Submicro-polymer particles bearing imidazoline-2-selenone: Dual mode adsorbents with color-sensing for halogens and mercury ions

Submicron-sized polymer particles (PSE) containing imidazoline selenones were prepared by co-polymerization of styrene derivative (MSE) bearing an imidazoline selenone moiety with 1,4-divinylbenzene (DVB). The size and chemical composition of PSE were controlled by changing the stoichiometric ratios of MSE to DVB. The physical and chemical properties of PSE were characterized by SEM, EDS and elemental analysis. PSE showed an interesting reactivity towards halogens with vivid color-change from white to red-orange, which is attributed to the reaction of selenium in imidazoline-2-selenone with halogens. Acid treatment of PSE generated the hydrophilic red-orange colored particles (PSEA) which showed very selective adsorption properties towards mercury ions with color change to pale yellow. To figure out the origin of color change, model studies were conducted using 1,3-dimethyl-imidazoline-2-selenone. The dimerization of 1,3-dimethyl-imidazoline-2-selenone through Se-Se bond formation by acid-treatment resulted in color change from colorless to red-orange. The coordination-induced cleavage of the Se-Se bond of the dimerized species by mercury ions resulted in color change from red-orange to pale yellow. These observations indicate that hydrophobic PSE and hydrophilic PSEA are efficient systems for adsorption of halogens and mercury ions with a vivid color-detection.