Biosensing applications
based on fluorescence detection often require
single-molecule sensitivity in the presence of strong background signals.
Plasmonic nanoantennas are particularly suitable for these tasks,
as they can confine and enhance light in volumes far below the diffraction
limit. The recently introduced antenna-in-box (AiB) platforms achieved
high single-molecule detection sensitivity at high fluorophore concentrations
by placing gold nanoantennas in a gold aperture. However, hybrid AiB
platforms with alternative aperture materials such as aluminum promise
superior performance by providing better background screening. Here,
we report on the fabrication and optical characterization of hybrid
AiBs made of gold and aluminum for enhanced single-molecule detection
sensitivity. We computationally optimize the optical properties of
AiBs by controlling their geometry and materials and find that hybrid
nanostructures not only improve signal-to-background ratios but also
provide additional excitation intensity and fluorescence enhancements.
We further establish a two-step electron beam lithography process
to fabricate hybrid material AiB arrays with high reproducibility
and experimentally validate the higher excitation and emission enhancements
of the hybrid nanostructures as compared to their gold counterpart.
We foresee that biosensors based on hybrid AiBs will provide improved
sensitivity beyond the capabilities of current nanophotonic sensors
for a plethora of biosensing applications ranging from multicolor
fluorescence detection to label-free vibrational spectroscopy.