Electrochemical quartzcrystal microbalance (EQCM) studied revealed that the electrochemical properties of polypyrrole (PPY) in aqueous solutions are greatly dependent n the solution pH. A PPY film immersed in an aqueous KCl solution shows redox processed which involve not prevails as has been widely recognized. It has been found form comparative studies using poly (N=methylpyrrole) that protonation and deprotonation at nitrogen atoms of PPY play a key role in the observed pH-dependent electrochemicl behavior. Deprotonated PPY allows transient incorporation of hydrated cations upon reduction in weak alkaline aqueous solution. followed by alsow ejection of the incorporated cations when conventional electrolytes such as KCl and NaClO4 are used, but not in NH4Cl solution. Discussion on the catin transport in PPY is made in termas of deprotonation and protonation of nitrogen atoms of pyrrole subunits in PPY.

The electrochemical redox processes of pyridoxine hydrochloride (VB6) at a poly (methylene blue) film modified glass carbon electrode (PMBE) in a phosphate buffer solution (PBS, pH 8.0) were studied by cyclic voltammetry. The VB6 electrode reaction with quasi-reversible characteristics was diffusion-controlled at low scan rates and adsorptioncontrolled at high scan rates. The anodic peak current positive to 0.6V (vs. SCE) was found to be proportional to the concentration of VB6 in the range of 0.010 to 1.03mg

ance (PQCI) analysis was proposed as a novel multiparameter method for investigating the cyclic voltammetric growth of poly(o-phenylenediamine) (PoPD) thin films at Au electrodes in aqueous solutions of various pH values and the potentiostatic microetching (localized degradation) of these films in 0.10mol/L aqueous H2-SO4 for comparative examinations on polymer porosity and stability. Two potential-sweep ranges, -0.4 to 0.9 (I) and 0 to 0.9 (II) V versus SCE, and four solutions, acidic (A, 0.20mol/L H2SO4 + 0.10mol/L Na2-SO4; B, 0.10 mol/L H2SO4+ 0.20mol/L Na2SO4), neutral (C, 0.10mol/L PBS + 0.20mol/L Na2SO4, pH 7.2), and alkaline (D, 0.20mol/L NaOH+ 0.20mol/L Na2SO4) aqueous solutions, were selected for PoPD growth. The pH increase for the polymerization solution increased the molar percentage of polyaniline-like chains in PoPD, as quantified from the current peaks at 0.6 V versus a saturated calomel electrode (SCE) for the oxidation of -NH2 groups in as-prepared PoPD (grown from solutions C and D) during their redox switching in 0.10mol/L aqueous H2SO4 for the first time. The unusual PQCI responses observed at negative potentials (potential range I) in the first several potential cycles during the cyclic voltammetric growth of PoPD in acidic and neutral solutions have been reasonably explained as being due to the precipitation/dissolution of the poorly soluble phenazinehydrine charge-transfer complexes developed during redox switching of oligomers for the first time, which brought about much less compact PoPD films and their higher degradability than those grown in the same solution but over potential range II. SECM, scanning electron microscopy (SEM), and piezoelectric quartz crystal (PQC) frequency were used to estimate the sizes of etched microscale spots. In addition, the x-, y-, or z-axis movement of a Pt microelectrode of 25-μm diameter near the PQC electrode was found to influence negligibly the PQCI responses in 1.0mol/L aqueous Na2SO4 containing K4Fe(CN)6 up to 0.10mol/L, and a new protocol of dynamically electrodepositing silver microwires via the chemical-lens method was proposed for examining the local mass-sensitivity distribution on the PQC surface.

An electrochemical quartz crystal impedance system (EQCIS) was used to study the resonance behavior of an AT-cut 9-MHz piezoelectric quartz crystal (PQC) with its Au electrode partially immersed in KCl, Na2SO4 and NaClO4 aqueous solutions, respectively. An in situ determination of the immersed area and the height of the electrode was achieved by simultaneous measurements of the PQC electroacoustic admittance and the electrochemical impedance. The rising of the solution meniscus for a gold electrode partially immersed in aqueous solutions was found at oxygen reduction potentials and evaluated versus the electrolyte, electrolyte concentration, solution pH and oxygen concentration. The solution meniscus rising was explained based on a lowering of the contact-angle hysteresis and a continued collection of the water product at the solid-gas-solution interface during oxygen reduction.