Preparation and Structural Analysis of Nano-Silver Loaded Poly(styrene-co-acrylic acid)

14 Pages·2017·10.33 MB·English

nanomaterials
Article
Preparation and Structural Analysis of Nano-Silver
Loaded Poly(styrene-co-acrylic acid) Core-Shell
Nanospheres with Defined Shape and Composition
JinZhang1,†,XiaoyuZhao1,*,†,YanfeiWang1,*,LiangZhu1,LibinYang1,GangLi2
andZuoliangSha1
1 TianjinKeyLaboratoryofMarineResourcesandChemistry,CollegeofChemicalEngineeringandMaterials
Science,TianjinUniversityofScienceandTechnology,Tianjin300457,China;
[email protected](J.Z.);[email protected](L.Z.);[email protected](L.Y.);
[email protected](Z.S.)
2 StateKeyLaboratoryofEnvironmentalChemistryandEcotoxicology,ResearchCenterfor
Eco-EnvironmentalSciences,ChineseAcademyofSciences,Beijing100085,China;[email protected]
* Correspondence:[email protected](X.Z.);[email protected](Y.W.);Tel.:[phone](X.Z.)
† J.Z.andX.Z.areco-firstauthors.
Received:30June2017;Accepted:18August2017;Published:23August2017
Abstract: Asystematicstudyforthepreparationandstructuralanalysisofpoly(styrene-co-acrylic
acid) composite nanospheres (PSA) and silver nanoparticles loaded poly(styrene-co-acrylic acid)
composite nanospheres (nAg@PSA) is reported. Poly(styrene-co-acrylic acid) nanospheres were
synthesized by soap-free emulsion polymerization of styrene (St) and acrylic acid (AA) in water.
Ag nanoparticles (Ag-NPs) were well-dispersed on the surfaces of poly(styrene-co-acrylic acid)
compositenanospheresbyinsituchemicalreductionofAgNO usingNaBH asareducingagent
3 4
in water. The particle size of PSA nanospheres was uniform. The surfaces of PSA nanospheres
weredistributedbyhighlyuniformhalf-spherearrays. Thosehalf-sphereprotrudedmorewiththe
increaseofthefeedingamountofAAorthefeedratiosofAAandSt. Thecarboxylgroupscontentof
nanosphereswasdirectlyproportionaltothenanospheresurfacearea. ThisrelationshipandX-ray
photoelectronspectroscopyandtransmissionelectronmicroscopyimagesofthePSAnanospheres
indicatethattheacrylicacidwasmainlydistributedonthesurfaceofthepolystyrenesphereswith
unnegligiblethickness. ThenumberofAg-NPsdependsonimmobilizedcarboxylgroupsonthe
surfaceofPSA,accordingtothermogravimetry,ultraviolet-visible,X-raydiffractionandtransmission
electronmicroscopyresults.
Keywords: core-shellstructure;compositenanospheres;polymers;synthesis;structuralanalysis
1. Introduction
Compositemicrospheresconsistingofdielectricpolymercoreandmetallicshellshavebecome
asubjectofintenseinterestinvariousfieldsduringpastdecades. Theinterestinthesemicrospheres
stems from their unique catalytic and optical properties, which are different from their bulk
counterparts and hence, lead to widespread applications in catalysis, photonics, and so on [1–15].
Core-shellcompositemicrospherescaneffectivelypreventmetalnanoparticlesfromaccumulationand
improvecatalyticstabilization[7].Byvariationoftheshellthicknessandthecoreradiusitispossibleto
adjusttheplasmonresonanceofthemetallicshellparticlesoverthewholevisibleandinfraredregion
ofthespectrum[5].Becauseoftheirmonodispersityandtunableopticalproperties,thesemicrospheres
may be used as building blocks for various applications such as for metallodielectric photonic
crystals. A great deal of effort has been focused on preparing core-shell composite nanospheres
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Nanomaterials2017,7,234 2of14
withnoblemetallicshells,becausetheyexhibitnovelopticalandcatalyticpropertiesand,inparticular,
surfaceenhancedRamanspectroscopy[16–18]. Jiangetal.[7]preparedSiO /Agcore-shellparticles
2
and investigated the catalytic properties of silver nanoparticles supported on silica spheres in a
colloidalsolution. Itwasexperimentallydemonstratedthatmetalnanoparticleshavehighcatalytic
activities. Huetal.[19]synthesizedAg-coatedFe O @SiO three-plycompositemicrosphereswith
3 4 2
surface-enhancedRamanscattering(SERS)properties. TheAg-coatedFe O @SiO microsphereswere
3 4 2
appliedtodetectingmelamine,andstrongSERSsignalswereobtainedwithmelamineconcentration
of1×10−6M.
Various synthesis methods have been developed, such as self-assembly [20], seeding plating
method[16],insitureductiondepositionmethod[21],andsoon. Cassagnneauetal.[20]proposed
thelayer-by-layer(LbL)self-assemblymethodtoformpoly(styrene)core/silvernanoparticlesshell
compositematerials. Zhangetal.[16]exploredtheseedingplatingapproach,basedonelectrostatic
attraction,toprepareacompletesilvershellwithcontrolledthicknessonsilicacolloids. Complete
andcontinuousmetallicshellscanbeformedbyrepeatingthereductionandgrowthprocess. Inthe
self-assemblyandseedingplatingmethods,theyhavemanycharacteristics: manypreparationsteps,
long time, complexity of operation and so on. Hence, it is difficult to control the repeatability of
theexperiment. Recently, aninsitureductiondepositionmethodhasbeenreported. Becausethis
methodforpreparingdielectriccore/metallicshellcompositematerialsissimple,reproducibleand
well-controlled,ithasattractedmuchattentionandiswidelyusedinthepreparationofcore-shell
structurecompositemicrospheres.
Herein,wereportthesystematicstudyofpoly(styrene-co-acrylicacid)compositenanospheres
(PSA)andthedepositionofuniformAg-NPsshellsonpoly(styrene-co-acrylicacid)nanospheresby
insitureductionofAgNO usingNaBH asareducingagentinwater. Thekeyfactorsonstructure
