Simultaneous Size- and Phase-Controlled Synthesis of Metal Oxide Nanocrystals through Esterification Reactions

Abstract

Here, we report on the synthesis of metal oxide (manganese oxide) nanocrystals with simultaneous size- and phase-controlled manners through thermal decomposition of metal oleate. Bulk manganese oxide powders were applied as precursors, which react with oleic acid to yield manganese oleate at elevated temperature. In the presence of long-chain alkyl alcohols, these as-formed manganese oleates would react with alcohol to yield esters, which consequently leads to manganese hydroxide (oxide) (MnO or Mn3O4) nanocrystals. In this way, the size of manganese oxide nanocrystals can be tuned by different amounts of alkyl alcohols. Furthermore, the phase of manganese oxide nanocrystals can also be simultaneously controlled, where a small amount and large amount of alkyl alcohols lead to the formation of MnO and Mn3O4 phase, respectively. These high-quality manganese oxide nanocrystals are able to self-assemble into ordered nanocrystal superlattices.