Roberto Matassa

Network assembly of gold nanoparticles linked through fluorenyl dithiol bridges

Gold nanoparticles stabilized by two novel bifunctional fluorenyl thiols, generated in situ from 9,9-didodecyl-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.

A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly.

The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble’s solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans.

Characterization of carbon structures produced by graphene self-assembly

Low-dimensional carbon-based materials, in particular two-dimensional graphenic carbon structures, have been produced from single-walled carbon nanotube disruption using high-shear mixing and/or treatments in sulfonitric acid mixtures at both room and high temperature. Among other two-dimensional graphenic carbon structures, colloidal dispersions of graphenic nanoflakes have been obtained. Different structural arrangements, resulting from the reorganization of carbon because of the disruption procedures applied, were observed through selected area electron diffraction (SAED) and through reflection high-energy electron diffraction (RHEED) analyses coupled to transmission and scanning electron microscopy observations. Such combined investigations in the real and reciprocal space provided structural information at the nanoscale on the clustering of graphene layers in nanoplatelets or/and on their assembly into highly ordered (single-crystal) nanosheets. Furthermore, a different carbon phase exhibiting an orthorhombic cell with Cmma symmetry has been detected by SAED and RHEED analyses. In addition, a variety of self-assemblies of hexagonal basal planes have been observed to occur as the result of their different rotational and/or translational stacking faults. Overall, the reported results contribute to define the conditions for a controlled self-assembly of graphene-based structures with tailored dimensions, which is an important technological challenge, as their structure at the nanoscale dramatically affects their electrical properties.

Phase formation in mixed TiO2-ZrO2 oxides prepared by sol-gel method

Pure titania, zirconia, and mixed oxides (3–37 mol.% of ZrO2) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3–13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700°C. The mixed oxide with 37 mol.% of ZrO2 treated at 550°C shows a new single amorphous phase with a surface area of the nanoparticles double with respect to the other crystalline samples and the formed srilankite structure (at 700°C). The anatase phase is not observed in the sample containing 37 mol.% of ZrO2. The treatment at 700°C causes the formation of the srilankite (Ti0.63Zr0.37Ox) phase.

In vivo protein corona patterns of lipid nanoparticles

In physiological environments (e.g. the blood), nanoparticles (NPs) are surrounded by a layer of biomolecules referred to as a ‘protein corona’ (PC). The most tightly NP-bound proteins form the so-called hard corona (HC), the key bio-entity that determines the NPs biological identity and physiological response. To date, NP-HC has been almost exclusively characterized in vitro, while NP–protein interactions under realistic in vivo conditions remain largely unexplored. In this study, we thoroughly characterized the in vivo HC of a NP formulation that forms around lipid nanoparticles with a lipid composition equal to that of clinically used liposomal amphotericin B (AmBisome®) after the recovery of the NPs from the blood circulation of FVB/N mice 10 minutes post intravenous administration. In vitro HC formed by 10 minutes incubation of NPs in FVB/N mouse plasma was used for comparison. Here we show that the biological identity (i.e. size, zeta-potential and aggregation state) of NPs in vivo is significantly different from that acquired in vitro. Furthermore, the variety of protein species in the in vivo HC was considerably larger. The present work has demonstrated that characterization of the in vivo HC is essential to provide an accurate molecular description of the biological identity of NPs in physiological environments.

Nanocarbon surfaces for biomedicine

The distinctive physicochemical, mechanical and electrical properties of carbon nanostructures are currently gaining the interest of researchers working in bioengineering and biomedical fields. Carbon nanotubes, carbon dendrimers, graphenic platelets and nanodiamonds are deeply studied aiming at their application in several areas of biology and medicine. Here we provide a summary of the carbon nanomaterials prepared in our labs and of the fabrication techniques used to produce several biomedical utilities, from scaffolds for tissue growth to cargos for drug delivery and to biosensors.

