A role of silica nanoparticles in layer-by-layer self-assembled carbon nanotube and In_2O_3 nanoparticle thin-film pH sensors: Tunable sensitivity and linearity

摘要

A role of the dielectric silica nanoparticle (SiO_2 NP) in nanomaterial chemoresistors and ion-sensitive field-effect transistors (ISFET) is demonstrated in this study. Single-walled carbon nanotubes (SWCNT) and indium oxide nanoparticles (In_2O_3 NP) are layer-by-layer self-assembled alternately with oppositely charged polyelectrolytes, respectively. Nanomaterial multilayer thin-film is patterned using photolithography and electrochemically characterized in various pH buffers. The pH sensors are implemented as resistor and transistor in absence and presence of SiO_2 NP layer. We observed tunable sensitivity and linearity of output current flowing through the conducting channel in SWCNT chemoresistor and ISFET. The role of SiO_2 NP is proven to modulate and linearize the sensitivity to pH. The linearization is attributed to a positive shift in pH gating voltage in p-type semiconducting SWCNTs. On the other hand, a tunable sensitivity is observed whereas the linearization is not demonstrated in In 2O_3 NP ISFETs. The increased sensitivity with SiO _2 NP in acidic region is caused by a positive shift in gate voltage due to the protonation of the surface hydroxyl groups. This facile modulation and linearization of the electrochemical sensitivity in semiconducting nanomaterial thin-film device by means of the additional SiO_2 NP layer is useful for developing various functional nanomaterial-based biosensors.