In Situ Study of Spinel Ferrite Nanocrystal Growth Using Liquid Cell Transmission Electron Microscopy

Abstract

We report transition metal oxide nanocrystal formation in a liquid cell using transmission electron microscopy (TEM). The growth of M–Fe–oxide (M = Ni, Mn, Co, or Zn) nanoparticles from a growth solution of metal acetylacetonates dissolved in oleylamine, oleic acid, and benzyl ether was studied. Nickel iron oxide nanocrystals with spinel structure were obtained under electron beam irradiation of the Ni–Fe growth solution, whereas iron oxide nanocrystals were achieved with Mn remaining in the Mn–Fe growth solution. Similarly, we achieved cobalt iron oxide nanocrystals in the Co–Fe precursor solution, while iron oxide nanoparticles were obtained in the Zn–Fe solution. By tracking nanoparticle size evolution as a function of time along the Ni–Fe–oxide nanoparticle growth trajectories, we found the growth kinetics follow a Lifshitz–Slyozov–Wagner (LSW) model suggesting surface reaction-limited growth. Ex situ characterization shows elemental distribution and structural and valence state of the different nanop...