Volume||4||Issue||05||May-2016||Pages-5391-5395||ISSN(e):2321-7545
Website: http://ijsae.in
DOI: http://dx.doi.org/10.18535/ijsre/v4i05.15
Bio-synthesis of Silver Nano-prisms from Ocimum sanctum manipulation of Localised
surface Plasmon through induced resonance
Authors
Waseem Bashir VK , Mohammed Sarfiras A2, Sajin KV3, Vijayarani N4
1,2,3,4
Department of Microbiology, Nehru Arts and Science College, Bharathiyar University, Coimbatore.
*Email id: vijayarani167@gmail.com
ABSTRACT
Localised surface Plasmon Resonance (LSPR) is a phenomenon in its starting stages that is being put
through study for its sensing applications. With the rise of a new innovation comes the lack of
considerations for the environment and this has been established by the many centuries of industrial
revolution all around the world. This work was initiated as an attempt to produce optically configured Silver
Nano-prisms through Eco-Friendly methodology and as an investigation to find an alternative to the
traditional. Ocimum sanctum leaf extract was utilised for the traditional precipitation-stabilization
biosynthetic method for its ease and efficiency. Preliminary analyses conducted, production of Silver Nano
particles were characterised. This was achieved by mixing 2.5 ml of extract in AgNO3 to arrive at the same.
A characteristic change in colour was observed towards an amber-brown from milky white to indicate the
formation of silver Nano-particles. A clear absorbance peak at around 410 nm indicating the presence of
silver Nano-particles. Now the resultant solution was exposed to varying optical condition to manipulate its
Surface Plasmon and preliminary analyses showed obvious changes in optical and physical properties of the
Nano-particles. These Nano-Prisms were characterised by a change in the entire particulate structure that
gave it a triangular, pyramidal shape .These changes were analysed and discussed after various tests and
imaging processes.
Keywords: Silver nano prisms, Ocimum sanctum, UV-Vis, SEM, Leaf extract
1
INTRODUCTION
In recent trends, all forms of medical, pharmaceutical and biological sciences, advents towards eco-friendly
technology that can sustain productivity and/or efficiency is very much in vogue. Metal nanoparticles are of
importance due to their potential applications in catalysis, photonics, biomedicine, antimicrobial activity and
optics ([1], [2], [3], [4]-[6]). The extensive investigation of these particles has been driven by their unique
optical properties, notably localized surface Plasmon resonance (LSPR). Localized surface Plasmon
resonance is the coherent oscillation of conduction electrons on the surface of metallic nanoparticles excited
by the varying electric field of incident electromagnetic radiation [7], [8]. Since nanoparticles exhibit
completely new or improved properties based on specific characteristics such as size, distribution and
morphology, new applications of nanoparticles and nano materials are emerging rapidly. A number of
synthesis techniques have been developed including the chemical reduction of silver ions in aqueous
solutions, with or without stabilizing agents, thermal decomposition in inorganic solvent, and chemical and
photo reduction. [9]. This Paper deals with a methodology that can Biosynthesise Silver Nano-Prisms
[AgNPm] [10]. Silver Nano-prisms are not essentially, as the name suggest traditional prisms in a Nano
scale. Technically, Nano-prisms are nano-particles that have attained a particular state in the dimensions of
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the surface Plasmon, provided the particle does have a surface Plasmon that can be moulded [11].
Biosynthesis of a nanostructure is an arena of methods that involve biological entities in a larger production
process, often these methods are associated with eco-friendly measures. Green-synthesis, Phyco-synthesis,
Myco-synthesis etc., are a part of the above mentioned biosynthetic arena.
