Prussian Blue-coated interdigitated array electrodes for possible analytical application

Thin films of iron(III) hexacyanoferrate(II) (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes, yielding systems which can be considered as chemiresistors in sensing alkali metal ion concentrations in an adjacent electrolyte. This is due to the fact that the conductivity of the film being measured by a steady-state current on application of a voltage to the two-fingered electrodes of the IDA depends on both the redox stare of the film and the cation concentration in the electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali metal ions and for mixtures of alkali metal ions, the possibilities of analytical application were elucidated. In addition, by using the methods of staircase coulometry and scanning conductivity, the electron diffusion coefficient De was determined as a function of the redox state of Prussian Blue. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali metal ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs

Alkali ion sensor based on Prussian blue-covered interdigitated array electrodes

Thin films of ferric ferrocyanide (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes yielding systems which can be considered as chemi-resistors in sensing alkali ion concentrations in an adjacent electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali ions and for mixtures of alkali ions, the possibilities of analytical application are elucidated. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs

Photoelektrochemische Untersuchungen an Hochtemperatur-Supraleitern Schlussbericht

YBa_2Cu_3O_7_-_#delta# ceramic superconductors exhibit a nearly metallic conductivity at room temperature. However, no experiences about the electrochemical- and photoelectrochemical behaviour of the material were available at the time when this contribution started. The aim of this project was the systematic investigation of thin films, poly- and single crystalline material of the superconductor YBa_2Cu_3O_7_-_#delta# concerning their electrode properties and their corrosion stability in various solvents. The following methods were applied: Cyclovoltammetry, Electrochemical Impedance Spectroscopy, XPS, in-situ Electroreflection Spectroscopy, Photocurrent Measurements. YBa_2Cu_3O_7_-_#delta# is stable in aprotic and unstable in protic solvents. In acetonitrile no electrocatalytic properties were observed. The exchange current densities are up to two magnitudes lower compared with platinum electrodes. Photoelectrochemical- and XPS-measurements suggest a heterogenous, partly semiconducting surface causing the electrochemical effect as well as the poor electrocatalytic activity of the material. No electrochemical treatment was successful to optimize the superconducting properties of YBa_2Cu_3O_7_-_#delta#. (orig.)Keramische Supraleiter vom Typ YBa_2Cu_3O_7_-_#delta# zeigen bei Raumtemperatur eine nahezu metallische Leitfaehigkeit. Ueber das elektrochemische- und photoelektrochemische Verhalten des Materials war bis zum Zeitpunkt der Antragstellung wenig bekannt. Ziel des Projekts war die systematische Untersuchung epitaktisch duenner Schichten, polykristallinen und einkristallinen Materials des Supraleiters YBa_2Cu_3O_7_-_#delta# bezueglich deren Elektrodeneigenschaften und deren Korrosionsbestaendigkeit gegenueber verschiedenen Loesungsmitteln. Folgende Untersuchungsmethoden wurden angewandt: Cyclovoltammetrie, Impedanzspektroskopie, XPS, in-situ Reflexionsspektroskopie Photostrom-Messungen. YBa_2Cu_3O_7_-_#delta# ist stabil in aprotischen und instabil in protischen Loesungsmitteln. Als Elektrodenmaterial in Acetonitril zeigt es keine elektrokatalytischen Eigenschaften. Die Austauschstromdichten sind bis zu zwei Groessenordnungen geringer als an Platinelektroden. Photoelektrochemische- und XPS-Messungen deuten auf eine heterogene, teilweise halbleitende Oberflaeche hin, worauf sowohl der photoelektrochemische als auch die geringe elektrokatalytische Aktivitaet begruendet wird. Mit elektrochemischen Methoden konnte keine Verbesserung der supraleitenden Eigenschaften erzielt werden. (orig.)SIGLEAvailable from TIB Hannover: D.Dt.F.QN1(8,2) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman