Oct 17, 2012
Molecular tunnel junctions configured with palladium electrodes
Molecular tunnel junctions are almost always made with gold because of a vast body of existing literature, both on the chemical functionalization of this surface, and the sculpting of nanostructures, from gaps fabricated by electromigration to mechanical break junctions. But gold is a poisonous material in a CMOS fab, introducing deep-level traps in silicon, which has led researchers to consider alternative materials. Reporting their results in the journal Nanotechnology, scientists based in the US have described recognition tunneling measurements made with palladium electrodes.
In recognition tunneling (see figure) each of the two electrodes is modified with an adaptor molecule that binds strongly to the electrode material and forms non-covalent bonds with the target analyte molecule. When the analyte binds across the shortest path, stochastic noise is generated that is characteristic of the binding of the analyte. This noise can be used to identify the four DNA bases, for example, as well as methylated cytosine, a DNA modification important in silencing genes. Not only is palladium compatible with CMOS technology, but it also gives much bigger signals than an equivalent gold junction.
This technology is being developed for DNA sequencing and the current work is the result of a collaboration between scientists at Arizona State University, Roche (454 Life Sciences) and IBM’s T J Watson Research Center.
More information can be found in the journal Nanotechnology.
About the author
Stuart Lindsay is director of the Center for Single Molecule Biophysics at Arizona State University, and Edward and Nadine Carson Professor of Physics and Chemistry.