The effect of preparation method and Sb content on SnO2-CuO sintering

The sintering behavior of SnO2-CuO system has been investigated for two preparation methods and as a function of antimony concentration. A chemical preparation (Pechini's method) resulted in powders with smaller particle sizes than for a conventional oxide mixture. This led to smaller grain sizes in Pechini's method ceramics. The microstructures were heterogeneous in both systems, showing grain coarsening. The densification was aided by liquid phase formation, due to copper, in both systems, but the temperature of maximum shrinkage rate was larger for the Pechini's method ceramic because copper had to diffuse to the grain surface. Independently of the preparation method, antimony did not aid densification, and increasing its concentration led to a higher densification temperature and lower shrinkage rate. (C) 2003 Kluwer Academic Publishers

Synthesis and characterization of antimony tartrate for ceramic precursors

Synthesis and characterization of antimony tartrate used as a precursor of ceramic powders obtained by Pechini's method were carried out. Antimony tartrate was chosen as a substitute for the antimony citrate commonly used in this chemical processing, because of difficulties in preparing the citrate. FTIR and TGA/DTA analysis showed that antimony tartrate, H-2[Sb-2(C4H2O6)(2)]. forms a polymeric structure. The procedure described indicates that the antimony chelate obtained is adequate for Pechini's method

The effect of Sb and Nb on the electrical conductivity of tin dioxide based ceramics

The electrical conductivity of Mn doped SnO2 systems prepared by an organic route (Pechini's method) has been investigated as a function of antimony and niobium concentration. The conductivity increases with the increase of both concentration ions, however, in a different manner. While the conductivity of niobium doped ceramics increases with the power of 1.6 for the entire range of concentrations studied (0.01-0.7 mol%), the conductivity of antimony doped ceramics increases with the power of 1.9 in the range 0.01-0.05 mol% of Sb; 3.7 in the range 0.05-0.30 mol% and 1.8 in the range 0.30-0.70 mol%. This behavior is attributed to the existence of two stable oxidation states for antimony: Sb3+ and Sb5+, while for niobium there is only one: Nb5+. The power of 3.7 for Sb would be related to the segregation of this ion on the grain boundary accompanied by an additional contribution coming from the substitution of Sn2+ by Sb3+ on the grain surface

Electroactive properties of 1-propyl-3-methylimidazolium ionic liquid covalently bonded on mesoporous silica surface: development of an electrochemical sensor probed for NADH, dopamine and uric acid detection

A hybrid organic-inorganic porous material was successfully prepared through chemical modification of a non-ordered mesoporous silica, obtained by the sol-gel process, with 1-propyl-3-methylimidazolium groups. The porous material was evaluated as a platform for the development of electrochemical sensors, here probed toward the electrooxidation of NADH (beta-nicotinamide adenine dinucleotide), uric acid (UA) and dopamine (DA). The presence of cationic imidazolium groups on the surface of the hybrid silica-based material allowed the electrochemical detection of these biomolecules without any other electron mediator or biomolecular recognition component. Such behavior highlights the potentiality of this material to be applied in the development of new electrochemical sensing devices. Theoretical calculations based on density functional theory emphasizes that the cationic character of imidazolium group provides better oxidation conditions if the solvent effect is minimized123435440CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESsem informação2013/08293-

Photophysical properties of asymmetric and water-soluble dinuclear lanthanide complexes of poly glycol chain functionalized-benzoic acid derivative: experimental and theoretical approaches

New water-soluble lanthanide complexes with a poly glycol chain (–OEtOEtOEtOMe) functionalized benzoic acid derivative ligand were synthesized and photophysically characterized. The results indicate a formation of an asymmetric dinuclear lanthanide complexes. The [Eu2(mee)6(H2O)2] complex shows emission in water solution and it was noted that after 48 h part of the ligands are replaced by water molecules resulting on quenching of the emission and decreasing of lifetimes by O–H oscillators from water molecules. The average Judd–Ofelt intensity parameters were determined experimentally from emission spectra of the europium(III) complex. Additionally, the contribution of each asymmetric europium(III) center to the JO intensity parameters were calculated independently using time resolved spectroscopy and the LUMPAC software helping the proposition of the polyhedral coordination sphere determined by the ground state geometry using the Sparkle/PM3 model. The transfer and back energy transfer rates were also calculated. The values obtained for energy transfer rates are lower than previous values obtained for europium(III) complexes with benzoic acid derivative ligands, indicating the role of the poly glycol chain on photophysical properties of the [Eu2(mee)6(H2O)2] complex.6103101133101141CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP159249/2014-7Sem informação2015/22426-5; 2013/22127-