Multimetallic Oxynitrides Nanoparticles for a New Generation of Photocatalysts

A versatile synthetic strategy for the preparation of multimetallic oxynitrides has been designed and here exemplarily discussed considering the preparation of nanoscaled zinc–gallium oxynitrides and zinc–gallium–indium oxynitrides, two important photocatalysts of new generation, which proved to be active in key energy related processes from pollutant decomposition to overall water splitting. The synthesis presented here allows the preparation of small nanoparticles (less than 20 nm in average diameter), well-defined in size and shape, yet highly crystalline and with the highest surface area reported so far (up to 80 m² g⁻¹). X-ray diffraction studies show that the final material is not a mixture of single oxides but a distinctive compound. The photocatalytic properties of the oxynitrides have been tested towards the decomposition of an organic dye (as a model reaction for the decomposition of air pollutants), showing better photocatalytic performances than the corresponding pure phases (reaction constant 0.22 h⁻¹), whereas almost no reaction was observed in absence of catalyst or in the dark. The photocatalysts have been also tested for H₂ evolution (semi-reaction of the water splitting process) with results comparable to the best literature values but leaving room for further improvement.     

A Luminescent and Sublimable Dy(III) -Based Single-Molecule Magnet

The reaction of [Ln(hfac)(3) ]?2?H(2) O and pyridine-N-oxide (PyNO) leads to isostructural dimers of the formula [Ln(hfac)(3) (PyNO)](2) (Ln=Eu, Gd, Tb, Dy). The Dy derivative shows a remarkable single-molecule magnet behavior with complex hysteresis at 1.4?K. The dynamics of the magnetization features are two relaxation regimes: a thermally activated one at high temperature (τ(0) =(5.62±0.4)×10(-11) s and Δ=(167±1)?K) and a quantum tunneling regime at low temperature with a tunneling frequency of 0.42?Hz. The analysis of the Gd derivative evidences intradimer antiferromagnetic interactions (J=(-0.034±0.001)?cm(-1) ). Moreover, the Eu, Tb, and Dy derivatives are luminescent with quantum yield of 51, 53, and 0.1?%, respectively. The thermal investigation of [Dy(hfac)(3) (PyNO)](2) shows that the dimers can be sublimated intact, suggesting their possible exploit as active materials for surface-confined nanostructures to be investigated by fluorimetry methods.     

Sensitivity improvement in 19F NMR-based screening experiments: theoretical considerations and experimental applications

NMR-based binding and functional screening performed with FAXS (fluorine chemical shift anisotropy and exchange for screening) and 3-FABS (three fluorine atoms for biochemical screening) represents a potential alternative approach to high-throughput screening for the identification of novel potential drug candidates. The major limitation of this method in its current status is its intrinsic low sensitivity that limits the number of tested compounds. One approach for overcoming this problem is the use of a cryogenically cooled (19)F probe that reduces the thermal noise in the receiver circuitry. Sensitivity improvement in the two screening techniques achieved with the novel cryogenic (19)F probe technology permits an increased throughput, detection of weaker binders and inhibitors (relevant in a fragment-based lead discovery program), detection of slow binders, and reduction in protein and substrate consumption. These aspects are analyzed with theoretical simulations and experimental quantitative performance evaluation. Application of 3-FABS combined with the cryogenic (19)F probe technology to rapid screening at very low enzyme concentrations and the current detection limits reached with this approach are also presented.     

Phenomenological and neural-network modeling of cephalosporin C production bioprocess

Cephalosporin C production process withCephalosporium acremonium ATCC 48272 in synthetic medium was investigated and the experimental results allowed the development of a mathematical model describing the process behavior. The model was able to explain fairly well the diauxic phenomenon, higher growth rate during the glucose-consumption phase, and the production occurring only in the sucrose-consumption phase. Moreover, the process was simulated utilizing the neural-networks technique. Two feed-forward neural-networks with one hidden layer were employed. Both models, phenomenological and neural-networks based, satisfactorily describe the bioprocess. The difficulties in determining kinetic parameters are avoided when neural networks are utilized.     

Interactions between naproxen and maltoheptaose,the non-cyclic analog ofβ-cyclodextrin

The crystallinity of naproxen in solid combinations with amorphous maltoheptaose, the non-cyclic analog of -cyclodextrin, was assessed using differential scanning calorimetry supported by X-ray powder diffractometry. Cogrinding induced a decrease in drug crystalinity to an extent which depended on the grinding time, and was most pronounced for the combination of equimolecular composition. Thermal analysis showed that the mechanism behind the conversion of crystalline naproxen into the amorphous state by cogrinding with maltoheptaose differed from that with randomly substituted, amorphous -cyclodextrins. Interactions of naproxen with maltoheptaose in aqueous solution were studied by means of fluorescence spectroscopy, phase-solubility analysis, and computeraided molecular modelling. Maltoheptaose can wrap up naproxen, taking on a cyclic conformation and forming a pseudo inclusion complex (apparent binding constant K_{1: 1} = 1.0 × 10³ (–20%) L mol^–1 at 25 °C) which is about as stable as the true inclusion complex with -cyclodextrin in the lowest temperature range (0-100 K). A better complexing ability for naproxen in terms of binding constant values, however, was displayed by both native and derivatized -cyclodextrins, the hosts with covalently-bound cyclic structures.     

Study of biocatalyst to produce ethanol from starch

This article presents a detailed study on the conditions for achieving a stable biocatalyst to be used in the production of ethanol from starch. Different pellets were used depending on which characteristic of the biocatalyst was being studied: (a) Saccharomyces cerevisiae entrapped in pectin or calcium alginate gel particles; (b) silica containing immobilized glucoamylase entrapped in pectin gel particles; or (c) pectin gel particles, with the silicaenzyme derivative and yeast coimmobilized. The influence of several variables on the mechanical resistance of the particle, on the viability of the microorganism, and on the rate of substrate hydrolysis was studied with biocatalyst. The best conditions found were 6% pectin gel, 2-mm particle diameter, and curein 0.2 M CaCl₂·2H₂O/60 mM acetate buffer, pH 4.2, for gel preparation; and 6.0 g/L of CaCl₂·2H₂O in the fermentation medium. Biocatalyst (c) was successfully tested for the production of ethanol from liquefield manioc flour syrup.