Silver Nanoparticles

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Silver Nanoparticles: Synthesis, Characterization and their Application as a Sustainable Catalyst for Organic Transformations Manohar A. Bhosale and Bhalchandra M. Bhanage* Department of Chemistry, Institute of Chemical Technology, Matunga, Mumbai 400 019, India Abstract: Size and shape selective syntheses of nanoparticles and their catalytic applications are gaining considerable interest in the recent years. Homogeneous catalysis is important due to its inherent advantages like mild reaction conditions and high selectivity. However, it suffers with serious drawback of catalyst-product separation and recycles as compared to their heterogeneous counterparts restricting their applications. The use of catalyst in the form of nano-size is an alternative methodology for combination of advantages of heterogeneous and homogeneous catalysis. Silver nanoparticles are important as they find applications in catalysis, organic transformations, synthesis of fine chemicals and organic intermediates. This review covers an overview of the synthesis of Ag nanoparticles, supported Ag nanoparticles and bimetallic Ag-metal nanoparticles Bhalchandra M. Bhanage Manohar A. Bhosale and their characterization by various techniques. The applications of Ag nanoparticles in several organic transformations including C-C, C-N, C-S, C-O bond formation reactions as well as reduction and oxidation reactions are also discussed. The use of Ag nanoparticles in catalysis is advantageous as it avoids the use of ligands; easy separation of catalyst for recyclability makes the protocol heterogeneous and economic. Ag nanoparticles gave good catalytic activity towards desired products due to high surface area. By considering these advantages, researchers have focused their attention towards applications of Ag nanoparticles in catalysis.

Keywords: Ag nanoparticles, characterization, catalysis, organic reaction. 1. INTRODUCTION Noble metal nanoparticles are well known for their novel applications in the field of catalysis, biotechnology, bio-engineering, textile-engineering, water treatment, and metal-based consumer products [1]. The nanoparticles also have wide applications in other areas such as biosensors, labelling for cells, biomolecules and cancer therapeutics, electronics, magnetics, optoelectronics, medicines, optics, catalysis, environmental and information storage [2]. The synthesis of noble metal nanoparticles and their applications in these areas are of interest for further study. The synthesis of size and shape selective nanosize nanoparticles has received considerable interest due to their unique structures, size and their distinct physical, chemical as well as biological properties compared with their bulk counterparts [1]. Silver is a coinage metal which is an important material throughout the history finding several important applications (Fig. 1) [3, 4]. Silver nanomaterials are used for the synthesis of industrially important compounds in pharmaceuticals, agrochemicals and their intermediates [5]. Several researchers have developed novel methods for the synthesis of Ag nanoparticles along with their applications in various fields such as plasmonics, sensors, opticals, electrochemicals, therapeutics, biomolecular detection and catalysis [2, 6]. The synthesis of Ag nanoparticles is also important because of their excellent optical properties such as surface-enhanced Raman scattering (SERS) [7] and plasmonic resonance [5]. Ag nanoparticles also showed the biological properties such as antimicrobial i.e. antibacterial, antifungal, antiviral activity [8-14], antioxidant, anticancer, cytotoxic [15-17], antiproliferation against human lung cancer cells [18], a hepatocurative activity [19] and larvicidal activity [20]. *Address correspondence to this author at the Department of Chemistry, Institute of Chemical Technology, Matunga, Mumbai 400 019, India; Tel: +91 22 3361 2601; Fax: +91 22 3361 1020; E-mails: [email protected]; [email protected]; [email protected] 1385-2728/15 $58.00+.00

Present review covers the synthesis of Ag nanoparticles by chemical, physical and biological methods along with their characterization by various techniques followed by a discussion on Ag nano catalysis. Ag nanoparticles played an important role as a catalyst due to their unique properties for several transformations which are discussed here. 1.1. Nanoparticles and Catalysis “Why are nanomaterials so interesting”? The nanometers are extremely small in structures, even more difficult to synthesize and handle than that of their conventional macro scale catalytic counterparts. It is known that the material in nanometer scale exhibits characteristically different properties than the bulk materials. The nanoparticles are in a specific size and specific shape, exhibiting remarkable specific properties. The size and shape of nanomaterials play significant role in catalysis. Nanocatalysis has attained great interest because most of the nanomaterials possess high surface to volume ratio, and large number of active sites on the surface which play a significant role for catalytic properties. Due to the availability of large surface area of nanoparticles to the reactants, the contacts of reactants increases on the surface of the catalyst and rapid reaction can occur. Nanocatalysis acts as bridge between homogeneous and heterogeneous catalysis. Mostly, the nanoparticles act as heterogeneous catalysts in the catalysis, it has several advantages in catalysis, namely low loading, no use of ligand, recyclability of catalyst, fast kinetics and lower temperature, less time with high efficiency and selectivity towards respective products. 1.2. Scope of the Review The current review primarily focuses on various preparation methods for the Ag nanoparticles, including chemical synthesis, physical synthesis and biological synthesis. The synthesis of Ag nanoparticles, Ag bimetallic nanoparticles, Ag supported and nano© 2015 Bentham Science Publishers

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Biosensors

Antimicrobial

Optoelectronics

Ag Nanoparticles

Anticancer

Optical

Electronic

Therapeutics

Catalysis Fig. (1). Applications of Ag nanoparticles in various field.

Wet chemical

Photo-reduction

Hydrothermal

Electrochemical

Ag Nanoparticles

Sonochemical

Microemulsion

Sol-gel

Microwave Fig. (2). Synthesis of Ag nanoparticles by different chemical methods.

composite materials followed by a discussion on characterization of Ag nanoparticles by XRD, various microscopic as well as spectroscopic techniques were discussed. The chemical synthesis was categorized in terms of reducing agents, capping agents and surfactants used for the synthesis of Ag nanoparticles. The physical method includes mostly evaporation-condensation method, ball milling method, and laser ablation method for the synthesis of Ag nanoparticles. The biological method discusses the synthesis of Ag nanoparticles which includes the use of various plant extracts, microorganisms as well as fungi. Furthermore, we have discussed the applications of Ag, bimetallic Ag, Ag supported and nanocomposite nanomaterials in various organic transformations including C-C, CN, C-S, C-O bond formation reactions as well as some reduction and oxidation reactions.

2. SYNTHESIS OF SILVER NANOPARTICLES 2.1. Chemical Approach In chemical synthesis, the chemical reduction method is generally used for the synthesis of nanoparticles. Along with this method, chemical synthesis includes a hydrothermal method [21, 22], sonochemical method [23], electrochemical method [24], microwave assisted method [25, 26], sol-gel method [27], photo-reduction method [28, 29], microemulsion method [30], reduction using spinning disk reactor [31] and wet chemical method [32] (Fig. 2) etc. for synthesis of Ag nanoparticles. In the case of chemical synthesis, silver salts are reduced by a chemical reducing agent forming a silver nucleus and the growth of the nucleus to a particle is controlled by a capping agent who also prevents aggregation by steric

Silver Nanoparticles: Synthesis, Characterization and their Application

hindrance or electrostatic repulsion. The synthesis of Ag nanoparticles with controlled size and shape, acts as the most impressive catalyst for organic reactions. At the time of preparation of Ag nanoparticles, the Ag precursor mixed with suitable solvent and capping agent is used to control the morphology to form well dispersed nanoparticles, which avoids agglomeration and an appropriate reducing agent reduces the starting Ag precursor in favourable conditions with the subsequent formation of Ag nanoparticles. In literature, many researchers have reported the synthesis of Ag nanoparticles with various sizes and morphology using different capping agents and reducing agents. The main role of a capping agent is to bind the surface of nanoparticles and avoid their agglomeration. For the synthesis of Ag nanoparticles, various reducing agents are used to reduce the Ag precursors to Ag(0) nanoparticles such as sodium citrate [33], NaBH4 [34, 35], hydrazine hydrate [36], ascorbic acid [37, 38], formaldehyde [39], dextrose [40, 41], ethylene glycol [42], sodium formaldehydesulfoxylate (SFS) [43], thiosalicylic acid (TSA) [44] and elemental hydrogen [45]. Along with these, the morphology of Ag nanoparticles is controlled by using different capping agents such as polyvinyl alcohol (PVA) [46], cetyl trimethyl ammonium bromide (CTAB) [47, 48], polysaccharides [40], polyglutamic acid (PGA) [41], thiosalicylic acid [44]. In most of the reports, polyvinyl pyrrolidone (PVP) was used as a capping agent to control the morphology of Ag nanoparticles (Fig. 3) [49-55] and it plays a major role to get the shape and size selective Ag nanoparticles. Navaladian et al. [56] achieved Ag nanoparticles synthesis with size distribution ranging from 3 nm to 9 nm via microwave-assisted method.

Fig. (3). a) A schematic of the nucleation and growth process, in which silver continuously deposits onto the {100} facet to eventually result in a completely {111}-bound octahedron. b-f) PVP capped SEM images of cubes, truncated cubes, cuboctahedra, truncatedoctahedra, and octahedra, respectively (scale bar: 100 nm) (Reprinted from ref. 55).

Recently our work demonstrates the synthesis of [email protected] nanoparticles using only AgNO3 as precursor and sugarcane juice as solvent at low temperature (80 °C) and less time (20 min). Here the sugarcane juice itself acts as a reducing as well as capping agent in the reaction [57]. Synthesis of silver and silver sulphide nanoma-

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terials has been achieved by electrodeposition approach using ionic liquids as greener and shape directing solvents [58]. In previous surveys, strong reducing agents like NaBH4 and hydrazine hydrate were used as reagents [34-36]. Recently, the use of mild reducing agents like ascorbic acid, sodium citrate, formaldehyde, ethylene glycol, dextrose were reported for the synthesis of Ag nanoparticles [33, 37-41]. Polymers and surfactants like sodium dodecycle sulfate (SDS) [35, 59], Daxad-19 and chitosan suspension are used as stabilizers to get the desired morphology of nanoparticles [60, 61]. 2.2. Physical Approach Chemical methods for the synthesis of nanoparticles usually involve toxic chemicals, which can be harmful to the environment. Although this method produces shape and size selective Ag nanoparticles, they require a capping agent, stabilizer as well as extra additives to avoid the agglomeration of Ag nanoparticles whereas, physical methods do not involve toxic chemicals and are usually faster. Kvitek et al. reported the progressive physical approach for synthesis of Ag and Au nanoparticles and the particles are spherical shape with average diameter of about 3.5 nm [62]. Physical synthesis mostly includes the evaporation-condensation method, ball milling method, laser ablation method, melt mixing method, pulsed wire discharge method and electric arc deposition method for synthesis of Ag nanoparticles (Fig. 4) [63-65]. There is no solvent contamination in the synthesis of thin films and formations of uniformity in nanoparticles distribution are the advantages of physical approaches in comparison with chemical synthesis. Jung et al. [66] reported the synthesis of Ag nanoparticles via tube-furnace evaporation/condensation method using a small ceramic heater with a local heating area. The Ag nanoparticles formed are spherical and well dispersed. This process has some drawbacks such as large space required to set up the system and high energy consumption needed to raise the environmental temperature around the source material and this process requires significant time to establish thermal stability. Lee and Kang [67] demonstrated the synthesis of Ag nanoparticles by thermal decomposition method using silver nitrate as precursor at 290 °C. It was observed that the nanoparticles are uniform with good dispersion and the mean size of the Ag nanoparticles is 9.5 nm with a standard deviation of 0.7 nm. The laser ablation method is one of the important physical methods used for the synthesis of nanoparticles. Mafune et al. [68] prepared size controlled Ag nanoparticles by laser ablation method in aqueous solution. The size of Ag nanoparticles was observed below 15 nm. Simakin et al. [69] synthesized nanodisks of Ag and Au by laser ablation in liquid environment with diameter in the range of 2060 nm. Chen and Yeh [70] also used laser ablation method for the synthesis of Ag nanoparticles. In this protocol surfactants like SDS and CTAB were used to obtain highly dispersed Ag particles. It was observed that by using a laser intensity of 120 mJ/pulse, the diameters of nanoparticles were 4.2 ± 1.9 nm in SDS and 7.8 ± 4.5 nm in CTAB. Bae et al. [71] reported Ag nanoparticles using laser ablation of Ag target in various concentrations of NaCl. The Ag nanoparticles produced were spherical in morphology with an average size of 26 nm. Okazaki et al. [72] reported the changes in morphology of silver colloids prepared by laser ablation in water. The formation of crystal-shaped particles such as nanoprisms and nanorods were observed. Kawasaki and Nishimura reported 1064-nm laser induced fragmentation of thin Au and Ag flakes in acetone [73]. Thang et al. [74] performed laser ablation to prepare Ag nanoparticles in various concentrations of aqueous solu-

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Pulsed wire discharge

Laser ablation

Electric arc deposition

Ag Nanoparticles

Melt mixing

Ball milling

Evaporation-condensation Fig. (4). Synthesis of Ag nanoparticles by different physical methods.

tions of PVP. Sylvestre et al. [75] used laser ablation method in aqueous cyclodextrins for the synthesis of size controlled Au nanoparticles. Furthermore, Tien et al. fabricated ionic silver in Ag nanoparticle suspension and Ag and Au nanofluids by arc discharge method [76, 77]. Ashkarran [78] prepared colloidal Ag nanoparticles by reducing silver nitrate by electrons produced from discharge between titanium electrodes in the water.

