Biosynthesis of PVA encapsulated silver nanoparticles Technology Journal of Applied Researchand

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Availableonlineatwww.sciencedirect.com

Journal of Applied Research and Technology

www.jart.ccadet.unam.mx JournalofAppliedResearchandTechnology14(2016)319–324

Original

Biosynthesis of PVA encapsulated silver nanoparticles

Sharmila Chandran

^a,∗

, Vinuppriya Ravichandran

^b

, Selvi Chandran

^b

, Jincy Chemmanda

^b

, Bellan Chandarshekar

^c

aAssistantProfessor,DepartmentofPhysics,PSGRKrishnammalCollegeforWomen,Coimbatore641004,TamilNadu,India

bResearchScholar,DepartmentofPhysics,PSGRKrishnammalCollegeforWomen,Coimbatore641004,TamilNadu,India

cAssistantProfessor,DepartmentofPhysics,KongunaduCollegeofArtsandScience,Coimbatore641029,TamilNadu,India Received28January2016;accepted25July2016

Availableonline13October2016

Abstract

Greensynthesisofmetalnanoparticlesisanimportanttechniqueinthemethodsofeco-friendlynanoparticleproduction.Thesynthesisofsilver nanoparticleswasaccomplishedusingOcimumsanctumleafextractatroomtemperature.Theseparticleswerethenencapsulatedwithpolyvinyl alcohol(PVA)polymermatrix.ThepresenceofsilverwasconfirmedbydifferentcharacterizationtechniquessuchasUV–visspectroscopy,Fourier transforminfraredspectroscopy(FTIR)andX-RayDiffraction(XRD).Scanningelectronmicroscopic(SEM)imagesofthesynthesizedpowder showssphericalshapedsilvernanoparticlesembeddedinsponge-likepolymermatrix.TheenergydispersiveX-rayanalysisconfirmsthepresence ofelementalsilveralongwithironsignal.EnergydispersivesignalcorrespondingtoelementalironhasbeenattributedtoO.sanctumplant.The silvernanoparticlesinPVAmatrixthusobtainedshowshighantibacterialactivityagainstgrampositiveStaphylococcusaureus(S.aureus)and gramnegativeEscherichiacoli(E.coli)waterbornebacteria.TheinhibitionzoneagainstS.aureusandE.coliwerealsocalculated.

Keywords:Silvernanoparticles;Ocimumsanctum;PVA;Antibacterialstudies

1. Introduction

Research on nanoparticles is currently an area of intense scientific interest due to its wide range of applications (Abdulrahman, Krajczewski, Aleksandrowska, & Kudelski, 2015;Park,Lee,&Lee,2016;Taylor,Coulombe,etal.,2013;

Yahyaei etal., 2016). In spite of being the size of the ultra- fineparticlesindividualmoleculesareusuallynotreferredtoas nanoparticles(Hewakuruppuetal.,2013).Nanoparticlesforma bridgebetweenbulkmaterialsandatomic/molecularstructures.

Nanoparticlesdonotneedtohaveconstantphysicalproperties, theymayvary(Taylor,Otanicar,etal.,2013).Thesizedepend- entpropertysuchasquantumconfinementcanbeobservedin semiconductor particles, surface plasmon resonanceis found insome metal particles and super magnetism is observed in magneticmaterials(Taylor,Otanicar,&Rosengarten,2012).

∗Correspondingauthor.

E-mailaddresses:[email protected],[email protected] (S.Chandran).

PeerReviewundertheresponsibilityofUniversidadNacionalAutónomade México.

Nowadays, metallic nanoparticles are the focus of inter- estbecauseof theirhuge potentialinnanotechnology(Mody, Siwale,Singh,&Mody,2010;Salunke,Sawant,Lee,&Kim, 2016).Metallicnanoparticleshavebeenembracedbyindustrial sectors because oftheir applications inthefieldof electronic storage systems (Kang, Risbud, Rabolt, & Stroeve, 1996), biotechnology(Pankhurst,Connolly,Jones,&Dobson,2003), magnetic separation and pre-concentration of target analysts, targeteddrugdelivery(Dobson,2006;Rudgeetal.,2001)and vehiclesforgeneanddrugdelivery.Withawiderangeofappli- cations available,theseparticleshavethepotential tomakea significantimpactonsociety.

