Journal of Industrial and Engineering Chemistry 20 (2014) 4473–4481

Contents lists available at ScienceDirect

Journal of Industrial and Engineering Chemistry

journal homepage: www.e lsev ier .com/ locate / j iec

One step green synthesis of hexagonal silver nanoparticles and

their biological activity

Samy M. Shaban a,*, Ismail Aiad a, Mohamed M. El-Sukkary a, E.A. Soliman b,Moshira Y. El-Awady a

a Petrochemical Department, Egyptian Petroleum Research Institute, Egyptb Faculty of Science, Ain Shams University, Cairo, Egypt

A R T I C L E I N F O

Article history:

Received 19 January 2014

Accepted 6 February 2014

Available online 14 February 2014

Keywords:

Photosynthesis

Hexaonal shapes

Zetapotential

Biological activity

A B S T R A C T

Hexagonal and spherical silver nanoparticles were prepared by in situ and green synthesis using sun

light as reducing agent with assistance newly prepared cationic surfactant which act also as capping

agents. The silver nanoparticles formation was investigated using UV–vis spectrophotometer,

transmission electron microscope (TEM), dynamic light scattering (DLS), energy dispersive X-ray

(EDX) and FTIR. The results showed formation uniform, well arrangement hexagonal and spherical

shapes. Increasing hydrophobic chain length increase the stability and amount of AgNPS. Both prepared

surfactants and surfactants capping silver nanoparticles showed high antimicrobial activity against

Gram-positive and Gram-negative bacteria.

� 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights

reserved.

1. Introduction

Nanotechnology is a field of applied science, focused on thedesign, synthesis, characterization and application of materialsand devices on the Nano scale, many techniques of synthesizingsilver nanoparticles (AgNPs) have been investigated. Some of themare chemical reduction [1], electrochemical [2], photochemicalreduction [3], microwave [4] microemulsion [5,6] and UV-irradiation [7], and. Nowadays special focus on ‘‘green chemistry’’by researchers because of increasing awareness about theenvironment. Utilization of nontoxic chemicals, environmentallybenign solvents and renewable materials are some of the keyissues that merit important consideration in a green synthesisstrategy [8,9]. Silver nano-particles have attracted considerableattention because of their potential applications in various fieldssuch as environmental friendly antimicrobial coatings [10],oxidative catalysis [11], nano electronics (single-electron transis-tors, electrical connects) [12], conductive coatings [13], biosensors[14,15], antibacterial activity [16].

The aim of the present work is to develop a simple and effectiveone-pot green approach toward the rapid synthesis and stabilization

* Corresponding author. Tel.: +20 127 679 2188; fax: +20 222 747 433.

E-mail address: samyshaban@yahoo.com (S.M. Shaban).

http://dx.doi.org/10.1016/j.jiec.2014.02.019

1226-086X/� 2014 The Korean Society of Industrial and Engineering Chemistry. Publis

of AgNPs using Sun light as reducing agent with assistance of theused cationic surfactants in reduction process. The used surfactantsact as stabilizing agent for the synthesized AgNPs. AgNPs withhexagonal shapes and others with spherical shapes were prepared inshort reaction time 5 min as maximum depending on the usedcapping agents without using complicated systems and any otherintermediate steps.

2. Materials and methods

2.1. Chemicals

Silver nitrate (AgNO3, 99%), were provided from Sigma–Aldrich/Germany. The used cationic surfactants were preparedaccording to reference [17]. All glassware was washed in a mixtureof distilled water and non-ionic detergent, followed by rinsing withdistilled water and ethanol for many times to get rid of anyremnants of non-ionic detergent then dried prior to use.

2.2. Synthesis

2.2.1. Preparation of cationic capping agents

The used cationic capping agents were reported [17].The chemical structure of prepared capping agents showed inScheme 1.

hed by Elsevier B.V. All rights reserved.

[(Scheme_1)TD$FIG]

Scheme 1. the chemical structure of prepared cationic capping agents.

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–44814474

2.2.2. Preparation of silver nanoparticles (AgNPs)

In situ, facile and green synthesis of silver nanoparticles wasprepared using sun light as reducing agent with assistance ofprepared surfactants [18].

