SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

Nanostructured Au and Ag thin films were ob- tained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other depo- sition parameters such as target to substrate distance, in- cidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10- 100 Pa) and on the laser pulse number (500 - 3x10 4 ). The control of these two parameters allows tailoring the mor- phology and correspondingly the optical properties of the films. The position and width of the surface plasmon reso- nance peak, in fact, can be varied with continuity. The films showed remarkable surface enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer sized area of both sil- ver and gold substrates. Selected dyes of interest in cultural heritage studies (alizarin, purpurin) have been also consid- ered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.