Presentation on theme: "QCM & EQCM - Principle & Application in Ion Transport State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese."— Presentation transcript:
QCM & EQCM - Principle & Application in Ion Transport State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences
Resonance & Standing Wave Standing Wave - A wave characterized by lack of vibration at certain points, between which areas of maximum vibration occur periodically. Resonance - The increase in amplitude of oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or very close to the natural undamped frequency of the system. External Stumili
Quartz Adsorbed Layer dqdq d a aa qq f0f0 qq fmfm f m – final or total frequency that we measured f 0 – intrinsic frequency of quartz crystal d q – thickness of quartz crystal q – velocity in crystal of wave transfer q – density of quartz crystal a – density of adsorbed layer d a – thickness of adsorbed layer Area=A
External Stumili Quartz Adsorbed Layer dqdq d a aa qq f0f0 qq fmfm Area=A Minute Change in Mass Constant f 0
S auerbrey, s equation, f = -2 mf 0 2 /A( ) 1/2 where m is the mass change of quartz crystal surface, f is the frequency change caused by m, f 0 is the fundamental resonant frequency of quartz crystal in the absence of the deposited mass, A is the geometric area of electrode, is the shear modulus of quartz and is the density of quartz. f = C m C is called as calibration constant of QCM Ref : Sauerbrey, G. Z. Phys. 1959, 155, 206.
Quartz Crystal Metal Electrode Front Lead Wire Back Lead Wire Illustration of quartz crystal oscillator The shearing stationary wave in quartz crystal and its propagation AT-Quartz Displacement y x hfhf Surface Mass Layer f, f Liquid ,
Ref.: S. Bruckenstein, M. Shay, Electrochim. Acta, 30(1985)1295. S. Bruckenstein, S. Swathnaian, Electrochim. Acta, 30(1985)851. Illustration of EQCM instrument Regulator Working Oscillator Potentiostat W R C f Counter Cell I, V, t f
Illustration of Time-resolved EQCM Reference Oscillator Mixer & Regulator Working Oscillator Potentiostat W R C Frequency- divider ff f/n Multi- trigger Counter Data Memory A/D-D/A interface Computer High Frequency Time-base fHfH Cell
Previous Methods for Determining the Calibration Constant C 0Calculation based upon the Sauerbrey formular (, ) Ref : Ostrom, G.S.& Buttry, D.A. J. Electroanal. Chem. 256(1988)411. 0Measurement based upon electrochemical deposition of Ag Ref : Bruckenstein, S. & Swathirajan, S. Electrochim. Acta, 30(1985)851. Keita, B.; Nadjo, L. ; Belanger, D. et al. J. Electroanal. Chem. 384(1995)155.
Typical EQCM Response at Bare Au Scan Rate : 100mV/s, in 1M H 2 SO 4
Typical EQCM Response of Bare Pt Scan Rate : 100mV/s, in 1M H 2 SO 4