  Nature has developed striking light-powered proteins such as
bacteriorhodopsin, which can convert light energy into conformational changes
for biological functions. Such natural machines are a great source of
inspiration for creation of their synthetic analogues. However, synthetic
molecular machines typically operate at the nanometre scale or below.
Translating controlled operation of individual molecular machines to a larger
dimension, for example, to 10-100 nm, which features many practical
applications, is highly important but remains challenging. Here we demonstrate
a light-driven plasmonic nanosystem that can amplify the molecular motion of
azobenzene through the host nanostructure and consequently translate it into
reversible chiroptical function with large amplitude modulation. Light is
exploited as both energy source and information probe. Our plasmonic nanosystem
bears unique features of optical addressability, reversibility and
modulability, which are crucial for developing all-optical molecular devices
with desired functionalities.