In a typical experiment, 10 mL of 2 mM aqueous solution ofAgNO3 were mixed with 10 mL of 2 mM aqueous solution ofprepared cationic surfactants then the solution was irradiated withsun light. It was noticed a very fast change in the color of thesolution to different colors like yellows with its different ranges ina time of 5 min maximum depending on the used capping agents asshown in Scheme 2.

2.3. Characterization techniques of silver nanoparticles

The formation of silver nanoparticles was confirmed by thefollowing instrumentations:

2.3.1. Transmission electron microscope (TEM)

A convenient way to produce good TEM samples is to usecopper grids. A copper grid pre-covered with a very thinamorphous carbon film. To investigate the prepared AgNPs usingTEM, small droplets of the liquid were placed on the carbon-coatedgrid. A photographic plate of the transmission electron microscopyemployed on the present work to investigate the microstructure ofthe prepared samples. Nanoparticle size was determined by usingTEM model ‘‘Jeol JeM – 2100 (Japan)’’ (Egyptian PetroleumResearch Institute ‘‘EPRI’’).

2.3.2. UV–visible spectroscopy

The photosynthesis of Ag nanoparticles was monitored periodi-cally by a UV–visible spectrophotometer (Shimadzu, UV-2550,

[(Scheme_2)TD$FIG]

Scheme 2. In situ photo prepara

Japan). For the analysis, 5 mL of 2 mM aqueous solution of silvernitrate were mixed with 5 mL of 2 mM of the used cationicsurfactant then it irradiated by sun light, until color change, then thesample was put in a cuvette for measurement.

2.3.3. Dynamic light scattering (DLS)

The hydrodynamic diameter and zeta potential of the samesolution which used in TEM, UV–vis and EDX, was characterizedby dynamic light scattering (DLS) using a Malvern ZetasizerNano (Malvern Instruments Ltd., Worcestershire, UK). EachDLS measurement was run in triplicate using automated,optimal measurement time and laser attenuation settings. Therecorded correlation functions and measured particles mobility’swere converted into size distributions and zeta potentials,respectively, using the Malvern Dispersion Software (V5.10,http://www.zetasizer.com/).

2.3.4. Energy dispersive X-ray (EDX) spectroscopy

The energy-dispersive X-ray (EDX) spectroscopy was recordedwith an EDX detector (Oxford LINKISIS 300) equipped on aTransmission electron microscope (TEM, Hitachi S-520) operatedat 10 kV accelerating voltage.

2.3.5. Fourier transform infrared spectrometer (FTIR)

FT-IR spectra was recorded using the obtained solid cationicsurfactants capped silver nanoparticle after centrifugation andwashings to remove the unassociated organic molecules. Spectrawas recorded on an ATI Mattson Infinity Series TM, Bench top 961controlled by win first TM V2.01 software (Egyptian PetroleumResearch Institute ‘‘EPRI’’).

tion of silver nanoparticles.

[(Fig._1)TD$FIG]S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–4481 4475

2.4. Biological activity

2.4.1. Biological activity against a wide range of bacteria and fungi

The antimicrobial activity of synthesized cationic surfactantsand their silver nanoform was measured against a wide range oftested organisms comprising: (bacteria and fungi)

1. S

ource of microorganisms:

The different species of tested organisms were obtained fromthe unit of operation development center, Egyptian petroleumresearch institute.

2. T

Fig. 1. Colors(For interpretation of the references to color in this figure legend, the

reader is referred to the web version of the article.) of prepared colloidal silver

nanoparticles with different capping agents.

he media

The following media used in the antimicrobial activity ofsynthesized products, the bacterial species grow on nutrientagar, while fungi mold grow on Czapek’s dox agar.

(a) N

utrient agar

Nutrient agar consists of beef extract (3.0 g/l); peptone(5.0 g/l), sodium chloride (3.0 g/l) and agar (20.0 g/l), then,complete the volume to one liter, heated the mixture until theboiling, and sterilize the media by autoclave.

(b) C

zapek’s Dox agar

Czapek’s Dox agar consists of sucrose (20.0 g/l), sodiumnitrate (2.0 g/l), magnesium sulfate (0.5 g/l), potassium Chlo-ride (0.5 g/l), ferrous sulfate (0.01 g/l) and agar (20.0 g/l), then,complete the volume to one liter, heated the mixture until theboiling, and sterilize the media by autoclave.

(c) M

icroorganisms

The used microorganisms were Gram-positive bacteria(Bacillus pumilus and Micrococcus luteus), Gram-negativebacteria (Pseudomonas aeuroginosa and Sarcina lutea) andFungi (Candida albicans and Penicillium chrysogenum).

