Synthesis and characterization of wurtzite-phase copper tin selenide nanocrystals

A new wurtzite phase of copper tin selenide (CTSe) was discovered, and the resulting nanocrystals were synthesized via a facile solution-phase method. The wurtzite CTSe nanocrystals were synthesized with dodecylamine and 1-dodecanethiol as coordinating solvents and di-tert-butyl diselenide ((t)Bu(2)Se(2)) as the selenium source. Specific reaction control (i.e., a combination of 1-dodecanethiol with (t)Bu(2)Se(2)) was proven to be critical in order to obtain this new phase of CTSe, which was verified by powder X-ray diffraction and selected area electron diffraction. The wurtzite CTSe nanocrystals possess an optical and electrochemical band gap of 1.7 eV and display an electrochemical photoresponse indicative of a p-type semiconductor.     

Fast electrodeposition of zinc onto single zinc nanoparticles

The zinc deposition reaction onto metallic zinc has been investigated at the single particle level through the electrode-particle collision method in neutral solutions, and in respect of its dependence on the applied potential and the ionic strength of a sulphate-containing solution. Depending on the concentration of sulphate ions in solution, different amounts of metallic zinc were deposited on the single Zn nanoparticles. Specifically, insights into the electron transfer kinetics at the single particles were obtained, indicating an electrically early reactant-like transition state, which is consistent with the rate-determining partial de-hydration/de-complexation process. Such information on the reaction kinetics at the nanoscale is of vital importance for the development of more efficient and long-lasting nanostructured Zn-based negative electrodes for Zn-ion battery applications.

     

Surfactant assisted zinc doped tin oxide nanoparticles for supercapacitor applications

Zinc doped tin oxide nanoparticles were synthesized by employing sol–gel method assisted with different surfactants namely cetyl trimethyl ammonium bromide (CTAB), hexamine and polyethylene glycol 400 (PEG-400). The synthesis of uniform distribution of spherical Zn-SnO₂ nanoparticles in presence of PEG-400 was optimized. The synthesized Zn-SnO₂ nanoparticles were characterized by employing standard characterization techniques. X-ray diffraction results confirmed the product high-quality crystalline formation. The photoluminescence peaks appeared at 360?nm revealed the recombination of electron and hole from band to band emission of SnO₂ optical properties. The vibrational properties of Zn-SnO₂ nanoparticles were confirmed by both Raman and infra red spectra. The spherical morphology and nano sized product was evident in 200?nm scale SEM images. The cyclic voltammetry result of the product Zn-SnO₂ assisted PEG-400 exhibited the specific capacitance value of 312.7?F/g at scan rate of 10?mV/s and revealed the superior electrochemical properties. Moreover, the EIS and GCD studies also revealed the good supercapacitor nature with specific capacitance of 132.1?F/g at current density of 1?A/g for the product Zn-SnO₂ (PEG-400).

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Diagrammatic representation of Zn doped SnO₂ synthesis by sol-gel method with enhanced specific capacitance of 132.1?F/g at 1?A/g for Zn-SnO₂ (PEG-400).

     

Coherent forward scattering technique to determine copper in steels,zinc and tin

Coherent forward scattering spectroscopy having the Voigt configuration was applied in the determination of copper in steels, zinc and tin. Copper (0.0005–0.2%) in these metals could be determined without preconcentration procedure. The relative standard deviations were 4.4% for 0.0035% copper and 7.1% for 0.067% copper in steel. The reproducibility of calibration curves for copper in steels (log-log plotting with a slope of about two) was about 18% and the limit of detection was about 0.4 ± 0.07 ng/10 μl.     

Mercury selenide stoichiometry and phase relations in the mercury-selenium system

The phase relations in the 0–65 at% Hg portion of the condensed mercury-selenium system were determined from liquidus temperatures to 250°C by evacuated silica tube experiments in which vapor is always a phase. Stoichiometric HgSe melts at 795 ± 2°C whereas Hg_0.51Se_0.49 melts at 797 ± 2°C and Hg_0.49Se_0.51 melts at 793 ± 2°C. In the HgSeSe portion of the system a monotectic exists at 683 ± 3°C and 71.5 at% Se and a liquid immiscibility field at this temperature extends from 71.5 to 85.5 at% Se. The presence of HgSe depresses the melting temperature of Se by about 8°C. An eutectic exists between HgSe and Se at 208°C and a composition of more than 99.95 at% Se. In the HgHgSe portion of the system a monotectic exists at 708 ± 3°C and about 25 at% Se. The solubility of Hg in HgSe was found to exceed stoichiometry by 1.11 ± 0.25 at% at 650°C whereas the solubility of Se in HgSe exceeds stoichiometry by 0.75 ± 0.25 at% Se at the same temperature. All synthetic mercury selenides show the sphalerite type structure. The unit cell dimension of stoichiometric HgSe is a₀ = 6.080 ± 0.001 Å. Mercury selenide synthesized in equilibrium with liquid Se gives a₀ = 6.082 ± 0.001 Å and mercury selenide synthesized in equilibrium with Hg gives a₀ = 6.078 ± 0.001 Å.     

