Selective Ligand-Doped Liquid Crystal-Based Sensing Platform for Detection of ClO^- Ions in Aqueous Media

The liquid crystal (LC) detection platform has been fabricated for the detection of hypochlorite ions (ClO^-) in aquatic solutions. In this system, an imine consisting of the ligand (E)-2-((4-(diethylamino)-2-hydroxybenzylidene)amino)-5-methoxybenzenesulfonic acid (MBA) was doped in 4-cyano-4'-pentyl biphenyl as a selecting LC for ClO^-. When immersing the platform in a solution containing ClO^-, hypochlorite appears to react with the imine bond in the MBA, and cause it to cleave, which eventually disrupts the direction of LC and causes a dark-to-bright conversion of the LC image. The detection limit for ClO^- is 0.05 μM. This sensory platform was unresponsive to NO₃ ^-, BrO₃ ^-, CH₃COO^-, CO₃ ^2-, and PO₄ ^3- ions. Our sensing platform also detected ClO^- in piped water. Since this sensory platform is colored under ambient light, it is easy for regular operators, and it can be used as a mobile tool for monitoring water quality anywhere.