Nano-silver Colloidal Solution Formation by a Simple and Green Method HAMID REZA GHORBANI

In recent years, the synthesis and applications of nanoparticles of noble metals have been of a great interest for researchers. Silver nanoparticles provide a wide range of valuable opportunities for such fields of science as catalysis, photonics, photography, chemical sensing, surface enhanced Raman scattering (SERS) and most importantly in the medicinal field as anti-microbial agents1-3. These properties extensively depend on the size and shape of the nanomaterial. Synthesis of silver particles is an important topic4. Development of methods for nanostructures synthesis is necessary to produce nanoparticles that can be employed in ORIENTAL JOURNAL OF CHEMISTRY


INTRODUCTION
In recent years, the synthesis and applications of nanoparticles of noble metals have been of a great interest for researchers.Silver nanoparticles provide a wide range of valuable opportunities for such fields of science as catalysis, photonics, photography, chemical sensing, surface enhanced Raman scattering (SERS) and most importantly in the medicinal field as anti-microbial agents [1][2][3] .These properties extensively depend on the size and shape of the nanomaterial.Synthesis of silver particles is an important topic 4 .Development of methods for nanostructures synthesis is necessary to produce nanoparticles that can be employed in In 2014, spherical Silver nanoparticles (SNPs) were synthesized by chemical reduction method from a metal precursor silver nitrate in presence of an anionic surfactant and strong reducing agent 9 .In another work, Metallic silver nanoparticles was reduced from silver nitrate by employing the extracellular enzymatic machinery of edible White button Mushroom (Agaricus bisporus) 10 .Ghorbani reported biosynthesis of silver nanoparticles using Salmonella typhirium The size of the nanoparticles was determined to be 87 ± 30 nm, applying dynamic light scattering 11 .In another paper, the Lens culinaris seed extract was used to green synthesis of silver nanoparticles at temperature of 25°C 12 .A green low-cost and reproducible yeast mediated synthesis of silver nanoparticles was reported by Jha et al., at room temperature 13 .This paper presents the synthesis of silver nanoparticles by simple and green route.In this paper, we employed silver nitrate as an initial reagent, dextrose as reducing agent, and polyvinyl pyrrolidone (pvp) as a stabilizer.

Materials
The silver nitrate as the precursor, Dextrose as the reducing agent and polyvinyl pyrrolidone (PVP) as the stabilizing agent to synthesize nano silver colloids were purchased from Sigma-Aldrich.

Preparation
1 ml of aqueous solution of dextrose (3 g/100 ml) and 1 ml polyvinylpyrrolidone (20 g/l) were added to 100 ml aqueous solution of silver nitrate (0.001 M).The reaction between this solution and Ag+ ions were carried out in bright conditions for 5 min.After 5 min, the colorless solution of silver nitrate in the container turns into brown color.This color change indicates a possibility of nano-silver colloidal solution production.

Characterization of Silver nanoparticles
Uv-vis spectroscopy was used to prove the existence of nanoparticles.The morphology and size was determined by the transitional electron microscopy (TEM), and DLS analysis.

RESULTS
For analytical study of the prepared sample, the amount of absorption within wave length of 350 -600 nm was observed by uv-vis spectroscopy.It is known that an absorption band at about 400-420 nm due to surface plasmon resonance in silver nanoparticles 14 .Fig. 1 shows the UV-Vis spectra of Nano-silver Colloidal Solution recorded between 350 and 600 nm.As illustrated the SPR band cantered 412 nm confirms the formation of silver nanoparticles in the solution 15 .It is well known that silver can be reduced from Ag+ to Ag0 by dextrose.Dynamic light scattering is a widely used technique for the determination of particle size in colloidal solution.As is seen in figure 2, average size of nanoparticle synthesized is 9 nm.The distribution of silver nanoparticles is about 6 nm which indicates narrow distribution of the nanoparticles.SEM analysis was carried out to understand the topology of silver nanoparticles.At the end, silver nanoparticles were studied by transitional electron microscopy (TEM).Fig. 3 confirms silver nanoparticles formation at nano size.

CONCLUSIONS
This is an environment friendly one-step method for synthesis of nano-silver colloid.The dextrose acted as a reducing agent of AgNO3 and polyvinylpyrrolidone (pvp) as a capping material.Nanoparticles in the range of ~9 nm are synthesized by dextrose when it is added to AgNO3.It seems this method is a fast and green method to form Ag nanopartciles.The Ag nanoparticles were characterized by UV-visible, TEM and DLS analysis.