DESC:FIELD OF THE INVENTION
The present invention relates to a process for the preparation of silk metal nanocomposites and use thereof in garments section, medical applications etc. In particular, the present invention relates to a process for the synthesis of silver nanoparticles (NPs) deposited silk fibre/threads to provide anti-microbial property to the silk fibres. This invention is mainly focused on the easy and environment friendly process for deposition of silver nanoparticles on silk thread by in-situ synthesis of silver nanoparticles to entrap the higher concentration of silver particles in the silk fibres wherein the developed nanocomposites are useful in applications such as medical treatment and garment sections and the like.

BACKGROUND OF INVENTION:
Silk due to its unique characteristics has a heritage and is being extensively used throughout the world. Silk is the natural protein fiber formed by silk fibroin class of insect larvae to produce cocoons. Some of the special properties of silk material include high tensile strength, mechanical superiority, elasticity, biocompatibility, bio-degradability environment friendly nature and functionalized tailoring. From ancient times in Indian culture, silk materials have been commonly used by Indians for textile clothing and bio-medical applications. Its role has been further extended for surgical applications including bandages, scaffold implant and emerging bio-medical applications.
Silver nanoparticles possess excellent anti-microbial properties. Therefore, tailored silver nanoparticles with silk fibre can effectively be used for intended applications.
It has been found that the synthesis cost of silver nanoparticles is also very high, therefore, it is important that the silver nanoparticles should be effectively deposited on silk fibres without being left undeposited in reaction bath and also have good wash fastness property for longer duration so that it does not easily get washed on laundering. Hence the need of improved process methods and parameters with the right chemicals and their quantity is crucial to hold silver nanoparticles on silk fibre surface and thereby imparting additional benefits is very useful.
There are numerous methods for synthesis of Silver Nanoparticles followed by different methods to incorporate the same on the natural fibers like silk, cotton etc. Thus, method for synthesis of controlled sized silver nanoparticles disclosed by publication of Hu et al. uses Silver nitrate and polyacrylic acid and ethylene glycol where ethylene glycol provides both the solvent and the reducing agent.
Further, numerous methods are disclosed for deposition of Nanoparticles on silk that includes physical, chemical or enzymatic. Physical methods can provide a high purity of AgNPs but have the defects of agglomeration of AgNPs, high requirement for binder coating that alters the fibre quality. Biological reduction methods, i.e. preparing AgNPs by using natural biological resources (bacteria, fungi, plant extracts, etc.) have drawback of high cost of enzymes and biological materials. In contrast, chemical reduction methods are simple and effective. Additionally, the chemical methods also provide control over size, shape, polydispersity and at the same time try to limit the extent of aggregation or agglomeration. But known chemical methods are using organic solvents, crosslinking agents and dispersants in the process, that may have certain biological toxicity and do harmful to environment and additional cost for extra chemicals.
Reference may be made to numerous processes wherein silk fibres are functionalized/coated with silver nanoparticles using techniques such as immersion, coating, padding, deposition, cross-linking etc.
• Green synthesis of silk sericin-capped silver nanoparticles and their potential antibacterial activity; P. Aramvit et al., Nanoscale Res. Lett. 2014, 9, 79.
• Microwave-mediated impregnation of silver nanoparticles on silk fabric for hygienic clothing; M.S. Smitha and R. Singh, J. Bacteriol. Mycol. 2017, 5(4), 335-338
• Silk Polymers and nanoparticles – a powerful combination for design of versatile biomaterials; C.B. Marin et al, Frontiers Chem. 2020, 8, Art. 604398.
• Method for improving antimicrobial activity of silver nanoparticles, CN 107486563.
• Flaky triangular silver nanoparticle antibacterial suspension as well as preparation method and application thereof, CN 107184981
• Colourful and antibacterial silk fibre from anisotropic silver nanoparticles; B. Tang et al., Ing. Eng. Chem. Res. 2013, 52(12), 4556 – 4563
• New material from silk protein with silver nanoparticles; Colloids Surf. B: Biointerfaces; 2019, 176, 150-155
• Synthesis of silver nanoparticles using polyethylene polyamine and antibacterial property of silk fabrics treated by silver nanoparticles; G. Zhang et al., Nanoscale Res. Lett. 2014, 9, 216.
One of the approaches of functionalizing silk with Silver particles includes in-situ synthesis of nanoparticles in the fibre pores, wherein in-situ synthesis usually involves immobilizing the metal ions onto the substrate before a chemical reduction reagent is employed to convert the ions into nanoparticles.
