Biosynthesis of ZnO nanoparticles using rambutan (Nephelium lappaceumL.) peel extract and their photocatalytic activity on methyl orange dye

Article abstract of DOI:10.1016/j.molstruc.2016.07.029

In the present study, describes the synthesis of ZnO nanoparticles from rambutan (Nephelium lappaceumL.) peel extract via bio synthesis method and developed a new low cost technology to prepare ZnO nanoparticles. During the synthesis, fruit peel extract act as a natural ligation agent. The successfully prepared product was analyzed with some standard characterization studies like X-Ray Diffraction (XRD), UV-VIS Diffuse reflectance spectra (UV–Vis DRS), Field Emission Scanning Electron Microscope (FESEM), High resolution transmittance electron microscope (HR-TEM), N₂ adsorption-desorption isotherm and UV–Vis absorption Spectroscopy. The photocatalytic activity of ZnO nanoparticles was evaluated by photodegradation of methyl orange (MO) dye under UV light and the result depicts around 83.99% decolorisation efficiency at 120?min of illumination. In addition with photodecolorisation, mineralization was also achieved. The mineralization has been confirmed by measuring Chemical Oxygen Demand (COD) values.

Full text of DOI:10.1016/j.molstruc.2016.07.029

Accepted Manuscript
Biosynthesis of ZnO nanoparticles using rambutan (Nephelium lappaceumL.) peel
extract and their photocatalytic activity on methyl orange dye
Thenmozhi Karnan, Stanly Arul Samuel Selvakumar
PII:
S0022-2860(16)30700-1
10.1016/j.molstruc.2016.07.029
MOLSTR 22732
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 12 March 2016
Revised Date: 1 July 2016
Accepted Date: 8 July 2016
Please cite this article as: T. Karnan, S.A.S. Selvakumar, Biosynthesis of ZnO nanoparticles using
rambutan (Nephelium lappaceumL.) peel extract and their photocatalytic activity on methyl orange dye,
Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.07.029.
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Biosynthesis of ZnO nanoparticles using Rambutan (Nephelium
lappaceumL.) peel extract and their photocatalytic activity on
methyl orange dye
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THENMOZHI KARNAN , STANLY ARUL SAMUEL SELVAKUMAR
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* Department of Chemistry , University College of Engineering Kanchipuram, Tamil Nadu- 631
552, India. Tel. : +91 8220600201, email : thenmozhikarnan@ymail.com
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Department of Applied Chemistry, Sri Venkateshwara College of Engineering, Sriperumpudur,
Tamil Nadu-602 117, India. Tel. : +91 9841552272, email : stanly@svce.ac.in
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Abstract
In the present study, describes the synthesis of ZnO nanoparticles from rambutan (Nephelium
lappaceumL.) peel extract via bio synthesis method and developed a new low cost technology to prepare
ZnO nanoparticles. During the synthesis, fruit peel extract act as a natural ligation agent. The successfully
prepared product was analyzed with some standard characterization studies like X-Ray Diffraction
(XRD), UV-VIS Diffuse reflectance spectra (UV-Vis DRS), Field Emission Scanning Electron
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Microscope (FESEM), High resolution transmittance electron microscope (HR-TEM), N adsorption-
desorption isotherm and UV–Vis absorption Spectroscopy. The photocatalytic activity of ZnO
nanoparticles was evaluated by photodegradation of methyl orange (MO) dye under UV light and the
result depicts around 83.99% decolorisation efficiency at 120 minutes of illumination. In addition with
photodecolorisation, mineralization was also achieved. The mineralization has been confirmed by
measuring Chemical Oxygen Demand (COD) values.
Keywords: ZnO nanoparticles, Bio synthesis, photocatalytic activity, methyl orange, UV light
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________________________________
*Corresponding author: Tel: +91 8220600201
E-mail: thenmozhikarnan@ymail.com
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1. Introduction
Toxic dye effluents discharged by textile mills severely affects the aquatic eco system and causes
environmental pollution [1]. In recent years, Semiconductor based photocatalyst has attracted substantial
attention because it affords a potential solution for environmental problems [2]. Hitherto, many kinds of
semiconducting material have been assessed as photocatalyst. ZnO is an important wide ranging band gap
semiconductor (3.37 eV) [3] and focused much attention because of its distinctive electrical and optical
properties. ZnO has wide range of application like photocatalysts, solar cells, chemical sensors,
piezoelectric transducers, transparent electrodes, electroluminescent devices, ultraviolet laser diodes,
electronic and optoelectronic devices, laser technology, antibacterial activity [4-7].Different strategies are
available to prepare ZnO nanoparticles, mainly include precipitation method[8], hydrothermal method
[9], micro emulsion method [10], microwave method [11], solvothermal route [12], non-hydrolytic
solution synthesis technique [13], thermal decomposition of oxalate Precursor [5] Emulsion
Precipitation Method [6].Although these techniques have been used to prepare ZnO nanparticles
prolifically, they need toxic chemicals as capping agents, sophisticated equipment, tedious procedures and
