Fe3O4 – Glutathione stabilized Ag nanoparticles: A new magnetically separable robust and facile catalyst for aqueous phase reduction of nitroarenes

Article abstract of DOI:10.1002/aoc.5223

The heterostructured Ag nanoparticles decorated Fe₃O₄ Glutathione (Fe₃O₄-Glu-Ag) nanoparticles (NPs) were synthesized by sonicating glutathione (Glu) with magnetite and further surface immobilization of silver NPs on it. The ensuing magnetic nano catalyst is well characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA). The prepared Fe₃O₄-Glu-Ag nanoparticles have proved to be an efficient and recyclable nanocatalyst with low catalyst loading for the reduction of nitroarenes and heteronitroarenes to respective amines in the presence of NaBH₄ using water as a green solvent which could be easily separated at the end of a reaction using an external magnet and can be recycled up to 5 runs without any significant loss in catalytic activity. Gram scale study for the reduction of 4-NP has also being carried out successfully and it has been observed that this method can serve as an efficient protocol for reduction of nitroarenes on industrial level.

Full text of DOI:10.1002/aoc.5223

Received: 14 January 2019
DOI: 10.1002/aoc.5223
Revised: 17 July 2019
Accepted: 29 July 2019
F U L L P A P E R
Fe3O4 – Glutathione stabilized Ag nanoparticles: A new
magnetically separable robust and facile catalyst for
aqueous phase reduction of nitroarenes
Mitlesh Kumari1 | Ragini Gupta1,2
| Yachana Jain1
1 Department of Chemistry, Malaviya
The heterostructured Ag nanoparticles decorated Fe3O4 Glutathione (Fe3O4‐
Glu‐Ag) nanoparticles (NPs) were synthesized by sonicating glutathione
(Glu) with magnetite and further surface immobilization of silver NPs on it.
The ensuing magnetic nano catalyst is well characterized by Fourier transform
infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high reso-
lution transmission electron microscopy (HRTEM), powder X‐ray diffraction
(PXRD), thermogravimetric analysis (TGA). The prepared Fe3O4‐Glu‐Ag nano-
particles have proved to be an efficient and recyclable nanocatalyst with low
catalyst loading for the reduction of nitroarenes and heteronitroarenes to
respective amines in the presence of NaBH4 using water as a green solvent
which could be easily separated at the end of a reaction using an external mag-
net and can be recycled up to 5 runs without any significant loss in catalytic
activity. Gram scale study for the reduction of 4‐NP has also being carried
out successfully and it has been observed that this method can serve as an effi-
cient protocol for reduction of nitroarenes on industrial level.
National Institute of Technology, Jaipur
302017, India
2 Materials Research Centre, Malaviya
National Institute of Technology, Jaipur
302017, India
Correspondence
Ragini Gupta, Department of Chemistry,
Malaviya National Institute of Technology
Jaipur 302017, India.
Email:
Email: rgupta.chy@mnit.ac.in
KEYWORDS
Fe3O4‐Glu‐AgNPs, magnetically separable, reduction of nitroarenes, silver nanoparticles
1 | INTRODUCTION
undesirable waste that is detrimental to the environ-
ment.[9] On the other hand, catalysts used for the cata-
The reduction of nitroarenes has attracted a great deal of
attention as the resulting anilines are important interme-
diates for the manufacture of pharmaceuticals, dyes, poly-
mers, and fine chemicals.[1] 4‐ nitrophenol being one of
the toxic pollutant as the United States Environmental
Agency has listed 4‐nitrophenol as ‘priority pollutant’
because it can be hardly removed through natural degra-
dation as a refractory pollutant and will cause serious risk
to both animal and human.[2] Generally, the synthesis of
anilines entails catalytic[3–5] and non‐catalytic methods
employing different reducing agents.[6–8] The non‐
catalytic processes uses either Bechamp or sulphide
reduction technology which generates large amounts of
lytic reduction of nitro compounds give priority to the
precious metals, such as Pd and Pt, which are expensive
and usually sensitive to both air and moisture.[10–13]
Another type of catalyst was the iron‐based compounds,
including FeCl3, iron oxides and FeOOH, which were
[14]
mainly explored for the reduction of nitroarenes
.
The preparation and use of magnetic nanoparticles
(MNPs) offers advantages in clean and sustainable chem-
istry as they are non‐toxic, readily accessible, and retriev-
able.[14,15] They have attracted more and more attention
because of their unique properties, such as large surface
area, multifunctionality, excellent loading capacity and
great potential applications in catalysis, drug carriers
Appl Organometal Chem. 2019;e5223.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 11
https://doi.org/10.1002/aoc.5223

2 of 11
KUMARI ET AL.
