Dissolution of elemental gold in organic solutions is ac ontemporary approach to lower the environmental burden associated with gold recycling.Herein, we describe fundamental studies on ah ighly efficient method for the dissolution of elemental Au that is based on DMF solutions containing pyridine-4-thiol (4-PSH) as ar eactive ligand and hydrogen peroxidea sa no xidant. Dissolution of Au proceeds through several elementary steps:i somerization of 4-PSH to pyridine-4-thione (4-PS), coordination with Au 0 ,and then oxidation of the Au 0 thione species to Au I simultaneously with oxidation of free pyridine thione to elemental sulfur and further to sulfuric acid. The final dissolution product is aA u I complex bearing two 4-PS ligands and SO 4 2À as ac ounterion. The ligand is crucial as it assists the oxidation process and stabilizes and solubilizes the formed Au cations.

CO2 binding by urea/thiourea compounds via the formation of carbamide–carboxylate (–CONH2–CO2) and carbamimidothiocarbonate (–NH–CS–CO2) sodium adducts.

We report the synthesis and monolayer properties of conventional and gemini surfactants composed of nicotinic acid-based head groups with an emphasis on assessing how chemical structures affect the behavior of monolayers. A combination of Brewster angle microscopy and atomic force microscopy showed that pure hexadecyl nicotinate formed rippled strands in monolayers, and the gemini correspondents with either flexible or rigid organic linkers resulted in lobed-compact domains, which provides a simple method for patterning air-water and solid-air interfaces. The structural differences between conventional and gemini nicotinic acid-based surfactants could be explained by the interplay between line tension (that favors the formation of circular domains), balanced by dipole−dipole repulsion interaction between headgroups, which promotes extended domains. Miscibility and morphology studies of the modified nicotinic acid surfactants with palmitic acid demonstrated that the properties of mixed films can be controlled by the structure of the former. Excess Gibbs free energies of mixing indicated that the mixed films were less stable than the pure monolayers, and the positive deviations from ideality were the largest in the case of gemini surfactants.