Maria F. Casula

Università degli studi di Cagliari, Cagliari, Sardinia, Italy

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Publications (106)447.14 Total impact

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    ABSTRACT: The structure of the iron oxyhydroxide called feroxyhyte (δ-FeOOH), which shows an elusive X-ray powder diffraction pattern, has been represented so far using models describing a mean structure based on the crystalline network of the iron(III) oxide hematite (α-Fe2O3). In this paper, a novel description of the mean structure of feroxyhyte is presented, which is based on the structure of the thermodynamically stable iron oxyhydroxide goethite. Starting from different local arrangements present in the goethite network, a mean structural model is determined which shows an X-ray powder diffraction pattern almost coincident with previous studies. This outcome enables to integrate the structure of feroxyhyte among those of other well characterized iron oxyhydroxides.
    Journal of Solid State Chemistry 05/2015; 225:256-260. DOI:10.1016/j.jssc.2015.01.003 · 2.20 Impact Factor
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    ABSTRACT: A new type of mesostructured hybrid organic-inorganic film has been synthesised by evaporation-induced self-assembly using 3-glycidoxypropyltrimethoxysilane as precursor and a tri-block copolymer, Pluronic F127, as template. The chemistry has been tuned to form in the sol bridged polysilsesquioxanes that self-organize into ordered lamellar structures. Controlled aging in highly basic conditions, which has been monitored by Raman and infrared spectroscopy, has been used to obtain the layered ordered hybrid structures in the precursor sol. The pH of the sol has been adjusted to form the micelles that act as templates during solvent evaporation. Self-assembly of the system has been studied in situ by small and wide angle X-ray scattering using a synchrotron light source, which have confirmed both the formation of hybrid layered structures and the organization of a rombohedral mesophase in the hybrid films. The present approach allows ordering the hybrid film in two different length scales; at the end of film processing, hybrid crystals are retained into the pore walls and the micelles are arranged within the films with a long range order.
    Physical Chemistry Chemical Physics 03/2015; 17(16). DOI:10.1039/C5CP00433K · 4.20 Impact Factor
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    ABSTRACT: A one-pot approach making use of a zinc oxide sol precursor and 14 carbon quantum dots, together with a partially fluorinated block copolymer as 15 templating agent, has been used to synthesize a porous matrix characterized by 16 interesting energy transfer properties. The choice of the fluorinated surfactant for 17 inducing the porosity into the inorganic matrix has allowed an easy removal of the 18 templating agent at low temperature, preserving at the same time the functional 19 properties of the carbon quantum dots. The resulting nanocomposite films have 20 been characterized by steady-state 3D mapping that has evidenced a complex 21 behavior as a function of the carbon quantum dots concentration. In particular, 22 the luminescence bands of the zinc oxide matrix appear to be modulated by the 23 broad emission of the carbon quantum dots, which depends on their aggregation 24 state. These results can be thus considered as a step further toward the fine-tuning 25 of the luminescence properties provided by zinc oxide-based nanocomposites as a 26 result of a doping effect due to the presence of carbon quantum dots.
    The Journal of Physical Chemistry C 01/2015; 119:2837-2843. DOI:10.1021/jp510661d · 4.84 Impact Factor
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    ABSTRACT: Export Date: 28 October 2014, Article in Press
    Journal of Porous Materials; 12/2014
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    ABSTRACT: Highly porous nanocomposite aerogels based on bimetallic Fe and Mo nanoparticles with a variable Fe:Mo weight ratio ranging from 5:1; 3:1; and 0.7:1 dispersed on amorphous silica were obtained. N2 physisorption, X-ray diffraction, and transmission electron microscopy indicate that the Fe/Mo-SiO2 nanocomposite aerogels as obtained by a co-gelation sol-gel route followed by supercritical drying and reduction treatment under H2 exhibit Fe and Mo nanocrystals with size in the range 4-10 and 15 nm, respectively, supported on highly porous silica. The catalytic performance of the Fe/Mo-SiO2 aerogels for the synthesis of multi wall carbon nanotubes (MWCNT) by catalytic chemical vapour deposition (CCVD) was evaluated in terms of amount and quality of the produced CNTs as assessed by gravimetric results, thermal analysis, and TEM. The effect of catalyst composition and CCVD temperature was investigated, pointing out that high reaction temperatures (800 °C) favor the formation of MWCNTs with high quality in elevated yield, the highest C uptake value being >400 %. Catalyst composition and CCVD temperature were also found to affect the homogeneity of CNT morphology, the best MWCNT quality (with outer diameter 23-25 nm) being achieved at 800 °C with the catalyst having the largest Mo content.
