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

## TL;DR

This paper shows how selenourea decomposes differently in various solvents, leading to different iron selenide nanoparticle phases.

## Contribution

The study identifies selenium allotropes as phase-determining intermediates in nanocrystal synthesis.

## Key findings

- Selenourea decomposes into red selenium with oleylamine, forming Fe7Se8.
- Selenourea decomposes into gray selenium with oleic acid, forming FeSe2.

## 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.