3 4
andmorphologyofPSAnanospheresandsilvernanoparticlesloadedpoly(styrene-co-acrylicacid)
compositenanospheres(nAg@PSA)compositenanosphereswerestudied. Specifically,therelationship
betweentheamountofcarboxylpernanosphereandsurfacegeometryofnanosphereswasrevealed
by titration combined with scanning electron microscopy (SEM) images. The surface geometry
of PSA nanospheres was related to the amount of carboxyl groups per nanosphere. The titration,
X-rayphotoelectronspectroscopy(XPS)andtransmissionelectronmicroscopy(TEM)resultsindicate
that the carboxyl groups were mainly distributed on the surface of poly(styrene-co-acrylic acid)
compositenanospherescomprisingstyrenecorecoveredwithacrylicacidshell. Agnanoparticleswere
immobilized onto the PSA nanospheres with linear relationship with carboxy amount. This work
mayrisewideinterestonstructureandcompositioncontrollablepreparationofcore-shellstructure
microsphereforapplicationincatalysis,antibacterial,substratematerialsforsurfaceenhancedRaman
spectroscopy,andsoon.
2. ExperimentalSection
2.1. Materials
Styrene (St) was supplied by Tokyo Chemical Industry Co., Ltd (Tokyo, Japan). Acrylic acid
(AA),potassiumpersulfate(KPS),sodiumborohydride(NaBH ),silvernitrate(AgNO )andsodium
4 3
hydroxidewerepurchasedfromTianjinChemicalReagentCo.,Ltd(Tianjin,China). Allchemicals
wereofanalyticalgrade,andwereusedasreceived. Distilledwaterwasusedinalltheexperiments.
Allglasswareusedintheexperimentswascleanedwithdistilledwaterbeforeuse.
2.2. SynthesisofPoly(styrene-co-acrylicacid)(PSA)CompositeNanospheres
Poly(styrene-co-acrylicacid)(PSA)compositenanosphereswerepreparedbysoap-freeemulsion
polymerizationofstyrene(St)andacrylicacid(AA)inwateraccordingtothemethodasdescribedin
theliterature[22–24]. Briefly,acertainamountofAAand130mLofH Owereinitiallychargedintoa
2
doublewalledcontainer,whichallowedethyleneglycol/watermixturetobecirculatedtokeepthe
Nanomaterials2017,7,234 3of14
Ntaenmompaeterraiatlus 2re01c7o, 7n, s2t3a4n t. AfterthefeedingAAwasfullydissolved,theamountofstyrenewasa3d odf e1d4 .
Thesolutionwaspurgedwithnitrogentoremoveoxygenfor30minandthenheatedto75◦Cunder
mixture to initiate the polymerization, and reaction was maintained at 75 °C for 12 h. The stirrer
stirring. AsolutionofKPSdissolvedin20mLofH Owasinjectedintothereactionmixturetoinitiate
2
stpheeepdo, ldyomseargiez aotfi osnty,raennde,r eaaccrtyiolinc awcaids manadin ptaoitnaesdsiautm75 p◦eCrsfuolrfa1t2e hw.eTrhee sshtoirwrenr sinp eTeadb,lde o1s.a Ages opfresptyarreende ,
PSA nanospheres were dispersed in water. The aqueous dispersion contained impurities caused by
acrylicacidandpotassiumpersulfatewereshowninTable1. AspreparedPSAnanosphereswere
incomplete reaction before purification. Impurity of ions in the suspensions might enhance
dispersedinwater. Theaqueousdispersioncontainedimpuritiescausedbyincompletereactionbefore
conduction unexpectedly by promoting dissociation of –COOH of PSA nanospheres. Conductance
purification.Impurityofionsinthesuspensionsmightenhanceconductionunexpectedlybypromoting
of a supernatant of the suspension is a measure of impurity of ion. The PSA suspension was
dissociationof–COOHofPSAnanospheres. Conductanceofasupernatantofthesuspensionisa
cmenetarsifuurgeeodf ifmorp u4r0i tmyoinf iaotn .thTeh eraPtSeA ofs u1s2p,0e0n0s ior·nmwina−s1 caenndtr itfhueg epdrefcoirp4it0amtei nwaatst hdeisrpateersoefd1 2i,n0 0300r ·mmLin o−f1
distilled water. By determining the variation of the conductivity of the supernatant with the number
and the precipitate was dispersed in 30 mL of distilled water. By determining the variation of
of iterations of the dispersion-centrifugation processes, the purity of final PSA aqueous dispersion
theconductivityofthesupernatantwiththenumberofiterationsofthedispersion-centrifugation
can be confirmed, as was shown in Figure 1. Values of conductivity of the PSA suspension decreased
processes,thepurityoffinalPSAaqueousdispersioncanbeconfirmed,aswasshowninFigure1.
with an increase of the iterative steps of centrifugation-redispersion, and tended towards stability at
Values of conductivity of the PSA suspension decreased with an increase of the iterative steps of
the seventh. Consequently, ionic impurities were removed basically, so that the dissociation of
centrifugation-redispersion,andtendedtowardsstabilityattheseventh.Consequently,ionicimpurities
–COOH of PSA maintains stable.
wereremovedbasically,sothatthedissociationof–COOHofPSAmaintainsstable.
Table 1. Recipes of poly(styrene-co-acrylic acid) (PSA) composite nanospheres.
Table1.Recipesofpoly(styrene-co-acrylicacid)(PSA)compositenanospheres.
Sample Code AA/g St/g KPS/g Stirrer Speed/r·min−1
SampPlSeAC0o de AA0/.1g S2t /g 0K.0P4S /g StirrerS4p0e0e d/r·min−1
PPSSAA01 0.01.6 62 0.102.0 4 30400 0
PPSSAA12 0.16.2 66 0.102.1 2 30300 0
PPSSAA23 1.12.5 66 0.102.1 2 30300 0
PPSSAA34 1.15.8 66 0.102.1 2 30300 0
PSA4 1.8 6 0.12 300
PSA5 2.1 6 0.12 300
PSA5 2.1 6 0.12 300
PSA6 0.3 6 0.24 300
PSA6 0.3 6 0.24 300
PSA7 0.3 6 0.36 300
PSA7 0.3 6 0.36 300
PSA8 0.3 6 0.48 300
PSA8 0.3 6 0.48 300
PPSSAA99 0.06.6 1122 0.204.2 4 30300 0
PPSSAA1100 0.09.9 1188 0.204.2 4 30300 0
PPSSAA1111 1.12.2 2244 0.204.2 4 30300 0
PPSSAA1122 0.03.3 66 0.204.2 4 20200 0
PPSSAA1133 0.03.3 66 0.204.2 4 50500 0

