Oxide-Free Gadolinium Nanocrystals with Large Magnetic Moments

Among the elements in the periodic table, gadolinium (Gd) has the highest number of unpaired electrons. However, the potential of this rare-earth metal has not yet been fully realized due to challenges in its chemical synthesis, namely, its high reduction potential, leading to the formation of oxides with suboptimal properties. This problem is also prevalent with other lanthanides, severely limiting their uses in industry. Herein, a fabrication approach along with a reduction process and appropriate capping have been developed to produce oxide-free, stable gadolinium nanoparticles. We demonstrate broad tunability of the particle size while maintaining remarkably narrow size distributions (<5%). The nanoconstructs displayed the highest magnetization measured to date for Gd, 206 emu/g Gd at 2 K along with a record high per particle nuclear magnetic resonance (NMR) transverse relaxivity (r(2)) of 2.7 x 10(8) mM(-1) s(-1), which corresponds to the highest per-particle r2 relaxivity reported for any T-2 contrast agents to date. Unlike traditional approaches, this process can be extended to produce oxide-free nanoconstructs of other lanthanides, making them accessible for technological or biomedical applications.