New Growth In Inorganic Nanopeapods

Nanoscientists have discovered a new way to grow inorganic nanopeapods —nanoscale shells that enclose a row of nanoparticles. The latest process, developed by Lifeng Liu of the Max Planck Institute of Microstructure Physics, in Halle, Germany; Woo Lee of the Korea Research Institute of Standards & Science, in Daejon, South Korea; and coworkers allows facile control of both the size and separation of platinum nanoparticles within a CoAl₂O₄ nanoshell (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200801931). To create the nanopeapods, the researchers first electrodeposit nanowires composed of alternating layers of cobalt and platinum within a nanoporous anodic aluminum oxide membrane. Annealing the membrane at 700 °C prompts the cobalt to react with the alumina, forming continuous CoAl₂O₄ "pods." The heating also causes the platinum to agglomerate into spherical "peas" within these shells. The lengths of the cobalt and platinum segments determine the diameter and distance between each of the platinum peas. Long cobalt segments lead to large spaces between the particles, whereas short cobalt segments form more tightly packed peas.