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. Author manuscript; available in PMC: 2011 Feb 10.
Published in final edited form as: Nano Lett. 2010 Feb 10;10(2):547. doi: 10.1021/nl9034219

Figure 3.

Figure 3

Sensing PSA/antibody conjugations by NW FET sensor: linear vs. subthreshold regime. (a) Schematic of PSA/PSA-Ab binding/unbinding equilibrium system. PSA-antibody molecules are first linked to nanowire surface. When there are PSA molecules present in sample solution, some antibody sites will be occupied by PSA. The binding of charged PSA molecules induces field gating effect which changes the device conductance. (b) Conductance vs. time data at electrolyte gate voltage Vg = 0, 0.15 and 0.45V when 15 pM PSA sample and buffer solution were sequentially delivered. The increased conductance between arrows was caused by binding of negatively charged PSA molecules on the p-type NW surface. (c) (Top panel) The absolute conductance change ΔG and relative conductance change ΔG/G vs Vg for sensing of 15 pM PSA. (Bottom panel) signal/noise ratio as a function of Vg for sensing 15pM PSA, which peaks at Vg = 0.45 V in the subthreshold regime before complete depletion of NW. (d) Electrolyte gating performance of this NW device with G in linear (left) or log (right) scale.