In: Silver Nanoparticles: Synthesis, Uses and Health Concerns ISBN: 978-1-62808-402-3

Editors: Ilaria Armentano and Jose Maria Kenny © 2013 Nova Science Publishers, Inc.

Chapter 5

SYNTHESIS METHODOLOGY FOR SIZE AND SHAPE

CONTROL OF SILVER NANOPARTICLES

M. A. Shenashen,1 S. A. El-Safty

1,2, and E. A. Elshehy

1

1National Institute for Materials Science (NIMS), Ibaraki-ken, Japan

2Graduate School for Advanced Science and Engineering,

Waseda University, Tokyo, Japan

Keywords: Silver, Nanostructures, Synthesis, Morphology

1. INTRODUCTION

Nanoparticles (NPs) have gained considerable interests because of their unique

properties. Novel metal NPs such as silver (Ag) have gained increasing attention because of

their distinctive physical and chemical properties, as well as wide potential applications. Ag

has several forms in the environment or in living organisms, such as metallic, ionic,

complexes, and colloidal. NPs possess small size and large surface to volume ratio, which

lead to both chemical and physical differences in their properties, such as mechanical,

biological, and sterical properties, catalytic activity, thermal and electrical conductivity,

optical absorption, and melting point, compared with their bulk counterparts. These properties

can be utilized in areas where high surface areas are critical for success. Ag NPs and their

related nanostructures have been investigated extensively because of their unique properties

and great potential applications in plasmonics, anti-bacterial materials, sensing, and

spectroscopy (Kosmala et al., 2011; Martínez-Castañónet al., 2008; Daniel et al., 2004;

Zharov et al., 2005; Klasen, 2000; Jain et al., 2009; Tian et al., 2007; Le et al., 2010;

Shrivastava et al., 2009; Le et al., 2010). For instance, the anti-bacterial activity and good

conductivity of Ag have been known since the ancient times, and are now widely investigated

for real applications (Kosmala et al., 2011; Martínez-Castañónet al., 2008; Daniel et al., 2004;

Zharov et al., 2005). Ag compounds have been used as anti-bacterial agents in burn and

E-mails: sherif.elsafty@nims.go.jp, sherif@aoni.waseda.jp.

The exclusive license for this PDF is limited to personal website use only. No part of this digital document may be reproduced, stored in a retrieval system or transmitted commercially in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 102

wound therapy (Klasen, 2000). In addition, Ag NPs exhibit the surface plasmon resonance

effect and strong bacterial resistance to antibiotics, making them ideal for biotechnological

applications (Kosmala et al., 2011; Martínez-Castañónet al., 2008; Daniel et al., 2004; Zharov

et al., 2005; Klasen, 2000; Jain et al., 2009; Tian et al., 2007).

The synthesis of Ag NPs has been investigated extensively. Ag NP antibacterial activity

against both Gram-negative Escherichia coli and Gram-positive Staphylococcus Aureus

bacteria has been reported (Le et al., 2010; Shrivastava et al., 2009; Le et al., 2010). Ag NPs

have also been impregnated with paper for water treatment (DankovichT et al., 2011).

Moreover, Ag NPs utilizing the surface plasmon resonance effect have been used to color

merino wool fibers and impart antimicrobial and antistatic properties to produce a novel Ag

NP−wool composite material (DankovichT et al., 2011). Ag NPs and various Ag-based

compounds containing ionic Ag or metallic Ag that exhibit antimicrobial activity have also

been synthesized (Le et al., 2012; Slawson et al., 1992; Zhao et al., 1998; Dura´n et al., 2007;

Cho et al., 2005). Thus, understanding the relationship between the physical and chemical

properties of nanomaterials and their potential risk to the environment and human health has

gained increasing interests. The availability of NP panels, where their size, shape, and surface

are precisely controlled, allows for a better correlation of the NP properties to their

toxicological effects (Albrecht et al., 2006).

This chapter introduces the synthesis of Ag NPs, as well as their separation and

purification. We separated the discussion into four sections. The Introduction section presents

the general overview of Ag NPs. The next section entitled ―General aspects of Ag NP

fabrication‖ reports the different techniques used for the preparation of Ag NPs. Controlling

the size and morphology of Ag NPs based on an indirect method is discussed the third

section. Finally, the fourth section presents the conclusion and outlook of this chapter.

2. GENERAL ASPECTS OF AG NPS FABRICATION

The optical properties of Ag NPs produce one of the most promising contributions in the

field of sensing and imaging applications. Ag NPs received considerable interests as a sensor

for ultrasensitive detection of a wide variety of compounds, ranging from chemical pollutants

to biomolecules, with detection thresholds as low as a single molecule (Kosmala et al., 2011;

Martínez-Castañónet al., 2008; Daniel et al., 2004; Zharov et al., 2005; Klasen, 2000;

DankovichT et al., 2011; Le et al., 2012; Zhao et al., 1998; Albrecht et al., 2006).

Synthesizing metallic NPs with different shapes is possible to date. Nanospheres, nanorods,

and nanocups are just a few of the shapes that have been grown, and the size of these particles

is also possible to control to some extent. The characteristics of the NPs can be determined

using analytic techniques. The ability to morphologically control (size, shape, and crystalline

structure) NPs during fabrications has an important role in numerous fields of application,

such as catalysis, medicine, and electronics. Using NPs in such applications also requires the

development of methods for NP assembly or dispersion in various media.

Recent studies on Ag synthesis have focused on the fabrication of a large volume and

high yield of Ag NPs with tunable particle shapes and sizes. However, synthesizing NPs with

uniform shapes and precise sizes still remains a challenge, attracting several researchers

worldwide. Ag NPs can be synthesized using various methods, such as chemical reduction

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 103

(Pal et al., 2007), electrochemical (Reetz., 1994; Santos et al., 2002), γ-radiation (Choi et al.,

2005), laser ablation (Amendola et al., 2007), solvothermal (Yang et al., 2007), hydrothermal

(Shen et al., 2007), photochemical (Henglein, 1998), sonochemical (Salkar et al., 1999), and

sputtering methods (Okumu et al., 2005). Ag NPs can be produced with various sizes and

shapes depending on the fabrication method. The different shapes of Ag NPs include spheres,

rods, wires, and plates, which can be produced by varying the manufacturing method. This

study reviews the most general routes to synthesize Ag NPs.

2.1. Chemical Approach

Chemical reduction is the important and most applicable route for the preparation of

stable Ag NPs and its colloidal dispersions in water or organic solvents (Tao et al., 2006;

Wiley et al., 2005). Different reducing agents, such as citrate, borohydride, ascorbic acid, and

elemental hydrogen, were used in this process (Figs. 1 and 2) (Shirtcliffe et al., 1999; Chou et

al., 2000; Sondi et al., 2003; Merga et al., 2007; Corato et al., 2012). The reduction of Ag ions

(Ag+) in aqueous solution generally yields colloidal Ag with particle diameters of several

nanometers. The first stage of the reduction process of different Ag complexes provides Ago

atoms. Oligomeric clusters were then formed by agglomeration, which eventually lead to the

formation of colloidal Ag particles (Kapoor et al., 1994). Chi et al. (2012) demonstrated an

effective route to prepare Fe3O4@SiO2–Ag core–shell structured nanocomposite by

combining the sol–gel process and a facile in situ wet chemistry method with the aid of the

dual function of PVP as both reductant and stabilizer.

Figure 1. Schematic of the chemical reduction of AgNO3 using NaBH4.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 104

Figure 2. Schematic illustration of the formation process of Fe3O4@SiO2–Ag nanocomposite (a), SEM

images of Fe3O4@SiO2 microspheres and Fe3O4@SiO2–Ag nanocomposite (b, c), TEM images of

Fe3O4@SiO2 microspheres and Fe3O4@SiO2–Ag nanocomposite (e, f) (Chi et al., 2012, © 2012

Elsevier Inc. All rights reserved).

Evanoff and Chumanov reported the size-controlled synthesis of Ag NPs through the

reduction of Ag(I) oxide. The synthesis was conducted using hydrogen gas in water by simple

bubbling of hydrogen gas through the saturated Ag oxide solution at an elevated temperature

(Evanoff et al., 2004). They varied the temperature to control the rate of the reaction and the

overall time required for the particles to grow in specific dimensions. The syntheses of NPs

by chemical reduction methods are therefore often performed in the presence of stabilizers to

prevent unwanted agglomeration of the colloids. Kim et al. (2012), reported various Ag2O

crystal morphologies fabricated using a simple precipitation method at room temperature

(Figure 3).

Liz-Marzán and Lado-Touriño (1996), reported the reduction and stabilization of Ag NPs

in ethanol using nonionic surfactants, such as Brij 92 [poly-(2)-oxyethylene oleyl ether], Brij

72 [poly-(2)-oxyethylene stearyl ether], Brij 97 [poly-(10)-oxyethylene oleyl ether], and

Tween 80 [(polyoxyethylene-(20)-sorbitan monooleate)]. They found that surfactants have an

important role in the stabilization of metallic colloids and the reduction of Ag ions to the

neutral state through the oxidation of oxyethylene groups into hydroperoxides. Oliveira et al.

