WO2014174394A2

WO2014174394A2 - Method of synthesis and composite thereof

Info

Publication number: WO2014174394A2
Application number: PCT/IB2014/060463
Authority: WO
Inventors: Dr. Swadhin K. MANDAL; Subhankar SANTRA
Original assignee: Mandal Dr Swadhin K; Santra Subhankar
Priority date: 2013-04-25
Filing date: 2014-04-06
Publication date: 2014-10-30
Also published as: WO2014174394A3

Abstract

The subject matter provides a method of synthesis of a composite that provides dispersing a carbon derivative and a second compound in a solvent to obtain a mixture, wherein the second compound is a salt of a metal; and heating the mixture to alter chemical nature of the second compound and to form the composite in the mixture, wherein the composite includes nanoparticles of the metal anchored with the carbon derivate. The heating includes pyrolysis of the second compound.

Description

"METHOD OF SYNTHESIS AND

COMPOSITE THEREOF"

CROSS-REFERENCE

[001] The subject matter of the research art icle Dr. Swad hin K Mandal at.al, Pal lad ium Nanopart icles on Graphite Oxide: A Recyclable Catalyst for the Synthesis of Biaryl Cores published in ACS Catal., 2013, 3 (12), pp 2776-2789 is incorporated in this specificat ion by reference.

TECHNICAL FIELD

[002] The present subject matter relates to a method of synthesis of a composit ion. More specifical ly, the present subject matter relates to a method of synthesis of a composite having nanopart icles anchored on a carbon derivat ive. Even more specifical ly, the present subject matter relates to a method of synthesis of a composite having metal nanopart icles anchored on a carbon derivat ive. The present subject matter also relates to the composit ion obtained from the method.

BACKGROUND

[003] Synthesizing composites having nanopart icles anchored on carbon derivates has remained a topic of specif ic interest of researchers and industries. Such composites are useful in a number of appl icat ions. Some appl icat ions may include use of the composites for developing and synthesizing core molecules for drug compounds etc.

[00 ] Pharmaceut ical industry is spend ing tremendous amount of money for developing drugs. About a tril l ion dol lars of business per year is observed during fair part of the first and second decade of 21^st century around top sel l ing drug molecules such as valsartan, telmisartan, agrochemical agent boscal id and select ive PPARy modulator (SPPARMy). At present, the use of noxious phosphine based homogeneous pal lad ium catalyst is considered as a viable route for the preparat ion of core moiet ies of a number of drugs. However, the effect ive syntheses of such core moiet ies with the convent ional catalysts have inherent hassles like the contaminat ion of precious metals with the product as wel l as the "use and throw" nature of the catalyst. Therefore, there is a need to develop a method and composite that may be used mult iple t imes as catalyst in product ion of these moiet ies and the catalyst is substant ial ly free of impurit ies and reduces possibilit ies of the contaminat ion of the moiet ies. Further, it is desirable that the composite is relat ively environment friend ly because of its recyclability in a number of catalyt ic cycles.

SUMMARY

[005] For the purpose of il lustrat ion, fol lowing d iscussion uses a method of synthesis of a composite, Graphite Oxide having anchored Pal lad ium Nanopart icles (GO- PdNPs) and the composite thereof, only as example for explaining the present subject matter. However, it shal l become clear to a person, after read ing this specif icat ion, that the subject matter may be pract iced without depart ing from the spirit of the present subject matter, for synthesis of other composites involving carbon derivates and nanopart icles, includ ing some of the metals such as Au, Ag, Pd, Co, Pd, Co, Au, Ag, Cu, Pt, Ni, Fe, Mn, Cr, V, Ti, Sc, Ce, Pr, Nd, Sm, Gd, Hm, Er, Yb, Al, Ga, Sn, Pb, In, Mg, Ca, Sr, Na, K, Rb, Cs etc.

[006] Synthesis of a composite that has carbon derivat ives and anchored nanopart icles, and that has desired structure and characterist ics present a number of chal lenges. This is because the structure and characterist ics of the composite greatly depend on method by which the composite is synthesized. Often a method for synthesizing the composite compels introducing reducing agents, surfactants and/or reagents during the process of synthesis of the composite. Such introduct ion also cause adverse effects on the structure and characterist ics and results in a poor quality composite. This presents a d ifficult situat ion, wherein, on one hand, the reducing agents, surfactants and/or reagents are required for the synthesis of the composite, on the other hand the quality of the synthesized composite is adversely affected because of the same reducing agents, surfactants and/or reagents. Therefore, to obtain higher quality of the composite possessing superior quality, a method for the synthesis of the composite is required that not only successful ly synthesizes the composite but also does not have adverse effects caused due to introduct ion of the reducing agents, surfactants and/or reagents. [007] The composite of the present subject matter may be general ly used as catalyst. The convent ional methods produce catalysts that are homogeneous in nature and the exist ing scient ific era lacks a potent ial heterogeneous catalyst which may be environmental ly benign and economical ly attract ive from the point of reusabil ity against the homogeneous catalyst. The homogeneous catalysts tend to d issolve in solvent in which f inal product is obtained and therefore present a considerable chal lenge in reclaiming the catalyst and/or purifying the f inal product. Whereas, the heterogeneous catalysts tend not to d issolve and therefore reclaiming the catalyst and purifying the f inal product turns out to be considerably convenient. The process of extract ing homogeneous catalyst from final product mixture is d ifficult and often leaves the catalyst impurity to a degree and it may not be used again as the catalyst may be destroyed. Whereas, extract ing heterogeneous catalyst from the final product may be as simple as f iltering and washing the catalyst and the process leaves the catalyst structure substant ial ly unaltered therefore enabl ing reuse of the catalyst for its catalyt ic act ivity. Further, obtaining the composite with specific structure, characterist ics, d istribut ion of nanopart icles, and substant ial ly free of impurit ies has been chal lenging. The present subject matter provides synthesis of composite that may be used as heterogeneous catalyst and/or is substant ial ly free from contaminat ions, have desired structural characterist ics, d istribut ion of nanopart icles and/or demonstrates reusabil ity. The present subject matter provides a composite that upon using as a catalyst remains act ive over many cycles. In some examples, the composite of the present subject matter demonstrates tolerance across mult iple drug moiet ies synthesis. Further the composite does not al low the metal part to be lost as an impurity in the solvents used in the chemical react ions in which the composite is used as a catalyst.