Publication “Functionalization of silk by silver nanoparticles synthesized using the aqueous extract from tea stem waste” by Tong-Huai Chenga, Zhi-Yi Yangb, Ren-Cheng Tanga, Ai-Dong Zhai et al. discloses a process of reducing silver nitrate using the aqueous extract from tea stem waste to synthesized AgNPs, and a functional finishing of silk material with the resulting AgNPs by an immersion technique.
Publication “Application of Nano Silver Particles on Textile Materials for Improvement of Antibacterial Finishes” by Gokarneshan N. and Velumani K. discloses that the silver nano particles have been synthesized by the reduction of silver nitrate with sodium borohydride in an aqueous medium. The silk protein sericin extracted from the silkworm cocoons has been used as capping agent to protect the unstable silver nanoparticles deposited on silk fabric.
Publication “A light-assisted in situ embedment of silver nanoparticles to prepare functionalized fabrics” by Shuang Toh et.al discloses the process comprising silver nitrate with capping agent and wavelengths of lights for optimizing a process for light-assisted synthesis of silver nanoparticles. They investigated the in-situ embedment of silver nanoparticle when textile fabrics soaked in a solution of capping agent (polyethyleneimine/PVP/PEG/citrate/PVA) having reducing properties and silver nitrate were exposed to light.
Despite having numerous methodologies to provide a functionalized silk fibric with metal nanoparticles, there is need to develop an improved process to save cost, time, chemicals and also there is need for a process that avoid use of organic solvents, so to provide an environment friendly process.
Hence, considering the drawbacks of the hitherto reported prior arts, the inventors of the present invention realized that there exists a dire need to provide a process for the preparation silver-deposited silk fibres that can provide an unique advantages such as minimum chemical agents usage, thereby low cost and eco-friendliness by avoiding use of organic solvents.
Therefore, the present invention provides a simple, aqueous, non-hazardous and scalable process for deposition of silver nanoparticles into silk fibres. The incorporated silver particles do not get easily washed on laundering. A different chemistry is used compared to existing methods of incorporating silver nanoparticles in silk fibres.

SUMMARY OF THE INVENTION:
The main objective of the present invention is to provide an easy and environment friendly process for deposition of silver nanoparticles on silk thread by in-situ synthesis of silver nanoparticles to entrap the higher concentration of silver particles in the silk fibres.
Therefore, the present invention provides a modified process for preparation of silver incorporated silk fibres with anti-microbial properties, comprising steps:
Step 1: Degumming: Treating the raw silk fiber in 0.1 to 10 % v/v in organic acid at temperature between 50°C and 100°C to obtain degummed silk fiber,
Step 2: Incorporation of silver metal: Contacting degummed silk fiber with solution of silver salts in water having concentration 1gm/Ltr to 100 gm/Ltr at temperature between 20°C and 40°C to obtain silver salt deposited silk fiber,
Step 3: Rinsing: Removal of excess Silver salt by rinsing with water.
Step 4: Reducing Silver ions to silver particles: Contacting silver salt deposited silk fiber with solution of reducing agent in water having concentration 0.1 to 20% w/v at temperature between 20°C and 40°C to obtain silver particle deposited silk fiber,
Step 5: Protection of Reduced Silver: Contacting silver particle deposited silk fiber with solution of antitarnish agent in water having concentration 1 mL/ltr to 50 mL/ltr at temperature between 20°C and 50°C to obtain protected silver particle deposited silk fiber,
Step 6: Rinsing: Rinsing protected silver particle deposited silk fiber with water at temperature between 30 to 80°C for 1 h to 5h.
Step 7: Drying in an oven at 60o C for 2 h.

In accordance to present invention, the organic acid are selected from Maleic anhydride, Malic Acid, Oxalic Acid, Tartaric Acid, Acetic Acid, Propionic Acid, Succinic Acid, Formic Acid, Fumaric Acid and combination thereof and more specifically selected from Maleic Anhydride and Oxalic Acid.
The non-limiting treatment time for step 1, step 2, step 4 and step 5 is selected between 30 seconds to 2 h.
Further, the non-limiting example of silver salt are selected from Silver nitrate, Silver methanesulphonate and Silver lactate and, more specifically, Silver nitrate.
