Nanometre-scale gold particles are currently intensively investigated for possible applications as catalysts, sensors, biolabels, drug delivery devices, biological contrast agents and as components in photonics and molecular electronics. The particles are prepared in a solution from gold salts and their reactive gold cores can be stabilized with various organic ligands. Particularly stable particles can be synthesized by using organothiol ligands that have a strong chemical interaction to gold, producing precise compositions in the size range of 1 to 3 nanometres. Modification of the protecting molecular overlayer is a key step in almost all applications. A detailed structural atomistic understanding of the processes of the exchange reaction has been lacking.
Now, professors Chris Ackerson in the Colorado State University in Ft. Collins, USA, and Hannu Hkkinen at the Nanoscience Center of the University of Jyvskyl, Finland, report the first structural study on the atomistic processes of a ligand-exchange reaction of a well-defined gold nanoparticle that has 102 gold atoms and 44 ligand sites in the molecular overlayer. The study was published in the Journal of the American Chemical Society on 21 July 2012 . Prof. Hkkinen's work is funded by the Academy of Finland and prof. Ackerson's work is funded by the Colorado State University and the American Federation for Aging Research.
The studied particle has a chemical formula of Au102(p-MBA)44 and it was made by using a water-soluble thiol (para mercapto benzoic acid, p-MBA) as the stabilizing molecule. The X-ray crystal structure of this particle was first reported as the cover article of Science in 2007 by the group of Roger D. Kornberg from Stanford University . Hkkinen led an international team of researchers that published a theoretical analysis of this and other thiol-stabilized gold nanoparticles in 2008 in the Proceedings of the National Academy of Sciences .
|Contact: Professor Hannu Hkkinen|
Academy of Finland