Aqueous Solutions Of Sodium Sulfide Research Articles

Synthesis of a stable colloidal solution of PbS nanoparticles

A method has been proposed for the synthesis of stable colloidal solutions of lead sulfide nanoparticles from aqueous lead acetate and sodium sulfide solutions. The citrate ion and ethylenediaminetetraacetic acid were used as complexing agents to stabilize the solution. The solutions obtained were shown to remain stable at room temperature for at least 30 days from the instant of synthesis, depending on the initial reactant concentration. According to X-ray diffraction and dynamic light scattering data, the stability and coagulation of the nanoparticles in solution were influenced by the lead and sulfur concentration, the presence of complexing agents, and the quantitative relation between the lead and complexing agent ions in solution. Optical absorption measurements for the colloidal PbS nanoparticle solutions showed that their absorbance was a nonlinear function of reactant concentration.

From hydrodynamic plumes to chemical gardens: the concentration-dependent onset of tube formation.

Many inorganic precipitation reactions self-organize macroscopic tubes known as chemical gardens. We study the nonequilibrium formation of these structures by injecting aqueous sodium sulfide solution into a reservoir of iron(II) chloride solution. Our experiments reveal a distinct, concentration-dependent transition from convective plumes of reaction-induced, colloidal particles to mechanically connected, hollow tubes. The transition concentration (0.1 mol/L) is widely independent of the injection rate and causes a discontinuous change from the radius of the plume stalk to the radius of the tube. In addition, tubes have lower growth speeds than plumes. At the transition concentration, one observes the initial formation of a plume followed by the growth of a mechanically weak tube around a jet of upward-moving precipitation particles. We find that the plumes' morphology and geometric scaling are similar to that of laminar starting plumes in nonreactive systems. The characterization of dried tubes by X-ray diffraction indicates the presence of greigite and lepidocrocite.

Chemical passivation of the InAs (100) surface by aqueous sodium sulfide solutions

Chemical passivation of the InAs (100) surface by aqueous sodium sulfide solutions

Electrochemical Preparation and Thermal Characterization of Copper Sulfide Nanoparticles

CuS nanoparticles in different sizes and shapes were synthesized by electrolysis of a copper plate as anode in sodium sulfide aqueous solutions. The results revealed that size and shape of the product could be tuned by the reaction parameters including electrolysis voltage and sulfide ion concentration as reactant. The results showed that the size of CuS nanoparticles decreased with increasing electrolysis voltage from 2 to 13 V. Meanwhile, the size and shape of the prepared CuS nanoparticles were found to be dependent on the concentration of sulfide solution used. Also, the results of characterization of the prepared CuS nanoparticles were reported.

Preparation of nanocrystalline lead sulfide powder with controlled particles size

Lead sulfide nanopowders have been prepared from aqueous solutions of lead acetate and sodium sulfide in the presence of sodium ethylenediaminetetraacetate or citrate. From microscopy and X-ray diffraction data purity and size of the formed nanoparticles are determined by the reagents concentrations, presence and nature of the complexing ligand, and the ratio of lead ions concentration to that of the ligand. PbS nanoparticles of the predefined size ranged from 5 to 55 nm can be prepared by controlled hydrochemical precipitation.

An investigation on SILAR deposited Cu$_{x}$S thin films

A copper sulfide thin film was deposited on glass substrate by successive ionic layer adsorption and reaction method at room temperature, using cupric sulfate and sodium sulfide aqueous solutions as precursors. The structural, surface morphological, optical, and electrical properties of the as-deposited film were investigated via X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, optical absorption, and d.c. 2-point probe methods. The film was found to be amorphous, dense, and uniform. Average atomic percentage of Cu:S in the as-deposited film was calculated as 63:37. The band gap energy of copper sulfide thin film was found to be 2.14 eV and the resistivity was 10^{-2} Omega cm at room temperature. The effect of annealing on crystal structure was also studied and reported. X-ray diffraction patterns revealed that annealing the film at various temperatures slightly improved the crystallinity. By using thermoelectric power measurement, p-type electrical conductivity was determined for as-deposited and annealed samples.