FFiigguurree 11.. DDeeppeennddeennceceo focfo ncdouncdtiuvcittyivoitfyt hoefP SthAes uPpSeArn astuapnetronnatthaentn uomn btehreo fnduismpebresri ono–f cednistrpifeurgsiaotnio–n
cpernotcriefsusgeas,tiaonca pseroocfePssSeAs,0 a. case of PSA0.
2.3. Preparation of nAg@PSA Composite Nanospheres
2.3. PreparationofnAg@PSACompositeNanospheres
A typical procedure for fabricating nAg@PSA nanocomposites is described as follows: 200 mL
AtypicalprocedureforfabricatingnAg@PSAnanocompositesisdescribedasfollows: 200mL
ooff aaqquueeoouuss PPSSAA ddiissppeerrssiioonn ((00..33 mmgg··mmLL−−1)1 w)wasa smmixiexded wwitihth 101 0mmLL oof f1100 mmMM AAggNNOO3 inin tthhee jjaacckkeetteedd
3
glass container. The mixture dispersion was stirred for 5 h with a magnetic bar at room temperature
glasscontainer. Themixturedispersionwasstirredfor5hwithamagneticbaratroomtemperatureto
to allow the ion exchanges on the surfaces of the nanospheres to reach equilibrium. After that, 10 mL
of 10 mM NaBH4 solution was added into the dispersion and the resulting mixture was allowed to
react at 0 °C for 2 h while stirring. The suspension was centrifuged for 20 min at the rate of 12,000
Nanomaterials2017,7,234 4of14
allowtheionexchangesonthesurfacesofthenanospherestoreachequilibrium. Afterthat,10mLof
10mMNaBH solutionwasaddedintothedispersionandtheresultingmixturewasallowedtoreact
4
at0◦Cfor2hwhilestirring. Thesuspensionwascentrifugedfor20minattherateof12,000r·min−1
andtheprecipitatewasdispersedin30mLofdistilledwater. Thiscentrifugation-redispersioncycle
wasrepeatedfourtimesinordertoremovetheun-reactingspecies.
2.4. CharacterizationofPSANanospheresandnAg@PSANanocomposites
ThemorphologiesandparticlesizesofPSAnanosphereswerecharacterizedviascanningelectron
microscopy(SEM;HitachiS4800,HitachiLtd.,Tokyo,Japan). Theappearanceofthenanosphereswere
observedbyscanningelectronmicroscopy. ThemeansizeofPSAwascalculatedbythesoftwareof
nanomeasurer.
The nAg@PSA composite materials were investigated by transmission electron microscopy
(TEM;JEOLJEM-2010,JEOLLtd.,Tokyo,Japan)todemonstratethenanoparticlefeatures,andthe
locationofthesilverparticlesonthelatexsurface.
TheamountofcarboxylgroupsonthePSAlatexparticlewasdeterminedbytitrationwithNaOH
standard volumetric solution under monitoring of the conductivity of the suspension. From the
turningpointofthetitrationcurve,wedeterminedthenumberofthecarboxylmoietyperparticle[25].
QuantitativedeterminationofthemainelementsonthePSAnanospheresurfacewasachievedby
X-rayphotoelectronspectroscopy(XPS;ThermoFisherScientificK-Alpha,ThermoFisherScientific,
Waltham,MA,USA).ChemicalbondinginformationwasobtainedfromthePSAnanospheresurface
byXPSanalysis.
The crystalline structures of silver particles supported on the PSA nanosphere surface
were characterized by X-ray diffraction (XRD; PANalytical X’pert Pro, PANalytical Co., Almelo,
TheNetherlands)andtheXRDdatawascollectedina2θrangeof30–80◦ atascanrateof4◦/min.
Ultraviolet-visible (UV-vis; Shimadzu UV-2550, Shimadzu, Kyoto, Japan) spectroscopy was
employedforqualitativecharacterizationoftheopticalpropertiesofsilvernanoparticlessupportedon
poly(styrene-co-acrylicacid)compositenanospheres. UV-visabsorptionspectrumwasobtainedinthe
rangefrom300to900nm. Thedistilledwaterwasusedasablanksolution.
Thecontentofsilvernanoparticlecoatingsonpoly(styrene-co-acrylicacid)compositenanospheres
wasanalyzedbythermogravimetricanalysis(TG;PerkinElmerPyris1,Perkin-ElmerCo.,Norwalk,CT,
USA).TGwascarriedoutataheatingrateof10◦C·min−1. ThermalbehaviorofnAg@PSAcomposite
nanospheresprovidesquantitativeresultsaboutAgnanoparticlescoveredoncompositenanospheres.
3. ResultsandDiscussion
3.1. EffectofDifferentFactorsontheParticleSizeandMorphologyofPSANanospheres
3.1.1. AmountofAcrylicAcid
Figure2showsSEMmicrographsofPSAnanospherespreparedwithdifferentamountofAA
underacertainamountofSt(6g)andinitiator(0.12g)withstirringatthespeedof300r·min−1. A–E
correspondtoPSA1–PSA5. TheparticlesizedistributionscouldbeobservedinFigure2. Theparticles
whichweresynthesizedbysoap-freeemulsionpolymerizationhaveuniformlydistributedgranular
diameters. The mean sizes of PSA were 220.48 ± 8.61 nm, 258.83 ± 9.48 nm, 220.46 ± 7.56 nm,
239.80±9.11nm,238.36±9.93nm,respectively. ThesizeofPSAnanosphereshadsignificantchanges
withanincreaseoftheAAamount(p=5.19×10−26<0.05). TheseSEMmicrographsalsoindicated
thatthesenanosphereshadinterestingsurfacegeometry. Thereweremanyhalf-spheres,whichwere
uniformlydistributedonthesurfaceofthePSAnanospheres. Thosehalf-spheresprotrudedmore
with increase of feeding amount of AA or the feed ratios of AA and St. The half-spheres became
almostsphericalwhenthemassofAAincreasedto2.1g. Thisisreasonable,sincepolyacrylicacidis
morehydrophilicthanpolystyrene,morepolyacrylicacidwillaccumulateandbulgeintoaqueous
Nanomaterials2017,7,234 5of14
bulksolutionwithanincreaseoftheamountofacrylicacid. XPSwasconductedtofurtherverifythe
elementalcompositionandchemicalstatusofPSAnanospheres. TheresultwasshowninFigure3. The
Nanomaterials 2017, 7, 234 5 of 14
spectrumindicatedtheexistenceofcarbonandoxygen(hydrogencannotbedetectedbyXPS).TheC1s
sCp1esc tsrpuemctriunmth eini ntsheet ionfsFeitg oufr eFi3gruervee 3a lreedvtehaaletdit tchoants iist tcsoonfstiwstos pofe atwksoa priesainkgs farroimsinCg– fCro/mC– CH–gCr/oCu–pHs
agnroduOps– Can=dO Og–roCu=pOs .gTrohuepOs.1 Tshspe eOct1rsu smpeicntrtuhmei nins etthoe finFsigetu oref F3icgaunreb e3 ficatnto btew fiot ptoe atwkso, wpehaikchs, cwahnibche
acattnr ibbuet eadttrtoibCut–eOd/ tCo= CO–gOr/oCu=pOs agnrdouOp–sC a=nOd gOro–uCp=sO,r egsrpoeucptisv, erlye.spTehcetsiveedlya.t aTphreosvee ddathtae pprroesveendc ethoef
cparrebsoexnycel gorfo cuaprsboonxythl egrsouurfpasc eoonf tPhSeA sunrafnaoces pohf ePreSsA. Tnhainsoinspdhicearteess. tThhatisp ionldyaiccartyelsic tahcaitd pwoalysadcirsytrliicb uatceidd
ownasth deissturribfaucteedo foPnS tAhen saunrofsapceh eorfe Ps.SA nanospheres.

