Characteristics and Performances of a Nanostructured Material for Passive Samplers of Gaseous Hg

Passive air samplers (PASs) have been used for mapping gaseous mercury concentrationin extensive areas. In this work, an easy-to-use and -prepare gold nanoparticle (NP)-based PAS hasbeen investigated. The PAS is constituted of a microfibrous quartz disk filter impregnated of goldNP photo-growth on TiO2 NPs (Au@TiO2) and used as gaseous mercury adsorbing material. Thedisk was housed in a cylinder glass container and subjected to an axial diffusive sampling. Theadsorbed mercury was measured by thermal desorption using a Tekran® instrument. Differentamounts of Au@TiO2 (ranging between 4.0 and 4.0 × 10-3 mg) were deposited by drop-casting ontothe fibrous substrate and assessed for about 1 year of deployment in outdoor environment with amercury concentration mean of about 1.24 ± 0.32 ng/m3 in order to optimize the adsorbing layer.PASs showed a linear relation of the adsorbed mercury as a function of time with a rate of 18.5 ± 0.4pg/day (?1.5% of the gaseous concentration per day). However, only the PAS with 4 mg ofAu@TiO2, provided with a surface density of about 3.26 × 10-2 mg/mm2 and 50 ?m thick inside thefibrous quartz, kept stability in working, with a constant sampling rate (SR) (0.0138 ± 0.0005m3/day) over an outdoor monitoring experimental campaign of about 1 year. On the other hand,higher sampling rates have been found when PASs were deployed for a few days, making thesetools also effective for one-day monitoring. Furthermore, these PASs were used and re-used aftereach thermal desorption to confirm the chance to reuse such structured layers within theirsamplers, thus supporting the purpose to design inexpensive, compact and portable air pollutantsampling devices, ideal for assessing both personal and environmental exposures. During thewhole deployment, PASs were aided by simultaneous Tekran® measurements.