Golden nuggets
11 Apr 2001
Porous gold could become an important material for catalysis, especially in biomedical applications, thanks to research from Johns Hopkins University's materials science department in Baltimore.
The material has been known for many centuries, but was not fully understood until now.
Research coordinator Jonah Erlebacher has been studying nanoporous gold for much of his career. It's easy to make, by dipping an alloy of gold and silver alloy into a strong acid - the silver dissolves, leaving the gold as a spongelike structure.
Erlebacher's team used scanning electron microscopy and computer modelling to study the surface of the nanoporous gold, and to simulate the processes which take place as the silver dissolves. 'As the silver atoms in the alloy are dissolved by the acid, the remaining atoms of gold gather together into clusters,' Erlebacher says.
This is related to the nature of the interface between alloy and acid. 'We believe that the de-alloyed gold atoms act like water droplets on a pane of glass, condensing into little clumps that grow into the backbone of the porous structure.'
With its large surface area and biological and chemical inertness, nanoporous gold could be an ideal support for biological catalysts. One use could be as a support for enzymes in sensor devices.