[008] To achieve the above -and those other object ives which wil l become apparent to a person after read ing this specif icat ion- the present subject matter provides a method for the synthesis of the composite, that does not require introducing any reducing agents, surfactants and/or reagents while st il l achieves the synthesis of the composite. The present subject matter ut il izes pyrolysis of a metal salt in the presence of carbon derivat ive in a solvent for the preparat ion of composite. Pyrolysis is a thermo- chemical decomposit ion of a material at elevated temperatures. [009] According to one aspect of the present subject matter, the method provides dispersing a carbon derivative and a second compound in a solvent to obtain a mixture, wherein the second compound is a salt of a metal; and heating the mixture to alter chemical nature of the second compound while maintaining structural order of the carbon derivative substantially unaltered to form the composite, and the composite includes nanoparticles of the metal anchored on the carbon derivate. The heating comprises heating the mixture at a temperature, wherein the temperature is selected from a range of temperature and the range of temperature is between a first temperature and a second temperature, wherein the first temperature is higher than the temperature required for altering the chemical nature of the second compound and the second temperature is lower than the temperature at which structural order of the carbon derivative deforms and wherein the first temperature is lower than the second temperature. In one aspect, the first temperature is about 90 degree Celsius and second temperature is about 140 degree Celsius. Dispersing the carbon derivative and the second compound to obtain the mixture and heating as discussed above, achieves the synthesis of the composite without requiring introduction of the reducing agents, surfactants and/or reagents. Therefore resulting in a higher quality of the composite for the reasons discussed above. According to one aspect, the ratio of carbon derivative and the salt of metal is 2:1.

[0010] According to one aspect the second compound is a salt at least one metal or alloy of one metal selected from Au, Ag, Pd. Co, Pd, Co, Au, Ag, Cu, Pt, Ni, Fe, Mn, Cr, V, Ti, Sc, Ce, Pr, Nd, Sm, Gd, Hm, Er,Yb, Al, Ga, Sn, Pb, In, Mg, Ca, Sr, Na, K, Rb, and Cs.

[0011] According to one aspect the dispersing comprises the dispersion of the carbon derivative and the second compound substantially uniformly across the solvent. In one aspect, the dispersing comprises subjecting the solution to ultrasonic exposure. According to a further aspect, the heating alters chemical valance of the second compound. In a further aspect, the carbon derivative may be graphite oxide. In some other aspect, the second compound may be palladium salt. In an aspect, the palladium salt has chemical valance +2. In another further aspect, the second compound is palladium acetate. According to one aspect of the heating alters the chemical valance of the palladium from +2 to zero. [0012] Accord ing to an aspect, the solvent may be an organic solvent. In a further aspect, the solvent may be a dry organic solvent. In another aspect, the solvent is toluene.

[0013] Accord ing to an aspect, the method is performed in substant ial ly inert environment. In a further aspect, the substant ial ly inert environment is substant ial ly free of oxygen and moisture. In a further aspect, the substant ial ly inert environment comprises any one or more of vacuum, nitrogen, argon, xenon and a substant ial ly inert gas. Accord ing to a further aspect, the method provides extract ing the composite. In one aspect, the extract ing includes filtering, washing and drying.

[001 ] Accord ing to an embod iment, the subject matter provides a composite obtained from the method d iscussed above. The composite comprises nanopart icles of a metal anchored on a carbon derivat ive, and the composite is obtained by d ispersing the carbon derivat ive and a salt of the metal in a solvent to obtain a mixture; and heat ing the mixture at a temperature that enables altering chemical nature of the salt of the metal to form the composite while substant ial ly maintaining structural order of the carbon derivat ive. Accord ing to one aspect, the carbon derivat ive is graphite oxide, the second compound is pal lad ium acetate, the solvent is toluene. Accord ing to an aspect of the subject matter, the salt has at least one metal selected from Au, Ag, Co, Pd, Co, Au, Ag, Cu, Pt, Ni, Fe, Mn, Cr, V, Ti, Sc, Ce, Pr, Nd, Sm, Gd, Hm, Er, Yb, Al, Ga, Sn, Pb, In, Mg, Ca, Sr, Na, K, Rb, and Cs. Accord ing to a further aspect of the subject matter, the composite is graphite oxide support pal lad ium nanopart icles (GO-PdNPs) obtained by pyrolysis of pal lad ium acetate. In one aspect, the composite comprises nanopart icles of a metal anchored on a carbon derivat ive wherein the rat io of carbon derivat ive and metal is 2:1. In further aspect, the composite is GO-PdNPs.

