BACKGROUND AND PRIOR ART
[0002] Metal nanoparticles have been extensively investigated because of their unique electronic and optical properties, which are substantially different from bulk materials. Silver nanoparticles has shown immense interest among researchers and remain versatile in use due to their wide applications and novel physico-chemical properties, which are different from those of bulk materials due to their extremely small size and large surface area. They are used in catalysis[l], antibacterial activity[2], nanocolorant[3], nanopaste for electrical circuits, electrodes[4], and substrates for surface-enhanced Raman scattering[5].For synthesis of metal nanoparticles having suitable sizes or shapes, many scientific approaches were taken such as co precipitation, gas-evaporation, sol- gel method, and sputtering[6]. Preparation of metal nanoparticles in reverse micelles has been attracted significant attention in recent years[6, 7].
[0003] The Chinese Patent Number CN1206071 C describes an oil soluble metal silver nanopowder and its preparation process. This invention discloses a sulfur containing organic surface generation phosphate ligand stabilized nanoparticles. It is dispersed in the benzene, gasoline and other non-polar solvent forming colloidal system. The resulting nanoparticles were intended to be used for lubricating oil additives.
[0004] The US Patent Number US20120115126 Al describes Solid state synthesis method of producing silver nanoparticles. The method includes mixing a silver salt and a water soluble polymer acting as both a reducing agent as well as protecting agent to produce a solid mixture, and milling the solid mixture by a high-speed vibration milling process to form silver nanoparticles within the water soluble polymer. The intended use is an antimicrobial use.
[0005] The US Patent Number US 8,287,771 B2 shows a method for producing a silver particle powder with dispersibility in a liquid organic medium having a low polarity, and suitable for forming a circuit micropattern, for example an interconnecting material for an inkjet method. The synthetic method comprises reducing a silver compound in an alcohol having a boiling point of from 80° C to 200° C under reflux. These resulted nanoparticles are suitable to use in microwiring formation.

[0006] The Japanese Patent Number JP-A 2001-35255 describes vapor phase method evaporating silver under a low pressure of 0.5 Torr or so in an inert gas atmosphere of helium or the like.
[0007] The Japanese Patent Number JP-A 11-319538 mentioned the liquid phase method of producing a silver colloid, which comprises reducing a silver ion with an amine in an aqueous phase and transferring the resulting silver particles into an organic solvent phase containing a high-molecular weight dispersant.
[0008] The Japanese Patent Number JP-A 2003-253311 pointed reducing a silver halide with a reducing agent (alkali metal hydroborate or ammonium hydroborate) in the presence of a thiol-type protective agent in a solvent.
[0009] Zhang, J.-p., et al., Sonochemical synthesis of colloidal silver catalysts for reduction of complexing silver in DTR system. Applied Catalysis A: General, 2004. 266(1): p. 49-54.
[0010] Lee, H., S. Yeo, and S. Jeong, Antibacterial effect of nanosized silver colloidal solution on textile fabrics. Journal of Materials Science, 2003. 38(10): p. 2199-2204.
[0011] Zhang, Q., et al., Colloidal synthesis of plasmonic metallic nanoparticles. Plasmonics, 2009. 4(1): p. 9-22.
[0012J Sridhar, A., D. Van Dijk, and R. Akkerman, Inkjet printing and adhesion characterisation of conductive tracks on a commercial printed circuit board material. Thin Solid Films, 2009. 517(16): p. 4633-4637.
[0013] Chen, J., et al., Surface-enhanced Raman scattering for immunoassay based on the biocatalytic production of silver nanoparticles. Analytical Sciences, 2009. 25(3): p. 347-352.
[0014] Uskokovic, V. and M. Drofenik, Synthesis of materials within reverse micelles. Surface Review and Letters, 2005.12(02): p. 239-277.
[0015] Shchukin, D.G. and G.B. Sukhorukov, Nanoparticle synthesis in engineered organic nanoscale reactors. Advanced Materials, 2004.16(8): p. 671-682.

[0016] The prior art cited above relates to the method for producing silver nanoparticles and nanopowderdemonstrated use of sophisticated techniques such as freeze drying and by designing of special apparatus even with getting very less yield; however large scale production approach with original activity and stability remains a major limitation. Additionally,the liquid-state synthesis method is not suited to mass production of commercial silver nanoparticles at low cost. These facts gives rise to the need of devising novel approaches to provide highly concentrated metal nanopowder with water redispersibility using one pot inexpensive technology relating to a method of producing dried silver nanopowder.
[0017] The present invention describes a very simple method for production of silver nanopowder where highly concentrated, pure nanoparticles are formed. The technology invented is less complex, less critical, single pot, inexpensive and does not require any specialized predesigned equipment.

OBJECTIVE OF THE INVENTION [0018] Objectives of present invention are;
1. One of the objectives of present invention is to synthesize stable silver nanoparticles.
2. Yet another objective of present invention is to produce pure and highly
concentratednanopowder with rapid water redispersibility so that nanoparticles will become
easily reactive.
3. One more objective of present invention is to synthesize free flow stable powdered silver nanoparticles; which are easy to handle for various chemical processes and easy for shipment.
4. Yet another objective of present invention is to develop one pot synthesis for silver nanoparticles without specific predesigned special instruments.
5. Yet another objective of present invention is to use silver nanoparticles for/in various applications, however not limited to, like nucleic acid complexation, dyes technology, antimicrobial utilization, plastic composite, polymer composite, electronic components, cooling technology, refrigeration technology, textile component and wound care applications.
6. Yet another objective of present invention is to develop affordable inexpensive methodology usingmicellarnanoreactors template to synthesize silver nanoparticles.
7. One more objective of present invention is to develop an industrial method to produce bulk quantity of the silver nanoparticles.

