Decomposition of Selenourea in Various Solvents: Red versus Gray Selenium in the Synthesis of Iron Selenide Nanoparticles

High Resolution Image Download MS PowerPoint Slide 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 Fe 7 Se 8 . When combined with oleic acid, selenourea decomposes into gray selenium, resulting in the formation of FeSe 2 . In this report, allotropes have been identified as phase-determining intermediates in nanocrystal synthesis.