Plant extract

Ag Nanoparticles

2.3. Biological Approach Currently, research in biosynthesis is a new and greener area for the synthesis of nanoparticles. The silver salt, reducing agent and capping agent are essential components in chemical approach for the synthesis of Ag nanoparticles. However, in biological approach, the reducing, capping or stabilizing agents can be used as natural sources from the plant extracts for the synthesis of Ag nanoparticles of desired size and shape. Many researchers have focused on simple and greener biological methods for the synthesis of nanoparticles (Fig. 5). Vilchis-Nestor et al. synthesized Ag nanoparticles in aqueous solution using green tea (Camellia sinensis) extract as reducing and stabilizing agent [79]. When a larger volume of C. sinensis extract was added to the silver ion solution, a rapid reduction of the Ag ions and fast growth of Ag nanoparticles were observed. Bar et al. applied greener route to the synthesis of Ag nanoparticles using the latex of Jatropha curcas as reducing and as capping agent with spherical particles, having size in the range of 20-30 nm [80]. Lin et al. reported the biosynthesis of Ag nanowires of diameter 50-60 nm using Cassia fistula leaf as reductant and capping agent at room temperature [81]. Ahmad et al. demonstrated biosynthesis of stable and spherical shaped Ag nanoparticles of average size 10 nm from the dried stem and root of Ocimum sanctum [82]. Khan and coworkers investigated the synthesis of Ag nanoparticles having a different morphology such as spherical, quantum dots, hexagons and polyhedral with Neem (Azadirachta indica) leaf extract and CTAB as a surfactant [83]. Recently, researchers developed protocols for the synthesis of Ag nanoparticles using several plant extracts as greener reducing as well as capping agents to get different sizes and shapes of Ag nanoparticles [84, 85]. For example, the Ag nanoparticles synthesis

Yeast

Algae

Fungi

Bacteria

Microorganisms Fig. (5). Synthesis of Ag nanoparticles from different biological sources.

was achieved using Kiwifruit Juice [86], Rumex hymenosepalus extract [87], Annona squamosa leaf extract [88], Podophyllum hexandrum leaf extract [89], extracts of Acalypha indica Linn. [90], Hibiscus cannabinus leaf extract [91], Macrotyloma uniflorum seed extract [92] etc. Tagad et al. demonstrated greener synthesis of Ag nanoparticles by using locust bean gum polysaccharide and their application for the development of optical fibre based hydrogen peroxide sensor [93]. The use of microorganisms [94, 95] and fungi [96, 97] plays an important role in the synthesis of Ag nanoparticles (Fig. 6). The reducing and stabilizing compounds can be found in bacteria, fungi, yeasts, algae or plants which reduce the Ag salt and control the size and shape of Ag nanoparticles. In biosynthesis, the Ag ions are precipitated and stabilized by functional groups on the cell wall of bacteria or fungi. Shivakrishna et al. demonstrated Ag nanoparticles from Marine Bacteria Pseudomonas aerogenosa [98], Sadowski et al. used the Penicillium fungi for the synthesis of Ag nanoparticles [99]. Recently, Otari et al. reported spherical Ag nanoparticles with

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Fig. (6). Chemical (A) versus biological synthesis using bacteria (B) (Reprinted from ref. 97)

an average size of 15 nm using microorganism and showed catalytic activity in a reduction of 4-nitrophenol to 4-aminophenol [100] and the Fungus Fusarium oxysporum was reported for the synthesis of Ag nanoparticles from silver nitrate as precursor and showed their antifungal activity against pathogenic yeasts [101]. In another study, Li et al. showed the fungus-mediated synthesis of Ag nanoparticles using Aspergillus terreus with spherical and polydisperse morphology with size 1-20 nm [102] and Ghaseminezhad et al. and Ahmad et al. reported the Ag nanoparticles using fungus [103, 104]. 3. SYNTHESIS OF SUPPORTED AND NANOCOMPOSITE SILVER NANOMATERIALS A generally significant and sometimes critical variable is the choice of support for silver nanoparticles. Each support has characteristic properties, depending on the supported nanomaterials which can be used for a specific application. Changing a support may completely alter the properties of the catalyst which increases or prevent the catalytic activity. There are many supports used for the synthesis of supported Ag nanoparticles such as graphene, mesoporous silica, tungsten oxide, aerogel matrix, Poly(DVBstyrene) matrix, TiO2, Al2O3, carbon nanotubes (CNT), including amorphous supports; alumina, silica, carbon supports, layered supports; clays and microporous supports; zeolites (molecular sieves) as well as polymers; and crosslinked or functionalized polymers. Supported metal nanoparticles containing silver are of immense importance in the field of heterogeneous catalysis [105]. Zhang et al. reported the preparation of Ag nanoparticles using various supports by supercritical fluids (SCFs) with highly dispersed nanoparticles with controllable metal content and particle size [106]. Signori et al. demonstrated the synthesis of Ag nanoparticles supported on branched polyethyleneimine derivatives are the most feasible catalysts for the reduction reaction [107]. Jiang et al. reported the ultrasound assisted synthesis of Ag nanoparticles on graphene nano platelets (Ag/GNP) which act as highly active catalysts for oxygen reduction reaction [108]. Morley et al. explained the synthesis of aerogel matrix and Poly (DVB styrene) matrix supported Ag nanoparticles via supercritical route [109]. Various polymers supported Ag nanoparticles and their applications in different field have been reported [110]. Ghosh et al. demonstrated the synthesis of silver supported tungsten oxide nanocatalyst for selective oxidation of cyclohexene to adipic acid [111]. Recently, there has been a renewed interest to synthesize bimetallic Ag nanoparticles and Ag nanocomposites materials

through greener approach [112]. The bimetallic or nanocomposite materials somehow cooperate to enhance activity and/or selectivity towards the catalysis related to catalysts with only one metal. Shankar et al. reported the synthesis of bimetallic Au core-Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth [113]. Chassagneux et al. synthesized bimetallic gold-silver nanoparticles supported on mesostructured silica films using HAuCl4 and AgNO 3 as precursors [114]. Hazarika et al. synthesized Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract with size in the range of 3.0 ± 0.2-45.0 ± 1.3 nm along with quantum dots [115]. Yan et al. achieved bimetallic AuxAg1x nanoparticles with uniform spherical shape and uniform size [116]. Syntheses of Ag nanocomposite materials have applications in various fields such as nonenzymatic H2O2 sensing [117], antibacterial activity [118122], antifungal activity [123], optical activity [124], metal-enhanced fluorescence [125], a photocatalytic activity [226], chemical and bacterial treatment of waste water [127], electrochemical sensing [128], ammonia sensing [129], antifouling properties [130] and photocatalyst [131] etc. Zhu et al. reported the synthesis of polyacrylamide-silver nanocomposites by -irradiation with particle sizes ranging from 2 to 20 nm [132]. Lesniak et al. synthesized water-soluble, biocompatible, fluorescent, and stable Ag/dendrimer nanocomposites and their application as cell biomarkers [133]. Gong et al. demonstrated the synthesis of Ag/SiO2 core-shell nanostructures using reverse micelle technology [134]. Bhattacharyya et al. achieved the insertion of Ag nanoparticles into 3-D mesoporous ZnO nanocomposites and nanorods using microwave-assisted method [135]. Gupta et al. reported the synthesis of Ag-graphene-based nanocomposites materials. The TEM micrograph showed that the Ag nanoparticles are in 3-12 nm size and they are embedded in the graphene oxide nanosheet [136]. Murthy et al. [137] reported semi-IPN hydrogel-silver nanocomposites. Xu et al. [138] synthesized [email protected] oxide nanocomposites, Matai et al. [139] reported the synthesis of Ag-ZnO nanocomposite and it showed antibacterial applications. Manikam et al. synthesized the Ag and Al nanoalloys via chemical reduction method [140]. Breitwieser et al. reported the synthesis of silver nanocomposites on cellulosic fibers by using conventional and microwave assisted heating [141]. Dubey et al. achieved graphene-carbon sphere hybrid aerogel with Ag nanoparticles and their catalytic as well as adsorption applications [142]. Many researchers synthesized the silver nanocomposites materials such as silver-polyvinyl alcohol nanocomposites, Ag/polyaniline core-shell nanocomposites, silver/clay nanocomposites, Ag nanoparticles loaded quaternized chitosan/clay nanocomposites, Ag nanoparticles on silica, [email protected]

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nanocomposites, silver nano-colloids and silver/polymer nanocomposites [143-148]. 4. CHARACTERIZATION OF SILVER NANOPARTICLES It is very important to characterize the synthesized nanomaterials to understand the control of size and morphology. The nanoparticles can be characterized by various techniques like powder X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area analyzer (BET) and UVVisible spectroscopy (UV-Vis) which provides the details about the specific properties of nanomaterials. 4.1. X-Ray Diffraction (XRD) X-ray diffraction is a non-destructive tool used for identifying the atomic and molecular structure of materials. It helps to identify the phases, orientation, structural properties and average crystallite size of the nanomaterials [149]. XRD method involves the interaction between the monochromatic X-ray with atoms of periodic lattice and diffracts into many specific directions, interfering constructively as described by the Braggs law: n = 2d sin  where, d is the spacing between diffracting planes,  is the incident angle, n is any integer and  is the wavelength of the beam. The average crystallite size of the nanomaterials was determined using Scherrer equation: D = K/cos where, D is the average crystallite size of material, K is a dimensionless shape factor with a typical value of about 0.9,  is the wavelength of the incident X-ray radiations,  is the line broadening at half the maximum intensity (FWHM) in radians. 4.2. Microscopy 4.2.1. Scanning Electron microscopy (SEM) SEM analysis provides the information about the surface topography and morphology of the nanomaterials. It is also gives the idea about the approximate size of particles and features. In SEM, highenergy electron beam encounters the nucleus of an element, it generates different types of signals in the sample. These signals include secondary electrons (SE), backscattered electrons (BSE), characteristic X-rays and transmitted electrons and emitted signals are detected by specialized detectors [150]. 4.2.2. Transmission Electron Microscopy (TEM) TEM technique is used for high resolution two-dimensional images of materials. It provides topographical, morphological, compositional and crystallographic information of the samples. This analysis also yields information of surface features, shape, size and structure of materials. This technique involves the high energy electron beam transmitted through a very thin section of a material; electrons are diffracted by the lattice of crystalline or semi crystalline material and propagated along with different directions. The imaging mode provides a highly magnified view of the micro and nano region [151]. 4.2.3. Scanning Tunneling Microscopy (STM) The STM is a type of electron probe microscopy that shows three-dimensional images of a sample. The structure of a surface of

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material is studied using a stylus that scans the surface at a fixed distance from it. The STM works by scanning a very sharp metal wire tip over the surface. By taking the metal tip close to the surface of the material, and by applying an electrical voltage to the tip or sample, the voltage will cause electrons to tunnel between the tip and sample, creating a current that can be measured. The image of the surface morphology in atomic resolution can be obtained when the tip is moved across the sample by x-y scan, the changes in surface height and density of states cause changes in current and these changes are mapped in the form of images. 4.2.4. Atomic Force Microscopy (AFM) or Scanning Force Microscopy (SFM) AFM is the type of high resolution scanning probe microscopy. The AFM consists of a cantilever (100-200 mm long) with a sharp tip (probe) which is used to scan the surface of the material. It operates by measuring force between a probe and the sample. The molecular force between two objects can be monitored by the deflection of a cantilever which is in turn amplified by the deflection of a laser beam according to Hooke's law. The constant force is maintained by adjusting the z-position of the surface of the material and an x-y scan will produce the morphology of the surface [152]. The different types of forces are measured with AFM including mechanical contact force, van der Waals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces, Casimir forces, solvation forces, etc. AFM have applications in imaging the topography, force mapping, nanofabrication and nanolithography. 4.3. Spectroscopy There are many spectroscopic techniques available for the measurement of specific properties of materials. The X-ray photoelectron spectroscopy (XPS) is one of the surface analytical techniques for assessing surface compositions of materials. XPS gives the information about the empirical formula, electronic state of the elements that exist within a material. Energy-dispersive X-ray spectroscopy (EDS or EDX) is the technique which detects x-rays emitted from the sample during bombardment by an electron beam to characterize the elemental composition of materials. UV-Visible spectroscopy (UV/Vis) is an analytical technique used for the measurement of absorption edge and band gap energies of the nanomaterials. The Raman spectroscopy is used to observe vibrational, rotational, and other low-frequency modes of materials across the structural phase transitions. The crystal orientation can usually be determined by using Raman spectroscopy. Fourier transform infrared spectroscopy (FTIR) technique is used to obtain an infrared spectrum of absorption, emission and photoconductivity of materials. 5. APPLICATIONS OF SILVER NANOPARTICLES: A SUSTAINABLE CATALYST FOR ORGANIC TRANSFORMATIONS The study of metal nanoparticle catalyzed reactions is projected in current research because nanoparticles act as heterogeneous or semi-heterogeneous catalysts in organic reactions. Nanomaterials exhibit good catalytic activity and selectivity due to their size, shape, and large surface area to volume ratio as well as a large percentage of metal atoms is available for the substrates [153, 154]. Ying and co-workers demonstrated that the nanostructure materials are attractive candidates as heterogeneous catalysts for various organic transformations [155]. The nanoparticles have several advantages in catalysis such as nanoparticles are insoluble in the reac-

Silver Nanoparticles: Synthesis, Characterization and their Application

Current Organic Chemistry, 2015, Vol. 19, No. ??

n

O R

H

+

Ag nanocatalyst n

H +

R1

7

N H

R = C6H5-, n-C5H11 n = 0,1 R1 = aryl, alkyl

N 100 oC, 12 h R1 R

Scheme 1. Ag nanoparticles catalyzed A3-coupling reaction of aldehyde, alkyne, and amine. Reagents and conditions: aldehyde (1 mmol), amine (1.1 mmol), alkyne (1.5 mmol), catalyst (1%), temp. (100 °C), PEG (2 ml), 12 h.

N H

R1 5

R

R 2

nano-Ag 1

O R1

H

+

N

N H

4 OH

H

R

R

OH

H2O H 3

R

Scheme 2. Plausible reaction mechanism for the A3-coupling reaction catalyzed by Ag nanoparticles.

tion medium, have high dispersion and easy separation of catalyst for recyclability like heterogeneous catalyst. Notably, the organic reactions using nanoparticles do not require any ligand source, they accelerate the reaction at low temperature with low catalyst loading, which makes the method simple, one step, economical and cost efficient. The Ag nanoparticles are ultrastable and have substantial impact on various fields, including catalysis, sensing, photochemistry, optoelectronics, energy conversion and medicine [156]. An Ag nanoparticle acts as a good catalyst in organic reaction over the bulk counterparts because of its size in nano region, shape and high surface area. Nowadays, several metal and metal oxide nanoparticles are applied as heterogeneous catalysts for organic reactions and showed extensive performance in catalysis [157-160]. 5.1. Silver Nanoparticles: Catalyst Towards C-C coupling Reaction Earlier, the emerging research interest was with several organic reactions involving silver salts as catalysts [161]. Today, noble nanoparticles are imperative catalysts for catalytic applications, which overcome the problem related to catalysis using bulk materials [162]. Wang and co-workers synthesized Ag nanoparticles in 8 nm to 10 nm in size using PEG with simple bubbling of H2 and

reported one pot synthesis of three-component coupling reaction of aldehyde, alkyne and amine using Ag nanoparticles as catalysts with high reactivity and high selectivity for the desired product (Scheme 1) [163]. The reaction mechanism (Scheme 2) describes the addition of Ag nanoparticles 1 and phenylacetylene 2, formation of intermediate 3. The coupling of aldehyde with amine results in species 4. Furthermore, species 3 reacts with 4, formation of desired product 5 and Ag nanoparticles are recovered. Li and co-workers also studied the three-component coupling of aldehyde, alkyne and amine using silver iodide as catalyst [164]. It was observed that there is no need of additional co-catalyst or activator. Claus and co-workers demonstrated that silica supported silver nanoparticles were in the range of 4-8 nm and applied as highly active catalysts for the regioselective hydrogenation of , unsaturated aldehyde citral (3,7-dimethyl-2,6-octadienal) [165]. Porco Jr. and co-workers synthesized silica-supported Ag nanoparticles of ~5 nm and proposed applications for Diels-Alder cycloadditions of 2-hydroxychalcones (Scheme 3) [166]. Here the silica-supported Ag nanoparticles are solid and recyclable catalysts with high yield and turnover number. In plausible mechanism (Scheme 4), single electron transfer (SET) from chal-

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OH

Bhosale and Bhanage

O

OAc Me

Ph

OH

Me

b) aq. NaHCO3 MeOH, 87%

+ MeO

MeO

a) Silica-supported Ag NPs, 85%

Me

OH

O

both steps in air

Me

Me

Me

Scheme 3. Diels-Alder cycloaddition reaction of 2-hydroxychalcones using a silica-supported Ag nanoparticle as catalyst. Reagents and conditions: (a) Silica-supported Ag NPs (0.5 mol% Ag loading), CH2Cl2, 50 °C, 48 h, (b) aq. NaHCO3 , MeOH, 40 °C, 6 h.