(Oliveira et al., 2005) reported that dodecanethiol was used as stabilization and capping agent

during the reduction process with sodium borohydride, which binds onto the surface of Ag

NPs, avoiding their aggregation and making them soluble in certain solvents.

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 105

Figure 3. Schematic of the morphological evolution of Ag2O microcrystals as a function of NaOH

concentration and the total AgNO3/pyridine/NaOH reactant concentration. (Modified Ref. Kim et al.,

2012, © 2012 American Chemical Society).

Meanwhile, several polymers were used as stabilizing agents, such as PEG, PMMA, and

PVP (Bai et al., 2007; He et al., 2004; Mock et al., 2002; Zhang et al., 2008; Liu et al., 2009).

Liu et al. (Liu et al., 2009) reported that Ag NPs were prepared under controlled conditions

using a surfactant of octanoic acid via a reverse micelle technique.

Reducing Ag by wet chemical method generates a wide range of particle shapes and

sizes. For instance, the Ag nanoprisms were prepared by boiling Ag nitrate in the presence of

stabilizer. A mixture of nanoprisms and nanospheroids were formed in a wide range of size

distribution using this synthesis pathway. Dong et al. also reported the synthesis of triangular

Ag nanoprisms via stepwise reduction of Ag nitrate with sodium borohydride and trisodium

citrate (Dong et al., 2010). The formation of the triangular nanoprisms is dependent on the

molar ratios of sodium borohydride and trisodium citrate used in the reactions, in which a

balance between the precursors contributed to the formation of the small spherical particles.

Kundu et al. applied a microwave irradiation for the rapid synthesis of size-controlled self-

assembling Ag NPs. They conducted the procedure in the presence of alkaline 2,7-dihydroxy

naphthalene as a reducing agent and nonionic surfactant (TX-100) media (Kundu et al.,

2009). They controlled the particle size to within 4 nm to 32 nm by varying the TX-100 to

Ag(I) molar ratio. The transformation of the spherical NPs is critical for the synthesis of the

triangular nanoprisms.

The chemical approach showed evidence of the simple control of particle morphology in

terms of size and shape. However, environment-friendly and green synthesis methods are still

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 106

needed. The most critical points that limited the domain of this chemical approach are as

follows:

Employing toxic chemicals

Sensitivity to atmospheric conditions

Often yielding particles in non-polar organic solutions

Leaving residual reducing agents

Final product needs further purification

Possible environmental toxicity and biological hazards

Therefore, development of a green method is needed to synthesize Ag NPs. Pietrobon

and Kitaev (2008), reported on the decahedral Ag NP synthesis with good morphology based

on the photochemical transformation of aqueous Ag NP precursors, where the precursor

solution transforms from a mixture of shapes dominated by small Ag platelets into the

decahedra. Scaiano et al. (2009), reported that ketyl radicals were generated by cleavage of

benzoins and photoreduction of aromatic ketones of reduced Ag ions to Ag NPs in aqueous or

micellar solutions. Potara et al. (2012), proposed an effective strategy for generating small

clusters of anisotropic Ag NPs enveloped in a shell of chitosan biopolymer and showed that

they can be implemented as highly efficient surface-enhanced Raman scattering

substrates for ultrasensitive detection of nonresonant analyte molecules. Different

morphological structures were obtained using chemical methods (Figure 4).

2.2. Physical Approach

Preparation of NPs based on physical method is generally fabricated using evaporation–

condensation, which can be carried out by a furnace at atmospheric pressure.

Figure 4. TEM Images of Ag NPs prepared using reduction method (A and B) (Sondi et al., 2003,

©2003 Elsevier), (C and D) (Dong et al., 2010, ©2010 American Chemical Society) and (E-H) (Wiley

et al., 2007, © 2007 American Chemical Society).

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 107

Figure 5. Ag NP fabrication based on laser ablation of microparticle technique.

The precursor of the metal at a definite temperature and pressure is vaporized into a

carrier gas, and NPs were produced using the evaporation/condensation technique (Kruis et

al., 2000; Magnusson et al., 1999). Jung et al. (2006), synthesized Ag NPs via a small ceramic

heater based on controlled-rate cooling, producing small Ag NPs in high concentration.

Fabrication of Ag NPs with laser ablation technique in solution strongly depends on

several parameters, such as the wavelength of the laser impinging the metallic target, duration

of the laser pulses, laser fluence, ablation time duration, and effective liquid medium, with or

without the presence of surfactants (Figure 5) (Kabashin et al., 2003; Sylvestre et al., 2004;

Hwang et al., 2000; Tarasenko et al., 2006; Nichols et al., 2006). Laser fluence is one of the

most important parameters. Particle size is based on the laser fluence, which increases with

increasing laser fluence. In addition, the concentration and morphology of particles were

based on the number of laser shots (i.e., the time spent during laser vaporization). The

presence of surfactant affected the particle size, in which, the higher the surfactant

concentration, the smaller the formation of NPs by laser ablation (Mafune et al., 2001). In

view of the advantages of physical design, this methodology offers interesting features as

follows:

Absence of solvent contamination

High purity compared with chemical method

By contrast, the physical approach has several disadvantages as follows:

Consumes a great amount of energy

Requires a great deal of time to achieve thermal stability

Produces small-scale products

2.3. Irradiation Approach

Ag NPs can be successfully synthesized using a variety of irradiation methods. A method

using gamma radiation provides more convenient and cleaner approach. Another approach for

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 108

the synthesis of Ag NPs is using high-intensity electromagnetic radiation for photoreduction

of Ag salt. For instance, Abid et al. introduced a method to fabricate a well-defined size and

shape distribution of Ag NPs using direct laser irradiation of an aqueous solution containing

Ag salt and a surfactant of sodium dodecyl sulfate (Abid et al., 2002). Using non-reducing

agents in their synthesis, Abid et al. generated spherical Ag NPs with particle sizes ranging

from 5 nm to 20 nm through this synthetic pathway. Ag NPs were synthesized by γ-ray

irradiation of acetic water solutions containing AgNO3 and chitosan (Chen et al., 2007). The

resulting particles with an average diameter of 4 nm to 5 nm were densely dispersed in the

solution because of the protection of chitosan chains. Large scale Ag NPs with different sizes

were prepared by a simple alteration of electron beam conditions, such as acceleration

voltage, current, and irradiation time (Figure 6) (Kim et al., 2012).

Li and Zhang (2010) reported that Ag NPs can be fabricated under electron beam

irradiation. The effect of time on the size and distribution of Ag NPs was discussed. Several

reports on the fabrication of Ag NPs based on irradiation methods exist (Bogle et al., 2006;

Wei et al., 2012; Shmakov et al., 2010; Tan et al., 2007; Park et al., 2011). Tan et al., (2007)

proposed a one-step photoreduction process as a developed strategy to synthesize positively

charged Ag NPs using branched polyethyleneimine (BPEI)/AgNO3/4-(2-hydroxyethyl)-1-

piperazineethanesulfonic acid (HEPES) solutions in the presence of oxygen. Particle size and

distribution can be controlled by the molar ratio between BPEI and Ag ions and/or by the

molecular weight of the BPEI chains (Figure 7). Figure 8 presented the morphological

structure of Ag NDs prepared by Park et al. (2011). Compared with other approaches, the

electron beam irradiation method showed a particular interest in the following:

Controlled fabrication of Ag NPs in a large-scale synthesis.

The choice of the laser photon energy determines the axial ratio of the particles.

Figure 6. Schematic of the preparation of Ag NPs using electron beam irradiation (Kim et al., 2012©

2012 Elsevier Ltd. All rights reserved).

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 109

Figure 7. Suggested mechanism for the synthesis of BPEI/HEPES reduced Ag [+] nanoparticles (Tan et

al., 2007© 2007 American Chemical Society].

Figure 8. TEM photo (A), ED (B) and HRTEM micrographs of a Ag NDs synthesized by UV exposure

for 60min (Park et al., 2011, Copyright © 2011 Hyeong-Ho).

2.4. Microwave-assisted Approach

Microwave-assisted synthesis is a promising method for the preparation of Ag NPs

(Sreeram et al., 2008; Komarneni et al., 2002; Zhu et al., 2004; He et al., 2003). Devi et al.

reported the synthesis of Ag NPs via microwave-assisted method using ethanol and PVP as

the reducing and stabilizing agents, respectively (Pal et al., 2009). The synthesized Ag NPs

exhibited spherical geometries and particle sizes ranging from 10 nm to 11 nm.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 110

Figure 9. SEM photo of Ag NPs based on microwave assisted technique (A- D) (Nadagouda et al., 2011

©2011 &2011 American Chemical Society), SEM photo of Ag NPs based on microwave assisted

technique, Ag NRs (E, F) (Zhu et al., 2004 © 2003 Elsevier B.V. All rights reserved), Ag dendrite (G,

H) (He et al., 2003 © 2003 Elsevier Science B.V. All rights reserved).

