生物电分析化学第一课overview

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生物电分析化学
Electroanalytical Chemsitry and
Its Biological Applications
刘宏
2015年秋
课程目标
 掌握核心概念和原理
 具备在该领域的继续学习的能力
Syllabus
 双语教学
 不点名,作业不计分
 开卷考试
 教师邮箱: [email protected]
 答疑与讨论:河海院121室
 课程网页: http://www.liuhong.info/?page_id=211
课程大纲
1. Overview of electrochemistry(电化学概论)
2. Equilibrium (平衡)
3. Electrochemical Kinetics (电化学动力学)
4. Mass-transfer(传质)
5. Potential step/sweep techniques (电势阶跃/扫描技术)
6. Ultra-microelectrode (超微电极,UME)
7. Scanning electrochemical Microscope (扫描电化学显微镜,SECM)
8. Finite-element simulation of electrochemical processes (电化学过程的有限元模拟)
9. Applications:biomedical diagnostics, sensors, biofuel cell, brain research and
single-cell studies(实际应用: 生物医学诊断、传感器、生物燃料电池、脑科学、单细胞研究)
Textbook
Allen Bard 教授
2013美国国家科学奖章
巴德(Bard A.J.),福克
纳(Faulkner L.R.)著,
邵元华 等译
化学工业出版社 2005-5-1
Electrochemistry
Electrochemistry is the study of chemical reactions which take place at
the interface of an electrode, usually a solid metal or a semiconductor,
and an ionic conductor, the electrolyte.
These reactions involve electric charges moving between the electrodes
and the electrolyte (or ionic species in a solution). Thus electrochemistry
deals with the interaction between electrical energy and chemical
change.
Overview of electrochemistry
1. Electrochemical cell (electrolytic, galvanic)
2. Half cell and standard reduction potential
3. Nernst equation
4. Three-electrode cell
5. Potential step techniques (chronoamperometry,
chronocoulometry)
6. Potential sweep techniques (LSV, CV)
Electrochemical parameters
1. Charge (q)
2. Potential (E)
3. Current (i)
4. Capacitance (C)
5. Resistance (R)
6. Conductance (G)
Electrochemical cell
 Spontaneous
 Non-spontaneous
 Generate power
 Consume power
 Cell voltage > 0
 Cell voltage < 0
Electrochemical cell
 Battery discharge: galvanic cell
 Battery charge: electrolytic cell
Half Cell
1.
E = 0.340 V
2.
E = -0.763 V
Cell voltage:
0.340 V - (-0.763 V) = 1.103 V
thermodynamic, at standard conditions
Nernst Equation
E0’ – standard reduction potential
R – gas constant R=8.314 (J/mol/K)
T- absolute temperature T=273.15+t (K)
n – electron transferred
F – Faraday constant F= 96485 (C/mol)
Co(x=0) – concentration of oxidized species
CR(x=0) – concentration of reduced species
X=0 means “on the electrode surface”
3
[
Fe(CN)
6 ]
E  E 0'  0.059 log
[Fe(CN)64 ]
Electrochemical Cells
Two-electrode cell:
iR drop: EiRs= iRs
If Rs=100 Ω, i=1mA, EiRs= 0.1V
Three-electrode cell:
Reference Electrode
E0’= 0.222 V vs. NHE
E  E 0'  0.059 log
1
[Cl ]
Faraday’s Law
 Faraday’s law:
n
it
zF
n is number of moles (n = m/M)
t is the total time the constant current was applied.
z is the no. of electrons transferred.
 Nonfaradaic processes
charging/discharging
 Faradaic processes
redox (reducing/oxidizing) events
Non-Faradaic Processes
Faradaic Processes
Electrochemical Kinetics
Mass Transfer
Nernst-Plank Equation:
Diffusion:
Migration:
Convection:
If the solution is kept still and excess supporting electrolyte (KCl or KNO3) is added to
the solution, the contribution of convection and migration can be negligible .
Potential Step Techniques
CO*
O
R
CO(x=0)
O + ne-
R
Cottrell equation for a planar electrode:
DO: diffusion coefficient of O
CO: concentration of O
Chronoamperometry:
Potential Sweep Techniques
Non-Faradaic Processes
Potential Sweep:
Faradaic Processes
Assignment
1. Select two half cells listed in the table on Page 13 to construct (a) an
electrolytic cell and (b) a galvanic cell. Write down the anodic, cathodic and
overall reactions. Calculate the cell voltages at (a) standard conditions and (b)
if the concentration of every solute is 1.00 mM.
2. Explain why we want to use a three electrode system in a potential-step
experiment.
3. A 0.1 cm2 electrode with Cd=20 mF/cm2 is subjected to a potential step under
conditions where Rs is 1, 10, 100 Ω. In each case, what is the time constant,
and what is the time required for the double-layer charging to be 95%
complete?
4. Consider the nernstian half-reaction:
A 3  2e  A 
E 0' A3 /A  - 0.500 V vs. NHE
the i-E curve for a solution at 25 0C containing 2.00 mM A3+ and 1.00 mM A+
in excess electrolyte shows il,c = 4.00 mA and il,a = -2.40 mA. Sketch the i-E
curve for this system.
Assignment
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