FORM 2
THE PATENT ACT 1370
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
'1. TITLE OF THE INVENTION "A METHOD OF MAKING NOBLE METAL
NANOPARTICLES FORMED BY GREEN CHEMISTRY TECHNIQUES"
2. APPLICANT (s)
(a) NAME: B. L. JADHAV
(b) NATIONALITY: INDIAN
(c)ADDRESS:DEPARTMENT OF LIFE SCIENCE, UNIVERSITY OF MUMBAI,
MUMBAI, 98
'3.PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.
4. DESCRIPTION
5. CLAIMS
"1/we Claim" on separate page)
6.DATE AND SIGNATURE (to be given at the end of last page_of_specification)
7. ABSTRACT OF THE INVENTION
Note: -
*Repeat boxes In case of more than one entry.
*'To be signed by the appllcant(s) or by authorized registered patent agent *Name of the applicant should be given in full, family name In the beginning. *Con.plete address of the applicant should be given stating the postal Index no,/code, state and country. Strike out the column which Is/are not applicable

The field of invention;
The present invention relates to a method of making noble rnetal nanoparticles formed by green chemistry techniques. Particularly, the present invention relates to noble metal nanoparticles formed with aqueous stem extract of Ceriops tagal, a Mangrove plant.
Background of invention and prior art;
Nanoparticles are particles ranging in size from 1 nm to 1 micron in diameter. "Nano" is a prefix which means one billionth (10') part of something, in recent years, the field of nanoparticles has grown due to their unique properties. Many industries utilize nanoparticles, for example the electronics industry, medical science, material science, and environmental science. Noble metal nanoparticles have found widespread use in several technological applications and various wet chemical methods have been reported. See, X. Wang and Y. Li, Chem. Commun., 2007, 2901; Y. Sun and Y. Xia, Science, 2002, 298, 2176; J. Chen, J. M. McLellan, A. Siekkinen, Y. Xiong, Z-Y Li and Y. Xia, J. Am. Chem. Soc, 2006, 128, 14776; J. W. Stone, P. N. Sisco, £. C. Goldsmith, S. C. Baxter and C. J. Murphy, NanoLett., 2007, 7, 116: B. Wiley, Y. Sun and Y. Xia, Ace. Chem. Res., 2007, 40, 1067. There is great interest in synthesizing metal and semiconductor nanoparticles due to their extraordinary properties, which differ from those of the corresponding bulk material. An example of a nanoparticle is nanoscale zero valent iron (nZVI). Generally, nanoparticles are synthesized in three ways: physically by crushing larger particles, chemically by precipitation, and through gas condensation. Chemical generation is highly varied and can incorporate laser pyrolysis, flame synthesis, combustion, and sol gel approaches. See, U.S. Pat. No. 6,881,490 (Apr. 19, 2005) N. Kambe, Y. D. Blum, B. Chaloner-Gill, S. Chiruvolu, S. Kumar, D. B. MacQueen. Polymer-inorganic particle composites; J. Du, B. Han, Z. Liu and Y. Liu, Cryst Growth and Design, 2007, 7, 900; B. Wiley, T. Herricks, Y. Sun and Y. Xia, Nano Lett., 2004, 4, 2057; C. J. Murphy, A. M. Gole, S. E. Hunyadi and C. J. Orendorff, Inorg. Chem., 2006, 45, 7544; B. J. Wiley, Y. Chen, J. M. McLellan, Y. Xiong, Z-Y. Li, D. Ginger, and Y. Xia, Nanoletters, 2007, 4, 1032; Y. Xiong, H. Cai, B. J. Wiley, J. Wang, M. J. Kim and Y. Xia, J. Am. Chem. Soc, 2007, 129, 3665; J. Fang, H. You, P. Kong, Y. Yi., X. Song, and B. Ding, Cryst. Growth and Design, 2007, 7, 864; A. Narayan, L. Landstrom and M. Boman, Appl. Surf. Sci., 2003, 137, 208; H. Song, R. M. Rioux, J. D. Hoefelmeyer, R. Komor, K. Niesz, M. Grass, P. Yang and G. A. Somorjai, J. Am. Chem. Soc, 2006, 128, 3027; C. C. Wang, D. H. Chen and

