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Toward Quantifying the Electrostatic Transduction Mechanism in Carbon Nanotube Molecular Sensors
journal contribution
posted on 2012-09-05, 00:00 authored by Mitchell
B. Lerner, James M. Resczenski, Akshay Amin, Robert R. Johnson, Jonas I. Goldsmith, A. T. Charlie JohnsonDespite the great promise of carbon nanotube field-effect
transistors
(CNT FETs) for applications in chemical and biochemical detection,
a quantitative understanding of sensor responses is lacking. To explore
the role of electrostatics in sensor transduction, experiments were
conducted with a set of highly similar compounds designed to adsorb
onto the CNT FET via a pyrene linker group and take on a set of known
charge states under ambient conditions. Acidic and basic species were
observed to induce threshold voltage shifts of opposite sign, consistent
with gating of the CNT FET by local charges due to protonation or
deprotonation of the pyrene compounds by interfacial water. The magnitude
of the gate voltage shift was controlled by the distance between the
charged group and the CNT. Additionally, functionalization with an
uncharged pyrene compound showed a threshold shift ascribed to its
molecular dipole moment. This work illustrates a method for producing
CNT FETs with controlled values of the turnoff gate voltage, and more
generally, these results will inform the development of quantitative
models for the response of CNT FET chemical and biochemical sensors.