and building blocks of photonic crystals.[16] Their insolu-
ble and superparamagnetic properties enable the catalysts
to be easily separated with an external magnetic field,
which eliminate the necessity of catalyst filtration.[17]
However, Fe3O4 nanoparticles as supports are vulnerable
to the air.[18] Unfortunately, they tend to aggregate due to
their high surface energy, leading to the drops of catalytic
performance. The immobilization of magnetic catalysts
on various supports is considered as one effective
approach to prevent nanostructures from aggregation.[19]
Thus, it was needed to functionalized it with organic
and inorganic supports.[20] Additionally, the activity and
selectivity of magnetic nano‐catalysts could be manipu-
lated by their surface modification.[21,22] The first stride
in the development of this concept was the selection of
amino acids for the functionalization of magnetic nano-
particles. We decided to explore highly benign tripeptide
glutathione, an essential component of plants and human
cell systems, as an organocatalyst. An additional benefit
of using glutathione is the presence of the highly reactive
thiol group, which could be used for anchoring to the
nano‐ferrite surfaces,[23] keeping active sites free for catal-
ysis. The support needed to be chemically stable, conve-
nient for the immobilization of Ag NPs as powdered Ag
NPs were not suitable for large scale applications in het-
erogeneous catalysis because they tend to aggregated
owing to their high surface energy, thus resulting in a
rapid reduction of their catalytic activity.[24] Ag NPs fur-
thermore difficult to be separated and recycled from the
reaction solution because of their ultrafine size. To over-
come the above problems, immobilization of Ag NPs on
the surface of suitable supporting substances such as
metal oxides, polymers, carbon materials becomes effi-
cient and the most adopted approach.[25–30]
In our study, silver nanoparticles were immobilized on
magnetite functionalized glutathione which was used as
catalyst for the preparation of aromatic amines by the
reduction of nitroarenes. The reaction was carried out
with sodium borohydride (NaBH4) in water. From earlier
reports it can be seen that quite a few noble metal cata-
lysts based on Pt, Pd, Ru, Au, Ag etc. have been designed
for this transformation (Xie et al. 2013; Shil et al. 2012;
Kim et al. 2012; Liu et al. 2013; Nemanashi et al. 2013).
Except Ag, all noble metals are very expensive. Thus,
Ag‐based recyclable catalysts reduce the cost of the reac-
tion.[31] Additionally, the catalytic reduction of nitroarene
compounds in sustainable method with green solvent like
water which has been one of the most important method
for decontamination of nitroarene compounds.[32–47]
Sodium borohydride (NaBH4) was a common reductant
for hydrogenation. When it was used for reduction reac-
tions with the help of transition metal catalysts, although
normal pressure and room temperature was available,
substantial molar excess of NaBH4 relative to the sub-
strates, usually exceeding 100‐fold excess, was
needed.[48,49] It is important to search suitable catalyst
which could increase the catalytic efficiency and decrease
[50]
the amount of NaBH4.
By considering all the above‐
mentioned points and in the course of our investigations
into the development of novel inorganic–organic hybrid
heterogeneous nanocatalysts in organic transforma-
tion,[51–53] the aim of this presented work is to highlight
the synergistic effects of the combined properties of mag-
netically stabilized glutathione, in the trapping and stabi-
lizing of the Ag nanoparticles in order to synthesize
highly efficient nanocatalyst for reduction of nitroarenes
and heteronitroarenes to the corresponding aromatic
amines by using NaBH4 in aqueous medium in very short
time with excellent reusability. Consequently, the opti-
mized conditions were used for the synthesis of various
aromatic amines.
2 | EXPERIMENTAL
2.1 | Materials and instruments
All chemicals and solvents purchased are of analytical
grade and used without further purification. Ferric chlo-
ride hexahydrate (FeCl3.6H2O, CDH), ferrous chloride
tetra hydrate (FeCl2.4H2O, Sigma Aldrich), sodium
hydroxide (NaOH, 98% Alfa Aesar), reduced glutathione
powder (CDH), silver nitrate (Molychem). Infrared spectra
were collected on a Bruker Fourier transform infrared
spectrophotometer (FTIR) (Alpha) with pressed KBr pel-
lets and were recorded in the range of 4000–400 wave
number (cm−1). The visualization of surface morphology
of MNPs was done by using a field‐ emission scanning
electron microscope (FESEM; NOVA nano SEM) operated
at a voltage 10 kV. Samples were prepared by putting a lit-
tle amount of fine powdered nanoparticles on black car-
bon tape. Their TEM images were recorded with a
Tecnai G2 20 (FEI) S‐Twin high‐resolution transmission
electron microscope (HRTEM) operating at 200 kV. Sam-
ples were prepared by drying the droplet of dispersed solu-
tion of MNPs on a 400 mesh carbon coated copper grid
under 100 W table lamp. Powder X‐ray diffraction (XRD)
pattern of the sample was obtained with X‐ray Diffractom-
eter (Panalytical X Pert Pro) using Cu Kα radiation.
Thermo gravimetric analysis (TGA) was performed on a
Mettler thermal analyzer in an inert atmosphere at a
heating rate of 10 °C/min. Melting points were determined
in open glass capillaries and are reported uncorrected. 1H
NMR were recorded on a Jeol ECS 400 MHz spectropho-
tometer using DMSO d6 as a solvent. TMS was taken as
an internal standard and chemical shifts are reported in

KUMARI ET AL.
