Green synthesis of gold nanoparticles was achieved using an extract of the medicinal plant Adhatoda vasica. The nanoparticles formed were predominantly spherical and monodisperse, with sizes ranging from 22 to 47 nm as determined through transmission electron microscopy analysis. Ultraviolet-visible spectroscopy and X-ray diffraction data confirmed the formation and crystalline nature of the gold nanoparticles. Functional groups present in the plant extract, such as hydroxyl and carboxyl groups, were found to play a role in both the reduction of gold ions and stabilization of the resulting nanoparticles. This green synthesis method using A. vasica extract could provide a means of producing biocompatible gold nanoparticles for applications such as drug delivery.

1. 192
Micro and Nanosystems, 2012, 4, 192-198
Green Synthesis of Well Dispersed Nanoparticles using Leaf Extract
of Medicinally useful Adhatoda Vasica Nees
V. Karthicka, V. Ganesh Kumara,*, T. Maiyalaganb, R. Deepaa, K. Govindarajua, A. Rajeswaria and
T. Stalin Dhasa
a
Nanoscience Division, Centre for Ocean Research, Sathyabama University,Chennai - 600 119, India
b
School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive Singapore 639798
Abstract: Development of reliable method for the green synthesis of gold nanoparticles (AuNPs) using medicinally
valued Adhatoda vasica Nees has been studied here. The color change and the Surface Plasmon Resonance (SPR)
confirmed the formation of AuNPs. The biosynthesized AuNPs were characterized using UV-visible Spectroscopy
(UV-vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy
(SEM), Energy Dispersive Spectroscopy (EDAX) and Transmission Electron Microscopy (TEM) analysis.
The nanoparticles synthesized were predominantly monodisperse, stable spherical in nature with well-defined dimensions
of size ranging from 22 to 47 nm. The crystalline nature of the synthesized particles was also evident by the X-ray
diffraction analysis.
Keywords: Adhatoda vasica, Gold nanoparticles, Biosynthesis, Electron Microscopy, Diffraction.
INTRODUCTION
Nanobiotechnology combines biological principles with
physical and chemical procedures to generate nano-sized
particles with well defined functions. Particles of
interestingly small size make the field of drug delivery more
interesting and effective. Synthesizing gold particles
(AuNPs) with medicinal applications is the recent trend in
the field of nanobiotechnology. The surface availability of
nanoparticles for binding/reactivity of other species on them
is an important function as it is synthesized in different
structures like nanorods, spheres, prims and hexagons. The
controlled growth of AuNPs of different morphologies and
the various chemical mechanisms involved in the anisotropic
growth were studied using different chemical procedures [1].
The low toxicity effects of green synthesized AuNPs on
biological systems made researchers to synthesize it by
biological method rather by chemical means. Extensive
studies were done on AuNPs and its binding affinity towards
nucleic acids and proteins in biological systems [2]. AuNPs
have been synthesized from various sources like plants [3],
microbes [4], seaweeds [5] and microalgae [6]”. Sastry et al.,
2007 have synthesized AuNPs using chitosan and showed
good control on postprandial hyperglycemia which when
loaded with insulin [7] proved AuNPs to be an effective drug
carrier. AuNPs can be used for the detection of nucleic acids
as Chandirasekar and co-worker have, 2011 synthesized
AuNPs using bile salts and particles with different geometry
was achieved by varying the reducing agent concentration
[8]. AuNPs have also been employed in the imaging of
cancer cells like AR42J pancreatic tumor cells by
synthesizing it using laser ablation technique and reported
that size of AuNPs plays a role in the intracellular uptake [9].
*Address correspondence to this author at the Nanoscience Division, Centre
for Ocean Research, Sathyabama University,Chennai - 600 119, India;
Tel: +91 44 24500646; Fax: +91 44 24503308; E-mail: ganesv@gmail.com
1876-4037/12 $58.00+.00
Adhatoda vasica Nees, a malabar nut tree belonging to
the family Acanthaceae is native of South Asia and is
exclusively studied for its active components like
quinazoline alkaloids, vasicine, vasicinone, deoxyvasicine,
oxyvasicinine, maiontone and other essential oils. The plant
parts have been traditionally used for curing diseases like
stomatitis, asthma and bronchititis [10]. The compound
73/602 an alkaloid isolated from the leaves and roots of A.
vasica is a structural analogue of vasicinone which shows
appreciable antiallergic activity in mice, rats and guinea pigs
[11]. Synthesis of AuNPs using medicinally useful plants
[12, 13] is gaining more importance in therapeutic
applications, where the reducing agent responsible for the
reduction of chloroauric acid will have its own effect on
biological systems. In our previous work, we have
demonstrated the use of antidiabetic potent plant Cassia
auriculata for the synthesis of AuNPs [14]. Herein, we have
used an antiallergic potent plant A. vasica for the synthesis of
AuNPs which may possess antiallergic effect on animals and
that will be a welcoming outcome in the field of drug
delivery.
MATERIALS USED
Chloroauric acid (HAuCl4·3H2O) was obtained from
Loba Chemie, India was used as received. All other reagents
used in the reaction were of analytical grade with maximum
purity. A. vasica Nees leaves were collected from forest area
of Vellore, Tamilnadu, India and was cleaned with tap water
and double distilled water twice to remove the dust. Further,
it is shade dried for a week at room temperature and
powdered for use.
SYNTHESIS OF GOLD NANOPARTICLES
For the preparation of A. vasica leaf extract, 4 g of
powdered leaves is taken in a conical flask along with 40 mL
of distilled water. The flask is then placed in an orbital
shaker for 4 h and then the extract is taken by filtering the
© 2012 Bentham Science Publishers