T. C. Huang, Colloids Surf., A 2001, 189, 145. Examples of mechanical processes for producing nanoparticles include mechanical attrition (e.g., ball milling), crushing of sponge iron powder, and thermal quenching. Examples of chemical processes for producing nanoparticles include precipitation techniques, sol-gel processes, and inverse-micelle methods. Other chemical or chemically-related processes include gas precipitation with a compressed fluid anti-solvent, and generation of particles from gas saturated solutions condensation methods, evaporation techniques, gas anti-solvent re-crystallization techniques. The commercial significance of nanoparticles is limited by the nanoparticle synthesis process, which is generally energy intensive or requires toxic chemical solvents and is costly. Thus, the science and circumstances have changed dramatically for the identification of new era of simple, eco-friendly and efficient biosynthesis of nanoparticles with less toxicity.
Description of drawing, figures and tables;
Figure 1: UV-Visible spectra recorded as a function of reaction time of 2mM AgN03 solution with CTSE at R.T.
Figure 2: TEM micrograph of silver nanoparticles from AgNCh salt with an inset of measured nanoparticles.
Figure 3: UV-Visible spectra recorded as a function of reaction time of ImM Ag2SO4Solution with CTSE at 40° C.
Figure 4: TEM micrograph of silver nanoparticles from Ag2SO4 salt with an inset of measured nanoparticles.
Figure 5: UV-Visible spectra recorded as a function of reaction time of 0.9mM HAuCl4 solution with CTSE at 40°C.
Figure 6: TEM micrograph of gold nanoparticles from HAuCU salt with an inset of measured nanoparticles.
Figure 7: UV-Visible spectra recorded as a function of reaction time of ImM CuS04Solution with CTSE at RT.
Figure 8: TEM micrograph of copper nanoparticles from CUSO4 salt.

Figure 9: UV-Visible spectra recorded as a function of reaction time of 2mM AgNO3:0.9mM HAuCl4, solution with CTSE at R.T.
Figure 10: TEM micrograph of bimetallic nanoparticles from 2mM AgNO3: 0.9mM HAuCl4 salt with an inset of measured nanoparticles.
Figure 11: UV-Visible spectra recorded as a function of reaction time of ImM Ag2SO4:0.9mM HAuCl4 solution with CTSE at R.T.
Figure 12: TEM micrograph of bimetallic nanoparticles from ImM Ag2S04: 0.9mM HAuCl4 salt with an inset of measured nanoparticles.
Tablel: Optimization of synthesis process.
Table2: XRD measurements of monometallic and bimetallic nanoparticles.
Table3: FT1R measurements of bioreduced monometallic and bimetallic nanoparticles.
Objects of the invention;
The main object of the present invention is to provide a method of making noble metal nanoparticles by bio reduction of metal salts using aqueous extract of the mangrove plant's parts.
It is also an object of the invention to provide a method of making monometallic nanoparticles from salt of silver, gold, copper and bimetallic nanoparticles from salt of silver and gold using aqueous stem extract of Ceriops tagal;
Another object of the invention is to provide rapid, non-hazardous, eco-friendjy method for making of monometallic nanoparticles from salt of silver, gold, copper and bimetallic nanoparticles from salt of silver and gold using aqueous stem extract of Ceriops tagal;
A further object of the invention is to provide green method for making of monometallic nanoparticles from salt of silver, gold, copper and bimetallic nanoparticles from salt of silver and gold using aqueous stem extract of Ceriops tagal;

