Thursday, February 16, 2012
Carnegie Mellon University Chemists Create "Giant" Gold Nanoparticle
Electrospray mass spectrum of a giant gold nanocrystal molecule
Chemists at Carnegie Mellon University have manufactured the largest atomically precise gold nanoparticle yet. It comes in at a whopping 333 gold atoms.
Gold nanoparticles, tiny particles that can vary from 1 to 100 nanometers in size, have unique optical, electrical and magnetic properties that have applications in a wide range of fields including electron microscopy, electronics, nanotechnology, materials science and health care. Because these special properties are directly related to the atomic composition of the nanoparticle, especially for the ultrasmall nanoparticles, each particle must be made to be precisely the same size and conformation — a process that has, until recently, eluded scientists.
Carnegie Mellon chemist Rongchao Jin has developed elegant chemical methods that allow him to precisely control the size and shapes of gold nanoparticles, a technique that will prove valuable in developing the particles for research and commercial use.
Most recently, graduate student Huifeng Qian and Jin were able to produce gold nanoparticles that were made up of precisely 333 gold atoms and 79 thiolate groups (Au333(SR)79), the largest gold nanoparticle of atomic precision created by the lab to-date. Using spectrophotometry, they found that these “large” nanoparticles were different than their smaller counterparts the research group had previously made, which include 25 and 38 gold atom nanoparticles.The large particles displayed metallic properties that were in contrast to the semiconducting properties of smaller gold nanoparticles.
“The attainment of this nanoparticle is a critical step toward the total structure determination of a metallic gold nanoparticle, as opposed to the semiconducting ones whose structures have been determined recently. The metallic behavior observed in Au333(SR)79 has shed some light on the origin of plasmon excitation in metallic nanoparticles as well as the semiconducting-to-metallic state transition occurring in metal nanoparticles with increasing size. This work could be far-reaching to the basic science of nanoparticles.”
The findings, which were published in the Proceedings of the National Academy of Sciences, will allow for further study of gold nanoparticles, and could help to inform the study of condensed matter physics, nanochemistry, and catalysis, say the researchers.
By: Jocelyn Duffy