Antonietta Guagliardi

National Research Council, Roma, Latium, Italy

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Publications (47)181.34 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The size-driven expansion and oxidation-driven contraction phenomena of nonstoichiometric magnetite–maghemite core–shell nanoparticles have been investigated by the total scattering Debye function approach. Results from a large set of samples are discussed in terms of significant effects on the sample average lattice parameter and on the possibility of deriving the sample average oxidation level from accurate, diffraction-based, cell values. Controlling subtle experimental effects affecting the measurement of diffraction angles and correcting for extra-sample scattering contributions to the pattern intensity are crucial issues for accurately estimating lattice parameters and cation vacancies. The average nanoparticle stoichiometry appears to be controlled mainly by iron depletion of octahedral sites. A simple law with a single adjustable parameter, well correlating lattice parameter, stoichiometry and size effects of all the nanoparticles present in the whole set of samples used in this study, is proposed.
    Journal of Applied Crystallography 10/2014; 47(5). · 3.34 Impact Factor
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    ABSTRACT: The introduction of side chains in π-conjugated molecules is a design strategy widely exploited to increase molecular solubility thus improve the processability, while directly influencing the self-assembly and consequently the electrical properties of thin films. Here, a multiscale structural analysis performed by X-ray diffraction, X-ray reflectivity, and atomic force microscopy on thin films of dicyanoperylene molecules decorated with either linear or branched side chains is reported. The substitution with asymmetric branched alkyl chains allows obtaining, upon thermal annealing, field-effect transistors with enhanced transport properties with respect to linear alkyl chains. Branched chains induce molecular disorder during the film growth from solution, effectively favouring 2D morphology. Post-deposition thermal annealing leads to a structural transition towards the bulk-phase for molecules with branched chains, still preserving the 2D morphology and allowing efficient charge transport between crystalline domains. Conversely, molecules with linear chains self-assemble into 3D islands exhibiting the bulk-phase structure. Upon thermal annealing, these 3D islands keep their size constant and no major changes are observed in the organic field effect transistor characteristics. These findings demonstrate that the disorder generated by the asymmetric branched chains when the molecule is physisorbed in thin film can be instrumental for enhancing charge transport via thermal annealing.
    Advanced Functional Materials 07/2014; · 10.44 Impact Factor
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    ABSTRACT: A multiscale approach, combining structural and microstructural characterizations, was applied to tackle an uncommon and so far unsolved structural problem occurring in group 11 nitropyrazolates. To this goal, the average structure of the [Ag(4-NO2-pz)]3 and [Cu(4-NO2-pz)]3 species was determined through ab initio X-ray powder diffraction techniques on high-resolution synchrotron data, and used to infer molecular models of randomly distributed defects within molecular stacks of trimeric molecules of D3h idealized symmetry. By cross-coupling the size and shape information on nanocrystalline coherent domains derived from tailored Debye function simulations with those obtained from scanning electron miscroscopy images on multidomain particles, the mechanism of structural disorder disrupting crystal periodicity is proposed. Such a model was further supported through the derivation of the pair distribution function, which affords local features to be sought independently from the presence of structural periodicity. Finally, the effects of stacking faults on the electrical properties of [Ag(4-NO2-pz)]3 have been experimentally evaluated.
    Crystal Growth & Design 04/2014; 14(6):2913–2922. · 4.69 Impact Factor
  • Norberto Masciocchi, Simona Galli, Antonietta Guagliardi
    02/2014; 29(01).
  • Advanced Functional Materials 02/2014; 24(8). · 10.44 Impact Factor
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    ABSTRACT: Bio-inspired apatite nanoparticles precipitated in the presence of citrate ions at increasing maturation times are characterized in terms of structure, size, morphology, and composition through advanced X-ray total scattering techniques. The origin of the platy crystal morphology, breaking the hexagonal symmetry, and the role of citrate ions is explored. By cross-coupling the size and shape information of crystal domains with those obtained by atomic force microscopy on multidomain nanoparticles, a plausible mechanism underlying the amorphous-to-crystal transformation is reconstructed. In the present study, citrate plays the distinct roles of inducing the platy morphology of the amorphous precursor and controlling the thickness of the Ca-deficient apatite nanocrystals. These findings can open new scenarios also in bone mineralization, where citrate might have a broader role to play than has been thought to date.