Still another object of the invention is to provide efficient and economical method for making of monometallic nanoparticles from salt of silver, gold, copper and bimetallic nanoparticles from salt of silver and gold using aqueous stem extract of Ceriops tagal;
Summary of the invention;
The present invention provides a method of making monometallic and bimetallic nanoparticles formed by green chemistry techniques. The method involves preparation of aqueous extract of Ceriops tagal, by extracting standard quantity of these stem , which is cleaned , dried, pulverised to fine powder, extracted at 100 °C, filtered and filtrate is used as bio-reductant for preparing nanoparticles of noble metals from its salts;
In an another aspect of the invention it is provided that standard solution of silver salts, gold salt, copper salt is prepared and added to the filtrate of the stem extract, the mixture of stem filtrate and metal ions is kept un-disturbed for 4-5 hrs, the change in colour of the solution is measured at the regular interval, by UV-spectrophotometer, as function of change of amount of metal salt in solution and formation of the metal nanoparticles,
Similarly, for preparation of bimetallic nanoparticles , standard molar solutions of noble metal salts are optimized for its molar concentration and mixture of that in the ratio of 1:1 v/v is reacted with stem filtrate to form bimetallic nanoparticles;
Detailed description of the invention;
In one of the aspect of present invention, a method for making nanoparticles from metal salts is disclosed; there is a current drive to produce 'green' nanoparticles from plants because of its eco friendliness, energy efficiency and convenience. Mangrove plants have distinctive characteristics such as the ability to sustain in high salinity, extreme temperatures, anaerobic and unstable substrates thus forming unique environments and floral-faunal assemblages and therefore, might produce special types of bioactive compounds than terrestrial plants.
The method involves use of the plant extract from mangrove species selected for the purpose; it is known that mangrove species are used for preparing nanoparticles synthesis. The species includes Rhizophora mucronata and Avicennia marina;

The most preferred aspect of the invention is mangrove Ceriops tagal is selected for a method of preparing noble metal nanoparticles;
The plant part stem is used to isolate bioactive compounds by using solvent, the solvents includes polar, non-polar solvents selected from Pentane, Cyclopentane, Hexane, Cyclohexane, Benzene, Toluene, 1,4-Dioxane, Chloroform, Diethyl ether, Ethyl acetate, Acetone, Dimethylformamide (DMF), Acetonitrile (MeCN), Isopropanol (IPA), n-Propanol, Ethanol, Methanol, Acetic acid, Nitromethane, Water or combinations thereof;
More preferably water is used for extraction of bioactive components from Ceriops tagal, it is a preferred mode of the invention the stem extract is used for the instant method.
It is known that Ceriops tagal contains condensed and hydrolysable tannins, aliphatic carboxylic acids, indole alkaloids, polyphenols, proteins, tannins, fatty acids, hydrocarbons, inorganic salts, inositols, steroids, carotenoids, chlorophyll a, b, a+b, etc. C.tagal stem is a rich source of monoterpenoids, diterpenoids, triterpenoids, flavonoids, alkaloids, polyphenols and saponins. A range of diterpenes, triterpenes and six new doJabranes named 'tagalsins' had been isolated from C.tagal; also, recently new dolabrane types diterpenes, namely tagalsins A-G and norditerpene tagalsin (H) are isolated from the stems and twigs of C tagal, hence forming main constituents of extract. Thus, it is a rich source of bio-reductant and stabilizers. The synthesis of nanoparticles from Ceriops tagal may further increase its activities and potency.
In one of the aspect of the invention noble metals selected from gold, copper, silver and their organic or inorganic salts , including gold salts such as Potassium gold cyanide Sodium aurothiomalate, Sodium aurothiosulfate, Disodium aurothiomalate, Gold thioglucose, Hydrogen tetrachloroaurate, Chlorauric acid, Aurochloric acid, Aurate(l-), tetrachloro-, Hydrogen aurichloride,
Silver salts such as silver nitrate, silver sulphate, silver carbonate, silver carbonate purum. oxides of silver,
Salts of copper includes copper sulphate, copper halide, copper acetate, copper nitrate, copper (I) sulphide, cupric and cuprous oxides,