BRIEF DESCRIPTION OF DRAWINGS

[0015] The subject matter shal l now be described with reference to the accompanying figures accord ing to one or more embod iments of the present subject matter, wherein: [0016] FIG. 1 shows a schemat ic d iagram of a graphite oxide structure;

[0017] FIG. 2 shows a schemat ic d iagram accord ing an embod iment of a method of the present subject matter;

[0018] FIG. 3 shows an Atomic Force Microscopy (AFM) image of GO-PdNPs;

[0019] FIG. (A) and FIG. 4(B) show a Field Emission Scanning Electron Microscope (FE-SEM or simply SEM) images of graphite oxide and GO-PdNPs respect ively;

[0020] FIG. 5(A) and FIG.s(B) show Transmission Electron Microscopy (TEM) images of the catalyst from ethanol ic, Dimethylformamide d ispersion (DMF-d ispersions) respect ively;

[0021] FIG. 6 shows Powder X-ray Diffract ion (PXRD) patterns of graphite, graphite oxide, and GO-PdNPs;

[0022] FIG.7 shows thermo-gravimetric analysis graphs of graphite, graphite oxide, and GO-PdNPs;

[0023] FIGs. 8(A) and 8(B) are Ultra-Violet (UV), Visible (Vis) and Near Infra-Red (NIR) rad iat ion (UV-Vis-NIR) spectra of DMF-d ispersions of GO and GO-PdNPs;

[0024] FIG. 9(A) and FIG g(B) show recyclability charts of the catalyt ic react ion lead ing to the boscal id nucleus and telemisartan nucleus;

[0025] FIG. 10 shows examples of some top-sel ling drug molecules containing the biaryl core that may employ composite of the present subject matter as catalysts;

[0026] FIGs. 11(A) through 11 (D) show TEM image of the composite after mult iple catalyt ic runs, High Resolut ion TEM (HRTEM) image of the composite, TEM image of the composite and selected area electron d iffract ion pattern respect ively; and

[0027] FIG. 12 shows X-ray photoelectron spectroscopy (XPS) of Pd 3d core level in GO-PdNPs sample according to an embodiment of the present subject matter. DETAILED DESCRIPTION

[0028] Before the present subject matter is described in further detail, it is to be understood that the subject matter is not limited to the particular embodiments described, and may vary as such. It is also to be understood that the terminology used throughout the preceding and forthcoming discussion is for the purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that as used herein, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise.

[0029] US Patent Publication number US 2013/0211106 Ai attempts production of graphene and nanoparticle catalysts supported on graphene using microwave radiation. The aforementioned publication provides methods and apparatuses which employ microwave radiation to reduce 1) solid graphite oxide (GO) to graphene, or 2) solution phase GO; as well as solid and solution phase methods to reduce a mixture of GO plus one or more metals to produce nanopart icle catalysts supported on graphene.

[0030] The problem with the above solution is that it employs microwave radiation to the extent where the graphite oxide and metal salt both are chemically altered, while the graphite oxide gets reduced to graphene and the metal salt also get altered. This may be understood by following equation (1). In the following equation (1) A is graphite oxide, B is metal salt, A' is graphene and B' is metal nanopart icles.

A

(Graphite Oxide)

Microwave Radiations

+ AB ,..(!}

(Graphene and Metai Nanopartides)

B

(Metal Salt}

[0031] Altering graphite oxide to graphene is disadvantageous, which is apparent, after reading this specification, that the graphite oxide shows better affinity and distribution of the nanoparticles. This is because graphene and the graphite oxide are structurally different from each other. Graphite oxide provides better grip of the nanoparticles because it has relatively higher number of oxygen functionalities to interact chemically with the metal nanopraticles, as compared to the graphene. The graphene supported palladium nanoparticles are not great recyclable catalyst because of the fact that these catalysts cannot hold the metal nanoparticles strongly during catalytic cycles. A better grip over the nanoparticles in a composite provides the composite higher reusability when the composite is used as a catalyst. Further a better affinity of the nanoparticles leaves relatively less contamination of the catalyst and it does not leach during the catalytic process. The present subject matter provides selectively heating the graphite oxide and metal salt such that only metal salt is reduced or chemically altered, without altering the structure of the graphite oxide. The present subject matter may be represented by equation (2). In equation (2) A is graphite oxide, B is metal salt, and B' is metal nanoparticles.

A

(Graphite Oxide)

Selective Heating

+ AB¹ ...{2}

(Graphite Oxide and Metal Nanoparticles)

B

(Metal Salt)

[0032] The distinguishing features of the present subject matter with that of the aforementioned US Patent Publication may be observed by comparing equation 1 above and the equation (2). More details of the subject matter shall become clear in the following discussion.