OH

O

Ph OH

Ag NPs

O

SET

Ph

Me

6

10 H+

Ag NPs HO

Ag NPs

Ag NPs O

Ph O

O

O

O Ph

Ph

9

Me 7a

Ag NPs H+

BET

O

7b

Me O

Ph

Me 8 Scheme 4. Plausible mechanism for the cycloaddition reaction catalyzed by Ag nanoparticles.

cone 6 to Ag nanoparticles result in intermediate 7a, which is in resonance with carbon-centered radical 7b, then concerted [4 + 2] cycloaddition of activated dienophile 7a/b and diene provides 8 which generates 9 via back electron transfer (BET) and protonation. Finally, the Ag nanoparticles get removed and form cycloaddition product 10. Sun and co-workers demonstrated the synthesis of Ag2O nanoparticles by wet chemical route with particle size 1-2 m and used as catalyst for three-component coupling reactions for the formation of propargylamines (Scheme 5) [167]. The catalyst could be recovered and reused three times showing an excellent activity towards the desired product. Barth and co-workers synthesized 1,4-Bis(3,5-diethynylphenyl)butadiyne-1,3 by catalytic homo-coupling of organic building block featuring terminal alkynes and a central butadiyne group on Ag (111) surface [168]. Zhang et al. (Scheme 6) reported the Ag

nanoparticles (4 nm in size) catalyzed tandem aerobic oxidation reaction for direct syntheses of styryl ethers from benzyl alcohols [169]. A plausible reaction mechanism as depicted in Scheme 7, nanosize Ag/C catalyzed aerobic oxidation of the benzyl alcohol results in benzyldehyde 11, followed by rapid condensation with DMSO to give the styryl sulfoxide 12. Then, Ag/C-catalyzed aerobic oxidation gave the styryl sulfone 13 and final addition of an alkoxide anion to the -position of the sulfone 13 formation of benzylic anion takes place, which underwent elimination to furnish the final product 14. There are several reports for the synthesis of silver nanoparticles which showed their catalytic activity for the reduction of aromatic nitro compounds to the aromatic amines in the presence of NaBH4 as reducing agent (Scheme 8) [170-174]. Wei and co-workers synthesized silica nanofibers containing silver nanoparticles via combining sol-gel chemistry and electro

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CHO

H N

+

9

nano-Ag2O (5 mol%)

+

N CHCl3, rt, 10 h

Scheme 5. Ag2O nanoparticles catalyzed three-component coupling of aldehyde, amine and phenylacetylene. Reagents and conditions: aldehyde (1 mmol), amine (1.1 mmol), phenylacetylene (1.2 mmol) and Ag2O nanoparticles (0.05 mmol) in chloroform (2 mL) at room temperature for 10 h. OH Ph

+ HO

Ph

DMSO, rt, 3 h, air

NO2

H

Ag/C, KOH

O

Ph

NH2

Ph

Ag nanoparticles

H

NaBH4

Scheme 6. Ag nanoparticles catalyzed oxidation reaction of benzyl alcohol to styryl ether. Reagents and conditions: benzyl alcohol (0.5 mmol, 1 eq.), KOH (0.5 mmol, 1 eq.), Ag/C nanocatalyst (0.005 mmol, 0.01 eq.), DMSO (2 mL), rt, 3 h.

OH

OH

Scheme 8. Ag nanoparticles catalyzed reduction of nitrophenol to amonophenol.

spinning technique and showed the catalytic application used in the reduction of methylene blue dye using NaBH4 as reducing agent [175]. Similar report was available for the synthesis of Ag nanoparticles using Terminalia chebula fruit extract with approximate size of particles as 25 nm and its catalytic application used in the reduction of methylene blue dye [176]. Jiang et al. synthesized the spherical shape Ag nanoparticles supported on silica and studied its catalytic properties for the reduction of various dyes like methylene blue (MB), eosin (EO), and rose bengal (RB) [177]. Chandrasekaran and co-workers demonstrated the Ag nanoparticles of size range between 5 nm to 40 nm are the efficient nanocatalysts for the catalytic reduction of starch hydrolysis by -amylase [178]. It was observed that the degradation of starch digestion kinetics is more in the presence of Ag nanoparticles. Chattopadhyay and coworkers (Scheme 9) reported the chitosan bound Ag nanoparticles (Chit-Ag NPs) as catalysts for selective C-C bond formation and in situ iodination of phenols using molecular iodine [179].

OH

OH OH

Chit-Ag NPs I 0.6 mol dm-3 of I2 H2O/ethanol, rt, 3 h

Scheme 9. Chit-Ag NP catalyzed o-p phenolic coupling reaction. Reagents and conditions: phenol (1 mol), Chit-Ag NPs (0.8 g/L), molecular iodine (0.6 mol), water (0.4 mL)/absolute ethanol (0.6 mL), rt, 3 h.

properties. Li and co-workers reported shape selective (spherical, truncated cubic, truncated triangular) Ag nanoparticles and their catalytic activity for the oxidation of styrene into benzyldehyde and styrene oxide [180]. The Kaneda and co-workers (Scheme 10) reported selective hydration of nitriles to amides in water as solvent using hydroxyapatite-supported Ag nanoparticles (size range 4-12 nm) as reusable heterogeneous catalysts [181]. Various aromatic nitriles including heterocyclic compounds with electron donating and withdrawing groups showed better catalytic activity. The catalyst was reused four times without losing its catalytic activity and selectivity which is the advantage of the protocol.

5.2. Silver Nanoparticles: Catalyst Towards C-N, C-O, C-S Coupling Reaction The noble metal nanoparticles have excited to a greater extent interest owing to their unusual and somewhat unexpected catalytic

O S

OH Ph

O

O Ag/C, O2 Ph

Slow

O

O

DMSO

S

S Ph

KOH

Fast 12

H

11

Ag/C, O2 Slowest O Ph

O 14

Ph

O

S

Ph O

O

S Ph

Ph

O

O 13

Scheme 7. Plausible mechanism for the Ag catalyzed synthesis of benzyl alcohol to styryl ethers.

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HCO4- ion formed during reaction could coordinate to the Mn ions on the surface of the Mn oxide. Then, the intermediate 17 transfers an oxygen atom to the olefin, and results in the formation of epoxide 18.

O

AgHAP R C N + H2O R = Aryl, alkyl

R

NH2

Scheme 10. AgHAP-catalyzed hydration of nitrile to amide. Reagents and conditions: nitrile (1 mmol), AgHAP (0.1 g, Ag: 0.03 mmol), water (3 mL), 140 °C, 3 h, under Ar.

R1

R2

R1

CH3CN, RT, 4 h

R1 = aryl, alkyl R2 = H, alkyl

Purcar and Luque reported the synthesis of Ag nanoparticles supported on hybrid films by two-step method with particle size 725 nm and showed its catalytic activity for the formation of C-O bond by the oxidation of styrene to styrene oxide under microwave irradiation with the reusability of catalyst upto 4th cycle (Scheme 11) [182]. Najafpour and group (Scheme 12) synthesized layered Mn oxides with deposited Au or Ag nanoparticles having size 10-25 nm as an efficient catalyst for epoxidation of olefins in the presence of H2O2 and NaHCO3 [183]. The catalyst was recycled up to sixth run with excellent catalytic activity. In mechanism (Scheme 13) for the epoxidation of olefins, in the first step, the olefin binds with intermediate 15 and results in the formation of intermediate 16. The

O

Ag-Mn oxide nanocatalyst

R2

Scheme 12. Epoxidation of olefin catalyzed by Ag-Mn oxide nanocatalyst. Reagents and conditions: olefin (0.5 mmol), catalyst (Ag 3.38%), CH3CN (1 mL), NaHCO 3 (0.1 mmol), H2O 2 (2 mmol), RT, 4 h.

Grunwaldt and co-workers (Scheme 14) developed Ag nanocatalysts supported on SiO2, Al2O3, Celite, CeO2, kaolin, MgO, and activated carbon showed their catalytic activity for the selective liquid-phase oxidation of benzyl alcohol to aldehyde [184]. A plausible mechanism was proposed (Scheme 15) for the oxidation reaction benzyl alcohol 19 absorbed on the silver surface, the alcohol is dehydrogenated forming a cationic intermediate 20, its further reaction results in benzaldehyde 21. O

O MW

CHO +

Ag-catalyst

+

OH

OH Scheme 11. Ag nanoparticles supported on hybrid films catalyzed oxidation of styrene. Reaction conditions: styrene (2 mmol), H2O2 (4 mmol), Ag catalyst (0.1 g), microwave irradiation, 300 W, 90-115 °C, 15 min.

Au/Ag

Au/Ag

MnOx

15

16

O

HCO4

18 O O Au/Ag

HCO3

O

O HCO3

MnOx

OH2

H2O2

MnOx

17 Scheme 13. Proposed mechanism for the epoxidation of olefins by Au-Mn oxide or Ag-Mn oxide in the presence of H2O2 and NaHCO3. The red arrows show electron exchanges between the Au or Ag and the Mn ions.

Silver Nanoparticles: Synthesis, Characterization and their Application

Current Organic Chemistry, 2015, Vol. 19, No. ??

O Supported Ag NPs

OH

OH

H

R1

Xylene, O2, Reflux, 3 h

R R = aryl, alkyl

O

Ag/HT R1

Xylene, 130 oC, 16 h,

R2

R1 = aryl, alkyl R2 = H, alkyl

Zhou and co-workers synthesized the Ag/MCM-41 by one-pot synthesis method using CTAB as a stabilizing agent and shown the catalytic performance for the C-O bond formation reaction by oxidation of cyclohexane to cyclohexanol and cyclohexanone using molecular oxygen as oxidant in the absence of solvent [185]. Kaneda and group (Scheme 16) reported that the Ag nanoparticles supported on hydrotalcite (Ag/HT) as heterogeneous catalysts for dehydrogenation of alcohols under oxidant and additive-free conditions with good conversion and selectivity [186]. The same Kaneda’s group (Scheme 17) reported the Ag nanoparticles supported on hydroxyapatite (Ag-HAp) exhibited high catalytic activity for the selective oxidation of silanes into silanols using water as an oxidant with excellent selectivity [187]. The Ag and Au nanoparticles supported on hydrotalcite (Ag/HT and Au/HT) are the excellent catalysts for the deoxygenation of epoxides into alkenes as reported (Scheme 18) [188]. Swarts and group (Scheme 19) reported the synthesis of supported Ag nanoparticles by spin coat impregnation method with Ag particles of size range 3-5 nm and shown their catalytic applications in aerobic oxidation of octadecanol to their corresponding carbonyl derivatives (a mixture of aldehyde and carboxylic acid). In short reaction time the product was enriched by aldehyde, while longer reaction time will lead to the product to be enriched with carboxylic acid [189].

Au/HT or Ag/HT Au: 0.45 mol%, Ag: 2 mol%

O R1

R2

R2

toluene, 2-PrOH (10 eq.), 110 oC, Ar

R1 = aryl, alkyl R2 = H, aryl, alkyl

Scheme 18. Ag/HT catalyzed deoxygenation of epoxides into alkenes. Reagents and conditions: substrate (1 mmol), catalyst (0.1 g), toluene (5 mL), 2-propanol (0.6 mL), 110 °C, 4-24 h.

Chakraborty and co-workers (Scheme 20) synthesized silicasupported Ag nanoparticles (particles size range from 2 nm to 50 nm) by chemical reduction method using silver nitrate as metal precursor, starch as protecting agent, and NaBH4 as a reducing agent. They achieved the oxidation of ethylbenzene using silicasupported Ag nanoparticles in liquid phase. The catalyst was recycled up to fourth recycle without the loss of its activity [190]. Linic’s group focused on the shape and size selective synthesis of Ag nanoparticles using ethylene glycol with PVP and their catalytic application in catalytic ethylene epoxidation [191]. Yadav Mewada have achieved the oxidation of 1-octanol to 1-octanal over nano-fibrous Ag-OMS-2 (Ag-octahedral molecular sieve type 2) catalyst synthesized through precipitation method under acidic conditions [192].

21

+ +

1/2 O2

2H+O

19

CeO2

Ag

SiO2 Scheme 15. Proposed mechanism of supported Ag nanoparticles catalyzed oxidation of benzyl alcohol. Me Ph

Si Me

H

+

H2O

H2

R1

H2O O

+

under Ar

O

OH

R2

Scheme 16. Dehydrogenation of alcohols catalyzed by Ag/HT. Reagents and conditions: alcohol (1 mmol), Ag/HT catalyst (Ag: 45 mmol), p-xylene (5 mL), 130 °C, 16 h.

Scheme 14. 10% Ag-SiO 2 and CeO2 catalyzed oxidation of benzyl alcohol to benzyldehyde. Reagents and conditions: benzyl alcohol (2 mmol), xylene (20 mL), biphenyl (0.10 g), Ag-SiO2 (50 mg), CeO2 (25 mg), reflux, O2 atmosphere, 3 h.

20

11

Me

Ag-HAp Ph 80 oC, Ar flow Selectivity = 99

Si

Me OH

Ph

+

Me

Si Me

:

Me O

Si Me

1

Scheme 17. Ag-HAp catalyzed oxidation of dimethylphenylsilane. Reagents and conditions: dimethylphenylsilane (1 mmol), H2O (2 mL), Ag-HAp catalyst (Ag: 0.03 mmol), 80 °C, Ar flow.

Ph

+

H2

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Bhosale and Bhanage

O

O Ag/Silicon wafer

Ag/Silicon wafer

OH

16

H

16

16

OH

Scheme 19. Consecutive air oxidation of octadecanol to its corresponding aldehyde and carboxylic acid as product.

O

OH

OOH ROO

+ +

Scheme 20. Proposed free radical mechanism for oxidation of ethylbenzene.

