Publications: Multifunctional Nanomaterials and Nanocomposites

Scientific publications of the research group on multifunctional nanomaterials and nanocomposites

13

Jun 2018

Synthesis, crystal structure, DFT (B3LYP/LanL2DZ) and photoluminescence study of new stanate (IV) based inorganic-organic hybrid

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A novel interesting metal hybrid stanate compound, named as hexachlorostanate (II) 4.4′ bipyridinium and formulated as (C10H10N2) SnCl6, was synthesized at room temperature by slow evaporation and then characterized by a single X-ray diffraction, spectroscopic measurements, Scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence technique. It crystallizes in the space group C2/c with the following unit cell parameters: a = 17.9611 (13) Å, b = 12.9274 (5) Å, c = 7.6305 (6) Å and β = 117.860 (10) °. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated [SnCl6] 2- octahedral anions and 4.4′ bipyridinium (C10H10N2) cations, which are connected via N-H⋯Cl hydrogen bonds forming a chain network. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. The optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the present compound were theoretically examined by the DFT/ B3LYP method with the LanL2DZ basis set. The X-ray powder is in agreement with the X-ray structure. 13C NMR spectrum shows three signals, confirming the solid state structure determined by X-ray diffraction. Photoluminescence measurements showed a strong emission line at 2.95 eV associated with radiative recombinations of excitons confined within the [SnCl6] 2- which were investigated at room temperature.

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26

Apr 2018

Metastable phase in binary and ternary 12-carat gold alloys at low temperature

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Low temperature phase transitions in 12-carat gold alloys have been investigated for binary Au-Cu and ternary Au-Cu-Ag compositions. The thermal analyses investigations using differential scanning calorimetry (DSC) and the dilatometry were performed in the 50–300 °C temperature range in order to detect the structural transformations. The thermal analyses were carried out on annealed samples at 700 °C for two hour followed by water quenching. They reveal an important new reaction for both used compositions and both thermal techniques confirm each other. This reaction has been assessed as pre-ordering reaction. SEM and STM imaging were performed on annealed samples at 700 °C for two hours and water quenched followed by a heating from room temperature up to the temperature of the new peaks obtained in the thermal study. The imaging reveals the relationship between the pre-ordering reaction and the surface aspect presented in the fact of dendrite precipitates. A series of SEM observation have been performed in order to follow the kinetic of the observed precipitates by the way of several series of heating up, from 140 to 220 °C for the binary composition and from 100 to 180 °C for the ternary composition. Furthermore, this study shows that the silver accelerates the ordering reaction.

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16

Apr 2018

Synthesis, crystal structure, photoluminescence and dielectric properties of a new organic–inorganic compound: tetrachlorocadmate (II) 2.2′-bipyridinium

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Single crystals of a new organic–inorganic compound (C10H10N2) CdCl4 were grown by the slow evaporation technique and characterized by X-ray diffraction, Hirshfeld surface, Infrared absorption, Solid state 13C NMR, photoluminescence (PL) properties, differential scanning calorimetry (DSC) and dielectric measurements. The title compound belongs to the monoclinic space group P21/c with the following unit cell parameters: a = 7.29420(1), b = 13.9206(3), c = 14.3880(3) Å, β = 100.247(2)° and Z = 4. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated [CdCl4]2− tetrahedral anions and 2.2′ bipyridinium (C10H10N2)2+ cations, which are connected via N–H⋯Cl hydrogen bonds. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. Furthermore, the room temperature infrared (IR) spectrum of the title compound was recorded and analyzed on the basis of detailed vibrational studies found in the literature; the detailed assignment confirms the presence of the organic groups. Solid state 13C NMR spectrum shows four signals, confirming the solid state structure determined by X-ray diffraction. Besides, photoluminescence measurements showed a strong emission line at 2.95 eV associated with radiative recombinations of excitons confined within the [CdCl4]2−which were investigated at room temperature. Finally, the thermal analysis studies were performed, and phase transition was found in the temperature range between 300 and 550 K, while the electrical measurements were performed to discuss the phase-transition mechanism.

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