Solvent effect and amine interference on colorimetric changes of azobenzene-conjugated dithiaazadioxo crown ether mercury sensor

The colorimetric behavior of an azobenzene-based dye containing dithiaazadioxo ring for Hg2+-detection was investigated in diverse solvents. The mercury specific ligand shows hypsochromic changes in pure and aqueous MeCN upon Hg2+-binding while strong bathochromic shift was observed in chloroform. In both solvent systems, dithiaazadioxo ring is revealed to be indispensable to the selective detection of mercury ion, and several binding schemes in different solvents were proposed on the selective Hg2+ binding. Grafted on cationic polymer (PEI) through amide coupling, it was observed that the ligand basically maintains the Hg2+ detection capability, but substantially hindered by amine moieties in PEI.