Detection of chemical agents and biological species using nanostructured materials has shown significant progress, driven by the high demand for superior analytical tools in areas such as environmental monitoring, new drug screening, and disease diagnosis. Various detection techniques have been proposed and demonstrated using a wide variety of nanomaterials. Device fabrication can be categorized into two methods: one is bottom up and the other is top down. Bottom up method normally starts from synthesizing nanowires using chemical vapor deposition (CVD) or laser assisted CVD. Top down approaches do not suffer from such limitation, and they utilize the mature and developed silicon technology. Device functionalization usually starts from depositing a linker molecule onto the sensor surface. The linker molecule then conjugates with the antibody and immobilizes the antibody as the capture probe onto the sensor surface, by a well developed biochemistry process. Many of the biosensing experiments have been carried out with the sensors and molecules submerged in a liquid environment.