Yang et al. synthesized Ag NPs by solvothermal method, in which the Ag NPs exhibited

multiple shape geometries, such as nanorods, triangular plates, hexagonal plates, nanocubes,

and polyhedrons (Yang et al., 2007). Different morphologies of Ag NPs were obtained during

the preparation from a solution of Ag nitrate in the presence of reducing agents based on the

microwave irradiation method (Sharma et al., 2008). Chen et al. (Chen et al., 2008) prepared

Ag NPs by a microwave-assisted method employing carboxymethyl cellulose sodium as a

reducing and stabilizing agent. The concentration of the reactants affected the size of the

resulting Ag NPs. The results confirmed that Ag NPs were stable and had a uniform structure

at room temperature for a long time. Yin et al. (Yin et al., 2002) reported that large-scale and

size-controlled Ag NPs were prepared rapidly using Ag NO3 and trisodium citrate in the

presence of formaldehyde as a reducing agent via microwave irradiation. The size and size

distribution of the produced Ag NPs were strongly dependent on the states of the Ag cations

in the initial reaction solution. Moreover, Hu et al. reported that amino acids (as reducing

agents) and soluble starch (as a protecting agent) were used to fabricate monodispersed Ag

NPs via microwave irradiation (Hu et al., 2008). Ag NPs and nanorods were prepared (Tsuji

et al., 2005; Tsuji et al., 2004; Navaladian et al., 2008; Nadagouda et al., 2011) based on the

microwave route. Several morphological nano-structures of Ag such as nanoplate, NR and

dendrite were obtained (Figure 9).

2.5. Electrochemical Approach

Several studies on Ag NPs electrochemical synthesis (Demarconnay et al., 2004) based

on the high activity of Ag toward oxygen reduction has been reported (Figure 10). Ag NPs

are a promising catalyst for the oxygen reduction reaction, have relatively low cost, and

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 111

withhold good alcohol-tolerance capacity (Lefevre et al., 2003; Meng et al., 2006; Blizanac et

al., 2007). Polyphenylpyrrole-coated Ag nanospheroids (3 nm to 20 nm) were synthesized by

electrochemical reduction at the liquid/liquid interface. This nanocompound was prepared by

transferring the Ag metal ion from the aqueous phase to the organic phase, where it reacted

with pyrrole monomer (Johans et al., 2007).

Ag dendrites are fabricated on the Ni/Cu substrate using a templateless, surfactantless,

electrochemical method (Gu et al., 2008). The applied potential affected the morphology and

structure of the prepared materials. The electrochemical route was used for the production of

Ag NPs using ionic liquids as eco-friendly green electrolytes and can be applied to various

types of oxygen reduction reaction-related studies (Tsai et al., 2010). Probe DNA

immobilized in a small gap between two electrodes was hybridized to a portion of the

unmodified target DNA. Improving the sensitivity of probe was achieved by precipitation of

Ag metal onto the gold NPs (Figure 11) (Drummond et al., 2003). Ag nano-inukshuks were

synthesized based on the galvanic replacement reaction by immersing n-type Ge(100) in

aqueous AgNO3 solution. AgNO3 solution was added dropwise on the pretreated wafer of

GaAs with HF to initiate the growth of Ag nanostructures, and the morphology was based on

the concentration of AgNO3. Ag nano-inukshuks were formed in aqueous AgNO3 solution at

room temperature on flat or rough, native oxide-capped germanium surfaces. The nano-

inukshuks had a diameter of 300 nm stacked hexagons with facets and were grown

perpendicular to the (111) planes of the Ag hexagons (Aizawa et al., 2005). Different

morphological nano-structures of Ag were presented in (Figure 12). The significant features

of electrochemical method of synthesis Ag NPs are as follows:

Cost effective and simple

Size and morphology control by adjusting the electrolysis parameters

Improves the homogeneity of Ag NPs by changing the composition of the

electrolytic solutions

Expensive equipment or vacuum is not needed.

Figure 10. Schematic of electrochemical formation of silver nanoparticles in distilled water.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 112

By contrast, the electrochemical method showed the following limitations:

Produces small-scale products

Consumes a great amount of energy

Requires a great deal of time

Figure 11. Precipitation of Ag metal onto the gold NPs (Drummond et al., 2003 © NATURE Publishing

Group).

Figure 12. SEM images with different magnifications of as-deposited Ag crystallites prepared by the

electrochemical process at different applied potentials for 30 min: (A, B) -0.4 V, (C, D) -1.0 V, and (E,

F) -2.0 V (Gu et al., 2008, © 2008 American Chemical Society). SEM image of Ag nano-inukshuks

(V), the Ag corners and dendritic structures are observed (K,L) (Sun et al., 2007, © 2007 American

Chemical Society). Ag nanoplates formed at a reaction time of 2 min. Low- and high-magnification

SEM images (G, H); and HRTEM image, the inset represents low TEM and an enlarged image of a

small area of (I) (Aizawa et al., 2005, © 2005 American Chemical Society).

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 113

Figure 13. Direct hydrothermal synthesis of Ag-MCM-41 (Gac et al., 2007 © 2006 Elsevier B.V. All

rights reserved).

2.6. Galvanic Replacement Reactions

The effectiveness and simplicity of operation and equipment of galvanic replacement

reactions caused a significant attention in the field of applications. Galvanic replacement

reactions can be described as the spontaneous reduction of metal ions to metallic particles and

films. The reduction process was based on the electrons derived from the valence band

electrons of the substrate. This process continues as long as the generated electrons from the

oxidized substrate still flow into the solution or until the oxidized substrate forms, thereby

arresting electron transfer. The preparation of metal nanostructure with controllable hollow

interiors and porous walls can be achieved based on the galvanic replacement reaction.

Fabrication of Ag nanoplates on GaAs wafer by galvanic reaction between AgNO3 and GaAs

has been reported (Sun et al., 2007).

2.7. Hydrothermal Approach

The hydrothermal method is an interesting synthetic protocol because of its low-cost and

environmentally friendly technique. This method can be used on a large area and for the

fabrication of several nanostructures. NPs are synthesized via hydro/solvothermal synthesis

method based on hot solvent in an autoclave under high pressure. Hot H2O serves both as a

catalyst and, occasionally, as a component of solid phases (Figure 13). Octahedral gold

nanocrystals were synthesized hydrothermally from an aqueous solution of HAuCl4, trisodium

citrate, and a surfactant (Gac et al., 2007; Chang et al., 2008; Yu et al., 2005). Yang and Pan

(Yang et al., 2012) reported the synthesis of Ag NPs based on the green chemistry principles

via a hydrothermal route, which is a very simple and economical method. Wiley et al. (2009),

reported the selective synthesis of pentagonal nanowires, cuboctahedra, nanocubes, nanobars,

bipyramids, and nanobeams of Ag with a solution-phase polyol synthesis. They obtained

noble metal NPs with different geometries, including spheres, polygonal plates, sheets, rods,

wires, tubes, and dendrites via such rapid synthesis.

Dong et al. demonstrated an effective hydrothermal route for the synthesis of multiple

poly(diallyl dimethylammonium) chloride (PDDA)-protected noble metal (e.g., Ag, Pt, Pd,

and Au) nanostructures in the absence of any seed and surfactant. In their proposed method,

an ordinary and water-soluble polyelectrolyte (PDDA) acts as both a reducing and stabilizing

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 114

agent (Chen et al., 2007). Ag nanocubes, Pt nanopolyhedrons, Pd nanopolyhedrons, and Au

nanoplates can also be obtained using this synthetic pathway. Yu and Yam reported the

controlled synthesis of monodisperse Ag nanocubes with an edge length of ~55 nm in water

based on the n-hexadecyl trimethylammonium bromide-modified Ag mirror reaction (Yu et

al., 2004). Sun and Li (Sun et al., 2004) achieved the synthesis of cylindrical Ag nanowires

using an amorphous coating to modify the growth behavior of Ag nanowires. In their

synthesis, Ag metal ions were reduced by glucose under hydrothermal conditions with the

presence of PVP in the temperature range of 140 °C to 180 °C. The control of Ag with nano-

structures and morphology can be achieved using hydrothermal technique (Figure 14).

The hydrothermal method included the following significant advantages:

Complex chemical composition

Controllable particle size and shape

Relatively cheap raw materials

Figure 14. TEM image of Ag NPs obtained at 100 oC for 6 h (A) and 12 h (B), and for 6 h at 120

oC (C)

and 180 oC (D) (Yang et al., 2012, © 2012 Acta Materialia Inc. Published by Elsevier Ltd). SEM and

TEM image of Ag nanocubes (E) (Chang et al., 2008, © 2008 American Chemical Society).TEM

images of Ag NPs synthesized with various molar ratios of HTAB/[Ag(NH3)2]+: 1, 1.5, 2.5, 3 (F- I,

respectively) (Yu et al., 2005© 2005 American Chemical Society).

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 115

Some drawbacks of the Ag NPs synthesis using the hydrothermal method are as follows:

Produces small-scale products

Requires a large space for installation

Consumes a great amount of energy while increasing environmental temperature

Requires a great deal of time to achieve thermal stability

Utilizes heat-controlled furnace that requires power consumption and preheating time

2.8. Biological-assisted Approaches

In the recent years, biological methods employing micro-organisms, such as bacteria,

fungus, or plant extracts, i.e., green chemistry, have emerged as a simple and viable

alternative to more complex chemical synthetic procedures to fabricate Ag NPs. Extracts

from bio-organisms act both as reducing and capping agents in Ag NP synthesis. Thus, Ag

NP preparation with desirable morphology and size based on green chemistry methods

became a major focus of researchers. Several studies used microorganisms and biological

approach to prepare Ag NPs (Huang et al., 2007; Korbekandi et al., 2009; Iravani et al., 2011;

Ankamwar et al., 2005). The extracellular synthesis of NPs is fast and eco-friendly, which are

the main advantages of this method. Moreover, it is clean, reliable, bio-compatible, and

benign process.

