Single nanowire devices were fabricated by electrochemical deposition followed by in situ etching of Au_0.18Ag_0.82 alloy nanowires in dilute nitric acid. The gold is etched from the alloy leaving an interconnected network of gold ligaments with feature sizes of about 10 nm (Fig. 1).

Fig. 1. SEM image of the cross section of a nanoporous gold nanowire.

Adsorption of a monolayer of octadecanethiol (ODT) onto the nanoporous gold nanowire results in a resistance change of about 3% as shown in the inset of Fig 2. The initial resistance of the nanowire is 236 Ohms and each aliquot results in a 1 Ohm increase in the resistance. The sensitivity factor of 1.0 x 10^-16 cm^2 is comparable to values reported for adsorption at ultrathin films. These results show that the single NPG nanowire devices have sensitivities comparable to relatively large area thin films.

Fig. 2. Normalized resistance change vs. the surface concentration of ODT. The inset shows the resistance for a single NPG nanowire device; the arrows indicate the injection of aliquots of 5 x 10^-11 moles ODT.