    Advanced Functional Materials 01/2014; 24(8):1090-1099. · 10.44 Impact Factor
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    ABSTRACT: Very small superparamagnetic iron oxide nanoparticles were characterized by innovative synchrotron X-ray total scattering methods and Debye function analysis. Using the information from both Bragg and diffuse scattering, size-dependent core–shell magnetite–maghemite compositions and full size (number- and mass-based) distributions were derived within a coherent approach. The magnetite core radii in 10 nm sized NPs well match the magnetic domain sizes and show a clear correlation to the saturation magnetization values, while the oxidized shells seem to be magnetically silent. Very broad superstructure peaks likely produced by the polycrystalline nature of the surface layers were experimentally detected in room temperature oxidized samples. Effective magnetic anisotropy constants, derived by taking the knowledge of the full size-distributions into account, show an inverse dependence on the NPs size, witnessing a major surface contribution. Finally, an additional amorphous component was uncovered within the diffuse scattering of the “ordered” magnetite–maghemite NPs. Under the hypothesis that this material may form an external dead layer, an additional thickness varying between 0.3 and 1.0 nm should be added to the overall core–shell NPs size.
    Chemistry of Materials. 11/2013; 25(23):4820–4827.
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    ABSTRACT: Total Scattering Methods are nowadays widely used for the characterization of defective and nanosized materials. They commonly rely on highly accurate neutron and synchrotron diffraction data collected at dedicated beamlines. Here, we compare the results obtained on conventional laboratory equipment and synchrotron radiation when adopting the Debye Function Analysis method on a simple nanocrystalline material (a synthetic iron oxide with average particle size near to 10 nm). Such comparison, which includes the cubic lattice parameter, the sample stoichiometry and the microstructural (size-distribution) analyses, highlights the limitations, but also some strengthening points, of dealing with conventional powder diffraction data collections on nanocrystalline materials.
    Powder Diffraction. 09/2013; 28(S2).
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    ABSTRACT: A versatile, rapid and easy synthesis of pure rare-earth-(RE) hexaboride powders was developed, without resorting to hazardous precursors or generating undesired, ineliminable, side products. To this purpose, we employed a metathesis reaction, typically starting from a mixture of a hydrated rare earth trichloride and MgB2, kept at 650 °C for 1 h under vacuum. This methodology affords nanosized RE hexaborides, with average crystallite (domain) sizes down to a few nanometers, useful for tailoring the functional performances of the MgB2 superconducting phase produced by the reactive liquid infiltration method. For the powders showing the lowest average domain sizes (YbB6 and EuB6), an unconventional microstructural analysis, based on Total Scattering methods and on the Debye Function Approach, was also performed, which provided the complete nanocrystal size distributions.
    ChemInform 07/2013; 21:32–36.
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    ABSTRACT: Bimodal MRI/OI imaging probes are of great interest in nanomedicine. Although many organic polymers have been studied thoroughly for in vivo applications, reports on the use of poly(amino acid)s as coating polymers are scarce. In this paper, poly-(d-glutamic acid, d-lysine) (PGL) has been used for coating maghemite and gold nanoparticles. An advantage of this flexible and biocompatible polymer is that, once anchored to the nanoparticle surface, dangling lysine amino groups are available for the incorporation of new functionalities. As an example, Alexa Fluor derivatives have been attached to PGL-coated maghemite nanoparticles to obtain magnetic/fluorescent materials. These dual-property materials could be used as bimodal MRI/OI probes for in vivo imaging.
