High-performance Nanocavities-based Meta-crystals for Enhanced Plasmonic Sensing

We report on a novel procedure of fabrication to easily obtain highly reproducible nanocavities-shaped photonic crystals with strong plasmonic performances. Thus, we also report on the morphological and optical characterization of the obtained structures. They are classifiable as 2-layers (organic and inorganic) photonic crystals based on iso-Y-shaped nano-cavities. Such novel designed structures are compelling candidates for the development of highly sensitive biosensors due to their unique surface plasmon resonances (SPRs) and SPR enabled surface-enhanced Raman spectroscopy (SERS). The planar photonic crystal comprises a polymeric (ZEP520A) layer (thickness ~80 nm) sandwiched between a layer of gold (~50 nm thickness) and a glass substrate. For what concerns the cavities’ shape, iso-Y units are chosen on the basis of their third order nonlinearity and are coupled in hexagonal-based configuration to produce extended meta-structures. The substrates are functionalized with a probe made by a self-assembling monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA). The average SERS Enhancement Factor >106 and SPR sensitivity of ~300 nm/RIU confirm that the proposed 2-layers iso-Y meta-structure is very suitable for high sensitive label-free plasmonic sensing.