Electrocatalysts based on monolayers of transition-metal complexes attached to electrode surfaces frequently follow mechanisms in which a chemical step is interposed between the first and subsequent electron-transfer steps. The cyclic voltammetric responses to be anticipated for such systems were calculated using finite difference procedures to solve the relevant differential equation. The calculated variation of the peak currents and peak potentials with the kinetic parameters governing the three steps in the mechanistic scheme are presented in graphical form. Application of the results to a specific experimental system, the catalysis of the electroreduction of 0, by a macrocyclic complex of Co"' adsorbed on graphite electrodes, produced reasonable agreement between calculated and observed cyclic voltammograms.The catalysis of electrode reactions that involve the transfer of multiple electrons, e.g. the reduction of 0, to H,O, or H,O, may proceed by a variety of conceivable mechanisms. One way to examine possible mechanistic schemes is to compare experimental current-potential responses with those calculated on the basis of feasible mechanisms. We have employed this approach in three recent studies in which the currentpotential responses to be expected were calculated for single monolayers of molecules adsorbed on electrode surfaces where they acted as catalysts in simple outer-sphere,' inner-sphere, or intramolecular3 electron-transfer mechanisms. In the present study we extend the approach to a somewhat more complex mechanism in which a chemical reaction is interposed between the first and subsequent electron-transfer steps and a separate response appears from an intermediate in the catalytic cycle. Such ECE4 mechanisms have been treated previously by Laviron5y6 but only for cases where the electrode reactions were assumed to be Nernstian and the chemical reaction was assumed to be totally irreversible. We were interested in cases where these restrictive assumptions were not made, in order to compare the calculated results with those obtained in an experimental system in which the catalysed reduction of 0, to H,O, by a complex of Co"' adsorbed on the surface of graphite electrodes appeared to proceed by such an ECE mechani~m.~ In our previous reports'-3 the calculational procedures employed were based primarily on the original treatments of Andrieux and Saveant' and Aoki et aL9 as elaborated and extended to encompass the mechanistic schemes of interest. In the present case it was possible to carry out all of the necessary calculations using finite difference procedures. '' Because of the availability of previous descriptions of the details of the calculations they are only outlined in the present report.The mechanism we wish to consider is depicted in Scheme I:The catalyst, consisting of the O/R couple, is confined in a monolayer on the electrode surface. The substrate, Z, can be reduced only after it is bound by the reduced form of the catalyst to form the adduct, (R-Z)ads. This reaction is governed by equil...

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A new electrogenerated chemiluminescence (ECL) sensor based on a self-assembled monolayer (SAM) of Ru(II)-bis(2,2'-bipyridyl)(aminopropyl imidazole) on a gold-deposited screen printed electrode (SPE) has been developed. Since the ECL emission of the Ru(II)-bis(2,2'-bipyridyl)(aminopropyl imidazole) complex can be easily obtained at an applied potential of less than + 0.8 V, the possibility of the oxidation of the Ru-complex SAM formed on gold-deposited SPE electrode surface was greatly diminished and thus the stability of the resulting Ru-complex SAM-based ECL sensor was enormously enhanced compared to the previously reported Ru(bpy) 3 2 + -derivative monolayer-based ECL sensors with applied potentials of more than + 1.0 V. In the present study, the gold deposited SPE with carbon nanotube paste was used in order to increase the amount of Ru-complex immobilized on the electrode surface through a large surface area of deposited gold nanoparticles causing good charge transport and thus leading to the increased sensitivity of the ECL sensor. The ECL characteristics obtained with the present Ru-complex SAM-based ECL sensor are compared with those obtained with other Ru(bpy) 3 2 + -SAM-based ECL sensors.

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Bradycardia is defined as a sinus rhythm of less than 60 beats per minute and atrial tachyarrhythmia including atrial fibrillation (AF) is frequently associated with bradycardia. Pacemaker is the only effective treatment for symptomatic bradycardia and automatic mode switching (AMS) function is built in pacemaker to switch mode in the presence of atrial tachyarrhythmia. AMS algorithms consider appropriate mode switching in case of undersensing or oversensing and this consideration makes their onset time and resynchronization time late. Current pacemakers have onset time from 2.5 seconds to 26 seconds and resynchronization time from 3.4 seconds to 143 seconds according to manufacturers. In this work, we proposed beat detection algorithm based on amplitude difference between peak and trough for accurate extraction of atrial rate achieving faster mode switching. Evaluation of beat detection algorithm was conducted with six canine AF electrogram (EGM) data. Result showed 96.64% sensitivity, 95.5% positive predictive value in average. With this, transition from AF to normal sinus rhythm could be detected faster than existing AMS algorithms. In conclusion, proposed algorithm can efficiently detect beats in EGM during AF and from this, we can implement faster AMS algorithm.