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

Elemental mercury (Hg<sup>0</sup>) sorption on Au thin films deposited over SiO<sub>2</sub> (SiO<sub>2</sub>:Au) and Ti (Ti:Au) support layer is investigated by quartz crystal microbalance (QCM) technique. The Hg<sup>0</sup> 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 SiO<sub>2</sub>:Au over Ti:Au films for the same Au film thickness. Furthermore, by increasing the Au film thickness, the total Hg<sup>0</sup> captured was observed to increase even though the mercury sorption efficiency (or mass ratio of Hg<sup>0</sup> to Au) was observed to decrease for a 8 h Hg<sup>0</sup> exposure period. Sticking probability calculations showed that the SiO<sub>2</sub>:Au substrate maintains a sticking probability of ∼10<sup>–6</sup>, which is at least 2 orders of magnitude greater than that of the Ti:Au surface, thus indicating that Hg<sup>0</sup> sorption capacity of a material can be greatly influenced by the choice of underlying support layer.