    Journal of Sol-Gel Science and Technology 10/2014; 73(2). DOI:10.1007/s10971-014-3544-9 · 1.55 Impact Factor
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    ABSTRACT: Silica-based ordered mesoporous materials are very attractive matrices to prepare smart depot systems for several kinds of therapeutic agents. This work focuses on the well known SBA-15 mesoporous silica and lysozyme, an antimicrobial protein. In order to improve the bioadhesion properties of SBA-15 particles, the effect of hyaluronic acid functionalization on lysozyme adsorption was investigated. SBA-15 samples having high (H-SBA) and low (L-SBA) levels of functionalization were analyzed during the three steps of the preparations: 1. introduction of the -NH2 groups to obtain the SBA-NH2 samples; 2. functionalization with hyaluronic acid to obtain the SBA-HA matrices; 3. adsorption of lysozyme. All silica matrices were characterized through N2-adsorption/desorption isotherms, SAXS, TEM, thermogravimetric analysis, and FTIR spectroscopy. The whole of the experimental data suggests that a high level of functionalization of the silica surface allows for a negligible lysozyme adsorption mainly due to unfavorable electrostatic interactions (H-SBA-NH2) or steric hindrance (H-SBA-HA). A low degree of functionalization of the silica surface brings about a very good performance towards lysozyme adsorption, being 71 % (L-SBA-NH2) and 63 % (L-SBA-HA) respectively, compared to that observed for original SBA-15. Finally, two different kinetic - a 'pseudo-second order' and a 'intraparticle diffusion' - models were compared to fit lysozyme adsorption data, the latter resulting more reliable than the former.
    Langmuir 10/2014; 30(43). DOI:10.1021/la503224n · 4.38 Impact Factor
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    ABSTRACT: Porous monoliths of nanocomposites containing Ni (5 wt.%) and FeNi (5 wt.%) nanoparticles dispersed on an SBA-16 type matrix were prepared following a templated-gelation method based on the sol-gel process. The nanocomposites were characterized by energy dispersive X-ray spectroscopy, N-2 physisorption at 77 K, X-ray diffraction and transmission and scanning electron microscopy. In particular, N-2 physisorption and transmission electron microscopy analysis show that the ordered mesoporous structure and the high surface area of all the samples are preserved after calcination in air at 500 degrees C and also after reduction in H-2 flux at 800 degrees C, indicating a very high thermal stability of the samples. As a result of the effective dispersion of the nanophase within the porous texture, nanocomposites containing Ni nanocrystals with an average size of 6 nm homogeneously dispersed within the pores of the amorphous silica matrix were obtained.
    Journal of Non-Crystalline Solids 10/2014; DOI:10.1016/j.jnoncrysol.2014.01.010 · 1.72 Impact Factor
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    ABSTRACT: Silica mesoporous nanocomposite films containing graphene nanosheets and gold nanoparticles have been prepared via a one-pot synthesis using silicon tetrachloride, gold(III) chloride tetrahydrate, a 1-N-vinyl-2-pyrrolidone dispersion of exfoliated graphene and Pluronic F127 as a structuring agent. The composite films have shown Graphene-mediated Surface-Enhanced Raman Scattering (G-SERS). Graphene has been introduced as dispersed bilayer sheets while gold has been thermally reduced in situ to form nanoparticles of around 6 nm which preferentially nucleate on the surface of the graphene nanosheets. The presence of graphene and gold nanoparticles does not interfere with the self-assembly process and silica mesoporous films ordered as 2D hexagonal structures. The material has shown a remarkable analytical enhancement factor ranging from 80 up to 136 using Rhodamine 6G as a Raman probe. The films have been characterised by grazing incidence X-ray diffraction, FTIR and UV-Vis spectroscopies; transmission electron microscopy and spectroscopic ellipsometry have been used to study the morphology, thickness and porosities of the samples. Raman spectroscopy has been employed to characterise the graphene nanosheets embedded into the mesoporous films and the Enhanced Raman Scattering.
