Silver nanocrystals by hyperbranched polyurethane-assisted p(2)

H.W.Luetal./MaterialsChemistryandPhysics81(2003)104–107

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stableanddidnotprecipitatewithin3months.Theresultingsolutionwascastedonaglasssubstrateanddriedatroomtemperaturefor12h,thenat30 Cinvacuumfor12h.Black lmswerepeeledoffforcharacterization.

剥离

TheX-raypowderdiffraction(XRD)patternswererecordedatascanningrateof4 min 1inthe2θrangeof20–60 usingaRigakuD/max AX-raydiffractome-terwithCuK radiation(λ=1.54178Å).Transmissionelectronmicroscopic(TEM)photographsweretakenonaHitachiS-530TEM.Ultraviolet-visible(UV-Vis)spec-traweremeasuredonaPerkin-ElmerLambda20UV-Visspectrophotometer.APerkin-ElmerParagon1000FTIRspectrophotometerwasusedforFTIRmeasurement.3.Resultsanddiscussion3.1.XRDanalysis

Fig.1showedthetypicalXRDpatternsoftheobtainedsamples.Allthediffractionpeakscouldbeindexedtoface-centeredcubicsilverphasewithcellconstantsa0=4.1Å.ThevalueswereclosetothoseintheJCPDScard(cardno.4-783).Theaveragecrystallinesize,whichwasdeterminedfromthehalf-widthofthediffractionusingtheDebye–Scherrerequation,approximately8nm.

Fig.2.TEMmicrographofsilvernanoparticlesobtainedinthepresenceofHPafter24hirradiationtime.

3.3.UV-Visspectra

Thegenerationofsilvernanoparticlescouldalsobeiden-ti edfromboththecolorchangeandtheUV-Visspectrumoftheas-preparedproducts.UponirradiationofthesolutioncontainingHPandAg+,colorationwasobserved.Fig.3showedtheUV-Visabsorptionspectraofthesilvernanopar-ticlesobtainedinthepresenceofHPwithdifferentirradia-tiontime.PureHPsolutionexhibitednearlynoabsorptionintheselectedregion.Theabsorptionbandatabout430nmmaybeattributedtothecharacteristicsurfaceplasmonres-onanceofsilvernanoparticles[17].Byincreasingtheirra-diationtime,thepeaksaround430nmshiftedtothelower

3.2.TEManalysis

Fig.2showedtheTEMmicrographsoftheas-preparedsilvernanoparticles.TheobtainedsilvernanoparticleswerewelldispersedinHP,withdifferentdiametersof5–10nmand15–20nm,respectively.Thesizeofthesmallerparticles(5–10nm)wasconsistentwithXRDresults.Thelargersilverparticles(15–20nm)wereprobablytheaggregatesofthesmallerones,duetothehighsurfaceenergyofthenanosized

crystals.

Fig.1.XRDpatternofsilvernanoparticlesobtainedinthepresenceofHPafter24hirradiation

time.