Quantitative and rapid detection of iodide ion via electrolyte-gated IGZO thin-film transistors

In this study, rapid-detection iodide ion sensors based on sol-gel indium-gallium-zinc-oxide electrolyte gated thin-film transistors (IGZO-EGTFTs) have been examined. With a high electrical-double-layer capacitance (6.2 μF/cm2) at the interface between IGZO channel and physiological fluid (i.e., phosphate-buffered saline and artificial urine solution), the EGTFTs can be operated under 0.5 V with a high ON and OFF state current ratio above 108, and transconductance value of 1.14 mS. In addition to excellent electrical characteristics, the novel electrochemical reaction of IGZO-EGTFTs enables high selectivity and linear response over a wide detection range of iodide ions concentration (from 1 to 104 μM), the limit of detection as low as 1 μM, and response time below 0.1 s. The mechanism of iodide ions detection of IGZO-EGTFT was investigated based on electrochemical impedance spectroscopy analysis. We expect that IGZO-EGTFTs will contribute to the development of point-of-care rapid and reusable ion-sensors for human urine and serum.