Silver nanoparticles have some advantages over other nanoparticlesbecausetheyarereportedtobenon-toxictohuman andmosteffectiveagainstbacteria,virusesandothereukarary- oliticmicro-organismsataverylowconcentration,withoutany knownsideeffects(Chauhan,Gupta,&Prakash,2012).Many effortshavebeentakentoincorporatesilvernanoparticlesinto a wide range of medical devices, such as bone cement, surgical instruments, surgical masks (Valente, Gaspar, Antunes, Countinho,&Correia,2013);however,ithasalsobeenshown that ionic silver in the right quantities is suitable in treating

http://dx.doi.org/10.1016/j.jart.2016.07.001

1665-6423/©2016UniversidadNacionalAutónomadeMéxico,CentrodeCienciasAplicadasyDesarrolloTecnológico.Thisisanopenaccessarticleunderthe CCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

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ingtheexcessive needsandcurrentmarket demands.Whena metalcoreiscappedwithaplantextractthenthesebiomateri- alswillactasamoreeffectivetherapeuticagent,comparedto thenanomaterialssynthesizedbyanychemicalmethod(Mittal, Chisti,&Banerjee,2013).Phytochemicals,suchasursolicacid, flavonoids,saccharidesandproteins,presentinplantextractare responsible for the reduction of silver ions (Bhaumik et al., 2015); hence this bioinspired synthesis of nanomaterials is highlyadvantageousasanaturalandcosteffectiveresource.

Recently many plants have gainedimportance because of theiruniqueproperties.Theseplantshaveversatileapplicabil- ityinvariousdevelopingfields of researchanddevelopment.

Amongthesemedicinalplants, thetulsileave(Ocimumsanc- tum)planthavehighrateofmedicinalvalue.Studieshaveshown thatsilvernanoparticlespreparedfromtulsileaveswereusedin different applications(Sharma, Yngard, &Lin, 2009; Zhang, Wu, Chen, & Lin, 2009). The leaves have a long historyof medicinaluses.O.sanctumleavesactasantifertility,anticancer, antidiabetic,antifungal&antimicrobialagents(Philip&Unni, 2011).EventhoughsilvernanoparticlesreducedbyO.sanctum leavesexhibithightherapeuticpotential,usingsilveraloneisa challengingtaskforapplicationsinfoodindustryandpharma- ceuticaltechnology.Henceattentionhasbeengiventopolymer metalcompositetopotentiatetheprotectionofbiologicalactive compoundsfromdegradation,controldrugrelease,andimprove absorptionofthetherapeuticagent(Ahmed&Aljaeid,2016).

Theaimofthepresentstudyistosynthesiseco-friendlysilver nanoparticlesbygreensynthesisfromfreshleavesofO.sanctum andtoencapsulatethesesilvernanoparticlesinaPVAmatrix.

Thesynthesisofnanoparticlesfromplantextractiscosteffective anddoesnotrequiremuchequipment.ThePVAencapsulated silvernanoparticlessynthesizedfromsuchtechniquearestable forseveralmonthsandcanbestoredatroomtemperaturewithout anyspecialattention.Differentcharacterizationtechniqueswere carriedouttoconfirmtheexistenceofsilvernanoparticles.

2. Materialsandmethods 2.1. Preparationofleafextract

FreshleavesofO.sanctumwerecollectedfromlocalresi- dencearoundCoimbatore,TamilNadu,India.Theleaveswere washedthoroughly severaltimes withdouble distilled water.

Leafextract usedfor thesynthesiswaspreparedbyweighing

light green to dark brown indicating the formation of silver nanoparticles.

2.3. PreparationofsilvernanoparticlesinPVAmatrix

Poly VinylAlcohol (PVA)(Himedia, Bangalore)of 0.14g wasmixedwith100mlofdoubledistilledwaterandstirredfor 2h. The solution was then slowly added with120mlof leaf extractAgNO3.

2.4. UV–visiblespectroscopy(UV)

The formationofsilver nanoparticlesfrom theleaf extract wascharacterizedbyUV–visibleSpectroscopyusingaCyber labUV-100doublebeamspectrophotometerinthewavelength rangeof300–800nm.Acomparativeabsorptionspectrumwas obtained between the pure silver nanoparticles and the PVA encapsulatedsilvernanoparticles.

2.5. X-raydiffraction(XRD)

ColloidalformofsilvernanoparticlesinthePVAmatrixwas coatedonawellcleanedglasssubstratebydroptechniqueand wasallowedtodryatroomtemperaturefor24h.Theglasssub- stratewasthencharacterizedusingSHIMADZULabXRD6000 withCuK␣radiationmonochromaticfilterintherange10^◦–80^◦. Debye-Scherer’sequationwasusedtocalculatetheparticlesize ofsilvernanoparticles.