    Physical Chemistry Chemical Physics 09/2014; DOI:10.1039/C4CP03582H · 4.20 Impact Factor
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    ABSTRACT: Porous monoliths of a 3D cubic cage mesostructured silica (SBA-16 type) and of composites containing Co (5% wt.) and FeCo (5% wt.) nanophases dispersed in the SBA-16 type matrix were prepared following a templated-gelation method. Optically clear disk-shaped monoliths with diameter around 10 cm were obtained whose absorption spectra are tunable based on the composition. Low-angle X-ray diffraction, N-2 physisorption and transmission electron microscopy show that the ordered mesoporous structure and high surface area are preserved after calcination at 500 degrees C and after reduction at 800 degrees C, indicating a very high thermal stability. X-ray absorption spectroscopy at the Fe and Co K-edges allowed us to identify the intermediate products before and after reduction. In particular, the formation of a nanophase of layered cobalt silicate hydroxide was determined in the Co containing sample calcined at 500 degrees C. This compound is easily reducible giving rise to a superparamagnetic nanocomposite containing pure fcc Co nanoparticles dispersed within the 3D mesoporous silica structure. Extensive characterization points out that the proposed procedure is promising in the preparation of functional nanocomposites with adjustable magnetic and optical properties.
    Microporous and Mesoporous Materials 08/2014; 194:157–166. DOI:10.1016/j.micromeso.2014.03.032 · 3.21 Impact Factor
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    ABSTRACT: Fabrication of graphene nanocomposite films via sol–gel chemistry is still a challenging task because of the low solubility of graphene in common solvents. In the present work we have successfully developed a suitable synthesis method employing a solution of exfoliated graphene in 1-vinyl-2-pyrrolidone that is added to an anhydrous sol of silicon tetrachloride in ethanol. Thin graphene–silica films with high optical transparency have been obtained; the graphene sheets are composed of two layers and do not aggregate at a large range of concentrations upon incorporation into the matrix. Thermal processing of the silica films allows complete removal of 1-vinyl-2-pyrrolidone without oxidation or degradation of the graphene sheets which are embedded in the oxide.
    New Journal of Chemistry 07/2014; 38(8). DOI:10.1039/C4NJ00535J · 3.16 Impact Factor
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    ABSTRACT: The possibility of extending the technological applications of photocatalytic mesoporous titania films relies upon the capability of lowering the processing temperature while maintaining its functional properties. Here we present a synthesis of mesoporous titania films, which makes use of a partially fluorinated surfactant Zonyl FS300 as a mesostructur-ing agent. The photoinduced degradation activity has been followed by FTIR spectroscopy as a function of the films' thermal annealing, ranging from 150 up to 400 °C, by using stearic acid as a model compound. The results have been compared with the benchmark templating agent Pluronic F127 and highlighted a constantly higher activity of the Zonyl-templated films, up to 50%, throughout the range of the temperatures analyzed. Raman spectroscopy indicates that Zonyl FS300 is capable of producing nanosized titania crystals at temperatures lower than Pluronic F127. This explains the different photocatalytic response of the corresponding mesoporous thin films processed at low temperatures.
    The Journal of Physical Chemistry C 05/2014; 118(22). DOI:10.1021/jp501653x · 4.84 Impact Factor
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    ABSTRACT: We report the detailed structural characterization and magnetic investigation of nanocrystalline zinc ferrite nanoparticles supported on a silica aerogel porous matrix which differ in size (in the range 4-11 nm) and the inversion degree (from 0.4 to 0.2) as compared to bulk zinc ferrite which has a normal spinel structure. The samples were investigated by zero-field-cooling-field-cooling, thermo-remnant DC magnetization measurements, AC magnetization investigation and Mössbauer spectroscopy. The nanocomposites are superparamagnetic at room temperature; the temperature of the superparamagnetic transition in the samples decreases with the particle size and therefore it is mainly determined by the inversion degree rather than by the particle size, which would give an opposite effect on the blocking temperature. The contribution of particle interaction to the magnetic behavior of the nanocomposites decreases significantly in the sample with the largest particle size. The values of the anisotropy constant give evidence that the anisotropy constant decreases upon increasing the particle size of the samples. All these results clearly indicate that, even when dispersed with low concentration in a non-magnetic and highly porous and insulating matrix, the zinc ferrite nanoparticles show a magnetic behavior similar to that displayed when they are unsupported or dispersed in a similar but denser matrix, and with higher loading. The effective anisotropy measured for our samples appears to be systematically higher than that measured for supported zinc ferrite nanoparticles of similar size, indicating that this effect probably occurs as a consequence of the high inversion degree.