Further, the reducing agent are selected from Hydrazine hydrate, Hydroxyl amine, Sodium borohydride, Sodium sulphite, Sodium metabisulphite and Sodium hypophosphite and, more specifically, Sodium hypophosphite.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Figure No. 1: Illustrates image of Raw silk grade 4A
Figure No. 2: Illustrates image of Degummed silk obtained in example no. 3 Test no, 24.
Figure No. 3: Illustrates image of Silver-incorporated silk obtained in Example no, 5 Test no. 40.
Figure No. 4 : Illustrates SEM image of silver-incorporated silk fibres obtained in Example no, 5 Test no. 38.
Figure No. 5: Illustrates SEM image of silver-incorporated silk fibres obtained in Example no, 5 Test no. 40.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention provides an improved process developed for incorporating Silver Particles in Silk Fibres. The process includes degumming, treatment with Silver containing solution, chemical reduction, anti-tarnishing treatment, laundering and drying. The modified silk fibres containing silk particles exhibit anti-microbial properties and therefore shall have wide ranging applications. The Silver particles have size distribution in the nanometer range (sub-micron range). Also, although the silk fibres contain silver nanoparticles, the silk fibres do not tarnish easily.
In accordance to present invention the silk fibre can be selected from 100% silk fibre or blended with other natural fibre or synthetic fibre.
The present invention provides a modified process for deposition/incorporation of silver ions into the silk fibric, wherein the modification involve the following steps:
Optimisation of Degumming– For the removal of sericin, initially, commercially available alkaline soak cleaners were tried at different concentrations at room temperature. However, they did not give satisfactory results. Various combinations of light soda ash and Sodium Lauryl Sulphate were also tried, but they too did not give satisfactory results. Acidic cleaners based on formic acid and phosphoric acid was also tried. Although degumming process improved, subsequent reduction of silver in the bath containing silver nitrate, ammonia and glucose did not give the desired results and the silver bath became unstable.
In view of the above observations, it was decided to study the feasibility of using Organic acids for this purpose. Organic acids are milder, are biodegradable and attack the fibres less.
Experiments were carried out with Maleic anhydride, Malic Acid, Oxalic Acid, Tartaric Acid, Acetic Acid, Propionic Acid, Succinic Acid, Formic Acid and Fumaric Acid. The concentrations tried ranged from 1%-5% by weight. The Degumming process was tried between 50°C and 100°C.
In most cases, it was observed that Degumming (removal of Sericin) was either insufficient or in excess. Besides, the mechanical strength of the fibres was found to deteriorate. After several experiments and trials, it was found that using Maleic Anhydride or Oxalic Acid at concentration range from 0.1 to 10 % by weight for time between 5 min to 2 h at 50°C to 95°C gave the best results for the next steps.
Moreover, it was observed that the Sericin obtained could serve as a useful biomaterial.
Incorporation of Silver – Water-soluble silver salts, such as Silver nitrate, Silver methanesulphonate and silver lactate were investigated. Silver nitrate Aqueous solutions in the concentration range of 1gm/Ltr to 100 gm/Ltr were investigated for their optimum absorption on the degummed silk fibres. The Dipping time was studied between 10 sec and 60 sec or 1 Hr. It was observed that at 50 gm/Ltr Silver Nitrate concentration, a substantial quantity of Silver nitrate was lost in the rinses. On the other hand, at lower concentrations (10gm/Ltr or less), the absorption of Silver nitrate was insufficient. The best conditions were found after several trials, namely, the use of Silver nitrate concentration of 25gm/Ltr (Concentration in range from 1gm/Ltr to 100gm/Ltr) and with the Dipping Time 1 minute to 2 Hr, and at room temperature or more. Excess of Silver nitrate was removed by rinsing twice in DI water. This silver nitrate rinse can be reused immediately. If it is stored for a long time and decomposes, then the silver metal can be recovered quantitatively by known methods. Silver lactate and silver methane sulphonate as the source of silver ions led to strong weakening of fibres.
Reduction of Silver ions to silver particles - Several reducing agents including Hydrazine hydrate, Hydroxyl amine, Sodium borohydride, Sodium sulphite, Sodium metabisulphite and Sodium hypophosphite were investigated. It was observed that Sodium hypophosphite functioned best in comparison with others. The optimum parameters for the reduction discovered were as follows:
Sodium hypophosphite 0.1 to 20% by weight, Dipping Time 60 sec to 2 h and at room temperature or more.