    Nanotechnology 01/2013; 24(7):075102. · 3.84 Impact Factor
  • Advanced Functional Materials 01/2013; Accepted (doi:10.1002/adfm.201302075). · 10.44 Impact Factor
  • Norberto Masciocchi, Antonietta Guagliardi, Simona Galli
    Powder Diffraction 09/2012; 27(03):217-218. · 0.54 Impact Factor
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    ABSTRACT: The specific routes of biomineralization in nature are here explored using a tissue engineering approach in which bone is formed in porous ceramic constructs seeded with bone marrow stromal cells and implanted in vivo. Unlike previous studies this model system reproduces mammalian bone formation, here investigated at high temporal resolution. Different mineralization stages were monitored at different distances from the scaffold interface so that their spatial analysis corresponded to temporal monitoring of the bone growth and mineralization processes. The micrometer spatial resolution achieved by our diffraction technique ensured highly accurate reconstruction of the different temporal mineralization steps and provided some hints to the challenging issue of the mineral deposit first formed at the organic-mineral interface. Our results indicated that in the first stage of biomineralization organic tissue provides bioavailable calcium and phosphate ions, ensuring a constant reservoir of amorphous calcium phosphate (ACP) during hydroxyapatite (HA) nanocrystal formation. In this regard we suggest a new role of ACP in HA formation, with a continuous organic-mineral transition assisted by a dynamic pool of ACP. After HA nanocrystals formed, the scaffold and collagen act as templates for nanocrystal arrangement on the microscopic and nanometric scales, respectively.
    Acta biomaterialia 06/2012; 8(9):3411-8. · 5.09 Impact Factor
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    ABSTRACT: The highly defective 1D polymer [Ru(CO)4]n species, in which Ru atoms are arranged in parallel chains well separated by the ligand shell, is here investigated by total scattering Debye function analysis on synchrotron powder diffraction data. A new chain packing model based on the presence of 2D paracrystalline effects in the ab plane is successfully proposed and well accounts for the unusual combination of sharp and very broad diffraction peaks not compatible with conventional size or strain models. Upon thermolysis, the collinear metal arrangement of the parallel [Ru(CO)4]n bundles in the polymer is not maintained in the Ru particles, whose nanocrystals are not significantly elongated and show a faulted hcp structure with much smaller domains than in the parent organometallic species. These results thus dismiss the appealing hypothesis that, by using a chain-like precursor, highly anisotropically shaped Ru-metal nanorods can be formed upon controlled pyrolysis.
    Crystal Growth & Design 05/2012; 12(7):3631–3637. · 4.69 Impact Factor
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    ABSTRACT: appealing characteristics, such as light weight, mechanical flexibility and low-cost production. These advantages make them promising candidates for a wide range of applications such as displays, [10–12] radio-frequency identification (RF-ID) tags, [13] and sensors. [14–17] To make full use of organic electronic circuitry, it is necessary to combine p-channel and n-channel transistors to produce complementary circuits, which show greater speed, reliability and stability than ambipolar ones. [18–21] While highly pure, stable and solution-processable p-type materials with a charge mobility of 1–10 cm 2 V −1 s −1 are nowadays available in production amounts, [22–27] n-type organic semiconductors of high air-stability and mobility are still a topic of research. Indeed, in the past few years, several high-performance n-type semiconductors have been developed, which also exhibit a high stability in ambient conditions, mostly used as films obtained from vapor deposition methods. [28,29] More recently, solution-processable and printable n-type semiconductors, both small molecules and polymers, [30–33] have been reported, allowing unprecedented OTFT characteristics. Perylene di-imide deriva-tives are considered to be among the most important n-type organic materials because of their relatively strong electron affinities and the tailoring of the charge-transport properties upon changing the substituents on the imide N atoms or on the perylene backbone. [34–42] In this paper, we focus on N,N′-bis(n-ctyl)-x:y,dicyanoperylene-3,4:9,10-bis(dicarboximide), PDI8-CN2, a derivative having two cyano groups directly bound to the aromatic core, which has been proved to be a suitable material for complementary cir-cuits [43] and shown to yield high-performance devices by subli-mation or from solution methods. [44] In spite of the potential of PDI8-CN2 and the importance attributed to the control of grain boundary effects in small-molecule device performance and reproducibility, experimen-tally derived knowledge of the crystal structure and molecular conformation and how these factors affect the multiscale organ-ization and microstructure in the film phase are still missing. The packing motif proposed by Rivnay et al. [44] relies on the combination of the X-ray scattering of thin films and pseudo-potential calculations, which is not as robust or conclusive as A multiscale investigation of N,N′-bis(n-octyl)-x:y, dicyanoperylene-3,4:9,10-bis(dicarboximide), PDI8-CN2, shows the same molecular arrangement in the bulk and in thin films sublimated on SiO 2 /Si wafers. Non-conventional powder diffraction methods and theoretical calculations concur to provide a coherent picture of the crystalline structure. X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses of films of different thickness depos-ited at different substrate temperatures indicate the existence of two temper-ature-dependent deposition regimes: a low-temperature (room temperature) regime and a high-temperature (80–120 °C) one, each characterized by dif-ferent growth mechanisms. These mechanisms eventually result in different morphological and structural features of the films, which appear to be highly correlated with the trend of the electrical parameters that are measured in PDI8-CN2-based field-effect transistors.
