WO2017168352A1

WO2017168352A1 - Antibacterial layered nanocomposite

Info

Publication number: WO2017168352A1
Application number: PCT/IB2017/051807
Authority: WO
Inventors: Divya SACHDEV; Neetu Kumra TANEJA
Original assignee: National Institute Of Food Technology Entrepreneurship And Management-Niftem
Priority date: 2016-03-30
Filing date: 2017-03-30
Publication date: 2017-10-05

Abstract

The present invention is in the field of nanocomposite. Particularly, the Invention provides highly efficient antibacterial layered nanocomposite based on Iron and silver oxide.

Description

'ANTIBACTERIAL LAYERED NANOCOMPOSITE'

Field of the Invention

The present invention is in the field of nanocomposites. Particularly, the invention provides antibacterial layered nanocomposites.

Background of the Invention

The following background discussion includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Pathogenic bacteria are a serious problem to human healthcare. It is estimated that almost 1 of every 6 person get sick due to pathogenic bacteria, and more than 23000 deaths take place every year. The major difficulty in controlling this burgeoning threat is the multidrug resistance and the dearth of antibiotics. Hence metal based nanomaterials or nanocomposites(NC) as an antibacterial are undergoing a renaissance. Metal- based nanoparticles especially like Zinc, copper, silver, titanium, gold nanoparticles have shown effectiveness as a bactericidal agent.

Many integrated studies have shown suspensions of Titanium oxide and its nanocomposites are effective against killing bacteria photocatalytically and therefore requires either UV- radiation or Visible radiation for killing pathogens. The light absorbing capacity of a material makes it effective but unstable in a long run, works for limited period of time[l]. Copper based nanoparticles of size ranging from (400nm-4nm) that include copper salts; copper iodide, copper chloride and copper bromide combined with silver salts and a functionalizing agent that include, amino acids, thiols, hydrophobic polymers and surfactants and stabilizing agents are added to prevent the microbial growth. The wide variety of surfactants and functionalizing agents along with copper alone and silver copper iodides, bromides, chlorides display tedious and costly process while giving lower antibacterial activity.

Zinc based nanoparticles especially zinc oxide synthesized by different routes like solvothermal, co-precipitation methods, microemulsion method have mostly shown potential as a bacterial inhibiting agent in visible light but in higher concentration range. Varied size of zinc nanoparticles either in reduced or in oxidised form is employed for antibacterial property; however the concentration used is on higher side.

Out of the different metals with antibacterial activity, silver is the most effective antibacterial agent. Silver nanoparticles of different sizes and shapes have been extensively explored for killing pathogens and have attained maximum activity. The optimal concentration required for the successful antibacterial varies from lOnM to 10 μΜ, but the high cost of silver itself makes the process more reluctant to be procured for several antibacterial applications.

Therefore in order to reduce the cost, synthesis of silver mediated with other metals is done to form nanocomposites. Varied antibacterial like silver-zinc, silver- titanium, silver copper and silver iron are synthesized via different methodologies.

Silver zinc composites are prepared as antibacterial material; the composites are prepared after heating at high temperatures. Similarly silver is combined in conjugation with magnetic nanoparticles like iron, cobalt, manganese, nickel. Magnetic hybrid colloids decorated with silver have been synthesized, many possible forms like Fe₃0₄@Ag-PEG, Ag-coated Fe304@SiC>2 magnetic, Ag-CuFe2C>4[2], Ag@Fe304-Si02 Janus nanorods (JNR), silver coated E-33/iron oxide, magnetic Ni/Ag core-shell nanostructures, Mn-Zn ferrite@Ag[3] , CoF₂0₄@polyaniline(PANI)@Ag[4], porous FesC shell/silver core nanoparticles [5]. Although these materials were synthesized for having an ability to be magnetically separated from aqueous solution but is associated with drawback of silver leaching out easily. Report of water soluble silver ferrite AgFe(¾@PEG was recently investigated for antibacterial activity, however the water soluble product shows almost nil activity in gram negative bacteria while almost high concentration gives positive antibacterial activity for gram positive bacteria. Another problem linked to the magnetic materials is the ease of their aggregation once they are in nanoscale and because of which capping and stabilizing agents are required which increases the cost of the material.

