Aug 10, 2010
Nanogold sensor provides rapid toxic metal ion detection
Nanotechnology can play an important role in water treatment. In particular, the design and synthesis of gold nanoparticles (AuNPs) functionalized with targeted functional molecules have attracted much attention and modified AuNPs have been extensively used as ultrasensitive detection probes for heavy metals and other contaminants.
Researchers in Iran based at Razi University have now developed a simple test to quickly and accurately measure lead (II) levels in aqueous solutions down to very low concentrations. The test uses a solution of azacrown ether-modified AuNPs, which changes colour 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 co-ordinated between two azacrown ether moieties that are attached to separate AuNPs. This inter-particle cross-linking (see image) results in aggregation and an apparent colour 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 Nanotechnology.
About the author
The work, performed in collaboration with different teams, has been managed by Dr Abdolhamid Alizadeh, head of the nanoparticle research group at the Nanoscience & Nanotechnology Research Center (NNRC), Razi University, Kermanshah, Iran, and 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 have been synthesized in collaboration with Prof. M S Workentin, Department of Chemistry, University of Western Ontario, Canada. The UV-Vis experiments have been conducted in collaboration with Prof. Mojtaba Shamsipur and his PhD student, Marzieh Sadeghi, 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.