2.8.1. Fungi-assisted Method

Fungi have an important role in the fabrication of Ag NPs based on the bioreduction

process. Ag NPs have long-term stability, which may be due to the stabilization of Ag NPs by

proteins. Strong interaction between Ag NPs and proteins, such as cytochrome c, has been

reported (Macdonald et al., 1996). This protein can be self-assembled on citrate-reduced Ag

colloid surface. Highly stable Ag NPs were produced by exposing Ag ions to Fusarium

oxysporum (Kumar et al., 2007), which functions as nitrate reductase and stabilizer by

releasing capping proteins; pH significantly affects NP stability. Ingle et al. (2008), reported

that spherical Ag NPs in the range of 5 nm to 40 nm, with an average diameter of 13 nm, can

be produced within 15 min to 20 min by Fusarium acuminatum Ell. and Ev. (USM-3793)

cell. In F. oxysporum fungus, the reduction of Ag ions was attributed to an enzymatic process

involving NADH-dependent reductase (Ahmad et al., 2003). The white rot fungus,

Phanerochaete chrysosporium, also reduced Ag ion to form Ag NPs; a protein was suggested

to cause the reduction (Vigneshwaran et al., 2006).

Aspergillus flavus was used not only as a bioreduction to form Ag NPs, but also as a

stabilizing agent. The product was stable for more than 3 months without aggregation

(Vigneshwaran et al., 2007). Jain et al. (2011), reported the use of a soil fungal isolate A.

flavus NJP08 for the extracellular synthesis of Ag NPs. Bhainsa and D‘Souza showed that

well-dispersed Ag NPs (5 nm to 25 nm) with variable shapes were produced by Aspergillus

fumigatus (Bhainsa et al., 2006). Ag NPs can be produced by incubation of Ag ions with

filtrate of Penicillium fellutanum under dark condition. The optimum condition of the highest

optical density at 430 nm is as follows: incubation time, 24 h; pH 6; 1 mM of Ag ions; 0.3%

NaCl; and 5 °C (Kathiresan et al., 2009). The synthesis of Ag NPs was achieved using the

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 116

genus Penicillium (Maliszewska et al., 2009). Sanghi and Verma (Sanghi et al., 2009)

reported that bioreduction of Ag ions to produce Ag NPs by Coriolus versicolor was

accelerated using alkaline conditions at pH 10 (reduced from 72 h to 1 h), indicating the

importance of glucose and S-H of the protein in the bioreduction process.

2.8.2. Bacteria-assisted Method

Kalishwaralal et al. reported that Bacillus licheniformis was used for the bioreduction of

Ag ions to produce highly stable Ag NPs (40 nm) and well-dispersed Ag nanocrystals

(50 nm) (Figure 15) (Kalishwaralal et al., 2008a; Kalishwaralal et al., 2008b). Saifuddin et al.

(2009), reported the extracellular biosynthesis of monodispersed Ag NPs (5 nm to 50 nm)

using supernatants of Bacillus subtilis. The extract of unicellular green algae Chlorella

vulgaris was used to synthesize single-crystalline Ag nanoplates at room temperature (Xie et

al., 2007). Ag nanocrystals of different compositions were successfully synthesized by

Pseudomonas stutzeri AG259. Larger particles were formed when P. stutzeri AG259

challenged with high concentrations of Ag ions during culture resulted in the intracellular

formation of Ag NPs that range from a few nanometers to 200 nm (Klaus-Joerger et al.,

2001). Rapid biosynthesis was obtained by the reduction of Ag ions by culture supernatants

of Klebsiella pneumonia, E. coli, and Enterobacter cloacae (Enterobacteriaceae) to produce

Ag NPs (Shahverdi et al., 2007). The reduction of [Ag (NH3)2] + using Aeromonas sp. SH10

and Corynebacterium sp. SH09 produces monodispersed and stable Ag NPs (Daohu et al.,

2006).

2.8.3. Plant-assisted Method

Camellia sinensis (green tea) has been used as a reducing and stabilizing agent for the

biosynthesis of Ag NP in an aqueous solution under ambient conditions (Vilchis-Nestor et al.,

2008). The results indicated that caffeine and theophylline are responsible for the formation

and stabilization process. When the C. sinensis extracts are increased, the Ag NPs became

larger and more spherical. Begum et al. (Begum et al., 2009) reported stable Ag NPs with

different morphologies in the bioreduction process using black tea leaf. The leaf extracts from

the aquatic medicinal plant, Nelumbo nucifera (Nymphaeaceae), have the ability to produce

Ag NPs with an average size of 45 nm in different morphologies (Santhoshkumar et al.,

2010). Ag NPs were produced from the reduction of aqueous AgNO3 solution with the aid of

black tea leaf extract (Figure 16) (Uddin et al., 2012).

Kasthuri et al. (Kasthuri et al., 2009) reported that stable Ag NPs in water for three

months can be prepared using apiin extracted from henna leaves. Stable and spherical Ag NPs

(16 nm to 40 nm) were obtained via geranium leaf broth and datura metel (Solanaceae) leaf

extract (Shankar et al., 2003; Kesharwani et al., 2009; Dar et al., 2012). Ag NPs were

prepared using the filtrate of Cryphonectria sp. isolated from chestnut trees (Figure 17) (Dar

et al., 2012). The synthesized AgNPs showed a small monodispersity in the range of 30 nm to

70 nm with a concentration of 6.82 × 108 particles per milliliter of solution. Several reports

presented the preparation of Ag NPs utilizing plants in the bioreduction process of Ag ions,

such as Brassica juncea and Medicago sativa (Harris et al., 2008), Sorbus aucuparia leaf

extract (Dubey et al., 2010), Pelargonium graveolens geraniol (Safaepour et al., 2009),

Euphorbia hirta leaf extract (Elumalai et al., 2002), Moringa oleifera leaf extract (Prasad et

al., 2011), Garcinia mangostana leaf extract (Veerasamy et al., 2011), Ocimum sanctum leaf

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 117

extract (Singhal et al., 2011), and Cinnamomum zeylanicum (Sathishkumar et al., 2009;

Daniel et al., 2004).

Figure 15. Possible mechanism for silver nanoparticle synthesis in B. licheniformis (Kalishwaralal et

al., 2008a © 2008 Elsevier B.V. All rights reserved).

Figure 16. Schematic of the formation of tea leaf extracts-Ag/PVA (EPSNP) nanocomposite film. [Ref.

Uddin et al., 2012, © 2012 Elsevier B.V. All rights reserved].

Figure 17. AgNPs obtained from Cryphonectria sp. isolated from chestnut trees (Dar et al., 2012© 2013

Elsevier Inc. All rights reserved).

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 118

Figure 18. Non-linker (A) and linker (B) routes for the formation of nanofilters for the ultra-fine

formation of spherical Ag NPs through nanofilteration of non-homogenous NPs.

3. INDIRECT CONTROL OF AG NPS MORPHOLOGY

The indirect morphological control of Ag NPs is based on the selective separation of

variable Ag NPs size and morphology using the membrane technique. To date, solution-phase

syntheses of Ag NPs have been extensively studied with the aim of fabricating a large volume

and high yield of Ag NPs (Alivisatos et al., 1996; Daniel et al., 2004; Zharov et al., 2005;

Klasen, 2000; Jain et al., 2009; Dura´n et al., 2007; Cho et al., 2005; Santos et al., 2002; Yang

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 119

et al., 2007; Chou et al., 2000; Sondi et al., 2003;), but these syntheses produce Ag NPs with

broad size distributions and with uncontrolled morphologies. Thus, the design of a universal

method for size-controlled size and shape of Ag NPs is highly desirable. El-Safty et al.

developed nanofilter membranes composed of mesoporous silica nanotubes with pre size

distribution of 4 nm through two pathways for NT fabrication are non-linker and linker routes

(Figure 18) (El-Safty et al., 2010a; El-Safty et al., 2010b; Mekawy et al., 2011; El-Safty et al.,

2011a; El-Safty et al., 2011b; El-Safty et al., 2011c). For this purpose, the dense silica NT

membranes with tunable and homogenous pore size distribution have been designed. The

design was achieved using the nanolinker approach templated inside the nanochannels of

AAM (Figure 18) (El-Safty et al., 2010a; El-Safty et al., 2010b; Mekawy et al., 2011; El-

Safty et al., 2011a; El-Safty et al., 2011b; El-Safty et al., 2011c). The key advantage of our

approach is the capability to control the building of mesopores throughout the AAM

nanochannels. This mesofilter membrane design is the key to broaden the nanofiltration

applications for Ag NP separation. Scanning electrochemical microscopy (SEM) images

revealed that the synthetic design allowed for the control of the strands‘ vertical alignment:

the silica NSs were well-aligned within the pores of the AAM (Figure 18). Silica NSs with

regular and continuous alignments along the perpendicular axis were observed. This

nanofilter design could be effectively used to size-selective control of Ag NPs that fabricated

with broad size distributions and with uncontrolled morphologies in both aqueous and organic

solution phases. This system would greatly assist in the production of well-defined,

monodispersity, and spherical Ag NPs (with size 4 nm) with unique properties. The color of

the membrane changed after the separation process because of the obstruction of large NPs

(Figure 18).

