Vapour sensing using surface functionalized gold nanoparticles

The electrical and optical response of thin films of surface functionalized nanoparticles upon exposure to various chemical vapours has been studied. It was found that the electrical response to chemical vapours adsorbed on the various nanoparticle films varied markedly and was determined by the surface functional groups. Ellipsometric studies revealed that the film thickness increased during exposure to the chemical vapours. These thickness changes of the films correlate with the changes in electrical conductivity. Two physical effects are believed to play a role in determining these conductivity changes. Under high partial pressure, the change in nanoparticle core-core separation is the main contribution to the change in conductivity and generally leads to a reduction in the conductivity. However, for relatively low partial pressures the adsorption of vapour molecules leads to permittivity changes that tend to increase the conductivity.