The solution approach was employed to yield multifunctional amorphous Gd2O(CO3)(2)center dot H2O colloidal spheres by reflux of an aqueous solution containing GdCl3 center dot 6H(2)O and urea. By elongating the reaction time, crystalline rhombus-shaped Gd2O(CO3)(2)center dot H2O with at least 87% yield could be formed and were also accompanied by some rectangular particles. High-resolution synchrotron powder X-ray diffraction provides crystal structure information, such as cell dimensions, and indexes the exact crystal packing with hexagonal symmetry, which is absent from the Joint Committee on Powder Diffraction Standards file, for the crystalline rhombus sample. Particle formation was studied based on the reaction time and the concentration ratio of [urea]/[GdCl3 center dot 6H(2)O]. After a calcination process, the amorphous spheres and crystalline rhombus Gd2O(CO3)(2)center dot H2O particles convert into crystalline Gd2O3 at temperatures above 600 degrees C. For in vitro magnetic resonance imaging (MRI), both Gd2O(CO3)(2)center dot H2O and Gd2O3 species show the promising T-1- and T-2-weighted effects and could potentially serve as bimodal T-1-positive and T-2-negative contrast agents. The amorphous Gd2O(CO3)(2)center dot H2O contrast agent further demonstrates enhanced contrast of the liver and kidney using a dynamic contrast-enhanced MR imaging (DCE-MRI) technique for in vivo investigation. The multifunctional capability of the amorphous Gd2O(CO3)(2)center dot H2O spheres was also evidenced by the formation of nanoshells using these amorphous spheres as the template. Surface engineering of the amorphous Gd2O(CO3)(2)center dot H2O spheres could be performed by covalent bonding to form hollow silica nanoshells and hollow silica@Fe3O4 hybrid particles.