rigorous experimental conditions [14, 15]. Hence, there is a great demand for the search of new synthesis
methods in order to overcome the existing difficulties. The biosynthesis from plant extract has led to the
formation of ZnO nanoparticles is encouraging. Because they are facile, clean, non-toxic, eco-friendly,
cost-effective, free from unwanted byproducts and it provides natural capping agents [16]. Based on the
literature, biosynthesis of ZnO nanoparticles from the plant extract including green tea [17], Hibiscus
rosa-sinensis[18], Azadirachta indica[19], Aloe vera [20], corriandrum sativum leaves[21] , Solanum
nigrum leaf [22],Anisochilus carnosus leaf extract[4] have been reported.
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In the present work, we describe the bio synthetic strategy to prepare ZnO nanoparticles from
rambutan (Nephelium lappaceum L.) peel extract. It is a tropical fruit belonging to the Sapindaceae family
and closely related to the lychee and longan [23]. Ellagic acid, corilagin, geranin and ellagitannins are the
primary higher phenolic components present in rambutan [24]. The formation scheme of ZnO
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nanoparticles from rambutan peel exract was depicted in Scheme 1. Here, plant extract act as ligation
agent. The aromatic hydroxyl groups present in polyphenolic ellagic acid ligate with Zinc ions at pH 5-7
lead to form a stable Zinc-ellagate complexe system and this system undergo direct decomposition at
450°C in static air atmosphere leads to the formation of ZnO nanoparticles[25] .
The present study focuses, the synthesis of ZnO nanoparticles from rambutan (Nephelium
lappaceumL.) peel extract [26] and their photocatalytic activity was studied against methyl orange dye
under direct UV light irradiation.
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2. Materials and Methods
2.1 Materials
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The Nephelium lappaceum L. (rambutan fruit) was collected from local market at Kanchipuram,
Tamilnadu, India. Zinc nitrate [Zn (NO ) .6H O], Methyl orange and ethanol were purchased from Merck
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chemicals Ltd., India and used without further purification. Double distilled water was used throughout
the experiment.
2.2 Preparation of the Extract
Fresh peels of Nephelium lappaceum L. were washed thoroughly with running water and
subsequently cut into small pieces and placed in a hot air oven at 50°C until complete dryness. About 3 g
of finely dried Nephelium lappaceum L. peels were boiled with 40 ml double distilled water and 20 ml
ethanol (2:1) for 10 min. The temperature was maintained at 80°C during extraction. The extract obtained
was filtered through Whatman No. 1 filter paper and the filtrate was collected in 100 ml conical flask and
stored in refrigerator for further use [26].
2.3 Bio-synthesis of Zinc Oxide Nanoparticles
Initially, 0.1 M aqueous solution of Zinc nitrate [Zn (NO
3 2 2
) .6H O] was prepared. Later, 10ml of
Nephelium lappaceum L. extract was added drop wise to 50ml of 0.1M Zinc nitrate hexa hydrate aqueous

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solution and stirred at 80°C for 2h. The particles formed after adequate time of stirring were collected by
centrifugation at 10000 rpm for 10minutes. Later, the centrifuged particles were washed with water and
again subjected to centrifugation at 1000 rpm for 10 minutes. The centrifuged sample was dried in hot air
oven at 90°C for 10 hours and powdered using mortar and pestle. This powdered sample was calcined in a
muffle furnace at 450°C to get pure ZnO nanoparticles.
2.4 Instrumentation
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A powder X-ray diffract meter (JEOL IDX 8030 instrument operating at 40 kV with a current of
30mA using Cu Kα) was used to determine the crystalline phases present in the sample. The optical
studies were carried out with diffuse reflectance spectrophotometer (DRS) Shimadzu (UV 2450) UV–
VIS– instrument in the wavelength range of 200–800 nm using BaSO as standard .The surface
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morphology of the powder was observed using a field emission scanning electron microscope (FESEM-
SUPRA 55) - CARL ZEISS, GERMANY and high resolution transmission electron microscope (HR-
TEM) (JEOL JEM 3010). Surface areas were obtained on a Micromeritics ASAP 2400 surface area
analyser. Degradation of Methyl orange solution was recorded from SHIMADZU UV-1650 PC UV-
Visible spectrophotometer.
2.5 Photocatalytic activity
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The photocatalytic experiment was carried out at three different conditions (i) without
photocatalyst under light irradiation (Blank) (ii) with photocatalyst in the absence of light irradiation
(Dark) and (iii) with photocatalyst under direct light irradiation. Methyl orange (MO), a water soluble
azo-dye was selected as the model pollutant with a concentration of 10 mg/l. The pH of the MO solution
was 7.01.The photocatalytic activity was examined by degradation of MO dye under UV light (364 nm).
The irradiation was done using an 8W medium pressure mercury vapour lamps (Heber Multi lamp
photoreactor HML MP 88). About 100mg of bio-synthesized ZnO nanoparticles was added to the 100ml