Accordingly one of the most important aspects of the invention is stem of mangrove plant Ceriops tagal, collected from Gorai creek, Mumbai, India. It was chopped, dried at 40° C-60 °C and pulverized to fine powder, ultra-pure water produced by MilliQ system is used throughout the experiment. Aqueous stem extract is prepared by soaking 5 g of stem powder in 100ml MilliQ water, kept undisturbed for 5 min and then the mixture is boiled at 100° C for 5 min. The freshly prepared extract is obtained by filtering it through Whatman filter paper No.l and used for further making of monometallic and bimetallic nanoparticles from noble metals including silver, gold, copper employing aqueous stem extract of C. tagal by reduction of aqueous Ag+, Ag2+ Au3+, Cu2+, Ag+ ; Au3+ and Ag2+ : Au3+ ions, also the effect of change of temperature and metal salts on the rate of synthesis is determined.
Synthesis of monometallic nanoparticles is initiated by adding 5ml of aqueous stem extract of Ceriops tagal in 95 ml aqueous AgNo3, Ag2S04, HAuCU and CuSo4 solution respectively while bimetallic nanoparticles are synthesized by adding 10ml of aqueous stem extract of Ceriops tagal in 190 ml of 1:1 aqueous solution of 2mM AgNo3 : 0.9mM HAuCU and ImM Ag2So4 : 0,9mM HAuCU- All the reactions are carried out at static condition.
Reduction of Ag+, Ag2+, Au3+, Cu2+, Ag+: Au3+ and Ag2+: Au3+ is monitored as a function of time by measuring UV-Vis spectra using UV-1650CP Schimadzu spectrophotometer operated at lnm resolution. Effect of temperature on rate of synthesis was studied by carrying out the reactions at Room temperature (RT), 40°C, 50°C and 60°C in water bath.
Concentration of metal salt varied from 0.5mM -ImM for chloroauric acid and from ImM -5mM for silver nitrate, silver sulphate and copper sulphate.
According to one of the aspects of the invention UV-visible spectrophotometry is used to monitor the bio-reduction of monometallic and bimetallic salts to respective metal ions in presence of stem extract of C. tagal (CTSE). Bio-reduction is monitored as a function of time. The surface plasmon resonance (SPR) peak of absorption spectra is found at 455nm, 444nm, 556nm and 500nm for monometallic nanoparticles synthesized using AgN03 (Fig I), Ag2S04 (Fig 3), HAuCU (Fig 5) and CuSO4 (Fig 7) salt solutions. Whereas only one Plasmon band at 535 nm (Fig 9 and 11), a characteristic peak for gold is seen for bimetallic nanoparticles prepared by simultaneous co-reduction of silver and gold. The Plasmon maximum is red shifted

from455 and 444 nm to 535 nm. This can be attributed to alloying and simultaneous co-reduction of silver and gold. The underlying Ag plasmon resonance band can be damped sufficiently with one monolayer of Au. The well-known intense brown and ruby red colour is observed after silver and gold nanoparticles formation. Copper nanoparticles exhibited yellowish brown colour while AgNO3: HAuCl4 and Ag2SO4; HAuCl4 showed grey and dark pink colour respectively. Reduction of Au3+, Ag+: Au3+ and Ag 2+; Au3+metal ions is very rapid; onset of colour change was seen within 5-10 min and more than 90% of reduction was achieved within 30-50min. Complete reduction of Ag+ metal ions was done in 120 min, while the colour change was observed after 15 min. Maximum reduction of Ag and Cu ions took place between 4-5 hr displaying colour change after 1 hr. The differences in the redox potential and solubility of metal ions are most likely to be considered for rate of synthesis of nanoparticles formation.
According to one of the aspects of the invention transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) measurements are used to determine the size and surface morphology of bio-reduced nanoparticles. Nanoparticle solution was drop coated on copper TEM grids, after which film was allowed to stand for 2 min and excess solution was blotted. The grid was dried properly prior to measurement. An energy dispersive spectrum was recorded with the same instrument at the energy range 0-20 keV. TEM micrograph confirmed the synthesis of monometallic and bimetallic nanoparticles. For elemental analysis of nanoparticles. a signature spectrum corresponding to each metal atom in the nanoparticles is obtained by EDS. Weak signals from oxygen, chloride, carbon etc are also seen which may have originated from the bio-molecules bound to the surface of the nanoparticles, while copper peaks may have origin from the copper grid. TEM diffraction pattern of all six types of nanoparticles is obtained. All monometallic and bimetallic nanoparticles synthesized are almost spherical with a small percentage being ellipsoidal, the exceptional being gold nanoparticles. From the few particle images we found that the size (diameter) varied from 5nm to 22nm and 14nm to 23 nm for silver nanoparticles synthesized employing AgNO3 (Fig 2) and Ag2S04 (Fig 4) salts respectively. Nanoparticles within the size range 1-10 nm have greatest biocidal activity against bacteria, it has been also reported that silver nanoparticles within the size range of lnm to 10 nm could attach to the HIV-1 virus and inhibit binding to the host cells of HIV. Gold nanoparticles (Fig 6) exhibited various shapes, such as nanotriangles, nanohexagons, nanotrapezoid while predominantly being nanospheres. It is well known that the shape of nanoparticles considerably