An assay was made to determine the ability of an antibiotic tokill or inhibit the growth of living microorganisms, the techniquethat used is filter-paper disk-agar diffusion (Kirby-Bauer) [19].

1. In

oculate flask of melted agar medium with the organism to betested.

2. P

our this inoculated medium into a Petri dish. 3. A fter the agar has solidified, a multilobed disk that impregnated

with different antibiotics laid on top of agar.

4. T he antibiotic in each lobe of disk diffuses into medium and if

the organism is sensitive to a particular antibiotic, no growthoccur in a large zone surrounding that lobe (clear zone).

5. T

he diameters of inhibition zones were measured after 24–48 hat 35–37 8C (for bacteria) and 3–4 days at 25–27 8C (for yeastand fungi) of incubation at 28 8C.

6. M

easure each clear zone and compare between them todetermine the antibiotic, which is more inhibitor.

3. Results and discussions

Aqueous solution of AgNO3 was reduced under exposure to sunlight as a gratis source of reducing agent with assistance ofprepared cationic surfactants. This technique is simple andinexpensive without any surplus material. It was found that inthe presence of prepared cationic surfactants, an aqueous solutionof AgNO3 was reduced and color of solution was changed todifferent colors like yellows with its different range, depending onthe used capping agent in a few minutes as 5 min maximum, asindicated in Fig. 1 and shown in Scheme 2 .The color changesimplied the occurrence of Ag+ reduction to AgNPs [20]. In a controlexperiment, when the sample (aqueous solution of silver nitratewith capping agent) was stored in a vial wrapped with aluminum

foil to exclude light, the solution did not change color or form anysolid precipitate over longer period. When the silver nitratesolution exposed to sun light without capping agent, after longtime exceed 2 months we notes very slight change in color withvery small precipitate on wall of glass vial.

3.1. Formation mechanism of silver nanoparticles

For the synthesis of AgNPs, the generally accepted mechanismsuggests a two-step process, i.e. atom formation and thenpolymerization of the atoms. In the first step, a portion of metalions in a solution reduced by a suitable reducing agent. The atomsthus produced act as nucleation centers and catalyze the reductionof the remaining metal ions present in the bulk solution.Subsequently, the atoms coalesce leading to the formation ofmetal clusters. The process stabilized by the interaction with theprepared capping agent so preventing further coalescence andaggregation [21,22].

When aqueous solutions subject to sun light irradiation (g-radiolysis), it produces the following species [23]:

H2O! e�aqu; H3Oþ; H2; H; OH; H2O2

The solvated electrons and H. atoms are strong reducing agents: E0

(H2O=e�aqu) = �2.87 V (SHE) and E0 (H+/H) = �2.3 V (SHE) and canreduce Ag+ ions to neutral Ag0 atoms:

Agþ þ e�aqu!Ag0

The reduction of Ag+ ions is the main process for the formation ofnanoparticles under g-radiolysis. So both oxidizing OH� radicalsand H� produced in radiolysis of water should be scavenged and itcan be done efficiently by capping agents to produce H2O, H2 andorganic radical.

Since the electrochemical potential of the organic radical ismore positive than that of the Ag+/Ag0 system [24], reaction oforganic radical obtained from capping agent with Ag+ ions isrelatively slow. Thus, during the process of irradiation, Ag+ ions areprimarily reduced by solvated electrons and give rise to Ag0. Thegrowth of silver nanoparticles by reduction of Ag+ to Ag0 isstepwise [25]. These neutral Ag0 atoms at first dimerize when theyencounter or associate with the excess Ag+ ions trapped in theindividual loops of capping agent.

From the above results, we can conclude that sun light act asreducing agent in the presence of prepared cationic surfactants,theses surfactants facilitating and increasing rate of silvernanoparticles formation in addition their role as capping agent.

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–44814476

3.2. Confirmation of silver nanoparticle formation

Stable silver nanoparticles were prepared. The shape and sizedistribution were characterized using TEM, SAED, UV, DLS, EDXand FTIR techniques as following

3.2.1. Transmission electron microscope (TEM) and selected area

electron diffraction (SAED)

The morphology of prepared silver nanoparticles (AgNPs) wereinvestigated by transmission electron microscope (TEM) Fig. 2 andthe selected area electron diffraction pattern (SAED) Fig. 3.