Protection of Reduced Silver - It was observed that discoloration (tarnishing) of the silk fibres containing particles occurred rapidly and had to be prevented. For this, different known antitarnish agents available commercially were tried. It was observed that the best protection against was given by certain anti-tarnish agents based on heavy aromatic hydrocarbons containing thiols. The protection obtained by another type of anti-tarnish agent, based on mercaptan nano component polymers and cyclodextrins, was less effective.
The optimum parameters for protection against tarnishing discovered were 10 mL/ltr of the antitarnish concentrate (In range from 1 mL/ltr to 50 mL/ltr), Temperature 20°C to 50°C and Dipping time 3 min. This was followed by rinsing in DI water at room temperature and at 30°C to 80°C for one minute, more preferably for 1 h or 5 h.
Therefore, the present invention process leads to a stable entrapment of silver nano particles since it withstands the laundering test. Also, the process gives an industrially significant concentration of silver in the silk fibres. This concentration ranges from 0.2 wt% to 2.0 wt% or more.
The present invention is further described with the help of the following examples, which are given by way of illustration and therefore should not be construed to limit the scope of the Invention as claimed in any manner.
Example 1: Effect of different Degumming agents on silk fibers
Degumming: Raw silk fiber were treated with different concentration of degumming agent in a bath solution having temperature between 50 to 90oC for 1 minute time ,
Incorporation of silver metal: The degummed silk fiber was dipped into the solution of silver salts (Silver ion 25g/L) in water at room temperature for 60 seconds,
Rinsing: Excess Silver salt was removed by rinsing with water,
Reducing Silver ions to silver particles: The rinsed fibric were dipped into in a bath containing solution of reducing agent (sodium hypophosphite-5% w/V) in water for 1 minute,
Final Rinsing: The treated fibric were rinsed with water at temperature between 30 to 80°C for 1 h to 5h.

The method used to detect % of silver metal incorporated: The Silver metal incorporated is analysed by wet analysis (Iodometry). To prepare the sample for analysis, the silver incorporated silk is stirred in 50 % HNO3 (w/V) at 90? For 30 mins. The silver gets dissolved in nitric acid and the solution of AgNO3 is titrated against 0.1 N sodium thiocyanate using ferric ammonium sulphate indicator.
Test No. Reagent and concentration in
Degumming Bath Temp
(? ) Loss of Sericin % by weight % Ag metal incorporated Remarks
1 Tartaric Acid, 3%w/V 90 29.27 0.286 Poor mech properties
2 Malic Acid, 5% w/V 90 30.08 Not analysed Fibre attacked
3 Acetic Acid 5% w/V 90 19.3 Not analysed Fibre attacked
4 Succinic Acid, 5%w/V 90 22.37 Not analysed Fibre attacked
5 Propionic Acid, 5% w/V 90 15.39 Not analysed Fibre attacked
6 Formic Acid 5%w/V 90 29.71 0.107 Fibre attacked
7 Fumaric Acid, 1% 50 13.83 Not analysed Fibre attacked
8 Fumaric Acid, 1% 90 29.06 0.383 Rough, weak
9 Light soda ash, 5%w/V 90 33.06 Not analysed Fibre attacked
10 Light soda ash, 2.5% 90 27.98 Not analysed Fibre attacked
11 Potassium Carbonate 5%w/V 90 30.79 Not analysed Fibre attacked
12 Potassium Carbonate 2.5%w/V 90 27.07 Not analysed Fibre attacked
13 NP EO 20, 1%w/V 90
2.59%
Not analysed Fibre attacked
14 Sunlight Bar Soap1%w/V 90 25.0% 0.289 Fibre attacked
TABLE NO. 1
Note: “Fibre attacked” means that the properties of the fibres are fully destroyed.
Example 2: Modification of Process of incorporation of silver metal on silk fibric:
Degumming: Treating the raw silk fiber with degumming agent,
Incorporation of silver metal: Contacting degummed silk fiber with solution of silver salts (Silver metal 25g/L) in water at room temperature for 60 seconds,
Rinsing: Removal of excess Silver salt by rinsing with water,
Reducing Silver ions to silver particles: Contacting silver salt deposited silk fiber with solution of reducing agent (sodium hypophosphite-5% w/V) in water for 1 minute,
Antitarnish Dip- Contacting silver particle deposited silk fiber with solution of antitarnish agent,
Rinsing: Rinsing protected silver particle deposited silk fiber with water at temperature between 30 to 80°C for 1h to 5h.