3 of 11
δ ppm. Resonance multiplicities are described as s (sin-
glet), d (doublet), t (triplet), q (quartet) and m (multiplet).
Ultrasonic bath; Elma S 70 H with 37 KHz with an output
frequency was used to carry out the sonochemical reac-
tions. UV–visible spectra were recorded on a Shimadzu
UV‐1800 in standard 3.5 ml quartz cells with 10 mm path
length. The purity of all the compounds was checked by
TLC using silica gel as adsorbent and solvents of increas-
ing polarity as mobile phase.
Reduced glutathione powder (0.2 gm) dissolved in deion-
ized water (5 ml) was added to the above solution and
again sonicated for another 2 hr. The glutathione func-
tionalized magnetic nanomaterial was then isolated by
using an external magnet, washed with water (2 x
30 ml) and methanol (2 x 30 ml), and dried in an oven
at 50–60 °C for 3 hr.
Step III
Glutathione functionalized nano Fe3O4 (1 gm) was dis-
persed in 20 ml of water‐ methanol mixture (1:1). Silver
nitrate (100 mg) solution in water was added to the reac-
tion mixture. Hydrazine monohydrate solution in water
was added drop wise to bring the pH of the mixture to
9–10 followed by the addition of 0.1 gm of NaBH4. The
reaction mixture was then sonicated for 4 hr after which
it was cooled down to room temperature and the black
precipitate of functionalised magnetic nanoparticles set-
tled down under the influence of an external magnet.
They were retrieved by magnetic decantation and washed
with deionised water (20 ml x 5). Thereafter they were
dried in vacuum oven for 2 hr at 60 °C.
2.2 | Synthesis of ag decorated Fe3O4
‐glutathione nanoparticles
Step I
The magnetite nanoparticles were synthesized by
chemical co‐precipitation method similar to previously
reported method with slight modification.[47] In a
250 ml round bottom flask 16 mmol of FeCl3.6H2O
(4.32 g) and 8 mmol of FeCl2.4H2O (1.59 g) were taken
in 50 ml of deionised (DI) water and ultrasonicated for
15 mins at room temperature (25 °C). Then slowly the
temperature was raised to 60 °C and maintained for fur-
ther 30 mins. After that 50 ml of 1 M NaOH solution
was added dropwise at the same temperature till the pH
of the solution became 10–11. It was further sonicated
for another 30 mins. The resulting black dispersion was
then allowed to remain undisturbed for one night and
the desired nanoparticles were separated by using an
external magnet then washed thoroughly with deionised
water (100 x 3 ml) followed by acetone, (2 x 50 ml) and
finally dried in a vacuum oven for 6 hr at 60 °C.
2.3 | General procedure for the reduction
of nitro compounds, catalysed by Fe3O4‐
Glu‐AgNps
In this protocol of reduction, to the suspension of 4‐ nitro
phenol (0.5 mmol) in water (10 ml), NaBH4 (4 mmol) was
added. Then add 60 mg of the catalyst to the reaction
mixture and ultrasonicated at 60 °C for 9 min. After com-
pletion of the reaction as indicated by TLC (EtOAc/n‐
hexane as eluent: 2/8), the nanocatalyst was separated
out using an external magnet and reaction mixture was
extracted with ethyl acetate and concentrated in rota
vapor to get the desired product. Further purification of
Step II
Nano Fe3O4 (0.5 gm) was dispersed in deionised water
(20 ml) and methanol (10 ml) and sonicated for 20 min.
SCHEME 1 Pictorial depiction for the
preparation of Fe3O4‐Glu‐AgNps

4 of 11
KUMARI ET AL.
the compounds were carried out by column chromatogra-
phy. The products were confirmed by their melting points
and H NMR spectroscopy.
3 | RESULTS AND DISCUSSIONS
1
3.1 | Characterization of Fe3O4‐Glu‐Ag
nanocatalyst
The synthetic route for the preparation of Ag incorpo-
rated glutathione conjugated magnetic nanoparticle, as
prepared with a multistep process has been outlined in
Scheme 1. Firstly Fe3O4 nanoparticles was prepared by
co‐precipitation of ferrous and ferric ions in basic aque-
ous solution followed by thermal treatment. Because of
the sensitivity of the Fe3O4 nanoparticles its surface was
coated with glutathione. Finally, embedding of the silver
nanoparticles into the nanocomposite magnetite‐
glutathione has been carried out by chemical reduction
AgNO3 by hydrazine hydrate and sodium borohydride.
The chemical structure of Fe3O4‐Glu‐AgNPs was ana-
lyzed by using various microscopic and spectroscopic
techniques such as FTIR, FESEM, EDS mapping, XRD,
HRTEM and TGA.
