Polyelectrolyte-induced H-aggregation of Merocyanine 540 and its application in metal ions detection as a colorimetric sensor

We report a controllable molecular aggregation of Merocyanine 540 (MC 540) with the assistance of polyethylenimine (PEI) in aqueous solution and its application in the detection of metal ions as a colorimetric sensor. Photophysical properties of MC 540 in aqueous solution was studied by using UV-Vis and fluorescence (steady-state and time-resolved) spectroscopies under various conditions. The spectroscopic data revealed that the interaction of MC 540 with PEI in aqueous solution triggered the formation of its nonfluorescence H-aggregates. The formation of H-aggregates of MC 540 was followed with photo physical parameters such as fluorescence quantum yield and fluorescence lifetime values along with spectroscopic measurements. It was concluded that H-type aggregation was mainly dependent on both MC 540 and PEI concentrations. The effects of pH, temperature and metal ions on H-aggregates of MC 540 in aqueous solution were explored in detail. Interestingly, it was observed that H-aggregates of MC 540 were destroyed and converted to its H-dimer states in the presence of Ni2+, Cu2+, Al3+, Fe3+, Sn4+ ions. Consequently, the controllable aggregation state of MC 540 with Ni2+, Cu2+, Al3+, Fe3+, Sn4+ ions was designed as a colorimetric sensor. (C) 2015 Elsevier B.V All rights reserved.