Ion-sensitive field-effect transistor based pH sensors using nano self-assembled polyelectrolyte/nanoparticle multilayer films

This paper demonstrates the fabrication and characterization of a pH sensor based on a layer-by-layer (LBL) self-assembly technique. This pH sensor is based on an ion-sensitive field-effect transistor (ISFET). Two types of self-assembled polyelectrolyte/nanoparticle multilayer films work as the critical components for the transistor. One multilayer film embedded with nanoparticles is PSS/In₂O₃ which operates as the channel, and the other multilayer film is PDDA/SiO₂ which serves as the gate dielectric. The mobility of the ISFET is 35.68 cm²/V s at room temperature. The drain current decreases distinctly with increasing pH values in a solution. The temperature effect on the mobility of the ISFET is also investigated in this research. Results show increasing temperature can greatly enhance the carrier mobility. The results introduce a new approach employing a low-cost layer-by-layer nano self-assembly technique to fabricate pH sensors with a high sensitivity and a good reproducibility.