Synthesis of Nickel Sulfides in Aqueous Solutions Using Sodium Dithionite

Abstract

Reaction of nickel chloride with sodium dithionite in aqueous solutions at ambient temperature has been investigated systematically to obtain nickel sulfides. The products are characterized by X-ray diffraction, thermogravimetric analysis, and electrical resistivity and magnetic susceptibility measurements. It is found that the compositions and structures of the products are controlled by the reaction pH and the amount of the reactants. While reactions under highly acidic (pH < or = 2) and basic (pH > or = 7) conditions yield crystalline sulfur and amorphous or poorly crystalline NiySx, respectively, those at intermediate 3 < or = pH < or = 6 give crystalline NiySx. Both crystalline Ni3S2 (heazlewoodite structure) and Ni3S4 (spinel structure) have been obtained at room temperature. Additionally, NiS (millerite structure) is obtained by carefully heating Ni3S4 at 200 degrees C in a mixture of 90% Ar and 10% H2. Ni3S4 is found to be metastable, and it begins to disproportionate above 100 degrees C. Both Ni3S2 and Ni3S4 show metallic behavior. While Ni3S2 exhibits temperature-independent magnetic susceptibility, Ni3S4 shows ferrimagnetic ordering below 20 K.

The Carbon Monoxide Dehydrogenase from Desulfovibrio vulgaris

“…We performed these experiments under anaerobic conditions, in the glovebox, at room temperature in 1.5 mL eppendorf tubes containing 25 to 100 µL of 0.44 µM enzyme solution in 0.1 M Tris/HCl pH 8 in the presence of exogenous nickel under reducing conditions or not, with 0 to 10 mM NiCl 2 and/or 0 to 10 mM NaDT for 1-60 min. In the solution containing both NiCl 2 and NaDT, a black precipitate formed, probably due to formation of nickel sulfides under basic conditions, as described previously [40]. A control experiment performed in the absence of enzyme showed that this precipitate has no CODH activity.…”

“…We have no clear explanation for this decrease in activity. However, we have observed that during activation (ie incubation of the enzyme with NaDT and NiCl 2 ), the solution progressively turns dark, probably because of nickel sulfide formation due to reaction of NaDT with NiCl 2 , as described in Jeong et al [40]. In consequence, the NaDT and NiCl 2 concentrations decrease over time and it may be that the optimal nickel concentration and/or the reducing power required for keeping the enzyme in a fully activated state are not maintained.…”

Factors Affecting the Reductive Properties of the Core-Shell SiO2-Coated Iron Nanoparticles

“…PEG is a dispersing agent and acts as a surfactant by adsorption at solid-liquid interfaces; forming a layer of molecules in a membrane prevents particles from being in contact with each other, reduces the surface tension and capillary adsorption capacity, and suppresses crystal growth, resulting in a small size distribution of the nanoparticles [15]. Based on these, the effects of PEG used in the synthesis of the SiO 2 -nZVI on the degradation of Malachite green were examined in this study, and the result was shown in those synthesized in the absence of PEG.…”

Seed-induced synthesis of h-NiS single-crystalline hexagonal nanoparticles

“…To achieve the aforementioned morphologies several synthesis methods have been employed, such as chemical vapor deposition [16], solvothermal [10,12], mechanical alloying [17], polyol method [18], solventless synthesis [19] and so on [20].…”