Green synthesis of silver nanoparticles using Terminalia cuneata and its catalytic action in reduction of direct yellow-12 dye

Article abstract of DOI:10.1016/j.saa.2016.02.044

Facile green synthesis of silver nanoparticles (AgNPs) using aqueous bark extract of Terminalia cuneata has been reported in this article. The effects of concentration of the extract, reaction time and pH were studied by UV-Vis spectroscopy. Appearance of yellow color with λ_max around ~ 420 nm suggested the formation of AgNPs. The stable AgNPs were further characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) with zeta potential and high resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The synthesized AgNPs were in the size range of 25-50 nm with a distorted spherical shape identified from HR-TEM analysis. The catalytic activity of AgNPs on the reduction of direct yellow-12 using NaBH₄ was analyzed using a UV-Vis spectrophotometer. This study showed the efficacy of biogenic AgNPs in catalyzing the reduction of direct yellow-12.

Full text of DOI:10.1016/j.saa.2016.02.044

Green synthesis of silver nanoparticles using Terminalia cuneata and its
catalytic action in reduction of direct yellow-12 dye
Thomas Nesakumar Jebakumar Immanuel Edison, Yong Rok Lee, Mathur
Gopalakrishnan Sethuraman
PII:
DOI:
Reference:
S1386-1425(16)30101-9
doi: 10.1016/j.saa.2016.02.044
SAA 14310
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Revised date:
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16 April 2015
2 July 2015
28 February 2016
Please cite this article as: Thomas Nesakumar Jebakumar Immanuel Edison, Yong Rok
Lee, Mathur Gopalakrishnan Sethuraman, Green synthesis of silver nanoparticles using
Terminalia cuneata and its catalytic action in reduction of direct yellow-12 dye, (2016),
doi: 10.1016/j.saa.2016.02.044
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ACCEPTED MANUSCRIPT
Green synthesis of silver nanoparticles using Terminalia cuneata and its catalytic action in
reduction of direct yellow-12 dye
Thomas Nesakumar Jebakumar Immanuel Edison a,b Yong Rok Lee a* and Mathur
Gopalakrishnan Sethuramanb**
a School of Chemical Engineering, Yeungnam University,
Gyeongsan – 712-749, Republic of Korea
b Department of Chemistry, Gandhigram Rural Institute – Deemed University,
Gandhigram – 624 302, Tamil Nadu, India
Abstract
Facile green synthesis of silver nanoparticles (AgNPs) using aqueous bark extract of
Terminalia cuneata has reported in this article. The effects of concentration of the extract,
reaction time and pH were studied by UV-Vis spectroscopy. Appearance of yellow color with
λmax around ~420 nm suggested the formation of AgNPs. The stable AgNPs were further
characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD),
Dynamic light scattering (DLS) with zeta potential and high resolution transmission electron
microscopy (HR-TEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The
synthesized AgNPs were in size ranging of 25-50 nm with distorted spherical shape identified
from HR-TEM analysis. The catalytic activity of AgNPs on the reduction of direct yellow-12
using NaBH4 was analyzed using UV-Vis spectrophotometer. This study showed the efficacy of
biogenic AgNPs in catalyzing the reduction of direct yellow-12.
Keywords
Silver nanoparticles; Green Synthesis; Terminalia cuneata bark; Catalyst; Direct yellow-12.
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Authors for correspondence
**Prof. M.G. Sethuraman
E-mail: mgsethu@gmail.com
Tel: +914512452371; Mobile: +919443021565
*Prof. Y. R. Lee
E-mail: yrlee@yu.ac.kr
Fax: +82-53-810-4631; Tel: +82-53-810-2529
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1.0 Introduction
Nanoscience has blossomed in the recent decades owing to its immense contribution in
diverse fields like sensors, catalysts and medicine [1]. The electronic, optical and chemical
properties of nanoparticles are entirely different from those of bulk of the same materials [2].
Among the nanoparticles, silver nanoparticles are of great interest of researchers due to its
applications towards medical, catalysis, optics and energy fields. Generally colloidal metal
nanoparticles are synthesized by chemical reduction of metal ions by reducing and capping
agents. The principal advantages of the reduction method are facile fabrication of nanoparticles
with various sizes and shapes viz., nanorods, nanowires, nanoprisms and nanoplates [3].
