Engineered nanopatterned substrates for high-sensitive localized surface plasmon resonance: an assay on biomacromolecules.

In this paper, we report on novel iso-Y-shaped-nanopillar based photonic crystals (PCs) engineered for plasmonic lab-on-a-chip advanced diagnostics. The iso-Y shaped units are selected on the basis of their plasmonic properties, analyzed numerically and experimentally. We show that by accurately choosing the nanopillar shape, dimensions and their geometrical disposal it is possible to obtain efficient optical 2D structures for biomolecule detection by high-sensitive localized surface plasmonic resonance (LSPR). In particular, an assay is realized by using bovine serum albumin (BSA), a widely recognized model for biosystem studies. BSA was simply deposited on a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA) previously grown-up on the plasmonic substrate. We demonstrate that the geometries considered allow the design of LSPR nano-assays working in the visible-NIR region based on both intensity interrogation and the resonance peak shift permitting the sensing of BSA with a limit of detection in the order of picomoles (LOD = 233 pM).