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 (Hg 2+ ) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methyl-N-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-4′-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 Hg 2+ 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 Hg 2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg 2+ ion is 0.5 μM. This sensor did not respond to other metal ions like Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , Na + , Mg 2+ and Ca 2+ , which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg 2+ 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. [ABSTRACT FROM AUTHOR]