O

O

O

Ag Nanoparticles R

R1

+

R2

NHR2

NH2 60 oC, Methanol

R1

R

R, R1 = alkyl or alkoxy R2 = alkyl or aryl Scheme 21. Ag nanoparticle catalyzed synthesis of enaminones and enamino esters. Reagents and conditions: dicarbonyl compound (1 mmol), amine (1 mmol), Ag NPs (0. 2 mmol), methanol (5 mL), time (2-8 h), temp. (60 °C).

O

O NH2

NH

O

Ag/CNTs

+ NH2

EtOH, ))))

H

NH

Scheme 22. Ag/CNTs catalyzed reaction of anthranilamide and aldehydes to quinazolinone by sonication. Reagents and conditions: anthranilamide (1 mmol), aromatic aldehydes (1 mmol), Ag/CNTs (0.04 g), ethanol (5 mL), sonication for 5 min.

Ag-CNT

Ag-CNT O

O

O

+ NH2

Ag-CNT

O

NH2 Ar

N

H

N H

H OH

N -H2O

H

Ar

Ar 23

Ag-CNT

Ag-CNT

22

O

OH N

N H

H

Ar

1,5-H transfer

N N 24

H

Ar

Scheme 23. Proposed mechanism for the synthesis of quinazolinones.

Bhanage and co-workers (Scheme 21) reported the use of Ag nanoparticles of average size 40 nm as an efficient, heterogeneous and recyclable catalyst for C-N bond synthesis of -enaminones and -enamino esters providing good to excellent yields of desired products [193]. The catalyst was recycled and reused up to fourth run without the loss of catalytic activity. Carbon nanotubes (CNTs) have been at the forefront of nanoscience and nanotechnology because of their remarkable properties. Safari and co-workers (Scheme 22) reported the Ag supported on carbon nanotubes (Ag-CNTs) as a heterogeneous catalyst for C-N bond formation reaction to the synthesis of 2-aryl-2,3dihydroquinazolin-4(1H)-ones using an ultrasound-accelerated

reaction in the presence of anthranilamide and aryl aldehydes as precursors [194]. The catalyst was recovered by simple work up procedure and reused up to fifth run with excellent yield of the desired product. The mechanism (Scheme 23) proposes that the electrophilicity of the carbonyl group in aldehyde get enhanced by using Ag-CNT. Then, the intermediate 22 is formed by the reaction of 2-aminobenzamide and activated aldehyde. The intermediate 22 is dehydrated, and results into imine intermediate 23. The part of imine in this intermediate could be activated by Ag metal and then through intramolecular nucleophilic attack of the amide nitrogen on activated imine group intermediate 24 is produced. Moreover, the formation of final product was done by 1, 5-proton transfer.

Silver Nanoparticles: Synthesis, Characterization and their Application

Current Organic Chemistry, 2015, Vol. 19, No. ??

H2N-R2

Ag/Al2O3 R1

OH

R1

1/2 O2, -H2O or -H2

R1 = aryl, alkyl R2 = aryl

O

R1

-H2O

N

13

R2

Scheme 24. Synthesis of imines by consecutive oxidative dehydrogenation and condensation of alcohol and amine using Ag/Al2O3 as a catalyst. Reagents and conditions: alcohol (2 mmol), amine (0.2 mmol), toluene (6 mL), 5 wt% Ag/Al2O 3 (100 mg), 100 °C, 24 h, atmospheric air.

NH2

Ag NPs

NH2

N

KOH, DMSO

+

N

Air, 60 oC, 24 h Scheme 25. Ag nanoparticle catalyzed oxidative coupling of aniline to azobenzene. Reagents and conditions: aniline (1 mmol), KOH (1 eq.), Ag NPs (1 mol %), DMSO (2 mL), air (1 atm), 60 °C, 24 h.

1)

O2

Ag0

Ag0

Ag+

O2

Ag+

O2

+

O2 25

NH2 2)

NH2 +

O2 25

NH2 3)

26 NH2

H H

N N

+

H N

O2 H

-H2O

H 27

26 H N

O2 N H

4)

N

N H 28

N

-H2O

29

28

Scheme 26. Plausible mechanism Ag nanoparticles catalyzed oxidative coupling of aniline. CHO Ar

H N

Ar

CHO O

OH

AgI NPs

H2N

O

32

OH

CH3

AgI NPs, 140 oC Solvent-free

DMF, POCl3, 70 oC 33

O

NHAc

+ ArCHO 30

H2N

H N

Ar NH2

AgI NPs, 140 Solvent-free

O O

oC

31

Scheme 27. AgI nanoparticle catalyzed synthesis of functionalized oxazine. Reagents and conditions: (1) 30 to 31: -naphthol (0.01 mol), aldehyde (0.01 mol), urea (0.012 mol), AgI NPs (0.03 g), 140 °C. (2) 30 to 32: -naphthol (1 mmol), aldehyde (1 mmol), AgI NPs (0.03 g), acetamide (1.2 mmol), 110 °C. (3) 32 to 33: acetamidonaphthols (1 mmol) DMF (1.2 eq.), POCl3 (0.8 eq.), 70 °C, 20 min.

Mielby et al. (Scheme 24) synthesized the Ag nanoparticles supported on alumina (Ag/Al2O3) by incipient wetness impregnation of the solid supports with an aqueous solution of AgNO3and shown their application in oxidative dehydrogenation and condensation of alcohols and amines in the formation of imines [195]. The reaction was performed with various alcohols and amines to demonstrate the wide range and versatility of the reaction. Wang and co-workers demonstrated that Ag nanostructures are excellent catalysts for oxygen reduction reaction in alkaline solutions [196]. The Yadav’s group reported the selective hydrogenation of nitrobenzene to aniline via azobenzene as intermediate using nano-fibrous Ag-OMS-2 as catalyst [197]. Li and co-workers

(Scheme 25) successfully achieved the synthesis of azobenzene by oxidative dehydrogenative coupling of anilines using Ag nanoparticles having average particle size from 8 nm to 25 nm [198]. Mechanistic study (Scheme 26) involves the oxidation of the nitrogen atom of aniline by 25 formation of aniline radical cation 26. Then the coupling between 26 and aniline results in a three-electron  bond in intermediate 27, which was the rate determining step of the overall reaction. Subsequently, the one-electron oxidation of intermediate 27 led to hydrazine intermediate 28, which was rapidly oxidized to the azo product 29. Ghomi et al. (Scheme 27) reported the synthesis of AgI nanoparticles using AgNO3 in water and SDS as surfactant under

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Current Organic Chemistry, 2015, Vol. 19, No. ??

Bhosale and Bhanage

TEOS + APTES

HCHO

NH2-SiO2

AgNO3

CH2O-SiO2

Ag/SiO2

Scheme 28. The synthesis process for Ag/SiO2 (TEOS = tetraethoxylsilicate, APTES = aminopropyltriethoxysilane).

NO2

NH2 Ag/SiO2

+ H2

140 oC, 3 h Cl

Cl

Scheme 29. Selective hydrogenation of chloronitrobenzene to chloroaniline over Ag/SiO2 catalyst. Reagents and conditions: chloronitrobenzene (0.5 g), H2 (2 MPa), Ag/SiO 2 (0.1 g), ethanol (25 mL), (140 °C), 3 h.

ultrasound power with particle size in the range of 40-50 nm. The synthesized AgI nanoparticles were applied as a heterogeneous nanocatalyst for the synthesis of (amidoalkyl)naphthol and oxazine derivatives under solvent-free conditions [199]. Notably, the reaction does not require any ligand source and requires low catalyst loading as well as moderate temperature with catalyst recyclability. 5.3. Bimetallic Silver Nanoparticles: Catalyst Towards Organic Transformations Bimetallic nanoparticles consist of a new set of catalysts which are synthesized by combining two metal components within a single catalyst. Bimetallic nanoparticles act as a green and sustainable catalyst in organic reactions [200]. Narayanan reported the recent development in noble metal nanocatalysts for Suzuki and Heck cross-coupling reactions [201]. Qiu and co-workers (Scheme 28)

synthesized Ag/SiO2 by an in situ reduction method which acts as a recyclable catalyst for the selective hydrogenation of chloronitrobenze to chloroaniline (Scheme 29) [202]. Huang and co-workers reported the two step synthesis of [email protected], first Ag2MoO4 was prepared by a typical microwaveassisted hydrothermal reaction and then AgCl was synthesized by the ion-exchange reaction between Ag2MoO4 and HCl. The application of [email protected] material showed it as efficient photocatalyst for the decomposition of methylic orange dye in solution under visiblelight irradiation [203]. Li and group [204], Wang and group [205] and Mou group [206] synthesized the Ag/MnO2 having particle size 2 nm to 10 nm by hydrothermal method, Au-Ag alloy nanoparticles having particle size between 8-10 nm and Au-Ag bimetallic nanocatalyst supported on an acidic mesoporous aluminosilicate ([email protected]) having particles size 3.7 ± 1.5 nm, respectively. They exposed the catalytic activity of catalysts for CO oxidation with high stability. Kim and Choi reported the synthesis of PdAg/ZnO nanoparticles by -irradiation at room temperature and exposed the catalytic activity for hydrogenation reaction for a reduction of nitrophenol and Suzuki reactions (Scheme 30) [207]. Santhanalakshmi and co-workers (Scheme 31) demonstrated the Au-Ag-Pd trimetallic nanoparticles with particle size 13 nm which are active catalysts for the Suzuki coupling reaction [208]. Zamborini and co-workers reported that the PdAg nanoparticles are active and stable catalysts for hydrogenation and isomerization

OH I 1)

B

Pd-Ag/ZnO

OH

+

K3PO4, EtOH OH B

2)

Pd-Ag/ZnO

OH

I +

S

K3PO4, EtOH

I

S

OH B

3)

+

O

Pd-Ag/ZnO

OH

B K3PO4, EtOH

B O

COOH Scheme 30. Catalytic efficiency of Pd-Ag/ZnO catalysts for Suzuki reaction. Reagents and conditions: aryl halide (3 mmol), boronic acid (6 mmol), Pd-Ag/ZnO catalysts (0.4 mmol), K3PO 4 (12 mmol), EtOH (50 mL), 78 °C, 3 h. HO

X

B

OH Pd-Ag-Au trimetallic NPs

R1

R2

+ R1

R2

CH3COONa, DMF-H2O

X = Cl, Br, I R1 = H, CH3, OCH3, COCH3, NO2 R2 = H, CH3, OCH3

Scheme 31. Au-Ag-Pd trimetallic nanoparticles catalyzed Suzuki cross-coupling reaction of aryl halides with boronic acids. Reagents and conditions: aryl halide (1 mmol), phenylboronic acid (1.05 mmol), CH3COONa (3 mmol), Pd-Ag-Au trimetallic nanocatalyst (0.5 mol%), DMFH2O (3:1), 100 °C, 12 h.

Silver Nanoparticles: Synthesis, Characterization and their Application

Current Organic Chemistry, 2015, Vol. 19, No. ??

Pd-Ag

15

34 HO

OH OH

M-H or H+ M = Pd or Ag HO HO H

38 HO

Pd-Ag

OH

35

O

HO

O

1/2 O2 OH

OH

HO

HO

HO O Pd

O

O*

H

O

Pd-Ag

Ag

36

37

H2O Scheme 32. Proposed mechanism of glycerol oxidation using Pd-Ag/C as nanocatalyst.

of allyl alcohol in the presence of H2 [209]. Santhanalakshmi and co-workers [210] reported the synthesis of mono- and bimetallic Au and Ag nanoparticles having particle size 8 nm to 12 nm, prepared by wet chemical method and their applications in oxidation of LLeucine in the presence and absence of H2O2. In this study, it was observed that, the Au-Ag bimetallic nanoparticles catalyzed oxidation of the amino acid provided higher selectivity than monometallic Au and Ag nanoparticles. Hirasawa et al. (Scheme 32) reported the Pd-Ag nanoparticle synthesized by co-impregnation method using mixed aqueous solutions and exposed the catalytic application for selective oxidation of glycerol to dihydroxyacetone [211]. In the study of mechanism, the substrate glycerol 34 is adsorbed on the surface of Ag to form 35. Then, the atomic oxygen activated on the Pd located next to Ag attacks the 2-position of the glycerol and result in the formation of 36 to break the C-H bond, and the carbonylic product 37 is produced by the scission of O-H bond. The final step will be the removal of the metal hydroxide by proton to form water and formation of final product 38, while recovering the initial metallic state. Lu and co-workers (Scheme 33) demonstrated the Au-Ag alloy nanoparticles prepared by a co-reduction method with average diameter 4-5 nm and are effective catalysts for aerobic oxidation of benzyl alcohol in aqueous solution [212]. The researchers synthesized the bimetallic nanoparticles with Ag metal and shown their

catalytic application as a robust catalyst for the reduction of nitrophenol to aminophenol [213-216]. O H

OH

Au O2

Ag

Scheme 33. Proposed aerobic oxidation of benzyl alcohol on the surface of Au and Au/Ag alloy nanoparticles.

Venkatesan and co-workers reported the encapsulation of Ag nanoparticles into graphite grafted with hyperbranched polyamidoamine (PAMAM) dendrimer and shown their catalytic application for the reduction of various derivatives of nitrobenzene in amino benzene in the presence of NaBH4 [217]. Zhang and coworkers achieved the spherical shape Ag-Fe3O4 [email protected] microparticles which were proved to be an efficient catalyst for the catalytic reduction of nitrophenol to aninophenol

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Current Organic Chemistry, 2015, Vol. 19, No. ??

with recyclability of catalyst [218]. There are various reports available for the reduction of nitro aromatics to amino aromatics using Ag nanoparticles supported on different supports [219-226]. 6. CONCLUSION Over the past decades, researchers have concentrated on the synthesis and development of shape and size selective synthesis of nanocrystals. Many researchers have made efforts towards the synthesis of Ag nanoparticles, supported Ag nanoparticles and bimetallic Ag nanoparticles but few of them achieved shape and size controlled nanoparticles. In this review, we firstly summarized the research and developments in the synthesis of Ag nanoparticles, including chemical, physical and biological synthesis approaches and their different properties. Then we discussed the characterization of Ag nanoparticles by various techniques. Finally, we have reviewed various silver nanoparticles catalyzed organic reactions such as coupling reactions containing C-C, C-N, C-O, C-S bond forming reactions, reduction and oxidation reactions. The nanoparticles are novel and efficient tools in various organic coupling reactions. Notably, the catalysis using Ag nanoparticles does not require any ligand source but low catalyst loading, easy separation of catalyst, and low temperature with catalyst recyclability. Nowadays, it is necessary to conduct research towards the synthesis of various heterogeneous catalysts using simpler, greener and economical approach. The inventions of novels as well as shape and size selective nanoparticles and their applications as a heterogeneous catalyst in organic transformations are the current challenges. However, numerous recent studies have shown that the use of various Ag nanoparticles in catalysis has proved that the life of these materials is sufficient and that they offer recyclability. These two properties are essential conditions for industrial applications of these original and powerful catalysts.