CONCLUSION AND OUTLOOK

Nanotechnology has received significant attention from scientists in the past few decades,

raising hopes of revolutionary developments in a wide range of technologies. This chapter

summarizes recent progresses in the area of Ag NPs. Ag NPs have exhibited significantly

distinct and unique optical, electrical, and biological properties that have attracted significant

attention because of their potential use in numerous applications, such as catalysis,

biosensing, drug delivery, and nanodevice fabrication.

These different applications will require particles of various dimensions and the ability to

tailor surface chemistry. The ideal methods of synthesis should yield essentially naked

particles so that different surface functionalities can be readily introduced for template-

assisted or self-assembly based fabrication methods for nanoscale devices. Over the years,

many methods for the synthesis of silver nanoparticles have been implemented. These

methods can be divided into several categories. The first is various modifications to either the

Creighton method, which employs the reduction of silver nitrate by sodium borohydride or

the Lee-Meisel method, which is generally considered to be the reduction of silver nitrate

with sodium citrate. AgNO3 is the most common source of silver ions, although Ag2SO4,

silver 2-ethylhexonate and silver perchlorate have also been used. NaBH4, sodium citrate,

ascorbic acid, DMSO, hydrazine dihydrochloride, potassium bitartate, ethanol, pyridine,

DMF and poly(ethylene glycol) have all been used as a reducing agents. The monovalent

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 120

silver ion has a large reduction potential, 0.7996 V and can be easily reduced by many

different organic and inorganic compounds. Stabilizers such as NaAOT, CTAB and PVP have

also been effectively used to direct the aspect ratio of the particles producing plates and rods

and other shapes. In general, all of the above methods produce mainly small particles,

although very careful control of the reducing environment and stabilizer concentration makes

it possible to synthesize larger particles as well.

The flexibility of Ag NP fabrication techniques and facile incorporation of Ag NPs into

inorganic and organic materials of various chemical, physical, and biological fabrication

approaches have been developed to obtain Ag NPs with various shapes and sizes. Most of

these methods are still in the development stages, and the problems experienced involved

stability and aggregation of NPs, control of crystal growth, morphology, size, and size

distribution.

REFERENCES

Abid, J. P., Wark, A. W., P. F. Brevet, P. F., Girault, H. H. (2002). Preparation of silver

nanoparticles in solution from a silver salt by laser irradiation. Chem. Commun. 7, 792-

793.

Ahmad, A., Senapati, S., Khan, M. I., Kumar, R., Ramani, R. Srinivas, V. (2003).

Intracellular synthesis of gold nanoparticles by a novel alkalotolerant actinomycete,

Rhodococcus species. Nanotechnology 14, 824.

Aizawa, M Cooper, A. M. Malac, M. J., Buriak, M. (2005). Silver nano-inukshuks on

germanium, Nano. Lett. 5, 815- 819.

Albrecht, M. A., Evans, C. W., Raston, C. L. (2006). Green chemistry and the health

implications of nanoparticles. Green Chem. 8, 417-432.

Alivisatos, A. P. (1996). Semiconductor clusters, nanocrystals, and quantum dots. Science

271, 933–937.

Amendola, V. Polizzi, S. Meneghetti, M. (2007). Free Silver Nanoparticles Synthesized by

Laser Ablation in Organic Solvents and Their Easy Functionalization. Langmuir 23,

6766–6770.

Ankamwar, B., Damle, C., Ahmad, A., Sastry, M. (2005). Biosynthesis of gold and silver

nanoparticles using Emblica officinalis fruit extract, their phase transfer and

transmetallation in an organic solution. J. Nanosci. Nanotechnol. 5, 1665-1671.

Bai, J., Li, Y., Du, J., Wang, S., Zheng, J., Yang, Q. Chen, X. (2007). One-pot synthesis of

poly acrylamide-gold nanocomposite, Mater. Chem. Phys. 106, 412-415.

Begum, N.A., Mondal, S, Basu, S., Laskar, R.A., Mandal, D. (2009). Biogenic synthesis of

Au and Ag nanoparticles using aqueous solutions of Black Tea leaf extracts. Colloid

Surface B. 71, 113–118.

Bhainsa, K. C., Souza, S. D. (2006). Extracellular biosynthesis of silver nanoparticles using

the fungus Aspergillus fumigates, Colloids Surface B 47, 160-164.

Blizanac, B. B., Ross, P. N., Markovic, N. M., (2007). "Oxygen electroreduction on Ag(111):

The pH effect. Electrochim. Acta 52, 2264-2271.

Bogle, K. A., Dhole, S. D., Bhoraskar, V. N. (2006) Silver nanoparticles: synthesis and size

control by electron irradiation. Nanotechnology 17, 3204–3208.

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 121

Chen, P., Song, L., Liu, Y-a., Fang Y-e (2007a). Synthesis of silver nanoparticles by γ-ray

irradiation in acetic water solution containing chitosan. Radiat. Phys. Chem. 76, 1165–

1168.

Chen, H., Wang, Y, Dong, S., (2007b). An Effective Hydrothermal Route for the Synthesis of

Multiple PDDA-Protected Noble-Metal Nanostructures, Inorg. Chem. 46, 10587–10593.

Chang, C-C., Wu, H-L., Kuo, C-H., Huang, M. H., (2008) hydrothermal synthesis of

monodisperesed octahedral gold nanocrystals with five different size ranges and their

self-assembled structures. Chem. Mater. 20, 7570-7574.

Chen, X., Schluesener, H. J. (2008) Nano-silver: A nanoproduct in medical application.

Toxicol. Lett. 176, 1-12.

Chi, Y., Yuan, Q., Li, Y., Tu, J., Zhao, L., Li, N., Li, X. (2012). Synthesis of Fe3O4@SiO2–

Ag magnetic nanocomposite based on small-sized and highly dispersed silver

nanoparticles for catalytic reduction of 4-nitrophenol, J. Colloid Interface Sci. 383, 96-

102.

Cho, K-H., Park, J-E., Osaka, T., Park, S. G., (2005). The study of antimicrobial activity and

preservative effects of nanosilver ingredient. Electrochimica Acta 51, 956-960.

Choi, S. H., Zhang, Y. P., Gopalan, A., Lee, K. P., Kang, H. D. (2005). Preparation of

catalytically efficient precious metallic colloids by -irradiation and characterization

Colloids Surf. A 256, 165-170.

Chou, K-S., Ren, C-Y., (2000). Synthesis of nanosized silver particles by chemical reduction

method. Mater. Chem. Phys. 64, 241-246.

Corato, R. D., Palumberi, D., Marotta, R., Scotto, M., Carregal-Romero, S., Rivera_Gil, P.,

Parak, W. J., Pellegrino, T., (2012). Magnetic Nanobeads Decorated with Silver

Nanoparticles as Cytotoxic Agents and Photothermal Probes. Small 8, 2731–2742.

Daniel, M. C., Astruc, D., (2004). Gold nanoparticles: assembly, supramolecular chemistry,

quantum-size-related properties, and applications toward biology, catalysis, and

nanotechnology. Chem. Rev. 104, 293-346.

Daohu, S. Qingbiao, L. Xueping, L. Lin, W. Mouxing, F. U. (2006). Studies on mechanisms

of silver biosorption by Aeromonas SH10, Acta Scientiae Circumstantiae 26, 1107-1110.

Dankovich, T. A., Gray, D. G., (2011). Bactericidal Paper Impregnated with Silver

Nanoparticles for Point-of-Use Water Treatment. Environ. Sci. Technol. 45, 1992–1998.

Dar, M. A., Ingle, A., Rai, M., (2012). Enhanced antimicrobial activity of silver nanoparticles

synthesized by Cryphonectria sp. evaluated singly and in combination with antibiotics.

Nanomed-Nanotechnol. doi:10.1016/j.nano.2012.04.007.

Demarconnay, L., Coutanceau, C., Le´ger, J.-M. (2004). Electroreduction of dioxgen (ORR)

in alkaline medium on Ag/C and nanostructured catalysts-effect of the presence of

methanol, Electrochim. Acta 49, 4513-4521.

Dong, X., Ji, X., Jing, J., Li, M., Li, J., Yang, W. (2010). Synthesis of Triangular Silver

Nanoprisms by Stepwise Reduction of Sodium Borohydride and Trisodium Citrate. J.

phys. chem. C 114, 2070-2074.

Drummond, M. G., Hill, M. G. Barton, J. K. (2003). Electrochemical DNA sensors, Nature

Biotechnology 21, 1192- 1199.