2.6. Fouriertransforminfraredspectroscopy(FTIR)

Toidentifythefunctionalgroupspresentinthecolloidalform ofthePVAembeddedsilvernanoparticles,theFouriertransform infrared(FTIR)analysiswascarriedoutusingIR-Affinity1,Shi- madzumakeFTIRSpectrometerinawavenumberrangefrom 500to3500cm⁻¹.

2.7. Scanningelectronmicroscopy(SEM)

ThePVAembeddedsilvernanoparticlescoatedontheglass substratebydropmethodwerecharacterizedusingaTESCAN makeScanningElectronMicroscope.SEMimagesweretaken for different magnifications. An elemental analysis was also donebyenergydispersiveX-rayanalysis(EDAX)alongwith thescanningelectronmicroscopy.

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Figure1.Increaseinthecolorintensityofthereactionmixturewithtimefor5,30and60min.

3. Resultsanddiscussions

3.1. UV–visiblespectroscopicanalysis

Theabsorptionspectraofpuresilvernanoparticles,andthe PVA encapsulated silver nanoparticles were carried out. The reductionofsilvernanoparticlesusingtulsi(O.sanctum)leaves wasevidencedvisuallybyachangeincolor,fromlightgreen todarkbrown.Colorintensityincreaseswithincreaseintime.

Initially when adding1×10⁻³M aqueoussilver nitrate with 20mlofleafextract,thecolorofthesolutionwasfoundtobe lightgreen;afteronehour,thecolorchangedfromreddishbrown todarkbrown(Fig.1).ThiseffectmaybeduetoSurfacePlasmon Vibration(Krasovskii&Karavanskii,2008;Sun&Xia,2002).

SPRpeaksfor puresilvernanoparticleswererecorded for differenttimeintervals(Fig.2).Theabsorptionpeakat480nm appearsbecauseofthepresenceofsilvernanoparticles,andthe resultsareingoodcorrelationbetweentheearlierreportedstud- ies(Sharma,Vendamani,Pathak,&Tiwari,2015).Theintensity oftheabsorptionpeakincreasessteadilyasafunctionoftime andwashighestfor1h.Theincreaseinintensityindicatesthe increase in concentration of the silver nanoparticles (Cheng, Hung,Chen,Liu,&Young2014).TheUV-spectrarecordedafter 2hdoesnotshowanyincreaseintheintensityoftheabsorption spectrum,whichshowsthatthereactionwascompletedwithin 2hwherethesilverionsgetsseparatedandsettleddownatthe bottomofthetubefromthesupernatantmotherliquidleavingit asacolorlesssolution.

AbroadSPRpeakwasobservedforthePVAencapsulated silver nanoparticles solution and the absorption spectra was observedfrom450nmto480nmand(Fig.2a).Thebroadnature of the band might be due to the presence of polymerin the solution.Thereactionmixturewasstablefor3monthsatroom temperaturewithoutanyspecialattention.

3.2. X-raydiffractionanalysis

Figure3showsthe XRDpattern forthe synthesizedsilver nanoparticlesinPVAmatrixanditisobservedthattheparticles arecrystalline innature. StrongpeaksfromBraggs reflection

Figure2.UV–vis absorptionspectraofpuresilvernanoparticlesfordiffer- enttimeintervals.(a)UV–visabsorptionspectraofPVAencapsulatedsilver nanoparticles.

wasobservedintheXRDpatternat2θ=12^◦,32^◦ and38^◦.It is well known that the peaks at 2θ less than 20^◦ are due to thecrystallinenatureofthePVApolymermolecule.Thelattice planes[101]correspondingto2θ=12^◦maybeformedasaresult ofstrongintermolecularandintramolecularhydrogenbonding

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Figure3.XRDpatternofPVAencapsulatedsilvernanoparticles

betweenthePVAchains.TheX-raydiffractionpeakcorrespond- ingto38^◦isduetothesilvernanoparticlescorrespondingtothe latticeplane[111].Thepeaksat32^◦mightbeduetothepres- enceofcertainimpuritieswhilebondingbetweenthePVAand thesilvermolecule(Kim,Kim,Lee,&Kim,1992;Guirguis&

Moselhey,2012).Thegrainsizeofsilvernanoparticleswerecal- culated using Debye-Scherer’sequation D=Kλ/βcosθ,where theaveragegrainsizewasfoundtobe20nm.

nanoparticles.