Bhosale and Bhanage

MW PEG PGA PVA PVP SCFs SDS SE SEM SERS SFS STM TEM TEOS TSA UV-Vis XPS XRD

[2]

[3] [4] [5]

[6]

[7]

[8]

ACKNOWLEDGEMENTS Author M.A.B. is thankful to Council of Scientific and Industrial Research (CSIR), India for providing a Senior Research Fellowship (SRF). We thank the Department of Science and Technology (DST), India for financial support under the Nano Mission project no. SR/NM/NS-1097/2011. This work is supported by DST and JSPS under the India-Japan Cooperative Science Program (IJCSP).

[9]

[10]

[11]

[12]

ABBREVIATIONS AFM APTES BET BSE CNT CTAB DLS DVB EDS FTIR FWHM

= = = = = = = = = = =

Atomic force spectroscopy Aminopropyltriethoxysilane Brunauer-Emmett-Teller surface area analyser Back scattered electrons Carbon nanotubes Cetyl trimethyl ammonium bromide Dynamic light scattering Divinylbenzene Energy-dispersive X-ray spectroscopy Fourier transform infrared spectroscopy Full width half maximum

Microwave Poly ethylene glycol Polyglutamic acid Polyvinyl alcohol Polyvinyl pyrrolidone Supercritical fluids Sodium dodecyl sulfate Secondary electrons Scanning electronic microscopy Surface-enhanced Raman scattering Sodium formaldehydesulfoxylate Scanning tunneling microscopy Transmission electron microscopy Tetraethoxylsilicate Thiosalicylic acid UV-Visible spectroscopy X-ray photoelectron spectroscopy X-ray diffraction

REFERENCES [1]

CONFLICT OF INTEREST The authors confirm that this article content has no conflict of interest.

= = = = = = = = = = = = = = = = = =

[13]

[14]

[15]

[16]

[17]

Chaudhuri, R.G.; Paria, S. Core/shell nanoparticles: Classes, properties, synthesis mechanisms, characterization, and applications. Chem. Rev., 2012, 112, 2373-2433. Hussain, I.; Brust, M.; Papworth, A.J.; Cooper, A.I. Preparation of acrylatestabilized gold and silver hydrosols and gold-polymer composite Films. Langmuir, 2003, 19, 4831-4835. Wertime, T.A. Man’s first encounters with metallurgy. Science, 1964, 146, 1257-1267. Wertime, T.A. The beginnings of metallurgy: A new look. Science, 1973, 182, 875-887. Rycenga, M.; Cobley, C.M.; Zeng, J.; Li, W.; Moran, C.H.; Zhang, Q.; Qin, D.; Xia, Y. Controlling the synthesis and assembly of silver nanostructures for plasmonic applications. Chem. Rev., 2011, 111, 3669-3712. Hemalatha, K.; Madhumitha, G.; Kajbafvala, A.; Anupama, N.; Sompalle, R.; Roopan, S.M. Function of nanocatalyst in chemistry of organic compounds revolution: An overview. J. Nano Mat., 2013, 2013, 1-23. Zhang, X.Y.; Hu, A.; Zhang, T.; Lei, W.; Xue, X.J.; Zhou, Y.; Duley, W.W. Self-assembly of large-scale and ultrathin silver nanoplate films with tunable plasmon resonance properties. ACS Nano, 2011, 5(11), 9082-9092. Okafor, F.; Janen, A.; Kukhtareva, T.; Edwards, V.; Curley, M. Green synthesis of silver nanoparticles, their characterization, application and antibacterial activity. Int. J. Environ. Res. Publ. Health, 2013, 10, 5221-5238. Radzig, M.A.; Nadtochenko, V.A.; Koksharova, O.A.; Kiwi, J.; Lipasova, V.A.; Khmel, I.A. Antibacterial effects of silver nanoparticles on gramnegative bacteria: Influence on the growth and biofilms formation, mechanisms of action. Colloids Surf., B, 2013, 102, 300-306. Zhang, D.; Liu, X.; Wang, X. Green synthesis of graphene oxide sheets decorated by silver nanoprisms and their anti-bacterial properties. J. Inorg. Biochem., 2011, 105, 1181-1186. Sondi, I.; Salopek-Sondi, B. Silver nanoparticles as antimicrobial agent: A case study on E. coli as a model for Gram-negative bacteria. J. Colloid Interface Sci., 2004, 275, 177-182. Priyadarshini, S.; Gopinath, V.; Priyadharsshini, N.M.; MubarakAli, D.; Velusamy, P. Synthesis of anisotropic silver nanoparticles using novel strain, Bacillus flexus and its biomedical application. Colloids Surf., B, 2013, 102, 232-237. Ramamurthy, C.H.; Padma, M.; Samadanam, I.D.M.; Mareeswaran, R.; Suyavaran, A.; Kumar, M.S.; Premkumar, K.; Thirunavukkarasu, C. The extra cellular synthesis of gold and silver nanoparticles and their free radical scavenging and antibacterial properties. Colloids Surf., B, 2013, 102, 808815. Sharma, V.K.; Yngard, R.A.; Lin, Y. Silver nanoparticles: Green synthesis and their antimicrobial activities. Adv. Colloid Interface Sci., 2009, 145, 8396. Dipankar, C.; Murugan, S. The green synthesis, characterization and evaluation of the biological activities of silver nanoparticles synthesized from Iresine herbstii leaf aqueous extracts. Colloids Surf., B, 2012, 98, 112-119. Niraimathi, K.L.; Sudha, V.; Lavanya, R.; Brindha, P. Biosynthesis of silver nanoparticles using Alternanthera sessilis [Linn.] extract and their antimicrobial, antioxidant activities. Colloids Surf., B, 2013, 102, 288-291. Abdel-Aziz, M.S.; Shaheen, M.S.; El-Nekeety, A.A.; Abdel-Wahhab, M.A. Antioxidant and antibacterial activity of silver nanoparticles biosynthesized

Silver Nanoparticles: Synthesis, Characterization and their Application

[18]

[19]

[20]

[21]

[22] [23]

[24]

[25] [26]

[27] [28]

[29]

[30]

[31]

[32]

[33]

[34]

[35] [36]

[37]

[38]

[39]

[40] [41]

[42]

[43]

[44]

[45]

using Chenopodium murale leaf extract. J. Saudi Chem. Soc., 2014, 18, 356363. Zhou, G.; Wang, W. Synthesis of silver nanoparticles and their antiproliferation against human lung cancer cells in vitro. Orient J. Chem., 2012, 28, 651655. Suriyakalaa, U.; Antony, J.J.; Suganya, S.; Siva, D.; Sukirtha, R.; Kamalakkannan, S.; Pichiah, P.B.T.; Achiraman, S. Hepatocurative activity of biosynthesized silver nanoparticles fabricated using Andrographis paniculata. Colloids Surf., B, 2013, 102, 189-194. Roopan, S.M.; Rohit; Madhumitha, G.; Rahuman, A.A.; Kamaraj, C.; Bharathi, A.; Surendra, T.V. Low-cost and eco-friendly phyto-synthesis of silver nanoparticles using Cocos nucifera coir extract and its larvicidal activity. Ind. Crop. Prod., 2013, 43, 631-635. Zou, J.; Xu, Y.; Hou, B.; Wu, D.; Sun, Y. Controlled growth of silver nanoparticles in a hydrothermal process. China Particuology, 2007, 5, 206212. Sun, X.; Luo, Y. Preparation and size control of silver nanoparticles by a thermal method. Mater. Lett., 2005, 59, 3847-3850. Liu, Y.C.; Lin, L.H. New pathway for the synthesis of ultrafine silver nanoparticles from bulk silver substrates in aqueous solutions by sonoelectrochemical methods. Electrochem. Commun., 2004, 6, 1163-1168. Rodriguez-Sanchez, L.; Blanco, M.C.; Lopez-Quintela, M.A. Electrochemical synthesis of silver nanoparticles. J. Phys. Chem. B, 2000, 104(41), 96839688. He, B.; Tan, J.J.; Liew, K.Y.; Liu, H. Synthesis of size controlled Ag nanoparticles. J. Mol. Catal. A: Chem., 2004, 221, 121-126. Yin, H.; Yamamoto, T.; Wada, Y.; Yanagida, S. Large-scale and sizecontrolled synthesis of silver nanoparticles under microwave irradiation. Mater. Chem. Phys., 2004, 83, 66-70. Feng, Q.; Dang, Z.; Li, N.; Cao, X. Preparation and dielectric property of Ag-PVA nano-composite. Mater. Sci. Eng., B, 2003, B99, 325-328. Courrol, L.C.; de Oliveira Silva, F.R.; Gomes, L.A simple method to synthesize silver nanoparticles by photo-reduction. Colloids Surf., A, 2007, 305, 5457. Jia, H.; Zeng, J.; Song, W.; An, J.; Zhao, B. Preparation of silver nanoparticles by photo-reduction for surface-enhanced Raman scattering. Thin Solid Films, 2006, 496, 281-287. Zhang, W.; Qiao, X.; Chen, J.; Wang, H. Preparation of silver nanoparticles in water-in-oil AOT reverse micelles. J. Colloid Interface Sci., 2006, 302, 370-373. Tai, C.Y.; Wang, Y.H.; Kuo, Y.W.; Chang, M.H.; Liu, H.S. Synthesis of silver particles below 10 nm using spinning disk reactor. Chem. Eng. Sci., 2009, 64, 3112-3119. Panigrahi, S.; Kundu, S.; Ghosh, S.K.; Nath, S.; Pal, T. Sugar assisted evolution of mono- and bimetallic nanoparticles. Colloids Surf., A, 2005, 264, 133138. Sileikaite, A.; Puiso, J.; Evas, Prosycevas, I.; Ius, Tamulevicius, S. Investigation of silver nanoparticles formation kinetics during reduction of silver nitrate with sodium citrate. Mater. Sci., 2009, 15(1), 21-27. Liu, J.; Li, X.; Zeng, X. Silver nanoparticles prepared by chemical reductionprotection method, and their application in electrically conductive silver nanopaste. J. Alloys Comp., 2010, 494, 84-87. Gao, X.; Gu, G.; Hu, Z.; Guo, Y.; Fu, X.; Song, J. A simple method for preparation of silver dendrites. Colloids Surf., A, 2005, 254, 57-61. Kim, K.D.; Han, D.N.; Kim, H.T. Optimization of experimental conditions based on the Taguchi robust design for the formation of nano-sized silver particles by chemical reduction method. Chem. Eng. J., 2004, 104, 55-61. Songping, W.; Shuyuan, M. Preparation of ultrafine silver powder using ascorbic acid as reducing agent and its application in MLCI. Mater. Chem. Phys., 2005, 89, 423-427. Qin, Y.; Ji, X.; Jing, J.; Liu, H.; Wu, H.; Yang, W. Size control over spherical silver nanoparticles by ascorbic acid reduction. Colloids Surf., A, 2010, 372, 172-176. Chou, K.S.; Lu, Y.C.; Lee, H.H. Effect of alkaline ion on the mechanism and kinetics of chemical reduction of silver. Mater. Chem. Phys., 2005, 94, 429433. Huang, H.; Yang, X. Synthesis of polysaccharide-stabilized gold and silver nanoparticles: A green method. Carbohydr. Res., 2004, 339, 2627-2631. Yu, D.G. Formation of colloidal silver nanoparticles stabilized by Na+poly[gamma-glutamic acid]-silver nitrate complex via chemical reduction process. Colloids Surf., B, 2007, 59, 171-178. Luo, C.; Zhang, Y.; Zeng, X.; Zeng, Y.; Wang, Y. The role of poly(ethylene glycol) in the formation of silver nanoparticles. J. Colloid Interface Sci., 2005, 288, 444-448. Khanna, P.K.; Subbarao, V.V.V.S. Nanosized silver powder via reduction of silver nitrate by sodium formaldehydesulfoxylate in acidic pH medium. Mater. Lett., 2003, 57, 2242-2245. Wu, R.T.; Hsu, S.L.C. Preparation of highly concentrated and stable suspensions of silver nanoparticles by an organic base catalyzed reduction reaction. Mater. Res. Bull., 2008, 43, 1276-1281. Bhatte, K.D.; Deshmukh, K.M.; Patil, Y.P.; Sawant, D.N.; Fujita, S.I.; Arai, M.; Bhanage, B.M. Synthesis of powdered silver nanoparticles using hydrogen in aqueous medium. Particuology, 2012, 10, 140-143.

Current Organic Chemistry, 2015, Vol. 19, No. ?? [46]

[47]

[48]

[49]

[50]

[51] [52] [53] [54]

[55] [56]

[57]

[58]

[59]

[60]

[61] [62]

[63]

[64]

[65]

[66]

[67]

[68]

[69]

[70] [71]

[72]

[73]

[74]

[75]

