In present experimental work rapid and simple method was applied for synthesis of silver nanoparticles using different type of medicinal plants viz.(Sphagneticola trilobata, Catharanthus roseus, Azadirachta indica and Dalbergia sissoo) aqueous leaf extracts are used as reducing agent as well as capping agent for silver nanoparticles synthesis. Green synthesis of silver nanoparticles (AgNPs) was characterized by UV-Visible spectroscopy. UV-Visible spectrophotometer showed surface plasmon absorbance peaks in range of 420-480 nm and we obtained 420 nm, 444 nm, 430 nm & 425 nm peak for Sphagneticola trilobata, Catharanthus roseus, Azadirachta indica and Dalbergia sissoo respectively.
Nanotechnology is a field of modern technology dealing with synthesis, strategy and manipulation of particle’s structure within 1-100 nm size range. Within this size range all the fundamental properties (chemical, physical and biological) changes as compared to their bulk molecules or atoms (Ahmed et al., 2014). Novel applications of nanoparticles and nanomaterials are growing rapidly on various fronts due to their absolutely new and enhanced properties based on there size, distribution and morphology. It is rapidly gaining renovation in a large number of fields such as health care, cosmetics, biomedical, food and feed, drug-gene delivery, environment, health, mechanics, optics, chemical industries, electronics, space industries, energy science, catalysis, light emitters, single electron transistors, nonlinear optical devices and photo-electrochemical applications.
The nanoparticles used for all the aforesaid purposes, the metallic nanoparticles considered as the most promising as they contain remarkable antibacterial properties due to their large surface area to volume ratio, which is of interest for researchers due to the growing microbial resistance against metal ions, antibiotics and the development of resistant strains(Khalil et al., 2013). Among the all noble metal nanoparticles, silver nanoparticle are an arch product from the field of nanotechnology which has gained boundless interests because of their unique properties such as chemical stability, good conductivity, catalytic and most important antibacterial, anti-viral, antifungal in addition to anti-inflammatory activities which can be incorporated into composite fibres, cryogenic superconducting materials, cosmetic products, food industry and electronic components.(Ahmed et al., 2016).
A number of methods are available for the syntheses of silver nanoparticles like ion sputtering, chemical reduction, sol gel, etc. (Bindhu & Umadevi;2015) unfortunately many of the nanoparticle syntheses methods involve the use of harmful chemicals, which are rather difficult and including wasteful purifications (Ikram & Swami; 2015). Thus; a scenario is that whatever the method followed, will always leading to the chemical contaminations during their syntheses procedures or in later applications with associated limitations. Yet; one cannot deny their ever growing applications in daily life. Hence, it is becoming a responsibility to emphasise on an alternate as the synthetic route which is not only cost effective but should be environment friendly in parallel. Keeping in view of the aesthetic sense, the green syntheses are rendering themselves as key procedure and proving their potential at the top. The techniques for obtaining nanoparticles using naturally occurring reagents such as sugars, biodegradable polymers (chitosan, etc.), plant extracts, and microorganisms as reductants and capping agents could be considered attractive for nanotechnology (Devi et al.,2015). Green synthesis of nanoparticles also provides advancement over other methods as they are simple, one step, cost-effective, ecofriendly and relatively reproducible and often results in more stable materials (Mittal et al., 2014). Microorganisms can also be utilized to produce nanoparticles but the rate of syntheses is slow compared to routes involving plants mediated synthesis (Ahmed et al., 2015). Although, the potential of higher plants as source for this purpose is still largely unexplored. Very recently plant extract of marigold flower (Padalia et al., 2014), Ziziphora tenuior (Sadeghi & Gholamhoseinpoor, 2015), Abutilon indicum (Ashokkumar, Ravi, & Velmurugan, 2013), Solanum tricobatum (Logeswari et al.,2013), Erythrina indica (Sre et al., 2015), beet root (Bindhu & Umadevi, 2015), Spirogyra varians (Salari et al., 2014), olive (Khalil et al., 2013), leaf extract of Acalypha indica with high antibacterial activities (Krishnaraj et al., 2010) and of Sesuvium portulacastrum also reported in literature with nanoparticle size ranging from 5 to 20 nm (Nabikhan et al.,2010) are brimming in literature as a source for the synthesis of silver nanoparticles as an alternative to the conventional methods. Considering the immense potentiality of plants as sources this work aims to apply a biological green technique for the synthesis of silver nanoparticles as an alternative to conventional methods. Silver nanoparticles can be produced at low concentration of leaf extract without using any additional harmful chemical/physical methods. The effect of concentration of metal ions and concentration of leaf extract quantity were also evaluated to optimize route to synthesise silver nanoparticle. The method applied here is simple, cost effective, easy to perform and sustainable.
