 15 min at 95°C.
Then, 500 mL water was added, followed by a slow
addition of 15 mL H2O2 (30%) which turned the color
of the solution from dark brown to yellow. The mixture
was filtered and washed with 10% HCl and water in
triplicate to remove the metal ions. The resulting solid
was dried in air or an oven at 35°C.
Characterization
The UV–Vis spectra were recorded on UV
1700/1800 spectrophotometer Shimadzu, Japan using
quartz cuvettes. The functional groups of
rGO@AuNCs were examined using a DRS 8000 IR
spectrophotometer Shimadzu 8400s, Japan. The mor-
phology of rGO@AuNCs was examined under Scan-
ning electron microscope (SEM); observations were
carried out on Bruker, 1530-2 FESEM/EDX, Ger-
many. Particle size and zeta potential of synthesized
rGO@AuNCs were measured using Nanoplus 3 Par-
ticulate System, Micromeritics, USA.
Dye Degradation Activity
The degradation of dyes was achieved using earlier
reported literature method [20].
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PATIL et al.
Abs.
4
Abs.
229 nm
(a)
(b)
3
2
1
300 nm
262 nm
400
2
0
536 nm
600
0
200
400
600
800 200
800
λ, nm
λ, nm
Fig. 1. UV–Vis spectrum of (a) GO, (b) rGO@AuNCs.
Catalytic Reduction of Nitroarene (4-Nitrophenol)
(for C–O (stretching)), and a broad band at around
3128 cm–1 for hydroxyl groups indicated the presence
of various oxygen-containing functional groups, such
as carboxylic, epoxy, and hydroxyl groups in GO [24].
The catalytic performance of synthesized
rGO@AuNCs was studied on 4-nitrophenol (4-NP)
to check the conversion into less toxic intermediate
which can be easily analyzed spectrophotometrically. Figure 2b represents the FTIR spectrum of synthe-
0.1 mM and 0.1 M concentration of 4-NP and NaBH4
were taken, respectively, pH of the reaction was mea-
sured intermittently and maintained at 7.2. After
instant addition of sodium borohydride, nitropheno-
late anion was formed, and hydrogen evolution was
observed. At that moment rGO@AuNCs catalyst was
added and reaction was monitored at 400 rpm and
equivalent amount was withdrawn after 5 min interval
of time and analyzed using UV–Vis spectrophotomet-
rically [21].
sized rGO@AuNCs. The peaks at 3597, 1713, 1619,
and 1076 cm–1 corresponding to the O‒H stretching,
C=O carbonyl, C–C vibrations, and C–O stretching
respectively. In addition, the intensity of characteristic
features for rGO was increased and slightly shifted to
the lower value which can be assigned to the formation
of gold nanoparticles on rGO surface. From above
results, it is established that the phytoconstituents fla-
vonoids, carbohydrate and phenolic content present
in the extract are responsible for the reduction of Au
ions and GO to fabricate rGO@AuNCs [25]. The phy-
tochemical analysis of extract as shown in Table 1.
RESULTS AND DISCUSSION
Characterization of Graphene Oxide and rGO@AuNCs
Scanning electron microscopic images represent
the surface morphologies of GO sheets. Figure 3a dis-
played a typical crumpled and wrinkled surface of
graphene, and the sheets stacked together to form a
typical multi-layer structure. The geometric wrinkling
arising from π–π* interaction within sheets of GO
minimize the surface energy. In addition, the wrinkled
structure of GO sheets provides a large rough surface
as a scaffold for further modification [26]. Figure 3b
also elucidates the exfoliation of rGO and conversion
of stacked sheets into more separated structure. While
an small particles are attached intermitantly within
and on the surface of sheet is of evenly dispersed Au
nanoparticles. These equal distribution of Au on sur-
face of rGO represents the strong interaction between
rGO and Au, where rGO act as carrier for Au. It also
The UV–Vis spectra of synthesized GO (Fig. 1a)
shows maximum absorption peak at ~229 nm and
shoulder peak at ~300 nm [22]. The conversion of GO
to rGO in presence of PPE extract, small changes in
structure of graphene can be addressed using UV
spectral analysis. Usually conversion of GO to rGO
shows a red shift due to transition of π– π* from 229 to
262 nm. The shoulder peak around 300 nm from GO
disappears which is due to n–π* transition and emer-
gence of a new peak at 536 nm. These transitional
changes during formation of rGO induced after react-
ing with PPE implies for the restorations of electronic
conjunction in rGO and preliminary confirms the
successful formation of rGO@AuNCs [23].
