In Situ Synthesis of Metal Nanoparticles and Selective Naked-Eye Detection of Lead Ions from Aqueous Media

Abstract

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 ζ 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.

Biogenic Synthesis of Nanoparticles and Potential Applications: An Eco- Friendly Approach

“…Moreover, dynamic light scattering is applied for determination of particles size distribution. Furthermore, X-ray diffraction is exercise for the determination of crystallinity, while UVVis spectroscopy is utilized to confirm sample formation by exhibiting the Plasmon resonance [69][70][71][72][73][74][75][76][77][78].…”

Cu/Cu2O/CuO loaded on the carbon layer derived from novel precursors with amazing catalytic performance

“…Therefore, here a novel, simple and efficient scheme (Fig.1) to fabricate Cu-MOF by Cu metal and gallic acid (GA) is presented. GA has been used in the green synthesis of AgNPs and AuNPs as well (Yoosaf et al, 2007). However, to the best of our knowledge, GA has not been utilized as organic ligands to synthesize hierarchical structured nanoparticles.…”

Gold Nanoparticles/Ionophore-Modified Screen Printed Electrode for Detection of Pb(II) in River Water Using Linear Sweep Anodic Stripping Voltammetry

“…, including spectral (8)(9)(10)(11) and electrochemical techniques. (12)(13)(14)(15)(16) However, the conventionally used spectral techniques require a long time and are cumbersome and are also not well suited for the in situ measurements of metals owing to the use of complex and unwieldy instruments.…”