Ajar Kamal

Electrochemical sensing of iron (III) by using rhodamine dimer as an electroactive material

The voltammetric and potentiometric sensors based on a novel electroactive rhodamine dimer (RD) have been developed for the determination of Fe (III) ions. The RD exhibits two anodic peaks at 0.5 V and 0.7 V vs. Ag/Ag(+) within the potential range of 0.2-1.2V, which on addition of Fe (III) ions get converted to single anodic peak with a shift toward more positive potential of 0.9 V vs. Ag/Ag(+) due to the formation of Fe (III)-RD complex. The voltammetric sensor has been found to work well in the concentration range of 1.5 × 10(-5)-3.5 × 10(-4)M with the detection limit of 3.3 × 10(-6)M. Further, the potentiometric response of proposed PVC based solid contact coated graphite electrode (CGE-1) was linear for Fe (III) ions in the concentration range of 1.0 × 10(-1)-1.0 × 10(-7)M. The electrode showed a slope of 18.8 mV/decade with a detection limit of 4.68 × 10(-8)M for Fe (III) ions. Both of the sensors revealed good selectivity towards Fe (III) ions in comparison to various diverse metal ions. The analytical utility of the proposed sensors has been confirmed by the estimation of the Fe (III) content in different sample matrices.

Detailed study of interactions between eosin yellow and gemini pyridinium surfactants

Interactions of dianionic dye, eosin yellow, with gemini pyridinium surfactants, 1,1′-(2-hydroxypropane-1,3-diyl)bis(3-(tetradecyloxy)pyridin-1-ium) bromide [14-3(OH)-14] and 1,1′-(2-hydroxypropane-1,3-diyl)bis(3-(hexadecyloxy)pyridin-1-ium) bromide [16-3(OH)-16], have been investigated using conductivity, UV-visible, fluorescence, cyclic voltammetry, differential pulse voltammetry, potentiometry and dynamic light scattering techniques. Micellar, thermodynamic and electrochemical parameters have been evaluated using conductivity and voltammetry. The critical micelle concentration of both the gemini pyridinium surfactants decreases in the presence of dye. The formation of dye-surfactant ion-pairs and premicellar dye–surfactant aggregates in the sub-micellar region of gemini pyridinium surfactants has been observed and their stoichiometry was determined using conductivity and UV-visible techniques. Dynamic light scattering measurements provided information regarding the size of aggregates in pre- and post-micellar region of gemini pyridinium surfactants in the absence and presence of dye. Quantitative evaluation of the interactions among dye and gemini pyridinium surfactants has been done in terms of quenching and binding parameters using fluorescence, UV-visible and voltammetry techniques.