3.3. FTIRanalysis

FTIR spectroscopyhasbeen provedtobeaverypowerful techniquetostudytheinternalstructureofpolymericmaterial andintra-molecularinteractionbetweenpolymericmaterialand filler.TheFTIRspectrumofthesynthesizedAgnanoparticles in PVA matrix is shown in Figure 4. Prominent peaks were observedat3340cm⁻¹,1637cm⁻¹,659cm⁻¹to553cm⁻¹.The peakobservedat3340cm⁻¹indicatesthepresenceofahydro- genbondbetweenthePVApolymerandleafcausingOH/NH2

Figure4. FouriertransforminfraredspectroscopyspectrumofsilvernanoparticlesinPVAmatrix.

Figure5.SEMimagesofsilvernanoparticlesinPVAmatrixondifferentnanometricscale.

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Figure7.AppearancesofinhibitoryzonesofPVAembeddedsilvernanoparticlesagainstS.aureusandE.coli.

Table1

EDAXelementalmicro-analysisofthePVAencapsulatedsilvernanoparticles.

Element Wt% At%

FeK-series 2.54 1.33

AgL-series 97.46 98.67

Matrix Correction ZAF

stretching.The peakat1637cm⁻¹maybeattributedtoC C, stretchingmode.Thepeaksfrom659cm⁻¹to553cm⁻¹might becausedbywaggingmodeofOHgroups(Agnihotri,Mukherji,

&Mukherji,2012;Chengetal.,2014).TheFTIRresultscon- firmthatthePVA,asacappingagent,playsanimportantrolein theformationofsilvernanoparticles.

3.4. SEManalysis

Morphologyof the synthesizedsilver nanoparticles inthe PVAmatrixwasobservedfromtheSEMmicrographs.Figure5 showstheSEMimagesfordifferentmagnifications.Fromthe graph, it is found that the spherical shaped silver nanoparti- cleswereembeddedinasponge-likePVAmatrix.Theenergy dispersiveX-rayanalysis(EDAX)revealsstrongsignalinthe silverregionandconfirmsthepresenceofsilvernanoparticles (Fig.6).Generallysilvernanoparticlesshowopticalabsorption peakapproximatelyat3keVduetosurfaceplasmonresonance (Ahmadetal.,2003).Alongwithsilver,Fenanoparticleswere alsofoundinthegraphwhichmightbecausedbytheironcontent presentintheO.sanctumleaves.Theatomicweightpercentage oftheelementspresentwastabulatedandisshowninTable1.

3.5. Antibacterialactivity

The antibacterial potential of silver has been known for manyyears. Antibacterialactivity of silvernanoparticleswas evaluated by agar disk diffusion method using Muller Hin- ton agar.The antibacterial effect of PVA encapsulated silver was tested against gram positive Staphylococcus aureus (S.

aureus)andgramnegative Escherichiacoli (E.coli) bacteria for different concentrations (Fig. 7). Eugenol (1-hydroxy-2- methoxy-4-allylbenzene),the active constituent presentin O.

Table2

Zoneofinhibitionagainstgramnegativeandgrampositivebacteria.

Concentration(␮l) Zoneofinhibition(mm)(halfdiameter)

Sample E.coli S.aureus

10 6 4

25 8 7

50 9 8

Ofloxacin(5mcg) 8 12

sanctum leaves has been found to be largely responsible for the plants therapeutic potential (Prakash &Gupta, 2005). Its antibacterialeffectwasevidencedbythevalueofdiameterof zone of inhibition. The inhibition zone for different concentrations isshown inTable 2. From the table,it is foundthat E.coliandS.aureusaresensitivetosilvernanoparticles. The observedvaluefromthe inhibitionzoneisingoodagreement withpreviousreportedstudies(Abishek&Amruthaa,2013).

4. Conclusion

Thereductionofsilvertosilvernanoparticlesfromgreensyn- thesisusing tulsileaveswascarried outatroomtemperature.

The greensynthesis methodfromplant extract providessim- ple,efficientandgoodcontroloversynthesizednanoparticles.

Biosynthesizedsilvernanoparticlesinanorganicpolymer(PVA) matrixwerecharacterizedusingUV–vis,XRD,FTIRandSEM spectroscopictechniques.Thepresenceofsilverwasevidenced using UVspectrum.From XRDstudies,the peakreveals the presenceof organicsubstanceandsilvernanoparticles,which wasagainconfirmedbytheFTIRspectrum.TheSEMimages show thepresence of sphericalshaped silver presentinsidea sponge-likePVAmatrix.Thepresence ofsilver andiron was observed from the EDAX studies. The investigation on the antibacterialeffectof nano-sizedsilver against E.coli andS.

aureusrevealsPVAencapsulatedsilvernanoparticlesasastrong antibacterial agent. The synthesized silver nanoparticles can show new pathways invarious fields like water purification, anticancerstudiesanddrugdeliverysystems.

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