17

Zieliska, A.; Skwarek, E.; Zaleska, A.; Gazda, M.; Hupka, J. Preparation of silver nanoparticles with controlled particle size. Procedia Chem., 2009, 1, 1560-1566. Lee, G.J.; Shin, S.I.; Kim, Y.C.; Oh, S.G. Preparation of silver nanorods through the control of temperature and pH of reaction medium. Mater. Chem. Phys., 2004, 84, 197-204. Khan, Z.; Al-Thabaiti, S.A.; Obaid, A.Y.; Al-Youbi, A.O. Preparation and characterization of silver nanoparticles by chemical reduction method. Colloids Surf., B, 2011, 82, 513-517. Shin, H.S.; Yang, H.J.; Kim, S.B.; Lee, M.S. Mechanism of growth of colloidal silver nanoparticles stabilized by polyvinyl pyrrolidone in -irradiated silver nitrate solution. J. Colloid Interface Sci., 2004, 274, 89-94. Deivaraj, T.C.; Lala, N.L.; Lee, J.Y. Solvent-induced shape evolution of PVP protected spherical silver nanoparticles into triangular nanoplates and nanorods. J. Colloid Interface Sci., 2005, 289, 402-409. Wang, H.; Qiao, X.; Chen, J.; Ding, S. Preparation of silver nanoparticles by chemical reduction method. Colloids Surf., A, 2005, 256, 111-115. Hsu, S.L.C.; Wu, R.T. Synthesis of contamination-free silver nanoparticle suspensions for micro-interconnects. Mater. Lett., 2007, 61, 3719-3722. Wang, H.; Qiao, X.; Chen, J.; Wang, X.; Ding, S. Mechanisms of PVP in the preparation of silver nanoparticles. Mater. Chem. Phys., 2005, 94, 449-453. Zhao, T.; Sun, R.; Yu, S.; Zhang, Z.; Zhou, L.; Huang, H.; Du, R. Sizecontrolled preparation of silver nanoparticles by a modified polyol method. Colloids Surf., A, 2010, 366, 197-202. Tao, A.; Sinsermsuksakul, P.; Yang, P. Polyhedral silver nanocrystals with distinct scattering signatures. Angew. Chem. Int. Ed., 2006, 45, 4597-4601. Navaladian, S.; Viswanathan, B.; Varadarajan, T.K.; Viswanath, R.P. Microwave-assisted rapid synthesis of anisotropic Ag nanoparticles by solid state transformation. Nanotechnology, 2008, 19, 045603. Kulkarni, A.A.; Bhanage, B.M. [email protected] nanomaterial synthesis using sugar cane juice and its application in degradation of azo dyes, ACS Sustainable. Chem. Eng., 2014, 2, 1007-1013. Patil, A.B.; Bhanage, B.M. Shape selectivity using ionic liquids for the preparation of silver and silver sulphide nanomaterials. Phys. Chem. Chem. Phys., 2014, 16, 3027-3035. Rahulan, K.M.; Ganesan, S.; Aruna, P. Occurrence of two-photon absorption saturation in Ag nanocolloids, prepared by chemical reduction method. Appl. Surf. Sci., 2012, 258, 8439-8443. Sondi, I.; Goia, D.V; Matijevic, E. Preparation of highly concentrated stable dispersions of uniform silver nanoparticles. J. Colloid Interface Sci., 2003, 260, 75-81. Twu, Y.K.; Chen, Y.W.; Shih, C.M. Preparation of silver nanoparticles using chitosan suspensions. Powder Technol., 2008, 185, 251-257. Siegel, J.; Kvitek, O.; Ulbrich, P.; Kolska, Z.; Slepicka, P.; Svorcik, V. Progressive approach for metal nanoparticle synthesis. Mater. Lett., 2012, 89, 47-50. Abou El-Nour, K.M.M.; Eftaiha, A.; Al-Warthan, A.; Ammar, R.A.A. Synthesis and applications of silver nanoparticles. Arab. J. Chem., 2010, 3, 135140. Tran, Q.H.; Nguyen, V.Q.; Le, A.T. Silver nanoparticles: Synthesis, properties, toxicology, applications and perspectives. Adv. Nat. Sci. Nanosci. Nanotechnol., 2013, 4, 033001. Iravani, S.; Korbekandi, H.; Mirmohammadi, S.V; Zolfaghari, B. Synthesis of silver nanoparticles: Chemical, physical and biological methods. Res. Pharm. Sci., 2014, 9(6), 385-406. Jung, J.H.; Oh, H.C.; Noh, H.S.; Ji, J.H.; Kim, S.S. Metal nanoparticle generation using a small ceramic heater with a local heating area. J. Aerosol Sci., 2006, 37, 1662-1670. Lee, D.K.; Kang, Y.S. Synthesis of silver nanocrystallites by a new thermal decomposition method and their characterization. ETRI J., 2004, 26(3), 252256. Mafune, F.; Kohno, J.; Takeda, Y.; Kondow, T. Formation and size control of silver nanoparticles by laser ablation in aqueous solution. J. Phys. Chem. B, 2000, 104(39), 9111-9117. Simakin, A.V.; Voronov, V.V.; Shafeev, G.A.; Brayner, R. Nanodisks of Au and Ag produced by laser ablation in liquid environment. Chem. Phys. Lett., 2001, 348, 182-186. Chen, Y.H.; Yeh, C.S. Laser ablation method: Use of surfactants to form the dispersed Ag nanoparticles. Colloids Surf., A, 2002, 197, 133-139. Bae, C.H.; Nam, S.H.; Park, S.M. Formation of silver nanoparticles by laser ablation of a silver target in NaCl solution. Appl. Surf. Sci., 2002, 197-198, 628-634. Tsuji, T.; Okazaki, Y.; Higuchi, T.; Tsuji, M. Laser-induced morphology changes of silver colloids prepared by laser ablation in water. J. Photochem. Photobiol., A, 2006, 183, 297-303. Kawasaki, M.; Nishimura, N. 1064-nm laser fragmentation of thin Au and Ag flakes in acetone for highly productive pathway to stable metal nanoparticles. Appl. Surf. Sci., 2006, 253, 2208-2216. Tsuji, T.; Thang, D.H.; Okazaki, Y.; Nakanishi, M.; Tsuboi, Y.; Tsuji, M. Preparation of silver nanoparticles by laser ablation in polyvinylpyrrolidone solutions. Appl. Surf. Sci., 2008, 254, 5224-5230. Sylvestre, J.P.; Kabashin, A.V; Sacher, E.; Meunier, M.; Luong, J.H.T. Stabilization and size control of gold nanoparticles during laser ablation in aqueous cyclodextrins. J. Am. Chem. Soc., 2004, 126(23), 7176-7177.

18 [76]

[77]

[78] [79]

[80]

[81]

[82]

[83]

[84] [85]

[86] [87]

[88]

[89]

[90]

[91]

[92] [93]

[94] [95] [96] [97]

[98]

[99]

[100]

[101]

[102]

Current Organic Chemistry, 2015, Vol. 19, No. ?? Tien, D.C.; Tseng, K.H.; Liao, C.Y.; Huang, J.C.; Tsung, T.T. Discovery of ionic silver in silver nanoparticle suspension fabricated by arc discharge method. J. Alloys Compd., 2008, 463, 408-411. Tien, D.C.; Chen, L.C.; Thai, N.V.; Ashraf, S. Study of Ag and Au nanoparticles synthesized by arc discharge in deionized water. J. Nanomater., 2010, 2010, 1-9. Ashkarran, A.A. A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid. Curr. Appl. Phys., 2010, 10, 1442-1447. Vilchis-Nestor, A.R.; Sanchez-Mendieta, V.; Camacho-Lopez, M.A.; GomezEspinosa, R.M.; Camacho-Lopez, M.A.; Arenas-Alatorre, J.A. Solventless synthesis and optical properties of Au and Ag nanoparticles using Camellia sinensis extract. Mater. Lett., 2008, 62, 3103-3105. Bar, H.; Bhui, D.K.; Sahoo, G.P.; Sarkar, P.; De, S.P.; Misra, A. Green synthesis of silver nanoparticles using latex of Jatropha curcas. Colloids Surf., A, 2009, 339, 134-139. Lin, L.; Wang, W.; Huang, J.; Li, Q.; Sun, D.; Yang, X.; Wang, H.; He, N.; Wang, Y. Nature factory of silver nanowires: Plant-mediated synthesis using broth of Cassia fistula leaf. Chem. Eng. J., 2010, 162, 852-858. Ahmad, N.; Sharma, S.; Alam, M.K.; Singh, V.N.; Shamsi, S.F.; Mehta, B.R.; Fatma, A. Rapid synthesis of silver nanoparticles using dried medicinal plant of basil. Colloids Surf., B, 2010, 81, 81-86. Khan, Z.; Hussain, J.I.; Hashmi, A.A. Shape-directing role of cetyltrimethylammonium bromide in the green synthesis of Ag-nanoparticles using Neem (Azadirachta indica) leaf extract. Colloids Surf., B, 2012, 95, 229-234. Iravani, S. Green synthesis of metal nanoparticles using plants. Green Chem., 2011, 13, 2638-2650. Tran, Q.H.; Nguyen, V.Q.; Le, A.T. Silver nanoparticles: Synthesis, properties, toxicology, applications and perspectives. Adv. Nat. Sci.: Nanosci. Nanotechnol., 2013, 4, 033001. Gao, Y.; Huang, Q.; Su, Q.; Liu, R. Green synthesis of silver nanoparticles at room temperature using kiwifruit juice. Spectrosc. Lett., 2014, 47, 790-795. Rodriguez-Leon, E.; Iniguez-Palomares, R.; Navarro, R.E.; Herrera-Urbina, R.; Tanori, J.; Iniguez-Palomares, C.; Maldonado, A. Synthesis of silver nanoparticles using reducing agents obtained from natural sources (Rumex hymenosepalus extracts). Nanoscale Res. Lett., 2013, 8, 318. Vivek, R.; Thangam, R.; Muthuchelian, K.; Gunasekaran, P.; Kaveri, K.; Kannan, S. Green biosynthesis of silver nanoparticles from Annona squamosa leaf extract and its in vitro cytotoxic effect on MCF-7 cells. Process Biochem., 2012, 47, 2405-2410. Jeyaraj, M.; Rajesh, M.; Arun, R.; MubarakAli, D.; Sathishkumar, G.; Sivanandhan, G.; Dev, G.K.; Manickavasagam, M.; Premkumar, K.; Thajuddin, N.; Ganapathi, A. An investigation on the cytotoxicity and caspase-mediated apoptotic effect of biologically synthesized silver nanoparticles using Podophyllum hexandrum on human cervical carcinoma cells. Colloids Surf., B, 2013, 102, 708-717. Krishnaraj, C.; Jagan, E.G.; Ramachandran, R.; Abirami, S.M.; Mohan, N.; Kalaichelvan, P.T. Effect of biologically synthesized silver nanoparticles on Bacopa monnieri (Linn.) Wettst. plant growth metabolism. Process Biochem., 2012, 47, 651-658. Bindhu, M.R.; Umadevi, M. Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity. Spectrochim. Acta, Part A, 2013, 101, 184-190. Vidhu, V.K.; Aromal, S.A.; Philip, D. Green synthesis of silver nanoparticles using Macrotyloma uniflorum. Spectrochim. Acta, Part A, 2011, 83, 392-397. Tagad, C.K.; Dugasani, S.R.; Aiyer, R.; Park, S.; Kulkarni, A.; Sabharwal, S. Green synthesis of silver nanoparticles and their application for the development of optical fiber based hydrogen peroxide sensor. Sens. Actuators, B, 2013, 183, 144-149. Korbekandi, H.; Iravani, S.; Abbasi, S. Production of nanoparticles using organisms. Crit. Rev. Biotechnol., 2009, 29(4), 279-306. Saklani, V.; Jain, V.K. Microbial synthesis of silver nanoparticles: A review. J. Biotechnol. Biomaterial., 2012, S13:007, doi: 10.4172/2155-952X.S13-007. Sastry, M.; Ahmad, A.; Khan, M.I.; Kumar, R. Biosynthesis of metal nanoparticles using fungi and actinomycete. Curr. Sci., 2003, 85(2), 162-170. Sintubin, L.; Verstraete, W.; Boon, N. Biologically produced nanosilver: Current state and future perspectives. Biotechnol. Bioeng., 2012, 109(10), 2422-2436. Shivakrishna, P.; Krishna, M.R.P.G.; Charya, M.A.S. Synthesis of silver nano particles from marine bacteria Pseudomonas aerogenosa. Octa J. Biosci., 2013, 1(2), 108-114. Sadowski, Z.; Maliszewska, I.H.; Grochowalska, B.; Polowczyk, I.; Kozlecki, T. Synthesis of silver nanoparticles using microorganisms. Mater. Sci. Poland, 2008, 26(2), 419-424. Otari, S.V; Patil, R.M.; Nadaf, N.H.; Ghosh, S.J.; Pawar, S.H. Green synthesis of silver nanoparticles by microorganism using organic pollutant: Its antimicrobial and catalytic application. Environ. Sci. Pollut. Res. Int., 2014, 21, 1503-1513. Ishida, K.; Cipriano, T.F.; Rocha, G.M.; Weissmuller, G.; Gomes, F.; Miranda, K.; Rozental. S. Silver nanoparticle production by the fungus Fusarium oxysporum: Nanoparticle characterisation and analysis of antifungal activity against pathogenic yeasts. Mem. Inst. Oswaldo Cruz, 2014, 109, 220-228. Li, G.; He, D.; Qian, Y.; Guan, B.; Gao, S.; Cui, Y.; Yokoyama, K.; Wang, L. Fungus-mediated green synthesis of silver nanoparticles using Aspergillus terreus. Int. J. Mol. Sci., 2012, 13, 466-476.

Bhosale and Bhanage [103]

[104]

[105]

[106] [107]

[108]

[109]

[110]

[111]

[112]

[113]

[114]

[115]

[116]

[117]

[118]

[119]

[120]

[121]

[122]

[123]

[124] [125]

[126]

[127]

[128]

[129]

