Silicon nanowire sensors for Hg2+ and Cd2+ ions

High-sensitivity detection of toxic heavy metal cations such as Hg ²⁺ and Cd²⁺ ions was demonstrated using single silicon nanowire field-effect transistors (SiNW-FETs). The conduct-ance of FET fabricated from thermally oxidized SiNWs functionalized with 3-mercaptopropyltriethoxysilane showed high sensitivity to Hg²⁺ and Cd²⁺ ions at a concentration down to 10-7 and 10-4 M, respectively. Linear relationship between the logarithmic concentration of metal ions and the current change was observed. The SiNW sensor could be recycled to regain nearly the same sensitivity. Comparative experiments showed that SiNW-FET sensors have great selectivity for detecting Hg²⁺ and Cd²⁺ over other metal cations. © 2009 American Institute of Physics.