Polymers and surfactants are served as capping agents for protecting the metal nanoparticles
from aggregation. Some of the reducing and capping agents are toxic to human beings and the
environment. To overcome this problem, researchers have started to synthesis nanoparticles
using bio sources such as microorganisms, fungi and plant extracts [4-9]. This method is very
easy, environment benign and cost effective. Moreover, different sizes and shapes of
nanoparticles can also be synthesized [10].
Direct yellow-12, an anionic azo dye, is readily soluble in polar solvents viz., water,
methanol and ethanol, and utilized in different processes including silk, wool, leather, jute,
cotton dyeing and paper printing. Direct yellow-12 dye must be present in the effluents of these
industries [11]. Direct yellow-12 dye is quite toxic to humans and all aquatic organisms, the
reduction of direct yellow-12 are industrially and environmentally important.
In the present work, AgNPs were synthesized using aqueous bark extract of Terminalia
cuneata. It is otherwise known as Arjun tree (Fig. 1) belonging to Combretaceae family. The
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major phytoconstituents present in the bark are tannins, triterpenoid saponins (arjunic acid,
arjunolic acid and arjungenin), flavonoids, gallic acid, ellagic acid and phytosterols [12, 13].
The formation of AgNPs and effect of concentration, reaction time, pH of the reaction
medium on AgNPs formation were analyzed by UV-Vis spectroscopy. The stable AgNPs were
further characterized by FT-IR, XRD, DLS with zeta potential and HR-TEM with EDS analysis.
The stable AgNPs were utilized as a catalyst for the reduction of carcinogenic direct
yellow-12 dye using NaBH4 as reducing agent. The catalytic activity of AgNPs was analyzed by
decrease in absorbance intensity of the dye at different time intervals using UV-Vis
spectrophotometer.
Fig. 1
2.0 Materials and Methods
2.1 Preparation of T. cuneata bark extract
T. cuneata barks were collected from Gandhigram Rural Institute campus, dried and
powdered. 0.50 g of the powdered bark was extracted with 100 ml of distilled water at 80˚ C for
15 min. The extract was filtered using Whatman No. 2 filter paper. Further, the filtrate was used
as reducing source for the synthesis of AgNPs.
2.2 Synthesis of AgNPs using T. cuneata
The synthesis of AgNPs were carried out by taking different concentrations of T. cuneata
extract viz., 0.50, 1.00, 1.75, 2.00 and 2.50 ml and adding to 24.50, 24.00, 23.25, 23.00 and
22.50 ml of 0.01 M AgNO3 (CDH Chemicals, Mumbai, India) solutions respectively at room
temperature. The total volume of the reaction was fixed as 25.00 ml.
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2.3 Characterization of AgNPs
2.3.1 UV-Vis spectroscopy
The formation of AgNPs was studied using Perkin Elmer Lamda 35 UV-Vis
spectrophotometer. The surface plasmon resonance (SPR) peak was observed in the range of
400-450 nm in visible region. The λmax values were recorded after 10 min of reaction time as
well as after 24 h so as to find out the stability of the biogenic AgNPs.
The effect of change of pH was studied by taking 1.75 mL of the bark extract of T. cuneata
and adding to 23.25 mL of 0.01 M AgNO3 at a given pH value. The pH was varied by the
addition of 0.1 M sulphuric acid in the acidic region and 0.1 M sodium hydroxide solution in the
basic region. The SPR peaks were recorded as before at various pH ranges such as 5, 6, 7, 8 and
9.
For UV-Vis spectroscopic studies, 0.30 ml of AgNPs was taken in a cuvette and diluted it to
2.00 ml by the addition of double distilled water. The absorbance of AgNPs was measured in the
wavelength range between 200 – 800 nm.
2.3.2 FT-IR spectroscopy
The functional groups present in the phytoconstituents on the bark extract of T. cuneata and
their involvement in the synthesis of AgNPs was determined by the FT-IR studies. The dried
aqueous extract and synthesized AgNPs were mixed with KBr to make pellet and the FT-IR
analysis was carried out by JASCO FT-IR 400.
2.3.3 XRD studies
The phytoreduced silver colloidal solution was drop-coated onto a glass substrate and the
XRD measurements were carried out using a Philips X’Pert Pro X-Ray diffractometer, with the
following working conditions: CuKα Ni-filtered radiation; 40 kV, 30 mA; divergence slit 0.47°.
