Graphene in trouble

10 January 2012 - Nanotech

Adriano Ambrosi of the Nanyang Technological University has a sobering message for all those involved in graphene research: the graphene you are working with may be contaminated with metals and these metals may seriously affect the graphene properties you are investigating (DOI). Sounds like the Its-the-contaminants-stupid! discussion al over that deals with organic reactions that may take place without any metal catalyst or take place with a hidden (or ignored) metal payload.
Here are the specifics: regular graphite is known to contain metal impurities, in the top-down approach, graphite is oxidized with strong acids to produce graphite oxide which is then exfoliated and reduced by shock treatment at 1000°C to form single-layer graphene sheets. Ambrosi demonstrates that the metal content (Co,Cu,Fe,Mo,Ni) goes up rather than down in this process with copper at 60 ppm in the final product.
A cyclic voltammetry plot of the graphene as an electrode against cumene hydroperoxide then gives an indication how the electrochemical properties are affected. Whereas the reference electrode made from glassy carbon starts reducing the peroxide at -0.6 V, the graphene electrode already does so at -0.2 V indicating electrocatalysis.
Not all bad new though: the bottom-up approach towards graphene using chemical vapor deposition should be okay.