The proposed technology deals with the development of active SERS (Surface Enhanced Raman Scattering) substrates ad hoc designed for diagnostics of cultural heritage. The substrates are prepared starting from common commercial 'polishing film' sheets (lapping optical fibers) showing an intrinsic roughness (48- 1000 nm) that favors the SERS effect. A pattern of silver or gold nanoparticles are deposited on these films through Pulsed Laser Deposition (PLD). PLD is a technique of growth of materials in the form of thin films where a high-power pulsed laser is focused on a target (Au/Ag) giving arise to the evaporation of a portion of the material in a controlled Argon atmosphere. The presence of the gas induces the formation of clusters and nanoparticles that are collected on the surface of the substrates positioned in front of the target itself. The morphology of the so formed nanostructures can be tuned changing some key parameters during the deposition phase.The procedure allow us to obtain a non-invasive 'sampler' easy to handle, low cost, of immediate use and able to capture single grain of material to be analyzed.
The main limitation working with cultural heritage consists in the difficulty to sampling even if in micro quantities. The technology here presented, based on the SERS technique, allows to overcome this problem, in fact simply swabbing the surface with the substrate it's possible to obtain a sample to analyze it in the laboratory. An innovative aspect is represented by the methodology used for the realization of substrates, PLD, a physical technique and therefore without any chemical residue, compared to traditional methods (e.g. Lee and Meisel). In addition, the intrinsic roughness of the substrates favors the collection of pigment single grains from the surface to be analyzed, the SERS effect is enhanced and the fluorescence phenomen, that often affect the Raman spectra of organic substances, is reduced. The substrates are characterized by high reproducibility, flexibility, portability and low cost. Different functionalization design are under consideration to make SERS substrates more specific and to expand the field of application.