The presence of intense bands in FTIR of GO
(Fig. 2a) at 1761 cm–1 (for C=O (stretching)),
1585 cm‒1 (for C=C (stretching)), 1058 and 1226 cm‒1 helps to stabilize the Au nanoparticles. This one pot
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(a)
2753
T, %
55
50
45
4000
T, %
3500
3000
2500
2000
1750
1500
1250
1000
750
500
ν, cm−1
(b)
55
50
45
ν, cm−1
4000
3500
3000
2500
2000
1750
1500
1250
1000
750
500
Fig. 2. FTIR spectrum of synthesized (a) GO, (b) rGO@AuNCs.
fabrication method revealed that, rGO@AuNCs was
Elemental analysis (EDX spectra) of synthesized
successfully formed by Au nanoparticles anchored rGO@AuNCs represents components of synthesized
onto the surface and within layers of exfoliated rGO.
nanocomposite and presence of impurities.
Table 1. Phytochemical Analysis of PPE extract
Results (confirms the
presence of phytochemicals)
Sr. no.
Test performed
Observation
1
2
3
Ferric chloride test
Molisch’s test
Intense green color observed
Violet ring formation
Phenol present
Carbohydrate
Flavonoids
Alkaline reagent test On addition of NaOH solution color turns into yellow
while after addition of HCl yellow color disappears
and solution turns to colorless
Results was compared with standard protocols and observations made in [16, 18].
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PATIL et al.
5 μm
2 μm
(а)
(b)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
(c)
(d)
6
5
4
3
2
1
O
C
C
Au
Au
O
0
2
4
6
8
10
12
14
2
4
6
8
10
12
14
keV
keV
Fig. 3. SEM Micrograph of (a) GO, (b) rGO@AuNCs with supportive elemental analysis of (c) GO and (d) rGO@AuNCs.
Figures 3c, 3d represent the EDX spectra of synthe- 0.512 and zeta potential is 11.47 mV. In case of nano-
sized GO and rGO@AuNCs, respectively. Synthe- composite rGO@AuNCs shows average particle size
sized GO revealed the presence of carbon (34.31%) was found to be 659.7 nm and zeta potential is
and oxygen (65.69%) signify the conversion of graph- ‒11.67 mV (Figs. 4c, 4d).
ite to graphene oxide by increasing the concentration
of oxygen after synthesis and represents the presence
Dye Degradation Study
of oxygen containing functional groups on surfaces.
While on similar tracks the effect of PPE on conver-
sion of GO to rGO@AuNCs shows the presence of Au
(23.29%), oxygen (26.23%), carbon (50.47%). During
conversion of GO to rGO relative decrease in concen-
tration of surface oxygen functionality such as
hydroxyl, epoxy, etc. get tend to decreases from 65.69
to 26.23%, respectively. Some of the surface groups
bind to Au nanoparticles for successful surface inter-
action. These data also represents the absence of any
types of impurities after synthesis.
An accurately weighed quantity of the dye was dis-
solved in distilled water to prepare a stock solution.
Experimental solutions of the desired concentration
were obtained by successive dilutions. MB and MG
dyes were subjected to catalytic degradation in the
presence of rGO@AuNCs synthesized using PPE in
dark condition (without Sunlight as well as UV light).
Figure 5a illustrates that both the dyes undergo
almost 93% dye degradation. This implies very effi-
cient dye removal property of rGO@AuNCs towards
At nanoscale prediction, particle size determina- carcinogenic dyes without the aid of light. The
tion is an important factor as it represents enhance- rGO@AuNCs synthesized using PPE used for MG
ment of surface characteristics of synthesized nano- dye degradation (Fig. 5a) exhibited 92.95% dye elim-
composites. While on the other side surface charge ination at 70 min because the Au ions loaded into the
(zeta potential) appraise the stability of particles in rGO@AuNCs was 23.29%. These results were
solvent medium and subsequent interaction in case recorded at 5 min time interval. The MB dye decol-
of catalytic approaches and adsorption of toxic inter- oration using rGO@AuNCs (Fig. 5b) exhibited
mediates. Figures 4a, 4b show the particle size of GO 93.85% degradation of dye at 80 min. The study con-
was near to 411.8 nm with polydispersity index is ducted at 5 min interval.
