Plasmonic nanoantennas for multispectral surface-enhanced spectroscopies

Plasmonic nanoantennas provide new routes for efficiently detecting, analyzing, and monitoring single biomolecules via fluorescence, Raman, and infrared absorption spectroscopies. The development of efficient biosensors for multispectral spectroscopy remains nevertheless limited by the narrowband responses of plasmonic devices, as they are generally designed to operate in a specific bandwidth, matching with the absorption, scattering, or emission frequency of target biomolecules under investigation. Therefore, performing biosensing from visible to infrared frequencies systematically requires designing and fabricating multiple plasmonic nanoantenna configurations and prevents the development of nanoscale integrated sensors for multispectral probing of random chemical species. Here, we propose to overcome these limitations by using broadband log-periodic nanoantennas designed to generate significant electromagnetic intensity enhancements from the visible to the mid-IR wavelength regions. We demonstrate simultaneous surface-enhanced fluorescence, Raman, and infrared absorption spectroscopies for biomolecules functionalized on top of single nanoantennas, which opens new opportunities for the development of integrated devices suitable for multispectral biosensing on the same chip.