changes their properties, bioactivities and further applications. Copper nanoparticles (Fig 8) showed a tendency to cluster with flower like outline; making it unfeasible to measure their diameter. A close examination of some large particles reveals the subtle cluster features. This observation hints at the possibility of coalescence of small particles. The coalescence process begins with the formation of 'neck' at the contacting planes when nanoparticles diffuse across the substrate. It can occur under the influence of high intensity electron beam as well as at RT or below RT. As coalescence proceeds, the planes starts aligning which results in unique fee crystal structure thus forming a new nanoparicle. Bimetallic nanoparticles produced using AgNO3 HA11Cl4 (Fig 10) are slightly clustered with size ranging from lOnm to 23nm whereas well separated nanoparticles are obtained from Ag2S04, HA11Cl4 (Fig 12) which are between 25nm-40nm. It is clear from the TEM measurements that the biosynthesized nanoparticles are poly-dispersed. TEM micrograph also indicates that the nanoparticles are capped by a thin layer which is supposed to be the organic material from CTSE, Therefore, it is possible that the bioactive principles present in plant are involved in capping thus offering stabilization and inhibiting aggregation of nanoparticles.
According to one of the aspects of the invention X-ray diffraction measurements is determined, after complete reduction of metal ions by stem extract of C, tagal CTSE; the solution was centrifuged at 10,000 rpm for 15 min at RT. The pellet obtained was re-dispersed and centrifuged with MilliQ water. This process was repeated three times to get rid of any free entities. Phase formation of nanoparticles was studied by preparing thin film of thoroughly dried nanoparticles on glass slides. Diffraction data was recorded on Schimadzu XRD 7000 diffractometer with Cu Ka radiation (1.54 A) source operating at 40 kV voltages and a current of 30 mA. The crystalline nature of nanoparticles was confirmed by X-ray diffraction analysis. The crystallite size of the nanoparticles was estimated from the Debye-Scherrer formula,

Where 0.9 is the shape factor, X is x-ray wavelength, 1.54 A, β full width at half the maximum intensity in radians, and θ is the Bragg angle.
Strong Bragg reflections are obtained corresponding to (111), (200) and (220) planes for all nanoparticles, which are the principal diffracting planes of face centered cubic symmetry (Table

2). High degree of crystallinity of the nanoparticles is reflected by the intensity of peaks. The crystallite size of silver nanoparticles synthesized using AgN03 and Ag2S04 is almost similar, whereas it is ~9 nm for bimetallic nanoparticles AgN03: HA11Cl4 and Ag2S04; HAuCl4 while it is ~1 nm and ~ 0.7 nm for gold and copper nanoparticles. The data obtained for gold nanoparticles matched with Joint Committee for Powder Diffraction Set (JCPDS) data 00-004-0784 confirming the cubic phase with lattice constant a = 4.079 A, however we did not got match for other nanoparticles.
According to one of the aspects of invention, Fourier Transform Infrared (FTIR) Spectroscopy is determined. FTIR spectrum of stem extract of C. tagal (CTSE) before and after reduction of metal ions using FTIR (Perkin Elmer) Frontier spectrophotometer. 5% plant extract and supernatant of bio-reduced samples was subjected to IR source 400 cm-1 - 4000 cm-1. FT-1R spectroscopic studies were carried out to identify the functional group involved in capping and efficient stabilization of the metal nanoparticles. Representative absorption peaks of the nanoparticles obtained in the present study is presented in Table 3. The plant extract shows intense broad stretching at 3550-3200 cm-1 which arises due to the free O-H groups present in alcohols and phenols, weak stretch at 2260 - 2100 cm~! is due to C=C from alkynes while the IR peak at 1690-1630 cm"1 could be assigned to characteristic asymmetrical stretch of carboxylate group. The shifting of peaks occurred after synthesis of nanoparticles for AgN03, Ag2S04, CUSO4 and Ag2S04. HA11CI4. Based on the band shift occurring at hydroxyl and carbonyl groups it can be concluded that both hydroxyl and carbonyl groups of C.tagal are involved in the synthesis of above nanoparticles.
While gold nanoparticles and bimetallic (AgNG3: HAuCU) nanoparticles have exhibited more number of peaks as compared to others indicating involvement of more number of functional groups in synthesis process. The peak 1207 cm-1 and 1101 cm-1 from gold nanoparticles can be attributed to C-O stretch from methyl formate or esters or ethers and C-O single bond. This suggests the attachment of some polyphenols components on to nanoparticles. This means the polyphenols attached to nano particles may have atleast one aromatic ring. The peaks at 1000-1200 cm-1 indicate C-O single bond and peaks at 1620-1636 cm-1 represent carbonyl groups (C~0) from polyphenols. The FTIR spectra of bimetallic nanoparticles made from AgNO3: HAuCl4 depicts absorption peak at 2982 cm-1 (Aliphatic C-H stretch), 1387 cm-1 (amide II

