Analytical Characterization of Microlithographically Fabricated Iridium-based Ultramicroelectrode Arrays

Rosemary Feeney, Janet Herdan, Melissa A. Nolan, Sandie H. Tan,
Vladislav V. Tarasov, and Samuel P. Kounaves*
Department of Chemistry, Tufts University, Medford, MA 02155 U.S.A.

*Author to whom correspondence should be addressed. (skounave[at]tufts.edu)

The analytical performance of several mercury-coated iridium ultramicroelectrode arrays (IrUMEAs) was studied using square wave anodic stripping voltammetry (SWASV) for determination of cadmium in a pH 4.5 acetate buffer. The microlithographically fabricated IrUMEAs consisted of either 20 or 25 individual disk shaped UMEs, each 10 mm in diameter. The insulating layer utilized in the fabrication process was either silicon dioxide (5000 Å) or silicon nitride (1500 Å or 2500 Å). Calibration curves demonstrated good linearity for cadmium from 0-100 ppb. Standard deviations, detection limits, and correlation coefficients were calculated to determine the stability and reproducibility of the IrUMEAs. Repetitive cycles of depositing and stripping Hg at the IrUMEA surface resulted in increased distortion and loss of the SWASV signal. Atomic Force Microscopy revealed a subtle transformation in the IrUMEA surfaces.