Real-time monitoring of the aging of single plasmonic copper nanoparticles

We demonstrate that the continuous real-time monitoring of the growth and surface oxidation process of single Cu nanoparticles (NPs) on an indium-tin oxide (ITO) substrate by dark-field microscopy (DFM) and plasmon resonance Rayleigh scattering (PRRS) spectroscopy is possible.     

Preparation of copper and zinc sulfide nanoparticles and their modification with cysteine

A new method for the preparation of copper and zinc sulfides nanoparticles in homogeneous aqueous solutions using cysteine as a surface modifier was proposed. The size of the particles obtained is 5–7 and 1.5–3 nm for copper and zinc sulfides, respectively, depending on the concentration of the reactants. Associates of the nanoparticles 10–30 nm in size are formed in the system with an increase in the total concentrations of the sulfides. Sols of the nanoparticles obtained in cysteine solutions are resistant to oxidation and coagulation within several weeks. The variation of the synthesis conditions makes it possible to obtain zinc sulfide particles with optical properties related to size effects.     

Substoichiometric determination of trace impurities in zinc selenide

Determination of trace impurities in zinc selenide was carried out by substoichiometric neutron activation analysis. Trace impurities were separated from matrix elements by suitable procedures and determined by substoichiometric methods, i.e., Au was extracted with rhodamine-B, Ag and Cu with dithizone, Cr with sodium diethyldithiocarbamate, Co with 1-nitroso-2-naphthol, and Sb with cupferron. Two sorts of zinc selenide single crystals were supplied for analysis and the following values were obtained as impurity concentration; Au 0.36, 0.076 ppb, Ag 42, 32 ppb, Cr. 1.8, 0.63 ppm, Co 0.16, 0.0079 ppm, Sb 8.5, 5.9 ppb and Cu 1.4, 0.44 ppm. The behavior of copper by heat-treatment of zinc selenide was also studied by means of substoichiometric isotope dilution analysis.     

Synthesis of zinc and copper borates in a single technological cycle

A zero-waste technology was developed for obtaining in a single technological cycle four valuable products: combustion retarder Zn₃B₁₀O₁₈ · 14H₂O, microfertilizer 2ZnO · 3B₂O₃ · 7H₂O, copper borate 3CuO · 2B₂O₃ · nH₂O · mNa₂SO₄, and wood antiseptic “Mebor.”     

Semiconducting thin films of zinc selenide quantum dots

A novel chemical route for deposition of zinc selenide quantum dots in thin film form is developed. The deposited films are characterized with very high purity in crystallographic sense, and behave as typical intrinsic semiconductors. Evolution of the average crystal size, lattice constant, lattice strain and the optical properties of the films upon thermal treatment is followed and discussed. The band gap energy of as-deposited ZnSe films is blue-shifted by ≈0.50 eV with respect to the bulk value, while upon annealing treatment it converges to 2.58 eV. Two discrete electronic states which originate from the bulk valence band are observed in the UV-VIS spectra of ZnSe 3D quantum dots deposited in thin film form via allowed electronic transitions to the 1S electronic state arising from the bulk conduction band—appearing at 3.10 and 3.50 eV. The splitting between these two states is approximately equal to the spin-orbit splitting in the case of bulk ZnSe. The electronic transitions in the case of non-quantized annealed films are discussed in terms of the direct allowed band-to-band transitions with the spin-orbit splitting of the valence band of 0.40 eV. The effective mass approximation model (i.e., the Brus model) with the static relative dielectric constant of bulk ZnSe fails to predict correctly the size dependence of the band gap energy, while only a slight improvement is obtained when the hyperbolic band model is applied. However, when substantially smaller value for ε_r (2.0 instead of 8.1) is used in the Brus model, an excellent agreement with the experimental data is obtained, which supports some earlier indications that the quantum dots ε_r value could be significantly smaller than the bulk material value. The ionization energy of a deep donor impurity level calculated on the basis of the temperature dependence of the film resistivity is 0.82 eV at 0 K.     

Porous copper zinc tin sulfide thin film as photocathode for double junction photoelectrochemical solar cells

Porous copper zinc tin sulfide (CZTS) thin film was prepared via a solvothermal approach. Compared with conventional dye-sensitized solar cells (DSSCs), double junction photoelectrochemical cells using dye-sensitized n-type TiO(2) (DS-TiO(2)) as the photoanode and porous p-type CZTS film as the photocathode shows an increased short circuit current, external quantum efficiency and power conversion efficiency.     