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2.3.4 Dynamic Light Scattering (DLS) and zeta potential measurements
In order to find out the stability and size distribution of AgNPs, the DLS and zeta
potential measurements were carried out using Zetasizer Nano S90 (Malvern).
2.3.5 HR-TEM with EDS analysis
The stable biogenic AgNPs were washed and diluted by distilled water to attain the
absorbance range of 0.50 a.u. Further, one drop of diluted AgNPs was placed on carbon coated
Cu grid and allowed to dry in-vacuo. After drying, the nanoparticles were visualized using JEOL
JEM 2100 high resolution transmission electron microscope at 200 kV of acceleration.
Simultaneously the energy dispersive spectrum (EDS) was also recorded.
2.4 Evaluation of the effect of stable AgNPs on the reduction of direct yellow-12 by NaBH4
Direct yellow-12 dye purchased from CDH Chemicals, India was used for this study. To
find out the catalytic activity of synthesized AgNPs, two reactions were carried out in a 3.50 ml
capacity quartz cuvette and absorbance values were monitored using UV-Vis spectrophotometer.
In the first reaction, 1 ml of direct yellow-12 (0.5 × 10-3 M) was mixed with 0.2 ml stable AgNPs
and 1.8 ml of freshly prepared NaBH4 (0.1 × 10-2 M). Further the control reaction was also
carried out without AgNPs. The reactions were continuously monitored by Perkin Elmer Lamda
35 UV-Vis spectrophotometer.
3.0 Results and Discussion
3.1 UV-Vis spectroscopy
AgNPs have optical properties and are sensitive to size, shape, concentration, agglomeration
state and refractive index near the nanoparticle surface, which makes UV-Vis spectroscopy a
valuable tool for identifying, characterizing and studying these AgNPs [14]. After addition of
different concentrations of the bark extract of T. cuneata to Ag+ solution, a visible color change
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(appearance of yellow color) was noticed. This indicates the formation of AgNPs [15]. The
intensity of the color increased while increasing the concentration of the extract and also the
reaction time [16]. After 24 h, the color intensity was even higher, giving it a dark look. This
clearly showed that the production of AgNPs increased with increase of concentration of extract
and time. The UV-Vis spectrum recorded beyond 24 h did not show much increase in the
absorbance.
UV-Vis spectra of synthesized AgNPs at different concentrations of the extract at two
different time intervals (10 min and 24 h) are shown in Fig. 2 and Fig. 3
Fig. 2 and Fig. 3
From the Figures, it can be seen that the sharp SPR peak for AgNPs appeared around 415
nm (at 10 min), which suggested that the spherical shapes of AgNPs [17]. Further, the SPR was
shifted to 422 nm on increasing of reaction time (24 h), suggesting that the size of AgNPs
increased upon increasing the reaction time [18]. AgNPs produced from T. cuneata were
observed to be very stable in solution, even after 3 months of synthesis.
The synthesis of nano-crystalline AgNPs using T. cuneata bark extract was tested over a
wider pH ranges from 5–9. The UV-Vis spectrum of AgNPs synthesized at different pH values at
two different time intervals are shown in Fig. 4 and 5. From the Fig. 4, SPR peak appeared at
417 nm in the acidic pH. While increasing the pH of the reaction, the SPR peak was shifted to
lower wavelength which suggested that large nanoparticles are formed at lower pH, whereas
highly dispersed, small nanoparticles are formed at high pH. At low pH, the aggregation of Ag
nanoparticles to form larger nanoparticles was believed to be favored over the nucleation to form
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new nanoparticles. At higher pH, a large number of AgNPs with smaller diameters are formed
[19].
From the Fig. 5, it could be inferred that, the SPR peak of AgNPs appeared at 420 nm in the
acidic region, which suggested the increasing of particle size with increasing of reaction time. In
the basic region, a blue shift was observed. Moreover at pH-9 after 24 h of reaction time, two
SPR peaks could be observed in the range of 399 nm and 545 nm. SPR peak at 545 nm could be
attributed to the formation of anisotropic structures [20].
Fig. 4 and Fig. 5
It is a known fact that metal nanoparticles need to be stabilized through an appropriate
capping agent. Plant extracts have been reported to function as reducing agents and stabilizing
agents in the synthesis of nanoparticles [21]. Bulut and his coworker had elaborated on the
capping mechanism of hydrolysable tannins which are the common phytoconstituents [22].
