Green synthesis of a Cu/MgO nanocomposite by: Cassytha filiformis L. extract and investigation of its catalytic activity in the reduction of methylene blue, congo red and nitro compounds in aqueous media

Article abstract of DOI:10.1039/c7ra13491f

This work reports the green synthesis of a Cu/MgO nanocomposite using Cassytha filiformis L. extract as a reducing agent without stabilizers or surfactants. The immobilization of Cu NPs was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-r

Full text of DOI:10.1039/c7ra13491f

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Green synthesis of a Cu/MgO nanocomposite by
Cassytha filiformis L. extract and investigation of its
catalytic activity in the reduction of methylene
blue, congo red and nitro compounds in aqueous
media
Cite this: RSC Adv., 2018, 8, 3723
ab
Zahra Issaabadia and S. Mohammad Sajadicd
*
Mahmoud Nasrollahzadeh,
This work reports the green synthesis of a Cu/MgO nanocomposite using Cassytha filiformis L. extract as
a reducing agent without stabilizers or surfactants. The immobilization of Cu NPs was confirmed by
Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron
microscopy (TEM), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray
spectroscopy (EDS). The Cu/MgO nanocomposite acts as a heterogeneous and recyclable catalyst for
the reduction of 4-nitrophenol (4-NP), 2,4-dinitrophenylhydrazine (2,4-DNPH), methylene blue (MB) and
congo red (CR) using sodium borohydride in aqueous media at room temperature. The catalyst was
recycled multiple times without any significant loss of its catalytic activity.
Received 20th December 2017
Accepted 10th January 2018
DOI: 10.1039/c7ra13491f
rsc.li/rsc-advances
supported on the various supports such as TiO2,21 graphene
oxide,22 Fe3O4,23 bentonite24, perlite25 and etc. Among hetero-
Introduction
geneous catalysts, MgO has been used widely as an efficient
support and catalyst in organic reactions due to good chemical
and thermal stability, low cost, high surface area, ease of
handling and high catalytic activity reusability.26
The presence of azo dyes and nitroarene compounds in waste
waters is of great concern for researchers. The dyes and nitro-
arene compounds used in various industries are oen highly
toxic to aquatic organisms because these are biologically and
chemically stable. Therefore, it is arduous to remove them by
natural degradation processes.1,2 Degradation of the dyes to
nondangerous products3–5 and also nitroarenes to useful
compounds6,7 are very important reactions. Recently, scientists
have introduced a reduction process in the presence of metal
nanoparticles (MNPs) with NaBH4 as a reducing agent for the
removal of pollutants from water.8–12
The MNPs are more active than their particulate metal
counterparts due to their properties, small sizes and large
surface areas. Among MNPs, copper nanoparticles (Cu NPs)
have attained a particular attention because its cheapness and
availability compared to other metal nanoparticles.13–15 Despite
the advantages of Cu NPs, their agglomeration is inevitable. The
synthesis of heterogeneous catalysts is one of the best ways to
overcome the agglomeration of MNPs.16–20 Recently, various
research groups reported the green synthesis of MNPs
Nowadays various techniques have been proposed for the
green synthesis of metal nanoparticles using plant extracts as
biological materials under mild conditions.27–30 Plants extract
mediated synthesis of NPs can be benecial for preparing
nanometals to control the size, shape and distribution size. The
green approach for the synthesis of MNPs by using plants
extract are very desirable compared to other physical and
chemical methods because their advantages such as use of
nontoxic solvents, simple work-up procedure, very mild reac-
tion conditions, cleaner reaction proles, elimination of toxic
and dangerous materials, elimination of high pressure, energy,
temperature, cost effectiveness and dangerous materials
without using of surfactant, capping agent and or template.31–33
Cassytha liformis L. from the Cassythaceae family is
a medicinal plant of tropical region of Asia and America which
mainly uses in traditional medicine for treatment of cancer,
Fig. 1. Because of the presence of its rich phytochemical content
in modern medical research, C. liformis has been investigated to
possess a number of biologically active chemical compounds
with the therapeutic potential in human health applications.34,35
Some of the isolated compounds from the extracts of this plant
are aporphine alkaloid, oxo-aporphine alkaloid, cassyformine,
liformine, cathaformine, lignan, actinodophine, and octenine.
