Synthesis of SERS-active substrates by pulsed laser ablation

Since the observation of the anomalous intensification of the Raman signal from pyridine molecules adsorbed on a rough metal surface [1] and the successive explanation of the phenomenon as the amplification of the Raman scattering cross section due to the presence of a nanostructured metal surface [2, 3], the research in this field grew rapidly and it is still growing as witnessed by about 2000 of papers published in this field just considering the year 2012. Two enhancement mechanisms of different origin were proposed to account for the observed giant amplification of the Raman signal: an electromagnetic and a chemical one [4, 5]. In the electromagnetic mechanism, the enhancement results from the coupling of the incident electromagnetic field with artificially metallic corrugated surface, in the chemical one, electronic states generated by the interaction between the metal and the molecules adsorbed on it are involved. In fact the order of magnitude of the resulting enhancements is very different: theoretical estimates for the enhancement factors point out for values up to 1010 [6, 7] for the electromagnetic and up to 103 for the chemical one [8]. Both mechanisms are still at the focus of intense research activity to clarify the physical basis underlying the phenomenon. © 2016 by Taylor & Francis Group, LLC.