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of aqueous methyl orange dye solution and the suspension was magnetically stirred for uniform mixing
without any permanent air bubbling. Before illumination, the reaction suspension was magnetically stirred
in the dark for over 1 h to ensure the establishment of an adsorption/desorption equilibrium between the
photocatalyst and dye. At frequent time intervals, 3ml suspensions were filtered and centrifuged to
remove photocatalyst using micro cooling centrifuge in the speed of 6000 rpm for 20 min. The filtrates of
methyl orange were analyzed by measuring the absorbance at 464 nm with the help of UV-Visible
spectrophotometer. At the end of decolorization, the efficiency percentage was calculated from the
formula,
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0 t
Decolorization efficiency (%) = (Absorbance) - (Absorbance) x 100
(Absorbance)
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Where (Absorbance) is the absorbance before irradiation and (Absorbance) is the absorbance
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at time t. After ensuring the decolorisation of dye solution, the mineralization was verified using a COD
value which was measured by using Chemical Oxygen Demand (COD) reduction method. COD of dye
solution was estimated pre and post photocatalytic treatment with a standard dichromate method, using
COD digester.
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3. Results and discussion
3.1 XRD patterns
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The crystalline phase of the as-prepared sample was characterized by XRD, which is shown in
Fig.1. The distinct diffraction peaks at 2θ= 31.71°, 34.38°, 36.21°, 47.52°, 56.54°, 62.84°, 66.23°, 67.95°,
69.05°, 72.53° and 77.14° were assigned to (100), (002), (101), (102), (110), (103), (200), (112), (201),
(004) and (202) planes respectively. In Fig.1, all the diffraction peaks were well indexed to the hexagonal
phase of ZnO, which are very close to the standard values (JCPDS No.79-2205). The sharp and narrow
peaks implied that the nanoparticles were highly crystallized. The crystallite size of the nanoparticles was
calculated through the Debye–Scherrer formula,

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D = 0.94
cos
Where K is the Scherrer constant (0.94),
width of half-maximum, and
λ
(1)
β
Ѳ
λ
is the X-ray wavelength (0.1541nm),
β
is the peak
θ
is the Bragg diffraction angle. The average crystallite size D was
calculated using equation (1) which was found to be 25.67 nm.
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3.2 SEM analysis
Fig.2. shows the particle size and morphology of bio synthesized ZnO nanoparticles. From the
SEM image, it is evident that the little bit of aggregation of nanoparticle which is ascribed to the cluster
formation. The nanoparticles are spherical shaped and the diameter of the particles being 25-40 nm which
is very similar to already reported works [27]. The particles are uniform in shape and well dispersed.
Homogenous particle size of the photocatalyst is one of the essential parameter for the photocatalytic
reaction to improve the efficiency.
3.3 TEM analysis
To provide further evidence in the formation of ZnO nanostructures, with different magnification,
HR-TEM analysis was carried out. HR-TEM image of typical ZnO nanoparticles is presented in Fig. 3,
indicating that the nanoparicles having spherical morphology and are self-assembled. The collective
behavior of vander Waals forces and electrostatic interactions would have favored the self-
aggregation/self-assembly of the ZnO nanoparticles as observed from the electron microscopy studies
[28].
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3.4 BET Surface Analysis
Generally, a high specific surface area has a beneficial effect on the activity for catalysts. In this
work, the surface areas of ZnO nanoparticles with spherical shaped morphologies is found to be 69.01

