Understanding the mechanism of adsorption of CTAB and polylysine on silver nanoparticles and detection of Hg2+: Experimental and DFT study

Fundamental aspects of poly-L-lysine (PLL) coated silver nanoparticles (AgNPs) are presented for their possible use in colorimetric sensing of heavy metal ions. For this purpose, cetyltrimethylammonium bromide (CTAB) is used, which acts as a stabilizing agent. At the molecular level, the adsorption behavior of PLL and CTAB is evaluated from first principles calculations. These studies demonstrate that PLL and CTAB interact with Ag cluster through NH2 group and positively charged trimethylammonium group, respectively. Surface adsorption of PLL and CTAB on AgNPs is studied under the effect of temperature and reaction time. Multidisciplinary approaches including UV-Visible absorption spectroscopy, Fourier-Transformed Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) are conducted to systematically investigate PLL coated AgNPs stabilized by CTAB (PL-CT-AgNPs). Thus, a combination of experimental and theoretical analysis helped us to identify specific sites, which promoted such interactions for surface adsorption on AgNPs. As synthesized PL-CT-AgNPs, are found to be highly sensitive and selective towards Hg2+ detection. The mechanism of detection of Hg2+ is studied on PL-CT-AgNPs surface using Density Functional Theory (DFT). (C) 2018 Elsevier B.V. All rights reserved.