Surface-induced structural modification in ZnO nanoparticles

Cobalt?Ccobalt carbide [Co _x C (x?=?2 or 3)] and cobalt (FCC-Co) microwires have been synthesized using a polyol method in the presence of a high external magnetic field of 4.3?kOe. It was reported before that the synthesis of these particles in the absence of magnetic field leads to the formation of spherical particles. Analysis of the X-ray diffraction (XRD) scans indicates that the synthesized Co _x C wires consist of four phases?? ??-Co, ??-Co, Co₃C, and Co₂C. The percent composition of these phases was 53.3?% Co₃C, 26.8?% Co₂C, 12.5?% ??-Co, and 7.4?% ??-Co. XRD analysis of the as-synthesized cobalt wires shows that it consists of single-phase FCC-Co. Based on Scherrer analysis of the XRD data, the average crystallite sizes of the cobalt carbide and the cobalt particles are 18.5 and 16.3?nm, respectively. Scanning electron microscopy (SEM) studies show that the diameter of Co _x C wires is in the range of 1.6(±0.2)???m with their length varying between 18 and 30???m while the diameter of the cobalt wires is 1.65(±0.1). The SEM results infer that the morphology of the growing particles was controlled by the magnetic field with the applied field directs the growth of the particles into wires. The magnetic measurements indicate a superparamagnetic character of the cobalt wires and a soft ferromagnetic nature of the synthesized Co _x C chains. The degree and field range of the interactions between magnetic domains have been investigated using a Henkel plot.     

The impact of chemical composition on the degradation kinetics of poly(lactic-co-glycolic) acid copolymers cast films in phosphate buffer solution

We have investigated the in vitro degradation of poly(lactic-co-glycolic) acid copolymer with different lactic to glycolic ratio: 50:50, 65:35, 75:25, 95:05 and 100:00 (mol. %). The degradation studies were performed on solvent cast films of controlled thickness and shape. The samples were incubated at 37 °C in phosphate buffered saline solution. The degradation was followed using potentiometry, light microscopy, gravimetry, size exclusion chromatography and differential scanning calorimetry. The same degradation process, as discussed in detail in our previous article for PLGA 50:50 (E. Vey et al., J. of Polym. Deg. and Stab. 2008, 93, 1896-1876), was observed for all the samples investigated, however the time scale over which the different events/degradation steps were observed increased with increasing lactic content of the polymer. The glass transition temperatures of the films increase with lactic content and are thought to have a significant impact on the rate of diffusion of water into the films - the higher the glass transition the slower the diffusion of water - and therefore on the degradation dynamics of the films. Kinetic parameters were extracted from the acid release, molecular weight and mass loss data. In each case linear correlations between the rate constants extracted and the lactic content of the polymer were found. The overall degradation rate of the films was found to decrease with increasing lactic content.     

Design of hierarchical porous aluminas by using one-pot synthesis and different calcination temperatures

Hierarchical aluminas with pore sizes ranging from a few nanometers to micrometers were obtained using an one-pot sol?Cgel synthesis. The aluminas were synthesized under acid conditions from aluminum isopropoxide in presence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template and decahydronaphthalene as emulsifier agent. High-resolution transmission electron microscopy, small-angle X-ray scattering, nitrogen physisorption isotherms and mercury intrusion porosimetry provided evidences of porous structure at different hierarchical levels. The produced aluminas possess hierarchical structure composed of different family of pores that coexist in form of cylinders, pyramids and stacking of platelets. The morphology observed by electron microscopy suggests that the cylindrical pores result from the stacking platelets and that the cylinders and pyramidal pores form the walls of macropores of circular section. These aluminas with hierarchical porous architecture present large surface areas (ca. 435?m² g^?1) and pore volumes (ca. 2.1?cm³ g^?1), tunable pore-size distributions and good thermal stability.     

