Rapid Detection of Mercury Ions in Water Using Functionalized Liquid Crystal Microdroplets

Abstract

In this study, we developed stimuli-responsive liquid crystal (LC) droplets coated with PEI/Tween-20 to detect mercury ions (Hg²⁺) in aqueous solutions. The PEI/Tween-20-coated LC droplets change their orientation from radial (homeotropic) to bipolar (planar) upon adding mercury ions in an aqueous solution. This phenomenon is attributed to the presence of amine groups in poly (ethylene imine). This approach provides a lowest response time of 10 seconds at a concentration as low as 59 mM. The detection limit in distilled water is 4.71 mM, based on 160 µL of mercury ion solution. The responsivity of the LC droplets depends on the volume of the mercury ion solution, the number of droplets, and the concentration of mercury ions. Our results demonstrate a conventional method for detecting Hg²⁺ ions in an aqueous environment, effectively replacing the need for sophisticated instruments. Additionally, this method reduces the concentration of metal ions in the aqueous environment through adsorption onto its surface.