FIGURE 1 FTIR spectrum of (a) glutathione (b) Fe3O4 (c) Fe3O4‐
Glu (c) Fe3O4‐Glu‐AgNPs
To confirm the immobilization of the active compo-
nents, FTIR spectroscopy was initially utilized. A strong
band at 583 cm−1 in Figure 1(b) was due to the vibration
of the Fe‐O of ferrite. Three characteristic bands
2947 cm−1 (C‐H stretching), 1648 cm−1 (cysteine car-
bonyl), and 1629 cm−1 (glutamic acid‐carbonyl) evidently
confirmed the attachment of glutathione on nano ferrite
surfaces. The molecule was firmly anchored via the thiol
group, as the IR band at 2558 cm−1 for S‐H stretching was
diminished after anchoring. In the IR spectrum of magne-
tite the characteristic Fe‐O streching peak initially comes
at 583 cm−1 shifted to 596 cm−1 in Fe3O4‐Glu‐AgNPs.
Figure 2 shows the X‐ray diffraction patterns of the
Fe3O4, glutathione and Fe3O4‐Glu‐AgNPs. According to
JCPDS card no. 19–0629, six diffraction peaks appearing
in Figure 2 (a) located at 30.4°, 35.5°, 43.3°, 53.4°, 57.2°
and 62.8° can be assigned to diffraction of Fe3O4 crystal
with an inverse spinal structure from the (220), (311),
FIGURE 2 XRD of (a) Fe3O4 (b) glutathione (c) Fe3O4‐Glu‐
AgNPs
FIGURE 3 TGA curve of (a) Fe3O4 (b) Fe3O4‐Glu‐AgNPs

KUMARI ET AL.
5 of 11
FIGURE 4 EDS spectrum of Fe3O4‐
Glu‐AgNPs
FIGURE 5 EDS elemental mapping of the Fe3O4‐Glu‐AgNPs
(400), (422), (511), and (440). XRD pattern of Fe3O4‐Glu‐
AgNPs shows same diffraction peaks as of magnetite. In
addition, obvious diffraction peaks at 2θ values of 38.2°,
64.3° and 77.3° has been also observed which were corre-
sponding to the (111), (220), and (311) planes of silver,
respectively. Thermal gravimetric analysis (TGA) of bare

6 of 11
KUMARI ET AL.
FIGURE 6 Low magnification TEM image of (a) Fe3O4 (b) Fe3O4‐Glu (c) and (d) HRTEM of Fe3O4‐Glu (e) TEM image of Fe3O4‐Glu‐
AgNPs (f) and (g) HRTEM image showing the interlayer planes of Fe3O4‐Glu‐AgNPs (h) Histogram showing size distribution of Fe3O4‐
Glu‐AgNPs (i) SAED pattern of the corresponding low magnification TEM image of Fe3O4‐Glu‐AgNPs
magnetite Fe3O4‐Glu‐AgNPs was performed within the
range of 25–900 °C under an inert atmosphere of nitro-
gen. As shown in Figure 3 (a) 3.5% weight loss was
observed due to presence of water and OH group
deteoration present on the surface of magnetite. In
Figure 3 (b) major weight loss of 18% at high temperature
was observed which confirms that glutathione was
chemically bounded to the magnetic nanoparticles. It
implies that thermal stability of synthesised Fe3O4‐Glu‐
AgNPs have been maintained at higher temperature.
Furthermore, the chemical composition of the Fe3O4‐
Glu‐Ag nanocomposite was determined by energy X‐ray
FIGURE 7 Optimisation of reductant amount and catalyst
loading for reduction of 4‐NP (reaction conditions: 0.5 mmol of 4‐
nitrophenol, 10 ml H2O, 60 °C, ultrasonicated in air)
FIGURE 8 Optimisation of time and temperature for reduction
of 4‐NP (reaction conditions: 0.5 mmol of 4‐nitrophenol, 4 mmol
of NaBH4, 10 ml H2O, 60 mg of catalyst ultrasonicated in air)

KUMARI ET AL.
7 of 11
from 1–25 nm with dominant particles in the range of
size 11–15 nm. The selected area electron diffraction pat-
tern as shown in Figure 6 (i) displayed that the particles
were polycrystalline in nature.
3.2 | Reduction of nitro compounds by
Fe3O4‐Glu‐ag nanocatalyst
After the successful preparation and characterization of
the Fe3O4‐Glu‐AgNPs, catalytic performance of the
nanocatalyst have been explored in the reduction of 4‐
nitrophenol (4‐NP) as model reaction in the presence of
NaBH4 as a reductant. Three experiments were per-
formed initially under ultrasonication (i) reduction in
the absence of the catalyst Fe3O4‐Glu‐Ag, no product
obtained; (ii) reduction was also performed in the pres-
ence of bare magnetite only, negligible conversion of
reactant was observed; (iii) when reaction was performed
in the presence of Fe3O4‐Glu‐Ag nanoparticles, products
were obtained in good yield. To explore the optimum
amount of needed catalyst and reductant, different cata-
lyst loadings (20, 40, 60, 80) were investigated at different
mmol (4, 5, 6) of reductant (Figure 7) which revealed that
60 mg of the catalyst and 4 mmol of reductant were the
optimum that afforded 98% of aminophenol. Next, the
reduction of nitrophenol was investigated varying tem-
perature and time (Figure 8). A poor yield was obtained
at 30 °C and at a time of 180 min. Then, the temperature
and time for the reaction was changed to 40 °C and
20 min, respectively, giving 90% of yield of 4‐amino phe-
nol. The temperature when increased to 60 °C over a time
period of 9 min, excellent yield was observed of 98%. No
notable change in yield was observed at temperature
greater than 60 °C and thus 60 °C and 9 min were chosen
as the optimized reaction temperature and time respec-
tively. As shown in Figure 9 the effect of different sol-
vents on the reduction of 4‐nitro phenol was also
FIGURE 9 Standarization of various solvents (1. Toluene 2.
