L-cysteine protected copper nanoparticles as colorimetric sensor for mercuric ions

This report demonstrates a novel, simple and efficient protocol for the synthesis of copper nanoparticles in aqueous solution using L-cysteine as capping or protecting agent. UV-visible (UV-vis) spectroscopy was employed to monitor the LSPR band of L-cysteine functionalized copper nanoparticles (Cyst-Cu NPs) based on optimizing various reaction parameters. Fourier Transform Infrared (FTIR) spectroscopy provided information about the surface interaction between L-cysteine and Cu NPs. Transmission Electron Microscopy (TEM) confirmed the formation of fine spherical, uniformly distributed Cyst-Cu NPs with average size of 34 +/- 2.1 nm. X-ray diffractometry (XRD) illustrated the formation of pure metallic phase crystalline Cyst-Cu NPs. As prepared Cyst-Cu NPs were tested as calorimetric sensor for determining mercuric (Hg2+) ions in an aqueous system. Cyst-Cu NPs demonstrated very sensitive and selective colorimetric detection of Hg2+ ions in the range of 0.5 x 10(-6)-3.5 x 10(-6) mol L-1 based on decrease in LSPR intensity as monitored by a UV-vis spectrophotometer. The developed sensor is simple, economic compared to those based on precious metal nanoparticles and sensitive to detect Hg2+ ions with detection limit down to 4.3 x 10(-8) mol L-1. The sensor developed in this work has a high potential for rapid and on-site detection of Hg2+ ions. The sensor was successfully applied for assessment of Hg2+ ions in real water samples collected from various locations of the Sindh River. (C) 2014 Elsevier B.V. All rights reserved.