Nano-assembled nanoparticle/polymer based field-effect transistors and their biosensing applications

The layer-by-layer nanoassembly technique is becoming a popular method for the synthesis of nanocomposite thin films and has attracted widespread interest. The process is low-cost, environmentally friendly, versatile, and can easily control the surface properties of existing objects and devices. Novel materials, e.g. nanoparticles and polymers, can be synthesized into multilayer films by this method. Since nanoparticles and polymers have better biocompatibility than silicon, the nanoparticle/polymer based biosensors can provide better performance than their silicon counterpart.; In this work, field-effect transistors based on layer-by-layer self-assembled nanoparticle/polymer thin films have been successfully fabricated and characterized. Some field-effect transistors use self-assembled indium oxide (In2O 3) nanoparticle thin films as the channel and silicon dioxide (SiO 2) nanoparticle thin films as the gate dielectric, while others use self-assembled polyaniline (PANI) polymer thin films as the channel and SiO 2 nanoparticle thin films as the gate dielectric. The In2O 3 nanoparticle transistor has a mobility of 4.24x10-3 cm2/Vs at microscale channel length, and a mobility of 0.928 cm2/Vs at nanoscale channel length. The PANI polymer transistor has a mobility of 2.01 X10-4 cm2/Vs at microscale channel length.; The layer-by-layer self-assembled nanoparticle/polymer thin films have been further applied to the fabrication of ion-sensitive field-effect transistors (ISFETs) as biosensors. The nanoparticle/polymer ISFETs can function effectively as biosensors to detect the acetylcholine concentrations. For the In 2O3 nanoparticle ISFET based acetylcholine biosensor, the mobility is 43.10 cm2/Vs when the ISFET in an acetylcholine solution of 10 mM, and the resolution is 100 nM. For the PANI ISFET acetylcholine biosensor, the mobility is 11.23 cm2/Vs when the transistor is in an acetylcholine solution of 10 mM, and the resolution is also 100 nM. The nanoparticle/polymer ISFETs can also effectively detect the glucose concentration. The In 2O3 nanoparticle ISFET based glucose biosensor has a mobility of 38.66 cm2/Vs in a glucose solution of 10 mM, and a sensitivity of 2.125 muA/mM. The PANI polymer ISFET based glucose biosensors has a mobility of 14.31 cm2/Vs in a glucose solution of 10 mM, and a sensitivity of 0.738 muA/mM. Compared with the published silicon transistor based biosensors, our nanoparticle/polymer transistor based biosensors have the advantages of lower cost and better performance.