Figure 2. SEM micrographs of PSA nanospheres under preparation conditions of the acrylic acid (AA)
Figure2.SEMmicrographsofPSAnanospheresunderpreparationconditionsoftheacrylicacid(AA)
amount (A) 0.6 g, (B) 1.2 g, (C) 1.5 g, (D) 1.8 g, (E) 2.1 g. Other conditions: St, 6 g; potassium persulfate
amount(A)0.6g,(B)1.2g,(C)1.5g,(D)1.8g,(E)2.1g.Otherconditions:St,6g;potassiumpersulfate
((KKPPSS)),, 00..1122 gg;; ssttiirrrreerr ssppeeeedd,, 330000 rr··mmiinn−−11. .EEfffefecctsts oof fAAAA ccoonntteenntt oonn tthhee pprroottrruuddeedd ddeeggrreeee ooff tthhee PPSSAA
nanospheres (F).
nanospheres(F).
Nanomaterials2017,7,234 6of14
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Nanomaterials 2017, 7, 234 6 of 14

Figure 3. XPS spectrum of PSA0 nanospheres.
FFiigguurree 33.. XXPPSS ssppeeccttrruumm ooff PPSSAA00 nnaannoosspphheerreess..
3.1.2. Amount of Initiator
33..11..22.. AAmmoouunntt ooff IInniittiiaattoorr
The micrographs of PSA nanospheres prepared with different initiator amount under a certain
TThhee mmiiccrrooggrraapphhss ooff PPSSAA nnaannoosspphheerreess pprreeppaarreedd wwiitthh ddiiffffeerreenntt iinniittiiaattoorr aammoouunntt uunnddeerr aa cceerrttaaiinn
aaammmooouuunnnttt ooofff SSSttt (((666 ggg))) aaannnddd AAAAAA ((0(00..33.3 ggg)) )wwwiittihhth ssttsiitrrirrriirnnigng g aatta ttthhteeh sesppseepeeedde dooffo 33f003000 rr0··mmr·iimnn−−i11n ww−e1errwee esshrheoowswhnno wiinnn FFiiignguuFrrieeg 4u4..r AeA–4–.
C correspond to PSA6–PSA8. Each PSA spheres uniformly dispersed with average diameters of
AC– cCorcroersrpeospnodn tdo toPSPAS6A–6P–SPAS8A. 8E.aEcahc hPSPASA spsphhereerse suunnifioformrmlyly ddisisppeersrseedd wwiitthh aavveerraaggee ddiiaammeetteerrss ooff
277.16 ± 6.90 nm, 271.45 ± 8.83 nm, 264.93 ± 9.08 nm, respectively. It can be seen that the dosage of the
227777..1166 ±± 66.9.900 nnmm, ,227711.4.455 ±± 8.883.8 n3mnm, 2,6246.943.9 ±3 9±.089 .n08mn, mre,spreescptievcetliyv.e Ilty .caItnc baen sbeeense tehnatt hthaet tdhoesdagoesa ogfe thoef
initiator has effect on the size of polymer microsphere (p = 0.0001 < 0.05) and has no significant effect
tihnietiiantiotira htoars hefafsecetf foenc tthoen stihzee soifz peoolfypmoelry mmeicrrmosipchroesrpe h(pe r=e 0(.p00=001. 0<0 00.015<) a0n.0d5 )haans dnoh asisgnnoifisciagnnti fiefcfaenctt
on the morphology.
eofnfe tchteo mnothrpehmoolorpgyh.o logy.

Figure 4. SEM micrographs of PSA nanospheres under preparation conditions of the initiator amount
Figure 4. SEM micrographs of PSA nanospheres under preparation conditions of the initiator amount
Figure4.SEMmicrographsofPSAnanospheresunderpreparationconditionsoftheinitiatoramount
(A) 0.24 g, (B) 0.36 g, (C) 0.48 g. Other conditions: AA, 0.3 g; St, 6 g; stirrer speed, 300 r·min−1. Effects
((AA)) 00..2244 gg,, ((BB)) 00..3366 gg,, ((CC)) 00.4.488g g.. OOtthheerrc coonnddititioionnss::A AAA,,0 0.3.3g g;;S St,t,6 6g g;;s tsitrirrerrers pspeeeded,3, 03000r ·rm·minin−−11.. EEffffeeccttss
of initiator content on the size of the PSA nanospheres (D).
of initiator content on the size of the PSA nanospheres (D).
ofinitiatorcontentonthesizeofthePSAnanospheres(D).
Nanomaterials2017,7,234 7of14
Nanomaterials 2017, 7, 234 7 of 14
33..11..33.. MMoonnoommeerr CCoonncceennttrraattiioonn
FFiigguurree 55 pprreesseennttss ththee tytyppiciacla SlESMEM phpohtootgorgarpahpsh osf othfet hPeSAPS sAphseprhese rseysnsthyenstihzeesdiz beyd 0b.2y4 0g. 2o4f KgPoSf
KatP tShea tsttihrreers tsiprreeerds opfe 3e0d0 orf·m3i0n0−1r w·mitihn −v1arwyiinthg avmaroyuinngt oafm moounnotmoefrm froonmo m12e.r6 fgr,o 1m8.91 2g. 6tog 2,51.28 .g9. gThtoe
2m5o.2ngo.mTehre rmatioon (osmtyerrenraet:iaocr(sytlyicr eanceid:a)c wryalisc 2a0c:i1d )byw wase2ig0h:1t.b Ay–wCe icgohrtr.eAsp–oCndco trore PsSpAon9d–PtoSAP1S1A. 9I–t PcaSnA 1b1e.
Isteceann thbeats etheen tPhSaAt tshpehPeSreAs saprhe earells saprheearlilcsapl hiner sichaalpine sahnadp aelamnodsta lmmoonsotdmisopneordseisdp ewrsitehd mweitahn msiezaens
sraiznegsinragn fgroinmg 2fr9o3m.632 ±9 39..6137 ±nm9,. 13732n.m10, ±3 382.0.150 n±m 8t.o0 537n5m.54t o± 397.752.5 n4m± w9i.t7h2 tnhme inwcirtehasthe eofi nmcroenaosme oerf
mcoonncoemnterartcioonnc. eInntdraivtiiodnu.aIlnlyd isvtiadbulael lpyasrttaicblleesp waretircel eosbwtaeirneeodb taati naeldl caotnacllecnotrnacteionntrsa toiof nmsoofnmomonero.m Aesr.
Amsomnoomnoerm ceornccoenncternattiroanti oinncirnecarseeads,e dth,eth reearecaticotnio nrartae tewwasa sspsepeedededed uupp, ,aanndd tthheenn tthhee llaarrggeerr ppaarrttiicclleess
wweerree oobbttaaiinneeddi nint hthees asammeet itmime.eT. hTehes usrufrafcaecme moroprhpohloogloygoyf oPfS PASnAa nnoasnpohseprheesrdesid dnido tncohta cnhgaenwgeit hwtihthe
vthaer ivatairoinatoiofnth oef mthoen momoneormcoenr cceonntcreantitorna.tion.

