Star-shaped self-assembly of an organic thin film transistor sensor in the presence of Cu2+ and CN- ions

Abstract

In this study we developed organic thin film transistors (OTFTs) for the sensing of metal ions and anions through the self-assembly of a pentacene/Schiff base pyrene derivative. Our bilayer OTFTs displayed attractive device parameters: an electron mobility (mu) of 0.12 cm(2) V-1 s(-1), a threshold voltage (Vth) of 22.20 V, and a five-orders-of-magnitude on/off ratio. This device was sensitive toward Cu2+ among 13 metal cations and toward CN among nine anions, as measured through changes in the values of Vth and I-off in the presence of Cu2+ cations and a change in the value of I-sat in the presence of CN anions. We observed selectivity toward both of these ions in mixed ion solutions, with sensitivity over different concentrations (from 20 to 350 mu M for Cu2+; from 100 to 350 mu M for CN ) as well as in sea water. The pyrene derivative self-assembled through pyrene-pyrene coordination in the presence of Cu2+ ions; the rods of the pyrene derivative broke into smaller pieces upon formation of benzoxazole rings in the presence of CN ions, as confirmed using atomic force microscopy and fourier transform attenuated total reflection spectroscopy. (C) 2013 Elsevier B.V. All rights reserved.