Support Layer Influencing Sticking Probability: Enhancement of Mercury Sorption Capacity of Gold

Elemental mercury (Hg0) sorption on Au thin films deposited over SiO2 (SiO2:Au) and Ti (Ti:Au) support layer is investigated by quartz crystal microbalance (QCM) technique. The Hg0 sorption capacity of Au thin films is shown to be greatly influenced by the underlying support layer, where an enhancement of 267% was observed for SiO2:Au over Ti:Au films for the same Au film thickness. Furthermore, by increasing the Au film thickness, the total Hg0 captured was observed to increase even though the mercury sorption efficiency (or mass ratio of Hg0 to Au) was observed to decrease for a 8 h Hg0 exposure period. Sticking probability calculations showed that the SiO2:Au substrate maintains a sticking probability of ∼10–6, which is at least 2 orders of magnitude greater than that of the Ti:Au surface, thus indicating that Hg0 sorption capacity of a material can be greatly influenced by the choice of underlying support layer.