    Physical Chemistry Chemical Physics 01/2014; 16(10). DOI:10.1039/c3cp54291b · 4.20 Impact Factor
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    ABSTRACT: We synthesize colloidal CdSe@CdS octapod nanocrystals decorated with Pt domains, resulting in a metal-semiconductor heterostructure. We devise a protocol to control the growth of Pt on the CdS surface, realizing both a selective tipping and a non-selective coverage. Ultrafast optical spectroscopy, particularly femtosecond transient absorption, is employed to correlate the dynamics of optical excitations with the nanocrystal morphology. We find two regimes for capture of photoexcited electrons by Pt domains: a slow capture after energy relaxation in the semiconductor, occurring in tipped nanocrystals and resulting in large spatial separation of charges, and an ultrafast capture of hot electrons occurring in nanocrystals covered in Pt, where charge separation happens faster than energy relaxation and Auger recombination. Besides the relevance for fundamental materials science and control at the nanoscale, our nanocrystals may be employed in solar photocatalysis.
    Nanoscale 01/2014; DOI:10.1039/c3nr05567a · 6.74 Impact Factor
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    ABSTRACT: Camptothecin (CPT; (S)-(+)-4-ethyl-4-hydroxy-1H-pyrano[3',4':6,7]indolizino[1,2- b]quinoline-3,14-(4H,12H)-dione) is a highly cytotoxic natural alkaloid that has not yet found use as chemotherapeutic agent due to its poor water-solubility and chemical instability and, as a consequence, no effective administration means have been designed. In this work, camptothecin has been successfully loaded into iron oxide superparamagnetic nanoparticles with average size 14 nm. It was found that surface modification of the nanoparticles by polyethylene glycol enables loading a large amount of camptothecin. While the unloaded nanoparticles do not induce apoptosis in H460 lung cancer cell line, the camptothecin-loaded nanoparticle formulations exhibit remarkable pro-apoptotic activity. These results indicate that camptothecin retains its biological activity after loading onto the magnetic nanoparticles. The proposed materials represent novel materials based on naturally occurring bioactive molecules loaded onto nanoparticles to be used as chemotherapeutic formulations. The procedure seems apt to be extended to other active molecules extracted from natural products. In addition, these materials offer the potential of being further implemented for combined imaging and therapeutics, as magnetic nanoparticles are known to be multifunctional tools for biomedicine.
    Beilstein Journal of Nanotechnology 01/2014; DOI:10.3762/bjnano.5.144 · 2.33 Impact Factor
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    ABSTRACT: To fully exploit the potential of self-assembly in a single step, we have designed an inte-grated process to get mesoporous graphene nanocomposite films. The synthesis allows in-corporating graphene sheets with a small number of defects into highly ordered and trans-parent mesoporous titania films. The careful design of the porous matrix at the mesoscale ensures the highest diffusivity in the films which exhibit an enhanced photocatalytic effi-ciency while the high order of the mesoporosity is not affected by the insertion of the gra-phene sheets and it is well preserved after controlled thermal treatment. The nanocomposite films can be easily processed by deep X-ray lithography to produce functional arrays.
    ACS Applied Materials & Interfaces 11/2013; 6(2). DOI:10.1021/am4027407 · 5.90 Impact Factor
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    ABSTRACT: In this work, we report on the synthesis and characterization of thermoresponsive poly(N-vinylcaprolactam), PNVCL, nanocomposite hydrogels containing nanocrystalline cellulose (CNC) by the use of frontal polymerization technique, which is a convenient, easy and low energy-consuming method of macromolecular synthesis. CNC was obtained by acid hydrolysis of commercial microcrystalline cellulose and dispersed in dimethylsulfoxide. The dispersion was characterized by TEM analysis and mixed with suitable amounts of N-vinylcaprolactam for the synthesis of PNVCL nanocomposite hydrogels having a CNC concentration ranging between 0.20 and 2.0 wt%. The nanocomposite hydrogels were analyzed by SEM and their swelling and rheological features were investigated. It was found that CNC decreases the swelling ratio even at small concentration. The rheological properties of the hydrogels indicated that CNC strongly influenced the viscoelastic modulus, even at concentrations as low as 0.1 wt%: both G′ and G″, and the viscosity increase with CNC content, indicating that the nanocellulose has a great potential to reinforce PNVCL polymer hydrogels.
