Chem120A+Notes+-+Biointerfaces+2

Chem120A+Notes+-+Biointerfaces+2 - Biointerfaces Catalysts...

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Surfaces Surfaces Electrochemistry Tribology Biointerfaces Nanomaterials Coatings Corrosion Integrated Circuitry Sensors Magnetic Information Storage Catalysts
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¾ Intense electric field induces 2 nd -order nonlinear polarization: P (2) = χ ijk (2) :E j cos( ω i t) E k cos( ω j t) P = P (0) + P (1) + P (2) +… P (1) = α ij (1) : E j cos( ω j t) ) ( ) ( ) ( IR vis 2 ) 2 ( SFG ω χ I I I ¾ Total SFG intensity is given by: 532 nm SF 2000 to 4000 cm -1 detector Nd:YAG OPG/OPA 1064nm ~20ps SFG: in situ surface-specific vibrational spectroscopy | ν 1 | ν 0 ω vis ω IR ω SFG |n Linear (IR, Raman) Nonlinear (SFG) P (2) = χ ijk (2) :E j E k [cos( ω j + ω k )t + cos( ω j ω k )t]
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Example: Alkanethiol self-assembled monolayer (SAM) SFG spectra: C-H stretching region 2800 2850 2900 2950 3000 3050 0.0 0.5 1.0 1.5 2.0 2.5 Wavenumber, cm -1 SFG signal CH 3 CH 3 CH 3 CH 3 CH 3 (s) CH 3 Fermi, (a) CH 2 (s) H H H H
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Surface Science at Liquid Interfaces • Surface Electrochemistry • Biointerfaces
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Electrochemical Cell
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Orientation of Acetonitrile on Pt(111) 2800 2900 3000 3100 0.00 0.02 0.04 0.06 0.08 0.10 SFG Intensity (a.u.) Wavenumber (cm -1 ) 200 mV (vs. RHE) 2800 2900 3000 3100 0.00 0.02 0.04 0.06 0.08 0.10 Wavenumber (cm -1 ) 1200 mV (vs. RHE) N C C H H H .. 200 mV (vs. RHE) N C C H H H .. 1200 mV (vs. RHE)
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Surface Segregation • Side Groups of Polymer Chains • End Groups of Polymer Chains • Low Surface Energy Component in Polymer Blends • Hydrophilic Groups in Water • Hydrophobic Groups in Air
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SFG spectrum of atactic polypropylene 2800 2850 2900 2950 3000 0.00 0.25 0.50 0.75 1.00 SFG signal Wavenumber, cm -1 aPP thin film glass s (Ey) s (Ey) p (Ez,Ex) CH 2 (s) CH 3 (s) CH 2 (a) CH 3 (a) C H H H μ c C H H H μ a air C H HH C H θ = 0-30 ° aPP
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2800 2850 2900 2950 3000 0.00 0.25 0.50 0.75 1.00 SFG signal Wavenumber, cm -1 polypropylene water aPP/water Polypropylene/water interface C H 0.00 0.25 0.50 0.75 1.00 SFG signal CH 3 (s) aPP/air CH 3 (a) Polypropylene CH 3 side branches tilt and/or disorder
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Polymer Blend Surfaces
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Friction images of 50% wt. blend 2800 2850 2900 2950 3000 3050 0.2 0.4 0.6 0.8 1.0 1.2 SFG and AFM show that polypropylene segregates to the surface when blended with ethylene-propylene copolymer. CH 2 from propylene CH 2 from ethylene CH 3 from propylene polypropylene (PP) ethylene-propylene copolymer (EPR) 50 wt.% blend PP and EPR Characterization of polyolefin blend surfaces After 30 second anneal After 20 minute anneal Dark areas = polypropylene Light areas = ethylene-propylene copolymer 30 x 30 μ m 30 x 30 μ m wavenumber, cm -1 SFG quantifies the ethylene to propylene ratio at the surface of polyolefins polyethylene (PE)
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Changes of Polymer Surface Composition at the Solid-Gas and Solid-Liquid Interfaces
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Structural rearrangement of pHEMA surface in response to water methyl hydroxyethyl Chen, Zhang, Somorjai, and Bertozzi J. Am. Chem. Soc. 121 , 446 (1999) Dehydration A B
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1.4 1.2 1.0 0.8 SQRT OF SF PEAK IN TENSITIES RATIO OF S 2919 /S 2851 80 70 60 50 40 30 20 10 0 HYDRATION TIME (HOUR) 95 90 85 80 75 CONTACT ANGLE SFG SIGNAL CONTACT ANGLE SF Signal and Contact Angle vs. Hydration Time
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pHEMA – poly(2-Hydroxyethyl Methacrylate) hydrophilic tail O O OH CH 2 CH 3 n dangling chain cross-link Contact lens:hydrogel
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contact lens mold polypropylene cover plate with 4mm dia. orifice (stainless steel) AFM detector laser saline solution
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This note was uploaded on 09/28/2009 for the course CHEM 120A taught by Professor Whaley during the Spring '07 term at Berkeley.

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Chem120A+Notes+-+Biointerfaces+2 - Biointerfaces Catalysts...

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