Characterization of Noble Metal Nanoparticles functionalized by molecule-capping method with mixed organic ligands carried out by SR-XPS and SERS

This work is focused on the study of the structural, electronic and morphological properties of Noble Metal Nanoparticles (MNP-s) for innovative applications in nano-medicine and nano-biotechnology.A key point for the... [ view full abstract ]

This work is focused on the study of the structural, electronic and morphological properties of Noble Metal Nanoparticles (MNP-s) for innovative applications in nano-medicine and nano-biotechnology.A key point for the technological development of nano-structured materials and practical biomedical devices based on MNP-s is the achievement of a fine control of the stability and toxicity of the system.The chemical functionalization of the MNP-s can be done by means of capping metallic clusters with appropriate organic ligands.The molecule-capping method provide a reliable control of particle composition, shape and size distribution making the MNP-s suitable for active purposes in catalysis, nanoelectronics, sensing and bioanalysis.In this communication, we present MNP-s (Au and Ag) functionalized with mixed organic ligands (DEA and 3MPS) prepared with different metal/thiol stoichiometric ratios.The molecular overlayer has been selected on purpose for the biomedical applications, as well as to stabilize the nanoparticles.The changes in the stoichiometric ratio between metal and different capping agents can influence the chemical properties of ligands functional groups and the dimension of the functionalized MNP-s.Moreover, the biocompatibility of the system depends strictly on the charge and thickness of capping molecules layer.Therefore, the study of the interaction at the interface between the organic ligand and MNP-s at atomic level is the first step for the fabrication and developing of very suitable nanomaterials for diagnostic and therapy.The characterization of the nano-systems was carried out by means of Synchrotron Radiation induced X-ray Photoelectron Spectroscopy (SR-XPS) and Self Enhanced Raman Spectroscopy (SERS).SR-XPS provides information on the local bonding environment of a given species and it has been demonstrated to be a unique tool for investigating the nature of the interaction at the capping agent/metal nanoparticle interface, as well as the chemical structure of MNPs surface.In SERS, the Raman intensity diffused by molecules close to a nano-curved metallic surface is highly enhanced by the the localized surface plasmon resonance (LSPR), allowing the spectroscopical investigation of molecular monolayers.In conclusion, we compared the semi-quantitative SR-XPS and SERS analysis to obtain a better understanding of the system exploring the potential synergy between different techniques in order to give new insights in the field of nanomaterials.