Structural diversity and versatility for organoaluminum complexes supported by mono- and di-anionic aminophenolate bidentate ligands

The present contribution describes the synthesis and structural characterization of structurally diverse organoaluminum species supported by variously substituted aminophenolate-type ligands: these Al complexes are all derived from the reaction of AlMe₃ with aminophenols 2-CH₂NH(R)-C₆H₃OH (1a, R = mesityl (Mes); 1b, R = 2,6-di-isopropylphenyl (Diip)) and 2-CH₂NH(R)-4,6-^tBu₂-C₆H₂OH (1c, R = Mes; 1d, R = Diip). The low temperature reaction of AlMe₃ with 1a–b readily affords the corresponding Al dimeric species [μ-η¹,η¹-N,O-{2-CH₂NH(R)-C₆H₄O}]₂Al₂Me₄ (2a–b), consisting of twelve-membered ring aluminacycles with two μ-η¹,η¹-N,O-aminophenolate units, as determined by X-ray crystallographic studies. Heating a toluene solution of 2a (80 °C, 3 h) affords the quantitative and direct formation of the dinuclear aluminium complex Al[η²-N; μ,η²-O-{2-CH₂N(Mes)-C₆H₄O}](AlMe₂) (4a) while species 2b, under the aforementioned conditions, affords the formation of the Al dimeric species [η²-N,O-{2-CH₂N(Dipp)-C₆H₄O}AlMe]₂ (3b), as deduced from X-ray crystallography for both 3b and 4a. In contrast, the reaction of bulky aminophenol pro-ligands 1c–d with AlMe₃ afford the corresponding monomeric Al aminophenolate chelate complexes η²-N,O-{2-CH₂NH(R)-4,6-^tBu₂-C₆H₂O}AlMe₂ (5c–d; R = Mes, Diip; Scheme 3) as confirmed by X-ray crystallographic analysis in the case of 5d. Subsequent heating of species 5c–d yields, via a methane elimination route, the corresponding Al-THF amido species η²-N,O-{2-CH₂N(R)-4,6-^tBu₂-C₆H₂O}Al(Me)(THF) (6c–d; R = Mes, Diip). Compounds 6c–6d, which are of the type {X₂}Al(R)(L) (L labile), may well be useful as novel well-defined Lewis acid species of potential use for various chemical transformations. Overall, the sterics of the aminophenol backbone and, to a lesser extent, the reaction conditions that are used for a given ligand/AlMe₃ set essentially govern the rather diverse “structural” outcome in these reactions, with a preference toward the formation of mononuclear Al species (i.e. species 5c–d and 6c–d) as the steric demand of the chelating N,O-ligand increases.     

Kinetics of ethanol fermentation with high biomass concentration considering the effect of temperature

A model of ethanol fermentation considering the effect of temperature was developed and validated. Experiments were performed in a temperature range from 28 to 40°C in continuous mode with total cell recycling using a tangential microfiltration system. The developed model considered substrate, product and biomass inhibition, as well as an active cell phase (viable) and an inactive (dead) phase. The kinetic parameters were described as functions of temperature.     

In Vitro Degradation of Poly(lactic-co2-glycolic) Acid Random Copolymers

We have investigated the in vitro degradation of poly(lactic-co-glycolic) acid copolymer with a lactic to glycolic ratio of 65/35. The degradation studies were performed on solvent-cast films of controlled thickness and shape. The samples were then incubated at 37 °C in phosphate buffered saline solution. The degradation was followed using potentiometry, light microscopy, gravimetry, gel permeation chromatography and differential scanning calorimetry. Water was found to diffuse inside the film as soon as the sample was placed in the degradation media. Wrinkles formed on the upper layer while degradation took place via chain scission in the bulk of the film. After 10 days, this led to the creation of a vesicle where liquid low molecular weight oligomers were trapped inside a thin film of high molecular weight polymer. This thin film acted as a membrane allowing only low molecular weight compounds to diffuse out of the film.     

Gelation of a Model Globular Protein

Hen egg white lysozyme (HEWL) was exposed to various physical and chemical denaturing environments to encourage protein denaturation and consequent gelation. Its phase behavior was examined as a function of pH, temperature and also in the presence of the reductant dithiothreitol (DTT). Transparent viscoelastic gels form at low pH values while opaque gels form under alkaline conditions. No increase in viscosity was observed for systems in pure water unless 20 mM of DTT was added, which is known to break the disulfide bridges present in HEWL. The microstructure of the gel was studied using transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM). Gels formed at low pH contain fibrils ∼10 nm in diameter with various lengths while at high pH the gels are dominated by particulate aggregates. Thinner fibrils that are 4–6 nm in diameter are observed in the gels formed in the presence of DTT. In this case the distinct feature of the gels is they are thermoreversible and can be melted and reformed easily by varying the temperature.     