group), while the absorbance peaks 1249 cm-1 ,1155 cm-1 , 1077 cm-1 can be assigned to C-N of amine. Thus the molecules attached with nanoparticles have amide group. These amide groups may possibly in the aromatic rings. This indicates that the compounds attached with nanoparticles could be polyphenols with aromatic ring and bound amide region. Therefore the synthesized nanoparticles were surrounded by proteins and metabolites such as terpenoids having functional groups of alcohols, phenois and carboxylic acids. As stated earlier, CTSE is mainly composed of terpenoids, flavonoids, alkaloids and ployphenols which may play an important role in reduction, stabilization and assembly of synthesized nanoparticles.
According to one of the aspect of the invention, pH of plant extract affects the binding trend of ions to functional groups of biomass and subsequently the shape and size of nanoparticles during synthesis. The pH of stem extract of C. tagal CTSE extract was 7.
According to one of the aspect of the invention optimization of different concentration of metal salts against kinetics of reaction was observed. The rate of synthesis is highest at 2mM for silver nitrate, ImM for silver sulphate, 0.9mM for chloroauric acid and ImM for copper sulphate. Maximum synthesis of bimetallic nanoparticles is achieved using 1:1 aqueous solution of choloroauric acid (0.9mM) each with silver nitrate (2mM) and silver sulphate (ImM). The lower salt concentration showed comparatively low rate of synthesis whereas higher salt concentration resulted in precipitation. Thus the optimization study revealed the significant effect of metal salt concentration on synthesis of nanoparticles (Table I).
According to one of the aspect on the invention the role of temperature on enhancement of the rate of synthesis by carrying the synthesis at R.T.. 40°C, 50°C and 60°C is determined. Maximum bio-reduction of Ag2+ to Ag° and Au3+ to Au° is achieved at 40° C, while RT is optimum for maximum synthesis of rest of the nanoparticles Although the reaction is fast at higher temperature and low at lower temperature with slight colour variation, indicating the dependence of temperature on bio-reduction process however no significant difference is observed in peaks.
According one of the aspects of the invention acute toxicity and LD50 of silver and gold nanoparticles made from silver sulphate and chioroauric acid solution is determined, animals were observed for behavioural, haematological, blood biochemistry and histopathological changes. No death was recorded in animals dosed with gold nanoparticles at 2,000 and 4, 000

