Utilization of nondestructive techniques for analysis of the Martian meteorite NWA 6963 and its implications for astrobiology

Martian meteorites are excellent study materials for understanding the present and past of Mars, as they are important historical astrophysical artifacts because they possess information about Martian geological evolution and physical and chemical characteristics. In our case, we analyzed the NWA 6963 Martian meteorite classified as basaltic shergottite because of its chemical structure. A computerized microtomography (μCT) study in the NWA 6963 Martian meteorite provided us with 2D and 3D images that were extremely useful for ascertaining the internal structure of the analyzed sample and gave us the opportunity to find a crumpled material with a very peculiar structural format. In addition, it was possible to observe through the μCT that this encrusted material also has a completely different density of the meteorite. Calcium, strontium, and potassium were detected qualitatively, among others through the technique of X‐ray fluorescence.     

Positron annihilation study of pore size in ordered SBA-15

Ordered mesoporous materials such as SBA-15 possess a network of channels and pores with a well-defined size in the nanoscale range (2–50 nm). This particular pore architecture makes them suitable candidates for a variety of applications. Different techniques have been used to measure pore diameters. PALS (positron annihilation lifetime spectroscopy) nanoprobe has been used to investigate free volume in several materials, including mesoporous silica. PALS can be used to find out if the micropore and mesopore structures of samples prepared under different experimental conditions are different. Indeed, considering that the pores present a cylindrical shape, an equation was developed that uses specific pore volumes, theoretical density, and specific surface measurements to evaluate structural connectivity. Our goal is to determine the influence of aging temperature on the porous structure of SBA-15 samples. The structural evolution was studied by PALS, small-angle X-ray (SAXS), N₂ adsorption desorption isotherms and computational modeling to evaluate connectivity. The variation of aging temperature changes the pore structure, indicating the presence of micropores and connections between mesopores. Materials aged at high temperatures present the lowest microporosity.     

Synthesis and molecular structure of cisoid and transoid isomers of [Re2(CO)6(1,1′-bis(indenylidene)] derived from the reaction of [Re2(CO)8(MeCN)2] and diazoindene

The compound [Re₂(CO)₈(MeCN)₂] reacts with diazoindene (C₉H₆N₂) while refluxing in THF to afford three dirhenium products in which C₉H₆N₂ is cleaved with loss of N₂ and with incorporation of the residual indenylidene group into the products. Two indenylidene groups are coupled in two diastereomers of [Re₂(CO)₆(μ,η⁵:η⁵-1,1′-C₁₈H₁₂)] where C₁₈H₁₂=bis(indenylidene). X-ray structures show that these isomers are related as RR/SS and RS isomers. These have the two Re(CO)₃ groups coordinated transoid and cisoid, respectively to a trans bis(indenylidene) bridge. The third product is the μ-indenylidene complex [Re₂(CO)₈(μ,η¹:η⁵-C₉H₆)], which was also structurally characterised by X-ray diffraction.     

Red Tomato Products as an Alternative to Reduce Synthetic Dyes in the Food Industry: A Review

Most dyes used in the food industry are synthetic and can be a health hazard. Red tomato may serve as a natural alternative dye to replace synthetic colorants. This study aimed to review the literature on the addition of red tomato products (powder tomato, paste, freeze-dried, tomato peel powder, tomato pomace) to reduce the usage of synthetic dyes in the food industry. Red tomato products have been used as coloring in pasta, bologna, sausages, cookies, crackers, macaroons, hamburgers, breads, muffins, cheeses, and nuggets. The trans-cis isomerization of lycopene by oxidative processes directly affects the color of the pigment. The lycopene contained in tomato has antioxidant activity and could reduce or eliminate other oxidants and/or synthetic preservatives in food. Moreover, tomatoes in foods have high sensory scores, nutritional appeal, and marketing potential. However, its use as a food colorant has been not extensively explored. Therefore, further studies are still required, especially on the stability of carotenoids in tomatoes used in processed foods.     

Ab initio calculations on XFnq (X = I,Xe, Cs,and Ba; n=1, 2, 4, and 6; q=−1, 0, +1, and +2) molecules

Ab initio calculations employing relativistic effective core potentials were carried out to investigate the electronic structure of xenon fluoride molecules. The chemical bonds and geometrical stability of some isoelectronic ions, which have the central atom replaced by iodine, cesium, and barium ions, were also investigated. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 238–245, 2001     

Raman scattering investigations of KY3F10

Single crystals of the fluoride compound KY₃F₁₀ (O_h⁵) were studied by Raman scattering from 40 to 950 K. Group theory analysis predicts 3A_1g + 4E_g + 6F_2g Raman-active modes, but the experimental spectra show two F_2g modes missing. Over the whole temperature range the frequency shifts are negligible whereas the line widths show a strong increase with temperature. Both reversible and irreversible line width behaviour are exhibited for different temperature runs, indicating a complex microscopic phenomenon underlying the creation of defects responsible for these line widths and their interaction with the different phonon modes. An approximate activation energy for defect creation of ΔE ≈︁ 0.3 eV can be obtained from the temperature behaviour of the line widths. This activation energy may be connected with the high-temperature ionic conduction mentioned previously for this crystal.     

Eco-friendly Synthesis of Silver Nanoparticles and its Application in Hydrogen Photogeneration and Nanoplasmonic Biosensing

Environmentally friendly methods for silver nanoparticles (AgNPs) synthesis without the use of hazardous chemicals have recently drawn attention. In this work, AgNPs have been synthesized by microwave irradiation using only honey solutions or aqueous fresh pink radish extracts. The concentrations of honey, radish extract, AgNO₃ and pH were varied. AgNPs presented mean sizes between 7.0 and 12.8 nm and were stable up to 120 days. The AgNPs were employed as co-catalyst (TiO₂@AgNPs) to increase the hydrogen photogeneration under UV-vis and only visible light irradiation, when compared to pristine TiO₂ NPs. The prepared photocatalyst also showed hydrogen generation under visible light. Additionally, AgNPs were used to assemble a nanoplasmonic biosensor for the biodetection of extremely low concentrations of streptavidin, owing to its specific binding to biotin. It is shown here that green AgNPs are versatile nanomaterials, thus being potential candidates for hydrogen photogeneration and biosensing applications.     

Cellulose derivatives as solid electrolyte matrixes

Cellulose derivatives like hydroxyethylcellulose (HEC) and carboxymethylcellulose (CMC) were submitted to the graftization reactions. The samples of HEC were grafted with monoisocyanate of poly(propylene oxide) (MPPO) and different diisocyanates of poly(ethylene oxide) (DPEO) and poly(propylene oxide) (DPPO) in the presence of LiClO₄. CMC was grafted with MPPO. These polyssacharides based samples were characterized by IR, NMR and thermal analysis (DSC and TGA). The samples of grafted polyssacharides derivatives showed glass transition temperatures (Tg) of −40°C for HEC/MPPO, −33°C for HEC/DPEO, −10°C for HEC/DPPO and 24�C for CMC/MPPO. The ionic conductivities of all samples were about 10⁻⁷‐10⁻⁶ S/cm at room temperature. The sample of CMC/MPPO presented conductivity value similar to HEC/DPPO but does not exhibit film‐forming characteristic indicating its use as solid polymer electrolytes only in the pellet form.