In a recent paper published in Nanotechnology, researchers from the University of Oklahoma, the University of Illinois at Urbana-Champaign and the University of Arkansas at Little Rock (UALR) reported the fabrication of ultra-sensitive, stable SERS substrates that are promising candidates for the direct detection (label-free) and analysis of various biological and chemical samples.

The team uses a novel route to prepare its SERS substrates, which is based on polymer–metal nanocomposites with a specific structure and composition just below the percolation threshold. The neighboring nanoparticles are still quite densely packed, but remain separated by narrow polymer gaps (<1 nm). Such a nanostructure allows the creation of densely packed hot spots where electromagnetic energy can be confined.

The polymer–metal nanocomposites are fabricated by a simple and single-step method of electron-beam-assisted vapor-phase co-deposition. As shown above, the preparation of the SERS substrates is based on a simple plasma-etching process, which removes the polymer structures that allow the formation of metal nanoparticle SERS nano-aggregates with very uniform and controllable inter-particle gaps. The method results in "ideal SERS hot spots" throughout the matrix. These hot spots can be created over very large areas.

The SERS substrate developed by the researchers has a number of major advantages: it is easy to produce, highly reproducible and cheap. The method could be leveraged to develop large-scale spectroscopic-based advanced detector systems for rapid and quantitative detection and analysis of various biological and chemical samples.

The researchers plan to extend their investigations to prepare robust SERS substrates for detecting viral pathogens, chemical and biological warfare agents and explosives. Their goal is to develop portable SERS modules that take advantage of the capabilities of these advanced nanocomposite films.