Synthesis in the liquid phase is done either by reduction method, sol-gel method, combustion method, sonochemical, solvothermal process, flame spray, hydrothermal syntheses are known for reducing silver nanparticles wherein reducing agents and capping agents like polyols, organic amines, formaldehyde, sodium borohydride, hydrogen peroxide.

These reducing agents and dispersants are mostly toxic and can lead to side effects on environment and organisms. Moreover the metals nanoparticles that are formed via reducing have the tendency to get oxidized in long period of time and ultimately will affect the efficiency of the nanomaterial. So far several nanoparticles have been developed for killing pathogens, however the problem is more acute in under-developed countries wherein the huge cost of metal nanoparticles especially used for antibacterial activity like Zinc, copper, silver, titanium, gold nanoparticles are a costly affair. So far, the antibacterial activity results indicate inhibition after 24 hours of incubation.

Thus, there is a high need of an effective antibacterial nanocomposite and an efficient method of its production.

Obiect(s) of the Invention:

A primary object of the present invention is to overcome the drawbacks associated with the prior art.

Yet another object of the present invention is to provide an antibacterial nanocomposite with higher efficiency of bacterial pathogen killing.

Yet another object of the present invention is to provide an efficient antibacterial nanocomposite which is extremely beneficial for disinfecting water.

Yet another object of the present invention is to provide an efficient antibacterial nanocomposite which shows broad antibacterial spectrum against gram positive and gram negative bacteria.

Yet another object of the present invention is to provide an efficient antibacterial nanocomposite with very low MIC₉₀ values for killing bacterial pathogens.

Yet another object of the present invention is to provide a highly efficient synthetic method for novel layered material containing silver and iron oxides nanocomposite.

Yet another object of the present invention is to provide synthesis of an economical antibacterial layered silver-iron oxide nanocomposite.

Yet another object of the present invention is to provide a method of synthesis which is energy saviour, cost effective and easy to perform.

Summary of the Invention In an aspect of the Invention, there is provided a silver-iron oxide antibacterial nanocomposite comprising silver and iron oxide present in a ratio ranging from 1 : 1 to 0.002:1.

In another aspect of the Invention, there is provided a layered antibacterial nanocomposite comprising silver and iron oxide present in a ratio ranging from 1 :1 to 0.2:1.

In another aspect of the Invention, there is provided a co-precipitation based method for the synthesis of silver iron oxide nanocomposite composition comprising:

a. Dissolving silver salt and Iron salt separately in water to result in solution (i) and (ii) respectively;

b. Mixing the solution (i) and (ii) resulting from the step (a) in a ratio ranging from 1 :1 to 0.002:1 to result into solution A;

c. Preparing an alkaline solution by adding alkali in water to result in solution B d. Mixing solution A and solution B in water under constant stirring achieving pH value of 10 to obtain solution C comprising a reddish brown precipitate; e. Retaining solution C with reddish brown precipitate at room temperature for approximately 4 to 5 hours followed by centrifuging the precipitate followed by washing and drying to obtain said nanocomposite;

where the resulting nanocomposite composition is in a layered structure.

Brief Description of the Drawings:

Figure 1: illustrates SEM micrograph of Layered Silver-Iron oxide nanocomposite Figure 2: illustrates TEM micrograph of nanoparticles adhering to E.coli bacteria

Figure 3: illustrates TEM Cross-section view of E.coli bacteria with silver-iron oxides Nanocomposites implicating direct interactions of bacteria and silver-iron oxides nanocomposites

Figure 4: Effect of different ratios of silver-iron oxide nanocomposites (range 0.002:1 to 1 : 1) in killing a) B. subtilis b) E. coli after 1 hour treatment. Figure 5: illustrates determination of MIC for a) B. subtilis b) E. coli by silver-iron oxide nanocomposites after 1 hour treatment

Figure 6: illustrates Time kinetics for killing of a) B. subtilis (1.22μg/ml) (b) E. coli (19.5 μg/ml) by silver-iron oxide nanocomposites

Figure 7: illustrates Antimicrobial spectrum of silver-iron oxide nanocomposites against Gram positive bacteria viz- B. subtilis and 5. aureus and Gram negative bacteria viz- E. coli, S. typhimurium and P. aeruginosa

Figure 8: illustrates Disinfection of bacterially spiked water by silver-iron oxide nanocomposites within 1 hour of treatment

Detailed Description of the Invention

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The Invention provides an antibacterial nanocomposite composition and method of its preparation. The antibacterial nanocomposite composition is highly efficient in terms of bacterial pathogen killing in terms of time and killing concentration (MIC).

