Introduction of Electrochemistry （電化學簡介） Electrochemical technique is a type of bio-sensing method.

Basis of Electrochemistry

Entropy (S) Entropy (S) Definition of Entropy: the amount of randomness, or molecular disorder, in a system. Example: icewater steam ice water steam Less disorder > More disorder Lower entropy > Higher entropy

Entropy change (∆S) Entropy change (∆S) ∆S = S final - S initial If ∆S is positive, the system has become more random. If ∆S is negative, the system has become less random.

Spontaneity of Reaction Reaction: a chemical or physical change Two factors that determine the spontaneity ( 自發性） of a reaction in a system: (1) a release or absorption of heat (∆H), (2) an increase or decrease in molecular randomness (∆S).

Gibbs Free-Energy Change (∆G) ∆G = ∆H - T ∆S Free-energy change Heat of reaction Temperature Entropy change  G > 0 Non-spontaneous reaction  G < 0 Spontaneous reaction

Potential Energy  G = - n F  E  G > 0 Non-spontaneous reaction  G < 0 Spontaneous reaction  G is free energy change.  E is applied voltage. F is Faraday constant n is number of mole

Chemical Reactions

Example of a spontaneous reaction Glucose+O 2 Gluconic acid+H 2 O 2 GOX: Glucose Enzyme Example of a non-spontaneous reaction H 2 O 2 O 2 +2H + +2 e - GOx Potential Examples of Electrochemical Reactions

Oxidation and Reduction A + e -  A - A  A + + e- Oxidation reaction Reduction reaction

Role of Enzyme in Chemical Reactions

What is Biosensor? A biosensor is normally defined as a device incorporating a biological molecular recognition component connected to a transducer which can output an electronic signal that is proportional to the concentration of molecule being sensed. Donal Leech, Chemical Society Reviews, 1994,

Components of Biosensor a) Biocatalyst - converts the analyte into product. b) Transducer - detects the occurrence of the reaction and converts it into an electrical signal. c) Amplifier - amplifies the usually tiny signal to a useable level. d) Microprocessor - signal is digitized and stored for further processing, e) Display - usually need a real-time display of the analyte concentration.

Analytes vs. Recognition Elements

Working electrode Glucose Gluconic acid Glucose oxidase (ox) Glucose oxidase (red) O2O2 H2O2H2O2 e-e- Analyte, Biocatalyst, and Product

Electrochemical Cell Transducer

Working electrode (WE) : 電化學反應進行的位置 Reference electrode (AE) : 工作電極之電位參考點 Counter electrode (CE): Cell 必須維持電中性，使 用 CE 維持 cell 的電中性。

Display Display Cyclic Voltammetry (CV) Voltage Scan rate (V/s) cycle Redox couple

CV 訊號 例一 受測溶液 : 黃血鹽 掃描電位： -1v ~ 1v 掃描速率： 0.1 v/sec 掃描時間： 20 秒

受測溶液 : H 2 O 2 掃描電位： -1v ~ 1v 掃描速率： 0.1 v/sec 掃描時間： 20 秒 CV 訊號 例二

電化學 電路區塊圖 RS-232 指令和訊號 傳輸系統 CEREWE 電解槽 Communications of Command and Signal

GUI and Display

Product Examples of Electrochemical Biosensor

Measurement of glucose in blood using an enzyme assay Glucose Meter Glucose Measurement

Commercial Glucose Meter