MeOH 3. EtOH 4. MeOH/H2O 5. H2O) (reaction conditions:
0.5 mmol of 4‐nitrophenol, 4 mmol of NaBH4, 60 °C, 9 min, 10 ml
H2O, 60 mg of catalyst ultrasonicated in air)
spectroscopy (EDS). It is found that the peaks of C, N, S,
O, Fe and Ag were observed. The percentage of each ele-
ment of nanocatalyst were obtained from energy disper-
sive X‐ray spectrum (Figure 4). The presence of silver
centers in the nanocomposite support Fe3O4‐Glu was
confirmed by elemental mapping images (Figure 5). The
result showed uniform distribution of silver nanoparticles
over the structure of the glutathione supported magnetite
nanoparticles. Transmission electron‐microscopy studies
as shown in Figure 6 (a, b) depicts the low magnification
TEM image of the Fe3O4, Fe3O4‐Glu and Figure 6 (c) and
(d) represented the HRTEM image of Fe3O4‐Glu showing
successfully coating of glutathione over magnetite.
Figure 6 (e) revealed the TEM image of Fe3O4‐Glu‐Ag
nanoparticles and described that the particles were
almost spherical and multifaceted cuboid in shape while
the histogram. Figure 6 (f) and (g) showed the HRTEM
image of nanocatalyst and also the lattice fringes with
d‐spacing 0.233 nm corresponds to the [311] plane of
the Fe3O4. The lattice fringes separated by 0.236 nm in
Figure 6 (g) are in good agreement with the [111] lattice
spacing of Ag. Figure 6 (h) showed that the size ranges
FIGURE 10 Time‐dependent UV–visible absorption spectra for the reduction of 4‐nitrophenol over Fe3O4‐Glu‐AgNPs in aqueous media at
60 °C, Figure 10 (a) and plot of ln (At/A0) versus time for reduction of 4‐nitrophenol, Figure 10 (b)

8 of 11
KUMARI ET AL.
TABLE 1 Catalytic reduction of nitroarenes over Fe3O4‐Glu‐Ag
nanocatalyst in aqueous media
investigated and it was discerned that the product yield
was not satisfactory in toluene as the reducing agent
was less soluble in it compared to other polar solvents.
Ethanol and methanol afforded moderate yield and mix-
ture of methanol and water showed good yield. The prod-
uct yield improved with the polarity of solvents and the
yield was highest in water as the solubility of NaBH4 in
water is high and thus water served as the best solvent.
The kinetics of the catalytic reduction was also studied
in a standard quartz cuvette with 1 cm path length and
4.5 ml volume. 3 ml of water was mixed with 20 μl
(10−2 M) of 4‐ nitro phenol solution, finally 150 μl
(10−1 M) was added. After mixing these solutions, 3 mg
of Fe3O4‐Glu‐AgNPs were added in cuvette to study the
reduction reaction. UV–visible spectra were recorded at
every 3 min interval in the range of 200–600 nm for
9 mins. The rate constant was determined by measuring
the change in absorbance (Figure 9 (a)) of a peak at
400 nm, the initially observed peak for the nitrophenolate
ion, as a function of time. The peak shows a gradual
decrease in intensity with time and a new peak appeared
at 295 nm indicating the formation of 4‐amino phenol. A
linear correlation between ln (At/A0) and reaction time,
where At and A0 represented the absorbance at the fixed
intervals and the absorbance at the initial stage, respec-
tively (Figure 10 (b)). This result confirmed that the reac-
tion is a pseudo‐first‐order and its rate constant (k) was
S.
No
Nitro
Compound
Time
(min)
Yield
(%)
Product
1
9
98
2
3
4
9
97
98
95
12
10
5
6
15
15
92
90
calculated from the slope to be 0.510 min−1
.
Using the optimized reaction conditions, (0.5 mmol of
4‐nitro phenol, 4 mmol of NaBH4, 60 mg of the catalyst at
60 °C in aqueous solution) the activity and synthetic
scope of the catalyst was demonstrated by reduction of a
series of nitroarenes (Table 1). As shown in Table 1, acti-
vated and deactivated groups have a very small authority
on the reaction times and yields. In all cases, correspond-
ing amines were found to be the exclusive product of the
reactions according to TLC and the azo, hydrazo and
azoxy groups as the usual side products in the reduction
of nitroarenes were not detected. A plausible reaction
mechanism for the reduction of aromatic nitro com-
pounds to corresponding amine using Fe3O4‐Glu‐Ag cata-
lyst with NaBH4 as hydrogen source showed in Scheme 2.