    Cellulose 10/2013; 20(5). DOI:10.1007/s10570-013-9988-1 · 3.03 Impact Factor
  • Nanopages 06/2013; 8(1):1-8. DOI:10.1556/Nano.2013.00002
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    ABSTRACT: A mesoporous ordered cubic Im3m silica (SBA-16) characterized by a three dimensional cage-like structure of pores was used as a host matrix for the preparation of a series of FeCo-SiO2 nanocomposites with different alloy loading and composition by the wet impregnation method. The mesoporous structure of the SBA-16-type support, prepared according to a versatile sol-gel templated synthetic method, which makes use of n-butanol as a co-surfactant, is stable during the treatments necessary to obtain the final nanocomposites, as pointed out by low-angle X-Ray diffraction, transmission electron microscopy, and N2 physisorption at 77 K. Wide-angle X-ray diffraction shows that upon reduction at 800 °C, FeCo nanocrystals (6–7 nm) with the typical bcc structure are formed and energy-dispersive X-ray spectroscopy analysis, performed by scanning transmission electron microscopy on one of the samples, shows that the Fe/Co atomic ratio in the alloy nanoparticles is very close to the expected value of two. Electron tomography was used for the first time to gain evidence on the highly interconnected mesoporous structure of SBA-16 and the arrangement of the nanoparticles within the matrix. It was found that spherical alloy nanocrystals with narrow size distribution are homogeneously distributed throughout the mesoporous matrix and that the resulting FeCo-SiO2 nanocomposite material displays superparamagnetic behavior with high strength dipolar interactions, as expected for particles with a large magnetic moment.
    ChemPlusChem 04/2013; 78(4):364. DOI:10.1002/cplu.201200283 · 3.24 Impact Factor
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    ABSTRACT: Magnetic and superparamagnetic colloids represent a versatile platform for the design of functional nanostructures which may act as effective tools for biomedicine, being active in cancer therapy, tissue imaging and magnetic separation. The structural, morphological and hence magnetic features of the magnetic nanoparticles must be tuned for optimal perfomance in a given application. In this work, iron oxide nanocrystals have been prepared as prospective heat mediators in magnetic fluid hyperthermia therapy. A procedure based on the partial oxidation of iron (II) precursors in water based media has been adopted and the synthesis outcome has been investigated by X-Ray diffraction and Transmission electron microscopy. It was found that by adjusting the synthetic parameters (mainly the oxidation rate) magnetic iron oxide nanocrystals with cubic and cuboctahedral shape and average size 50 nm were obtained. The nanocrystals were tested as hyperthermic mediators through Specific Absorption Rate (SAR) measurements. The samples act as heat mediators, being able to increase the temperature from physiological temperature to the temperatures used for magnetic hyperthermia by short exposure to an alternative magnetic field and exhibit a reproducible temperature kinetic behavior.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2013; DOI:10.1117/12.2003180 · 0.20 Impact Factor
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    ABSTRACT: We present a systematic experimental comparison of the superparamagnetic relaxation time constants obtained by means of dynamic magnetic measurements and (1)H-NMR relaxometry, on ferrite-based nanosystems with different composition, various core sizes and dispersed in different solvents. The application of a heuristic model for the relaxivity allowed a comparison between the reversal time of magnetization as seen by NMR and the results from the AC susceptibility experiments, and an estimation of fundamental microscopic properties. A good agreement between the NMR and AC results was found when fitting the AC data to a Vogel-Fulcher law. Key parameters obtained from the model have been exploited to evaluate the impact of the contribution from magnetic anisotropy to the relaxivity curves and estimate the minimum approach distance of the bulk solvent.
    Journal of Physics Condensed Matter 01/2013; 25(6):066008. DOI:10.1088/0953-8984/25/6/066008 · 2.22 Impact Factor

Publication Stats

2k Citations
447.14 Total Impact Points

Institutions

  • 2000–2015
    • Università degli studi di Cagliari
      • • Department of Chemical and Geological Science
      • • Department of Surgical Science
      Cagliari, Sardinia, Italy
  • 2006
    • University of California, Berkeley
      • Department of Chemistry
      Berkeley, MO, United States
  • 2005
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany