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  1. Article ; Online: Adsorption Geometry of Alizarin on Silver Nanoparticles

    Cristina Gellini / Marina Macchiagodena / Marco Pagliai

    Nanomaterials, Vol 11, Iss 860, p

    A Computational and Spectroscopic Study

    2021  Volume 860

    Abstract: The knowledge of the adsorption geometry of an analyte on a metal substrate employed in surface enhanced Raman scattering (SERS) spectroscopy is important information for the correct interpretation of experimental data. The adsorption geometry of ... ...

    Abstract The knowledge of the adsorption geometry of an analyte on a metal substrate employed in surface enhanced Raman scattering (SERS) spectroscopy is important information for the correct interpretation of experimental data. The adsorption geometry of alizarin on silver nanoparticles was studied through ab initio calculations in the framework of density functional theory (DFT) by modeling alizarin taking into account all the different charged species present in solution as a function of pH. The calculations allowed a faithful reproduction of the measured SERS spectra and to elucidate the adsorption geometry of this dye on the silver substrate.
    Keywords Alizarin ; Raman spectroscopy ; SERS ; silver nanoparticles ; DFT calculations ; Chemistry ; QD1-999
    Language English
    Publishing date 2021-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Genesis of Complex Polyiodide Networks

    Matteo Savastano / Carla Bazzicalupi / Cristina Gellini / Antonio Bianchi

    Crystals, Vol 10, Iss 387, p

    Insights on the Blue Box/I − /I 2 Ternary System

    2020  Volume 387

    Abstract: The Stoddart’s blue box (BB) (cyclobis(paraquat-p-phenylene))/iodide binary system was recently demonstrated to give rise to porous three-dimensional networks which can hardly be classified as common XOF-type materials (X = M, C, S, i.e., metal, covalent, ...

    Abstract The Stoddart’s blue box (BB) (cyclobis(paraquat-p-phenylene))/iodide binary system was recently demonstrated to give rise to porous three-dimensional networks which can hardly be classified as common XOF-type materials (X = M, C, S, i.e., metal, covalent, or supramolecular organic frameworks), leading to the definition of permutable organized frameworks (POFs). The ternary BB/iodide/iodine system was reported to generate pentaiodide-based structures constituted by the most complex interlocked polyiodides so far isolated (up to an infinite supramolecular pseudopolyrotaxane with a poly[3]catenane axle). The missing link, i.e., the XRD structure of the BB/triiodide complex, is herein reported: structural similarities and novel Raman evidence, opening perspectives in the genesis of solid-state BB-based complex polyiodide networks from solution.
    Keywords supramolecular chemistry ; polyiodides ; Stoddart’s blue box ; pentaiodide ; anion-π interactions ; self-assembly ; Crystallography ; QD901-999
    Subject code 540
    Language English
    Publishing date 2020-05-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: SERS active Ag–SiO2 nanoparticles obtained by laser ablation of silver in colloidal silica

    Cristina Gellini / Francesco Muniz-Miranda / Alfonso Pedone / Maurizio Muniz-Miranda

    Beilstein Journal of Nanotechnology, Vol 9, Iss 1, Pp 2396-

    2018  Volume 2404

    Abstract: Highly stable Ag–SiO2 nanoparticle composites were first obtained by laser ablation of a silver target in an aqueous colloidal dispersion of silica and examined by UV–vis absorption spectroscopy, transmission electron microscopy and Raman spectroscopy. ... ...

    Abstract Highly stable Ag–SiO2 nanoparticle composites were first obtained by laser ablation of a silver target in an aqueous colloidal dispersion of silica and examined by UV–vis absorption spectroscopy, transmission electron microscopy and Raman spectroscopy. The surface enhanced Raman scattering (SERS) activity of these nanocomposites was tested using 2,2’-bipyridine as a molecular reporter and excitation in the visible and near-IR spectral regions. The computational DFT approach provided evidence of ligand adsorption on positively charged adatoms of the silver nanostructured surface, in a very similar way to the metal/molecule interaction occurring in the corresponding Ag(I) coordination compound.
    Keywords 2,2’-bipyridine ; DFT ; laser ablation ; silica ; silver ; Technology ; T ; Chemical technology ; TP1-1185 ; Science ; Q ; Physics ; QC1-999
    Language English
    Publishing date 2018-09-01T00:00:00Z
    Publisher Beilstein-Institut
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

    Pier Remigio Salvi / Cristina Gellini

    Symmetry, Vol 2, Iss 4, Pp 1846-

    2010  Volume 1924

    Abstract: The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, ... ...

