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Mukherjee S.,University Pierre and Marie Curie | Datta A.,Saha Institute of Nuclear Physics | Biswas N.,Indian Institute of Science | Giglia A.,TASC INFM National Laboratory | And 2 more authors.
Materials Research Express | Year: 2014

Atomic force microscopy (AFM) shows that Langmuir-Blodgett (LB) deposition of dissimilar metal stearates (MSt, M = Co, Zn, Cd) on templates of Costearate (Co-T) and Cd-stearate (Cd-T) results in self-assembly of MSts into nanocrystalline grains having clear and consistent morphological habits. The grains are better formed and well separated on Cd-T than on Co-T. Fourier transform infrared spectroscopy (FTIR) results show that the headgroup coordination of the overlayer is tuned by the coordination of the Cd-T template and remains unaffected by that of the Co-T template. They also indicate co-existence of a different kind of headgroup structure that is close to the undissociated fatty acid headgroup but differing more in the two types of carbon-oxygen bonds, suggesting an inter-headgroup bonding such as hydrogen bond that may exist on a nanocrystal surface. Results of synchrotron x-ray diffraction at C K-edge, of ZnSt on Cd-T (ZnSt/Cd-T) and Co-T (ZnSt/Co-T), point to a non-closed packed structure for ZnSt/Cd-T and a closed-packed structure for ZnSt/Co-T, with significant superlattice order in the former. The presence of crystalline phases of ZnSt in the nanometer scale, on LB templates, in contrast to the the presence of lamellar phase in bulk ZnSt, is attributed to the the presence of unidentate metalcarboxylate coordination in the former and absence of it in the latter, creating different gradients of dipolar forces at template overlayer interface. Relative strength of this long-range force over short-range intermolecular forces in the templates qualitatively explains better crystallinity and higher ordering in ZnSt/Cd-T compared to ZnSt/Co-T. We propose that the role of dipole moment gradient between template and overlayer in tuning of these metal-organic nanoparticles may be somewhat similar to structural and optical tunability of semiconductor nanocrystals by thermal and self-equilibrium strain. © 2014 IOP Publishing Ltd.

Montini T.,University of Trieste | Montini T.,CNR Institute of Chemistry of organometallic Compounds | Gombac V.,University of Trieste | Gombac V.,CNR Institute of Chemistry of organometallic Compounds | And 6 more authors.
Chemical Physics Letters | Year: 2010

Tungstates of divalent transition metals (MIIWO4, M = CoII, NiII, CuII, ZnII) were synthesized by reaction of transition metal nitrates with sodium tungstate. The precipitates were then calcined at 500 °C. The materials were characterized by means of ICP-AES elemental analysis, UV-Visible spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and surface area analysis. The higher activity for the decolourization of Methylene Blue (MB) and Methyl Orange (MO) of ZnWO4 compared to that of the other investigated tungstates was correlated with its strong tendency of excitons self-trapping. © 2010 Elsevier B.V. All rights reserved.

Latawiec D.,International School for Advanced Studies | Latawiec D.,Italian Institute of Technology | Herrera F.,International School for Advanced Studies | Herrera F.,Italian Institute of Technology | And 18 more authors.
PLoS ONE | Year: 2010

The action of dopamine on the aggregation of the unstructured alpha-synuclein (α-syn) protein may be linked to the pathogenesis of Parkinson's disease. Dopamine and its oxidation derivatives may inhibit α-syn aggregation by non-covalent binding. Exploiting this fact, we applied an integrated computational and experimental approach to find alternative ligands that might modulate the fibrillization of α-syn. Ligands structurally and electrostatically similar to dopamine were screened from an established library. Five analogs were selected for in vitro experimentation from the similarity ranked list of analogs. Molecular dynamics simulations showed they were, like dopamine, binding non-covalently to α-syn and, although much weaker than dopamine, they shared some of its binding properties. In vitro fibrillization assays were performed on these five dopamine analogs. Consistent with our predictions, analyses by atomic force and transmission electron microscopy revealed that all of the selected ligands affected the aggregation process, albeit to a varying and lesser extent than dopamine, used as the control ligand. The in silico/in vitro approach presented here emerges as a possible strategy for identifying ligands interfering with such a complex process as the fibrillization of an unstructured protein. © 2010 Latawiec et al.

