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In this report, we present the synthesis of few layer MoS2 and polyaniline/MoS2 nanocomposites with a complete structural characterization by atomic force microscopy, small-angle X-ray scattering, X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy followed by AC impedance spectroscopy and thermoelectric characterizations. Our structural studies revealed that the intercalation of MoS2 nanosheets into polyaniline fibers produces a decrease in the MoS2 interlayer distance and a slight increase in the degree of order of the nanocomposites. In addition, an increment in the polaron Raman signature was observed with the addition of MoS2 nanosheets into polyaniline nanocomposites in agreement with the enhancement of the electrical conductivity, i.e. up to ~ 2.5 S cm−1. The addition of low amounts of MoS2 also lead to an increment of the seebeck coefficient (up to 5.3 µV K−1) and power factor (up to 0.0070 µV m−1 K−2). This report showed excellent synergistic effect between PANI and MoS2 nanosheets which could be of great importance for future applications of these nanocomposites, mainly as thermoelectric materials. [ABSTRACT FROM AUTHOR]

A first principles simulation of the crystal structure of potassium peroxocarbonate is presented, using density functional methods (both local and semilocal) for the calculations. An experimental crystal structure with a seemingly inconsistent disposition of the peroxide bonds was used as initial input. Both geometry optimizations of the molecular structure and optimization of the cell size were performed. While cell parameters and heavier atom positions determined at the GGA level are very close to the experimental ones, there are important discrepancies in the positioning of the hydrogen atoms. As a result of these calculations, it was shown that the assignment of the peroxydic hydrogens and the peroxydic bond in the experimental structure was incorrect. A more accurate structure is presented and geometrical as well as cell parameters described. It is also shown that LDA is not accurate enough to describe this type of ionic crystals, because of overbinding of the ions, leading to incorrect cell parameters and volume. Our methodology was validated using DFT methods with several basis sets. [ABSTRACT FROM AUTHOR]

In this report, we prepare LLTO ceramics by the sol-gel method in acetic medium. Raman spectroscopy showed the formation of lanthanum and titanium acetates precursors, which after calcination, lead to formation of the LLTO nanoparticles. Raman spectra were scanned directly over the LLTO pellets and the disappearance of impurities was observed during the microstructure evolution with increasing sintering temperature. X-ray diffraction characterization, including full pattern profile fitting refinements, showed no drastic changes in the unit cell parameters of the LLTO perovskite, but a large increase in the crystallite size domain was observed with increasing sintering temperature. Additionally, an interesting structural phase transition for the Li 0.30 La 0.57 TiO 3 perovskite structure was observed, from tetragonal P4/mmm to distorted-cubic Pm-3m spacegroup, for the highest sintering temperature (Ts=1300 °C). Experimental and theoretical simulations of Raman spectroscopy confirmed the formation of a distorted-cubic phase and confocal Raman spectroscopy showed the presence of traces of impurities at the grain boundary region. In spite of the low total lithium conductivity observed, the electrochemical impedance spectroscopy analysis showed a remarkable increase in the lithium bulk conductivity for Ts=1300 °C. This fact could be attributed to the structural phase transition from tetragonal to the cubic crystal system. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low formation energy for ultrathin TiO2 (B) (001) bilayers. [•] Formation energy comparable with Anatase (101). [•] Formic acid is adsorbed in monodentate configuration through carbonyl group in dry TiO2 (B) (001). [•] TiO2 (B) (001) seems to be adequate for anchoring common dyes for solar cells applications. [ABSTRACT FROM AUTHOR]

Two flexible ligands derived from iminodiacetic acid, N-methyliminodiacetic acid and N-(2-hydroxyethyl)iminodiacetic acid have been used as ligands towards lanthanide ions. Polymeric cationic networks have been prepared and fully characterized. The influence of the substitution on N atom in the ligand is discussed. Two flexible ligands derived from iminodiacetic acid, N-methlyiminodiacetic acid (H 2 mida) and N-(2-hydroxyethyl)iminodiacetic acid (H 2 hida) have been used as ligands towards lanthanide ions. Potentiometric studies (25.0 °C, 0.50 mol L−1 Me 4 NCl) revealed the predominance of stable species at acidic pH values. With this information, the synthesis of the coordination compounds was afforded in aqueous solution and the polymeric solids [Sm(Hmida) 2 (H 2 O) 2 ]ClO 4 ·1/6NaClO 4 ·9H 2 O and [Ln(hida)(H 2 O) 2 ](F 3 CSO 3)·H 2 O (Ln = Ho, Yb) were prepared and characterized. The samarium compound consists of a cationic 2D polymeric structure in which the ligand is protonated in the N atom, preventing coordination to the central atom. The structure presents channels along one crystallographic direction. Ho and Yb coordination compounds are isostructural. A 2D polymeric cationic network is also observed. In this case, the additional hydroxyethyl group and the unprotonated N atom participate in the coordination. [ABSTRACT FROM AUTHOR]

Highlights: [•] [Na2(H2O)8][Fe4(μ-O)2(O2CPh)7(pic)2]2·2H2O was obtained from [Fe3O(O2CPh)6(H2O)3]+. [•] Competing magnetic interactions in the {Fe4} core lead to an S =0 ground state. [•] The magnetic properties were also studied by DFT methods. [ABSTRACT FROM AUTHOR]

The synthesis, crystal structures and luminescence of a novel family of lanthanide polymer complexes with general formula [Ln 2 (Hmidp) 3 (H 2 O) 3 ](ClO 4 ) 3 ·6H 2 O (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Tm; H 2 midp = N-methyliminodipropionic acid) are reported. The compounds were obtained by direct reaction of H 2 midp and lanthanide(III) perchlorate in aqueous solution. The choice of the conditions of synthesis were selected from speciation studies. The structure of the polymer complexes contains bimetallic cationic units [Ln 2 (Hmidp) 3 (H 2 O) 3 ] 3+ in which one of the Ln ions is eight-coordinated and the other nine-coordinated, linked by carboxylate bridges. This is expanded to a 2D network through carboxylate linkers. The solid state luminescence of the Eu complex was observed and an average lifetime value of 0.5 ms was verified for the red emitting 5 D 0 excited state. [ABSTRACT FROM AUTHOR]

Abstract: The stoichiometric reaction of copper(II) chloride with iminodiacetic acid (H2ida), and lanthanide(III) chloride in water yields the heteropolynuclear complexes [Ln2Cu3(ida)6]·xH2O. In this work, the synthesis and full characterization of those complexes with Ln=Ce, Ho is presented. The structures are based on [Cu(ida)2] building blocks, linked by the Ln ions via carboxylate bridges. The formation of nanochannels along the crystallographic c axis is verified. The comparison with analogous complexes containing other Ln ions, shows that the channels are perfectly tuneable in size along the series. These chemical systems were also investigated in solution (25.0°C, I =0.5M Me4NCl) by potentiometry. The same kind of polynuclear species have been found in aqueous solution. [Copyright &y& Elsevier]