Layer-by-layer films containing SiO2 nanoparticles as field-effect pH sensors

Devices for pH monitoring based on separative structures and high input impedance readout circuit were fabricated using silicon dioxide nanoparticles (SiO2-Np). SiO2-Np were self-assembled onto gold substrates via layer-by-layer (LbL) technique using poly(allylamine) hydrochloride (PAH) as the counter-ion. The pH sensing properties of PAH/SiO2-Np LbL films were examined upon buffer solutions from pH 2 to 12, exhibiting pH sensitivity in agreement with other pH sensitivity membranes based on SiO2. The presence of nanoparticles improved the electrode contact area, ideal for enzyme immobilization, suggesting that PAH/SiO2-Np are suitable platforms to be applied in field-effect based biosensors