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m /g. High specific surface area of ZnO was beneficial to photocatalytic activity via enhancing the
adsorption of MO, which is the determining step in the photocatalytic reaction.
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3.5 UV–Visible diffuse reflectance spectra
The optical property of the ZnO nanoparticles was investigated by the UV–Vis diffuse reflectance
spectroscopy as shown in Fig.4. It clearly shows that, their absorption edges are located around 373 nm
for bio ZnO, suggesting that ZnO can be excited by UV as well as visible light. The band gap energy (Eg)
of ZnO obtained from the wavelength value corresponding to the intersection point of the vertical and
horizontal part of the spectrum, using the following equations,
E
g
= hc eV ;
E
g
= 1240 eV
(2)
λ
λ
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Where, E is the band gap energy (eV), h is the Planck's constant (6.626 x 10 Js), C is the light
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velocity (3 x 10 m/s) and
λ is the wavelength (nm) [4]. From Fig.4, the absorption edges were positioned
around 373 nm and the band gap value was calculated from equation (2) which was found to be 3.32 eV.
The wide band gap is apparently due to small average particle size [29].
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3.6 FT-IR Spectral analysis
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In order to identify the existence of organic species in bio synthesized ZnO nanoparticles, we
performed FT-IR spectroscopic studies which is shown in Fig.5.The intense absorption band around
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3439cm , 1629 cm , 1383 cm ,446 cm owing to O-H stretching vibration, H-O-H bending vibration
due to absorption of moisture, –C–O and –C–O–C stretching modes and Zn-O stretching vibration [25,
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be attributed to the existence of some bio molecules used as ligation agent that remained even with
repeated washing.

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3.7 Photocatalytic activity investigation
3.7.1 UV Spectral Analysis
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The photocatalytic activity of bio synthesized ZnO nanoparticles was investigated using methyl
orange as the model pollutant under direct UV light illumination. MO is an azo dye containing sulphonate
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(SO ) and azo group (–N=N-). Here, the azo group will act as a chromophoric group and produce strong
orange color. During the direct UV light illumination in the presence of ZnO nanoparticles, the strong
orange color was gradually changed into colorless as shown in Fig.6 (a). It denotes the destruction of
chromophoric group (–N=N-) and photo decomposition of organic dye.
This is further confirmed by UV-Visible spectrum (200nm-600nm) of MO solution at different
time intervals as shown in Fig. 6(b). In order to study the stability of the photocatalyst, the MO solution
was first subjected to photolysis process. The photolysis process, results show that only 6% degradation
was observed in blank and about only 7% degradation was observed in dark. The degradation result of
dark was similar to that of the blank test. There was no detectable changes occurred. This means that the
necessity of both photocatalyst and light be required to for the acceleration of photocatalytic reaction.
The figure 6(b) shows MO dye having the strong absorption maxima at 464 nm due to chromophoric
group and it was diminished as the UV light exposure time increases to 120 minutes and attains about
83.99% degradation efficiency. This clearly shows the cleavage of chromophoric group. Fig.6 (b)
demonstrates blue shift from 464nm to 442 nm due to the deamination from MO [31].
The plot of concentration of dye (C/C ) as a function of time was evaluated as shown in Fig.6(c).
O
After 120 minutes around 83.99% of MO was photo degraded under UV light appreciably because of
efficient oxidation through hydroxyl radicals produced from photocalytic reaction. The detailed
mechanism was depicted in scheme 2.The photodecolorisation efficiency of methyl orange solutions on
ZnO nanoparticles at different reaction conditions were shown in Table 1. We have compared our

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results with ZnO prepared by other plant extracts as well as chemically synthesized ZnO [32-37]
and given the results in Table 2. ZnO nanoparticles successfully decomposed the methyl orange azo dye
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and forming less toxic end products like CO , NO and NO.
3.7.2 Mineralization Studies of MO dye
In order to confirm the efficiency of minaralisation, the degradation part was evaluated using
COD values. The COD values were determined for pre and post photocatalytic treatment. The COD
values were significantly reduced from 6162 mg/l to 481mg/l after 120 mins of UV illumination. The
decreasing value of COD confirms the degradation efficiency of bio synthesized ZnO nanoparticles.
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4. Conclusion
Herein, ZnO nanoparticles has been successfully prepared using rambutan (Nephelium lappaceum
L.) peel extract .The formation of crystalline phases were confirmed by XRD and a band gap of 3.32 eV
was confirmed by UV-DRS. Spherical shape of ZnO nanoparticles with grain size 25-40 nm was
confirmed by FESEM and HR-TEM. The bio synthesized nanoparticles having the surface area 69.01
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m /g shown virtuous photocatalytic activity against methyl orange dye. The photocatalytic results for
methyl orange degradation show that nanoparticles of bio synthesized ZnO can effectively degrade
83.99% within 120 min under UV light. Finally, concluded that methyl orange dye was decomposed into
colorless fragment soundly and subsequently mineralize into less toxic end products using as-prepared
bio-synthesized ZnO nanoparticles.
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Acknowledgement
The authors are grateful to (i) The Dean, University college of Engineering Kanchipuram (ii)
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The Principal and Management, Sri Venkateshwara college of Engineering, Sriperumpudur for providing
the infrastructural support and other facilities to carry out the research work successfully. Also, we thank