[0033] FIG.1 shows a schematic diagram of structure of a graphite oxide. FIG.1 shows representative function groups 101, 103, 105, 107 and 109. The functional groups 103 and 107 demonstrate somewhat similar chemical behavior.

[003 ] FIG 2 shows a schematic diagram of a method 200 according to one embodiment of the present subject matter. The method 200 is a method of synthesis of a composite that includes nanoparticles of a metal anchored on a carbon derivative.

[0035] According to one aspect of the method 200, at block 201, the carbon derivative and a second compound is dispersed in a solvent to obtain a mixture. The second compound is a salt of the metal. In one example, the carbon derivative is graphite oxide. In another example, the salt is a palladium salt. In some other example, palladium salt has chemical valance +2. In some other example, the second compound is palladium acetate. In some embodiments, the block 201 is performed in the substantially inert environment. [0036] The block 201, may include a block 211. At block 211, the carbon derivat ive and the second compound are mixed. At block 211, the mixed carbon derivat ive and the second compound may be subject to a substant ial ly inert environment. Subject ing the mixed carbon derivat ive and the second compound to the substant ial ly inert environment removes act ive or react ive elements. In some examples, elements such as oxygen and moisture are removed from the substant ial ly inert environment. In some other examples, the substant ial ly inert environment comprises any one or more of vacuum, nitrogen, argon, xenon and a substant ial ly inert fluid. Accord ing to one example, the graphite oxide and the pal lad ium acetate are mixed and subjected to the substant ial ly inert environment.

[0037] The block 201, may further include a block 221. At block 221, the mixed carbon derivat ive and the second compound are d ispersed in the solvent to obtain the mixture of the solvent, the carbon derivat ive and the second compound. In some example, the solvent may be an organic solvent. In some other example, the solvent may be a dry organic solvent. In a further example, the solvent may be toluene. At block 231, for d ispersing the carbon derivat ive and the second compound substant ially uniformly in the solvent, the mixture may be subjected to an ultrasonic exposure. Exposing the mixture to ultrasound enhances d istribut ion of the carbon derivat ive and the second compound across the solvent. At block 231, the second compound which is the salt of the metal may d issolve in the solvent. Accord ing to one example, the graphite oxide and the pal lad ium acetate are d ispersed in the toluene at block 231. At the block 231, pal lad ium acetate may d issolve in toluene and exposing the mixture of the toluene, pal lad ium acetate and the graphite oxide to ultrasound may enhance d istribut ion of pal lad ium acetate over graphite oxide.

[0038] The method 200 includes a block 203. In some examples, the block 203 may be within the block 201. At block 203 the mixture is heated under substant ial ly oxygen free environment. This process is also known as pyrolysis in which a material is thermo chemical ly decomposed. The heat ing may be performed by exposing the mixture to microwaves or by exposure of the mixture to a flame of a gas burner or keeping the mixture in a hot oil bath or by any other means that achieves object of extract ing from or impart ing to the mixture a predetermined amount of energy. Accord ing to an aspect, the chemical natu re of the second compound is altered by heat ing. That is, in one example, the chemical natu re of the pal lad ium acetate is altered. The present subject matter, on the other hand provides altering the chemical nature of the second compound without introducing any reducing agents or surfactants. Instead, the chemical nature of the second compound is altered by select ively heat ing the mixture at a temperature that is high enough to alter the chemical nature of second compound but is below the temperature at which the carbon derivat ive deforms or changes or alters its structure or chemical nature. In one example, the composite is GO-PdNPs. Removing the requirement of introducing reducing agents, surfactants and/or reagents in the mixture of graphite oxide, pal lad ium acetate and the toluene is useful because they may react with the graphite oxide of the mixture and either reduces the number of funct ional groups (ioi, 103, 105, 107 and 109 shown in FIG.1) or change the structure of the graphite oxide in the composite thereby provide a poor qual ity composite. The nanopart icles of metal get anchored on the funct ional groups. Therefore reduced funct ional groups of graphite oxide means less anchoring groups available for nanopart icles and hence result ing in a composite that may be less useful for some appl icat ions. One such adverse effect is the composite may not be recyclably used as catalyst in synthesis of some core molecules of drug compounds. The present subject matter achieves alterat ion of chemical nature of the second compound that is the pal lad ium acetate by heat ing the mixture. However, heat ing of the mixture is performed such that, it achieves the chemical alterat ion of the second compound but at the same t ime it does not deform the structure of the graphite oxide. Therefore, leaving large nu mber of funct ional groups for anchoring the nanopart icles. The mixture is heated at a temperature, wherein the temperature selected from a range of temperatures, wherein the temperature is between a first temperature and the second temperature. The first temperature is higher than the temperature at which the chemical alterat ion of the second compound takes place and the second temperature is lower than the temperature at which the carbon derivat ive deforms. Select ively heat ing the mixtu re ensures that the desired composite is achieved without the introduct ion of reducing agents, surfactants and/or reagents. Therefore, the composite synthesized by this method is free of adverse effects caused by the introduct ion of reducing agents, surfactants and/or reagents in the mixture. I n one example, the mixture of toluene, graphite oxide and pal lad ium acetate is heated at a temperature that is in the range of about 90 degree Celsius and about 120 degree Celsius. Altering chemical nature of the second compound also starts forming metal nanopart icles. The metal nanopart icles get anchored on the carbon derivate to form the composite. Accord ing to one example, heat ing the mixture of the toluene, graphite oxide and pal lad ium acetate reduces the chemical valence of the pal lad ium acetate from +2 to o while having minimal affect on the structure and characterist ics of the graphite oxide. Altering the chemical nature of the pal lad ium acetate also starts forming of the pal lad ium nanopart icles, these nanopart icles form the composite GO-PdNPs.