Figure 5. SEM micrographs of PSA nanospheres under preparation conditions of the total monomer
Figure5.SEMmicrographsofPSAnanospheresunderpreparationconditionsofthetotalmonomer
aammoouunntt ((AA)) 1122.6.6 gg, ,(B(B) )181.89. 9g,g (,C()C 2)5.225 g.2. Og.thOerth ceorndcoitniodnitsi:o KnPs:S,K 0P.2S4, g0;. 2s4tirgr;esr tsiprreeerds, p3e0e0d r,·m30in0−1r.· mEfifnec−t1s.
of the total monomer amount on the size of the PSA nanospheres (D).
EffectsofthetotalmonomeramountonthesizeofthePSAnanospheres(D).
3.1.4. Stirrer Speed
3.1.4. StirrerSpeed
In Figure 6, the PSA nanospheres prepared by 0.3 g of AA, 6 g of St, 0.24 g of KPS with varying
InFigure6,thePSAnanospherespreparedby0.3gofAA,6gofSt,0.24gofKPSwithvarying
tthhee ssttiirrrreerr ssppeeeedd ffrroomm 220000 r·rm·minin−1−, 310,03 0r·0mri·nm−1i nto− 510t0o r5·m00inr−·1m wine−re1 swhoewrens.h Ao,w Bn, C. A co,rBr,eCspcoonrdre tsop PoSnAd1t2o,
PSA6, PSA13. The average diameters of the polymer spheres rose from 268.69 ± 6.06 nm, 277.16 ± 6.90
PSA12, PSA6, PSA13. The average diameters of the polymer spheres rose from 268.69 ± 6.06 nm,
2n7m7 .1to6 ±3060..9309 n±m 7.t4o2 3n0m0.3 a9s± th7e. 4s2tinrrmera sspteheeds tiinrrcerreasspeede dfrionmcr e2a0s0e dr·mfroinm−1,2 03000r ·rm·mini−n1−1, 3to0 05r0·0m ri·nm−i1nt−o1,
respectively. With an increasing stirrer speed, the monomer is dispersed into monomer droplets, and
500r·min−1,respectively. Withanincreasingstirrerspeed,themonomerisdispersedintomonomer
the surface area of monomer droplets per unit volume solution is larger. Larger specific surface area
droplets,andthesurfaceareaofmonomerdropletsperunitvolumesolutionislarger. Largerspecific
causes more free radicals to adsorb onto the surface of monomer droplets and less effective free
surfaceareacausesmorefreeradicalstoadsorbontothesurfaceofmonomerdropletsandlesseffective
radicals for the formation of micelles. Therefore, this leads to a decrease in the number of polymer
freeradicalsfortheformationofmicelles. Therefore,thisleadstoadecreaseinthenumberofpolymer
particles formed, and the size of the particle becomes larger.
particlesformed,andthesizeoftheparticlebecomeslarger.
Nanomaterials2017,7,234 8of14
Nanomaterials 2017, 7, 234 8 of 14
Nanomaterials 2017, 7, 234 8 of 14

