The local atomic structure and chemical nature of newly synthesized silver nanoparticles (AgNPs) functionalized with the organic thiol allylmercaptane (AM) have been probed combining synchrotron radiation-based techniques: Xray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS). Complementary information about the chemical and electronic structure is obtained combining XAES and XPS data. These results coherently suggest a core shell morphology of the NPs resulting in metallic Ag cores surrounded by Ag2S-like phase. The external layer of AM molecules is grafted to the NPs surface through Ag-S chemical bonds. NP size and composition were found as a function of the chemical synthetic route (i.e., Ag/A.M molar ratio). It was observed that by increasing the Ag/AM ratio, larger AgNPs were obtained. It was found that a higher Ag/AM molar ratio leads to an increasing of the Ag2S layer thickness, while the external AM layer remains unvaried. TEM analysis showed well-separated and dispersed nanoparticles, and ED pattern allowed one to identify two different phases of single crystal corresponding to the presence of Ag face-center-cubic single-crystal symmetry, together with weak diffraction spots in agreement with Ag2S cubic symmetry in Im3m space groups

In vitro and in vivo biological identity of nanoparticles are substantially different.

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Gold nanoparticles stabilized by two novel bifunctional fluorenyl thiols, generated in situ from 9,9-idodecyl-2,7-bis(acetylthio) fluorene (1) and 9,9-didodecyl-2,7-bis(acetylthiophenylethynyl) fluorene (2), exhibit bridged structures which self-assemble in parallel lines. The size, shape and structure of the AuNPs have been determined by means of dynamic light scattering (DLS), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). AuNPs modified with fluorenyl thiol derivatives show diameters in the range of 3-7 nm. The linkage between the nanoparticles can be envisaged with the formation of dyads supported by TEM analysis and XPS measurements. Remarkably, investigation by scanning electron microscopy of the AuNP films revealed an ordered distribution of well-separated individual nanoparticles to form a 2D network. The formation of interconnected networks between AuNPs with different distances, depending on the nature of the thiol linkers (1) or (2), and the photoluminescence properties open perspectives for applications in optical devices and electronics