Test
No. Silk Treatment Degumming agent Degumming agent
% Degumming Time Degumming Temperature
15 Raw silk - - - -
16 Degummed silk Maleic anhydride 2% 10 min 300C
17 Degummed silk Maleic anhydride 2% 10 min 300C
18 Degummed silk Maleic anhydride 3% 10 min 300C
19 Degummed silk Maleic anhydride 3% 10 min 300C
20 Degummed silk Maleic anhydride 4%/ 10 min 300C
21 Degummed silk Maleic anhydride 3% 1Hr 90?
22 Degummed silk Maleic anhydride 5% 1Hr 90?
23 Degummed silk Oxalic acid 3% 1Hr 90?
TABLE NO. 2

Test
No. Degumming/Activation Treatment at 300C Time %w/w Ag metal incorporated Observations
15 Raw silk-No degumming - 0.616 Rough in appearance
16 Activated Silk in Maleic anhydride-2% 10 min 0.56 Rough, poor and partial degumming
17 Activated silk in Maleic anhydride 2% 20 min 0.57 Rough, poor and partial degumming
18 Activated silk in Maleic anhydride 3% 10 min 0.76 Rough, poor and partial degumming
19 Activated silk in Maleic anhydride 3% 20 min 0.60 Rough, poor and partial degumming
20 Activated silk in Maleic anhydride 4% 10 min 0.61 Rough, poor and partial degumming
21 Degummed silk in Maleic anhydride 3 % 1 Hr 0.442 Soft, smooth
22 Degummed silk in Maleic anhydride 5 % 1 Hr 0.378 Soft, smooth
23 Degummed silk in Oxalic acid 3% 1 Hr 0.418 Soft, smooth
TABLE NO. 3
Note :-1. Activated silk means degumming of silk carried out at room temperature, with less Sericin loss. 2. The physical properties of the silk fibre after treatment (appearance, smoothness, pulling strength etc) were judged by three chemists independently and the average taken.
Figure no. 1 illustrates the image of raw silk-Grande 4A.

Example 3: Effect of degumming temperature on incorporation of silver metal on silk fibric: The process steps are same as disclosed in example no. 2 for time 1Hr. Only Condition and temperature of degumming was mentioned in following table:
Test
No. Degumming bath condition Degumming temperature °C Loss of Sericin,% by weight %age Ag metal incorporated Remarks
24 Maleic anhydride, 3%w/V 90 24.01 0.442 Very Good
25 Maleic anhydride, 3%w/V 100 34.70 0.490 Poor
26 Maleic anhydride, 3%w/V 80 14.20 0.108 Good
27 Maleic anhydride, 3%w/V 70 11.90 0.072 Good
28 Maleic anhydride, 3%w/V 50 3.19 0.060 Good
29 Maleic anhydride, 5%w/V 90 25.77 0.378 Poor
30 Oxalic acid 3% 90 28.36 0.418 Very Good
TABLE NO. 4
Note: Strength and smoothness of silk fibres was manually checked by 3 different chemists by stretching and grades are given in scale of Poor30d
43 pro nice aqua*, 3 min @ 40 deg C Tarnishing starts on day 3
44 M-100** 3 min @ 40 deg C followed by pro nice aqua, 3 min @ 40 deg C Tarnishing observed on day 2
45 pro nice aqua, 3 min @ 40 deg C followed by M-100, 3 min @ 40 deg C No tarnishing after >30d
TABLE NO. 7
Wherein: *pro nice aqua is a product of nanocraft GmbH, Germany;
** M-100 is a product of METAKEM GmbH, Germany.
The method used to evaluate tarnishing was as follows: The samples were exposed to industrial laboratory atmosphere (T 27oC-35oC, RH 80%) on a petridish and compared with reference (raw silk fibres and only degummed silk fibres) initially on an hourly basis and then on a daily basis. Where the tarnish resistance was poor, the samples turned light brown and then dark brown quickly. Those samples which had good tarnish resistance retained their colour even after two months of exposure.
Treatment of the fibres with Silver Antitarnish M-100 alone as well as after prior treatment with pronice aqua gave very good resistance against tarnishing. Only pronice aqua treatment or pronice aqua after M-100 treatment resulted in poor tarnish resistance.
A. It was observed that discoloration (tarnishing) of the silk fibres containing particles occurred rapidly and had to be prevented. For this, different known anti tarnish agents available commercially were tried. It was observed that the best protection against tarnishing was given by certain anti-tarnish agents based on heavy aromatic hydrocarbons containing thiols. The protection obtained by another type of anti-tarnish agent, based on the principle of mercaptan nano component polymers and cyclodextrins, was less effective.