In an aspect of the Invention, there is provided a layered silver-iron oxide antibacterial nanocomposite comprising silver and iron oxide present in a ratio ranging from 1 : 1 to

0.002:1.

In an embodiment, the nanocomposite comprises silver and iron oxide in a ratio ranging from 1 : 1 to 0.2:1.

In an embodiment, the nanocomposite composition comprises silver nitrate.

In another embodiment, the nanocomposite composition comprises iron acetate.

The present Invention describes antibacterial nanocomposite composition based on silver nitrate and iron acetate as a preferred embodiment of the Invention, however it cannot be considered as restricting the scope of Invention and the Invention may be achieved by other salts of silver and Iron as well. The Invention is applicable for other salts of silver and Iron, silver salts such as silver sulfate, silver acetate and iron as iron acetylacetonate (II), iron (II) nitrate. The antibacterial layered composite of the present Invention works with all the water soluble salts of Iron and silver, which effectively do not form precipitate with each other. In an embodiment, the nanocomposite composition kills more than 90-95% of pathogens in approximately 0.5 to 1 hour of time.

In another embodiment, approximately 19.5ug/ml of nanocomposite antibacterial composition kills population of Gram negative bacteria within 0.5 hour.

In another embodiment, approximately 1.2ug/ml of nanocomposite antibacterial composition kills population of Gram positive bacteria within 1 hour.

The comparative data to show the antibacterial activity of present nanocomposite against gram-positive bacteria (B. subtilis) and gram-negative bacteria (E. coli) has been given in the Fig. 4, 5 and 6. It clearly shows that the gram-positive bacteria (B. subtilis) are killed >90% within 60 minutes of exposure at 1.2 μg/ml concentration of the nanocomposite. The gram- negative bacteria (E. coli) is killed > 90% at 19.5 μg/ml within 30 minutes of exposure.

A comparison of inhibition of E. coli (test organism) by present nanocomposite vis a vis other available Titanium based nanocomposites is tabulated below.

Table 1 As is evident from the table above, the present nanocomposite is much more efficient in killing bacteria Ag:Fe (0.2: 1) (MIC90 ~ 19.5 μg/ml achieved in lh only) as compared to other Titanium based nanocomposites Ti: Ag (25: 1)(MIC90 > 130 μg/ml achieved in 24 h) by the microdilution broth assay, as cited in literature. It is evident from the above table 1 that it is not only the time taken to exhibit the killing of bacteria by the present nanocomposite (i.e. 1 h) that is much shorter than most cited literature for Titanium based nanocomposites (i.e. 18-24 h) but also the silver content is reduced from 1 to 0.2 or 100 to (75-85%).

The antibacterial activity of nanocomposite was also tested against gram-positive bacteria and gram-negative bacteria at concentrations 1.2 μg/ml and 19.5 μg/ml respectively. Gram- positive bacteria, Staphylococcus aureus and Bacillus subtilis were killed upto 78% and 90% respectively. Gram-negative bacteria, E. coli and Pseudomonas aeruginosa were killed >90% and Salmonella typhimurium showed killing upto 70% at the test concentrations.

In another aspect of the Invention, there is provided a method for the preparation of silver iron oxides nanocomposite composition. The method is a co-precipitation based method comprising following steps:

c. Preparing an alkaline solution by adding alkali in water to result in solution B; d. Mixing solution A and solution B in water under constant stirring achieving pH value of 10 to obtain solution C comprising a reddish brown precipitate; e. Retaining solution C with reddish brown precipitate at room temperature for approximately 4 to 5 hours followed by centrifuging the precipitate followed by washing and drying to obtain said nanocomposite;

where the resulting nanocomposite composition is in a layered structure. In an embodiment, the silver salt comprises silver nitrate, silver sulfate, silver acetate.

In another embodiment, the iron salt comprises Iron acetate, Acetylacetonate (II), Iron (II) nitrate.

In another embodiment, the alkali comprises sodium hydroxide, magnesium hydroxide, calcium hydroxide, ammonium hydroxide.

