A hydrogel modified electrode for application as a voltammetric temperature sensor and its use in oxygen detection

Abstract

We report a hydrogel modified electrode based voltammetric “thermometer” and its application in amperometric oxygen detection so avoiding the need for external temperature monitoring to allow the rigorous measurement of oxygen concentrations. A platinum electrode was modified with a layer of agarose hydrogel containing decamethylferrocene (DmFc) and bisferrocene (BisFc) and a layer of pure ionic liquid containing no ferrocenes as solvent. The differences of the formal potentials between these redox couples were measured using square wave voltammetry and a linear increase of peak separations with temperature was observed so providing a basis for measuring temperature. This system was then applied to the analysis of dry oxygen. The temperature was monitored either by a conventional external thermometer or by the internal voltammetry confined to the agarose hydrogel layer on the electrode surface. The concentration and diffusion coefficient of oxygen were obtained with excellent precision using chronoamperometry over a range of temperatures. Excellent agreement between the two approaches was found showing that the voltammetric redox couples provide a good basis for an in situ “thermometer”.