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A selective non-enzymatic sensor for catechol using Copper -Polypyrrole composite modified glassy carbon electrode (Cu-PPy/GCE) is reported. The modified electrode was prepared in a facile manner by a two step potentiostatic process of electropolymerization of pyrrole on the bare electrode, followed by deposition of Copper. The modified electrodes were characterized using electron microscopic, spectroscopic and electrochemical techniques. The selective non-enzymatic detection of catechol was analyzed through differential pulse voltammetry and chronoamperometry. Under optimized experimental conditions, the Cu-PPy/GCE was found to span a wide linear range from 0.05 to 1000 μM with a lower limit of detection (3σ/m) of 0.010 μM using chronoamperometry. The selectivity of the modified electrode was also investigated in the presence of typical interfering agents like hydroquinone, ascorbic acid, etc. The practical feasibility of the proposed method was demonstrated through the estimation of catechol in tap water samples.

The present paper reports the effect of iron doping (0.5, 1.5 mol%) on the densification and electrical properties of cerium oxide (CeO 2 ) and 20 mol% samarium-doped cerium oxide (SDC) electrolytes for intermediate temperature solid oxide fuel cell (ITSOFC) applications. A single-step solution combustion method was used for doping and the resultant powder was compacted into green pellets and subsequently sintered at 1200 C. X-ray diffraction (XRD) studies indicated the presence of a cubic fluorite CeO 2 structure without the formation of a secondary phase and the stoichiometry was confirmed by X-ray fluorescence spectroscopy. In the as-compacted green pellets, the XRD peak position shifted to lower or higher angles depending on the ionic radii of the dopants due to lattice level mixing. Addition of iron resulted in smaller crystallite sizes (<11 nm) in the case of the green pellet, while an opposite trend was observed (>40 nm) after sintering. Densification was found to be higher (95%) in iron-doped samples than in bare samples (<90%) due to viscous flow sintering. Upon sintering the calculated strain value showed a lower value due to the segregation of iron from the lattice. Raman spectroscopic studies indicate that sintering marginally modifies the oxygen vacancy concentration in the SDC system, and found it to be higher than in CeO 2 . Addition of iron into the SDC improved the grain boundary conductivity 1.8 fold, but only a minor change was noticed for CeO 2 . The activation energy for the grain boundary conductivity was found to be lower for 1.5 mol% (1.06 eV) iron-doped SDC than for pure SDC (1.24 eV). Our results indicate that lattice level mixing of iron in SDC improves the density at relatively lower sintering temperatures and scavenges the grain boundary impurities, thereby increasing the grain boundary conductivity.

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