Previous studies on the plant extract strongly support the
aDepartment of Chemistry, Faculty of Science, University of Qom, Qom 3716146611,
Iran. E-mail: mahmoudnasr81@gmail.com
bCenter of Environmental Researches, University of Qom, Qom, Iran
cScientic Research Center, Soran University, PO Box 624, Kurdistan Regional
Government, Soran, Iraq
dDepartment of Pharmacy, Rwandz Private Technical Institute, Kurdistan Regional
Government, Rwandz, Iraq
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ꢀ
diffractometer type PW 1373 goniometer (Cu Ka ¼ 1.5406 A).
The scanning rate was 2ꢀ minꢁ1 in the 2q range from 10 to 90ꢀ.
Preparation of Cassytha liformis L. fruit extract
50 g of dried powder of the plant fruit was added to 250 mL
double distillated water in 500 mL ask and well mixed. The
preparation of extract was using magnetic heating stirrer at 70 ꢀC
for 30 min. The obtained extract was centrifuged in 7000 rpm and
ltered then ltrate was kept at refrigerator to use further.
Fig. 1 Image of Cassytha filiformis L. plant.
presence of bioactive phytochemicals such as alkaloids, pheno-
lics, avonoids, glycosides, resins, proteins, carbohydrates, sap-
onines and tannins.36–39 Through this research the aqueous
extract of the Cassytha liformis L. was used as reducing media to
biosynthesis of stable nanostructures without application of
poisonous chemicals and harsh reaction conditions.
In this work, we reported the preparation of Cu/MgO nano-
composite via a new, fast, simple, green, cost effective and eco-
friendly process by using Cassytha liformis L. extract as stabi-
lizing and reducing agent for the reduction of Cu2+ ion to Cu0.
Then, the catalytic activity of Cu/MgO nanocomposite was
investigated against organic dyes such as CR, MB and nitro
compounds such as 2,4-DNPH and 4-NP using NaBH4 as the
source of hydrogen.
Green synthesis of Cu NPs
In a 250 mL conical ask, 10 mL solution of CuCl2$2H2O (5 mM)
was mixed with 100 mL of the aqueous plant extract along with
vigorous shaking until gradually changing the color of the
mixture from yellow to dark during 5 min indicating the
formation of Cu NPs (as monitored by UV-vis spectrum). The
mixture then ltered and centrifuged at 7000 rpm for 30 min
and obtained precipitation washed with n-hexane and absolute
ethanol to remove possible impurities, Scheme 1.
Preparation of the Cu/MgO nanocomposite using the aqueous
extract of the Cassytha liformis L.
For green synthesis of Cu NPs immobilized on MgO as
a support, 25 mL of CuCl2$2H2O (5 mM) was added dropwise
Experimental
Reagents and methods
All materials with commercial reagent grade were obtained
from the Merck and Aldrich companies and used without
further purication. FT-IR spectra were recorded on a Nicolet
370 FT/IR spectrometer (Thermo Nicolet, USA) using pressed
KBr pellets. The formation of nanoparticles was recorded by UV-
visible spectral analysis on a double-beam spectrophotometer
(Hitachi, U-2900). The shape and size of the Cu/MgO nano-
composite were identied by transmission electron microscope
(TEM) using a Philips EM208 microscope operating at an
accelerating voltage of 90 kV. Field emission scanning electron
microscopy (FE-SEM) was performed on a cam scan MV2300.
EDS (energy dispersive X-ray spectroscopy) was utilized for
chemical analysis of prepared nanostructures. X-ray diffraction
(XRD) mensuration were carried out using a Philips powder Fig. 2 UV-vis spectra of the plant extract and green synthesized Cu NPs.
Scheme 1 Proposed mechanism for green synthesis of Cu NPs.
3724 | RSC Adv., 2018, 8, 3723–3735
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Fig. 3 FT-IR spectra of biosynthesized Cu NPs and plant extract.
to a well-mixed solution of the above extract and 1.0 g of MgO
with constant stirring at 80 C for 4 h. Finally, the prepared
General procedure for the reduction of 4-NP at room
temperature
ꢀ
Cu/MgO nanocomposite was separated by centrifugation,
washed several times with distilled water and then dried at
90 C for 2 h.
To evaluate the catalytic activity, a mixture containing 10.0 mg
of Cu/MgO nanocomposite and 25 mL of 4-NP aqueous solution
ꢀ
Fig. 4 The XRD pattern and TEM image of biosynthesized Cu NPs.