In another embodiment, the silver salt and Iron salt solution are mixed in a ratio of 1 :1 to 0.2:1. The method is highly rapid and efficient in bacterial pathogen killing. The co-precipitation method employed for the synthesis is also economical, simple and energy saviour. The method steps prepare the composite where solution of silver nitrate and anhydrous iron acetate (II) is mixed in ratios of 1 :1 to 0.002: 1. The silver-iron oxides nanocomposites displayed inhibition of pathogenic bacterial count upto 90-95% in an hour time. The heterogeneity and high surface area of the silver iron oxides nanocomposites due to layered structure ensures good stability resulting in an increased efficiency and performance which is a necessity for commercially disinfecting water. Figure 1 illustrates SEM micrograph of Layered Silver-Iron oxide nanocomposite of an embodiment of the Invention.

Technical advantages of the Invention:

a) Antibacterial Nanocomposite composition:

i. The present invention provides a novel silver-iron oxide antibacterial nanocomposite having a layered structure.

ii. The composition is extremely beneficial for disinfecting water, inhibiting bacterial growth, rapid killing of pathogens etc.

iii. The composition comprises reduced concentration of silver. The amount of silver in the composition is reduced to 16% while still achieving the same efficiency of disinfection.

iv. Silver-iron oxide nanocomposite of the present Invention shows broad antibacterial spectrum against gram positive and gram negative bacteria.

v. The optimum concentrations utilized to kill pathogens are very low.

vi. The silver -iron nanocomposites showed broad antibacterial spectrum against gram- positive and gram negative bacteria.

vii. The invention demonstrates direct interaction between silver-iron oxide nanocomposite and bacteria.

viii. Gram negative bacteria are killed within 0.5 hour rather than 24 hours.

ix. Gram positive bacteria are killed within 1 hour rather than 24 hours.

x. Optimum concentration of Layered silver-iron oxide nanocomposite for killing gram negative bacteria E.coli is 19.5 μg/ml.

xi. Tested for disinfecting water, which killed not less than 90% of gram positive B.subtilis and 80% of gram negative E.coli, extremely useful for water industry. xii. In order to be employed as antibacterial in paint, shoe, textiles, medical devices layered silver iron oxides nanocomposites were capped with citrate that showed inhibition of bacterial pathogens.

xiii. Layered structure formation makes it porous with high surface area.

xiv. Rapid killing of 90-95% pathogens was observed in 0.5-1 hour time while the silver content was reduced from 100% to 16%.

xv. Optimum concentration of layered silver-iron oxide nanocomposite for killing gram positive bacteria B.subtilis is l ^g/ml.

xvi. The composition is environment friendly and thus useful.

xvii. The nanocomposite is safe to use. b) Method for producing Antibacterial Nanocomposite composition:

i. Energy saviour, cost effective and easy procedure of synthesis.

ii. The co -precipitation method employed in the invention is simplest of all methods to synthesize silver-iron oxide nanocomposite.

iii. The method is cost effective in terms of performance and synthesis both.

iv. While the methodology employed for the synthesis do not use any heat, which makes it an energy saviour synthesis.

v. Non-magnetic material makes it more stable and does not lead to aggregation of iron in the present invention and no increase in nanoscale sizes and hence no change in activity after 12months also.

The Invention is further described with the help of non- limiting examples:

Example 1:

Silver -iron oxide nanocomposite synthesis

0.0849 g of silver nitrate and 0.100 g of iron acetate were dissolved separately in 20 ml distilled water each. The solutions prepared were mixed in ratio of 1 : 1 and was poured in a burette marked as solution A. Then 0.8g of sodium hydroxide was dissolved in 40 ml of distilled water and poured in burette marked as solution B. The solution A and solution B were poured simultaneously in a 100ml of distilled water under constant stirring fitted with a pH electrode to attain pHlO. The reddish-brown precipitate starts forming. Once both the solutions are over the final solution C with precipitate was aged at room temperature for 4-5 hours. Centrifuged the precipitate from solution C and washed it with distilled water 3-4 times to remove the presence of excess sodium hyroxide. The precipitate was dried at room temperature and named as Ag-Fe-NC (1 :1).

The said precipitate was characterized by UV-Vis spectroscopy that showed broad absorption peak at 423nm indicating small size and incorporation of silver nanoparticles in nanocomposites, while a hump at 241 nm indicates incorporation of iron nanoparticles in the nanocomposites. SEM image indicates spherical structure of nanocomposites.