Aqueous Sulfur Passivation of N-Type GaSb Substrates Studied by Photoluminescence Spectroscopy

In this work the influence of aqueous sulfur passivation on the surface of n-type (100) GaSb single crystals has been studied through low-temperature photoluminescence (PL) characterization. The samples were passivated at different times using aqueous solutions of sodium sulfide. PL spectroscopy was used to determinate the optimum time of sulfur passivation, through the measurement of the PL intensity for the different passivation times. For the samples measured, the PL spectra show the presence of two emission bands, whose intensity and energy position change for the different passivation times of the GaSb samples. According to the PL results, a passivation surface treatment of 6 min shows the highest PL intensity spectrum.

Chemical deposition of nanocrystalline lead sulfide powders with controllable particle size

Abstract For the first time the systematic study of the effect of synthesis conditions (concentrations of reactants, the presence or lack of a complexing agent and its type, the exposure time of deposited PbS particles in the matrix solution) on the size of lead sulfide nanoparticles, their phase composition and the presence of impurity phases is performed. PbS nanopowders are synthesized by deposition from aqueous solutions of lead acetate and sodium sulfide in the presence of EDTA-H 2 Na 2 or sodium citrate. It is found that the phase composition of the deposit and the size of the nanoparticles depend on the initial concentrations of lead and sulfur ions, the presence and type of complexing agents, as well as on the quantitative ratio between the content of lead ions and complexing ions in the solution. The possibility of controllable hydrochemical deposition of PbS nanoparticles with preassigned size from 5 to 55 nm is shown.

Effect of complexing agent TEA: The structural, morphological, topographical and optical properties of FexSx nano thin films deposited by SILAR technique

Iron sulfide thin films (FexSx) (x=0.05M, 0.10M, 0.15M, 0.20M and 0.25M) were deposited by SILAR method from equimolar and equivolume aqueous solutions of ferrous nitrate and sodium sulfide with the addition of complexing agent TEA. The structural, morphological and optical characteristics of the films were derived from X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectral techniques. The mixed characteristics (crystalline and amorphous) of the deposited films and the increasing crystalline qualities with the concentrations were understood from the XRD analysis. The grain sizes and roughness of the films were decreases with the increasing concentration and also at the higher concentration films are shown by the same images presence of hexagonal like crystallite structure. The influence of complexing agent TEA on the surface roughness and morphological properties are confirmed by the atomic force microscope (AFM) results. The effect of increasing substrate concentration on the absorption and transmission measurements and its impact on the optical band-gap energy were enumerated from the UV–vis analysis.

Effect of the Method of Preparation of ZnO/CdS and TiO2/CdS Film Nanoheterostructures on Their Photoelectrochemical Properties

A study was carried out on the photoelectric properties of ITO/TiO2/CdS and ITO/ZnO/CdS nanostructurized films obtained by the SILAR method and the photocatalytic reduction of sulfur by ethanol in the presence of Cd(II) salts. The nanostructures obtained by the latter method display much higher photocurrent density (by a factor of 2 in the case of systems derived from ZnO and a factor of 5 in systems derived from TiO2) upon irradiation with white light (λ > 400 nm) in aqueous solutions of sodium sulfide than the heterostructures obtained by the traditional SILAR method.

Chemical passivation of InSb (100) substrates in aqueous solutions of sodium sulfide

The elemental composition and electronic structure of both native-oxide-covered InSb (100) substrates and substrates treated in aqueous solutions of sodium sulfide are analyzed by X-ray photoelectron spectroscopy. It is found that, as a result of treatment in a 1 M aqueous solution of Na2S and subsequent annealing in vacuum at 150°C, the surface layer consisting of complex antimony and indium oxides of nonstoichiometric composition is removed completely with the formation of a continuous layer of chemisorbed sulfur atoms coherently bound to indium atoms. According to atomic-force microscopy data, no etching of the host substrate material occurs during sulfide passivation. A shift (by 0.37 eV) of the In-Sb bulk photoemission towards higher binding energies is found, which indicates that the surface Fermi level shifts deeper into the conduction band.

