Frequency Domain Potential-Modulation Spectroscopy

When the film is moving fast enough, the image of the ball becomes resolved to an image of the ball itself the ball moves a small amount on each frame. 

TR in potential modulation experiments is limited to 10 -10 s by the response of the thin-layer cell and, in the case of ATR, to 10 s by the response of the electrochemical equipment, especially the potentiostat (0.5-10 p,s) [478] and the A/D converter [473] used. The first millisecond time-resolved IR spectra of an ultrathin film at the electrode-electrolyte interface were also measured with a dispersive spectrometer by repetitive measurements of IR absorption at fixed wavenumbers and conversion of the data into TR spectra [623]. The disadvantage of this technique was long collection times (on the order of a few tens of hours). 

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In part II, the photoresponses for the heterogeneous quenching of ZnTPPC by ferrocene derivatives were studied by intensity-modulated photocurrent spectroscopy (IMPS). The different contributions, that is, the electron injection, the recombination-product separation competition, and the attenuation due to the uncompensated resistance and interfacial capacitance (RC) time constant of the cell were deconvoluted in the frequency domain. The flux of electron injection was described as a competition between the relaxation of the porphyrin-excited state and the electron-transfer step. Experimental results confirmed that the electron-transfer rate increases with the Galvani potential difference (Butler-Volmer behavior), but the ZnTPPC coverage was potential-dependent. 

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