Elemental mercury vapor chemoresistors employing TIO<inf>2</inf> nanofibers photocatalytically decorated with Au-nanoparticles

Abstract

The toxicity of mercury, its ubiquitous presence and the complexity of its cycle in the environment push for urgent actions at both local and global level to develop detection and monitoring systems characterized by fast responses, low cost, low maintenance and ease of use. As a result of the combination of gold affinity for mercury with the nanoscale size of the frameworks, gold nanostructures look the most promising nanomaterials for creating novel sensors with sensing features comparable to those of commercial complex and expensive analytical systems currently available. Composite nanofibrous electrospun layers of titania decorated with gold nanoparticles (AuNPs) were fabricated to obtain nanostructured materials capable of adsorbing elemental mercury. Linker-free gold nanoparticles were grown on the electrospun titania nanofibers through the photocatalytic reduction of tetrachloroauric acid carried out by UV-irradiated nanofibers of titania in the presence of an organic capping reagent. Chemoresistors employing such decorated nanomaterials were then created in order to detect mercury vapors in the atmosphere. Various decorations of titania nanofibers with gold nanoparticles deposited onto distinct substrates were morphologically investigated at nanoscale. The electrical properties of the resulting chemoresistors were assessed. The capacity of chemoresistors employing various amounts of AuNPs for detecting low concentrations of mercury vapors (tens of ppt) in both static and dynamic (i.e. under a carrier gas flow – synthetic air) conditions was tested. The potential of the resulting sensors in environmental monitoring of elemental mercury vapors is discussed.