Figure 6. SEM micrographs of PSA nanospheres under preparation conditions of the stirrer speed (A)
Figure6. SEMmicrographsofPSAnanospheresunderpreparationconditionsofthestirrerspeed
200 r·min−1, (B) 300 r·min−1, (C) 500 r·min−1. Other conditions: AA, 0.3 g; St, 6 g; KPS, 0.24 g. Effects of
(A)200r·min−1,(B)300r·min−1,(C)500r·min−1. Otherconditions: AA,0.3g;St,6g;KPS ,0.24g.
stirrer speed on the size of the PSA nanospheres (D).
EffectsFoifgsutrierr 6e.r SsEpMee mdicornogthraepshisz eofo PfStAh enaPnSoAspnhaenreoss upnhdeerer spr(Dep)a.ration conditions of the stirrer speed (A)
200 r·min−1, (B) 300 r·min−1, (C) 500 r·min−1. Other conditions: AA, 0.3 g; St, 6 g; KPS, 0.24 g. Effects of
3.2. Amount of Carboxyl in PSA Nanospheres
stirrer speed on the size of the PSA nanospheres (D).
3.2. AmountofCarboxylinPSANanospheres
The density of PSA suspension was determined by drying and weighing a sample volume of
PTSh3Ae.2 s.du Aesmpnesoniutsnyito oonf.f CTPahrSebA osxizyselu sis nop fPe tSnhAse i Nsoanamnowpslpaehsse wrdeese rtee remxaimneindedb ybyd SrEyMin agndan thdenw tehieg hmiincgrosaphsaerme pvloeluvmoel ume
of PSaAnd ssuusrpfaecne sairoena .wTerhee casliczuelsatoedf tvhiae tshaem paprlteicslew seizree. Texhae mvoinluemdeb wyasS EcoMnvaenrtdedt ihneton tthhee wmeiigchrto bspy here
The density of PSA suspension was determined by drying and weighing a sample volume of
use of the density of polystyrene (1.05 g·cm−3) on the assumption that the density of the poly(styrene-
volumePSaAn dsussuprefnascioena. rTehaew siezrees ocfa ltchue lsaatmedplvesia wtehree epxaarmtiicnleeds ibzye .SETMh eanvdo ltuhmene thwe amsiccroonsvpehretreed voinlutometh e
weigcho-taabncyrdy usliucsr eafacoicfde)t a hwreeaads wethneesr eist aycmaolcefu aplsao ttelhydas tvt yoiafr etphnoeel yp(s1atry.0tri5eclngee ·s.c iTmzhe.−e Tn3 h)teho env ontluhumembaees wrs uoamfs tcphoetni nvoaenrnttoehsdap tihntethroee tsh doeef wnas esiittgoyhcotk bfyth e
suspension was calculated.
poly(stuyrsee noef -tchoe- adcernysliitcya ocfi dpo)lwysatsyrtehnees (a1m.05e ga·scmth−a3)t oonf tphoel ayssstuymrepnteio.nT htheant tthhee dneunmsitbye orfo tfhteh peonlya(nstoysrpehnee-res
Amount of carboxyl groups on the particle was determined by titration with NaOH under
ofastoccok-ascuryslpice nacsiido)n wwasa sthcea lscaumlaet aesd t.hat of polystyrene. Then the number of the nanospheres of a stock
monitoring of the conductivity. The conductivity decreased initially with addition of NaOH because
Amsuospuenntsioofn cwaarbs ocaxlycullgatreodu. ps on the particle was determined by titration with NaOH under
the molar conductivity of sodium ion is smaller than that of hydrogen ion. Further addition of NaOH
Amount of carboxyl groups on the particle was determined by titration with NaOH under
monoitvoerri nthge oefquthiveacleonntd puocintitv iintcyr.eTasheedc tohne dcouncdtiuvcittiyvidtye,c breecaasuesde ionfi etixatrllay awmiotuhnatsd odfi tNioan+ aonfdN OaHO−.H Frboemc ause
monitoring of the conductivity. The conductivity decreased initially with addition of NaOH because
themthoel aturrcnoinngd upcotiinvti otyf tohfes toitdraiutimon icounrvise,s wmea dlleetrertmhainnetdh aamtoofuhnyt dofr ocagrebnoxioynl o.fF tuhret hsuesrpaedndsiiotino, naso wfNasa OH
the molar conductivity of sodium ion is smaller than that of hydrogen ion. Further addition of NaOH
overshthoewenq iun iFviagluernet 7p. oTihnet niunmcrbeears eodf ththe ecacrobnodxyulc ptievri tpya,rtbicelcea wusaes coaflceuxltartaeda bmyo tuhen tcsarobfoxNyal +amanoudnOt H−.
over the equivalent point increased the conductivity, because of extra amounts of Na+ and OH−. From
Fromoft hthee tsuursnpienngsipono ianntdo tfhteh neutmitrbaetri oofn thcue rnvaen,owspehdereetse. rminedamountofcarboxylofthesuspension,
the turning point of the titration curve, we determined amount of carboxyl of the suspension, as was
aswasshowninFigure7. Thenumberofthecarboxylperparticlewascalculatedbythecarboxyl
shown in Figure 7. The number of the carboxyl per particle was calculated by the carboxyl amount
amounotfo tfhteh seusspuesnpseinonsi aonnda tnhde nthuemnbuerm obf ethreo nfathnoesnpahneoressp. heres.

Figure 7. Conductometric titration curves of the PSA suspension, a case of PSA4.

FigureFi7g.uCreo n7.d Cuocntodmucettormicettirtirca ttiitoranticounr cvuersveosf othf ethPe SPASAs ususpspeennssiioonn,, aa ccaassee ooff PPSSAA44. .
NNaannoommaatteerriaialsls2 2001177,,7 7,,2 23344 99o off1 144
Nanomaterials 2017, 7, 234 9 of 14
From the linear fit in Figures 8 and 9, not only the nanosphere surface area but also the volume
From the linear fit in Figures 8 and 9, not only the nanosphere surface area but also the volume
had Fa rloinmeatrh reellianteioanrsfihtipin wFiitghu trhees n8uamndbe9r, onfo –tCoOnlOyHth peenra pnaorstpichlee.r Tehseu rcfoarcreelaarteioanb cuoteaflfsiociethnet bveotlwumeeen
had a linear relationship with the number of –COOH per particle. The correlation coefficient between
hthade anulimnebaerrr oelfa –tiCoOnsOhHip pweirth ptahretincluem abnedr tohfe– vCoOluOmHe pwerasp a0r.9ti0c7le7., Tahned ctohrarte lbaetitowneceone tfhfiec iennutmbbetewr eoef n–
the number of –COOH per particle and the volume was 0.9077, and that between the number of –
tCheOOnuHm pbeerr poafrt–icCleO aOnHd tpheer npaanrotsicplheearne dsutrhfaecveo alruema weawsa 0s.907.1940.7 C7,omanpdartehda twbiethtw theee nlintheaern cuormrebleartioonf
COOH per particle and the nanosphere surface area was 0.9714. Compared with the linear correlation
–bCeOtwOeHenp etrhep anrutimclebaern doft h–eCnOanOoHsp pheerre psaurrtfiacclee aarneda wthaes v0.o9l7u1m4.eC, othmep lairneedarw citohrrtehleatliionnea brectowrreeelant itohne
between the number of –COOH per particle and the volume, the linear correlation between the
bneutwmebeenr tohfe –nCuOmObeHr opfe–rC pOaOrtHiclpe earnpda rtthicel enaanndosthpehevroel usmuref,atchee alirneeaa rwcaosr rsetlraotniognerb.e Ftwigeuerne th10e nshuomwbeedr
number of –COOH per particle and the nanosphere surface area was stronger. Figure 10 showed
olofg–aCrOitOhmHicp verarpiaartitoicnle oaf nthdet hneumnabneor sopfh tehree lsouardfeadce caarrebaoxwya mssotireotnyg peer.r Fpiagrutircele1 0agshaionwste tdhelo dgiaarmithetmerisc.
logarithmic variation of the number of the loaded carboxy moiety per particle against the diameters.
vTahriea tpiolont ohfatdh ean luinmebaer rroeflatthioenlo waditehd tchaer bsoloxypem oofi e2t.y2,p ienrdpicaarttiicnlge athgaaitn tshtet hceardbiaomxye twerosu.lTdh ebep lmotahinaldy
The plot had a linear relation with the slope of 2.2, indicating that the carboxy would be mainly
adliisntreiabrurteelda tiino nthwe istphhtehreicsalol spuerofafc2e..2 P,iSnAd incaantionsgpthheartetsh sehcoawrbeodx dyewfinoiuteld bboeunmdaairnileys dbiesttwriebeunte tdhein cothree-
distributed in the spherical surface. PSA nanospheres showed definite boundaries between the core-
ssphheellr isctarluscuturfraec ae.nPdS tAhen tahniocksp shheerlel,s assh oinwdeicdadteedfi ninit eFibgouurne d1a1r ibeys btheetw yeeellnowth earcroorwe-ss hinel lpsatrrtu Act uarneda nthde
shell structure and the thick shell, as indicated in Figure 11 by the yellow arrows in part A and the
tdhaesthheicdk lisnhee laln,ads yineldloicwat aedrroinwF iing upraert1 1B.b Fyrothme yFeiglluorwe 3a,r rthowe psrienspenarcteA ofa cnadrbtohxeydla gsrhoeudplsi noena tnhde syuerllfoawce
dashed line and yellow arrow in part B. From Figure 3, the presence of carboxyl groups on the surface
aorfr oPwSAin npaanrtoBsp.Fhreormes Fwigausr epr3o,vtheedp. rSeos,e nPcSeAo fisc atrhbeo xsytylrgernoeu pcsoroen/atchreysliucr faacciedo sfhPeSlAl nnaannoosspphheerreess, wanasd
of PSA nanospheres was proved. So, PSA is the styrene core/acrylic acid shell nanospheres, and
pcraorvbeodx.ySl og,rPoSuApsi sarthe edsitsytrriebnuetecodr ue/naifcorrymliclya coind tshhee lllanteaxn osusprfhaecree.s ,andcarboxylgroupsaredistributed
carboxyl groups are distributed uniformly on the latex surface.
uniformlyonthelatexsurface.

