Gas and vapour sensing characteristics of Langmuir-Schaeffer thiol encapsulated gold nanoparticle thin films

Thiol encapsulated gold nanoparticles can be used as sensitive probes of gas and vapour concentrations. The conductivity of a thin film of two or more layers of such nanoparticle arrays can be measured using interdigitated gold electrodes. The conductivity arises as a result of quantum tunnelling between adjacent conductive gold nanoparticle cores via the insulating thiol/air medium between them. It is very sensitive to small changes in the inter-nanoparticle separation and/or the permittivity of the medium between the gold cores.The conductivity of Langmuir-Schaeffer films of gold nanoparticles functionalised with 4-methylbenzenethiol, 1-hexanethiol and 1-dodecanethiol has been examined. The response of the films to NO2 gas and toluene vapour has been measured, as well as their recovery after exposure and longer term degradation after repeated exposure of the films. The film I–V characteristics were also measured at 22–110 °C showing semiconductor-like characteristics at low temperatures.