Dubey, S. P., Lahtinen, M., Särkkä, H., Sillanpää, M. (2010). Bioprospective of Sorbus

aucuparia leaf extract in development of silver and gold nanocolloids. Colloid Surface B

80, 26-33.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 122

Dura´n, N., Marcato, P. D., De, S., Gabriel, I. H., Alves, O. L., Esposito, E., (2007).

Antibacterial effect of silver nanoparticles produced by fungal process on textile fabrics

and their effluent treatment. J. Biomed. Nanotechnol. 3, 203-208.

El-Safty, S. A., Mekawy, M., Yamaguchi, A., Shahat, A., Ogawa, K., Teramae, N. (2010).

Organic–inorganic mesoporous silica nanostrands for ultrafine filtration of spherical

nanoparticles, Chem. Commun. 46, 3917-3919.

El-Safty, S. A., Shahat, A., Mekawy, M., Nguyen, H., Warkocki, W., Ohnuma, M., (2010).

Mesoporous silica nanotubes hybrid membranes for functional nanofiltration.

Nanotechnology 21, 375603.

El-Safty, S. A., Shahat, A. Awual, Md. R., Mekawy, M. (2011a). Large three-dimensional

mesocage pores tailoring silica nanotubes as membrane filters: nanofiltration and

permeation flux of proteins. J. Mater. Chem. 21:5593-5603.

El-Safty, S. A., Shahat, A., Warkocki, W., Ohnuma, M., (2011b). Building-Block-Based

Mosaic Cage Silica Nanotubes for Molecular Transport and Separation. Small 7:62–65;

El-Safty, S. A., Shenashen, M. A., (2011c). Size-selective separations of biological

macromolecules on mesocylinder silica arrays. Anal. Chim. Act. 2011, 694, 151-161.

Elumalai, E. K., Prasad, T. N. V. K. V., Hemachandran, J., Therasa, S. V., Thirumalai, T.,

David, E., (2010). Extracellular synthesis of silver nanoparticles using leaves of

Euphorbia hirta and their antibacterial activities. J. Pharm. Sci. Res. 2, 549-554.

Evanoff, D. D., Chumanov, G., (2004). Size-controlled synthesis of nanoparticles. 1. `Silver

only` aqueous suspension via hydrogen reduction. J. Phys. Chem. B 108, 13948–56.

Gac, W., Derylo-Marczewska, A., Pasieczna-Patkowska, S., Popivnyak, N. Zukocinski, G.

(2007). The influence of the preparation methods and pretreatment conditions on the

properties of Ag-MCM-41 catalysts. J. Mol. Catal. A Chem. 268, 15–23.

Gu, C., Zhang, T-Y. (2008). Electrochemical synthesis of silver polyhedrons and dendritic

films with superhydrophobic surfaces. Langmuir 24, 12010-12016.

Harris, A. T., Bali, R., (2008). On the formation and extent of uptake of silver nanoparticles

by live plants. J. Nanopart. Res. 10, 691-695.

He, R., Qian, X., Yin, J., Zhu Z. (2003). Formation of silver dendrites under microwave

irradiation, Chem. Phys. Lett. 369, 454–458.

He, B., Tan, J., Liew, K., Liu, H, (2004). Synthesis of size controlled Ag nanoparticles. J.

Mol. Catal. A: Chem. 221, 121-126.

Henglein, A. (1998). Colloidal Silver Nanoparticles: Photochemical Preparation and

Interaction with O2, CCl4, and Some Metal Ions. Chemistry of Materials, 10, 444–450.

Hu, B., Wang, S-B., Wang, K., Zhang, M., Yu, S. H., (2008). Microwave-assisted rapid facile

―green‖ synthesis of uniform silver nanoparticles: Self-assembly into multilayered films

and their optical properties. J. Phys. Chem. C 112, 11169–11174.

Huang, J., Li, Q., Sun., D. Lu, Y., Su, Y., Yang, X. Wang, H., Wang, Y., Shao, W., He, N.,

Hong, J., Chen, C., (2007). Biosynthesis of silver and gold nanoparticles by novel

sundried Cinnamomum camphora leaf. Nanotechnology, 18, 105-104.

Hwang, C., Fu, Y., Lu, Y., Jang, S., Chou, T., Wang, C., Yu, S., (2000). Synthesis,

characterization and highly efficient catalytic reactivity of suspended palladium

nanoparticles. J. Catal. 195, 336-341.

Ingle, A., Gade, A., Pierrat, S., Sönnichsen, C., Mahendra, R. (2008) Mycosynthesis of silver

nanoparticles using the fungus Fusarium acuminatum and its activity against some human

pathogenic bacteria. Curr. Nanosci. 4, 141-144.

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 123

Iravani, S., (2011). Green synthesis of metal nanoparticles using plants. Green Chem. 13,

2638-2650.

Jain, J., Arora, S., Rajwade, J. M., Omray, P., Khandelwal S., Paknikar, K. M. (2009). Silver

Nanoparticles in Therapeutics: Development of an Antimicrobial Gel Formulation for

Topical Use. Mol. Pharmaceutics. 6, 1388–1401.

Jain, N., Bhargava, A., Majumdar, S., Tarafdar, J. C., Panwar, J., (2011). Extracellular

biosynthesis and characterization of silver nanoparticles using Aspergillus flavus NJP08:

A mechanism perspective, Nanoscale, 3, 635–641.

Johans, C., Clohessy, J., Fantini, S., Kontturi, K., Cunnane, V. J. (2002). Electrosynthesis of

polyphenylpyrrole coated silver particles at a liquid-liquid interface. Electrochim. Acta 4,

227–230.

Jung, J., Oh, H. Noh, H., Ji, J., Kim, S., (2006) Metal nanoparticles generation using a small

ceramic heater with a local heating area. Aerosol Sci. 37, 1662-1670.

Kabashin, A. V., Meunier, M., (2003). Synthesis of colloidal nanoparticles during

femtosecond laser ablation of gold in water. J. appl. phys. 94, 7941-7943.

Kalishwaralal, K., Deepak, V., Ramkumarpandian, S., Bilal, M., Sangiliyandi, G. (2008).

Biosynthesis of silver nanocrystals by Bacillus licheniformis. Colloids Surf. B:

Biointerfaces, 65, 150-153.

Kalishwaralal, K., Deepak, V., Ramkumarpandian, S., Nellaiah, H.; Sangiliyandi, G. (2008).

Extracellular biosynthesis of silver nanoparticles by the culture supernatant of Bacillus

licheniformis, Mater. Lett. 62, 4411-4413.

Kapoor, S., Lawless, D., Kennepohl, P., Meisel, D., Serpone, N. (1994). Reduction and

aggregation of silver ions in aqueous gelatin solutions, Langmuir 10, 3018-3022.

Kesharwani, J., Yoon, K. Y., Hwang, J., Rai, M. (2009). Phytofabrication of silver

nanoparticles by leaf extract of Datura metel: hypothetical mechanism involvedin

synthesis. J. Bionanoscience 3, 1-6.

Kasthuri, J., Veerapandian, S., Rajendiran, N., (2009). Biological synthesis of silver and gold

nanoparticles using apiin as reducing agent. Colloid Surf. B 68, 55-60.

Kathiresan, K., Manivannan, S., Nabeel, M. A., Dhivya, B. (2009) Studies on silver

nanoparticles synthesized by a marine fungus, Penicillium fellutanum isolated from

coastal mangrove sediment, Colloids Surf. B 71, 133-137.

Kim, M-J., Cho, Y-S., Park, S-H., Huh, Y-D., (2012). Facile Synthesis and Fine

Morphological Tuning of Ag2O. Cryst. Growth Des. 12, 4180−4185.

Kim, S-E., Park, J.H., Lee, B.C., Lee, J-C., Kwon, Y. K., (2012). Large-scale synthesis of

silver nanoparticles using Ag(I)–S12 polymer through electron beam irradiation. Radiat.

Phys. Chem. 81, 978–981.

Klasen, H. J., (2000). A historical review of the use of silver in the treatment of burns. II.

Renewed interest for silver. Burns. 26, 131-138.

Klaus-Joerger, T., Joerger, R., Olsson, E., Granqvist, C.G. (2001). Bacteria as workers in the

living factory: metal-accumulating bacteria and their potential for materials science.

Trends Biotechnol. 19,15–20.

Komarneni, S., Li, D. S., Newalker, B., Katsuki, H., Bhalla, A. S. (2002). Microwave-polyol

process for pt and Ag nanoparticles, Langmuir 18, 5959-5962.

Korbekandi, H., Iravani, S., Abbasi, S., (2009). Production of nanoparticles using organisms.

Crit. Rev. Biotechnol. 29, 279-306.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 124

Kosmala, A., Wright, R., Zhang, Q., Kirby, P., (2011). Synthesis of silver nanoparticles and

fabrication of aqueous Ag inks for inkjet printing. Mat. Chem. Phys. 129, 1075–1080.

Kruis, F., Fissan, H., Rellinghaus, B., (2000). Sintering and evaporation characteristics of

gas-phase synthesis of size-selected nanoparticles. Mater. Sci. Eng. B 69, 329-334.

