There’s something in the water — Aquatically-derived food supplies often contain the water-soluble mercuric ion (Hg²⁺), which is toxic to humans.

Kim et al, KAIST, Korea, report an ultrasensitive and selective single gold nanowire-on-film (SNOF) surface-enhanced resonance Raman scattering sensor (SERS) for Hg²⁺ detection. The sensor is based on structure-switching double stranded DNAs; when Hg²⁺ is bound, a conformational change occurs enabling a Raman reporter to get close to the single gold nanowire-on film structure and turn on the signal.

The SNOF sensor has a detection limit of 100 pM, about 50 times lower than previously reported nucleic-acid-based Hg²⁺ SERS sensors. The sensor also exhibited good reproducibility, high selectivity, long-term stability, and reusability.

Development of a multiplex sensor of various ions may also be possible by combining nanowires modified by multiple types of nucleic-acid-binding macromolecules.

Image: (c) Wiley-VCH

• Au Nanowire-on-Film SERRS Sensor for Ultrasensitive Hg²⁺ detection
  T. Kang, S. M. Yoo, I. Yoon, S. Lee, J. Choo, S. Y. Lee and B. Kim
  Chem. Eur. J. 2011.
  DOI: 10.1002/chem.201001663