2015學術(shù)論壇物化分組12

1、Noble Metal Thin Film Stripping by Contact with Ionic LiquidsSept. 26th, 2015Alexandra BaylesProf. Matthew Helgeson Yuning ShenBackgroundIonic Liquids (ILs)Saltsmelting points below 100 CCnmim+ Cnmpyr+Cnmpyrr+Nnnnn+Pnnnn+Common Anions Br- Cl- I-PF6-NTF2-BF4-X-Common Cations 1BackgroundPropertiesNegl

2、igible volatilityNo flammability Wide thermal & electrochemical windowModerate ion conductivity ApplicationsSupercapacitors - Dye-sensitized solar cells Batteries - Electrodeposition of metalsCatalysisIonic Liquids (ILs)Saltsmelting points below 100 CMetal surfaces(electrodes)Ionic Liquids(electroly

3、tes)2Ag (60 nm)Au (50 nm)BackgroundIonic Liquids (ILs)Saltsmelting points below 100 CAg (60 nm)Au (50 nm)Stripping !3No published paper discusses this phenomenonOur objectives:What types of ILs strip thin films?How fast is the stripping?What is the mechanism of stripping?What factors interfere with

4、the stripping process?Is it possible to control stripping?.Objectives4Five Ionic liquidsSix Metal surfacesAg,Sputter depositionGlassTi (5 nm), electron-beam depositionMetal (50/60nm), electron-beam depositionMicaSurfaces type 1Surfaces type 2Combinatorial Contact StudyC6mim+l-C6mim+Cl-C4mim+Br-C2mim

5、+Br-C4mim+PF6-Au(50 nm, Ti)Au(50nm, Ti, silanized)Ag(50nm, Ti, oxidized)Ag(60nm, Ti, oxidized)Ag(50nm, Mica)In oven7080 C5Ag(50nm, Ti)Ionic Liquids(Pure)C6mim+l-C4mim+Br-C2mim+Br-C6mim+Cl-C4mim+PF6-Au(50 nm, Ti)StrippedFew hoursStripped4+ weeksStripped4+ weeksStripped4+ weeksNo strippingAu(50 nm,Ti,

6、 silanized)StrippedFew hoursStripped4+ weeksStripped4+ weeksStripped4+ weeksNo strippingAg(50 nm, Ti)StrippedFew hoursStripped 23 DaysStripped 23 DaysStripped 23 DaysNo strippingAg(50 nm, Ti, oxidized)StrippedFew hoursStripped 23 DaysStripped 23 DaysStripped 23 DaysNo strippingAg(60 nm,Ti, oxidized)

7、StrippedFew hoursStripped 23 DaysStripped 23 DaysStripped 23 DaysNo strippingAg(50nm,Mica)StrippedFew hoursStripped 23 DaysStripped 23 DaysStripped 23 DaysNo strippingAnion-dependent: Halide-based (Cl-, Br-,I-) ILs can strip Ag and Au IL with I- can strip Ag and Au at faster rate.Ti has no obvious i

8、nfluence on strippingCombinatorial Contacts Study6Salt solutionsNaClKClCaCl2CaI2NaFAu(50 nm, Ti)No strippingNo strippingNo strippingStripped No strippingAu(50 nm,Ti, silanized)No strippingNo strippingNo strippingStripped No strippingAg(50 nm, Ti)No strippingNo strippingNo strippingStripped No stripp

9、ingAg(50 nm, Ti, oxidized)No strippingNo strippingNo strippingStripped No strippingAg(60 nm,Ti, oxidized)No strippingNo strippingNo strippingStripped No strippingAg(Mica)No strippingNo strippingNo strippingStripped No stripping*We keep concentration of anion as 1 molL-1 in all solutionsAnion-depende

10、nce confirmed:CaI2 is the only salt that strips metals in experimentBut CaI2 strips more slowly than C6mim+I- does.Combinatorial Contacts StudyTo confirm anion-dependence7Signal IntensityStrippingSignal intensity changes during stripping (exposure time: 0.10 s)Kinetic StudyBright Field MicroscopySam