TEM photographs indicate that the nanosilver solution consistof well dispersed agglomerates of spherical and cubic shapesnanoparticles depending on the hydrophobic chain length of theused capping agents. In this agglomeration, the formed nanopar-ticles are not fused, i.e. each particle keep a distance fromsurrounding other particles and these distance increase byincreasing chain length, and this was confirmed also by zetapotential values indicated in Table 2.

Fig. 2 shows TEM morphology of prepared silver nanoparticlescapped with C10Dim, C12Dim and C16Dim. AgNPs capped byC10Dim have spherical shape some particles have hexagonalshape, AgNPs capped by C12Dim have hexagonal shape whileAgNPs capped by C16Dim have spherical shape. We note also byincreasing the alkyl chain length of prepared capping agent thedispersion between particles increase (aggregation decrease)which confirmed by zeta potential values indicated in Table 2.

The selected area electron diffraction pattern of capped AgNPs(SAED) is shown in Fig. 3. Where when the electron diffraction iscarried out on a limited number of crystals one observes somespots of diffraction distributed on concentric circles [26], indicat-ing that the prepared silver nanoparticles are polycrystalline [27].

[(Fig._2)TD$FIG]

Fig. 2. TEM image of prepared silver nanoparticle cappe

3.2.2. UV–vis spectroscopy

UV–vis spectroscopy is quite sensitive to the formation of silvernanoparticles due to surface plasmon excitation [28].

Fig. 4 shows absorption spectra of AgNPs capped by preparedsurfactants, which show absorption band at lmax 418, 412 and420 nm for C10Dim, C12Dim and C16Dim, respectively which anindication on formation silver nanoparticles, due to surfaceplasmon resonance of colloidal silver nanoparticles [29,30]. Bandat lmax range from 290 to 306 nm characteristic for the usedcapping agents, which matches with the band appeared foraqueous solution of the used capping agents alone. It is known thatthe amount and size of Ag nanoparticles are positively related withthe adsorption peak intensity and the lmax on the UV–vis spectra[31–34], respectively.

From Fig. 4, there are increasing in the intensity (absorbance), ofthe bands at lmax range from 412 to 420 nm with increasinghydrophobic chain length of the used capping agent, which giveindication on increasing formation percent of silver nanoparticles.For example, C10Dim, C12Dim and C16Dim have lmax at 418, 412and 420 nm respectively with absorbance intensity 0.49, 0.79 and0.89 respectively.

Fig. 4 shows very small shift in value of lmax of prepared silvernanoparticles by increasing hydrophobic chain length of cappingagent, which indicate that the in situ photo-reduction using sunlight as reducing agent in the presence of the used capping agent,give similar size distribution.

3.2.3. Dynamic light scattering (DLS)

Dynamic light scattering technique (DLS) was performed tounderstand the size distribution of silver nanoparticles capped byprepared cationic surfactants and their stability by zeta potentialvalues.

d by (A) (C10Dim), (B) (C12Dim) and (C) (C16Dim).

[(Fig._3)TD$FIG]

Fig. 3. SAED image of prepared silver nanoparticles capped by (A) (C10Dim), (B) (C12Dim) and (C) (C16Dim).

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–4481 4477

Particle size distribution of silver nanoparticles in aqueoussolution of capping agents are listed in Table 1 and shown in Fig. 5.which indicate that the in situ photo-reduction using sun light asreducing agent in the presence of capping agent, give similar sizedistribution, these results matches with data obtained from UV–visspectroscopy as shown in Fig. 4.

Stability of nanoparticles is crucially important for manyapplications and can be determined using zeta potential measure-ments [35]. Zeta potential is the net surface charge of thenanoparticles when they are inside a solution. The fact that

[(Fig._4)TD$FIG]

Fig. 4. UV spectra of prepared silver nanoparticles using C10Bn, C12Bn and C16Bn as

capping agent.

particles push each other and their agglomeration behaviordepends on large negative or positive zeta potential. The zetapotential playing an important role limits in the stability ofsolutions is +30 mV or �30 mV. To regard the particles as stable,zeta potential should be either higher than +30 mV or lower than�30 mV [36].

