Designer molecules from a nanotech library

Nanoparticles have been coaxed to morph into colloidal spheres that give a choice of designer particles for use as dyes, catalysts or biolabels, claim US chemists.

Chad Mirkin and Moonhyun Oh at the Institute for Nanotechnology, Northwestern University, have made what Mirkin said is a new class of material. Mirkin and Oh got nanoparticles to form spontaneously from solutions of metal ions and organometallic complexes (known as metalloligands when the different groups attached to the metal are incorporated). These particles, 100 to 200 nm in diameter, coalesced to form bigger particles, which were 1 to 5 ?m across. The properties of the final larger spheres depended on which metalloligand and metal ions were chosen. 

’Almost all inorganic nanoparticles are made from elemental precursors,’ Mirkin told Chemistry World. ’By moving to molecular rather than atomic building blocks, we have an inherently greater level of tailorability.’ Mirkin and Oh’s nanoparticles are porous, unlike most other nanoparticles, which makes them ideal for catalysis - reactions can happen on their surface and within the pores.

The reaction to make the larger spheres is reversible. Certain small molecules can reverse the reaction, and allow the starting materials to be recovered and used to build other structures.

Mirkin and Oh have collated a library of different precursors, which they use to produce ’truly designer molecules’. Mirkin said the biggest drawback to this was deciding what type of nanoparticle to focus on. ’The menu has been dramatically expanded,’ he said. Katharine Sanderson