Abstract
Ligands are a fundamental part of nanocrystals. They control and direct nanocrystal syntheses and provide colloidal stability. Bound ligands also affect the nanocrystals’ chemical reactivity and electronic structure. Surface chemistry is thus crucial to understand nanocrystal properties and functionality. Here, we investigate the synthesis of metal oxide nanocrystals (CeO2-x, ZnO, and NiO) from metal nitrate precursors, in the presence of oleylamine ligands. Surprisingly, the nanocrystals are capped exclusively with a fatty acid instead of oleylamine. Analysis of the reaction mixtures with nuclear magnetic resonance spectroscopy revealed several reaction byproducts and intermediates that are common to the decomposition of Ce, Zn, Ni, and Zr nitrate precursors. Our evidence supports the oxidation of alkylamine and formation of a carboxylic acid, thus unraveling this counterintuitive surface chemistry.
Highlights
Ligands are a fundamental part of nanocrystals
In reactions where several organic ligands can bind to the NCs, the surface chemistry is typically studied in detail by nuclear magnetic resonance (NMR) spectroscopy, e.g., for CdSe,[28,33] PbS,[34−36] and InP29,37,38 NCs
We disclose an even more extreme example, where alkylamine ligands are oxidized into carboxylic acids during the synthesis of CeO2‐x NCs from cerium nitrate
Summary
J.L. is a Serra Huń ter Fellow and is grateful to ICREA Academia program and MICINN/FEDER RTI2018-093996-B-C31 and GC 2017 SGR 128 projects
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