Antibacterial activity of Ag-Fe-NC (1 : 1) was done via plate count method and the percentage killing for Gram negative bacteria (E.coli) is not less than 95% and for Gram positive bacteria (B.subtilis) is not less than 90% in one hour time. Figure 2 illustrates TEM micrograph of nanoparticles adhered to E.coli bacteria while Figure 3 represents TEM Cross- section view of E.coli bacteria with silver-iron oxides Nanocomposites implicating direct interactions of bacteria and silver-iron oxides nanocomposites

Example 2:

0.0849 g of silver nitrate and 0.100 g of iron acetate were dissolved separately in 20 ml distilled water each. The solutions prepared were mixed in ratio of 0.02:1 and was poured in a burette marked as solution A. Then 0.8g of sodium hydroxide was dissolved in 40 ml of distilled water and poured in burette marked as solution B. The solution A and solution B were poured simultaneously in a 100ml of distilled water under constant stirring fitted with a pH electrode to attain pHlO. The reddish-brown precipitate starts forming. Once both the solutions are over the final solution C with precipitate was aged at room temperature for 4-5 hours. Centrifuged the precipitate from solution C and washed it with distilled water 3-4 times to remove the presence of excess sodium hyroxide. The precipitate was dried at room temperature and named as Ag-Fe-NC (0.02:1).

The said precipitate was characterized by UV-Vis spectroscopy absorption hump at 237 to 324 nm indicating small size and higher percentage of iron nanoparticles incorporated in the nanocomposites while the peak at 423nm for silver nanoparticles seen for Ag-Fe-NC (1 : 1) shifted and merged in 324nm only .

Antibacterial activity of Ag-Fe-NC (0.02:1) was done via method and the percentage killing for Gram negative bacteria (E.coli) is not less than 25% and for Gram positive bacteria (B.subtilis) not less than 20% in one hour time (illustrated in figure 4)

Example 3: 0.0849 g of silver nitrate and 0.100 g of iron acetate were dissolved seperately in 20 ml distilled water each. The solutions prepared were mixed in ratio of 0.2:1 and was poured in a burette marked as solution A. Then 0.8g of sodium hydroxide was dissolved in 40 ml of distilled water and poured in burette marked as solution B. The solution A and solution B were poured simultaneously in a 100ml of distilled water under constant stirring fitted with a pH electrode to attain pHlO. The reddish-brown precipitate starts forming. Once both the solutions are over the final solution C with precipitate was aged at room temperature for 4-5 hours. Centrifuged the precipitate from solution C and washed it with distilled water 3-4 times to remove the presence of excess sodium hyroxide. The precipitate was dried at room temperature and named as Ag-Fe-NC (0.2: 1).

The said precipitate was characterized by UV-Vis spectroscopy absorption hump from 285- 386 nm indicating small size and higher percentage of iron nanop articles incorporated in the nanocomposites while the peak at 423nm for silver nanoparticles seen for Ag-Fe-NC (1 : 1) shifted and merged in 386nm only. SEM image shows layered structure of nanocomposites indicating layer-by- layer pattern, Images of the Ag-Fe-NC (0.2:1) synthesized suggests that the Nanocomposite has porous structure, which leads to higher surface area.

The microdilution method for estimation of minimum inhibitory concentration values was done to evaluate the antibacterial activity against both Gram-positive (B. subtilis) and Gram- negative (E.coli) bacteria. The MIC₉₀ values were determined on 96-well microdilution plates and according to published protocols. Initially Ag-Fe-NC(0.2:l) dilution suspended in certain solvent and subsequent 2-fold serial dilutions were performed in 0.1 ml PBS/media in 96 well microplates. 100 μΐ of bacterial culture (OD-0.001 i.e. 5xl0⁵CFU/ml) was added to each well such that the final volume in each well of microplate was 200μ1. Culture alone wells were kept as control. The micro titer plate was incubated at 37°C for 1 hr and the contents from each well were subsequently assayed for CFU counting. The MIC value is expressed as the minimum concentration of the said compound inhibiting the growth by 90% vis-a-vis control bacteria.

The MIC₉0 of Ag-Fe-NC (0.2:1) against E. coli (Gram negative) was found to be -19.5 μg/ml whereas, B. subtilis (Gram positive) was killed -1.2 μg/ml (as shown in Figure 5).

Example 4:

Time kinetics for antibacterial effect Kinetic effects of Ag-Fe-NC (0.2: 1) for antibacterial activity were done. The MIC₉₀ concentration i.e. 1.2 μg/ml and 19.5 μg/ml for B. subtilis and E. coli (respectively) were employed for the studies wherein the nanocomposite was allowed to interact with bacteria for 2, 5, 10, 20, 30, 60 and 90 min by microdilution plate assay.