[0039] At the block 205, the composite is extracted. The extract ing may include f iltering the mixture. The mixture may be filtered through a membrane and washed and dried to obtain the composite. In one example, the membrane is a paper. In one example, the mixture having the composite of GO-PdNPs is f iltered through the membrane of 0.22 microns. The sol id obtained from filtering is washed using acetone, ethanol and d iethyl ether. The washed solid may be dried under vacuum to obtain the composite.

[00 0] The fol lowing d iscussion provides details of a method of synthesis of graphite oxide. In one example, the method also provides synthesis of graphite oxide. For synthesis of graphite oxide, about 5 g of graphite (Sigma-Aldrich), about 100 mL of concentrated sulfuric acid (H₂S0 98%), and about 2.5 g sod ium nitrate (NaN0₃) may be mixed to obtain a f irst mixture. About 20 grams of potassium permanganate (KMn0 ) may be then added to the f irst mixture. In one embod iment, the temperature of the f irst mixture is maintained at 35 degree Celsius. For maintaining the temperature, the mixture may be iced bathed. During this process, the first mixture may be st irred. In one possibil ity the first mixture may be st irred using magnet ic st irrer. In this example, st irring of about an hour results in the f irst mixture viscous enough that it may not be st irred easily anymore. The viscous mixture is cooled to reach a temperature about 10 degree Celsius. The viscous mixture may be d iluted by add ing about 1 liter of deionized (Dl) water. In some embod iments, the d iluted mixture may change color to dark brown upon d ilut ing. Hydrogen peroxide (H₂0₂, 30%) may be then added to the d iluted mixture. In some embod iment, the d iluted mixture may change color close to green upon add ing hydrogen peroxide. At this point, the graphite oxide is almost ready, which can be recovered by f iltering. To aid filtrat ion, 50 mL of concentrated hydrochloric acid (HCI, 37.5%) may be added and st irring is performed for about 30 mins. The graphite oxide may be recovered by following filtering process of final mixture: (i) washing in deionized water, centrifugation followed by filtration; (ii) washing in ethanol/HCI solution, centrifugation followed by filtration; (iii) washing in diethyl ether, centrifugation followed by filtration; (iv) washing in diethyl ether followed filtration. The resultant mass is graphite oxide, the graphite oxide may be air dried and used for obtaining the composite GO-PdNPs in the following process.

[00 1] The following discussion shall provide more details of the method 200 in respect of obtaining the composite GO-PdNPs. According to one example, about 600 mg graphite oxide may be combined in about 300 mg of palladium acetate and may be then subjected to vacuum for about 1 hour. Subjecting to vacuum restricts access to oxygen, moisture and other undesired reactive volatile elements. The ratio of the graphite oxide and palladium acetate generally may be about 2:1 of weights. The combined graphite oxide and palladium acetate may be then introduced in dry toluene to obtain a mixture. In one possibility, the mixture may be obtained in an atmosphere having nitrogen or argon or any other non-reactive fluid. In one possibility the dry toluene may be about 300 ml_. The mixture may be then subjected to ultrasonic exposure at room temperature for about 1 hour or so long as the mixture becomes nearly homogenous mixture. During this period, exfoliation of graphite oxide occurs followed by the arrest of palladium acetate molecules along over the graphite oxide sheet. The mixture may be then heated at in a temperature range about 90-120 degree Celsius for about 4 hours. The time for heating the mixture may be determined based on the quantity of the mixture. Heating the mixture results into forming the composite in the mixture. The mixture may be then cooled at about 25 degree Celsius and filtered and washed with ethanol, acetone and diethyl ether. In one example, the mixture may be filtered through 0.22 μηη membrane paper (Millipore). The resultant residue is the composite. The composite may be dried under vacuum prior to use.

[00 2] The composite GO-PdNPs is characterized using variety of scientific techniques including AFM, X-ray diffraction (XRD), electron microscopy (SEM or TEM or both) etc. Results of some of the characterizations are discussed in the subsequent discussion. Powder X-ray diffraction (PXRD) data are collected on a Rigaku Smart Lab diffracto meter. TEM analysis is performed either on a JEOL JEM 2011 or on a FEITECNAI G2 20 S-TWIN operated at 200 kV. UV-vis-NIR spectral stud ies are carried out on a HITACHI UV4100 spectrophotometer. AFM stud ies are carried out on an NTMDT instrument, model no. AP-oioo, in semicontact mode after placing a 5 μΙ_ drop of d ispersed solut ion in EtOH containing GO-PdNPs on a cleaned glass coverslip slide and al lowing it to dry in the air.