Figure 8. Variation of n (the number of the carboxyl moiety per PSA nanosphere) with V (the PSA
FFigiguurere8 .8.V Vaariraiatitoionno offn n( t(htheen nuummbbeerro offt htheec acrabrbooxxyyllm mooieiteytyp pererP PSSAAn nananoospsphheerer)e)w witihthV V( t(htheeP PSSAA
nanosphere volume).
nnaannoospsphheererev voolulumme)e.).

Figure9. Variationofn(thenumberofthecarboxylmoietyperPSAnanosphere)withA(thePSA
Figure 9. Variation of n (the number of the carboxyl moiety per PSA nanosphere) with A (the PSA
nFaingousrpeh 9e.r eVsaurriafaticoena orefa n). (the number of the carboxyl moiety per PSA nanosphere) with A (the PSA
nanosphere surface area).
nanosphere surface area).
Nanomaterials2017,7,234 10of14
Nanomaterials 2017, 7, 234 10 of 14
Nanomaterials 2017, 7, 234 10 of 14
Nanomaterials 2017, 7, 234 10 of 14

Figure1F0ig.uLreo g10a.r Litohgmariitchpmlioc tpslootfs nof( nth (ethne unmumbbeerr ooff tthhee ccaarbrboxoyxly mlomieotyie ptyer pPeSrAP nSaAnosnpahneores)p ahgeairnes)t against
Figure 10. Logarithmic plots of n (the number of the carboxyl moiety per P SA nanosphere) against
diametedrisamofetPeSrsA ofn PaSnAo nspanhoesrpehse,r2ers, 2.r0.
dFiiagmureet e1r0s. oLfo PgSaAri tnhamniocs pphloetrse os,f 20nr 0(. the number of the carboxyl moiety per PSA nanosphere) against
diameters of PSA nanospheres, 2r0.

Figure 11. TEM images of the PSA0 nanospheres with different scale bars (A) 100 nm, (B) 50 nm.