On the anodic decomposition of the zinc selenide electrode

The electrochemical decomposition of n-type zinc selenide has been studied in connection with the chemisorption of the OH^? groups onto the semiconductor surface, depending on the band bending. The influence of oxidizing agents such as the illumination of the electrode or the presence of ferricyanide ions in the solution, leading to injection of holes into the valence band, has also been put in evidence. In contrast with the usual decomposition models that are rather simple, a complex and multistep mechanism is proposed here in order to account for the different observations made on these electrodes: the triangular decomposition pits, the deep red layer of amorphous selenium and the bright grey layer of zinc oxide.     

Electrochemical formation of zinc selenide from acidic aqueous solutions

An investigation on electrochemical ZnSe thin film growth from acidic aqueous baths of Se(IV) and Zn(II) species is described. The range of co-deposition potentials is predicted on a thermodynamic basis according to a known electrochemical model. A study on the voltammetric behavior of Ti and Ni electrode substrates in the working solutions at various temperatures provides the main features of the applied electrochemical process. Cathodic electrodeposition at high temperatures (>65 °C) results in the formation of polycrystalline cubic, randomly oriented, ZnSe crystallites suffering, in general, from the presence of a crystalline Se phase in excess. Annealing of as-grown films adjusts the stoichiometry and leads to the production of semiconductive ZnSe with a band gap width of 2.7 eV. Electronic Publication     

Reactivity of nanoparticles; interaction between zinc and copper oxide nanoparticles and iron ions in an alkaline medium

The reactivity of zinc and copper oxide nanoparticles was investigated upon their interaction with iron oxides. It was ascertained that, depending on the reaction conditions, nanoparticles of zinc and copper ferrites (ZnFe₂O₄ and CuFe₂O₄) or core/shell nanoparticles (Fe₃O₄/ZnO) are produced. Size, composition, and structure of the resulting nanoparticles were determined by transmission electron microscopy and X-ray diffraction analysis. The average size of zinc and copper ferrite nanoparticles was ascertained to be 9–10 and 2–3 nm, respectively. For core/shell Fe₃O₄/ZnO nanoparticles, the average size is 20 nm. It was experimentally proved that the photoluminescence radiative characteristics of ZnO nanoparticles are retained in core/shell Fe₃O₄/ZnO nanoparticles.     

Routes to copper zinc tin sulfide Cu2ZnSnS4 a potential material for solar cells

Power generation through photovoltaics (PV) has been growing at an average rate of 40% per year over the last decade; but has largely been fuelled by conventional Si-based technologies. Such cells involve expensive processing and many alternatives use either toxic, less-abundant and or expensive elements. Kesterite Cu(2)ZnSnS(4) (CZTS) has been identified as a solar energy material composed of both less toxic and more available elements. Power conversion efficiencies of 8.4% (vacuum processing) and 10.1% (non-vacuum processing) from cells constructed using CZTS have been achieved to date. In this article, we review various deposition methods for CZTS thin films and the synthesis of CZTS nanoparticles. Studies of direct relevance to solar cell applications are emphasised and characteristic properties are collated.     

Potassium sodium tin selenide,K3NaSn3Se8

The title compound, tripotassium sodium tritin octaselenide, K₃NaSn₃Se₈, has a molecular (zero‐dimensional) structure containing trimeric [Sn₃Se₈]^4? units which consist of three edge‐sharing SnSe₄ tetrahedra. The [Sn₃Se₈]^4? anions and the tetrahedrally coordinated Na⁺ cations are arranged in an alternating fashion along the c axis to form SiS₂‐like chains, which are then separated by eight‐coordinate K⁺ cations. The Sn—Se bond distances are normal, being in the range 2.477 (1)–2.612 (1) Å.     

The direct electrochemical synthesis of tin,cobalt, copper,zinc, cadmium and silver 7-formyl-8-hydroxyquinoline complexes

Summary Main group and transition metal complexes of 7-formyl-8-hydroxyquinoline have been synthesized by an electrochemical technique using a sacrifical anode in a non-aqueous solution of the ligand, and characterized by elemental analyses and i.r. spectra. The ligand acts as a monobasic tri-dentate chelating agent coordinating through C=N, C=O and OH groups by replacement of a proton from the latter group. The electrical conductivities of the complexes were measured at different temperatures and annealing times. Their activation energies were calculated; the value obtained for the Zn^II complex lay in the range reported for semiconducting materials.Physics Department, Faculty of Science, Sana'a University.