SUMMARY OF THE INVENTION
[0019] The present invention is related to novel synthesis and purification procedure for silver nano-powders. Micellar systems were synthesized using surfactant e.g. sucrose ester of fatty acids.. The method for synthesizing silver nano powders in micellar solution comprises following steps a. enabling silver salt solid powder type surface active agent micelle to react with reducing agents b. These agents are solubilized in the surface active agent micellar solution c. The reaction is carried out for several hours under stirring at room temperature, drying, washing and followed by another step of drying at 49-120° C temperature. The present invention discloses a highly efficient method for generation of monodispersed silver nanoparticulate water redispersible powder, with mean particle diameters between 1 nm to 100 nm.

DETAILED DESCRIPTION OF INVENTION
[0020] Silver nanoparticles have been widely used in various fields such as catalyst, optical, biotechnology and electronics. These remain unstable without use of stabilizing agents such as polymers for long term storage and to retain the water redispersibility. It is still challenging to produce highly concentrated silver nanoparticles with straight scale up approach due to nanoparticles aggregations. Hence there is an urge of producing highly concentrated powdered nanoparticles with redispersibility in water.
[0021] It is well known fact that metal nanoparticles can be synthesized into micellar and reverse/inverse micellar systems to get narrow particle size with reproducibility. The current investigation was thus aimed at designing method of producing silver nanopowder using bulk powder - liquid nanoparticles - bulk nanopowder - pure nanopowder i.e. three step platform approach in single pot since simpler commercialization of inorganic nanoparticles is urgent need of hour. The investigation was aimed at exploring both uses silver nanopowder and its inexpensive cost with immense potential of scalability to widen the arena of application of the developed system.
The general procedure adopted for preparing the highly concentrated silver nanoparticles in micellarnanoreactors as follows;
[0022] The present method involves selecting asuitable surface-active agent for making micelles and dissolving it in a mixture of suitable organic solvents. The solvents used are of high boiling alcohols or mixtures thereof. This involves preparation of micellarnanoreactors followed by addition of solid reducing agent and silver salt for few hours so as to form a semidried mass of silver nanoparticles. The synthesized semidried silver nanoparticles were dried at the 40-120°C temperature environment to make a dried nanopowder. The dried powder was then subjected to multiple washing using a suitable non aqueous solvent. The purified and solvent washed above nanopowder were dried at the 40-120°C temperature environment to make highly concentrated silver nanopowder. The above material was triturated and sifted through suitable size of mesh to obtain the final finished free flowing nanopowder as a product. According to the one embodiment herein the present invention does not require any special apparatus or even strict

temperature conditions in reaction. The silver nanoparticles are completely redispersible in the water hence antimicrobial activity can be easily determined.
[0023] According to the one embodiment herein the present invention produces stable monodispersed silver nanoparticles with UV range falling in range from 400 - 430 nm.
[0024]According to the one embodiment herein the present invention produces stable monodispersed silver nanoparticles with narrow size from 1 -100 nm.
[002 5] According to the one embodiment herein the present invention produces stable monodispersed silver nanoparticles and X Ray diffraction reveals orthorhombic structure with face centered cubic morphology.
[0026]According to the one embodiment herein the present invention produces stable monodispersed silver nanoparticles and FTIR analysis shows the polymer used having ester group is responsible for providing the stability to nanopowder at room temperature storage conditions in all season (10-40°C).
[0027]According to the one embodiment herein the present invention produces stable monodispersed silver nanoparticles and potential antibacterial activity against wide ranges of microorganisms was determined using, P. Aerugenosa, E. coli as well asS. Aureus. Additionally this silver nanopowder can be used in the field of catalysis, textiles, electronics and substrates for various materials.
[0028] The solvents used for dissolving polymer are mixture of two or more non polar solvents. The solvents used are of higher alkanes and derivatives thereof and lower to higher alcohols. The polymers used for micelle formation are derivatives of fatty acids such as alcohols, ethers, esters thereof. The chosen polymer is from anionic, cationic and non-ionic nature. The reducing agent used is the derivatives of citrate, acetate or borohydride whereas silver salt used may be the acetate or nitrate. The solvent used for purification may be the primary to tertiary alcohol from low molecular weight to the high molecular weight. These are methanol, ethanol, n-propanol, iso-propanol, tertiary butyl alcohols.

CLAIM
[0029] The following information has been claimed in present invention;
1. The method for manufacturing silver nanopowder which comprises the reaction of metal salt with reducing agent inside the core ofmicellarnanoreactors formed using suitable polymer surface active agent at following specified temperature and producing highly concentrated silver nanopowder in one pot process which is readilyredispersible using varieties of solvent for different applications.
2. The process of claim 1, wherein the said silver salt is nitrate or acetate.
3. The process of claim 1, wherein maximum UV wavelength observed in range of 400 -430 nm.
4. The process of claim 1, wherein ratio of n-butanol and iso-octane varies from 1:2 to 2:8.
5. The process of claim 1, wherein silver nanoparticles were synthesized in polymeric micelles based nanoreactors.
6. The process of claim 1, wherein polymer used is surface active agents to prepare micelles and also used as desegregant or stabilizer.
7. The process of claim 1, wherein polymer used is sugar ester of fatty acids type surface active agents to prepare micelles.
8. The process of claim 1, wherein the reaction temperature is 1 - 100°C.
9. The process of claim 1, wherein the pH of the redispersed nanoparticles ranges from 3-9.
10. The process of claim 1, wherein said silver nanopowder has a spherical shape andhave diameter in range of 1-100 nm.