Nanopits based novel hybrid plasmonic nanosensor fabricated by a facile nanofabrication technique for biosensing

Hybrid plasmonic nanosensors that harness the benefits of both localized and propagating surface plasmons are progressing toward practical real-life applications in point-of-care diagnosis. Here, we demonstrate a novel hybrid plasmonic nanosensor composed of random nanopits in Ag thin film prepared using a simple, single-step, and cost-effective nanofabrication technique. The nanopits are asymmetric in shape with trench-shaped sharp bottom and possess high aspect ratios. Morphology of the nanopits is significantly distinct from other look-alike nanostructures such as nanowells, nanoslits and nanotrenches. The high bulk sensitivity (1292 nm/RIU) of the nanosensor and lowest detectable surface concentration of BSA molecules (0.59-1.1 ng mm^-2) are better than many of the contemporary nanosensors that include nanowells and nanovoids. We postulate the better sensing performance to result from the Fano-type resonances and unique morphology of hotspots in nanopits.