Kumar, S. A., Majid Kazemian, A., Gosavi, S. W., Sulabha, K. K., Renu, P., Ahmad A.;

Khan, M. I. (2007). Nitrate reductase-mediated synthesis of silver nanoparticles from

AgNO3. Biotechnol. Lett. 29, 439-445.

Kundu, S. Wang K. Liang, H. (2009). Size-Controlled Synthesis and Self-Assembly of Silver

Nanoparticles within a Minute Using Microwave Irradiation. J. Phys. Chem. C 113, 134–

141.

Le, A. T., Huy, P. T., Tam, P. D., Huy, T. Q., Cam, P. D., Kudrinskiy, A. A., Krutyakov, Y.

A. (2010). Green synthesis of finely-dispersed highly bactericidal silver nanoparticles via

modified Tollens technique. Curr. Appl. Phys.10, 910-916.

Le, A, T., Tam, L. T., Tam, P. D., Huy, P. T Huy, T. Q., Hieu, N. V., Kudrinskiy, A. A,

Krutyakov, Y. A., (2010). Synthesis of oleic acid-stabilized silver nanoparticles and

analysis of their antibacterial activity. Mater. Sci. Eng. C, 30, 910-916.

Le, A-T., Le, T. T., Nguyen, V. Q., Tran, H. H., Dang, D. A., Tran, Q. H., Vu, D. L., (2012).

Powerful colloidal silver nanoparticles for the prevention of gastrointestinal bacterial

infections. Adv. Nat. Sci. Nanosci. Nanotechnol. 3, 1-10.

Lefevre, M., Dodelet, J. P., (2003). Fe based catalysts for the reduction of oxygen in polymer

elyctrolyte memberane fuel cell conditions: determination of amount of peroxide released

durin elctroreduction and its influence on the stability of the catalysts, Electrochim. Acta

48, 2749-2760.

Li, K., Zhang F-S. (2010). A novel approach for preparing silver nanoparticles under electron

beam irradiation. J. Nanopart. Res. 12, 1423–1428.

Liu, J-H., Tsai, C-Y., Chiu, Y-H., Hsieh F-M., (2009). The fabrication of polycrystalline

silver nanowires via self-assembled nanotubes at controlled temperature. Nanotechnology

20, 035301.

Liz-Marzán, L. M., Lado-Touriño, I., (1996). Reduction and stabilization of silver

nanoparticles in ethanol by nonionic surfactants. Langmuir 12, 3585-3589.

Macdonald, I. D. G., Smith, W. (1996). Orientation of Cytochrome c adsorbed on a citrate-

reduced silver colloid surface. Langmuir, 12, 706-713.

Mafune, F., Kohno, J., Takeda, Y., Kondow, T., Sawabe, H. (2001). Formation of gold

nanoparticles by laser ablation in aqueous solution of surfactant. J. Phys. Chem. 105,

5114-1120.

Magnusson, M., Deppert, K., Malm, J., Bovin, J., Samuelson, L., (1999). Gold nanoparticles:

production, reshapingand thermal charging. J. Nanoparticle Res. 1, 243-251.

Maliszewska, I., Szewczyk, K., Waszak, K. (2009). Biological synthesis of silver

nanoparticles, J. Phys. Conf. Ser. 146, 1-6.

Martínez-Castañón, G. A., Niño-Martínez, N., Martínez-Gutierrez, F., Martínez-Mendoza J.

R.; Ruiz, F., (2008). Synthesis and antibacterial activity of silver nanoparticles with

different sizes. J. Nanopart. Res. 10, 1343–1348.

Mekawy, M., Yamaguchi, A., El-Safty, S. A., Itoh, T., Teramae, N. (2011). Mesoporous

silica hybrid membranes for precise size-exclusive separation of silver nanoparticles, J.

Colloid Interface Sci. 355, 348–358.

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 125

Meng, H., Shen, P.K. (2006). Novel Pt-free catalyst for oxgen electroreduction. Electrochem.

Commun. 8, 588-594.

Merga, G., Wilson, R., Lynn, G., Milosavljevic, B. H., Meisel, D. (2007). Redox Catalysis on

―Naked‖ Silver Nanoparticles. J. phys. Chem. C, 111, 12220-26.

Mock, J., Barbic, M., Smith, D., Schultz, D., Schultz, S. (2002). Shape effects in Plasmon

resonance of individual colloidal silver nanoparticles. J. Chem. Phys. 116, 6755-6760.

Nadagouda, M. N., Speth, T. F., Varma, P. S., (2011). Microwave-Assisted Green Synthesis

of Silver Nanostructures. Accounts of Chem. Res. 44, 469–478.

Navaladian, S., Viswanathan, B., Varadarajan, T. K.;Viswanath, R. P. (2008). Microwave–

assisted rapid synthesis of anisotropic Ag nanoparticles by solid state transformation,

Nanotechnology 19, 1-7.

Nichols, W., Sasaki, T., Koshisaki, N., (2006). Laser ablation of a platinum target in water, II.

Ablation rate and nanoparticles size distributions. J. appl. Phys. 100, 114913-16.

Okumu, J., Dahmen, C., Sprafke, A. N., Luysberg, M. Plessen, G. V., Wuttig, M., (2005).

Photochromic silver nanoparticles fabricated by sputter deposition. J. appl. Phys. 97,

94305-6.

Oliveira, M., Ugarte, D., Zanchet, D., Zarbin, A., (2005). Influence of synthetic parameters on

the size, structure, and stability of dodecanethiol-stabilized silver nanoparticles. J.

Colloid Interface. Sci. 292, 429-435.

Pal, A., Shah S., Devi, S. (2007). Synthesis of Au, Ag and Au–Ag alloy nanoparticles in

aqueous polymer solution. Colloids Surf. A 302, 51-57.

Pal, A., Shah, S., Devi, S. (2009). Microwave-Assisted Synthesis of silver nanoparticles using

ethanol as a reducing agent. Mater. Chem. Phys. 114, 530– 532.

Park, H-H., Zhang, X., Choi, Y-J., Park, H-H., Hill, R. H. (2011). Synthesis of Ag

Nanostructures by Photochemical Reduction Using Citrate-Capped Pt Seeds. J.

Nanomaterials 265287, doi:10.1155/2011/265287.

Pietrobon, B., Kitaev V., (2008). Photochemical Synthesis of Monodisperse Size-Controlled

Silver Decahedral Nanoparticles and Their Remarkable Optical Properties. Chem. Mater.

20, 5186–5190.

Potara, M., Baia, M., Farcau, C., Astilean S. (2012). Chitosan-coated anisotropic silver

nanoparticles as a SERS substrate for single-molecule detection. Nanotechnology 23,

55501-11.

Prasad, T. N. V. K. V., Elumalai, E. (2011). Biofabrication of Ag nanoparticles using

Moringa oleifera leaf extract and their antimicrobial activity. Asian Pac. J. Trop. Biomed.

1, 439-442.

Reetz M. T., Helbig, W., (1994). Size-Selective Synthesis of Nanostructured Transition Metal

Clusters. J. Am. Chem. Soc. 116, 7401-7402.

Safaepour, M., Shahverdi, A.R., Shahverdi, H.R., Khorramizadeh, M.R., Gohari, A.R.,

(2009). Green synthesis of small silver nanoparticles using geraniol and its cytotoxicity

against Fibrosarcoma-Wehi 164, Avicenna J. Med. Biotech. 1, 111-115.

Saifuddin, N., Wong, C. W., Nur Yasumira, A. A. (2009). Rapid biosynthesis of silver

nanoparticles using culture supernatant of bacteria with microwave irradiation. E-J.

Chem. 6, 61-70.

Salkar, R. A., Jeevanandam, P., Aruna, S. T., Koltypin Y., Gedanken, A. (1999). The

sonochemical preparation of amorphous silver nanoparticles, J. Mater. Chem. 9, 1333-

1335.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 126

Sanghi, R. Verma, P. (2009). Biomimetic synthesis and characterization of protein capped

silver nanoparticles, Bioresource Technol. 100, 501–504.

Santhoshkumar, T., Rahuman, A. A., Rajakumar, G., Marimuthu, S., Bagavan, A.,

Jayaseelan, C., Zahir, A. A., Elango, G., Kamaraj, C. (2010). Synthesis of silver

nanoparticles using Nelumbo nucifera leaf extract and its larvicidal activity against

malaria and filariasis vectors. Parasitol Res. 108, 693-702.

Santos, I. P., Liz-Marzan, L. M., (2002). Synthesis of Silver Nanoprisms in DMF. Nano Lett.

2, 903-905.

Sathishkumar, M., Sneha, K., Won, S. W., Cho, C-W., Kim, S., Yun, Y. S., (2009).

Cinnamon zeylanicum bark extract and powder mediated green synthesis of nano-

crystalline silver particles and its bactericidal activity. Colloid Surface B 73, 332–338.

Scaiano, J. C., Billone, P., Gonzalez, C. M., Maretti, L., Marin, M. L., McGilvray, K. L.,

Yuan N. (2009). Photochemical routes to silver and gold nanoparticles. Pure Appl. Chem.

81, 635–647.

Shahverdi, A. R., Minaeian, S., Shahverdi, H. R., Jamalifar, H., Nohi, A. (2007). Rapid

synthesis of silver nanoparticles using culture supernatants of Enterobacteria: A novel

biological approach. Process Biochemistry 42, 919-923.