The mechanism was proposed based on the reported liter-
ature.[31] The reaction pathway follow direct route where
[BH4]− ion and the substrate adsorption–desorption takes
place at the silver nanoparticle surface. The aromatic
nitro compound then get reduced to the corresponding
nitroso compounds. Those were again converted to
hydroxylamines and lastly after further reduction, desired
substituted aromatic amines were obtained. The recycla-
bility of the catalyst is certainly very essential, therefore
we examined the recyclability of our developed catalyst
for the reduction of 4‐NP as a model substrate under
7
8
10
10
95
94
9
18
15
90
88
10
Reaction conditions: 4‐nitrophenol (0.5 mmol), NaBH4 (4 mmol), Fe3O4‐Glu‐
Ag (60 mg),
10 ml of H2O, 60 °C, ultrasonicated in open air
the optimized conditions. After completion of the reac-
tion, the catalyst could be easily separated using an exter-
nal magnet. The separated spent catalyst was then
washed with ethanol and dried before reuse. This process
was repeated 5 times successfully without any noticeable
decrease in catalytic activity (Figure 11) suggesting that
the catalyst could find application in the practical

KUMARI ET AL.
9 of 11
SCHEME 2 Possible reaction pathway for the catalytic reduction of nitroarene
reduction of nitroarenes on industrial scale. The leaching
aspect of any silver after recycling was examined by deter-
mining the metal content of reaction solution using AAS
(atomic absorption spectroscopy) after removing of the
catalyst and founded that metal leaching was negligible.
To demonstrate the superiority of Fe3O4‐Glu‐Ag over
the reported catalysts, the reduction of 4‐NP was consid-
ered as a representative example (Table 2). The results
clearly demonstrate that the nanocomposite is an equally
or more efficient catalyst for this reaction. A gram scale
reaction was also setup with a Fe3O4‐Glu‐Ag nanocatalyst
to show industrial application. In our present study, 4‐
nitrophenol (10 mmol), NaBH4 (80 mmol), were added
in water (40 ml). Then add 1.2 gm of the catalyst to the
reaction mixture and ultrasonicated at 60 °C for 10 min.
After completion of the reaction as indicated by TLC
(EtOAc/n‐hexane as eluent: 2/8), the nanocatalyst was
separated out using an external magnet and reaction mix-
ture was extracted with ethyl acetate and concentrated in
rota vapor to get the desired product. Further purification
of the compounds were carried out by column chroma-
tography. Proton NMR of the products are given in
supporting information.
FIGURE 11 Recyclability of Fe3O4‐Glu‐AgNPs in the reduction
of 4‐NP under optimized conditions
TABLE 2 Comparative study of catalytic activity of Fe3O4‐Glu‐Ag for reduction of nitroarene with previously reported systems
Entry
Catalyst
Catalyst amount
Reaction Conditions
Rate constant k
Reference
[31]
1.
2.
3.
4.
5.
6.
7.
8.
9.
10
mPMF‐Ag nanocatalyst
Ag‐SiO2NWs
40 mg
H2O, 60 °C
H2O, RT
H2O, RT
H2O, RT
H2O, RT
H2O, RT
H2O, RT
H2O, RT
H2O, RT
H2O, 60 °C
Not mentioned
2.535 × 10−3 s−1
0.0266 s−1
[54]
[55]
[56]
[57]
[58]
[59]
[60]
[61]
2 mg ml−1, 100 μL
0.06 ml, 0.250 ml
1 mg
Au@NiAg
−1
Cu2O‐Ag NPs
0.38 min−1 mg
PSMAA/Ag
2 mg
3.19 0.22 × 10−3 s‐1
1.5285 min−1
Fe3O4@P (MBAAm‐co‐MAA)@Ag
Ag‐NP‐SPBs
2 mg
5.0× 10−4 mol dm3
0.1772 min−1
Ag@PS
1 mg
0.54 min−1
Ag@Gd‐MOFs
Fe3O4‐Glu‐AgNPs
1.0 mg
21.33 × 10−3 s−1
0.510 min−1
60 mg
‐

10 of 11
KUMARI ET AL.
[9] X. J. Yang, B. Chen, L. Q. Zheng, L. Z. Wu, C. H. Tung, Green
Chem. 2014, 16, 1082.
4 | CONCLUSION
In summary, we have established
[10] M. Li, L. Hu, X. Cao, H. Hong, J. Lu, H. Gu, Chem. – Eur. J.
2011, 17, 2763.
a
robust,
chemoselective and magnetically recyclable catalyst for
the reduction of industrially valuable nitroarenes sub-
strates in the presence of other sensitive reducible func-
tional groups. The catalyst could be recovered from the
reaction mixture by using an external magnetic field
and reused for five consecutive runs without any signifi-
cant loss of yield. The simple work up, separation proce-
dure, purity of product and using water as reaction
media makes the whole process green and sustainable
for environment.