mg/kg body weight. During the observation period, the mice dosed with silver nanoparticles at 4000 mg/kg body weight died after 12 hr. While there was no significant difference in the percentage of weight gain between the control and treatment groups of mice before and after giving colioidal silver and gold nanoparticles orally. No significant changes in water / food consumption were observed. There was no significant difference in behavioural, haematoiogical, blood biochemistry and histopathological results of control and nanoparticles tested mice. Thus, result of acute oral toxicity indicated that the LD50 of the colloidal silver and gold nanoparticles is greater than 3000 mg/ kg and 4000 mg/kg body weight of mice respectively as per the OECD 425 guideline.
Example I;
Preparation of aqueous stem extract of Ceriops tagal;
Mangrove plant Ceriops tagal is collected from the beach of Mumbai, the plant is cleaned and dried in sunlight, the stem of Ceriops tagal is dried at elevated temperature in the range of 40-60 °C, after drying; the stem is pulverized to fine powder form, exactly weighed 5.0 g stem powder is added to 100 ml ultra-filtered water, kept undisturbed for 5.0 min, and then boiled for 5.0 min at 100° C, and filtered through whatman filter paper No 1, freshly prepared extract is used as reducing agent for preparing noble metal nanoparticles;
Example 2;
Synthesis of monometallic silver nanoparticles from silver nitrate;
5.0 ml of aqueous stem extract of Ceriops tagal as prepared in example 1 is added to 95.0 ml of 2 mM silver nitrate solution; the mixture is kept at R.T., change in colour of solution is measured at the interval of 15 minutes, it is observed that complete conversion of silver ions to nanoparticles takes place in 4-5 hrs, the amount of the obtained silver nanoparticles is 20 mg/ml;
Example 3;
Synthesis of monometallic silver nanoparticles from silver sulphate;
5.0 ml of aqueous stem extract of Ceriops tagal as prepared in example 1 is added to 95.0 ml of ImM silver sulphate solution; the mixture is kept at 40 °C, change in colour of solution is

measured at the interval of lhr, it is observed that complete conversion of silver ions to nanoparticles takes place in 4-5 hrs, the amount of the obtained silver nanoparticles is 140 mg/ml;
Example 4;
Synthesis of monometallic gold nanoparticles from chloroauric acid nanoparticles;
5.0 ml of aqueous stem extract of Ceriops tagal as prepared in example 1 is added to 95.0 ml of 0.9 mM chloroauric acid solution; the mixture is kept at 40 °C, change in colour of solution is measured at the interval of 10 min, it is observed that complete conversion of gold ions to nanoparticles takes place in 1 hr4 the amount of the obtained gold nanoparticles is 120 mg/ml;
Example 5;
Synthesis of monometallic Copper nanoparticles from copper sulfate nanoparticles;
5.0 ml of aqueous stem extract of Ceriops tagal as prepared in example 1 is added to 95.0 ml of 1 mM copper sulphate solution; the mixture is kept at Room temperature, change in colour of solution is measured at the interval of lhr, it is observed that complete conversion of copper ions to nanoparticles takes place in 5 hr, the amount of the obtained copper nanoparticles is 20 mg/ml;
Example 6;
Synthesis of bimetallic nanoparticles from silver nitrate and chloroauric acid;
Bimetallic nanoparticles are synthesized by adding 10ml aqueous stem extract of Ceriops tagal as prepared in example 1 to 190 ml of 1:1 aqueous solution of 2mM AgN03: 0.9mM HAuCl4, the mixture is kept at Room temperature, change in colour of solution is measured at the interval of 10 min, it is observed that complete conversion of ions to bimetallic nanoparticles takes place in 30 min. the amount of the obtained bimetallic nanoparticles is 200 mg/ml;
Example 7;
Synthesis of bimetallic nanoparticles from stiver sulphate and chloroauric acid;