The MIC₉0 values were determined on 96-well microdilution plates and according to published protocols. Initially Ag-Fe-NC (0.2:1 ) dilution suspended in certain solvent and subsequent 2-fold serial dilutions were performed in 0.1 ml PBS/media in 96 well microplates. 100 μΐ of bacterial culture (OD-0.001 i.e. SxlO'CFU/ml) was added to each well such that the final volume in each well of microplate was 200μ1. Culture alone wells were kept as control. The microtiter plate was incubated at 37°C for varied time intervals (2, 5, 10, 20, 30, 60 and 90 min) and the contents from each well were subsequently assayed for CFU counting. The Gram-negative bacteria showed killing within just 30 min of incubation with NC whereas Gram positive bacteria were killed in 60 min (as shown in Figure 6).

Example 5:

Disinfecting Water sample

The antimicrobial activity of Ag-Fe-NC (0.2:1 ) against removal of B. subtilis (Gram-positive bacteria) and E. coli (Gram-negative bacteria) from water was investigated. Ag-Fe-NC (0.2: 1) (~\9.5μ^πύ) was allowed to incubate with water spiked with bacteria (-5X10⁶ CFU/ml) at room temperature for 1 hour followed by plate counting wherein tenfold serial dilutions of spiked water sample were prepared in 1ml PBS and plated on nutrient agar plates. The plates were incubated at 37°C for 24 hours and the colonies were counted. It was observed that not less than 97% of Gram positive bacteria (B. subtilis) and 82% Gram negative bacteria (E.coli) were killed (Figure 8).

Figure 4 illustrates percent inhibition of a) B. subtilis ( \ .2μg/mΐ) b) E. coli (19^g/ml) by silver-iron oxide nanocomposite of the present Invention after 1 hour treatment.

Claims

Claims:

1. A layered silver- iron oxide antibacterial nanocomposite comprising silver and iron oxide present in a ratio ranging from 1 :1 to 0.002:1.

2. The nanocomposite as claimed in claim 1 , wherein said antibacterial nanocomposite comprises silver and iron oxide present in a ratio ranging from 1 :1 to 0.2:1.

3. The nanocomposite as claimed in claim 1 , wherein said composition kills more than 90% of pathogens in approximately 0.5 to 1 hour of time.

4. The nanocomposite as claimed in claim 1 , wherein approximately 19.5ug/ml of said composition kills population of Gram negative bacteria within 0.5 hour.

5. The nanocomposite as claimed in claim 1 , wherein approximately 1.2ug/ml of said composition kills population of Gram positive bacteria within 1 hour.

6. The nanocomposite as claimed in claim 1 , wherein said nanocomposite kills Gram positive bacteria within 1 hour.

7. The nanocomposite as claimed in claim 1, wherein said composite inhibits bacterial growth while reducing the silver content to 75% to 85%.

8. A co-precipitation based method for the synthesis of silver iron oxide nanocomposite composition comprising:

f. Dissolving silver salt and Iron salt separately in water to result in solution (i) and (ii) respectively;

g. Mixing the solution (i) and (ii) resulting from the step (a) in a ratio ranging from 1 :1 to 0.002:1 to result into solution A;

h. Preparing an alkaline solution by adding alkali in water to result in solution B i. Mixing solution A and solution B in water under constant stirring achieving pH value of 10 to obtain solution C comprising a reddish brown precipitate; j. Retaining solution C with reddish brown precipitate at room temperature for approximately 4 to 5 hours followed by centrifuging the precipitate followed by washing and drying to obtain said nanocomposite;

where the resulting nanocomposite composition is in a layered structure.

9. The method as claimed in claim 8, wherein said silver salt comprises silver nitrate, silver sulfate, silver acetate.

10. The method as claimed in claim 8, wherein said iron salt comprises Iron acetate, Acetylacetonate (II), Iron (II) nitrate.

11. The method as claimed in claim 8, wherein said alkali comprises sodium hydroxide, magnesium hydroxide, calcium hydroxide, ammonium hydroxide.

12. The method as claimed in claim 8, wherein said silver salt and Iron salt solution are mixed in a ratio of 1 :1 to 0.2:1.