Photocatalytic degradation of organic dye on porous iron sulfide film surface

Thin films of nanocrystalline and porous FeS2 with marcasite phase have been deposited from a greenish-blue iron nitroprusside precursor film, which readily gives FeS2 on reacting with an aqueous solution of sodium sulfide. High resolution X-ray diffraction (HRXRD) pattern indicated the formation of polycrystalline and orthorhombic (marcasite) phase of FeS2, whereas the field emission scanning electron microscopy (FESEM) showed the morphology of the films to be consisted of grains of average 25nm diameter with unevenly distributed numerous pores. Optical characterization (UV–Vis and photoluminescence) revealed significant amount of blueshift in the band gap energy of the deposited material, which is attributed to the strong quantum confinement effect exerted by the FeS2 nanocrystals. The deposited FeS2 films showed good photocatalytic activity toward the degradation of Rose Bengal dye and could be found efficient for wastewater treatment.

Sulfidation of electrodeposited microcrystalline/nanocrystalline cuprous oxide thin films for solar energy applications

Grain size of polycrystalline semiconductor thin films in solar cells is optimized to enhance the efficiency of solar cells. This paper reports results on an investigation carried out on electrodeposited n-type cuprous oxide (Cu2O) thin films on Ti substrates with small crystallites and sulfidation of them to produce a thin-film solar cell. During electrodeposition of Cu2O films, pH of an aqueous acetate bath was optimized to obtain films of grain size of about 100 nm, that were then used as templates to grow thicker n-type nanocrystalline Cu2O films. XRD and SEM analysis revealed that the films were of single phase and the substrates were well covered by the films. A junction of Cu2O/CuxS was formed by partially sulfiding the Cu2O films using an aqueous sodium sulfide solution. It was observed that the photovoltaic properties of nano Cu2O/CuxS heterojunction structures are better than micro Cu2O/CuxS heterojunction solar cells. Resulting Ti/nano Cu2O/CuxS/Au solar cell structure produced an energy conversion efficiency of 0.54%, Voc = 610 mV and Jsc = 3.4 mA cm−2, under AM 1.5 illumination. This is a significant improvement compared to the use of microcrystalline thin film Cu2O in the solar cell structure where the efficiency of the cell was limited to 0.11%. This improvement is attributed mainly to the increased film surface area associated with nanocrystalline Cu2O films.

New photocatalysts based on cadmium and zinc sulfides for hydrogen evolution from aqueous Na2S-Na2SO3 solutions under irradiation with visible light

Noble metal-free, Cd1 − xZnxS-based photocatalysts for hydrogen evolution from aqueous solutions of sodium sulfide and sodium sulfite upon irradiation with visible light (λ > 420 nm) have been synthesized and characterized by a complex of physicochemical methods. The effects of pH and catalyst and substrate concentrations on the rate of photocatalytic hydrogen evolution have been investigated. Under the optimal conditions, the quantum efficiency of the process is up to 12.9%.

Enhanced hydrogen production from biomass via the sulfur redox cycle under hydrothermal conditions

A new method of hydrogen production from biomass via a sulfur redox cycle at moderate temperatures has been proposed. This method, which can utilize excess sulfur from hydrocarbon refining processes and waste or geothermal heat, consists of two half cycles: (1) hydrogen production from an aqueous alkaline solution at subcritical conditions of water, where sulfide, HS − and S 2−, acts as a reducing agent of water, and (2) sulfide regeneration under much milder conditions, with an organic compound derived from biomass acting as a reducing agent of polysulfide, S n 2−, and sulfur oxyanion, S xO y 2−, formed in the first half cycle. During a 60-min reaction of an aqueous sodium sulfide solution, hydrogen production was observed at ≥280 °C and corresponding saturated vapor pressures. Addition of D-glucose, C 6H 12O 6, to the solution after hydrogen production at 300 °C resulted in sulfide regeneration at temperatures ≥60 °C in the present 10-min reaction. Moreover, hydrogen production from glucose via the sulfur redox cycle was demonstrated, where the hydrogen production and sulfide regeneration were conducted at 300 °C and 105 °C, respectively. Results indicated that hydrogen production from 1 mol glucose was greater than that by hydrothermal gasification of glucose at much higher temperatures up to 500 °C.

Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy

We present results from X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) of oxidized polycrystalline copper surfaces [Cu(I) and Cu(II), respectively] exposed to a aqueous solution of (sodium sulfide) for several hours. Scanning electron microscopy reveals that the Cu oxide surfaces attain a much rougher texture upon sodium sulfide exposure, and that the exposed Cu(II) oxide sample exhibits areas with crystallites. The XAS spectra show that sodium sulfide effectively reduces Cu(II) oxide to Cu(I) compounds. The RIXS spectra of the exposed surfaces closely resemble those of the reference sample with the notable exception of their Cu -RIXS spectra. We conclude that copper evidently forms a Cu(I) compound with oxygen but with a Cu -band of much reduced width, pointing to the possibility of a more complex compound containing both oxygen and sulfur.

