Superparamagnetic ironoxide nanoparticles via ligand exchange reactions: Organic 1,2-diols as versatile building blocks for surface engineering

A method for the preparation of ligand-covered superparamagnetic iron oxide nanoparticles via exchange reactions is described. 1,2-diol-ligands are used to provide a stable binding of the terminally modified organic ligands onto the surface of gamma-Fe2O3-nanoparticles ( r similar to 4 nm). The 1,2-diol-ligands are equipped with variable terminal functional groups (i. e., hydrogen bonding moieties, azido- bromo-, fluorescent moieties) and can be easily prepared via osmium tetroxide-catalyzed 1,2-dihydroxylation reactions of the corresponding terminal alkenes. Starting from octylamine-covered gamma-Fe2O3-nanoparticles, ligand exchange was effected at 50 degrees C over 24-48 hours, whereupon complete ligand exchange is taking place as proven by thermogravimetric (TGA)- and IR-spectroscopic measurements. A detailed kinetic analysis of the ligand exchange reaction was performed via TGA analysis, demonstrating a complete ligand exchange after 24 hours. The method offers a simple approach for the generation of various gamma-Fe2O3-nanoparticles with functional organic shells in a one-step procedure.