Micro Solid-Contact Ion-Selective Electrode Using a Carbon Nanotube Tower as Ion-to-Electron Transducer and Conductive Substrate

Solid contact (SC) ion-selective electrodes (ISEs) have been recognized as the next generation of ISEs. In this work, the electrical conductivity and mechanical strength of a carbon nanotube (CNT) tower enable it to play the dual roles of transducer and substrate for micro SC-ISEs. The electrode had a close to Nernstian slope of 35 mV/decade a(Ca2+), a linear range of four orders of magnitude of calcium ion activity (10(-5.6) to 10(-1.8) M), and a detection limit of 1.6x10(-6) M. The simplified fabrication by a one-step drop casting makes miniaturizing SC-ISEs and fabricating sensor arrays easier to achieve.