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2755
Frequency, Hz
−150 −100 −50
20
0
50
100
150
200
250
5
100
75
(b)
(a)
15
10
5
1
50
25
0
0
0
5
1
100 1000 10 000
Diameter, nm
200
0
0
−200
−400
Zeta potential, mV
Frequency, Hz
−150 −100 −50
20
50
100
150
200
250
(d)
(c)
100
15
10
5
1
75
50
25
0
0
0
10
100 1000 10 000
Diameter, nm
200
0
−200
−400
Zeta potential, mV
Fig. 4. (a) Particle size of synthesized GO, (b) zeta potential of synthesized GO, (c) particle size of synthesized rGO@AuNCs,
(d) zeta potential of synthesized rGO@AuNCs.
0.5
1.1
(a)
(b)
1.0
0.5
0
4
3
2
1
0
(c)
0.4
0.3
0.2
0.1
0
1
400
500
600
700
800 400
nm
500
600
700
800 200
nm
400
600
800
nm
Fig. 5. Dye degradation analysis and catalytic performance of rGO@AuNCs using UV–Vis spectrophotometer; (a) MG degra-
dation (top–down) 10 to 70 min, (b) MB degradation (top–down) 10 to 70 min, (c) catalytic reduction of 4-nitrophenol
(1) 4-nitrophenol, other spectra (top–down) 10 to 35 min.
Catalytic Reduction of 4-Nitrophenol
performance of
cules which is high in absence of intermediates. The
rGO@AuNCs start to catalyze reaction immediately
Catalytic
synthesized
after addition, as it overcomes the kinetic barrier by
rGO@AuNCs nanocomposite tested by using reduc-
tion of 4-NP to 4-aminophenol (4-AP) analyzed using
UV–Vis spectroscopy as shown in Fig. 5b. Signifi-
−
enabling the electron transfer from
to 4-NP. The
BH4
4-NP shows absorbance maxima at ∼317 nm in aque-
cance of NaBH4 during the conversion of 4-NP to 4- ous solution, which shifts to 400 nm after formation of
4-nitrophenolate ion. This red shift in absorption
spectrum is due to presence of NaBH4. The relative
decrease in the absorption intensity at 400 nm corre-
AP was by formation of intermediate 4-nitrophenolate
anion. The reduction mechanism is thermodynami-
cally favorable in presence of NaBH4; reduces the
kinetic barrier between the donor and acceptor mole- sponds to 4-nitrophenolate ion. After addition of
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PATIL et al.
4. T. Wu, L. Zhang, J. Gao, Y. Liu, and C. Gao, J. Mater.
rGO@AuNCs, rapidly decrease in the absorption
intensity at 400 nm and emerges of new peak at 298 nm
indicates the formation of 4-aminophenol, which is a
reduced form of 4-NP [21].
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The rGO@AuNCs has been successfully prepared
with a novel, one-step green method, using peanut
peel extract as a reducing agent. This method has
proved to be facile, cost-effective and environmen-
tally-friendly to obtain graphene-based gold nano-
composite, which exhibited very good performance
for the removal of MG and MB from aqueous solu-
tion. This nanocomposite can resolve two difficulties:
the disposal of this industrial-agro waste material and
the removal of a dyestuff from the water. Catalytic per-
formance of rGO@AuNCs was tested on reducing the
4-NP to 4-AP in the presence of NaBH4. Within a
fraction of min it starts to reduce the substrate, this
immediate performance based ability helps to develop
and efficient carrier for reduction of many toxic mate-
rials and intermediates at larger scale. Recyclability
and reuse of synthesized rGO@AuNCs can be possi-
ble and have better performance as of synthesized. The
present process is efficient and easy to fabricate at
larger scale and could be helpful for textile and other
chemical industries for waste management.
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ACKNOWLEDGMENTS
(Pragati Books, Mumbai, 2008).
Authors are thankful to Management, Principal,
SES, H.R. Patel Institute of Pharmaceutical Educa-
tion and Research, Shirpur for providing necessary
facilities to do research work effectively. Authors are
also thankful for North Maharashtra University, Jal-
goan for their kind support in analytical facilities.
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