Aging of 1,ω-Alkyldithiol Interlinked Au Nanoparticle Networks

To identify the aging processes during long-term storage under different storage conditions, we investigated the composition of films comprising gold nanoparticles interlinked with 1,9-nonanedithiol and 1,16-hexadecanedithiol during a 44 month period using X-ray photoelectron spectroscopy (XPS). Additionally, we compared the initial structure and sensing properties toward toluene, 1-propanol, water, and hydrogen sulfide with the morphology and sensitivity after storage. Films stored under ambient conditions showed oxidation of sulfur and carbon and appearance of nitrogen, a significant loss of sulfur and the formation of larger particles in the film. The chemical selectivity of these films changed toward hydrophilic vapors and they became sensitive toward hydrogen sulfide. This is explained by the reaction of the thiol groups with ozone from the air, which destabilizes the network and significantly influences the particle/organic interface acting as sorption sites for gases. For films stored under argon only, an increase in free thiol groups in conjunction with a structural rearrangement of the film was observed. The selectivity of these films changed slightly toward hydrophilic analytes but they were still insensitive toward hydrogen sulfide.