[00 3] FIG. 3 shows AFM image of GO-PdNPs. FIG. shows FE-SEM images of (A) graphite oxide and (B) GO-PdNPs. FIG. 5(A) shows TEM images of the catalyst (GO-PdNPs) from ethanolic and FIG. 5(B) DMF-d ispersions. Microscopic techniques such as AFM [FIG.3], SEM [FIG. (B)], and TEM [FIG. 5(A) and FIG. 5(B)] of GO-PdNPs reveal that spherical shaped metal lic nanopart icles are d istributed uniformly over the GO sheet. The TEM images further unveil that pal lad ium nanopart icles have an average d iameter of 13-14 nm.

[00 ] FIG. 6 shows PXRD patterns of graphite 601, graphite oxide 603, and GO- PdNPs 605. PXRD patterns reveal structural d ivergence of the graphite, graphite oxide and GOPdNPs. The characterist ic (002) peak of graphite, observable at 26.5⁰ (2Θ), relocate at 10.04° (2Θ) in the case of graphite oxide [FIG. 6]. In add it ion to the shift of (002) peak posit ion, the increment in the interlayer separat ion value from graphite to graphite oxide (from 3.36 to 8.8 Λ) reflects inclusion of various oxygen containing funct ional groups in between the layers during the oxidat ion process (Yeh, T.-F. et. ai, Adv. Funct. Mater. 2010, 20, 2255-2262). The PXRD pattern of GO-PdNPs exhibits wel l-defined peaks at 39.7°, 46.5°, 67.2°, and 80.9°, which can be attributed to the d ist inct ive (111), (200), (220), and (311) crystal line planes for a face centered cubic pal lad ium (o) latt ice, respect ively (Yang, S. et.al J. Electrochim. Acta 2012, 62, 242-249). The preservat ion of (002) peak at 10° for GO-PdNPs validates restorat ion of the wel l-ordered lamel lar structure of the GO sample in GO-PdNPs.

[00 5] FIG.7 shows Thermo-Gravimetric Analysis (TGA) graphs of graphite 701, graphite oxide 703, and GO-PdNPs 705. The structural d ifference is captured in the TGA analysis of graphite, GO, and GO-PdNPs samples [FIG. 7]. Graphite oxide d isplays the weight loss in two successive steps. The f irst one is a steady weight loss (up to 30%, attributed to the vaporizat ion of intercalated water molecules) which is not iced around 100 °C fol lowed by a rapid loss (-65%, pointed toward the decomposit ion of funct ional groups) around 205 °C in comparison with nearly o% weight loss of the parent graphite material in the experimental temperature range. In contrast, GO-PdNPs shows overal l 38% weight loss in the respective temperature range.

[00 6] FIGs.8(A) and 8(B) show UV-Vis-NIR spectra of DMF-dispersions of GO 801, 805 and GO-PdNPs 803, 807 respectively. UV-Vis-NIR spectroscopy of GO in DMF features three type of absorpt ion bands; (i) a broad band around 320 nm [FIG.8(A)], (ii) sharp peaks at 810 nm [FIG.8(A)] and (iii) at 2012 nm [FIG.8(B)]. Under identical conditions, the first two peaks are absent in case of GO-PdNPs while generating a new one at 1925 nm [FiG. 8(B)]. The absorption intensity of 2012 nm peak is reduced after palladium nanoparticle's decoration. A similar pattern of intensity reduction in NIR region is also observed when PdNPs are anchored onto carboxylic acid functionalized single walled carbon nanotubes (Santra, S.et. al. RSC Adv.zoiz, 2, 7523-7533).

[00 7] The composite prepared in accordance with the present subject matter may be employed in electrocatalysis, gas detection studies, hydrogenation, oxidation, reduction, reactions and as a catalyst in cross-coupling reactions. In an aspect, the Suzuki-Miyaura coupling reaction is chosen as a model to check the feasibility of GO- PdNPs as a heterogeneous catalyst. The Suzuki react ion is the organic react ion classified as a coupling reaction between a boronic acid and a halide. The reaction is catalyzed by a palladium(o) complex. It is observed that GO-PdNPs exhibits excellent catalytic activity for a variety of aryl as well as heteroaryl halides containing nitro (-NO2), acetyl (-C(O)Me), hydroxyl (-OH), and amine (-NH2) etc functional groups delivering respective biaryl products nearly in quantitative yield.

