Electrodeposition of Heterogeneous Mn-Bi Thin Films from a Sulfate-Nitrate Bath: Nucleation Mechanism and Morphology

International audienceIn this paper, we report on the nucleation and the growth of heterogeneous Mn-Bi thin films on Cu substrate from a mixed sulfate-nitrate bath using direct current plating. The electrolytic bath is characterized by the presence of ammonium sulfate which was used as complexing agent to avoid the precipitation of Mn hydroxides. Cyclic voltammetry and chronoamperometry measurements are used to study the reaction mechanisms of the Mn-Bi electrodeposition as a function of the ammonium sulfate concentration and the pH value: the optimized conditions for a stable bath are obtained for 2.5 mol. L−1 of ammonium sulfate and pH 2.3. The Scharifker and Hills (SH) model was used to analyze the current transients at the initial stage of deposition; it was revealed that Mn-Bi electrocrystallization process is governed by three-dimensional nucleation. But as the electrochemical deposition clearly involves the simultaneous presence of the proton cathodic reaction, another model developed by Palomar-Pardavé and co. was used to explain the nucleation mechanism and to describe the individual contribution of both the metallic ions and the proton reduction process. The morphology and chemical composition of the films were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The deposits have a cauliflower-shaped appearance with a heterogeneous distribution of manganese and bismuth. The energy dispersive spectroscopy analysis reveals the presence of manganese and bismuth peaks with almost the same relative intensities. The X-rays diffraction analysis shows characteristic peaks of manganese and bismuth

Habitat discrimination of big-scale sand smelt Atherina boyeri Risso, 1810 (Atheriniformes: Atherinidae) in eastern Algeria using somatic morphology and otolith shape

Somatic morphology and otolith shape were used to discriminate four samples of Atherina boyeri from three different habitats: Mellah lagoon (n = 269), Annaba Gulf (144 punctuated and 194 unpunctuated individuals) and Ziama inlet (n = 147) in eastern Algeria. For each individual, somatic morphology was described with 13 metrics and eight meristic measurements, while the otolith contour shape of 452 individuals from the three habitats was analysed using Fourier analysis. Then, two discriminant analyses, one using the 13 metric measurements and the other using Fourier descriptors, were used in order to discriminate populations of A. boyeri. The results of the discriminant analyses based on the two methods were similar, and showed that this species could be discriminated into three distinct groups: (1) marine punctuated, (2) lagoon and marine unpunctuated and (3) estuarine. These results are consolidated by the comparison of the Mayr, Linsley and Usinger coefficient of difference for the meristic parameters according to the location origin, where the difference reached a racial or even sub-specific level for some characters, depending on which pairs of populations were compared

Otolith shape analysis and mitochondrial DNA markers distinguish three sand smelt species in the Atherina boyeri species complex in western Mediterranean

International audienceAtherina boyeri is a common euryhaline teleost fish in the Mediterranean and adjacent areas, which inhabits coastal and estuarine waters, including coastal lagoons and more rarely inland waters. Several recent studies have pointed the possible existence of three distinct groups or species, one lagoon/freshwater group and two `punctuated and unpunctuated on the flanks' marine groups, within an A. boyeri species complex. This study is a combined approach using otolith shape and molecular markers to better define the structure of the species in the western Mediterranean. Genetic differentiation and species delimitation among nine Atherina boyeri populations from several marine and lagoon/brakish habitat sites in Algeria, Tunisia and France were investigated using three mitochondrial (control region, Cyt b and 16S) and one nuclear markers (2nd intron of S7). For further phylogenetic and phylogeographic study, we added sequences from Genbank covering more areas (Ionian Sea, Adriatic Sea, Tyrrhenian Sea, Black Sea, Atlantic). Five groups were found. Two of them perfectly corresponded to two species already recognized Atherina presbyter and Atherina hepsetus, both living in marine waters; and three additional, including Atherina boyeri (brackish and freshwater environments) and two independent groups of marine punctated and unpunctated individuals. Those findings are corroborated by the study of the otolith contour shape of 362 individuals of seven populations from different habitats using Fourier analysis. Individuals could be discriminated into five groups based on the first two functions (Wilk's lambda = 0.07, p \textless 0.001). Samples from Ziama inlet, marine punctuated individuals and unpunctuated marine specimens from Annaba's Gulf formed three well separated groups. Specimens from Mellah and Mauguio lagoons formed another group. The last one includes individuals from Bizerte and Thau lagoons. The divergences between them strongly support the potential species within the A. boyeri species complex. (C) 2016 Elsevier Ltd. All rights reserved