ChemInform Abstract: Synthesis and Some Reactions of Arylpyridylsulfide Derivatives.

Abstract The title compound (I) was prepared from the reaction of 2-chloro-3-cyano-4,6-dimethylpyridine and 4-bromonitrobenzene in aqueous sodium sulfide solution. Condensation of I with aromatic aldehydes, 2-methyl benzoxazin-4-one, azalactone and succinic anhydride afforded the expected products (IV, VI, VIII and XV). Coupling of diazotized I with active methylene compounds gave the corresponding hydrazones Xa,b. Cyclization of hydrazone Xa with AICl3 gave the cinnoline derivative XII, which condensed with phenylhydrazine to give the pyrazolocinnoline derivative XIII. Oxidation of some of the prepared sulfides with H2O2 in AcOH afforded the corresponding sulfones.

Dual-Pathway Kinetics Assessment of Sulfur Poisoning of the Hydrogen Oxidation Reaction at High Surface-Area Platinum/Vulcan Carbon Electrodes

The kinetics of the hydrogen oxidation reaction (HOR) were measured at high surface-area platinum/Vulcan carbon (Pt/VC) films before and after exposure to aqueous solutions of either sodium sulfide or mercaptopropionic acid (MPA, ) using rotating disk electrode (RDE) voltammetry. At 45–90% blocking of surface Pt atoms by inorganic sulfur, sulfur appears to adsorb as oligomerized sulfur . Current–potential RDE data for the HOR at -exposed Pt/VC films were fitted to a recently developed dual-pathway kinetics model. At a submonolayer coverage of surface Pt atoms, the exchange current densities for the potential-independent Tafel–Volmer pathway, or two-site HOR pathway, decrease by about –50-fold compared to electrochemically cleaned Pt/VC films. Exchange current densities for the single-site, potential-dependent Heyrovsky–Volmer pathway decrease by comparable factors at the same levels of sulfur exposure. The potential-range constant γ increases in the presence of adsorbed . The exposure of Pt/VC to aqueous solutions of MPA, an organosulfur species, results in similarly diminished HOR exchange current densities at Pt/VC, as observed for exposure, but yields higher values of γ. The model is sufficiently sensitive to delineate the effects of different catalyst poisons on HOR kinetics at carbon-supported nanoscopic Pt.

Sulfide passivation of InAs(100) substrates in Na2S solutions

Treatment of the InAs(100) surface with a 1M aqueous solution of sodium sulfide (Na2S) is found to result in the removal of a natural oxide layer from this surface with the formation of a continuous chemisorbed passivating layer of sulfur atoms that are coherently bonded to indium atoms of the crystal surface. No etching of the InAs surface in the sulfide solution occurs. The passivated InAs samples are characterized by a multiple increase in the photoluminescence intensity. The sulfide layer is desorbed from the InAs surface at temperatures of ∼400°C. This leads to the formation of a clean In-stabilized (100) surface with a (4 × 2) reconstruction. A simple technique is developed using sulfide passivation for preparing atomically smooth (2 × 4) growth surfaces of the InAs(100) substrates that are suitable for molecular-beam epitaxy of highly perfect layers of compounds based on CdSe.

The Use of Methyltricaprylylammonium Chloride as a Phase Transfer Catalyst for the Destruction of Methyl Bromide in Air Streams

Methyl bromide has been used for decades as a pesticide, primarily as an insecticide. It has also been recently advocated as an excellent agent for the destruction of anthrax spores via fumigation. Related to this use is the need to efficiently destroy methyl bromide safely, once fumigation is complete. This paper describes the selection of a nucleophile for instantaneous decomposition of methyl bromide to destroy methyl bromide in a fumigation vent air stream from an office trailer. Our preliminary data showed that sulfide anion dissolved in water is an exceptionally effective nucleophile for the purpose of CH3Br decomposition. We show data proving the effectiveness of the sodium sulfide aqueous solution accompanied by methyltricaprylylammonium chloride as a phase transfer catalyst for scrubbing methyl bromide present in air.