An Extended-Gate Field-Effect Transistor With Low-Temperature Hydrothermally Synthesized $\hbox {SnO}_{2}$ Nanorods as pH Sensor

An extended-gate field-effect transistor (EGFET) with low-temperature hydrothermally synthesized SnO₂ nanorods as the pH sensor was demonstrated for the first time. The SnO₂ nanorod sensor exhibited the higher sensitivity of 55.18 mV/pH and larger linearity of 0.9952 in the wide sensing range of pH 1-13 with respect to the thin-film one. The nearly 15% sensitivity enhancement for such a sensor was attributed to the high surface-to-volume ratio of the nanorod structure, reflecting larger effective sensing areas. The characteristics of the output voltage versus sensing time also indicated good reliability and durability for the SnO₂ nanorod sensor. Furthermore, the hysteresis was only 3.69 mV after the solution was changed as pH7 → pH3 → pH7 → pH11 → pH7.