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生物感測器原理與應用. 訊號傳送元件介紹. Biosensor. --- a device incorporating a biological sensing element to a transducer. Transducer. --- converts an observed change (physical or chemical) into a measurable signal. Electrochemical transducers Potentiometry, Voltammetry (Amperometry)
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生物感測器原理與應用 訊號傳送元件介紹
Biosensor --- a device incorporating a biological sensing element to a transducer
Transducer • --- converts an observed change (physical or chemical) • into a measurable signal. • Electrochemical transducers • Potentiometry, Voltammetry (Amperometry) • Conductimetry • Optical transducers • Piezoelectric devices • Surface acoustic waves • Thermal methods
Potentiometry There is charge separation between the metal and solution. --- electron pressure, usually called a potential. --- One-half cell cannot be measured directly.
Daniell Cell Cu2+ + Zn = Cu + Zn2+ ΔG = - nFE n: no. of e- F: Faraday const. E: emf of cell ΔG < 0 E > 0
Standard Hydrogen Electrode H+ + e- = ½ H2 ΔG = 0 ECu = + 0.34 V EZn = - 0.76 V Ecell = 0.34 – (-0.76) = 1.10 V
Reference Electrodes -- SHE involves flowing H2 gas
The Nernst Equation Basic Nernst Eq.: ΔG = - RT lnK For the half-cell reaction Ox + ne- = R E = E0 + 2.303 (RT/nF) log([Ox]/[R]) The reduced species, R, is often a metal E = E0 + 0.06 log[Ox] Useful practical form E = K + S log[Ox]
Optical Transducers pyruvate + NADH + H+ L-lactate + NAD +
Beer’s Law log(I/I0) = A = E C l
Total Internal Reflection When = /2 = c critical angle of TIR
