Potentiometric oxygen sensing with copper films: Response mechanism and analytical implications

Abstract

The electrochemical response mechanism of a previously reported potentiometric oxygen (0,) sensing system based on thin films of copper sputtered on single crystal Si(100) is examined. The potentiometric 0 2 response of such films is shown to depend on sample stirring rate as well as the pH, ionic strength and nature of the buffer salts within the test solution. XPS studies of the copper films exposed to solution for several days confirm the presence of compper corrosion products on the surface. These findings, in conjunction with cyclic voltammetric measurements, suggest that the potentiometric 0 2 response originates from slow corrosion of copper and simultaneous reduction of 0, -at the surface of the thin films. A steady-state situation exists when the rates of these two reactions are equal, resulting in a corrosion potentlal (also referred as rest potential E, for the system) that varies in a near Nernstian (1 e-) manner with the partial pressure of 0 2 in solution. A mathematical formulation for this type af response, based on the Butler-Volnier equation, is presented. The analytical implications of these findings with respect to devising useful potentiometric O2 sensors based on copper films are discussed.

Active Potentiometry for Dissolved Oxygen Monitoring with Platinum Electrodes

“…Additionally, a potentiometric sensor provides a direct measurement of the oxygen concentration, independent of the diffusion situation inside the sensor and the analyte. Different potentiometric sensors for dissolved oxygen have been realized based on sodium tungsten bronzes [ 6 , 7 ], antimony [ 8 ], copper [ 9 , 10 ], cobalt [ 11 , 12 ], and ruthenium oxide [ 13 ] as material for the indicator electrode. Among them, most promising is the usage of copper and cobalt electrodes because of their applicability in neutral pH media and up to air-saturated oxygen concentrations as well as the availability of these metals in microfabrication technology.…”

Potentiometric Detection of Oxygen Based on the Mixed Potential of Zinc

“…As shown in Figure 3, for sufficiently noble metal electrodes (such as copper in [8]) both the rates of metal oxidation and of oxygen reduction can exhibit potential dependences (curves on the right of the Fig. 3).…”

“…Recently, however, there has been an increase in interest in developing reliable potentiometric sensors for room-temperature aqueous-phase measurements, based not on the reversible oxygen potential but rather on the mixed potential resulting from metallic corrosion and simultaneous oxygen reduction. Several rather noble metals, including palladium [6] and cobalt-polyamine complexes on platinum [7] have been tested and show oxygen sensitivity, but the most promising results are those of Meruva and Meyerhoff on copper-film electrodes [8] and metallic cobalt wires [9].…”

“…The aim of the present study is to examine the performance of a system similar to that proposed in [8], but with the copper-film electrode replaced by zinc. Contrary to copper sensors, whose response may depend on interfacial oxygen-reduction kinetics, the mixed potential of a less-noble metal, such as zinc, should be fixed by diffusion-limited oxygen reduction, thereby offering the simplicity and reliability of Clark-type sensors, but in a potentiometric configuration.…”

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

“…Examples include water and soil samples [ 7 , 13 , 14 , 15 , 16 , 17 , 18 ], blood and blood products [ 19 , 20 , 21 , 22 ], milk [ 23 ], tea fermentation [ 24 ], fish [ 25 , 26 ], and cheese making [ 27 ]. Under certain conditions, the direct potentiometric determination of small molecules and ions such as hydrogen peroxide [ 28 , 29 ], oxygen [ 30 , 31 ], phosphate [ 32 ], and ascorbate [ 33 , 34 ] can be achieved using different metal electrodes and/or polymer coatings to enhance specificity and sensitivity. In more recent work, gold gate field-effect transistor (FET) based sensors for biomolecules have also been reported [ 35 , 36 ].…”