Bridging the gap: Rigid DNA linkers (blue, see picture) between microspheres (green) for high‐resolution single‐molecule mechanical experiments were constructed using DNA origami. The resulting DNA helical bundles greatly reduce the noise generated in studies of conformation changes using optical tweezers and were applied to study small DNA secondary structures.
Surface-enhanced vibrational spectroscopy strongly increases the
cross section of Raman scattering and infrared absorption, overcoming
the limited sensitivity and resolution of these two powerful analytic
tools. While surface-enhanced setups with maximum enhancement have
been studied widely in recent years, substrates with reproducible,
uniform enhancement have received less attention although they are
required in many applications. Here, we show that plasmonic supercrystals
are an excellent platform for enhanced spectroscopy because they possess
a high density of hotspots in the electric field. We describe the
near field inside the supercrystal within the framework of plasmon
polaritons that form due to strong light-matter interaction. From
the polariton resonances we predict resonances in the far-field enhancement
for Raman scattering and infrared absorption. We verify our predictions
by measuring the vibrations of polystyrene molecules embedded in supercrystals
of gold nanoparticles. The intensity of surface-enhanced Raman scattering
is uniform within 10% across the crystal with a peak integrated enhancement
of up to 300 and a peak hotspot enhancement of 10
5
. The
supercrystal polaritons induce pairs of incoming and outgoing resonances
in the enhanced cross section as we demonstrate experimentally by
measuring surface-enhanced Raman scattering with multiple laser wavelengths
across the polariton resonance. The infrared absorption of polystyrene
is likewise enhanced inside the supercrystals with a maximum enhancement
of 400%. We show with a coupled oscillator model that the increase
originates from the combined effects of hotspot formation and the
excitation of standing polariton waves. Our work clearly relates the
structural and optical properties of plasmonic supercrystals and shows
that such crystals are excellent hosts and substrates for the uniform
and predictable enhancement of vibrational spectra.
The mechanism of hydrogen gas formation by [FeFe] hydrogenase is probed under whole cell conditions, revealing the formation of reactive metal hydride species under physiologically relevant conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.