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(2.5 mM) was stirred for 3 min in a beaker. In the next step,
freshly prepared NaBH4 aqueous solution (0.25 M, 25 mL) was
added and stirred for 5 min at room temperature. The
concentration of 4-NP was determined using a Hitachi, U-2900
spectrophotometer. Aer completion of the reaction, the cata-
lyst was simply separated by brief centrifugation and washed
successively with distilled water, dried and used for successive
cycles.
General procedure for the reduction of MB and CR at room
temperature
In a typical reduction protocol, 25 mL of organic dye solution
(MB: 3.1 ꢂ 10ꢁ5 M, CR: 1.44 ꢂ 10ꢁ5 M) was mixed with 10.0 mg
of the Cu/MgO nanocomposite and the mixture was stirred at
room temperature. Then a freshly prepared NaBH4 aqueous
solution (5.3 ꢂ 10ꢁ3 M, 25 mL) was added and mixture was
stirred at room temperature. The reaction was monitored using
the UV-vis spectroscopy. At the end of the reaction, the catalyst
was simply separated from the reaction system by brief centri-
fugation and washed with doubly distilled water and then dried
General procedure for the reduction of 2,4-DNPH at room
temperature
ꢀ
at 100 C for 2 h for the next cycle.
In a typical experiment, freshly prepared aqueous NaBH4
solution (7.91 mM, 25 mL) was added to an aqueous solution
that contained 2,4-DNPH (10.076 mM, 25 mL) and 10.0 mg of
the Cu/MgO nanocomposite and stirred at room temperature
and the reduction process was monitored by recording UV-vis
spectra. Aer completion of the reaction process, the catalyst
Results and discussion
Preparation and characterization of the Cu/MgO
nanocomposite
was ltered, washed with doubly distilled water and then In this study, the plant extract was used as a reducing and
reused. stabilizing agent for the synthesis of Cu NPs without addition of
Fig. 5 UV-vis and FT-IR spectra of biosynthesized Cu/MgO nanocomposite.
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Fig. 6 FESEM images of the Cu/MgO nanocomposite.
any other external reducing agent. Moreover, the UV spectrum stable with no signicant variance in the shape, position and
of extract (Fig. 2) shows bands at 375 nm (band I) and 288 nm symmetry of the absorption peak even aer 22 days.
(band II) assigned to the cinnamoyl and benzoyl systems of
Furthermore, Fig. 3 shows the FT-IR spectrum of Cu NPs and
phenolics compounds. Therefore, the UV results support the plant extract for comparison in which shows the interaction
presence of phenolics in plant extract as reported by between CuCl2$2H2O and involved sites of phytochemicals to
literatures.36–39
synthesis of Cu NPs (Fig. 3). The peaks at 3500, 1695, 1432, 1300
The UV-vis spectrum of green synthesized Cu NPs using the and 1000 cmꢁ1 represent the OH functional groups, carbonyl
plant extract (Fig. 2) showed the signicant changes in the group (C]O), stretching C]C aromatic ring and C–OH
absorbance maxima due to surface plasmon resonance. The stretching vibrations, respectively. Phytochemicals could
color of the mixture changed into dark aer 5 min at 555 nm adsorb on the surface of metal nanoparticles, possibly by
indicating formation of Cu NPs as characterized by UV-vis interaction through p-electrons interaction in the absence of
spectrum. The synthesized Cu NPs by this method are quite other strong ligating agents.
Fig. 7 EDS spectrum of the Cu/MgO nanocomposite.
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Fig. 8 TEM images and histogram of particle size distribution of the Cu/MgO nanocomposite.
changing the color of the reaction (whitish to dark) and
decrease the maxima ranging 500–580 nm indicates the
reduction process and formation of nanoparticles. As moni-
tored by UV-vis the synthesized nanoparticles by this method
are quite stable with no signicant variance in the shape,
position and symmetry of the absorption peak even aer 30
days which indicates the stability of product.
Furthermore, FT-IR spectrum of Cu/MgO nanocomposite is
shown in Fig. 5. The appeared bands are lattice vibration modes
indicating the functional groups of sample. The bands below
1000 cmꢁ1 are related to the Mg-O absorption. A high absorp-
tion band, which appeared at 1610 cmꢁ1, is also observed in the
MgO spectrum, which is related to bending vibration of absor-
bed water and surface hydroxyl (OH). The peak at 1485 cmꢁ1 is
assigned to the bending vibration of OH bond. The sharp
absorption peak at 3697 cmꢁ1 is due to the antisymmetric
stretching vibration in the Mg(OH)2.