    Abstract The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]- and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.
    Keywords annulenes ; aromaticity ; antiaromaticity ; symmetry ; porphyrins ; Physics ; QC1-999 ; Science ; Q ; DOAJ:Physics (General) ; DOAJ:Physics and Astronomy
    Subject code 541
    Language English
    Publishing date 2010-11-01T00:00:00Z
    Publisher Molecular Diversity Preservation International
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: A Photochromic Azobenzene Peptidomimetic of a β-Turn Model Peptide Structure as a Conformational Switch

    Francesca Nuti / Cristina Gellini / Maud Larregola / Lorenzo Squillantini / Riccardo Chelli / Pier Remigio Salvi / Olivier Lequin / Giangaetano Pietraperzia / Anna Maria Papini

    Frontiers in Chemistry, Vol

    2019  Volume 7

    Abstract: The insertion of azobenzene moiety in complex molecular protein or peptide systems can lead to molecular switches to be used to determine kinetics of folding/unfolding properties of secondary structures, such as α-helix, β-turn, or β-hairpin. In fact, in ...

    Abstract The insertion of azobenzene moiety in complex molecular protein or peptide systems can lead to molecular switches to be used to determine kinetics of folding/unfolding properties of secondary structures, such as α-helix, β-turn, or β-hairpin. In fact, in azobenzene, absorption of light induces a reversible trans ↔ cis isomerization, which in turns generates a strain or a structure relaxation in the chain that causes peptide folding/unfolding. In particular azobenzene may permit reversible conformational control of hairpin formation. In the present work a synthetic photochromic azobenzene amino acid derivative was incorporated as a turn element to modify the synthetic peptide [Pro7,Asn8,Thr10]CSF114 previously designed to fold as a type I β-turn structure in biomimetic HFA/water solution. In particular, the P-N-H fragment at positions 7–9, involved in a β-hairpin, was replaced by an azobenzene amino acid derivative (synthesized ad hoc) to investigate if the electronic properties of the novel peptidomimetic analog could induce variations in the isomerization process. The absorption spectra of the azopeptidomimetic analog of the type I β-turn structure and of the azobenzene amino acid as control were measured as a function of the irradiation time exciting into the respective first ππ* and nπ* transition bands. Isomerization of the azopeptidomimetic results strongly favored by exciting into the ππ* transition. Moreover, conformational changes induced by the cis↔ trans azopeptidomimetic switch were investigated by NMR in different solvents.
    Keywords azobenzene ; cis/trans photoisomerization ; photoswitchable peptide ; optical control ; NMR spectroscopy ; UV/Vis spectroscopy ; Chemistry ; QD1-999
    Subject code 540 ; 500
    Language English
    Publishing date 2019-03-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Surface-Enhanced Raman Spectroscopy for Bisphenols Detection

    Eleonora Roschi / Cristina Gellini / Marilena Ricci / Santiago Sanchez-Cortes / Claudia Focardi / Bruno Neri / Juan Carlos Otero / Isabel López-Tocón / Giulietta Smulevich / Maurizio Becucci

    Nanomaterials, Vol 11, Iss 881, p

    Toward a Better Understanding of the Analyte–Nanosystem Interactions

    2021  Volume 881

    Abstract: Silver nanoparticles functionalized with thiolated β-cyclodextrin (CD-SH) were employed for the detection of bisphenols (BPs) A, B, and S by means of surface-enhanced Raman spectroscopy (SERS). The functionalization of Ag nanoparticles with CD-SH leads ... ...

    Abstract Silver nanoparticles functionalized with thiolated β-cyclodextrin (CD-SH) were employed for the detection of bisphenols (BPs) A, B, and S by means of surface-enhanced Raman spectroscopy (SERS). The functionalization of Ag nanoparticles with CD-SH leads to an improvement of the sensitivity of the implemented SERS nanosensor. Using a multivariate analysis of the SERS data, the limit of detection of these compounds was estimated at about 10 −7 M, in the range of the tens of ppb. Structural analysis of the CD-SH/BP complex was performed by density functional theory (DFT) calculations. Theoretical results allowed the assignment of key structural vibrational bands related to ring breathing motions and the inter-ring vibrations and pointed out an external interaction due to four hydrogen bonds between the hydroxyl groups of BP and CD located at the external top of the CD cone. DFT calculations allowed also checking the interaction energies of the different molecular species on the Ag surface and testing the effect of the presence of CD-SH on the BPs’ affinity. These findings were in agreement with the experimental evidences that there is not an actual inclusion of BP inside the CD cavity. The SERS sensor and the analysis procedure of data based on partial least square regression proposed here were tested in a real sample consisting of the detection of BPs in milk extracts to validate the detection performance of the SERS sensor.
    Keywords SERS ; cyclodextrin ; bisphenol A ; bisphenol B ; bisphenol S ; DFT calculations ; Chemistry ; QD1-999
    Subject code 540
    Language English
    Publishing date 2021-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article: Bifunctional Fe3O4/Ag nanoparticles obtained by two-step laser ablation in pure water

