IIT-Madras team turns silver nano-particles into gold

Chennai: A group of researchers from IIT Madras has successfully turned nanoscale pieces of silver to gold and gold to silver with a series of atom-by-atom changes from simple chemical reactions.

The structure of these materials before and after transformation is identical, although they are completely different chemically. “This is like transforming a silver Nataraja sitting on your table to a gold equivalent, by atom-by-atom changes. Although this is possible only at the nanoscale, that too with limited systems today, there is a hope that such changes can occur in the macroscopic world in the future” said Professor T. Pradeep, department of chemistry, IIT Madras, and the corresponding author of the paper.

“This is not alchemy, the medieval quest for converting everything into gold. Here, gold does not become silver. A structure of gold becomes another identical structure of silver or vice versa. The number of atoms of gold and silver is the same. There is no magic, no principle of science is violated,” Pradeep said in a release on Wednesday.

“We are only creating conditions such that one structure can become another,” he added. During such transformations, alloys composed of both gold and silver are formed, containing identical structures.

The atom by atom replacement takes place when nanoparticles of gold and silver are mixed in solution at room temperature. The chemistry occurs between a 25-atom piece of gold (Au) and a corresponding piece of silver (Ag) composed of 25 atoms of silver. The silver atom removed from the silver nanoparticle, in turn, takes the place of the gold atom in the gold nanoparticle to form an AgAu24 alloy.

Such processes go on until gold (Au25) becomes silver (Ag25) and silver (Ag25) becomes gold (Au25). “Precision control of this kind in solution may be useful in technology. Also, the properties of in-between structures could be very new,” Pradeep said.