By inspection data in Table 2, it was found that the zetapotential values of prepared silver nanoparticle encapsulated bythe prepared cationic surfactants are greater than +30 mV, whichbe indication on high stability of prepared silver nanoparticlesagainst agglomeration. High value of zeta potential indicate thatthe surface charge on nano-silver is high so the electrostaticrepulsion between particles increase, keeping particles withoutagglomeration and stable for long time. The acquired positivecharge of zeta potential is mainly due to the used capping agent iscationic surfactant (carry positive charge) [37], while zetapotential of silver nanoparticle prepared without using cappingagent and after irradiation to sun light for 1 month was�0.386 mV.

Also we found that zeta potential values of prepared silvernanoparticles are positively related with hydrophobic chain lengthof added capping agents, where by increase chain length of capping

Table 1Size distribution of prepared silver nanoparticles using prepared capping agents.

Capping agent Distribution range Maximum

distribution range

Size

(nm)

Number (%) Size (nm) Number (%)

AgNPs capped by C10Dim 15–50 97 15–38 92.2

AgNPs capped by C12 Dim 18–50 98.3 21–38 87.4

AgNPs capped by C16Dim 18–50 97.2 21–44 91.6

[(Fig._5)TD$FIG]

Fig. 5. Size distribution of silver nanoparticles using prepared capping agents determined by DLS.

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–44814478

agent, zeta potential increase, which be indication on increasingstability of prepared silver nanoparticle against agglomeration forexample zeta potential of prepared silver nanoparticle capped byC10Dim, C12 Dim and C16 Dim are 34.1 � 10.4, 48.9 � 9.9 and52 � 10.7 respectively.

3.2.4. Energy dispersive X-ray (EDX)

EDX spectroscopy results confirmed the significant presence ofpure 100% silver with no other contaminants. The opticalabsorption peak at 3 keV, is typical for the absorption of metallicsilver nanocrystallites due to surface plasmon resonance [38].

Fig. 6 shows the EDX analysis of the AgNPs capped by theprepared cationic surfactants. The EDX spectrum showed a strongand typical optical absorption peak at approximately 3 keV, whichwas attributed to the SPR of the metallic Ag nanocrystals [38]. Thisresult indicated that AgNPs were formed in the reaction medium.Beside of Ag there are others bands for C, O and Br elements peakswhich appeared due to the scattering caused by the compounds thatare bound to the surface of silver which indicating that the usedcationic surfactants act as capping agents for silver nanoparticles.

Table 2Zeta Potential and conductivity of prepared silver nanoparticle by dynamic light

Scattering (DLS).

Capping agent Zeta

potential (mV)

Conductivity

(mS/cm)

No capping and irradiation for 1 month �0.386 1.64

AgNPs Capped by C10Dim 34.1�10.4 0.183

AgNPs Capped by C12Dim 48.9�9.95 0.169

AgNPs Capped by C16Dim 52�10.7 0.152

3.2.5. FT-IR spectroscopy

FT-IR spectroscopy is used in order to understand the role ofprepared capping agent in the formation of silver nanoparticlesand the chemical environment of the final product. In Fig. 7, allbands around 2926, 2853, 1500 and 1642 cm�1 indicating thepresence of capping agent with the nanoparticles. Bands at 2926and 2853 cm�1 corresponds to asymmetric and symmetric C–Hstretching of alkyl chain of C12Dim. Band at 1642 cm�1

correspond to Schiff base group (–C55N–). On comparing IRbands of silver nanoparticles capped by surfactants in Fig. 7 withIR bands of surfactant alone in Fig. 8, we notes that some bandsmaxima are little blue shifted and some bands are also little redshifted. These relatively small shifts are mostly due to theconstraint of the capping molecular motion, which presumablyresulted from the attachment on the nanoparticles surface [39].Also we note increasing in the intensity of the band around1375 cm�1 by 50–80% than band of capping agents alone, whichindicate presence co-ordination bond between CH2 of hydro-phobic chain length of capping agent and silver nanoparticlessurface. This co-ordination bond enhance role of capping agentschain lengths in shaping, sizing and distribution as indicated byboth transmission electron microscope, UV–vis spectroscopyand dynamic light scattering.

3.3. Evaluation of the synthesized surfactants as antibacterial and

antifungal

We evaluated the prepared cationic surfactants and theircapped form with silver nanoparticles as biocide against somepathogenic Gram-positive (B. pumilus and M. luteus) and Gram-negative (P. aeuroginosa and S. lutea) bacteria and also, some

[(Fig._6)TD$FIG]

Fig. 6. EDX silver nanoparticles capped by prepared surfactants: (A) is C10Dim, (B) is C12Dim and (C) is C16Dim.

