Can you tell me what is p-MBA and more details about it (especially related with nanogold)?
The 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. Häkkinen 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.
In the new study, Ackerson's group succeeded in making heterogeneous crystals of samples of Au102 particles that had undergone a ligand-exchange reaction where the p-MBA thiols in the molecular overlayer had been partially exchanged to a similar thiol containing a Bromine atom, the so-called para -- bromo benzene thiol (p-BBT), under a fast 5-minute reaction. The Au102(p-MBA)44 nanoparticle has a thiol overlayer where almost every thiol ligand site has its own reaction rate due to a highly heterogeneous structure of the overlayer. "The Au102(p-MBA)44 nanoparticle has a structure reminiscent of a protein, with a rigid inorganic gold core analogous to the alpha-carbon backbone of a protein core and chemically modifiable functional groups in the low-symmetry molecular overlayer.