    Muniz-Miranda, Maurizio / Cristina Gellini / Emilia Giorgetti / Giancarlo Margheri

    Journal of colloid and interface science. 2017 Mar. 01, v. 489

    2017  

    Abstract: Bimetallic nanoparticles made of iron oxide and Ag could be fabricated by pulsed laser ablation of iron and silver targets in pure water by a two-step route. These nanoparticles could exhibit both magnetic and plasmonic properties.Bimetallic ... ...

    Abstract Bimetallic nanoparticles made of iron oxide and Ag could be fabricated by pulsed laser ablation of iron and silver targets in pure water by a two-step route. These nanoparticles could exhibit both magnetic and plasmonic properties.Bimetallic nanoparticles were fabricated by using a focused Nd:YAG nanosecond laser source emitting a 1064nm wavelength radiation and characterized with ζ-potential, Dynamic Light Scattering (DLS), UV–vis absorption, Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM), Energy Dispersive X-ray Spectrometry (EDX), and Selected Area Electron Diffraction (SAED). The magnetic character of the nanoparticles was ascertained by observing attraction by a magnet and complete removing from the water environment, while their SERS (surface-enhanced Raman scattering) response was checked by decorating them with 2,2′-bipyridine as molecular reporter and performing Raman tests with green (514.5nm) and far-red (785nm) excitation wavelengths.The observed magnetic attraction was due to magnetite (Fe3O4), the only ferromagnetic iron oxide form evidenced by the characterization tests in the aqueous colloidal system, where silver nanoparticles were also embedded. UV–vis and SERS spectra confirmed the presence of nanostructured silver as plasmonic constituent of the fabricated metal nanoparticles.
    Keywords energy-dispersive X-ray analysis ; iron ; light scattering ; magnetic materials ; magnetism ; magnetite ; nanoparticles ; nanosilver ; Raman spectroscopy ; silver ; transmission electron microscopy ; ultraviolet-visible spectroscopy ; wavelengths ; zeta potential
    Language English
    Dates of publication 2017-0301
    Size p. 100-105.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 241597-5
    ISSN 1095-7103 ; 0021-9797
    ISSN (online) 1095-7103
    ISSN 0021-9797
    DOI 10.1016/j.jcis.2016.08.040
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Following ligand migration pathways from picoseconds to milliseconds in type II truncated hemoglobin from Thermobifida fusca.

    Agnese Marcelli / Stefania Abbruzzetti / Juan Pablo Bustamante / Alessandro Feis / Alessandra Bonamore / Alberto Boffi / Cristina Gellini / Pier Remigio Salvi / Dario A Estrin / Stefano Bruno / Cristiano Viappiani / Paolo Foggi

    PLoS ONE, Vol 7, Iss 7, p e

    2012  Volume 39884

    Abstract: CO recombination kinetics has been investigated in the type II truncated hemoglobin from Thermobifida fusca (Tf-trHb) over more than 10 time decades (from 1 ps to ∼100 ms) by combining femtosecond transient absorption, nanosecond laser flash photolysis ... ...

    Abstract CO recombination kinetics has been investigated in the type II truncated hemoglobin from Thermobifida fusca (Tf-trHb) over more than 10 time decades (from 1 ps to ∼100 ms) by combining femtosecond transient absorption, nanosecond laser flash photolysis and optoacoustic spectroscopy. Photolysis is followed by a rapid geminate recombination with a time constant of ∼2 ns representing almost 60% of the overall reaction. An additional, small amplitude geminate recombination was identified at ∼100 ns. Finally, CO pressure dependent measurements brought out the presence of two transient species in the second order rebinding phase, with time constants ranging from ∼3 to ∼100 ms. The available experimental evidence suggests that the two transients are due to the presence of two conformations which do not interconvert within the time frame of the experiment. Computational studies revealed that the plasticity of protein structure is able to define a branched pathway connecting the ligand binding site and the solvent. This allowed to build a kinetic model capable of describing the complete time course of the CO rebinding kinetics to Tf-trHb.
    Keywords Medicine ; R ; Science ; Q
    Subject code 612
    Language English
    Publishing date 2012-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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