  Chirality is a highly important topic in modern chemistry, given the
dramatically different pharmacological effects that enantiomers can have on the
body. Chirality of natural molecules can be controlled by reconfiguration of
molecular structures through external stimuli. Despite the rapid progress in
plasmonics, active regulation of plasmonic chirality, particularly in the
visible spectral range, still faces significant challenges. In this Letter, we
demonstrate a new class of hybrid plasmonic metamolecules composed of magnesium
and gold nanoparticles. The plasmonic chirality from such plasmonic
metamolecules can be dynamically controlled by hydrogen in real time without
introducing macroscopic structural reconfiguration. We experimentally
investigate the switching dynamics of the hydrogen-regulated chiroptical
response in the visible spectral range using circular dichroism spectroscopy.
In addition, energy dispersive X-ray spectroscopy is used to examine the
morphology changes of the magnesium particles through hydrogenation and
dehydrogenation processes. Our study can enable plasmonic chiral platforms for
a variety of gas detection schemes by exploiting the high sensitivity of
circular dichroism spectroscopy.
