Liquid crystal based sensor system for the real time detection of mercuric ions in water using amphiphilic dithiocarbamate

We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg2+) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methylN-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-41-pentyl biphenyl (5CB) LC, which align LC molecules at aqueous interface and polar head group of the amphiphile acts as mecuric ion specific chelating ligand. When this sensor system was incubated in the aqueous solution containing Hg2+ ions, a dark to bright transition of the image of LCs was observed. This was caused due to rapid and stable complex formation between dithiocarbamate chelating group of MeDTC with Hg2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg2+ ion is 0.5 M. This sensor did not respond to other metal ions like Pb2+, Cd2+, Cu2+, Na2+, Mg2+ and Ca2+, which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg2+ ions in real water samples (tap water). The very simple and effective procedure reported here should facilitate the development of real time, portable and reliable LC based sensor for mercury pollution control. (C) 2015 Elsevier B.V. All rights reserved.