These tannins which are polyhydroxylated macromolecules, characterized by supra molecular
associations facilitated by hydrogen bonding, act as templates for nanoparticle growth. The UV-
Vis spectrum recorded after 24 h of reaction time clearly explains the stability of the biogenic
AgNPs which can also be ascribed to the presence of polyphenols, tannins and gallic acid present
as phytoconstituents in T. cuneata.
3.2 FT-IR spectroscopy
The FT-IR spectrum of dried aqueous T. cuneata extract and synthesized AgNPs are
shown in Fig. 6. The main chemical constituents present in the bark are tannins, triterpenoid
saponins (arjunic acid, arjunolic acid and arjungenin), flavonoids, gallic acid, ellagic acid and
phytosterols [12]. The FT-IR-spectrum of T. cuneata bark extract showed an absorption band at
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3385 cm-1 which is characteristic of the –OH stretching of hydrogen bonded phenolic group
present in the phytoconstituents. The band at 1625 cm-1 was assigned to C=C stretching vibration
of the phytoconstituents. The band at 1050 cm-1 was due to the vibrations of –C-O group of
constituents and the band at 1440 cm-1 could be due to aromatic –CH stretching vibrations.
Further, the IR spectra of biogenic AgNPs showed an absorption band at 1383 cm-1,
corresponding to –NO3 stretching comes from silver nitrate [23]. Comparison of the FT-IR
spectra of biogenic AgNPs with that of the aqueous extract revealed that these major
phytoconstituents are indeed responsible for the capping of AgNPs.
Fig. 6
3.3 XRD studies
As a primary characterization tool for obtaining critical features such as crystal structure,
crystallite size and strain, X-ray diffraction patterns have been widely used in nanoparticle
research. The XRD pattern of synthesized AgNPs using T. cuneata is shown in Fig. 7. There are
four major peaks appeared at 38.2°, 44.5°, 64.5° and 77.6°. These peaks correspond to the (111),
(200), (220) and (311) planes of face-centered-cubic (fcc) geometry of AgNPs, which is in
agreement with the JCPDS file No. 42-0783. The ratio between the intensities of (111) and (200)
diffraction peaks was relatively higher than the usual values which indicate that the experimental
system had AgNPs oriented in (111) plane [24]. XRD pattern thus revealed the fcc geometry of
AgNPs synthesized with mostly oriented in (111) plane.
Fig. 7
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3.4 DLS with zeta potential analysis
The particle size distribution of AgNPs in solution was directly determined by DLS
measurements. The size distribution images of stable AgNPs synthesized using T. cuneata is
shown in Fig. 8. From the results, the calculated particle size distribution of AgNPs is 25-50 nm.
The zeta potential of stable AgNPs is calculated as -32.6 mV (pH-6.95) (Fig. 9). This
suggests the high stability of biogenic AgNPs [25]. The large negative potential value could be
due to the capping of polyphenolic constituents present in the plant extracts. In the colloidal
solution, nitrate and gallate ions (from phytoconstituents) are present adsorbed on the surface of
AgNPs. Hence as a result the surface charge of the Ag nanoparticles will be negative [26].
Fig. 8 and Fig. 9
3.5 HR-TEM with EDS analysis
The HR-TEM and SAED pattern of stable AgNPs synthesized using T. cuneata are
depicted in Fig. 10. The calculated average particle size is approximately 25 nm. Further the
synthesized AgNPs are mostly in distorted spherical shape. White dots in the SAED pattern of
AgNPs revealed the crystalline nature. The EDS of stable AgNPs is shown in Fig. 11. From the
figure, a strong signal of the Ag atoms is observed and the weak signals of O and C are also seen.
Thus the TEM studies revealed the crystalline nature of the biogenic AgNPs and also the size of
AgNPs.
Fig. 10 and Fig. 11
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3.6 Mechanism of formation and protection of AgNPs by the phytoconstituents of T.
cuneata
Proposing the mechanism of reduction of Ag+ using phytoconstituents is very difficult,
because they contain diverse molecular structures. Generally, in the synthesis of metal
nanoparticles using plant extracts, the plant extracts play a dual role viz., reduction of metal ions
and capping of metal nanoparticles (protection from aggregation) [27]. The plausible mechanism
is represented in Fig. 12. In this mechanism, the optimum concentration of the extract for
reduction and stabilization of AgNPs is taken in to account.
