Electrochemically deposited ZnO films: an XPS study on the evolution of their surface hydroxide and defect composition upon thermal annealing

Electrodeposition from ZnCl₂ aqueous solution was performed to grow ZnO thin films on the surface of polycrystalline copper plates. Electrochemical parameters for deposition were optimized by means of cyclic voltammetry (CV). The morphology of the deposits was studied via scanning electron microscopy (SEM), and their chemical composition was ascertained by means of X-ray photoelectron spectroscopy (XPS). The effects of changing the deposition bath temperature (T _bath) and the role played by post-deposition treatments, such as temperature and time of annealing in air, were studied. SEM images of freshly deposited vs. annealed samples have shown that in the former case the films display a rough morphology with mixed grain/hexagonal platelets structures and in the latter smaller but more uniformly dispersed cubic grains. T _bath is found to be the key parameter to induce the different morphology in the deposited films, which reflects in a different chemical reactivity of surface species, as found on the basis of the binding energies and relative quantitative ratios between Zn 2p and O 1s peaks. In fact, a higher T _bath favours a more efficient desorption of OH groups upon annealing, the O 1s peak resulting to much more drastically modified oxide/hydroxide intensity ratio with respect to the case of the sample deposited at lower T _bath.     

Micro-Mesoporous Carbons from Cyclodextrin Nanosponges Enabling High-Capacity Silicon Anodes and Sulfur Cathodes for Lithiated Si-S Batteries

Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si−S cell.     

Agent-based model of multicellular tumor spheroid evolution including cell metabolism

The European Physical Journal E - A common simplification used in different physical contexts by both experimentalists and theoreticians when dealing with essentially non-spherical drops is...     

Disambiguation of Isomeric Procyanidins with Cyclic B-Type and Non-cyclic A-Type Structures from Wine and Peanut Skin with HPLC-HDX-HRMS/MS

Hydrogen/deuterium exchange coupled with high-resolution mass spectrometry was successfully applied for the identification of A-type tetrameric, pentameric, and hexameric procyanidins in peanut skin. This extended a previous study on isomeric cyclic B-type unconventional tetramer, pentamer, and hexamer procyanidins found in wine and cranberries. Not only had the method successfully identified the procyanidins with a single A-linkage (e.g., tetrameric m/z 1153.2608) by means of distinguishing them from their isomeric cyclic B-type analogues, but this method also worked for procyanidins with two or more A-linkages (such as the tetrameric m/z 1151.2452). As a further consequence, B-type cyclic pentamers and hexamers in wine have been elucidated with hydrogen/deuterium exchange (HDX) for the first time.

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Semi-preparative HPLC purification of δ-tocotrienol (δ-T3) from Elaeis guineensis Jacq. and Bixa orellana L. and evaluation of its in vitro anticancer activity in human A375 melanoma cells

In this work, we report a rapid and convenient HPLC-UV-DAD method for the isolation of δ-T3 on semi-preparative scale from two different vitamin E rich processed, commercially available products obtained from the fruits of Elaeis guineensis Jacq. (oil palm) and from the seeds of Bixa orellana L. (achiote tree). Chromatography was run using reverse phase (RP) C-18 columns and HPLC-grade acetonitrile as mobile phase. The purity of the isolated δ-T3, assessed by GC–MS and ¹H NMR was above 98%. The δ-T3 cytotoxic activity found in vitro against the proliferation of human A375 melanoma cells compared to that of the other δ-T3 free tocols mixture suggest its primary role in the experimental anticancer activity observed for palm oil derived products. Taken altogether, the results of this study highlight the importance of the application of suitable purification systems for the preparations of tocotrienols prior to their experimental or clinical testing.     

Reduction of nitroarenes,azoarenes and hydrazine derivatives by an organic super electron donor

Reduction of nitrobenzene by excess organic electron donor, 12, affords diphenylhydrazine in a reaction where azobenzene oxide and azobenzene are likely intermediates. No cleavage of the N-N σ-bond is seen under photoactivation conditions, whereas traces are seen under thermal activation. Hydrazone derivatives were prepared to explore the cleavage of N-N σ-bonds; the results show that a low-lying LUMO assists the transition state for accepting an electron, and the stabilisation that the potential fragments from N-N bond cleavage afford to the fragments is important in determining whether cleavage is observed.     

Adsorption of transition metal atoms on the NiO(100) surface and on NiO/Ag(100) thin films

We have studied the adsorption of Au, Pd, and Pt atoms on the NiO(100) surface and on NiO/Ag(100) thin films using plane wave DFT+U calculations. The scope of this work is to compare the adsorption properties of NiO, a reducible transition metal oxide, with those of MgO, a simple binary oxide with the same crystal structure and similar lattice parameter. At the same time, we are interested in the adsorption characteristics of NiO ultra-thin films (three atomic layers) deposited on Ag(100) single crystals. Also in this case the scope is to compare NiO/Ag(100) with the corresponding MgO/Ag(100) films which show unusual properties for the case of Au adsorption. The results show that the transition metal atoms bind in a similar way on NiO(100) and NiO/Ag(100) films, with Pt, Pd, and Au forming bonds of decreasing strength in this order. No charging effects occur for Au adsorbed on NiO/Ag(100) films, at variance with MgO/Ag(100). The reasons are analyzed in terms of work function of the metal/oxide interface. Possible ways to modify this property by growing alternate layers of MgO and NiO are discussed.