Oxidation and photooxidation of sulfide and thiosulfate ions catalyzed by transition metal chalcogenides and phthalocyanine complexes

Singlet Oxygen Generation Driven by Sulfide Ligand Exchange on Porphyrin-Gold Nanoparticle Conjugates

Here, we report a switching method of singlet oxygen (¹O₂) generation based on the adsorption/desorption of porphyrins to gold nanoparticles driven by sulfide (thiol or disulfide) compounds. The generation of ¹O₂ by photosensitization is effectively suppressed by the gold nanoparticles and can be restored by a sulfide ligand exchange reaction. The on/off ratio of ¹O₂ quantum yield (Φ_Δ) reached 7.4. By examining various incoming sulfide compounds, it was found that the ligand exchange reaction on the gold nanoparticle surface could be thermodynamically or kinetically controlled. The remaining gold nanoparticles in the system still suppress the generation of ¹O₂, which can be precipitated out simultaneously with porphyrin desorption by the proper polarity choice of the incoming sulfide to restore the ¹O₂ generation.

Effects of Iron Doping on the Physical Properties of Quaternary Ferromagnetic Sulfide: Ba2Fe0.6V1.4S6

The mixed-metal sulfide compound with the formula Ba₂Fe_0.6V_1.4S₆ was successfully synthesized via solid-state reaction. Ba₂Fe_0.6V_1.4S₆ has a quasi-one-dimensional structure and crystallizes in the hexagonal space group P6₃/mmc. The structure is composed of face-sharing anion octahedron [MS₆]^8- (M = V or Fe) units to construct infinite chains along the c axis, in which the Fe atoms randomly occupy the V sites. The Ba²⁺ ions reside between adjacent chains. Magnetic susceptibility measurements reveal a transition between paramagnetism and ferromagnetism around 25 K. The small polaron hopping (SPH) conduction behavior has been observed in the higher temperature region (75-300 K), while in the lower temperature region (25-74 K), the resistivity features a variable range hopping mechanism (VRH). The analysis of density of states indicates that Fe-3d_z² and S-3p states mainly dominate the valence band maximum, while Fe-3d_z² states contribute significantly to the magnetic susceptibility.

Materials for selective photo-oxygenation vs. photocatalysis: preparation, properties and applications in environmental and health fields

Photosensitizing materials made of organic dyes embedded in various supports are compared to usual supported TiO₂-based photocatalysts.

Synthesis, crystal structure and physical properties of FeV4S8and KFe2V8S16

Two compounds with the formulae FeV₄S₈and KFe₂V₈S₁₆were successfully synthesizedviaa melting salt method.

Time-resolved insight into the photosensitized generation of singlet oxygen in endoperoxides

A synergistic approach combining high-level multiconfigurational static calculations and full-dimensional ab initio surface hopping dynamics has been employed to gain insight into the photochemistry of endoperoxides. Electronic excitation of endoperoxides triggers two competing pathways, cycloreversion and O–O homolysis, that result in the generation of singlet oxygen and oxygen diradical rearrangement products. Our results reveal that cycloreversion or the rupture of the two C–O bonds occurs via an asynchronous mechanism that can lead to the population of a ground-state intermediate showing a single C–O bond. Furthermore, singlet oxygen is directly generated in its most stable excited electronic state 1Δg. The triplet states do not intervene in this mechanism, as opposed to the O–O homolysis where the exchange of population between the singlet and triplet manifolds is remarkable. In line with recent experiments performed on the larger anthracene-9,10-endoperoxide, upon excitation to the spectroscopic ππ* electronic states, the primary photoreactive pathway that governs deactivation of endoperoxides is O–O homolysis with a quantum yield of 65%.

Observation on symmetry properties of sodium zinc(II)-2,9,16,23-phthalocyanine tetracarboxylate in water:NaOH solution

The shift of the Q-band of sodium zinc(II)-2,9,16,23-phthalocyanine tetracarboxylate (ZnPc(COONa)4) to about 800 nm is attributed to the influence of the electron-donating property of the carboxylate groups substituted in the β-position. ZnPc(COONa)4 which was found to have a symmetry of D 2h characterized by a splitting of the Q transition. This splitting was interpreted by the formation of dianionic symmetric ZnPc(COONa)4 resulting from the dissociation of the pyrrole protons as well as the possibility of Na(+) dissolution of ZnPc(COONa)4 in the aqueous solution of NaOH.

Metal Mobilization from Complex Sulfide Ore Concentrate: Effect of Light and pH

The aim of this study was to determine the influence of photo-irradiation and pH on the mobilization of metals from a complex sulfide ore concentrate containing known semiconductors (PbS, ZnS, CdS, FeS2, and CuFeS2). The mobilization of Zn, Fe, and Cd increased under illumination, which is attributed to the semiconductor nature of ZnS, FeS2, and CdS, respectively. An increase in mobilization of Zn, Fe, and Cd under light is observed with decreasing pH, because of increased surface protonation and the greater oxidizing property of photoholes. The semiconductor nature of PbS and CuFeS2 is observed at pH 2. However, at higher pH the concentrations of mobilized Pb and Cu are greater in darkness than under illumination. This is attributed to the light enhanced exchange reactions involving dissolved Pb and Cu with metal sulfides more soluble than PbS and CuS.

Heterogeneous water phase catalysis as an environmental application: a review

Catalytic water phase processes as an environmental application is a relatively novel subject with tremendous potential in the near future. This review of 120 references presents the wide scale of heterogeneous water phase applications studied mainly within past five years. Both oxidation and hydrogenation processes are included as well as TiO2 assisted photocatalysis. According to the references, heterogeneous catalysis is developing rapidly. New bimetallic catalysts and supports with higher surface area have improved catalytic efficiency in both oxidation and hydrogenation processes. It also seems that study on use of some waste materials such as red mud as catalyst is a very progressive field. On the whole, the chemical aspects are pretty well known, but the catalyst durability, and in many cases activity as well, has to be improved.