B. The optimum parameters for protection against tarnishing discovered were 10 mL/ltr of the anti-tarnish concentrate M-100, temperature 40 deg C and Dipping time 3 min. This was followed by rinsing in DI water at room temperature and at 60 deg C for one minute.

Example 7: Wash fastness of silver-incorporated silk fibres:
Test No. Treated Silk Temperature Time Ag % w/w Remark
46 Washing with Ariel detergent (1%) 300C 12 hr 0.365% Ag % reduced by 17.5%
47 Washing without detergent in plain water 300C 12 hr 0.442% No loss
TABLE NO. 8

For determining the wash fastness of silver-incorporated silk fibres, 1 gram samples from Test No. 40 were dipped either in 100 mL plain water or in detergent-containing solution for 12 h at RT, with occasional stirring with a glass rod. At the end of 12h, the fibres were filtered off and the silver content in the filtrate analysed by wet analysis.

Example 8: Anti-bacterial and anti-fungal properties of improved process fiber in comparison with known process:
The anti-microbial properties of the silver-incorporated silk fibres from Test No. 40 were determined on bacteria and fungi. The anti-bacterial activity was determined on Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352 by ISO 20743:2021 method.
The antibacterial activity value A for S. aureus was found to be A=4.16.
The antibacterial activity value A for K. pneumoniae was found to be A = 3/20.
Implying strong anti-bacterial activity.
The antifungal activity was tested on Aspergillus niger ATCC 6275 using the same method on silk fibres from Test No. 40. No growth was observed above the fabric, implying strong anti-fungal activity.
,CLAIMS:We claim;
1. A process for preparation of silver incorporated silk fibres with anti-microbial properties, comprising steps:
Step 1: Degumming: Treating the raw silk fiber in 0.1 to 10 % v/v in organic acid at temperature between 50°C and 100°C to obtain degummed silk fiber,
Step 2: Incorporation of silver metal: Contacting degummed silk fiber with solution of silver salts in water having concentration 1gm/Ltr to 100 gm/Ltr at temperature between 20°C and 40°C to obtain silver salt deposited silk fiber,
Step 3: Rinsing : Removal of excess Silver salt by rinsing with water,
Step 4: Reducing Silver ions to silver particles: Contacting silver salt deposited silk fiber with solution of reducing agent in water having concentration 0.1 to 20% w/v at temperature between 20°C and 40°C to obtain silver particles deposited silk fiber,
Step 5: Protection of Reduced Silver: Contacting silver particle deposited silk fiber with solution of antitarnish agent in water having concentration 1 mL/ltr to 50 mL/ltr at temperature between 20°C and 50°C to obtain protected silver particle deposited silk fiber,
Step 6: Rinsing : Rinsing protected silver particle deposited silk fiber with water at temperature between 30 to 80°C for 1 Hr to 5Hr.
Step 7: Drying in an oven at 600C for 2 hours.

2. The process for preparation of silver incorporated silk fibres as claimed in claim 1, wherein organic acid are selected from Maleic anhydride, Malic Acid, Oxalic Acid, Tartaric Acid, Acetic Acid, Propionic Acid, Succinic Acid, Formic Acid, Fumaric Acid and combination thereof.
3. The process for preparation of silver incorporated silk fibres as claimed in claim 2, wherein organic acid specifically selected from Maleic Anhydride and Oxalic Acid.
4. The process for preparation of silver incorporated silk fibres as claimed in claim 1, wherein the treatment time for step 1, step 2, step 4 and step 5 is selected between 5 min to 2 Hr.
5. The process for preparation of silver incorporated silk fibres as claimed in claim 1, wherein silver salt are selected from Silver Nitrate, Silver Methanesulphonate and Silver Lactate.
6. The process for preparation of silver incorporated silk fibres as claimed in claim 5, wherein silver salt specifically selected is Silver Nitrate.
7. The process for preparation of silver incorporated silk fibres as claimed in claim 1, wherein reducing agent are selected from Hydrazine Hydrate, Hydroxyl Amine, Sodium Borohydride, Sodium Sulphite, Sodium Metabisulphite and Sodium Hypophosphite.
8. The process for preparation of silver incorporated silk fibres as claimed in claim 7, wherein reducing agent specifically selected is Sodium hypophosphite.
9. The process for preparation of silver incorporated silk fibres as claimed in claim 1, wherein anti-tarnish agents are selected from commercially available products such as M-100 and pro nice aqua.