Gold particles have been grown inside silica nanoshells in an inside out approach to synthesis.

Coating silica onto metal nanoparticles is a known method of stabilising and functionalising nanoparticles, but a technique developed by researchers in Germany and the UK takes the reverse approach, using hollow silica particles as nanoreactors to grow gold particles.  

The scientists, led by Sara Cavaliere-Jaricot at Albert-Ludwig University, Freiburg, Germany, and Thomas Nann at the University of East Anglia, Norwich, UK, added a gold precursor and a reducing compound to the silica's cavity to form silica coated gold nanocomposites. The size of the nanocomposites can be controlled by tailoring the cavity size of the silica reactors. 

The silica's cavity (yellow) was filled with a gold precursor (orange), which was reduced to form the gold core (pink) of the nanocomposite

Nann believes these nanoparticles could be used as functional carriers for drugs or contrast agents, or as surface rich materials for gas sensing or storage.

'There are so many challenges in this field,' said Nann. For him, the biggest challenge is the complete understanding and ability to control the surface chemistry of nanoparticles. 'In my opinion, this is the key to almost any successful future application,' he said.

Elinor Richards