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–4481 4479

pathogenic fungi (C. albicans and P. chrysogenum). The aim of theformation silver nanoparticles capped by cationic compounds is toincrease their potency against microorganisms.

The results of antimicrobial activity are recorded in Table 3,indicating that the synthesized compounds have antimicrobialactivity rang from a moderate to slight high effect on Gram-negative bacteria and from slight high to high on Gram- positivebacteria and very high effect on fungi compared to the drugreference used.

The biological activities of surfactants often show a non-lineardependence on their chain length, where bactericides andfungicide activity increase by increasing hydrophobic chain length[(Fig._7)TD$FIG]

Fig. 7. FTIR spectrum C12Dim c

[40], in our work the optimal alkyl chain length has been noted tobe twelve carbon atoms, which has the maximum inhibition zonewhere compounds with twelve carbon chain higher than thesewith ten carbon atoms chain which higher than these of sixteencarbon atoms. These results are agreement with results obtainedbefore [40–44], this behavior known by cut-off effect whichobserved for the first time more than 70 years ago, in which theactivity increases progressively in a homologous series ofcompounds, with increasing chain length up to a critical point,beyond which the activity decreases [45].

Several theories have been postulated as to why this cut-offeffect occurs, first have associated this cutoff with a limit in

apped silver nanoparticle.

[(Fig._8)TD$FIG]

Fig. 8. IR spectrum of N-(3-((3,4-dimethoxybenzylidene)amino)propyl)-N,N-dimethyldodecan-1-ammonium (C12Dim).

Table 3Antimicrobial activity of synthesized surfactants and their nano form against pathogenic bacteria and fungi.

Inhibition zone diameter (mm)

Pseudomonas aeuroginosa Sarcina lutea Bacillus pumilus Micrococcus luteus Candida albicans Penicillium chrysogenum

Erythromycin 30 44 32 32 – –

Metronidazole – – – – 27 25

C10Dim 13 29 17 22 24 17

C12Dim 16 37 18 31 28 19

C16Dim 15 24 16 22 23 16

AgNPs capped by C10Dim 16 29 23 25 27 25

AgNPs capped by C12Dim 17 38 24 32 36 29

AgNPs capped by C16Dim 16 26 17 22 24 25

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–44814480

solubility, they proposed that as the alkyl chain increases, lipidsolubility increases at a rate faster than the change in partitioncoefficient (lipid/aqueous) theory. At these higher chain length,partitioning is limited, making the concentration at the site ofaction insufficient to have a significant effect on the membrane ofthe cell wall [46] and hence according to this theory the activity ofcompounds should be ordered as follow C10? C12 ? C16 chain dueto increase lipid solubility from C10 to C16.

Other accounts attribute this cut-off to a decrease in perturba-tion of the membrane at higher chain lengths, proposing that thelonger alkyl chain molecules better mimic molecules in the lipidbilayer, causing less of a disruption in the membrane [47].

Other theory based on critical micelle concentration (CMC), assurfactants chain length increase, their tendency toward micelleformation is greater, noted by the lower CMCs at higher chainlengths. This tendency to form micelles becomes greater than thetendency to move toward the interface (the membrane), and thusthe concentration at the action site becomes decreased, also, as thesize of the diffusing species increases from the size of a monomerto that of micelles, their diffusibility and permeation abilities willdecrease, affecting their action on the microbial cell wall and henceaccording to this theory the activity of compounds should beordered as follow C10? C12 ? C16.

Other theory based on surface and thermodynamic propertiessurfactants which showed tendency of prepared compound

toward adsorption at the interfaces which facilitate their role ofadsorption at the bacterial cell membrane, where increasingDGo

ads enhances the higher adsorptivity of prepared compound,from previous thermodynamic results DGo

ads increase by increas-ing chain length [17], and hence according to this theory theactivity of compounds should be ordered as follow C16 ? C12 ? C10chain.

From that we can conclude that factors effects on cut-off pointof homologous series of surfactants varying in chain length, aresolubility, critical micelle concentration, (CMC), size of diffusingspecies and change in free energy of adsorption. Magnitude ofthese factors determines when cut-off occurs, according to data inTable 3, the cut-off was observed with surfactants with chainlength (C16) for all prepared compounds.