Resta A.,European Synchrotron Radiation Facility | Felici R.,European Synchrotron Radiation Facility | Kumar M.,TASC INFM National Laboratory | Pedio M.,TASC INFM National Laboratory
Journal of Non-Crystalline Solids | Year: 2010

Structural profiles and electronic properties of a CuOEP and NiOEP ordered monolayer on an Au(111) substrate were studied by photoemission and Low Energy Electron Diffraction (LEED). The porphyrin molecules were deposited on Au(111) under Ultra High Vacuum (UHV) conditions. In this study, we focused on the central atom's effect on the molecule-substrate interaction. In the photoemission valence band measurements, the energy separation among different molecular states was measured and was found smaller than in free molecules. The smaller energy separation value suggested a charge transfer mechanism in the interface bond formation. The LEED showed that the monolayer depositions exhibited well ordered patterns and that the structures depended on the central atoms. © 2010 Elsevier B.V. All rights reserved.

Mukherjee S.,Saha Institute of Nuclear Physics | Datta A.,Saha Institute of Nuclear Physics | Giglia A.,TASC INFM National Laboratory | Mahne N.,TASC INFM National Laboratory | And 2 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

Atomic force microscopy (AFM) of cadmium stearate (CdSt) and cobalt stearate (CoSt) Langmuir-Blodgett films show differences in their in-plane morphologies. CdSt films, with a huge number of in-plane "pinhole" defects, follow self-affine behavior, whereas CoSt films, which are almost void of such in-plane defects, show deviation from self-affinity especially at small length scales, suggesting liquidlike behavior, imparting flexibility to the system, in plane. Phase images of CoSt obtained from tapping mode AFM show gentle undulations or hemispherelike features in contrast to its smooth topography, unlike the CdSt system where both height and phase images show self-affine domains. Near edge x-ray absorption fine structure spectroscopy indicates no preferred in-plane orientation of the head group in CoSt films. The undulating features in CoSt is explained by invoking a radially symmetric orientational distribution in the tilt of adjacent hydrocarbon tails, causing a small in-plane density variation which shows up in the phase image. These orientational disorders in adjacent tails probably allow "filling up" of in-plane defects thereby giving rise to its excellent in-plane coverage and hence a "liquidlike" behavior in CoSt. Brewster angle microscopy shows that parent Langmuir monolayers of stearic acid in the presence of Cd and Co ions in the aqueous subphase behave as two-dimensional "solids" and "liquids," respectively, suggesting the phenomena to be inherent in the amphiphiles and probably independent of their organization as monolayers and multilayers. © 2011 American Physical Society.

Wen M.,Tongji University | Huang Q.,Tongji University | She R.,Tsinghua University | Jiang L.,Tongji University | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

X-ray reflection near the Brewster's angle by multilayer mirrors can be used to detect the polarization from X-ray sources. The photon emission spectra from some isolated neutron stars and AGN/blazars etc. show that their emission is peaked at low energies near 250eV, which is just below carbon K-absorption edge. The Lightweight Asymmetry and Magnetism Probe (LAMP) is proposed as a micro-satellite mission dedicated for astronomical X-ray polarimetry working at 250 eV and is currently under early phase study. Co/C multilayers are selected and designed at the energy near 250eV with a grazing incident angle of 45°. The carbon layer thickness ratio is optimized to get the highest integral reflectivity which means larger effective signals in the astrophysics observation. The multilayer coatings were manufactured by direct current magnetron sputtering on D263 glasses and electroformed nickels and characterized using Grazing incidence X-ray reflectometry at 8keV. Reactive sputtering with 4%, 6% and 8% nitrogen were used to improve the Co/C multilayer interfaces respectively. Reflectivity for s-polarization and p-polarization light was measured at BEAR beamline in Elettra synchtron facility. Co/C multilayer deposited with 6% nitrogen exhibits the best performance comparing to other multilayers with different nitrogen content. © 2015 SPIE.

PubMed | University of Padua, CNR Institute for Organic Syntheses and Photoreactivity, TASC INFM National Laboratory, University of Ferrara and University Paris Diderot
Type: Journal Article | Journal: Chemistry, an Asian journal | Year: 2016

Since the first report in 2012, molecular copper complexes have been proposed as efficient electrocatalysts for water oxidation reactions, carried out in alkaline/neutral aqueous media. However, in some cases the copper species have been recognized as precursors of an active copper oxide layer, electrodeposited onto the working electrode. Therefore, the question whether copper catalysis is molecular or not is particularly relevant in the field of water oxidation. In this study, we investigate the electrochemical activity of copper(II) complexes with two tetraaza macrocyclic ligands, distinguishing heterogeneous or homogeneous processes depending on the reaction media. In an alkaline aqueous solution, and upon application of an anodic bias to working electrodes, an active copper oxide layer is observed to electrodeposit at the electrode surface. Conversely, water oxidation in neutral aqueous buffers is not associated to formation of the copper oxide layer, and could be exploited to evaluate and optimize a molecular, homogeneous catalysis.

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