Characterization of Biologically Synthesised Silver Nanoparticles from Euphorbia hirta

S. Sathish Kumar¹ and G. Melchias²

¹Department of Botany, St. Joseph’s College (Autonomous), Trichy-2, Tamil Nadu, India.

²Associate Professor of Botany, Department of Botany, St. Joseph’s College (Autonomous),

Trichy-2, Tamil Nadu, India.

*Corresponding Author E-mail:- gmelchias@yahoo.in

ABSTRACT:

Nanotechnology is the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanoscale. It involves the production, manipulation and use of materials ranging in size from less than a micron to that of individual atoms from not only chemical approaches but also biological materials. Silver nanoparticles were successfully synthesized from AgNo₃ through a simple green and natural route using the aqueous extract of shade dried leaves of Euphorbia hirta (L). Nano particle synthesis is proved under UV-Vis absorption spectroscopy. By using plant extract, silver nano particles synthesized which are quite stable and no visible changes are observed even after a month or so, if the nanoparticle solutions are kept in light proof condition. As nanoparticles have great application in medical world like gene therapy, cancer therapy, drug delivery etc. So medical world also easily accept the plant world for nanoparticle synthesis and welcome the higher plants for their potentiality of synthesis of non polluted, environmentally acceptable, safety for human health nanoparticles. Physical evolutions by Field Emission Scanning Electron Microscopy (FESEM) were used to differentiate the Ag nanoparticles shape and structures. FESEM image divulges that silver nanoparticles are quite poly dispersed, the size ranging from 5.1642d.nm to 98.65d.nm measured by Diffuse Light Scattering (DLS) method. That is smaller than the nanometer. To that the plant E. hirta having the silver nanoparticles in the globular in shape .The move towards extracellular synthesis of Ag nanoparticles using dried biomass appears to be cost effective, ecological to that of conservative methods of green nanoparticles synthesis.

KEYWORDS: Nanotechnology, Euphorbia hirta, Silver nanoparticles.

INTRODUCTION:

There the field of nanotechnology has been impressive developments in the modern past year, with numerous methodologies developed to synthesize various types in nanoparticles of particular shape and size depending on specific requirements based on the metal composition [1]. Nanoparticles can be termed as the synthesis, characterization, investigation and function of nanosized (1-100 nm) materials for the development of science in advances [2]. The fundamental properties of functional metal nanoparticles are mainly determined by size, shape, composition, crystallinity, viscosity, density and morphology [3]. In modern years, nanotechnology and nanoparticles has been embraced by industrial sectors due to its applications in the field of electronic, electromagnetic storage systems, [4] biotechnology [5], magnetic separation and pre concentration of target analysis, drug delivery system [6,7] and vehicles for gene and drug delivery.

Nanotechnology is mainly concerned with synthesis of nanoparticles of variable sizes, shapes, compositions and controlled dispersity of their potential use for human benefits [8]. Biosynthesis of nanoparticles as an emerging highlight of the intersection of nanotechnology and biotechnology has received increased attention due to growing need to develop environmentally benign technologies in material synthesis [9]. A great deal of effort has been put into the biosynthesis of inorganic material, especially metal nanoparticle using microorganisms and plants [10, 11]. The rate of reduction of metal ions using plants extract has been found to be much faster as compared to micro-organisms and stable formation of metal nanoparticles has been reported. The reduction of silver ions (Ag+) in aqueous solution generally yields colloidal silver with particle diameters of several nanometers. Traditional Medicinal herbs are the local heritage with global importance. The native (Nattu Vaithyuam) system of medicine, namely, Ayurvedic, Siddha, and Unani, has been in existence for many world countries. Some drugs from Ayurveda medicine approaches to modern diseases, have already reached the market place in low cost [12]. There are many other species of Euphorbia which are used in traditional medicines [13]. There are many report expose the various activity like anxiolytic, analgesic, antipyretic, and anti-inflammatory activities of E. hirta stem [14], antimicrobials and anti malarial activities [15]. Because of these application we synthesis and characterized the silver nanoparticles from E. hirta.

MATERIALS AND METHODS:

Chemicals

AgNO₃ was purchased from Himedia laboratories Pvt. Ltd., Mumbai, India. The water used was obtained through glass double distillation.

Glassware

Borosil (India) glass wares (Conical flasks, Measuring cylinders, Beakers, Petri plates and Test tubes etc.) were washed and sterilized as per standard microbiological procedures.

Preparation of Plant extract

Euphorbia hirta plants were collected locally and confirmed to their identified taxonomic position with help from the Rapinat Herbarium, Tiruchirappalli. The plants were washed in running water and blotted dry. The leaves were harvested and shade dried 4 days before pulverized into fine powder. One gram of the fine filtered powder was boiled in 100 ml distilled water for 15 minutes at 70⁰C and cooled to room temperature. The filtrate was decanted and filtered first through Whatman No.1 filter paper (0.45μm) and then through 0.22μm sized filters. The filtrate was stored in sterile vials and kept in ambient temperature.

Table 1. Preparation of reaction medium for the synthesis of Silver nanoparticle mediated by E. hirta leaf extract

No.	Aqueous AgNO₃stock(ml)	Plant Extract (ml)	Final volume(ml)	Incubation (Hours)
1	99.0	1.0	100	24
2	97.5	2.5	100	24
3	95.0	5.0	100	24
4	90.0	10	100	24
5	80.0	20	100	24

Synthesis of silver nanoparticles from E. hirta leaf extract

A 1 ml of plant extract was added into 99 ml of aqueous solution of 1mM silver nitrate (AgNO₃) for reduction of silver nitrate into Ag+ ions and kept at room temperature for up to 24 hours. After 10-20 minutes the color of the solution changed into reddish brown indicating the formation of silver nanoparticles. The bio reduced silver nanoparticle solution was measured using UV-Visible absorbance. The synthesis was based on the various concentrations, the concentration are in table 1.

