Development of novel LSM/GDC composite and electrochemical characterization of LSM/GDC based cathode-supported direct carbon fuel cells

(La_0.8Sr_0.2)_0.95MnO_3?δ (LSM)–Gd_0.1Ce_0.9O_2?δ (gadolinium-doped ceria, GDC) composite cathode material was developed and characterized in terms of chemical stability, sintering behaviour, electrical conductivity, mechanical strength and microstructures to assess its feasibility as cathode support applications in cathode-supported fuel cell configurations. The sintering inhibition effect of LSM, in the presence of GDC, was observed and clearly demonstrated. The mechanical characterization of developed composites revealed that fracture behaviour is directly affected by pore size distribution. The Weibull strength distribution showed that for bimodal pore size distribution, two different fracture rates were present. Furthermore, the contiguity of LSM and GDC grains was calculated with image analysis, and correlation of microstructural features with mechanical and electrical properties was established. Subsequently, an LSM/GDC-based cathode-supported direct carbon fuel cell (DCFC) with Ni/ScSZ (scandia-stabilised zirconia) anode was successfully fabricated via slurry coating and co-firing techniques. The microstructures of electrodes and electrolyte layers were observed to confirm the desired morphology after co-sintering, and a single cell was electrochemically characterized in solid oxide fuel cell (SOFC) and DCFC mode with ambient air as oxidant. The higher values of open-circuit voltage indicated that the electrolyte layer prepared by vacuum slurry coating is dense enough. The corresponding peak power densities at 850 °C were 450 and 225 mW cm^?2 in SOFC and DCFC mode, respectively. Electrochemical impedance spectroscopy was carried out to observe electrode polarization and ohmic resistance.     

Stability-Indicating Densitometric High-Performance Thin-Layer Chromatographic Method for the Quantitative Analysis of Biomarker Naringin in the Leaves and Stems of Rumex vesicarius L.

JPC – Journal of Planar Chromatography – Modern TLC - A simple, sensitive, and stability-indicating high-performance thinlayer chromatography (HPTLC)-densitometric method was developed...     

Facile Electrochemical Hydrogenation and Chlorination of Glassy Carbon to Produce Highly Reactive and Uniform Surfaces for Stable Anchoring of Thiolated Molecules

Carbon is a highly adaptable family of materials and is one of the most chemically stable materials known, providing a remarkable platform for the development of tunable molecular interfaces. Herein, we report a two‐step process for the electrochemical hydrogenation of glassy carbon followed by either chemical or electrochemical chlorination to provide a highly reactive surface for further functionalization. The carbon surface at each stage of the process is characterized by AFM, SEM, Raman, attenuated total reflectance (ATR) FTIR, X‐ray photoelectron spectroscopy (XPS), and electroanalytical techniques. Electrochemical chlorination of hydrogen‐terminated surfaces is achieved in just 5 min at room temperature with hydrochloric acid, and chemical chlorination is performed with phosphorus pentachloride at 50 °C over a three‐hour period. A more controlled and uniform surface is obtained using the electrochemical approach, as chemical chlorination is observed to damage the glassy carbon surface. A ferrocene‐labeled alkylthiol is used as a model system to demonstrate the genericity and potential application of the highly reactive chlorinated surface formed, and the methodology is optimized. This process is then applied to thiolated DNA, and the functionality of the immobilized DNA probe is demonstrated. XPS reveals the covalent bond formed to be a C?S bond. The thermal stability of the thiolated molecules anchored on the glassy carbon is evaluated, and is found to be far superior to that on gold surfaces. This is the first report on the electrochemical hydrogenation and electrochemical chlorination of a glassy carbon surface, and this facile process can be applied to the highly stable functionalization of carbon surfaces with a plethora of diverse molecules, finding widespread applications.     

Significance of Branching for Transfection: Synthesis of Highly Branched Degradable Functional Poly(dimethylaminoethyl methacrylate) by Vinyl Oligomer Combination

A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA counterpart as gene‐delivery vectors. The branched PDMAEMA copolymers were synthesized by controlled radical cross‐linking copolymerization based on the “vinyl oligomer combination” approach. Efficient degradation properties were observed for all of the copolymers. The degree of branching was found to have a big impact on performance in transfection when tested on different cell types. The product with the highest degree of branching and highest degree of functionality had a superior transfection profile in terms of both transfection capability and the preservation of cell viability. These branched PDMAEMA copolymers show high potential for gene‐delivery applications through a combination of the simplicity of their synthesis, their low toxicity, and their high performance.     

Quadratic autocatalysis with non-linear decay

We provide a detailed, and thorough, investigation into the concentration multiplicity and dynamic stability of a prototype non-linear chemical mechanism: quadratic autocatalysis subject to non-linear decay in a continuously stirred tank reactor. This model was previously investigated in the literature using numerical path-following techniques. The contribution of this study is the application of singularity theory and degenerate Hopf-bifurcation theory to obtain analytical representations of many of the features of interest in this system. In particular, we use these presentations to identify critical values of an unfolding parameter below which specified phenomenon are no longer exhibited.     

Kinetic and mechanistic investigations on the oxidation of N’-heteroaryl unsymmetrical formamidines by permanganate in aqueous alkaline medium

Kinetic studies on the oxidation of two substituted azinyl formamidines (Azn-Fs), namely N,N-dimethyl-N’-(pyrimidin-2-yl) formamidine (Pym-F) and N,N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F), by alkaline permanganate have been performed by spectrophotometry. The spectroscopic and kinetic evidence reveals the formation of 1:1 intermediate complexes between the oxidant and substrates. The influence of pH on the oxidation rates indicated that the reactions are base-catalyzed. The reactions show identical kinetics, being first order each in [MnO₄ ^?]₀ and [Azn-F]₀, but with a fractional first-order dependence on [OH^?]. The effect of temperature on the reaction rate has been studied. Increasing ionic strength has no significant effect on the rate. The final oxidation products of Pym-F and Py-F were identified as 2-aminopyrimidine and 2-aminopyridine, respectively, in addition to dimethyl amine and carbon dioxide. Under comparable experimental conditions, the oxidation rate of Py-F is higher than that of Pym-F. A reaction mechanism adequately describing the observed kinetic behavior is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-limiting step of the reactions, along with thermodynamic quantities, are presented and discussed.     

An efficient and facile multicomponent synthesis of 4,6-diarylpyridine derivatives under solvent-free conditions

We present an efficient and facile synthesis of 4,6-diaryl-2-oxo-1,2-dihydropyridine-3-carbonitriles (5a–j) via a four-component system of aromatic aldehydes (1), acetophenones (2), ethyl cyanoacetate (3), and ammonium acetate (4). The short reaction time coupled with the simplicity of the reaction procedure and clean reaction make this method one of the most efficient methods for synthesis of this class of compounds.     

Long-Lived Charge-Transfer State Induced by Spin-Orbit Charge Transfer Intersystem Crossing (SOCT-ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long-lived triplet charge-transfer (³CT) state, based on the electron spin control using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT-ISC takes 8 ns to produce the ³NI* state. Then the slow secondary CS (125 ns) gives the long-lived ³CT state (0.94 μs in deaerated n-hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as ¹NI*→¹CT→³NI*→³CT. With time-resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state. Our spiro compact dyad structure and the electron spin-control approach is different to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory.