Adv. Mater.http://dx.doi.org/10.1002/adma.201101976 (2011)

Monitoring gas concentrations is crucial for many processes, for example to ensure efficiency as well as safety of catalytic processes. The use of plasmonic nanostructures, where the presence of gas molecules leads to changes in optical properties, has already enabled sensing on the nanoscale and with single-molecule precision. Timur Shegai and Christoph Langhammer have now implemented a nanofabrication strategy for tunable plasmonic nanostructures suitable for hydrogen monitoring in ultrasmall volumes. Using a single-step lithographic approach, they fabricated truncated gold nanocones, followed by the deposition of an insulating spacer layer and a palladium layer on top of the cones. Palladium readily absorbs hydrogen in its crystal lattice, which alters the plasmon resonance of the palladium, an effect that is further enhanced by the gold nanocones. In this way, small changes in hydrogen pressure can readily be detected, with the benefit that only a single nanocone device needs to be used. Moreover, through the use of other metals a broad range of catalytic processes could be monitored on the nanoscale.