Nicoleta Cioatera

Mesoporous silica functionalized with 1-furoyl thiourea urea for Hg(II) adsorption from aqueous media.

New organic-inorganic hybrid materials were prepared by covalently anchoring 1-furoyl thiourea on mesoporous silica (SBA-15). By means of various characterization techniques (X-ray diffraction, nitrogen adsorption-desorption, thermogravimetric analysis, and FTIR spectroscopy) it has been established that the organic groups were successfully anchored on the SBA-15 surfaces and the ordering of the inorganic support was preserved during the chemical modifications. The hybrid sorbents exhibited good ability to remove Hg(II) from aqueous solution. Thus, at pH 6, the adsorption capacity of mercury ions reached 0.61 mmol g(-1).

New biologically active mixed-ligand Co(II) and Ni(II) complexes of enrofloxacin

New mixed-ligand Co(II) and Ni(II) complexes with enrofloxacin and 1,10-phenanthroline/8-hydroxyquinoline have been synthesized. The metal complexes have been characterized by elemental analyses, molar conductance, FT-IR, solid reflectance, magnetic moment, thermal analyses, X-ray powder diffraction (XRD) and SEM analysis. Conductance measurements indicate that all the complexes are non-electrolytes. Spectral IR data showed that the deprotonated enrofloxacin is bidentately bound to the metal ion through the pyridone oxygen and the carboxylated oxygen; 1,10-phenanthroline acts as neutral bidentate ligand coordinated through two nitrogen donor atoms, and the deprotonated 8-hydroxyquinoline is coordinated through nitrogen and oxygen donor atoms. The geometry of the complexes was elucidated with solid reflectance UV and magnetic moments. Thermal analysis recorded that TG/DTG/DSC experiments revealed the thermal stability of metal complexes and confirmed their compositions suggested by the analytical data. In addition to experimental data, a molecular modelling study has been performed to establish the optimized geometries of metal complexes. The XRD analysis of powders evidences the nanocrystalline nature of all complexes. The results are in agreement with molecular modelling data. SEM images revealed highly agglomerated particles with irregular shape with sizes in the micrometre range. The ligand and their metal complexes were screened for their antimicrobial activity against Escherichia coli 25922, Staphylococcus aureus 25923, Pseudomonas aeruginosa 27853 and Candida albicans 10231. The metal complexes were also investigated for their cytotoxicity using an in vitro assay.

Morphological and Thermophysical Behavior of Hidroxyapatite Powders Processed by Mechanical Milling

The current research represents one section of our studies concerning the improvement of the biocompatibility related to the biocomposite materials for bone grafts application. The submicronic/nanometric hydroxyapatite stands for the progress in biocompatibility. This study highlights the wet mechanical milling process and its effects on the morphological and thermophysical properties of the hydroxyapatite powder particles (30-50µm as raw material) obtained by this method (500 nm average). The scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) facility point out the morphological and chemical compositional features of the processed powders during 10 hours in dry argon atmosphere. The thermal analysis (TA) in argon atmosphere, too, reveals the influence of the milling parameters on the thermal effects generated by the processed hydroxyapatite powders. The experimental results of our research validate some milling mechanisms reported by the literature for wet/dry mechanochemical process conditions.

Influence of cerium dopant on pyrochlore structure evolution under highly reducing atmosphere

Sm₂Ti₂O₇ and Sm₂Ti_1.8Ce_0.2O₇ samples have been synthesized using a modified Pechini method. The evolution of structure and morphology under highly reducing atmosphere was evidenced using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy. Ceria seems to facilitate the reduction of titania, leading to the formation of orthorombic SmTiO₃.

Synthesis and characterization of La10Si6O27

Oxide ion conductors are an important group of materials which have been increasingly studied due to their applications in many devices of high technological interest, especially in Solid Oxide Fuel Cells (SOFC) which are efficient and environmentally friendly energy convertors. In this work we study an inexpensive, suitable and recyclable material with apatite structure. Lanthanum silicate with apatite type structure, La10Si6O27,was synthesized by two pathways: sol-gel and co-precipitation. The as-obtained powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. Samples with different morphologies consisting of a mixture of phases were obtained.

Cuspidine-type Solid Oxides for Fuel Cell applications

Cuspidine-type solid oxides having the compositions La₄(Ti₂O₈)O₂ and La₄(Ti_1.5Al_0.5O_8-δ)O₂ were synthesized using a modified Pechini method at much lower temperature than the one corresponding to the state of the art ceramic method. Their thermal behaviour was evaluated using TG/DSC techniques. Reduction-oxidation processes were evidenced on both heating and cooling stages, their amplitude depending on gas atmosphere and sample composition.

Effect of dopant on the thermal and electrical behavior of nanostructured ceria materials

Nanopowders with compositions Ce<inf>0.8</inf>Gd<inf>0.2</inf>O<inf>2−δ</inf> (CG), Ce<inf>0.8</inf>Sm<inf>0.2</inf>O<inf>2−δ</inf> (CS), and Ce<inf>0.9</inf>Eu<inf>0.1</inf>O<inf>2−δ</inf> (CE) have been synthesized by a modified Pechini method. X-ray diffraction (XRD) revealed that all powders calcined at 550°C were single phase, with the cubic fluorite-type structure. The good sintering properties of the synthesized nanopowders allowed us to obtain dense ceramics (>97% theoretical density). The ionic conductivities of doped ceria ceramics were investigated as a function of temperature by using AC impedance spectroscopy in the temperature range 300–800°C. The best conductivity was evidenced for the Ce<inf>0.8</inf>Sm<inf>0.2</inf>O<inf>2−δ</inf> sample.