Alkylthiol-functionalized gold nanoparticles for sensing organic vapours: The connection between the adsorption isotherm and the sensor resistance

Gold nanoparticles stabilized with alkylthiols were synthesized and employed as organic vapour sensor. Interdigitated microelectrodes were covered by the functionalized gold nanoparticles and the conductance was detected in different organic vapour pressures. The toluene and carbon tetrachloride molecules adsorbed between the alkyl chains causing the separation of the gold nanoparticles from each other and decreasing in the electronic conductivity in the gold nanoparticles layer on the surface of interdigital microelectrode (IME) sensor. To clarify the connection between the adsorbed amount and the electronic properties of the sensor, adsorption of toluene and carbon tetrachloride on gold/alkylthiol surface was quantitatively characterized by quartz crystal microbalance. The adsorption isotherm was calculated and according to the BET equation the monolayer adsorption capacity was determined. Comparing the adsorption amount of organic vapours with the measured resistance of the sensor, a direct correlation was recognized among them.