Congratulations to Andrey Shults and the team members in the Macdonald lab! Andrey’s paper, 鈥淒ecomposition of Selenourea in Various Solvents: Red versus Gray Selenium in the Synthesis of Iron Selenide Nanoparticles,鈥� has been selected as a VINSE spotlight publication.
Control over nanoparticle structure and stoichiometry is complex and largely related to the intricate precursor chemistry. Preceding colloidal nucleation and growth are the many interactions between the solvent, ligand, and organic metal reagents. While trends in nanoparticle phase composition can be inferred through numerous synthesis trials, understanding what happens inside the reaction vessel can simplify and accelerate our efforts in achieving nanocrystalline phase control.
In this work, we follow the decomposition pathway of selenourea, a common reagent used in metal selenide synthesis, in oxidizing and reducing environments. We find that in the presence of oleic acid, selenourea decomposes into grey selenium and reacts with the iron precursor to form FeSe2. When oleylamine is used, we detect red selenium which reacts with iron to form Fe7Se8. Through the combination of powder X-ray diffraction, nuclear magnetic resonance, and gas phase infrared spectroscopy, we map the interactions of all reagents and their decomposition products to justify the observed phase control events.
Andrey Shults graduated in May 2025 with a Ph.D. in Chemistry and is currently a postdoc at Pennsylvania State University.
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Authors: Andrey A. Shults, Alexandra C. Koziel, Joshua D. Caldwell and Janet E. Macdonald
Abstract: Selenourea is a useful reagent for the synthesis of metal chalcogenides. Its low decomposition temperature allows it to bypass the usual harsh conditions used in nanoparticle synthesis.
Here, we show that selenourea decomposes differently based on its chemical environment, a phenomenon that can be used for the phase control of iron selenide nanoparticles. Two solvents (oleylamine and oleic acid) were tested for their interactions with selenourea to control the phase of iron selenides as they are ubiquitous in nanocrystal synthesis. It was found that in the presence of oleylamine, selenourea decomposes into red selenium resulting in the formation of Fe7Se8. When combined with oleic acid, selenourea decomposes into gray selenium, resulting in the formation of FeSe2. In this report, allotropes have been identified as phase-determining intermediates in nanocrystal synthesis.