Nanosatellites for quantum science and technology

Bringing quantum science and technology to the space frontier offers exciting prospects for both fundamental physics and applications such as long-range secure communication and space-borne quantum probes for inertial sensing with enhanced accuracy and sensitivity. But despite important terrestrial pathfinding precursors on common microgravity platforms and promising proposals to exploit the significant advantages of space quantum missions, large-scale quantum test beds in space are yet to be realised due to the high costs and lead times of traditional ‘Big Space’ satellite development. But the ‘small space’ revolution, spearheaded by the rise of nanosatellites such as CubeSats, is an opportunity to greatly accelerate the progress of quantum space missions by providing easy and affordable access to space and encouraging agile development. We review space quantum science and technology, CubeSats and their rapidly developing capabilities and how they can be used to advance quantum satellite systems.     

Utilization of Agro-Industrial Residues in the Rearing and Nutritional Enrichment of Zophobas atratus Larvae: New Food Raw Materials

Edible insects are a potential alternative food source of high feed conversion efficiency and protein content. Zophobas atratus is an edible insect that adapts to different diets, enabling sustainable rearing by adding value to by-products and agro-industrial residues. This study aimed to evaluate the performance and nutritional characterization of Zophobas atratus larvae fed with different proportions of grape residue. Physicochemical analysis of the diets and larvae (AOAC procedures), fatty acid profile (chromatographic techniques), metals and non-metals (inductively coupled plasma optical emission spectrometry), larval mass gain, feed conversion efficiency, and mortality rate were assessed. The replacement of 25% of the conventional diet with grape residue increased lipid, ash, and fiber contents and reduced protein, carbohydrates, and energy. It promoted greater mass gain, lower mortality rate, and reduced larval growth time by 51%. Among the replacements, 25% resulted in the second-highest content of calcium, sodium, magnesium, and zinc, and the lowest content of potassium and phosphorus in the larvae. The 100% replacement resulted in the highest amounts of C18:2n6 (27.8%), C18:3n3 (2.2%), and PUFA (30.0%). Replacing 25% of the conventional diet with grape residue is equivalent to the conventional diet in many aspects and improves several larvae performance indices and nutritional values.     

Eco-Friendly Synthesis of an Oxovanadium(IV)-bis(abietate) Complex with Antimicrobial Action

The search for less expensive and viable products is always one of the challenges for research development. Commonly, the synthesis of coordination compounds involves expensive ligands, through expensive and low-yield routes, in addition to generating toxic and unusable residues. In this work, the organic ligand used is derived from the resin of a reforestation tree, Pinus elliottii var. elliottii. The synthesis method used Pinus resin and an aqueous solution of vanadium(III) chloride at a temperature of 80 °C. The procedure does not involve organic solvents and does not generate toxic residues, thus imparting the complex formation reaction a green chemistry character. The synthesis resulted in an unprecedented oxovanadium(IV)-bis(abietate) complex, which was characterized by mass spectrometry (MS), chemical analysis (CHN), vibrational (FTIR) and electronic spectra (VISIBLE), X-ray diffraction (XRD), and thermal analysis (TG/DTA). Colorimetric studies were performed according to the CIELAB color space. The structural formula found, consisted of a complex containing two abietate ligands, [VO(C₂₀H₂₉O₂)₂]. The VO(IV)-bis(abietate) complex was applied against microorganisms and showed promising results in antibacterial and antifungal activity. The best result of inhibitory action was against the strains of Gram-positive bacteria S. aureus and L. monocytogenes, with minimum inhibitory concentration (MIC) values of 62.5 and 125 μmol L⁻¹, respectively. For Gram-negative strains the results were 500 μmol L⁻¹ for E. coli; and 1000 μmol L⁻¹ for Salmonella enterica Typhimurium. Antifungal activity was performed against Candida albicans, where the MIC was 15.62 μmol L⁻¹, and for C. tropicalis it was 62.5 μmol L⁻¹. According to the MFC analysis, the complex presented, in addition to the fungistatic action, a fungicidal action, as there was no growth of fungi on the plates tested. The results found for the tests demonstrate that the VO(IV)-bis(abietate) complex has great potential as an antimicrobial and mainly antifungal agent. In this way, the pigmented ink with antimicrobial activity could be used in environments with a potential risk of contamination, preventing the spread of microorganisms harmful to health.