The morphology of the Cu/MgO nanocomposite is revealed
by FESEM. FESEM analysis (Fig. 6) of the Cu/MgO nano-
composite prepared by Cassytha liformis L. showed that copper
particles deposited on the rough surface of MgO with ake- and
sheet-shaped morphology.
Scheme
temperature.
2 The catalytic reduction of 4-NP to 4-AP at room
Fig. 4 shows the X-ray diffraction pattern and TEM analysis of
the Cu NPs. The patterns at 2q values 43.7ꢀ, 50.7ꢀ and 74.5ꢀ can
be assigned to (1 1 1), (2 0 0) and (2 2 0) crystal planes in Cu cubic
structure which agrees with the standard Cu (JCPDS 71-4610).
The biosynthesized Cu NPs structure and size was examined
using TEM analysis. It is clear from Fig. 4 that the sizes of the Cu
NPs are narrow, and the particles are mainly spherical in shape.
The stable Cu/MgO nanocomposite obtained was fully
characterized by UV-vis, FT-IR, TEM, SEM and EDS.
Fig. 5 shows the absorption spectrum of Cu/MgO nano-
composite due to surface plasmon resonance (SPR) of metallic
nanoparticles. At compare with spectra related to Cu NPs,
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Fig. 9 UV-visible spectra of the 4-NP reduced by the Cu/MgO nanocomposite. Reaction conditions: 10.0 mg of Cu/MgO nanocomposite,
25 mL of 4-NP aqueous solution (2.5 mM) and 25 mL of NaBH4 aqueous solution (2.5 mM) at room temperature.
The elemental composition of the Cu/MgO nanocomposite in water at room temperature was chosen as a pattern reaction
was determined by EDS analysis (Fig. 7). Presence of magne- to evaluate the catalytic activity of Cu/MgO nanocomposite.
sium (Mg), oxygen (O) and copper (Cu) was conrmed by EDS
spectroscopy.
Catalytic ability of Cu/MgO nanocomposite for reduction of 4-
NP at room temperature
A close examination of the TEM images in Fig. 8 reveals that
the nanoparticles are spherical morphology in shape. As may be
seen in the TEM images, the average diameter of particles is
19 nm.
In present work, the catalytic activity of the Cu/MgO nano-
composite was evaluated by the reduction of 4-NP as hazardous
matter to 4-AP in the presence of NaBH4 as reducing agent in
water (Scheme 2).
Catalytic ability of Cu/MgO nanocomposite for reduction of 4-
NP, 2,4-DNPH, MB and CR
4-NP in aqueous medium has a maximum absorption at 317.
Aer the addition of the NaBH4 solution, the new absorption
peak at 400 nm is appeared due to formation of 4-nitro-
phenolate (Fig. 9). In the presence of 4-NP + NaBH4 solution and
in the absence of Cu/MgO nanocomposite does not happen any
Catalytic ability and application of the synthesized Cu/MgO
nanocomposite investigated in the reduction of 2,4-DNPH, 4-
NP, CR and MB. In the present method, the catalytic reduction
of nitro compounds and organic dyes in the presence of NaBH4
Table 1 Completion time for the reduction 4-NP to 4-AP at room
temperature using different amounts of Cu/MgO nanocomposite
NaBH4
(equivalents)
Time
(min)
Entry
Catalyst (mg)
1
2
3
4
—
100
100
0.0
140 mina
40 minb
300 minb
270 s
MgO (10.0)
Cu/MgO nanocomposite (7.0)
Cu/MgO nanocomposite
(10.0)
100
5
6
7
Cu/MgO nanocomposite (7.0)
Cu/MgO nanocomposite (5.0)
Cu/MgO nanocomposite
(10.0)
100
100
79
280 s
537 s
477 s
8
Cu/MgO nanocomposite
(10.0)
Cu NPs
50
10 min
9
10
0.0
100
300 minb
520 s
Cu NPs
Scheme 3 Possible mechanism for the catalytic reduction of 4-NP to
4-AP by Cu/MgO nanocomposite at room temperature.
a
No reaction. b Not completed.
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the reaction time (entry 3 and 9). The best result was obtained
with 10.0 mg of Cu/MgO nanocomposite with 100 equivalents of
NaBH4 (Table 1, entry 4). Aer completion of the reaction and
conversion of 4-NP to 4-AP, the peak at 400 nm was disappeared.
