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.