Surface-binding-mediated growth of monodisperse cobalt-doped ceria nanocrystals†
In this study, we explore a new strategy to tailor the growth process of monodisperse nanocrystals. By means of X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, and X-ray absorption spectroscopy, it is found that the growth of ceria followed Ostwald ripening, and polydispersed ceria nanocrystals were obtained in a hydrothermal condition. With the addition of cobalt to the growing ceria nanocrystals, cobalt acted as a surface dopant and preferred to bind on the surface of large-sized ceria nanocrystals via Co–O–Ce bonds. The binding could modulate the Ostwald ripening process and narrow the size distribution. With the competition between cobalt dopants and Ce monomers onto the surface of nanocrystals, monodisperse cobalt-doped nanocrystals were formed. This route is expected to be applicable to a variety of monodisperse doped nanocrystals.