Transition metal based single chained surfactants: synthesis, aggregation behavior and enhanced photoluminescence properties of fluorescein

Abstract

Four different metal based surfactants were synthesized using hexadecyltrimethyl ammonium chloride and metal chlorides (FeCl₂, CoCl₂, NiCl₂ and CuCl₂) in 1 : 1 ratios. The prepared metal complexes were characterized by different techniques such as FTIR, CHNS elemental analysis, atomic absorption spectrophotometry and NMR. The effect of metal counter ion on the thermal and aggregation behaviour of CTAC was studied by TGA, conductivity and surface tension. The results reveal that metal incorporation decreases the CMC value and increases the thermal stability in the order Cu(II) > Co(II) > Ni(II) > Fe(II). The study of absorption and fluorescence spectra of fluorescein in pre and post micellar concentration of metallosurfactants was carried out. The binding constant and number of binding sites was evaluated by using Stern–Volmer equation. Fluorescence quantum yield (Φ_F) of fluorescein (FL) was premeditated in prepared metallosurfactants (FeC I, CoC I, NiC I, CuC I). This single alkyl chain system was used to gain reliable insight into the contribution of metal towards the Φ_F of FL. The analysis of results indicate that among all, copper surfactant exhibited high fluorescence quantum yield due to increase in the radiative decay of FL. Even as the concentration of metallosurfactant goes from pre-micellar to post-micellar, the Φ_F of FL was increased.