11、ple cellMetalSide viewVertical viewMetalObjectiveSample cellGlass8Kinetic StudyI-based ILs strips faster than CaI2 or Cl-based ILsStripping Rate of C6mim+I-, C6mim+Cl-and CaI2 with Ag (60nm, oxidized)9Stripping Rate of Different Concentrations of C6mim+I- Aqueous Solution with Ag(60nm, oxidized)Kine

12、tic StudyWater can significantly accelerate stripping Low concentration ( 0.8)High measure errorAttenuator = 11 (maximum)Sample are not qualified, few particles in instrument size range were detected.no metal particles or particles are highly aggregatedTimeCorrelation coefficientSizePDI (Polydispers

13、ity Index)Mechanism Hypothesis I Dynamic Light ScatteringTimeIntensityHowever12SurfacesAu(50 nm)Au(50 nm, Silanized)Ag(50 nm)Ag(50nm, Oxidized)C6mim+I-48.04 nm52.90 nm66.05 nm2.981 nm3.047 nm32.71 nm4.999 nm3.514 nm3.143 nm4.318 nm5.297 nm36.65 nmCitrate capped Au nanoparticles in H2O (100 nm, same

14、concentration)Au surface-contacted C6mim+l-ParticlesObjectiveCondenserMechanism Hypothesis I The “particles” in Au surface-contacted C6mim+l- may be impuritiesThere are no Au particles observed in ILs Hypothesis I may not be rightDark Field Microscopy13DI waterI-AuI2-OxidantAuI2-SubstrateReducedAu(I

15、)Aue-AuI2-Electrochemical corrosione-Mechanism Hypothesis II Oxidants exist in ILs, reduced by AuAu is oxidized to Au(I)Au(I) is stabilized by I-T. A. Green, Gold Bulletin, 2014, 47, 205216.Anodic Au - e- + 2I- AuI2-Cathodic Ox. + ne- Red.Possibly I3-+ 2e- 3I-O2+ 4e-+ 2H2O 4OH-14Mechanism Hypothesis

16、 II UV-Vis SpectrumNo Au(0) particle absorption peakSome species are consumed or converted20% C6mim+I-20% C6mim+I- contacted with Au(50nm,Ti)15Mechanism Hypothesis II UV-Vis Spectrum Kinetic Study13 min15 min17 min19 min21 min22 min23 minSpecies are consumed/converted1620% C6mim+I- contacts with Au(

17、50nm, Ti) Mechanism Hypothesis II UV-Vis Spectrum Kinetic Study0.86 molL-1 CaI2* contacts with Au(50nm, Ti) * Same concentration of I- with 50% C6mim+I- baseline18 hours24 hoursI- may be the specie reactedSpecies are consumed/converted17ConclusionsThe stripping process is anion-dependentThe rate of

18、stripping is given by I Br/ClPF6Mechanism II may exist during stripping. Metalsare oxidized by oxidants and stabilized by anions.Though the oxidants and products are need to bedetermined.Pure ILs strips faster than aqueous salt solutions(same anion and concentration). Water canaccelerate stripping.

19、Mechanisms are still understudy.18Future WorkOxidants?Au, Au(I) or Au(III)EPRSEMElectro-chemicalMethodHypothesis II is rightWhy do certain ILs strips faster?Why does H2O accelerate stripping?Can we control/adjust the stripping?Hypothesis IIIHypothesis IVHypothesis V19AcknowledgmentsMentor Alexandra

20、BaylesProf. Matthew Helgeson Arash Nowbahar, Doug Vogus, Alex Heilman and Matt Gebbie for thin film preparation.Marisa Gliege for NMR.All Helgeson group membersAll CISEI/RISE and other program membersFund NSF Award No. DMR -08-43934.1H-NMR 1H-NMR (Au contacted)No peak shiftWider peaksC6mim+I-/H2O solution20 wt%50 wt%80 wt%Stable Solutionstrip the Au(50 nm) in 20 min20 wt%10 wt%Phase separationDark Field Microscopy of contacted samplesI