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Open Access Nano Express

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

Seiji Takeda1*, Motonori Nakamura1, Atsushi Ishii1, Agus Subagyo2, Hirotaka Hosoi1, Kazuhisa Sueoka2 and Koichi Mukasa1

Author Affiliations

1 Creative Research Initiative “Sousei”, Hokkaido University, Sapporo, 001-0021, Japan

2 Graduate School of Information Science and Technology, Hokkaido University, Sapporo, 060-0814, Japan

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Nanoscale Research Letters 2007, 2:207-212  doi:10.1007/s11671-007-9053-9

Published: 30 March 2007

Abstract

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.

Keywords:
Carbon nanotube; Field effect transistor; pH; Glass; Immobilization