2. Green Synthesis of Well Dispersed Nanoparticles
Micro and Nanosystems, 2012, Vol. 4, No. 3
193
Fig. (1A). Aqueous extract of A. vasica (B) Chloroauric acid solution (C) Ruby red colour indicating the formation of gold nanoparticles.
Fig. (2). UV-vis spectrum of the gold nanoparticles recorded immediately after synthesis (after 5 min).
whole content using whatman No.1 filter paper. The filtrate
is then stored in refrigerator for further use. The reaction is
carried out using different concentrations of plant extract and
finally optimized to a ratio of 1:10 (Extract: Chloroauric acid
solution). Further 3 mL of extract is added to 30 mL aqueous
solution of chloroauric acid (10-3 M) and kept in an orbital
shaker at room temperature. Formation of AuNPs takes place
within 4 min, evident from the development of a stable ruby
red color (Fig. 1) in the solution indicates the reduction of
Au3+ to Au0 with no color change further. The experiment was
repeated thrice to check the formation of AuNPs. The
synthesized AuNPs are stable at a pH range of 3.6-9.1 showed
no precipitation and color change for a period of 45 days.
CHARACTERIZATION OF GOLD NANOPARTICLES
The UV-vis spectra were recorded using Thermo
Scientific Spectrascan UV 2700 with samples in quartz
cuvette. FT-IR of Perkin Elmer spectrophotometer was used
to identify the possible groups responsible for the reduction
of chloroauric acid at a resolution of 4 cm-1 in the range of
4000-450 cm-1 and the FT-IR spectrum was recorded by
employing KBr pellet technique using Perkin Elmer model-
983/G detector double beam spectrophotometer. XRD
pattern of the A. vasica reduced AuNPs was carried out using
a Rich Seifert P3000 instrument operated at a voltage of 40
kV with Cu K radiations. SEM-EDAX was studied to check
the surface morphology and elemental analysis of the AuNPs
using XL30 FESEM, Philips. TEM studies were carried out
by drop coating AuNPs onto carbon-coated TEM grids using
Philips Technai-10.
RESULTS AND DISCUSSION:
The formation of AuNPs is noted down by the color
change after the addition of aqueous extract to chloroauric
acid solution as illustrated in (Fig. 1). The formation and
stability of metal nanoparticles in aqueous solution is studied
using UV-vis spectrophotometer. The surface plasmon
resonance (SPR) arising due to the oscillation of free
conduction electrons induced by the absorption of
electromagnetic field [15] as a absorption band with a
maximum at 532 nm has been observed in the spectrum
(Fig. 2). To identify the possible functional groups
responsible for the reduction of chloroauric acid the FTIR spectrum is taken and the interaction of biomolecules have

