A highly porous and conductive composite gate electrode for OTFT sensors

Ionic/protonic to electronic transducers based on organic thin film transistors have shown great promise for applications in bioelectronic interface devices and biosensors, and development of materials that exhibit mixed ionic/electronic conduction are an essential part of these devices. In this work, we investigated the proton sensing properties of an all solid-state and low voltage operating organic thin film transistor (OTFT) that uses the organic mixed conductor poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) as the gate electrode. To address the limited sensitivity due to the lack of porosity in PEDOT:PSS base sensors, we proposed a composite gate electrode material composed of PEDOT:PSS and proton conducting mesoporous SO₃H-Si-MCM-41 nanoparticles for improved proton sensitivity. The composite gate electrode doubles the proton sensitivity of the OTFT, indicating a clear advantage of adding SO₃H-Si-MCM-41 in the PEDOT:PSS gate. Moreover, the OTFTs with the composite gate electrode maintained OTFT characteristics similar to that of the PEDOT:PSS gated OTFT. A detailed and systematic study of the effect of variation in the composition of PEDOT:PSS:SO₃H-Si-MCM-41 on OTFT characteristics and sensing properties is carried out. Our results open up the possibility of combining inorganic nanomaterials with organic conductors in the development of highly efficient bioelectronic sensing platforms.