Nano Archive

In situ synthesis of metal nanoparticles and selective naked-eye detection of lead ions from aqueous media

Yoosaf, Karuvath and Ipe, Binil Itty and Suresh, Cherumuttathu H. and Thomas, K. George (2007) In situ synthesis of metal nanoparticles and selective naked-eye detection of lead ions from aqueous media. JOURNAL OF PHYSICAL CHEMISTRY C, 111 (34). pp. 12839-12847.

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A novel one step synthesis of water soluble Au and Ag nanoparticles has been reported at room temperature using a naturally occurring bifunctional molecule, namely, gallic acid. The mechanistic details of nanoparticle formation were elucidated by carrying out control experiments using a variety of model compounds. The newly synthesized nanoparticles are extremely stable in the pH range of 4.5-5.0, due to (i) the strong electrostatic interaction of the carboxylate anion of the capping agent with the surface of the nanoparticle and (ii) a very high zeta potential (-45 mV). Under these pH conditions, it is difficult to bring nanoparticles in proximity due to strong interparticle electrostatic repulsion. However, the unique coordination behavior of Pb2+ ions (coordination number up to 12, flexible bond length and geometry) allows the formation of a stable supramolecular complex resulting in plasmon coupling and a visual color change. Because of the rigid coordination geometry, other metal cations (Ca2+, Cu2+, Cd2+, Hg2+, Mg2+, Ni2+, and Zn2+) interact only with lesser numbers of ligands, leaving the nanoparticles isolated; hence, no spectral change was observed under the experimental conditions. The ratiometric plots of the aggregated to the isolated forms indicate a high sensitivity as well as selectivity of Au and Ag nanoparticles toward Pb2+ ions. One of the significant features of the present system is its ability to detect micromolar quantities (ppm level) of Pb2+ ions in the presence of other metal cations in water. Further, we have theoretically modeled the interaction between the newly synthesized nanoparticles and the Pb2+ ion, and various optimized geometries are evaluated. On the basis of the experimental and theoretical studies, a tentative structure of the supramolecular complex leading to a strong interparticle interaction is provided.

Item Type:Article
Subjects:Physical Science > Nano objects
Analytical Science > Nanotechnology for sensing and actuating
Material Science > Nanochemistry
ID Code:2679
Deposited By:Anuj Seth
Deposited On:06 Jan 2009 18:17
Last Modified:20 Jan 2009 11:04

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