The influence of the mixed phase (Ti-TiO<SUB>2</SUB>(A): TiO<SUB>2</SUB>(R)) on the optical band gap of TiO<SUB>2</SUB> nanotubes heat treated at different temperatures

International audienceHighly ordered TiO2 nanotubes (NTs) were synthesized by electrochemical anodization than annealed at different temperatures between 300 and 900 °C for 3 h. The elaborated NTs adhere well to the Ti substrate over the annealing temperature range of 300-600 °C. The TiO2 NTs morphology begins to gradually evolve for temperatures up to 700 °C and approaches that of nanoparticles until the latter become predominant at T above 800 °C. Reflection measurements show that the NTs present reflection of 7% at 600 °C, corresponding to the lowest band gap 2.59 eV. This can be related to the presence of the mixed phase (Ti-TiO2(A)-TiO2(R)).The charge carrier density decreases from 2.34 × 10+21 to 3.61 × 10+13 cm−3when the annealing temperature increases, that accompanied by a reduction in the resistivity from 142.23 to 29.56Ω.cm which is adequate to photo anode application

Effect of bismuth oxide nanoparticles on the physicochemical properties of porous silicon thin films

International audienceIn this work, bismuth oxide nanoparticles were successfully deposited on porous silicon (PSi) in order to enhance the light absorption and reduce the optical losses. The obtained bismuth oxide (Bi2O3)/PSi samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS), atomic force microscopy (AFM), photoluminescence (PL), UV–visible absorption and reflection spectroscopy techniques. The XRD studies revealed the formation of the monoclinic α-Bi2O3 phase. The XPS analysis demonstrates the formation of highly pure Bi2O3 nanoparticles in accordance with XRD results. The SEM and AFM analyses confirmed that the bismuth oxide nanoparticles are well incorporated and uniformly distributed over the surface of PSi without changes in the arrangement and shape of the pores, resulting in an optimized microstructure. The Bi2O3/PSi films showed better absorption than PSi layers as indicated by UV–Vis absorption technique. The reflection measurements confirmed a further reduction in reflectivity of PSi from 6.4 to 3.5% after the inclusion of Bi2O3 nanoparticles, which is of significant importance for solar cells application since it can enhance its conversion efficiency. The Bi2O3/PSifilms have a great promise to be used as efficient antireflection coatings in innovative concepts of higher efficiency and cost-effective solar cells

Effect of bismuth oxide nanoparticles on the physicochemical properties of porous silicon thin films

International audienceIn this work, bismuth oxide nanoparticles were successfully deposited on porous silicon (PSi) in order to enhancethe light absorption and reduce the optical losses. The obtained bismuth oxide (Bi2 O 3)/PSi samples were characterizedby means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electronmicroscopy (SEM) combined with energy-dispersive spectroscopy (EDS), atomic force microscopy (AFM), photolumines-cence (PL), UV–visible absorption and reflection spectroscopy techniques. The XRD studies revealed the formation of themonoclinic α-Bi2 O3 phase. The XPS analysis demonstrates the formation of highly pure Bi 2 O 3 nanoparticles in accordancewith XRD results. The SEM and AFM analyses confirmed that the bismuth oxide nanoparticles are well incorporated anduniformly distributed over the surface of PSi without changes in the arrangement and shape of the pores, resulting in anoptimized microstructure. The Bi2 O 3/PSi films showed better absorption than PSi layers as indicated by UV–Vis absorptiontechnique. The reflection measurements confirmed a further reduction in reflectivity of PSi from 6.4 to 3.5% after the inclu-sion of Bi 2 O 3 nanoparticles, which is of significant importance for solar cells application since it can enhance its conversionefficiency. The Bi2 O3/PSi films have a great promise to be used as efficient antireflection coatings in innovative conceptsof higher efficiency and cost-effective solar cells