Biochemical Sensors: Comparison of the Performance of TiO2, SnO2:F and ITO Used as the Main Sensing Element

Nanostructured oxide materials have been widely studied for use in sensors. Titanium dioxide (TiO2) is a material with a large range of applications, such as biosensors, gas sensors and photovoltaic cells, due to its biocompatibility, photo-stability and high refractive index [1] . Other oxide materials have also been investigated. This work presents the study of several oxides thin films, such as titanium dioxide, fluorine-doped tin oxide (FTO) and indium tin oxide (ITO), used as the sensitive extended gate for a field effect transistors (EGFET), with a final purpose to construct a biosensor. The EGFET device is compose by a sensitive electrode as an extended gate that is immersed on a solution, connected on a commercial MOSFET [2] . This apparatus can be used as several different biosensors, depending on the functionalization of the oxide surface with the enzyme of interest. For instance pH and urea were studied to be detected and quantified, and comparison with the three oxide thin films was made with the intention to construct a biosensor with a high sensitivity, high selectivity and fast response. Different techniques for oxide thin films preparation were used, such as sputtering, anodic oxidation and sol-gel dipcoating. TiO2 samples prepared by sputtering and anodic oxidation presented pH sensitivities about 34.4mV/pH and 43.6 mV/pH, respectively, as shown in figure 1, for measurements performed in buffer solutions with a pH range from 2 to 12. 2 4 6 8 1 0 1 2 -0 .0 5 0 .0 0 0 .0 5 0 .1 0 0 .1 5 0 .2 0 0 .2 5 0 .3 0 0 .3 5