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CHAPTER - VII
7. Green Synthesis, Characterization and Application of NiO Nanoparticles
using Rambutan Peel Extract
7.1. Introduction
Nanoparticles exhibit novel material properties due to their small size that are
significantly different from those of their bulk counterparts. Transition metal oxide
nanoparticles have been investigated by several workers in the last few years. Nanoscale
oxide particles of transition metals are gaining continuous importance for various
applications such as catalysts, passive electronic components and ceramic materials [1].
Nickel oxide (NiO) nanoparticles with a uniform size and well dispersion are desirable for
many applications in designing ceramic, magnetic, electro chromic and heterogeneous
catalytic materials [2]. Several researchers have prepared NiO nanoparticles by various
methods like sol–gel [3], surfactant-mediated synthesis [4] thermal decomposition [5],
polymer-matrix assisted synthesis [6] and spray-pyrolysis [7]. Ultrasonic radiation,
hydrothermal synthesis, carbonyl method, laser chemical method, pyrolysis by microwave,
precipitation-calcination, micro emulsion method and combustion [8-13]. However, to the
best of our knowledge, most of the reported experimental techniques for the synthesis of
nanopowders are still limited in laboratory scale due to some unresolved problems, such as
special conditions, tedious processes, complex apparatus, low yield and high cost [14].
Environmentally benign nanoparticles synthesis procedures do not use any toxic
chemicals in the synthesis protocols. In these aspects synthetic methods based on naturally
occurring biomaterials provide an alternative means for obtaining these nanoparticles. The
spectacular success in this field has opened up the prospect of developing bio-inspired
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methods of synthesis of metal nanoparticles with tailor-made structural properties. Though
numerous chemical methods are available for metal nanoparticles synthesis, many reactants
and starting materials are used in these reactions that are toxic and potentially hazardous.
Increasing environmental concerns over chemical synthesis routes have resulted in attempts
to develop bio-mimetic approaches. One of them is the synthesis using plant extracts
eliminating the elaborate process of maintaining the microbial culture and often found to be
kinetically favourable than other bioprocesses. Bio-molecules as reducing agents are found to
have a significant advantage over their counterparts as protecting agents [15].
The rambutan (Nephelium lappaceum L) belongs to the subtropical fruits, which is a
tropical species common to Southeast Asia. This fruit is an importantly commercial crop in
Asia, where it is consumed fresh, canned, or processed, and appreciated for its refreshing
flavor and exotic appearance. After being processed, the residues consist principally of seeds
and peels. Solis-Fuentes and others [16] reported that the seeds of rambutan were rich edible
fat. Palanisamy and others [17] have studied the phenolic contents of the fruit pulp, seed,
peel, and leaf of rambutan and the antioxidant activities of ethanolic extracts, which indicated
that rambutan peel was a potential source of natural antioxidants. Okonogi and others [18]
reported the high scavenging free radical activities of the ethanolic extract of rambutan peel.
Khonkarn and others [19] studied the effects of different solvents on the yields of total
phenolics of rambutan peel and the antioxidant activities of ethanolic extract.
Textiles made from natural fibres such as cotton also well known to be more
susceptible to microorganisms than the synthetic fibres because they are predominantly
hydrophilic in nature. As a result, they are capable of easily holding water, oxygen and
nutrients and therefore provide a favourable environment for bacterial growth. The major
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benefits of antimicrobial finishing of textile materials are to control the onset and spread of
diseases and to prevent or control the development of odor from perspiration [20]. Our recent
report deals with the antibacterial effect of novel synthesized sulphated-cyclodextrin
crosslinked cotton fabric and its improved antibacterial activities with ZnO, TiO2 and Ag
nanoparticles also reported [21]. Modification of fibre surfaces has been one of the main
areas of research in the development of functional fibres. Surface modification and
antibacterial behavior of magnesium oxide nanoparticles using Rambutan Peel Extract has
been reported [22].
Preparation of NiO nanoparticles by greener method is discussed in this chapter. The
synthesised NiO nanoparticles using Rambutan Peel Extract (RPE) were characterized by
XRD, SEM, TEM and antibacterial analysis. The prepared NiO nanoparticles coated on
cotton fabric and characterized by SEM with EDX and antibacterial analysis. The schematic
representation is given in figure 7.1.
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Figure 7.1: Schematic representation of NiO nanoparticle synthesis
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7.2. Results and discussion
The possible mechanism on the formation of NiO nanoparticles using rambutan peel
extract is similar to the MgO nanoparticle which is already discussed in chapter IV. Among
the various active ingredients present in rambutan peel extract, polyphenolic compounds such
as ellagic acid, corilagin, ellagitannins and geranin are mainly responsible for the formation
of NiO nanoparticles by their chelating effect.