The phytoconstituents such as polyphenols, tannins and gallic acid contain high density
of hydroxyl groups. On addition of extracts to the Ag+ solution, the Ag+-phytoconstituent
complex was formed as intermediate. Further, the Ag+ ions were converted to Ag atoms followed
by coalescence, cluster formation and growth of clusters finally yielding AgNPs [22, 28]. The
phenolic groups present in the phytoextract subsequently undergo oxidation and converted to its
quinone form. The electrochemical potential difference between Ag+ and phytoconstituents
drives the reaction. The formed AgNPs were stabilized through the lone pair of electrons and pi
electrons of quinone structures.
Fig. 12
3.7 Catalytic activity of AgNPs on reduction of direct yellow-12 by NaBH4
The reduction of direct yellow-12 by NaBH4 was also carried out using stable 25 nm
sized biogenic AgNPs as a catalyst. Generally azo dyes are commonly prepared by coupling of a
diazotized aromatic amine with a phenol or aromatic amine. It is often subjected to reductive or
oxidative processes to remove color. Recently, an investigation of the ability of aqueous Na2S2O4
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and SnCl2 for reductive cleavage of azo dyes resulted in nearly complete reduction of the azo
bond to form the corresponding amines [29]. Generally, direct yellow-12 shows absorption
maxima in the range of 404 nm. After addition of stable AgNPs to the reaction mixture
containing direct yellow-12 and NaBH4, color of the dye gradually disappeared. Complete
decolorization of direct yellow-12 could be observed within 40 min after the reaction
commenced (Fig. 13). It was inferred that in the absence of AgNPs and NaBH4, the
decolorization (reduction) of direct yellow-12 did not occur. This reaction is not kinetically
favored but it is thermodynamically favored in presence of metal catalysts [30-31].
The reduction of direct yellow-12 can be explained in terms of Langmuir–Hinshelwood
model [32-33]. In this reduction, NaBH4 act as electron donor as well as hydrogen supplier in
addition that, it also changed the pH of the entire solution [34]. Hence the surface charge of
–
AgNPs changed to positive. The BH4 and direct yellow-12 are concomitantly adsorbed on the
positively charged AgNPs surface. Then the catalytic reduction is started by relaying electrons
-
-
from the donor BH4 to direct yellow-12, where the AgNPs accept electrons from BH4 ions and
convey them to the dye molecule [35]. In the presence of AgNPs, large volume of hydrogen
supplied by NaBH4 could result in the hydrogenation of azo dyes.
There are several reports available on the catalytic activity of noble metal particles in the
reduction of azo dyes. Mohapatra et al had investigated the azo bond cleavage of methyl red via
hydrogenation using Pt nanowires [36]. Pd nanoparticles generated using microbes were reported
to degrade azo dyes via reductive hydrogenation of the azo linkage. Methyl orange was degraded
to give N,N-Dimethyl-benzene-1,4-diamine and Sulfanilic acid as the products. Concomitantly
generated hydrogen was proposed to be the cause for hydrogenation [37]. In the light of the
above reports, it is suggested that in the degradation of direct yellow-12 by NaBH4 in the
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presence of biogenic AgNPs, the simultaneous cleavages of two azo bonds occur resulting in the
formation of corresponding amines viz., 4-ethoxyaniline and disodium (E)-6,6'-(ethene-1,2-
diyl)bis(3-aminobenzenesulfonate) (Fig. 14). This may due to large surface area of AgNPs which
could offer more catalytic sites toward the reduction of direct yellow-12 as well as high negative
potential of AgNPs (-1.80 V Vs NHE) [38].
Fig. 14
4.0 Conclusions
The study has demonstrated that AgNPs could be prepared instantly by making use of
aqueous bark extract of T. cuneata. The phytoconstituents (mostly tannins and poly phenols)
present in the extracts of T. cuneata act as reducing agents as well as capping agents providing
stability to AgNPs as evident from FT-IR study. The phytosynthesized AgNPs were found to
have a crystalline structure with face centered cubic geometry oriented in (111) plane as studied
by XRD method. The synthesized AgNPs have the size ranging approximately 25-50 nm with
distorted spherical shape as studied by HR-TEM and DLS studies. The high negative zeta
potential values of AgNPs, confirmed the high stability. The biogenic AgNPs prepared using T.
cuneata were tested for its efficacy in degrading direct yellow-12. The results of the study
demonstrated the ability of biogenic AgNPs as excellent catalyst in the degradation of direct
yellow-12.
