PH -dependent conductance behaviors of layer-by-layer self-assembled carboxylated carbon nanotube multilayer thin-film sensors

Dongjin Lee, Tianhong Cui

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

The authors report pH -dependent conductance behaviors of single-walled carbon nanotube (SWCNT) multilayer thin-film sensors. SWCNTs are functionalized with carboxylic groups, and layer-by-layer assembled alternatively with polycation, polydiallyldimethyammonium chloride on the microfabricated metal electrodes. Current-voltage (I-V) characteristics show that the conductance of SWCNT multilayer thin-film sensors decreases with increase of pH values. On the other hand, the multilayer resistors with polymethylmethacrylate (PMMA) as a passivation layer demonstrate the increasing conductance with pH, opposite to the case of the absence of PMMA layer. The conductance change in the absence of PMMA attributes to doping/undoping of holes as charge carriers by molecular protonation/deprotonation of p -type semiconducting SWCNTs. With PMMA layer, concentration gradient of hydrogen ions on the dielectric forms the gate bias voltage, which changes the conductance of underlying semiconducting SWCNT layer. Each pH -dependent behavior has versatile applications for chemical and biological detections.

Original languageEnglish (US)
Pages (from-to)842-848
Number of pages7
JournalJournal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume27
Issue number2
DOIs
StatePublished - 2009

Bibliographical note

Funding Information:
This work was partially supported by the DARPA M/NEMS Science and Technology Fundamental Research Program through the Micro/Nano Fluidic Fundamental Focus (MF3) Center. The authors would like to thank the Nanofabrication Center and Characterization Facility at the University of Minnesota for the help with fabrication and characterization.

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