Highly-sensitive full-scale organic pH sensor using thin-film transistor topology

Here, we demonstrated a highly sensitive pH sensor using organic thin-film as the sensing layer. It works as a low-voltage operated ion-sensitive organic thin-film transistor incorporating analyte drop as gate dielectric for which pH needs to be measured as the gate dielectric. The analytes of varying pH were prepared in an aqueous medium and used as gate dielectric to an OTFT with bottom-contact top-gated (BCTG) configuration operated at voltages below 1.0 V. It effectively senses pH values ranging from 3 to 12 with a dual sensitivity of about 1.2 mu A/ pH and 53 mV/pH with a response speed of a few milliseconds. Therefore, this depicts rapid, calibration-free, and stable performance over a period of 300 s without any signs of degradation. Our device also shows a slow degradation rate of-2.2 mV/h at neutral pH for three days. Hence, the results obtained in this report alter the concept of cheaper and eco-friendly broad-range organic pH sensor design.