As shown in Table 1, the reaction took place aer 520 s in the
presence of Cu NPs. According the results, Cu/MgO nano-
composite is much more reactive than Cu NPs and the reaction
was completed during 270 s in the presence of the Cu/MgO
nanocomposite. The MgO is not only a support to prevent
aggregation of the Cu NPs, but also can provide a synergistic
effect in reduction process, which allow more molecules to be in
contact with the surface of Cu NPs.
The reduction process of 4-NP to 4-AP is usually carried out in
presence of a catalyst in aqueous media at room temperature.
Therefore, presence of the Cu/MgO nanocomposite as a catalyst
and NaBH4 as a reducing agent is necessary for reduction of 4-NP.
In the absence of the Cu/MgO nanocomposite and NaBH4,
reduction reaction did not proceed even aer a long time (Table 1).
The catalytic reduction of the 4-NP by using Cu/MgO nano-
composite is an electron transfer (ET) process. The reaction was
carried out in two steps (Scheme 3). In the rst step of process,
4-NP and BH4 diffuse from aqueous solution to the surface of
catalyst via p–p stacking interactions. In the next step, aer
electron transfer from the BH4ꢁ (reductant) and 4-NP (oxidant)
near to the Cu NPs on the MgO surface as the electron mediator,
the hydrogen atoms, which are formed from BH4ꢁ, attack 4-NP
molecule to reduce it. Finally, the corresponding product was
desorbed from the surface of the catalyst. These observations
indicate that the MgO can stabilize the supported Cu NPs
against aggregation also enhance the catalytic activity through
a synergistic effect.
Scheme 4 The catalytic reduction of 2,4-DNPH to 2,4-DAPH in
aqueous medium at room temperature.
Table 2 Completion time for the reduction 2,4-DNPH to 2,4-DAPH at
room temperature using different amounts of Cu/MgO nano-
composite and NaBH4
NaBH4
Entry
Catalyst (mg)
(equivalents)
Time
1
2
3
4
5
6
—
104
104
75
104
104
50
120 mina
7 min
MgO (10.0)
Cu/MgO nanocomposite (5.0)
Cu/MgO nanocomposite (5.0)
Cu/MgO nanocomposite (7.0)
Cu/MgO nanocomposite
(10.0)
Cu/MgO nanocomposite
(10.0)
Cu/MgO nanocomposite
(10.0)
25 minb
5 min
220 s
15 minb
7
8
75
15 minb
160 s
104
a
No reaction. b Not completed.
reduction process under alkaline conditions (Table 1, entry 1).
As show in Fig. 9, aer the addition of the Cu/MgO nano-
composite to 4-NP + NaBH4 solution, a new absorption signal at
300 nm is appeared following the formation of 4-AP and the
solution color changes from yellow to colorless. We also inves-
tigated the effect of the amount of the NaBH4 for the reduction
of 4-NP. In the absence of NaBH4, no reduction occurred within
Catalytic ability of Cu/MgO nanocomposite for reduction of
2,4-DNPH at room temperature
The catalytic reduction of 2,4-DNPH aqueous solution with
NaBH4 at room temperature has also been used as another
Fig. 10 UV-visible spectra of the 2,4-DNPH reduced by the Cu/MgO nanocomposite. Reaction conditions: 10.0 mg of Cu/MgO nanocomposite,
25 mL of 2,4-DNPH (10.076 mM) and 25 mL of NaBH4 solution (7.91 mM) at room temperature.
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Fig. 11 UV-visible spectra of the MB (a) and CR (b) reduced by using Cu/MgO nanocomposite at room temperature.
model reaction to check the catalytic activity of the Cu/MgO
nanocomposite (Scheme 4).
Table 3 Optimization of reaction conditions for reduction of the MB
and CR
The Cu/MgO nanocomposite demonstrated high activity for
reduction of 2,4-DNPH to 2,4-DAPH in very short time (Table 2).
