Liquid Hydrogenation of Plasmonic Nanoantennas via Alcohol Deprotonation

Yttrium is a metal whose optical properties are tunable by hydrogen incorporation. Commonly, this happens via exposure to hydrogen gas. Here, we demonstrate that the hydrogenation of yttrium is also possible via the deprotonation of alcoholic liquids. Palladium-covered yttrium is placed in an ethanol bath that causes the deprotonation of ethanol and the hydrogenation of yttrium to yttrium dihydride. Proof-of-concept is presented with a study on thin films, which is followed by tuning the optical properties of plasmonic nanoantennas. The liquid hydrogenation causes the plasmonic resonance to shift by more than 300 nm in the near-infrared spectral range. Consequently, we show that our plasmonic nanoantennas serve as a local nanooptical indicator for the deprotonation process. Our findings pave to road toward a (nano)­optical investigation and detection of catalytic processes in liquids without the need of electrical, chemical, or electrochemical read-out.