Electrochemical-to-Optical Signal Transduction for Ion-Selective Electrodes with Light-Emitting Diodes.

Optical ion sensors normally have a relative narrow sensitive detection window. Here, based on multicolor light-emitting diodes (LEDs), we report on an electrochemical-to-optical signal transduction scheme under chronoamperometry control to convert the potentiometric response of ion-selective electrodes (ISEs) to optical output with tunable sensitivity and much wider response range. The sensing principle was demonstrated on K, Ca, and Pb. LED light intensity was found to depend linearly on the concentration of monovalent ions. Optical signals could be captured with photomultiplier tubes or digital cameras, and a visual alarming system to monitor abnormal ion concentration was also developed from super-Nernstian electrodes.