It was observed from data in Table 3, that biological activity(inhibition zone) of silver nanoparticle in capsulated with preparedcationic surfactants higher than corresponding prepared cationicsurfactant, this can be attributed to silver nanoparticle alone hasbiological activity, so prepared surfactant capped silver nanopar-ticles have higher activity, this can be attributed to the highersurface area of prepared nanoparticles and the acquired positivecharge of prepared silver nanoparticles (as indicated in zetapotential values in Table 2) in addition positive charge of cationicsurfactants, where these positive charge facilitate adsorption atnegative cell wall membrane of bacteria.

S.M. Shaban et al. / Journal of Industrial and Engineering Chemistry 20 (2014) 4473–4481 4481

4. Conclusion

From the obtained results, we can conclude:

� I

n situ, facile and green synthesis of silver nano particles weredeveloped using sun light as reducing agent with assistance ofprepared surfactants. � T he prepared surfactants act as capping agents (DLS, EDX and

FTIR).

� I ncreasing hydrophobic chain length of the capping agents, the

stability of prepared AgNPs increase.

� I ncreasing hydrophobic chain length of the capping agents, the

amount of AgNPs increase (Increasing absorbance in UV–visspectra).

� H exagonal AgNPs were prepared. � T he silver nanoparticles increase the biological activity of the

capping agents.

References

[1] S.D. Solomon, M. Bahadory, A.V. Jeyarajasingam, S.A. Rutkowsky, C. Boritz, L.Mulfinger, J. Chem. Educ. 84 (2007) 322.

[2] L. Rodrıguez-Sanchez, M.C. Blanco, M.A. Lopez-Quintela, J. Phys. Chem. B 104(2000) 9683.

[3] H.H. Huang, X.P. Ni, G.L. Loy, C.H. Chew, K.L. Tan, F.C. Loh, J.F. Deng, G.Q. Xu,Langmuir 12 (1996) 909.

[4] M. Tsuji, Y. Nishizawa, K. Matsumoto, N. Miyamae, T. Tsuji, X. Zhang, Colloids Surf.A 293 (2007) 185.

[5] M.M. Cai, J.L. Chen, J. Zhou, Appl. Surf. Sci. 226 (2004) 422.[6] A. Taleb, C. Petti, M.P. Pileni, Chem. Mater. 9 (1997) 950.[7] D.M. Cheng, X.D. Zhou, H.B. Xia, H.S.O. Chan, Chem. Mater. 17 (2005) 3578.[8] M. Poliakoff, P. Anastas, Nature 413 (2001) 257.[9] P. Raveendran, J. Fu, S.L. Wallen, J. Green Chem. 8 (2006) 34.

[10] C. Aymonier, U. Schlotterbeck, L. Antonietti, P. Zacharias, R. Thomann, J.C. Tiller, S.Mecking, Chem. Commun. 24 (2002) 3018.

[11] Y. Shiraishi, N. Toshima, Colloids Surf. A 169 (2000) 59.[12] T. Sato, H. Ahemd, D. Brown, B.F.G. Johnson, J. Appl. Phys. 82 (1997) 696.[13] W.P. Wuelfing, F.P. Zamborini, A.C. Templeton, X.G. Ween, H. Yoon, R.W. Murray,

Chem. Mater. 13 (2001) 87.[14] F. Frederix, J.M. Friedt, K.H. Choi, W. Laureyn, A. Campetelli, D. Mondelears, G.

Maes, G. Borghs, Anal. Chem. 75 (2003) 6894.[15] E. Bakker, Anal. Chem. 76 (2004) 3285.[16] I. Sondi, B. Salopek-Sondi, J. Colloids Interface Sci. 275 (2004) 177.

[17] I. Aiad, M.M. El-Sukkary, E.A. Soliman, M.Y. El-Awady, S.M. Shaban, J. Ind. Eng.Chem. (2013), http://dx.doi.org/10.1016/j.jiec.2013.08.010.

[18] I. Aiad, M.M. El-Sukkary, E.A. Soliman, M.Y. El-Awady, S.M. Shaban, J. Ind. Eng.Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.031.

