TEHRAN (INIC)- The Iranian researchers at Razi University developed a simple test to quickly and accurately measure the lead (II) levels in aqueous solutions down to very low concentrations.

The test uses a solution of azacrown ether-modified AuNPs, which changes color in the presence of the toxic metal ion. This colour change is visually discernible by an appearance of the surface plasmon band (SPB) at 520 nm.

The recognition mechanism is attributed to the unique structure of monoazacrown ether attached to AuNPs and metal sandwiches coordinated between two azacrown ether moieties that are attached to separate AuNPs. This inter particle cross-linking results in aggregation and an apparent color change from brown to purple.

The sensor is selective against alkali-, alkaline-earth- and heavy-transition-metal ions. Such selectivity is essential for applications involving real environmental samples. Compared with many current optical chemosensors for lead (II), this sensor is rapid, cost-effective and enzyme-free.

The system allows easy detection of lead ions by the naked eye without resorting to any expensive instruments. Significantly, this method can, in principle, be used to detect other metal ions by changing the structure and the size of ionophores that selectively bind other metal ions.

More details can be found in the journal of Nanotechnology.

About the Author

The work, performed in collaboration with different teams, was managed by Dr Abdolhamid Alizadeh, the head of the nanoparticle research group at the Nanoscience and Nanotechnology Research Center (NNRC), Razi University, Kermanshah, western Iran,

Also Prof. Mohammad M Khodaei, University President. Changiz Karami is a graduate student in the group of Dr Alizadeh and is supported by a scholarship of the Iran Nanotechnology Initiative Council (INIC).

The functionalized thiols were synthesized in collaboration with Prof. M S Workentin, Department of Chemistry, University of Western Ontario, Canada. The UV-Vis experiments were conducted in collaboration with Prof. Mojtaba Shamsipour and his PhD student, Marzieh Sadeqi, in the Chemistry Department at Razi University.

The main research interest of Alizadeh's group is directed towards the investigation of parameters that affect the mechanisms and dynamics of organic reactions, such as condensation, coupling and complexation, occurring in ordered environments like gold nanoparticle surfaces.

The team is currently exploring new and selective protocols for adding (or removing) functionality to the surface of metallic nanoparticles.