This process was monitored by UV-vis spectroscopy. The 2,4-
DNPH in aqueous medium has a maximum absorption at
353 nm (Fig. 10). Aer the addition of NaBH4 to 2,4-DNPH
solution in the absence of the Cu/MgO nanocomposite no
change in the color of the solution and absorption spectrum
was observed even aer 120 min (Table 2, entry 1). Aer the
addition of Cu/MgO nanocomposite to the solution, a new
absorption signal at 290 nm is appeared due to the formation of
2,4-DAPH. The effect of the concentration of NaBH4 and catalyst
Entry
Dye (M)
Catalyst (mg)
Time (s)
1
2
3
MB (3.1 ꢂ 10ꢁ5
MB (3.1 ꢂ 10ꢁ5
MB (3.1 ꢂ 10ꢁ5
)
)
)
Cu/MgO nanocomposite (5.0)
Cu/MgO nanocomposite (7.0)
Cu/MgO nanocomposite
(10.0)
6
3
1
4
5
6
7
MB (3.1 ꢂ 10ꢁ5
)
Cu NPs (10.0)
17
CR (1.44 ꢂ 10ꢁ5
CR (1.44 ꢂ 10ꢁ5
CR (1.44 ꢂ 10ꢁ5
)
)
)
Cu/MgO nanocomposite (5.0)
Cu/MgO nanocomposite (7.0)
Cu/MgO nanocomposite
(10.0)
300
256
190
8
CR (1.44 ꢂ 10ꢁ5
)
Cu NPs (10.0)
410
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Table 4 Data for the catalytic reduction of 4-NP, 2,4-DNPH, CR and MB in presence of NaBH4 by different catalysts
Substrate
4-NP
Catalyst
Concentration (mL, mM)
NaBH4 (mL, mM)
Time (min)
Ref.
Au@PZS@CNTs (0.3 mL, 1 mg mLꢁ1
Au–GO (0.25 mL, 1.4 ꢂ 10ꢁ4 M)
Ni NPs (3.0 mg)
Cu microspheres (0.5 mg)
Pd–FG (1.0 mg)
)
1.7, 0.2
10, 0.750
3.0, 0.1
30.0, 0.2
1.0, 15.0
16
7
16
18
12
40
41
42
43
1.0, 2.22 ꢂ 10ꢁ3
0.3, 200.0
10.0, 25.0
0.1, 10.0
2.9, 0.1
44
Cu/MgO nanocomposite (10.0 mg)
Ag@AgCl NPs (150 mL, (0.008 g))
Cu/MgO nanocomposite (10.0 mg)
Cu@SBA-15 (1.0 mg)
Cu/MgO nanocomposite (10.0 mg)
Au@TiO2 (2.0 mg)
25, 2.5
25.0, 250.0
350.0 mL, 0.1 M
25.0, 7.91
5.0, 200.0
25.0, 5.3
2.0, 100.0
25.0, 5.3
25.0, 5.3
4
60
150 s
7
130 s
12
This work
45
This work
46
This work
47
48
2,4-DNPH
CR
60.0 mL, 6.0
25.0, 10.076
22.5, 0.09
25.0, 1.44 ꢂ 10ꢁ2
20.0, 0.04
25.0, 0.03
25.0, 3.1 ꢂ 10ꢁ2
MB
Natrolite zeolite/Pd (7.0 mg)
Cu/MgO nanocomposite (10.0 mg)
1 s
1 s
This work
Fig. 12 FESEM images of recovered Cu/MgO nanocomposite.
Fig. 13 EDS analysis of recovered Cu/MgO nanocomposite.
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Fig. 14 TEM images of recovered Cu/MgO nanocomposite.
loading was studied by carrying out the reduction reaction in the NaBH4 or catalyst. The effect of the catalyst loading is
the presence of varying amounts of the NaBH4 and catalyst. In a signicant issue for the reduction of dyes. As shown in Table
the absence of NaBH4, no reduction occurred within the reac- 3, it was observed that reduction of MB and CR occurred within
tion time. The best result was obtained with 104 equivalents of 1 s and 190 s, respectively in the presence of 10.0 mg of the Cu/
NaBH4 and 10.0 mg of the Cu/MgO nanocomposite (Table 2, MgO nanocomposite. The progress of the reaction was moni-
entry 8).
tored using UV-visible measurements at ordered intervals of
time. The catalytic activity of the prepared Cu NPs by Cassytha
liformis L. extract was also tested for the reduction of MB and
CR (Table 3, entry 4 and 8). It is interesting to note that the Cu
NPs gave poorer activity.
