Kinetics of Iron Oxide Nanoparticle Nucleation, Growth, and Assembly

Abstract

Iron oxides are ubiquitous in nature and serve as a platform for a variety of engineered applications, including biomedical imaging and therapeutic procedures. Interactions between minerals, organic molecules, and ions in aqueous environments are fundamental for both engineered nanoparticles that interface with complex biological media, and for naturally occurring particles in delicate environmental systems. To directly observe and quantify dynamic phase changes of iron oxide nanoparticles in solution I use in situ Transmission Electron Microscopy (TEM). To systematically study colloidal stability at the nanoscale we alter surface chemistry by with organic molecules and solution chemistry with the electron beam. TEM is a powerful materials characterization tool capable of imaging, diffraction, and spectroscopy with atomic resolution. Recent advances in in situ TEM techniques and instrumentation enable direct nanoscale imaging and spectroscopy in relevant environments. Specialized holders encapsulate liquid samples, allowing direct observation of dynamic aqueous phenomena under controlled electron dose conditions. Imaging can be complemented by other characterizations available in the TEM including electron energy loss spectroscopy (EELS) and diffraction for structural and chemical characterization. By observing nanoparticles in situ, nucleation, growth, and dissolution kinetics are quantified in real-time to improve our understanding of natural systems and optimize nanoparticle synthesis.