Nickel(II) 3,4;9,10-Perylenediimide bis-Phosphonate Pentahydrate: A Metal−Organic Ferromagnetic Dye

The new metal-organic compound nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate, i.e. Ni(2)[(PDI-BP)(H(2)O)(2)]·3H(2)O (1), has been synthesized and its structural and magnetic properties have been studied. Reaction of 3,4;9,10-perylenediimide bis-phosphonate (PDI-BP, hereafter) ligand and nickel chloride in water resulted in the precipitation of a red and poorly crystalline solid (1). As the solid shows a poor crystalline organization of aggregates, the energy dispersive X-ray diffraction analysis (EDXD) technique has been used to obtain short-range order structural information of the single nanoaggregates by radial distribution function analysis. The overall structure of the compound is characterized by layers containing perylene planes shifted in the direction perpendicular to the stacking axes in such a way that only the outer rings overlap. The edges of the perylene planes are connected to the phosphonate groups through an imido group. The oxygen atoms of the [-PO(3)](2-) group and those of the water molecules are bonded to the nickel ions resulting in a [NiO(6)] octahedral coordination sphere. The Ni-O bond lengths are 0.21 ± 0.08 nm and the Ni-O-Ni angles of aligned moieties are 95 ± 2°. The oxygen atoms of the water molecules and the nickel atoms are nearly planar and almost perpendicular to the perylene planes forming chains of edge-sharing octahedra. The magnetic properties of (1) show the presence of intrachain ferromagnetic Ni-Ni interactions and a long-range ferromagnetic order below 21 K with a canting angle and with a spin glasslike behavior due to disorder in the inorganic layer. Hysteresis cycles show a coercive field of ca. 272 mT at 2 K that decreases as the temperature is increased and vanishes at ca. 20 K.

Organometallic Oligomer Resolved by Radial Distribution Function of X-ray Diffraction Analysis

Platinum-organic oligomers are actively studied for their large physical and functional properties such as solubility, processability, color, luminescence, and optoelectronics related to the different metal groups and auxiliary coligands around the metal coordination spheres. Previous studies on nanotechnology devices have shown that the structural organization of handled metallopolymer generates several 2D or 3D nano-objects, but only based on trans polymorph chains. Here we report the first self-assembly of powder cis-Pt-DEBP oligomers that shows great self-assembling ability to form nanoscale supramolecular architectures. As a powder is obtained that shows a poor crystalline organization of the aggregates, the energy-dispersive X-ray diffraction is the nondestructive technique of choice to obtain short-range order structural parameters of a single nano-object by radial distribution function analysis. The supramolecular architecture of 8-units-long chains reveals a self-assembling organization of 18 chains exhibiting an overall linear inverted open square structure. The ensemble of oligomer chains form a parallelepiped shape with small internal square cavities of approximately 3.2 nm diameter capable of hosting smaller molecules, which opens up to all applications where sieving and sensing is important. This structural investigation of short-range order materials has provided a substantial additional impetus to the field by opening up the area of self-assembled supramolecular materials based on metallopolymers for technological applications.

Structural and morphological peculiarities of hybrid Au/nanodiamond engineered nanostructures

Nanostructured Au nano-platelets have been synthesized from an Au(III) complex by growth process triggered by nanodiamond (ND). An electroless synthetic route has been used to obtain 2D Au/ND architectures, where individual nanodiamond particles are intimately embedded into face-centered cubic Au platelets. The combined use of high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), was able to reveal the unusual organization of these hybrid nanoparticles, ascertaining the existence of preferential crystallographic orientations for both nanocrystalline species and highlighting their mutual locations. Detailed information on the sample microstructure have been gathered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) of HR-TEM images, allowing us to figure out the role of Au defects, able to anchor ND crystallites and to provide specific sites for heteroepitaxial Au growth. Aggregates constituted by coupled ND and Au, represent interesting systems conjugating the best optoelectronics and plasmonics properties of the two different materials. In order to promote realistically the applications of such outstanding Au/ND materials, the cooperative mechanisms at the basis of material synthesis and their influence on the details of the hybrid nanostructures have to be deeply understood.

A NANOSTRUCTURED POLYMORPH OF μ-OXOBIS(PHTHALOCYANINATOIRON(III)) STUDIED BY ANGULAR AND ENERGY DISPERSIVE X-RAY DIFFRACTION

A new approach of X-ray diffraction was used to investigate the nanostructured μ-Oxo(2) polymorph of μ-oxo-bis(phthalocyaninatoiron(III)), [PcFe–O–FePc]. The packing of the dinuclear units was determined by the Rietveld method on Angular Dispersive X-ray Diffraction (ADXD) data, whereas the intramolecular geometry was optimized by Energy Dispersive X-ray Diffraction (EDXD) exploiting the peculiar strength of those techniques. The dimension of the nanoparticles was estimated from the Fourier transform of the EDXD experimental structural function.