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the Coordinator, Science Instrumentation Center, SFR College for Women, Savakis for recording diffuse
reflectance spectra and FT-IR spectra.
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Figure captions
Scheme 1 Possible mechanism of formation of ZnO nanoparticles from rambutan peel extract
Scheme 2 Photocatalytic reaction mechanism of bio synthesized ZnO nanoparticles
Fig. 1 XRD pattern of biosynthesized ZnO nanoparticles
Fig. 2 FESEM image of bio synthesized ZnO nanoparticles
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Fig. 3 (a) TEM images of ZnO nanoparticles at different magnification (b) particle size
distribution histogram of nanoparticles
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Fig.4 UV-Vis DRS spectra of bio synthesized ZnO nanoparticle
Fig.5 FT-IR spectra of bio synthesized ZnO nanoparticle
Fig.6 (a) Gradual change of dye color from orange to colorless
Fig.6 (b) UV-Vis absorption spectra of photocatalytic degradation of MO dye with reaction time
Fig.6(c) Degradation of MO solution as a function of different time intervals.
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Table 1 The photodegradation efficiency of MO solutions on ZnO nanoparticles obtained from
different reaction conditions
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Table 2: Comparison of photocatalytic activity of ZnO nanoparticles prepared from
different methods

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Table 1
Sample
Light
Dye
Decolorization efficiency (%)
________________________________
Time
_
Blank
6%
Dark Photocatalysis
7% 83.99%
ZnO
UV light
Methyl
Orange
120 mins
Nanoparticles
_
____________________________________________________________________________________

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Table 2
_____________________________________________________________________________
_
Materials Synthesizing
Used Method
_____________________________________________________________________________
ZnO biologically Nephelium Methyl 83.99% 120 mins Present work
Synthesized lappaceumL. Orange
Biological Pollutant Degradation Time of
Reference
Entity Efficiency Degradation
_
_
_____________________________________________________________________________
Sr doped
ZnO
chemically
synthesized
___
Methylene
blue
78.5%
120 mins
[32]
[33]
_
_____________________________________________________________________________
Bare ZnO chemically
synthesised
___
Methylene
blue
37%
120 mins
ZnO+rGO chemically
synthesised
___
Methylene
blue
92.5%
120 mins
_
_____________________________________________________________________________
ZnO
biologically
Synthesized
Pyrus
pyrifolia
Methylene
blue
80.3%
210 mins
[34]
_
_____________________________________________________________________________
ZnO
biologically
Synthesized
corriandrum Anthracene
sativum
81.9%
240 mins
[35]
_
_____________________________________________________________________________
ZnO
biologically
Synthesized
Plectranthus Methyl
amboinicus red
92.45% 180 mins
[36]
_
____________________________________________________________________________
ZnO
biologically
Synthesized
Corymbia
citriodora
Methylene
blue
83.45%
90 mins
[37]
_
_____________________________________________________________________________

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O
HO
HO
O
OH
OH
Zn(NO3)2
O
+
O
+
NO3- OH2
2
O
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OH2
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NO -
O
O
3
o
o
O
Zn 2+
+
O
O
o
o
NO - OH2
2
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o
Zn 2+
o
o
O
o
OH2
+
Zn 2+
O
o
OH2
+
o
o
OH
2
o
+
Calcination
O
HO
HO
O
OH
OH
+
ZnO
+
NO2 + O2
O
nanoparticles
O
Scheme 1

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Scheme 2

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theta
Fig. 1

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Fig. 2

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Fig. 3

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Fig.4

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Fig.5

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Pure MO
30 min
60 min
90 min
120 min
(
after dark)
Fig.6 (a)

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min(after dark)
30min
0min
0min
20min
0
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.8
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0.0
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Fig.6 (b)

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Blank(without photocatalyst)
Dark
bio ZnO
0
30
60
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120
Time (min)
Fig.6(c)