[00 8] In an embodiment, recycling aptitude of GO-PdNPs is tested by synthesizing of core biaryls for boscalid and telmisartan in a recyclable manner. The recycling experiments are carried out after the isolation of the solid catalyst through membrane filtration techniques followed by a fresh batch of reactions with the recovered catalyst under identical reaction conditions. After completion of each catalytic cycle, the reaction mixture is first cooled down to room temperature and then filtered through a 0.22 μηη membrane filter, washed sufficiently with ethanol and acetone, and finally with diethyl ether. The next catalytic cycle is carried out using the dried black residue collected on the membrane filter. The recycling experiments are performed maintaining the catalyst to substrate ratio. The recycling experiments for boscalid and telmisartan nuclei are performed under dioxane-NaOMe and 'PrOH-K₂C0₃ combinations, respectively. FIG. g(A) and FIG. g(B) show recyclability charts of the catalytic reaction leading to the boscalid nucleus and telmisartan nucleus, respectively. The results establish that GO-PdNPs remains equally active for 16 and more cycles and 12 or more catalytic cycles for the synthesis of boscalid [FIG.9(A)] and telmisartan nuclei [FIG.g(B)], respectively, without any decay of the catalytic activity during the consecutive cycles. This recycling outcome of the present catalyst clearly points out the robust and sustained nature of the nanocatalyst. Further, a control catalyt ic experiment is performed using a physical mixture of GO and Pd(OAc)2 for the synthesis of the boscalid nucleus under identical reaction condition (dioxane-NaOMe combination), adopted with the isolated GO-PdNPs. It shows that the first catalytic cycle leads to a much lower yield (34%) of the desired product as compared to the GO-PdNPs catalyst, and the recyclability experiment leads to no conversion in the second cycle. This indicates that the isolation and prior preparation of the catalyst may provide better results. This behavior may be due to the fact that the palladium particles gets gripped during the isolation and prior preparation overthe GO surface to ensure sustained recyclability.

[00 9] FIG.10 shows Examples of some top-selling drug molecules containing the biaryl core that may employ composite of the present subject matter. According to some resources, sales of Micardis registered about US $ 704 million in 2004. According to some other sources the sales of Diovan is registered as high as US $ 3.1 billion in the year 2004; Boscalid, sales were registered as high as€ 150 million. Leading pharmaceutical company GSK has completed phase 1 clinical test forthe treatment of type 2 diabetes mellitus.

[0050] FIGs.11 (A) through (D) show TEM images. In that, FIG.11(A) is the TEM image of the catalyst after the 16th cycle of boscalid nucleus synthesis from a very dilute ethanolic dispersion, FIG.ii(B) is HRTEM image of the same revealing the lattice fringe of PdNPs. FIG.ii(C) is TEM image of the catalyst after the 12th cycle of telmisartan-nucleus synthesis from a very dilute ethanolic dispersion and FIG.ii(D) selected area electron diffraction pattern of C. HR-TEM studies after 16th and 12th catalytic cycles reveal that during the course of the syntheses of boscalid and telmisartan nuclei, respectively, the palladium particles still anchored to the GO surface for further catalytic runs despite the harsh catalytic reaction conditions [FIG.n(A), FIG.n(C)]. [0051] XPS analysis demonstrates that the GO-PdNPs sample contains mainly Pd metal with a signif icant amount of Pd-0 and Pd-C bonded species. FIG. 12 represents a comparison of the Pd 3d core level XPS spectra for the GO-PdNPs sample before catalysis [shown in top of FIG. 12] and after catalysis [shown in bottom of FIG. 12]. The after catalysis sample is prepared from the catalyt ic run lead ing to the synthesis of -methyl biphenyl under a d ioxane- NaOMe combinat ion. The Pd 3d core level spectrum of the sample after catalysis shows metal lic Pd as wel l as Pd-0 and Pd-C bonded species.

[0052] Accord ingly, the composite when used as a catalyst, the composite remains act ive for at least 16 consecut ive catalyt ic cycles without losing the catalyt ic act ivity. A number of cycles more than 16 may be carried out. Further, the composite does not release the metal part as an impurity in the solvents used in the used in the chemical react ions in which the composite is used as a catalyst. The sustained catalytic activity of the present catalyst is attributed to a strong multi-centered bonding interaction with palladium nanoclusters and different chemical anchoring points present on the GO surface, which holds the palladium nanoclusters from leaching during catalysis.

[0053] Further, the below TABLE A table shows a comparison of yields obtained accord ing to present subject matter and convent ional methods.

Table A

[005 ] The yield -I represent yield from react ion cond it ion: Pd(OAc)2 (2.2 mg), aryl hal ide (1 mmol), boronic acid (1.5 mmol) and base (2 mmol) reacted in 5 mL of solvent under appropriate cond it ion. And Yield -II shows yields accord ing to present subject matter. It clear from the above table that the present subject matter result in better yields. [0055] Accord ing to a further aspect, the composite of present subject matter shows other advantage over convent ional methods. For example, below react ion shows comparison between convent ional industrial rout of preparing boscalid and as against the one pot rout that may be employed using the composite of present subject matter as catalyst,

