Bandgap engineering of colloidal zinc oxysulfide via lattice substitution with sulfur

Metal Oxysulfides: From Bulk Compounds to Nanomaterials

This review summarizes the syntheses and applications of metal oxysulfides. Bulk compounds of rare earth and transition metals are discussed in the section Introduction. After a presentation of their main properties and applications, their structures are presented and their syntheses are discussed. The section Bulk Materials and Their Main Applications is dedicated to the growing field of nanoscaled metal oxysulfides. Synthesis and applications of lanthanide-based nanoparticles are more mature and are discussed first. Then, works on transition-metal based nanoparticles are presented and discussed. Altogether, this review highlights the opportunities offered by metal oxysulfides for application in a range of technological fields, in relation with the most advanced synthetic routes and characterization techniques.

Cluster expansion based configurational averaging approach to bandgaps of semiconductor alloys

Configurationally disordered semiconducting materials including semiconductor alloys [e.g., (GaN)_1-x(ZnO)_x] and stoichiometric materials with fractional occupation (e.g., LaTiO₂N) have attracted a lot of interest recently in search for efficient visible light photo-catalysts. First-principles modeling of such materials poses great challenges due to the difficulty in treating the configurational disorder efficiently. In this work, a configurational averaging approach based on the cluster expansion technique has been exploited to describe bandgaps of ordered, partially disordered (with short-range order), and fully disordered phases of semiconductor alloys on the same footing. We take three semiconductor alloys [Cd_1-xZn_xS, ZnO_1-xS_x, and (GaN)_1-x(ZnO)_x] as model systems and clearly demonstrate that semiconductor alloys can have a system-dependent short-range order that has significant effects on their electronic properties.

Removal of sulfur by adding zinc during the digestion process of high-sulfur bauxite

This paper proposes a novel approach to sulfur removal by adding zinc during the digestion process. The effects of zinc dosage on the concentrations of different valence sulfur in sodium aluminate solution were investigated at length to find that high-valence sulfur (S₂O₃²⁻, SO₃²⁻, SO₄²⁻) concentration in sodium aluminate solution decreases, but the concentration of the S²⁻ in the sodium aluminate solution increases as zinc dosage increases. This suggests that zinc can react with high-valence sulfur to generate S²⁻ at digestion temperature, which is consistent with our thermodynamic calculation results. In this study, as zinc dosage increases, sulfur digestion rate decreases while sulfur content in red mud markedly increases when zinc dosage was below 4%; the digestion rates of sulfur and sulfur content in red mud remains stable when zinc dosage was above 4%; the alumina digestion rate, conversely, increased slightly throughout the experiment. This suggests that high-valence sulfur in sodium aluminate solution can be converted to S²⁻ and then enter red mud to be removed completely by adding zinc during the digestion process.

The magnetic and adsorption properties of ZnO1-xSx nanoparticles

Sulfur is easy to be incorporated into ZnO nanoparticles by the solution-combustion method. Herein, the magnetic and adsorption properties of a series of ZnO_1-xS_x (x = 0, 0.05, 0.1, 0.15, and 0.2) nanoparticles were systematically investigated. The X-ray diffraction patterns show that the as-prepared ZnO_1-xS_x nanoparticles have the hexagonal wurtzite structure of ZnO with a low sulfur content that gradually transforms into the zinc blende structure of ZnS when the x value is greater than 0.1. PL spectra show several bands due to different transitions, which have been explained by the recombination of free excitons or defect-induced transitions. The introduction of sulfur not only modifies the bandgap of ZnO, but also impacts the concentration of Zn vacancies. The as-prepared ZnO shows weak room-temperature ferromagnetism, and the incorporation of sulfur improves the ferromagnetism owing to the increased concentration of Zn vacancies, which may be stabilized by the doped sulfur ions. The adsorption capability of ZnO_1-xS_x nanoparticles has been significantly improved, and the process can be well described by the pseudo-first-order kinetic model and the Freundlich isotherm model. The mechanism has been confirmed to be due to the active sulfate groups existing in zinc oxysulfide nanoparticles.

Green synthesis of zinc oxysulfide quantum dots using aegle marmelos fruit extract and their cytotoxicity in HeLa cells

Zinc oxysulfide quantum dots have been attracting increasing research interest due to their tunable electronic, optical and magnetic properties.

Morphogenesis of ZnO nanostructures: role of acetate (COOH−) and nitrate (NO3−) ligand donors from zinc salt precursors in synthesis and morphology dependent photocatalytic properties

We investigated how the presence of one anion effects the overall ZnO growth in the presence of another anion.