It is clear from the study of researches done in the past that biologically synthesized silver nanoparticles finds various applications in the field of biomedicine. Therefore the present research work was planned to explore four different plants for the biosynthesis of silver nanoparticles whole work was carried out under following objectives: synthesis of Silver nanoparticles and its characterization by using UV-Vis spectroscopy.
Materials and methods
Typically, a plant extract-mediated bio reduction involves mixing the aqueous extract with an aqueous solution of the appropriate metal salt. The synthesis of nanoparticle occurs at room temperature and completes within a few minutes to overnight incubation.
Preparation of plant extract
Sphagneticola trilobata, Catharanthus roseus, Spilanthes paniculata, Azadirachta indica and Dalbergia sissoo leaves extracts were used to prepare silver nanoparticles on the basis of cost effectiveness, ease of availability and its medicinal property. Fresh leaves were collected from college campus in month of october. They were surface cleaned with running tap water to remove debris and other contaminated organic contents, followed by distilled water and air dried at room temperature. About 10 gm of finely cut leaves were kept in a beaker containing 100 ml distilled water and boiled for 30 min. The extract was cooled down and filtered with Whatman filter paper no.1 (Cat.no. 1001125) and extract was stored at 4ºC for further use (Harekrishna bar et al.,2009).
Green synthesis of silver nanoparticles
100 ml, 1 mM solution of silver nitrate was prepared in 250 ml conical flask. Then 12 ml of silver nitrate solution was added in 88 ml of plant extract. This reaction mixture was incubated in a dark chamber to minimize photo-activation of silver nitrate at room temperature and observed for reaction to colour change (Obaiad et al.,2015).
Characterization of synthesised silver nanoparticles
UV-Vis spectral analysis was done by using UV-Visible spectrophotometer (Systronics, UV-1300). 3 ml of sample mixture was took and subjected to test in UV-Visible absorption spectrophotometer with a resolution of 1 nm between 200 and 800 nm was used.
Results and discussion
In our experiment, addition of plant leaf extracts of Sphagneticola trilobata, Catharanthus roseus, Spilanthes paniculata, Azadirachta indica and Dalbergia sissoo into the flasks containing aqueous solution of silver nitrate led to the change in the colour of the solution to yellowish to reddish brown (shown in Fig. 1) within reaction duration due to excitation of surface plasmon vibrations in silver nanoparticles (Veerasamy et al., 2011). On addition of different concentration (1-5mL) of leaf extracts to aqueous silver nitrate solution keeping its concentration 10 mL (1 mM) constant, the colour of the solution changed from faint light to yellowish brown and finally to colloidal brown indicating formation of silver nanoparticles. Silver nanoparticles were synthesized from different leaves extract using 1 mM of silver nitrate were analysed by UV spectra of Plasmon resonance band observed at 420-480 nm.
Similar study done by Afrah Eltayeb Mohammed,(2013) were used aqueous extract of E. Camaldulensis leaf and synthesized silver nanoparticle got absorption value between 400-450 nm for the extract and the colour change to dark brown were corresponding to the plasmon absorbance of AgNPs.
Geethalakshmi and sarada, (2010) were Synthesized silver nanoparticles by using Trianthema decandra leaf extract and characterized by using UV-Vis spectroscopy Absorption spectra formed in the reaction media shows absorbance peak at 450 nm.
A simple green synthesis of silver nanoparticles using Sphagneticola trilobata, Catharanthus roseus, Spilanthes paniculata, Azadirachta indica and Dalbergia sissoo leaf extract at room temperature was reported in this study. Synthesis was found to be efficient in terms of reaction time as well as stability of the synthesized nanoparticles which exclude external stabilizers/reducing agents. It proves to be an eco-friendly, rapid green approach for the synthesis providing a cost effective and an efficient way for the synthesis of silver nanoparticles. Therefore, this reaction pathway satisfies all the conditions of a 100% green chemical process. Benefits of using plant extract for synthesis is that it is energy efficient, cost effective, protecting human health and environment leading to lesser waste and safer products. This eco-friendly method could be a competitive alternative to the conventional physical/chemical methods used for synthesis of silver nanoparticles.
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