Bimetallic nanoparticles are synthesized by adding 10ml aqueous stem extract of Ceriops tagal as prepared in example J to 190 ml of 1:1 aqueous solution oflmM AgS04: 0.9mM HAuCl4, the mixture is kept at Room temperature, change in colour of solution is measured at the interval of 10 min, it is observed that complete conversion of ions to bimetallic nanoparticles takes place in 40 min, the amount of the obtained bimetallic nanoparticles is 120 mg/ml;
Claims;
1. A method of making noble metal nanoparticles by green chemistry techniques comprising
(a) Pulverising Ceriops tagal plant part to fine powder;
(b) Extracting the fine powder in a solvent at an elevated temperature;
(c) Reacting the standard molar solution of noble metal salt with an extract of the Ceriops tagal in the ratio of 5-95 v/v;
2. A method of making noble metal nanoparticles by green chemistry techniques according to
claim 1 wherein Ceriops tagal plant part is stem;
3.A method of making noble metal nanoparticles by green chemistry techniques according to claim 1 wherein solvent is selected from Pentane, Cyclopentane, Hexane, Cyclohexane, Benzene. Toluene, 1,4-Dioxane, Chloroform, Diethyl ether, Ethyl acetate, Acetone, Dimethylformamide (DMF), Acetonitrile (MeCN), Isopropanol (IPA), n-Propanoi, Ethanol, Methanol, Acetic acid, Nitromethane, Water.
4.A method of making noble metal nanoparticles by green chemistry techniques according to claim 1 or 3 solvent is polar solvent selected from Acetonitrile (MeCN), Isopropanol (IPA). n-Propanol, Ethanol, Methanol, Acetic acid, Nitromethane, Water.
5. A method of making noble metal nanoparticles by green chemistry techniques according to claim any of preceding claim wherein solvent is water.
6. A method of making noble metal nanoparticles by green chemistry techniques according to claim 1 wherein temperature is 90-100 °C;

7. A method of making noble metal nanoparticles by green chemistry techniques according to claim 1 wherein in noble metal is selected from the gold salt, silver salt, copper salt.
8. A method of making noble metal nanoparticles by green chemistry techniques according to claim 1 or 8 wherein in gold salt is selected from Potassium gold cyanide Sodium aurothiomalate, Sodium aurothiosulfate, Disodium aurothiomalate, Gold thioglucose, Hydrogen tetrachloroaurate, Chlorauric acid, Aurochloric acid, Aurate(l-), tetrachloro-, Hydrogen aurichloride;
9. A method of making noble metal nanoparticles by green chemistry techniques according to
claim 1 or 8 silver salt is selected from Silver salts such as silver nitrate, silver sulphate,
silver carbonate, silver carbonate purum, oxides of silver.
10. A method of making noble metal nanoparticles by green chemistry techniques according to
claim 1 or 8 copper salt is selected from Salts of the copper includes copper sulphate, copper
halide, copper acetate, copper nitrate, copper (1) sulfide, cupric and cuprous oxides.

Sr.No Salts in
millimolar
concentration Temperature in degrees Colour observed Absorbance at λmax
1. 2 mMAgN03 R.T. Intense brown 455 nm
2. 1 mM Ag2S04 40° C Intense brown 444 nm
3. 0.9 mM HAuC14 40° C Ruby red 556 nm
4. 1 mM CuS04 R.T. Intense brown 500 nm
5. 2 mM AgN03: 0.9 mM HAuCl4, R.T. Grey 535 nm
6. 1 mMAg2S04: 0.9mMHAuCl4 R.T. Dark pink 535 nm
Table 1: Optimization of synthesis process

Sr.No. Nanoparticles
synthesized from
salt Crystal structure 20 of the intense peak (deg) hkl Crystallite
size
1. AgN03 FCC a. 27.756
b. 32.174
c. 46.300 (111) (200) (220) ~6 nm
2. Ag2S04 FCC a. 27.530
b. 31.960
c. 45.980 (111) (200) (220) -5 nm
3. HAuCl4 FCC a. 37.97 (111) ~1 nm
4. CuS04 FCC a. 09.35
b. 10.70 (111) (200) ~0.7nm
5. AgN03 :HAuCl4 FCC a. 27.56
b. 31.97
c. 45.98 (111) (200) (220) ~9 nm
6. Ag2S04:HAuCl4 FCC a. 27.53
b. 31.96
c. 45.97 (111) (200) (220) ~9 nm
Table2: XRD measurements of monometallic and bimetallic nanoparticles.

Sample
FT1R peaks in cm'1
Plant 3306.66 2119.25 1634.46
AgNo3 3271.40 2103.33 1634.52
Ag2S04 3271.38 2108.56 1634.94
HAuCl4 3271.53 2114.3 1634.12 1207.8 1101.5
CuS04 3271.77 2111.01 1634.35
AgN03: HAuCl4 3271.45 2982 2122.53 1634.99 1387.8 1249 1155.1 1077.6
Ag2S04:HAuCl4 3306.52 2110.91 1634.13
Table3: FTIR measurements of bioreduced monometallic and bimetallic nanoparticles.