A facile method was successfully developed to prepare strontium-tantalum perovskite oxynitride, SrTaO 2 N, and its solid solutions. Urea was employed as a solid nitriding agent to eliminate the use of toxic NH 3 gas. In addition, utilization of sol-gel derived Ta 2 O 5 gel as a Ta precursor allowed for completion of nitridation within a shorter period and at a lower calcination temperature compared with the conventional ammonolysis process. Optimization of the reaction conditions, such as the urea content, allowed for production of solid solutions of SrTaO 2 N and Sr 1.4 Ta 0.6 O 2.9 . The products exhibited optical absorption and chromatic colors because of the narrower band gaps of oxynitrides compared with those of oxides. The O/N ratios of the solid solutions were easily adjusted by varying the amount of urea in the mixture of precursor. As a result, the colors of the products ranged from yellow to brown. The nitridation process and products developed in this study are interesting environmentally-benign alternatives to conventional inorganic pigments.

Two-dimensional materials modified with low molecular weight species are known to show unique electronic properties. In this study, we focus on the synthesis and electrochemical investigation of metal hydroxide salt monolayer nanoparticles modified with different molecules toward improved electrochemical functions. Nickel hydroxide carboxylate nanoparticles were successfully prepared through the epoxide-mediated alkalinization method using alkylcarboxylates. It was found that the monolayer nanoparticles with a size of approximately 2 nm were formed directly from an ionic precursor or after ultrasonication post-treatment. Manganese, iron, and cobalt hydroxide carbonates were found to form monolayer nanoparticles through the same procedure. Synthesized nickel hydroxide carbonate monolayer nanoparticles with a short alkylcarboxylate showed enhanced redox processes and electrochemical functions due to higher proton diffusion coefficient, lower electron transfer resistance, and improved intrinsic catalytic activity. We propose that the results obtained in this study will provide a novel design strategy for metal hydroxide monolayer nanoparticulate catalysts toward high functionality.

Calcium–tantalum based perovskite oxynitrides were successfully prepared without ammonolysis. The colour of La3+-doped CaTa(O,N)3 was comparable to that of CaTaO2N prepared by ammonolysis and inorganic yellow pigments using heavy metals.

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