MATERIALS AND METHOD
Fresh silver nitrate (AgNO3) was prepared and Ocimum sanctum leaves were collected from surroundings
areas of Palakkad, India. The fresh leaves extract used for the reduction of Ag+ ions to Ag° was prepared by
taking 20g of thoroughly washed finely cut leaves in 500 ml Erlenmeyer flask that was cleaned with acetone
along with 100 ml of distilled water and then boiling the mixture for 5 min before decanting it. Further the
extract was filtered with Whatman No. 1 filter paper and stored at 4°C and used for further experiments. In a
typical experiment, the leaf extract (0.5 ml) was added to 10 ml of 1 mM AgNO3 aqueous solution, drop
wise. In three test tubes cleaned with acetone, 3 ml of extract containing the nanoparticles were taken and
closed with cotton plugs that have a monochromatic LED light fixed into it [11]. The three test tubes are
exposed to Blue Green and red lights respectively by the set up. The test tubes with its corresponding LED
was closed with aluminium foil to enable maximal exposure of the extract to the LED light as well as to
keep out other light rays.
RESULTS
A characteristic change in colour was observed toward an amber-brown from milky white to indicate the
formation of silver Nano-particles. Primary colorimetric graph was drawn for the various measures of
absorbance ranges between samples that were described as earlier exposed to varying monochromatic Light
sources and conditions. The obvious changes that the treated samples of extract showed was noted [Fig.
1].The three treated samples were run through UV-VIS spectrophotometry and it was noted that there was a
clear absorbance peak at around 410 nm indicating the presence of silver Nano-particles. The entire graph
was almost completely in synchronisation, the Nano particle absorption peak mentioned above alone showed
clear and distinct shifts. This clear shift in the peak attributed to the Localised Surface Plasmon resonance.
[Fig. 2]. SEM analysis showed these Nano-Prisms were characterised by a change in the entire particulate
structure that gave it a triangular, pyramidal shape [Fig. 3].
Fig 1: Plant extract [Left] and Ag No3 [Right}
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Fig 2: UV-VIS Spectrophotometry
Fig 3: SEM micrograph showing triangular silver nanoprisms
DISCUSSION
Metal nanoparticles are among the most promising systems for applications mainly because of their
characteristic large electric-field enhancement. The plasmon resonance conditions depend on a number of
parameters, such as particle size, surface charge, the nature of the dielectric environment, and inter-particle
coupling, but the particle morphology has been shown to play a fundamental role. A reduction method was
developed for the synthesis of triangular silver nanoprisms. It could be a eco-friendly alternative to chemical
and physical method which involves a myrid of chemicals. Similar observation was also made in papaya
fruit extract [12].
The bimodal peaks observed in the UV-Visible spectrum indicate a mixture of particle size and morphology.
The peak located near 410 nm can be attributed to absorbance by small, spherical Ag particles, on the order
of only a few nanometres in diameter. Similar peak or shoulder was apparent for each sample between 400
and 450 nm, which can be attributed to the in-plane quadrupole of the nanoplates and/or nanoprisms [13].
The obtained Nano-Prisms were characterised by a change in the entire particulate structure that gave it a
triangular, pyramidal shape. The spherical pattern previously obtained in vilangam and in Euphorbia hirta
[14]. Besides spherical, polyhedral, cuboidal and unisotropic nanoparticles have also been reported [13].
Thus we concluded that the usage of induced resonance into the Plasmon of a biosynthesised nanostructure
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was in many ways a better alternative to the traditional in vitro synthesis involving toxic chemicals and
cryogenics. Exceptional optical limiting properties were observed in two kinds of Ag nanoprisms, pure Ag
nanoprisms and Au @Ag core shell nano prisms. Their optical limiting properties were even slightly better
than that of CNT suspension, which was known as a benchmark optical limiter. Compared to CNT, these
nanoprims was attractive as optical limiting materials because they were easy to prepare, highly soluble and
stable in an aqueous medium.
CONCLUSION
In conclusion, we present the development of a reproducible method for the synthesis of highly uniform Ag
nanoprisms. Thus it was concluded that leaf extract of Ocimum sanctum, could be a potential source of
phyto-constituent for the synthesis of silver nanoprisms and the method was also quite eco-friendly when
compared to existing chemical and physical methods.
Acknowledgement
The authors are grateful to Nehru Arts and Science College, Bharathiyar University, Coimbatore, , India for
their constant encouragement and support and providing all the research facilities for carrying out this
study.
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