Temperature-Controllable Electrodes with a One-Parameter Calibration.

ABSTRACT

Electrically heated electrodes have been applied for various chemical and biological sensors. However, previous electrically heated electrodes, including microwires and microdiscs, are usually small and often suffer from the requirement of frequent calibrations of the electrode surface temperature ( Ts) at different environment temperatures. Here, we fabricate a temperature-controllable disk electrode (TCDE) with a conventional size (3-5 mm in diameter). A one-parameter temperature calibration is proposed using a temperature transfer coefficient α and a structural model ( Ts = Te + α ( Th - Te)) to estimate Ts ( Th and Te are the temperature of the heating element and environment, respectively). The value of α is unique for a TCDE and mainly dependent on the structure and materials of the electrodes and the solution in nature. Once α is experimentally determined, Ts can be calibrated and found to be applicable to wide fluctuations in room temperature (15.0-33.0 °C) with errors below 1.5% for three types of disk electrodes (gold, glassy carbon, and platinum). The required Ts can be obtained by just setting Th without thermal characterization between the heating power and Ts. A simple relationship for exploring the dependence of α on the height ( H) and radius ( R) of the electrode materials and other constants ( a, b, c, and R0), α = 1 - c - aH - b ( R - R0)2, is revealed by numerical simulations (COMSOL). The impact of the radii of both the insulating materials of the electrode and the electrochemical cells on Ts is also considered. The effect of the solution thermal conductivity on α is studied. TCDEs are expected to be used as a sensor platform with enhanced performance.