Modifying gold nanoparticles with zinc porphyrins leads to enhanced anion recognition properties claims a team of inorganic chemists from the University of Oxford.

Paul Beer, David Cormode and Jason Davis prepared a new zinc porphyrin containing pendant disulfide groups which were subsequently bound to the surface of gold nanoparticles via self-assembly. They then used UV-visible spectroscopy to measure the anion binding affinities of the functionalised nanoparticles and the free zinc porphyrins in various solvents.

The results clearly show that the porphyrins attached to the nanoparticles bind some anions significantly more strongly than the free zinc porphyrins do. The researchers suggest that 'pre-organising' the metalloporphyrin receptors on the nanoparticle surface may be one of the reasons for the enhanced anion binding affinity since it reduces their conformational flexibility.

'The surface pre-organisation of optical and/or electrochemical-group functionalised host systems offers the opportunity to fabricate highly-sensitive sensory devices', they conclude.

Caroline Evans