Reaction

[0056] Convent ional industrial rout for synthesis of boscal id does not employ haloaryl amine for synthesis of biaryls. This is because, the amine in haloaryl amine tend to contaminate and poison catalyst in Suzuki coupling and therefore result in a contaminated f inal product as wel l as contaminated catalyst. In this process the catalyst is often becomes unusable for further catalyt ic purposes, because funct ional group on which the pal lad ium nanopart icles latch ends up react ing with the amine group and hence the pal lad ium nanopart icles are left with reduced numbers of funct ional groups to latch on and thereby rendering the catalyst unusable as catalyst, as wel l as contaminat ing the final product. Therefore, instead of using haloaryl amine, the industry employs mult i step process for synthesis of molecules such as boscal id which employ amine group. In this process, the haloaryl nitrobenzene is used for in Suzuki coupl ing to obtain nitrobiphenyl. The nitrobiphenyl is then hydrogenated to obtain biaryl that has an amine group as shown above. The hydrogenat ion process is expensive and environmental ly unfriend ly. [0057] On the other hand, the catalyst of the present subject matter shows robustness even with haloaryl amine and therefore may produce the boscal id d irectly by employing the haloaryl amine in the Suzuki coupling removing the requirement of the expensive and hazardous step of hydrogenat ion as shown in the above react ion. The catalyst of the present subject matter, not only remains substant ial ly unaltered during the coupling process even with aryls such has haloaryl amines but also shows reusability. The one-pot synthesis of boscalid may be accompl ished by introducing 2-nicot inyl chloride after the cross-coupling react ion is complete. Accord ing to an aspect, the method may yield about 67% of isolated boscalid. The GO-PdNPs may be used for number of consecut ive cycles in cross-coupling react ion of haloaryl amine and boronic acid to achieve quant itat ive yield of '-chlorobiphenyl-2-amine.

[0058] While the subject matter may be suscept ible to various mod ificat ions and alternat ive forms, specific embod iments have been shown by way of example in the drawings and have been described herein. Alternate embod iments or mod ificat ions may be pract iced without depart ing from the spirit of the subject matter. The drawings shown are schemat ic drawings and may not be to the scale. While the drawings show some features of the subject matter, some features may be omitted. In some other cases, some features may be emphasized while others are not. Further, the methods d isclosed herein may be performed in manner and/or order in which the methods are explained. Alternat ively, the methods may be performed in manner or order d ifferent than what is explained without depart ing from the spirit of the present subject matter. It should be understood that the subject matter is not intended to be l imited to the part icular forms d isclosed. Rather, the subject matter is to cover al l mod ificat ions, equivalents, and alternat ives fal ling within the spirit and scope of the subject matter as described above.

Claims

What is claimed is:

1. A method of synthesis of a composite comprising: d ispersing a carbon derivat ive and a second compound in a solvent to obtain a mixture, wherein the second compound is a salt of a metal; and heat ing the mixture to alter chemical nature of the second compound while maintaining structural order of the carbon derivat ive substant ial ly unaltered to form the composite, and the composite includes nanopart icles of the metal anchored on the carbon derivate.

2. The method of claim ι, wherein the rat io of carbon derivat ive and the salt of metal is 2:i.

3. The method of claim 1, wherein heat ing includes pyrolysis of the second compound in presence of the carbon derivate. it. The method of claim 1, wherein the solvent is toluene.

5. The method of claim 1, wherein the method is performed in a substant ial ly inert environment that is substant ial ly free of oxygen and moisture and comprises any one or more of vacuum, Nitrogen, Argon, Xenon and a substant ial ly inert gas.

6. The method of claim 1, wherein the carbon derivat ive is graphite oxide.

7. The method of claim 1, wherein the second compound is a salt at least one metal selected from Au, Ag, Co, Pd, Co, Au, Ag, Cu, Pt, Ni, Fe, Mn, Cr, V, Ti, Sc, Ce, Pr, Nd, Sm, Gd, Hm, Er, Yb, Al, Ga, Sn, Pb, I n, Mg, Ca, Sr, Na, K, Rb, and Cs.

8. The method of claim 1, wherein the second compound is pal lad ium acetate.

9. The method of claim 1, wherein the method comprises extract ing the composite from the mixture, the extract ing includes f iltering, washing and drying, wherein, extract ing includes washing the mixture in any one or more of ethanol, acetone and d iethyl ether.

10. The method of claim 1, wherein the carbon derivat ive is graphite oxide (GO), the second compound is pal lad ium acetate, the solvent is toluene and the temperature range between which the mixture is heated ranges between about 90 degree Celsius and about 140 degree Celsius and the composite is graphite oxide based pal lad ium nanopart icles (GOPd-NPs).

11. A composite comprising of nanopart icles of a metal anchored on a carbon derivat ive, and the composite is obtained by d ispersing the carbon derivat ive and a salt of the metal in a solvent to obtain a mixture; and heat ing the mixture at a temperature that enables altering chemical nature of the salt of the metal to form the composite while substant ial ly maintaining structural order of the carbon derivat ive.

12. The composite of claim 11, wherein the rat io of carbon derivat ive and the salt of metal is 2:1

13. The composite of claim 11, wherein the carbon derivat ive is graphite oxide.

14. The composite of claim 11, wherein the second compound is pal lad ium acetate.

15. The composite of claim 11, wherein the solvent is toluene.

16. The composite of claim 11, wherein the salt has at least one metal selected from Au, Ag, Co, Pd, Co, Au, Ag, Cu, Pt, Ni, Fe, Mn, Cr, V, Ti, Sc, Ce, Pr, Nd, Sm, Gd, Hm, Er, Yb, Al, Ga, Sn, Pb, I n, Mg, Ca, Sr, Na, K, Rb, and Cs.

17. The composite of claim 11, wherein the composite is graphite oxide su pport pal lad ium nanopart icles (GO-Pd NPs) obtained by pyrolysis of pal lad ium acetate.