7.2.1. XRD study of NiO nanoparticles
The obtained XRD patterns were verified using the JCPDS software. The size of the
nanoparticles was calculated through the Scherrer’s equation. The distinct Bragg reflections
corresponding to (111), (200) and (220) sets of lattice planes were manifested for the X-ray
diffraction patterns shown in figure 7.2. They may be indexed on the basis of face-centered
cubic structure of nickel oxide. The obtained data was matched with the Joint Committee on
Powder Diffraction Standards (JCPDS) file no. (04-0835). The crystallite size was 2θ
determined as 61.54, 56.76 and 56.10 nm corresponding to the position as 36.90, 42.85 and
62.23.
7.2.2. SEM and TEM study of NiO nanoparticles
Scanning electron microscope analysis was employed to study the morphology of the
nanoparticles that were formed. Representative SEM micrographs of the reaction synthesized
nanoparticles were carried out at different magnifications such as X 2,500, X 5,000, X 10,000
and X 30,000 are shown in figure 7.3 a, b, c and d respectively. From the SEM images it is
noticed that the surface morphologies are existing as granular and clusters in the form of
assemblies. The size of nanoparticle around 50 nm is shown in figure 7.3 (d). NiO
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nanoparticles have agglomerated into clusters because of attractive forces bringing them
together into groups.
TEM analysis was carried out to further confirm the nanosize of nickel oxide
nanoparticles. Figure 7.4 (a & b) shows representative TEM images of NiO nanoparticles. It
can be seen that the uniform NiO nanoparticles have flower like shapes with weak
agglomeration but reasonable distribution. The average particle size from TEM images is 50
nm which agrees well with the size examined from SEM analysis.
7.2.3. SEM & EDX studies of NiO nanoparticles treated and untreated fabrics
The morphological changes of cotton samples after the treatment with nickel oxide
substances can be clearly observed from the SEM images. Figure 7.5 (a1, a2 & b1, b2, b3)
shows the morphology of normal and nickel oxide nanoparticles treated cotton samples. SEM
images clearly show the significant difference between the untreated and treated cotton
fibers, the former has a smooth and uniform surface, whereas the latter is rough due to the
change in position of nickel oxide nanoparticles onto the surface of the fibers. The
micrographs figure 7.5 (b1 & b2) shows that the nickel oxide nanoparticles in the nanoscale
range are well distributed onto the fabric. Figure 7.5 (b3) at 30 micrometer the nickel oxide
nanoparticles are well distributed and absorbed into the fabric.
Energy dispersive X-ray spectroscopy (EDX) was employed to establish the chemical
identity of the observed particles. Figure 7.6 & 7.7 shows the unmodified and modified EDX
images of the cotton samples. It can be clearly seen that in unmodified fabrics (Fig.7.6), there
is no evidence for the existence of nickel ions whereas the nickel ions existed on the surfaces
of the cotton fibers after modified with NiO nanoparticles are clearly exhibited from the EDX
image (Fig.7.7).
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7.2.4. Antibacterial studies of NiO nanoparticles
Figure 7.8 reveals the antibacterial activities of NiO nanoparticles. Antibacterial
activities of NiO nanoparticles have been tested on both gram positive (S.aureus) and gram
negative (E.coli) bacteria. Antibacterial activity towards bacteria E.coli ATCC 10536 and
S.aureus ATCC 11632 of nickel oxide nanoparticles were performed using Kirby-Bauer
diffusion method. The antibacterial activity was evaluated by measuring the zone of
inhibition against the test organisms. Zone of inhibition is the area in which the bacterial
growth is stopped due to bacteriostatic effect of the compound and it measures the inhibitory
effect of compound towards a particular microorganism. The NiO nanoparticles showed zone
of inhibition found in both bacterias and S.aureus found more inhibition compared to the
E.coli.
Figure 7.9 (a & b) shows the antibacterial activity of nickel oxide nanoparticles
treated and untreated fabrics. S.aureus and E. coli were used as test microorganisms to detect
the antibacterial activity. Tabl 7.2 shows the antibacterial results of nickel oxide
nanoparticles. The antibacterial performance of NiO nanoparticles treated fabrics was done
by using disc diffusion method. The disc diffusion method for antibiotic susceptibility testing
is the Kirby-Bauer method. The agar used is Muller-Hinton agar that is rigorously tested for
composition and pH. Further the depth of the agar in the plate is a factor to be considered in
the disc diffusion method. This method is well documented and standard zones of inhibition
have been determined for susceptible and resistant values. There is also a zone of
intermediate resistance indicating that some inhibition occurs using this antimicrobial but it
may not be sufficient inhibition to eradicate the organism from the body. The zone of
inhibition increases with the increase in nickel oxide nanoparticles concentration and
decrease in particle size.