Catalytic ability of the Cu/MgO nanocomposite for reduction
of the MB and CR at room temperature
The catalytic activity of the prepared Cu/MgO nano-
composite towards 2,4-DNPH, 4-NP, MB and CR reduction was
compared with reported catalysts in the literature. According to
Table 4, the Cu/MgO nanocomposite exhibited a higher cata-
lytic activity than other catalysts. As shown in Table 4, the best
result was obtained with Cu/MgO nanocomposite at room
temperature with shorter reaction times. In addition, the Cu/
MgO nanocomposite were synthesized by a green technique
In addition, the reduction of the MB and CR were chosen to
evaluate the performance of the as-prepared Cu/MgO nano-
composite. The catalytic reduction of MB and CR was investi-
gated with 25 mL of fresh NaBH4 aqueous solution (5.3 ꢂ 10ꢁ3
M) and different amounts of catalyst at room temperature. The
MB and CR dyes represented a characteristic SPR band at lmax
663 and 493 nm, respectively (Fig. 11). It is mentioned here that
the no decolorization of dye could be detected in the absence of
Fig. 15 FT-IR spectrum of recovered Cu/MgO nanocomposite.
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using Cassytha liformis L. extract without use of dangerous and
toxic reagents or capping agent and surfactant.
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Catalyst recyclability
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RSC Adv., 2015, 5, 74575.
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A. Semnani, J. Hazard. Mater., 2009, 162, 674.
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Appl. Phys., 2004, 4(6), 647.
The recyclability of the catalysts is one of the advantages of
heterogeneous catalysts. The stability and reusability of the Cu/
MgO nanocomposite was tested in the reduction of CR with
NaBH4. The Cu/MgO nanocomposite can be separated from the
reaction mixture by mild centrifugation and washed with
distilled water several times, dried and then reused at least six
times without signicant loss of catalytic activity. The high
activity of catalyst conrms the high stability of Cu/MgO
nanocomposite under the reaction conditions. As shown in
TEM, FESEM, FT-IR images and EDS analysis of the recycled
catalyst (Fig. 12–15), no obvious change in structure, chemical
composition, morphology and size of NPs were observed. The
XRD patterns before and aer the reaction revealed that the Cu/
MgO nanocomposite retained its crystallinity throughout.
17 G. N. Panin, A. N. Baranov, Y. J. Oh, T. W. Kang and
T. W. Kim, J. Cryst. Growth, 2005, 279(3–4), 494.
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10332.
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6(1), 46.
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Mater. Sci.: Mater. Electron., 2015, 26, 3309.
22 J. Choi, D. Reddy, M. Islam, B. Seo, S. Joo and T. Kim, Appl.
Surf. Sci., 2015, 358, 159.
Conclusion
The green synthesis of copper nanoparticles using Cassytha
liformis L. extract provides a rapid and simple route for the
preparation of Cu/MgO nanocomposite. The avonoids present
in extract of Cassytha liformis L. act as both reducing and
capping/stabilizing agents. The synthesized Cu and Cu/MgO
nanocomposite were characterized by XRD, SEM, EDS, TEM,
FT-IR and UV-vis spectroscopic techniques. The catalyst
exhibits high catalytic activity for the reduction of 2,4-DNPH, 4-
NP, MB and CR by using NaBH4 in aqueous medium at room
temperature. The signicant advantages of this methodology
are elimination of hazardous materials, short reaction time,
mild reaction conditions and simple work-up procedure.
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2015, 12, 76.
24 Z. Issaabadi, M. Nasrollahzadeh and S. M. Sajadi, J. Cleaner
Prod., 2017, 142, 3584.
Conflicts of interest
25 A. R. Vartooni, M. Nasrollahzadeh and M. Alizadeh, J. Alloys
Compd., 2016, 680, 309.
There are no conicts to declare.
26 N. Muhd Julkapli and S. Bagheri, Rev. Inorg. Chem., 2016, 36,
1.
Acknowledgements
27 M. N. Nadagouda and R. S. Varm, Green Chem., 2008, 10, 859.
28 J. Y. Song and B. S. Kim, Bioprocess Biosyst. Eng., 2009, 32, 79.
29 H. Bar, D. K. Bhui, G. P. Sahoo, P. Sarkar, S. Pyne and
A. Misra, Colloids Surf., A, 2009, 348, 212.
30 A. K. Mittal, Y. Chisti and U. C. Banerjee, Biotechnol. Adv.,
2013, 31, 346.
We gratefully acknowledge the Iranian Nano Council and the
University of Qom for the support of this work.
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