Biosynthesis of silver nanocrystals, their kinetic profile from nucleation to growth and optical sensing of mercuric ions

With the increase in intensive use of chemicals especially metal ions, there is an increase in the pollution level, so there is an urgent need of monitoring as well as the removal of the toxic chemical/ions by the material which itself is nontoxic. Herein, we explore the green technology for fabricating silver nanocrystals (Ag NCs) which have been attained by using Syzygium aromaticum extract. Different physiochemical parameters have been studied for optimization of the synthesis. With an increase in the concentration of Syzygium aromaticum concentration of Ag NCs increase but at the same time broadening of the UV-vis. peaks appear, revealing the increase in polydispersity of the Ag NCs. Similarly, when the different concentration of the Ag ions has been exposed with the fixed concentration of Syzygium aromaticum, there is an increase in the concentration of Ag NCs along with red shift revealing the increase in particle size. In case of optimization of temperature studies, with an increase in temperature, the red shift appears in absorption spectrum revealing the increase in size due to increase in the collision between the Ag ion and Syzygium aromaticum extract. The optimization study reveals that 1 mL of Syzygium aromaticum in 1000 mL distilled water is sufficient to reduce 1 mM Ag ion solution at room temperature and works well near neutral pH solution. Kinetic studies reveal the formation of Ag NCs via. three step process, i.e. nucleation, growth and stabilization. The rate constant comes out to be 0.4645 (R-2 = 0.9700) and 0.03593 min(-1) (R-2 = 0.99942) for nucleation and growth, respectively. The surface functionalization of Ag NCs has been verified using Fourier Transformation Infra-Red spectroscopy. Further, the synthesized Ag NCs have been devoted to the optical monitoring of the Hg2+ ions. Absorbance results reveal that the Ag NCs act as a selective and sensitive sensor for Hg2+ ions that works quite efficiently with the minimum concentration of 2.0 mu M. (C) 2019 Elsevier Ltd. All rights reserved.