Banana pulp extract mediated synthesis of Cu2O nanoparticles: An efficient heterogeneous catalyst for the ipso-hydroxylation of arylboronic acids

A green and facile novel procedure has been developed for the synthesis of Cu₂O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu₂O nanoparticles as a catalyst and aqueous H₂O₂ as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields.     

Catalytic reaction mechanism of Mn-doped nanoporous aluminophosphates for the aerobic oxidation of hydrocarbons

In this work we apply state-of-the-art electronic-structure-based computational methods based on hybrid-exchange density functional theory to study the mechanism of the aerobic oxidation of hydrocarbons catalysed by Mn-doped nanoporous aluminophosphates (Mn-AlPOs). We compare our results with available experimental data. We show that the catalytic efficiency of Mn-AlPOs in oxidation reactions is intrinsically linked to 1) the Mn redox activity, in particular between 2+ and 3+ oxidation states, and 2) the coordinative insaturation of tetrahedral Mn embedded in AlPO frameworks, which facilitates the reaction by stabilising oxo-type radicals through the formation of Mn complexes. Our mechanism demonstrates the crucial role of both Mn(III) and Mn(II) in the reaction mechanism: Mn(III) sites undergo an initial reaction cycle that leads to the production of the alkyl hydroperoxide intermediate, which can only be transformed into the oxidative products (alcohol, aldehyde and acid) by Mn(II). A preactivation step is required to yield the reduced Mn(II) sites able to decompose the hydroperoxide intermediates; this step takes place through a transformation of the hydrocarbon into the corresponding peroxo-derivative, stabilised by forming a complex with Mn(III) and yielding at the same time reduced Mn(II) sites. Both species enter a subsequent propagation cycle in which Mn(II) catalyses the dissociation of the hydroperoxide that proceeds until the formation of the oxidative products by two parallel pathways, through alkoxy- or hydroxy-radical-like intermediates, whilst the Mn(III)-peroxo complex enables further production of the hydroperoxide intermediate.     

Transition Metal Ions or Acid-induced Suppression of Photoinduced Proton Transfer and Electron Transfer Reaction in 5-(4-Fluorophenyl)-2-hydroxypyridine: A Molecule of Dual Mode Fluorosensitivity

The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) at different pH and its fluorescence response toward different transition metal ions have been studied by steady-state absorption and emission spectroscopy in combination with quantum chemical calculations. Although keto-enol tautomerization is observed in the excited state, the molecule is weakly fluorescent due to the presence of electron-rich nitrogen atom and relatively electron-deficient fluorine atom, which may lead to photoinduced electron transfer process. In the presence of the transition metal ions, such as Zn²⁺, Cd²⁺, Hg²⁺, etc., the studied molecule exhibits changes in its absorption and emission properties. The present system shows fluorescence enhancement instead of usual quenching in presence of the transition metal ions, such as Fe²⁺ and Cu²⁺. Spectral observation leads to the interpretation that this structurally simple molecule can be effectively utilized as a chelation-enhanced fluorescence-based chemosensor for the detection of transition metal ions. The experimental findings corroborate well with theoretical calculations at Hartree–Fock level using 6-31G** and lanl2dz basis sets.     

Determination of molybdenum(VI) by differential pulse polarographic technique using 4-(2-hydroxy phenyl ethaminodiol), benzene-1,3-diol(4-2-HPEDB-1,3,D)

A novel analytical reagent 4-(2-hydroxy phenyl ethaminodiol), benzene-1,3-diol(4-2-HPEDB-1,3,D) was synthesized for the determination of molybdenum(VI). The present paper reveals the detailed study of electroanalytical behaviour for [Mo-(4-2-HPEDB-1,3,D)] complex under optimized conditions. The peak obtained for [Mo-(4-2-HPEDB-1,3,D)] prevent the interference of foreign ions which shows the sensitivity of the proposed method. The linearity was maintained at the concentration range of 0.5–200 μg/mL at pH 4.5 with correlation factor 0.9997. The present method was successfully applied for the analysis of molybdenum(VI) in biological fluids and plant material. The results obtained from the proposed method show good agreement with reference method.     

Tunable and rapid crystallisation of phase pure Bi2MoO6 (koechlinite) and Bi2Mo3O12 via continuous hydrothermal synthesis

Herein, we report the rapid single step hydrothermal synthesis of phase pure Bi₂MoO₆ (koechlinite) and Bi₂Mo₃O₁₂, via a continuous hydrothermal flow synthesis (CHFS) reactor, which uses supercritical water of 375–450 °C at a pressure of 24.1 MPa as a crystallising medium. The product being obtained as highly crystalline nano-materials with high surface area. Simple variation in synthesis condition and appropriate solution stoichiometry were shown to be sufficient to select the phase of the product. The materials synthesised showed significant photcatalytic activity towards the decolourisation of methylene blue in comparison to a commercial gold standard photocatalyst.     

Do Two Flavour Oscillations Explain both KamLAND Data and the Solar Neutrino Spectrum?

The recent measurement of Δ _sol by the KamLAND experiment with very small errors, makes definitive predictions for the energy dependence of the solar neutrino survival probability P _ee . We fix Δ _sol to be the KamLAND best fit value of 8×10⁻⁵ eV² and study the energy dependence of P _ee for solar neutrinos, in the framework of two flavour oscillations and also of three flavour oscillations. For the case of two flavour oscillations, P _ee has a measurable slope in the 5–8 MeV range but the solar spectrum measurements in this range find P _ee to be flat. The predicted values of P _ee , even for the best fit value of θ _sol , differ by 2–3 σ from the Super-K measured values in each of the three energy bins of the 5–8 MeV range. If future measurements of solar neutrinos by Super-K and SNO find a flat spectrum with reduced error bars (by a factor of 2), it will imply that two flavour oscillations can no longer explain both KamLAND data and the solar spectrum. However a flat solar neutrino spectrum and the Δ _sol measured by KamLAND can be reconciled in a three flavour oscillation framework with a moderate value of θ ₁₃≈13°.     

Conditional spin squeezing of a large ensemble via the vacuum Rabi splitting

We use the vacuum Rabi splitting to perform quantum nondemolition measurements that prepare a conditionally spin squeezed state of a collective atomic psuedospin. We infer a 3.4(6) dB improvement in quantum phase estimation relative to the standard quantum limit for a coherent spin state composed of uncorrelated atoms. The measured collective spin is composed of the two-level clock states of nearly 10(6) (87)Rb atoms confined inside a low finesse F=710 optical cavity. This technique may improve atomic sensor precision and/or bandwidth, and may lead to more precise tests of fundamental physics.     

Dynamic multiscaling in two-dimensional fluid turbulence

We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.     

Persistence problem in two-dimensional fluid turbulence

We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter Λ to distinguish between vortical and extensional regions. We then use a direct numerical simulation of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with an exponent θ=2.9±0.2.