Shankar, S.S., Absar, A., Murali, S., (2003). Geranium leaf assisted biosynthesis of silver

nanoparticles. Biotechnol. Prog. 19, 1627-1631.

Sharma, S., Thakur, M., Deb, M. K. (2008). Preparation of Silver Nanoparticles by

Microwave Irradiation. Curr. Nanosci. 4, 138-140.

Shen, J., Shi, M., Yan, B., Ma , H., Li N., Ye, M. (2011) One-pot hydrothermal synthesis of

Ag-reduced graphene oxide composite with ionic liquid J. Mol. Catal. A 21, 7795-7801.

Shirtcliffe, N., Nickel, U., Schneider, S., (1999). Reproducible Preparation of Silver Sols with

Small Particle Size Using Borohydride Reduction: For Use as Nuclei for Preparation of

Larger Particles. J. Colloid Interface Sci. 211, 122-129.

Shmakov, S.N., Pinkhassik E. (2010). Simultaneous templating of polymer nanocapsules and

entrapped silver nanoparticles. Chem. Commun. 46, 7346–7348.

Shrivastava, S., Bera, T., Singh, S.K., Singh, G., Ramachandrarao P., Dash D. (2009).

Characterization of Antiplatelet Properties of Silver Nanoparticles. ACS Nano. 3, 1357–

1364.

Singhal, G., Bhavesh, R., Kasariya, K., Sharma, A.R.; Singh, R.P. (2011). Biosynthesis of

silver nanoparticles using Ocimum sanctum (Tulsi) leaf extract and screening its

antimicrobial activity. J. Nanopart. Res., 13, 2981-2988.

Slawson, R. M. Dyke, M. I. V., Lee, H., Trevors, J. T. (1992). Germanium and silver

resistance, accumulation and toxicity microrgansms. Plasmid 27, 72-79.

Sondi, I., Goia, D. V., Matijević, E., (2003). Preparation of highly concentrated stable

dispersions of uniform silver nanoparticles. J. Colloid Interface, Sci. 260, 75-81.

Sreeram, K. J., Nidhin, M., Nair, B. U., (2008). Microwave assisted template synthesis of

silver nanoparticles‖ Bull. Mater. Sci. 31, 937–942.

Sun, X. M., Li, Y. M., (2005). Cylindrical silver nanowires: Preparation, structure, and

optical properties. Adv. Mater. 17, 2626-2630.

Sun, Y. (2007). Direct growth of dense, pristine metal nanoplates with well-controlled

dimensions on semiconductor substrates. Chem. Mater. 19, 5845-5847.

Synthesis Methodology for Size and Shape Control of Silver Nanoparticles 127

Sylvestre, J. P., Kabashin, A. V., Sacher, E., Meunier, M., Luong, J. H. T., (2004).

Stabilization and size control of gold nanoparticles during laser ablation in aqueous

cyclodextrins. J. Amer. Chem. Soc. 126, 7176-7177.

Tan, S., Erol, M., Attygalle, A., Du, H., Sukhishvili, S., (2007). Synthesis of positively

charged silver nanoparticles via photoreduction of AgNO3 in branched

polyethyleneimine/HEPES Solutions, Langmuir 23, 9836-9843.

Tao, A., Sinsermsuksaku, P., Yang, P., (2006). Polyhedral silver nanocrystals with distinct

scattering segnetures. Angew Chem. Int. Ed. 45, 4597-2601.

Tarasenko, N., Butsen, A., Nevar, E., Savastenko, N. (2006). Synthesis of nanosized particles

during laser ablation of gold in water. Appl. Surf. Sci. 252, 4439-44.

Tian, C., Mao, B., Wang, E., Kang, Z., Song, Y., Wang, C., Li S., Xu, L., (2007). One-step,

size-controllable synthesis of stable Ag nanoparticles. Nanotechnology 18, 285607-14.

Tsai, T-H., Thiagarajan, S., Chen S-M. (2010) Green Synthesis of Silver Nanoparticles Using

Ionic Liquid and Application for the Detection of Dissolved Oxygen. Electroanalysis 22,

680–687.

Tsuji, M. L., Nizhizawa, Y., Hashimoto, M., Tsuji, T., (2004). Syntheses of silver nanofilms,

nanorods, and nanowires by a microwave-polyol method in the presence of Pt seeds and

polyvinylpyrrolidone. Chem. Lett. 33, 370-371.

Tsuji, M. Hashimoto, M., Nishizawa, Y., Kubokawa, M., Tsuji, T., (2005). Microwave-

Assisted Synthesis of Metallic Nanostructures in Solution. Chem. Eur. J. 11, 440–452.

Uddin, B. Md J. ChaudhuriPramanik, K. Middya, T.R. Chaudhuri, B. (2012). Black tea leaf

extract derived Ag nanoparticle-PVA composite film: Structural and dielectric properties.

Mater. Sci. Eng. 177, 1741–1747.

Veerasamy, R., Xin, T. Z., Gunasagaran, S., Xiang, T. F. W., Yang, E. F. C., Jeyakumar, N.,

Dhanaraj, S. A. 2011. Biosynthesis of silver nanoparticles using mangosteen leaf extract

and evaluation of their antimicrobial activities. J. Saudi Chem. Soc. 15, 113-120.

Vigneshwaran, A., Kathe, A. A., Varadarajan, P. V., Nachne, R. P., Balasubramanya. R. H.,

(2006). Biomimetics of silver nanoparticles by white rot fungus, Phaenerochaete

chrysosporium, Colloids Surface B 53, 55–59.

Vigneshwaran, N., Ashtaputre, N. M., Varadarajan, P. V., Nachane, R. P., Paralikar, K. M.,

Balasubramanya, R., (2007). Biological synthesis of silver nanoparticles using the fungus

Aspergillus flavus, Mater. Lett. 61,1413-1418.

Vilchis-Nestor, A. R., Sánchez-Mendieta, V., Camacho-López, M. A., Gómez-Espinosa, R.

M., Camacho-López, M. A. Arenas-Alatorre, J. (2008). Solventless synthesis and optical

properties of Au and Ag nanoparticles using Camellia sinensis extract. Mater. Lett. 62,

3103–3105.

Wei, X., Luo, M., Li, W., Yang, L., Liang, X., Xu L, Kong P., Liu, H., (2012). Synthesis of

silver nanoparticles by solar irradiation of cell-free Bacillus amyloliquefaciens extracts

and AgNO3. Bioresource Technol. 103, 273-278.

Wiley, B., Sun, Y., Mayers, B., Xi Y., (2005). Shape-controlled synthesis of metal

nanostructures: the case of silver. Chem-Eur. J. 11, 454-463.

Wiley, B. Sun, Y. Xia, Y., (2007). Synthesis of silver nanostructures with controlled shapes

and properties. Pure Appl. Chem 40, 1067-1076.

Yang, J., Pan J., (2012). Hydrothermal synthesis of silver nanoparticles by sodium alginate

and their applications in surface-enhanced Raman scattering and catalysis. Acta

Materialia 60, 4753–4758.

M. A. Shenashen, S. A. El-Safty and E. A. Elshehy 128

Yang, Y., Matsubara, S., Xiong, L.; Hayakawa, T., Nogami, M. (2007). Sovothermal

Synthesis of Multiple Shapes of Silver Nanoparticles and Their SERS Properties. J. Phys.

Chem. C, 111, 9095–9204.

Yin, Y., Li, Z-Y., Zhong, Z., Gates, B., Venkateswaran, S., (2002). Synthesis and

characterization of stable aqueous dispersions of silver nanoparticles through the Tollens

process. J. Mater. Chem. 12, 522-527.

Yu, D., Yam, V. W., (2004). Controlled Synthesis of Monodisperse Silver Nanocubes in

Water. J. Amer. chem. Soc. 126, 13200–13201.

Yu, D., Yam V. W-W., (2005). Hydrothermal-Induced assembly of colloidal silver spheres

into various nanoparticles on the bases of HTAB-modified silver mirror reaction. J. Phys.

Chem. B 109, 5497-5503.

Xie, J., Lee, J. Y., Wang, D. I. C., Ting, Y. P., (2007). Silver Nanoplates: From Biological to

Biomimetic Synthesis. ACS Nano. 1, 429-439.

Zhang, Y., Peng, H., Huang, W., Zhou, Y., Yan, D. (2008). Facile preparation and

characterization of highly antimicrobial colloid Ag or Au nanoparticles. J. Colloid

Interface Sci. 325, 371-376.

Zhao, G. J., Stevens, S. E., (1998). Multiple parameters for comprehension evaluation of

susceptibility Escherichia col. Biometals 11, 27-32.

Zharov, V. P., Kim, J-W., Curiel, D. T., Everts, M. (2005). Self-assembling nanoclusters in

living systems: application for integrated photothermal nanodiagnostics and nanotherapy.

Nanomed-Nanotechnol. 1, 326-345.

Zhu, Y-J., Hu X-L., (2004). Microwave-assisted polythiol reduction method: a new solid–

liquid route to fast preparation of silver nanowires. Mater. Lett. 58, 1517– 1519.