Kinetics and mechanism of the reduction of colloidal MnO2 by glycyl-leucine in the absence and presence of surfactants

AbstractThe kinetics of the reduction of water-soluble colloidal manganese dioxide by glycyl-leucine (Gly-Leu) has been investigated in the presence of perchloric acid both in aqueous as well as micellar media at 35°C. The study was carried out as functions of [MnO2], [Gly-Leu] and [HClO4]. The first-order-rate is observed with respect to [MnO2], whereas fractional-order-rates are determined in both [Gly-Leu] and [HClO4]. Addition of sodium pyrophosphate and sodium fluoride enhanced the rate of the reaction. Further, the use of surfactant micelles is highlighted as, in favourable cases, the micelles help the redox reactions by bringing the reactants into a close proximity due to hydrogen bonding. While the ionic surfactants SDS and CTAB have not shown any effect on the reaction rate, the nonionic surfactant TX-100 has catalytic effect which is explained in terms of the mathematical model proposed by Tuncay et al. (1999). The Arrhenius and Eyring equations are valid for the reaction over the range of temperatures used and different activation parameters (Ea, ΔH#, ΔS# and ΔG#) have been evaluated. Kinetic studies show that the redox reaction between MnO2 and Gly-Leu proceeds through a mechanism combining one- and two-electron pathways: Mn(IV)→Mn(III)→Mn(II) and Mn(IV)→Mn(II). On the basis of the observed results, a possible mechanism has been proposed and discussed

Preparation and characterization of silver nanoparticles using aniline

AbstractUV–Vis spectroscopy, transmission electron microscopy (TEM) and selected area electron diffraction (SAED) have been employed to characterize silver nanoparticles (AgNPs) using aniline and silver nitrate as reductant and oxidant, respectively. A broad surface resonance plasmon (SRP) band appears at 400nm, indicating that the AgNPs are spherical. The TEM images show that AgNPs aggregated in an unsymmetrical manner, leading to the formation of beautiful silver nanocrystals. Aniline adsorbed onto the surface of Ag-nanocrystals through electrostatic, van der Walls forces and hydrogen bonding. Cetyltrimethylammonium bromide (CTAB) acted as a stabilizer and/or capping agent

Cross-linked single-walled carbon nanotube aerogel electrodes via reductive coupling chemistry

Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties

2-[(1-Methyl-1H-pyrrol-2-yl)methyl­idene]propane­dinitrile

In the title compound, C9H7N3, the N-bound methyl group and vinyl H atom are syn. The 12 non-H atoms comprising the mol­ecule are essentially coplanar (r.m.s. deviation = 0.071 Å). Supra­molecular tapes feature in the crystal packing, orientated perpendicular to [10-1], and are formed by C—H⋯N inter­actions involving each cyano N atom. The tapes are connected into layers via π–π inter­actions occurring between translationally related pyrrole rings [ring centroid–centroid distance = 3.8754 (10) Å]; the layers stack along the b axis

Современные концепции управления высшим учебным заведением

Целью и задачами статьи является исследование современных подходов к управлению вузом, их критический анализ и возможность оптимизации процессов деятельности вуза

Solvent-Free Biginelli Reactions Catalyzed by Hierarchical Zeolite Utilizing a Ball Mill Technique: A Green Sustainable Process

A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing of solvent was applied. The hierachical zeolite catalyst (MFI27_6) showed high yield (86%–96%) of DHPMs in a very short time (10–30 min). The recyclability of the catalyst for the subsequent reactions was examined in four subsequent runs. The catalyst was shown to be robust without a detectable reduction in catalytic activity, and high yields of products showed the efficient protocol of the Biginelli reactions

Self-decoration of Pt metal particles on TiO2 nanotubes used for highly efficient photocatalytic H2 production

Pt decorated TiO2 has, over the past decades, been a key material for photocatalytic hydrogen production. The present work shows that growing anodic self-organized TiO2 nanotubes from Ti–Pt alloy with a low Pt content of 0.2 at% leads to oxide nanotube layers that are self-decorated with Pt nanoparticles of 4–5 nm in diameter. The average particle spacing is in the range of ~50 nm and is partially adjustable by the anodization conditions. This intrinsic decoration of TiO2 nanotubes with Pt leads to a highly active photocatalyst for the production of H2 under UV or visible light conditions

Chemical Vapor Deposition Synthesis and Optical Properties of Nb2O5 thin films with Hybrid Functional Theoretical Insight into Band Structure and Band Gaps

Nb2O5 is an important material able to exist in many polymorphs with unique optical properties and morphologies that are dependent on the synthetic route. Here we report a novel ambient-pressure chemical vapor deposition route to Nb2O5 via aerosol-assisted chemical vapor deposition. The amorphous as-deposited films were annealed in air to obtain the the three most stable crystal structures: orthorhombic, tetragonal, and monoclinic. The films were thoroughly characterized for their material properties, and an in-depth study into the optical properties was carried out using state-of-the-art hybrid functional theory that allowed more insight into the optical properties of the materials

NH3 treatment of TiO2 nanotubes: from N-doping to semimetallic conductivity

In the present work we show that a suitable high temperature ammonia treatment allows for the conversion of single-walled TiO2 nanotube arrays not only to a N-doped photoactive anatase material (which is already well established), but even further into fully functional titanium nitride (TiN) tubular structures that exhibit semimetallic conductivity

Two polymeric 36-metal pure lanthanide nanosize clusters

973 Program [2011CBA00507, 2011CB932504]; National Natural Science Foundation of China [21131006]; Natural Science Foundation of Fujian ProvinceTwo rarely seen 2D coordination polymers based on huge 36-metal pure lanthanide clusters, {[Gd-36(NA)(36)(OH)(49)(O)(6)(NO3)(6)(N-3)(3)(H2O)(20)]Cl-2 center dot 28H(2)O}(n) (1) and {[Dy-36(NA)(36)(OH)(49)(O)(6)(NO3)(6)(N-3)(3-)(H2O)(20)]Cl-2 center dot 28H(2)O}(n) (2) (HNA = nicotinic acid), were synthesized and structurally characterized. The spherical Ln(36) skeleton can be viewed as the aggregation of one cyclohexane chair-like Ln(24) wheel and two identical tripod-like Ln(6) units. The coordination of the carboxylic groups of the NA ligands with the Ln(III) cations results in a square layer. Additionally, compound 1 possesses a large MCE of 39.66 J kg(-1) K-1 and compound 2 exhibits slow relaxation of the magnetization