Chem120A+Notes+-+Biointerfaces

Chem120A+Notes+-+Biointerfaces - a) Soft Contact Lens Soft...

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soft contact lens cornea tear flow limbus sclera tear flow keeps lens afloat Soft contact lens: crosslinked pHEMA In water, it swells and forms a hydrogel. CH 3 C CH 2 C=O O C 2 H 4 OH n Soft Contact Lens a) b) c) pHEMA = poly(2-hydroxyethyl methacrylate) Polyurethane Under Reversible Loading (Fatigue Test) 3.2 billion heart valve loading cycles in ~80 years of normal heart function. d) Stent Prosthesis
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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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¾ SFG intensity from a centrosymmetric medium is parity-forbidden. x = -x y = -y z = -z χ xyz = χ (-x)(-y)(-z) = – χ xyz = 0 ¾ z -z at an interface (usually): χ xyz = χ (-x)(-y)(z) = χ xyz χ (2) is nonzero Æ surface-specific signal 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 x y z
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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 x y z ¾ SFG intensity from a centrosymmetric medium is parity-forbidden. x = -x y = -y z = -z χ xyz = χ (-x)(-y)(-z) = – χ xyz = 0 ¾ z -z at an interface (usually): χ xyz = χ (-x)(-y)(z) = χ xyz χ (2) is nonzero Æ surface-specific signal
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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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Comparison of the SFG and FTIR spectra generated from different thickness polyethylene glycol films 120nm thick 550nm thick 700nm thick
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Z d c Atomic Force Microscopy (AFM) AFM image of the silicon 7x7 reconstruction
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AFM Curve Schematic Force ( F ) 0 0 Piezo Extension ( z ) + _ Non-contact snap-out (adhesion) Contact 1 10 5 1 10 6 1 10 7 1 10 8 1 10 9 0 0.5 1 Stiffness Elastic Modulus Modulus Elastic ) ( / Stiffness ) / ( tip retract = = z A z F z F Contact snap-in
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Different modes of Atomic Force Microscopy AFM (Atomic Force) or SPM (Scanning Probe) Tracking Topography LFM (Lateral Force) or FFM (Friction Force) Twisting Friction Force Modulation Bouncing Elasticity Viscosity Force-Distance Curves Sticking Adhesion/ Repulsion Microscopy Mode Motion Data
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Tacticity of Polypropylene Isotactic Polypropylene Elastic Modulus (GPa) Hardness (MPa) I-PP 1.09 125 A-PP 0.15 1.4 CH 2 CH 2 CH 2 C C C C H H H H CH 3 CH 3 CH 3 CH 3 Atactic Polypropylene CH 2 CH 2 CH 2 C C C C CH 3 H H H CH 3 CH 3 CH 3 H
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Chem120A+Notes+-+Biointerfaces - a) Soft Contact Lens Soft...

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