[19] D.N. Muanza, B.W. Kim, K.L. Euler, L. Williams, Int. J. Pharmacogn. 32 (1994) 337.[20] Y. Yang, J. Shi, T. Tanaka, M. Nogami, Langmuir 23 (2007) 12042.[21] D.V. Goia, J. Mater. Chem. 14 (2004) 451.[22] M.H. El-Rafie, M.E. El-Naggar, M.A. Ramadan, M.M.G. Fouda, S.S. Al-Deyab, A.

Hebeish, Carbohyd. Polym. 86 (2011) 630.[23] J.W.T. Spinks, R.J. Woods, Year, Water and Inorganic Aqueous Systems: An

introduction to Radiation Chemistry, 3rd ed., Wiley Interscience, New York,1990p. 255.

[24] A. Henglein, Chem. Mater. 10 (1998) 444.[25] J. Belloni, M. Mostafavi, H. Remita, J.L. Marignier, M.O. Delcourt, New J. Chem. 22

(1998) 1239.[26] M.G. Guzman, J. Dille, S. Godet, World Acad. Sci. Eng. Technol. 43 (2008) 357.[27] W. Chun-Hua, L. Li-Ren, Y. Ai-Min, Z. Yu, L. De-An, H. Zhi-Juan, Chin. Phys. 16

(2007) 100.[28] Lilia Coronato Courrol, Flavia Rodrigues de Oliveira Silva, Laercio Gomes, Colloids

Surf. A: Physicochem. Eng. Aspects 305 (2007) 54.[29] K.L. Kelly, E. Coronado, L.L. Zhao, G.C. Schatz, J. Phys. Chem. B 107 (2003) 668.[30] I. Pastoriza-Santos, C. Serra-Rodrıguez, L.M. Liz-Marzan, J. Colloid Interface Sci.

221 (2000) 236.[31] S. Jradi, L. Balan, X.H. Zeng, J. Plain, D.J. Lougnot, P. Royer, Nanotechnology 21

(2010) 95605.[32] M.V. Roldan, L.B. Scaffardi, O. de Sanctis, N. Pellegri, Mater. Chem. Phys. 112

(2008) 984.[33] G. Wei, L. Wang, L.L. Sun, Y.H. Song, Y.J. Sun, C.L. Guo, J. Phys. Chem. C 111 (2007)

1976.[34] M. Chen, Y.G. Feng, X. Wang, T.C. Li, J.Y. Zhang, D.J. Qian, Langmuir 23 (2007) 5296.[35] Y. Zhang, M. Yang, N.G. Portney, D. Cui, G. Budak, E. Ozbay, M. Ozkan, C.S. Ozkan,

Biomed. Microdevices 10 (2008) 321.[36] J. Ho, M.K. Danquah, H. Wang, G.M. Forde, J. Chem. Technol. Biotechnol. 83 (2008)

351.[37] J. Hedberg, M. Lundin, T. Lowe, E. Blomberg, S. Wold, I. Odnevall Wallinder, J.

Colloid Interface Sci. 369 (2012) 193.[38] G. Magudapatty, P. Gangopaghyayrans, B.K. Panigrahi, K.G.M. Nair, S. Dhara, Phys.

B: Condens. Matter 299 (2001) 142.[39] J.D.S. Newman, G.J. Blanchard, Langmuir 22 (2006) 5882.[40] P. Balgavy, F. Devinsky, Adv. Colloid Interface Sci. 66 (1996) 23.[41] H. Nagamune, T. Maeda, K. Ohkura, K. Yamamoto, M. Nakajima, H. Kourai, Toxicol.

In Vitro 14 (2000) 139.[42] C.R. Birnie, D. Malamud, R.L. Schnaare, Antimicrob. Agents Chemother. 44 (2000)

2514.[43] J. Pernak, J. Kalewska, H. Ksycinska, J. Cybulski, Eur. J. Med. Chem. 36 (2001) 899.[44] G. Viscardi, P. Quagliotto, C. Barolo, P. Savarino, E. Barni, E. Fisciaro, J. Argo Chem.

65 (2000) 8197.[45] C. Campanac, L. Pineau, A. Payard, G. Baziard-Mouysset, C. Roques, Antimicrob.

Agents Chemother. 46 (2002) 1469.[46] A. Janoff, M. Pringle, K. Miller, Biochim. Biophys. Acta 649 (1981) 125.[47] M. Pringle, K. Brown, K. Miller, Mol. Pharmacol. 19 (1981) 49.