Ghaseminezhad, S.M.; Hamedi, S.; Shojaosadati, S.A. Green synthesis of silver nanoparticles by a novel method: Comparative study of their properties. Carbohydr. Polym., 2012, 89, 467-472. Ahmad, A.; Mukherjee, P.; Senapati, S.; Mandal, D.; Khan, M.I.; Kumar, R.; Sastry, M. Extracellular biosynthesis of platinum nanoparticles using the fungus Fusarium oxysporum. Colloids Surf., B, 2003, 28, 313-318. Mitsudome, T.; Mikami, Y.; Matoba, M.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Design of a silver-cerium dioxide core-shell nanocomposite catalyst for chemoselective reduction reactions. Angew. Chem. Int. Ed., 2012, 51, 136-139. Zhang, Y.; Erkey, C. Preparation of supported metallic nanoparticles using supercritical fluids: A review. J. Supercrit. Fluids, 2006, 38, 252-267. Signori, A.M.; Santos, K.D.O.; Eising, R.; Albuquerque, B.L.; Giacomelli, F.C.; Domingos, J.B. Formation of catalytic silver nanoparticles supported on branched polyethyleneimine derivatives. Langmuir, 2010, 26(22), 1777217779. Jiang, R.; Moton, E.; McClure, J.P.; Bowers, Z. A highly active and alcoholtolerant cathode electrocatalyst containing Ag nanoparticles supported on Graphene. Electrochim. Acta, 2014, 127, 146-152. Morley, K.S.; Marr, P.C.; Webb, P.B.; Berry, A.R.; Allison, F.J.; Moldovan, G.; Brown, P.D.; Howdle, S.M. Clean preparation of nanoparticulate metals in porous supports: A supercritical route. J. Mater. Chem., 2002, 12, 18981905. Sarkar, S.; Guibal, E.; Quignard, F.; SenGupta, A.K. Polymer-supported metals and metal oxide nanoparticles: Synthesis, characterization, and applications. J. Nanopart. Res., 2012, 14(2), 715. Ghosh, S.; Acharyya, S.S.; Adak, S.; Konathala, L.N.S.; Sasaki, T.; Bal, R. Selective oxidation of cyclohexene to adipic acid over silver supported tungsten oxide nanostructured catalysts. Green Chem., 2014, 16, 2826-2834. Froggett, S.J.; Clancy, S.F.; Boverhof, D.R.; Canady, R.A. A review and perspective of existing research on the release of nanomaterials from solid nanocomposites. Part. Fibre Toxicol., 2014, 11, 17. Shankar, S.S.; Rai, A.; Ahmad, A.; Sastry, M. Rapid synthesis of Au, Ag, and bimetallic Au core-Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth. J. Colloid Interface Sci., 2004, 275, 496-502. Chassagneux, F.; Bois, L.; Simon, J.P.; Desroches, C.; Brioude, A. Elaboration and characterization of bimetallic gold-silver nanoparticles supported on mesostructured silica films. J. Mater. Chem., 2011, 21, 11947-11955. Tamuly, C.; Hazarika, M.; Borah, S.C.; Das, M.R.; Boruah, M.P. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: Green chemistry approach. Colloids Surf., B, 2013, 102, 627-634. Yan, T.; Zhong, X.; Rider, A.E.; Lu, Y.; Furman, S.A; Ostrikov, K.K. Microplasma-chemical synthesis and tunable real-time plasmonic responses of alloyed AuxAg1-x nanoparticles. Chem. Commun., 2014, 50, 3144-3147. Abdelwahab, A.A.; Shim, Y.B. Nonenzymatic H2O2 sensing based on silver nanoparticles capped polyterthiophene/MWCNT nanocomposite. Sens. Actuators, B, 2014, 201, 51-58. Shen, J.; Shi, M.; Li, N.; Yan, B.; Ma, H.; Hu, Y.; Ye, M. Facile synthesis and application of Ag-chemically converted graphene nanocomposite. Nano Res., 2010, 3, 339-349. Chen, S.F.; Li, J.P.; Qian, K.; Xu, W.P.; Lu, Y.; Huang, W.X.; Yu, S.H. Large scale photochemical synthesis of [email protected] nanocomposites [M = Ag, Pd, Au, Pt] and their optical properties, CO oxidation performance, and antibacterial effect. Nano Res., 2010, 3, 244-255. Zhang, H.; Chen, G. Potent antibacterial activities of Ag/TiO2 nanocomposite powders synthesized by a one-pot sol-gel method. Environ. Sci. Technol., 2009, 43(8), 2905-2910. Egger, S.; Lehmann, R.P.; Height, M.J.; Loessner, M.J.; Schuppler, M. Antimicrobial properties of a novel silver-silica nanocomposite material. Appl. Environ. Microbiol., 2009, 75(9), 2973-2976. Diaz, M.; Barba, F.; Miranda, M.; Guitian, F.; Torrecillas, R.; Moya, J.S. Synthesis and antimicrobial activity of a silver-hydroxyapatite nanocomposite. J. Nanomater., 2009, 2009, 1-6. Prucek, R.; Tucek, J.; Kilianova, M.; Panacek, A.; Kvitek, L.; Filip, J.; Kolar, M.; Tomankova, K.; Zboril, R. The targeted antibacterial and antifungal properties of magnetic nanocomposite of iron oxide and silver nanoparticles. Biomater., 2011, 32, 4704-4713. Evanoff, D.D.; Chumanov, G. Synthesis and optical properties of silver nanoparticles and arrays. Chemphyschem, 2005, 6, 1221-1231. Aslan, K.; Wu, M.; Lakowicz, J.R.; Geddes, C.D. Fluorescent core-shell [email protected] nanocomposites for metal-enhanced fluorescence and single nanoparticle sensing platforms. J. Am. Chem. Soc., 2007, 129(6), 1524-1525. Li, H.; Bian, Z.; Zhu, J.; Huo, Y.; Li, H.; Lu, Y. Mesoporous Au/TiO2 nanocomposites with enhanced photocatalytic activity. J. Am. Chem. Soc., 2007, 129(15), 4538-4539. Yahyaei, B.; Azizian, S.; Mohammadzadeh, A.; Pajohi-Alamoti, M. Preparation of clay/alumina and clay/alumina/Ag nanoparticle composites for chemical and bacterial treatment of waste water. Chem. Eng. J., 2014, 247, 16-24. Bai, W.; Nie, F.; Zheng, J.; Sheng, Q. Novel Silver nanoparticle-Manganese oxyhydroxide-graphene oxide nanocomposite prepared by modified silver mirror reaction and its application for electrochemical sensing. ACS Appl. Mater. Interfaces, 2014, 6, 5439-5449. Guo, H.; Tao, S. Silver nanoparticles doped silica nanocomposites coated on an optical fiber for ammonia sensing. Sens. Actuators, B, 2007, 123, 578-582.

Silver Nanoparticles: Synthesis, Characterization and their Application [130]

[131]

[132]

[133]

[134]

[135]

[136] [137]

[138]

[139]

[140]

[141]

[142]

[143]

[144]

[145]

[146]

[147]

[148]

[149] [150] [151] [152] [153] [154] [155] [156]

[157]

Lee, S.Y.; Kim, H.J.; Patel, R.; Im, S.J.; Kim, J.H.; Min, B.R. Silver nanoparticles immobilized on thin film composite polyamide membrane: Characterization, nanofiltration, antifouling properties. Polym. Adv. Technol., 2007, 18, 562-568. Cozzoli, P.D.; Fanizza, E.; Comparelli, R.; Curri, M.L.; Agostiano, A.; Laub, D. Role of metal nanoparticles in TiO2/Ag nanocomposite-based microheterogeneous photocatalysis. J. Phys. Chem. B, 2004, 108(28), 9623-9630. Zhu, Y.; Qian, Y.; Zhang, M. -Radiation synthesis and characterization of polyacrylamide-silver nanocomposites. Chem. Commun., 1997, (12), 10811082. Lesniak, W.; Bielinska, A.U.; Sun, K.; Janczak, K.W.; Shi, X.; Baker, J.R.; Balogh, L.P. Silver/dendrimer nanocomposites as biomarkers: Fabrication, characterization, in vitro toxicity, and intracellular detection. Nano lett., 2005, 5(11), 2123-2130. Gong, J.L.; Jiang, J.H.; Liang, Y.; Shen, G.L.; Yu, R.Q. Synthesis and characterization of surface-enhanced Raman scattering tags with Ag/SiO2 coreshell nanostructures using reverse micelle technology. J. Colloid Interface Sci., 2006, 298, 752-756. Bhattacharyya, S.; Gedanken, A. Microwave-assisted insertion of silver nanoparticles into 3-D mesoporous zinc oxide. J. Phys. Chem. C, 2008, 112(3), 659-665. Pasricha, R.; Gupta, S.; Srivastava, A.K. A facile and novel synthesis of Aggraphene-based nanocomposites. Small, 2009, 5(20), 2253-2259. Murthy, P.S.K.; Mohan, Y.M.; Varaprasad, K.; Sreedhar, B.; Raju, K.M. First successful design of semi-IPN hydrogel-silver nanocomposites: A facile approach for antibacterial application. J. Colloid Interface Sci., 2008, 318, 217224. Xu, W.P.; Zhang, L.C.; Li, J.P.; Lu, Y.; Li, H.H.; Ma, Y.N.; Wang, W.D.; Yu, S.H. Facile synthesis of [email protected] oxide nanocomposites and their enhanced antibacterial properties. J. Mater. Chem., 2011, 21, 4593-4597. Matai, I.; Sachdev, A.; Dubey, P.; Kumar, S.U.; Bhushan, B.; Gopinath, P. Antibacterial activity and mechanism of Ag-ZnO nanocomposite on S. aureus and GFP-expressing antibiotic resistant E. coli. Colloids Surf., B, 2014, 115, 359-367. Manikam, V.R.; Cheong, K.Y.; Razak, K.A. Chemical reduction methods for synthesizing Ag and Al nanoparticles and their respective nanoalloys. Mater. Sci. Eng., B, 2011, 176, 187-203. Breitwieser, D.; Moghaddam, M.M.; Spirk, S.; Baghbanzadeh, M.; Pivec, T.; Fasl, H.; Ribitsch, V.; Kappe, C.O. In situ preparation of silver nanocomposites on cellulosic fibers-microwave vs. conventional heating. Carbohydr. Polym., 2013, 94, 677-686. Dubey, S.P.; Dwivedi, A.D.; Kim, I.C.; Sillanpaa, M.; Kwon, Y.N.; Lee, C. Synthesis of graphene-carbon sphere hybrid aerogel with silver nanoparticles and its catalytic and adsorption applications. Chem. Eng. J., 2014, 244, 160167. Mbhele, Z.H.; Salemane, M.G.; Sittert, C.G.C.E.V.; Nedeljkovic, J.M.; Luyt, A.S. Fabrication and characterization of silver-polyvinyl alcohol nanocomposites. Chem. Mater., 2003, 15(26), 5019-5024. Jing, S.; Xing, S.; Yu, L.; Wu, Y.; Zhao, C. Synthesis and characterization of Ag/polyaniline core-shell nanocomposites based on silver nanoparticles colloid. Mater. Lett., 2007, 61, 2794-2797. Ahmad, M.B.; Shameli, K.; Darroudi, M.; Yunus, W.M.Z.W.; Ibrahim, N.A. Synthesis and characterization of silver/clay nanocomposites by chemical reduction method. Am. J. Appl. Sci., 2009, 6(11), 1909-1914. Liu, B.; Shen, S.; Luo, J.; Wang, X.; Sun, R. One-pot green synthesis and antimicrobial activity of exfoliated Ag NP-loaded quaternized chitosan/clay nanocomposites. RSC Adv., 2013, 3, 9714-9722. Perez-Liminana, M.A.; Aran-Ais, F.; Orgiles-Barcelo, C. Novel waterborne polyurethane adhesives based on [email protected] nanocomposites. J. Adhes., 2014, 90, 437-456. Yang, Z.; Zhai, D.; Wang, X.; Wei, J. In situ synthesis of highly monodispersed nonaqueous small-sized silver nano-colloids and silver/polymer nanocomposites by ultraviolet photopolymerization. Colloids Surf., A, 2014, 448, 107-114. Bragg, W.H.; Bragg, W.L. The Crystalline State, Vol. 1; McMillan: New York, 1949. Goldstein, J.I.; Yakowitz, H. Practical scanning electron microscopy; Plenum Press: New York, 1975. Fryer, J.R. Chemical Applications of Transmission Electron Microscopy; Academic Press: London, 1979. Cappella, B.; Dietler, G. Force-distance curves by atomic force microscopy. Surf. Sci. Rep., 1999, 34(1-3), 1-104. Roucoux, A.; Schulz, J.; Patin, H. Reduced transition metal colloids: A novel family of reusable catalysts? Chem. Rev., 2002, 102(10), 3757-3778. Wu, Y.; Wang, D.; Li, Y. Nanocrystals from solutions: Catalysts. Chem. Soc. Rev., 2014, 43, 2112-2124. Chng, L.L.; Erathodiyil, N.; Ying, J.Y. Nanostructured catalysts for organic transformations. Acc. Chem. Res., 2013, 46(8), 1825-1837. Desireddy, A.; Conn, B.E.; Guo, J.; Yoon, B.; Barnett, R.N.; Monahan, B.M.; Kirschbaum, K.; Griffith, W.P.; Whetten, R.L.; Landman, U.; Bigioni, T.P. Ultrastable silver nanoparticles. Nature, 2013, 501(7467), 399-402. Corma, A.; Garcia, H. Supported gold nanoparticles as catalysts for organic reactions. Chem. Soc. Rev., 2008, 37, 2096-2126.

Current Organic Chemistry, 2015, Vol. 19, No. ?? [158]

[159] [160]

[161] [162]

[163]

[164] [165]

[166]

[167]

[168]

[169]

[170] [171]

[172]

[173]

[174]

[175]

[176]

[177] [178]

[179]

[180]

[181]

[182]

[183]

[184]

19

Bhosale, M.A.; Sasaki, T.; Bhanage, B.M. A facile and rapid route for the synthesis of Cu/Cu2O nanoparticles and their application in the Sonogashira coupling reaction of acyl chlorides with terminal alkynes. Catal. Sci. Technol., 2014, 4, 4274-4280. Srimani, D.; Bej, A.; Sarkar, A. Palladium nanoparticle catalyzed Hiyama coupling reaction of benzyl halides. J. Org. Chem., 2010, 75(12), 4296-4299. Bhosale, M.A.; Bhanage, B.M. A facile one-step approach for the synthesis of uniform spherical Cu/Cu2O nano- and microparticles with high catalytic activity in the Buchwald-Hartwig amination reaction. RSC Adv., 2014, 4, 15122-15130. Halbes-letinois, U.; Weibel, J.M.; Pale, P. The organic chemistry of silver acetylides. Chem. Soc. Rev., 2007, 36, 759-769. Mohanty, A.; Garg, N.; Jin, R.A. universal approach to the synthesis of noble metal nanodendrites and their catalytic properties. Angew. Chem. Int. Ed., 2010, 49, 4962-4966. Yan, W.; Wang, R.; Xu, Z.; Xu, J.; Lin, L.; Shen, Z.; Zhou, Y.A. Novel, practical and green synthesis of Ag nanoparticles catalyst and its application in three-component coupling of aldehyde, alkyne, and amine. J. Mol. Catal. A: Chem., 2006, 255, 81-85. Wei, C.; Li, Z.; Li, C. The first silver-catalyzed three-component coupling of aldehyde, alkyne, and amine. Org. Lett., 2003, 5(23), 4473-4475. Steffan, M.; Jakob, A.; Claus, P.; Lang, H. Silica supported silver nanoparticles from a silver(I) carboxylate: Highly active catalyst for regioselective hydrogenation. Catal. Commun., 2009, 10, 437-441. Cong, H.; Becker, C.F.; Elliott, S.J.; Grinstaff, M.W.; Porco, Jr, J.A. Silver nanoparticle-catalyzed Diels-Alder cycloadditions of 2-hydroxychalcones. J. Am. Chem. Soc., 2010, 132(21), 7514-7518. Zhou, X.; Lu, Y.; Zhai, L.L.; Zhao, Y.; Liu, Q.; Sun, W.Y. Propargylamines formed from three-component coupling reactions catalyzed by silver oxide nanoparticles. RSC Adv., 2013, 3, 1732-1734. Cirera, B.; Zhang, Y.Q.; Klyatskaya, S.; Klappenberger, F.; Barth, J.V. 2D self-assembly and catalytic homo-coupling of the terminal alkyne 1, 4-bis (3, 5-diethynyl-phenyl)butadiyne-1,3 on Ag(111). ChemCatChem., 2013, 5(11), 3281-3288. Zhang, Q.; Cai, S.; Li, L.; Chen, Y.; Rong, H.; Niu, Z.; Liu, J.; He, W.; Li, Y. Direct syntheses of styryl ethers from benzyl alcohols via Ag nanoparticlecatalyzed tandem aerobic oxidation. ACS Catal., 2013, 3, 1681-1684. Pradhan, N.; Pal, A.; Pal, T. Silver nanoparticle catalyzed reduction of aromatic nitro compounds. Colloids Surf., A, 2002, 196, 247-257. Jia, X.; Ma, X.; Wei, D.; Dong, J.; Qian, W. Direct formation of silver nanoparticles in cuttlebone-derived organic matrix for catalytic applications. Colloids Surf., A, 2008, 330, 234-240. Lee, J.H.; Kang, S.; Lee, J.Y.; Jung, J.H. A tetrazole-based metallogel induced with Ag+ ion and its silver nanoparticles in catalysis. Soft Matter., 2012, 8, 6557-6563. Oh, J.H.; Kim, D.Y.; Lee, J.S. Synthesis of large bumpy silver nanostructures with controlled sizes and shapes for catalytic applications. Bull. Korean Chem. Soc., 2014, 35(4), 1001-1004. Junejo, Y.; Baykal, A.: Sirajuddin. Green chemical synthesis of silver nanoparticles and its catalytic activity. J. Inorg. Organomet. Polym., 2014, 24, 401-406. Patel, A.C.; Li, S.; Wang, C.; Zhang, W.; Wei, Y. Electrospinning of porous silica nanofibers containing silver nanoparticles for catalytic applications. Chem. Mater., 2007, 19(6), 1231-1238. Edison, T.J.I.; Sethuraman, M.G. Instant green synthesis of silver nanoparticles using Terminalia chebula fruit extract and evaluation of their catalytic activity on reduction of methylene blue. Process Biochem., 2012, 47, 13511357. Jiang, Z.J.; Liu, C.Y.; Sun, L.W. Catalytic properties of silver nanoparticles supported on silica spheres. J. Phys. Chem. B, 2005, 109(5), 1730-1735. Ernest, V.; Shiny, P.J.; Mukherjee, A.; Chandrasekaran, N. Silver nanoparticles: A potential nanocatalyst for the rapid degradation of starch hydrolysis by -amylase. Carbohydr. Res., 2012, 352, 60-64. Murugadoss, A.; Goswami, P.; Paul, A.; Chattopadhyay, A. ‘Green’ chitosan bound silver nanoparticles for selective C-C bond formation via in situ iodination of phenols. J. Mol. Catal. A: Chem., 2009, 304, 153-158. Xu, R.; Wang, D.; Zhang, J.; Li, Y. Shape-dependent catalytic activity of silver nanoparticles for the oxidation of styrene. Chem. Asian J., 2006, 1, 888-893. Mitsudome, T.; Mikami, Y.; Mori, H.; Arita, S.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Supported silver nanoparticle catalyst for selective hydration of nitriles to amides in water. Chem. Commun., 2009, (22), 3258-3260. Purcar, V.; Donescu, D.; Petcu, C.; Luque, R.; Macquarrie, D.J. Efficient preparation of silver nanoparticles supported on hybrid films and their activity in the oxidation of styrene under microwave irradiation. Appl. Catal., A, 2009, 363, 122-128. Najafpour, M.M.; Amini, M.; Sedigh, D.J.; Rahimi, F.; Bagherzadeh, M. Activated layered manganese oxides with deposited nano-sized gold or silver as an efficient catalyst for epoxidation of olefins. RSC Adv., 2013, 3, 2406924074. Beier, M.J.; Hansen, T.W.; Grunwaldt, J.D. Selective liquid-phase oxidation of alcohols catalyzed by a silver-based catalyst promoted by the presence of ceria. J. Catal., 2009, 266, 320-330.