F3i.g3u. FEriefgfeu1cr1te .o 1Tf 1tEh. MTe EAiMmm oiaumgnaetgs oeofs Cf otafhr tbehoePx yPSlAS oA0n0 nt hnaean nDooesspppohhsieetrrioeenss wowfi iAtthhg d dNifiaffenfreoerpneatnr tsticcsalcelaes lbeabrsa r(As)( A10)01 n0m0n, (mB), 5(B0 )n5m0. nm.
Figure 11. TEM images of the PSA0 nanospheres with different scale bars (A) 100 nm, (B) 50 nm.
3.3. EffecBt aosfe tdh eo nA mthoeu mnte tohf oCda rinb otxhyel Eoxnp tehrei mDeenptoasli tsieocnt ioofn A, ag sNeraineosp oafr tniAclges@ PSA composite nanospheres
3.3. Effewcteoref tphreepAamreodu unstinofg Cvaarrbioouxsy PlSoAn tnhaenDosepphoesrietsio wnhoifleA kgeeNpainngo paallr toitchleesr parameters unvaried, and
3.3.t EhBeffaiersc etT doE fMo tnh e itm hAaemg moeuse ntahtr oeo fd sC hianorw bthonxe y iEnl xoFpnieg truhireme D e1en2pt.oa Nsl istoie ocinst oioolfan At,e gad NsAeargni eonspa aonrfot inpcaAlersgt i@clPesS Ath acto mhapvoes iftaell nena nooffs pthhee res
wBearspeeoB dplayrsmoeenpdear t orhnenead nt mhouesse pimtnhhgeeor thevdsao irdanir oietnu h sote bhPsEeSe xrEAvpx ependrea irnimniom seietpn,n htwtaearlhle isscseeh cwc ttciihlooeinalner,, layka essseeheproriiewinesg sot haof alfnlt AnothAtghe@g ePar@l SlpP AtaSh rcAeao mAmceogpt meoNrspsPi toseu s nanirvtaeean rfnoiiresampdnh,lo yeas rnpedsh eres
weretwhpeerriearenp TcpahErroeeMrpdea duirm eosdnian gtughesesvi pnaaogrrl eiyvo msauhresioroP wsupSsnhA ePirnSne AasF.n iFngorauosnpmreoh sFe1pirg2he.u esrNrewe o1sh 2 wiDislo,eh wliakleetee cekdape neAi ngpgagi ninnag alm lnaoololrtp ehoa ietnrhrtseiipcgrl aheprst aa intrmhatomae ttt ehehterea smrvsuei cnu rfnvoasvaltlareriurneic edtodu,f,rfa e an tnhdde their
TEMpthiomeliyoramf gTAeeEgrsM nnaa arninemoopsashagproehtiswec lraenersse.i TnashrhFeeo ilgwoatbuntsir ceeiern vf1 re2Find.igg Nueinsro eoi fit1 s,t 2how.el a hNstiielcovhd ei rsAc onlelagaantrnoelpdyaa n sArothigpco lawenr wa ttniihctohlape tt ashtrehtth ielcaa ltaettilschl etat hhsvpaeeta cAfhianaglgv l eNeon fPf aaosbl floaefurnteth 0oef.fi2rfp3 m tohllyey mer
nanoapsnopclyhnhmmoerr eeecrdso rnoaranernse tpohoosebnp pdshoeeedlrryve mtseo de atrrh iesne p o(hi1bte,1sr1ewe)rs vh.p eFildacrnho iemnc o l Feift ia,gs riuwllvyrheeri s1c hch2roD ycws,l tewaatlehr, lcawyat hnsti hhcghoea wicnao lmtnlhftoiahrrtme et eihAndes g itaghNlhal ttP t iAhsnegta o Arw tehgafie sN rmsmuPiccslcr yeoasrsasetnfr uufclichlrytmou rrleyed on
the poaonf lcAydhgmeo pnreeoadrsni tooseppnda h.t rhBeteeirc seplisedo.sel.ys TF,m htrhoeeer ml saXptRtFhiDciege rp uefarsrit.en tFegrr1eon2s mDa ol sFf, oitwg hpueer roseciv la1ivd2neeDrd gn, eawavineniod cpemanancro etgri aceolifen it n whmseioi tgwhreh et hlitln-eids nlieagtftohitnitce tiedhn estAop gmath cciiercn ymrgso tioascfltrl roaizubsatcotrtiuuoutcnr t0.eu .2ro3ef Ag
nanonopfm aA Arcgtsoi cnrlsarehensoso.pwpTonanh rdteiinecl dlaeF tstit.goi Tcu ethrheef e rl 1ia(n3t1,tg 1ic1eseh)s afporriplfna tnghpeeees a ooskfifs l stvhiwelevre esrnirel avconerbryo ssnpetaraavnlr,eo tdiwpc alhaerittc iwch2l θiect hwoonifttf hhi3re m8th.l1aee°dt ,lt ai4tctht4eia.c3ste° p ,As ap6gca4 ic.wn4i°nga, gso a ofnsfud aac bbc7ooe7suu.s5ttf° u0,0 .l.2l2y33 nm
corresponding to diffractions from the (111), (200), (220), and (311) planes of face centered cubic (fcc)
corrednsmeppo pocnhsoadirtseereedd so.p tfB ooAentsghdi dee(JedC(s 1,Pt 1otDh1 S)eth pcXeal Rra(dnD1 1eN 1poo)a f.t pt0sel4iarl-nnv0e7 ea 8rol3scf)o ,r syrpieslrsvtopaevelr,ic dtcwiervyhdesl iyteca.vh lAi,d cbwoesnnhocfiirecprh tmoi ofc enotd hnsefpti herwcmatetrelaAld -do gtfeh wfPainStaA esAd sn gAua ncwgco aecssprs yshssfeuutracellclslye iazsdnasftdeui pollnoy.s ited.
Adesp oshsiotewdn. Biens idFeigsu, trhe e 1X3R, Dsh paartpt erpne aaklsso wpreorve idoebds eervviedde nacte o2fθ thoef w3e8l.l1-°d, ef4i4n.e3d°, A6g4 .c4r°y, satanldli za7t7i.o5n°,.
Besidesn,Athge@PXSRAD copmapttoesritne anlasnoospprhoevreisd earde eshvoidwenn icne Foigfutrhee 1w4. eTlhl-ed aebfisonrepdtioAng spcercytrsutamll iozf [email protected] shown
in FicAgousr rrneseahsnp1ooo3wsn,pndhs iehnirnaeg rs t pFsohi gdpouiwefrafserk aasc 1pt3iweo,a nekssr ha efatr r4oop0mb 7s pntehemraev k w(es1d h1i1wca)h,et r(c22eo0 θr0roeo)b,s fsp(e2o3r2n8v0d.e)1i,dn ◦a g,n a4tdto4 (t.23h3θ1e◦1 ,s)ou 6pfr4 lfaa.34cn8◦ee. ,1sp° alo,a nfs 4dmf4ao.c73en°7 ,ca. 5eb6n◦s4o,te.r4crp°oet,di ror ancenu s(dbSp Pioc7R n(7)f d.c5ci°n), g to
pcohrarosefes t phooef n nAdaginn og(sJ iCtlovP edDri Spff arcraatcirctdlieo sNn. so f.r o04m-0 t7h8e3 ()1, 1r1e)s,p (e2c0t0iv),e (l2y2. 0A),b asnodrp (t3i1o1n) psplaenctersa o of ff aPcSeA ce nnatenroesdp chuebreics (afcncd)
diffractionsfromthe(111),(200),(220),and(311)planesoffacecenteredcubic(fcc)phaseofAg(JCPDS
npAhags@eP oSfA A cgo m(JCpPosDitSe cnaarndo Nspoh. e0r4e-s0 a7r8e3 )s, hroewspne citniv Feilgyu. rAe b1s4o.r pTthieo na bsspoercptrtaio nof sPpSeAct rnuamn oosfp nhAerge@s PaSnAd
cardnnNaAnogo.@s0Pp4Sh-Ae0r 7ecs8o 3smh),porowesssit paee pnceatianvkoe salpyt h.4e0Ar7eb sns maorr ewp sthihioconhw csnop rienrce tsFrpiagounordfeiP n1Sg4A .t oTn hthaeen a osbussprofhrapceteri eopsnla assnpmdeocntnr Auabmgs@ oorPfp SntiAAongc @(oSPmPSRAp)o site
nanoonsfap nthhoeesr pnehasenaroresesi lssvhheoor wwpsan rati inpcleFeasikg. uart e40174 .nTmh ewahbicsho rcportiroesnpsopnedcitnrgu mto othfen sAugrf@acPeS pAlansmanoons pabhseorrepstisohno (wSPsRa)p eak
at40o7f nthme nwahniocshilvceorr rpeasrptioclneds.i ngtothesurfaceplasmonabsorption(SPR)ofthenanosilverparticles.

Figure12.Cont.