    Advanced Functional Materials 03/2012; 22(5):943. · 10.44 Impact Factor
  • Angewandte Chemie International Edition 09/2011; 50(46):10828-33. · 11.34 Impact Factor
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    ABSTRACT: Nanocrystalline TiO(2) samples, prepared for smart textiles applications by the sol-gel technique in acidic or basic media, have been characterized by synchrotron X-ray powder diffraction and total scattering methods based on a fast implementation of the Debye function and original algorithms for sampling interatomic distances. Compared to the popular and widely used Rietveld-based approaches, our method is able to simultaneously model both Bragg and diffuse contributions and to quantitatively extract either sizes and size distribution information from the experimental data. The photocatalytic activity of the investigated samples is here systematically correlated to the average sizes and size distributions of anisotropically shaped coherent domains, modeled according to bivariate populations of nanocrystals grown along two normal directions.
    Journal of the American Chemical Society 02/2011; 133(9):3114-9. · 10.68 Impact Factor
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    Michele Zema, Marco Milanesio, Simona Galli, Antonietta Guagliardi
    Powder Diffraction 01/2011; 26(4):353-. · 0.54 Impact Factor
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    ABSTRACT: The Debye Function Analysis of diffraction patterns from nanosized mineral crystals showing different average degrees of maturity was carried out on engineered bone samples. The analysis relied on a bivariate family of atomistic hydroxyapatite nanocrystal models and provided information about crystal structure, size and shape distributions of the mineral component of the newly formed bone. An average rod-like shape of nanocrystals was found in all samples, with average sizes well matching the collagen I gap region. The diffraction patterns investigated through the Debye Function Analysis were used as signal models to perform the Canonical Correlation Analysis of high resolution X-ray micro-diffraction patterns collected on porous and resorbable hydroxyapatite/silicon-stabilized tricalcium phosphate (Si-TCP) implants. The nosologic maps clearly showed a size gradient in the new formed bone that validates the mechanism (mimicking the bone remodelling in orthotopic bones) of a continuous deposition of bone by osteoblasts, an increasing mineralization of the newly deposited bone, a growth of the new crystals, at the same time that osteoclasts adhere to the scaffold surface and resorb the bioceramic. The comparison of samples at different implantation times proved that the selective resorption of Si-TCP component from the scaffold was already evident after two and almost complete after six months.
    Biomaterials 11/2010; 31(32):8289-98. · 8.31 Impact Factor
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    ABSTRACT: Pd nanoparticles exhibiting permanent magnetism at room temperature have been prepared within the apoferritin cavity. Pd nanoparticles in air and under an inert atmosphere were synthesized to study the influence of the aerobic and anaerobic conditions in the final magnetic properties. The surface of nanoparticles as well as the type of crystalline phase could determine the magnetic properties. X-ray powder diffraction, including Debye-function analysis, transmission electronic microscopy, and magnetization measurements have been used for characterizing the nanoparticles.
    Nanotechnology 07/2010; 21(27):274017. · 3.84 Impact Factor

Publication Stats

168 Citations
181.34 Total Impact Points

Institutions

  • 2004–2014
    • National Research Council
      • • Institute of Crystallography IC
      • • Institute for Photonics and Nanotechnologies IFN
      Roma, Latium, Italy
  • 2011–2013
    • University of Insubria
      Varese, Lombardy, Italy
  • 2010–2013
    • Università degli Studi dell'Insubria
      • Department of Science and High Technology
      Varese, Lombardy, Italy
  • 2006–2010
    • Paul Scherrer Institut
      • Laboratory for Neutron Scattering (LNS)
      Villigen, AG, Switzerland