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  • Nano Express
  • Open Access

A pH sensor based on electric properties of nanotubes on a glass substrate

  • 1Email author,
  • 1,
  • 1,
  • 2,
  • 1,
  • 2 and
  • 1
Nanoscale Research Letters20072:207

  • Received: 28 December 2006
  • Accepted: 5 March 2007
  • Published:


We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface.


  • Carbon nanotube
  • Field effect transistor
  • pH
  • Glass
  • Immobilization




This work was supported by the Japan Securities Scholarship Foundation, the Technology and New Energy and Industrial Technology Development Organization (NEDO), and Special Coordination Funds for Promoting Science.

Authors’ Affiliations

Creative Research Initiative “Sousei”, Hokkaido University, Sapporo 001-0021, Japan
Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan


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© to the authors 2007