Easy route to stable silver nanoparticles

Nature News ^ | 04 September 2013 | Mark Peplow

[neverdem]

Cheap synthesis offers edge over gold particles for biomedicine and solar cells.

In the realm of nanoparticles, gold reigns supreme. Stable and easy to handle, gold nanoparticles have been used to image cells, deliver drugs and detect disease biomarkers. Silver, by contrast, has suffered from a tarnished reputation, because it is more easily oxidized than gold. It is cheaper, but its nanoparticles degrade far too easily for most uses.

Two teams of chemists are now burnishing silver’s status. They have independently developed methods to make robust silver nanoparticles on a large scale — and have worked out what makes them stable. “It bodes very well for manufacture,” says Terry Bigioni, a chemist at the University of Toledo in Ohio, who led one of the groups and hopes to use the nanoparticles to build more efficient solar cells.

The core of each nanoparticle behaves like a single ‘superatom’, with electrons orbiting it in a configuration simlar to that seen in the noble gas krypton. This makes the silver atoms there extremely resistant to chemical attack.

Bigioni’s nanoparticles each contain 44 atoms of silver, arranged in a highly symmetrical pattern. The heart of each particle is a hollow icosahedron of 12 silver atoms, surrounded by a dodecahedron of a further 20 atoms to produce a compact and extremely stable structure. The remaining 12 silver atoms are bonded to sulphur-containing molecules to form a protective cage around the core (see image above).

Each particle is less than 3 nanometres wide, a scale where the silver has very different optical and chemical properties to the bulk metal.

Bigioni’s recipe mixes one of the cheapest silver salts — silver nitrate — with other inexpensive reagents in water and ethanol. The simple, reliable method gives yields higher than 95%, and can produce up to 140 grams...

[neverdem]

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[Wonder Warthog]

Hmmmm......I wonder if this synthesis will work with palladium......or nickel??