Fabrication of Anodically Electrodeposited Iridium Oxide Film pH Microelectrodes for Microenvironmental Studies

Abstract

A new method for fabrication of anodically electrodeposited iridium oxide film pH microelectrodes has been developed in this study. Novel for its tip size (3-10-microm tip diameter), the microelectrode is fabricated in a tapered glass micropipet filled with a low melting point alloy. The tapered end is recessed and platinized. Thereafter, iridium oxide is electrodeposited over the platinized end in the recessed part. The microelectrode has a very short response time (t80 < 5 s) in the pH range of 0-12 with an accuracy of 0.05 pH unit. The pH microelectrode is not affected by most ions and complexing agents of relevance in environmental and biological studies; it can be used in fluids over wide ranges of stirring speeds (0-55 rpm) and temperatures (approximately 5-40 degrees C). Redox agents such as dissolved oxygen and hydrogen peroxide have no effect on the pH response while quinhydrone, ferro- and ferricyanide, and sodium sulfide have marked effects. However, the microelectrode can still be used in any sample when calibration is done in standards having similar redox characteristics.

pH, redox, and oxygen microprofiles in rhizosphere of bulrush (Scirpus validus) in a constructed wetland treating municipal wastewater

“…The pH microelectrode was constructed by anodic electrodeposition of iridium oxide on the platinum metal (Bezbaruah and Zhang, 2002b). A current of 0.03 -0.13 pA (current density of 0.0002 -0.0004 mA cm À2 ) at 0.3 -0.5 V was used for f20 min.…”

Fabrication and Characterization of Dual Function Nanoscale pH-Scanning Ion Conductance Microscopy (SICM) Probes for High Resolution pH Mapping

“…When deployed as the tip in scanning electrochemical microscopy (SECM), these electrodes have enabled the measurement of pH with high spatial resolution at interfaces. [11][12][13][14] The scale on which pH electrodes can be made has advanced in recent years to the micro 15,16 and nano scale. 17,18 SECM pH probes employing a variety of metal/metal oxides have been reported previously.…”

Electrochemical techniques and sensors for ocean research

“…Taking pH determination as an example one finds different solid state electrodes such as antimony oxide (Horrocks et al, 1993), iridium oxide (Marzouk et al, 1998;Wipf et al, 2000;Bezbaruah and Zhang, 2002;Hassan et al, 2002), tungsten oxide or palladium hydride (Imokawa et al, 2006) which provide a Nernstian response with pH. Many potential selective electrodes rely on solid state membranes to provide selectivity.…”