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Figure captions
Fig. 1 Photograph of Terminalia cuneata plant Inset: Barks of T. cuneata
Fig. 2 Effect of concentration of the T. cuneata extract on AgNPs synthesis (after 10 min)
Fig. 3 Effect of concentration of the T. cuneata extract on AgNPs synthesis (after 24 h)
Fig. 4 UV–Vis spectra of AgNPs prepared using T. cuneata at various pH ranges (after 10 min)
Fig. 5 UV–Vis spectra of AgNPs prepared using T. cuneata at various pH ranges (after 24 h)
Fig. 6 FT-IR spectra of aqueous fruit extract of T. cuneata (A) and synthesized AgNPs with
capping of phytoconstituents of T. cuneata (B)
Fig. 7 XRD pattern of synthesized AgNPs using T. cuneata extract
Fig. 8 DLS size distribution of AgNPs synthesized using T. cuneata extract
Fig. 9 Zeta potential of AgNPs synthesized using T. cuneata extract
Fig. 10 HR-TEM and SAED images of AgNPs synthesized using T. cuneata under different
magnifications
Fig. 11 EDS pattern of AgNPs synthesized using T. cuneata extract
Fig. 12 Mechanism of formation and protection of AgNPs by T. cuneata
Fig. 13 Reduction of direct yellow-12 by NaBH4 in presence of AgNPs as a catalyst
Fig. 14 Catalytic action of AgNPs synthesized using T. cuneata on the reduction of direct
yellow-12.
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Figures
.
Fig. 1
0.20
0.50 ml (413 nm)
1.00 ml (415 nm)
1.75 ml (415 nm)
2.00 ml (415 nm)
2.50 ml (415 nm)
0.15
0.10
0.05
0.00
200
300
400
500
600
700
800
Wavelength ( (nm))
Fig. 2
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0.50 ml (422 nm)
1.00 ml (422 nm)
1.75 ml (423 nm)
2.00 ml (424 nm)
2.50 ml (426 nm)
0.5
0.0
200
300
400
500
600
700
800
Wavelength ( (nm))
Fig. 3
417 nm
417 nm
416 nm
416 nm
413 nm
0.5
pH - 9
pH - 8
pH - 7
pH - 6
pH - 5
0.0
200
300
400
500
600
700
800
Wavelength ( (nm))
Fig. 4
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1.0
420 nm
418 nm
417 nm
412 nm
399 & 545 nm
pH - 9
pH - 8
0.5
pH - 7
pH - 6
pH - 5
0.0
200
300
400
500
600
700
800
Wavelength ( (nm))
Fig. 5
A
B
80
60
40
20
0
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Fig. 6
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7000
38.2 (1 1 1)
6000
5000
4000
3000
64.5 (2 2 0)
2000
44.5 (2 0 0)
77.6 (3 1 1)
1000
0
30
40
50
60
70
80
2
Fig. 7
Fig. 8
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Fig. 9
22

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Fig. 10
23

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Fig. 11
Fig. 12
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1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Initial
5 mins
10 mins
.
.
.
40 mins
300
400
500
Wavelength () (nm)
Fig. 13
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Fig. 14
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Green synthesis of silver nanoparticles using Terminalia cuneata and its catalytic action in
reduction of direct yellow-12 dye
Thomas Nesakumar Jebakumar Immanuel Edison a,b Yong Rok Lee a* Mathur Gopalakrishnan
Sethuraman b**
a School of Chemical Engineering, Yeungnam University,
Gyeongsan – 712-749, Republic of Korea
b Department of Chemistry, Gandhigram Rural Institute – Deemed University,
Gandhigram – 624 302, Tamil Nadu, India
Graphical Abstract
AgNO
Characterization
AgNP
Terminalia
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Highlights:
 Synthesis of silver nanoparticles using Terminalia cuneata bark is reported
 The size of the silver nanoparticles is in the range of 20-50 nm
 The catalytic reduction of direct yellow-12 was achieved using NaBH4
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