Chemical Detection of H2 Gas

We have, in collaboration with the group of Dr. Eric Borguet (Chemistry Dept., Temple University), demonstrated the optical detection of H₂ using substrate-immobilized Au nanoparticles. Prior to the discovery, plasmonic sensing modes for H₂ were indirect in that they required the Au nanoparticle to be in close proximity to Pd; detection occurs because the uptake of hydrogen by Pd triggers changes to the dielectric environment of the Au nanoparticle which results in a shift of a localized surface plasmon resonance (LSPR). Our discovery demonstrated that the hot electron-induced photocatalytic activity of standalone substrate-based Au nanoparticles was sufficient to enable the rapid (< 1 s) detection of H₂. Detection was possible by merely measuring changes to the transmission of light from an incandescent bulb which was filtered to become resonant with the LSPR. The surfactant-free nature of the nanoparticle synthesis is important to the detection mode in that it allows for intimate contact between the H₂ molecules and the Au nanoparticle and eliminates unwanted reductions to the hot electron lifetimes caused by surfactants. Further benefit was derived from the near-hemispherical shape exhibited by substrate-immobilized nanostructures formed through solid state dewetting since such structures give rise to strong plasmonic near-fields at the nanostructure-substrate interface.

Real-time monitoring of the transmitted light through substrate-based Au nanoparticles during the on/off cycling of H₂. Plasmonic near-fields for a spherical and hemispherical Au nanostructure.