ZnO nanorod/wire is a nanomaterial that possessing high surface area to volume ratio and excellent optical and electrical properties, indicating its promising sensing capabilities in various applications. Here, we present the research work of ZnO nanorod/wire based sensors carried out in our lab, which were used in the optical, electrical and mechanical sensing areas, respectively. In optical sensing, a ZnO nanorod array was fabricated at the endface of an optical fiber, forming a sensing probe, whose interference spectrum shifts upon the exposure to gas analyte. In electrical sensing, the ZnO nanowires decorated extended-gate field-effect transistor was used as a pH sensor, whose source-drain current changed dramatically under different pH values when applying the same gate voltage. Finally, regarding to the mechanical sensing, the ZnO nanorods were applied to the surface of the solidly mounted resonator for gas detecting, whose resonant frequency shifts due to the absorption of gas analytes.
We proposed a ZnO nanorod array based optical sensor for highly sensitive refractive index (RI) detection. The sensor was fabricated by sequentially growing a seed layer and ZnO nanorod array at the endface of an optical fiber. The light coupled into the optical fiber is partially reflected at the seed layer and nanorod arry-air interface, respectively, generating an interference spectrum. When the RI of the media filled among the ZnO nanorods changes, the light path between the two reflective surfaces changes, resulting in the shift of the interference spectrum. Therefore, by monitoring the interference shift, it is able to detect the RI change. The advantages of the sensor are that 1) small size and low cost; 2) easy access to analytes and integration with micro-fluidic system; 3) easy fabrication; 4) highly sensitive. Experiments demonstrated that the proposed sensor can detect the RI change caused by exposing it to various vapor-phase analytes, leading to a potential capability of gas sensing.