Cobalt Based Nanoparticles Embedded Reduced Graphene Oxide Aerogel for Hydrogen Evolution Electrocatalyst

Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS₂, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm^?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec^?1 and a charge transfer resistance (R_ct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer.     

On strongly stable normal operators in Krein spaces

For bounded normal operators in Krein spaces we give a necessary and sufficient condition for strong stability. The same result for unitary operators was obtained by M.G.Krein [1] (see also [2]). For selfadjoint operators we refer to the papers of P.Jonas, H.Langer [3] and H.Langer [4].     

Synthesis, characterization, and electron transfer reaction of some surfactant–cobalt(III) complex ions

Abstract  

The surfactant complex ion cis-[Co(tmd)₂(C₁₂H₂₅NH₂)₂]³⁺ (tmd = 1,3-propanediamine, C₁₂H₂₅NH₂ = dodecylamine) has been synthesized and characterized by elemental analysis and spectral data. In addition we have determined the critical micelle concentration of the surfactant–cobalt(III) complex and studied the kinetics and mechanism of the complex with ferrocyanide anion. The reaction is found to be second order, and the second-order rate constant increases with increasing initial concentration of the surfactant–cobalt(III) complex due to the presence of self-micelles formed by the complex itself. The thermodynamic parameters were determined. The results have been analyzed.     

Studies on outer sphere electron transfer reactions of some surfactant-cobalt(III) complexes with ferrocyanide anion

The kinetics and mechanism of reduction of the surfactant-cobalt(III) complex ions, cis-[Co(bpy)₂(C₁₂H₂₅NH₂)₂]³⁺ and cis-[Co(phen)₂(C₁₂H₂₅NH₂)₂]³⁺ (bpy = bipyridyl, phen = 1,10-phenan-throline, C₁₂H₂₅NH₂ = dodecylamine) by Fe(CN₆)⁴⁻ in self-micelles were studied at different temperatures. Experimentally the reaction was found to be second order and the electron transfer postulated as outersphere. The rate constant for the electron transfer reaction for both the complexes was found to increase with increase in the initial concentration of the surfactant-cobalt(III) complex. This peculiar behaviour of dependence of second-order rate constant on the initial concentration of one of the reactants has been attributed to the presence of various concentration of micelles under different initial concentration of the surfactantcobalt(III) complexes in the reaction medium. The effect of inclusion of the long aliphatic chain of the surfactant complex ions into β-cyclodextrin on these reactions has also been studied.     

Magnetic, dielectric and complex impedance spectroscopic studies of nanocrystalline Cr substituted Li-ferrite

Nanocrystalline Li_0.5Fe_2.5−xCr_xO₄ (2.5≤x≥0) ferrites were prepared by a sol-gel autocombustion route. X-ray diffraction was employed to confirm the cubic spinel phase formation of the ferrites. The lattice parameter decreases with increase in Cr content. The saturation magnetization, coercivity and remanance were studied as a function of Cr content. The dielectric constant and dielectric loss were measured as a function of frequency in the frequency range 20 Hz-1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. In order to understand the conduction mechanism, complex impedance measurements were carried out. The substitution of chromium plays an important role in changing the dielectric and magnetic properties of lithium ferrites.     

The reaction of 2‐aroyl‐3,3‐bis(alkylsulfanyl)acrylaldehydes and hydroxylamine hydrochloride: Facile synthesis of differently substituted isoxazoles

2‐Aroyl‐3,3‐bis(alkylsulfanyl)acrylaldehyde was utilized for the synthesis of three different isoxazoles by reacting with hydroxylaminehydrochloride. We synthesized differently substituted isoxazoles like (aryl)[5‐(methylsulfanyl)‐4‐isoxazolyl]methanones, 3‐(methylsulfanyl)‐5‐phenyl‐4‐isoxazolecarbonitriles and 5‐aryl‐3‐(methylsulfanyl)‐4‐isoxazolecarbaldehyde oximes in good yields by varying the substratereagent stoichiometry and temperature of the reaction medium.     

Photoluminescence properties of Sm3+-doped SFB glasses for efficient visible lasers

The photoluminescence properties of different concentrations of Sm³⁺ ions doped sodium fluoroborate (SFB) glasses of composition Na₂O–LaF₃–CaF₂–AlF₃–B₂O₃–SmF₃ have been investigated. The energy level analysis is carried out using free-ion Hamiltonian model. The Judd–Ofelt intensity parameters are used to evaluate the laser characteristic parameters such as spontaneous transition probability, radiative lifetime and fluorescence branching ratio for ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2 and 11/2) emission transitions of Sm³⁺ ion. The principal photoluminescence transitions of interest are identified by recording the emission spectra for different Sm³⁺ ion concentrations and measuring their emission cross-sections, integrated absorption cross-sections and optical gain parameters. The decay profiles from the ⁴G_7/2 excited manifold state to its lower lying energy levels have been recorded by monitoring the excitation and emission wavelengths at 402 and 600 nm, respectively. The dependence of effective fluorescence lifetime on the Sm³⁺ concentration is also discussed.     

Ultraheavy Yukawa-bound states of fourth-generation at Large Hadron Collider

A study of bound states of the fourth-generation quarks in the range of 500?C700 GeV is presented, where the binding energies are expected to be mainly of Yukawa origin, with QCD subdominant. Near degeneracy of their masses exhibits a new ??isospin??. The production of a colour-octet, isosinglet vector meson via $q\bar q \to \omega_8$ is the most interesting. Its leading decay modes are $\pi_8^\pm W^\mp$ , $\pi_8^0Z^0$ , and constituent quark decay, with $q\bar q$ and $t\bar t'$ and $b\bar b'$ subdominant. The colour octet, isovector pseudoscalar ?? ₈ meson decays via constituent quark decay, or to Wg. This work calls for more detailed study of fourth-generation phenomena at LHC.