The combination of scanning electrochemical microscopy (SECM) with piezoelectric quartz crystal impedance (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, 0.10mol/L H2SO4 + 0.20mol/L Na2SO4), neutral (C, 0.10 mol/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-

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.

An electrochemical quartz crystal impedance system (EQCIS) was used to investigate depletion layer effects on equivalent circuit parameters of piezoelectric quartz crystal resonance in electrochemical processes of CoSO4 aqueous solutions containing 0.4mol/L ethylenediamine +0.5mol/L Na2SO4, 0.2mol/L 1,10-phenanthroline +0.5mol/L Na2SO4 and K3Fe(CN)6, or K4Fe(CN)6 aqueous solutions containing 1.0mol/L KCl in potential cycling experiments, respectively. The impedance data were analyzed according to Martin's model. For the former two systems, motional resistance R1, series resonant frequency fs, and motional inductance L1 changed reversibly with potential, and the observed values of △R1, △L1, and△fs roughly satisfied equations reflecting liquid loadingeffects, suggesting that changes in these parameters mightbe mainly governed by local variations in solution densityand viscosity near the electrode surface. For the latter two systems, reversible changes in R1 with potential coincided well with the simulated results from variations in solution density and viscosity near the electrode surface; however, besides reversible changes of △L1 and △fs with potential, rising drifts of fs and decreasing drifts of L1 were found at oxidation potentials. The drifts of fs and L1 observed are believed to result from mass changes of the gold electrode, and cyanide and chloride corrosion of the gold electrode at oxidation potentials may play an important role for the drifting phenomena. It is concluded that quantitative analyses of △R1, △L1, and △fs obtained from the EQCIS provide the possibility for differentiating the net depletion layer effect with the change in electrode mass, and the ¢R1 response may be well used for evaluating local changes in liquid loading inside the depletion layer compared with responses of △fs and △L1.

The equivalent-circuit parameters of the 9-MHz piezoelectric quartz crystal (PQC) resonance were measured in situ during the galvanostatic polymerization of aniline on 4-aminothiophenol(4-ATP)-modified and bare Au electrodes for ca. 2000s, respectively. Two polymerization media, 0.100mol L-1 aniline in 1.0mol L-1 H2SO4 and in 2.0mol L-1 HClO4 aqueous solutions, and two values of the current density, 12 and 36μA cm-2, were used. At identical levels of the resonant frequency shifts in the solutions, obviously greater increases in the motional resistance (R1) were found afteraniline polymerization on bare Au electrodes, though the absolute values of Δf0/ΔR1 were all large; also, the resonant frequency shifts in air (Δf0g) were considerably smaller for PANI films grown on bare Au electrodes. It is thus concluded that, under identical polymerization conditions, (1) the PANI film grown on a bare gold electrode is rougher, less compact, and can entrap solution more notably; (2) the deposition efficiency of PANI is higher on a 4-ATP-modified Au electrode, owing to a significantly greater observed "dry" frequency shift, and thus a greater "net" mass value of the polyaniline backbone. SEM observations have confirmed that PANI films on 4-ATP-modified Au electrodes were smoother and more compact than those grown on bare Au ones under identical polymerization conditions. In addition, a technique of simultaneous measurements of the electroacoustic admittance of the PQC resonance and the electrochemical impedance was used to monitor the adsorption of 4-ATP onto a PQC gold electrode.

Piezoelectric diffuse reflectance spectroelectrochemistry (PDRSEC), a new technique of diffuse reflectance spectroelectrochemistry (DRSEC) in combination with electrochemical quartz crystal microbalance (EQCM), was developed to study the electrochemical copolymerization of aniline and o-anthranilic acid in 1.0mol l−1 HClO4 and the properties of these copolymers. The DRSEC using an integral sphere was proven to possess a higher optical sensitivity at the unpolished piezoelectric quartz crystal electrodes used than the mirror reflectance spectroelectrochemistry mode. The copolymers grown from the copolymerization bath of different molar fractions of o-anthranilic acid (F1, relative to the total amount of the two monomers) showed intermediate properties between those of the homopolymers, which varied gradually with F1. The swelling/dissolution behavior of the copolymers vs solution pH was traced via the EQCM frequency and resistance signals, and its large dependence on F1 was found and discussed. In a HAc-NaAc buffer solution at pH 5.6, the amount of adsorbed lysozyme was found to be positively correlated with F1, via an EQCM impedance investigation, demonstrating the feasibility of using poly (aniline-co-o-anthranilic acid) as a load-adjustable immobilization matrix for cationic proteins. The novel PDRSEC method proposed is highly recommended for surface electrochemistry studies at relatively rough electrodes.