[11] M. B. Gawande, R. Luque, R. T. Zboril, Chem. Cat. Chem. 2014,
6, 3312.
[12] H. Wu, L. M. Zhuo, Q. He, X. P. Liao, B. Shi, Appl. Catal. A.
Gen. 2009, 366, 44.
[13] A. J. Amali, R. K. Rana, Green Chem. 2009, 11, 1781.
[14] (a)R. B. N. Baig, R. S. Varma, Chem. Commun. 2013, 49, 752.
(b)V. Polshettiwar, R. S. Varma, Green Chem. 2010, 12, 743.
[15] B. Duan, F. Liu, M. He, L. Zhang, Green Chem. 2014, 16, 2835.
[16] X. Zhang, W. Jiang, Y. Zhou, S. Xuan, C. Peng, L. Zong, X.
Gong, Nanotechnology 2011, 22, 375701.
[17] X. Du, J. He, J. Zhu, L. Sun, S. An, Appl. Surf. Sci. 2012, 258,
2717.
SUPPLEMENTARY MATERIALS
[18] F. Yazdani, M. Seddigh, Mater. Chem. Phys. 2016, 184, 318.
1HNMR spectra of the product obtained can be found via
the “Supplementary Content” section of this article
webpage.
[19] M. Nasr‐Esfahani, Z. Rafiee, M. Montazerozohori, H. Kashi,
RSC Adv. 2016, 6, 47298.
[20] M. Azaroon, A. R. Kiasat, Catal. Lett. 2017, 148, 745.
[21] K. Lamei, H. Eshghi, M. Bakavoli, S. Rostamnia, Catal. Lett.
2016, 312, 215.
ACKNOWLEDGMENTS
[22] P. S. Rathore, R. Patidar, T. Shripathi, S. Thakore, Catal. Sci.
Technol. 2014, 55, 2912.
Authors are thankful to Materials Research Centre, MNIT
Jaipur for providing spectral analysis facilities. M. Kumari
acknowledge to Department of Science and technology
(DST), India, for providing JRF under INSPIRE fellowship
scheme (IF140506). One of the author Y. Jain is grateful to
MNIT Jaipur for proving financial assistance.
[23] V. Polshettiwar, B. Baruwati, R. S. Varma, Chem Commun.
2009, 0, 1837.
[24] H. Woo, K. Lee, S. Park, K. H. Park, Molecules 2014, 19, 699.
[25] Y. Shiraishi, T. Kanzaki, H. Sawai, H. Asano, Y. Du, N.
Toshima, Bull. Soc. Photogr. Imag. Japan. 2017, 27, 13.
[26] Y. Liang, C. Lin, J. Guan, Y. Li, RSC Adv. 2017, 7, 7460.
[27] M. J. Nasab, A. R. Kiasat, RSC Adv. 2016, 6, 41871.
ORCID
[28] R. Saravanan, V. K. Gupta, E. Mosquera, F. Gracia, V.
Narayanan, A. Stephen, J Saudi Chem Soc. 2015, 19, 521.
Ragini Gupta https://orcid.org/0000-0001-9287-0537
[29] R. Saravanan, M. M. Khan, V. K. Gupta, E. Mosquera, F.
Gracia, V. Narayanan, A. Stephen, RSC Adv. 2015, 5, 34645.
REFERENCES
[30] T. A. Saleh, V. K. Gupta, Environ. Sci. Pollut. Res. 2012, 19,
1224.
[1] S. Doherty, J. G. Knight, T. Backhouse, A. Bradford, R. A. B.
Saunders, T. W. Chamberlain, R. Stones, A. Clayton, K. Love-
lock, Catal. Sci. Technol. 2018, 8, 1454.
[31] S. S. Islam, R. A. Molla, K. Ghosh, D. Das, S. M. Islam, Natur.
Resour. Eng. 2017, 2, 13.
[32] P. Li, S. Li, Y. Wang, Y. Zhang, G. Han, Colloids Surf A. 2017,
520, 26.
[2] G. Xiao, Y. Zhao, L. Li, J. O. Pratt, H. Su, T. Tan, Nanotechnol-
ogy 2018, 29, 155601.
[33] G. Luo, L. Kang, M. Zhu, B. Dai, Fuel Process. Technol. 2014,
118, 20.
[3] A. M. Tafesh, J. Weiguny, Chem. Rev. 1996, 96, 2035.
[4] I. Sorribes, G. Wienhöfer, C. Vicent, K. Junge, R. Llusar, M.
[34] A. S. Lu, J. Yu, Y. Cheng, A. Barras, W. Xu, S. Szunerits, D.
Beller, Angew Chem Int. 2012, 51, 7794.
Cornu, R. Boukherroub, Appl. Surf. Sci. 2017, 411, 163.
[5] G. Wienhöfer, I. Sorribes, A. Boddien, F. Westerhaus, K. Junge,
H. Junge, R. Llusar, M. Beller, J. Am. Chem. Soc. 2011, 133,
12875.
