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Electrochemical Methods
Prof. Jin Ho Bang
Biosensors
Nature Biotechnology 2019, 37, 389–406.
Basic Principle of Biosensors
Glucose Amperometric Biosensor
Potential step methods
Potential step methods
Chronoamperometry
Chronocoulometry
Cu2+ + 2e → Cu0 (electrochemical reduction)
Fe2+ → Fe3+ + e (electrochemical oxidation)
Anode: electrochemical oxidation
Cathode: electrochemical reduction
Electrochemical reactions
Oxidation: electron moves to electrode.
Reduction: electron moves from electrode.
• Electron tunneling: an electron can penetrate a potentialbarrier higher than the kinetic energy of the electron.
Heterogeneous charge transfer
Cu2+ + 2e → Cu
Heterogeneous charge transfer reaction;
Electron tunneling at electrode/solution interface
Electrode potential is an expression of electron energy
Current is an expression of reaction rate
Current (i) ∝ Reaction rate
Pathway of a general electrode reaction
Potential step methods
Potential step methods
Cottrell equation
Laplace transformation (partial to ordinary)
CO(x,t) by Laplace transformation
Error function
Simulation of CO(x,t)
Limitation of potential step method
Limitation of potential step method
Equivalent circuit for 3-electrode cell
Ref
Ctr
RW
Ru
Cdl
etrue
eref
WkWk
Cdl
etrue
eref
RW
Ru
Rct
Ref
Ctr
Limitation of potential step method
Time constant = RuCdl
etrue
erefe
0 Time
Limitation of potential step method
1. Three-electrode configuration
2. Electrode area; small
- CO*, CR*; constant
3. Mass transfer; no migration (electrolytes)
- Diffusion
- No convection; no stirring
4. Spherical diffusion
Ultra microelectrode
Planar vs. Planar ultra microelectrode
Planar microelectrode Planar ultra microelectrode
• The flux per unit area in spherical diffusion is greater than that in linear diffusion.
• Current decrease by decreased concentration gradient is compensated by the
increased flux. As a result, current density per unit area is greater in UME.
Planar ultra microelectrode
Planar ultra microelectrode
Planar ultra microelectrode
• The used of UME alleviates issues associated with charging time and rising time.
• It also allows to measure steady current within a short time.
• From the steady current measured, parameters related to diffusion can be
determined.
과제:
• 블랙보드에업로드된논문중 관심부분을골라요약 정리하고, 블랙보드를
통해온라인제출
• 제출기한: 9월 20일까지
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