Phase Evolution and Electrochemical Properties of Nanometric Samarium Oxide for Stable Protonic Ceramic Fuel Cells

Electrochemical properties of metal oxide have a strong correlation with the crystalline structures. In this work, the effect of calcination temperature on the phase evolution and electrochemical properties of Sm₂O₃ was systematically evaluated. The results demonstrate that the sample calcinated at 700 °C (SM-700) is composed of a pure cubic phase while it begins to convert into a monoclinic phase at a temperature above 800 °C and fully converts into a monoclinic phase at 1100 °C. Moreover, the evolution process causes atomic redistribution, and more oxygen vacancies are formed in cubic phase Sm₂O₃, contributing to the improved ionic conductivity. The ionic conductivity of 0.138 S cm⁻¹ and maximum power density of 895 mW cm⁻² at 520 °C are achieved using SM-700 as electrolyte for protonic ceramic fuel cell (PCFC). The cubic structure remains stable in the durability testing process and the SM-700 based fuel cell delivers enhanced stability of 140 mW cm⁻² for 100 h. This research develops a calcination evolution process to improve the ionic conductivity and fuel cell performance of the Sm₂O₃ electrolyte for stable PCFC.     

The barrier to enantiomerization of N-Boc-2-lithiopyrrolidine: the effect of chiral and achiral diamines

(-)-Sparteine and TMEDA dramatically lower both enthalpy and entropy of activation for the barrier to enantiomerization of N-Boc-2-lithiopyrrolidine in diethyl ether, whereas N,N'-diisopropylbispidine has little effect; the entropy of activation for enantiomerization is zero in the presence of TMEDA and slightly negative in the presence of sparteine; these data suggest a subtle change in mechanism of enantiomerization in the presence of TMEDA and sparteine.     

Flow-Injection Determination of Cephalosporin Antibiotic Cefixime in Pharmaceutical Formulations with Luminol-Diperiodatoargentate(III) Chemiluminescence Detection

Journal of Analytical Chemistry - A simple and sensitive flow injection chemiluminescence method was developed for the determination of cefixime trihydrate (CFX) based on its enhancing effect on...     

Rational Enzyme Design without Structural Knowledge: A Sequence-Based Approach for Efficient Generation of Transglycosylases

Glycobiology is dogged by the relative scarcity of synthetic, defined oligosaccharides. Enzyme-catalysed glycosylation using glycoside hydrolases is feasible but is hampered by the innate hydrolytic activity of these enzymes. Protein engineering is useful to remedy this, but it usually requires prior structural knowledge of the target enzyme, and/or relies on extensive, time-consuming screening and analysis. Here, a straightforward strategy that involves rational rapid in silico analysis of protein sequences is described. The method pinpoints 6–12 single-mutant candidates to improve transglycosylation yields. Requiring very little prior knowledge of the target enzyme other than its sequence, the method is generic and procures catalysts for the formation of glycosidic bonds involving various d /l -, α/β-pyranosides or furanosides, and exo or endo action. Moreover, mutations validated in one enzyme can be transposed to others, even distantly related enzymes.     

The effect of matrix on melting and solidification behaviours of embedded Pb-Sn alloy nanoparticles

The present investigation is aimed at understanding the effect of a matrix on the phase transformation of biphasic embedded Pb–Sn alloy nanoparticles. The melting and solidification behaviours of eutectic (Pb_26.1Sn_73.9) nanoparticles embedded in icosahedral (IQC) as well as decagonal quasicrystalline (DQC) matrix have been studied. Electron microscopic observations reveal that the major portion of the alloy nanoparticle consists of body-centred tetragonal β-(Sn) with face-centred cubic (Pb) constituting the cap. (Pb) bears specific orientation relationships (OR) with the surrounding IQC matrix, whereas β-(Sn) does not have any specific OR. For alloy particles embedded in the DQC matrix, both (Pb) and β-(Sn) bear specific OR. In case of IQC matrix, differential scanning calorimetric measurements reveal sharp melting but diffuse solidification peaks for the embedded nanoparticles. On the other hand, sharp melting and solidification peaks are observed for the nanoparticles embedded in the DQC matrix. The IQC and DQC are heat-treated at different temperatures to observe the effect of the matrix on the phase transformation of the alloy nanoparticles. The formation of well- developed facets in the nano-particles and defects in the matrix have been found to play a crucial role in determining the phase transformation of the alloy nanoparticles in the heat-treated samples. The experimental observations are rationalized using available literature.     

Molecular core-valence correlation effects involving the post-d elements Ga-Rn: benchmarks and new pseudopotential-based correlation consistent basis sets

Correlation consistent basis sets that are suitable for the correlation of the outer-core (n-1)spd electrons of the post-d elements Ga-Rn have been developed. These new sets, denoted by cc-pwCVXZ-PP (X=D,T,Q,5), are based on the previously reported cc-pVXZ-PP sets that were built in conjunction with accurate small-core relativistic pseudopotentials (PPs) and designed only for valence nsp correlation. These new basis sets have been utilized in benchmark coupled cluster calculations of the core-valence correlation effects on the dissociation energies and spectroscopic properties of several small molecules. As expected, the most important contribution is the correlation of the (n-1)d electrons. For example, in the case of the group 13 homonuclear diatomics (Ga(2),In(2),Tl(2)), this leads to a dissociation energy increase compared to a valence-only treatment from 1.5 to 3.2 kcal/mol, bond length shortenings from -0.076 to -0.125 A?, and harmonic frequency increases of 7-8?cm(-1). Even in the group 15 cases (As(2),Sb(2),Bi(2)), the analogous effects of (n-1)d electron correlation are certainly not insignificant, the largest values being +4.4?kcal/mol, -0.049 A?, and +9.6?cm(-1) for the effects on D(e), r(e), and ω(e), respectively. In general, the effects increase in magnitude down a group from 4p to 6p. Correlation of the outer-core (n-1)p electrons is about an order of magnitude less important than (n-1)d but larger than that of the (n-1)s. The effect of additional tight functions for Hartree-Fock and valence sp correlation was found to be surprisingly large, especially for the post-4d and post-5d elements. The pseudopotential results for the molecules containing post-3d elements are also compared to the analogous all-electron calculations employing the Douglas-Kroll-Hess Hamiltonian. The errors attributed to the PP approximation are found to be very small.     

Enhanced electrochemical performance of La- and Zn-co-doped LiMn2O4 spinel as the cathode material for lithium-ion batteries

We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles?? surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500???g/cm³ in 24?h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.     

FeCl3-Catalyzed Pechmann Synthesis of Coumarins in Ionic Liquids

The synthesis of coumarin derivatives via Pechmann reaction using anhydrous FeCl₃ as Lewis acid catalyst in ionic liquid medium has been carried out. The best results were obtained (yields as high as 89%) with ionic liquids having bis(triflic)imide as a counteranion. The ionic liquid could easily be recovered and reused.