The analytical technique surface plasmon resonance (SPR) is mainly defined by two classes of plasmonic materials: nanoparticles (mostly nanospheres) and thin films. Both classes exhibit nanometric physical features and present distinct optical characteristics fitting different applications. For instance, nanoparticles are the most sensitive materials but they cannot be deployed in complex media such biofluids (e.g., blood, serum, urine) for SPR measurements as the media will generate optical interferences.
Although less sensitive, thin films address all the complex media issue in addition to be easier to manufacture for large scale deployment in industry applications. Effort to combine the strength of both plasmonic materials into a single one have been driven by researchers. Most successful efforts started from the thin film end of the spectrum and moved towards integrating nanoparticle features to thin films.