A chemically-responsive nanojunction within a silver nanowire.

The formation of a nanometer-scale chemically responsive junction (CRJ) within a silver nanowire is described. A silver nanowire was first prepared on glass using the lithographically patterned nanowire electrodeposition method. A 1-5 nm gap was formed in this wire by electromigration. Finally, this gap was reconnected by applying a voltage ramp to the nanowire resulting in the formation of a resistive, ohmic CRJ. Exposure of this CRJ-containing nanowire to ammonia (NH(3)) induced a rapid (<30 s) and reversible resistance change that was as large as ΔR/R(0) = (+)138% in 7% NH(3) and observable down to 500 ppm NH(3). Exposure to water vapor produced a weaker resistance increase of ΔR/R(0,H(2)O) = (+)10-15% (for 2.3% water) while nitrogen dioxide (NO(2)) exposure induced a stronger concentration-normalized resistance decrease of ΔR/R(0,NO(2)) = (-)10-15% (for 500 ppm NO(2)). The proposed mechanism of the resistance response for a CRJ, supported by temperature-dependent measurements of the conductivity for CRJs and density functional theory calculations, is that semiconducting p-type Ag(x)O is formed within the CRJ and the binding of molecules to this Ag(x)O modulates its electrical resistance.