Analytical Sciences

A Cobalt-Nickel Metal-Alloy Thin-Film Sensor for Hydrogen-Phosphate Ion

Hideyasu NAKAMURA, Satoko TAKASE, and Youichi SHIMIZU

Department of Applied Chemistry, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata, Kitakyushu, Fukuoka 804-8550, Japan

Cobalt-nickel alloy thin-films were prepared by electrodepositing on Au-coated Al₂O₃ substrate from aqueous solutions of metal-salts, and applied as a potentiometric hydrogen-phosphate ion sensor. A doping of 20 mol% nickel in cobalt contributed to enhancing hydrogen-phosphate ion sensing performances, i.e., the sensing range and response time were drastically improved. The Co₈₀Ni₂₀ thin-film electrode showed good potentiometric response to hydrogen-phosphate ion between 1.0 × 10⁻⁵ and 1.0 × 10⁻³ M with a slope of –59 mV/decade and high anion selectivity. The 90% response time to 1 mM H₂PO₄⁻ was as short as 15 s at pH 5.0, 30°C. A mixed potential sensing mechanism could be proposed on the basis of the results.

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