Air-assisted growth of tin dioxide nanoribbons

SnO₂ nanoribbons have been synthesized by annealing of a milled SnO₂ powder, which is able to evaporate efficiently at the temperature as low as 1100 °C due to the metastable structure created by ball milling treatment. When the milled powder was annealed in an assembly of two combustion boats, SnO₂ nanoribbons formed on the surface of the milled powder. The nanoribbons tend to grow along the [101] crystallographic direction and their side surfaces are represented by ±(010) and ±(101) facets. The oxygen plays an important role in enhancing their formation.

Improved hydrogen monitoring properties based on p-NiO/n-SnO2 heterojunction composite nanofibers

Here we demonstrate the preparation and improved hydrogen monitoring properties based on p-NiO/n-SnO2 heterojunction composite nanofibers via the electrospinning technique and calcination procedure. NiO/SnO2 heterojuction composite nanofibers were spin-coated on the ceramic tube with a pair of Au electrodes for the detection of hydrogen. Extremely fast response−recovery behavior (̰3s) has been obtained at the operable temperature of 320 °C, based on our gas sensor, with the detection limit of approximate 5 ppm H₂. The role of the addition of NiO into the SnO₂ nanofibers and the sensing mechanism has also been discussed in this work.

Supplementing cold plasma with heat enables doping and nano-structuring of metal oxides

Nitrogen doped SnO2 polycrystalline nanostructures were produced from commercial SnO powders in a new system that combines a low-temperature plasma with heating. The method has the potential to improve the initial efficiency and the cycling performance of SnO2 anodes in Li-ion batteries. With this system, the temperature of the SnO to SnO2 conversion was lowered from 430 to 320 °C, up to 5 at% of doped nitrogen was detected and a nano-scale polycrystalline structure was observed in the product. Combining heat and low-pressure plasma is a promising approach for the production and treatment of enhanced energy storage materials.

Energy dissipation and geometry effects over stepped spillways

The energy dissipation process is the major significant point in the designof hydraulic structure. The dissipation of high energy on stepped weirsprevents any damage in the weir itself and channels the energy ownstream to reduce the stilling basin size. In this study, four physical models are used to evaluate the impact of adding end sills that have a quarter circle shape at step edges. The amount of energy loss on weirs under different flow regimes is investigated by experimental work. Stepped weirs have a suitable number of steps and two different ratios of the width to height (2.22, and 2.40). The scale of the physical models is 20:1. The outcomes of the dimensional analyses refer to the critical depth for flow in weirs to the height of step yc/h, the end sill radius, and the number of steps N are more effective parameters than others inthe energy loss process. Moreover, for small values of yc/h, the energydissipation is the greatest. Any increase in yc/h leads to a decrease in theenergy dissipation, while the energy dissipation increases with the number of steps (N).

Organotin(IV) complexes derived from proteinogenic amino acid: Synthesis, structure and evaluation of larvicidal efficacy on Anopheles stephensi mosquito larvae

Five new organotin(IV) complexes of composition [Bz2SnL1]n (1), [Bz3SnL1HH2O] (2), [Me2SnL2H2O] (3), [Me2SnL3] (4) and [Bz3SnL3H]n (5) (where L1 = (2S)-2-([(E)-(4-hydroxypentan-2-ylidene)]amino)-4-methylpentanoate, L2 = (rac)-2-([(E)-1-(2-hydroxyphenyl)methylidene]amino)-4-methylpentanoate and L3 = (2S)- or (rac)-2-([(E)-1-(2-hydroxyphenyl)ethylidene]amino)-4-methylpentanoate) were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques. The crystal structure of 2 reveals a distorted trigonal-bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L3H (5) consists of polymeric chains, in which the ligand-bridged tin atoms adopt the same trans-Bz3SnO2 trigonal-bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H2O. In 2, the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative 5, the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the C=N group. For the dibenzyltin derivative 1, a polymeric chain structure is observed as a result of a long intermolecular SnO bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin-complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes 3 and 4 display discrete monomeric structures with a distorted octahedral- and trigonal-bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes (2 and 5) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph3SnL1H]n and [Ph3SnL3H]n. The results demonstrate that the compounds containing Sn-Ph ligands are more effective than those with Sn-Bz ligands.