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7.2.5. Wash durability
Wash durability test carried out with the test fabrics showed that the significant
antimicrobial activity was actively retained in the NiO nanoparticles treated fabrics up to 4
washes (Table 7.1) even after repeated wash. Compared to the previous chapters (IV,V & VI)
it show good washing durability. The untreated control fabrics were not subjected to any
wash durability test as it has no antibacterial activity.
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7.3. Conclusion
Rambutan peel extract have been effectively used for the synthesis of NiO
nanoparticles. We have utilized the natural, renewable and low cost biomaterial for the
synthesis of NiO nanoparticles. The XRD and SEM analysis supports the crystallinity and
surface morphology of the biosynthesized nanoparticles. The average crystallite size for the
intense peak measured were 56 nm from XRD analysis. The SEM image shows granular
nanoparticles around 50 nm. TEM analysis confirmed the NiO nanoparticles. SEM and EDX
images confirmed the adsorption of NiO nanoparticles on the cotton fabric. The fabric
strongly increases adsorption of NiO nanoparticles on the surface of the fibres due to the
crosslinker (citric acid) and change of surface charge on the cellulose fibres. The NiO
nanoparticles treated cotton fabric exhibited stronger antibacterial activity due to the
increasing NiO nanoparticles absorption on the surface of cellulosic fibres.
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7.4. References
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[8] D. A. Sverjensky, Nature 364:776 (2003)
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[15] J. Huang, Q. Li, D. Sun, Y. Lu, Y. Su, X. Yang, H. Wang, Y. Wang, W. Shao, N. He, J.
Hong, and C. Chen, Nanotechnology 18, 105104 (2007)
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7.5. Legends
7.5.1. Tables
Table. 7.1. Wash durability of NiO nanoparticles treated cotton fabric
Table.7.2. Antibacterial assessment by agar diffusion method
7.5.2. Figures
Figure 7.1. Schematic representation of Nickel Oxide nanoparticle synthesis
Figure 7.2. XRD spectrum of Nickel Oxide Nanoparticles
Figure 7.3. SEM image of Nickel Oxide Nanoparticles at different magnifications
Figure 7.4. TEM images of Nickel Oxide nanoparticles in 2D and 3D forms Figure 7.5. SEM images of Nickel Oxide nanoparticles (a) untreated (b) treated fabrics
at X100 and X500 magnification
Figure 7.6. EDX image of untreated cotton fabric
Figure 7.7. EDX image of treated cotton fabric with Nickel Oxide nanoparticles
Figure 7.8. Antibacterial activity of Nickel Oxide nanoparticles against (a) S.aureus
(b) E.coli
Figure 7.9. Antibacterial activity of (a) untreated (b) NiO treated cotton fabrics against E.coli
and S.aureus
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Table 7.1: Wash durability of NiO nanoparticles treated cotton fabric
Table.7.2: Antibacterial assessment by agar diffusion method
Fabric treated Organism Zone of Inhibition (in cm)
Fabrics without NiO nanoparticles (Control) S.aureus 0
E.coli 0
Fabrics treated with NiO nanoparticles S.aureus 35
E.coli 25
No. of Washing cycles
Fabrics treated with NiO nanoparticles
% Bacterial Reduction
S.aureus
E.coli
1 80.11 77.10
2 78.21 73.50
5 75.02 70.15
10 62.50 58.50
15 30.20 24.50
20 12.85 10
25 0 0
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Figure 7.2: XRD spectrum of Nickel Oxide Nanoparticles
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Figure 7.3: SEM image of Nickel Oxide Nanoparticles at different magnifications
a) X 2,500 b) X 5, 000 c) X 10, 000 and d) X 30, 000
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Figure 7.4: TEM images of Nickel Oxide Nanoparticles
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Figure 7.5: SEM images of NiO nanoparticles untreated (a1, a2) treated fabrics (b1, b2,
b3) with different magnification (500µm, 100µm & 30µm)
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Figure 7.6: EDX image of untreated cotton fabric
Figure 7.7: EDX image of treated cotton fabric with Nickel Oxide nanoparticles
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Figure 7.8: Antibacterial activity of Nickel Oxide nanoparticles against (a) S.aureus
(b) E.coli
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Figure 7.9: Antibacterial activity of (a) untreated (b) NiO treated cotton fabrics against
E.coli and S.aureus