[35] R. Saravanan, V. K. Gupta, E. Mosquera, F. Gracia, J. Mol. Liq.
2014, 198, 409.
[36] R. Saravanan, T. Prakash, V. K. Gupta, A. Stephen, J. Mol. Liq.
2014, 193, 160.
[6] D. Cantillo, M. Baghbanzadeh, C. O. Kappe, Angew Chem Int.
2012, 51, 10190.
[37] R. Saravanan, N. Karthikeyan, V. K. Gupta, E. Thirumal, P.
Thangadurai, V. Narayanan, A. Stephen, Mater. Sci. Eng. C.
2013, 33, 2235.
[7] A. Corma, P. Serna, H. Garcia, J. Am. Chem. Soc. 2007, 129,
6358.
[8] R. V. Jagadeesh, G. Wienhöfer, F. A. Westerhaus, A. E. Surkus,
M. M. Pohl, H. Junge, K. Junge, M. Beller, Chem Commun.
2011, 47, 10972.
[38] R. Saravanan, V. K. Gupta, V. Narayanan, A. Stephen, J. Mol.
Liq. 2013, 181, 133.

KUMARI ET AL.
11 of 11
[39] V. K. Gupta, A. Nayak, Chem. Eng. J. 2012, 180, 81.
[56] A. K. Sasmal, J. Pal, R. Sahoo, P. Kartikeya, S. Dutta, T. Pal,
J. Phys. Chem. C 2016, 120, 21580.
[40] T. A. Saleh, V. K. Gupta, J. Colloid Interface Sci. 2012, 371, 101.
[57] G. Liao, J. Chen, W. Zeng, C. Yu, C. Yi, Z. Xu, J. Phys. Chem. C
2016, 120, 25935.
[41] R. Saravanan, E. Sacari, F. Gracia, M. M. Khan, E. Mosquera,
V. K. Gupta, J. Mol. Liq. 2016, 221, 1029.
[58] W. Zhou, Y. Zhou, Y. Liang, X. Feng, H. Zhou, RSC Adv. 2015,
5, 50505.
[42] M. Devaraj, R. Saravanan, R. Deivasigamani, V. K. Gupta, F.
Gracia, S. Jayadevan, J. Mol. Liq. 2016, 221, 930.
[59] J. Liu, J. Wang, Z. Zhu, L. Li, X. Guo, S. F. Lincoln, R. K.
[43] S. Rajendran, M. M. Khan, F. Gracia, J. Qin, V. K. Gupta, S.
Prud'homme, AIChE J. 2014, 60, 1977.
Arumainathan, Sci. Rep. 2016, 6, 31641.
[60] X. Hu, Z. Zhang, Y. Lu, R. Liu, L. Sun, I. P. Parkin, X. Zhang,
[44] T. A. Saleh, V. K. Gupta, J. Colloid Interface Sci. 2011, 362, 337.
Appl. Organomet. Chem. 2019, 33, 4428.
[45] M. Ahmaruzzaman, V. K. Gupta, Ind. Eng. Chem. Res. 2011, 50,
[61] Y. P. Wu, G. W. Xu, W. W. Dong, J. Zhao, D. S. Li, J. Zhang, X.
13589.
Bu, Inorg. Chem. 2017, 56, 1402.
[46] N. Mohammadi, H. Khani, V. K. Gupta, E. Amereh, S.
Agarwal, J. Colloid Interface Sci. 2011, 362, 457.
[47] R. Saravanan, F. Gracia, M. M. Khan, V. Poornima, V. K.
SUPPORTING INFORMATION
Gupta, V. Narayanan, A. Stephen, J. Mol. Liq. 2015, 209, 374.
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
[48] H. Wei, Y. Lu, Chem. – Asian J. 2012, 7, 680.
[49] K. Kurodaa, T. Ishidaa, M. Haruta, J Mol Catal A‐Chem. 2009,
298, 7.
[50] K. Layek, M. Lakshmi‐Kantam, M. Shirai, D. Nishio‐Hamane,
T. Sasaki, M. Maheswaran, Green Chem. 2012, 14, 3164.
[51] M. Kumari, R. Gupta, Y. Jain, Synth. Commun. 2019, 49, 529.
[52] Y. Jain, R. Gupta, P. Yadav, M. Kumari, ACS Omega 2019, 4,
How to cite this article: Kumari M, Gupta R,
Jain Y. Fe3O4 – Glutathione stabilized Ag
nanoparticles: A new magnetically separable robust
and facile catalyst for aqueous phase reduction of
nitroarenes. Appl Organometal Chem. 2019;e5223.
https://doi.org/10.1002/aoc.5223
3582.
[53] Y. Jain, M. Kumari, R. Gupta, Tetrahedron Lett. 2019, 60, 1215.
[54] H. Zhang, T. Duan, W. Zhu, W.‐T. Yao, J. Phys. Chem. C 2015,
119, 21465.
[55] S. Kulkarni, M. Jadhav, P. Raikar, S. Raikar, U. Raikar, Ind.
Eng. Chem. Res. 2019, 58, 3630.