Electronic Detection and Influence of Environmental Factors on Conductivity of Single DNA Molecule Using Single-walled Carbon Nanotube Electrodes

Rapid detection of ultra low concentration or even single DNA molecules are essential for medical diagnosis and treatment, pharmaceutical applications, gene sequencing as well as forensic analysis. In this work we demonstrate the use of single-walled carbon nanotubes as nanoscale electrodes for electronic detection of single DNA molecules. A detailed study on electrical conductivity and influence of environmental factors on a double-stranded DNA molecule bridging a single-walled carbon nanotube (SWNT) gap is presented. The amine terminated DNA molecule was trapped between carboxyl functionalized SWNT electrodes by dielectrophoresis. Typically, a current of tens of picoamperes at 1 V was observed at ambient conditions, with a decrease in conductance of about 30% in high vacuum conditions. As the intrinsic conductivity of the DNA molecule is strongly influenced by environmental factors we study the conductivity of DNA under the influence of counterion variation, salt concentration, and pH. The counterion variation was analyzed by changing the buffer type. A reversible shift in the current signal was observed for pH variation.