3. 194 Micro and Nanosystems, 2012, Vol. 4, No. 3
Karthick et al.
Fig. (3). FT-IR spectra of dried powder of (A) A. vasica extract (B) gold nanoparticles.
been studied (Fig 3). The spectrum show a clear difference in
the functional group shifts. The peak seen at 3358 cm-1
corresponds to the –OH or –COOH group which has shifted
to higher wavelength 3687 cm-1 thus, implying that the –OH
or –COOH group might have stabilized the AuNPs.
The stretching of C=O can be observed in the spectrum
indicating the red shift from 1625 to 1675 cm-1. The
peak 1406 cm-1 corresponds to the –COO- also shows a shift

4. Green Synthesis of Well Dispersed Nanoparticles
Micro and Nanosystems, 2012, Vol. 4, No. 3
195
Fig. (4). Diffraction pattern of gold nanoparticles synthesized using A. vasica.
Fig. (5A). SEM image shows the presence of bioorganic compounds involved in the reduction (B) EDAX showing strong signals for gold
nanoparticles.

5. 196 Micro and Nanosystems, 2012, Vol. 4, No. 3
Karthick et al.
Fig. (6A&B). TEM image taken at various magnifications showing gold nanospheres.
which confirms the contribution of carboxylate groups in the
reduction. In the spectrum aromatic resonances have not
been identified indicating the absence of aromatic groups in
the stabilizing compounds. Thus by using FT-IR, it is
concluded that –OH or –COOH, -C=O, -COO- groups has
involved in the stabilization of AuNPs. The crystalline nature
of AuNPs was examined using XRD where three diffraction
peaks were observed in the 2 range of 10º to 70º which can
be indexed as (111), (200) & (220) reflections of fcc (face
centered cubic) matches with Joint Committee on Powder
Diffraction Standards (JCPDS No: 04-0784) revealing that
synthesized AuNPs are composed of pure crystalline gold as
there is no other peak found (Fig. 4). The XRD patterns
obtained were similar to the results reported earlier on
AuNPs [16]. The particle size of the AuNPs formed were
calculated using Debye-Scherrer equation
D = K / cos
Where D is the average crystalline domain size
perpendicular to the reflecting planes, K the Scherrer
constant with value from 0.9 to 1, is the wavelength of the
X-ray source, is the full width at half maximum (FWHM)
and
is the Diffraction angle. From this equation, the
particle size calculated was found to be 39 nm which is
similar to the size observed in TEM image of the AuNPs.
The surface morphology and the scale in which the size of
the nanoparticle synthesized can be studied using the SEM.
The presence of bioactive components responsible for the
reduction of the chloroauric acid to AuNPs was revealed
using SEM imaging (Fig. 5A). The image confirms the
presence bioorganic compounds which has stabilized the
AuNPs. The EDAX profile has showed strong signal for
gold atoms (Fig. 5B) and weak signals for chlorine, oxygen,
sodium and magnesium which implies that these signals
might be from the biomolecules present in the aqueous
extract. The morphology of the synthesized nanoparticles
were determined by TEM image and shown in (Fig. 6A&B).
For the analysis the image is taken in a random place on the
grid and the morphology is observed carefully. The particles
as seen in TEM image are triangular and spherical in shape

6. Green Synthesis of Well Dispersed Nanoparticles
Micro and Nanosystems, 2012, Vol. 4, No. 3
197
Fig. (7). Possible mechanism for the reduction of chloroauric acid by bioactive compounds.
with an average size of 38 nm with many similar sized
particles except a few. The uniformity in size is a welcoming
result in the green synthesis as in most of the cases the
particle size varies with greater range which is a concern
when applied in a targeted drug for therapeutic applications.
The particle shape usually observed in most of the green
synthesis is triangles and spheres and sometimes hexagon
[14]. The synthesis of gold nanoprisms has been
demonstrated [17] using a plant Cymbopogon flexuosus and
a very clear image of prism structures have been observed in
TEM. The possible mechanism for the stabilization of
AuNPs is illustrated in (Fig. 7). However, finding the exact
chemistry involved in reduction and elucidating the capping
agent need further substantiation.
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CONCLUSION
In the present work, a simple and more rapid method to
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researchers to synthesize AuNPs using green synthesis than
chemical methods. The formation of AuNPs in the reaction
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applications and it may have antiallergeic activity if tested on
a suitable animal model.
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CONFLICT OF INTEREST
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The author(s) confirm that this article content has no
conflicts of interest.
ACKNOWLEDGEMENT
We thank DST-Nanomission, Government of India for its
financial support for the project (SR/NM/NS-06/2009) and
the management of Sathyabama University, Chennai for its
stanch support in research activities.
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