  The chiral state of a molecule plays a crucial role in molecular recognition
and biochemical reactions. Because of this and owing to the fact that most
modern drugs are chiral, the sensitive and reliable detection of the chirality
of molecules is of great interest to drug development. The majority of
naturally occurring biomolecules exhibit circular dichroism (CD) in the
UV-range. Theoretical studies and several experiments have demonstrated that
this UV-CD can be transferred into the plasmonic frequency domain when metal
surfaces and chiral biomolecules are in close proximity. Here, we demonstrate
that the CD transfer effect can be drastically enhanced by placing chiral
molecules, here double-stranded DNA, inside a plasmonic hotspot. By using
different particle types (gold, silver, spheres and rods) and by exploiting the
versatility of DNA origami we were able to systematically study the impact of
varying particle distances on the CD transfer efficiency and to demonstrate CD
transfer over the whole optical spectrum down to the near infrared. For this
purpose, nanorods were also placed upright on our DNA origami sheets, this way
forming strong optical antennas. Theoretical models, demonstrating the
intricate relationships between molecular chirality and achiral electric
fields, support our experimental findings.
