Los Alamos researchers develop new nanotech for biofuel cell design

Los Alamos National Laboratory researchers and external collaborators have synthesised and characterised a new DNA-templated gold nanocluster (AuNC) that could resolve a critical methodological barrier for efficient biofuel cell design.

Ligands, molecules that bind to a central metal atom, are necessary to form stable nanoclusters.

For this study, the researchers chose single-stranded DNA as the ligand, as DNA is a natural nanoscale material having high affinity for metal cations and can be used to assembly the cluster to other nanoscale material such as carbon nanotubes.

Saumen Chakraborty, a scientist on the project, says the research seeks to boost electron transfer efficiency, creating a potential candidate for the development of cathodes in enzymatic fuel cells.

‘Enzymatic fuel cells and nanomaterials show great promise, and as they can operate under environmentally benign neutral pH conditions, they are a greener alternative to existing alkaline or acidic fuel cells, making them the subject of worldwide research endeavours,’ says Chakraborty.

In enzymatic fuel cells, fuel is oxidised on the anode, while oxygen reduction reactions take place on the cathode, often using multi copper oxidases.

Enzymatic fuel cell performance depends critically on how effectively the enzyme active sites can accept and donate electrons from the electrode by direct electron transfer (ET).

However, the lack of effective ET between the enzyme active sites, which are usually buried ~10Å from their surface, and the electrode is a major barrier to their development.

Therefore, effective mediators of this electron transfer are needed, and to this end the team developed a new DNA-templated AuNC that enhanced electron transfer.

This novel role of the AuNC as enhancer of electron transfer at the enzyme-electrode interface could be effective for cathodes in enzymatic fuel cells, thus removing a critical methodological barrier for efficient biofuel cell design.

Hypothesizing that due to the ultra-small size (the clusters are ~7 atoms, ~0.9 nm in diameter), and unique electrochemical properties, the AuNC can facilitate electron transfer to an oxygen-reduction reaction enzyme-active site and, therefore, lower the overpotential of the oxygen reaction, which is the extra amount of energy required to drive an electrochemical reaction.

Although AuNCs have been used in chemical catalysis, this is the first time it has been demonstrated they can also act as electron relaying agents to enzymatic oxygen reduction reaction monitored by electrochemistry.

The research was published in the Journal of the American Chemical Society.

Los Alamos National Laboratory is a multidisciplinary research institution engaged in strategic science on behalf of US national security.