20 [185]

[186]

[187]

[188]

[189]

[190]

[191] [192]

[193]

[194]

[195]

[196]

[197]

[198]

[199]

[200]

[201] [202]

[203]

[204]

[205]

[206]

Current Organic Chemistry, 2015, Vol. 19, No. ??

Bhosale and Bhanage

Zhao, H.; Zhou, J.; Luo, H.; Zeng, C.; Li, D.; Liu, Y. Synthesis, characterization of Ag/MCM-41 and the catalytic performance for liquid-phase oxidation of cyclohexane. Catal. Lett., 2006, 108(1-2), 49-54. Mitsudome, T.; Mikami, Y.; Funai, H.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Oxidant-free alcohol dehydrogenation using a reusable hydrotalcitesupported silver nanoparticle catalyst. Angew. Chem. Int. Ed., 2008, 47, 138141. Mitsudome, T.; Arita, S.; Mori, H.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Supported silver-nanoparticle-catalyzed highly efficient aqueous oxidation of phenylsilanes to silanols. Angew. Chem. Int. Ed., 2008, 47, 7938-7940. Mitsudome, T.; Noujima, A.; Mikami, Y.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Supported gold and silver nanoparticles for catalytic deoxygenation of epoxides into alkenes. Angew. Chem. Int. Ed., 2010, 49, 5545-5548. Erasmus, E.; Thune, P.C.; Verhoeven, M.W.G.M.; Niemantsverdriet, J.W.; Swarts, J.C. A new approach to silver-catalysed aerobic oxidation of octadecanol: Probing catalysts utilising a flat, two-dimensional silicon-based model support system. Catal. Commun., 2012, 27, 193-199. Raji; Vadakkekara; Chakraborty, M.; Parikh, P.A. Catalytic performance of silica-supported silver nanoparticles for liquid-phase oxidation of ethylbenzene. Ind. Eng. Chem. Res., 2012, 51, 5691-5698. Christopher, P.; Linic, S. Shape and size-specific chemistry of Ag nanostructures in catalytic ethylene epoxidation. ChemCatChem., 2010, 2, 78-83. Yadav, G.D.; Mewada, R.K. Selectivity engineering in the synthesis of value added chemicals: Oxidation of 1-octanol to 1-octanal over nano-fibrous AgOMS-2 catalysts. Chem. Eng. Res. Des., 2011, 90, 86-97. Bhatte, K.D.; Tambade, P.J.; Dhake, K.P.; Bhanage, B.M. Silver nanoparticles as an efficient, heterogeneous and recyclable catalyst for synthesis of enaminones. Catal. Commun., 2010, 11, 1233-1237. Safari, J.; Gandomi-Ravandi, S. Silver decorated multi-walled carbon nanotubes as a heterogeneous catalyst in the sonication of 2-aryl-2, 3dihydroquinazolin-4(1H)-ones. RSC Adv., 2014, 4, 11654-11660. Mielby, J.; Poreddy, R.; Engelbrekt, C.; Kegnæs, S. Highly selective formation of imines catalyzed by silver nanoparticles supported on alumina. Chin. J. Catal., 2014, 35(5), 670-676. Yang, X.; Gan, L.; Zhu, C.; Lou, B.; Han, L.; Wang, J.; Wang, E. A dramatic platform for oxygen reduction reaction based on silver nanoclusters. Chem. Commun., 2014, 50, 234-236. Yadav, G.D.; Mewada, R.K. Novelties of azobenzene synthesis via selective hydrogenation of nitrobenzene over nano-fibrous Ag-OMS-2 mechanism and kinetics. Chem. Eng. J., 2013, 221, 500-511. Cai, S.; Rong, H.; Yu, X.; Liu, X.; Wang, D.; He, W.; Li, Y. Room temperature activation of oxygen by monodispersed metal nanoparticles: Oxidative dehydrogenative coupling of anilines for azobenzene syntheses. ACS Catal., 2013, 3, 478-486. Ghomi, J.S.; Zahedi, S.; Ghasemzadeh, M.A. AgI nanoparticles as a remarkable catalyst in the synthesis of (amidoalkyl)naphthol and oxazine derivatives: An eco-friendly approach. Monatsh Chem., 2014, 145, 1191-1199. Sankar, M.; Dimitratos, N.; Miedziak, P.J.; Wells, P.P.; Kiely, C.J.; Hutchings, G.J. Designing bimetallic catalysts for a green and sustainable future. Chem. Soc. Rev., 2012, 41, 8099-8139. Narayanan, R. Recent advances in noble metal nanocatalysts for Suzuki and Heck cross-coupling reactions. Molecules, 2010, 15, 2124-2138. Chen, Y.; Wang, C.; Liu, H.; Qiu, J.; Bao, X. Ag/SiO2: A novel catalyst with high activity and selectivity for hydrogenation of chloronitrobenzenes. Chem. Commun., 2005, 5298-5300. Wang, P.; Huang, B.; Qin, X.; Zhang, X.; Dai, Y.; Wei, J.; Whangbo, M.H. [email protected]: A highly efficient and stable photocatalyst active under visible light. Angew. Chem. Int. Ed., 2008, 47, 7931-7933. Xu, R.; Wang, X.; Wang, D.; Zhou, K.; Li, Y. Surface structure effects in nanocrystal MnO2 and Ag/MnO2 catalytic oxidation of CO. J. Catal., 2006, 237, 426-430. Wang, C.; Yin, H.; Chan, R.; Peng, S.; Dai, S.; Sun S. One-pot synthesis of oleylamine coated Au Ag alloy NPs and their catalysis for CO oxidation. Chem. Mater., 2009, 21(3), 433-435. Yen, C.W.; Lin, M.L.; Wang, A.; Chen, S.A.; Chen, J.M.; Mou, C.Y. CO oxidation catalyzed by Au-Ag bimetallic nanoparticles supported in mesoporous silica. J. Phys. Chem. C, 2009, 113(41), 17831-17839.

Received: August 30, 2014

[207]

[208]

[209]

[210]

[211]

[212]

[213]

[214]

[215]

[216]

[217]

[218]

[219]

[220]

[221]

[222]

[223]

[224]

[225]

[226]

Kim, M.R.; Choi, S.H. One-step synthesis of Pd-M/ZnO (M=Ag, Cu, and Ni) catalysts by  -irradiation and their use in hydrogenation and Suzuki reaction. J. Nanomater., 2009, 2009, 302919. Venkatesan, P.; Santhanalakshmi, J. Synthesis, characterization and catalytic activity of trimetallic nanoparticles in the Suzuki C-C coupling reaction. J. Mol. Catal. A: Chem., 2010, 326, 99-106. Moreno, M.; Kissell, L.N.; Jasinski, J.B.; Zamborini, F.P. Selectivity and reactivity of alkylamine- and alkanethiolate- stabilized Pd and PdAg nanoparticles for hydrogenation and isomerization of allyl alcohol. ACS Catal., 2012, 2, 2602-2613. Venkatesan, P.; Santhanalakshmi, J. Kinetics of oxidation of L-Leucine by mono and bimetallic gold and silver nanoparticles in hydrogen peroxide solution. Chin. J. Catal., 2012, 33(8), 1306-1311. Hirasawa, S.; Watanabe, H.; Kizuka, T.; Nakagawa, Y.; Tomishige, K. Performance, structure and mechanism of Pd-Ag alloy catalyst for selective oxidation of glycerol to dihydroxyacetone. J. Catal., 2013, 300, 205-216. Huang, X.; Wang, X.; Wang, X.; Wang, X.; Tan, M.; Ding, W.; Lu, X. P123stabilized Au-Ag alloy nanoparticles for kinetics of aerobic oxidation of benzyl alcohol in aqueous solution. J. Catal., 2013, 301, 217-226. Harish, S.; Sabarinathan, R.; Joseph, J.; Phani, K.L.N. Role of pH in the synthesis of 3-aminopropyl trimethoxysilane stabilized colloidal gold/silver and their alloy sols and their application to catalysis. Mater. Chem. Phys., 2011, 127, 203-207. Tsao, Y.C.; Rej, S.; Chiu, C.Y.; Huang, M.H. Aqueous phase synthesis of Au-Ag core shell nanocrystals with tunable shapes and their optical and catalytic properties. J. Am. Chem. Soc., 2014, 136, 396-404 . Hernandez-Gordillo, A.; Gonzalez, V.R. Silver nanoparticles loaded on Cudoped TiO2 for the effective reduction of nitro-aromatic contaminants. Chem. Eng. J., 2014, DOI: 10.1016/j.cej.2014.05.148. Adekoya, J.A.; Dare, E.O.; Mesubi, M.A.; Nejo, A.A.; Swart, H.C.; Revaprasadu, N. Synthesis of polyol based Ag/Pd nanocomposites for applications in catalysis. Result. Phys., 2014, 4, 12-19. Rajesh, R.; Venkatesan, R. Encapsulation of silver nanoparticles into graphite grafted with hyperbranched poly (amidoamine) dendrimer and their catalytic activity towards reduction of nitro aromatics. J. Mol. Catal. A: Chem., 2012, 359, 88-96. Duan, B.; Liu, F.; He, M.; Zhang, L. Ag-Fe3O4 [email protected] microspheres constructed by in situ one-pot synthesis for rapid hydrogenation catalysis. Green Chem., 2014, 16, 2835-2845. Shin, K.S.; Choi, J.Y.; Park, C.S.; Jang, H.J.; Kim, K. Facile synthesis and catalytic application of silver-deposited magnetic nanoparticles. Catal. Lett., 2009, 133(1-2), 1-7. Das, S.K.; Khan, M.M.R.; Guha, A.K.; Naskar, N. Bio-inspired fabrication of silver nanoparticles on nanostructured silica: Characterization and application as a highly efficient hydrogenation catalyst. Green Chem., 2013, 15, 25482557. Panigrahi, R.; Srivastava, S.K. Ultrasound assisted synthesis of a polyaniline hollow microsphere/Ag core/shell structure for sensing and catalytic applications. RSC Adv., 2013, 3, 7808-7815. Fernandez-Merino, M.J.; Guardia, L.; Paredes, J.I.; Villar-rodil, S.; MartinezAlonso, A.; Tascon J.M.D. Developing green photochemical approaches towards the synthesis of carbon nanofiber and graphenesupported silver nanoparticles and their use in the catalytic reduction of 4-nitrophenol. RSC Adv., 2013, 3, 18323-18331. Davarpanah, J.; Kiasat, A.R. Catalytic application of silver nanoparticles immobilized to rice husk-SiO2-aminopropylsilane composite as recyclable catalyst in the aqueous reduction of nitroarenes. Catal. Commun., 2013, 41, 6-11. Deshmukh, S.P.; Dhokale, R.K.; Yadav, H.M.; Achary, S.N.; Delekar, S.D. Titania- supported silver nanoparticles: An efficient and reusable catalyst for reduction of 4-nitrophenol. Appl. Surf. Sci., 2013, 273, 676-683. Ji, Z.; Shen, X.; Yang, J.; Zhu, G.; Chen, K. A novel reduced graphene oxide/Ag/CeO2 ternary nanocomposite: Green synthesis and catalytic properties. Appl. Catal., B, 2014, 144, 454-461. Dong, Z.; Le, X.; Li, X.; Zhang, W.; Dong, C.; Ma, J. Silver nanoparticles immobilized on fibrous nano-silica as highly efficient and recyclable heterogeneous catalyst for reduction of 4-nitrophenol and 2-nitroaniline. Appl. Catal., B, 2014, 158-159, 129-135.

Revised: October 22, 2014

Accepted: February 03, 2015

DISCLAIMER: The above article has been published in Epub (ahead of print) on the basis of the materials provided by the author. The Editorial Department reserves the right to make minor modifications for further improvement of the manuscript.