Transient response curves kinetic parameters

The voltammetric behavior of the first-order catalytic process in DDPV for different values of the kinetic parameter Zi(= ( 1 + V) Ti) at spherical and disc electrodes with radius ranging from 1 to 100 pm can be seen in Fig. 4.25. For this mechanism, the criterion for the attainment of a kinetic steady state is %2 > 1-5 (Eq. 4.232) [73-75]. In both transient and stationary cases, the response is peakshaped and increases with j2. h is important to highlight that the DDPV response loses its sensitivity toward the kinetics of the chemical step as the electrode size decreases (compare the curves in Fig. 4.25a, c). For the smallest electrode (rd rs 1 pm, Fig. 4.25c), only small differences in the peak current can be observed in all the range of constants considered. Thus, the rate constants that can... 

This is a system of stiff, second-order partial differential equations which can be solved numerically to yield both transient, and steady state concentration profiles within the layer. Comparison of the experimental calibration curves and of the time response curves with the calculated ones provides the verification of the proposed model from which it is possible to determine the optimum thickness of the enzyme layer. Because the Thiele modulus is the controlling parameter in the diffusion-reaction equation it is obvious from Eq.6 that the optimum thickness L will depend on the other constants and functions included in the Thiele modulus. Because of this the optimum thickness will vary from one kinetic scheme to another. 

In Fig. 7 we showed some possible theoretical ILIT responses. The nature of the response will depend upon the relationship between the parameter which defines the amplitude of nonkinetic component of the ILIT response [see Eq. (47)], and the parameter B, which defines the amplitude of the kinetic component of the ILIT response (see Eq. (5) and see Sec. IV.A for complete discussion). Parameter A will depend dramatically on the potential of zero response (pzr), which is primarily a property of the diluent component of the SAM. A nice demonstration of this is shown in Fig. 14 for two ILIT transients (plotted as AFoc/ATeq vs. t) for two different ferrocene-containing SAMs one (upper curve) formed from a mixture of HS-[- -C=C-]2 Fc and HS(CH2)gCH3 and the other (lower curve) from a mixture of HS-[-i )-C=C]2 Fc and HS(CH2)gOH. The qualitative difference in the two transients is caused by the difference in the pzr of the diluents (see Fig. 3, which shows that the pzr for the methyl- and hydroxy-terminated thiols differs by nearly 2 V). But that is not the only difference. There is also a difference in the E° (0.375 V vs. SSCE for the... 

Fig. 11. Transient absorption kinetics. Open symbols are measured data, curves are fits, and instrument responses are represented by dotted curves a) SE decay probed at 600 nm b) excited state evolution ( MLCT—> MLCT) probed at 690 nm c) formation of the triplet state at 1050 nm the data are well fitted with rise times of 30 5 fs (for RuN3-TiO triangles) and 70 15 fs (for RuN3-EtOH squares) d) early-time transient absorption kinetics of oxidized RuN3 cation-Ti02 measured at 860 nm parameters of the fit are given in the caption of Figure 10.

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