Monitoring pH with organic-based field-effect transistors

In this paper we propose a simple device and a method for pH monitoring, using an organic thin-film transistor as transducer. Such organic transducers may show potential advantages for sensor technology in terms of fabrication cost and biocompatibility. To explore the applicability of organic transistors in the area of bioanalytics, we have realized a proton sensitive organic transistor and an analogue interface that takes into account the particularities of the transistor in order to illustrate the pH response. The detection principle is based on the field-enhanced conductivity of the poly(3-hexylthiophene) semiconducting polymer. The device was characterized electrically in different pH buffers. To display directly the pH response, the detector was connected to a specially developed low-noise, low-power amplifier system. The device concept, electrical characteristics, pH sensitivity and stability are discussed.