Engineering SERS-active substrates: design and characterization of advanced structures

We investigated the creation of SERS-active hierarchical substrates based on self-assembled nanospheres (HSNs). We demonstrate how the "hierarchical" approach could be systematically exploited to extend the SERS hotspots into the third dimension, by enhancing the hot-spots spatial density and intensity. The proposed hierarchical substrates take advantage of the single layer hexagonal closed packed array nanospheres (CPA). An additional layer of upper nanospheres to obtain dense and intense hot spots pattern is employed. To predict the SERS performance and to identify the promising architectures, a numerical analysis is carried out, offering design criteria, an overview of the operating mechanisms and conditions that affect the SERS behavior of substrates. We fabricated HSNs by using a self-assembling approach and the preliminary results reported. The results highlight that HSNs can be used as cost-effective SERS substrates with better performance than simpler single-layer CPA configurations.