Palladium Nanorods with Magnetic Properties

Palladium as free atom has all filled atomic orbitals, hence diamagnetic behavior is observed based on Hund's rule. However, in confined nanoscale systems, more localized electronic states as well as narrower bands are usually supposed to increase the densities of states and lead to the exotic magnetic behavior.

These magnetic behavior can be controlled by changing the shape and size of nano-particles. Studies based on the feasibility of tuning the magnetic property of Pd at the nanoscale is facilitating, both the understanding of fundamental magnetism and the future application of spintronic technology.

Despite all the efforts put by scientific community in this field, it remains a great challenge to achieve shape-controlled synthesis of single crystalline palladium nanostructures in a large scale, particularly the 1D structure.

In a recently published scientific article, authors have successfully demonstrated the synthetic approach toward single crystalline Pd nanorods with a controlled aspect ratio in large quantities via a simple one-pot solution method.They have observed the ferromagnetic properties of Pd nanorods at room temperature, and proved that the onset of ferromagnetic behavior to be highly related to the unique 1D growth behavior.

In a simple solution phase chemistry, through tuning the molar ratio of two surfactants, cetyltrimethylammonium bromide (CTAB) and poly(vinyl pyrrolidone) (PVP), single crystalline palladium nanorods with different aspect ratios have been synthesized in large quantities.

The introduction of cosurfactant CTAB is critical to the growth of palladium nanorods. Its headgroup CTA+ and counterion Br- anion act as stabilizing species and etchant, respectively.

Compared with PVP-capped Pd nanoparticles, the Pd nanorods show a ferromagnetism behavior at 5 and 300 K. Pd nanorods at different temperatures were measured by SQUID. It has been concluded that a permanent magnetic moment is an intrinsic property of a Pd nanorod based on EELS study and M-H curve of PVP.

Although the detailed mechanism is still elusive, the morphology- related magnetism is believed to be meaningful in the exploration of novel magnetism in other nonmagnetic metals at nanoscale.

Ref: J. Phys. Chem. C, 2009, 113 (31), 13466–13469