Characterization of the silver nanoparticles

The characterization of silver nanoparticles was carried out by different instruments and techniques. It includes UV- visible, FESEM, Particle analyzer and Fourier Transform Infrared (FTIR).

UV-visible Spectroscopy

The reduction of pure Ag+ ions was monitored by measuring the UV-Vis spectrum of the reaction medium at 24 hours after diluting a small aliquot of the sample into distilled water. UV-Vis spectral analysis was done by using UV-VIS spectrophotometer UV-2450 (UV Winlab).

FTIR

Infra red spectroscopy was used to investigate and predict any physicochemical interactions between different components in a formulation using FT-IR. FTIR spectroscopy measurements were taken for the AgNPs synthesized after 24 hrs of reaction. These measurements were carried using a FTIR SHIMADZU 8400S instrument with a wavelength range of 4000 to 400 nm where the samples were incorporated with KBr pellets to acquire the spectra. The results were compared for shift in functional peaks.

FESEM Microscopy

FESEM was used to characterize mean particle size, morphology of the AgNPs. FESEM produces clear images with spatial resolution down to 1 1/2 nm that are electro-statically less distorted, i.e. 3 to 6 times better than conventional SEM. The powder sample and freeze dried sample of the AgNPs solution was sonicated with distilled water; small drop of this sample was placed on glass slide allowed to dry. A thin layer of platinum was coated to make the samples conductive Jeol JSM-6480 LV FESEM machine was operated at a vacuum of the order of 10-5 torr. The accelerating voltage of the microscope was kept in the range 10-20 kV.

Particle Size Analyzer (DLS method)

In most applications theoretical calculations predict the relative effects of particle size, particle composition, composition of the surrounding medium and wavelength of light. In order to find out the particles size distribution the Ag powder was dispersed in water by horn type ultrasonic processor (Vibronics, VPLP1). The data on particle size distribution were extracted in Zetasizer Ver. 6.20 (Mal1052893, Malvern Instruments).

RESULTS AND DISCUSSION:

UV- Vis Spectral analysis

A blue shift in the UV absorption peak from 400nm to 190 nm indicates the particle size reduction. A typical peak of λmax at 432 nm was obtained due to the surface plasmon resonance of silver nanoparticles were shown in Table 1 and Figure 1. The surface plasmon absorption peaks depends on the size and shape of the metal nanoparticles as well as on the dielectric constant of the metal itself and the surrounding medium [16].

FTIR: In order to determine the functional groups on the synthesized silver nanoparticles from E. hrita plant FTIR analysis was performed. The band intensities in the different regions of the spectra for the control and test samples (before, after reaction) were analyzed and the results have been abstracted in Table 2 and Figure 2.

Figure 2. FTIR spectra of silver nanoparticles synthesized from Euphorbia hirta extract by treating 1mM silver nitrate after 24 hours

Table 2. Summary of FTIR analysis

Composition AgNO₃ : Extract 99 : 1	Frequency range cm^-1	Bond	Compound type
24 hrs	3419.51 3.23	O-H	Alcohol, phenols
	2073.47 85.61	C⁰C	Alkynes
	1638.53 24.98	NO₂	Nitro compounds
	689.06 53.04	C-H	Alkynes

Figure 3. FESEM of silver nanoparticles synthesized from Euphorbia hirta extract by treating 1mM silver nitrate after 24 hours

Table 3. Summary of Particle size analysis

Record No	Count rate (kcps)	Z- Average (d.nm)	Size (d.nm)	Intensity (%)	Width (d.nm)	Pdl /Intercept
1	200.0	43.58	97.72	85.1	53.06	0.637/ 0.855
			12.26	8.1	1.448
			4.934	6.9	3.971
2	200.2	43.42	96.30	87.2	53.26	0.633/ 0.856
			7.587	12.8	3.568
3	200.4	43.45	94.98	87.8	50.00	0.631/ 0.852
			6.503	12.2	2.632

FESEM analysis

FESEM analysis is employed to analyze the morphology of the silver nanoparticles. Representative FESEM images of the silver particles collected after 24 hrs of reaction incubation followed by precipitation using 1mM AgNO₃ with plant extract. The images (Figures 3) taken off the powder collected from the colloids reveal the silver nanoparticles coalesced to nano-clusters made of nanocrystals, predominantly globe shaped nanocrystals.

Particle Size Analysis (DLS method)

The particle size distribution was observed by diffuse light scattering (DLS) method 24 hours after the formation the Ag colloids (Figures 4a,b,c). The particle size has been tested for freshly prepared and also after 24 hours of E. hrita reaction with AgNO_3.The results are abstracted in Table 3. The maximum size was observed 98.6d.nm. The smallest particles were of the size of 1.983d.nm. Based on the count rates the particle size may vary.

Figure 4 (a-c). DLS of silver nanoparticles synthesized from Euphorbia hirta extract by treating 1mM silver nitrate after 24 hours

CONCLUSION:

The present work is premised on two well documented facts – that metallic nanoparticles are increasingly recognized for their potential applications of relevance to human welfare, and that biologically formed nanoparticles circumvent several demerits of their chemical counterparts. Therefore we formulated the hypothesis that medicinal herbs with their rich constituents of capping properties can present an ideal platform for nanoparticle synthesis.

ACKNOWLEDGEMENTS:

The authors are thankful to the Bank of Baroda, Mannachanallur Branch, Tiruchirappalli for providing the financial assistance for the research work.

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Received on 22.03.2014 Accepted on 27.03.2014

Asian J. Pharm. Tech. 2014; Vol. 4: Issue 1, Pg 01-05